- Ruhr-Universität Bochum

The magnetic order for several compositions of CaK(Fe 1-x Mn x )4As4 has been studied by nuclear magnetic resonance (NMR), Mössbauer spectroscopy, and neutron diffraction. Our observations for the Mn-doped 1144 compound are consistent with the hedgehog spin vortex crystal (hSVC) order which has previously been found for Ni-doped CaKFe4As4 . The hSVC state is characterized by the stripe-type propagation vectors (π0) and (0π) just as in the doped 122 compounds. The hSVC state preserves tetragonal symmetry at the Fe site, and only this SVC motif with simple antiferromagnetic (AFM) stacking along c is consistent with all our observations using NMR Mössbauer spectroscopy, and neutron diffraction. We find that the hSVC state in the Mn-doped 1144 compound coexists with superconductivity, and by combining the neutron scattering and Mössbauer spectroscopy data we can infer a quantum phase transition, hidden under the superconducting dome, associated with the suppression of the AFM transition temperature (T N) to zero for x ≈ 0.01. In addition, unlike several 122 compounds and Ni-doped 1144, the ordered magnetic moment is not observed to decrease at temperatures below the superconducting transition temperature (T c). © 2023 The Author(s). Published by IOP Publishing Ltd.

Reactions between a gas phase and a solid material are of high importance in the study of alternative ways for energy conversion utilizing otherwise useless carbon dioxide (CO2). The photocatalytic CO2 reduction to hydrocarbon fuels like e.g., methane (CH4) is such a potential candidate process converting solar light into molecular bonds. In this work, the design, construction, and operation of a high-purity gas–solid photoreactor is described. The design aims at eliminating any unwanted carbon-containing impurities and leak points, ensuring the collection of reliable and reproducible data in photocatalytic CO2 reduction measurements. Apart from the hardware design, a detailed experimental procedure including gas analysis is presented, allowing newcomers in the field of gas–solid CO2 reduction to learn the essential basics and valuable tricks. By performing extensive blank measurements (with/without sample and/or light) the true performance of photocatalytic materials can be monitored, leading to the identification of trends and the proposal of possible mechanisms in CO2 photoreduction. The reproducibility of measurements between different versions of the here presented reactor on the ppm level is evidenced. © 2023 The Authors

For the development of a wearable artificial kidney (WAK) that uses a small dialysate volume that is continuously regenerated, it is essential that urea, one of the main uremic retention solutes, is removed. Despite advances in sorbent technology or electro-oxidation no safe, efficient and selective method for urea removal has been reported that allows miniaturization of the artificial kidney to wearable proportions. Here we have developed a flow cell for light-driven, photo-electrocatalytic (PEC) urea removal for use in a WAK. We use a photo-active material (hematite) coated with a catalyst (NiOOH) as working electrode for selective urea oxidation and a silver-chloride (AgCl) cathode. The use of the AgCl counter electrodes eliminates the need for an external bias voltage, and allows operation under light illumination only. Using LED illumination (460 nm) we show that urea is selectively oxidized over chloride. N2 formation is confirmed by gas-phase analysis of the headspace of the sample vial, using mass spectrometry. Other nitrogen containing products include nitrite but importantly ammonia and nitrate are not detected. Using the PEC concept a urea removal rate of 2.5 μmol/cm2h (or 0.15 mg/cm2h) has been achieved. Extrapolating our results to an upscaled system, a surface area of 0.5 m2 would enable efficient removal of the daily produced amount of urea (∼300 mmol) urea within 24 h, when driven by LED illumination only. © 2023 The Authors

Large amounts of carbon monoxide are produced by industrial processes such as biomass gasification and steel manufacturing. The CO present in vent streams is often burnt, this produces a large amount of CO2, e.g., oxidation of CO from metallurgic flue gasses is solely responsible for 2.7% of manmade CO2 emissions. The separation of N2 from CO due to their very similar physical properties is very challenging, meaning that numerous energy-intensive steps are required for CO separation, making the CO separation from many process streams uneconomical in spite of CO being a valuable building block in the production of major chemicals through C1 chemistry and the production of linear hydrocarbons by the Fischer-Tropsch process. The development of suitable processes for the separation of carbon monoxide has both industrial and environmental significance. Especially since CO is a main product of electrocatalytic CO2 reduction, an emerging sustainable technology to enable carbon neutrality. This technology also requires an energy-efficient separation process. Therefore, there is a great need to develop energy efficient CO separation processes adequate for these different process streams. As such the urgency of separating carbon monoxide is gaining greater recognition, with research in the field becoming more and more crucial. This review details the principles on which CO separation is based and provides an overview of currently commercialised CO separation processes and their limitations. Adsorption is identified as a technology with the potential for CO separation with high selectivity and energy efficiency. We review the research efforts, mainly seen in the last decades, in developing new materials for CO separation via ad/bsorption and membrane technology. We have geared our review to both traditional CO sources and emerging CO sources, including CO production from CO2 conversion. To that end, a variety of emerging processes as potential CO2-to-CO technologies are discussed and, specifically, the need for CO capture after electrochemical CO2 reduction is highlighted, which is still underexposed in the available literature. Altogether, we aim to highlight the knowledge gaps that could guide future research to improve CO separation performance for industrial implementation. © 2023 The Royal Society of Chemistry

Interfacial reactions drive all elemental cycling on Earth and play pivotal roles in human activities such as agriculture, water purification, energy production and storage, environmental contaminant remediation, and nuclear waste repository management. The onset of the 21st century marked the beginning of a more detailed understanding of mineral aqueous interfaces enabled by advances in techniques that use tunable high-flux focused ultrafast laser and X-ray sources to provide near-atomic measurement resolution, as well as by nanofabrication approaches that enable transmission electron microscopy in a liquid cell. This leap into atomic- and nanometer-scale measurements has uncovered scale-dependent phenomena whose reaction thermodynamics, kinetics, and pathways deviate from previous observations made on larger systems. A second key advance is new experimental evidence for what scientists hypothesized but could not test previously, namely, interfacial chemical reactions are frequently driven by "anomalies" or "non-idealities" such as defects, nanoconfinement, and other nontypical chemical structures. Third, progress in computational chemistry has yielded new insights that allow a move beyond simple schematics, leading to a molecular model of these complex interfaces. In combination with surface-sensitive measurements, we have gained knowledge of the interfacial structure and dynamics, including the underlying solid surface and the immediately adjacent water and aqueous ions, enabling a better definition of what constitutes the oxide- and silicate-water interfaces. This critical review discusses how science progresses from understanding ideal solid-water interfaces to more realistic systems, focusing on accomplishments in the last 20 years and identifying challenges and future opportunities for the community to address. We anticipate that the next 20 years will focus on understanding and predicting dynamic transient and reactive structures over greater spatial and temporal ranges as well as systems of greater structural and chemical complexity. Closer collaborations of theoretical and experimental experts across disciplines will continue to be critical to achieving this great aspiration. © 2023 American Chemical Society. All rights reserved.

Machine learning potentials (MLP) enable atomistic simulations with first-principles accuracy at a small fraction of the costs of electronic structure calculations. Most modern MLPs rely on constructing the potential energy, or a major part of it, as a sum of atomic energies, which are given as a function of the local chemical environments up to a cutoff radius. Since analytic forces are readily available, nowadays it is common practice to make use of both, reference energies and forces, for training these MLPs. This can be computationally demanding since often large systems are required to obtain structurally converged reference forces experienced by atoms in realistic condensed phase environments. In this work we show how density-functional theory calculations of molecular fragments, which are too small to provide such structurally converged forces, can be used to learn forces exhibiting excellent transferability to extended systems. The general procedure and the accuracy of the method are illustrated for metal-organic frameworks using second-generation high-dimensional neural network potentials. © 2023 The Royal Society of Chemistry.

Following nature's example, there is currently strong interest in using adenosine 5′-triphosphate (ATP) as a fuel for the self-assembly of functional materials with transient/non-equilibrium behaviours. These hold great promise for applications, e.g. in catalysis and drug delivery. In a recent seminal work [Maiti et al., Nat. Chem., 2016, 8, 725], binding of ATP to the metallosurfactant zinc hexadecyl-1,4,7-triazacyclononane ([ZnC16 TACN]2+) was exploited to produce ATP-fueled transient vesicles. Crucial to the complex formation is the ability of ATP to bind to the metal ion. As a first step to unveil the key elements underlying this process, we investigate the interaction of ATP with Zn2+ and with methyl-1,4,7-triazacyclononane ([ZnCH3 TACN]2+), using all-atom molecular dynamics simulations. The free energy landscape of the complex formation is sampled using well-tempered metadynamics with three collective variables, corresponding to the coordination numbers of Zn2+ with the oxygen atoms of the three phosphate groups. We find that the structure of the ternary complex is controlled by direct triphosphate coordination to zinc, with a minor role played by the interactions between ATP and CH3 TACN which, however, may be important for the build-up of supramolecular assemblies. © 2023 The Royal Society of Chemistry.

The determination of catalyst nanostructures with first-principles accuracy using genetic algorithms (GA) is very demanding due to the cubic scaling of the computational cost of density functional theory (DFT) calculations. Here, we demonstrate, for the case of Ziegler-Natta MgCl2/TiCl4nanoplates, how this structure determination can be accelerated by employing a high-dimensional neural network potential (HDNNP) of essentially DFT accuracy. First, when building HDNNPs for MgCl2/TiCl4clusters with computationally tractable sizes, we found that the structural diversity in the training set is crucial for obtaining HDNNPs reliably describing the large variety of structures generated by GA. The resulting HDNNPs dramatically accelerated the structure determination while yielding results consistent with DFT. Subsequently, we developed a multistep adaptive procedure to construct a HDNNP for MgCl2/TiCl4clusters consistent in size and TiCl4coverage with experiments where prior DFT results were scarcely collected. The structure determination and analyses underline the importance of system size and composition in order to predict some experimentally known facts such as the surface morphology and population of isospecific sites. © 2023 American Chemical Society.

BACKGROUND: Sodium chlorate (NaClO3) is extensively used in the paper industry, but its production uses strictly regulated highly toxic Na2Cr2O7 to reach high hydrogen evolution reaction (HER) Faradaic efficiencies. It is therefore important to find alternatives either to replace Na2Cr2O7 or reduce its concentration. RESULTS: The Na2Cr2O7 concentration can be significantly reduced by using Na2MoO4 as an electrolyte co-additive. Na2MoO4 in the millimolar range shifts the platinum cathode potential to less negative values due to an activating effect of cathodically deposited Mo species. It also acts as a stabilizer of the electrodeposited chromium hydroxide but has a minor effect on the HER Faradaic efficiency. X-ray photoelectron spectroscopy (XPS) results show cathodic deposition of molybdenum of different oxidation states, depending on deposition conditions. Once Na2Cr2O7 was present, molybdenum was not detected by XPS, as it is likely that only trace levels were deposited. Using electrochemical measurements and mass spectrometry we quantitatively monitored H2 and O2 production rates. The results indicate that 3 μmol L−1 Na2Cr2O7 (contrary to current industrial 10–30 mmol L−1) is sufficient to enhance the HER Faradaic efficiency on platinum by 15%, and by co-adding 10 mmol L−1 Na2MoO4 the cathode is activated while avoiding detrimental O2 generation from chemical and electrochemical reactions. Higher concentrations of Na2MoO4 led to increased oxygen production. CONCLUSION: Careful tuning of the molybdate concentration can enhance performance of the chlorate process using chromate in the micromolar range. These insights could be also exploited in the efficient hydrogen generation by photocatalytic water splitting and in the remediation of industrial wastewater. © 2023 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI). © 2023 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

In recent years, significant progress has been made in the development of machine learning potentials (MLPs) for atomistic simulations with applications in many fields from chemistry to materials science. While most current MLPs are based on environment-dependent atomic energies, the limitations of this locality approximation can be overcome, e.g., in fourth-generation MLPs, which incorporate long-range electrostatic interactions based on an equilibrated global charge distribution. Apart from the considered interactions, the quality of MLPs crucially depends on the information available about the system, i.e., the descriptors. In this work we show that including─in addition to structural information─the electrostatic potential arising from the charge distribution in the atomic environments significantly improves the quality and transferability of the potentials. Moreover, the extended descriptor allows current limitations of two- and three-body based feature vectors to be overcome regarding artificially degenerate atomic environments. The capabilities of such an electrostatically embedded fourth-generation high-dimensional neural network potential (ee4G-HDNNP), which is further augmented by pairwise interactions, are demonstrated for NaCl as a benchmark system. Employing a data set containing only neutral and negatively charged NaCl clusters, even small energy differences between different cluster geometries can be resolved, and the potential shows an impressive transferability to positively charged clusters as well as the melt.

Direct mechanocatalysis (DM) describes solvent-free catalytic reactions that are initiated by mechanical forces in mechanochemical reactors such as ball mills. The distinctive feature of DM is that the milling materials, e.g. the milling balls themselves are the catalyst of the reaction. In this article we follow the historical evolution of this novel concept and give a guide to this emerging, powerful synthesis tool. Within this perspective we seek to highlight the impact of the relevant milling parameters, the nature of the catalyst and potential additives, the scope of reactions that are currently accessible by this method, and the thus far raised hypotheses on the underlying mechanisms of direct mechanochemical transformations. © The Royal Society of Chemistry.

Antimicrobial resistance is a worldwide threat to modern health care. Low-profit margin and high risk of cross-resistance resulted in a loss of interest in big pharma, contributing to the increasing threat. Strategies to address the problem are starting to emerge. Novel antimicrobial compounds with novel modes of action are especially valued because they have a lower risk of cross-resistance. Up to now determining the mode of action has been very time and resource consuming and will be performed once drug candidates were already progressed in preclinical development. BioSAXS is emerging as a new method to test up to thousands of compounds to classify them into groups based on ultra-structural changes that correlate to their modes of action. First experiments in E. coli (gram-negative) have demonstrated that using conventional and experimental antimicrobials a classification of compounds according to their mode of action was possible. Results were backed up by transmission electron microscopy. Further work showed that also gram-positive bacteria (Staphylococcus aureus) can be used and the effects of novel antimicrobial peptides on both types of bacteria were studied. Preliminary experiments also show that BioSAXS can be used to classify antifungal drugs, demonstrated on Candida albicans. In summary, BioSAXS can accelerate and enrich the discovery of antimicrobial compounds from screening projects with a novel mode of action and hence de-risk the development of urgently needed antimicrobial drugs. Copyright © 2022 Rumancev, Rosenhahn and Hilpert.

The enormous magnitude of 2 billion tons of alloys produced per year demands a change in design philosophy to make materials environmentally, economically, and socially more sustainable. This disqualifies the use of critical elements that are rare or have questionable origin. Amongst the major alloy strengthening mechanisms, a high-dispersion of second-phase precipitates with sizes in the nanometre range is particularly effective for achieving ultra-high strength. Here, we propose an alternative segregation-based strategy for sustainable steels, free of critical elements, which are rendered ultrastrong by second-phase nano-precipitation. We increase the Mn-content in a supersaturated, metastable Fe-Mn solid solution to trigger compositional fluctuations and nano-segregation in the bulk. These fluctuations act as precursors for the nucleation of an unexpected α-Mn phase, which impedes dislocation motion, thus enabling precipitation strengthening. Our steel outperforms most common commercial alloys, yet it is free of critical elements, making it a new platform for sustainable alloy design. © 2022, The Author(s).

Deciphering the influence of nanocatalyst morphology on their catalytic activity in the oxygen evolution reaction (OER), the limiting reaction in water splitting process, is essential to develop highly active precious metal-free catalysts, yet poorly understood. The intrinsic OER activity of Co3O4 nanocubes and spheroids is probed at the single particle level to unravel the correlation between exposed facets, (001) vs. (111), and activity. Single cubes with predominant (001) facets show higher activity than multi-faceted spheroids. Density functional theory calculations of different terminations and reaction sites at (001) and (111) surfaces confirm the higher activity of the former, expressed in lower overpotentials. This is rationalized by a change in the active site from octahedral to tetrahedral Co and the potential-determining step from *OH to *O for the cases with lowest overpotentials at the (001) and (111) surfaces, respectively. This approach enables the identification of highly active facets to guide shape-selective syntheses of improved metal oxide nanocatalysts for water oxidation. © 2022 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH.

Physics-based crystal plasticity models rely on certain statistical assumptions about the collective behavior of dislocation populations on one slip system and their interactions with the dislocations on the other slip systems. One main advantage of using such physics-based constitutive dislocation models in crystal plasticity kinematic frameworks is their suitability for predicting the mechanical behavior of polycrystals over a wide range of deformation temperatures and strain rates with the same physics-based parameter set. In this study, the ability of a widely used temperature-dependent dislocation-density-based crystal plasticity formulation to reproduce experimental results, with a main focus on the yield stress behavior, is investigated. First, the material parameters are identified from experimental macroscopic stress–strain curves using a computationally efficient optimization methodology that uses a genetic algorithm along with the response surface methodology. For this purpose, a systematic set of compression tests on interstitial free (IF) steel samples is performed at various temperatures and strain rates. Next, the influence of the individual parameters on the observed behavior is analyzed. Based on mutual interactions between various parameters, the ability to find a unique parameter set is discussed. This allows identifying shortcomings of the constitutive law and sketch ideas for possible improvements. Particular attention is directed toward identifying possibly redundant material parameters, narrowing the acceptable range of material parameters based on physical criteria, and modifying the crystal plasticity formulation numerically for high-temperature use. © 2021 The Author(s)

The Al0.75CoCrFeNi alloy (Al16Co21Cr21Fe21Ni21 in at.%) presents a lamellar microstructure in the as-cast state consisting of a spinodally-decomposed B2/BCC matrix and Widmanstätten-type FCC plates. In this study, to retain the lamellar microstructure and improve tensile strength, Al16Co21Cr21-xFe21Ni21Mox alloys with x ≤ 10 at.% were investigated. For x = 2 at.%, the Widmanstätten microstructure changed into a vermicular one due to the stabilization of the BCC phase. With increasing the Mo/Cr ratio, the BCC phase transformed into topologically close-packed (TCP) phases, i.e., σ phase for x = 4 at.% and R phase for x ≥ 6 at.%, whose volume fractions increases with x. The as-cast alloys with x = 10 and 4 at.% presented the largest microhardness of ~600 HV0.5. The former had the highest volume fraction in TCP phases, which are hard and brittle while the latter presented the finest microstructure (enhanced phase boundary strengthening). While the alloys with x > 4 at.% were too brittle to machine tensile specimens, the others were tested between 20 and 700 °C. The ultimate tensile strength increased with increasing x up to ~1460 MPa for x = 4 at.% at 400 °C. At 700 °C, the strength of all alloys significantly decreased due to the softening of the B2 phase. Most of them had limited ductility and showed intergranular fracture except for x = 4 at.% presenting pronounced necking with ~38% ductility. The latter effect was attributed to the occurrence of interfacial sliding resulting in cavitation at grain boundaries and interphase boundaries. © 2021 The Author(s)

Kolbe already discovered in 1849 that electrochemical oxidative decarboxylation of carboxylic acids is feasible and leads to formation of alkanes and CO2, via alkyl radical intermediates. We now show for Pt electrodes that Kolbe electrolysis of acetic acid is favored in electrolytes with a pH similar to, or larger than the pKa of acetic acid, suppressing the formation of O2. However extended duration of electrolysis of acetate at basic pH results in loss of Faradaic efficiency to ethane, compensated by the formation of methanol. This change in selectivity is likely caused by the dissolution of CO2 near the electrode-electrolyte interface, resulting in enlarged concentration of bicarbonate/carbonate. On the positively polarized, and oxidized Pt surface, these anions seem to inhibit homocoupling of methyl radicals to ethane. These results demonstrate that reaction selectivity in acetic acid (acetate) oxidation using oxidized Pt electrodes is determined by the pH and the anionic composition of the electrolyte. © 2022 The Authors. ChemCatChem published by Wiley-VCH GmbH.

High-resolution three-dimensional crystal plasticity simulations are used to investigate deformation heterogeneity and microstructure evolution during cold rolling of interstitial free (IF-) steel. A Fast Fourier Transform (FFT)-based spectral solver is used to conduct crystal plasticity simulations using a dislocation-density-based crystal plasticity model. The in-grain texture evolution and misorientation spread are consistent with experimental results obtained using electron backscatter diffraction (EBSD) experiments. The crystal plasticity simulations show that two types of strain localization features develop during the large strain deformation of IF-steel. The first type forms band-like areas with large strain accumulation that appear as river patterns extending across the specimen. In addition to these river-like patterns, a second type of strain localization with rather sharp and highly localized in-grain shear bands is identified. These localized features are dependent on the crystallographic orientation of the grain and extend within a single grain. In addition to the strain localization, the evolution of in-grain orientation gradients, misorientation features, dislocation density, kernel average misorientation, and stress in major texture components are discussed. © 2022 The Author(s)

Protein aggregation is a hallmark of several severe neurodegenerative disorders such as Huntington's, Parkinson's, or Alzheimer's disease. Metal ions play a profound role in protein aggregation and altered metal-ion homeostasis is associated with disease progression. Here we utilize μ-X-ray fluorescence imaging in combination with rapid freezing to resolve the elemental distribution of phosphorus, sulfur, potassium, and zinc in huntingtin exon-1-mYFP expressing HeLa cells. Using quantitative XRF analysis, we find a threefold increase in zinc and a 10-fold enrichment of potassium that can be attributed to cellular stress response. While the averaged intracellular ion areal masses are significantly different in aggregate-containing cells, a local intracellular analysis shows no different ion content at the location of intracellular inclusion bodies. The results are compared to corresponding experiments on HeLa cells forming pseudoisocyanine chloride aggregates. As those show similar results, changes in ion concentrations are not exclusively linked to huntingtin exon-1 amyloid formation. © 2022 The Authors. Published by Wiley-VCH GmbH.

The design and application of electrocatalysts based on Earth-abundant transition-metal oxides for biomass valorization remain relatively underexplored. Here, we report a nanocasting route to synthesize mesoporous δ-MnO2 with a high surface area (198 m2/g), high pore volume, and narrow pore size distributions to address this issue. By taking structural advantages of mesoporous oxides, this mesoporous δ-MnO2 is employed as a highly efficient, selective, and robust anode for 5-hydroxymethylfurfural (HMF) electrochemical oxidation to 2,5-furandicarboxylic acid (FDCA) with a high yield (98%) and faradic efficiency (98%) under alkaline conditions. The electrocatalyst is also effective for the more difficult HMF electro-oxidation under acidic conditions, forming both FDCA and maleic acid as value-added products in a potential-dependent manner. Experimental results combined with theoretical calculations provide insights into the reaction kinetics and the reaction pathways of electrochemical HMF oxidation over this advanced electrocatalyst. This work thus showcases the rational design of non-noble metal electrodes for multiple applications, such as oxygen evolution, water electrolysis, and biomass upgrading with high energy efficiency. © 2022 The Authors. Published by American Chemical Society and Division of Chemical Education, Inc.

Yttria-stabilized zirconia (YSZ) is the state-of-the-art top coat material for thermal barrier coatings (TBCs) applied on highly loaded gas turbine parts. During operation at high temperatures, stresses are induced by the thermal expansion coefficient mismatch between the ceramic TBC and the metallic substrate. As a consequence cracks can grow, propagate and finally lead to a spallation of the top coat. Using atmospheric plasma spraying (APS), so-called self-healing MoSi2 particles can be incorporated into the YSZ matrix to mitigate the propagation of cracks leading to a lifetime gain and possibly higher temperature capability of the TBC. In the present work, the healing process is realized by the oxidation of the self-healing particles, which introduces a volume expansion by a formation of reaction products, which can seal the cracks. The self-healing particles were introduced within the first 150 μm of the YSZ coating matrix immediately on top of the bond coat. The degradation and lifetime of such systems were studied in furnace cycling and in burner rig tests, in which a temperature gradient through the sample was applied. The lifetime of the self-healing coatings was then compared to the lifetime of an YSZ coating without self-healing particles. In burner rig tests a clear lifetime extension of the self-healing TBCs was observed. The origin of this different behavior was investigated by microstructural analysis in scanning electron microscopy. A further insight into the failure mechanisms was gained by the analysis of a self-healing TBC cycled in a furnace cycling test only for about 55% of its expected lifetime. © 2022 Elsevier B.V.

The Atomic Cluster Expansion (Drautz (2019) [21]) provides a framework to systematically derive polynomial basis functions for approximating isometry and permutation invariant functions, particularly with an eye to modelling properties of atomistic systems. Our presentation extends the derivation by proposing a precomputation algorithm that yields immediate guarantees that a complete basis is obtained. We provide a fast recursive algorithm for efficient evaluation and illustrate its performance in numerical tests. Finally, we discuss generalisations and open challenges, particularly from a numerical stability perspective, around basis optimisation and parameter estimation, paving the way towards a comprehensive analysis of the convergence to a high-fidelity reference model. © 2022 Elsevier Inc.

Strengthening of metals by incorporating nano-scale coherent twin boundaries is one of the important breakthroughs of recent years in overcoming the strength-ductility trade-off. To this effect, also twin boundaries in nano-lamellar lightweight Ti-Al alloys promise a great potential, but their contribution to the deformation and fracture behavior needs to be better understood for designing optimal microstructures. To this end, we carry out linear elastic fracture mechanics informed large-scale atomistic simulations of fully lamellar microstructures consisting of the so-called ”true twin” boundaries in γ-TiAl. We find that nano-scale lamellae are not only effective in improving the fracture toughness and crack growth resistance, but also that the lamellar size controls the crack tip mechanisms. We identify a critical lamella thickness in the region between 1.64 and 3.04 nm, above which the crack tip events are primarily dislocation-based plasticity and the critical fracture initiation toughness exhibits an increasing trend with decreasing lamella size. Below the critical thickness, a decline in fracture toughness is observed and the crack tip propagation mechanisms are quasi-brittle in nature, i.e. the cleavage of atomic bonds at the crack tip is accompanied by plasticity events, such as twin-boundary migration and dislocation nucleation. A layer-wise analysis of the unstable stacking fault energy, the energy barrier for dislocation nucleation, that the critical thickness is of a similar value as the distance from the twin boundary at which bulk properties are restored. © 2022

We investigate the effect of low temperature (cryogenic) thermal cycling on dynamics of a generic model glass via molecular dynamics simulations. By calculating mean squared displacements after a varying number of cycles, a pronounced enhancement of dynamics is observed. This rejuvenation effect is visible already after the first cycle and accumulates upon further cycling in an intermittent way. Our data reveal an overall deformation (buckling of the slab-shaped system) modulated by a heterogeneous deformation field due to deep cryogenic thermal cycling. It is shown via strain maps that deformation localizes in the form of shear-bands, which gradually fill the entire sample in a random and intermittent manner, very much similar to the accumulation effect observed in dynamics. While spatial organization of local strain may be connected to the specific geometry, we argue that the heterogeneity of the structure is the main cause behind rejuvenation effects observed in the present study. © 2022 Author(s).

During reactive layer growth in binary diffusion couples new phases can nucleate and grow. In the present work we perform in- and ex-situ interdiffusion studies in the system Ni-Al using X-ray diffraction (XRD) and analytical transmission electron microscopy (TEM). We investigate the reaction between 270 °C and 500 °C. We show that in the early stages of the solid-state reaction a small polycrystalline aluminide layer forms, while preferential grain growth follows in the later stage. In the reaction layer we detect the presence of Al3Ni by XRD and electron diffraction. Local chemical analysis by EDX in the TEM suggests that a second aluminide phase forms simultaneously. An in-situ TEM study at 380 °C shows layer growth of about 0.042 nm/s with a linear time dependence. We interpret this rate law on the basis of an interface-controlled reaction and discuss our results in the light of what is known about layer growth in thin film diffusion couples (presence/absence of predicted phases, linear/parabolic rate laws) and in view of results from the Ni-Al system published in the literature. Areas in need of further work are identified. © 2022 The Authors

We investigate the effect of low temperature (cryogenic) thermal cycling on a generic model glass and observe signature of rejuvenation in terms of per-particle potential energy distributions. Most importantly, these distributions become broader and its average values successively increase when applying consecutive thermal cycles. We show that linear dimension plays a key role for these effects to become visible, since we do only observe a weak effect for a cubic system of roughly one hundred particle diameter but observe strong changes for a rule-type geometry with the longest length being two thousand particle diameters. A consistent interpretation of this new finding is provided in terms of a competition between relaxation processes, which are inherent to glassy systems, and excitation due to thermal treatment. In line with our previous report (Bruns et al., PRR 3, 013234 (2021)), it is shown that, depending on the parameters of thermal cycling, rejuvenation can be either too weak to be detected or strong enough for a clear observation. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

The quartz crystal microbalance (QCM) measurement technique is utilized in a broad variety of scientific fields and applications, where surface and interfacial processes are relevant. However, the costs of purchasing QCMs is typically high, which has limited its employment in education as well as by scientists in developing countries. In this article, we present an open-source QCM, built on the OpenQCM project, and using an impedance-based measurement technique (QCM-I), which can be built for <200 euro. Our QCM allows for simultaneous monitoring of the frequency change and dissipation, such that both soft and rigid materials can be characterized. In addition, our QCM measurements can be combined with simultaneous electrochemical measurement techniques (EQCM-I). We demonstrate the validity of our system by characterizing the electrodeposition of a rigid metallic film (Cu) and by the electropolymerization of aniline. Finally, we discuss potential improvements to our system. © 2022 The Author(s)

Electrochemical analysis relies on precise measurement of electrical signals, yet the distortions caused by potentiostat circuitry and filtering are rarely addressed. Elucidation of these effects is essential for gaining insights behind sensitive low-current and short-duration electrochemical signals, e.g., in single-entity electrochemistry. We present a simulation approach utilizing the Electrical Simulation Program with Integrated Circuit Emphasis (SPICE), which is extensively used in electronic circuit simulations. As a proof-of-concept, we develop a universal electrical circuit model for single nanoparticle impact experiments, incorporating potentiostat and electronic filter circuitry. Considering these alterations, the experimentally observed transients of silver nanoparticle oxidation were consistently shorter and differently shaped than those predicted by established models. This reveals the existence of additional processes, e.g., migration, partial or asymmetric oxidation. These results highlight the SPICE approach's ability to provide valuable insights into processes occurring during single-entity electrochemistry, which can be applied to various electrochemical experiments, where signal distortions are inevitable. © 2022 American Chemical Society. All rights reserved.

The inline equation for the Ginzburg number, Gi, in the right column of page 9 of the paper had a typo, displaying a wrong power of θ0. (Formula Presented). This typo did not affect the value of Gi for CaKFe 4 As 4 evaluated in the paper or any discussions and conclusions. © 2022 American Physical Society. All rights reserved.

Nanocatalyst optimisation through electrochemical dealloying has been employed as a successful strategy to increase catalytic activity, while reducing the need for precious metals. We present here a new pathway to influence the electrochemical dealloying, through external homogeneous magnetic fields. A homogeneous magnetic field with a flux density of 450 mT in two orientations, parallel or perpendicular to the current direction, was used during electrochemical dealloying using cyclic voltammetry of AgAu nanoparticles. We found increased porosity for low dealloying cycle numbers and improved catalytic properties after longer cycling, compared to nanoparticles dealloyed in the absence of magnetic fields. These findings demonstrate that magnetic fields applied during electrochemical dealloying have currently untapped potential that can be used to influence material properties in a new way and give researchers another powerful tool for material design. © 2022

EuMnSb2 is a candidate topological material which can be tuned towards a Weyl semimetal, but there are differing reports for its antiferromagnetic (AFM) phases. The coupling of bands dominated by pure Sb layers hosting topological fermions to Mn and Eu magnetic states provides a potential path to tune the topological properties. Here we present single-crystal neutron diffraction, magnetization, and heat-capacity data as well as polycrystalline Eu151 Mössbauer data which show that three AFM phases exist as a function of temperature, and we present a detailed analysis of the magnetic structure in each phase. The Mn magnetic sublattice orders into a C-type AFM structure below TNMn=323(1)K with the ordered Mn magnetic moment μMn lying perpendicular to the layers. AFM ordering of the Eu sublattice occurs below TNEu1=23(1)K with the ordered Eu magnetic moment μEu canted away from the layer normal and μMn retaining its higher temperature order. μEu is ferromagnetically aligned within each Eu layer but exhibits a complicated AFM layer stacking. Both of these higher-temperature phases are described by magnetic space group (MSG) Pn′m′a′ with the chemical and magnetic unit cells having the same dimensions. Cooling below TNEu2=9(1)K reveals a third AFM phase where μMn remains unchanged but μEu develops an additional substantial in-plane canting. This phase has MSG P1121a′. We also find some evidence of short-range magnetic correlations associated with the Eu between 12K T 30K. Using the determined magnetic structures, we postulate the signs of nearest-neighbor intralayer and interlayer exchange constants and the magnetic anisotropy within a general Heisenberg model. We then discuss implications of the various AFM states in EuMnSb2 and their potential for tuning topological properties. © 2022 American Physical Society. All rights reserved.

La2Ni7 is an intermetallic compound that is thought to have itinerant magnetism with small moment (∼0.15μB/Ni) ordering below 65 K. A recent study of single crystal samples by Ribeiro et al. [Phys. Rev. B 105, 014412 (2022)2469-995010.1103/PhysRevB.105.014412] determined detailed anisotropic H-T phase diagrams and revealed three zero-field magnetic phase transitions at T1∼61.0 K, T2∼56.5 K, and T3∼42 K. In that study only the highest temperature phase is shown to have a clear ferromagnetic component. Here we present a single crystal neutron diffraction study determining the propagation vector and magnetic moment direction of the three magnetically ordered phases, two incommensurate and one commensurate, as a function of temperature. The higher temperature phases have similar, incommensurate propagation vectors, but with different ordered moment directions. At lower temperatures, the magnetic order becomes commensurate with magnetic moments along the c direction as part of a first-order magnetic phase transition. We find that the low-temperature commensurate magnetic order is consistent with a proposal from earlier DFT calculations. © 2022 American Physical Society.

In this work, the plasma generated by the cascaded SinplexProTM plasma spray gun was studied by means of numerical simulation. Special attention is given to the laminarity of the plasma flow. The simulation part is divided into two parts: arcing simulation inside the spray gun and plasma jet simulation outside the spray gun. A laminar as well as a turbulent model is used in each case. The results show that, under the investigated conditions, the internal flow of the plasma torch can be considered as laminar with low turbulence and can, hence, be regarded as quasi-laminar flow. If carrier gas is injected into the plasma jet, the ideal laminar plasma jet is often greatly affected. However, the turbulent plasma jet with low turbulence intensity generated by the cascaded SinplexProTM plasma spray gun is less affected and can remain stable, which is beneficial to the plasma-spraying process. © 2022 by the authors.

The reduction of iron ore with carbon-carriers is one of the largest sources of greenhouse gas emissions in the industry, motivating global activities to replace the coke-based blast furnace reduction by hydrogen-based direct reduction (HyDR). Iron oxide reduction with hydrogen has been widely investigated both experimentally and theoretically. The HyDR process includes multiple types of chemical reactions, solid state and defect-mediated diffusion (of oxygen and hydrogen species), several phase transformations, as well as massive volume shrinkage and mechanical stress buildup. However, studies focusing on the chemo-mechanical interplay during the reduction reaction influenced by microstructure are sparse. In this work, a chemo-mechanically coupled phase-field (PF) model has been developed to explore the interplay between phase transformation, chemical reaction, species diffusion, large elasto-plastic deformation and microstructure evolution. Energetic constitutive relations of the model are based on the system free energy which is calibrated with the help of a thermodynamic database. The model has been first applied to the classical core-shell (wüstite-iron) structure. Simulations show that the phase transformation from wüstite to α-iron can result in high stresses and rapidly decelerating reaction kinetics. Mechanical stresses create elastic energy in the system, an effect which can negatively influence the phase transformations, thus causing slow reaction kinetics and low metallization. However, if the elastic stress becomes comparatively high, it can shift the shape of the free energy from a double-well to a single-well case, speed up the transformation and result in a higher reduction degree compared to the low-stress double-well case. The model has been applied to simulate an experimentally characterized iron oxide specimen with its complex microstructure. The observed microstructure evolution during reduction is well predicted by the model. The simulation results also show that isolated pores in the microstructure are filled with water vapor during reduction, which can influence the local reaction atmosphere and dynamics. © 2022

Iron and cobalt-based oxides crystallizing in the spinel structure are efficient and affordable catalysts for the oxidation of organics, yet, the detailed understanding of their surface structure and reactivity is limited. To fill this gap, we have investigated the (001) surfaces of cobalt ferrite, CoFe2O4, with the A- and B-layer terminations using density functional theory (DFT/PBE0) and an embedded cluster model. We have considered the five-fold coordinated Co2+/3+ (Oh), two-fold coordinated Fe2+ (Td), and an oxygen vacancy, as active sites for the adsorption of water and short-chain alcohols: methanol, ethanol, and 2-propanol, in the low coverage regime. The adsorbates dissociate upon adsorption on the Fe sites whereas the adsorption is mainly molecular on Co. At oxygen vacancies, the adsorbates always dissociate, fill the vacancy and form (partially) hydroxylated surfaces. The computed vibrational spectra for the most stable configurations are compared with results from diffuse reflectance infrared Fourier transform spectroscopy. © 2022 The Royal Society of Chemistry.

The charge state of dielectric surfaces in aqueous environments is of fundamental and technological importance. Here, we study the influence of dissolved molecular CO2on the charging of three chemically different surfaces (SiO2, Polystyrene, Perfluorooctadecyltrichlorosilane). We determine their charge state from electrokinetic experiments. We compare an ideal, CO2-free reference system to a system equilibrated against ambient CO2conditions. In the reference system, the salt-dependent decrease of the magnitudes of ζ-potentials follows the expectations for a constant charge scenario. In the presence of CO2, the starting potential is lower by some 50%. The following salt-dependent decrease is weakened for SiO2and inverted for the organic surfaces. We show that screening and pH-driven charge regulation alone cannot explain the observed effects. As an additional cause, we tentatively suggest dielectric regulation of surface charges due to a diffusively adsorbed thin layer of molecular CO2. The formation of such a dynamic layer, even at the hydrophilic and partially ionized silica surfaces, is supported by a minimal theoretical model and results from molecular simulations. © 2022 American Chemical Society. All rights reserved.

Spokes are long wavelength oscillations observed in the magnetized region of direct current magnetron sputtering (DCMS), high power impulse magnetron sputtering (HiPIMS), as well as other E → × B → discharges. Spokes rotate in front of the cathode with velocities between about 2 km s−1 and 15 km s−1, making it difficult to perform quantitative measurements. This is overcome by synchronizing Langmuir probe measurements to the movement of spokes in DCMS to obtain the probe current-voltage (I-V) characteristic without averaging out the spoke influence. The I-V curves are then evaluated using magnetized probe theory, revealing the strong plasma parameter modulations, caused by the spokes. The plasma density was found to oscillate between 2.5 × 1016 m−3 and 1.7 × 1017 m−3, which corresponds to a modulation strength of more than 70% or an almost seven times increase of density. In good agreement with previous work, a plasma potential minimum of −55 V is found ahead of the spoke followed by a sudden increase to about 2 V inside the spoke. The electron temperature was found to oscillate between 3 eV and 7 eV. On top of that oscillation, electrons experience a sudden energy increase as they move inside the spoke, crossing the potential jump at the leading edge for the spoke. On basis of these observations a model is presented to explain spokes in DCMS. These results are then compared to HiPIMS spokes under otherwise similar conditions. The plasma parameter modulation found for HiPIMS is much weaker than for DCMS, which is explained by the higher collision frequency for electrons in HiPIMS plasmas. © 2022 The Author(s). Published by IOP Publishing Ltd.

Artificial neural networks are used to solve different tasks of daily life, engineering and medicine. In this work, we investigate its suitability for the examination of simulation results of cancellous bone with the aim to evaluate whether the bone is affected by osteoporosis. This bone disease is characterized by a reduction of the cortical bone phase, one of the two main components of the bone. The neural network predicts the simulated volume fraction in different parts of a cylinder, which models the bone. As a basis for its calculations, the neural network gets the information about the magnetic field inside the cylinder from finite element simulations. Examinations show that it is possible to train neural networks on solving that task with very high accuracies. © 2022 The Authors. ZAMM - Journal of Applied Mathematics and Mechanics published by Wiley-VCH GmbH.

Water diffusion across the surfaces of materials is of importance to disparate processes such as water purification, ice formation, and more. Despite reports of rapid water diffusion on surfaces the molecular level, details of such processes remain unclear. Here, with scanning tunneling microscopy, we observe structural rearrangements and diffusion of water trimers at unexpectedly low temperatures (<10 K) on a copper surface, temperatures at which water monomers or other clusters do not diffuse. Density functional theory calculations reveal a facile trimer diffusion process involving transformations between elongated and almost cyclic conformers in an inchworm-like manner. These subtle intermolecular reorientations maintain an optimal balance of hydrogen-bonding and water–surface interactions throughout the process. This work shows that the diffusion of hydrogen-bonded clusters can occur at exceedingly low temperatures without the need for hydrogen bond breakage or exchange; findings that will influence Ostwald ripening of ice nanoclusters and hydrogen bonded clusters in general. © 2021 American Chemical Society

The demand for safety and reliability in pipelines has been increasing steadily. Dual-phase steels, especially with a bainite matrix and a well-dispersed martensite–austenite constituent (MA), provide ingredients necessary for the improvement of the yield ratio and toughness. To design alloy elements and ensure that dual-phase steels have the required mechanical properties, an understanding of the governing microscopic deformation mechanisms is essential. For this purpose, multi-constitutive crystal plasticity simulation coupled with local strain/stress partitioning, ductile damage and transformation-induced plasticity evolution was employed. Microstructural cell responses were captured by fast Fourier transform crystal plasticity analysis. Representative microstructural patches with the same high spatial resolution as those obtained by electron backscatter diffraction (EBSD) tomography provide new insights into the deformation mechanism in dual-phase microstructures, especially regarding the effects of the matrix and secondary phase distribution on the strain, ductile damage and transformation localization behavior. © 2022 Japan Society for Technology of Plasticity. All rights reserved.

Herein we report the mechanochemical Friedel-Crafts alkylation of 1,3,5-triphenylbenzene (TPB) with two organochloride cross-linking agents, dichloromethane (DCM) and chloroform (CHCl3), respectively. During a thorough milling parameter evaluation, the DCM-linked polymers were found to be flexible and extremely sensitive toward parameter changes, which even enables the synthesis of a polymer with a SSABET of 1670 m2/g, on par with the solution-based reference. Contrary, CHCl3-linked polymers are exhibiting a rigid structure, with a high porosity that is widely unaffected by parameter changes. As a result, a polymer with a SSABET of 1280 m2/g could be generated in as little as 30 minutes, outperforming the reported literature analogue in terms of synthesis time and SSABET. To underline the environmental benefits of our fast and solvent-free synthesis approach, the green metrics are discussed, revealing an enhancement of the mass intensity, mass productivity and the E-factor, as well as of synthesis time and the work-up in comparison to the classical synthesis. Therefore, the mechanochemical polymerization is presented as a versatile tool, enabling the generation of highly porous polymers within short reaction times, with a minimal use of chlorinated cross-linker and with the possibility of a post polymerization modification. © 2021 The Authors. Journal of Polymer Science published by Wiley Periodicals LLC.

Mechanochemistry - the utilization of mechanical forces to induce chemical reactions - is a rarely considered tool for polymer synthesis. It offers numerous advantages such as reduced solvent consumption, accessibility of novel structures, and the avoidance of problems posed by low monomer solubility and fast precipitation. Consequently, the development of new high-performance materials based on mechanochemically synthesised polymers has drawn much interest, particularly from the perspective of green chemistry. This review covers the constructive mechanochemical synthesis of polymers, starting from early examples and progressing to the current state of the art while emphasising linear and porous polymers as well as post-polymerisation modifications. © 2022 The Royal Society of Chemistry

Titanium alloys can suffer from halide-associated stress corrosion cracking at elevated temperatures e.g., in jet engines, where chlorides and Ti-oxide promote the cracking of water vapour in the gas stream, depositing embrittling species at the crack tip. Here we report, using isotopically-labelled experiments, that crack tips in an industrial Ti-6Al-2Sn-4Zr-6Mo alloy are strongly enriched (>5 at.%) in oxygen from the water vapour, far greater than the amounts (0.25 at.%) required to embrittle the material. Surprisingly, relatively little hydrogen (deuterium) is measured, despite careful preparation and analysis. Therefore, we suggest that a combined effect of O and H leads to cracking, with O playing a vital role, since it is well-known to cause embrittlement of the alloy. In contrast it appears that in α + β Ti alloys, it may be that H may drain away into the bulk owing to its high solubility in β-Ti, rather than being retained in the stress field of the crack tip. Therefore, whilst hydrides may form on the fracture surface, hydrogen ingress might not be the only plausible mechanism of embrittlement of the underlying matrix. This possibility challenges decades of understanding of stress-corrosion cracking as being related solely to the hydrogen enhanced localised plasticity (HELP) mechanism, which explains why H-doped Ti alloys are embrittled. This would change the perspective on stress corrosion embrittlement away from a focus purely on hydrogen to also consider the ingress of O originating from the water vapour, insights critical for designing corrosion resistant materials. © 2022 Acta Materialia Inc.

The number of active sites and their intrinsic activity are key factors in designing high-performance catalysts for the oxygen evolution reaction (OER). The synthesis, properties, and in-depth characterization of a homogeneous CoNiFeCu catalyst are reported, demonstrating that multimetal synergistic effects improve the OER kinetics and the intrinsic activity. In situ carbon corrosion and Cu leaching during the OER lead to an enhanced electrochemically active surface area, providing favorable conditions for improved electronic interaction between the constituent metals. After activation, the catalyst exhibits excellent activity with a low overpotential of 291.5 ± 0.5 mV at 10 mA cm−2 and a Tafel slope of 43.9 mV dec−1. It shows superior stability compared to RuO2 in 1 m KOH, which is even preserved for 120 h at 500 mA cm−2 in 7 m KOH at 50 °C. Single particles of this CoNiFeCu after their placement on nanoelectrodes combined with identical location transmission electron microscopy before and after applying cyclic voltammetry are investigated. The improved catalytic performance is due to surface carbon corrosion and Cu leaching. The proposed catalyst design strategy combined with the unique single-nanoparticle technique contributes to the development and characterization of high-performance catalysts for electrochemical energy conversion. © 2022 The Authors. Advanced Materials published by Wiley-VCH GmbH

We demonstrate by Raman Spectroscopy that simultaneous reduction of NO3- and CO2 on Cu surfaces leads to formation of Cu-C[tbnd]N–like species, showing Raman bands at 2080 and 2150 cm−1 when associated with reduced or oxidized Cu surfaces, respectively. Furthermore Cu-C[tbnd]N–like species are soluble, explaining vast restructuring of the Cu surface observed after co-electrolysis of CO2 and nitrate. Oxidation of deposited Cu-C[tbnd]N–like species results in the formation of NO. Cu-C[tbnd]N–like species do not form in electrolytes containing i) NH4+ and CO2, or ii) NO3- and HCOO-, suggesting these likely originate from Cu-CO, the commonly accepted intermediate in electrochemical reduction of CO2, and Cu-NHx species, previously identified in the literature as intermediate towards C-N bond formation. The implications of the previously unresolved formation of Cu-C[tbnd]N–like species for the development of electrodes and processes for electrochemical formation of carbon-nitrogen bonds, including urea, amines or amides, are briefly discussed. © 2022 The Authors

The circular lining in mechanized tunnelling consists of concrete segments, which are exposed to different loading cases during tunnel construction. One of the most critical loading condition is the thrust jack force, which is induced to the lining segments by the Tunnel Boring Machine (TBM) during construction. Experimental campaigns showed that steel fibre reinforced concrete is suitable for bearing such loads and could replace conventional reinforcement schemes. In this contribution, a numerical model is presented, which allows to directly track the influence of important design parameters such as fibre type, fibre orientation, fibre content and concrete strength on the structural response of steel-fibre reinforced segments. For this purpose, submodels on the single fibre level are combined into a crack bridging model considering the fibre orientation and the fibre content. The submodels are integrated into a finite element model to perform numerical structural analyses. Two validation examples demonstrate that the modelling approach is capable to predict the failure loads as well as the crack development of fibre reinforced specimens subjected to localized loads. Finally, an optimization procedure is carried out to determine a robust and cost-effective design of a fibre reinforced segmental linings. A hybrid reinforcement scheme consisting of two layers of fibre reinforced concrete is employed in order to provide an improved material utilization. The thickness of the segment and the fibre content are optimized taking uncertainties of the material parameters and construction tolerances as uncertain a priori parameters into account. A sufficient load bearing capacity and serviceability performance under all possible conditions is ensured by the consideration of accepted failure probabilities as constraints in the optimization task. © 2022 Elsevier Ltd

The measurement of diffusivity within porous solids is vital for the characterization of materials, especially in heterogeneous catalysis and separation processes. Numerous methods have been developed to measure gas-phase diffusivities within materials. However, establishing correlations between the diffusivities and the properties of a material is challenging. Herein, we report a method for obtaining trends in gas-phase diffusivity of N2 at 77 K within three different sets of mesoporous materials, disordered, ordered silica, and carbons-based materials. Synthesis procedures are reproducible and controlled precisely to achieve monodisperse particle size and defined pore size distributions. A standard physisorption device, Micromeritics 3Flex, is used to obtain the required transient data. These two aspects offer a suitable database of materials to identify trends and reduce the challenges associated with obtaining experimental data. A simplified model is fitted over the transient data with MATLAB to obtain empirical diffusivities used for trend analysis. The trends are based on a constant Dτ, an ensemble value representing various diffusion processes occurring during a transient uptake process. The analysis identifies several correlations between the diffusivity and properties of materials, such as type of pore structure, pore size, and the chemical nature of the material. Based on the principles reported, this study can be extended to other adsorptive molecules or different temperatures. The possibility of using standard sorption instrumentation will allow a broader user community to employ the reported methodology. © 2021 Elsevier Inc.

Reduction of nitric oxide was investigated using Cu electrodes in acid and neutral pH conditions. Analysis of Cu discs in stagnant electrolyte by Electrochemical Mass Spectrometry (EC-MS), revealed the favorable formation of ammonia (and hydrogen) in acidic electrolyte, while N2O and N2 are formed in significant quantities at neutral conditions. Additional performance evaluation of Cu electrodes in hollow fiber geometry, was performed using 10 vol % NO in Ar supplied through the porous electrode structure and off-line determination of ammonia by 1H NMR spectroscopy. The pH dependent performance of the Cu hollow fiber is in agreement with EC-MS data at low gas flow rates, showing the highest ammonia selectivity in acidic conditions. However, at relatively high gas flow rates, almost 90 % faradaic efficiency and a NH3 production rate of 400 μmol h−2 cm−2 were obtained in neutral electrolyte at −0.6 V vs RHE, likely due to enhanced availability of NO at the electrode surface, suppressing the hydrogen evolution reaction. This approach shows conversion of waste NO gas to valuable green fertilizer components is possible. © 2021 The Authors. ChemElectroChem published by Wiley-VCH GmbH

Graphene and other single-layer structures are pursued as high-flux separation membranes, although imparting porosity endangers their crystalline integrity. In contrast, bilayer silica composed of corner-sharing (SiO4) units is foreseen to be permeable for small molecules due to its intrinsic lattice openings. This study sheds light on the mass transport properties of freestanding 2D SiO2 upon using atomic layer deposition (ALD) to grow large-area films on Au/mica substrates followed by transfer onto Si3N4 windows. Permeation experiments with gaseous and vaporous substances reveal the suspended material to be porous, but the membrane selectivity appears to diverge from the size exclusion principle. Whereas the passage of inert gas molecules is hindered with a permeance below 10-7 mol·s-1·m-2·Pa-1, condensable species like water are found to cross vitreous bilayer silica a thousand times faster in accordance with their superficial affinity. This work paves the way for bilayer oxides to be addressed as inherent 2D membranes. © 2022 American Chemical Society.

Inefficient fertilizer use in agriculture causes nitrate runoff, polluting rivers and streams. This pollution can be mitigated by partially converting nitrate into ammonia - rebalancing the composition to ammonium nitrate, and allowing recycling of fertilizer. Here, we present efficient electrochemical conversion of nitrate (50 mM) to ammonia in acidic electrolyte using tubular porous Ti electrodes. A high faradaic efficiency (FE) of 58% and partial current density to ammonia of −33 mA cm−2 at −1 V vs. RHE were achieved in the absence of inert gas purge. Additionally, we reveal that hydroxylamine is formed, as well as NO and N2O by spontaneous decomposition of nitrite, as has been determined by EC-MS analysis. The effective increase in local mass transport by introducing a flow of inert gas exiting the wall of the hollow fiber electrode results in an unprecedently high partial current density to ammonia of ∼−75 mA cm−2, while maintaining a faradaic efficiency to ammonia of up to 45%. This concept facilitates nitrate conversion at high FE even at low concentrations, and holds promise for development to practical scale if electrochemical potential and exiting gas flow rate are well controlled. © 2022 The Royal Society of Chemistry.

In this contribution, a Finite Element modelling scheme for steel-fibre reinforced concrete (SFRC) is proposed with which the post-cracking response of fibre reinforced structural members can be predicted. In contrast to the common guidelines, the post-cracking response of SFRC is derived from the actual fibre properties instead of indirectly from bending tests. The numerical model is designed to directly track the influence of design parameters such as fibre type, fibre orientation, fibre content and concrete strength on the structural response. For this purpose, sub models on the single fibre level are combined into a crack bridging model, considering the fibre orientation and the fibre content, and are integrated into a finite element model for the purpose of numerical structural analysis. The predictive capability of the proposed numerical multi-level model for SFRC is systematically validated by means of test series performed on the fibre, crack and the structural level. The experimental study comprises pull-out tests of Dramix 3D fibres, uniaxial tension tests involving different fibre contents and fibre types as well as three-point bending tests on notched beams with 23 and 57 kg/m3 Dramix 3D fibres. Furthermore, the results are compared to the modelling approach presented in the fib model code 2010 and an inverse analysis approach. © 2022, RILEM.

Machine learning methods have become increasingly central in the development of a large variety of versatile tools for molecular simulations, many of which have the potential to advance significantly the fields of computational chemistry and physics. In this chapter, we present a framework for combining machine learning for local structure classification with the definition of a global classifier space as a basis for enhanced sampling of structural transformations in condensed phase systems. The transformation is represented by a path in classifier space, and the associated path collective variable is used to drive the process derived from changes in local structural motifs. Enhanced sampling along this type of path collective variable yields insight into the physical mechanism as well as corresponding free energy barriers of the transition. The idea is generally applicable, and the approach, as outlined here, can be adapted to a wide range of systems. © The Royal Society of Chemistry 2022.

The risk assessment of tunneling-induced damage in buildings is a challenging task in geotechnical and structural engineering. It is important to consider the soil-structure interaction during the tunnel construction process. In this paper, finite-element (FE) simulation models of mechanized tunneling processes are combined with FE models of buildings to predict tunneling-induced damage. The soil-structure interaction is taken into account by considering the building stiffness in the tunneling process simulation model and by applying the computed foundation settlements as boundary conditions of the building model. The building damage risk is assessed by means of strains in the structural members and a corresponding category of damage is determined. Uncertainties of the geotechnical parameters and the structural parameters are quantified as random variables and intervals in the framework of polymorphic uncertainty modeling. For real-time predictions, the FE simulation models are approximated by artificial neural networks. This makes it possible to predict the structural damage risk according to scenarios of the operational tunneling process parameters in order to assist machine drivers during tunnel construction. © 2021 American Society of Civil Engineers.

One of the key factors, which hampers the application of metallic glasses as structural components, is the localization of deformation in narrow bands of a few tens up to one hundred nanometers thickness, the so-called shear bands. Processes, which occur inside shear bands are of central importance for the question whether a catastrophic failure of the material is unavoidable or can be circumvented or, at least, delayed. Via molecular dynamics simulations, this study addresses one of these processes, namely the local temperature rise due to viscous heat generation. The major contribution to energy dissipation is traced back to the plastic work performed by shear stress during steady deformation. Zones of largest strain contribute the most to this process and coincide with high-temperature domains (hottest spots) inside the sample. Magnitude of temperature rise can reach a few percent of the sample’s glass transition temperature. Consequences of these observations are discussed in the context of the current research in the field. © 2022 by the authors.

The current Coronavirus Disease 19 (COVID-19) pandemic has exemplified the need for simple and efficient prevention strategies that can be rapidly implemented to mitigate infection risks. Various surfaces have a long history of antimicrobial properties and are well described for the prevention of bacterial infections. However, their effect on many viruses has not been studied in depth. In the context of COVID-19, several surfaces, including copper (Cu) and silver (Ag) coatings have been described as efficient antiviral measures that can easily be implemented to slow viral transmission. In this study, we detected antiviral properties against Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) on surfaces, which were coated with Cu by magnetron sputtering as thin Cu films or as Cu/Ag ultrathin bimetallic nanopatches. However, no effect of Ag on viral titers was observed, in clear contrast to its well-known antibacterial properties. Further enhancement of Ag ion release kinetics based on an electrochemical sacrificial anode mechanism did not increase antiviral activity. These results clearly demonstrate that Cu and Ag thin film systems display significant differences in antiviral and antibacterial properties which need to be considered upon implementation. © 2022, The Author(s).

Recent demonstrations using electron spins stored in quantum dot array as qubits are promising for developing a scalable quantum computing platform. An ongoing effort is, therefore, aiming at the precise control of the quantum dot parameters in larger and larger arrays which represents a complex challenge. Partitioning of the system with the help of the inter-dot tunnel barriers can lead to a simplification for tuning and offers a protection against unwanted charge displacement. In a triple quantum dot system, we demonstrate a nanosecond control of the inter-dot tunnel rate permitting to reach the two extreme regimes, large GHz tunnel coupling, and sub-Hz isolation between adjacent dots. We use this development to isolate a subpart of the array in a metastable configuration while performing charge displacement and readout in the rest of the system. The degree of control over tunnel coupling achieved in a unit cell should motivate future protocol development for tuning, manipulation, and readout including this capability. © 2022 Author(s).

The influence of a deformable mirror on spatial light modulation in ultrafast lasers processing is demonstrated. The deformable mirror was integrated into an optical setup which contains an additional lens for generating a nearly linear focus shift in the focal plane behind the f-theta lens. The deformation of the mirror surface can be described by the Zernike terms Defocus, Astigmatism, and a combination of both, resulting in a cylindric lens behavior. The influence of the mirror surface deformation in this optical setup on the intensity distribution in the focal plane was simulated. From the simulation results, the caustic in the focal plane was calculated. The simulation results were compared to experiments using a picosecond laser with a maximum pulse energy of about 60 µJ. We demonstrate that the initial astigmatism of the raw beam can be reduced using the deformable mirror. A linear focus shift (R2=98.7%) and the generation of elliptical/ line intensity distributions are shown. Line intensity distribution was used to demonstrate slit drilling application in thin metal foils. © 2021

Nickel-based superalloys have a wide range of applications in high temperature and stress domains due to their unique mechanical properties. Under mechanical loading at high temperatures, rafting occurs, which reduces the service life of these materials. Rafting is heavily affected by the loading conditions associated with plastic strain; therefore, understanding plastic strain evolution can help understand these material's service life. This research classifies nickel-based superalloys with respect to creep strain with deep learning techniques, a technique that eliminates the need for manual feature extraction of complex microstructures. Phase-field simulation data that displayed similar results to experiments were used to build a model with pre-trained neural networks with several convolutional neural network architectures and hyper-parameters. The optimized hyper-parameters were transferred to scanning electron microscopy images of nickel-based superalloys to build a new model. This fine-tuning process helped mitigate the effect of a small experimental dataset. The built models achieved a classification accuracy of 97.74% on phase-field data and 100% accuracy on experimental data after fine-tuning. © 2022 The Author(s). Published by IOP Publishing Ltd.

The superior properties of high-entropy multi-functional materials are strongly connected with their atomic heterogeneity through many different local atomic interactions. The detailed element-specific studies on a local scale can provide insight into the primary arrangements of atoms in multicomponent systems and benefit to unravel the role of individual components in certain macroscopic properties of complex compounds. Herein, multi-edge X-ray absorption spectroscopy combined with reverse Monte Carlo simulations was used to explore a homogeneity of the local crystallographic ordering and specific structure relaxations of each constituent in the equiatomic single-phase face-centered cubic CrMnFeCoNi high-entropy alloy at room temperature. Within the considered fitting approach, all five elements of the alloy were found to be distributed at the nodes of the fcc lattice without any signatures of the additional phases at the atomic scale and exhibit very close statistically averaged interatomic distances (2.54 – 2.55 Å) with their nearest-neighbors. Enlarged structural displacements were found solely for Cr atoms. The macroscopic magnetic properties probed by conventional magnetometry demonstrate no opening of the hysteresis loops at 5 K and illustrate a complex character of the long-range magnetic order after field-assisted cooling in± 5 T. The observed magnetic behavior is assigned to effects related to structural relaxations of Cr. Besides, the advantages and limitations of the reverse Monte Carlo approach to studies of multicomponent systems like high-entropy alloys are highlighted. © 2022 Elsevier B.V.

We study the effect of laser shock peening (LSP) without protective coating on the surface mechanical property of NiTi alloy. The Vickers microhardness and wear resistance are measured to determine the mechanical property of NiTi samples treated with different LSP parameters (3 J with 10 ns and 5 J with 20 ns). From the electron backscatter diffraction (EBSD) analysis, it can be found that the laser shock peening does not induce obvious grain refinement in the surface region of NiTi alloy. Both compressive and tensile residual stress in the top layer are determined using the hole drilling method. The results show that the LSP treatment without a protective coating increases the roughness and enhances the surface mechanical properties of NiTi alloy. © 2021 Elsevier B.V.

Catalysis is involved in around 85 % of manufacturing industry and contributes an estimated 25 % to the global domestic product, with the majority of the processes relying on heterogeneous catalysis. Despite the importance in different global segments, the fundamental understanding of heterogeneously catalysed processes lags substantially behind that achieved in other fields. The newly established Max Planck–Cardiff Centre on the Fundamentals of Heterogeneous Catalysis (FUNCAT) targets innovative concepts that could contribute to the scientific developments needed in the research field to achieve net zero greenhouse gas emissions in the chemical industries. This Viewpoint Article presents some of our research activities and visions on the current and future challenges of heterogeneous catalysis regarding green industry and the circular economy by focusing explicitly on critical processes. Namely, hydrogen production, ammonia synthesis, and carbon dioxide reduction, along with new aspects of acetylene chemistry. © 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.

In this article, we present the first archaeological evidence for crucible steel production in Anatolia uncovered in recent excavations at Kubadabad, which was built as a palace by the Anatolian Seljuks in the early 13th century AD. Along with plenty of crucible sherds recovered at the site, blades made of crucible steel, production waste-iron chunks and manganese oxide pellets also revealed remarkable information about the process of production. Based on the results of the archaeometry analysis of crucibles of a unique shape with a pointed base, it was discovered that the fabric of the crucible was tempered with finely crushed charcoal, straw and quartz-containing sand. In addition, metallography and SEM analysis conducted on the metal finds demonstrated that high-quality tools were produced from manganese alloy crucible steel ingots at the site. This study evaluates most of the finds found at Kubadabad from the end of the 13th century AD, when some of the buildings were converted into workshops for decorated ceramic tiles and metal production under Ilkhanid patronage or Turkish beyliks. Using analytical results and archaeological findings, we discuss the historical connections of crucible steel production in Kubadabad, which differs from the Central Asian and Persian traditions, but shares similarities with the Southern Asian tradition. © 2021 Elsevier Ltd

Mixing and segregation in a tri-disperse granular assembly of polyoxymethylene (POM) spheres induced by the moveable stoking bars of a generic batch grate system are examined. Each particle size class features a separate colour. Stroke bar velocity and stroke length are varied. Different moving modes of the bars are analysed. Optically transparent walls of the grate allow for the localization of the visible particles. Based on the visible particle positions a segregation index is calculated. The initial arrangement of the particles in the experiments, which exhibits small statistical differences introduced by the grate filling procedure, has an influence on the progression of the segregation index. The experiments are compared with discrete element (DEM) simulations employing an in-house DEM code. Experiments are in good general agreement with the simulations. The particle rearrangement during bar movement is characterized by an initially fast mixing on short time-scales and a slow process to reach a final state of segregation. These two processes are influenced by the penetration depth of the bars into the bed and the specific movement mode. Three modes predominantly showed segregation in the direction of bar movement, whereas two modes showed large-scale spatial particle rearrangement. Two moving modes show bridging at the beginning of the experiments, an effect that could be reproduced by the DEM simulations. The influence of the modes and their specific parameters on segregation indices, a mixing rate and a segregation efficiency are discussed in detail. © 2022 Elsevier B.V.

In conventional processing, metals go through multiple manufacturing steps including casting, plastic deformation, and heat treatment to achieve the desired property. In additive manufacturing (AM) the same target must be reached in one fabrication process, involving solidification and cyclic remelting. The thermodynamic and kinetic differences between the solid and liquid phases lead to constitutional undercooling, local variations in the solidification interval, and unexpected precipitation of secondary phases. These features may cause many undesired defects, one of which is the so-called hot cracking. The response of the thermodynamic and kinetic nature of these phenomena to high cooling rates provides access to the knowledge-based and tailored design of alloys for AM. Here, we illustrate such an approach by solving the hot cracking problem, using the commercially important IN738LC superalloy as a model material. The same approach could also be applied to adapt other hot-cracking susceptible alloy systems for AM. © 2022, The Author(s).

Three different Si/Yb-silicate environmental barrier coating systems (EBCs) were atmospheric plasma sprayed using various spray currents (275, 325, 375 A) for Yb-silicate deposition. The EBCs were thermally cycled between room temperature and 1300 °C up to 1000 h in air. Additionally, bare Si coatings were tested under isothermal and thermal cycling conditions in the as-sprayed state and after polishing at 1300 °C in air. Parabolic oxidation kinetics were observed and oxidation protection provided by Yb-silicate was found to be influenced by the spray conditions, i.e. only at 325 A, Yb-silicate was effectively protecting the bond coat. The controlling mechanism was attributed to densification in the Yb-silicate layer during thermal cycling, which was quantified via image analysis. The surface finish of the Si coating was also found to be influencing the oxidation rate. The TGO was thinner and less cracked on polished APS Si coating in comparison with the as-sprayed Si coating surface. © 2022 Elsevier Ltd

Atom probe tomography (APT) analysis is being actively used to provide near-atomic-scale information on the composition of complex materials in three-dimensions. In recent years, there has been a surge of interest in the technique to investigate the distribution of hydrogen in metals. However, the presence of hydrogen in the analysis of almost all specimens from nearly all material systems has caused numerous debates as to its origins and impact on the quantitativeness of the measurement. It is often perceived that most H arises from residual gas ionization, therefore affecting primarily materials with a relatively low evaporation field. In this work, we perform systematic investigations to identify the origin of H residuals in APT experiments by combining density-functional theory (DFT) calculations and APT measurements on an alkali and a noble metal, namely Na and Pt, respectively. We report that no H residual is found in Na metal samples, but in Pt, which has a higher evaporation field, a relatively high signal of H is detected. These results contradict the hypothesis of the H signal being due to direct ionization of residual H2 without much interaction with the specimen's surface. Based on DFT, we demonstrate that alkali metals are thermodynamically less likely to be subject to H contamination under APT-operating conditions compared to transition or noble metals. These insights indicate that the detected H-signal is not only from ionization of residual gaseous H2 alone, but is strongly influenced by material-specific physical properties. The origin of H residuals is elucidated by considering different conditions encountered during APT experiments, specifically, specimen-preparation, transportation, and APT-operating conditions by taking thermodynamic and kinetic aspects into account. © 2022 The Author(s). Published by IOP Publishing Ltd on behalf of the Institute of Physics and Deutsche Physikalische Gesellschaft.

Most functional microelectronic devices as well as hard coatings use brittle ceramics like Titanium Nitride (TiN) in nanostructured, thin film form. Damage tolerance is critical to their deployment in service, and life extension. In this study, we explore multilayering to enhance the damage tolerance of such material systems. Ti/TiN is a model metal/ceramic system with a strong interface, where elastic-plastic mismatch could potentially be used to modify the crack driving force. We carry out systematic numerical simulations of crack driving force in Ti/TiN multilayers with changing layer spacing. Micro-cantilever experiments are then carried out on a selected set of multilayers to determine the fracture toughness as a function of the number of interfaces. The 50 layer multilayer exhibits a fracture toughness that is 82% higher than the single layer TiN while maintaining a comparable hardness to the latter. The weak intercolumnar boundaries of sputtered films are found to be a limitation in fully exploiting the advantage of the shielding effect due to alternating stiff and compliant layers. The results are discussed in the context of design parameters for multilayering in metal/ceramic thin film systems in general. © 2022 Acta Materialia Inc.

Numerous metallurgical and materials science applications depend on quantitative atomic-scale characterizations of environmentally-sensitive materials and their transient states. Studying the effect upon materials subjected to thermochemical treatments in specific gaseous atmospheres is of central importance for specifically studying a material’s resistance to certain oxidative or hydrogen environments. It is also important for investigating catalytic materials, direct reduction of an oxide, particular surface science reactions or nanoparticle fabrication routes. This manuscript realizes such experimental protocols upon a thermochemical reaction chamber called the "Reacthub" and allows for transferring treated materials under cryogenic & ultrahigh vacuum (UHV) workflow conditions for characterisation by either atom probe or scanning Xe+/electron microscopies. Two examples are discussed in the present study. One protocol was in the deuterium gas charging (25 kPa D2 at 200°C) of a high-manganese twinning-induced-plasticity (TWIP) steel and characterization of the ingress and trapping of hydrogen at various features (grain boundaries in particular) in efforts to relate this to the steel’s hydrogen embrittlement susceptibility. Deuterium was successfully detected after gas charging but most contrast originated from the complex ion FeOD+ signal and the feature may be an artefact. The second example considered the direct deuterium reduction (5 kPa D2 at 700°C) of a single crystal wüstite (FeO) sample, demonstrating that under a standard thermochemical treatment causes rapid reduction upon the nanoscale. In each case, further studies are required for complete confidence about these phenomena, but these experiments successfully demonstrate that how an ex-situ thermochemical treatment can be realised that captures environmentally-sensitive transient states that can be analysed by atomic-scale by atom probe microscope. © 2022 Khanchandani et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Cu and Ag precursors that are volatile, reactive, and thermally stable are currently of high interest for their application in atomic-layer deposition (ALD) of thin metal films. In pursuit of new precursors for coinage metals, namely Cu and Ag, a series of new N-heterocyclic carbene (NHC)-based CuI and AgI complexes were synthesized. Modifications in the substitution pattern of diketonate-based anionic backbones led to five monomeric Cu complexes and four closely related Ag complexes with the general formula [M(tBuNHC)(R)] (M=Cu, Ag; tBuNHC=1,3-di-tert-butyl-imidazolin-2-ylidene; R=diketonate). Thermal analysis indicated that most of the Cu complexes are thermally stable and volatile compared to the more fragile Ag analogs. One of the promising Cu precursors was evaluated for the ALD of nanoparticulate Cu metal deposits by using hydroquinone as the reducing agent at appreciably low deposition temperatures (145–160 °C). This study highlights the considerable impact of the employed ligand sphere on the structural and thermal properties of metal complexes that are relevant for vapor-phase processing of thin films. © 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.

There are several facets of aluminum when it comes to sustainability. While it helps to save fuel due to its low density, producing it from ores is very energy-intensive. Recycling it shifts the balance towards higher sustainability, because the energy needed to melt aluminum from scrap is only about 5% of that consumed in ore reduction. The amount of aluminum available for recycling is estimated to double by 2050. This offers an opportunity to bring the metallurgical sector closer to a circular economy. A challenge is that large amounts of scrap are post-consumer scrap, containing high levels of elemental contamination. This has to be taken into account in more sustainable alloy design strategies. A “green aluminum” trend has already triggered a new trading platform for low-carbon aluminum at the London Metal Exchange (2020). The trend may lead to limits on the use of less-sustainable materials in future products. The shift from primary synthesis (ore reduction) to secondary synthesis (scrap melting) requires to gain better understanding of how multiple scrap-related contaminant elements act on aluminum alloys and how future alloys can be designed upfront to become scrap-compatible and composition-tolerant. The paper therefore discusses the influence of scrap-related impurities on the thermodynamics and kinetics of precipitation reactions and their mechanical and electrochemical effects; impurity effects on precipitation-free zones around grain boundaries; their effects on casting microstructures; and the possibilities presented by adjusting processing parameters and the associated mechanical, functional and chemical properties. The objective is to foster the design and production of aluminum alloys with the highest possible scrap fractions, using even low-quality scrap and scrap types which match only a few target alloys when recycled. © 2022 The Authors

The microstructure of advanced high-strength steels often shows a sensitive dependence on alloying. For example, adding Cr to improve the corrosion resistance of medium-Mn steels also enhances the precipitation of carbides. The current study focuses on the behavior of H in such complex multicomponent carbides by employing different methodological strategies. We systematically analyze the impact of Cr, Mn, and Fe using density functional theory (DFT) for two prototype precipitate phases, M3C and M23C6, where M represents the metal sublattice. Our results show that the addition of these alloying elements yields strong nonmonotonic chemical trends for the H solubility. We identify magnetovolume effects as the origin for this behavior, which depend on the considered system, the sites occupied by H, and short- vs long-range interactions between H and the alloying elements. We further show that the H solubility is directly correlated with the occupation of its nearest-neighbor shells by Cr and Mn. Based on these insights, DFT data from H containing binary-metal carbides are used to design a ridge regression based model that predicts the solubility of H in the ternary-metal carbides (Fe-Cr-Mn-C). © 2022 authors. Published by the American Physical Society.

Deep drawing dies are manufactured using metal sheets. Laser metal deposition is used for bonding the sheets and smoothening the edges. The strength and surface finish of the dies are the key challenges. Milling, roller burnishing, and laser treatment are applied as post-processing for improving the surface finish. A semi-analytical model is developed for selecting the sheet combination for sufficient strength. The new rapid prototyping process offers high flexibility for complex die geometries. The evaluation by deep drawing experiments using DC06 and high-strength HC380LA blanks revealed the feasibility of the new manufacturing routes regarding deep drawability and surface finish. © 2022 CIRP

We demonstrate the growth of large (Mg,Zr):SrGa12O19(SGMZ) single crystals and use a combination of X-ray imaging techniques to analyze their structural and chemical homogeneity. Single-crystal cylinders with lengths and diameters up to about 2.5 cm are achieved. Our characterization of polished sections reveals a localized (0001) facet that is typically formed at the center of the growth interface. Such facets are seen as the key factor limiting the growth of large-area crystals with excellent structural quality due to local deviations in the segregation behavior of the dopants. We developed a lab-based X-ray diffraction imaging technique with high sensitivity that exposes subtle variations in lattice parameters and lattice tilts, which are attributed to changes in the chemical composition and the resulting elastic deformation. The relationship between unit-cell dimensions and composition is verified by micro X-ray fluorescence mapping. In this way, we find a Ga-rich center region with a reduced unit-cell volume that is surrounded by a ring of increased tilt and elastic strain. Furthermore, we observe a 6-fold in-plane anisotropy of dopant incorporation and tree-ring-shaped structures caused by macrosteps. With rocking curve widths below 23 arcsec in ∼90% of the crystal, SGMZ crystals are largely homogeneous and hence suitable for the preparation of high-quality substrates. For most applications, the substantially enhanced crystal size enabled by very high Mg and Zr codoping levels outweighs the issues related to concentration variations arising from their addition. © 2022 American Chemical Society. All rights reserved.

Tissue degradation plays a crucial role in vascular diseases such as atherosclerosis and aneurysms. Computational modeling of vascular hemodynamics incorporating both arterial wall mechanics and tissue degradation has been a challenging task. In this study, we propose a novel finite element method-based approach to model the microscopic degradation of arterial walls and its interaction with blood flow. The model is applied to study the combined effects of pulsatile flow and tissue degradation on the deformation and intra-aneurysm hemodynamics. Our computational analysis reveals that tissue degradation leads to a weakening of the aneurysmal wall, which manifests itself in a larger deformation and a smaller von Mises stress. Moreover, simulation results for different heart rates, blood pressures and aneurysm geometries indicate consistently that, upon tissue degradation, wall shear stress increases near the flow-impingement region and decreases away from it. These findings are discussed in the context of recent reports regarding the role of both high and low wall shear stress for the progression and rupture of aneurysms. © 2022, The Author(s).

Many solutions exist for optical simulations. Many of them are isolated solutions, are complex to use due to their wide range of applications, or are difficult to adapt to new problems. Therefore, there is a need for easy-to-use, flexibly adaptable program packages. For this reason, we present here a programming library for the simulation of optical problems, which is based on geometrical optics due to its high flexibility. Special attention was paid to a flexible adaptability to different problems and an easy usability. The program package is freely available as an open-source project implemented in C++ and can be downloaded from the GitHub platform (Weigel, GitHub, 2021). © 2022 Optica Publishing Group.

The mechanical behavior and deformation mechanisms of a body-centered cubic (BCC) Ti29Zr24Nb23Hf24 (at%) high entropy alloy (HEA) was investigated in temperatures and strain rates from 700° to 1100 °C and 10−3 to 10 s−1, respectively. The HEA exhibits a substantial increase in yield stress with increasing strain rate. The strain rate sensitivity (SRS) coefficient is ~3 times that of BCC alloy Nb-1Zr and even ~3.5 times that of pure Nb. This high SRS is attributed to the high Peierls stress of the HEA, which is about twice the Peierls stress of pure Nb. On the other hand, the flow stress exhibits a tendency from strain softening to strain hardening with the increase of strain rate especially at the relatively low temperatures. This behavior is explained by a change in dislocation motion from climbing to multiple slip with the increase of strain rate. Taking the specimen subjected to 800 ºC for example, dislocation walls formed at the early stage of deformation and at low strain rate of 10−3 s−1. In this case there is sufficient time to activate dislocations climb, which results in discontinuous dynamic recrystallization, and strain softening. However, when the strain rate amounts to 1 s−1, thermally activated processes such as dislocation climb are too sluggish. As a consequence, multiple slip systems are activated, and the dislocation interactions lead to the evolution of deformation bands, leading to strain hardening. © 2021 Elsevier B.V.

Drilling into unknown soil during mechanized tunneling may cause damage of the tunnel boring machine or delays in the construction process. A full waveform inversion can prevent these issues supplying a detailed image of the subsoil, but claims several challenges like the need for an adequate method or the need for an appropriate utilization of seismic sources and receivers. In this research, a small-scale surrogate model is constructed in order to create representative tunneling field data in a laser laboratory. With the experimental model, ultrasonic data is generated. After constructing an adequate forward model, two non-gradient full waveform inversion methods based on parameter identification are applied to the measurement data in order to determine the inner structure of the model out of seismic waveforms. Furthermore, the positioning of seismic sources and receivers is investigated. The algorithms are found to perform well on the acquired measurement data, with different precisions dependent on the utilized method and on the source-receiver configuration. The comparability of the ultrasonic data to tunneling field data is analyzed. © 2021 Elsevier Ltd

Coupled cluster theory is a general and systematic electronic structure method, but in particular the highly accurate "gold standard"coupled cluster singles, doubles and perturbative triples, CCSD(T), can only be applied to small systems. To overcome this limitation, we introduce a framework to transfer CCSD(T) accuracy of finite molecular clusters to extended condensed phase systems using a high-dimensional neural network potential. This approach, which is automated, allows one to perform high-quality coupled cluster molecular dynamics, CCMD, as we demonstrate for liquid water including nuclear quantum effects. The machine learning strategy is very efficient, generic, can be systematically improved, and is applicable to a variety of complex systems. © 2022 American Physical Society.

Amphiphilic coatings are promising materials for fouling-release applications, especially when their building blocks are inexpensive, biodegradable, and readily accessible polysaccharides. Here, amphiphilic polysaccharides were fabricated by coupling hydrophobic pentafluoropropylamine (PFPA) to carboxylate groups of hydrophilic alginic acid, a natural biopolymer with high water-binding capacity. Layer-by-layer (LbL) coatings comprising unmodified or amphiphilic alginic acid (AA*) and polyethylenimine (PEI) were assembled to explore how different PFPA contents affect their physicochemical properties, resistance against nonspecific adsorption (NSA) of proteins, and antifouling activity against marine bacteria (Cobetia marina) and diatoms (Navicula perminuta). The amphiphilic multilayers, characterized through spectroscopic ellipsometry, water contact angle goniometry, elemental analysis, AFM, XPS, and SPR spectroscopy, showed similar or even higher swelling in water and exhibited higher resistance toward NSA of proteins and microfouling marine organisms than multilayers without fluoroalkyl groups. © 2022 American Chemical Society. All rights reserved.

During curing or hydration processes, materials such as polymers or fresh concrete undergo microstructural changes, which manifest themselves on the macroscopic scale as evolving material properties like strength or stiffness. Considering the increasing importance of additive manufacturing techniques using this type of “aging” materials, which typically undergo large deformations during the extrusion and deposition processes, a consistent finite strain model is required that takes evolving material properties and the proper characterization of the large deformation kinematics into account. In the proposed formulation, the problem of evolving stiffness is solved, in contrast to hypoelastic rate formulations typically used for this type of problems, by means of a multiplicative split of the deformation gradient into elastic and non-recoverable aging parts and the adoption of a hyperelastic potential. The existence of a hyperelastic potential is an advantage as it easily allows accounting for thermodynamic consistency. By introducing an internal aging parameter, a hyperelastic model based on principal logarithmic strains is adopted, to derive a novel and consistent evolution law for the aging part of the deformation gradient. The incremental and temporal discretization of the proposed constitutive model leads to a stress update scheme, which is reduced to a single multiplication of the principal logarithmic strains by a certain factor. As only minor adaptions are necessary, the proposed model is very attractive for implementations in already existing numerical models. In a benchmark study, the main aspects of the formulation are discussed, and the applicability of the proposed model is demonstrated by a computational analysis of a 3D printed concrete wall. © 2022 Elsevier B.V.

The deformation-induced phase transition from fcc to hcp causes local embrittlement of the metal matrix in Cobalt-base alloys, facilitating subcritical crack growth under cyclic loading and reducing fatigue resistance. Our approach to increasing the fatigue life of Co-based hard alloys is to suppress the phase transition from fcc to hcp by an alloy modification that increases the stacking fault energy (SFE) of the metal matrix. Therefore, we substitute various contents (15, 25, and 35 mass pct) of Co by Fe and analyze the effect on the fatigue life and resistance against subcritical crack growth. Subcritical crack growth in the specimens takes place in a cyclic load test. The proceeding crack growth and the occurrence of phase transformations are monitored by scanning electron microscope (SEM) investigations and electron backscatter diffraction (EBSD). We determined an SFE of 35 mJ/m2 at an iron content of 35 mass pct, which leads to a change of the main deformation mechanism from deformation-induced martensitic transformation to deformation twinning. Analysis of cyclically loaded specimens revealed that the resistance against subcritical crack growth in the metal matrix is facilitated with increasing Fe content, leading to a significant increase in fatigue life. © 2022, The Author(s).

The detailed catalytic influence of minerals on solid biomass in oxy-fuel combustion is yet to be fully understood. The catalytic influence of metal sulfates on a mineral-free, cellulose-based model biomass was investigated during slow and high heating in air and oxy-fuel combustion. Measurements were performed in a thermogravimetric setup in air with slow heating rates and in a flat-flame burner in oxy-fuel combustion atmosphere with high heating rates. Temperature-programmed experiments identified the catalytic activity scale of Fe > K > Na > Mg ∼ Ca in synthetic air (20% O2/He) for the sulfates. The highly active metals Fe and K were chosen for more detailed investigations in oxy-fuel combustion experiments using an additional loading of Mg as less-volatile mineral tracer. Samples doped with Fe and Mg (FeMg-MH) exhibited lower thermal stability and higher particle combustion temperatures in the flat-flame burner compared with the undoped model fuel, while the combination of K and Mg (KMg-MH) decreased the particle combustion temperature drastically during oxy-fuel combustion. X-ray diffraction patterns acquired between 25 and 800 °C showed that in FeMg-MH the mineral phases FeSO4 and MgSO4 were still separated and independently active, while the addition of MgSO4 to K2SO4 formed the stable mineral phase Langbeinite inhibiting the K mobility. The influence of metal chlorides and nitrates was also investigated by slow heating rate TGA experiments showing an overlapping of metal salts decomposition and carbon devolatilization and oxidation. © 2022 Elsevier Ltd

Superhydrophobic surfaces are capable to resist the adhesion of organisms through a surface bound air layer, known as a plastron. However, the lifetime of such plastrons is limited and their decay results in the loss of the protective barrier against organism attachment. Here a method is established to replenish the plastron by Joule heating of electrically conductive, superhydrophobic laser-induced graphene (SLIG) coatings. Local heating with a DC current reduces the water solubility of gases and the growth of an initial microplastron into a macroplastron through gas nucleation at the liquid–air interface is observed. Small temperature differences between the surface and the surrounding water could induce this effect. Different SLIG surfaces are challenged against biofouling by the diatom Navicula perminuta under dynamic conditions and it is shown that surfaces with intact plastron resist diatom accumulation. Surfaces without the protective air layer are found to accumulate high amounts of diatoms. The results underline the promising potential of plastron-based antifouling approaches because plastrons can be stabilized for extended times. This strategy could be applied to many other materials for an effective protection against fouling organism. © 2022 The Authors. Advanced Materials Interfaces published by Wiley-VCH GmbH.

We present a first-principles approach for the computation of the magnetic Gibbs free energy of materials using magnetically constrained supercell calculations. Our approach is based on an adiabatic approximation of slowly varying local moment orientations, the so-called finite-temperature disordered local moment picture. It describes magnetic phase transitions and how electronic and/or magnetostructural mechanisms generate a discontinuous (first-order) character. We demonstrate that the statistical mechanics of the local moment orientations can be described by an affordable number of supercell calculations containing noncollinear magnetic configurations. The applicability of our approach is illustrated by firstly studying the ferromagnetic state in bcc Fe. We then investigate the temperature-dependent properties of a triangular antiferromagnetic state stabilizing in two antiperovskite systems Mn3AN (A=Ga, Ni). Our calculations provide the negative thermal expansion of these materials as well as the ab initio origin of the discontinuous character of the phase transitions, electronic and/or magnetostructural, in good agreement with experiment. © 2022 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Open access publication funded by the Max Planck Society.

Product quality and processing of additively manufactured concrete components strongly depend on the flow processes during material extrusion. To control layer deformations and enable purposeful design, numerical analyses with varying process and material parameters were performed to obtain a deeper understanding of flow processes and forces developing in the vicinity of the nozzle using the Lagrangian-based Particle Finite Element Method in association with a Bingham constitutive model. This model was validated by comparing the simulated layer geometries with those obtained from laboratory 3D-printing experiments. Within the investigated parameter range, the forces generated under the extrusion nozzle can be 6 times higher than those induced by self-weight and may cause deformations in substrate layers. Since the distribution of extrusion forces may change substantially under the nozzle for varying parameters, a novel indicator based on the yielding material is introduced to find optimal 3D-printing parameters to prevent plastic deformations in substrate layers. © 2022 Elsevier B.V.

The solid-electrolyte interphase (SEI) plays a key role in the stability of lithium-ion batteries as the SEI prevents the continuous degradation of the electrolyte at the anode. The SEI acts as an insulating layer for electron transfer, still allowing the ionic flux through the layer. We combine the feedback and multi-frequency alternating-current modes of scanning electrochemical microscopy (SECM) for the first time to assess quantitatively the local electronic and ionic properties of the SEI varying the SEI formation conditions and the used electrolytes in the field of Li-ion batteries (LIB). Correlations between the electronic and ionic properties of the resulting SEI on a model Cu electrode demonstrates the unique feasibility of the proposed strategy to provide the two essential properties of an SEI: ionic and electronic conductivity in dependence on the formation conditions, which is anticipated to exhibit a significant impact on the field of LIBs. © 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.

The solution of saddle-point problems, such as the Stokes equations, is a challenging task, especially in large-scale problems. Multigrid methods are one of the most efficient solvers for such systems of equations and can achieve convergence rates independent of the problem size. The smoother is a crucial component of multigrid methods and significantly affects its overall efficiency. We propose a Vanka-type smoother that we refer to as Restricted Additive Vanka and investigate its convergence in the context of adaptive geometric multigrid methods for the Stokes equations. The proposed smoother has the advantage of being an additive method and provides favorable properties in terms of algorithmic complexity, scalability and applicability to high-performance computing. We compare the performance of the smoother with two variants of the classical Vanka smoother using numerical benchmarks for the Stokes problem. We find that the restricted additive smoother achieves comparable convergence rates to the classical multiplicative Vanka smoother while being computationally less expensive per iteration, which results in faster solution runtimes. © 2022 Elsevier Inc.

The synthesis of single-cycle pulses of compressed light and microwave signals sparked novel areas of fundamental research. In the field of acoustics, however, such a generation has not been introduced yet. For numerous applications, the large spatial extent of surface acoustic waves (SAW) causes unwanted perturbations and limits the accuracy of physical manipulations. Particularly, this restriction applies to SAW-driven quantum experiments with single flying electrons, where extra modulation renders the exact position of the transported electron ambiguous and leads to undesired spin mixing. Here, we address this challenge by demonstrating single-shot chirp synthesis of a strongly compressed acoustic pulse. Employing this solitary SAW pulse to transport a single electron between distant quantum dots with an efficiency exceeding 99%, we show that chirp synthesis is competitive with regular transduction approaches. Performing a time-resolved investigation of the SAW-driven sending process, we outline the potential of the chirped SAW pulse to synchronize single-electron transport from many quantum-dot sources. By superimposing multiple pulses, we further point out the capability of chirp synthesis to generate arbitrary acoustic waveforms tailorable to a variety of (opto)nanomechanical applications. Our results shift the paradigm of compressed pulses to the field of acoustic phonons and pave the way for a SAW-driven platform of single-electron transport that is precise, synchronized, and scalable. © 2022 authors. Published by the American Physical Society.

The reaction pathways of higher alcohol synthesis over a bulk Co−Cu catalyst (Co : Cu=2 : 1) were investigated by applying high-pressure pulse experiments as a surface-sensitive operando method at 280 °C and 60 bar. Using high-pressure CO and H2 pulses in a syngas flow with a H2:CO ratio of 1, it was shown that the surface of the working 2CoCu catalyst is saturated with adsorbed CO, but not with adsorbed atomic hydrogen, because only the H2 pulses increased the yields of all alcohols and alkanes. The reverse water gas shift reaction (WGSR) was investigated by pulsing CO2. The CO2 pulses poisoned the formation of methanol, ethanol, and 1-propanol, and the absence of significant CO and H2O responses indicates that the WGSR is not efficiently catalyzed by the applied 2CoCu catalyst excluding the presence of exposed Cu0 sites. A series of ethylene pulses showed that when a threshold mole fraction of ethylene of about 1 vol % is surpassed, 2CoCu is an active catalyst for the hydroformylation of ethylene to 1-propanol pointing to the presence of highly coordinatively unsaturated Co sites. © 2022 The Authors. ChemCatChem published by Wiley-VCH GmbH.

The elastic energy of mixing for multi-component solid solutions is derived by generalizing Eshelby's sphere-in-hole model. By surveying the dependence of the elastic energy on the chemical composition and lattice misfit, we derive a lattice strain coefficient λ*. Studying several high-entropy alloys and superalloys, we propose that most solid solution multi-component alloys are stable when λ*<0.16, generalizing the Hume-Rothery atomic-size rule for binary alloys. We also reveal that the polydispersity index δ, frequently used for describing strain in multi-component alloys, directly represents the elastic energy (e) with e=qδ2, q being an elastic constant. Furthermore, the effects of (i) the number and (ii) the atomic-size distribution of constituting elements on the phase stability of high-entropy alloys were quantified. The present derivations and discussions open for richer considerations of elastic effects in high-entropy alloys, offering immediate support for quantitative assessments of their thermodynamic properties and studying related strengthening mechanisms. © 2021

The steel industry is responsible for a quarter of all industrial greenhouse gas emissions. So far, the environmental savings are mainly due to steel recycling. Besides recycling, the circular economy offers strategies to increase material efficiency and thus decrease the primary raw material demand. However, the potentials remain unexploited because circular economy concepts with a higher degree of circularity are not considered. The presented case study of an industrial machining knife illustrates how the production process can be improved by implementing various circular strategies. The environmental performance is analyzed by calculating and comparing the carbon footprint, the cumulative energy demand and the material footprint, and the material efficiency indicator. The results show that the implementation of the three overarching strategies of the circular economy - narrowing, closing, and slowing – contributes to a significant increase in material efficiency. The implementation also has a positive effect on the overall environmental performance. The circular production processes require less energy and resources and cause fewer emissions. Auxiliary processes such as additional transport routes are relevant, as they can reduce or even overcompensate for savings. These processes must be adequately considered and designed. © 2022 Elsevier Ltd

Since its discovery in 1954, the omega (ω) phase in titanium and its alloys has attracted substantial attention from researchers. The β-to-ω and ω-to-α phase transformations are central to β-titanium alloy design, but the transformation mechanisms have been a subject of debate. With new generations of aberration-corrected transmission electron microscopy and atom probe tomography, both the spatial resolution and compositional sensitivity of phase transformation analysis have been rapidly improving. This review provides a detailed assessment of the new understanding gained and related debates in this field enabled by advanced characterization methods. Specifically, new insights into the possibility of a coupled diffusional-displacive component in the β-to-ω transformation and key nucleation driving forces for the ω-assisted α phase formation are discussed. Additionally, the influence of ω phase on the mechanical properties of β-titanium alloys is also reviewed. Finally, a perspective on open questions and future direction for research is discussed. © This material is authored by Battelle Memorial Institute with the US Department of Energy under Contract No. DE-AC05-76RL01830. The US Government retains for itself, and others acting on its behalf, a paid-up, non-exclusive, and irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.

The molecular Suzuki cross-coupling reaction was conducted mechanochemically, without solvents, ligands, or catalyst powders. Utilizing one catalytically active palladium milling ball, products could be formed in quantitative yield in as little as 30 min. In contrast to previous reports, the adjustment of milling parameters led to the complete elimination of abrasion from the catalyst ball, thus enabling the first reported systematic catalyst analysis. XPS, in situ XRD, and reference experiments provided evidence that the milling ball surface was the location of the catalysis, allowing a mechanism to be proposed. The versatility of the approach was demonstrated by extending the substrate scope to deactivated and even sterically hindered aryl iodides and bromides. © 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.

Nanosecond plasmas in liquids are often generated by applying a short high voltage pulse to an electrode immersed in a liquid for biomedical or environmental applications. The plasmas appear as streamers that propagate through the liquid. The understanding of the ignition of these nanosecond plasmas in liquids, however, is an open question. The occurrence of any traditional gas phase ignition mechanism is unlikely, because the formation of a gas bubble prior to ignition is suppressed by the inertia of the liquid. Therefore, either electron multiplication inside nanopores that are induced by an electric field pressure gradient or field effects at the tip and at the ionization front of the liquid streamer may act as electron generation mechanisms. A deeper understanding can be achieved by comparing the velocity and dynamic of the plasma propagation with modeling, where the individual mechanisms and transport coefficients can be analyzed. Here, we are using intensified charge-coupled device imaging to investigate the time dependence of the streamer dynamic and compare this with a 1D fluid code for negative voltages. It is shown that the maximum streamer length scales with the applied electric field, indicating that an electric stability field in the liquid streamer channel is important, as known for gas streamers. The 1D fluid code can reproduce the proper streamer velocities, if transport coefficients for hydrated electrons are chosen. The model suggests that the propagation of liquid streamers is dominated by the local ionization rate at the ionization front rather than by advection or diffusion of electrons as in gases. This also explains the finding that positive and negative streamers exhibit almost identical electron densities. © 2022 Author(s).

The adsorption orientation of molecules on surfaces influences their reactivity, but it is still challenging to tailor the interactions that govern their orientation. Here, we investigate how the substituent and the surface structure alter the adsorption orientation of halogenated benzene molecules from parallel to tilted relative to the surface plane. The deviation of the parallel orientation of bromo-, chloro-, and fluorobenzene molecules adsorbed on Cu(111) and Cu(110) surfaces is determined, utilising the surface selection rule in reflection-absorption infrared spectroscopy. On Cu(111), all three halogenated molecules are adsorbed with their molecular plane almost parallel to the surface at low coverages. However, they are tilted at higher coverages; yet, the threshold coverages differ. On Cu(110), merely bromo- and chlorobenzene follow this trend, albeit with a lower threshold for both. In contrast, fluorobenzene molecules are tilted already at low coverages. The substantial influence of the halogen atom and the surface structure on the adsorption orientation, resulting from an interplay of molecule-molecule and molecule-surface interactions, is highly relevant for reactivity confined to two dimensions. © 2022 the Owner Societies.

The three dominating polyzwitterion families, polyphosphatidylcholines, polycarboxybetaines, and polysulfobetaines, all of which provide high fouling resistance, have been complemented by a fourth one recently, the so-called polysulfabetaines that combine ammonium with sulfate moieties. To elucidate the relationship between their structure and antifouling potential, coatings of a set of systematically varied poly(sulfabetaine methacrylate)s are investigated. In particular, the effects of the spacer groups, either separating the zwitterionic units from the polymer backbone, or the cationic from the anionic charges, are explored, studying the resistance against non-specific protein adsorption and the accumulation of single species of marine biofouling organisms. All polysulfabetaines are at least as effective, or even more potent than the structurally closely related standard poly(sulfobetaine methacrylate). Their resistance against proteins and fouling organisms can be tuned via the betaine-to-backbone spacer. Overall, the polysulfabetaine coatings with the shorter ethylene spacer show higher resistance against non-specific adsorption of proteins, in particular of lysozyme, or against colonization by diatoms. This may result from the higher steric constraints of the polymer attached zwitterions, favoring particularly advantageous conformations. Moreover, a shorter spacer between the oppositely charged ionic groups of the zwitterionic moiety reduces the settlement of cyprid larvae more effectively. © 2022 The Authors. Advanced Materials Interfaces published by Wiley-VCH GmbH.

The influence of short-time heat treatment on the widely used and commercially available ledeburitic cold-work tool steel 1.2379 (X153CrMoV12; AISI D2) is examined herein. Starting from a soft annealed initial condition, the influence of different austenitizing temperatures and holding times on the metastable microstructural states after heat treatment/hardening is investigated. The experimental implementation of the heat treatment is used in a quenching dilatometer, and a microstructural simulation model is built using these results. As validation of the model, on the one hand, the martensite start temperature (Ms) is used, measured experimentally by dilatometry. Additionally, the carbide content and distribution, as determined by quantitative image analysis, are compared with the simulated data and used as an indicator of the model accuracy. Through the developed simulation model, arbitrary heat treatment-induced metastable microstructural states can be calculated. As a possible application of this model, the live-adaption of the industrial heat treatment process in dependence on the batch chemical composition is discussed. © 2022 The Authors. Steel Research International published by Wiley-VCH GmbH.

Recent advances in the field of diffusion in multiprincipal element systems are critically reviewed, with an emphasis on experimental as well as theoretical approaches to determining atomic mobilities (tracer diffusion coefficients) in chemically complex multicomponent systems. The newly elaborated and augmented pseudobinary and pseudoternary methods provide a rigorous framework to access tracer, intrinsic, and interdiffusion coefficients in alloys with an arbitrary number of components. Utilization of the novel tracer-interdiffusion couple method allows for a high-throughput determination of composition-dependent tracer diffusion coefficients. A combination of these approaches provides a unique experimental toolbox to access diffusivities of elements that do not have suitable tracers. The pair-exchange diffusion model, which gives a consistent definition of diffusion matrices without specifying a reference element, is highlighted. Density-functional theory-informed calculations of basic diffusion properties mdash asrequired for the generation of extensive mobility databases for technological applications mdash are also discussed. © 2022 Annual Reviews Inc.. All rights reserved.

In this paper, a framework for the simulation of crack propagation in brittle and ductile materials is proposed. The framework is derived by extending the eigenerosion approach of Pandolfi and Ortiz (Int J Numer Methods Eng 92(8):694–714, 2012. https://doi.org/10.1002/nme.4352) to finite strains and by connecting it with a generalized energy-based, Griffith-type failure criterion for ductile fracture. To model the elasto-plastic response, a classical finite strain formulation is extended by viscous regularization to account for the shear band localization prior to fracture. The compression–tension asymmetry, which becomes particularly important during crack propagation under cyclic loading, is incorporated by splitting the strain energy density into a tensile and compression part. In a comparative study based on benchmark problems, it is shown that the unified approach is indeed able to represent brittle and ductile fracture at finite strains and to ensure converging, mesh-independent solutions. Furthermore, the proposed approach is analyzed for cyclic loading, and it is shown that classical Wöhler curves can be represented. © 2022, The Author(s).

The effect of the non-equilibrium vacancy on the Kirkendall porosity formation was studied by means of a developed model of the multi-component diffusion with vacancies (MDV) which includes the intrinsic fluxes with vacancy gradient and non-ideal sources and sinks for vacancies. For this study, the diffusion couple experiments in multi-component alloys were chosen. To handle the case of concentration-dependent equilibrium vacancy concentration, we introduced the interaction parameters between the components and vacancies, which can have strong effects on the equilibrium vacancy concentration in alloys and on thermodynamic factors. The diffusion profiles of components and vacancies were simulated by using thermodynamic and kinetic data. The different intensity of the vacancy annihilation/generation and different initial vacancy distributions were considered. Furthermore, we show that the conventional model of diffusion in multi-component systems is a particular case of the MDV with a specific sink/source term. The conventional model was extended by the vacancy diffusion term, similar to the MDV, which significantly reduces the vacancy gradient and the pore formation near the Matano plane. The numerical results demonstrate that the diffusion profiles of substitutional components slightly depend on the sink/source intensity if the none-zero net flux of substitutional components is not significant and the sources and sinks of vacancies are not sparse, whereas the porosity depends very strongly and correlates with the vacancy distribution. For the simulation of variable equilibrium vacancy concentrations using the MDV, the corresponding interaction parameters related to vacancies are necessary to be included in the thermodynamic assessment. © 2022 Acta Materialia Inc.

The development of NbC-containing martensitic stainless steels has made it possible to unite the properties of high corrosion resistance and wear resistance. If NbC is used as a hard phase instead of chromium carbide, the abrasive wear resistance of the steels is increased due to the greater hardness of NbC. The solubility of chromium in NbC is low. For this reason, chromium is fully available to form a passive surface layer to increase the corrosion resistance. In the steel melt, niobium leads to the formation of primary NbC, which grows very rapidly. Atomization of PM steels leads to the formation of coarse primary hard phases that clog the nozzle. Therefore, until now, steels with NbC as a hard phase are produced using the PM route with so-called diffusion alloying; however, this production route is very complex and expensive. Herein, a novel Nb-rich MC-containing wear- and corrosion-resistant steel that is produced using the usual PM route is presented. This steel consists of a martensitic matrix with evenly dispersed Nb-rich MC having a volume of 2.5%. Due to the high hardness (>750 HV30) in combination with high resistance to pitting corrosion, the steel exhibits outstanding tribocorrosion resistance in 0.9% NaCl solution. © 2022 The Authors. Steel Research International published by Wiley-VCH GmbH.

The modeling of damage processes in materials constitutes an ill-posed mathematical problem which manifests in mesh-dependent finite element results. The loss of ellipticity of the discrete system of equations is counteracted by regularization schemes of which the gradient enhancement of the strain energy density is often used. In this contribution, we present an extension of the efficient numerical treatment, which has been proposed by Junker et al. in 2019, to materials that are subjected to large deformations. Along with the model derivation, we present a technique for element erosion in the case of severely damaged materials. Efficiency and robustness of our approach is demonstrated by two numerical examples including snapback and springback phenomena. © 2021 The Authors. International Journal for Numerical Methods in Engineering published by John Wiley & Sons Ltd.

Abstract: Combining thin film deposition with in situ heating electron microscopy allows to understand the thermal stability of complex solid solution nanomaterials. From a CrMnFeCoNi alloy target a thin film with an average thickness of ~10 nm was directly sputtered onto a heating chip for in situ transmission electron microscopy. We investigate the growth process and the thermal stability of the alloy and compare our results with other investigations on bulk alloys or bulk-like films thicker than 100 nm. For the chosen sputtering condition and SiNx substrate, the sputter process leads to the Stranski–Krastanov growth type (i.e., islands forming on the top of a continuous layer). Directly after sputtering, we detect two different phases, namely CoNi-rich nanoscale islands and a continuous CrMnFe-rich layer. In situ annealing of the thin film up to 700°C leads to Ostwald ripening of the islands, which is enhanced in the areas irradiated by the electron beam during heating. Besides Ostwald ripening, the chemical composition of the continuous layer and the islands changed during the heating process. After annealing, the islands are still CoNi-rich, but lower amounts of Fe and Cr are observed and Mn was completely absent. The continuous layer also changed its composition. Co and Ni were removed, and the amount of Cr lowered. These results confirm that the synthesis of a CrMnFeCoNi thin film with an average thickness of ~10 nm can lead to a different morphology, chemical composition, and stability compared to thicker films (>100 nm). Impact statement: Exploring stability of a complex solid solution thin film by in situ heating transmission electron microscopy is a study of the thermal stability of sputtered complex solid solution thin films with thicknesses of ~10 nm. Complex solid solution materials have a promising electrocatalytic behavior due to the interplay of multi-element active sites. In order to understand their catalytic properties, it is important to identify the different structure-composition-activity correlations. Thus, our investigation helps to clarify and to understand the stability of nanoscale complex solid solution with an average film thickness of ~10 nm. Graphic abstract: Combining sputter deposition with in situ heating transmission electron microscopy allows to understand the thermal stability of nanoscale complex solid solution thin films. [Figure not available: see fulltext.] © 2022, The Author(s).

In the present study, the CPD model originally developed based on predictions from heated grid (HGR) and entrained flow (EFR) experiments, has been adapted to analyze pyrolysis kinetics in a small-scale fluidized bed reactor. Impacts of particle feed, particle heat up as well as tar cracking reactions in the gas phase are considered. Furthermore, an optimized solver structure allows a time step independent solution and enables the use of implicit methods. A comparison with experimental results is undertaken for pulverized Rhenish lignite fuel particles in the temperature range from 673 to 973 K in N2 atmosphere. The comparison between simulated and experimentally derived volatile release rates reveals a good agreement, indicating that the high temperature derived kinetic parameters from HRG and EFR experiments can be extrapolated to lower temperatures. Nevertheless, discrepancies in the tar to light gas ratio occur with the proposed model implementation. © 2022 Taylor & Francis Group, LLC.

An automated assessment procedure is performed in order to establish a sophisticated kinetic data bank, introduced and modified by applying consequential iteration steps through the cross-validation method. The nonlinear curve-fitting of the end-member parameters is replaced by a simple linear fitting function via the logarithmic form of the Arrhenius equation. The applied modifications allow us to increase the precision of the method by decreasing the fitting errors. The input data employed here are the tracer diffusion coefficients in the well investigated high entropy alloy Co–Cr–Fe–Mn–Ni. The resulting parameters are in an acceptable agreement with the previously defined parameters in the literature while providing an efficient robust tool for kinetic data base development so that it enable an adequate prediction of diffusion transport. © 2022 Elsevier Ltd

The mechanochemical synthesis of nitrogen-rich nanoporous carbon materials has been scaled up using an extruder. Lignin, urea, and K2CO3 were extruded under heat and pressure to yield nanoporous carbons with up to 3500 m2 g−1 specific surface area after pyrolysis. The route was further broadened by applying different nitrogen sources as well as sawdust as a low-cost renewable feedstock to receive carbons with a C/N ratio of up to 15 depending on nitrogen source and extrusion parameters. The texture of obtained carbons was investigated by scanning electron microscopy as well as argon and nitrogen physisorption, while the chemical structure was analyzed by X-ray photoelectron spectroscopy. The received carbon was tested as a supercapacitor electrode, showing comparable performance to similar ball-mill-synthesized materials. Lastly, the space-time yield was applied to justify the use of a continuous reactor versus the ball mill. © 2022 The Authors. ChemSusChem published by Wiley-VCH GmbH.

Powder metallurgical (PM) parts usually benefit from more homogenous and finer mi-crostructures as opposed to conventionally processed material. In particular, hot isostatic pressing (HIP) combined with near-net-shape technologies can produce almost defect free PM tools with com-plex geometries. Recent advances in the plant technology of smaller HIP units allow the integration of hardening heat treatments in HIP processes. Thus, additional processing steps, transportation, energy consumption and cost are reduced. However, it is known that high pressure influences phase stability and transformation temperatures. Still, knowledge of the martensite start temperature (MS) is crucial for the design of hardening heat treatment. Since the influence of pressure on MS in HIP heat treatment is insufficiently investigated, it is the aim of this study to deploy a measurement method that allows to record MS as a function of pressure, temperature and cooling rate. Taking the hot working tool steel AISI H11 (X37CrMoV5-1, 1.2343) as the reference material, in this study for the first time the method of an in-situ electrical resistivity measurement was used to measure MS within a HIP. To investigate the influence of HIP pressure on Ms, resulting microstructures and hardness, specimens were austenitized at a temperature of TAUS = 1050◦ C for tAUS = 30 min at pAUS = 25, 50, 100 or 150 MPa. Additionally, the MS temperature of the same material was determined by quenching dilatometry at ambient pressure for comparison purposes. Characterization of microstructures was conducted by scanning electron microscopy while hardness as an important technological property of tool steels was measured according to the Vickers method. Furthermore, the CALPHAD method was used to compute the thermodynamic influence of pressure on phase stabilities. The experimental results indicate that the method of in-situ resistivity measurement can be used to measure MS during an integrated HIP heat-treatment process. Besides, a stabilizing effect of pressure on the close packed crystal structure of the austenitic fcc phase is clearly detected, resulting in a reducing influence on the MS temperature of AISI H11 by up to 90 K. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

In this paper, the investigation of laser-induced periodic surface structures (LIPSSs) on a polycrystalline diamond substrate using synthetic optical holography (SOH) is demonstrated. While many techniques for LIPSS detection operate with sample contact and/or require preparation or processing of the sample, this novel technique operates entirely non-invasively without any processing of or contact with the LIPSS sample at all. The setup provides holographic amplitude and phase images of the investigated sample with confocally enhanced and diffraction-limited lateral resolution, as well as three-dimensional surface topography images of the periodic structures via phase reconstruction with one single-layer scan only. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

Polyimides were obtained in 99 % yield in under 1 h through the “beat and heat” approach, involving solvent-free vibrational ball milling and a thermal treatment step. The influence of a plethora of additives was explored, such as Lewis acids, Lewis bases, and dehydrating agents, and the mechanochemical reaction was identified to run via a polyamic acid intermediate. The protocol was adopted to a range of substrates inaccessible through solution-based processes, including perylene tetracarboxylic acid dianhydride and melamine. Furthermore, quantum chemical calculations were conducted to identify the water removal as the crucial step in the reaction mechanism. The presented method is substantially faster and more versatile than the solution-based process. © 2021 The Authors. ChemSusChem published by Wiley-VCH GmbH

Abstract: Molecular simulations are a powerful tool in the study of crystallization and polymorphic transitions yielding detailed information of transformation mechanisms with high spatiotemporal resolution. However, characterizing various crystalline and amorphous phases as well as sampling nucleation events and structural transitions remain extremely challenging tasks. The integration of machine learning with molecular simulations has the potential of unprecedented advancement in the area of crystal nucleation and growth. In this article, we discuss recent progress in the analysis and sampling of structural transformations aided by machine learning and the resulting potential future directions opening in this area. Graphical Abstract: [Figure not available: see fulltext.]. © 2022, The Author(s), under exclusive License to the Materials Research Society.

The purpose of this study is to find a direct and quantitative correlation of the structure of Co3-xFexO4nanoparticles with catalytic performance in 2-propanol oxidation. Eight nanocrystalline samples with varying iron contents are synthesized, and quantitative information regarding their structure is obtained from nitrogen physisorption, X-ray diffraction (XRD), X-ray absorption near-edge structure (XANES), and extended X-ray absorption fine structure (EXAFS) analyzed by reverse Monte Carlo simulations. The catalytic performance is tested in 2-propanol oxidation in the gas phase. Overall, catalytic conversion data as a function of temperature are deconvoluted to obtain conversion and half-conversion temperatures as quantitative parameters for the different catalytic reaction channels. The crystal structure is described by a spinel structure with interstitial cation defects. These defects result in a reduced electronic state of the nanoparticles. The defect density depends on the cationic composition. We also observe a complex cationic distribution on tetrahedral and octahedral sites, which is strongly influenced by the overall cationic composition. In the catalytic tests, the samples exhibit a low-temperature pathway, which is deactivated in subsequent runs but can be recovered by an oxidative treatment of the catalyst. We find that the frequency of cation pairs CoO-CoOand CoO-CoTof the individual samples correlates directly to their catalytic activity and selectivity. © 2022 American Chemical Society. All rights reserved.

Mo is widely used as an effective microalloying element to improve mechanical performance of interphase precipitation steels, but the precise role of Mo in interphase precipitation behavior is not fully understood. In this contribution, interphase precipitation behavior in a series of Ti-Mo-bearing low carbon steels is systematically studied, and the role of Mo in interphase precipitates and its coarsening behavior is revisited. It is found that (Ti, Mo)C precipitates instead of TiC are formed in the Mo-containing alloys, and the average site fraction of Mo in (Ti, Mo)C is almost independent of the bulk Mo content. Moreover, the number density of interphase precipitates can be substantially enhanced by a minor addition of Mo, albeit it does not further rise with increasing the bulk Mo content. This is because the Mo fraction in (Ti, Mo)C rather than the bulk Mo content governs the driving force for precipitation nucleation and the interfacial energy of the (Ti, Mo)C/α and (Ti, Mo)C/γ interfaces. In addition to the reduced interfacial energy, decrease of Ti trans-interface diffusivity has been identified as another key reason for the enhanced carbide coarsening resistance in Mo-containing alloys. © 2021 Acta Materialia Inc.

We have developed a deep-learning-based framework for understanding the individual and mutually combined contributions of different alloying elements and environmental conditions towards the pitting resistance of corrosion-resistant alloys. A fully connected deep neural network (DNN) was trained on previously published datasets on corrosion-relevant electrochemical metrics, to predict the pitting potential of an alloy, given the chemical composition and environmental conditions. Mean absolute error of 170 mV in the predicted pitting potential, with an R-square coefficient of 0.61 was obtained after training. The trained DNN model was used for multi-dimensional gradient descent optimization to search for conditions maximizing the pitting potential. Among environmental variables, chloride-ion concentration was universally found to be detrimental. Increasing the amounts of dissolved nitrogen/carbon was found to have the strongest beneficial influence in many alloys. Supersaturating transition metal high entropy alloys with large amounts of interstitial nitrogen/carbon has emerged as a possible direction for corrosion-resistant alloy design. © 2022, The Author(s).

Although the term ‘confinement’ regularly appears in electrochemical literature, elevated by continuous progression in the research of nanomaterials and nanostructures, up until today the various aspects of confinement considered in electrochemistry are rather scattered individual contributions outside the established disciplines in this field. Thanks to a number of highly original publications and the growing appreciation of confinement as an overarching link between different exciting new research strategies, ‘electrochemistry under confinement’ is the process of forming a research discipline of its own. To aid the development a coherent terminology and joint basic concepts, as crucial factors for this transformation, this review provides an overview on the different effects on electrochemical processes known to date that can be caused by confinement. It also suggests where boundaries to other effects, such as nano-effects could be drawn. To conceptualize the vast amount of research activities revolving around the main concepts of confinement, we define six types of confinement and select two of them to discuss the state of the art and anticipated future developments in more detail. The first type concerns nanochannel environments and their applications for electrodeposition and for electrochemical sensing. The second type covers the rather newly emerging field of colloidal single entity confinement in electrochemistry. In these contexts, we will for instance address the influence of confinement on the mass transport and electric field distributions and will link the associated changes in local species concentration or in the local driving force to altered reaction kinetics and product selectivity. Highlighting pioneering works and exciting recent developments, this educational review does not only aim at surveying and categorizing the state-of-the-art, but seeks to specifically point out future perspectives in the field of confinement-controlled electrochemistry. © 2022 The Royal Society of Chemistry

Early damage identification and continuous system monitoring save dramatically maintenance costs and increase the lifespan of priceless structures. Convolutional neural networks (CNNs) have attracted the attention of the structural health monitoring (SHM) community in recent years due to their great potential for identifying underlying data patterns. However, employing two-dimensional convolutional layers in a CNN necessitates the use of strong computing resources. Therefore, based on the present state-of-the-art technical solutions, a two-dimensional CNN is not suitable for real-time SHM applications with stand-alone processing units. One-dimensional convolutional networks (1D-CNN) have recently been employed in Ultrasonic Guided Wave-based (UGW-based) damage detection to address the aforementioned disadvantage. In this paper, a methodology for damage assessment at three levels – detection, localization, and characterization – based on 1D-CNN is put forward. Furthermore, the sequence length of the time-domain signals is significantly shortened by the application of a novel approach for processing them. Additionally, it is shown to what extend this method can improve the distinguishability between datapoints obtained from various damage scenarios. Consequently, by reducing the dimensionality of the problem, the proposed approach significantly reduces the memory usage of the classification algorithm. Experimental measurements as well as Numerical simulations, in which various damage scenarios such as corrosion, circular hole and cracks have been considered, are carried out to evaluate the efficacy of the proposed algorithm. It is shown that the suggested approach has benefits in terms of true classification rate of instances (above 93 percent for detection, localization, and characterization), computing time, in-situ monitoring, and noise resilience. © 2022 Elsevier Ltd

Electric current-assisted sintering (ECAS) technologies are highly promising for processing of NdFeB magnets. Due to the combination of direct Joule heating and application of external load, even powders, whose particle size distribution and morphology are not optimum for conventional powder processing like melt-spun powders or magnet scrap, can be easily sintered to high densities. A systematic study is done to demonstrate the potential of field-assisted sintering technique/spark plasma sintering (FAST/SPS) and flash spark plasma sintering (flash SPS) for sintering of NdFeB powders. Melt-spun, commercial NdFeB powder (Magnequench MQU-F) is used as starting material. Its platelet-like shape makes this powder extremely difficult to sinter by conventional methods. This study clearly reveals that especially in the case of flash SPS application of external pressure in combination with short cycle times enables to achieve well-pronounced anisotropic magnetic properties without the need of subsequent upset forging. Optimized flash SPS parameters are applied to NdFeB magnet scrap with broad particle size distribution, demonstrating the general potential of ECAS technologies for recycling of waste magnet materials. Finally, the results are benchmarked with respect to established NdFeB processing technologies and electrodischarge sintering (EDS), another promising ECAS technology with very short cycling time. © 2022 The Authors. Advanced Engineering Materials published by Wiley-VCH GmbH.

Identification of damage in its early stage can have a great contribution in decreasing the maintenance costs and pro-longing the life of valuable structures. Although conventional damage detection techniques have a mature background, their widespread application in industrial practice is still missing. In recent years the application of Machine Learning (ML) algorithms have been more and more exploited in structural health monitoring systems (SHM). Because of the superior capabilities of ML approaches in recognizing and classifying available patterns in a dataset, they have demonstrated a significant improvement in traditional damage identification algorithms. This review study focuses on the use of machine learning (ML) approaches in Ultrasonic Guided Wave (UGW)-based SHM, in which a structure is continually monitored using permanent sensors. Accordingly, multiple steps required for performing damage detection through UGWs are stated. Moreover, it is outlined that the employment of ML techniques for UGW-based damage detection can be sub-tended into two main phases: (1) extracting features from the data set, and reducing the dimension of the data space, (2) processing the patterns for revealing patterns, and classification of instances. With this regard, the most frequent techniques for the realization of those two phases are elaborated. This study shows the great potential of ML algorithms to as-sist and enhance UGW-based damage detection algorithms. © 2022, Prognostics and Health Management Society. All rights reserved.

The present review details a chronological description of the events that took place during the development of mesoporous materials, their different synthetic routes and their use as drug delivery systems. The outstanding textural properties of these materials quickly inspired their translation to the nanoscale dimension leading to mesoporous silica nanoparticles (MSNs). The different aspects of introducing pharmaceutical agents into the pores of these nanocarriers, together with their possible biodistribution and clearance routes, would be described here. The development of smart nanocarriers that are able to release a high local concentration of the therapeutic cargo on-demand after the application of certain stimuli would be reviewed here, together with their ability to deliver the therapeutic cargo to precise locations in the body. The huge progress in the design and development of MSNs for biomedical applications, including the potential treatment of different diseases, during the last 20 years will be collated here, together with the required work that still needs to be done to achieve the clinical translation of these materials. This review was conceived to stand out from past reports since it aims to tell the story of the development of mesoporous materials and their use as drug delivery systems by some of the story makers, who could be considered to be among the pioneers in this area. © 2022 The Royal Society of Chemistry

Fossil-free ironmaking is indispensable for reducing massive anthropogenic CO2 emissions in the steel industry. Hydrogen-based direct reduction (HyDR) is among the most attractive solutions for green ironmaking, with high technology readiness. The underlying mechanisms governing this process are characterized by a complex interaction of several chemical (phase transformations), physical (transport), and mechanical (stresses) phenomena. Their interplay leads to rich microstructures, characterized by a hierarchy of defects ranging across several orders of magnitude in length, including vacancies, dislocations, internal interfaces, and free surfaces in the form of cracks and pores. These defects can all act as reaction, nucleation, and diffusion sites, shaping the overall reduction kinetics. A clear understanding of the roles and interactions of these dynamically-evolving nano-/microstructure features is missing. Gaining better insights into these effects could enable improved access to the microstructure-based design of more efficient HyDR methods, with potentially high impact on the urgently needed decarbonization in the steel industry. © 2022 The Author(s)

The atomic cluster expansion (ACE) provides a general, local, and complete representation of atomic energies. Here we present an efficient framework for parametrization of ACE models for elements, alloys, and molecules. To this end, we first introduce general requirements for a physically meaningful description of the atomic interaction, in addition to the usual equivariance requirements. We then demonstrate that ACE can be converged systematically with respect to two fundamental characteristics—the number and complexity of basis functions and the choice of nonlinear representation. The construction of ACE parametrizations is illustrated for several representative examples with different bond chemistries, including metallic copper, covalent carbon, and several multicomponent molecular and alloy systems. We discuss the Pareto front of optimal force to energy matching contributions in the loss function, the influence of regularization, the importance of consistent and reliable reference data, and the necessity of unbiased validation. Our ACE parametrization strategy is implemented in the freely available software package pacemaker that enables largely automated and GPU accelerated training. The resulting ACE models are shown to be superior or comparable to the best currently available ML potentials and can be readily used in large-scale atomistic simulations. ©2022 American Physical Society

Steel production causes a third of all industrial CO2 emissions due to the use of carbon-based substances as reductants for iron ores, making it a key driver of global warming. Therefore, research efforts aim to replace these reductants with sustainably produced hydrogen. Hydrogen-based direct reduction (HyDR) is an attractive processing technology, given that direct reduction (DR) furnaces are routinely operated in the steel industry but with CH4 or CO as reductants. Hydrogen diffuses considerably faster through shaft-furnace pellet agglomerates than carbon-based reductants. However, the net reduction kinetics in HyDR remains extremely sluggish for high-quantity steel production, and the hydrogen consumption exceeds the stoichiometrically required amount substantially. Thus, the present study focused on the improved understanding of the influence of spatial gradients, morphology, and internal microstructures of ore pellets on reduction efficiency and metallization during HyDR. For this purpose, commercial DR pellets were investigated using synchrotron high-energy X-ray diffraction and electron microscopy in conjunction with electron backscatter diffraction and chemical probing. Revealing the interplay of different phases with internal interfaces, free surfaces, and associated nucleation and growth mechanisms provides a basis for developing tailored ore pellets that are highly suited for a fast and efficient HyDR. © 2022, The Author(s).

We describe a novel computational framework based on the cut finite element method (CutFEM) for process-oriented simulation in mechanized tunneling. The framework incorporates all relevant components required for the simulation of the tunnel advance process, namely the ground, the staged installation of the lining support, the tail void grouting and the tunnel boring machine. We demonstrate that CutFEM concepts can significantly facilitate the modeling, discretization and coupling of the different components, while maintaining the same accuracy as the standard boundary-fitted finite element method. The proposed CutFEM technology, which is being applied and investigated in the context of advancement simulations in mechanized tunneling for the first time, enables the seamless analysis of an arbitrary number of different tunnel alignment variants on the same structured background mesh without the need to set up a new model for each variant. This is a shift of paradigm in simulation-supported tunnel design, as the CutFEM based framework considerably facilitates a direct integration of geometric, building information and simulation models in early stages of a tunnel project. The simulation model allows for the damage assessment of the buildings during tunnel advancement with regards to different excavation scenarios, as shown in the numerical examples in this paper. © 2022 Elsevier Ltd

Advanced lightweight high-strength steels are often compositionally and microstructurally complex. While this complex feature enables the activation of multiple strengthening and strain-hardening mechanisms, it also leads to a complicated damage behavior, especially in the presence of hydrogen (H). The mechanisms of hydrogen embrittlement (HE) in these steels need to be properly understood for their successful application. Here we focus on a high-Mn (∼20 wt.%), high-Al (∼9 wt.%) lightweight steel with an austenite (∼74 vol.%) and ferrite (∼26 vol.%) two-phase microstructure and unravel the interplay of H-related decohesion and localized plasticity and their effects on failure. We find that HE in this alloy is driven by both, H-induced intergranular cracking along austenite-ferrite phase boundaries and H-induced transgranular cracking inside the ferrite. The former phenomenon is attributed to the mechanism of H-enhanced decohesion. For the latter damage behavior, systematic scanning electron microscopy-based characterization reveals that only parts of the transgranular cracks inside ferrite are straight (∼52% proportion) and along the cleavage plane. Other portions of these transgranular cracks show a distinct deviation from the {100} planes at certain stages of crack propagation, which is associated with a mechanism transition from the H-enhanced transgranular decohesion of the ferrite by cleavage to the H-associated localized plasticity occurring near the propagating crack tip. These mechanisms are further discussed based on a detailed comparison to the damage behavior at cryogenic temperatures and on the nanoindentation results performed with in-situ H-charging. The findings provide new insights into the understanding of the interplay between different HE mechanisms operating in high-strength alloys and their synergistic effects on damage evolution. © 2022 Acta Materialia Inc.

The choice of substrate orientation for semiconductor quantum dot circuits offers opportunities for tailoring spintronic properties such as g-factors for specific functionality. Here, we demonstrate the operation of a few-electron double quantum dot circuit fabricated from a (110)-oriented GaAs quantum well. We estimate the in-plane electron g-factor from the profile of the enhanced inter-dot tunneling (leakage) current near-zero magnetic field. Spin blockade due to Pauli exclusion can block inter-dot tunneling. However, this blockade becomes inactive due to hyperfine interaction mediated spin flip-flop processes between electron spin states and the nuclear spin of the host material. The g-factor of absolute value ∼0.1 found for a magnetic field parallel to the direction [1 ¯ 10] is approximately a factor of four lower than that for comparable circuits fabricated from a material grown on widely employed standard (001) GaAs substrates and is in line with reported values determined by purely optical means for quantum well structures grown on (110) GaAs substrates. © 2022 Author(s).

Traditionally, interatomic potentials assume local bond formation supplemented by long-range electrostatic interactions when necessary. This ignores intermediate-range multiatom interactions that arise from the relaxation of the electronic structure. Here, we present the multilayer atomic cluster expansion (ml-ACE) that includes collective, semi-local multiatom interactions naturally within its remit. We demonstrate that ml-ACE significantly improves fit accuracy and efficiency compared to a local expansion on selected examples and provide physical intuition to understand this improvement. © 2022 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Aluminum oxides, oxyhydroxides, and hydroxides are important in different fields of application due to their many attractive properties. However, among these materials, tohdite (5Al2O3·H2O) is probably the least known because of the harsh conditions required for its synthesis. Herein, we report a straightforward methodology to synthesize tohdite nanopowders (particle diameter ∼13 nm, specific surface area ∼102 m2g-1) via the mechanochemically induced dehydration of boehmite (γ-AlOOH). High tohdite content (about 80%) is achieved upon mild ball milling (400 rpm for 48 h in a planetary ball mill) without process control agents. The addition of AlF3can promote the crystallization of tohdite by preventing the formation of the most stable α-Al2O3, resulting in the formation of almost phase-pure tohdite. The availability of easily accessible tohdite samples allowed comprehensive characterization by powder X-ray diffraction, total scattering analysis, solid-state NMR (1H and 27Al), N2-sorption, electron microscopy, and simultaneous thermal analysis (TG-DSC). Thermal stability evaluation of the samples combined with structural characterization evidenced a low-temperature transformation sequence: 5Al2O3·H2O → κ-Al2O3→ α-Al2O3. Surface characterization via DRIFTS, ATR-FTIR, D/H exchange experiments, pyridine-FTIR, and NH3-TPD provided further insights into the material properties. © 2022 American Chemical Society. All rights reserved.

The three-dimensional (3D) distribution of individual atoms on the surface of catalyst nanoparticles plays a vital role in their activity and stability. Optimising the performance of electrocatalysts requires atomic-scale information, but it is difficult to obtain. Here, we use atom probe tomography to elucidate the 3D structure of 10 nm sized Co2FeO4 and CoFe2O4 nanoparticles during oxygen evolution reaction (OER). We reveal nanoscale spinodal decomposition in pristine Co2FeO4. The interfaces of Co-rich and Fe-rich nanodomains of Co2FeO4 become trapping sites for hydroxyl groups, contributing to a higher OER activity compared to that of CoFe2O4. However, the activity of Co2FeO4 drops considerably due to concurrent irreversible transformation towards CoIVO2 and pronounced Fe dissolution. In contrast, there is negligible elemental redistribution for CoFe2O4 after OER, except for surface structural transformation towards (FeIII, CoIII)2O3. Overall, our study provides a unique 3D compositional distribution of mixed Co-Fe spinel oxides, which gives atomic-scale insights into active sites and the deactivation of electrocatalysts during OER. © 2022, The Author(s).

Ball milling is growing increasingly important as an alternative synthetic tool to prepare catalytic materials. It was recently observed that supported metal catalysts could be directly obtained upon ball milling from the coarse powders of metal and oxide support. Moreover, when two compatible metal sources are simultaneously subjected to the mechanochemical treatment, bimetallic nanoparticles are obtained. A systematic investigation was extended to different metals and supports to understand better the mechanisms involved in the comminution and alloying of metal nanoparticles. Based on this, a model describing the role of metal-support interactions in the synthesis was developed. The findings will be helpful for the future rational design of supported metal catalysts via dry ball milling. © 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.

Pulsed laser ablation is steadily gaining popularity in micromachining to keep pace with the increasing demand for precision manufacturing and functional surfaces. However, efficient laser processing under atmospheric conditions primarily suffers from particle redeposition and therefore requires additional cleaning steps to obtain high surface quality. To reduce additional cleanings steps after manufacturing, laser ablation in liquid allows for a significant reduction in particle redeposition as particles rapidly cool down and penetrate into the liquid without stitching to the surface. However, laser ablation in liquid is accompanied by the complex interaction between the hot molten material, the generated plasma and the over-critical liquid in the ablation zone. During this interaction, chemical reactions at the surface can take place and cause a persistent change of surface chemistry. Since the surface chemistry is a key aspect for micromachining, the interaction has to be studied to determine whether laser processing in liquids can be a feasible alternative to laser processing under ambient atmospheric conditions while reducing the problem of redeposition. Here, we present the results on the change of surface chemistry by laser ablation in liquid of a pristine silicon substrate. The micromachining process is either performed in an aqueous or gaseous environment and studied in dependence of laser intensity. The changes in surface chemistry are evaluated by micro-Raman spectroscopy and EDX. Copyright © 2022 SPIE.

Nanoparticulate CoxFe3−xO4 (0 ≤ x ≤ 3) catalysts were prepared by spray-flame synthesis and applied in liquid-phase cyclohexene oxidation with O2 as oxidant. The catalysts were characterized in detail using N2 physisorption, XRD, TEM, XPS, FTIR, Raman, and Mössbauer spectroscopy. A volcano plot was obtained for the catalytic activity in cyclohexene oxidation as a function of the Co content with a maximum at x = 1. Thus, CoFe2O4 achieved the highest degree of cyclohexene conversion and the fastest decomposition rate of the key intermediate 2-cyclohexene-1-hydroperoxide. Kinetic studies and a stability test were performed over CoFe2O4, showing that cyclohexene oxidation follows first-order kinetics with an apparent activation energy of 58 kJ mol−1. The catalytic hydroperoxide decomposition during cyclohexene oxidation was further investigated using H2O2 and tert-butyl hydroperoxide as simpler surrogates resulting in similar volcano-type correlations. The increase in catalytic activity with increasing Fe content with a maximum at x = 1 is ascribed to the increasing concentration of octahedrally coordinated Co2+ cations in the spinel structure leading to the presence of coordinatively unsaturated Co3c2+ surface sites, which are identified to be the most active sites for 2-cyclohexene-1-hydroperoxide decomposition in cyclohexene oxidation. © 2022 The Royal Society of Chemistry

When they are damaged or injured, soft biological tissues are able to self-repair and heal. Mechanics is critical during the healing process, as the damaged extracellular matrix (ECM) tends to be replaced with a new undamaged ECM supporting homeostatic stresses. Computational modeling has been commonly used to simulate the healing process. However, there is a pressing need to have a unified thermodynamics theory for healing. From the viewpoint of continuum damage mechanics, some key parameters related to healing processes, for instance, the volume fraction of newly grown soft tissue and the growth deformation, can be regarded as internal variables and have related evolution equations. This paper is aiming to establish this unified framework inspired by thermodynamics for continuum damage models for healing of soft biological tissues, in which we introduce for the first time the coupled description of damage/healing and growth/remodeling based on thermodynamic considerations. Therefore, this new model is more concise and offers a universal approach to simulate the healing process. Three numerical examples are provided to demonstrate the effectiveness of the proposed model, which are in good agreement with the existing works, including an application for balloon angioplasty in an arteriosclerotic artery with a fiber cap. © 2021

Introduction: Coracoid fractures after arthroscopic treatment of acromioclavicular (AC) joint separations lead to poor clinical outcomes. In this study, different configurations of bone tunnels in the lateral clavicle and coracoid were examined concerning the amount of stress induced in the coracoid. Methods: An authentic 3D finite element model of an ac joint was established. Three 2.4 mm bone tunnels were inserted in the lateral clavicle, which were situated above, medially and laterally of the coracoid. Then, two 2.4 mm bone tunnels were inserted in the latter, each simulating a proximal and a distal suture button position. Von Mises stress analyses were performed to evaluate the amount of stress caused in the coracoid process by the different configurations. Then, a clinical series of radiographs was examined, the placement of the clavicle drill hole was analyzed and the number of dangerous configurations was recorded. Results: The safest configuration was a proximal tunnel in the coracoid combined with a lateral bone tunnel in the clavicle, leading to an oblique traction at the coracoid. A distal bone tunnel in the coracoid and perpendicular traction as well as a proximal tunnel in the coracoid with medial traction caused the highest stresses. Anatomical placement of the clavicle drill hole does lead to configurations with smaller stresses. Conclusion: The bone tunnel placement with the smallest amount of shear stresses was found when the traction of the suture button was directed slightly lateral, towards the AC joint. Anatomical placement of the clavicle drill hole alone was not sufficient in preventing dangerous configurations. Level of evidence: Controlled laboratory study. © 2022, The Author(s).

This paper discusses an application of machine-learning solution for processing of the dynamical sensing responses collected with a multiplexed microresonator detector. Performance of a long short-term memory network (LSTM) out of bidirectional and dropout layers is analyzed on example of the experimental data collected for a temporal gradient of the local refractive index. We experimentally demonstrate the possibility for analyte parameters prediction with accuracy of > 99% based on a set of complex non-linear highly specific time sequences of the intensities radiated by the microcavities which is obtained within a timescale 4 times shorter than required to reach the steady state. Optimization possibilities in terms of the number of microresonator signals to consider for the LSTM network training along with the complexity of its architecture are analyzed. © 2022 SPIE.

Single entity electrochemistry is employed to gain insights into ion solvation in solvent mixtures. To this end, the time required for the oxidation of individual indicator nanoparticles to sparingly soluble products is used to probe ionic diffusion, and hence gain new insights into the solvation properties of solvent mixtures. Herein, water-ethanol or water-methanol mixtures of different compositions are analyzed following this new approach, using silver nanoparticle oxidation in the presence of chloride and iodide as a complementary indicator reaction. For increasing concentrations of the bulkier alcohol molecules in the mixtures with water, an increasing content of alcohol molecules in the halide's solvation shell is detected by the observation of hindered halide diffusion. The extent of this solvent replacement is shown to scale with the charge density of the ions and the experimental results are rationalized with respect to literature-derived thermodynamic data, highlighting the ability of single entity electrochemistry to explore solvation in solvent mixtures. © 2022 The Authors. ChemElectroChem published by Wiley-VCH GmbH.

The use of photosynthetic biohybrids to drive redox reactions in vitro is a promising strategy due to the natural abundance and high quantum efficiency of the bio-components. Here, we present different tools for the fabrication of photosystem I-based biohybrid devices by using redox-active polymers, 3D-structured electrodes as well as additional light-harvesting antennae modules. © 2022, Die Autorinnen und Autoren.

Spokes appear as zones of increased ionisation in magnetron sputtering discharges. They rotate in front of a 2″ target at a natural frequency between a few 10 kHz and several 100 kHz and move in E → × B → or anti E → × B → direction depending on plasma power. Spokes are known to cause strong gradients in plasma density and potential and can, thus, increase the ion transport from target to substrate. Here, we explore the possibility to control spokes by applying a given frequency f to a set of control probes around the plasma to lock the spoke movement. The efficiency of this locking is analyzed by diagnostic probes and energy resolved mass spectrometry, which measure the integrated ion fluxes leaving the magnetic trap region. It was found that the spoke movement could be locked to the external control signal at frequency f around the natural spoke frequencies f 0. The additional control signal affects the ion flux twofold: (i) a 15% increase in ion flux towards the substrate and a 15% reduction in radial direction irrespective of control frequency is observed, which is explained by a change in plasma confinement since electric fluctuations at the separatrix are induced; (ii) the locking at f causes an increase in ion current in normal as well as in radial direction for f < f 0 and a reduction for f > f 0. This is explained by either longer or shorter residence times of ions in the electric fields caused by the spoke, or by an enhancement of these fields caused by the control. Using this spoke controlling technique an overall increase of ion flux towards the substrate of up to 30% was realized. © 2022 The Author(s). Published by IOP Publishing Ltd.

The TriplexPro™-210 plasma spray torch (Oerlikon Metco) is a three-cathode plasma generator. It became a kind of workhorse for the wide range of tasks handled at the Jülich Thermal Spray Center (JTSC). Compared to conventional single-cathode torches, the cascaded design of the nozzle suggests low fluctuations of the arc and thus high stability. However, after a certain time, degradation sets in even with such a torch, impairing the reliability of the process. It is therefore important to detect indications of performance loss in time and not only during the inspection of the deposited layer. In this study, standard samples of YSZ thermal barrier coatings were sprayed regularly over a period of two years. Operational data and feedstock characteristics were collected and correlated with the area-specific mass deposition. It turned out that the measured substrate surface temperature showed a distinct correlation. Searching for the reasons for the temperature variations, several process parameters could be ruled out as they are monitored by calibrated sensors, controlled, and their time course is recorded by the control unit. Moreover, there are other parameters, which can have a considerable impact such as the robot alignment or the substrate cooling conditions. However, the purposeful experimental variation of such variables resulted in a variability of the mass deposition being considerably smaller than observed over the two years. Thus, it can be concluded that torch degradation had a pronounced effect, too. The substrate surface temperature can be used as indicator for the torch status and the reliability of the spray process. © 2022 by the authors.

Electrocatalytic recycling of waste nitrate (NO3−) to valuable ammonia (NH3) at ambient conditions is a green and appealing alternative to the Haber−Bosch process. However, the reaction requires multi-step electron and proton transfer, making it a grand challenge to drive high-rate NH3 synthesis in an energy-efficient way. Herein, we present a design concept of tandem catalysts, which involves coupling intermediate phases of different transition metals, existing at low applied overpotentials, as cooperative active sites that enable cascade NO3−-to-NH3 conversion, in turn avoiding the generally encountered scaling relations. We implement the concept by electrochemical transformation of Cu−Co binary sulfides into potential-dependent core−shell Cu/CuOx and Co/CoO phases. Electrochemical evaluation, kinetic studies, and in−situ Raman spectra reveal that the inner Cu/CuOx phases preferentially catalyze NO3− reduction to NO2−, which is rapidly reduced to NH3 at the nearby Co/CoO shell. This unique tandem catalyst system leads to a NO3−-to-NH3 Faradaic efficiency of 93.3 ± 2.1% in a wide range of NO3− concentrations at pH 13, a high NH3 yield rate of 1.17 mmol cm−2 h−1 in 0.1 M NO3− at −0.175 V vs. RHE, and a half-cell energy efficiency of ~36%, surpassing most previous reports. © 2022, The Author(s).

The non-oxidative dehydrogenation of methanol to formaldehyde is considered a dream reaction compared with the classical oxidative route, because the valuable coupled product hydrogen is formed instead of water, and the produced anhydrous formaldehyde is highly suitable for the further synthesis of oxygenated synthetic fuels. This study reports on the high catalytic performance of pure β-Ga2O3 in this reaction at temperatures between 500 °C and 650 °C. At 550 °C and a GHSV of 45500 h−1, an initial selectivity to formaldehyde of 77 % was obtained at a methanol conversion of 72 %. Performing the reaction at temperatures beyond this range and lower GHSV resulted in a lower formaldehyde selectivity. The catalyst suffered from deactivation caused by formation of carbon deposits, but it was possible to regenerate its initial activity at 500 °C and 550 °C completely by an oxidative treatment. Irreversible deactivation occurred at 650 °C due to partial volatilization of Ga2O3. © 2022 The Authors. ChemCatChem published by Wiley-VCH GmbH.

This study presents a new laser-cladding-based additive manufacturing technique named Clad2Z. Using a robot-mounted confocal powder nozzle with axial infrared laser beam, ceramic columns with a diameter of 450 µm and an adjustable height are developed. Influence of laser parameters and robot movements on shape and microstructure is analyzed. As an example application, the common material yttria-stabilized zirconia (YSZ) is used to deposit columnar-structured thermal barrier coatings (TBCs). The excellent thermal cycling performance of the Clad2Z samples is demonstrated by burner rig tests and comparing lifetime and failure mechanism with conventional TBC systems. © 2022 The Authors. Advanced Materials Technologies published by Wiley-VCH GmbH.

Results are presented reporting on the martensite domain variant selection and stress-induced martensite morphology in [001]-oriented superelastic Co49Ni21Ga30 shape memory alloy (SMA) single crystals under tensile load. In situ neutron diffraction, as well as in situ optical- and confocal laser scanning microscopy were conducted focusing on three differently treated samples, i.e. in the as-grown, solution-annealed and aged condition. An aging treatment performed at 350 °C promotes the precipitation of nanoprecipitates. These second phase precipitates contribute to an increase of the number of habit plane interfaces, while reducing lamellar martensite plate thickness compared to the as-grown and solution-annealed (precipitate free) samples. During tensile loading, all samples show a stress-induced formation of martensite, characterized by one single domain variant (“detwinned”) and one set of parallel habit planes in a shear band. The results clearly show that γ’ nanoprecipitates do not necessarily promote multi-variant interaction during tensile loading. Thus, reduced recoverability in Co-Ni-Ga SMAs upon aging cannot be solely attributed to this kind of interaction as has been proposed in literature so far. © 2022

Thermal barrier coatings (TBCs) are commonly used to protect gas turbine components from high temperatures and oxidation. Such coatings consist of ceramic top coats and metallic bond coats. The mismatch in thermal expansion of the top coat, the bond coat and the component material is one main factor leading to the failure of the coating system. Columnar-structured top coats offer an enhanced tolerance to the strain during thermal cycling. On a flat bond coated surface, these TBCs reach higher thermal cycling performance. However, on rough surfaces, as used for thermal spray coatings, the performance of these thermal barrier coatings seems to be restricted or even stays below the performance of atmospheric-plasma-sprayed (APS) thermal barrier coatings. This low performance is linked to out-of-plane stresses at the interface between the top coat and the bond coat. In this study, a thin additional oxide-dispersion-strengthened (ODS) bond coat with high alumina content provides a reduced mismatch of the coefficient of thermal expansion (CTE) between the top coat and the bond coat. Columnar suspension plasma sprayed (SPS), yttria-stabilized zirconia (YSZ) TBCs were combined with low-CTE ODS bond coats. The behavior of these TBCs was characterized with respect to thermal cycling performance and degradation in a burner-rig facility. The comparison showed an up-to-four-fold increase in the performance of the new system. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

In this work, a modular, multi-electrode surface dielectric barrier discharge system for the decomposition of polluted air streams at high volumetric flows, necessary for industrial applications, is designed and constructed. The system is demonstrated for the decomposition of butoxyethanol and n-butane in ambient air flows of up to almost 500 slm (standard litres per minute) (≙ 30 m3 h−1) at concentrations between 50 ppm and 1000 ppm. With an energy density of (78.3 ± 3.6) J L−1 a maximum relative conversion of about 27% of butoxyethanol is achieved. n-Butane was used to enable comparison with previous studies. Here it could be demonstrated that the scaled-up source achieved higher conversion at lower energy densities in comparison to the original design used at lower volumetric flow rates. Additionally, the density of ozone, which is a toxic by-product of the overall process, was measured in the exhaust gas under different operating conditions and its degradation with activated carbon filters was studied. At an energy density of 79.6 J L−1 a maximum ozone molecule flow of (9.02 ± 0.19) × 1018 s−1 was measured which decreases with increasing energy density, because among other possible effects the rising temperature accelerates its decay. One of the activated carbon filters was able to reduce the concentration of toxic ozone by 100% under conditions where a preheated airstream is used. © 2022 The Royal Society of Chemistry.

It has been recently shown that doping-like properties can be introduced into functional ceramics by inducing dislocations. Especially for TiO2, donor and acceptor-like behavior were observed depending on the type of introduced mesoscopic dislocation network. However, these early reports could not fully elucidate the mechanism behind it. In this work, we rationalize the electrical properties of dislocations by targeted microelectrode impedance measurements, local conductivity atomic force microscopy, and Kelvin probe force microscopy on deformed single crystals, comparing dislocation-rich and deficient regions. With the help of finite element method calculations, a semi-quantitative model for the effect of dislocations on the macroscopic electrical properties is developed. The model describes the dislocation bundles as highly conductive regions in which respective space charges overlap and induce temperature-independent, highly stable electronic conductivity. We illustrate the mechanism behind unique electrical properties tailored by introducing dislocations and believe that these results are the cornerstone in developing dislocation-tuned functionality in ceramics. © 2021 Elsevier Ltd

The development of noble-metal-free electrocatalysts is regarded as a key factor for realizing industrial-scale hydrogen production powered by renewable energy sources. Inspired by nature, which uses Fe-and Ni-containing enzymes for efficient hydrogen generation, Fe/Ni-containing chalcogenides, such as oxides and sulfides, received increasing attention as promising electrocatalysts to produce hydrogen. We herein present a novel synthetic procedure for mixed Fe/Ni (oxy)sulfide materials by the controlled (partial) sulfidation of NiFe2O4 (NFO) nanoparticles in H2S-containing atmospheres. The variation in H2S concentration and the temperature allows for a precise control of stoichiometry and phase composition. The obtained sulfidized materials (NFS) catalyze the hydrogen evolution reaction (HER) with increased activity in comparison to NFO, up to −10 and −100 mA cm−2 at an overpotential of approx. 250 and 450 mV, respectively. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

Liquid-infused surfaces are based upon the infusion of a liquid phase into a porous solid material to induce slippery and repellent character. In this context, porous SiOx plasma polymer films represent a relevant candidate for a robust nanoporous carrier layer. Intermittent low-pressure plasma etching of O2/hexamethyldisiloxane-derived coatings is investigated to enhance the intrinsic porosity inherent to residual hydrocarbons in the silica matrix. Simulations of the resulting Si–O ring network structure using reactive molecular dynamics indicate formation of interconnected voids with Si–OH functionalized pore walls allowing water penetration with almost Fickian diffusive behavior. The corresponding porosity of up to 18%, well agreeing with simulations, Fourier-transform infrared spectroscopy, and ellipsometry measurements, was found to be suitable for the liquid infusion of polyethylene glycol molecules into about 80 nm thick SiOx films providing ongoing lubricating properties, thus revealing their suitability as liquid-infused surfaces. © 2022 The Authors. Plasma Processes and Polymers published by Wiley-VCH GmbH.

In this work, a novel in situ auto-reduction strategy was developed to encapsulate uniformly dispersed Pd clusters/nanoparticles in MIL-125-NH2. It is demonstrated that the amino groups in MIL-125-NH2 can react with formaldehyde to form novel reducing groups (-NH[sbnd]CH2OH), which can in situ auto-reduce the encapsulated Pd2+ ions to metallic Pd clusters/nanoparticles. As no additional reductants are required, the strategy limits the aggregation and migration of Pd clusters and the formation of large Pd nanoparticles via controlling the amount of Pd2+ precursor. When applied as catalysts in the hydrogenation of phenol in the aqueous phase, the obtained Pd(1.5)/MIL-125-NH-CH2OH catalyst with highly dispersed Pd clusters/nanoparticles with the size of around 2 nm exhibited 100% of phenol conversion and 100% of cyclohexanone selectivity at 70 °C after 5 h, as well as remarkable reusability for at least five cycles due to the large MOF surface area, the highly dispersed Pd clusters/nanoparticles and their excellent stability within the MIL-125-NH-CH2OH framework. © 2021

Current energy and environmental challenges demand the development and design of multifunctional porous materials with tunable properties for catalysis, water purification, and energy conversion and storage. Because of their amenability to de novo reticular chemistry, metal-organic frameworks (MOFs) have become key materials in this area. However, their usefulness is often limited by low chemical stability, conductivity and inappropriate pore sizes. Conductive two-dimensional (2D) materials with robust structural skeletons and/or functionalized surfaces can form stabilizing interactions with MOF components, enabling the fabrication of MOF nanocomposites with tunable pore characteristics. Graphene and its functional derivatives are the largest class of 2D materials and possess remarkable compositional versatility, structural diversity, and controllable surface chemistry. Here, we critically review current knowledge concerning the growth, structure, and properties of graphene derivatives, MOFs, and their graphene@MOF composites as well as the associated structure-property-performance relationships. Synthetic strategies for preparing graphene@MOF composites and tuning their properties are also comprehensively reviewed together with their applications in gas storage/separation, water purification, catalysis (organo-, electro-, and photocatalysis), and electrochemical energy storage and conversion. Current challenges in the development of graphene@MOF hybrids and their practical applications are addressed, revealing areas for future investigation. We hope that this review will inspire further exploration of new graphene@MOF hybrids for energy, electronic, biomedical, and photocatalysis applications as well as studies on previously unreported properties of known hybrids to reveal potential "diamonds in the rough". ©

The use of enzymes as catalysts in chemical synthesis offers advantages in terms of clean and highly selective transformations. Galactose oxidase (GalOx) is a remarkable enzyme with several applications in industrial conversions as it catalyzes the oxidation of primary alcohols. We have investigated the wiring of GalOx with a redox polymer; this enables mediated electron transfer with the electrode surface for its potential application in biotechnological conversions. As a result of electrochemical regeneration of the catalytic center, the formation of harmful H2O2 is minimized during enzymatic catalysis. The introduced bioelectrode was applied to the conversion of bio-renewable platform materials, with glycerol as model substrate. The biocatalytic transformations of glycerol and 5-hydroxymethylfurfural (HMF) were investigated in a circular flow-through setup to assess the possibility of substrate over-oxidation, which is observed for glycerol oxidation but not during HMF conversion. © 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.

Enhancing the efficiency of water electrolysis, which can be severely impacted by the nucleation and growth of bubbles, is key in the energy transition. In this combined experimental and numerical study, in-situ bubble evolution and dissolution processes are imaged and compared to numerical simulations employing the immersed boundary method. We find that it is crucial to include solutal driven natural convection in order to represent the experimentally observed bubble behaviour even though such effects have commonly been neglected in modelling efforts so far. We reveal how the convective patterns depend on current densities and bubble spacings, leading to distinctively different bubble growth and shrinkage dynamics. Bubbles are seen to promote the convective instability if their spacing is large (≥4 mm for the present conditions), whereas the onset of convection is delayed if the inter-bubble distance is smaller. Our approach and our results can help devise efficient mass transfer solutions for gas evolving electrodes. © 2021 The Authors

Compressive stresses in sputter deposited thin films are generally assumed to be caused by forward sputtered (peened) built-in particles and entrapped working gas atoms. While the former are assumed to be predominant, the effect of the latter on interaction dynamics and thin film properties is scarcely clarified (concurrent or causative). The overlay of the ion bombardment induced processes renders an isolation of their contribution impracticable. This issue is addressed by two molecular dynamics case studies considering the sputter deposition of Al thin films in Ar working gas. First, Ar atoms are fully retained. Second, they are artificially neglected, as implanted Ar atoms are assumed to outgas anyhow and not alter the ongoing dynamics significantly. Both case studies share common particle dose impinging Al(001) surfaces. Ion energies from 3 to 300 eV and Al / Ar + flux ratios from 0 to 1 are considered. The surface interactions are simulated by hybrid reactive molecular dynamics/force-biased Monte Carlo simulations and characterized in terms of mass density, Ar concentration, biaxial stress, shear stress, ring statistical connectivity profile, Ar gas porosity, Al vacancy density, and root-mean-squared roughness. Implanted Ar atoms are found to form subnanometer sized eventually outgassing clusters for ion energies exceeding 100 eV. They fundamentally govern a variety of surface processes (e.g., forward sputtering/peening) and surface properties (e.g., compressive stresses) in the considered operating regime. © 2022 Author(s).

Single photons role in the development of quantum science and technology. They can carry quantum information over extended distances to act as the backbone of a future quantum internet1 and can be manipulated in advanced photonic circuits, enabling scalable photonic quantum computing2,3. However, more sophisticated devices and protocols need access to multi-photon states with particular forms of entanglement. Efficient light–matter interfaces offer a route to reliably generating these entangled resource states4,5. Here we utilize the efficient and coherent coupling of a single quantum emitter to a nanophotonic waveguide to realize a quantum nonlinear interaction between single-photon wavepackets. We demonstrate the control of a photon using a second photon mediated by the quantum emitter. The dynamical response of the two-photon interaction is experimentally unravelled and reveals quantum correlations controlled by the pulse duration. Further development of this platform work, which constitutes a new research frontier in quantum optics6, will enable the tailoring of complex photonic quantum resource states. © 2022, The Author(s), under exclusive licence to Springer Nature Limited.

Second nearest neighbor modified embedded atom method (2NN-MEAM) interatomic potentials are developed for the Ni, Re, and Ni-Re binaries. To construct the potentials, density functional theory (DFT) calculations have been employed to calculate fundamental physical properties that play a dominant role in fracture. The potentials are validated to accurately reproduce material properties that correlate with material's fracture behavior. The thus constructed potentials were applied to perform large scale simulations of mode I fracture in Ni and Ni-Re binaries with low Re content. Substitutional Re did not alter the ductile nature of crack propagation, though it resulted in a monotonous increase of the critical stress intensity factor with Re content. © 2021 The Author(s). Published by IOP Publishing Ltd.

The propagation and interaction between surface streamers propagating over dielectric pellets in a packed bed plasma reactor operated in Helium are studied using phase and space resolved optical emission spectroscopy and simulations. Such a discharge is known to generate cathode directed positive streamers in the gas phase at the positions of minimum electrode gap followed by surface streamers that propagate along the dielectric surface. By systematically varying the gap between neighboring dielectric pellets, we observe that a larger gap between adjacent dielectric pellets enhances plasma emission near the contact points of the dielectric structures. In agreement with the experiment, the simulation results reveal that the gap influences the attraction of streamers towards adjacent dielectric pellets via polarization of the surface material and the repulsion induced by nearby streamers. For a smaller gap, the streamer propagation changes from along the surface to propagation through the volume and back to surface propagation due to a combination of repulsion between adjacent streamers, polarization of adjacent dielectric surfaces, as well as acceleration of electrons from the volume towards the streamer head. For a wider gap, the streamer propagates along the surface, but repulsion by neighboring streamers increases the offset between the streamers. The streamer achieves a higher speed near the contact point earlier in the absence of an adjacent streamer, which indicates the role of mutual streamer interaction via repulsion. © 2022 The Author(s). Published by IOP Publishing Ltd.

Phase-field-based models have become common in material science, mechanics, physics, biology, chemistry, and engineering for the simulation of microstructure evolution. Yet, they suffer from the drawback of being computationally very costly when applied to large, complex systems. To reduce such computational costs, a Unet-based artificial neural network is developed as a surrogate model in the current work. Training input for this network is obtained from the results of the numerical solution of initial–boundary-value problems (IBVPs) based on the Fan–Chen model for grain microstructure evolution. In particular, about 250 different simulations with varying initial order parameters are carried out and 200 frames of the time evolution of the phase fields are stored for each simulation. The network is trained with 90% of this data, taking the ith frame of a simulation, i.e. order parameter field, as input, and producing the (i+1)-th frame as the output. Evaluation of the network is carried out with a test dataset consisting of 2200 microstructures based on different configurations than originally used for training. The trained network is applied recursively on initial order parameters to calculate the time evolution of the phase fields. The results are compared to the ones obtained from the conventional numerical solution in terms of the errors in order parameters and the system's free energy. The resulting order parameter error averaged over all points and all simulation cases is 0.005 and the relative error in the total free energy in all simulation boxes does not exceed 1%. © 2022 Elsevier B.V.

Path sampling approaches have become invaluable tools to explore the mechanisms and dynamics of the so-called rare events that are characterized by transitions between metastable states separated by sizable free energy barriers. Their practical application, in particular to ever more complex molecular systems, is, however, not entirely trivial. Focusing on replica exchange transition interface sampling (RETIS) and forward flux sampling (FFS), we discuss a range of analysis tools that can be used to assess the quality and convergence of such simulations, which is crucial to obtain reliable results. The basic ideas of a step-wise evaluation are exemplified for the study of nucleation in several systems with different complexities, providing a general guide for the critical assessment of RETIS and FFS simulations. © 2022 Author(s).

The entropy coefficient is an important quantity to describe thermodynamic processes of battery cells and to model the temperature dependency of the open-circuit voltage. Determining the entropy via potentiometric measurements is often time-consuming. Therefore, several methods were developed to quickly estimate the entropy coefficient. This paper presents a new method, which is relatively simple in its execution and evaluation. The method is based on relating a dynamic temperature change to the cell's voltage change at an induced exponential temperature progression. Due to the dynamic of this process, the measurement time will be reduced compared to the potentiometric method by factor 13 for the executed experiments under its stated conditions. © 2022 Elsevier Ltd

We report the design and one-pot synthesis of Ag-doped BiVO4 embedded in reduced graphene oxide (BiVO4:Ag/rGO) nanocomposites via a hydrothermal processing route. The binary heterojunction photocatalysts exhibited high efficiency for visible light degradation of model dyes and were correspondingly used for the preparation of photocatalytic membranes using polyvinylidene fluoride (PVDF) or polyethylene glycol (PEG)-modified polyimide (PI), respectively. The surface and cross-section images combined with elemental mapping illustrated the effective distribution of the nanocomposites within the polymeric membranes. Photocatalytic degradation efficiencies of 61% and 70% were achieved after 5 h of visible light irradiation using BiVO4:Ag/rGO@PVDF and BiVO4:Ag/rGO@PI (PEG-modified) systems, respectively. The beneficial photocatalytic performance of the BiVO4:Ag/rGO@PI (PEG-modified) membrane is explained by the higher hydrophilicity due to the PEG modification of the PI membrane. This work may provide a rational and effective strategy to fabricate highly efficient photocatalytic nanocomposite membranes with well-contacted interfaces for environmental purification. © 2022 IOP Publishing Ltd.

The full-cell entropy and its temperature dependency were measured for automotive lithium-ion cells with a graphite anode in dependence of the state of charge. Resulting entropy curves can be related to certain characteristic conditions of the graphite anode. Those characteristics are induced by a certain lithium-ion concentrations within the graphite. Comparing the entropy curves of fresh to aged cells shows a shift in the characteristics of these curves at a similar charge input. Those shifts were assigned to a change in the anodic net capacity, enabling an entropy based state of health estimation of the anode. The execution of the differential voltage analysis leads to similar results. © 2022 Elsevier Ltd

High entropy alloys (HEA) comprise a huge search space for new electrocatalysts. Next to element combinations, the optimization of the chemical composition is essential for tuning HEA to specific catalytic processes. Simulations of electrocatalytic activity can guide experimental efforts. Yet, the currently available underlying model assumptions do not necessarily align with experimental evidence. To study deviations of theoretical models and experimental data requires statistically relevant datasets. Here, a combinatorial strategy for acquiring large experimental datasets of multi-dimensional composition spaces is presented. Ru–Rh–Pd–Ir–Pt is studied as an exemplary, highly relevant HEA system. Systematic comparison with computed electrochemical activity enables the study of deviations from theoretical model assumptions for compositionally complex solid solutions in the experiment. The results suggest that the experimentally obtained distribution of surface atoms deviates from the ideal distribution of atoms in the model. Leveraging both advanced simulation and large experimental data enables the estimation of electrocatalytic activity and solid-solution stability trends in the 5D composition space of the HEA system. A perspective on future directions for the development of active and stable HEA catalysts is outlined. © 2022 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH

Capacitively coupled micro atmospheric pressure plasma jets are important tools for the generation of radicals at room temperature for various applications. Voltage waveform tailoring (VWT), which is based on the simultaneous use of a set of excitation frequencies, has been demonstrated to provide an efficient control of the electron energy probability function (EEPF) in such plasmas and, thus, allows optimizing the electron impact driven excitation and dissociation processes as compared to the classical single-frequency operation mode. In this work, the effects of changing the driving frequencies on the spatio-temporally resolved electron power absorption dynamics, the generation of helium metastables and the dissociation of nitrogen molecules are investigated in He/N2 plasmas based on experiments and simulations. We find that under a single-frequency excitation, the plasma and helium metastable densities are enhanced as a function of the driving frequency at a fixed voltage. When using valleys-type driving voltage waveforms synthesized based on consecutive harmonics of the fundamental driving frequency, the spatial symmetry of the electron power absorption dynamics and of the metastable density profile is broken. Increasing the fundamental frequency at a constant voltage is found to drastically enhance the plasma and metastable densities, which is a consequence of the change of the EEPF. Finally, we compare the energy efficiency of the formation of radicals under single-frequency and VWT operation at different driving frequencies. For a given power dissipated in the plasma, VWT yields a higher helium metastable as well as electron density and a higher dissociation rate of N2. © 2021 IOP Publishing Ltd.

Bounded plasmas are characterized by a rapid but smooth transition from quasi-neutrality in the volume to electron depletion close to the electrodes and chamber walls. The thin non-neutral region, the boundary sheath, comprises only a small fraction of the discharge domain but controls much of its macroscopic behavior. Insights into the properties of the sheath and its relation to the plasma are of high practical and theoretical interest. The recently proposed smooth step model (SSM) provides a closed analytical expression for the electric field in a planar, radio-frequency modulated sheath. It represents (i) the space charge field in the depletion zone, (ii) the generalized Ohmic and ambipolar field in the quasi-neutral zone, and (iii) a smooth interpolation for the transition in between. This investigation compares the SSM with the predictions of a more fundamental particle-in-cell/Monte Carlo collisions simulation and finds good quantitative agreement when the assumed length and time scale requirements are met. A second simulation case illustrates that the model remains applicable even when the assumptions are only marginally fulfilled. © 2022 The Author(s). Published by IOP Publishing Ltd.

The water/fluorite interface is of relevance to diverse industrial, environmental, and medical applications. In this contribution we review some of our recent results on the dynamics of water in contact with the solid calcium fluoride at low pH, where localised charge can develop upon fluorite dissolution. We use ab initio molecular dynamics simulations, including the full electronic structure, to simulate the vibrational energy relaxation and to quantify the heterogeneity of the interfacial water molecules. We find that strongly hydrogen-bonded OH groups display very rapid spectral diffusion and vibrational relaxation; for weakly H-bonded OD groups, the dynamics is instead much slower. Detailed analysis of the simulations reveals the molecular origin of energy transport through the local hydrogen-bond network. In particular, we find that the water molecules in the adsorbed layer, whose orientation is pinned by the localised charge defects, can exchange vibrational energy using just half a solvation shell, thanks to the strong dipole-dipole alignment between H-bond donor and acceptor. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2021.

A method for combinatorial sputter deposition of thin films on microparticles is presented. The method is developed for a laboratory-scale magnetron sputter system and uses a piezoelectric actuator to agitate the microparticles through oscillation. Custom-made components enable to agitate up to nine separate batches of particles simultaneously. Due to the agitation, the whole surface of the particles can be exposed to the sputter flux and thus completely covered with a thin film. By sputtering a CrMnFeCoNi high entropy alloy target, separate batches of polystyrene microspheres (500 μm monodisperse diameter), Fe alloy particles (300 μm mean size) and NaCl salt particles (350 μm mean size) were simultaneously coated with a homogeneous thin film. In contrast, a CrMnFeCoNi thin film that was deposited on agglomerating Al particles (5 μm mean size) only partially covers the surface of the particles. By co-sputtering a CrMn, an FeCo and a Ni target, nine separate batches of Al particles (25 μm mean size) were coated with a CrMnFeCoNi thin film with a composition gradient. These depositions demonstrate the ability to coat different types of particles with uniform films (from elemental to multinary compositions) and to deposit films with composition gradients on uniform particles. © 2022 Elsevier B.V.

Tungsten-tungsten carbide (W/W2C) composites are considered as possible structural materials for future nuclear fusion reactors. Here, we report on the effect of helium (He) implantation on microstructure evolution of polycrystalline W/W2C composite consolidated by field-assisted sintering technique (FAST), homogenously implanted at room temperature with 1 MeV 4He+ ions at the fluence of 8 × 1016 ions cm−2 and annealed at 1873 K for 20 minutes. Samples were analysed by scanning and transmission electron microscopy to study the presence and size of He bubbles. Monomodal He bubbles in W (30-80 nm) are limited to point defects and grain boundaries, with a considerable void denuded zone (150 nm). Bubbles do not form in W2C, but at the W|W2C interface and are considerably larger (200-400 nm). The experimental observations on He behaviour and migration in W and W2C were assessed by density functional theory (DFT) calculations, suggesting He migration and accumulation in the composite are determined by the effective He-He binding in clusters, which will give rise to decohesion. In the presence of He clusters, the decohesion of bulk W into free surfaces is energetically highly favourable but not sufficient in the W2C; hence bubbles are only observed in W grains and interfaces and not within bulk W2C. © 2022

Deformation-induced martensitic transformation (DIMT) has been used for designing high-performance alloys to prevent structural failure under static loads. Its effectiveness against fatigue, however, is unclear. This limits the application of DIMT for parts that are exposed to variable loads, although such scenarios are the rule and not the exception for structural failure. Here we reveal the dual role of DIMT in fatigue crack growth through in situ observations. Two antagonistic fatigue mechanisms mediated by DIMT are identified, namely, transformation-mediated crack arresting, which prevents crack growth, and transformation-mediated crack coalescence, which promotes crack growth. Both mechanisms are due to the hardness and brittleness of martensite as a transformation product, rather than to the actual transformation process itself. In fatigue crack growth, the prevalence of one mechanism over the other critically depends on the crack size and the mechanical stability of the parent austenite phase. Elucidating the two mechanisms and their interplay allows for the microstructure design and safe use of metastable alloys that experience fatigue loads. The findings also generally reveal how metastable alloy microstructures must be designed for materials to be fatigue-resistant. © 2022 National Academy of Sciences. All rights reserved.

Cementite (Fe3C) plays a major role in the tribological performance of rail and bearing steels. Nonetheless, the current understanding of its deformation behavior during wear is limited because it is conventionally embedded in a matrix. Here, we investigate the deformation and chemical evolution of bulk polycrystalline cementite during single-pass sliding at a contact pressure of 31 GPa and reciprocating multi-pass sliding at 3.3 GPa. The deformation behavior of cementite was studied by electron backscatter diffraction for slip trace analysis and transmission electron microscopy. Our results demonstrate activation of several deformation mechanisms below the contact surface: dislocation slip, shear band formation, fragmentation, grain boundary sliding, and grain rotation. During sliding wear, cementite ductility is enhanced due to the confined volume, shear/compression domination, and potentially frictional heating. The microstructural alterations during multi-pass wear increase the subsurface nanoindentation hardness by up to 2.7 GPa. In addition, we report Hägg carbide (Fe5C2) formation in the uppermost deformed regions after both sliding experiments. Based on the results of electron and X-ray diffraction, as well as atom probe tomography, we propose potential sources of excess carbon and mechanisms that promote the phase transformation. © 2022 The Author(s)

Understanding the acid/base behavior of environmentally relevant organic acids is of key relevance for accurate climate modelling. Here we investigate the effect of pH on the (de)protonation state of pyruvic acid at the air-water interface and in bulk by using the analytical techniques surface-specific vibrational sum frequency generation and attenuated total reflection spectroscopy. To provide a molecular interpretation of the observed behavior, simulations are carried out using a free energy perturbation approach in combination with electronic structure-based molecular dynamics. In both the experimental and theoretical results we observe that the protonated form of pyruvic acid is preferred at the air-water interface. The increased proton affinity is the result of the specific microsolvation at the interface. © 2022 The Royal Society of Chemistry

Electrode erosion through continual long-timescale operation (60 min) of identical twin surface dielectric barrier discharges (twin SDBDs) powered either by a microsecond (μs) or a nanosecond timescale (ns) voltage source is investigated. The twin SDBDs are characterized using current-voltage measurements, optical emission spectroscopy, and phase integrated ICCD imaging. The temporally and spatially averaged gas temperature, consumed electric power, and effective discharge parameters (reduced electric field, and electron density) are measured. The μs twin SDBD is shown to operate in a filamentary mode while the ns twin SDBD is shown to operate in a more homogeneous mode (i.e. non filamentary). Despite a similarity of the effective discharge parameters in both the μs and ns twin SDBD, erosion of the nickel coated electrodes caused by operation of the twin SDBD differs strongly. Only the formation of a moderate number of nickel oxide species is observed on the surface of the ns twin SDBD electrodes. In contrast, the nickel coated electrodes are locally melted and considerably higher densities of oxides are observed around the eroded areas of the μs twin SDBD, due to the filamentary nature of the discharge. © 2022 The Author(s). Published by IOP Publishing Ltd.

Abstract: Alloys processed by laser powder-bed fusion show distinct microstructures composed of dislocation cells, dispersed nanoparticles, and columnar grains. Upon post-build annealing, such alloys show sluggish recrystallization kinetics compared to the conventionally processed counterpart. To understand this behavior, AISI 316L stainless steel samples were constructed using the island scan strategy. Rhodonite-like (MnSiO3) nanoparticles and dislocation cells are found within weakly-textured grains in the as-built condition. Upon isothermal annealing at 1150 °C (up to 2880 min), the nucleation of recrystallization occurs along the center of the melt pool, where nuclei sites, high stored elastic energy, and local large misorientation are found in the as-built condition. The low value of the Avrami coefficient (n = 1.16) can be explained based on the non-random distribution of nucleation sites. The local interaction of the recrystallization front with nanoparticles speeds up their coarsening causing the decrease of the Zener-Smith pinning force. This allows the progression of recrystallization in LPBF alloys, although sluggish. These results allow us to understand the progress of recrystallization in LPBF 316L stainless steel, shedding light on the nucleation mechanisms and on the competition between driving and dragging pressures in non-conventional microstructures. They also help to understand the most relevant microstructural aspects applicable for tuning microstructures and designing new LPBF alloys. Graphical abstract: [Figure not available: see fulltext.] © 2022, The Author(s).

Ever more stringent regulations on greenhouse gas emissions from transportation motivate efforts to revisit materials used for vehicles1. High-strength aluminium alloys often used in aircrafts could help reduce the weight of automobiles, but are susceptible to environmental degradation2,3. Hydrogen ‘embrittlement’ is often indicated as the main culprit4; however, the exact mechanisms underpinning failure are not precisely known: atomic-scale analysis of H inside an alloy remains a challenge, and this prevents deploying alloy design strategies to enhance the durability of the materials. Here we performed near-atomic-scale analysis of H trapped in second-phase particles and at grain boundaries in a high-strength 7xxx Al alloy. We used these observations to guide atomistic ab initio calculations, which show that the co-segregation of alloying elements and H favours grain boundary decohesion, and the strong partitioning of H into the second-phase particles removes solute H from the matrix, hence preventing H embrittlement. Our insights further advance the mechanistic understanding of H-assisted embrittlement in Al alloys, emphasizing the role of H traps in minimizing cracking and guiding new alloy design. © 2022, The Author(s).

Chirality switching of self-assembled molecular structures is of potential interest for designing functional materials but is restricted by the strong interaction between the embedded molecules. Here, we report on an unusual approach based on reversible chirality changes of self-assembled oligomers using variable-temperature scanning tunneling microscopy supported by quantum mechanical calculations. Six functionalized diazomethanes each self-assemble into chiral wheel-shaped oligomers on Ag(111). At 130 K, a temperature far lower than expected, the oligomers change their chirality even though the molecules reside in an embedded self-assembled structure. Each chirality change is accompanied by a slight center-of-mass shift. We show how the identical activation energies of the two processes result from the interplay of the chirality change with surface diffusion, findings that open the possibility of implementing various functional materials from self-assembled supramolecular structures. © 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.

Although the formation of insulating ionic layers on metal surfaces has been well studied, their growth mechanisms are still controversial. Here, we report several innovative approaches to trigger in situ growth to understand this growth mechanism. The modification of the layer and its in situ growth is followed by time-lapsed scanning tunneling microscopy at room temperature with atomic resolution. The NaBr molecules form bilayer and trilayer islands when deposited at room temperature. These stable layers begin to disintegrate when the voltage exceeds the threshold voltage during scanning. The molecules released from the modified layer subsequently attach to the preexisting layer in a predefined scan region. Scanning of two neighboring trilayer islands traps the mobile molecule between them, leading to their coalescence. Time-lapsed measurements offer a step-by-step realization of the in situ controlled growth of an ionic layer at the atomic scale. © 2022 American Chemical Society.

Entanglement is the fuel of advanced quantum technology, enabling, e.g., measurement-based quantum computing and loss-tolerant encoding of quantum information. In photonics, entanglement has traditionally been generated probabilistically, requiring massive multiplexing for scaling up to many photons. An alternative approach utilizing quantum emitters in nanophotonic devices can realize deterministic generation of entangled photons. However, such sources generate polarization entanglement that is incompatible with spatial dual-rail qubit encoding employed in scalable photonic quantum-computing platforms utilizing integrated circuits. Here we propose and experimentally realize an on-demand source of dual-rail photon pairs using a quantum dot in a planar nanophotonic waveguide. The source exploits the cascaded decay of a biexciton state and chiral light-matter coupling to achieve deterministic generation of spatial dual-rail Bell pairs with the amount of entanglement determined by the chirality. The operational principle can readily be extended to multiphoton entanglement generation required for efficient preparation of resource states for photonic quantum computing. © 2022 authors. Published by the American Physical Society.

Laser additive manufacturing (LAM) techniques, such as laser-powder bed fusion (L-PBF) or laser-directed energy deposition (L-DED), allow for the production of complex-shaped parts by either the local melting of a metallic powder bed by a laser beam (L-PBF) or a local application and laser beam melting of powder material by a nozzle (L-DED). In the case of carbon-martensitic tool steels, their cold crack susceptibility limits their LAM processability and is usually counteracted by substrate preheating. As preheating can increase the oxygen take-up of the powder and alter the part microstructure, it can be disadvantageous for part quality and powder reusability. In this study, it is investigated a carbon-martensitic steel designed for the production of parts with low crack density by LAM without preheating, focusing on the microstructure and hardness of the L-PBF- and L-DED-manufactured steel. The steel can be LAM-processed without preheating, resulting in specimens with low crack densities and martensitic microstructure with retained austenite. The hardness of the as-built material (L-PBF: 542HV30 and L-DED: 623HV30) is increased by quenching and tempering up to 693HV30. Direct tempering of the as-built specimen without previous quenching leads to a shift of the secondary hardness maximum from 500 to 530 °C. © 2022 The Authors. Steel Research International published by Wiley-VCH GmbH.

In recent years, many types of machine learning potentials (MLPs) have been introduced, which are able to represent high-dimensional potential-energy surfaces (PESs) with close to first-principles accuracy. Most current MLPs rely on atomic energy contributions given as a function of the local chemical environments. Frequently, in addition to total energies, atomic forces are also used to construct the potentials, as they provide detailed local information about the PES. Since many systems are too large for electronic structure calculations, obtaining reliable reference forces from smaller subsystems, such as molecular fragments or clusters, can substantially simplify the construction of the training sets. Here, we propose a method to determine structurally converged molecular fragments, providing reliable atomic forces based on an analysis of the Hessian. The method, which serves as a locality test and allows us to estimate the importance of long-range interactions, is illustrated for a series of molecular model systems and the metal-organic framework MOF-5 as an example for a complex organic-inorganic hybrid material. © 2022 Author(s).

The classical approach to analyze pharmacokinetic (PK) data in bioequivalence studies aiming to compare two different formulations is to perform noncompartmental analysis (NCA) followed by two one-sided tests (TOST). In this regard, the PK parameters area under the curve (AUC) and $C_{\max}$ are obtained for both treatment groups and their geometric mean ratios are considered. According to current guidelines by the U.S. Food and Drug Administration and the European Medicines Agency, the formulations are declared to be sufficiently similar if the $90\%$ confidence interval for these ratios falls between $0.8$ and $1.25 $. As NCA is not a reliable approach in case of sparse designs, a model-based alternative has already been proposed for the estimation of $\rm AUC$ and $C_{\max}$ using nonlinear mixed effects models. Here we propose another, more powerful test than the TOST and demonstrate its superiority through a simulation study both for NCA and model-based approaches. For products with high variability on PK parameters, this method appears to have closer type I errors to the conventionally accepted significance level of $0.05$, suggesting its potential use in situations where conventional bioequivalence analysis is not applicable. © The Author 2020. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Automated additive printer farms, which operate several printers in parallel and thus increase the productivity, are an efficient way to realize a fully flexible mass production, as has been shown by a number of examples. By means of a specifically developed calculation method and virtual representations of various printer farm concepts in a simulation environment, various farm concepts are analyzed regarding the cost structure and the productivity. Also, an automated farm consisting of several low-cost printers is compared to an industrial printer. Subsequently, future scenarios are set up taking into account economic and technological trends allowing an estimation of the impact on the manufacturing costs of automated additive printer farms. In this paper, the analysis is based upon the Fused Layer Modeling (FLM) process, but to a large extent the findings can be transferred to other additive manufacturing processes, for example stereolithography (SL) or digital light processing (DLP). © 2022 Published under licence by IOP Publishing Ltd.

Metal oxides with high specific surface areas have essential roles in numerous applications. Over the past decades, various efforts to increase their surface areas have been made. One of the most important ways is to create nanopores inside the solids, resulting in mesoporous materials. However, ordered mesoporous metal oxides with crystalline framework, regular arrangement of pores, and very high surface areas have scarcely been achieved due to structural collapse during the high-temperature treatment. Herein, a family of mesoporous metal oxides with crystalline framework, hollow mesostructure, and ultrahigh surface area is synthesized by a surface-casting method. The strong interaction between the silica template surface and the precursors is vital in the formation of a thin layer of metal oxides on the nanopore surface. Metal oxides with tubular, hollow sphere, or hollow vesicle structures can be obtained after the templates are removed. The obtained surface-cast oxides (SCOs), including ZrO2, Fe2O3, CrOx, TiO2, and others, exhibit ultrahigh surface areas of up to 400 m2g-1. The high surface area feature of the SCO material can even be retained after calcination up to 800 °C. Catalytic tests reveal that the SCO materials with more exposed active sites have better activities than their conventional counterparts. © 2022 American Chemical Society. All rights reserved.

We present capacitance-voltage [C(V)] measurements of self-assembled wurtzite-GaN quantum dots (QDs). The QDs are embedded in a charge-tunable diode structure and were grown by molecular beam epitaxy in the Stranski-Krastanov growth method. The internal electric fields present in GaN and its alloys together with its wide bandgap make this material system an ideal candidate for high-temperature quantum applications. Charges and the internal electric fields influence the energy spacing in the QDs. We correlate photoluminescence measurements with C(V) measurements and show single-electron charging of the QDs and a Coulomb blockade energy of around 60 meV at room temperature. This finding demonstrates the possibility of quantum applications at room temperature. © 2022 Author(s).

Creating high surface area nanocatalysts that contain stacking faults is a promising strategy to improve catalytic activity. Stacking faults can tune the reactivity of the active sites, leading to improved catalytic performance. The formation of branched metal nanoparticles with control of the stacking fault density is synthetically challenging. In this work, we demonstrate that varying the branch width by altering the size of the seed that the branch grows off is an effective method to precisely tune the stacking fault density in branched Ni nanoparticles. A high density of stacking faults across the Ni branches was found to lower the energy barrier for Ni2+/Ni3+oxidation and result in enhanced activity for electrocatalytic oxidation of 5-hydroxylmethylfurfural. These results show the ability to synthetically control the stacking fault density in branched nanoparticles as a basis for enhanced catalytic activity. © 2022 American Chemical Society. All rights reserved.

We report a method for integrating GaAs waveguide circuits containing self-assembled quantum dots on a Si/SiO2 wafer, using die-to-wafer bonding. The large refractive-index contrast between GaAs and SiO2 enables fabricating single-mode waveguides without compromising the photon-emitter coupling. Anti-bunched emission from individual quantum dots is observed, along with a waveguide propagation loss <7 dB/mm, which is comparable with the performance of suspended GaAs circuits. These results enable the integration of quantum emitters with different material platforms, towards the realization of scalable quantum photonic integrated circuits. © 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.

Grain boundaries are intrinsic and omnipresent microstructural imperfections in polycrystalline and nanocrystalline materials. They are short-circuit diffusion paths and preferential locations for alloying elements, dopants, and impurities segregation. They also facilitate heterogeneous nucleation and the growth of secondary phases. Therefore, grain boundaries strongly influence many materials' properties and their stabilities during application. Here, we propose an approach to measure diffusion, segregation, and segregation-induced precipitation at grain boundaries at a sub-nanometer scale by combining atom probe tomography and scanning transmission electron microscopy. Nanocrystalline multilayer thin films with columnar grain structure were used as a model system as they offer a large area of random high-angle grain boundaries and inherent short diffusion distance. Our results show that the fast diffusion flux proceeds primarily through the core region of the grain boundary, which is around 1 nm. While the spatial range that the segregated solute atoms occupied is larger: below the saturation level, it is 1,2 nm; as the segregation saturates, it is 2–3.4 nm in most grain boundary areas. Above 3.4 nm, secondary phase nuclei seem to form. The observed distributions of the solutes at the matrix grain boundaries evidence that even at a single grain boundary, different regions accommodate different amounts of solute atoms and promote secondary phase nuclei with different compositions, which is caused by its complex three-dimensional topology. © 2021 Acta Materialia Inc.

La-based perovskites are versatile materials that are of interest for solid oxide fuel cells and electrocatalytic water splitting. During fabrication of composition spread thin-film libraries of La—Co-based oxide systems, an unusual phase formation phenomenon is observed: instead of the expected continuous composition gradient, single-phase regions with homogeneous composition form (La2O3 or stoichiometric La-perovskite). This phenomenon, which occurs during reactive cosputtering, is independent of the used substrate. However, a dependency on the O2-portion in the process gas and the substrate temperature is observed. It can be described as a self-organized growth, where excess transition metal cannot be incorporated into the lattices of the forming single-phase regions, and therefore, not into the growing film. It is hypothesized that due to the high reactivity of La and the significantly low formation energies of La2O3 and La-perovskites, the reactive sputter deposition of La-based oxide films, which is a physical vapor deposition process, can turn partially—regarding film growth—into a chemical vapor deposition-like process. The described single-phase regions form and lead to a discontinuous composition spread, with preferred growth of the thermodynamically most stable phases. This phenomenon can be leveraged for the exploration of multinary perovskite thin-film libraries, where the B-site atoms of La-perovskites are systematically substituted. © 2022 The Authors. Advanced Engineering Materials published by Wiley-VCH GmbH.

Low temperature (1023 K) high stress (800 MPa) tensile creep behavior of the superalloy single crystal ERBO-1 (CMSX-4 type) is investigated. Three loading directions are compared: precise [001] and 15 ° deviations from [001] towards [111] and [011]. It is found that creep rates ε˙ scale as ε˙[001]→[111]>ε˙[001]>ε˙[001]→[011]already in the early stages of creep (ε≤1%), where dislocation network formation and planar fault intersections cannot rationalize the observed rate effects. An analysis based on Peach-Köhler force calculations suggests, that fast creep rates are observed, when dislocations from two octahedral systems, which are required to react and form the leading part of a planar fault ribbon in the γ’-phase, experience similar driving forces. Creep data, micromechanical calculations and TEM results are in good qualitative agreement. From a technological point of view, the results show that while 15 ° deviations from [001] towards [011] can be tolerated, deviations towards [111] must be avoided. © 2021

In this paper, a topology optimization approach is presented, where uncertain load and uncertain material parameters are considered. The concept of compliance minimization, i.e., stiffness maximization, is applied based on a plane stress finite element formulation. In order to take uncertain structural load parameters and uncertain material behavior into account, the topology optimization is embedded into a reliability-based design optimization approach. Uncertain structural parameters and design variables are quantified as random variables, intervals and probability boxes (p-boxes). This allows to consider aleatory and epistemic uncertainties by means of polymorphic uncertainty models within the topology optimization. Solving optimization problems with random variables, intervals and p-boxes leads to a high computational effort, because the objective functions and constraints have to evaluated millions of times. To speed up the optimization process, the finite element simulation of the topology optimization is replaced by artificial neural networks. This includes the topology dependent maximal stresses and displacements of the structure, which are used as constraints, and also the material density distribution inside the design domain. The reliability-based optimization of structural topologies approach is applied to a cantilever structure and a single span girder. © 2022 Elsevier Ltd

We report the cyclic deformation behavior of CoCrNi at 550 °C under a strain amplitude of ± 0.5% and compare it to that of CoCrFeMnNi. CoCrNi manifests cyclic hardening followed by minor softening and a near-steady state until failure. Transmission electron microscopy investigations of CoCrNi revealed that increasing the number of cycles from 10 to 2500/5000 leads to a transition of dislocation arrangements from slip bands to tangles. Compared to CoCrFeMnNi, CoCrNi exhibits higher strength, longer lifetime and persistent serrated flow. Owing to its lower stacking fault energy (even at 550 °C), planar slip is more pronounced in CoCrNi than CoCrFeMnNi, which additionally shows wavy slip. © 2022 Acta Materialia Inc.

One of the major challenges in reusing cooling tower blowdown water (CTBD) utilizing membrane processes is its remaining organic compounds, e.g., humic substances leading to biofouling. Besides, the possible abundance of chloride in CTBD imposes the concern of the formation of chlorinated by-products. To choose a pre-treatment process for the studied CTBD composition, various advanced oxidation processes (AOPs), including electrooxidation (EO), photocatalytic degradation (PCD), heat-activated persulfate oxidation (PS), UVC/vacuum UV (UVC/VUV), and UVC processes, were evaluated and compared based on two main targets: i) highest removal and mineralization of the organics, especially humic substances; and ii) lowest formation of chlorinated by-products including adsorbable organic halides and oxychlorides. All the processes were conducted in the natural condition of the real CTBD, while solution pH was monitored. Based on results of chemical oxygen demand, total organic carbon, dissolved organic carbon, UV254 absorbance, liquid-chromatography–organic carbon detection (LC-OCD), and fluorescence excitation-emission matrices (FEEM), it is concluded that PS leads to complete removal of organic compounds along with the lowest formation of low molecular weight organic acids and organic neutrals. FEEM and LC-OCD data also indicated that EO, PCD, and UVC/VUV processes brought about substantial removal of organic compounds and broke down the humic substances into low molecular weight building blocks and organics. Besides, EO exhibited the highest AOX and oxychlorides formation, while these were limited when using the other AOPs. Summarizing, PS, PCD, and UVC/VUV were efficient processes for the degradation and mineralization of organics without generating significant amounts of chlorinated by-products. © 2021 The Author(s)

High- and medium-entropy alloys (HEAs) are a quite new class of materials. They have a high potential for applications from low to high temperatures due to the excellent combination of their structural properties. Concerning their application as components; processing properties, such as machinability, have hardly been investigated so far. Hence, machinability analyses with a focus on the influence of the milling process and its basic parameters (cutting speed, feed per cutting edge) on the resulting surface integrity of specimens from an equiatomic high- (CoCrFeMnNi) and a medium- (CoCrNi) entropy alloy have been carried out. A highly innovative milling process with ultrasonic assistance (USAM) was compared to conventional milling processes. Recent studies have shown that USAM has a high potential to significantly reduce the mechanical load on the tool and workpiece surface during milling. In this study, the basic machining and ultrasonic parameters were systematically varied. After machining, the surface integrity of the alloys was analyzed in terms of topography, defects, subsurface damage, and residual stresses. It was observed that USAM reduces the cutting forces and increases the surface integrity in terms of lower tensile residual stresses and defect density near the surfaces for the CoCrFeMnNi alloy. It was shown that the cutting forces and the metallurgical influence in the sub surface region are reduced by increasing the cutting speed and reducing the feed rate per cutting edge. With the CoCrNi alloy, the tool revealed severe wear. As a result, for this alloy no influence of the parameters on the machinability could be determined. © 2021 Elsevier B.V.

For more than 6 decades, thermal barrier coatings have been used to protect structural parts in both stationary and aviation gas turbines. These coatings allow the use of significant higher operation temperatures and hence increased efficiencies. In the 1970s, yttria-stabilized zirconia (YSZ) was identified as outstanding material for this application. As major deposition technologies both electron beam physical vapor deposition (EB-PVD) and atmospheric plasma spraying (APS) have been established. Although the topic is already rather old, there are still frequent activities ongoing to further improve the technology, both with respect to materials and microstructural issues also regarding the use of advanced coating technologies, especially in the field of thermal spray. The paper tries to summarize major developments in both fields, the materials and the processing focusing on thermal spray methods. The impact of both materials and processing are summarized by the results of burner rig tests for various systems. Furthermore, a short outlook on possible future directions of developments will be given. © 2022, The Author(s).

This paper focuses on the oxidation behavior of novel double-ceramic-layer thermal barrier coatings (DCL TBCs) deposited by atmospheric plasma spraying (APS) and suspension plasma spraying (SPS). Four kinds of APS-SPS DCL TBCs with dense/porous columnar structured or vertically cracked microstructures were prepared. The oxidation behavior of the APS-SPS DCL TBCs were tested and the underlying mechanisms were further discussed. Results showed that the developed APS-SPS DCL TBCs have a better oxidation resistance than the single layer SPS TBC that was tested for comparison. In the long-term oxidation, the thermally grown oxide (TGO) can be divided into two layers, the outer mixed oxide and inner Al2O3 layer, in which the growth rate of mixed oxide in TGO changed during oxidation. In terms of the oxidation rate and oxidation lifetime, segmented APS-SPS TBCs has a slightly better performance than the columnar APS-SPS TBCs. Among the four different APS-SPS TBCs, the segmented dense APS-SPS TBCs with low vertical crack density appears to have more potential to be used for industrial application. © 2022

Biofouling is an ongoing challenge for water treatment membrane processes. Reducing biofilm growth on the membrane surface or on the polymeric feed spacer will reduce operation, maintenance, and module replacement costs. Laser-induced graphene (LIG) is a low cost, environmentally friendly, electrically conductive carbon material shown to have antibiofouling properties. Here it has been shown that an electrically conductive LIG-coated polypropylene (PP) feed spacer has both antimicrobial and antifouling effects under a low electrical current, and when implemented into a spiral wound membrane module reduced biofilm growth on both the membrane and the spacer components. The antibacterial property of the LIG spacer is tested using Pseudomonas aeruginosa and the brackish water Rheinheimera sp. as model organisms. Using a voltage of 12 V, P. aeruginosa is completely inactivated in 10 h, while a dynamic accumulation assay employing Rheinheimera sp. showed significant reduction (p < 0.05) in bacterial adhesion compared to an uncoated spacer. The spacer is incorporated into a spiral wound reverse osmosis (RO) membrane module, and reduced biofouling is observed on both the membrane and LIG spacers components using brackish water and 12 V. This study demonstrates the feasibility of electrically conductive feed spacer components in spiral wound RO membrane modules. © 2022 The Authors. Advanced Materials Interfaces published by Wiley-VCH GmbH.

The development of electrodes for efficient CO2reduction while forming valuable compounds is critical. The use of enzymes as catalysts provides the advantage of high catalytic activity in combination with highly selective transformations. We describe the electrical wiring of a carbon monoxide dehydrogenase II from Carboxydothermus hydrogenoformans (ChCODH II) using a cobaltocene-based low-potential redox polymer for the selective reduction of CO2to CO over gas diffusion electrodes. High catalytic current densities of up to -5.5 mA cm-2are achieved, exceeding the performance of previously reported bioelectrodes for CO2reduction based on either carbon monoxide dehydrogenases or formate dehydrogenases. The proposed bioelectrode reveals considerable stability with a half-life of more than 20 h of continuous operation. Product quantification using gas chromatography confirmed the selective transformation of CO2into CO without any parasitic co-reactions at the applied potentials. © 2022 American Chemical Society. All rights reserved.

An enzymatic biofuel cell is integrated on a screen-printed electrode as a basis for a self-powered biosensor. A glucose/O2 biofuel cell consisting of a pyrroloquinoline quinone-dependent glucose dehydrogenase embedded within an Os-complex modified redox polymer bioanode to oxidize glucose and a non-limiting bilirubin oxidase-based gas diffusion biocathode in the direct-electron transfer regime for the reduction of O2 showed a glucose-dependent current and power output. For full integration on a single screen-printed electrode, a miniaturized agar salt bridge was introduced between the two bioelectrodes to ensure operation of the assembly in a two-compartment configuration with each electrode operating at optimal conditions. © 2022 The Authors. Electroanalysis published by Wiley-VCH GmbH.

Processing of tungsten carbide‑cobalt (WC-Co) by laser-based powder bed fusion (PBF-LB) can result in characteristic microstructure defects such as cracks, pores, undesired phases and tungsten carbide (WC) grain growth, due to the heterogeneous energy input and the high thermal gradients. Besides the processing conditions, the material properties are affected by the initial powder characteristics. In this paper, the impact of powder composition on microstructure, phase formation and mechanical properties in PBF-LB of WC-Co is studied. Powders with different cobalt contents from 12 wt.-% to 25 wt.-% are tested under variation of the laser parameters. Furthermore, the impact of vanadium carbide (VC) and chromium (Cr) additives is investigated. Both are known as grain growth inhibitors for conventional sintering processes. The experiments are conducted at a pre-heating temperature of around 800 °C to prevent crack formation in the samples. Increasing laser energy input reduces porosity but leads to severe embrittlement for low cobalt content and to abnormal WC grain growth for high cobalt content. It is found that interparticular porosity at low laser energy is more severe for low cobalt content due to poor wetting of the liquid phase. Maximum bending strength of σB > 1200 MPa and Vickers hardness of approx. 1000 HV3 can be measured for samples generated from WC-Co 83/17 powder with medium laser energy input. The addition of V and Cr leads to increased formation of additional phases such as Co3W3C, Co3V and Cr23C6 and to increased lateral and multi-laminar growth of the WC grains. In contrast to conventional sintering, a grain growth inhibiting effect of V and Cr in the laser molten microstructure is not achieved. © 2022 Elsevier Ltd

This work investigated processing of stainless steel powders and powder mixtures using powder bed fusion - laser beam/metal (PBF-LB/M), which produced different ferritic and austenitic phase fractions in the as-built state. The rapid cooling and solidification rates in the PBF-LB/M process led to the formation of an extremely small-structured microstructure in which the austenitic phase was found on the grain boundaries and as acicular Widmanstätten austenite (width < 1 µm) within the primary δ-ferritic solidified matrix. This work shows that the time-saving quantification of the ferritic and austenitic phase fractions of these particular microstructures is nontrivial. Common time-efficient phase quantification methods such as image analysis of etched cross-sections or magneto-inductive methods (Feritscope®) have proven to be inaccurate. On the other hand, electron backscattered diffraction (EBSD) investigations proved to be extremely time-consuming in order to resolve the small microstructural constituents sufficiently well and to obtain a reliably large sample section. The highest accuracy was achieved with X-ray diffraction. Two different methods were considered: the Debye-Scherrer method, which was characterized by short measuring times, and the Bragg-Brentano method (quantification using Rietveld refinement), which showed the highest accuracy for the entire range of ferritic-austenitic phase fractions. © 2022 Acta Materialia Inc.

To better understand why amines catalyze the reactivity of SiOH with silanes, we examined the adsorption of trimethylamine under a low pressure (10-9-10-8 mbar) and a low temperature (105-160 K) on water-terminated (H,OH)-Si(001), which is both a model surface for adsorption studies and a promising starting substrate for atomic layer deposition. Trimethylamine bonding configurations were determined by combining real-time synchrotron radiation X-ray photoelectron spectroscopy (XPS) and high-resolution electron energy loss spectroscopy (HREELS) with density functional theory (DFT) calculations of core-level ionization energies and vibrational spectra. Both spectroscopies showed that the majority of species are trimethylamine molecules making acceptor H bonds with surface hydroxyls. Moreover, HREELS indicated that the hydrogen-bonding modes (single and double hydrogen acceptor bonds) depend on temperature and/or coverage, which may in turn affect the weakening of the O-H bond, and hence the catalytic effects of trimethylamine. XPS also clearly detected a minority species, trimethylamine, datively bonded to the isolated silicon dangling bonds (a few 1/100th of a monolayer). This species is prone to breaking, and a detailed analysis of the reaction products was made. The reactivity of the electrically active isolated silicon dangling bonds with the amine may impact the Fermi-level position in the gap. © 2022 American Chemical Society

Duplex stainless steels exhibit an excellent combination of corrosion resistance and strength and are increasingly being manufactured through powder metallurgy (PM) to produce large, near-net-shaped components, such as those used for offshore applications. Hot isostatic pressing (HIP) is often used for PM production, in which pre-alloyed powders are compacted under high pressures and temperatures. Recent developments in HIP technology enable fast cooling as part of the process cycle, reaching cooling rates comparable to oil quenching or even faster. This enables the integrated solution annealing of duplex stainless steels directly after compaction. In contrast to the conventional HIP route, which requires another separate solution annealing step after compaction, the integrated heat treatment within the HIP process saves both energy and time. Due to this potential gain, HIP compaction at a high pressure of 170 MPa and 1150 °C with integrated solution annealing for the production of duplex stainless steels was investigated in this work. Firstly, the focus was to investigate the influence of pressure on the phase stability during the integrated solution annealing of the steel X2CrNiMoN22-5-3. Secondly, the steel X2CrNiMoCuWN25-7-4, which is highly susceptible to sigma phase embrittlement, was used to investigate whether the cooling rates used in the HIP are sufficient for preventing the formation of this brittle microstructural constituent. This work shows that the high pressure used during the solution heat treatment stabilizes the austenite. In addition, it was verified that the cooling rates during quenching stage in HIP are sufficient for preventing the formation of the sigma phase in the X2CrNiMoCuWN25-7-4 duplex stainless steel. © 2022 by the authors.

Deformation twinning is rarely found in bulk face-centered cubic (FCC) alloys with very high stacking fault energy (SFE) under standard loading conditions. Here, based on results from bulk quasi-static tensile experiments, we report deformation twinning in a micrometer grain-sized compositionally complex steel (CCS) with a very high SFE of ~79 mJ/m2, far above the SFE regime for twinning (<~50 mJ/m2) reported for FCC steels. The dual-nanoprecipitation, enabled by the compositional degrees of freedom, contributes to an ultrahigh true tensile stress up to 1.9 GPa in our CCS. The strengthening effect enhances the flow stress to reach the high critical value for the onset of mechanical twinning. The formation of nanotwins in turn enables further strain hardening and toughening mechanisms that enhance the mechanical performance. The high stress twinning effect introduces a so far untapped strengthening and toughening mechanism, for enabling the design of high SFEs alloys with improved mechanical properties. © 2022, The Author(s).

We present an atomistic study of heterogeneous nucleation in Ni employing transition path sampling, which reveals a template precursor-mediated mechanism of crystallization. Most notably, we find that the ability of tiny templates to modify the structural features of the liquid and promote the formation of precursor regions with enhanced bond-orientational order is key to determining their nucleation efficiency and the polymorphs that crystallize. Our results reveal an intrinsic link between structural liquid heterogeneity and the nucleating ability of templates, which significantly advances our understanding toward the control of nucleation efficiency and polymorph selection. © 2022 American Physical Society.

Hydrogen production via plasma methane pyrolysis is investigated using a microwave plasma torch (MPT) and a gliding arc plasmatron (GAP). The performance of the two plasma sources in terms of methane conversion, product spectrum, and energy efficiency is compared. The physical and chemical properties of the produced carbon particles are compared. The methane conversion is higher in the GAP than in the MPT. In the MPT amorphous spherical carbon particles are produced in the volume of the plasma source. In the GAP methane pyrolysis in the volume stops after the production of acetylene. The conversion of acetylene into solid carbon takes place in a heterogeneous reaction on top of the electrode surfaces instead. This leads to a lower hydrogen selectivity, higher acetylene selectivity and more platelet-like morphology of the produced carbon particles when compared to the MPT. © 2022 The Authors. Plasma Processes and Polymers published by Wiley-VCH GmbH.

The electrical double-layer plays a key role in important interfacial electrochemical processes from catalysis to energy storage and corrosion. Therefore, understanding its structure is crucial for the progress of sustainable technologies. We extract new physico-chemical information on the capacitance and structure of the electrical double-layer of platinum and gold nanoparticles at the molecular level, employing single nanoparticle electrochemistry. The charge storage ability of the solid/liquid interface is larger by one order-of-magnitude than predicted by the traditional mean-field models of the double-layer such as the Gouy–Chapman–Stern model. Performing molecular dynamics simulations, we investigate the possible relationship between the measured high capacitance and adsorption strength of the water adlayer formed at the metal surface. These insights may launch the active tuning of solid–solvent and solvent–solvent interactions as an innovative design strategy to transform energy technologies towards superior performance and sustainability. © 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH

A scale for magnetic field resilience of a superconductor is set by the paramagnetic limit. Comparing the condensation energy of the Bardeen-Cooper-Schrieffer (BCS) singlet ground state with the paramagnetically polarized state suggests that for an applied field μ 0 H > 1.8 T c (in SI), singlet pairing is not energetically favorable. Materials exceeding or approaching this limit are interesting from fundamental and technological perspectives. This may be a potential indicator of triplet superconductivity, Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) pairing, and other mechanisms involving topological aspects of surface states and may also allow Cooper pair injection at high magnetic fields. We have analyzed the microscopic composition of such a material arising from an unexpected source. A microjet of an organo-metallic gas, W [(CO) 6], can be decomposed by a gallium ion-beam, leaving behind a track of complex residue of gallium, tungsten, and carbon with remarkable superconducting properties, like an upper critical field, H c 2 > 10 T, above its paramagnetic limit. We carried out atomic probe tomography to establish the formation of nano-crystalline tungsten carbide (WC) in the tracks and the absence of free tungsten. Supporting calculations show that for Ga distributed on the surface of WC, its s,p-orbitals enhance the density of states near the Fermi energy. The observed variation of H c 2 (T) does not show features typical of enhancement of critical field due to granularity. Our observations may be significant in the context of some recent theoretical calculation of the band structure of WC and experimental observation of superconductivity in a WC-metal interface. © 2022 Author(s).

Grazing incidence X-ray diffraction (GIXRD) and scanning transmission electron microscopy (STEM) combined with energy dispersive X-ray spectroscopy (EDS) were employed to study the microstructure evolution and stress development in the nanocrystalline Cu100−X-ZrX (2.5 at% ≤ x ≤ 5.5 at%) alloy thin films. Small Zr additions to Cu led to significant lattice parameter anisotropy in the as-deposited Cu-Zr thin films both due to macroscopic lattice strain and stacking faults in the Cu matrix. Strain free lattice parameters obtained after the XRD stress analysis of Cu-Zr thin films confirmed formation of a supersaturated substitutional Cu-Zr solid solution. For the first time, the study of film microstructure by XRD line profile analysis (XLPA) confirmed progressive generation of dislocations and planar faults with increasing Zr composition in Cu-Zr alloy films. These microstructural changes led to the generation of tensile stresses in the thin films along with considerable stress gradients across the films thicknesses which are quantified by the traditional dψhkl−Sin2ψ and GIXRD stress measurement methods. The origin of tensile stresses and stress gradients in the Cu-Zr film are discussed on the basis of film growth and heterogeneous microstructure with changing Zr composition. © 2021

Physical properties of ten single-phase FCC CrxMn20Fe20Co20Ni40-x high-entropy alloys (HEAs) were investigated for 0 ≤ x ≤ 26 at%. The lattice parameters of these alloys were nearly independent of composition while solidus temperatures increased linearly by ∼30 K as x increased from 0 to 26 at.%. For x ≥ 10 at.%, the alloys are not ferromagnetic between 100 and 673 K and the temperature dependencies of their coefficients of thermal expansion and elastic moduli are independent of composition. Magnetic transitions and associated magnetostriction were detected below ∼200 K and ∼440 K in Cr5Mn20Fe20Co20Ni35 and Mn20Fe20Co20Ni40, respectively. These composition and temperature dependencies could be qualitatively reproduced by ab initio simulations that took into account a ferrimagnetic ↔ paramagnetic transition. Transmission electron microscopy revealed that plastic deformation occurs initially by the glide of perfect dislocations dissociated into Shockley partials on {111} planes. From their separations, the stacking fault energy (SFE) was determined, which decreases linearly from 69 to 23 mJ·m−2 as x increases from 14 to 26 at.%. Ab initio simulations were performed to calculate stable and unstable SFEs and estimate the partial separation distances using the Peierls-Nabarro model. While the compositional trends were reasonably well reproduced, the calculated intrinsic SFEs were systematically lower than the experimental ones. Our ab initio simulations show that, individually, atomic relaxations, finite temperatures, and magnetism strongly increase the intrinsic SFE. If these factors can be simultaneously included in future computations, calculated SFEs will likely better match experimentally determined SFEs. © 2022

Cu films were grown on (0001) α-Al2O3 single-crystals by magnetron sputtering. The growth behavior was manipulated by Ar+-ion sputter cleaning of the substrates at kinetic energies between 100 and 500 eV, changing the sputter rate from 0.75 to 1.1 nm/s, and using nominal substrate temperatures of 100 and 200 °C, respectively. Polycrystalline Cu films formed on α-Al2O3 substrates after an Ar+-ion bombardment at 500 eV, while epitaxial Cu films evolved when Ar+-ion energies of 100 and 200 eV were used. The epitaxial Cu films always consisted of two twin-related growth variants. However, two different orientation relationships emerged which differ by a 30° in-plane rotation of the (111) oriented Cu films when the deposition rate is changed from 0.75 to 1.1 nm/s. The results will be discussed on the basis of differences in the growth process. © 2005 Carl Hanser Verlag, München.

To advance the understanding of the degradation of the liquid electrolyte and Si electrode, and their interface, we exploit the latest developments in cryo-atom probe tomography. We evidence Si anode corrosion from the decomposition of the Li salt before charge-discharge cycles even begin. Volume shrinkage during delithiation leads to the development of nanograins from recrystallization in regions left amorphous by the lithiation. The newly created grain boundaries facilitate pulverization of nanoscale Si fragments, and one is found floating in the electrolyte. P is segregated to these grain boundaries, which confirms the decomposition of the electrolyte. As structural defects are bound to assist the nucleation of Li-rich phases in subsequent lithiations and accelerate the electrolyte's decomposition, these insights into the developed nanoscale microstructure interacting with the electrolyte contribute to understanding the self-catalyzed/accelerated degradation Si anodes and can inform new battery designs unaffected by these life-limiting factors. © 2022 American Chemical Society.

Complex stress states due to torsion lead to dislocation structures characteristic for the chosen torsion axis. The formation mechanism of these structures and the link to the overall plastic deformation are unclear. Experiments allow the analysis of cross sections only ex situ or are limited in spacial resolution which prohibits the identification of the substructures which form within the volume. Discrete dislocation dynamics simulations give full access to the dislocation structure and their evolution in time. By combining both approaches and comparing similar measures the dislocation structure formation in torsion loading of micro wires is explained. For the «100»torsion axis, slip traces spanning the entire sample in both simulation and experiment are observed. They are caused by collective motion of dislocations on adjacent slip planes. Thus these slip traces are not atomically sharp. Torsion loading around a «111»axis favors plasticity on the primary slip planes perpendicular to the torsion axis and dislocation storage through cross-slip and subsequent collinear junction formation. Resulting hexagonal dislocation networks patches are small angle grain boundaries. Both, experiments and discrete dislocation simulations show that dislocations cross the neutral fiber. This feature is discussed in light of the limits of continuum descriptions of plasticity. © 2022 The Author(s). Published by IOP Publishing Ltd.

The distribution of water on metal supported oxides is an important step in understanding heterogeneous catalysis such as in the water gas shift reaction. Here, we study water structures on Ag(111)-supported graphitic zinc oxide islands by variable temperature scanning tunneling microscopy around 150 K and ab initio calculations. Water clusters, accumulating on the ZnO islands, are confined to the hcp regions of the ZnO moiré pattern. A significantly higher cluster density at the island border is related to the dimensions of its capture zone. This suggests an upward mass transport of the water from the supporting metal to the ultrathin oxide film, increasing the water density at the active metal-oxide border. © 2022 American Chemical Society. All rights reserved.

Metal nanogels combine a large surface area, a high structural stability, and a high catalytic activity toward a variety of chemical reactions. Their performance is underpinned by the atomic-level distribution of their constituents, yet analyzing their subnanoscale structure and composition to guide property optimization remains extremely challenging. Here, we synthesized Pd nanogels using a conventional wet chemistry route, and a near-atomic-scale analysis reveals that impurities from the reactants (Na and K) are integrated into the grain boundaries of the poly crystalline gel, typically loci of high catalytic activity. We demonstrate that the level of impurities is controlled by the reaction condition. Based on ab initio calculations, we provide a detailed mechanism to explain how surface-bound impurities become trapped at grain boundaries that form as the particles coalesce during synthesis, possibly facilitating their decohesion. If controlled, impurity integration into grain boundaries may offer opportunities for designing new nanogels. © 2022 The Authors. Published by American Chemical Society

Today's society relies on energy storage on a day-to-day basis, e.g. match energy production and demand from renewable sources, power a variety of electronics, and enable emerging technologies. As a result, a vast range of energy storage technologies has emerged in the last decades. Among them, rechargeable Zn–Air batteries have held great promises for a long time. However, the severe challenges related to the reversible O2 reactions and poor cyclability at the positive and negative electrodes, respectively, have severely hindered the success of this technology. Herein, electrically-conducting and semi-flowable Zn semi-solid electrodes are proposed to revive the appealing concept of a mechanically–rechargeable alkaline Zn–Air battery, in which the spent negative electrodes are easily substituted at the end of the discharge process (refillable primary battery). In this proof-of-concept study energy densities of ca. 1500 Wh L−1 (1350 Ah Lelectrode−1 and utilization rate of 85%) are achieved thanks to the compromised flowability of the proposed Zn semi-solid electrodes. In this way, semi-solid Zn electrodes become a type of green energy carrier having intrinsic advantages over gas and liquid fuels. Zn semi-flowable electrode can be generated elsewhere using renewable sources, easily stored, transported, and used to produce electricity. © 2022 The Authors

Water nucleation on alkali precovered metal-supported oxide surfaces is an important step in understanding water as one of the reactants in alkali-assisted heterogeneous catalysis. For instance, alkali metals as catalyst dopants enhance the water-gas shift reaction that catalyzes on ZnO-metal nanostructures. Here, we investigate the hydration of cesium on a Ag(111)-supported graphitic zinc oxide ultrathin film using scanning tunneling microscopy at (160 ± 30) K. Upon hydrating the pristine graphitic ZnO film, the water forms well-separated clusters on the hcp regions of the ZnO moiré pattern at water coverages below 85% ML. In the presence of cesium on the fcc regions of the ZnO moiré pattern, the water clusters coalesce across hcp regions at water coverages above ∼32% ML, forming unique one-dimensional water-Cs chains along the high-symmetry directions of the ZnO moiré pattern. Our study demonstrates that the alkali doping of an oxide surface alters the dimensionality of water structures redirecting it partially to other adsorption regions, possibly influencing its reactivity. © 2022 American Chemical Society.

Fuel cells recombine water from H2 and O2 thereby can power, for example, cars or houses with no direct carbon emission. In anion-exchange membrane fuel cells (AEMFCs), to reach high power densities, operating at high pH is an alternative to using large volumes of noble metals catalysts at the cathode, where the oxygen-reduction reaction occurs. However, the sluggish kinetics of the hydrogen-oxidation reaction (HOR) hinders upscaling despite promising catalysts. Here, the authors observe an unexpected ingress of B into Pd nanocatalysts synthesized by wet-chemistry, gaining control over this B-doping, and report on its influence on the HOR activity in alkaline conditions. They rationalize their findings using ab initio calculations of both H- and OH-adsorption on B-doped Pd. Using this “impurity engineering” approach, they thus design Pt-free catalysts as required in electrochemical energy conversion devices, for example, next generations of AEMFCs, that satisfy the economic and environmental constraints, that is, reasonable operating costs and long-term stability, to enable the “hydrogen economy.”. © 2022 The Authors. Advanced Materials published by Wiley-VCH GmbH.

In a chiral one-dimensional atom, a photon propagating in one direction interacts with the atom; a photon propagating in the other direction does not. Chiral quantum optics has applications in creating nanoscopic single-photon routers, circulators, phase-shifters, and two-photon gates. Here, we implement chiral quantum optics using a low-noise quantum dot in an open microcavity. We demonstrate the non-reciprocal absorption of single photons, a single-photon diode. The non-reciprocity, the ratio of the transmission in the forward-direction to the transmission in the reverse direction, is as high as 10.7 dB. This is achieved by tuning the photon-emitter coupling in situ to the optimal operating condition (β = 0.5). Proof that the non-reciprocity arises from a single quantum emitter lies in the photon statistics—ultralow-power laser light propagating in the diode’s reverse direction results in a highly bunched output (g(2)(0) = 101), showing that the single-photon component is largely removed. © 2022, The Author(s).

In recent years, machine learning potentials (MLP) for atomistic simulations have attracted a lot of attention in chemistry and materials science. Many new approaches have been developed with the primary aim to transfer the accuracy of electronic structure calculations to large condensed systems containing thousands of atoms. In spite of these advances, the reliability of modern MLPs in reproducing the subtle details of the multi-dimensional potential-energy surface is still difficult to assess for such systems. On the other hand, moderately sized systems enabling the application of tools for thorough and systematic quality-control are nowadays rarely investigated. In this work we use benchmark-quality harmonic and anharmonic vibrational frequencies as a sensitive probe for the validation of high-dimensional neural network potentials. For the case of the formic acid dimer, a frequently studied model system for which stringent spectroscopic data became recently available, we show that high-quality frequencies can be obtained from state-of-the-art calculations in excellent agreement with coupled cluster theory and experimental data. © 2022 The Royal Society of Chemistry.

To successfully transition from fossil-fuel to sustainable carbon-free energy carriers, a safe, stable and high-density energy storage technology is required. The combustion of iron powders seems very promising in this regard. Yet, little is known about their in-process morphological and microstructural evolution, which are critical features for the circularity of the concept, especially the subsequent reduction of the combusted oxide powders back to iron. Here, we investigated two iron powder combustion pathways, one in air and one with the assistance of a propane pilot flame. Both processes resulted in spherical hollow particles composed of a complex microstructure of wüstite, magnetite and/or hematite. Partial evaporation is indicated by the observation of nanoparticles on the micro-sized combustion products. The associated gas production inside the liquid droplet could be the origin of the internal porosity and micro-explosion events. Cracking at the end of the combustion process results in mostly open porosity, which is favorable for the subsequent reduction process. With this study, we aim to open the perspective of iron metal fuel from macroscopic combustion analysis towards a better understanding of the underlying microscopic thermodynamic, kinetic, microstructural and thermomechanical mechanisms. © 2022 Acta Materialia Inc.

The commonly employed supercell approach for defects in crystalline materials may introduce spurious interactions between the defect and its periodic images. A rich literature is available on how the interaction energies can be estimated, reduced, or corrected. A simple and seemingly straightforward approach is to extrapolate from a series of finite supercell sizes to the infinite-size limit, assuming a smooth polynomial dependence of the energy on inverse supercell size. In this work, we demonstrate by means of explict density-functional theory supercell calculations and simplified models that wave-function overlap and electrostatic interactions lead to more complex dependencies on supercell size than commonly assumed. We show that this complexity cannot be captured by the simple extrapolation approaches and that suitable correction schemes should be employed. Published by the American Physical Society

Bimetallic tandem catalysts have emerged as a promising strategy to locally increase the CO flux during electrochemical CO2 reduction, so as to maximize the rate of conversion to C−C-coupled products. Considering this, a novel Cu/C−Ag nanostructured catalyst has been prepared by a redox replacement process, in which the ratio of the two metals can be tuned by the replacement time. An optimum Cu/Ag composition with similarly sized particles showed the highest CO2 conversion to C2+ products compared to non-Ag-modified gas-diffusion electrodes. Gas chromatography and in-situ Raman measurements in a CO2 gas diffusion cell suggest the formation of top-bound linear adsorbed *CO followed by consumption of CO in the successive cascade steps, as evidenced by the increasingνC−H bands. These findings suggest that two mechanisms operate simultaneously towards the production of HCO2H and C−C-coupled products on the Cu/Ag bimetallic surface. © 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.

High-entropy alloys are solid solutions of multiple principal elements that are capable of reaching composition and property regimes inaccessible for dilute materials. Discovering those with valuable properties, however, too often relies on serendipity, because thermodynamic alloy design rules alone often fail in high-dimensional composition spaces. We propose an active learning strategy to accelerate the design of high-entropy Invar alloys in a practically infinite compositional space based on very sparse data. Our approach works as a closed-loop, integrating machine learning with density-functional theory, thermodynamic calculations, and experiments. After processing and characterizing 17 new alloys out of millions of possible compositions, we identified two high-entropy Invar alloys with extremely low thermal expansion coefficients around 2 × 10−6 per degree kelvin at 300 kelvin. We believe this to be a suitable pathway for the fast and automated discovery of high-entropy alloys with optimal thermal, magnetic, and electrical properties. Copyright © 2022 The Authors, some rights reserved.

Single particle electrochemical oxidation of polyvinylpyrrolidone-capped silver nanoparticles at a microdisk electrode is investigated as a function of particle shape (spheres, cubes, and plates) in potassium nitrate and potassium hydroxide solutions. In potassium nitrate, extreme anodic potentials (1500 mV vs Ag/AgCl (3 M KCl)) are necessary to achieve oxidation, while lower anodic potentials are required in potassium hydroxide (900 mV vs Ag/AgCl (saturated KCl)). Upon oxidation, silver oxide is formed, readily catalyzing water oxidation, producing a spike-step current response. The spike duration for each particle is used to probe effects of particle shape on the oxidation mechanism, and is substantially shorter in nitrate solution at the large overpotentials than in hydroxide solution. The integration of current spikes indicates oxidation to a mixed-valence complex. In both electrolytes, the rate of silver oxidation strongly depends on silver content of the nanoparticles, rather than the shape-dependent variable surface area. The step height, which reflects rate of water oxidation, also tracks the silver content more so than shape. The reactivity of less-protected citrate-capped particles toward silver oxidation is also compared with that of the polymer-capped particles under these anodic conditions in the nitrate and hydroxide solutions. © 2022 Electrochemical Society Inc.. All rights reserved.

Non-classical alternatives to the silver contact and the Formox processes comprise the thermal non-oxidative dehydrogenation of methanol, for which new catalysts are needed to achieve high formaldehyde selectivity at high conversion at temperatures below 600 °C. The electro- or photocatalytic conversion of methanol to formaldehyde is not applied either industrially but is attractive because of mild reaction conditions and high formaldehyde selectivities. Novel gas-phase approaches yielding (anhydrous) formaldehyde are presented describing lab-scale setups and the challenges for up-scaling. © 2022 The Authors. Chemie Ingenieur Technik published by Wiley-VCH GmbH.

When computing finite-temperature properties of materials with atomistic simulations, nuclear quantum effects are often neglected or approximated at the quasiharmonic level. The inclusion of these effects beyond this level using approaches like the path integral method is often not feasible due to their large computational effort. We discuss and evaluate the performance of a temperature-remapping approach that links the finite-temperature quantum system to its best classical surrogate via a temperature map. This map, which is constructed using the internal energies of classical and quantum harmonic oscillators, is shown to accurately capture the impact of quantum effects on thermodynamic properties at an additional cost that is negligible compared to classical molecular dynamics simulations. Results from this approach show excellent agreement with previously reported path integral Monte Carlo simulation results for diamond cubic carbon and silicon. The approach is also shown to work well for obtaining thermodynamic properties of light metals and for the prediction of the fcc to bcc phase transition in calcium. © 2022 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Open access publication funded by the Max Planck Society.

Soft magnetic materials (SMMs) serve in electrical applications and sustainable energy supply, allowing magnetic flux variation in response to changes in applied magnetic field, at low energy loss1. The electrification of transport, households and manufacturing leads to an increase in energy consumption owing to hysteresis losses2. Therefore, minimizing coercivity, which scales these losses, is crucial3. Yet meeting this target alone is not enough: SMMs in electrical engines must withstand severe mechanical loads; that is, the alloys need high strength and ductility4. This is a fundamental design challenge, as most methods that enhance strength introduce stress fields that can pin magnetic domains, thus increasing coercivity and hysteresis losses5. Here we introduce an approach to overcome this dilemma. We have designed a Fe–Co–Ni–Ta–Al multicomponent alloy (MCA) with ferromagnetic matrix and paramagnetic coherent nanoparticles (about 91 nm in size and around 55% volume fraction). They impede dislocation motion, enhancing strength and ductility. Their small size, low coherency stress and small magnetostatic energy create an interaction volume below the magnetic domain wall width, leading to minimal domain wall pinning, thus maintaining the soft magnetic properties. The alloy has a tensile strength of 1,336 MPa at 54% tensile elongation, extremely low coercivity of 78 A m−1 (less than 1 Oe), moderate saturation magnetization of 100 A m2 kg−1 and high electrical resistivity of 103 μΩ cm. © 2022, The Author(s).

We report on experimental observations of charge-spin cooperative dynamics of two-electron states in a GaAs double quantum dot located in a nonequilibrium phonon environment. When the phonon energy exceeds the lowest excitation energy in the quantum dot, the spin-flip rate of a single electron strongly enhances. In addition, originated from the spatial gradient of phonon density between the dots, the parallel spin states become more probable than the antiparallel ones. These results indicate that spin is essential for further demonstrations of single-electron thermodynamic systems driven by phonons, which will greatly contribute to understanding of the fundamental physics of thermoelectric devices. © 2022 American Physical Society.

Gas diffusion electrodes (GDE) obtained by sputtering metal films on polytetrafluoroethylene (PTFE) membranes are among the most performant electrodes used to electrochemically reduce CO2. The present work reveals several essential aspects for fabricating performant PTFE-based gas diffusion electrodes (GDEs) for CO2 electroreduction (CO2R). We show that adding an additive layer (a mixture of carbon and Nafion™ or Nafion™ only) is required for stabilizing the metal catalyst film (Cu), deposited via sputtering on the PTFE membrane, during the CO2R experiments. We found that the PTFE membrane thickness used in the GDE fabrication plays an essential role in electrode performance. The quantification of the products formed during the CO2R conducted in a flow-cell electrolyzer revealed that on thinner membranes, CO2R is the dominant process while on thicker ones, the H2 formation is promoted. Thus, the PTFE membrane influences the CO2 transport to the catalyst layer and can be used to promote the CO2R while maintaining a minimum H2 production. © 2021 The Authors. ChemElectroChem published by Wiley-VCH GmbH

While pure titanium is a material of choice for medical applications for its excellent mechanical and chemical properties, further improving its surface-related functionalities by surface texturing is also promising. In the present work, we experimentally investigate the fabrication, as well as the resulting functionalities of surface wettability and biocompatibility, of precise mesh-type surface textures on pure titanium by picosecond pulsed laser ablation operating at 1064 nm wavelength. Specifically, the dependence of microgroove morphology on average power and scanning speed is evaluated to yield optimized laser processing parameters, which are utilized to fabricate high precision mesh-type surface textures with uniform feature size and limited thermal effects on pure titanium. Subsequent performance evaluation tests demonstrate that the mesh-type surface textures induce a beneficial effect on the biocompatibility with respect to BMSC cells due to the enhanced hydrophilicity. © 2022, The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature.

The application of electric fields to conductive coatings is an environmentally friendly way to reduce biofilm formation. In particular alternating potentials (APs) have received increasing attention in recent studies. Here, an electrochemical rotating disk setup for dynamic field exposure experiments was developed to study how APs alter the attachment of fouling organisms in a multispecies ocean environment. A specific focus of the device design was proper integration of the potentiostat in the strongly corroding saltwater environment. The effect of APs on the accumulation of fouling organisms in short term field exposures was studied. Potentials on conductive gold surfaces were periodically switched between −0.3 V and 0.3 V or between −0.8 V and 0.6 V at a frequency of 0.5 Hz. APs were capable of significantly reducing the attachment of marine fouling organisms compared with the conductive samples immersed at open circuit potentials. © 2022 Informa UK Limited, trading as Taylor & Francis Group.

The conventional processing route of TNM (Ti-Nb-Mo) alloys combines casting and Hot Isostatic Pressing (HIP) followed by forging and multiple heat treatments to establish optimum properties. This is a time-consuming and costly process. In this study we present an advanced alternative TNM alloy processing route combining HIP and heat treatments into a single process, which we refer to as IHT (integrated HIP heat treatment), applied to a modified TNM alloy with 1.5B. A Quintus HIP lab unit with a quenching module was used, achieving fast and controlled cooling, which differs from the slow cooling rates of conventional HIP units. A Ti-42.5Al-3.5Nb-1Mo-1.5B (at.%) was subjected to an integrated two HIP steps at 200 MPa, one at 1250◦ C for 3 h and another at 1260◦ C for 1 h, both under a protective Ar atmosphere and followed by cooling at 30 K/min down to room temperature. The results were compared against the Ti-43.5Al-3.5Nb-1Mo-0.8B (at.%) thermomechanically processed in a conventional way. Applying IHT processing to the 1.5B alloy does indeed achieve good creep strength, and the secondary creep rate of the IHT processed materials is similar to that of conventionally forged TNM alloys. Thus, the proposed advanced IHT processing route could manufacture more cost-effective TiAl components. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

We present strategies for controlling growth parameters of local droplet etched GaAs quantum dots. We manage the local QD density and emission wavelength by gradient material deposition. We find regions with no light-emitting quantum dots sharply separated from regions with strong quantum dot luminescence. Close to this transition, we expect the lowest quantum dot densities possible under the used parameters. The maximum wavelength shift achieved due to a variation of GaAs hole filling level on a single 3-inch wafer ranges from 731 to 795 nm. By locally controlling the surface roughness, a profound additional influence on the emission wavelength and density is found. We show how to control this modulation on a millimeter-scale over the whole wafer. © 2022 Elsevier B.V.

Green microalgae are gaining attention in the renewable energy field due to their ability to convert light into energy in biophotovoltaic (BPV) cells. The poor exogenous electron transfer kinetics of such microorganisms requires the use of redox mediators to improve the performance of related biodevices. Redox polymers are advantageous in the development of subcellular-based BPV devices by providing an improved electron transfer while simultaneously serving as immobilization matrix. However, these surface-confined redox mediators have been rarely used in microorganism-based BPVs. Since electron transfer relies on the proximity between cells and the redox centres at the polymer matrix, the development of molecularly tailored surfaces is of great significance to fabricate more efficient BPV cells. We propose a bioanode integrating Chlorella vulgaris embedded in an Os complex-modified redox polymer. Chlorella vulgaris cells are functionalized with 3-aminophenylboronic acid that exhibits high affinity to saccharides in the cell wall as a basis for an improved integration with the redox polymer. Maximum photocurrents of (5 ± 1) µA cm−2 are achieved. The developed bioanode is further coupled to a bilirubin oxidase-based biocathode for a proof-of-concept BPV cell. The obtained results encourage the optimization of electron-transfer pathways toward the development of advanced microalgae-based biophotovoltaic devices. © 2022 The Authors

Although titanium nitride (TiN) is among the most extensively studied and thoroughly characterized thin-film ceramic materials, detailed knowledge of relevant dislocation core structures is lacking. By high-resolution scanning transmission electron microscopy (STEM) of epitaxial single crystal (001)-oriented TiN films, we identify different dislocation types and their core structures. These include, besides the expected primary a/2{110}〈11–0〉 dislocation, Shockley partial dislocations a/6{111}〈112–〉 and sessile Lomer edge dislocations a/2{100}〈011〉. Density-functional theory and classical interatomic potential simulations complement STEM observations by recovering the atomic structure of the different dislocation types, estimating Peierls stresses, and providing insights on the chemical bonding nature at the core. The generated models of the dislocation cores suggest locally enhanced metal–metal bonding, weakened Ti-N bonds, and N vacancy-pinning that effectively reduces the mobilities of {110}〈11–0〉 and {111}〈112–〉 dislocations. Our findings underscore that the presence of different dislocation types and their effects on chemical bonding should be considered in the design and interpretations of nanoscale and macroscopic properties of TiN. © 2022 The Authors

Laser additively manufactured duplex stainless steels contain mostly ferrite in the as-built parts due to rapid solidification of the printed layers. To achieve duplex microstructures (ferrite and austenite in roughly equal proportions) and, thus, a good combination of mechanical properties and corrosion resistance, an austenitic stainless steel powder (X2CrNiMo17-12-2) and a super duplex stainless steel powder (X2CrNiMoN25-7-4) were mixed in different proportions and the powder mixtures were processed via PBF-LB/M (Laser Powder Bed Fusion) under various processing conditions by varying the laser power and the laser scanning speed. The optimal process parameters for dense as-built parts were determined by means of light optical microscopy and density measurements. The austenitic and ferritic phase formation of the mixed alloys was significantly influenced by the chemical composition adjusted by powder mixing and the laser energy input during PBF-LB/M. The austenite content increases, on the one hand, with an increasing proportion of X2CrNiMo17-12-2 in the powder mixtures and on the other hand with increasing laser energy input. The latter phenomenon could be attributed to a slower solidification and a higher melt pool homogeneity with increasing energy input influencing the phase formation during solidification and cooling. The desired duplex microstructures could be achieved by mixing the X2CrNiMo17-12-2 powder and the X2CrNiMoN25-7-4 powder at a specific mixing ratio and building with the optimal PBF-LB/M parameters. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

Objective: Because full functional recovery after spinal cord injury (SCI) remains a major challenge, stem cell therapies represent promising strategies to improve neurologic functions after SCI. The olfactory mucosa (OM) displays an attractive source of multipotent cells for regenerative approaches and is easily accessible by biopsies because of its exposed location. The regenerative capacity of the resident olfactory stem cells (OSCs) has been demonstrated in animal as well as clinical studies. This study aims to demonstrate the feasibility of isolation, purification and cultivation of OSCs. Methods: OM specimens were taken dorso-posterior from nasal middle turbinate. OSCs were isolated and purified using the neurosphere assay. Differentiation capacity of the OSCs in neural lineage and their behavior in a plasma clot matrix were investigated. Results: Our study demonstrated that OSCs differentiated into neural lineage and were positive for GFAP as well as β-III tubulin. Furthermore, OSCs were viable and proliferated in a plasma clot matrix. Conclusions: Because there are no standard methods for purification, characterization, and delivery of OSCs to the injury site, which is a prerequisite for the clinical approval, this study focuses on the establishment of appropriate methods and underlines the high potential of the OM for autologous cell therapeutic approaches. © 2022 Elsevier Inc.

The high-temperature austenite phase is the initial state of practically all technologically relevant hot forming and heat treatment operations in steel processing. The phenomena occurring in austenite, such as recrystallization or grain growth, can have a decisive influence on the subsequent properties of the material. After the hot forming or heat treatment process, however, the austenite transforms into other microstructural constituents and information on the prior austenite morphology are no longer directly accessible. There are established methods available for reconstructing former austenite grain boundaries via metallographic etching or electron backscatter diffraction (EBSD) which both exhibit shortcomings. While etching is often difficult to reproduce and strongly depend on the investigated steel’s alloying concept, EBSD acquisition and reconstruction is rather time-consuming. But in fact, though, light optical micrographs of steels contrasted with conventional Nital etchant also contain information about the former austenite grains. However, relevant features are not directly apparent or accessible with conventional segmentation approaches. This work presents a deep learning (DL) segmentation of prior austenite grains (PAG) from Nital etched light optical micrographs. The basis for successful segmentation is a correlative characterization from EBSD, light and scanning electron microscopy to specify the ground truth required for supervised learning. The DL model shows good and robust segmentation results. While the intersection over union of 70% does not fully reflect the model performance due to the inherent uncertainty in PAG estimation, a mean error of 6.1% in mean grain size derived from the segmentation clearly shows the high quality of the result. Copyright © 2022 Bachmann, Müller, Britz, Durmaz, Ackermann, Shchyglo, Staudt and Mücklich.

This study aims to develop a method for on-site metallography, enabling the characterization of carbide banding in cold-work steels via cellulose acetate film replication. It will be demonstrated that for this purpose, it is sufficient to grind the sample surface using P1500 mesh SiC abrasive paper and etch it with V2A etchant or nitric acid for 7 minutes. By sample preparation and etching, the matrix of the parent material is sufficiently removed for the carbides to leave a "negative"impression on the film. This negative replica can then be studied under reflected light microscope, enabling the characterization of carbide banding. © 2022 Walter de Gruyter GmbH, Berlin/Boston, Germany.

The electrochemical properties of high strength 7xxx aluminium alloys strongly depend on the substitutional occupancy of Zn by Cu and Al in the strengthening η-phase with the two-sublattice structure, and its microstructural and compositional prediction is the key to design of new generation corrosion resistant alloys. In this work, we have developed a chemical-potential-based phase-field model capable of describing multi-component and two-sublattice ordered phases, during commercial multi-stage artificial ageing treatments, by directly incorporating the compound energy CALPHAD formalism. The model developed has been employed to explore the complex compositional pathway for the formation of the η-phase in Al-Zn-Mg-Cu alloys during heat treatments. In particular, the influence of alloy composition, solute diffusivity, and heat treatment parameters on the microstructural and compositional evolution of η-phase precipitates, was systematically investigated from a thermodynamic and kinetic perspective and compared to electron probe microanalysis validation data. The simulated η-phase growth kinetics and the matrix residual solute evolution in the AA7050 alloy indicates that Zn depletion mainly controlled the η-phase growth process during the early stage of ageing, resulting in fast η-phase growth kinetics, enrichment of Zn in the η-phase, and an excess in residual Cu in the matrix. The gradual substitution of Zn by Cu atoms in the η-phase during the later ageing stage was in principle a kinetically controlled process, owing to the slower diffusivity of Cu relative to Zn in the matrix. It was also found that the higher nominal Zn content in alloys like the AA7085 alloy, compared to the AA7050 alloy, could significantly enhance the chemical potential of Zn, but this had a minor influence on Cu, which essentially led to the higher Zn content (and consequently lower Cu) seen in the η-phase. Finally, substantial depletion of Zn and supersaturation of Cu in the matrix of the AA7050 alloy was predicted after 24 h ageing at 120 ∘C, whereas the second higher-temperature ageing stage at 180 ∘C markedly enhanced the diffusion of Cu from the supersaturated matrix into the η-phase, while the matrix residual Zn content was only slightly affected. © 2021 The Author(s)

Europium sulfide (EuS) thin films are appealing as ferromagnetic semiconductors and luminescent and optomagnetic materials owing to their unique functional properties. With the emerging field of spintronics and magneto-optical devices, chemical vapor deposition (CVD) offers a versatile platform to tune the material properties and the method to fabricate device structures needed for such applications. Herein, we report the growth of high-quality cubic EuS via a versatile CVD process where the new Eu(III) precursors employed facilitate the formation of the target EuS layers under moderated process conditions. Based on the prior evaluation of the physicochemical properties of these precursors using thermal analysis and density functional theory studies, adequate volatility, thermal stability, and sufficient reactivity toward potential co-reactants, namely, elemental sulfur, could be inferred. Thus, the use of toxic hydrogen sulfide generally needed for sulfide film depositions could be avoided, which is a significant advantage in terms of simplifying the deposition process. The as-deposited thin films were analyzed in terms of the structure, composition, and morphology, revealing highly oriented polycrystalline and stoichiometric EuS films. UV/vis measurements yielded a band gap of around 1.6 eV, and Raman spectroscopy exhibited a coupling between the phonons and electron spin systems of EuS. These findings, together with the soft ferromagnetic character of the films derived from semiconducting quantum interference device measurements, signify the potential of CVD-grown EuS for future technological applications. © 2021 American Chemical Society.

While age-hardened austenitic high-Mn and high-Al lightweight steels exhibit excellent strength-ductility combinations, their properties are strongly degraded when mechanically loaded under harsh environments, e.g. with the presence of hydrogen (H). The H embrittlement in this type of materials, especially pertaining to the effect of κ-carbide precipitation, has been scarcely studied. Here we focus on this subject, using a Fe-28.4Mn-8.3Al-1.3C (wt%) steel in different microstructure conditions, namely, solute solution treated and age-hardened. Contrary to the reports that grain boundary (GB) κ-carbides precipitate only during overaging, site-specific atom probe tomography and scanning transmission electron microscopy (STEM) reveal the existence of nanosized GB κ-carbides at early stages of aging. We correlate this observation with the deterioration of H embrittlement resistance in aged samples. While H pre-charged solution-treated samples fail by intergranular fracture at depths consistent with the H ingress depth (∼20 µm), age-hardened samples show intergranular fracture features at a much larger depth of above 500 µm, despite similar amount of H introduced into the material. This difference is explained in terms of the facile H-induced decohesion of GB κ-carbides/matrix interfaces where H can be continuously supplied through internal short-distance diffusion to the propagating crack tips. The H-associated decohesion mechanisms are supported by a comparison with the fracture behavior in samples loaded under the cryogenic temperature and can be explained based on dislocation pileups and elastic misfit at the GB κ-carbide/matrix interfaces. The roles of other plasticity-associated H embrittlement mechanisms are also discussed in this work based on careful investigations of the dislocation activities near the H-induced cracks. Possible alloying and microstructure design strategies for the enhancement of the H embrittlement resistance in this alloy family are also suggested. © 2022

Interstitials, e.g., C, N, and O, are attractive alloying elements as small atoms on interstitial sites create strong lattice distortions and hence substantially strengthen metals. However, brittle ceramics such as oxides and carbides usually form, instead of solid solutions, when the interstitial content exceeds a critical yet low value (e.g., 2 at.%). Here we introduce a class of massive interstitial solid solution (MISS) alloys by using a highly distorted substitutional host lattice, which enables solution of massive amounts of interstitials as an additional principal element class, without forming ceramic phases. For a TiNbZr-O-C-N MISS model system, the content of interstitial O reaches 12 at.%, with no oxides formed. The alloy reveals an ultrahigh compressive yield strength of 4.2 GPa, approaching the theoretical limit, and large deformability (65% strain) at ambient temperature, without localized shear deformation. The MISS concept thus offers a new avenue in the development of metallic materials with excellent mechanical properties. © 2022, The Author(s).

In the present work, we use an advanced EBSD method to analyze the two prominent types of martensite microstructures that are found in the binary Fe-Ni system, lath martensite (27.5 at.% Ni) and plate martensite (29.5 at.% Ni). We modify, document, and apply an analytical EBSD procedure, which was originally proposed by Yardley and Payton, 2014. It analyzes the distributions of the three KSI-angles (ξ1, ξ2, and ξ3, KSI after Kurdjumov and Sachs), which describe small angular deviations between crystal planes in the unit cells of martensite and austenite—which are related through specific orientation relationships. The analysis of the angular distributions can be exploited to obtain high-resolution, color-coded micrographs of martensitic microstructures, which, for example, visualize the difference between lath and plate martensite and appreciate the microstructural features, like midribs in large plate martensite crystals. The differences between the two types of martensite also manifest themselves in different distributions of the KSI-angles (wider for lath and narrower for plate martensite). Finally, our experimental results prove that local distortions result in scatter, which is larger than the differences between the orientation relationships of Kurdjumov/Sachs, Nishiyama/Wassermann, and Greninger/Troiano. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

Although highly desired and studied for decades, direct methane functionalization to liquid products remains a challenge. We report an electrochemical system using a boron-doped diamond (BDD) anode in concentrated sulfuric acid that is able to convert methane to methyl bisulfate and methanesulfonic acid without the use of a catalyst by indirect electrochemical oxidation. Due to its high material stability, BDD can be operated at high current densities. High temperature (140 °C) and pressure (70 bar) support the formation of methyl bisulfate to concentrations as high as 160 mM in 3 h and methanesulfonic acid to concentrations of up to 750 mM in 8 h. We present a novel way of catalyst-free electrochemical methane oxidation and show general trends and limitations of this reaction. © 2021 The Authors. ChemElectroChem published by Wiley-VCH GmbH

Premature failure of rail and bearing steels by White-Etching-Cracks leads to severe economic losses. This failure mechanism is associated with microstructure decomposition via local severe plastic deformation. The decomposition of cementite plays a key role. Due to the high hardness of this phase, it is the most difficult obstacle to overcome in the decaying microstructure. Understanding the mechanisms of carbide decomposition is essential for designing damage-resistant steels for industrial applications. We investigate cementite decomposition in the bearing steel 100Cr6 (AISI 52100) upon exposure to high-pressure torsion (maximum shear strain, Ƴmax = 50.2). Following-up on our earlier work on cementite decomposition in hardened 100Cr6 steel (Qin et al., Act. Mater. 2020 [1]), we now apply a modified heat treatment to generate a soft-annealed microstructure where spherical and lamellar cementite precipitates are embedded in a ferritic matrix. These two precipitate types differ in morphology (spherical vs. lamellar), size (spherical: 100–1000 nm diameter, lamellar: 40–100 nm thickness) and composition (Cr and Mn partitioning). We unravel the correlation between cementite type and its resistance to decomposition using multi-scale chemical and structural characterization techniques. Upon high-pressure torsion, the spherical cementite precipitates did not decompose, but the larger spherical precipitates (≥ 1 μm) deformed. In contrast, the lamellar cementite precipitates underwent thinning followed by decomposition and dissolution. Moreover, the decomposition behavior of cementite precipitates is affected by the type of matrix microstructure. We conclude that the cementite size and morphology, as well as the matrix mechanical properties are the predominating factors influencing the decomposition behavior of cementite. The compositional effects of Cr and Mn on cementite stability calculated by complementary density functional theory (DFT) calculations are minor in the current scenario. © 2021 Elsevier B.V.

The direct sulfonation of methane to methanesulfonic acid was achieved in an electrochemical reactor without adding peroxide initiators. The synthesis proceeds only from oleum and methane. This is possible due to in situ formation of an initiating species from the electrolyte at a boron-doped diamond anode. Elevated pressure, moderate temperature and suitable current density are beneficial to reach high concentration at outstanding selectivity. The highest concentration of 3.7 M (approximately 62 % yield) at 97 % selectivity was reached with a stepped electric current program at 6.25–12.5 mA cm−2, 70 °C and 90 bar methane pressure in 22 hours. We present a novel, electrochemical method to produce methanesulfonic acid, propose a reaction mechanism and show general dependencies between parameters and yields for methanesulfonic acid. © 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.

Mitigating high energy costs related to sustainable H2 production via water electrolysis is important to make this process commercially viable. Possible approaches are the investigation of low-cost, highly active oxygen evolution reaction (OER) catalysts and the exploration of alternative anode reactions, such as the electrocatalytic isopropanol oxidation reaction (iPOR) or the glycerol oxidation reaction (GOR), offering the possibility of simultaneously lowering the anodic overpotential and generating value-added products. A suitable class of catalysts are non-noble metal-based perovskites with the general formula ABO3, featuring rare-earth metal cations at the A- and transition metals at the B-site. We synthesised a series of LaFe1-xCoxO3 materials with x=0–0.70 by automated co-precipitation at constant pH and subsequent calcination at 800 °C. X-ray diffraction studies revealed that the phase purity was preserved in samples with x≤0.3. The activity towards the OER, iPOR, and GOR was investigated by rotating disk electrode voltammetry, showing a relation between structure and metal composition with the activity trends observed for the three reactions. Additionally, GOR product analysis via high-performance liquid chromatography (HPLC) was conducted after 24 and 48 h electrolysis in a circular flow-through cell setup, pointing out a trade-off between activity and selectivity. © 2022 The Authors. ChemElectroChem published by Wiley-VCH GmbH

Ion-induced secondary electron emission at a target surface is an essential mechanism for laboratory plasmas, i.e. magnetron sputtering discharges. Electron emission, however, is strongly affected by the target condition itself such as oxidation. Data of oxidized targets, however, are very sparse and prone to significant systematic errors, because they were often determined by modeling the complex behavior of the plasma. Thus, it is difficult to isolate the process of ion-induced electron emission from all other plasma-surface-interactions. By utilizing ion beams, the complex plasma environment is avoided and electron yields are determined with higher accuracy. In this study, ion-induced secondary electron emission coefficients (SEECs) of clean, untreated (air-exposed), and intentionally oxidized copper and nickel surfaces were investigated in such a particle beam experiment. Pristine and oxidized metal foils were exposed to beams of singly charged argon ions with energies of 0.2 keV-10 keV. After the ion beam treatment, the surface conditions were analyzed by ex-situ X-ray photoelectron spectroscopy measurements. Further, a model for the electron emission of a partly oxidized surface is presented, which is in agreement with the experimental data. It was found, that oxidized and untreated/air-exposed surfaces do not show the same SEEC: for intentionally oxidized targets, the electron yields were smaller by a factor of 2 than for untreated/air-exposed surfaces. SEECs of oxides were found to be between the values for clean and for untreated metal surfaces. Further, the SEEC was at maximum for untreated/air-exposed surfaces and at minimum for clean surfaces; the electron yields of untreated/air-exposed and clean surfaces were in agreement with values reported in the literature. © 2022 The Author(s). Published by IOP Publishing Ltd.

The influence of bed agitation during the combustion of biomass pellets was investigated experimentally and numerically. In the experiments, a bulk of straw pellets was burnt in a batch-operated reactor. The reactor allows for air staging and mixing of the fuel bed by vertically moveable mixing elements. The primary to secondary air ratio was varied and the reactor was operated either in the agitated (moving mixing elements) or the static mode (mixing elements at rest). The overall mass of the bulk was measured continuously during the combustion process. The results show a significant increase of the mass loss rate by almost 60% when the bed was agitated compared to the static case. Samples of the residual material of the pellets reveal a totally different amount of molten and agglomerated ash particles for the different operational conditions. Decreased primary to secondary air ratios as well as agitation of the fuel bed did lead to less agglomeration of the ash. The Discrete Element Method (DEM) was coupled with a Computational Fluid Dynamics (CFD) simulation. Coupled DEM/CFD simulations of the batch reactor were performed to get access to bulk internal data of the solid material and the fluid phase. Simulations identified that a reduced amount of ash exposed to the volatile flame through agitation of the fuel bed was the main reason for minimized ash agglomeration. © 2019 Taylor & Francis Group, LLC.

Unlike other thermal spraying methods, it is difficult to determine the temperature of the particles during cold gas spraying due to the relatively low radiation. In the present study, the velocities and in-flight temperatures of metal particles were measured during cold gas spraying. A state-of-the-art high-speed infrared camera was used to study the behavior of two different base materials, In718 and TiAlCrNb, both used as structural materials in gas turbine engines. The experiments aimed to improve the fundamental understanding of the process, in particular the heating of the particles, and to compare the experimental results with theoretical calculations of the particle temperatures. © 2022, The Author(s).

Co-Ni-Ga shape memory alloys attracted scientific attention as promising candidate materials for damping applications at elevated temperatures, owing to excellent superelastic properties featuring a fully reversible stress-strain response up to temperatures as high as 500 °C. In the present work, the effect of aging treatments conducted in a wide range of aging temperatures and times, i.e. at 300–400 °C for 0.25–8.5 h, was investigated. It is shown that critical features of the martensitic transformation are strongly affected by the heat treatments. In particular, the formation of densely dispersed γ’-nanoparticles has a strong influence on the martensite variant selection and the morphology of martensite during stress-induced martensitic transformation. Relatively large, elongated particles promote irreversibility. In contrast, small spheroidal particles are associated with excellent functional stability during cyclic compression loading of 〈001〉-oriented single crystals. In addition to mechanical experiments, a detailed microstructural analysis was performed using in situ optical microscopy and neutron diffraction. Fundamental differences in microstructural evolution between various material states are documented and the relations between thermal treatment, microstructure and functional properties are explored and rationalized. © 2022 Acta Materialia Inc.

Grain boundaries (GBs) are planar lattice defects that govern the properties of many types of polycrystalline materials. Hence, their structures have been investigated in great detail. However, much less is known about their chemical features, owing to the experimental difficulties to probe these features at the atomic length scale inside bulk material specimens. Atom probe tomography (APT) is a tool capable of accomplishing this task, with an ability to quantify chemical characteristics at near-atomic scale. Using APT data sets, we present here a machine-learning-based approach for the automated quantification of chemical features of GBs. We trained a convolutional neural network (CNN) using twenty thousand synthesized images of grain interiors, GBs, or triple junctions. Such a trained CNN automatically detects the locations of GBs from APT data. Those GBs are then subjected to compositional mapping and analysis, including revealing their in-plane chemical decoration patterns. We applied this approach to experimentally obtained APT data sets pertaining to three case studies, namely, Ni-P, Pt-Au, and Al-Zn-Mg-Cu alloys. In the first case, we extracted GB specific segregation features as a function of misorientation and coincidence site lattice character. Secondly, we revealed interfacial excesses and in-plane chemical features that could not have been found by standard compositional analyses. Lastly, we tracked the temporal evolution of chemical decoration from early-stage solute GB segregation in the dilute limit to interfacial phase separation, characterized by the evolution of complex composition patterns. This machine-learning-based approach provides quantitative, unbiased, and automated access to GB chemical analyses, serving as an enabling tool for new discoveries related to interface thermodynamics, kinetics, and the associated chemistry-structure-property relations. © 2022 The Authors

A seamless and lossless transition of the constitutive description of the elastic response of materials between atomic and continuum scales has been so far elusive. Here we show how this problem can be overcome by using artificial intelligence (AI). A convolutional neural network (CNN) model is trained, by taking the structure image of a nanoporous material as input and the corresponding elasticity tensor, calculated from molecular statics (MS), as output. Trained with the atomistic data, the CNN model captures the size- and pore-dependency of the material’s elastic properties which, on the physics side, derive from its intrinsic stiffness as well as from surface relaxation and non-local effects. To demonstrate the accuracy and the efficiency of the trained CNN model, a finite element method (FEM)-based result of an elastically deformed nanoporous beam equipped with the CNN as constitutive law is compared with that obtained by a full atomistic simulation. The trained CNN model predicts the elasticity tensor in the test dataset with a root-mean-square error of 2.4 GPa (3.0% of the bulk modulus) when compared to atomistic calculations. On the other hand, the CNN model is about 230 times faster than the MS calculation and does not require changing simulation methods between different scales. The efficiency of the CNN evaluation together with the preservation of important atomistic effects makes the trained model an effective atomistically informed constitutive model for macroscopic simulations of nanoporous materials, optimization of nanostructures, and the solution of inverse problems. © 2022, The Author(s).

This study presents an investigation on the specific electrical conductivity of the cathode materials used in an aluminium electrolysis cell over a temperature range between room temperature and 950 °C. Those materials are subjected to a diffusion related aging process due to the high operating temperature of the cell, leading to a change in chemical composition and microstructure. The materials were investigated both in the initial state before use in an aluminium electrolysis cell and after an operating period of 5 years. It is shown that the changes in chemical composition and thus also in microstructure over the service life at elevated operating temperature exert an effect on the electrical conductivity. In addition, calculations based on thermodynamic data were used to relate phase transformations to the changes in electrical conductivity. On the one hand, the electrical conductivity of the collector bar at 950 °C is reduced by about 11% after 5 years of service. On the other hand, the ageing process has a positive influence on the cast iron with an increased conductivity by about 41% at 950 °C. The results provide an understanding how diffusion related processes in the cathode materials affect energy efficiency of the aluminium electrolysis cell. © 2022, The Author(s).

The complex interplay between chemistry, microstructure, and behavior of many engineering materials has been investigated predominantly by experimental methods. Parallel to the increase in computer power, advances in computational modeling methods have resulted in a level of sophistication which is comparable to that of experiments. At the continuum level, one class of such models is based on continuum thermodynamics, phase-field methods, and crystal plasticity, facilitating the account of multiple physical mechanisms (multi-physics) and their interaction during microstructure evolution. This paper reviews the status of simulation approaches and software packages in this field and gives an outlook towards promising research directions. © 2022, The Author(s).

Single Pt atom catalysts are key targets because a high exposure of Pt substantially enhances electrocatalytic activity. In addition, PtRu alloy nanoparticles are the most active catalysts for the methanol oxidation reaction. To combine the exceptional activity of single Pt atom catalysts with an active Ru support we must overcome the synthetic challenge of forming single Pt atoms on noble metal nanoparticles. Here we demonstrate a process that grows and spreads Pt islands on Ru branched nanoparticles to create single-Pt-atom-on-Ru catalysts. By following the spreading process by in situ TEM, we found that the formation of a stable single atom structure is thermodynamically driven by the formation of strong Pt–Ru bonds and the lowering of the surface energy of the Pt islands. The stability of the single-Pt-atom-on-Ru structure and its resilience to CO poisoning result in a high current density and mass activity for the methanol oxidation reaction over time. [Figure not available: see fulltext.] © 2022, The Author(s), under exclusive licence to Springer Nature Limited.

Deterministic sources of multiphoton entanglement are highly attractive for quantum information processing but are challenging to realize experimentally. In this Letter, we demonstrate a route toward a scaleable source of time-bin encoded Greenberger-Horne-Zeilinger and linear cluster states from a solid-state quantum dot embedded in a nanophotonic crystal waveguide. By utilizing a self-stabilizing double-pass interferometer, we measure a spin-photon Bell state with (67.8±0.4)% fidelity and devise steps for significant further improvements. By employing strict resonant excitation, we demonstrate a photon indistinguishability of (95.7±0.8)%, which is conducive to fusion of multiple cluster states for scaling up the technology and producing more general graph states. © 2022 American Physical Society.

The gradient microstructures of surface layer in single crystal nickel-based superalloy were produced by creep-feed grinding. The mechanical properties (i.e., hardness, elastic modulus) and room-temperature (RT) creep behavior of such structures were evaluated using a nano-indentation technique. Results show that the gradient structures along depth from ground surface consisted of nanograins, submicron grains and lamellar-shape structures, and dislocation structures. Furthermore, it was found that the hardness and elastic modulus of gradient structures were higher by 8–10% than that of bulk material on average. However, the regions containing nanograins showed a remarkable increase in creep depth compared to bulk material, implying that the creep behavior of ground layer was changed unfavorably. The obtained stress exponents of gradient structures suggested that dislocation activities were the main mechanism for indentation creep deformation. © 2021 Elsevier B.V.

Ni-Mn-based Heusler alloys have a high technical potential related to a large change of magnetization at the structural phase transition. These alloys show a subtle dependence of magnetic properties and structural phase stability on composition and substitution by 3d elements and although they have been extensively investigated, there are still ambiguities in the published results and their interpretation. To shed light on the large spread of reported properties, we perform a comprehensive study by means of density functional theory calculations. We focus on Cr and Co co-substitution whose benefit has been predicted previously for the expensive Ni-Mn-In-based alloy and study the more abundant iso-electronic counterpart Ni-Mn-Ga. We observe that substituting Ni partially by Co and/or Cr enhances the magnetization of the Heusler alloy and at the same time reduces the structural transition temperature. Thereby, Cr turns out to be more efficient to stabilize the ferromagnetic alignment of the Mn spins by strong antiferromagnetic interactions between Mn and Cr atoms. In a second step, we study Cr on the other sublattices and observe that an increase in the structural transition temperature is possible, but depends critically on the short-range order of Mn and Cr atoms. Based on our results, we are able to estimate composition dependent magnetic phase diagrams. In particular, we demonstrate that neither the atomic configuration with the lowest energy nor the results based on the coherent potential approximation are representative for materials with a homogeneous distribution of atoms and we also predict a simple method for fast screening of different concentrations which can be viewed as a blueprint for the study of high entropy alloys. Our results help to explain the large variation of experimentally found materials properties. © 2021 The Author(s). Published by IOP Publishing Ltd.

Alkaline anodic oxidation of glycerol suffers from facile C−C bond cleavage, especially when using non-precious metal electrocatalysts, which limits the yield of more valuable C3 oxygenates. Usually, a high C3 selectivity is a tradeoff with conversion for most catalysts. Thus, we used solketal as the reactant, which is acetal-protected glycerol with acetone. CV experiments showed that solketal is oxidized over nickel boride (NixB) at potentials where NiOOH is formed. Electrolysis over NixB in a thin-film spectroelectrochemical flow cell at 1.58 V vs. RHE to avoid pronounced oxygen evolution showed a stable current density of ca. 6 mA cm−2. Simultaneously recorded ATR-FTIR spectra revealed solketal conversion to solketalate and formate. Indeed, 59 % conversion and 77 % selectivity to glyceric acid were determined by HPLC after acidic cleavage of the acetal, resulting in a yield of 45 %. Therefore, solketal is a promising reactant for the selective electrosynthesis of glyceric acid. © 2021 The Authors. ChemElectroChem published by Wiley-VCH GmbH.

Tunnel-coupled pairs of optically active quantum dots—quantum dot molecules (QDMs)—offer the possibility to combine excellent optical properties such as strong light-matter coupling with two-spin singlet–triplet ((Formula presented.)) qubits having extended coherence times. The (Formula presented.) basis formed using two spins is inherently protected against electric and magnetic field noise. However, since a single gate voltage is typically used to stabilize the charge occupancy of the dots and control the inter-dot orbital couplings, operation of the (Formula presented.) qubits under optimal conditions remains challenging. Here, an electric field tunable QDM that can be optically charged with one (1h) or two holes (2h) on demand is presented. A four-phase optical and electric field control sequence facilitates the sequential preparation of the 2h charge state and subsequently allows flexible control of the inter-dot coupling. Charges are loaded via optical pumping and electron tunnel ionization. One- and two-hole charging efficiencies of (93.5 ± 0.8)% and (80.5 ± 1.3)% are achieved, respectively. Combining efficient charge state preparation and precise setting of inter-dot coupling allows for the control of few-spin qubits, as would be required for the on-demand generation of 2D photonic cluster states or quantum transduction between microwaves and photons. © 2022 The Authors. Advanced Quantum Technologies published by Wiley-VCH GmbH.

Electrocatalytic oxidation of glycerol (GOR) as the anode reaction in water electrolysis facilitates the production of hydrogen at the cathode at a substantially lower cell voltage compared with the oxygen evolution reaction. It simultaneously provides the basis for the production of value-added compounds at the anode. We investigate earth-abundant transition-metal oxide nanoparticles (Fe, Ni, Mn, Co) embedded in multiwalled carbon nanotubes as GOR catalysts. Out of the four investigated composites, the Ni-based catalyst exhibits the highest catalytic activity toward the GOR according to rotating disk electrode voltammetry, reaching a current density of 10 mA cm–2 already at 1.31 V vs RHE, a potential below the formation of Ni3+. Chronoamperometry conducted in a flow-through cell followed by HPLC analysis is used to identify and quantify the GOR products over time, revealing that the applied potential, electrolyte concentration, and duration of the experiment impact strongly the composition of the products’ mixture. Upon optimization, the GOR is directed toward oxalate production. Moreover, oxalate is not further converted and hence accumulates as a major organic product under the chosen conditions in a concentration ratio of 60:1 with acetate as a minor product after 48 h electrolysis in 7 M KOH, which represents a promising route for the synthesis of this highly valued product. © 2022 American Chemical Society

The tensors of thermal expansion of monoclinic RCa4O(BO3)3 with R = Er, Y, Dy, Gd, Sm, Nd, La were studied in the temperature range from 100 K to 1373 K using high-resolution dilatometry. Reproducible anomalies, characterized by an excess strain at high temperatures, occur at different temperatures depending on the type of the R3+ cation. Additional single-crystal diffraction experiments on quenched samples and heat capacity measurements indicate that non-convergent cation ordering processes involving Ca2+ and R3+ play an essential role here. The cation distribution on the specific structural sites and the evolution of disorder with temperature are mainly influenced by the size of the trivalent cation, with the minimization of internal stresses being the driving force. The onset temperatures and the specific anisotropy of the anomalies in the thermal expansion are directly related to these processes. © 2022 The Authors

Halogen bonding has recently been recognized as an interaction whose relevance is on par with hydrogen bonding. While observed frequently in solution chemistry, the significance of halogen bonds in forming extended supramolecular structures on surfaces is less explored. Herein, we report on the self-assembly of chlorobenzene molecules adsorbed on the Cu(111) surface into nanosized clusters at submonolayer coverages, where the molecular planes are close to parallel to the surface. A comprehensive study of the role of intermolecular interactions through both halogen and weak hydrogen bonds on nanocluster formation is presented, gained by combining the results of temperature-programmed desorption, reflection-absorption infrared spectroscopy, scanning tunneling microscopy, and density functional theory calculations. Based on an unprecedented precise determination of the molecules’ orientation within the clusters, the binding motifs that lead to the formation and stability of nanoclusters with magic sizes are identified and explained. A complex and delicate interplay of halogen bonds with weak hydrogen bonds, van-der-Waals forces, and surface–adsorbate interactions leads to a preference for hexamers and tetramers with an observable propensity for halogen bonding over weak hydrogen bonding when adsorbed to the Cu(111) surface. © 2021 American Chemical Society

A twin surface dielectric barrier discharge (SDBD) ignited in a dry synthetic air gas stream is studied regarding the formation of reactive oxygen and nitrogen species (RONS) and their impact on the conversion of admixed n-butane. The discharge is driven by a damped sinusoidal voltage waveform at peak-to-peak amplitudes of 8 kVpp-13 kVpp and pulse repetition frequencies of 250 Hz-4000 Hz. Absolute densities of O3, NO2, NO3, as well as estimates of the sum of the densities of N2O4 and N2O5 are determined temporally resolved by means of optical absorption spectroscopy using a laser driven broadband light source, suitable interference filters, and a photodiode detector. The measured densities are acquired across the center of the reactor chamber as well as at the outlet of the chamber. The temporal and spatial evolution of the species' densities is correlated to the conversion of n-butane at concentrations of 50 ppm and 400 ppm, measured by means of flame ionization detectors. The n-butane is admixed either before or after the reactor chamber, in order to separate the impact of short- and long-lived reactive species on the conversion process. It is found that, despite the stationary conversion at the selected operating points, at higher voltages and repetition frequencies the densities of the measured species are not in steady state. Based on the produced results it is presumed that the presence of n-butane modifies the formation and consumption pathways of O3. At the same time, there is no significant impact on the formation of dinitrogen oxides (N2O4 and N2O5). Furthermore, a comparatively high conversion of n-butane, when admixed at the outlet of the reactor chamber is observed. These findings are discussed together with known rate coefficients for the reactions of n-butane with selected RONS. © 2022 The Author(s). Published by IOP Publishing Ltd

Precise control of the properties of semiconductor quantum dots (QDs) is vital for creating novel devices for quantum photonics and advanced opto-electronics. Suitable low QD-densities for single QD devices and experiments are challenging to control during epitaxy and are typically found only in limited regions of the wafer. Here, we demonstrate how conventional molecular beam epitaxy (MBE) can be used to modulate the density of optically active QDs in one- and two- dimensional patterns, while still retaining excellent quality. We find that material thickness gradients during layer-by-layer growth result in surface roughness modulations across the whole wafer. Growth on such templates strongly influences the QD nucleation probability. We obtain density modulations between 1 and 10 QDs/µm2 and periods ranging from several millimeters down to at least a few hundred microns. This method is universal and expected to be applicable to a wide variety of different semiconductor material systems. We apply the method to enable growth of ultra-low noise QDs across an entire 3-inch semiconductor wafer. © 2022, The Author(s).

Powder bed fusion of metals using a laser beam system (PBF-LB/M) of highly complex and filigree parts made of tool steels is becoming more important for many industrial applications and scientific investigations. To achieve high density and sufficient chemical homogeneity, pre-alloyed gas-atomized spherical powder feedstock is used. For high-performance materials such as tool steels, the number of commercially available starting powders is limited due to the susceptibility to crack formation in carbon-bearing steels. Furthermore, scientific alloy development in combination with gas-atomization is a cost-intensive process which requires high experimental effort. To overcome these drawbacks, this investigation describes the adaption of a hot work tool steel for crack-free PBFLB/M-fabrication without any preheating as well as an alternative alloying strategy which implies the individual admixing of low-cost aspherical elemental powders and ferroalloy particles with gas-atomized pure iron powder. It is shown that the PBF-LB/M-fabrication of this powder mixture is technically feasible, even though the partly irregular-shaped powder particles reduce the flowability and the laser reflectance compared to a gas-atomized reference powder. Moreover, some high-melting alloying ingredients of the admixed powder remain unmolten within the microstructure. To analyze the laser energy input in detail, the second part of the investigation focuses on the characterization of the individual laser light reflectance of the admixed alloy, the gas-atomized reference powder and the individual alloying elements and ferroalloys. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

Mechanochemistry has proven to be an excellent green synthesis method for preparing organic, pharmaceutical, and inorganic materials. Mechanocatalysis, inducing a catalytic reaction by mechanical forces, is an emerging field because neither external temperature nor pressure inputs are required. Previous studies reported enhanced catalytic activity during the mechanical treatment of supported gold catalysts for CO oxidation. So far, the processes inside the milling vessel during mechanocatalysis could not be monitored. In this work, the results of high-energy operando X-ray powder diffraction experiments and online gas analysis will be reported. A specific milling setup with a custom-made vessel and gas dosing system was developed. To prove the feasibility of the experimental setup for operando diffraction studies during mechanocatalysis, the CO oxidation with Au@Fe2O3 as a catalyst was selected as a well-known model reaction. The operando studies enabled monitoring morphology changes of the support as well as changes in the crystallite size of the gold catalyst. The change of the crystal size is directly correlated to changes in the active surface area and thus to the CO2 yield. The studies confirm the successful implementation of the operando setup, and its potential to be applied to other catalytic reactions. © 2022 The Authors. ChemCatChem published by Wiley-VCH GmbH.

Iron- and steelmaking cause ∼7% of the global CO2 emissions, due to the use of carbon for the reduction of iron ores. Replacing carbon by hydrogen as the reductant offers a pathway to massively reduce these emissions. However, the production of hydrogen using renewable energy will remain as one of the bottlenecks at least during the next two decades, because making the gigantic annual crude steel production of 1.8 billion tons sustainable requires a minimum stoichiometric amount of ∼97 million tons of green hydrogen per year. Another fundamental aspect to render the ironmaking sector more sustainable lies in an optimal utilization of green hydrogen and energy, thus reducing efforts for costly in-process hydrogen recycling. We therefore demonstrate here how the efficiency in hydrogen and energy consumption during iron ore reduction can be dramatically improved by the knowledge-based combination of two technologies: partially reducing the ore at low temperature via solid-state direct reduction (DR) to a kinetically defined degree, and subsequently melting and completely transforming it to iron under a reducing plasma (i.e. via hydrogen plasma reduction, HPR). Results suggest that an optimal transition point between these two technologies occurs where their efficiency in hydrogen utilization is equal. We found that the reduction of hematite through magnetite into wüstite via DR is clean and efficient, but it gets sluggish and inefficient when iron forms at the outermost layers of the iron ore pellets. Conversely, HPR starts violent and unstable with arc delocalization, but proceeds smoothly and efficiently when processing semi-reduced oxides, an effect which might be related to the material's high electrical conductivity. We performed hybrid reduction experiments by partially reducing hematite pellets via DR at 700 °C to 38% global reduction (using a standard thermogravimetry system) and subsequently transferring them to HPR, conducted with a lean gas mixture of Ar-10%H2 in an arc-melting furnace, to achieve full conversion into liquid iron. This hybrid approach allows to exploit the specific characteristics and kinetically favourable regimes of both technologies, while simultaneously showing the potential to keep the consumption of energy and hydrogen low and improve both, process stability and furnace longevity by limiting its overexposure to plasma radiation. © 2022 Elsevier Ltd

Scanning tunneling microscopy (STM) and density functional theory (DFT) were used to study the tautomerization reaction of an H2Pc molecule adsorbed on a Ag(100) surface. The presence of two hydrogen atoms in the cavity of the H2Pc molecule enforces the existence of two molecular tautomers. It causes a reduction from 4- to 2-fold symmetry in STM images that can be recorded as two current states over the H2Pc molecule with a high-to-low current state ratio of ∼1.2. These findings are confirmed by the spatial distributions of the all-atom electron charge density calculated by using DFT and transmission maps together with tunneling current ratios (∼1.2) determined from the nonequilibrium Green's function transport calculations. Therefore, we demonstrate that an H2Pc molecule adsorbed on a Ag(100) surface is a good candidate for a bistable molecular conductance switch since neither the presence of the Ag(100) surface nor that of the STM tip alters the tautomerization. © 2022 American Chemical Society.

Domain walls and phase boundaries are fundamental ingredients of ferroelectrics and strongly influence their functional properties. Although both interfaces have been studied for decades, often only a phenomenological macroscopic understanding has been established. The recent developments in experiments and theory allow to address the relevant time and length scales and revisit nucleation, phase propagation and the coupling of domains and phase transitions. This review attempts to specify regularities of domain formation and evolution at ferroelectric transitions and give an overview on unusual polar topological structures that appear as transient states and at the nanoscale. We survey the benefits, validity, and limitations of experimental tools as well as simulation methods to study phase and domain interfaces. We focus on the recent success of these tools in joint scale-bridging studies to solve long lasting puzzles in the field and give an outlook on recent trends in superlattices. © 2021 IOP Publishing Ltd.

We investigated the effects of interstitial N and C on the stacking fault energy (SFE) of an equiatomic CoCrNi medium entropy alloy. Results of computer modeling were compared to tensile deformation and electron microscopy data. Both N and C in solid solution increase the SFE of the face-centered cubic (FCC) alloy matrix at room temperature, with the former having a more significant effect by 240% for 0.5 at % N. Total energy calculations based on density functional theory (DFT) as well as thermodynamic modeling of the Gibbs free energy with the CALPHAD (CALculation of PHAse Diagrams) method reveal a stabilizing effect of N and C interstitials on the FCC lattice with respect to the hexagonal close-packed (HCP) CoCrNi-X (X: N, C) lattice. Scanning transmission electron microscopy (STEM) measurements of the width of dissociated ½<110> dislocations suggest that the SFE of CoCrNi increases from 22 to 42–44 mJ·m−2 after doping the alloy with 0.5 at. % interstitial N. The higher SFE reduces the nucleation rates of twins, leading to an increase in the critical stress required to trigger deformation twinning, an effect which can be used to design load-dependent strain hardening response. © 2022 The Author(s). Published by National Institute for Materials Science in partnership with Taylor & Francis Group.

On-demand single-photon sources emitting pure and indistinguishable photons at the telecommunication wavelength are critical assets toward the deployment of fiber-based quantum networks. Indeed, single photons may serve as flying qubits, allowing communication of quantum information over long distances. Self-assembled InAs quantum dots embedded in GaAs constitute an excellent nearly deterministic source of high-quality single photons, but the vast majority of sources operate in the 900–950 nm wavelength range, precluding their adoption in a quantum network. A quantum frequency conversion scheme is presented here for converting single photons from quantum dots to the telecommunication C band, around 1550 nm, achieving 40.8% end-to-end efficiency, while maintaining both high purity and a high degree of indistinguishability during conversion with measured values of (Formula presented.) and (Formula presented.), respectively. © 2022 The Authors. Advanced Quantum Technologies published by Wiley-VCH GmbH.

Abstract: A set of ab initio calculations of the energy of the ground state as a function of volume, elastic properties, and phonon spectra of tin selenide in its different crystal modifications has been performed. Based on the data set we obtained, the SnSe interatomic interaction potential has been built by implementing the atomic cluster expansion method. The potential has been used to study the temperature dependences of the thermal and elastic characteristics of SnSe in the quasi-harmonic approximation. © 2022, Pleiades Publishing, Ltd.

The microhardness distribution in the different zones of a friction stir welded reduced activation ferritic/martensitic steel has been investigated and correlated to the hierarchical martensitic microstructure in the respective zones, characterized by electron backscatter diffraction orientation analysis. It is found that the variation of prior austenite grain size, packet size, and block width in different subzones is influenced by the peak temperature and effective strain rate during the friction stir welding process. The distribution of the microhardness correlates directly with the geometrically necessary dislocation density observed in the different zones. © 2021

In the version of this article initially published, there was a citation error in the sixth paragraph, now reading in part, “The calculation of the two-photon response was obtained following an approach as outlined in ref. 43,” where ref. 43 (Ramos, T. & García-Ripoll, J. J. Phys. Rev. Lett. 119, 153601 (2017)) replaces the originally cited ref. 44 (Houck, M. et al. Phys. Rev. Lett. 124, 16051 (2020)), which has been removed from the reference list. The change has been made to the HTML and PDF versions of the article © 2022 The Author(s), under exclusive licence to Springer Nature Limited.

Nanomaterials are frequently employed in daily life goods, including health, textile, and food industry. A comprehensive picture is lacking on the role of the capping agents, added ligand molecules, in case of nanoparticle reactions and degradation in aqueous solutions, like surface waters or biofluids. Here, we aim to elucidate the capping agent influence on nanoparticle reactivity probing two commonly employed capping agents citrate and polyvinylpyrrolidone (PVP). Their influence on silver nanoparticle (AgNP) transformation is studied, which is particularly important due to its application as an antimicrobial agent. We induce oxidation and reduction processes of AgNPs in halide solutions and we monitor the associated transformations of particles and capping agents by spectro-electrochemical surface-enhanced Raman spectroscopy (SERS). Raman bands of the capping agents are used here to track chemical changes of the nanoparticles under operando conditions. The sparingly soluble and non-plasmon active silver salts (AgBr and AgCl) are formed under potential bias. In addition, we spectroscopically observe plasmon-mediated structural changes of citrate to cis- or trans-aconitate, while PVP is unaltered. The different behavior of the capping agents implies a change in the physical properties on the surface of AgNPs, in particular with respect to the surface accessibility. Moreover, we showcase that reactions of the capping agents induced by different external stimuli, such as applied bias or laser irradiation, can be assessed. Our results demonstrate how SERS of capping agents can be exploited to operando track nanoparticle conversions in liquid media. This approach is envisaged to provide a more comprehensive understanding of nanoparticle fates in complex liquid environments and varied redox conditions. [Figure not available: see fulltext.] © 2021, The Author(s).

Using high-pressure methanol and methyl formate pulses as a surface-sensitive operando method for high-pressure methanol synthesis over Cu/ZnO/Al2O3, the recently found autocatalytic pathway was confirmed. The autocatalytic effect is assumed to result from the faster hydrogenation of the formed methyl formate ester at high methoxy coverages compared with the rate-determining hydrogenation of formate to dioxomethylene. When pulsing increasing amounts of methanol at 60 bar and 210 °C under kinetically controlled conditions in 13.5 vol% CO, 3.5 vol% CO2, and 73.5 vol% H2, higher amounts of methanol were observed in response. The surplus of formed methanol was found to increase exponentially as a function of the dosed amount of methanol and the applied residence time. To further investigate the methanol-assisted autocatalytic pathway, methyl formate as the predicted intermediate was pulsed, which was rapidly converted into methanol. Instead of the expected 2 : 1 stoichiometry of methanol : methyl formate, only one methanol molecule was produced per dosed methyl formate molecule. It is concluded that methyl formate is split into methoxy and formate species by dissociative adsorption, but only methoxy species are rapidly further hydrogenated to desorbing methanol, whereas formate hydrogenation to methanol is too slow on the time scale of the pulse experiments. © 2022 The Royal Society of Chemistry.

We study single-site and two-site defect structures in B2-type Fe-Al alloys by means of density functional theory supercell calculations. The defect formation energies are calculated as functions of the chemical potential, which are used to obtain the dependence of the defect concentrations on Al content at different temperatures. We also examine the converging behavior of the formation energies with respect to the supercell size to study the corresponding limit of dilute defects. The effect of magnetism is investigated by considering nonmagnetic, ferromagnetic, and paramagnetic states, calculations for the latter showing that the magnitude of the local magnetic moments strongly impacts the defect formation energies. The methodological studies are used to provide explanations for the wide spread of defect formation energies reported by experiments and other theoretical investigations. Based on these insights, the stability of the B2-FeAl structure as a function of Al concentration is obtained and discussed. © 2022 authors. Published by the American Physical Society.published article's title, journal citation, and DOI. Open access publication funded by the Max Planck Society.

The use of nanoparticles and nanostructured electrodes are abundant in electrocatalysis. These nanometric systems contain elements of nanoconfinement in different degrees, depending on the geometry, which can have a much greater effect on the activity and selectivity than often considered. In this Review, we firstly identify the systems containing different degrees of nanoconfinement and how they can affect the activity and selectivity of electrocatalytic reactions. Then we follow with a fundamental understanding of how electrochemistry and electrocatalysis are affected by nanoconfinement, which is beginning to be uncovered, thanks to the development of new, atomically precise manufacturing and fabrication techniques as well as advances in theoretical modeling. The aim of this Review is to help us look beyond using nanostructuring as just a way to increase surface area, but also as a way to break the scaling relations imposed on electrocatalysis by thermodynamics. © 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.

Chromium-oxyhydroxide (CrxOyHz)-based thin films have previously been shown in photocatalysis and industrial chlorate production to prevent unwanted reduction reactions to occur, thereby enhancing the selectivity for hydrogen evolution and thus the overall process efficiency. Here, a highly reproducible synthesis protocol was developed to allow for the electrodeposition of CrxOyHz-based thin films with controlled thickness in the range of the sub-monolayer up to (>4) multilayer coverage. Electrodeposited CrxOyHz coatings were electrochemically characterized using voltammetry and stripping experiments, allowing thickness-dependent film selectivity to be deduced in detail. The results are discussed in terms of mass transport properties and structure of the electrodeposited chromium oxyhydroxide films. It is shown that the permeation of diatomic probe molecules, such as O2 and CO, was significantly reduced by films as thin as four monolayers. Importantly, it is shown that the prepared thin film coatings enabled prolonged hydrogen oxidation in the presence of CO (up to 5 vol.%), demonstrating the benefits of thin-film-protected electrocatalysts. In general, this study provides insight into the synthesis and use of thin-film-protected electrodes leading to improvements in (electro)catalyst selectivity and durability. © 2022 by the authors.

Dislocation-enhanced electrical conductivity is an emerging topic for ceramic oxides. In contrast to the majority of present studies which focus on large-scale crystal deformation or thin film fabrication to introduce dislocations, we use a nanoindentation “pop-in stop” method to locally generate 〈011〉 edge-type dislocations at room temperature, without crack formation, on the (100) surface of a rutile TiO2 single-crystal. Ion beam assisted deposition of microcontacts allowed for both deformed and non-deformed zones to be locally probed by impedance spectroscopy. Compared to the dislocation-free region, a local enhancement of the electrical conductivity by 50% in the dislocation-rich regions is found. The study paves the way for local “mechanical-doping” of ceramics and oxide materials, allowing for the use of dislocations to tune the local conductivity with high spatial resolution. © 2022 The Author(s)

Selective laser melting (SLM), taking advantage of its inherent rapid cooling rates and near-net-shape forming ability, has been employed to fabricate bulk metallic glasses (BMGs). However, crystallization is frequently triggered during the SLM process, which results in the loss of advantageous properties of BMGs, such as extremely high hardness and near-theoretical yield strength. Although many studies have been conducted to investigate SLM of BMGs, there is still a lack of knowledge about the microstructural and compositional evolution during the laser beam processing, particularly the micromechanical property response upon crystallization. In the present work, a systematic investigation is performed to gain a much better understanding about the evolution of microstructure and composition as well as the corresponding micromechanical property change during multiple laser beam melting. The material used in this study is an industrial-grade Zr-based BMG Zr59.3Cu28.8Al10.4Nb1.5 (AMZ4) with two different oxygen levels. AMZ4 demonstrates its good thermal stability by the fact that observable crystalline structure appears around the melt pool only after more than once laser beam treatment. The compositional stability of AMZ4 is manifested by the homogeneous elemental distribution on the melt pool area after even twenty-five laser beam remelting. The laser-metal interaction, melting and subsequent solidification are not effectively influenced by the emerging and expanding of crystallization zone (or heat affected zone, HAZ). Higher oxygen content results in not only a larger HAZ but also more quenched-in nuclei at the melt pool bottom. The HAZ does not exhibit a fully crystallized structure, but rather has a mixture of amorphous and crystalline phases. Crystallization of AMZ4 leads to an increase in hardness and Young's modulus of the material. © 2022 Elsevier B.V.

The microporosity, structure and permeability of SiOx thin films deposited by microwave plasma-enhanced chemical vapour deposition (PE-CVD) and plasma-enhanced atomic layer deposition (PE-ALD) on polydimethylsiloxane (PDMS) substrates were investigated by positron annihilation spectroscopy and complementary technique, such as X-ray photoelectron spectroscopy, infrared spectroscopy, time of flight mass spectroscopy and atomic force microscopy. The SiOx films were deposited onto spin-coated PDMS substrates, which were previously exposed to an oxygen plasma thus achieving the conversion of the top polymer layer into SiOx. The presence of this oxidised surface near the region led to an overall decrease in micropore density and to a shift towards smaller pore sizes within the deposited SiOx films. A correlation between the oxygen fluence during the oxygen plasma treatment and the microporosity of the PE-CVD and PE-ALD SiOx films could be established. © 2022 The Authors. Plasma Processes and Polymers published by Wiley-VCH GmbH.

Photonic quantum technology provides a viable route to quantum communication1,2, quantum simulation3 and quantum information processing4. Recent progress has seen the realization of boson sampling using 20 single photons3 and quantum key distribution over hundreds of kilometres2. Scaling the complexity requires architectures containing multiple photon sources, photon counters and a large number of indistinguishable single photons. Semiconductor quantum dots are bright and fast sources of coherent single photons5–9. For applications, a roadblock is the poor quantum coherence on interfering single photons created by independent quantum dots10,11. Here we demonstrate two-photon interference with near-unity visibility (93.0 ± 0.8)% using photons from two completely separate GaAs quantum dots. The experiment retains all the emission into the zero phonon line—only the weak phonon sideband is rejected; temporal post-selection is not employed. By exploiting quantum interference, we demonstrate a photonic controlled-not circuit and an entanglement with fidelity of (85.0 ± 1.0)% between photons of different origins. The two-photon interference visibility is high enough that the entanglement fidelity is well above the classical threshold. The high mutual coherence of the photons stems from high-quality materials, diode structure and relatively large quantum dot size. Our results establish a platform—GaAs quantum dots—for creating coherent single photons in a scalable way. © 2022, The Author(s), under exclusive licence to Springer Nature Limited.

Direct experimental evaluation of the anisotropic yield locus (YL) of a given material, representing the zeros of the material's yield function in the stress space, is arduous. It is much more practical to determine the YL by combining limited measurements of yield strengths with predictions from numerical models based on microstructural features such as the orientation distribution function (ODF; also referred to as the crystallographic texture). For the latter, several different strategies exist in the current literature. In this work, we develop and present a new hybrid method that combines the numerical efficiency and simplicity of the classical crystallographic yield locus (CYL) method with the accuracy of the computationally expensive crystal plasticity finite element method (CPFEM). The development of our hybrid approach is presented in two steps. In the first step, we demonstrate for diverse crystallographic textures that the proposed hybrid method is in good agreement with the shape of the predicted YL estimated by either CPFEM or experiments, even for pronounced plastic anisotropy. It is shown that the calibration of only two parameters of the CYL method with only two yield stresses for different load cases obtained from either CPFEM simulations or experiments produces a reliable computation of the polycrystal YL for diverse crystallographic textures. The accuracy of the hybrid approach is evaluated using the results from the previously established CPFEM method for the computation of the entire YL and also experiments. In the second step, the point cloud data of stress tensors on the YL predicted by the calibrated CYL method are interpolated within the deviatoric stress space by cubic splines such that a smooth yield function can be constructed. Since the produced YL from the hybrid approach is presented as a smooth function, this formulation can potentially be used as an anisotropic yield function for the standard continuum plasticity methods commonly used in finite element analysis. © 2022 The Author(s). Published by IOP Publishing Ltd.

Trihalide salts were found to efficiently promote photochemical dediazotizing halogenations of diazonium salts. In contrast to classical Sandmeyer reactions, no metal catalysts are required to achieve high yields and outstanding selectivities for halogenation over competing hydridodediazotization. Convenient protocols are disclosed for synthetically meaningful brominations, iodinations, and chlorinations of diversely functionalized derivatives. © 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH

Nitrogen (N) in steels can improve their mechanical strength by solid solution strengthening. Processing N-alloyed steels with additive manufacturing, here laser powder bed fusion (PBF-LB), is challenging as the N-solubility in the melt can be exceeded. This degassing of N counteracts its intended positive effects. Herein, the PBF-LB processed 316L stainless steel with increased N-content is investigated and compared to PBF-LB 316L with conventional N-content. The N is introduced into the steel by nitriding the powder and mixing it with the starting powder to achieve an N-content of approximately 0.16 mass%. Thermodynamic calculations for maximum solubility to avoid N outgassing and pore formation under PBF-LB conditions are performed beforehand. Based on the results, a higher defect tolerance under fatigue characterized by Murakami model can be achieved without negatively influencing the PBF-LB processability of the 316L steel. The increased N-content leads to higher hardness (+14%), yield strength (+16%), tensile strength (+9%), and higher failure stress in short time fatigue test (+16%). © 2022 The Authors. Advanced Engineering Materials published by Wiley-VCH GmbH.

The vision to replace coal with hydrogen goes back to Jules Verne in 1874. However, sustainable hydrogen production remains challenging. The most elegant approach is to utilize photosynthesis for water splitting and to subsequently save solar energy as hydrogen. Cyanobacteria and green algae are unicellular photosynthetic organisms that contain hydrogenases and thereby possess the enzymatic equipment for photosynthetic hydrogen production. These features of cyanobacteria and algae have inspired artificial and semi-artificial in vitro techniques, that connect photoexcited materials or enzymes with hydrogenases or mimics of these for hydrogen production. These in vitro methods have on their part been models for the fusion of cyanobacterial and algal hydrogenases to photosynthetic photosystem I (PSI) in vivo, which recently succeeded as proofs of principle. © 2022 The Author(s)

Metal–organic frameworks (MOFs) are a highly versatile group of porous materials suit-able for a broad range of applications, which often crucially depend on the MOFs’ heat transport properties. Nevertheless, detailed relationships between the chemical structure of MOFs and their thermal conductivities are still largely missing. To lay the foundations for developing such rela-tionships, we performed non-equilibrium molecular dynamics simulations to analyze heat transport in a selected set of materials. In particular, we focus on the impact of organic linkers, the inorganic nodes and the interfaces between them. To obtain reliable data, great care was taken to generate and thoroughly benchmark system-specific force fields building on ab-initio-based refer-ence data. To systematically separate the different factors arising from the complex structures of MOF, we also studied a series of suitably designed model systems. Notably, besides the expected trend that longer linkers lead to a reduction in thermal conductivity due to an increase in porosity, they also cause an increase in the interface resistance between the different building blocks of the MOFs. This is relevant insofar as the interface resistance dominates the total thermal resistance of the MOF. Employing suitably designed model systems, it can be shown that this dominance of the interface resistance is not the consequence of the specific, potentially weak, chemical interactions between nodes and linkers. Rather, it is inherent to the framework structures of the MOFs. These findings improve our understanding of heat transport in MOFs and will help in tailoring the thermal conductivities of MOFs for specific applications. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

The lattice of the flexible Metal–Organic Framework (MOF) MIL-88B(Fe)-Cl is strongly modified when it is subjected to methanol vapor, increasing its volume by more than 130 %. We use a newly developed interaction model belonging to the extended MOF-FF family to perform classical Molecular Dynamics (MD) simulations of this MOF with varying amounts of methanol guest molecules. This work focuses on the evolving intermolecular structure of the counterions and guest molecules when their number is increased from 1 to 30 per cavity. Two mobile Cl−-counterions are, on the average, present in each lattice cavity to neutralize the framework charges. At low loadings (in the closed (or semi-closed) systems), the methanol molecules aggregate around these ions, which are themselves pegged, at the time scale of the simulation, to the Fe3-centers of the MOF. At loadings just below the transition, such methanol aggregates may link two counterions on opposite Fe3-centers, thus preventing the MOF from opening unless more methanol is added. In all closed systems, the methanol self-diffusion is almost two orders of magnitude lower than in the bulk liquid. Once the MOF opens, i.e., at loadings higher than about 12 to 13 methanol molecules per cavity, structural features typical of liquid methanol become more and more apparent. However, the evolution is not monotonous, there is a transitional region up to about 22 molecules par cavity. Increasing the loading further, all features more and more resemble the ones of bulk liquid methanol. © 2022 Elsevier B.V.

In the past two decades, machine learning potentials (MLPs) have reached a level of maturity that now enables applications to large-scale atomistic simulations of a wide range of systems in chemistry, physics, and materials science. Different machine learning algorithms have been used with great success in the construction of these MLPs. In this review, we discuss an important group of MLPs relying on artificial neural networks to establish a mapping from the atomic structure to the potential energy. In spite of this common feature, there are important conceptual differences among MLPs, which concern the dimensionality of the systems, the inclusion of long-range electrostatic interactions, global phenomena like nonlocal charge transfer, and the type of descriptor used to represent the atomic structure, which can be either predefined or learnable. A concise overview is given along with a discussion of the open challenges in the field. © 2022 Annual Reviews Inc.. All rights reserved.

A large number of simulation models have been proposed over the years to mimic the electrical behavior of memristive devices. The models are based either on sophisticated mathematical formulations that do not account for physical and chemical processes responsible for the actual switching dynamics or on multi-physical spatially resolved approaches that include the inherent stochastic behavior of real-world memristive devices but are computationally very expensive. In contrast to the available models, we present a computationally inexpensive and robust spatially 1D model for simulating interface-type memristive devices. The model efficiently incorporates the stochastic behavior observed in experiments and can be easily transferred to circuit simulation frameworks. The ion transport, responsible for the resistive switching behavior, is modeled using the kinetic cloud-in-a-cell scheme. The calculated current-voltage characteristics obtained using the proposed model show excellent agreement with the experimental findings. © 2022 Author(s).

Selective photocatalytic oxidation of alcohols into value-added aldehydes or ketones is a promising alternative for alcohol oxidation concerning the mild reaction conditions and the controllable selectivity. To increase the activity, defective Bi2WO6 with abundant oxygen vacancies (OVs) was synthesized via substitution of W by Ta. The resulting Ta-doped Bi2WO6 loaded with Pt nanoparticles as co-catalyst efficiently converted aromatic and aliphatic alcohols into the corresponding carbonyl compounds with high selectivity (>99%) in aqueous solution under visible-light irradiation and anaerobic conditions, with equivalent H2 as a coupled product. The optimal amount of benzyl alcohol converted by the Ta-doped catalyst was two times higher than that of the undoped catalyst. Surface OVs were found to favor the dissociative adsorption of the alcohols and to prolong the life time of the charge carriers. More importantly, isotopic labelling experiments confirmed that over Pt-loaded pristine undoped Bi2WO6, the coupled H2 product results from water reduction, while over Pt-loaded Ta-doped Bi2WO6, the produced H2 originates from benzyl alcohol, implying that benzyl alcohol can be photo-oxidized via a complete dehydrogenation pathway. Thus, enriched surface OVs in photocatalysts can activate α-C-H bonds in alcohols, boosting the photocatalytic oxidation performance. © 2021 Elsevier B.V.

DEM applications require versatile representations of the particle shapes. The downside of resolved shapes is the required computational effort. In this short communication, we propose new measures to reduce the computational effort needed to evaluate the pairwise contact of resolved polytopes in DEM simulations. Employing the Gilbert–Johnson–Keerthi (GJK) and Expanding Polytope algorithm (EPA) algorithm it is demonstrated that restricting the particle vertices to the actually required ones, which can be obtained from a directional tabulation prior to the simulation, reduces the computational effort drastically. The feasibility of this strategy is evaluated and discussed. Applicability is demonstrated by comparing the simulated granular outflow of regular polyhedrons with differently resolved edges from a hopper with experimental data. The results obtained disclose the strong effect of geometric features on particle discharge. © 2022 Elsevier B.V.

Proton transfer is vital for many biological and chemical reactions. Hydrogen-bonded water-containing networks are often found in enzymes to assist proton transfer, but similar strategy has been rarely presented by synthetic catalysts. We herein report the Co corrole 1 with an appended crown ether unit and its boosted activity for the hydrogen evolution reaction (HER). Crystallographic and 1H NMR studies proved that the crown ether of 1 can grab water via hydrogen bonds. By using protic acids as proton sources, the HER activity of 1 was largely boosted with added water, while the activity of crown-ether-free analogues showed very small enhancement. Inhibition studies by adding 1) external 18-crown-6-ether to extract water molecules and 2) potassium ion or N-benzyl-n-butylamine to block the crown ether of 1 further confirmed its critical role in assisting proton transfer via grabbed water molecules. This work presents a synthetic example to boost HER through water-containing networks. © 2021 Wiley-VCH GmbH

In the present study, we investigate pseudoelastic pull-pull cycling of ultra-fine-grained (40 nm) Ni-rich (50.9 at.% Ni) NiTi shape-memory wires at temperatures ranging from 301 to 323 K. Strain-controlled experiments were performed using incremental strain steps and different constant maximum strains. Pull-pull cycling results in decreasing/increasing plateau stresses characterizing the forward/reverse transformations and an accumulation of non-recoverable strain. Saturation is reached after 30 cycles. We interpret our results in terms of a microstructural scenario where dislocations, which are introduced during the martensitic transformation (lattice invariant shear) and during pull-pull cycling (dislocation plasticity), interact with the stress-induced formation of martensite. We show that the slopes of stress-strain curves naturally depend on the total strain imposed in strain-controlled testing. We also provide a dislocation-based explanation for the evolving stress levels of the loading and unloading plateaus during pseudoelastic cycling. And most importantly, we show how dislocations act as microstructural markers which allow the material to remember its previous stress-strain history. © 2005 Carl Hanser Verlag, München.

Defect-engineered or substoichiometric TiOx is of interest for use in photo- and electrocatalytic processes both as active material and catalyst support. Electrochemical doping of TiO2 via cathodic polarization is an appealing preparation method and frequently employed. Here, we explored the electrochemical preparation of TiOx in an undivided cell using iridium-based (iridium mixed-metal-oxide) and boron doped diamond (BDD) counter electrodes. Cyclic voltammetry and impedance spectroscopy revealed superior charge transfer properties of crystalline TiOx electrodes prepared with BDD (TiOx-BDD). It is shown that the electrochemical properties correlate well with intensities of the H-signals determined using Time of Flight - Secondary Ion Mass Spectrometry (ToF-SIMS). Thus, it is concluded that electrochemical preparation using BDD causes favourable H+ intercalation and/or H diffusion into the sub-surface layers of TiOx. Our extensive analysis using a combination of electrochemical and surface characterization (LEIS and XPS) techniques, additionally suggests that cathodic deposition of Ir, originating from the Ir-based counter electrode, present in sub-ppm concentrations only results in less-efficient doping. Instead in the presence of sub-ppm level Ir contamination hydrogen evolution is favoured during cathodic polarization. The results presented within this study highlight the necessity to use inherently stable counter electrodes for electrochemical preparation and reveal the pronounced influence of trace contamination in electrochemistry in general and the doping mechanism of TiOx electrodes in particular. © 2020 Elsevier B.V.

In this study the partially divorced eutectic microstructure of α-Mg and β-Mg17Al12 was investigated by electron backscatter diffraction, transmission electron microscopy, and phase-field modeling in hypoeutectic Mg-Al alloys. The orientation relationships between the individual eutectic α grains, eutectic β phase, and primary α grains were investigated. While the amount of eutectic morphology is primarily determined by the Al content, the in-depth microstructure analyses and the phase-field simulation suggest non-interactive nucleation and growth of eutectic α phase in the β phase grown on the interdendritic primary α dendrites. Also, phase-field simulations showed a preferred nucleation sequence where the β phase nucleates first and subsequently triggers the nucleation of eutectic α phase at the moving β phase solidification front, which supports the microstructural analysis results. © 2021

The capability of high-resolution modeling of crystals subjected to large plastic strain is essential in predicting many important phenomena occurring in polycrystalline materials, such as microstructure, deformation localization and in-grain texture evolution. However, due to the heterogeneity of the plastic deformation in polycrystals, the simulation mesh gets distorted during the deformation. This mesh distortion deteriorates the accuracy of the results, and after reaching high local strain levels, it is no longer possible to continue the simulation. In this work, two different adaptive remeshing approaches are introduced for simulating large deformation of 3D polycrystals with high resolution under periodic boundary conditions. In the first approach, a new geometry with a new mesh is created, and then the simulation is restarted as a new simulation in which the initial state is set based on the last deformation state that had been reached. In the second approach, the mesh is smoothened by removing the distortion part of the deformation, and then the simulation is continued after finding a new equilibrium state for the smoothed mesh and geometry. The first method is highly efficient for conducting high-resolution large-deformation simulations. On the other hand, the second method's primary advantage is that it can overcome periodicity issues related to shear loading, and it can be used in conjunction with complex loading conditions. The merits of the methodologies are demonstrated using full-field simulations performed using a dislocation-density-based crystal plasticity model for Interstitial free (IF-) steel. Particular emphasis is put on studying the effect of resolution and adaptive meshing. The algorithms presented have been implemented into the free and open-source software package, DAMASK (Düsseldorf Advanced Material Simulation Kit). © 2021 The Author(s)

Using the mixed-metal approach, a direct synthesis route at ambient pressure was developed for a new type of bimetallic metal-organic framework based on the CPO-27 structure. The structural characterization of CPO-27(Cu0.6−CS−Co0.4) using X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray mapping and X-ray absorption spectroscopy revealed that the Cu2+ and Co2+ ions were exclusively incorporated at the metal positions of the CPO-27 lattice, but with a core-shell distribution within the crystallites. The parent framework material was then utilized as a precursor for the generation of novel bimetallic carbon-supported materials using the controlled thermal decomposition in a reducing atmosphere. During this decomposition process, the distribution of the two metals remained the same, which resulted in unique needle-shaped particles with a high dispersion of cobalt at the periphery of the amorphous carbon and agglomerated copper particles in the inside. © 2021 The Authors. European Journal of Inorganic Chemistry published by Wiley-VCH GmbH

In the present work, interactions of nanoindentation-induced dislocations (NIDs) with a low-angle grain boundary (LAGB) are investigated in a single-crystalline CrCoNi medium-entropy alloy (MEA). Microstructural evolutions before and after nanoindentation were examined using accurate electron channeling contrast imaging (A-ECCI). In the as-grown state, the alloy microstructure consists of subgrains separated by LAGBs. After nanoindentation on the (001) plane far away from LAGBs, the load-displacement curves exhibit the typical behavior of metals and alloys with a pop-in marking the elastic-plastic transition. This pop-in is related to the nucleation of NIDs that are observed to form pile-ups on {111} planes. In contrast, when indents are performed in the vicinity of a LAGB with a low misorientation angle of 0.24° and consisting of dislocations spaced ~60 nm apart, different micromechanical responses and deformation mechanisms are observed depending on the distance between the LAGB and the nanoindenter tip. When the distance between the LAGB and the nanoindenter tip is larger than four times the size of the indent (corresponding ratio: R > 4), the LAGB does not affect the micromechanical response nor interact with NIDs. In contrast, when the indenter comes in direct or indirect contact with the LAGB (R < 1), the load-displacement curve deviates at low loads from the elastic stage, and pop-ins are not observed. In this case, the continuous deformation is accommodated by the movement of the pre-existing LAGB dislocations. For intermediate cases with 1 < R < 4, the load of the initial pop-in is dependent on the local defect density. In this latter case, the pile-ups of NIDs directly impinge on the LAGB. Microstructural analyses reveal that the LAGB accommodates plasticity by blocking the NIDs, activating a dislocation nucleation site in the adjacent subgrain/emission of dislocation from the LAGB, and inducing slight motions of its constituent dislocations. © 2021 Elsevier B.V.

We studied the electronic structure of PtPb4 using laser angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT) calculations. This material is closely related to PtSn4, which exhibits exotic topological properties such as Dirac node arcs. The Fermi surface (FS) of PtPb4 consists of two electron pockets at the center of the Brillouin zone (BZ) and several hole pockets around the zone boundaries. Our ARPES data reveal significant Rashba splitting at the Γ point, in agreement with DFT calculations. The presence of Rashba splitting may render this material of potential interest for spintronic applications. © 2021 American Physical Society.

X-ray fluorescence analysis enables the study of trace element distributions in biological specimens. When this analysis is done under cryogenic conditions, cells are cryofixed as closely as possible to their natural physiological state, and the corresponding intracellular elemental densities can be analyzed. Details about the experimental setup used for analysis at the P06 beamline at Petra III, DESY and the used cryo-transfer system are described in this work. The system was applied to analyze the elemental distribution in single HeLa cells, a cell line frequently used in a wide range of biological applications. Cells adhered to silicon nitride substrates were cryoprotected within an amorphous ice matrix. Using a continuous scanning scheme and a KB x-ray focus, the distribution of elements in the cells was studied. We were able to image the intracellular potassium and zinc levels in HeLa cells as two key elements relevant for the physiology of cells. © 2021 Author(s).

The unique structural and electronic properties of transition metal dichalcogenides (TMDs) and in particular tungsten disulphide (WS2) make them interesting for a variety of applications such as the electrocatalytic hydrogen evolution reaction (HER) for water splitting devices and chemiresistive gas sensors. The key parameter for the realisation of these devices is the controlled large-area growth of WS2 combined with tuning the surface morphology and electronic properties which is achieved by bottom-up fabrication methods such as chemical vapour deposition (CVD). In this study, 2H-WS2 films are fabricated by a new metal-organic CVD (MOCVD) process resulting in the growth of crystalline, pure, and stoichiometric films which was accomplished at temperatures as low as 600 °C as confirmed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectrometry (RBS)/nuclear reaction analysis (NRA), and Raman spectroscopy. The surface morphology of WS2 layers was investigated by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM). Following successful process development, the WS2 layers were deposited on conducting FTO/glass substrates and their catalytic activity for the HER was evaluated in a linear sweep voltammetry (LSV) experiment. Furthermore, the temperature-dependent sensor response towards NO2, CO, and NH3 was investigated for WS2 films deposited on special sensor chips, revealing a p-type response towards NO2 and NH3 and sensitivities of around 20% for NO2 and NH3 concentrations of 1.5 ppm and 7.6 ppm, respectively. These promising results demonstrate the effectiveness of scalable CVD-grown WS2 and pave the way for practical applications by modulating the properties of materials to achieve enhanced electrocatalytic and sensing performances employing WS2 layers. © 2021 The Royal Society of Chemistry.

Single-entity electrochemistry allows for assessing electrocatalytic activities of individual material entities such as nanoparticles (NPs). Thus, it becomes possible to consider intrinsic electrochemical properties of nanocatalysts when researching how activity relates to physical and structural material properties. Conversely, conventional electrochemical techniques provide a normal-ized sum current referring to a huge ensemble of NPs constituting, along with additives (e.g., bind-ers), a complete catalyst-coated electrode. Accordingly, recording electrocatalytic responses of single NPs avoids interferences of ensemble effects and reduces the complexity of electrocatalytic pro-cesses, thus enabling detailed description and modelling. Herein, we present insights into the oxygen evolution catalysis at individual cubic Co3O4 NPs impacting microelectrodes of different support materials. Simulating diffusion at supported nanocubes, measured step current signals can be analyzed, providing edge lengths, corresponding size distributions, and interference-free turnover frequencies. The provided nano-impact investigation of (electro-)catalyst-support effects contra-dicts assumptions on a low number of highly active sites. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

Pinning-type magnets with high coercivity at high temperatures are at the core of thriving clean-energy technologies. Among these, Sm2Co17-based magnets are excellent candidates owing to their high-temperature stability. However, despite intensive efforts to optimize the intragranular microstructure, the coercivity currently only reaches 20–30% of the theoretical limits. Here, the roles of the grain-interior nanostructure and the grain boundaries in controlling coercivity are disentangled by an emerging magnetoelectric approach. Through hydrogen charging/discharging by applying voltages of only ≈1 V, the coercivity is reversibly tuned by an unprecedented value of ≈1.3 T. In situ magneto-structural characterization and atomic-scale tracking of hydrogen atoms reveal that the segregation of hydrogen atoms at the grain boundaries, rather than the change of the crystal structure, dominates the reversible and substantial change of coercivity. Hydrogen reduces the local magnetocrystalline anisotropy and facilitates the magnetization reversal starting from the grain boundaries. This study opens a way to achieve the giant magnetoelectric effect in permanent magnets by engineering grain boundaries with hydrogen atoms. Furthermore, it reveals the so far neglected critical role of grain boundaries in the conventional magnetization-switching paradigm of pinning-type magnets, suggesting a critical reconsideration of engineering strategies to overcome the coercivity limits. © 2020 The Authors. Advanced Materials published by Wiley-VCH GmbH

LaCrGe3 has attracted attention as a paradigm example of the avoidance of ferromagnetic (FM) quantum criticality in an itinerant magnet. Here, we combined thermodynamic (specific heat and thermal expansion), transport, x-ray, and neutron scattering as well as μSR measurements to obtain insights on the temperature-pressure phase diagram of LaCrGe3. Consistent with previous studies of the phase diagram by transport measurements, our thermodynamic data shows clearly that the FM transition at TFM changes its character from second order to first order when it is suppressed to low temperatures by pressure. In addition, previous studies demonstrated that for high pressures a new phase occurs below T2, which was proposed to be a long-wavelength antiferromagnetic state (AFMq). In this paper, we provide evidence from our thermodynamic data that this phase transition is preceded by yet another phase transition at T1>T2. Our μSR data indicate that full magnetic volume fraction is only established below T2, but that this magnetism is characterized by a short correlation length. Within the experimental resolution, our neutron-scattering data is not able to identify any magnetic Bragg peaks. Overall, the microscopic magnetic data is therefore consistent with the formation of FM clusters in the proximity of the avoided FM quantum critical point in LaCrGe3. This conclusion is at odds with the previous proposal of AFMq order and raises questions on the role of disorder in this stochiometric compound. © 2021 American Physical Society.

X-ray-based analytics are routinely applied in many fields, including physics, chemistry, materials science, and engineering. The full potential of such techniques in the life sciences and medicine, however, has not yet been fully exploited. We highlight current and upcoming advances in this direction. We describe different X-ray-based methodologies (including those performed at synchrotron light sources and X-ray free-electron lasers) and their potentials for application to investigate the nano-bio interface. The discussion is predominantly guided by asking how such methods could better help to understand and to improve nanoparticle-based drug delivery, though the concepts also apply to nano-bio interactions in general. We discuss current limitations and how they might be overcome, particularly for future use in vivo. ©

Body-centered cubic (bcc) Fe-Mn systems are known to exhibit a complex and atypical magnetic behavior from both experiments and 0 K electronic-structure calculations, which is due to the half-filled 3d band of Mn. We propose effective interaction models for these alloys, which contain both atomic-spin and chemical variables. They were parameterized on a set of key density functional theory (DFT) data, with the inclusion of noncollinear magnetic configurations being indispensable. Two distinct approaches, namely a knowledge-driven and a machine-learning approach have been employed for the fitting. Employing these models in atomic Monte Carlo simulations enables the prediction of magnetic and thermodynamic properties of the Fe-Mn alloys, and their coupling, as functions of temperature. This includes the decrease of Curie temperature with increasing Mn concentration, the temperature evolution of the mixing enthalpy, and its correlation with the alloy magnetization. Also, going beyond the defect-free systems, we determined the binding free energy between a vacancy and a Mn atom, which is a key parameter controlling the atomic transport in Fe-Mn alloys. © 2021 American Physical Society.

Electrochemical oxidation of biomass substrates to valuable bio-chemicals is highly attractive. However, the design of efficient, selective, stable, and inexpensive electrocatalysts remains challenging. Here it is reported how a 3D highly ordered mesoporous Co3O4/nickel foam (om-Co3O4/NF) electrode fulfils those criteria in the electrochemical oxidation of 5-hydroxymethylfurfural (HMF) to value-added 2,5-furandicarboxylic acid (FDCA). Full conversion of HMF and an FDCA yield of >99.8 % are achieved with a faradaic efficiency close to 100 % at a potential of 1.457 V vs. reversible hydrogen electrode. Such activity and selectivity to FDCA are attributed to the fast electron transfer, high electrochemical surface area, and reduced charge transfer resistance. More impressively, remarkable catalyst stability under long-term testing is obtained with 17 catalytic cycles. This work highlights the rational design of metal oxides with ordered meso-structures for electrochemical biomass conversion. © 2021 The Authors. ChemSusChem published by Wiley-VCH GmbH

Laser metal deposition (LMD) was used to in-situ alloy a crack-free Al0.6CoCrFeNi compositionally complex alloy (CCA) with 3 at.% Ti and 0.25 at.% C additions on an initially ferritic H10 tool steel from an elemental powder blend. After LMD, the material was annealed at 900 °C for 30 min to induce martensitic hardening in the substrate. The CCA in both as-deposited and annealed states exhibited a lamellar microstructure consisting of four phases: a matrix of interwoven disordered and ordered body-centered cubic phases, titanium carbides distributed randomly within the microstructure, and disordered face-centered cubic (FCC) plates that precipitated at the grain boundaries and grew towards the center of the grains. Chemical analyses along the build-up direction of the coating revealed a compositional gradient, similar in both as-deposited and annealed states, due to the intermixing between the substrate and the CCA. Despite a strong variation of the Fe-content, the hardness and the microstructure remain roughly constant in the major part of the as-deposited coating, which contains a large fraction of FCC plates that are beneficial to increase ductility and ensure a good compatibility with the substrate. In contrast, the upper part of the as-deposited coating, corresponding to the last solidified melt pool after LMD, has a much lower FCC fraction with an enhanced hardness. After annealing, the hardness of the tool steel substrate significantly increased and the FCC volume fraction in the coating increased from ~16% (as-deposited) to ~58%. Overall the microstructure of the coating became more homogeneous while its hardness decreased only by 10–15%. These results demonstrate that the CCA can be employed as a protective coating on a less expensive tool steel to improve its lifetime during service. © 2021 The Author(s)

In this study, we report on face-centered cubic structured CoCrFeNi high-entropy alloy thin films with finely dispersed nano-oxide particles which are formed by internal oxidation. Analytical scanning transmission electron microscopy imaging found that the particles are Cr2O3. The oxide particles contribute to the hardening of the film increasing its hardness by 14% compared to that of the film without precipitates, through the Orowan-type strengthening mechanism. Our novel approach paves the way to design medium- and high-entropy alloys with high strength by making use of oxide phases. © 2021

Differential scanning calorimetry measurements on different bulk metallic glasses show no measurable rejuvenation upon deeply cooled (cryogenic) thermal cycling. This applies both to as-quenched and well-annealed samples. Extensive molecular dynamics simulations of a generic model glass former corroborate these observations. We disentangle the effects of aging from those of thermal treatment and show that aging is slowed down but not stopped - neither reversed - during thermal cycling. These observations are corroborated further by a survey of energy distribution, which continues narrowing, albeit with a smaller rate. © 2021 authors.

Glucose bio-sensing technologies have received increasing attention in the last few decades, primarily due to the fundamental role that glucose metabolism plays in diseases (e.g., diabetes). Molecularly imprinted polymers (MIPs) could offer an alternative means of analysis to a field that is traditionally dominated by enzyme-based devices, posing superior chemical stability, cost-effectiveness, and ease of fabrication. Their integration into sensing devices as recognition elements has been extensively studied with different readout methods such as quartz-crystal microbalance or impedance spectroscopy. In this work, a dummy imprinting approach is introduced, describing the synthesis and optimization of a MIP toward the sensing of glucose. Integration of this polymer into a thermally conductive receptor layer was achieved by micro-contact deposition. In essence, the MIP particles are pressed into a polyvinyl chloride adhesive layer using a polydimethylsiloxane stamp. The prepared layer is then evaluated with the so-called heat-transfer method, allowing the determination of the specificity and the sensitivity of the receptor layer. Furthermore, the selectivity was assessed by analyzing the thermal response after infusion with increasing concentrations of different saccharide analogues in phosphate-buffered saline (PBS). The obtained results show a linear range of the sensor of 0.0194–0.3300 mM for the detection of glucose in PBS. Finally, a potential application of the sensor was demonstrated by exposing the receptor layer to increasing concentrations of glucose in human urine samples, demonstrating a linear range of 0.0444–0.3300 mM. The results obtained in this paper highlight the applicability of the sensor both in terms of non-invasive glucose monitoring and for the analysis of food samples. © 2021 The Authors. Published by American Chemical Society

A cancer stem cell (CSC) active, solution stable, silver(i) polymeric complex bearing a dithiacyclam ligand is reported. The complex displays similar potency towards CSCs to salinomycin in monolayer and three-dimensional cultures. Mechanistic studies suggest CSC death results from cytosol entry, an increase in intracellular reactive oxygen species, and caspase-dependent apoptosis. © The Royal Society of Chemistry 2021.

The internal twin-boundaries in lamellar γ-TiAl alloys, namely true-twin (TT), rotational boundary (RB), and pseudo-twin (PT), are known to be effective in strengthening the TiAl microstructures. Nevertheless, for designing microstructures with optimised mechanical properties, a better understanding of the role of these boundaries on fracture behavior is still required. To this end, we study how and to what degree crack advancement is affected by the local lattice orientation and atomic structure at the various twin boundaries. Molecular statics simulations were performed in conjunction with a linear elastic fracture mechanics based analysis, to understand the inter-lamellar and as well as trans-lamellar crack advancement at a TT, RB, and PT interface. The fracture toughness as well as the crack advancement mechanisms of the inter-lamellar cracks depend critically on the propagation direction. For instance, cracks along 〈112¯] in the TT, RB, and PT plane always emit dislocations at the crack tip, while the cracks along the opposite direction are brittle in nature. When it comes to trans-lamellar crack advancement, the crack tip shows significant plastic deformation and toughening for all interfaces. However, at a TT, a brittle crack is able to penetrate through the interface at a higher applied load, and propagates in the adjacent γ′ phase, while in the case of RB and PT, the crack tip is blunted and arrested at or near the boundary, resulting in dislocation emission and crack tip toughening. This suggests that a variation of the sequence of the different rotational boundaries could be a possibility to tune the crack tip plasticity and toughening in lamellar TiAl. © 2021 The Author(s)

In a radiative Auger process, optical decay leaves other carriers in excited states, resulting in weak red-shifted satellite peaks in the emission spectrum. The appearance of radiative Auger in the emission directly leads to the question if the process can be inverted: simultaneous photon absorption and electronic demotion. However, excitation of the radiative Auger transition has not been shown, neither on atoms nor on solid-state quantum emitters. Here, we demonstrate the optical driving of the radiative Auger transition, linking few-body Coulomb interactions and quantum optics. We perform our experiments on a trion in a semiconductor quantum dot, where the radiative Auger and the fundamental transition form a Λ-system. On driving both transitions simultaneously, we observe a reduction of the fluorescence signal by up to 70%. Our results suggest the possibility of turning resonance fluorescence on and off using radiative Auger as well as THz spectroscopy with optics close to the visible regime. © 2021, The Author(s).

Abstract: The present work shows that thermal expansion experiments can be used to measure the γʼ-solvus temperatures of four Ni-base single-crystal superalloys (SX), one with Re and three Re-free variants. In the case of CMSX-4, experimental results are in good agreement with numerical thermodynamic results obtained using ThermoCalc. For three experimental Re-free alloys, the experimental and calculated results are close. Transmission electron microscopy shows that the chemical compositions of the γ- and the γʼ-phases can be reasonably well predicted. We also use resonant ultrasound spectroscopy (RUS) to show how elastic coefficients depend on chemical composition and temperature. The results are discussed in the light of previous results reported in the literature. Areas in need of further work are highlighted. Graphical abstract: [Figure not available: see fulltext.] © 2021, The Author(s).

In this study, multi-wall carbon nanotubes (MWCNTs) were electrochemically modified with nitrogen and phosphorus species and employed as platform to immobilize pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH) for the fabrication of bioelectrodes for glucose detection. Depending on the upper potential limit used during the electrochemical modification of MWCNTs, the nature and amount of the nitrogen and phosphorus species incorporated in the carbon material surface can be selectively controlled. These species act as anchoring groups for the immobilization of the PQQ-GDH. The value of the upper potential limit used in the electrochemical modification influences the electron-transfer rate between the electrode and the enzyme. The performance of the bioelectrodes for glucose oxidation and detection is improved by the electrochemical modification conditions, leading to an increased sensitivity towards glucose oxidation from 39.2 to 53.6 mA gMWCNT−1 mM−1 in a linear range between 0.1 to 1.2 mM. This electrochemical modification is considered as an alternative for the preparation of highly sensitive glucose bioelectrodes. © 2021

The aluminum alloy 2618A is applied for engine components such as radial compressor wheels which operate for long time at elevated temperatures. This results in coarsening of the hardening precipitates and degradation in mechanical properties during the long-term operation, which is not taken into account in the current lifetime prediction models due to the lack of quantitative microstructural and mechanical data. To address this issue, a quantitative investigation on the evolution of precipitates during long-term aging at 190 °C for up to 25,000 h was conducted. Detailed transmission electron microscopy (TEM) was combined with Brinell hardness measurements and thorough differential scanning calorimetry (DSC) experiments. The results show that GPB zones and S-phase Al2CuMg grow up to < 1,000 h during which the GPB zones dissolve and S-phase precipitates form. For longer aging times, only S-phase precipitates coarsen, which can be well described using the Lifshitz–Slyozov–Wagner theory of ripening. A thorough understanding of the underlying microstructural processes is a prerequisite to enable the integration of aging behavior into the established lifetime models for components manufactured from alloy 2618A. © 2021, The Author(s).

This article studies the problem whether two convex (concave) regression functions modelling the relation between a response and covariate in two samples differ by a shift in the horizontal and/or vertical axis. We consider a nonparametric situation assuming only smoothness of the regression functions. A graphical tool based on the derivatives of the regression functions and their inverses is proposed to answer this question and studied in several examples. We also formalize this question in a corresponding hypothesis and develop a statistical test. The asymptotic properties of the corresponding test statistic are investigated under the null hypothesis and local alternatives. In contrast to most of the literature on comparing shape invariant models, which requires independent data the procedure is applicable for dependent and non-stationary data. We also illustrate the finite sample properties of the new test by means of a small simulation study and two real data examples. © 2021, The Institute of Statistical Mathematics, Tokyo.

Atom probe tomography (APT) provides three-dimensional compositional mapping with sub-nanometre resolution. The sensitivity of APT is in the range of parts per million for all elements, including light elements such as hydrogen, carbon or lithium, enabling unique insights into the composition of performance-enhancing or lifetime-limiting microstructural features and making APT ideally suited to complement electron-based or X-ray-based microscopies and spectroscopies. Here, we provide an introductory overview of APT ranging from its inception as an evolution of field ion microscopy to the most recent developments in specimen preparation, including for nanomaterials. We touch on data reconstruction, analysis and various applications, including in the geosciences and the burgeoning biological sciences. We review the underpinnings of APT performance and discuss both strengths and limitations of APT, including how the community can improve on current shortcomings. Finally, we look forwards to true atomic-scale tomography with the ability to measure the isotopic identity and spatial coordinates of every atom in an ever wider range of materials through new specimen preparation routes, novel laser pulsing and detector technologies, and full interoperability with complementary microscopy techniques. © 2021, Springer Nature Limited.

Plasma catalysis, the combination of plasma and catalysis, is used to achieve efficient molecule conversion, supporting the flexibility of operating parameters and feed gases. By combining plasmas with conventional thermal catalysis, the temperature windows may be changed and the process may be made insensitive to catalyst poisoning. However, understanding plasma catalysis mechanisms is extremely difficult, due to the strong coupling between plasma, gas-phase chemistry and surface. A multitude of reaction pathways may be enhanced or reduced by the presence of a plasma that provides excited species as reaction partners. We developed a robust setup to analyse those processes, based on a parallel-plate atmospheric-pressure plasma jet that allows a plug flow design. The plasma chemistry is analysed by Fourier transform infrared absorption spectroscopy and mass spectrometry. The electrodes in contact with the plasma are temperature controlled and can easily be replaced to apply a catalyst on top of them. The basic characteristics of the setup are discussed and three examples for its application are given: (a) the analysis of methane oxidation using the plug flow scheme; (b) the plasma catalytic conversion of CO2, and (c) the plasma catalytic conversion of methane in methane–oxygen mixtures. © 2021 IOP Publishing Ltd.

High power ultrafast lasers in the short-wave mid-IR wavelength region (2-3m) are of great interest for a large number of applications in science and technology. Finding paths to increase the average power of ultrafast laser systems directly emitting in this wavelength region has seen particularly strong interest, due to the potential of these sources as direct drivers for the generation of XUV, mid-IR and THz. Among different power-scalable technologies, the development of thin-disk lasers (TDLs) at 2m is very promising for power and energy scaling of ultrafast lasers in this wavelength range, but only very few results have so far conclusively shown this potential [1] , [2]. Recently, we have shown the potential of Ho:YAG for further power scaling by demonstrating a cw, single fundamental-mode 2-m TDL with >100 W and 54% optical-to-optical efficiency, representing the highest power TDL around 2m [3]. In the present work, we report first high-power modelocking SESAM-modelocking of this system, reaching an average power of 40-W in ps-pulses, which respresents the highest average power from a modelocked oscillators in the wavelength region. © 2021 IEEE.

Complex solid solutions (“high entropy alloys”), comprising five or more principal elements, promise a paradigm change in electrocatalysis due to the availability of millions of different active sites with unique arrangements of multiple elements directly neighbouring a binding site. Thus, strong electronic and geometric effects are induced, which are known as effective tools to tune activity. With the example of the oxygen reduction reaction, we show that by utilising a data-driven discovery cycle, the multidimensionality challenge raised by this catalyst class can be mastered. Iteratively refined computational models predict activity trends around which continuous composition-spread thin-film libraries are synthesised. High-throughput characterisation datasets are then used as input for refinement of the model. The refined model correctly predicts activity maxima of the exemplary model system Ag-Ir-Pd-Pt-Ru. The method can identify optimal complex-solid-solution materials for electrocatalytic reactions in an unprecedented manner. © 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH

Nd2Fe14B-type materials exhibit the highest energy product around room temperature and hence dominate the high-performance permanent magnet market. Intensive research efforts aim at alternative material systems containing less critical elements with similar or better magnetic properties. Nd- and Sm-based compounds with a ThMn12-type structure exhibit intrinsic properties comparable or even superior to Nd2Fe14B. However, it has not been possible to achieve technically relevant coercivity and remanent magnetization in ThMn12-based bulk sintered magnets. Using SmFe11Ti as a prototypical representative, we demonstrate that one important reason for the poor performance is the formation of twins inside micro-crystalline grains. The nature of the twins in SmFe11Ti was investigated in twinned “single crystals” and both bulk and thin film poly-crystalline samples, using advanced electron microscopy and atom probe tomography as well as simulations and compared with benchmark Nd2Fe14B. Both micro-twins and nano-twins show a twin orientation of 57±2° and an enrichment in Sm, which could affect domain wall motion in this material. Micromagnetic simulations indicate that twins act as nucleation centers, representing the magnetically weakest link in the microstructure. The relation between twin formation energies and geometrical features are briefly discussed using molecular dynamic simulations. © 2021

Co3O4 nanospheres with a mean diameter of 19 nm were applied in the selective oxidation of 2-propanol to acetone in the gas phase. Compared with 9 nm spheres, the 19 nm spheres exhibited superior catalytic activity and stability with 100% selectivity to acetone up to 500 K. Transmission electron microscopy, N2 physisorption, 2-propanol and O2 temperature-programmed desorption, and 2-propanol temperature-programmed surface reaction in O2 were applied to characterize the bulk and surface properties. Despite the smaller specific surface area (35 m2 g-1), an increased 2-propanol adsorption capacity was observed for the larger nanospheres ascribed to a preferential (110) surface orientation. Temperature-programmed oxidation experiments after reaction showed multilayer coke deposition and severe reduction of the Co3O4 surface, but excellent stability was maintained at 430 K using the 19 nm spheres in a steady-state oxidation experiment for 100 h with only 10% loss of the initial activity. The good agreement of the 2-propanol decomposition profiles indicates that the superior activity is caused by the enhanced interaction of the larger nanospheres with O2. A Mars-van Krevelen mechanism on the (110) surface was identified by density functional theory calculations with a Hubbard U term, favoring faster reoxidation compared with the (100) surface predominantly exposed by the 9 nm spheres. © The Royal Society of Chemistry.

Thin-disk lasers (TDLs) have made spectacular progress in the last decades both in continuous-wave (CW) and ultrafast operation. Nowadays, single thin-disk oscillators with >16 kW of CW-power have been demonstrated and ultrafast amplifiers have largely surpassed the kilowatt milestone with pulse energies in the multi-100 mJ range. This amazing development has been demonstrated in the 1 µm wavelength range, using Yb-doped materials and supported by industrially available components. Motivated by both strong scientific and industrial applications, interest in expanding this performance to longer wavelength regions continues to increase. In particular, TDLs emitting directly in the short-wave mid-infrared (SW-MIR) region (2-3 µm) are especially sought after, and although many early studies have been reported, most remained in the proof-of-principle stage and the potential for multi-100 W operation remained undemonstrated. Here, we report on our recent results of a single fundamental-mode CW Ho:YAG thin-disk oscillator with >100 W of power, surpassing previous single-mode TDLs by a factor of >4, and marking a first milestone in the development of high-power SW-MIR TDLs. In optimized conditions, our laser system emitting at ≈2.1 µm reaches an output power of 112 W with 54.6% optical-to-optical efficiency and an M2 = 1.1. This system is ideally suited for future direct modelocking at the 100 W level, as well as for ultrafast amplification. We start the discussion with a review of the state-of-the-art of TDLs emitting directly in the vicinity of 2 µm, and then discuss difficulties and possible routes both towards ultrafast operation and next possible steps for power scaling. © 2021 The Author(s). Published by IOP Publishing Ltd

The design of high performance structural materials is always pursuing combinations of excellent yet often mutually exclusive properties such as mechanical strength, ductility and thermal stability. Although crystal-glass composite alloys provide better ductility compared to fully amorphous alloys, their thermal stability is poor, due to heterogeneous nucleation at the crystal-glass interface. Here we present a new strategy to develop thermally stable, ultrastrong and deformable crystal-glass nanocomposites through a thermodynamically guided alloy design approach, which mimics the mutual stabilization principle known from symbiotic ecosystems. We realized this in form of a model Cr-Co-Ni (crystalline)/Ti-Zr-Nb-Hf-Cr-Co-Ni (amorphous) laminate composite alloy. The symbiotic alloy has an ultrahigh compressive yield strength of 3.6 GPa and large homogeneous deformation of ∼15% strain at ambient temperature, values which surpass those of conventional metallic glasses and nanolaminate alloys. Furthermore, the alloy exhibits ∼200 K higher crystallization temperature (TX > 973 K) compared to that of the original TiZrNbHf-based amorphous phase. The elemental partitioning among adjacent amorphous and crystalline phases leads to their mutual thermodynamic and mechanical stabilization, opening up a new symbiotic approach for stable, strong and ductile materials. © 2021 Elsevier Ltd

Diurnal fluctuations in volatility are a well-documented stylized fact of intraday price data. This warrants an investigation how this intraday periodicity (IP) affects both finite sample as well as asymptotic properties of several popular realized estimators of daily integrated volatility which are based on functionals of a finite number of intraday returns. It turns out that most of the estimators considered in this study exhibit a finite-sample bias due to IP, which can however get negligible when the number of intraday returns diverges to infinity. The appropriate correction factors for this bias are derived based on estimates of the IP. The adequacy of the new corrections is evaluated by means of a Monte Carlo simulation study and an empirical example. © 2021 EcoSta Econometrics and Statistics

A series of Co1+xFe2–xO4 (0≤x≤2) spinel nanowires was synthesized by nanocasting using SBA-15 silica as hard template, which was characterized by X-ray powder diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The Co1+xFe2–xO4 spinels were applied in the aerobic oxidation of aqueous 2-propanol solutions to systematically study the influence of exposed Co and Fe cations on the catalytic properties. The activity of the catalysts was found to depend strongly on the Co content, showing an exponential increase of the reaction rate with increasing Co content. Ensembles of Co3+cus (coordinatively unsaturated) sites were identified as the active sites for selective 2-propanol oxidation, which are assumed to consist of more than six Co ions. In addition, gas-phase oxidation with and without water vapor co-feeding was performed to achieve a comparison with liquid-phase oxidation kinetics. An apparent activation energy of 94 kJ mol−1 was determined for 2-propanol oxidation over Co3O4 in the liquid phase, which is in good agreement with the gas-phase oxidation in the presence of water vapor. In contrast to gas-phase conditions, the catalysts showed high stability and reusability in the aqueous phase with constant conversion in three consecutive runs. © 2021 The Authors. ChemCatChem published by Wiley-VCH GmbH

Simulations of solid particle combustion rely on models to approximate the reactions on the surface of the particle and in the surrounding gas. These models, in turn, depend on many model parameters, which are determined, most commonly, by experiments and contain a certain level of uncertainty. It is therefore essential to correctly determine the sensitivities of measured quantities of interest, with respect to the existing model parameters. This study, concentrates on a one-step model describing the heterogeneous reaction on the surface of a char particle, and in particular, the surface model presented by Schiemann et al. [24]. Adjoint-based methods are then employed to extract sensitivities of various quantities of interests, including the burning rate and total heat release, with respect to surface model parameters, such as, the activation energy, and the pre-exponential factor. The variation of these sensitivities are then assessed as the particle size and free stream composition are varied. © 2020 Elsevier Ltd

Bis-tren (tren = tris(2-aminoethyl)amine) azacryptands were previously studied profoundly for the coordination of two +iimetals and subsequent binding of substrates within their cavity. Likewise, cryptates including metals in different oxidations states were reported with the rather unstable hexa-imine analogues but also revealed only little stability. In this work, we report the synthesis of an asymmetric hexa-amine cryptand analogue by selectively exchanging three of the secondary amines of one binding site with sulphur atoms. We show that the presence of two distinct binding sites allows for the selective formation of stable dinuclear complexes of metals with different oxidation numbers and present the formation of distinct CuICoII, CuINiIIand CuICuIIIcryptates. © The Royal Society of Chemistry 2021.

In this work, we studied the effects of hot isostatic pressing and surface anodizing on the behavior of an in-situ surface modified magnesium matrix nano-composite with different wt.% of hydroxyapatite by stir-centrifugal casting. The hot isostatic pressing and anodizing were conducted to reduce the defects and to replace the surface of Mg/HA with a ceramic matrix nano-composite layer of MgO/HA, respectively. The composition of the conversion layer of anodizing was evaluated using energy dispersive spectroscopy and X-ray diffraction. The electrochemical tests were conducted in the simulated body fluid. The results show that the dominant deposition is vertical Mg(OH)2 nano-rods on the hot isostatic pressed-anodized surface during immersion in the simulated body fluid. According to the electrochemical results, a homogeneous distribution of 1.8 wt% nano-hydroxyapatite in the magnesium oxide matrix with a well-arranged nanostructure on the surface, after hot isostatic pressing and anodizing, reduces the H2 release and corrosion rate. Also, the mentioned specimen demonstrates the lowest thermodynamic tendency for corrosion (−1.345 V) and the corrosion rate of 3.8388 mm × year−1 with the highest protection efficiency of 42.26% compared to the as-cast pure magnesium. Therefore, it can be considered as a promising material in designing biomedical bone implants. © 2020 Elsevier B.V.

High entropy alloys (HEAs) provide superior mechanical and functional properties. However, these advantages may disappear when a metastable single-phase solid solution decomposes at low temperatures upon long-term annealing. Therefore, understanding the underlying phase separation mechanisms is important for the design of new HEAs with controlled properties. In the current work, the thermal stability of a nanocrystalline CrMnFeCoNi HEA was investigated at different annealing conditions using a combinatorial processing platform, involving fast and parallel synthesis of nanocrystalline thin films, short annealing time for a rapid phase evolution, and direct characterization by atom probe tomography. The microstructural features of the decomposed CrMnFeCoNi alloy as well as its decomposition process were analyzed in terms of elemental distributions at the near-atomic scale. The results show that the segregation of Ni and Mn to grain boundaries in the initial single-phase alloy is a prerequisite and is observed to be the only occurring physical process at the early stage of phase decomposition. When the concentrations of Ni and Mn reach a certain value, phase decomposition starts and a MnNi-rich phase forms at grain boundaries. Next, two Cr-rich phases form at the interface between the MnNi-rich phase and the matrix. Meanwhile, a FeCo-rich phase forms in the grain interior. Based on these observations, the underlying mechanisms involving nucleation, diffusivity as well as thermodynamic considerations were discussed. © 2021 Author(s).

In human-made malleable materials, microdamage such as cracking usually limits material lifetime. Some biological composites, such as bone, have hierarchical microstructures that tolerate cracks but cannot withstand high elongation. We demonstrate a directionally solidified eutectic high-entropy alloy (EHEA) that successfully reconciles crack tolerance and high elongation. The solidified alloy has a hierarchically organized herringbone structure that enables bionic-inspired hierarchical crack buffering. This effect guides stable, persistent crystallographic nucleation and growth of multiple microcracks in abundant poor-deformability microstructures. Hierarchical buffering by adjacent dynamic strain–hardened features helps the cracks to avoid catastrophic growth and percolation. Our self-buffering herringbone material yields an ultrahigh uniform tensile elongation (~50%), three times that of conventional nonbuffering EHEAs, without sacrificing strength. © 2021 American Association for the Advancement of Science. All rights reserved.

Canfieldite, Ag8SnS6, is a semiconducting mineral notable for its high ionic conductivity, photosensitivity, and low thermal conductivity. We report the solution growth of large single crystals of Ag8SnS6 of mass up to 1 g from a ternary Ag–Sn–S melt. On cooling from high temperature, Ag8SnS6 undergoes a known cubic (F4̅3m) to orthorhombic (Pna21) phase transition at ≈460 K. By studying the magnetization and thermal expansion between 5–300 K, we discover a second structural transition at ≈120 K. Single crystal X-ray diffraction reveals the low-temperature phase adopts a different orthorhombic structure with space group Pmn21 (a = 7.662 9(5) Å, b = 7.539 6(5) Å, c = 10.630 0(5) Å, Z = 2 at 90 K) that is isostructural to the room-temperature forms of the related Se-based compounds Ag8SnSe6 and Ag8GeSe6. The 120 K transition is first-order and has a large thermal hysteresis. On the basis of the magnetization and thermal expansion data, the room-temperature polymorph can be kinetically arrested into a metastable state by rapidly cooling to temperatures below 40 K. We last compare the room- and low-temperature forms of Ag8SnS6 with its argyrodite analogues, Ag8TQ6 (T = Si, Ge, Sn; Q = S, Se), and identify a trend relating the preferred structures to the unit cell volume, suggesting smaller phase volume favors the Pna21 arrangement. We support this picture by showing that the transition to the Pmn21 phase is avoided in Ge alloyed Ag8Sn1–xGexS6 samples as well as in pure Ag8GeS6 © 2021 American Chemical Society

For additive manufacturing materials, different process parameters might cause non-negligible microstructural defects. Due to the deficient or surplus energy input during the process, porosity would result in significantly different mechanical responses. In addition, the heterogeneity of the microstructure of additive manufactured material could increase the anisotropic behavior in both deformation and failure stages. The aim of this study is to perform a numerical investigation of the anisotropic plasticity affected by the microstructural features, in particular, texture and porosity. The coupling of the synthetic microstructure model and the crystal plasticity method is employed to consider the microstructural features and to predict the mechanical response at the macroscopic level, including both flow curve and r-value evolution. The additive manufactured 316L stainless steel is chosen as the reference steel in this study. Porosity decreases the stress of material, however, it reduces the anisotropy of material with both two types of textures. Regardless of porosity, grains with <111>//BD fiber of reference material is preferable for high strength requirement while the random orientations are favorable for homogeneous deformation in applications. © ESAFORM 2021 - 24th Inter. Conf. on Mat. Forming. All rights reserved.

Laser shock peening is a surface treatment technology inducing high-pressure shock waves on metallic materials and structures. In this study, the life cycle performance improvement in high-strength steel by nanosecond laser shock peening is investigated. It is found that microstructures formed by laser shock peening lead to higher microhardness, corrosion resistance, and fatigue life, which are significantly beneficial for preventing life cycle failure of mega-scale engineering structures in critical environments. The residual stress is also measured on the surface of samples, which shows that the compressive residual stress can be found in the treated area. © 2021 Elsevier B.V.

Dislocation glide is a general deformation mode, governing the strength of metals. Via discrete dislocation dynamics and molecular dynamics simulations, we investigate the strain rate and dislocation density dependence of the strength of bulk copper and aluminum single crystals. An analytical relationship between material strength, dislocation density, strain rate and dislocation mobility is proposed, which agrees well with current simulations and published experiments. Results show that material strength displays a decreasing regime (strain rate hardening) and then increasing regime (classical forest hardening) as the dislocation density increases. Accordingly, the strength displays universally, as the strain rate increases, a strain rate-independent regime followed by a strain rate hardening regime. All results are captured by a single scaling function, which relates the scaled strength to a coupling parameter between dislocation density and strain rate. Such coupling parameter also controls the localization of plasticity, fluctuations of dislocation flow and distribution of dislocation velocity. © 2021, The Author(s).

Flow dynamics and temperatures of solid fuel particles strongly influence flame stabilization, local heat release and fuel conversion inside pulverized solid fuel combustors. To investigate these phenomena, experiments are carried out under well-controlled inflow and boundary conditions inside a gas-assisted, swirled oxy-fuel combustion chamber. Flow fields of small particles that represent the gas phase velocity are determined in the near-burner region by PIV using a particle separation algorithm. Trajectories of large solid fuel particles are evaluated in a two-dimensional plane using a combined high-speed PIV/PTV approach. Particle temperatures and particles sizes are measured at different levels downstream the burner exit to reveal different stages of combustion. Therefore, a two-color pyrometer is used that dissolve single particles to achieve local particle temperature and particle size distributions. Two oxy-fuel operation conditions with an oxygen fraction of 33%V and a reference operation point in air are investigated within this study. In the flow fields of the gas phase the impact of the atmosphere is clearly visible in the spatial expansion of the internal recirculation area. Regions of high slip velocities and high heat release could be identified by analyzing particle trajectories in terms of direction, velocity and acceleration. Residence times of small and large particles are estimated from the flow fields. Significantly larger residence times are observed for large particles which leads to higher burn out rates in the near-burner region. Furthermore, particle temperature measurements reveal similar particle temperatures for the investigated oxy-fuel and air operation conditions. © 2020 Elsevier Ltd

Achieving a selective 2 e− or 4 e− oxygen reduction reaction (ORR) is critical but challenging. Herein, we report controlling ORR selectivity of Co porphyrins by tuning only steric effects. We designed Co porphyrin 1 with meso-phenyls each bearing a bulky ortho-amido group. Due to the resulted steric hinderance, 1 has four atropisomers with similar electronic structures but dissimilar steric effects. Isomers αβαβ and αααα catalyze ORR with n=2.10 and 3.75 (n is the electron number transferred per O2), respectively, but ααββ and αααβ show poor selectivity with n=2.89–3.10. Isomer αβαβ catalyzes 2 e− ORR by preventing a bimolecular O2 activation path, while αααα improves 4 e− ORR selectivity by improving O2 binding at its pocket, a feature confirmed by spectroscopy methods, including O K-edge near-edge X-ray absorption fine structure. This work represents an unparalleled example to improve 2 e− and 4 e− ORR by tuning only steric effects without changing molecular and electronic structures. © 2021 Wiley-VCH GmbH

Performance of smart piezoelectric structures strongly depends on placement of integrated piezoelectric actuators and sensors, which may be implemented in the form of thin film layers on the structure surface or embedded within the structure. In both cases actuator and sensor placement plays an important role, since after applying they remain permanently integrated with structure. In this paper the optimization procedure for piezoelectric structures with curved surfaces is proposed based on the Software-in-the-Loop (SiL) methodology and balanced modal order reduction in combination with H2 and H∞ norms used in placement indices. The optimization procedure is a global one, since it seeks for optima across the entire domain of the structure. A special challenge is tackling the problem of curved surfaces. This problem is solved in this work for a funnel shaped structure – inlet of the magnetic resonance imaging tomopraph. A thorough mesh convergence study with respect to the eigenfrequency analysis is performed in order to obtain a reliable numeric finite element model for further optimization purposes. Material parameter optimization is performed as well. Based on placement indices optimal placement study is performed under consideration of several eigenmodes of interest. The optimization is performed for individual modes as well as for simultaneous consideration of multiple modes. The SiL approach with recurrent communication in each iteration of the optimization between the numerical simulation FE software and optimization tool designed in Python is implemented through the evaluation of the placement indices for candidate locations over the entire curved surface of the structure. Depending on support conditions, optimal locations of piezoelectric actuators and sensors are proposed. © 2020 Elsevier Ltd

A single-photon source is an enabling technology in device-independent quantum communication1, quantum simulation2,3, and linear optics-based4 and measurement-based quantum computing5. These applications employ many photons and place stringent requirements on the efficiency of single-photon creation. The scaling on efficiency is typically an exponential function of the number of photons. Schemes taking full advantage of quantum superpositions also depend sensitively on the coherence of the photons, that is, their indistinguishability6. Here, we report a single-photon source with a high end-to-end efficiency. We employ gated quantum dots in an open, tunable microcavity7. The gating provides control of the charge and electrical tuning of the emission frequency; the high-quality material ensures low noise; and the tunability of the microcavity compensates for the lack of control in quantum dot position and emission frequency. Transmission through the top mirror is the dominant escape route for photons from the microcavity, and this output is well matched to a single-mode fibre. With this design, we can create a single photon at the output of the final optical fibre on-demand with a probability of up to 57% and with an average two-photon interference visibility of 97.5%. Coherence persists in trains of thousands of photons with single-photon creation at a repetition rate of 1 GHz. © 2021, The Author(s), under exclusive licence to Springer Nature Limited.

Cu-based catalysts have shown structural instability during the electrochemical CO2reduction reaction (CO2RR). However, studies on monometallic Cu catalysts do not allow a nuanced differentiation between the contribution of the applied potential and the local concentration of CO as the reaction intermediate since both are inevitably linked. We first use bimetallic Ag-core/porous Cu-shell nanoparticles, which utilise nanoconfinement to generate high local CO concentrations at the Ag core at potentials at which the Cu shell is still inactive for the CO2RR. Usingoperandoliquid cell TEM in combination withex situTEM, we can unequivocally confirm that the local CO concentration is the main source for the Cu instability. The local CO concentration is then modulated by replacing the Ag-core with a Pd-core which further confirms the role of high local CO concentrations. Product quantification during CO2RR reveals an inherent trade-off between stability, selectivity and activity in both systems. © The Royal Society of Chemistry 2021.

We use molecular dynamics (MD) simulation with numerical characterisation and statistical analysis to study the mechanisms of damage evolution and p-type doping efficiency by aluminum (Al) ion implantation into 3C silicon carbide (SiC) with subsequent annealing. By incorporating the electronic stopping power for implantation, a more accurate description of the atomic-scale mechanisms of damage evolution and distribution in SiC can be obtained. The simulation results show a novel observation that the recrystallization process occurs in the region below the subsurface layer, and develops from amorphous-crystalline interface to the damage center region, which is a new insight into previously published studies. During surface recrystallization, significant compressive stress concentration occurs, and more structural phase transition atoms and dislocations formed at the damage-rich-crystalline interface. Another point of interest is that for low-dose implantation, more implantation-induced defects hamper the doping efficiency. Correspondingly, the correlation between lattice damage and doping efficiency becomes weaker as the implant dose increases under the same annealing conditions. Our simulation also predicts that annealing after high temperature (HT) implantation is more likely to lead to the formation of carbon vacancies (VC). © The Royal Society of Chemistry 2021.

A splitting of the fundamental optical modes in micro- and nanocavities comprising semiconductor heterostructures is commonly observed. Given that this splitting plays a role in light-matter interaction and hence quantum technology applications, a method for controlling the mode splitting is useful. In this work we use an open microcavity composed of a "bottom"semiconductor distributed Bragg reflector (DBR) incorporating a n-i-p heterostructure, paired with a "top"curved dielectric DBR. We measure the mode splitting as a function of wavelength across the stopband. We demonstrate a reversible in situ technique to tune the mode splitting by applying uniaxial stress to the semiconductor DBR. The method exploits the photoelastic effect of the semiconductor materials. We achieve a maximum tuning of approximately 11 GHz. The stress applied to the heterostructure is determined by observing the photoluminescence of quantum dots embedded in the sample, converting a spectral shift to a stress via deformation potentials. A thorough study of the mode splitting and its tuning across the stopband leads to a quantitative understanding of the mechanism behind the results. © 2021 authors. Published by the American Physical Society.

The edge chlorination of the benchmark nanographenes triphenylene and hexa-peri-hexabenzocoronene is conducted mechanochemically. This approach overcomes solubility limitations and eliminates the need for elaborate chlorination conditions. Additionally, the planarization of oligophenylenes and their edge-chlorination can be combined in a one-pot approach requiring as little as 60 minutes. © The Royal Society of Chemistry.

The electronic ground state of iron-based materials is unusually sensitive to electronic correlations. Among others, its delicate balance is profoundly affected by the insertion of magnetic impurities in the FeAs layers. Here, we address the effects of Fe-to-Mn substitution in the non-superconducting Sm-1111 pnictide parent compound via a comparative study of SmFe1-xMnxAsO samples with x(Mn) = 0.05 and 0.10. Magnetization, Hall effect, and muon-spin spectroscopy data provide a coherent picture, indicating a weakening of the commensurate Fe spin-density-wave (SDW) order, as shown by the lowering of the SDW transition temperature TSDW with increasing Mn content, and the unexpected appearance of another magnetic order, occurring at T∗≈ 10 and 20 K for x= 0.05 and 0.10, respectively. We attribute the new magnetic transition at T∗, occurring well inside the SDW phase, to a reorganization of the Fermi surface due to Fe-to-Mn substitutions. These give rise to enhanced magnetic fluctuations along the incommensurate wavevector Q2= (π± δ, π± δ) , further increased by the RKKY interactions among Mn impurities. © 2021, The Author(s).

The antagonism between strength and resistance to hydrogen embrittlement in metallic materials is an intrinsic obstacle to the design of lightweight yet reliable structural components operated in hydrogen-containing environments. Economical and scalable microstructural solutions to this challenge must be found. Here, we introduce a counterintuitive strategy to exploit the typically undesired chemical heterogeneity within the material’s microstructure that enables local enhancement of crack resistance and local hydrogen trapping. We use this approach in a manganese-containing high-strength steel and produce a high dispersion of manganese-rich zones within the microstructure. These solute-rich buffer regions allow for local micro-tuning of the phase stability, arresting hydrogen-induced microcracks and thus interrupting the percolation of hydrogen-assisted damage. This results in a superior hydrogen embrittlement resistance (better by a factor of two) without sacrificing the material’s strength and ductility. The strategy of exploiting chemical heterogeneities, rather than avoiding them, broadens the horizon for microstructure engineering via advanced thermomechanical processing. © 2021, The Author(s).

The present study aims to investigate a liquid state method of stir and centrifugal casting as an in-situ and cost-attractive processing technology for the production of magnesium/hydroxyapatite surface metal matrix nano-composites (Mg/HA surface metal matrix nano-composite). The main contribution of this study is to design the best condition for achieving a uniform Mg/HA surface nano-composite as a potential bone implant. It was shown how casting parameters and the distribution of hydroxyapatite affect mechanical properties of nano-composites measured using nano-indentation, nano-scratch, and compression tests. Response surface method in Design Expert software was used to predict the best model and the optimum condition of casting based on the experimentally measured data. The surface metal matrix nano-composites, consisting of a magnesium matrix with different amounts of nano-sized hydroxyapatite and silicon-doped hydroxyapatite (0.75-3 wt%) particles, were prepared. Hot isostatic pressing was used to homogenize the nano-composites in terms of particle distribution and to reduce porosity. It was shown that the weight percent of hydroxyapatite reinforcement is the parameter which is best suited to tailor targeted strength values. The target values of maximum compression strength (187 MPa) and elastic modulus (33 GPa) were achieved with a combination of the following parameters: 1.83 wt% hydroxyapatite, 800 rpm mold rotational speed, and a propeller rotational time of 6.3 min. A specimen prepared under these conditions had a homogeneous distribution of nano-hydroxyapatite in magnesium metal matrix after hot isostatic pressing at 450 °C and 100 MPa for a holding time of 120 min. It indicated the best mechanical resistance in terms of hardness and material loss during the nano-scratch testing. Moreover, the XRD results show that there is no considerable chemical reaction between the reinforcement particles of n-HA and Mg metallic matrix during casting at 700 °C and thermo-mechanical treatment of HIP at 450 °C. © 2020

The ability to shuttle coherently individual electron spins in arrays of quantum dots is a key procedure for the development of scalable quantum information platforms. It allows the use of sparsely populated electron spin arrays, envisioned to efficiently tackle the one- and two-qubit gate challenges. When the electrons are displaced in an array, they are exposed to site-dependent environment interactions such as hyperfine coupling with substrate nuclear spins. Here, we demonstrate that the electron multidirectional displacement in a 3×3 array of tunnel-coupled quantum dots enhances the spin-coherence time via the motional narrowing phenomenon. More specifically, up to ten charge configurations are explored by the electrons to study the impact of the displacement on spin dynamics. An increase of the coherence time by a factor up to 10 is observed in the case of fast and repetitive displacement. A simple model quantitatively captures the physical mechanism underlying this enhancement of the spin-coherence time induced by displacement. The implications on spin-coherence properties during the electron displacement are discussed in the context of large-scale quantum circuits. © 2021 authors.

Mass spectrometry is a widespread approach used to work out what the constituents of a material are. Atoms and molecules are removed from the material and collected, and subsequently, a critical step is to infer their correct identities based on patterns formed in their mass-to-charge ratios and relative isotopic abundances. However, this identification step still mainly relies on individual users' expertise, making its standardization challenging, and hindering efficient data processing. Here, we introduce an approach that leverages modern machine learning technique to identify peak patterns in time-of-flight mass spectra within microseconds, outperforming human users without loss of accuracy. Our approach is cross-validated on mass spectra generated from different time-of-flight mass spectrometry (ToF-MS) techniques, offering the ToF-MS community an open-source, intelligent mass spectra analysis. Time-of-flight mass spectrometry (ToF-MS) is a mainstream analytical technique widely used in biology, chemistry, and materials science. ToF-MS provides quantitative compositional analysis with high sensitivity across a wide dynamic range of mass-to-charge ratios. A critical step in ToF-MS is to infer the identity of the detected ions. Here, we introduce a machine-learning-enhanced algorithm to provide a user-independent approach to performing this identification using patterns from the natural isotopic abundances of individual atomic and molecular ions, without human labeling or prior knowledge of composition. Results from several materials and techniques are compared with those obtained by field experts. Our open-source, easy-to-implement, reliable analytic method accelerates this identification process. A wide range of ToF-MS-based applications can benefit from our approach, e.g., hunting for patterns of biomarkers or for contamination on solid surfaces in high-throughput data. A machine-learning application for the accelerated data processing and interpretation of time-of-flight mass spectrometry is presented. The machine learns patterns in a human-label-free manner, making the process easy to implement and the result highly reproducible. © 2020 The Authors

During the planning phase of tunneling projects, in particular in urban areas, it is crucial to assess the likely extent of structural damage caused by the tunnel construction in close vicinity to existing surface structures. Tunneling inevitably causes ground movements which in turn may have an impact on deformations and stresses of the above-ground structures. For this reason, a reliable estimate of the soil-structure interactions due to tunnelling-induced settlements is essential. In this contribution, various approaches that differ in precision and complexity are employed to predict the magnitude of expected settlements and the vulnerability of structures with regard to tunneling induced damage. In addition, a three-step damage assessment concept adjustable to the necessary level of detail is suggested. Firstly, ground movements are predicted using analytical or numerical approaches. Secondly, the above-ground structures are idealized by means of surrogate beam-, slab- or 3D-models. Finally, structural damage is assessed according to the computed strain pattern or the tilt of the building. This method enables the evaluation of the potential damage to above ground structures associated with planned tunnel alignment. When developing 3D numerical models, the main focus will be to ensure that the building and the soil-structure interactions are represented with an appropriate level of detail. To this end, this paper aims to provide recommendations for a sufficient level of detail (LOD) of surface structures for the assessment of tunneling induced damage in computational simulations in mechanized tunneling. © 2021, The Author(s), under exclusive license to Springer Nature Switzerland AG.

We conducted a series of high-temperature experiments where single crystals of CaTiO3 were embedded in PbTiO3 powder for durations of 4 to 502 h at temperatures between 753 and 1207 °C. Combined with results from a previous study (Beyer et al. 2019), these experiments allow us to explore the influence of chemical potential gradients on the mechanisms of incorporation of Pb in CaTiO3. Unlike in the previous study where Pb diffused into CaTiO3, here we find that the rims of the CaTiO3 crystals recrystallize to form a polycrystalline aggregate of [PbxCa(1-x)]TiO3 solid solutions. The width of the recrystallized front increases with run duration, and the contact to the single crystal becomes progressively wavy. The concentration of Pb decreases within the recrystallized front toward the interior of the single crystal, and the newly formed crystals are of different chemical compositions and orientations and are themselves chemically zoned. There is a discontinuous jump in Pb-concentration at the contact of the recrystallized front with the single crystal (termed "the migrating interface"). The development of chemical concentration gradients, combined with the fact that the width of the front grows as the square-root of time indicates a role of diffusion in the process; the formation of new crystals with different composition and no orientation relation to the precursor, and the jump in concentration at the boundary between the newly formed crystals and the single crystal indicates a dissolution-precipitation type process. Thus, this is a novel mechanism where diffusion, as well as dissolution-precipitation (in the sense that the structure of the single crystal is destroyed and replaced by new crystals), occurs simultaneously in a coupled manner and neither is rate-determining. The observations in this experimental study provide several insights into the mechanisms of chemical transformation in such non-metallic materials: (1) chemical differences can trigger mechanical deformation, which in turn can control chemical fluxes; (2) newly formed crystals, even at the high temperatures of the experiments, evolve continuously in chemistry and are not of an equilibrium composition; (3) the activation energy of the overall process (~70 kJ/mol) is lower than that for diffusion and provides a more effective means of chemical transformation, even though diffusion plays a central role in the process; and (4) it underscores the role of surface/interface free energy in the evolution of the transformation process. These results have important consequences for the reading of the petrological and geochemical signatures of the rock record - notably, in addition to knowing when a phase becomes chemically stable, it is also important to know when a particular crystal of the phase begins to exist. Some possible implications for thermobarometry, isotopic dating, and geospeedometry/ diffusion chronometry are discussed. © 2021 Mineralogical Society of America.

Most oxide ceramics are known to be brittle macroscopically at room temperature with little or no dislocation-based plasticity prior to crack propagation. Here, we demonstrate the size-dependent brittle to ductile transition in SrTiO3 at room temperature using nanoindentation pop-in events visible as a sudden increase in displacement at nominally constant load. We identify that the indentation pop-in event in SrTiO3 at room temperature, below a critical indenter tip radius, is dominated by dislocation-mediated plasticity. When the tip radius increases to a critical size, concurrent dislocation activation and crack formation, with the latter being the dominating process, occur during the pop-in event. Beyond the experimental examination and theoretical justification presented on SrTiO3 as a model system, further validation on α-Al2O3, BaTiO3, and TiO2 are briefly presented and discussed. A new indentation size effect, mainly for brittle ceramics, is suggested by the competition between the dislocation-based plasticity and crack formation at small scale. Our finding complements the deformation mechanism in the nano-/microscale deformation regime involving plasticity and cracking in ceramics at room temperature to pave the road for dislocation-based mechanics and functionalities study in these materials. © 2021 The Authors. Journal of the American Ceramic Society published by Wiley Periodicals LLC on behalf of American Ceramic Society (ACERS)

Reducing the strong beam divergence inherent to Orbital Angular Momentum waves (also known as OAM waves or vortex waves), a tailored lens and a tailored reflector are presented in this study. The generation of the OAM waves is accomplished by a Uniform Circular Patch Antenna Array (UCA) operating at 10 GHz. Here, the tailored lens and reflector are set up by two correspondingly designed shape functions rotated around the antenna's center axis in broadside direction (i.e. body of revolution approach). Initially, the tailored lens is introduced to be compared to the UCA in the presence and absence of the conventional lens separately. Upon the usage of the tailored lens, a gain improvement of 5.8 dB has been obtained in the simulation compared to a gain of 4.8 dB in the measurement. On the other hand, the tailored reflector is set under the same procedure to be compared also to the UCA with and without a conventional reflector. Both of the reflectors are simulated under idealized conditions with the aid of an OAM impressed field source used as an emitter for a meaningful comparison. The simulated gain has shown a better performance accomplished by the tailored reflector as the height r0 reaches a level less than 1.5 λ as well as the opening angle θ is less than 38° (given an UCA with an element separation distance d=λ/2). Furthermore, three different ground plane shapes with realistic UCA are applied for the simulation procedure where each of them is perturbing the radiation of the reflector. All of the lenses and the reflectors are manufactured and later measured in an anechoic chamber to undergo a comparison with the simulated results. This article demonstrates that the vortex waves need a tailored lens or a tailored reflector to decrease the beam divergence effectively especially when the radius of the UCA becomes increasingly large. © 2013 IEEE.

In order to enable the application of atomic probe tomography combinatorial processing platforms for atomic-scale investigations of phase evolution at elevated temperatures, the pre-sharpened Si tip of 10–20 nm in diameter must be protected against interdiffusion and reaction of the reactive Si with a film of interest by a conformal coating on the Si tip. It is shown that unwanted reactions can be suppressed by introducing a 20-nm-thick intermediate Al2O3 layer grown by atomic layer deposition (ALD). As a representative case, Pt is chosen as a film of interest, as it easily forms silicides. Whereas without the ALD coating diffusion/reactions occur, with the protective film, this is prevented for temperatures up to at least 600°C. The effectiveness of the Al2O3 layer serving as a diffusion barrier is not limited to a sharpened Si tip but works generally for all cases where a Si substrate is used. © 2021 The Authors. Surface and Interface Analysis published by John Wiley & Sons Ltd.

In the present article, we present a data compilation reflecting recrystallized microstructures and the corresponding mechanical properties of an equiatomic, single-phase face-centered cubic (FCC) CrFeNi medium-entropy alloy (MEA). For the analysis, interpretation, and discussion of the data, the reader can refer to the original research article entitled “Effects of temperature on mechanical properties and deformation mechanisms of the equiatomic CrFeNi medium-entropy alloy”, see Ref. (Schneider and Laplanche, Acta Mater. 204, 2020). The data related to recrystallized microstructures comprise raw backscatter electron (BSE) micrographs (tif-files) obtained using a scanning electron microscope (SEM) for six grain sizes in the range [10–160 µm], optical micrographs of the alloy with the largest grain size (d = 327 µm), pdf-reports and tables presenting the corresponding grain-size distributions (d, accounting for grain boundaries only) and crystallite-size distributions (c, which accounts for both grain and annealing twin boundaries), the annealing twin thicknesses (t), the average number of annealing twin boundaries per grain (n), and the average Taylor factor (M) of each recrystallized microstructure. These are benchmark datasets that may serve to develop new algorithms for the automated evaluation of microstructural parameters. Such algorithms would help to speed up the analyses of microstructures and improve their reliability. Furthermore, several groups pointed out that in addition to the mean grain size, other microstructural parameters such as the grain size distribution (Raeisinia et al., Model. Simul. Mater. Sc. 16, 2008) and the average number of twins per grain (Schneider et al., Int. J. Plasticity, 124, 2020) may affect some material properties (e.g. Hall-Petch strengthening). Therefore, an effort was made here to determine and report almost all the microstructural parameters describing recrystallized microstructures of FCC alloys. The mechanical-properties data are provided as excel-sheets in which the raw stress-strain curves can be found. Compression tests for alloys with different grain sizes were performed at room temperature. Additional compression tests and tensile tests for the grain size d = 160 µm were performed at temperatures between 77 K and 873 K. Characteristic mechanical properties, such as yield stresses at 0.2% plastic strain (σ0.2%) and Hall-Petch parameters (σ0 and ky) are given for all temperatures in the tables below. Moreover, the Hall-Petch parameters as well as the mechanical data reported in the present study could be used for data mining and implemented in programs used for alloy design. © 2021 The Author(s)

Persistent photoconductivity of GaAs/AlGaAs heterostructures has hampered the measurement of charge- and spin-related quantum effects in gate-defined quantum devices and integrated charge sensors due to Si-dopant-related deep donor levels (DX centers). In this study, this effect is overcome by using an undoped GaAs/AlGaAs heterostructure for photonic purposes. We also measure the electron transport before and after LED illumination at low temperatures. In addition to a regular rapid saturation showing the increased carrier density, a slow accumulation of illumination effects appeared when different top-gate voltages were applied during illumination, which indicated the redistribution of charge at the oxide-GaAs interface. This study provides interesting insights into the development of optically stable devices for efficient semiconductor quantum interfaces. © 2021 Author(s).

An equiatomic CrFeNi medium-entropy alloy (MEA) that constitutes a cornerstone of austenitic stainless steels and Fe-based superalloys is investigated. Anneals at various temperatures revealed that CrFeNi forms a stable face-centered cubic (FCC) solid solution above ~1223 K. Based on this result, this alloy was cold-worked and recrystallized between 1273 K and 1473 K to produce different grain sizes. Compression tests were carried out at 293 K to investigate grain boundary strengthening (Hall-Petch slope: 966 MPa µm1/2) and this contribution was then subtracted from the overall strength to reveal the intrinsic uniaxial lattice strength (80 MPa). Additional compression and tensile tests were performed between 77 K and 873 K to study the effect of temperature on mechanical properties and deformation mechanisms. Ductility, yield and ultimate tensile strengths increased with decreasing temperature. To reveal the active deformation mechanisms in CrFeNi with the coarsest grain size (160 µm), tensile tests at 77 K and 293 K were interrupted at different strains followed by transmission electron microscopy analyses. In all cases, the deformation was accommodated by dislocation glide at low strains, while twinning additionally occurred above a critical resolved shear stress of 165 MPa, which was roughly temperature independent. This value compares well with predictions (180 MPa) based on the Kibey's model for twin nucleation. Moreover, the fact that this value is roughly temperature-independent is also consistent with the Kibey's model since the twin nucleation barrier (unstable twin stacking fault energy) of FCC metals and alloys does not vary significantly with temperature. © 2020 Acta Materialia Inc.

Zwitterionic peptides are facile low-fouling compounds for environmental applications as they are biocompatible and fully biodegradable as their degradation products are just amino acids. Here, a set of histidine (H) and glutamic acid (E), as well as lysine (K) and glutamic acid (E) based peptide sequences with zwitterionic properties were synthesized. Both oligopeptides (KE)4K and (HE)4H were synthesized in d and l configurations to test their ability to resist the nonspecific adsorption of the proteins lysozyme and fibrinogen. The coatings were additionally tested against the attachment of the marine organisms Navicula perminuta and Cobetia marina as well as the freshwater bacterium Pseudomonas fluorescens on the developed coatings. While the peptides containing lysine performed better in protein resistance assays and against freshwater bacteria, the sequences containing histidine were generally more resistant against marine organisms. The contribution of amino acid-intrinsic properties such as side chain pKa values and hydrophobicity, as well as external parameters such as pH and salinity of fresh water and seawater on the resistance of the coatings is discussed. In this way, a detailed picture emerges as to which zwitterionic sequences show advantages in future generations of biocompatible, sustainable, and nontoxic fouling release coatings. © 2021 The Authors. Published by American Chemical Society.

The rate of charging of supercapacitors depends on how quickly ions can reach and accommodate the surface of electrodes. Diffusivity, a parameter reflecting the speed of ions’ migration, is believed to be crucial in designing supercapacitor electrodes. Herein, this belief is questioned, shedding light on a puzzling and potentially critical feature of ionic dynamics denoted as confinement-induced ion–solvent separation. This effect can lead to a strong slowdown of the ion mobility inside hierarchical pore networks. Explanations for when such an effect occurs and how it can be circumvented are provided. Furthermore, this microscopic picture of diffusion seen by NMR is bridged with the macroscopic charging behavior of supercapacitors investigated by impedance spectroscopy. Quantifying the average residence time of ions within carbon particles shows that the nanopore environment may not be the rate-limiting factor for the overall ion mobility and thus performance of a cell—as commonly expected. Combining direct diffusion studies performed with neat and solvated ionic liquids and those on organic electrolytes, the so far lacking criteria for the rational selection of electrolyte–carbon systems is developed and recommendations for the preparation of transport-optimized materials for supercapacitors to minimize ionic diffusion limitations are given. © 2021 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH

The main focus of this work is to correlate the basic plasma properties with morphological, structural and mechanical properties of thin films to bridge the gap between the energy source, the plasma and materials. For this purpose, the deposition and growth of thin titanium films deposited by high power impulse magnetron sputtering (HiPIMS) at various discharge power densities, from 0.17 kW/cm2 to 3.5 kW/cm2 were studied, both experimentally and by kinetic Monte Carlo simulation. Simulations of film growth were performed with a three-dimensional kinetic Monte Carlo code (NASCAM) with ion fraction and species energy determined experimentally by mass spectroscopy. Our approach, which is not purely empirically driven, intends to reveal some insights of the mechanisms underlying the synthesis process, which determine the intrinsic material properties. In order to link HiPIMS plasma parameters and Ti film properties, we used different techniques to analyse Ti films. TEM, X-ray diffraction and AFM were used to evaluate the structural and morphological properties of the films, and nano indention was used to evaluate their mechanical properties. We observed that the orientation of micro-crystals, which constitute the films, changes when the discharge power density increases. At the same time, we show that the films nano hardness changes non-monotonically with the increase of the discharge power density; it decreases first, then increases. The surface roughness behaviour is also non-monotonic; first increasing, then decreasing with the further increase of the discharge power density. 3D modelling helped to reveal that these non-monotonic evolutions are due to a transition between thermally-driven to ballistically-driven Ti atom mobility. © 2021 Elsevier B.V.

Atomic environment fingerprints are widely used in computational materials science, from machine learning potentials to the quantification of similarities between atomic configurations. Many approaches to the construction of such fingerprints, also called structural descriptors, have been proposed. In this work, we compare the performance of fingerprints based on the overlap matrix, the smooth overlap of atomic positions, Behler–Parrinello atom-centered symmetry functions, modified Behler–Parrinello symmetry functions used in the ANI-1ccx potential and the Faber–Christensen–Huang–Lilienfeld fingerprint under various aspects. We study their ability to resolve differences in local environments and in particular examine whether there are certain atomic movements that leave the fingerprints exactly or nearly invariant. For this purpose, we introduce a sensitivity matrix whose eigenvalues quantify the effect of atomic displacement modes on the fingerprint. Further, we check whether these displacements correlate with the variation of localized physical quantities such as forces. Finally, we extend our examination to the correlation between molecular fingerprints obtained from the atomic fingerprints and global quantities of entire molecules. © 2021 The Author(s). Published by IOP Publishing Ltd

Hydrogen spillover is the phenomenon where a hydrogen atom, generated from the dissociative chemisorption of dihydrogen on the surface of a metal species, migrates from the metal to the catalytic support. This phenomenon is regarded as a promising avenue for hydrogen storage, yet the atomic mechanism for how the hydrogen atom can be transferred to the support has remained controversial for decades. As a result, the development of catalytic support for such a purpose is only limited to typical reducible oxide materials. Herein, by using a combination of in situ spectroscopic and imaging technique, we are able to visualize and observe the atomic pathway for which hydrogen travels via a frustrated Lewis pair that has been constructed on a nonreducible metal oxide. The interchangeable status between the hydrogen, proton, and hydride is carefully characterized and demonstrated. It is envisaged that this study has opened up new design criteria for hydrogen storage material. © 2021 American Chemical Society.

Ammonia synthesis via the high-temperature and high-pressure Haber-Bosch process is one of the most important chemical processes in the world. In spite of numerous attempts over the last 100 years, continuous Haber-Bosch type ammonia synthesis at room-temperature had not been possible, yet. We report the development of a mechanocatalytic system operating continuously at room-temperature and at pressures down to 1 bar. With optimized experimental conditions, a cesium-promoted iron catalyst was shown to produce ammonia at concentrations of more than 0.2 vol. % for over 50 hours. © 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH

Tissue degradation plays a crucial role in the formation and rupture of aneurysms. Using numerical computer simulations, we study the combined effects of blood flow and tissue degradation on intra-aneurysm hemodynamics. Our computational analysis reveals that the degradation-induced changes of the time-averaged wall shear stress (TAWSS) and oscillatory shear index (OSI) within the aneurysm dome are inversely correlated. Importantly, their correlation is enhanced in the process of tissue degradation. Regions with a low TAWSS and a high OSI experience still lower TAWSS and higher OSI during degradation. Furthermore, we observed that degradation leads to an increase of the endothelial cell activation potential index, in particular, at places experiencing low wall shear stress. These findings are robust and occur for different geometries, degradation intensities, heart rates and pressures. We interpret these findings in the context of recent literature and argue that the degradation-induced hemodynamic changes may lead to a self-amplification of the flow-induced progressive damage of the aneurysmal wall. Copyright © 2021 Wang, Balzani, Vedula, Uhlmann and Varnik.

Rational design of highly active electrocatalysts for the oxygen evolution reaction (OER) is critical to improving overall electrochemical water splitting efficiency. This study suggests hollow CeO2@Co2N nanosheets synthesized using Co-ZIF-L as a precursor, followed by a hydrothermal reaction and a nitridation process as very attractive OER catalysts. The increased activity is supposed to be due to nitridation and strong electronic interaction between CeO2 and Co2N that contribute to the formation of active CoOOH phase. The synthesized CeO2@Co2N exhibits low overpotentials of 219 and 345 mV at OER current densities of 10 and 100 mA cm–2, respectively, as well as a long-term durability of 30 h at a comparatively high current density of 100 mA cm−2. © 2021 The Authors. Advanced Materials Interfaces published by Wiley-VCH GmbH

Photoelectrochemical water splitting is mostly impeded by the slow kinetics of the oxygen evolution reaction. The construction of photoanodes that appreciably enhance the efficiency of this process is of vital technological importance towards solar fuel synthesis. In this work, Mo-modified BiVO4 (Mo:BiVO4), a promising water splitting photoanode, was modified with various oxygen evolution catalysts in two distinct configurations, with the catalysts either deposited on the surface of Mo:BiVO4 or embedded inside a Mo:BiVO4 film. The investigated catalysts included monometallic, bimetallic, and trimetallic oxides with spinel and layered structures, and nickel boride (NixB). In order to follow the influence of the incorporated catalysts and their respective properties, as well as the photoanode architecture on photoelectrochemical water oxidation, the fabricated photoanodes were characterised for their optical, morphological, and structural properties, photoelectrocatalytic activity with respect to evolved oxygen, and recombination rates of the photogenerated charge carriers. The architecture of the catalyst-modified Mo:BiVO4 photoanode was found to play a more decisive role than the nature of the catalyst on the performance of the photoanode in photoelectrocatalytic water oxidation. Differences in the photoelectrocatalytic activity of the various catalyst-modified Mo:BiVO4 photoanodes are attributed to the electronic structure of the materials revealed through differences in the Fermi energy levels. This work thus expands on the current knowledge towards the design of future practical photoanodes for photoelectrocatalytic water oxidation. © 2020, The Author(s).

Heavy plate steels with bainitic microstructures are widely used in industry due to their good combination of strength and toughness. However, obtaining optimal mechanical properties is often challenging due to the complex bainitic microstructures and multiple phase constitutions caused by different cooling rates through the plate thickness. Here, both conventional and advanced microstructural characterization techniques which bridge the meso- and atomic-scales were applied to investigate how microstructure/mechanical property-relationships of a low-carbon low-alloyed steel are affected by phase transformations during continuous cooling. Mechanical tests show that the yield strength increases monotonically when cooling rates increase up to 90 K/s. The present study shows that this is associated with a decrease in the volume fraction of polygonal ferrite (PF) and a refinement of the substructure of degenerated upper bainite (DUB). The fine DUB substructures feature C-rich retained austenite/martensite-austenite (RA/M-A) constitutes which decorate the elongated micrograin boundaries in ferrite. A further increase in strength is observed when needle-shaped cementite precipitates form during water quenching within elongated micrograins. Pure martensite islands on the elongated micrograin boundaries lead to a decreased ductility. The implications for thick section plate processing are discussed based on the findings of the present work. © 2021, The Author(s).

Electron spins in gate-defined lateral quantum dots (QDs) are a suitable platform for qubits and have the capacity for coherent coupling to freespace photons. Superposition state transfer from single photon polarizations to single spins has been realized using a GaAs gate-defined QD. However, its efficiency is limited by the small size of the QDs. Here, we use a surface plasmon antenna on a GaAs gate-defined QD and demonstrate that the photoelectron detection probability is enhanced by 5.3-9.2 times. This result contributes to the development of photon-spin quantum interface using gate-defined lateral QDs. © 2021 The Japan Society of Applied Physics.

Laser shock peening is a new and important surface treatment technique that can enhance the mechanical properties of metal materials. Normally, the nanosecond laser with pulse-width between 5 ns and 20 ns is used to induce a high-pressure shock wave that can generate plastic deformation in the top layer of metals. The femtosecond laser shock peening in the air has been studied recently, which can induce higher pressure shock wave than that of traditional nanosecond laser shock peening in a very short time. The NiTi alloy is processed by femtosecond laser shock peening, then a nanoindentation device is used to measure its surface hardness and residual stress. The hardness results of NiTi alloy before and after treatment show that the femtosecond laser shock peening can increase the hardness of NiTi alloy, which also shows that the femtosecond laser can be used to perform laser shock peening on NiTi alloy without coating. © 2021 SPIE.

A single Cr-rich σ-phase alloy with a composition of Co17Cr46Fe16.3Mn15.2Ni5.5 (at.%) and a tetragonal lattice structure was produced. The tracer diffusion coefficients of Ni and Fe were measured by secondary electron mass spectroscopy using the highly enriched 64Ni and 58Fe natural isotopes. On the homologous temperature scale, Ni and Fe diffuse in the σ phase faster as compared to the corresponding diffusion rates in the equiatomic and face-centered cubic CoCrFeMnNi alloy. In contrast, on the absolute temperature scale, these elements diffuse roughly at the same rates in both materials. Factors influencing element diffusion and phase stability of the σ phase compared to the equiatomic alloy are discussed. © 2020 Acta Materialia Inc.

Quantum repeater composed of a quantum memory and an interface between photon qubits and memory qubits is indispensable for long-distance quantum communication. Gate-defined lateral quantum dots (QDs) can be a suitable platform for such quantum repeaters because of its aptitude for spin qubit and feasibility of quantum state transfer from photon polarization to electron spin. So far, the reported photoelectron excitation probabilities in such a QD are not high enough to implement practical repeater protocols. To improve the photoexcitation probability, we combine a surface plasmon antenna (SPA) with QDs. We fabricated a SPA designed to enhance the optical transmission to the QDs in a practical illumination setup in a refrigerator and characterized the fabricated antenna by measuring photocurrents at room temperature. © 2021 The Japan Society of Applied Physics

Despite outstanding accomplishments in catalyst discovery, finding new, more efficient, environmentally neutral, and noble metal-free catalysts remains challenging and unsolved. Recently, complex solid solutions consisting of at least five different elements and often named as high-entropy alloys have emerged as a new class of electrocatalysts for a variety of reactions. The multicomponent combinations of elements facilitate tuning of active sites and catalytic properties. Predicting optimal catalyst composition remains difficult, making testing of a very high number of them indispensable. We present the high-throughput screening of the electrochemical activity of thin film material libraries prepared by combinatorial co-sputtering of metals which are commonly used in catalysis (Pd, Cu, Ni) combined with metals which are not commonly used in catalysis (Ti, Hf, Zr). Introducing unusual elements in the search space allows discovery of catalytic activity for hitherto unknown compositions. Material libraries with very similar composition spreads can show different activities vs. composition trends for different reactions. In order to address the inherent challenge of the huge combinatorial material space and the inability to predict active electrocatalyst compositions, we developed a high-throughput process based on co-sputtered material libraries, and performed high-throughput characterization using energy dispersive X-ray spectroscopy (EDS), scanning transmission electron microscopy (SEM), X-ray diffraction (XRD) and conductivity measurements followed by electrochemical screening by means of a scanning droplet cell. The results show surprising material compositions with increased activity for the oxygen reduction reaction and the hydrogen evolution reaction. Such data are important input data for future data-driven materials prediction. [Figure not available: see fulltext.] © 2021, The Author(s).

The catalytic effects of mineral compounds on the conversion of a biomass-derived char in air- and oxyfuel-related atmospheres were investigated by thermogravimetric analysis at atmospheric pressure. The applied char originated from the hydrothermal carbonization (HTC) of cellulose followed by pyrolysis at 1073 K and subsequent mixing with 20 wt% of minerals by grinding to achieve tight contact. The reactivities of the mineral-loaded HTC chars were evaluated based on isothermal experiments in O2-, CO2-, and H2O-containing atmospheres as a function of their composition applying a magnetic suspension balance. The reactivity sequence K2CO3 > Na2CO3 ≫ Fe2O3 > CaO > MgO ≥ mineral-free was derived consistently for char oxidation in O2/inert as well as for char gasification in diluted H2O and CO2 mixtures. In addition to this qualitative assessment, the kinetic experiments were first modelled based on a simple global nth-order power-law rate expression. Then, the more complex Carbon Burnout Kinetics (CBK/G) model and the PoliMi model were applied. All three modeling approaches enabled a systematic quantification of the catalytic effects and led to a comparable lowering in the apparent activation energy. In combination with the kinetic parameters determined for the mineral-free char, the lowered apparent activation energies specific for the applied mineral and atmosphere facilitate the implementation of catalytic effects on the conversion of biomass-derived char into combustion models. © 2020 Elsevier Ltd

Abstract: In molecular simulations, the identification of suitable reaction coordinates is central to both the analysis and sampling of transitions between metastable states in complex systems. If sufficient simulation data are available, a number of methods have been developed to reduce the vast amount of high-dimensional data to a small number of essential degrees of freedom representing the reaction coordinate. Likewise, if the reaction coordinate is known, a variety of approaches have been proposed to enhance the sampling along the important degrees of freedom. Often, however, neither one nor the other is available. One of the key questions is therefore, how to construct reaction coordinates and evaluate their validity. Another challenges arises from the physical interpretation of reaction coordinates, which is often addressed by correlating physically meaningful parameters with conceptually well-defined but abstract reaction coordinates. Furthermore, machine learning based methods are becoming more and more applicable also to the reaction coordinate problem. This perspective highlights central aspects in the identification and evaluation of reaction coordinates and discusses recent ideas regarding automated computational frameworks to combine the optimization of reaction coordinates and enhanced sampling. Graphic abstract: [Figure not available: see fulltext.] © 2021, The Author(s), under exclusive licence to EDP Sciences, SIF and Springer-Verlag GmbH Germany, part of Springer Nature.

The electron mobility in shallow GaAs/AlxGa1−xAs heterostructures is strongly suppressed by charge wafer surface, which arises from native surface oxide layers formed when the wafer is removed from the crystal growth system. Here an in situ epitaxial aluminum gate, grown as part of the wafer, is used to eliminate surface charge scattering. Transmission electron microscope characterization shows that the in situ epitaxial aluminum is crystalline, and the wafer surface is free of native oxide. The influence of Al thickness and the use of different semiconductor wetting layers at the semiconductor-aluminum interface are examined and correlated with electron mobility. The electron mobility is found to strongly depend on aluminum thickness. For 8 nm thick aluminum, the electron mobility is also influenced by the wetting layer, with aluminum grown on GaAs producing higher mobility compared to AlAs or Al0.33Ga0.67As wetting layers. The suppression of surface charge scattering in these all-epitaxial devices allows for high mobilities across a wide density range despite the shallow conduction channel (35 nm below the gate). These measurements also provide a uniquely sensitive method of determining the electrical quality of the semiconductor–metal interface, relevant to the formation of hybrid semiconductor–superconductor devices. © 2021 Wiley-VCH GmbH

The production of thin-wall ductile iron (TWDI) by high-pressure die-casting (HPDC) is complex because of several metallurgical and microstructural challenges. The present work aims to evaluate the austemperability of components (4 mm thickness) produced by HPDC process. The graphitization kinetics, the pearlite formation during continuous cooling, and the effect of austempering on the evolution of the ausferritic microstructure were investigated using dilatometric tests, microstructural analysis as well as Vickers hardness tests and tensile tests. Results show that components exhibit a brittle behavior because of white structures, small shrinkage cavities, and microporosity in the as-cast condition. Graphitization at 1100 °C allows rapid formation of small graphite particles within a short time (40 s). The critical cooling time (t8/5) to avoid the formation of pearlite upon cooling was found to be 5 s at a martensite start temperature of 193 ± 14 °C. Austempering at 360 °C for 40 min results in an ausferritic microstructure with stable carbon-enriched austenite which provides a high hardness (355 ± 4 HV10) and tensile strength (Rm = 709 ± 65 MPa). The results represent main criteria regarding the producibility of die-casted TWDI, which are helpful for future alloy and heat treatment design. © 2021, The Author(s).

Recent experiments show that the chemical composition of body-centered cubic (bcc) refractory high entropy alloys (HEAs) can be tuned to enable transformation-induced plasticity (TRIP), which significantly improves the ductility of these alloys. This calls for an accurate and efficient method to map the structural stability as a function of composition. A key challenge for atomistic simulations is to separate the structural transformation between the bcc and the ω phases from the intrinsic local lattice distortions in such chemically disordered alloys. To solve this issue, we develop a method that utilizes a symmetry analysis to detect differences in the crystal structures. Utilizing this method in combination with ab initio calculations, we demonstrate that local lattice distortions largely affect the phase stability of Ti–Zr–Hf–Ta and Ti–Zr–Nb–Hf–Ta HEAs. If relaxation effects are properly taken into account, the predicted compositions near the bcc–hcp energetic equilibrium are close to the experimental compositions, for which good strength and ductility due to the TRIP effect are observed. © 2021, The Author(s).

Measurements have shown that the pressure distribution at the front of an EPB shield drilling in saturated granular material is not symmetric with respect to the vertical plane. This was confirmed recently by computational simulations of the material flow within different EPB pressure chambers. The fluid pressure is higher in the part where the cutting wheel is moving upwards, compared to the pressure in the part where the movement is downward. This unbalance may influence both the steering of the TBM and the stability of the tunnel face. The pressure distribution as measured with pore pressure gauges at the cutting wheel are used to calculate the centre of gravity of the muck in an EPB and the measured pressure differences are compared with theoretical calculations. The pore pressure distribution in the mixing chamber along lines parallel to the tunnel axis is discussed. © 2021 ISSMGE, London, UK

The electronic structure in unconventional superconductors holds a key to understanding the momentum-dependent pairing interactions and the resulting superconducting gap function. In superconducting Fe-based chalcogenides, there have been controversial results regarding the importance of the kz dependence of the electronic dispersion, the gap structure, and the pairing mechanisms. Here, we use density functional theory to investigate the underlying structural properties in combination with a sophisticated real-space treatment of magnetic disorder for the prototype system FeSe. Our calculations demonstrate that interlayer and intralayer interactions need to be considered and that charge-driven van der Waals interactions between Se atoms instead of magnetic coupling effects drive the interlayer binding. The methodological advances and physical insights are important for upcoming investigations of the three-dimensional effects, including nontrivial topology, of FeSe1-xTex and FeSe1-xSx systems. © 2021 American Physical Society.

Modeling of cancellous bone has important applications in the detection and treatment of fatigue fractures and diseases like osteoporosis. In this paper, we present a fully coupled multiscale approach considering mechanical, electric and magnetic effects by using the multiscale finite element method and a two-phase material model on the microscale. We show numerical results for both scales, including calculations for a femur bone, comparing a healthy bone to ones affected by different stages of osteoporosis. Here, the magnetic field strength resulting from a small mechanical impact decreases drastically for later stages of the disease, confirming experimental research. © 2021, The Author(s).

We demonstrate by time-resolved resonance fluorescence measurements on a single self-assembled quantum dot an internal photoeffect that emits electrons from the dot by an intraband excitation. We find a linear dependence of the optically generated emission rate on the excitation intensity and use a rate equation model to deduce the involved rates. The emission rate is tunable over several orders of magnitude by adjusting the excitation intensity. Our findings show that a process that is well known in single atom spectroscopy (i.e., photoionization) can also be observed in the solid state. The results also quantify an important, but mostly neglected, mechanism that may fundamentally limit the coherence times in solid-state quantum optical devices. © 2021 American Physical Society.

Upscaling of nanoparticle fabrication by sputtering into an ionic liquid is shown for the example of Cu. Long-time sputtering (24 h) into a large amount (50 mL) of the ionic liquid 1-butyl-3-methylimidazolium bis-(trifluoromethylsulfonyl)imide [Bmim][(Tf)2 N] yields an amount of approximately 1 g Cu nanoparticles (mean spherical diameter (2.6 ± 1.1) nm), stabilized in ionic liquid without agglomerations. Extraction of Cu nanoparticles from the stabilizing ionic liquid was performed with the capping agent hexadecylamine. Extracted particles could be redispersed in other solvents, thus enabling applications of sputtered nanoparticles beyond ionic liquids. © 2021, The Author(s).

We outline the mathematical model of the ultrasonic response of cancellous bone and its time harmonic formulation. In contrast to the Biot model, the fluid is not inviscid. Our fluid is viscous, but does not interact with the solid components. © 2021 Informa UK Limited, trading as Taylor & Francis Group.

In a combined experimental and theoretical study we assess the role of Co incorporation on the OER activity of LaCoxFe1−xO3. Phase pure perovskites were synthesized up to (Formula presented.) in 0.025/0.050 steps. HAADF STEM and EDX analysis points towards FeO2-terminated (001)-facets in LaFeO3, in accordance with the stability diagram obtained from density functional theory calculations with a Hubbard U term (DFT+U). Linear sweep voltammetry conducted in a rotating disk electrode setup shows a reduction of the OER overpotential and a nonmonotonic trend with x, with double layer capacitance measurements indicating an intrinsic nature of activity. This is supported by DFT+U results that show reduced overpotentials for both Fe and Co reaction sites with the latter reaching values of 0.32–0.40 V, ∼0.3 V lower than for Fe. This correlates with a stronger reduction of the binding energy difference of the *O and *OH intermediates towards an optimum value of 1.6 eV for (Formula presented.), the OH deprotonation being the potential limiting step in most cases. Significant variations of the magnetic moments of both surface and subsurface Co and Fe during OER demonstrate that the beneficial effect is a result of a concerted action involving many surrounding ions, which extends the concept of the active site. © 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH

The formation of nanoparticles by sputtering on ionic liquids could occur at the surface or in the volume of the liquid. To clarify which process occurs, Cu was sputtered in inert and oxidative plasma onto two different ionic liquids. 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [Bmim][(Tf)2N] and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [Emim][(Tf)2N] were selected for their low solubility of oxygen and their different surface tensions to differentiate the influence of the ionic liquid characteristics on the formation process and characteristics of nanoparticles. The chemical state of nanoparticles in the ionic liquids, metallic or oxidized, was analyzed by X-ray photoelectron spectroscopy. Transmission electron microscopy was performed to acquire nanoparticle size distributions and shapes. The results indicate that nanoparticle formation occurs within the ionic liquid volume, contradicting the prevailing assumption that nanoparticle formation begins at the ionic liquid surface. Nanoparticle size distributions indicate that a higher viscosity of the ionic liquid results in higher nanoparticle diameters. © 2021 The Authors. Published by American Chemical Society.

It has been shown that a weak shear can induce crystallisation in a disordered, glassy state. In this study, we use molecular dynamics simulations in order to investigate the out-of-equilibrium properties of [BMIM][BF4] confined between metal slabs. In particular, we want to understand the extent to which the shear flow modifies the interfacial properties. In particular, the questions we address here are (i) is the shear able to promote the crystalline phase in [BMIM][BF4]? (ii) Can, as a consequence of shear flow, a solid-like layer develop at the interface with a metallic surface? (iii) What are the tribological properties of nanoconfined [BMIM][BF4]? We find that the system behaves quite differently from the ideal linear Couette flow. Indeed, the portion of fluid closer to the shearing slabs behaves as a disordered, solid-like layer, which, under the investigated conditions extends to a few nanometres. The linear velocity regime is only recovered in the central region of the ionic liquid slab. The formation of such a solid-like glassy rather than crystalline layer is in agreement with recent mechanical impedance measurements performed on nano-confined ionic liquids. © the Owner Societies 2021.

We outline the mathematical model of the ultrasonic response of wet cortical bone and its time-harmonic formulation. We employ an energetic approach based on the Reuss bound of the free energy of a porous material consisting of a piezo-electric solid and a conducting fluid part. Magnetic effects are taken into consideration. Corresponding boundary value problems are stated, and associated theorems are established. A conclusion is included concerning future developments of this formulation. © 2021 John Wiley & Sons, Ltd.

We investigate gate voltage dependence of electrical readout noise in high-speed rf reflectometry using gallium arsenide quantum dots. The fast Fourier transform spectrum from the real time measurement reflects build-in device noise and circuit noise including the resonator and the amplifier. We separate their noise spectral components by model analysis. Detail of gate voltage dependence of the flicker noise is investigated and compared to the charge sensor sensitivity. We point out that the dominant component of the readout noise changes by the measurement integration time. © 2021 The Japan Society of Applied Physics

Argon plasma coagulation is a promising new approach to combat obesity. During the procedure, a large area of the gastric lamina mucosae and the parietal cells that are located in this layer are ablated. This reduces the secretion of the hormone ghreline, which is known to play a major role in inducing appetite. One hypothesis is that this procedure partly suppresses the feeling of hunger which lowers the food-intake and body weight effectively. To rule out side effects, the treatment of other structures of the gastric wall that are much more sensitive to thermal injury, such as the tela submucosa and the lamina muscularis propria, needs to be avoided. The possibility of layer specific tissue differentiation is explored in this work using optical emission spectroscopy on ex vivo human stomach tissue. The optical emission generated during the plasma treatment of each layer is measured with two different spectrometers. The three main layers of the gastric wall can be differentiated by specific emissions lines of electrolytic ions and trace elements. In order to evaluate the diagnostic quality of this method a linear support vector classifier is used to differentiate the three layers against each other on the basis of these emission lines of these elements. This differentiation between 'mucosa' and 'submucosa' results in a sensitivity of up to 82% and specificity of up to 92%. However, a lower sensitivity and specificity is found for a classification between 'submucosa' and 'muscularis' which implies that a classification between 'mucosa' and 'not mucosa' would be a much more suitable classification for a later clinical application. © 2021 The Author(s). Published by IOP Publishing Ltd.

Classical change point analysis aims at (1) detecting abrupt changes in the mean of a possibly nonstationary time series and at (2) identifying regions where the mean exhibits a piecewise constant behavior. In many applications however, it is more reasonable to assume that the mean changes gradually in a smooth way. Those gradual changes may either be nonrelevant (i.e., small), or relevant for a specific problem at hand, and the present paper presents statistical methodology to detect the latter. More precisely, we consider the common nonparametric regression model Xi = μ(i/n) + εi with centered errors and propose a test for the null hypothesis that the maximum absolute deviation of the regression function μ from a functional g(μ) (such as the value μ(0) or the integral 01 μ(t)dt) is smaller than a given threshold on a given interval [x0, x1] ⊆ [0, 1]. A test for this type of hypotheses is developed using an appropriate estimator, say d∞,n, for the maximum deviation d∞ = supt∈[x0,x1] |μ(t) − g(μ)|. We derive the limiting distribution of an appropriately standardized version of d∞,n, where the standardization depends on the Lebesgue measure of the set of extremal points of the function μ(·) − g(μ). A refined procedure based on an estimate of this set is developed and its consistency is proved. The results are illustrated by means of a simulation study and a data example. © Institute of Mathematical Statistics, 2021

A cellular automaton algorithm for curvature-driven coarsening is applied to a cold-rolled interstitial-free steel's microstructure - obtained through electron backscatter diffraction (EBSD). Recrystallization nucleation occurs naturally during the simulation, due to the highly heterogeneous and hence competitive growth among pre-existing (sub) grains. The spatial inhomogeneity of the subgrain growth that takes place derives from the large local variations of subgrain sizes and misorientations that comprise the prior deformed state. The results show that capillary-driven selective growth takes place to the extent that the prior elongated and deformed grains are replaced by equiaxed grains with no interior small-angle boundaries. Additionally, during the simulation certain texture components intensify and others vanish, which indicates that preferential growth occurs in a fashion that relates to the crystal orientations’ topology. The study of the early stages of recrystallization (i.e. nucleation) shows that the pre-existing subgrains that eventually recrystallize, exhibit certain topological characteristics at the prior deformed state. Successful nucleation occurs mostly for pre-existing matrix subgrains abutting shear bands or narrow deformation bands and particularly at regions where the latter intersect. © 2021 The Author(s)

An active learning approach to train machine-learning interatomic potentials (moment tensor potentials) for multicomponent alloys to ab initio data is presented. Employing this approach, the disordered body-centered cubic (bcc) TiZrHfTax system with varying Ta concentration is investigated via molecular dynamics simulations. Our results show a strong interplay between elastic properties and the structural ω phase stability, strongly affecting the mechanical properties. Based on these insights we systematically screen composition space for regimes where elastic constants show little or no temperature dependence (elinvar effect). © 2021 American Physical Society.

In the case of a sudden change in the geology in front of the Tunnel Boring Machine (TBM) during mechanized tunneling processes, non-appropriate investigation and process adaptation may result in non-desirable situations that can induce construction and machine defects. Therefore, subsurface anomalies detection is necessary to trigger alarm to update the process. This paper presents an approach for geological anomaly detection using data produced by the TBM. The data observations are continuously produced at a motion of 10 to 15 s from hundreds of sensors around the TBM. Unsupervised machine learning techniques are applied to analyze the online streaming data. As a result, a model, which is able to learn the system characteristics from normal operational condition and to flag any unanticipated or unexpected behavior, is established. The proposed approach has been tested on the data of the Wehrhahn-Linie metro project in Düsseldorf in Germany. The model can accurately detect the presence of concrete walls in the ground domain with a distance up to around one meter before the TBM approaches the walls. The developed method can thus be used as a monitoring system for ground risks detection to ensure safe and sustainable constructions in mechanized tunneling. © 2021, The Author(s), under exclusive license to Springer Nature Switzerland AG.

In this paper we propose statistical inference tools for the covariance operators of functional time series in the two sample and change point problem. In contrast to most of the literature, the focus of our approach is not testing the null hypothesis of exact equality of the covariance operators. Instead, we propose to formulate the null hypotheses in the form that “the distance between the operators is small”, where we measure deviations by the sup-norm. We provide powerful bootstrap tests for these type of hypotheses, investigate their asymptotic properties and study their finite sample properties by means of a simulation study. © 2021, The Institute of Statistical Mathematics, Tokyo.

The emergence of novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern with increased transmission dynamics has raised questions regarding stability and disinfection of these viruses. We analyzed surface stability and disinfection of the currently circulating SARS-CoV-2 variants B.1.1.7 an