In the realm of materials design, understanding and manipulating the behaviour of dislocations — key drivers of plastic deformation — is a cornerstone. However, while dislocations are well-explored in simple crystalline materials, their structure and mechanisms of motion remain largely enigmatic for complex crystals, such as topologically closed-packed phases. This vast class of materials contains many intermetallics ranging from high-temperature structural materials to functional crystals that can act as superconductors, magnets, magneto-caloric or hydrogen storage materials. In all of these applications, structural integrity and therefore controlled plasticity is essential. This study bridges our current knowledge gap in plasticity of complex crystals by delving into the most prevalent among them, the Laves phase. Utilizing transmission electron microscopy, we unveil previously unreported defect structures in the cubic CaAl2 Laves phase. Complementing these observations, atomistic simulations elucidate the underpinning mechanisms, revealing novel deformation behaviours. We spotlight the role of full dislocations traversing multiple {1 1 n} slip planes, a departure from the conventional confinement to {1 1 1} planes. This multi-plane dislocation activity, including frequent cross-slipping, emerges as a pivotal factor in accommodating plastic deformation. Our findings not only challenge an existing paradigm in intermetallic plasticity but also propose a tangible pathway to understand the ductility of brittle complex alloys as a stride forward in phase selection and materials engineering.

Gold nanostars (AuNS) exhibit morphology-dependent optical properties that make them attractive for photothermal and photoacoustic applications; however, their limited thermal stability remains a critical challenge. In this work, we investigate the thermal behavior of AuNS synthesized using Good's buffers, specifically 4-(2-hydroxyethyl)-1-piperazinepropanesulfonic acid (EPPS) and 3-(N-morpholino)propanesulfonic acid (MOPS), by combining ex situ and in situ characterization techniques. Ex situ heating revealed collective deformation at elevated temperatures, while in situ heating enabled the real-time observation of individual particle reshaping. AuNS-EPPS displayed reshaping rates more than twice those of AuNS-MOPS, caused by both the thermal treatment and electron beam effects. Direct visualization revealed gold migration from branches to the core, a mechanism previously hypothesized. Despite pronounced morphological changes, the crystal structure remained intact. These results clarify the deformation mechanisms of AuNS and inform the design of more thermally robust nanostructures for (photo)thermal applications.

Abstract Arene hydrogenation constitutes a direct and strategically valuable entry to three-dimensional molecular architectures from abundant aromatic feedstocks. Despite its conceptual simplicity, the intrinsic stability of aromatic systems typically necessitates forcing conditions, i.e., elevated hydrogen pressures and temperatures, which in turn demand specialized infrastructure and constrain broader adoption in synthetic endeavors. Here, we report a simple strategy for generating a highly active, heterogeneous catalyst in situ that enables the efficient hydrogenation of benzene and pyridine derivatives under ambient conditions. Central to this approach is the combination of bench-stable [Ru(NH3)5(OTf)](OTf)2 and Pd/C pre-catalysts, which form a catalytically competent and recyclable nanocrystalline Ru-Pd solid solution under the reaction conditions. Comprehensive characterization utilizing microscopic and spectroscopic material analysis techniques is reported, revealing detailed information about the composition of the active catalyst. Further mechanistic investigations and comparative studies with other ruthenium sources underscore the distinctive role of [Ru(NH3)5(OTf)](OTf)2 in the catalyst formation process, demonstrating stepwise reductive decomposition of pentaammineruthenium. Collectively, these findings outline a practical approach to arene hydrogenation under ambient conditions while providing important mechanistic insight into the genesis of in situ-formed heterogeneous hydrogenation catalysts.

Hydrogen (H) is essential for the high performance of advanced crystalline silicon (c-Si) solar cells. Recently, H-related ultraviolet-induced degradation (UVID), which can compromise module stability, has attracted increasing attention from the photovoltaic (PV) industry, yet its underlying mechanisms remain incompletely understood. Here, the severity of UVID in silicon heterojunction (SHJ) solar cells is shown to depend strongly on the illuminated-side passivating-contact design, with transparent passivating contacts (TPCs) exhibiting markedly larger losses in open-circuit voltage (V OC), short-circuit current (J SC), and fill factor (FF) than conventional hydrogenated amorphous silicon (a-Si:H)-based SHJ contacts. Combined material characterizations and device analysis support a picture in which the high transparency of TPC shifts UV energy deposition toward the c-Si near-interface region, where UV-driven Si & horbar;H bond dissociation increases interfacial recombination and degrades chemical passivation. In parallel, UV exposure induces a pronounced resistivity increase in the hydrogenated nanocrystalline silicon carbide (nc-SiC:H) contact stack, consistent with local microstructural/electronic disorder and the possible involvement of enhanced sub-bandgap absorption, thereby raising series resistance (R s) and limiting carrier collection. Collectively, these findings link contact optical transparency, H-related bond dynamics, and nc-SiC:H transport degradation to the distinct UVID signatures of SHJ architectures.

Zeolite flexibility triggered by ion-exchange tuning pore geometry impacts the responsive interactions with guest species in selective adsorption and industrial catalysis. However, direct observation of their local atomic structure deformation and subsequent fundamental flexibility correlation between ions and atomic microenvironment remains elusive. Here, we report atomic-resolution imaging of the microscopic ring flexibility in ion-exchanged MFI zeolites, revealing how ion-induced electric field alterations drive the framework distortions. Specifically, extra-framework Ba2+ ions confined within the 10-membered rings (10-MRs) trigger a 0.5 Å channel expansion, which exceeds the 0.2 Å expansion induced by Na+ ions while maintaining the framework's macroscopic rigidity. Using differential phase contrast imaging, we visualize the local coupling of the internal electric field between confined ions and the MFI framework. The combination of our theoretical analysis, which is based on the structure and the charge distribution, demonstrates that the electric field generated by the Ba2+ results in an 8° deformation in the nearby T-O-T bond angles, thereby distorting the 10-MR. The ion-exchange-driven 10-MR flexibility was further experimentally verified by the adsorption and separation of CO2, as this molecular size matches the expanded rings. This work resolves a long-term unsettled issue on the ion-exchange effect of pore size deformation in zeolites, offering insights into electric field-driven framework dynamics and introducing the intrinsic behavior of ions confined in zeolites.

Controlled breakdown has emerged as an effective method for fabricating solid-state nanopores in thin suspended dielectric membranes for various biomolecular sensing applications. On an unpatterned membrane, the site of nanopore formation by controlled breakdown is random. Nanopore formation on a specific site on the membrane has previously been realized using local thinning of the membrane by lithographic processes or laser-assisted photothermal etching under immersion in an aqueous salt solution. However, these approaches require elaborate and expensive cleanroom-based lithography processes or involve intricate procedures using custom-made equipment. Here, we present a rapid cleanroom-free approach using single pulse femtosecond laser exposures of 50 nm thick silicon nitride membranes in air to localize the site of nanopore formation by subsequent controlled breakdown to an area less than 500 nm in diameter on the membrane. The precise positioning of the nanopores on the membrane could be produced both using laser exposure powers which caused significant thinning of the silicon nitride membrane (up to 60% of the original thickness locally), as well as at laser powers which caused no visible modification of the membrane at all. We show that nanopores made using our approach can work as single-molecule sensors by performing dsDNA translocation experiments. Due to the applicability of femtosecond laser processing to a wide range of membrane materials, we expect our approach to simplify the fabrication of localized nanopores by controlled breakdown in a variety of thin film material stacks, thereby enabling more sophisticated nanopore sensors.

Layered 2D semiconductors have shown enhanced ion migration capabilities along their van der Waals (vdW) gaps and on their surfaces. This effect can be employed for resistive switching (RS) in devices for emerging memories, selectors, and neuromorphic computing. To date, all lateral molybdenum disulfide (MoS2)-based volatile RS devices with silver (Ag) ion migration have been demonstrated using exfoliated, single-crystal MoS2 flakes requiring a forming step to enable RS. Herein, present volatile RS with multilayer MoS2 grown by metal-organic chemical vapor deposition (MOCVD) with repeatable forming-free operation is presented. The devices show highly reproducible volatile RS with low operating voltages of ≈2 V and fast-switching times down to 130 ns considering their micrometer-scale dimensions. The switching mechanism is investigated based on Ag ion surface migration through transmission electron microscopy, electronic transport modeling, and density functional theory. Finally, a physics-based compact model is developed and the implementation of the volatile memristors as artificial neurons in neuromorphic systems is exploredd.

The early failures in rolling bearings made of 100Cr6 (SAE 52100) steel have been observed in various industrial applications, which are associated with high maintenance and downtime costs. The damage is usually characterized in the form of axial cracks or volumetric breakouts on the running surface of the bearing components. Metallographic examinations revealed areas below the raceway that do not react to etching with alcoholic nitric acid and therefore appear visually white. These areas are referred to as "white etching areas" or "WEA" for short. Cracks that lead to bearing damage along these WEA are accordingly referred to as "white etching cracks" (WEC). This subsurface damage initiated from non-metallic inclusions has been identified as the dominant initiation mechanism in the formation of butterflies. This study presents a comprehensive analysis of the intricate mechanisms governing the formation of butterflies in SAE 52100 bearing steel, utilizing multiscale finite element modeling and detailed microstructural investigations. The research offers valuable insights into the role of non-metallic inclusions, such as MnS, in butterfly formation, emphasizing that MnS influences butterfly formation through its size, orientation, and interactions with the inclusion-matrix interface. Moreover, it classifies butterflies into propagating and non-propagating types based on their interactions with the inclusion-matrix interface, revealing that non-propagating butterflies can coexist within the steel without causing bearing failure under specific conditions. In contrast, propagating butterflies, which lead to WEA formation, are unequivocally linked with bearing failure.

Lithium (Li) plating on graphite is a significant degradation mechanism in Li-ion batteries. While numerous experimental techniques have been used to study Li plating in laboratory cells, investigations of commercial high-energy cells often rely on electrochemical methods. Here we present and classify various methods for detecting Li plating on a commercial A123 pouch cell. In a round robin study across multiple battery research laboratories, Li-plated graphitic electrode material was analyzed using electrochemical, microscopic, and spectroscopic methods capable of detecting metallic Li deposits. After cell opening, their overall distribution on the anode surface was examined using a flatbed scanner to ensure comparability of the samples. Optical and electron microscopy provided detailed surface and, in combination with a focused ion beam, subsurface structure and morphology. Spectroscopic methods confirmed the presence and onset of plated Li with varying sensitivity. Moreover, spectroscopic and imaging techniques were combined correlatively where possible. Availability and measurement duration of each technique was compared. Optical methods are fast and easy to use; thus, they are recommended for most samples, with spectroscopic confirmation reserved for reference samples. This multimodal study demonstrates a range of methods that can be used alone or in combination to qualitatively or quantitatively detect Li-plating.

Advanced microscopy techniques have been employed to resolve the microstructure of transparent conductive oxide (TCO) contacts in silicon heterojunction solar cells. Aluminum-doped zinc oxide (AZO) stands out as a TCO material because of its low cost, abundance, and good optoelectrical properties. The polycrystalline AZO thin films have yielded promising results in solar cell design. However, understanding the nanostructure of AZO thinfilm materials is vital for enhancing the cell performance by focusing on the formation of large grains and their influence on the charge-carrier mobility of the film. Therefore, we employed high-resolution transmission electron microscopy (HRTEM) and precession-assisted four-dimensional scanning transmission electron microscopy (4D-STEM) with an automated crystal orientation analysis. These techniques can be used to determine the grain sizes of AZO films sputtered on hydrogenated amorphous silicon (a-Si:H) and hydrogenated nanocrystalline silicon (nc-Si:H) layers. Columnar grains in the AZO/a-Si:H film are evident in the grain mapping with diameters greater than 10 nm, whereas in the AZO/nc-Si:H film, the grains begin at diameters less than 10 nm, showing smaller grains near the substrate than at the top of the film. Additionally, the double-layer with indium-thin doped oxide (ITO)/AZO stack started with grain diameters varying from 5 to 90 nm. They exhibit significantly larger and irregular boundaries. Therefore, microstructural characterization showed that larger columnar grains might lead to higher mobility in the AZO layer. This finding indicates that the impact of the ITO seed layer on AZO significantly enhances grain size, improves charge carrier mobility, and overall improves the power conversion efficiency (eta) to be 23.6% comparable to those of AZO on a-Si:H and nc-Si:H.

Mg-Al-Ca alloys, composed of a soft Mg matrix and hard and brittle Laves phases, are suitable for applications at elevated temperatures. Unfortunately, the reinforcing skeleton is brittle and leads to premature failure due to cracking and decohesion from the matrix. In the present study, we achieve a largely self-similar reduction in microstructural length scale by increasing the cooling rate of an as-cast Mg-4.7Al-2.9Ca alloy. We observe this refinement mostly in terms of intermetallic strut spacing and width reduction, while the present intermetallic phase is determined to be C36. Upon refinement, the microstructures exhibit increasing compressive ultimate stress and yield stress from 96 +/- 4 MPa and 223 +/- 4 MPa at the coarsest microstructure to 117 +/- 2 MPa and 244 +/- 2 MPa at the finest microstructure. In addition, microstructure refinement leads to a change in governing damage mechanisms, which we quantified by means of both automated and manual analysis of large area scanning electron micrographs. Brittle cracking of the intermetallic skeleton dominates by a factor of 10 over the occurrence of decohesion at the Mg/intermetallic interface and both are reduced with decreasing microstructural length scale. This is accompanied by an increase of plastic slip transmission in the Laves phase from 50 to 250 slip events per 0.2 mm2, which goes alongside a reduction of the brittle phase from 290 to 33 per 0.2 mm2. We therefore propose that refinement of the microstructure may be used as an additional design parameter to manipulate the deformability of skeleton-reinforced Mg-Al-Ca alloys.

In this work, we investigate for the first time the resistive switching (RS) behavior in a bilayer stack of SiOx and vertically aligned MoS2 (VAMoS(2)). We demonstrate threshold switching by forming silver (Ag) conductive filaments (CFs) in an amorphous SiOx layer combined with VAMoS(2) obtained through molybdenum (Mo) sulfurization. The SiOx/VAMoS(2) devices exhibit repeatable RS with faster switching times and higher hold voltages compared to SiOx devices without VAMoS(2). The RS enhancement through VAMoS(2) layers shows promise for compact vertical device architectures for emerging memories and neuromorphic computing applications.

The present investigation is aimed at exploring the microstructural stability of the ultra-fine grain (UFG) non-heat treatable Al-alloy AA5024 (Al-Mg-Sc-Zr), containing thermally stable and coherent Al3(Scx, Zr1-x) precipitates. The alloy has been purposefully given severe rolling reductions of 90%, 95% and 98% in uni-directional (UDR) and cross-directional (CR) rolling and was subsequently annealed at 350 degrees C starting from 1 to 100 h to assess the role of the defect-populated microstructure and crystallographic texture on the stability of this alloy. An interesting observation has been made that recovery is prevalent, with very slow kinetics, which has been attributed to the stability of the precipitates during annealing. The crystallographic texture is Cu type (a typical high SFE alloy) that remains identical for annealed and deformed states for both UDR and CR sheets. However, a decrease in orientation distribution function (ODF) strength has been observed at 98% of UDR, whereas this decrease comes at 95% in the CR case. These findings indicate the possibility for intermittent dynamic recovery just before these reduction levels and a slight increase in the fraction of recrystallised grains. A comparison of texture obtained from the visco-plastic self-consistent crystal plasticity (VPSC) simulation with the experimental texture clearly showed the contribution of recrystallisation in overall texture that caused a drop in texture intensity.

Carbon (C) residuals at specific microstructural features are detected in a correlative way in the metal injection molded (MIM) Mg-0.6Ca material. Micro Raman mappings revealed Raman modes at nearly 1370 cm-1 and 1560 cm-1 that can be ascribed to elemental C, and C-C stretching at 1865 cm-1. The MIM Mg feedstock contained PPcoPE based backbone polymer that dissociates during thermal debinding (380 °C - 550 °C) prior to argon atmosphere sintering (644 °C). The decomposition of MgC2 and Mg2C3 carbides at 450 °C and 600 °C respectively, releases free C that can be trapped in the Mg matrix. The presence of calcium (Ca) leads to the formation of CaC2 phases during sintering that retains in the microstructure. Energy dispersive x-ray (EDX) analysis revealed the SiO2 impurities adjacent to the C, Ca and oxide detections. These findings can provide insights about the cell adhesion characteristics of PM Mg materials.

Topological polar structures, in analogy to spin vortices and skyrmions, have received tremendous attention for their fascinating prospects in future device applications. However, in the widely studied ferroelectric-based superlattices, the epitaxial heterointerfaces, yielding desired strain, depolarization, and gradient energies, greatly confine the mobility of the topological solitons. Here, we report observation of polar vortex-antivortex pairs near junctions of antiphase boundaries in antiferroelectric PbZrO3 thin films by using atomic-resolution scanning transmission electron microscopy. Our temporal-resolved lattice analysis reveals that the local strain gradient caused by an incommensurate modulation constructs the smallest topological units reported to date. Our phase-field simulations unveil that the Pb-O vacancy-induced random electric fields account for their three-dimensional formation, and the stimulus of electron-beam irradiation can drive their dynamic migration. The findings offer a new approach to comprehend fundamental physics about antiferroelectricity and the design of functional devices based on topological structures in antiferroelectric thin films.

Developing electronic devices capable of emulating biological functions is essential for advancing brain-inspired computation paradigms such as neuromorphic computing. In recent years, two-dimensional materials have emerged as promising candidates for neuromorphic electronic devices. This work addresses the coexistence of volatile and nonvolatile resistive switching in lateral memristors based on molybdenum disulfide with silver as the active electrode. The fabricated devices exhibited switching voltages of ∼0.16 V and ∼0.52 V for volatile and nonvolatile operation, respectively, under direct-current measurements. They also displayed the essential synaptic functions of paired-pulse facilitation and short- and long-term plasticity under pulse stimulation. The operation mechanism was investigated by in situ transmission electron microscopy, which showed lateral migration of silver ions along the molybdenum disulfide between electrodes. Based on the experimental data, a macroscopic semiclassical electron transport model was used to reproduce the current-voltage characteristics and support the proposed underlying switching mechanisms.

Achieving control over properties such as density and lateral distribution of catalytic nanoparticles under operation conditions is a major challenge for the development of active and durable catalysts, where nanoparticle coarsening is often the cause of performance degradation. While metal exsolution catalysts are regarded to be robust against this degradation mode, coarsening and increased concentrations of exsolved metal nanoparticles have been detected near extended defects. The present study examines the role of dislocations in metal exsolution reactions and explores the potential of dislocation-engineering for the synthesis of dislocation-associated nanoparticles. An atomic-level correlation between bulk dislocations and surface nanoparticle locations is demonstrated through a novel approach for engineering epitaxial thin films with confined regions of increased dislocation densities in combination with in situ scanning transmission electron microscopy. While nanoparticle exsolution proceeds across the entire sample, two primary reasons for the frequent nucleation of dislocation-associated nanoparticles are identified: the accumulation of exsolution-active acceptors along dislocations and lattice distortions that are likely to lower the energy barrier for nanoparticle nucleation. This work establishes a proof of concept for using engineered dislocations in exsolution catalysts to synthesize nanoparticles with modified nanoparticle-support properties relevant for the thermal stability and the lateral distribution of exsolved nanoparticles.

Exsolution-active catalysts allow for the formation of highly active metallic nanoparticles, yet recent work has shown that their long-term thermal stability remains a challenge. In this work, the dynamics of exsolved Ni nanoparticles are probed in-situ with atomically resolved secondary electron imaging with environmental scanning transmission electron microscopy. Pre-characterization shows embedded NiOx nanostructures within the parent oxide. Subsequent in-situ exsolution demonstrates that two populations of exsolved particles form with distinct metal-support interactions and coarsening behaviors. Nanoparticles which precipitate above embedded nanostructures are observed to be more stable, and are prevented from migrating on the surface of the support. Nanoparticle migration which fits random-walk kinetics is observed, and particle behavior is shown to be analogous to a classical wetting model. Additionally, DFT calculations indicate that particle motion is facilitated by the support oxide. Ostwald ripening processes are visualized simultaneously to migration, including particle redissolution and particle ripening.

In this study, a correlative approach using Raman spectroscopy and scanning electron microscopy (SEM) is introduced to meet the challenges of identifying impurities, especially carbon-related compounds in metal injection-molded (MIM) Mg-0.6Ca specimens designed for biomedical applications. This study addresses, for the first time, the issue of carbon residuals in the binder-based powder metallurgy (PM) processing of Mg-0.6Ca materials. A deeper understanding of the material microstructure is important to assess the microstructure homogeneity at submicron levels as this later affects material degradation and biocompatibility behavior. Both spectroscopic and microscopic techniques used in this study respond to the concerns of secondary phase distributions and their possible stoichiometry. Our micro-Raman measurements performed over a large area reveal Raman modes at ~1370 cm−1 and ~1560 cm−1, which are ascribed to the elemental carbon, and at ~1865 cm−1, related to C≡C stretching modes. Our study found that these carbonaceous residuals/contaminations in the material microstructure originated from the polymeric binder components used in the MIM fabrication route, which then react with the base material components, including impurities, at elevated thermal debinding and sintering temperatures. Additionally, using evidence from the literature on thermal carbon cracking, the presence of both free carbon and calcium carbide phases is inferred in the sintered Mg-0.6Ca material in addition to the Mg2Ca, oxide, and silicate phases. This first-of-its-kind correlative characterization approach for PM-processed Mg biomaterials is fast, non-destructive, and provides deeper knowledge on the formed residual carbonaceous phases. This is crucial in Mg alloy development strategies to ensure reproducible in vitro degradation and cell adhesion characteristics for the next generation of biocompatible magnesium materials.

Heterogeneous catalysts based on Pt alloys are widely employed in propane dehydrogenation (PDH), yet challenges such as coking and poor nanoparticle stability hinder their broader industrial deployment. Strategies to enhance dispersion and tune the catalyst surface properties remain at the forefront of catalyst design. Here, we demonstrate a new class of PtSn 2 -based catalysts promoted by rare-earth elements for efficient and stable PDH. Among the rare-earth screened, europium (Eu) delivers the most pronounced promotional effect, enabling the formation of ∼1.3 nm PtSn 2 nanoparticles with improved thermal stability. Through its redox flexibility (Eu 3+ /Eu 2+ ), Eu modulates the electronic environment of Pt, tunes surface acidity, and suppresses coke accumulation by directing carbon species away from active sites and onto the support. This work shows that rare-earth elements can serve as multifunctional promoters in alloy catalysts, influencing both structural dispersion and catalytic surface chemistry. The optimized catalyst (0.5% Pt-3% Sn-2% Eu on γ-Al 2 O 3 ) achieves a 40.6% propylene yield at 575 °C and a low deactivation rate (0.047 h −1 ), under conditions relevant to industrial practice. Our findings offer a new strategy for designing high-performance diluted alloy catalysts through rare-earth promotion, applicable to other dehydrogenation and hydrocarbon upgrading reactions where coke suppression and acid–base balance are critical.