Twin Structure Research Articles

Electrodeposition of Cu nanowires with ultrahigh-density twin boundaries: an electrochemical perspective on nanotwinning.

Many spectacular nanotwinned Cu (nt-Cu) properties depend on the spacing of adjacent twin boundaries (TBs) inside crystal grains. The average TB spacing is typically 10-100 nm in electrodeposited nt-Cu films. This study employed template-assisted electrodeposition to grow nt-Cu nanowires with high-density TBs (average TB spacing <5 nm). The effects of Cu seed annealing and template pore size on TB spacing were systematically investigated through microstructural characterization and electrochemical analysis. A model based on the stress accumulation level and electrochemical parameters was proposed to assess the twinning criteria during the electrodeposition of nt-Cu nanowires. This research provides mechanistic insights into the nanotwinning process and highlights the potential for the control of twin structures in nanomaterials.

A five‐fold twin structure copper for enhanced electrocatalytic nitrogen reduction to sustainable ammonia

AbstractUtilizing N₂ from the air and water for the electrocatalytic nitrogen reduction reaction shows promise for NH₃ synthesis under mild conditions. However, the chemical stability of N₂ and the thermodynamic limitations of NH₃ synthesis hinder its effectiveness. Herein, we integrated a specially designed Cu nanowire catalyst with a five‐fold twin structure (T‐CuNW) into an electrocatalytic system, combining electrocatalytic nitrogen reduction with nonthermal plasma‐assisted N₂ activation. This work achieved an NH₃ yield of 45 mg·mgcat.−1·h−1 and a Faradaic efficiency of over 95% at −0.5 V versus RHE after a 90‐h stability test. In situ characterization revealed that the T‐CuNW's twin structure plays a crucial role for the generation of a large quantity of Hads, essential for the hydrogenation of nitrate intermediates, particularly nitrite (NO₂−). This enhanced hydrogenation process significantly contributes to the high performance of the ammonia synthesis system.

Direct simulation and machine learning structure identification unravel soft martensitic transformation and twinning dynamics

Phase transition between ordered phases has garnered attention from the viewpoint of materials science as well as statistical physics. One interesting example is martensitic transformation and the resulting formation of twin structures, in which atoms or molecules that form one crystalline phase move in a concerted and diffusionless manner toward another crystalline phase. Recently martensitic transformation has been observed experimentally also in various soft materials. However, the complex internal structures involving many molecules have eluded direct investigation of the dynamical processes of martensitic transformation. Here, we carry out a direct simulation of mesoscale structural transition of a liquid crystalline blue phase (BP) of cubic symmetry, known as BP II. The dynamics is simulated by a Langevin-type equation for the orientational order parameter with thermal fluctuations. We demonstrate that machine-learning-aided analysis of local structures successfully unravels the transformation process from a perfect lattice of BP II to a twinned lattice of another BP (BP I). The nucleation of BP I is initiated by the breakup of junctions of line defects (disclinations), followed by the deformation of disclination network. We further show that twinned BP I is reversibly transformed to a perfect lattice of BP II by temperature variation. Order-parameter-based simulations with machine-learning-aided local structure identification provide valuable insights into not only the martensitic transformation of soft materials but also a wider class of complex structural transitions between ordered phases.

Deformation pseudo-twinning of the L21-ordered intermetallic superlattice

Ordered intermetallic materials are promising candidates for applications in extreme environments due to the strong localized bonding schemes that stabilize the structures against degradation. Here, we investigate the propensity for deformation twinning modes in the L21-ordered MnCu2Al intermetallic by inducing a state of severe plastic deformation. Post-mortem microstructural analysis reveals the presence of meso-scale deformation twins accompanied by a high degree of nano-scale crystalline heterogeneity. The orientation relationship between the parent and twin structures is consistent with activation of the 〈111〉{112} deformation twinning mode. Ab initio generalized stacking fault energy curve calculations corresponding to 〈111〉{112} twinning shear suggest that the magnitude of the twinning partial is 14〈111〉{112} and results in the local formation of a metastable orthorhombic phase within the pseudo-twin. This work highlights the discrepancy between the deformation modes of ordered/disordered structures and promotes an increased awareness for the role that long-range chemical order plays in determining deformation modes.

High Efficiency Electroplating (220)-Orientation Nano-Twinned Copper in Methanesulfonic Acid System and Mechanism Analysis

Nano-twinned copper, distinguished by intricately arranged twin boundaries within each grain, manifests superior mechanical properties compared to commercial copper foil. The cohesive twin structure effectively impedes dislocation motion through intricate interactions between twin boundaries and slip bands. Consequently, copper endowed with a twinned structure achieves an ultrahigh tensile strength of approximately 1 GPa, surpassing the performance of coarse-grained polycrystalline copper, which attains only around 200 MPa under equivalent testing conditions. Furthermore, the resistivity of coherent twin boundaries is approximately half that of stacking faults and grain boundaries. This characteristic allows twinned copper to attain heightened tensile strength without significant compromises in conductivity. In the context of resistance to electromigration, the twinned structure significantly hampers copper's atomic diffusion by an order of magnitude at the triple points where twin and grain boundaries intersect, compared to commercial copper. Moreover, in certain instances, nano-twinned copper demonstrates exceptional thermal stability, maintaining elevated hardness levels even subsequent to annealing at 800 °C, in contrast to nanocrystalline copper. In a distinct scenario, annealing at 250 °C for a duration of 3 hours results in only a marginal reduction in tensile strength, stabilizing at approximately 700 MPa.Given the exemplary performance demonstrated by nano-twinned structures, the imperative is to devise efficient methodologies for the production of high-density nano-twinned copper films. High-speed electroplating emerges as a viable approach to achieve this objective, attributed to its one-step process and facile control.Mainly because the high current density induces the higher copper nucleation rate, making interfacial energy larger, so that copper films would easier to proceed twin formation reaction to lower the residual stress. Numerous scholarly works underscore the application of high-speed electroplating in producing nano-twinned copper films, particularly through the pulse electrodeposition mode. This mode, characterized by a clear nucleation mechanism and well-defined performance metrics, facilitates the systematic creation of nano-twinned structures. However, the incorporation of a pulse-off period resulted in a reduction of the average current density, which was suboptimal from an efficiency standpoint. Consequently, specific scholarly works explore the electroplating of a twin-crystal structure through DC electroplating, aiming for enhanced efficiency with higher average current density. Presently, the literature reports instances of achieving elevated current densities, reaching up to 40 ASD, to produce nano-twinned copper with a (111) orientation and an average twin spacing of approximately 100 nm. Nevertheless, the solubility of cupric ions serves as a limiting factor for the overall electroplating reaction rate efficiency. Consequently, an inherent upper limit to efficiency exists within the copper sulfate system, posing a challenging constraint to ameliorate through adjustments to temperature or additives.However, existing literature indicates that the cupric ions' solubility in copper sulfate is 1.35 M, while copper methanesulfonate demonstrates an impressive solubility of up to 2 M, as confirmed through vacuum filtration. The heightened ion solubility provides the opportunity to increase current density without inducing deleterious powdery deposition issues, thereby maintaining a uniformly conductive surface. Also, the higher current density would conduct better twin formation condition. Thus, the metal methanesulfonate solution, constituting an organic acid system designed to enhance the solubility of metal ions, involves the substitution of metal sulfate with metal methanesulfonate and the replacement of sulfuric acid with methanesulfonic acid, can be considered as a feasible optimization for efficiency issue and twin formation.In the copper sulfonate system, the induction of a nano-twinned structure involves adding organic additives to form an ionic complex with Cu+ in remediation and chloride ions, subsequently altering the deposition route and nucleating copper crystals through a stress relaxation process. Conversely, in the copper methanesulfonate system, chloride ions exhibit an antagonistic effect with organic additives. Moreover, the use of organic additives is associated with potential challenges related to aging, chain scission and cracking issues, potentially transforming the system into a batch manufacturing paradigm. Therefore, investigating the possibility of directly improving the electrochemical mechanism on the negative surface through chloride ions in this organic system to plate nano-twin crystals is a question worth exploring in order to create a sustainable electroplating process for commercial nano-twinned copper manufacture.Here presents a novel approach to the production of (220) orientation nano-twinned copper films, achieved through the incorporation of chloride ions as additives in a high-concentration methanesulfonate copper solution. The primary objective is to leverage chloride ions for the induction of numerous twin boundaries on the copper surface, enabling meticulous control of the average twin spacing at the nanoscale.The investigation herein provides a comprehensive analysis of the nuanced role played by chloride ion distribution in the formation of nano-twinned copper. Figure 1

(110)-Surface Strained-Channel MOSFETs

Improvement of semiconductor device performances have been brought about by innovations in device structures such as SOI, FinFET and gate-all around FET. The FinFET devices saw a remarkable success owing to their high hole mobility. FinFET devices attain this preferable feature by having the (110)-surface channel. Recently, considerable progress has been made in the nanosheet transistor technology. Owing to the gate-all-around structure and the added dimension, the nanosheet transistor technology has an enormous potential for realization of the electronic devices with a significantly high performance. An issue for the nanosheet transistor is the degradation of the hole mobility. This problem stems from the following factors. First, currently developed nanosheet transistors are characterized as (100)-channel devices which have inferior character regarding the hole mobility. Secondly, for fabrication of nanosheet transistors, crystal growth of multiply stacked Si/SiGe layers is an essential process, which involves deterioration of the crystalline quality. The degradation of the crystalline quality is severer in the case of crystal growths on the (110)-surface than those on the (100)-surface. Therefore, the use of the (110)-wafer is challenging and methods to grow Si/SiGe multilayers on (110)-wafers with high quality is to be developed. The authors have been involved in the crystal growth and characterizations of Si/SiGe heterostructures on Si(110) wafers [1-4]. In these studies, a significant enhancement of the hole mobility in the strained Si layer was demonstrated. The results indicate the effect of the lattice strain on the energy band structure can overcome the adverse effects of the crystalline defects. In addition, characteristic features of the crystalline defects generated in the (110)-oriented heterostructures have been revealed. Along with the knowledge on the defect generation and the formation process of the surface morphology, the effect of strain is also a focus of this talk. We discuss first the effect of strain on the valence band structure of Si. It is shown that the effect of strain in reducing the hole cyclotron effective mass is more significant when the surface is (110) compared to the case where the surface is (100). Interestingly, the strain dependences of the hole cyclotron effective mass differ in these two cases. The computational investigation indicates that the lattice strain combined with the (110)-oriented surface is an effective method to increase the hole mobility. Next, a formation mechanism of the crystalline defects in SiGe grown on the (110) wafer is discussed. The TEM observations clearly show that the dominant crystalline defect induced by strain is a twin structure having the {111} twin boundary. The reason for the twin generation is understood in the framework of a dislocation theory. The shear stress acting on a (111) plane drives the atomic layer to form a stacking fault and/or a twin structure. The strength of the shear stress is higher in the case of the (110)-oriented SiGe film compared to the case of the (100) counterpart, which explains the small critical layer thickness of the SiGe on a Si(110) wafer. Finally, the formation process of the surface morphology during the growths of SiGe on Si(110) wafers is discussed. Even at the initial stages of the SiGe, difficulty in obtaining a flat surface is recognized [4]. Based on currently obtained experimental results, we discuss the effect of a surface inclination on the surface morphology.[1] K. Arimoto et al., Jpn. J. Appl. Phys. 59, SGGK06 (2020).[2] D. Namiuchi et al., Materials Science in Semiconductor Processing 113, 105052 (2020).[3] K. Arimoto et al., ECS Transactions 98 (5), 277 (2020).[4] S. Saito et al., Materials Science in Semiconductor Processing 113, 105042 (2020).

Additives for the Formation of Cu Twin Structure by Electrodeposition

Transistor scaling has faced limitations due to the inherent physical properties of semiconductors and challenges in fabrication processes. In light of this, the emergence of 3D packaging for semiconductors offers a promising avenue for achieving continual enhancement in the performance of electronic devices. The packaging technology facilitates the efficient arrangement of chips in both 2D and 3D configurations, enabling effective connections among multiple chips via metal interconnections. To achieve further performance improvements, there has been continuous emphasis on interconnection scaling in semiconductor packaging, driving extensive research into technologies capable of achieving smaller interconnection pitches. Hybrid bonding stands out as one of the next-generation technologies for stacking chips with much smaller pitches, relying on direct bonding between Cu pads and dielectrics. However, a significant challenge in direct Cu bonding is the high bonding temperature, which must be addressed through the development of better interconnection materials and bonding technologies. Recent studies have shown that the temperature for Cu-Cu direct bonding can be reduced by adopting highly (111)-oriented Cu or nano-twinned Cu. Nano-twinned Cu, in particular, ensures the formation of a (111)-oriented surface, leading to relatively rapid surface diffusion of Cu. Moreover, it has been reported that the strain energy released during the annealing of nano-twinned Cu can promote Cu-Cu direct bonding. Given the confirmed advantages of nano-twinned Cu in hybrid bonding, this study investigates the types of additives that induce nanotwin formation during Cu electrodeposition. We examine the effects of electrodeposition conditions, types, and concentrations of additives on Cu microstructures. By combining analytical results, we aim to suggest the optimal molecular structure and electrodeposition conditions to achieve twin structures effectively.

Improving the strength-ductility synergy and surface properties of NiFe29Cr21CuMo-based alloy laser welding subsequent deep cryogenic treatment and vacuum plasma WC20Cr3C2NiX coating

The novel research work focused on enhancing the mechanical properties and joining strengths of laser welding (LW) procedures on a sample of NiFe29Cr21CuMo-based alloy. Moreover, the surface properties and microstructure were improved by vacuum plasma spraying the WC20Cr3C2NiX coating (vacuum plasma spray coating (VPSC)) and deep cryogenic treatment (DCT). Based on temperature, two DCTs (DCT-(L)–(H)) were carried out: −180°C and 250°C on twin boundaries structure, NiFeCr phase, CrMo structure, and µ-austenite lattice structure was observed of the inner surface layer. The plasma spray WC20Cr3C2NiX coating technology was used to improve the outer layer and residual stress. The DCT and VPSC process investigations using electron backscatter diffraction demonstrated unambiguously that the inner and outer surface layer of the µ′(Ni–Fe2Cr3), Fe–CrC, β′-Fe2Cr4, CrCoMn structure, and twin boundary's structure were present. Heat inputs on plasma spray coating samples were more affected in the inner and outer surface layer to the formation of strong crystallographic NiCr phase, β′-Ni/Cr, and CrC/Mn structure. Moreover, the CrMn structure, Fe(AsO4) phase, and NiFeBCr phase abruptly increased the hardness value of DCT-(L) samples of the outer surface. The DCT-(H)–VPSC method yielded a hardness value of 18% highly present. Peak profile investigation revealed the various ranges: 0 to −600 µm for LW + DCT-(H) coating samples, 225–350 µm for LW + DCT-(L) coating samples, and −100 to −200 µm for LW + DCT-(L)–(H) coating. Electrochemical analysis employing potential dynamic polarization was used to assess each sample's corrosion resistance. The corrosion resistance and surface characteristics of DCT and VPSC were superior.

Balancing the Charge Separation and Surface Reaction Dynamics in Twin-Interface Photocatalysts for Solar-to-Hydrogen Production.

Solar-driven photocatalytic green hydrogen (H2) evolution reaction presents a promising route toward solar-to-chemical fuel conversion. However, its efficiency has been hindered by the desynchronization of fast photogenerated charge carriers and slow surface reaction kinetics. This work introduces a paradigm shift in photocatalyst design by focusing on the synchronization of charge transport and surface reactions through the use of twin structures as a unique platform. With CdS twin structure (CdS-T) as a model, the role of twin boundaries in modulating surface reactions and facilitating charge migration is systematically investigated. Utilizing transient absorption (TA) and time-resolved infrared (TRIR) spectroscopies, it is revealed that CdS-T achieves charge separation on a picosecond timescale and, importantly, the surface reaction at the twin boundary with the involvement of holes also occurs within 100ps to 3ns. This synchronization of charge donation and surface regeneration significantly enhances the hydrogen evolution process. Accordingly, CdS-T exhibits superior activity for visible light photocatalytic H2 production, withthe H2 production rate of 55.61mmol h-1 g-1 and remarkable stability (>30h), outperforming pristine CdS significantly. This study underscores the transformative potential of twin structures in photocatalysis, offering a new avenue to synchronize charge transport and surface reactions.

Effects of twin thickness, strain rate, and temperature on the mechanical properties of nanotwinned diamond

Nanotwinned (NT) diamond is a superior ceramic material known for its extreme hardness and strength. Both intrinsic and extrinsic factors strongly affect the mechanical properties of NT diamond. Here, we perform molecular dynamics (MD) simulations to study the mechanical properties of NT diamond under uniaxial tension, emphasizing the effects of twin thickness, strain rate, and temperature. The structural evolution, crack initiation and propagation, and scaling laws of strength and toughness are studied. Our findings reveal that a higher number of branching cracks enhance the mechanical properties of NT diamond, particularly when compared to single-crystal diamond. The presence of twin structures alters the orientation of diamond atoms, changing the direction of crack propagation and resulting in increased branching cracks upon fracture. Within constrained geometries, a “thinner is stronger” trend is observed concerning twin thickness. Our quantitative analysis further shows that mechanical properties decline with decreasing strain rates and increasing temperatures. This strain rate effect is attributed to the relaxation of residual stress, where the released energy compensates for the formation of new surfaces. We also provide a predictive model for the mechanical properties of NT diamond, offering valuable insights for the development of high-performance NT superhard materials.

Additive manufacturing Cr-Mo-Si-V steel: Systematic parameter assessments, precipitation behavior of in-situ VC-M23C6 and strengthening mechanisms

To obtain the H13 steel with defect-structure-performance compatibility fabricated by laser powder bed fusion (LPBF), a systematic optimisation framework was employed to get optimal process window in this paper. Subsequently, the microstructural evolutions, nanoprecipitation behaviors and strengthening mechanisms of H13 steels built at recommended parameters were in-depth analyzed. The evolutions of submicron sized cellular and columnar dendritic crystal were explained as well as the phase transformation process including lath martensite with a twin substructure and the carbon-rich residual austenite (RA) films were revealed. Two nano carbides, MC (rich in V and Mo) as well as M23C6 (rich in Cr and Mn), with diameters of 10–40 nm, were precipitated due to the intrinsic heat treatment (IHT) in LPBF process. Cr23C6 particles preferentially nucleated at the grain and subgrain boundaries due to the presence of crystalline defects such as dislocations and stacking faults caused by lattice distortion. It then grew by alloying elemental depletion while remaining semi-coherency with the α-Fe matrix. VC particles nucleated in situ within M23C6 as V atoms accumulated and replaced M atoms in the M23C6 lattice. With the growth of VC nuclei, the strain energy caused by local lattice misfit increased. This was offset by the development of self-accommodating twins featuring a long-period stacking order substructure within the VC particles. Eventually, spheroidal VC with twin structure were embedded in or adjacent to M23C6 carbides, and the orientation relationships for VC/M23C6 and VC/α-Fe were revealed. The as-built H13 steel exhibited excellent hardness and strength compared to wrought H13 steel, which was mainly attributed to dislocation strengthening and grain boundary strengthening, with precipitation strengthening playing a secondary role due to the low amount of nanoprecipitates. The low elongation (El) at fracture was closely related to the instability of RA films as well as the residual stress.

In-plane and out-of-plane orientations of YBCO and their correlation with a/b-axis twin structures

This study employed the low-fluorine metal-organic deposition method to fabricate YBCO films with both c-axis and a/b-axis orientations, systematically investigating their lattice structure, in-plane and out-of-plane orientation relationships, phase formation, and morphology. First, the study focused on the coexistence of in-plane and out-of-plane orientations of the a- and b-crystal axes in YBCO films, clarifying their distribution within the texture and the factors influencing them, which in turn lead to the formation of a/b-axis twins. Secondly, the experiment revealed the impact of residual stress within the film on the a/b-axis twins and confirmed that the number of twins can be directionally regulated by applying external stress, thereby improving the critical current density of the film at low temperatures. Further investigation showed that the misfit stress between the substrate and the YBCO lattice significantly affects the in-plane and out-of-plane orientations, as well as the growth parameter window. By using substrates with different lattice structures, the issue of inconsistent in-plane orientation in a/b-axis oriented YBCO films was successfully resolved, reducing high-angle grain boundaries and enhancing current flow along the Cu-O planes, thus challenging the conventional understanding of their low performance. This work fills a research gap in the field of YBCO high-temperature superconducting coated conductors regarding the in-plane and out-of-plane orientations of the a/b-axis, providing theoretical foundations and experimental guidance, and laying a material foundation for applications in superconducting weak current technologies.

Self-activated epitaxial growth of ScN films from molecular nitrogen at low temperatures

Unlike naturally occurring oxide crystals such as ruby and gemstones, there are no naturally occurring nitride crystals because the triple bond of the nitrogen molecule is one of the strongest bonds in nature. Here, we report that when the transition metal scandium is subjected to molecular nitrogen, it self-catalyzes to break the nitrogen triple bond to form highly crystalline layers of ScN, a semiconductor. This reaction proceeds even at room temperature. Self-activated ScN films have a twin cubic crystal structure, atomic layering, and electronic and optical properties comparable to plasma-based methods. We extend our research to showcase Sc’s scavenging effect and demonstrate self-activated ScN growth under various growth conditions and on technologically significant substrates, such as 6H–SiC, AlN, and GaN. Ab initio calculations elucidate an energetically efficient pathway for the self-activated growth of crystalline ScN films from molecular N2. The findings open a new pathway to ultralow-energy synthesis of crystalline nitride semiconductor layers and beyond.

In situ atomic observations of aggregation growth and evolution of penta-twinned gold nanocrystals

The twin boundaries and inherent lattice strain of five-fold twin (5-FT) structures offer a promising and innovative approach to tune nanocrystal configurations and properties, enriching nanomaterial performance. However, a comprehensive understanding of the nonclassical growth models governing 5-FT nanocrystals remains elusive, largely due to the constraints of their small thermodynamically stable size and complex twin configurations. Here, we conducted in situ investigations to elucidate the atomic-scale mechanisms driving size-dependent and twin configuration-related aggregation phenomena between 5-FT and other nanoparticles at the atomic scale. Our results reveal that surface diffusion significantly shapes the morphology of aggregated nanoparticles, promoting the symmetrical formation of 5-FT, especially in smaller nanoparticles. Moreover, the inherent structural characteristics of 5-FT mitigate the dominance of surface diffusion in its morphological evolution, retarding the aggregation evolution process and fostering intricate twin structures. These findings contribute to advancing our capacity to manipulate the configuration of twinned particles, enabling more predictable synthesis of functional nanomaterials for advanced engineering applications.

Open-Source Solutions for Real-Time 3D Geospatial Web Integration

Abstract. The recent development of Urban Digital Twin (UDT) structures and the spread of Internet of Things (IoT) technology have extended the concept of Digital Twin (DT) to urban environment representation, enabling real-time connections between geospatial representations and their real-world counterparts. Concurrently, advancements in surveying technologies and web geospatial services have facilitated the acquisition of extensive 2D and 3D geospatial data, making their spatial integration essential. While some proprietary software solutions have recently enabled initial examples of UDT by integrating various 3D geospatial data and real-time sensor acquisition, the development of open-source solutions for real-time web-based geospatial management remains a challenge. This work demonstrates a possible open-source solution for developing a UDT accessible via the web. The case study involves the web visualization platform of the new Faculty of ITC building at the University of Twente in Enschede (The Netherlands), which is connected in real-time with weather data services provided by Visual Crossing (1). The platform is based on an HTML5 framework and employs WebGL JavaScript graphic libraries to visualize different modules of 3D web visualization that integrate various local and remote 3D datasets. The framework adopted in this experiment can be used in the future for developing low-cost UDT web platforms beneficial for researchers, municipalities, and private companies interested in the real-time geospatial management of urban environments.

Microstructural Evolution and Mechanical Properties of Extruded AZ80 Magnesium Alloy during Room Temperature Multidirectional Forging Based on Twin Deformation Mode.

This study investigates the preparation of ultrahigh-strength AZ80 magnesium alloy bulks using room temperature multidirectional forging (MDF) at different strain rates. The focus is on elucidating the effects of multidirectional loading and strain rates on grain refinement and the subsequent impact on the mechanical properties of the AZ80 alloy. Unlike hot deformation, the alloy subjected to room temperature MDF exhibits a lamellar twinned structure with multi-scale interactions. The key to achieving effective room temperature MDF of the alloy lies in combining multidirectional loading with small forging strains per pass (6%). This approach not only maximizes the activation of twinning to accommodate deformation but ensures sufficient grain refinement. Microstructural analysis reveals that the evolution of the grain structure in the alloy during deformation results from the competition between {101¯2} twinning or twinning variant interactions and detwinning. Increasing the forging rate effectively activates more twin variants, and additional deformation passes significantly enhance twin interaction levels and dislocation density. Furthermore, at a higher strain rate, more pronounced dislocation accumulation facilitates the transformation of twin structures into high-angle grain boundaries, promoting texture dispersion and suppressing detwinning. The primary strengthening mechanisms in room temperature MDF samples are grain refinement and dislocation strengthening. While increased dislocation density raises yield strength, it reduces post-yield work hardening capacity. After two passes of MDF at a higher strain rate, the alloy achieves an optimal balance of strength and ductility, with a tensile strength of 462 MPa and an elongation of 5.1%, significantly outperforming hot-deformed magnesium alloys.

Austenite-martensite interfacial patterns and energy dissipation of phase transformation in Ni-Mn-Ga single crystal

The martensitic phase transformation occurs in Shape Memory Alloys (SMA) via the nucleation/propagation of the Austenite-Martensite interface (A-M interface), which is a transition region (domain) between the two coexisting phases. For providing compatibility, the transition region consists of various martensitic twin structures (laminates), forming different interfacial patterns, such as parallel laminates and branching laminates. Due to the energy accumulation in the interfacial structures (e.g., elastic mismatch and twin-boundary surface energy), the interfacial patterns should be relevant to the driving force (energy dissipation) and the associated kinetics of the phase transformation. In this paper, we adopt a special thermal loading, small-temperature-gradient “heating-cooling-reheating”, to control the A-M interface's forward and reverse propagation to generate different interfacial patterns in a Ni-Mn-Ga single crystal SMA with the observation on the twin structures (by optical microscope and SEM) and the InfraRed measurement on the temperature hysteresis of the interface propagation (for characterizing the thermal driving force). Simple energetic analysis indicates that the thermal driving force (energy dissipation) is directly related to the stored energy in the interfacial structure, particularly the large mismatch elastic energy near the habit plane. This study not only provides the details of the various interfacial patterns and their dependence on the loading path, but also indicates the driving force and the associated mechanism about the pattern evolution to understand the phase transformation process.

Coupling defect-inherent built-in electric fields to promote directional charge migration for rapid photocatalytic degradation of levofloxacin

By enhancing the intrinsic built-in electric field (IEF) of the catalyst through defect engineering, and coupling the IEF of the catalyst via an S-type heterojunction structure, a 3-in-1 IEF is formed, which drives the directional migration of electrons and holes, and can effectively improve photocatalytic performance. In this paper, an oxygen vacancy-type Bi2WO6 (Ov-BWO) composite with twin-type Zn0.5Cd0.5S (ZCS) was synthesized to construct an S-scheme heterojunction. The twin structure results in an IEF in ZCS that points from the twin plane Zn to the twin boundary S. The oxygen vacancies, on the other hand, create an internal electric field from Bi and W to O by altering the local charge density. By coupling the IEF of the catalyst through the S-type heterojunction, an enhanced IEF is formed, pointing from the twin plane Zn to the O in Ov-BWO, enabling rapid directional migration of photogenerated charge carriers. Furthermore, potential Levofloxacin (LVFX) intermediates and degradation pathways were found by combining Liquid chromatography-mass spectrometry (LC-MS) data with Density Functional Theory (DFT) simulations. This study systematically elucidates the photocatalytic degradation system, from catalyst design to the degradation process of pollutants, through the analysis of theoretical calculations and experimental results.

Adapting Segment Anything Model for 3D Brain Tumor Segmentation With Missing Modalities

ABSTRACTThe problem of missing or unavailable magnetic resonance imaging modalities challenges clinical diagnosis and medical image analysis technology. Although the development of deep learning and the proposal of large models have improved medical analytics, this problem still needs to be better resolved.The purpose of this study was to efficiently adapt the Segment Anything Model, a two‐dimensional visual foundation model trained on natural images, to address the challenge of brain tumor segmentation with missing modalities. We designed a twin network structure that processes missing and intact magnetic resonance imaging (MRI) modalities separately using shared parameters. It involved comparing the features of two network branches to minimize differences between the feature maps derived from them. We added a multimodal adapter before the image encoder and a spatial–depth adapter before the mask decoder to fine‐tune the Segment Anything Model for brain tumor segmentation. The proposed method was evaluated using datasets provided by the MICCAI BraTS2021 Challenge. In terms of accuracy and robustness, the proposed method is better than existing solutions. The proposed method can segment brain tumors well under the missing modality condition.

Effects of laser non-uniform shock peening on the microstructure and fatigue performance of SUS 304 stainless steel welded joints

Residual tensile stresses and microstructural heterogeneity in welded joints are primary factors that degrade fatigue performance. As an effective post-weld strengthening method, Laser Shock Peening (LSP) can address these issues. Given the personalized demands of different regions, this paper proposes a Laser Non-Uniform Shock Peening (LNUSP) technique. This approach involves applying high pulse energy to the weld zone (WZ) and heat-affected zone (HAZ), and low pulse energy to the base material (BM) to achieve a more uniform residual compressive stress distribution and refined microstructure, thereby improving overall performance and service life. Results indicate that LSP transforms residual tensile stresses on the weld surface into compressive stresses. Compared to original samples, uniformly LSP-treated samples, and locally LSP-treated samples, LNUSP-treated samples exhibit more uniform residual stress and hardness distribution. LSP significantly increases surface hardness, with LNUSP-treated samples achieving a maximum hardness of 308.3 HV. Additionally, LSP induces martensitic transformation in the BM and WZ areas, alters grain orientation, and promotes dislocation movement, resulting in dislocation tangling, dislocation networks, and twin structures, which refine grain size. Consequently, LSP markedly improves joint fatigue performance, delaying fatigue crack propagation. The fatigue life of LNUSP-treated samples is increased by 25.41 % compared to original samples, reaching levels comparable to high-energy large-area impacts. This enhancement is attributed to the uniform residual stress and refined grain structure.