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Rapid crystallization behavior of amorphous Tex Se 1 − x thin films limits the use of these alloys as coatings and in optoelectronic devices. Understanding the short- and medium-range ordering of the amorphous structure and the fundamental physics governing the crystallization of the films is crucial. Although the lack of long range crystalline order restricts the characterization of the amorphous films, electron microscopy offers a way to extract information about the nanoscale ordering. In this paper, the local ordering of amorphous Tex Se 1 − x thin films with x = 0.22 , 0.61 , 0.70 , 0.90 , and 1 grown by thermal evaporation is investigated using radial distribution function (RDF) and fluctuation electron microscopy (FEM) analysis. RDF results show that the nearest-neighbor distances of selenium (Se) and tellurium (Te) in their crystalline structure are preserved, and their bond lengths increase with the addition of Te. Density functional theory (DFT) calculations predict structures with interatomic distances similar to those measured experimentally. Additionally, fluctuations in atomic coordination are analyzed. Medium range order (MRO) analysis obtained from FEM and DFT calculations suggests that there are at least two populations within the chain network structure, which are close to the Se–Se and Te–Te intrachain distances. For the binary alloy with x > 0.61, Tex Se 1 − x , Te–Te like populations increase and Te fragments might form, suggesting that the glass forming ability decreases rapidly. [ABSTRACT FROM AUTHOR]

In this work, we employ a phase field dislocation dynamics technique to simulate dislocation motion in body centered cubic refractory metals with diffusing interstitials. Two distinct systems are treated, Nb with O interstitials and W with H interstitials, to consider both relatively small and large atomic size interstitials. Simulations without and with driving stress are designed to investigate the role of interstitial type and mobility on the glide of edge- and screw-character dislocations. The simulations reveal the various short- and long-range dislocation-interstitial interactions that can take place and their dependency on interstitial type, site occupation, stress state, and mobility of the interstitials relative to dislocations. We show that while interstitial O increases the breakaway stress for both screw and edge dislocations in Nb, interstitial H in low H concentrations makes screw dislocations easier and the edge dislocations harder to move. The simulations find that screw dislocation glide is enhanced by the presence of interstitials in both systems. Edge dislocation glide is enhanced in W–H and inhibited in Nb–O. [ABSTRACT FROM AUTHOR]

Based on literary and experimental data, the effects accompanying the passage of pulsed current and associated structural changes in metals and alloys have been considered briefly. The special role of the type and modes of current, as well as the nature of the material, has been shown. The results of studies of the interaction of electric current and plastic deformation by quasi-static tension in pure metals, titanium alloys with martensitic transformation, and steels have been presented. It is assumed that the causes of the detected deformation effects are the ratio of the period and duration of the pulse, cycling of stress and temperature, changes in the deformation mechanism, reversible transformations, changes in grain size, and the appearance of particles of second phases. Variation of the duty cycle makes it possible to regulate the ratio of thermal and electroplastic effects and thereby influence the mechanisms of hardening/softening. [ABSTRACT FROM AUTHOR]

Monoatomic-layered carbon materials, such as graphene 1 and amorphous monolayer carbon 2,3 , have stimulated intense fundamental and applied research owing to their unprecedented physical properties and a wide range of promising applications 4,5 . So far, such materials have mainly been produced by chemical vapour deposition, which typically requires stringent reaction conditions compared to solution-phase synthesis. Herein, we demonstrate the solution preparation of free-standing nitrogen-doped amorphous monolayer carbon with mixed five-, six- and seven-membered (5-6-7-membered) rings through the polymerization of pyrrole within the confined interlayer cavity of a removable layered-double-hydroxide template. Structural characterizations and first-principles calculations suggest that the nitrogen-doped amorphous monolayer carbon was formed by radical polymerization of pyrrole at the α, β and N sites subjected to confinement of the reaction space, which enables bond rearrangements through the Stone-Wales transformation. The spatial confinement inhibits the C-C bond rotation and chain entanglement during polymerization, resulting in an atom-thick continuous amorphous layer with an in-plane π-conjugation electronic structure. The spatially confined radical polymerization using solid templates and ion exchange strategy demonstrates potential as a universal synthesis approach for obtaining two-dimensional covalent networks, as exemplified by the successful synthesis of monolayers of polythiophene and polycarbazole., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

Anisotropic effect of two-dimensional materials remains one of the most attractive properties, introducing an additional degree of freedom for tuning physical performances. In this work, we investigate the anisotropies of electronic, transport, piezoelectric, and optoelectronic properties of Janus In2 XY (X / Y = S, Se, Te) monolayers (J-In2 XY MLs) by performing first-principles calculations. We find that such J-In2 XY MLs possess moderate bandgap (2.07–2.29 eV), high carrier mobility (∼103 cm−2V−1s−1), visible light absorption (∼105 cm−1), large out-of-plane piezoelectric response (d 31 = 0.35 pm V − 1 ) and ultra-soft mechanical nature (C 11 = 32.84 N m − 1 ) . We construct a kind of J-In2 XY- based phototransistor to investigate the optoelectronic properties under linearly polarized light. We find that the low recombination probability of photogenerated carriers ensured by anisotropic effect enhances the photocatalytic potential of J-In2 XY MLs. And the pivotal role induced by anisotropy in photocurrent can cause a prominent on/off ratio (∼100), considerable responsivity (0.038 AW−1, 0.036 AW−1) and external quantum efficiency (10.6%, 11.5%). Our study provides an avenue for the design of future anisotropic J-In2 XY- based multifunctional optoelectronic device. [ABSTRACT FROM AUTHOR]

The effect of a pulsed current on titanium tensile deformation obtained by postdeformation annealing after cold rolling of the coarse-grained and ultrafine-grained states has been considered. The effect of the duty cycle of the pulse current over a wide range on the shape of the stress–strain curves and mechanical properties has been studied. It is shown that an increase in the duty cycle results in an enhancement in the thermal effect of the current and a decrease in the flow stresses, strength, and plasticity, as well as in intense necking. A decrease in the duty cycle leads to the absence of heating and the occurrence of the electroplastic effect and an increase in the strength and plasticity, which depends on the structural state of coarse-grained titanium and the method of titanium production. The possible physical mechanisms of hardening associated with twinning, strain aging, and low-cycle fatigue have been considered. [ABSTRACT FROM AUTHOR]

Hydrogen energy, a new type of clean and efficient energy, has assumed precedence in decarbonizing and building a sustainable carbon-neutral economy. Recently, hydrogen production from water splitting has seen considerable advancements owing to its advantages such as zero carbon emissions, safety, and high product purity. To overcome the large energy barrier and high cost of water splitting, numerous efficient electrocatalysts have been designed and reported. However, various difficulties in promoting the industrialization of electrocatalytic water splitting remain. Further, as high-performance electrocatalysts that satisfy industrial requirements are urgently needed, a better understanding of water-splitting systems is required. In this paper, the latest progress in water electrolysis is reviewed, and experimental evidence from in situ/operando spectroscopic surveys and computational analyses is summarized to present a mechanistic understanding of hydrogen and oxygen evolution reactions. Furthermore, some promising strategies, including alloying, morphological engineering, interface construction, defect engineering, and strain engineering for designing and synthesizing electrocatalysts are highlighted. We believe that this review will provide a knowledge-guided design in fundamental science and further inspire technical engineering developments for constructing efficient electrocatalysts for water splitting. [ABSTRACT FROM AUTHOR]

The development of prosthesis implantation as a means to treat bone defects in the field of orthopedic surgery is booming. Some materials with excellent biocompatibility are available for practical application, while new materials are being continuously developed. Gum metal is a new type of multifunctional β-type titanium alloy, and its basic composition can be expressed as Ti-24(Ta + Nb + V)-(Zr, Hf)-O. Gum metal has a good combination of a low elastic modulus and high strength, which promotes its emergence in the biological field. Moreover, gum metal combines the advantages of nonlinear elasticity, low work hardening rate and nontoxicity, making it a new material with potential in the future. This review begins with the design origin of gum metal and the influence of various elements on this kind of alloy. Second, the fabrication process and deformation mechanism of gum metal are summarized. Finally, the properties and current application fields of gum metal are introduced. A concise review of recent advances in gum metal. A comprehensive assessment of the essential characteristics. An introduction of various synthetic strategies for the fabrication of gum metal. A brief overview on fundamental is presented to better understand super-elasticity. An overview of representative biomedical, industry and manufacturing of gum metal. [ABSTRACT FROM AUTHOR]

Refractory alloys often possess superior thermomechanical properties compared to conventional materials, such as steels, Ni-based superalloys, and Ti alloys, especially in high-temperature environments. While these materials promise to revolutionize numerous industries, significant hurdles remain for insertion into applications due to an incomplete understanding of structure-property relationships and conventional processing challenges. We explore laser-based additive manufacturing (AM) to construct refractory alloys consisting of combinations of Mo, Nb, Ta, and Ti with systematically increasing compositional complexity. Microstructure, composition, and hardness of the AM-processed alloys were characterized. Results are discussed in the context of pairing additive manufacturing with refractory metals to enable next-generation alloys. [ABSTRACT FROM AUTHOR]

Molecular dynamics (MD) modeling of the thermophysical properties of pure metallic gold (Au) and hysteresis is considered in order to study its behavior during melting–crystallization phase transformations, i.e., in the transition from solid to liquid. The results of computational experiments are presented, in which the temperature dependences of a number of thermophysical characteristics of the metal are obtained. The possibility of the formation of highly superheated metastable states of the solid phase upon rapid heating of Au has been confirmed. [ABSTRACT FROM AUTHOR]

Nonpolar m-plane AlGaN offers the advantage of polarization-free multiple quantum wells (MQWs) for ultraviolet (UV) emission and can be achieved on the sidewalls of selective area grown GaN nanowires. We reveal that the growth of AlGaN on GaN nanowires by metal organic chemical vapor deposition (MOCVD) is driven by vapor-phase diffusion, and consequently puts a limit on the pitch of nanowire array due to shadowing effect. An insight into the difficulty of achieving metal-polar AlGaN nanowire by selective area growth (SAG) in MOCVD is also provided and can be attributed to the strong tendency to form pyramidal structure due to a very small growth rate of { 10 1 ¯ 1 } semipolar planes compared to (0001) c-plane. The nonpolar m-plane sidewalls of GaN nanowires obtained via SAG provides an excellent platform for growth of nonpolar AlGaN MQWs. UV emission from m-plane AlxGa1−xN/AlyGa1−yN MQWs grown on sidewalls of dislocation-free GaN nanowire is demonstrated in the wavelength range of 318–343 nm. [ABSTRACT FROM AUTHOR]

Group-VI elemental two-dimensional (2D) materials (e.g., tellurene (Te)) have unique crystalline structures and extraordinarily physical properties. However, it still remains a great challenge to controllably grow 2D Te with good repeatability, uniformity, and highly aligned orientation using vapor growth method. Here, we design a Cu foil-assisted alloy-buffer-controlled growth method to epitaxially grow aligned single-crystalline 2D Te on an insulating mica substrate. The in-situ formation of Cu−Te alloy plays a key role on 2D Te growth, alleviating the spatial and temporal non-uniformity of precursor in conventional vapor deposition process. Through transmission electron microscopy (TEM) analysis combined with theoretical calculations, we unveil that the alignment growth of Te in the [110] direction is along the [600] direction of mica, owing to the small lattice mismatch (0.15%) and strong binding strength. This work presents a method to grow aligned high-quality 2D Te in a controllable manner. [ABSTRACT FROM AUTHOR]

Precipitation hardening is one of the most important strengthening mechanisms in metallic materials, and thus, controlling precipitation is often critical in optimizing mechanical performance. Also other performance requirements such as functional and degradation properties are critically depending on precipitation. Control of precipitation in metallic materials is, thus, vital, and the approach presently in the limelight for this purpose is an integrated approach of theory, computations and experimental characterization. An empirical understanding is essential to build physical models upon and, furthermore, quantitative experimental data is needed to build databases and to calibrate the models. The most versatile tool for precipitation characterization is the transmission electron microscope (TEM). The TEM has sufficient resolving power to image even the finest precipitates, and with TEM-based microanalysis, overall quantitative data such as particle size distribution, volume fraction and number density of particles can be gathered. Moreover, details of precipitate structure, morphology and chemistry, can be revealed. TEM-based postmortem and in situ analysis of precipitation has made significant progress over the last decade, largely stimulated by the widespread application of aberration corrected microscopes and accompanying novel analytics. The purpose of this report is to review these recent developments in precipitation analysis methodology, including sample preparation. Application examples are provided for precipitation analysis in metals, and future prospects are discussed. [ABSTRACT FROM AUTHOR]

IIIâ€"V semiconductors such as InP and GaAs are direct bandgap semiconductors with significantly higher absorption compared to silicon. The high absorption allows for the fabrication of thin/ultra-thin solar cells, which in turn permits for the realization of lightweight, flexible, and highly efficient solar cells that can be used in many applications where rigidity and weight are an issue, such as electric vehicles, the internet of things, space technologies, remote lighting, portable electronics, etc. However, their cost is significantly higher than silicon solar cells, making them restrictive for widespread applications. Nonetheless, they remain pivotal for the continuous development of photovoltaics. Therefore, there has been a continuous worldwide effort to reduce the cost of IIIâ€"V solar cells substantially. This topical review summarises current research efforts in IIIâ€"V growth and device fabrication to overcome the cost barriers of IIIâ€"V solar cells. We start the review with a cost analysis of the current state-of-art IIIâ€"V solar cells followed by a subsequent discussion on low-cost growth techniques, substrate reuse, and emerging device technologies. We conclude the review emphasizing that to substantially reduce the cost-related challenges of IIIâ€"V photovoltaics, low-cost growth technologies need to be combined synergistically with new substrate reuse techniques and innovative device designs. [ABSTRACT FROM AUTHOR]

The results of experimental studies of the laser shock waves initiated by a picosecond pulse in iron are presented. Experimental measurements are processed and analyzed using theoretical approaches and numerical simulation. Interest in picosecond actions is caused by uniquely high strain rates, in particular, the dependence of the thresholds of elastoplastic and polymorphic transformations on the strain rate. Investigations are necessary for the development of the field of laser hardening of metals. The first steps in this direction have been taken, although this kind of approach to laser forging hardening is already widely used in practice. Modern developments in the field of shock wave generation and their experimental diagnostics are used, and the related methods of theoretical interpretation of experimental data are being developed. The difficulty lies in the picosecond time scale, since the diagnostics of experiments is limited by kinematics, namely, measuring the coordinates of the free surface. To elucidate the polymorphic transformation kinetics on picosecond time scales, the technique of inverse analysis of the free surface velocity is used for the first time. This technique is validated using the results of hydrodynamic and molecular dynamics simulation with direct extraction of mechanical stresses and strains. A theoretical study of reconstructed free surface velocity profiles by traditional methods confirms the results obtained in the field of their applicability, specifically, on elastic and plastic shock wave fronts. The transformation of iron into the ε phase takes place in the initial region of shock wave propagation, as long as a shock wave has a sufficient amplitude. The cause is a pressure limitation of 40 GPa because of optical breakdown in glass and shock wave attenuation during wave propagation. [ABSTRACT FROM AUTHOR]

A precise model for calculating the dependence of the composition of self-catalyzed Ga(As,P) nanowires on the growth parameters without any fitting parameters is proposed. It is shown that the Ga(As, P)-nanowire composition does not depend on the growth rate at a fixed ratio of the total fluxes of Group-V- and Group-III atoms. The results of modeling are in good agreement with the experimentally observed dependence of the Ga(As,P) nanowire composition on the ratio of the fluxes of As and P atoms. [ABSTRACT FROM AUTHOR]

The strain has been employed for controlled modification of electronical and mechanical properties of two-dimensional (2D) materials. However, the thermal strain-engineered behaviors of the CVD-grown MoS2 have not been systematically explored. Here, we investigated the strain-induced structure and properties of CVD-grown triangular MoS2 flakes by several advanced atomic force microscopy. Two different kinds of flakes with sharp-corner or vein-like nanostructures are experimentally discovered due to the size-dependent strain behaviors. The critical size of these two kinds of flakes can be roughly estimated at ∼17 μm. Within the small flakes, the sharp-corner regions show specific strain-modified properties due to the suffering of large tensile strain. While in the large MoS2 flakes, the complicated vein-like nanoripple structures were formed due to the interface slipping process under the larger tensile strain. Our work not only demonstrates the size-specific strain behaviors of MoS2 flakes but also sheds light on the artificial design and preparation of strain-engineered nanostructures for the devices based on the 2D materials. [ABSTRACT FROM AUTHOR]