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Five high entropy carbide ceramics, (Hf0.2,Nb0.2,Ta0.2,Ti0.2,Zr0.2)C, (Cr0.2,Hf0.2,Ta0.2,Ti0.2,Zr0.2)C, (Hf0.2,Mo0.2,Ta0.2,Ti0.2,Zr0.2)C, (Hf0.2,Ta0.2,Ti0.2,W0.2,Zr0.2)C, and (Hf0.2,Mo0.2,Ti0.2,W0.2,Zr0.2)C, were synthesized by carbothermal reduction of oxides and direct current sintering. The five high entropy carbide ceramics were determined to be nominally phase-pure with relative densities of more than 98.9% and mean grain sizes of less than 5 μm. Average Vickers hardness values ranged from 19.2 ± 0.4 GPa for (Hf0.2,Nb0.2,Ta0.2,Ti0.2,Zr0.2)C at a load of 2 kgf to 43.5 ± 0.4 GPa for (Hf0.2,Mo0.2,Ti0.2,W0.2,Zr0.2)C at a load of 0.05 kgf. Hardness generally increased with increasing the valence electron concentration and strain as measured by the Williamson–Hall analysis. However, neither correlation was conclusive enough to be a clear indicator of hardness. Instead, it was determined that a combination of effects that includes the valence electron concentration, lattice strain, and grain size all contribute to the hardness of high entropy carbide ceramics. [ABSTRACT FROM AUTHOR]

Alloying heavy metals (HMs) has been an effective method for enhancing the efficiency of spin–orbit torque. In this study, we demonstrate that Pt100−xWx/Pt/Co/Ta multilayers still maintain perpendicular magnetic anisotropy after high-temperature annealing. Doping tungsten (W) into HM platinum (Pt) at the bottom of a Pt/Co/Ta multilayer significantly increases the spin Hall angle (θ S H ) and reduces the critical switching current density (Jc). The harmonic Hall test results show that the θ S H of the Pt88W12 alloy film is approximately 0.29, which is higher than that of the pure Pt film (0.15). The magnetization switching test reveals that the Jc of Pt94W6 alloy film is approximately 4.892 × 106 A/cm2, which is 51.9% lower than that of the pure Pt film. This study offers a valuable method for reducing power consumption and enhancing the efficiency of related application devices. [ABSTRACT FROM AUTHOR]

In this work, the distribution and segregation behaviors of helium (He) and the effect of yttrium (Y) on these behaviors in the symmetrical tilt tungsten (W) Σ5(310)/[001] grain boundary (GB) region were studied using first-principles calculations. The results revealed that the GB has a significant impact on the behaviors of He in W. The solution and segregation energies of He in the W Σ5(310)/[001] GB region increase with increasing the distance from He to the GB and are inversely proportional to the effective electrons of He. The density of states analysis showed that the GB can suppress partial hybridization between He and W atoms. In addition, we find that the strengthening element Y facilitates the dissolution of He in the W GB region. [ABSTRACT FROM AUTHOR]

Analyzing plastic flow in refractory alloys is relevant to many different commercial and technological applications. In this study, screw dislocation statics and dynamics were studied for various compositions of the body-centered cubic binary alloy tungsten–molybdenum (W–Mo). The core structure did not appear to change for different alloy compositions, consistent with the literature. The pure tungsten and pure molybdenum samples had the lowest plastic flow, while the highest dislocation velocities were observed for equiatomic, W0.5Mo0.5 alloys. In general, dislocation velocities were found to largely align with a well-established dislocation mobility phenomenological model supporting two discrete dislocation mobility regimes, defined by kink-pair nucleation and migration and phonon drag, respectively. Velocities were observed to increase with temperature and applied shear stress and with decreasing kink-pair formation energies. The 50 at. % W alloy was found to possess the lowest kink-pair formation energy, consistent with its higher dislocation velocity. Furthermore, molybdenum segregation to the dislocation line was found to be thermodynamically favorable specifically at low temperatures and was observed to significantly delay the onset of dislocation glide and then generally enhance dislocation velocities thereafter. This behavior was explained by examining the energy landscape of dislocation glide. Furthermore, a segregation/de-segregation phase transition was observed to occur around 2500 K beyond which no preferential segregation to the dislocation was found. Overall, our findings suggest strong dependencies of plastic flow in W–Mo alloys on composition and elemental segregation, in agreement with the available literature, and may provide useful information to guide the design of next generation structural materials. [ABSTRACT FROM AUTHOR]

Understanding the behavior of intrinsic defects and helium (He) in tungsten oxides is useful for the application of tungsten (W) in a fusion environment because of the oxidation of W surfaces. The formation and diffusion energies of intrinsic defects and He in monoclinic γ-WO3 have been investigated using first-principles density functional theory calculations. The formation energy and diffusion activation energy of O defects are lower than W defects. O vacancy prefers to diffuse along the ⟨ 001 ⟩ direction, then followed by ⟨ 010 ⟩ and ⟨ 100 ⟩ directions; however, the W vacancy is immobile at temperatures lower than 2000 K. The stability of Schottky defects (SDs) is sensitive to their geometry and orientation. W interstitials prefer to move along the [100] direction, while O interstitials jump around W atoms rather than through the W quasi-cubic centers. He interstitial atoms are predicted to have a high solubility and an anisotropic diffusion mechanism in γ-WO3. In addition, the effect of biaxial strain on the solubility and diffusivity of He interstitials was investigated. He interstitials prefer to reside at individual sites rather than clusters. He atoms are weakly trapped by single vacancies or SDs. Vacancies assist the local migration of nearby He. Correspondingly, He self-clustering and bubble formation are less likely to form in γ-WO3 relative to bcc W. The energetics obtained in this work can be used to predict the microstructure evolution of the WO3 layer on a W substrate exposed to He plasmas at different temperatures. [ABSTRACT FROM AUTHOR]

In this study, the WIEN2k code, utilizing the full potential linearized augmented plane wave (FPLAPW) approach within the framework of density functional theory (DFT), explicitly employing the PBEsol approximation, is employed to investigate the fundamental properties of W-doped and (Mo, W) co-doped cubic CeO2. Herein, lattice constants, bulk modulus and cell volumes were evaluated for structural properties. The total density of states (TDOS) for various doped and co-doped CeO2 systems was used to explain the origin of magnetic behavior. The band structure (BS) calculations show that the doped and co-doped materials exhibit semiconductor behavior with a direct bandgap in both spin channels. The calculated total spin magnetic moments of W/CeO2 and (Mo, W)/CeO2 alloys are 2.002 μ B and 4.007 μ B , respectively. Furthermore, the optical absorption shows absorption peaks in the visible range and a redshift. As a result, adding molybdenum and tungsten additives improves the electro-optical properties of previous materials. [ABSTRACT FROM AUTHOR]

The microstructure and mechanical properties of tungsten powder reduction furnace tube are investigated in this work. After service, the lamellar and skeleton-shape primary carbides of FeCr26Ni36Co15W5 alloy coarsened and formed a continuous network, much fine secondary carbide precipitated in the dendrite interior. The tensile strength and ductility of FeCr26Ni36Co15W5 alloy decreased. And, the creep strength of FeCr26Ni36Co15W5 alloy has reached the end of the service life. Meanwhile, the corrosion products were studied by XRD and XRF. It was found that the corrosion products were Na2WO4·2 h2O, Na2CO3·H2O and Cr4Ni15W，and the evaporation of catalyst (Na2CO3) results in a large amount of Na2CO3·H2O in the corrosion products. The hot corrosion mechanism of the reduction furnace tube is Type I hot corrosion. [ABSTRACT FROM AUTHOR]

Tungsten (W) and tungsten alloys are being considered as leading candidates for structural and functional materials in future fusion energy devices. The most attractive properties of tungsten for the design of magnetic and inertial fusion energy reactors are its high melting point, high thermal conductivity, low sputtering yield, and low long-term disposal radioactive footprint. Despite these relevant features, there is a lack of understanding of how the structural and mechanical properties of W-based alloys are affected by the temperature in fusion power plants. In this work, we present a study on the thermo-mechanical properties of five W-based plasma-facing materials. First-principles density functional theory (DFT) calculations are combined with the quasi-harmonic approximation (QHA) theory to investigate the electronic, structural, mechanical, and thermal properties of these W-based alloys as a function of temperature. The coefficient of thermal expansion, temperature-dependent elastic constants, and several elastic parameters, including bulk and Young's modulus, are calculated. Our work advances the understanding of the structural and thermo-mechanical behavior of W-based materials, thus providing insights into the design and selection of candidate plasma-facing materials in fusion energy devices. [ABSTRACT FROM AUTHOR]

In order to further improve the density and properties of high-entropy boride ceramics, (Hf,Zr,W,Mo,Ti)B2 high-entropy boride ceramics were prepared by boro/carbothermal reduction combined with SPS. The phase composition, microstructure, and mechanical properties of the ceramics were studied, and the results showed that (Hf,Zr,W,Mo,Ti)B2 high-entropy boride powder contained a highentropy phase, an oxides impurities phase, a WB phase, and a HfB2 phase at 1600 °C. After sintering at 2000 °C, there was no oxide impurity in the (Hf,Zr,W,Mo,Ti)B2 high-entropy boride ceramics, which consisted of a high-entropy phase and a small amount of WB second phase. The hardness and fracture toughness were 29.9 ± 1.0 GPa and 3.36 ± 0.21 MPa·m1/2, respectively. The hardness was higher than the high-entropy boride ceramics with the same components prepared by in situ reactive sintering and borothermal reduction. The mechanical properties of the high-entropy ceramics obtained by boro/carbothermal reduction was excellent. and were higher than those reported in the literature of the same component. [ABSTRACT FROM AUTHOR]

Direct current (DC) and pulsed DC tungsten inert gas (TIG) additive manufacturing processes were employed to fabricate GH4169 high-temperature alloy specimens. Upon comparing and analysing the two additive manufacturing methods, the evolution of microstructure and mechanical properties of the additively manufactured specimens were discussed. It provided a useful reference for the engineering application of pulsed DC TIG technology. The results showed that the overall forming process of the specimen was relatively stable under the DC TIG additive manufacturing and pulsed DC TIG additive manufacturing processes. The aspect ratio of the deposited layer of the pulsed DC-deposited specimen was relatively low, and the deposited layer of the pulsed DC specimen became flatter, which was conducive to maintaining the stability of the molten pool during the deposition process and improving forming accuracy. The microstructure distribution of the deposited layer from bottom to top was relatively uneven, with columnar dendrites in the bottom layer, cellular crystals in the middle layer, and equiaxed crystals in the top layer. Compared with the DC TIG additive manufacturing of GH4169 high-temperature alloy specimens, the Laves phase of the pulsed DC specimens was significantly reduced, which improved the plasticity and brittleness of the material. [ABSTRACT FROM AUTHOR]

Over 60% of reported failures for reactive power compensation systems are given for damage to electrical circuit breaker contacts. This paper presents a study on the development of microwave technology for sintering of W–Cu–Cr alloys at 1012 °C for 65 min using 623.38 W microwave power, as well as microwave joining at 231 °C of the W–Cu–Cr composite material on body contact using 475 W microwave power for 55 s. The joined components were subjected to mechanical and electrical tests in accordance with ICE standards to validate the applied technology. Tests of connection–disconnection of the electrical contacts were carried out in accordance with the maximum number of disconnections allowed by the manufacturer (2 cycles/min): 25 s rest time and 5 s operating time under load. The components of the electrical contact after 111237 switches were analyzed under a microscope revealing a reduction of the damaged area by 27% compared with the original contact. [ABSTRACT FROM AUTHOR]

The paper presents the results of studying the structure and phase state of tungsten and tungsten-copper alloy after pulsed action of compression plasma flows and irradiation with helium ions. The compression plasma flows were used to modify the surface layer of tungsten, as well as to create an alloy based on tungsten and copper. Using scanning electron microscopy and X-ray structural analysis, the formation of radiation defects on the tungsten surface was detected in the form of local areas of exfoliation and destruction, which begin to form at helium ion irradiation doses of 2 × 1017 cm−2. It is shown that preliminary plasma treatment of the surface in the melting mode leads to the complete disappearance of surface radiation defects up to a dose of 2 × 1017 cm−2, which may be associated with the formation of a fine-crystalline grain structure, the intergranular boundaries of which serve as effective sinks for primary radiation defects. [ABSTRACT FROM AUTHOR]

Platinum (Pt)‐based compounds are the benchmarked catalysts for hydrogen evolution reaction (HER) but exhibit slow kinetics in alkaline environments. The *OH accumulation on Pt surface can block active sites, affecting proton reduction and water re‐adsorption. Alloying Ruthenium (Ru) with Pt sites can significantly modulate the adsorption and desorption of water dissociation intermediates. Choosing suitable supports and utilizing metal‐support interaction (MSI) is crucial for active site optimization. PtRu alloy anchored on tungsten oxide (WO3) with rich oxygen vacancies (OV) is prepared through an ultrafast microwave‐assisted approach. Benefiting from the coupling effects between alloying and MSI, PtRu/WO3‐OV exhibits exceptionally high HER activity. In 1 m KOH, 1 m KOH + seawater, and 0.5 m H2SO4, it requires ultralow overpotentials of 9, 26, and 6 mV to achieve 10 mA cm−2, respectively. The designed catalyst surpasses commercial Pt/C in mass activity and demonstrates considerable potential for intermittent energy integration. Density functional theory reveals that alloying Ru with Pt sites significantly reduces the energy barrier of dissociating *OH, modulating blockage on the surface and then promoting the overall alkaline HER process. This study offers insights into the rapid synthesis of non‐carbon supported catalysts with Pt site modulation for alkaline hydrogen generation. [ABSTRACT FROM AUTHOR]

This paper is a study of mechanical properties and microstructure of rotary friction welded tungsten heavy alloy with aluminum alloy (AA). A plastic deformation is visible on AA side. Effects of friction time (FT) and friction pressure (FP) on the ultimate tensile strength (UTS) were studied by plotting graphs. The UTS of joints increases with increasing FP and FT and then decreases after reaching the maximum value. The fracture proceeds through the cleavage planes at the interface. Scanning electron microscopy for investigation of the fracture morphology and phase transformations taking place during friction welding process was used. Chemical compositions of the interfaces of the welded joints were determined by using energy-dispersive X-ray spectroscopy (EDS). EDS analyses across the interface of tungsten and nickel have not confirmed the diffusion to AA side. Microstructure of friction welds consisted of equiaxed grains formed due to dynamic recrystallization and coarse grains in the periphery region on AA side. [ABSTRACT FROM AUTHOR]

Ti(C, N)‐based cermets have been considered to be the most potential candidates for WC‐Co cemented carbides as tool material due to their various advantages. However, the trade‐off between hardness/strength and toughness limits their further application. Herein, we present new (Ti, W, Mo, Cr)(C, N)‐based cermets showing superior mechanical properties with hardness of 1525 MPa, transverse rupture strength of 2428 MPa, and fracture toughness of 11.44 MPa·m1/2 by compositional and interfacial modification. The strengthening and toughening mechanisms were revealed by experimental observation and theory calculation. It could be clarified that the high elastic modulus caused by a polar covalent bond in the hard phase and solid solution strengthening of the binder phase attributed to the hardness. The strong interface bonding between the core/rim, inner/outer rim, and rim/binder phases stemming from the composition optimization contributed to super crack resistance. Intergranular fracture in submicron‐scaled hard phases led to the crack deflection, transgranular fracture in the micron‐scaled hard phases consumed more energy due to their high intrinsic hardness and excellent interface coordination. The synergy of multi‐scaled hard particles brought about excellent comprehensive mechanical properties. [ABSTRACT FROM AUTHOR]

AISI-1045 steel is a medium-carbon, medium-strength steel that usually requires surface engineering to be usable in industrial applications. Using the cathodic cage plasma deposition technique, transition metal (Nb, V, W) nitride coating is deposited on this steel using cathodic cage lids of these metals. The hardness of untreated steel (1.8 GPa) is upgraded to 11.2, 12.2, and 9.7 GPa for niobium nitride, vanadium nitride, and tungsten nitride coating, respectively. The elastic modulus, the ratio of hardness-elastic modulus (H/E, H2/E, and H3/E2), and the plasticity factor depict the improvement in mechanical and elastic properties. The sample treated with a niobium cage lid exhibits the Nb4N5 phase, the vanadium cage lid shows the VN phase (along with the Fe4N phase), and the tungsten cage lid consists of W2N3, WFeN2, and Fe4N phases. Among these coatings, the thickness of niobium nitride coating is maximum (1.87 μm), and a low deposition rate is obtained for tungsten nitride coating (0.83 μm). In addition to this coating, a nitrogen diffusion zone (∼60 μm) is also formed beneath the coating, which creates a hardness gradient between the coating and the substrate. The ball-on-disc wear tester shows that niobium nitride coating deposition reduces the wear rate from 19.5 × 10−3 to 8.8 × 10−3 mm3/N m and exhibits excellent wear performance. [ABSTRACT FROM AUTHOR]

The Ni electrodeposition combined with multilayered structure film is a promising strategy in modern optical manufacturing, while less effort has been devoted to comprehending the electrochemical reaction process, which is essential for their practical applications. In view of this, the initial reduction dynamics and nucleation mechanisms of Ni electrodepositions on multilayer W/Si and Cr/C films were analyzed in this work, and the morphological, crystal, and mechanical characteristics of produced Ni electrodeposits were further determined and compared. The results show that the considerably irregular crystals accompanied by high tensile stress of 119.5 MPa were formed for the Ni electrodeposit on W/Si film, which were mainly attributed to the progressive nucleation process with more severe side reaction of hydrogen evolution. By contrast, the instantaneous nucleation mode with lower reduction resistance were revealed for the Ni electrodeposition on Cr/C film, which presented a comparatively fine–grained texture, less roughness, and smaller stress structure. To summarize, the more stable electrochemical reaction process and improved structure uniformity are obtained for the Ni electrodeposition on metal/C–based film, which offers a theoretical guidance for optimized fabrication of multilayer optical devices in extreme ultraviolet, x-ray, and neutron focusing fields. [ABSTRACT FROM AUTHOR]

By dispensing with all the atoms and only focusing on dislocation lines, the computational method of Discrete Dislocation Dynamics (DDD) gains greatly over Molecular Dynamics (MD) in simulation efficiency of metal plasticity. But whereas in MD dislocations follow natural dynamics of atomic motion, DDD must rely on a dislocation mobility function to prescribe how a dislocation line should respond to the driving force exerted on it. However, reflecting our still incomplete understanding of ways in which dislocations move, mobility functions presently employed in DDD simulations entail simplifications and approximations of limited or, worse still, unknown accuracy and applicability. Here we introduce a data-driven approach in which the dislocation mobility function is modeled as a graph neural network (GNN) trained on large-scale MD simulations of crystal plasticity. We apply our proposed approach to predicting plastic strength of body-centered-cubic (BCC) metal tungsten and show that, once implemented in a DDD model, our GNN dislocation mobility function accurately reproduces the challenging tension/compression asymmetry of plastic flow observed both in ground-truth MD simulations and in experiment. Furthermore, subsequently validated by MD simulations, the same function accurately predicts plastic response of tungsten under conditions not previously seen in training. By demonstrating its ability to learn relevant physics of dislocation motion, our DDD+ML approach opens a promising avenue to bringing fidelity of DDD models closer in line with direct MD simulations at a much reduced computational cost. [ABSTRACT FROM AUTHOR]

MoS 2 and WS 2 as typical two-dimensional transition metal dichalcogenides have been investigated since of rich physicochemical properties. To deposit MoS 2 and WS 2 thin films, chemical solution deposition as a facile route had been used showing the advantages of high component controllability, low cost, sequential processing of device, easy preparation of large-size films and facile preparation of films on irregular substrates. Here, Mo 1-x W x S 2 (0 ≤ x ≤ 1) thin films were successfully prepared by chemical solution deposition method. The phases as well as microstructures were investigated using field emission scanning electron microscope, atomic force microscopy, transmission electron microscopy, Raman and x-ray photoelectron spectroscopy measurements. The prepared Mo 1-x W x S 2 thin films are used as hydrogen evolution reaction (HER) catalyst electrodes for water splitting. The Mo 0·3 W 0·7 S 2 thin film catalyst shows an overpotential of 345 mV at a current density of 10 mA cm−2 and the corresponding Tafel slope of 169 mV dec−1 in 0.5 M sulfuric acid. The results will provide a facile method to deposit MX 2 thin films. MX 2 (M = Mo, W) are a class of two-dimensional materials with layered structure. Due to their unique physicochemical properties, MX 2 have attracted great attention in various fields. Chemical solution deposition (CSD) method shows that high-quality MS 2 films can be used in a variety of electronic devices. Here, Mo 1-x W x S 2 (0 ≤ x ≤ 1) thin films are firstly designed and prepared. The prepared films were dense and uniform with 2H phase. As HER catalyst electrodes for water splitting, the Mo 0·3 W 0·7 S 2 thin film catalyst shows an overpotential of 345 mV at a current density of 10 mA cm−2 and the corresponding Tafel slope is 169 mV dec−1 in 0.5 M sulfuric acid. The results will provide a facile method to prepare large-area two-dimensional transition metal dichalcogenides thin films with low cost. [Display omitted] • MS 2 (M = Mo, W) thin films were deposited by chemical solution deposition method. • The phases and microstructures were investigated for dense and uniform with 2H phase. • The prepared Mo 1-x W x S 2 thin films shows promising HER activities. • A facile method for low cost and large-area two-dimensional transition metal chalcogenide films was investigated. [ABSTRACT FROM AUTHOR]

In this study, novel compositionally graded tungsten alloys incorporating ceramics were prepared using mechanical alloying and pressure-assisted vacuum hot press (VHP) sintering. Three distinct tungsten compositions (W1, W2, and W3) were developed with varying alloying elements and reinforcements, were stacked layer-wise, and then sintered using VHP. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques were employed to analyze the morphology and microstructural features of synthesized alloys. The effect of alloying elements and reinforcements on mechanical properties and wear behavior was examined. The results showed improvement in mechanical characteristics and enhanced wear resistance of the compositionally graded tungsten alloys. The hardness was increased due to the formation of carbide phases during milling and sintering. The W1 side exhibited a hardness of 8.4 GPa, while the W3 side reached a hardness of 13.3 GPa. Additionally, the wear behavior of both sides (W1 and W3) was also investigated under different applied loads. At a load of 10 N, the W1 surface exhibited a minimum specific wear rate of 3 × 10−6 mm3/Nm, attributed to the presence of MWCNTs and WC phase. However, the W3 surface reinforced with TiC and cBN showed a minimum specific wear rate of 9 × 10−7 mm3/Nm at a higher load of 20 N. This indicates that the W3 side possessed superior hardness and wear resistance ability as compared to the W1 side of compositionally graded tungsten alloys. The novel compositionally graded approach is useful for developing tungsten alloys with tailored mechanical properties for wear resistance applications. [ABSTRACT FROM AUTHOR]

The burst of edge‐localized modes (ELMs) leads to an increase in the energy and particle fluxes to the divertor target. Tungsten (W) is chosen as the primary candidate material for plasma‐facing components (PFCs) in the future fusion devices, and EAST has already upgraded all divertors to use W. Therefore, understanding tungsten target erosion during ELMs and finding the correlation between erosion rate and key ELM parameters are crucial for steady‐state operation. In this work, based on the Vlasov–Poisson model (VPM), we develop a one‐dimensional kinetic parallel transport code to investigate the parallel transport of particles in the EAST device during ELMs and the resulting target erosion. The EAST experiment (#102182) is simulated by VPM code. The simulation results are compared with experimental data as well as free‐stream model (FSM) calculation, showing the accuracy of the code. Considering the presence of lithium (Li) impurities in EAST discharge, the erosion of the W target is simulated. The results indicate that during the burst of ELM, the total average tungsten erosion rate, ΓtotalAVG$$ {\Gamma}_{total}^{AVG} $$, is determined by both deuterium (D) and Li ions. D ions dominate the erosion when the ELM frequency (fELM) is low (ranging from 50 to 175 Hz), while Li impurities become more important than D+ in high‐frequency ELMs (fELM > 175 Hz). As fELM increases, the time‐averaged erosion of the W target first increases and then decreases. Therefore, the reduction of W erosion benefits from high‐frequency ELMs, with impurity ions being the primary contributor to the erosion. [ABSTRACT FROM AUTHOR]

W-(0, 0.1, 0.3, 0.5) wt.% Hf (mass fraction, wt.%) materials were fabricated by the powder metallurgy method and hot rolling. The microstructure, mechanical properties, and high-temperature stability of alloys with varying compositions were systematically studied. The active element Hf can react with the impurity O segregated at the grain boundary to form fine dispersed HfO2 particles, refining the grains and purifies and strengthening the grain boundary. The average size of the sub-grains in the W-0.3 wt.% Hf alloy is 4.32 μm, and the number density of the in situ-formed second phase is 6.4 × 1017 m−3. The W-0.3 wt.% Hf alloy has excellent mechanical properties in all compositions of alloys. The ultimate tensile strength (UTS) is 1048 ± 17.02 MPa at 100 °C, the ductile fracture occurs at 150 °C, and the total elongation (TE) is 5.91 ± 0.41%. The UTS of the tensile test at 500 °C is 614 ± 7.55 MPa, and the elongation is as high as 43.77 ± 1.54%. However, more Hf addition will increase the size of the second-phase particles and reduce the number density of the second-phase particles, resulting in a decrease in the mechanical properties of the tungsten alloy. The isochronal annealing test shows that the recrystallization temperature of W-Hf alloy is 1400 °C, which is 200 °C higher than rolling pure tungsten. [ABSTRACT FROM AUTHOR]

Lightweight applications in aerospace and automotive fields generally dictate the joining of dissimilar materials. Such lightweight materials are also finding applications in bio-implant-related applications. This study aims to determine the best possible combination of process parameters to ensure good joints of AZ31B alloy with Ti-6Al-4V alloy sheets. The defects associated with the joints are also discussed in detail. While choosing the level of current for this dissimilar material combination, care should be exercised. A low level of current (50 A) induces problems associated with poor wettability of magnesium, whereas a high current (75 A) leads to the excessive evaporation of magnesium. Macroscopically good-quality joints are processed with a welding current of 60 A and a welding speed of 0.13 m/min. During tensile-shear testing, good quality joints could sustain the ultimate load of 2073 N, while similar joints at the same parameter with microporosities have failed at 985 N. Defect-free joints have exhibited a 110% increase in joint strength when compared with the strength of the joints having microporosities at the interface. [ABSTRACT FROM AUTHOR]

This study investigated the viability of Hf and/or W doping in Li7La3Zr2O12 (LLZO) through an alkoxide derived sol-gel process aimed at stabilizing the ion-conductive cubic garnet phase. Results revealed that Hf doping tends to favor the tetragonal garnet phase, while co-doping with Hf and W effectively stabilizes the cubic garnet structure. This stabilization is attributed to the similar ionic radii of Hf4+ (0.71 Å) and the slightly smaller W6+ (0.62 Å) compared to Zr4+ (0.72 Å), considering charge neutrality. In both doping scenarios, a coexisting Li-deficient pyrochlore phase is observed, likely due to the use of HfCl4 and WCl6 as starting reagents in the alkoxide process, which results in reduced Li-coordinated carboxyl sites attached to chelated Zr alkoxide. However, increasing the Li excess content above 30% effectively eliminates the pyrochlore phase, thus stabilizing the cubic garnet phase. Impedance measurements conducted on Hf-doped LLZO and Hf,W co-doped LLZO (with 40% excess Li) sintered ceramics reveal a significant enhancement in bulk ion conductivity, with the Hf,W co-doped LLZO pellet exhibiting two orders of magnitude higher conductivity (1.09 × 10−4 S cm−1). This finding confirms the stability of the cubic phase even with partial substitution of W and with 40% excess Li. [ABSTRACT FROM AUTHOR]

In high-tech areas such as nuclear fusion, aerospace, and high-performance tools, tungsten and its alloys are indispensable due to their high melting point, low thermal expansion, and excellent mechanical properties. The rise of Additive Manufacturing (AM) technologies, particularly Laser Powder Bed Fusion (L-PBF), has enabled the precise and rapid production of complex tungsten parts. However, cracking and densification remain major challenges in printing tungsten samples, and considerable efforts have been made to study how various processing conditions (such as laser power, scanning strategy, hatch spacing, scan speed, and substrate preheating) affect print quality. In this review, we comprehensively discuss various critical processing parameters and the impact of oxygen content on the control of the additive manufacturing process and the quality of the final parts. Additionally, we introduce additive manufacturing-compatible W materials (pure W, W alloys, and W-based composites), summarize the differences in their mechanical properties, densification, and microstructure, and further provide a clear outlook for developing additive manufactured W materials. [ABSTRACT FROM AUTHOR]

The present study reports the feasibility of a metal hydride (MH) purification technology employed for hydrogen produced via SRM using Cu/ZnO/Al 2 O 3 catalysts. The catalysts were synthesized by using the coprecipitation method and characterized by various techniques such as XRD, BET, FESEM, FETEM, EDX, XPS, TGA, FTIR, TPR and N 2 O chemiosorption. SRM was carried out under varying operating conditions viz., temperature 200–320 °C, water to methanol molar ratio (W/M) 1–1.7, and a feed flow rate (F M /W) 2.78–27.78 mmol·min−1g−1. Increasing the reaction temperature raised the methanol conversion rate, reaching 100 % at 300 °C, but it simultaneously promoted the formation of CO via rWGS. The increase in W/M ratio increases the methanol conversion rate while reducing the CO selectivity. The impact of feed flow rate (F CH3OH /W cat) on conversion and selectivity revealed that both methanol conversion and CO selectivity decreased at higher feed flow rates, but the rate of hydrogen production increased significantly. Specifically, raising F CH3OH /W cat from 2.78 to 27.8 mmol·min−1g−1 led to a decline of methanol conversion from 97% to 30% and CO selectivity from 0.8 % to 0 %, but the hydrogen production rate was increased from 180 to 570 mL min−1g−1 at 280 °C. The integration of MH based purification system to the production line resulted in the production of highly pure hydrogen (nearly 99% purity) using low-grade heat input (50–60 °C), for an impurity range of up to 40%. [Display omitted] • The Cu/ZnO/Al 2 O 3 catalyst was synthesized by using the coprecipitation method. • Catalyst was characterized using XRD, BET, FESEM, FETEM, EDX, XPS, TGA, and FTIR. • Cu/ZnO/Al 2 O 3 was tested for SRM reaction under various operating conditions. • Metal hydride-based hydrogen purification was employed for H 2 purification. • TCD was employed to analyize the gas composition during H 2 production and purification. [ABSTRACT FROM AUTHOR]

The main purpose of this work is to optimize the mechanical properties of tungsten–copper (W–Cu) nanocomposite fabricated by the sintering process. For this purpose, the parameters of sintering temperature, sintering time and weight percentage of copper were selected to optimize the compression strength, impact strength, hardness and corrosion resistance of the W–Cu nanocomposite using the desirability function procedure and response surface method. The analyses of transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) were also performed to examine the microstructure of W–Cu nanocomposite. The results exhibited that a rise in the sintering temperature from 1000∘C to 1150∘C significantly enhanced the impact strength of W–Cu nanocomposite, while a rise in the sintering temperature from 1150∘C to 1300∘C deteriorated the impact strength. Moreover, the compression strength and hardness of the W–Cu nanocomposite continuously improved by elevation of sintering temperature from 1000∘C to 1300∘C. A rise in the amount of Cu from 20 wt.% to 40 wt.% led to a reduction in the hardness of the W–Cu nanocomposite, while a rise of Cu content improved the impact and compression strengths. The results also indicated that the mechanical properties of W–Cu nanocomposite enhanced simultaneously by using 27 wt.% Cu at sintering temperature of 1197∘C and sintering time of 2.7 h. The samples sintered at the optimal conditions indicated a higher corrosion resistance than that sintered at the initial conditions. [ABSTRACT FROM AUTHOR]

As the penetration technology develops and the projectile velocity increases, it becomes imperative to investigate the protection mechanism of high-performance ceramic under hypervelocity impact. The impact process of tungsten alloy projectile penetrated into B 4 C–TiB 2 –SiC composite ceramic target using ballistic test and finite element simulation at an ultra-high velocity of 2154 m/s was researched in the present study. Additionally, the protection mechanisms were described in terms of the morphology of target damage, the behavior of projectile kinetic energy dissipation, and the temperature field cloud. The findings from the ballistic experiments highlighted that the formation of macro-damage areas (concentrated damage, cone crack, circumferential crack, and radial crack areas) and micro-fragmentation zones could consume a significant amount of impact energy. The mixed fracture mode and the typical inelastic deformation characteristics (dislocations and micro-twinning) contributed to the energy dissipation. Simulation results indicated that the surface dwell effect of the projectile exhibited the highest rate of energy consumption. Furthermore, the temperature field results indicated that the maximum temperature on composite ceramic surface could reach 2310 K, which was below the melting point of B 4 C ceramic (2723 K). However, this temperature could cause the melting of the majority of metal materials. Therefore, ceramic materials exhibited a significant advantage under conditions of ultra-high impact velocities. [ABSTRACT FROM AUTHOR]

Despite having otherwise outstanding hardness and oxidation resistance, CrAlN-based hard coatings are limited by poor fracture toughness and high friction. Although incorporating alloying elements such as C and Magnéli phase-forming elements like V, W, Nb, etc, offer one opportunity for additional toughness and low friction, it requires significant and undesirable compromises to high-temperature performance. Therefore, this work explores an alternative, facile route to achieve ultrastrong-tough CrAlN-based coatings with low friction by incorporating Y. The results indicated that the doped Y elements primarily dissolved in the CrAlN crystalline lattice. Increasing the Y content from 0 to 2 at.% resulted in a change in preferred orientation from (111) to (200), accompanied by a crystal transition from typical columnar grains to unusual equiaxed grains. Notably, when the Y content was about 1.2 at.%, the coating exhibited the maximum toughness of 9.65 MPa·m1/2, almost 2 times larger than that of pure CrAlN coating. Additionally, this coating demonstrated a high hardness of 36.7 GPa and a reduced coefficient of friction (COF) of 0.32. These improvements were attributed to the synergistic contribution of the ultrastrong-tough capability and the formation of Cr 2 O 3 lubricating phases, facilitated by the small amount of Y doping. [ABSTRACT FROM AUTHOR]

In the current study, micro-electric discharge drilling (µEDD) is conducted on a titanium grade 2 alloy using a tungsten carbide (WC) tool electrode of 496 µm diameter. Capacitance, voltage, and feed rate are selected as machining variables to conduct the experiments based on the full factorial experimental design method. Overcut, material removal rate (MRR), circularity, and hole taper are considered as performance measures. Furthermore, overall evaluation criteria (OEC) is utilized for multiple-objective optimization by allotting varying and equal weight percentages to each response measure. The results of OECs are compared with a revolutionary heuristic multi-objective genetic algorithm (MOGA), resulting in a similar optimal parametric combination and close response measures are obtained. Micrographic investigation demonstrates that at lower capacitance and voltage levels, there is less burr formation, recast layer, and circularity error. Moreover, FESEM and EDS analyses are employed to investigate the machined surface topology and elemental composition respectively. [ABSTRACT FROM AUTHOR]

The development of disruptive artificial neural networks (ANNs) endowed with brain-inspired neuromorphic capabilities is emerging as a promising solution to deal with the challenges of the artificial intelligence era. The fabrication of robust and accurate ANNs is strongly associated with the design of new electronic devices. The intriguing properties of memristors render them suitable as building blocks within ANNs. However, the impact of the operating electrodes on the dynamics of the switching process and the relaxation effect remains elusive. It is, thus, apparent that a deep understanding of the underlying electrochemical metallization mechanism that affects the formation of the conductive filament is of great importance. Along these lines, in this work, the impact of various materials as inert electrodes (Pt NPs, ITO, n++ Si, TiN, and W) on tuning the switching mode of low power SiO2-based conductive bridge random access memory devices was systematically investigated. A comprehensive model was applied to interpret the threshold and bipolar switching patterns and shed light on the respective physical mechanisms. The model incorporated the different coefficients of thermal conductivity of the various materials and attempted to associate them with the Soret coefficient and the activation energy of thermophoresis to interpret the experimental outcomes. Our work provides valuable insight for the realization of memristive devices with tunable properties, which can be directly leveraged for implementing a variety of neuromorphic functionalities, such as synaptic plasticity and spike generation. [ABSTRACT FROM AUTHOR]

Context: This research aims to offer a deeper understanding of the bonding interactions between M-Se and M-CO and how these interactions change across the group 6 transition metal series: [Se2M3(CO)10]2- (M = Cr, Mo, W). It also seeks to explore the impact of carbonyl groups on M-M interactions within the clusters. Seven criteria, which are based on QTAIM properties, have been considered and compared with the corresponding criteria in other transition metal clusters. The results confirm that no such bond critical points or bond baths occur between transition metals, which instead have 5c–7e bonding interactions delocalized over their five-membered M3(μ-Se)2 ring, as evidenced by the non-negligible nonbonding delocalization indices. The topological properties of three bond clusters, Cr-Se, Mo-Se, and W-Se, resemble those of "intermediate closed shell characters," which combine covalent and electrostatic properties. Source function calculations indicated that the bonded Se atom contributed the most to each Cr-Se and Mo-Se bcp. The OCO atoms and nonbonded Se atoms also contributed to some extent. However, metal atoms act as sinks rather than as sources of electron density. In contrast, the majority of the metal atoms, both bonded and nonbonded, contribute to Cr-W bcps. Analysis of the delocalization indices δ(M...O) in the three clusters indicates that CO significantly contributes to Cr π-back donation in cluster 1. In contrast, no π-back donation occurs from CO to Mo or W in clusters 2 or 3, respectively. Methods: The B3P86 hybrid functional was used for computations in the Gaussian 09 software. The LanL2DZ basis set was employed for Cr, Mo, and W, while the 6-31G (d, p) basis set was used for C, O, and Se atoms. We performed QTAIM analysis using the AIM2000 and Multiwfn packages, incorporating B3P86/WTBS for Cr, Mo, and W atoms. The 6-311++G(3df,3pd) basis set was used for C, O, and Se atoms. Additionally, we utilized the ELF and SF. [ABSTRACT FROM AUTHOR]

In this study, based on different element configurations within constant atomic ratio of elements, (Ti 0.93 W 0.07 Mo 0.07)C–20%Ni and (Ti 0.93 W 0.07 Mo 0.07)CN 0.3 -20%Ni derived cermets have been synthesized. The basis for the difference in the production route was whether the carbides were formed by carbothermic reaction from the metal oxide together or separately, or in the case of Mo 2 C, the carbide is added to the mixture together with the binder after reduction and just before consolidation. Another basis for the difference was whether the cermet was a carbide or a carbonitride. To investigate the influence of the different production routes, the crystal structure, microstructure, and mechanical properties of the cermets produced were examined using XRD, FESEM, STEM, and Vickers indentation. The XRD spectra of all the cermets were found to be very similar to those of TiC-based cermets, indicating that the additive carbides in the TiC or Ti(CN) phases of the cermets dissolve perfectly during the high vacuum sintering process at 1510 °C. The highest toughness (14.65 MPa m1/2) was obtained in (Ti 0.93 W 0.07) C–8%Mo 2 C–20Ni cermets with a core-rim structure. In addition, the use of nitrogen leads to a dramatic reduction in particle size. The use of molybdenum and tungsten in the form of separate carbides had little effect on limiting the expansion of crystal size and grain size compared to the scenario where the dissolution of these elements took place within the primary core-rim structure. However, in terms of hardness and toughness, it was found that, in addition to grain size, the route taken in the addition of molybdenum and tungsten was also important. [ABSTRACT FROM AUTHOR]

MSi 2 -type multicomponent silicide coatings were prepared on Nb alloys by spark plasma sintering using mixed powders of Mo, Ta, W, Zr, Ti and Si. The coatings were composed of thick outer layers and thin inner layers (interdiffusion zone). A two-phase structure consisting of C11b (Mo,Ta,W,Ti)Si 2 and C40 (Ti,Ta,Zr)Si 2 was observed in the outer layers of all the coatings sintered for holding times ranging from 15 s to 5 min, but the distribution of these elements in each phase gradually became uniform with increasing holding time. The coatings demonstrated excellent protection during oxidation at 1300 °C for 100 h, and a continuous dense oxide scale mainly composed of ZrSiO 4 and SiO 2 was generated. The alternation of heating and cooling during oxidation caused cracks to appear at the interface between the outer layer and inner layer due to a mismatch of thermal expansion coefficients. However, crack extension was observed only along the inner layer toward the interior due to the multicomponent structure of the outer layer of the coating. The microstructural development and oxidation behavior of the coatings were discussed. [ABSTRACT FROM AUTHOR]

In the present investigation, wear-resistant NiFeCuAlCr high entropy alloy claddings were developed on a 1045 steel substrate using the tungsten inert gas welding process. The welding process parameters, such as current and torch scanning speed, were varied to study the effect of heat input on the microstructure and wear properties of the cladding. The wear behaviour of cladding was examined using a pin-on-disc wear tribometer at room temperature. The XRD, FE-SEM, optical microscopy and EDS analyses were performed to characterize the claddings. The S1 cladding fabricated with a welding current of 90 A and torch speed of 150 mm/min exhibited microhardness and weight loss of 702.4 HV0.3 and 7.9 mg, respectively. Whereas, the S7 cladding developed using the current of 110 A and torch speed of 150 mm/min showed microhardness and weight loss of 617.8 HV0.3 and 24.3 mg, respectively. The S1 cladding exhibited a dense equiaxed-grained microstructure with a small heated affected zone of 14.45 mm2 owing to minimum heat input. However, the S7 cladding showed a coarse columnar grain structure and a large heated affected zone of 27.80 mm2 due to the higher heat input. The equiatomic composition claddings developed at different parametric settings showed 2.14-6.60 times improved wear resistance compared to the substrate due to fine-grain microstructure and high hardness. Microstructural investigation of the worn-out surfaces revealed the presence of wear debris, minor deeper groves, and shallow groves in S1 cladding due to the abrasion. In contrast, the S7 cladding showed micro-cracking, severe plastic deformation, and voids formation due to the combined abrasion and adhesive wear. [ABSTRACT FROM AUTHOR]

In this article, we investigate the potential feasibility of new Janus XMPYS (X = Se, Te; M = Mo, W; Y Al, Ga) monolayers using first-principles calculations. All eight studied monolayers are shown to be direct semiconductors with moderate bandgaps ranging from 1.30 eV to 1.47 eV. The asymmetric structure of Janus XMPYS together with the presence of heavy transition metals (M = Mo, W) results in the considerable valley and Rashba spin-splittings desirable for valleytronic and spintronic applications. It is also shown that strain can be used to modulate the spin-related properties of the proposed structures. Among XMPYS monolayers, the four with X = Se meet the band alignment requisite for overall water splitting. Moreover, these monolayers are predicted to have excellent solar-to-hydrogen efficiency of 25.61%–28.08%. Excitingly, it is found that by applying tensile strain an impressive efficiency of 39% can be achieved in SeWPAlS and SeWPGaS monolayers. • The spintronic and photocatalytic properties of XMPYS monolayers are investigated. • All studied monolayers are direct semiconductors with bandgaps in the range of 1.3–1.47 eV. • Broken mirror and inversion symmetry lead to Rashba and valley spin-splittings. • The SeMPYS monolayers satisfy the band alignment requirement for overall water splitting. [ABSTRACT FROM AUTHOR]

This study investigates the phase composition, microstructure, and their influence on the properties of Mo-W-C nanocomposite films deposited by dual-source magnetron sputtering. The synthesised films consist of metal carbide nanograins embedded in an amorphous carbon matrix. It has been found that nanograins are composed of the hexagonal β-(Mo2 + W2)C phase at a low carbon source power. An increase in the power results in the change in the structure of the carbide nanoparticles from a single-phase to a mixture of the β-(Mo2 + W2)C and NaCl-type α-(Mo + W)C(0.65≤k≤1) solid-solution phases. The analysis of electrical properties demonstrates that the nanograin structure of the films favours the occurrence of hopping conductivity. The double-phase structure leads to a twofold increase in the relaxation time compared to the single-phase one. Films with both types of nanograin structures exhibit tunnelling conductance without the need for thermal activation. The average distance between the potential wells produced by the carbide nanograins in nanocomposite films is approximately 3.4 ± 0.2 nm. A study of tribomechanical properties showed that Mo-W-C films composed of a mixture of the β-(Mo2 + W2)C and α-(Mo + W)C(0.65≤k≤1) phases have the highest hardness (19–22 GPa) and the lowest friction coefficient (0.15–0.24) and wear volume (0.00302–0.00381 mm2). Such a combination of electrical and tribomechanical properties demonstrates the suitability of Mo-W-C nanocomposite films for various micromechanical devices and power electronics. [ABSTRACT FROM AUTHOR]

Aluminum/polytetrafluoroethylene (Al/PTFE) is an impact‐initiated material that is extensively utilized in military and civilian applications due to its insensitivity, high energy density and ease of manufacturing. To increase both its compressive strength and energy density, Al/PTFE was doped with various amounts of W and CuO particles. These polymer composites exhibit elastoplastic properties, as well as significant strain hardening and strain‐rate hardening during compression deformation. At a strain rate of 5000 s−1, the compressive strength of the Al/PTFE/W and Al/PTFE/CuO specimens with an additive content of 30% reaches a peak of 194.1 and 189.2 MPa, which corresponds to an increase of 40.3% and 36.8%, respectively, compared with the compressive strength of Al/PTFE (138.3 MPa). The homogeneous bonding strength between the additives and PTFE and the fact that the elastic PTFE nanofibers inhibit the extension of microcracks are the main mechanical strengthening mechanisms. The reaction of the composites under high‐speed impact is violent and accompanied by sputtering sparks, and the reaction efficiency was determined using an improved drop‐hammer apparatus. As the W content increases, the impact reactivity of Al/PTFE/W decreases monotonically. However, as CuO content increases, the reaction intensity of Al/PTFE/CuO initially increases, and then decreases. At a CuO content of 30%, the energy release efficiency of Al/PTFE/CuO reaches its maximum (10.49%), which is 84.4% higher than that of Al/PTFE. TG‐DSC and XRD tests were performed to analyze the pyrolysis process and elucidate the reaction mechanism. A gas–solid chemical reaction model was developed, and the reactivity arises from multiple factors. Highlights: Typical elastoplastic characteristics as well as strain hardening and strain‐rate hardening were observed.The mechanical strengthening effect of W particles is higher than that of CuO particles of Al/PTFE specimen.The addition of W particles decreases the impact reactivity, but the addition of CuO particles improves the energy density of Al/PTFE.The reaction efficiency of Al/PTFE/CuO reaches a peak of 10.49%, which increased by 84.4% compared with that of Al/PTFE. [ABSTRACT FROM AUTHOR]

The recent discovery of ferroelectric properties in HfO2 has sparked significant interest in the fields of nonvolatile memory and neuromorphic computing. Yet, as device scaling approaches sub-nanometer dimensions, leakage currents present a formidable challenge. While tungsten (W) electrodes are favored over traditional TiN electrodes for their superior strain and interface engineering capabilities, they are significantly hampered by leakage issues. In this study, we elucidate a positive feedback mechanism attributable to W electrodes that exacerbates oxygen vacancy defects, as evidenced by density functional theory computations. Specifically, intrinsic oxygen vacancies facilitate the diffusion of W, which, in turn, lowers the formation energy of additional oxygen vacancies. This cascade effect introduces extra defect energy levels, thereby compromising the leakage characteristics of the device. We introduce a pre-annealing method to impede W diffusion, diminishing oxygen vacancy concentration by 5%. This reduction significantly curtails leakage currents by an order of magnitude. Our findings provide a foundational understanding for developing effective leakage suppression strategies in ferroelectric devices. [ABSTRACT FROM AUTHOR]

Tungsten heavy alloys (WHAs) have superior usage performance in various applications and are expected to be used as key components in nuclear energy, aerospace and precision instruments. As a strain-rate sensitive material, the material properties of WHA will change greatly with different grinding parameters during processing. However, most of the existing material removal models are established based on the static properties of the material. The precision grinding of WHA still lacks theoretical guidance. In this research, the effects of strain, strain rate, and temperature on the dynamic properties of WHA under high temperature and high pressure during face grinding are considered. The maximum undeformed chip thickness model for vertical-spindle face grinding with cup wheels is established. The relationship between the undeformed chip thickness, grinding quality, and grinding parameters was investigated. Experimental results show that the maximum undeformed chip thickness under the same conditions is 3.16 times smaller than conventional grinding, and the critical strain rate for ductile-brittle transformation is about 1.46 × 107 s−1. The grinding specific energy of WHA decreases with the increase of the maximum undeformed chip thickness and decreases with the increase of the material removal rate, reaching a minimum of 121.6 J/mm3. This study not only provides a new method for predicting the grinding condition of WHAs but also enhances the understanding of the cup wheel face grinding process and provides theoretical guidance for reducing the machining damage of WHA. [Display omitted] • The maximum undeformed chip thickness model (UCT) for the vertical-spindle face grinding (VSFG) is established. • The critical UCT model for VSFG considering the effects of strain, strain rate, and temperature is established. • The criterion for determining the ductile-brittle transition in tungsten heavy alloy grinding under VSFG is obtained. • The critical strain rate for ductile-brittle transformation is given. [ABSTRACT FROM AUTHOR]

To investigate the influence of different rhenium contents on the helium desorption behavior in tungsten–rhenium alloys, pure tungsten and tungsten–rhenium alloys were irradiated with helium under the same conditions. All irradiated samples were characterized using TDS and DBS techniques. The results indicate that the addition of rhenium can reduce the total helium desorption quantity in tungsten–rhenium alloys and slightly accelerate the reduction in the concentration of vacancy-type defects accompanying helium dissociation. The desorption activation energy of helium is approximately 2 eV at the low-temperature peak (~785 K) and about 4 eV at the high-temperature peak (~1475 K). An increase in rhenium content causes the desorption peak to shift towards higher temperatures (>1473 K), which is attributed to the formation of the stable complex structures between rhenium and vacancies. Besides, the migration of He-vacancy complexes towards traps and dynamic annealing processes both lead to the recovery of vacancy-type defects, resulting in a decrease in the positron annihilation S parameters. [ABSTRACT FROM AUTHOR]

Using the solid-state reactions method Na0.55(Co,M)O2 (M = Cr, Ni, Zn, W, and Bi) ceramics were prepared and their crystal structure, microstructure, electrophysical, thermophysical, and thermoelectric properties were studied. Doping of Na0.55CoO2 by transition or heavy metal oxides led to the increase in the grain size of ceramics, a decrease in electrical resistivity and thermal diffusivity values, and a sharp increase in the Seebeck coefficient, which resulted in essential enhancement of their thermoelectric properties. The largest power factor (1.04 mW/(m·K2) at 1073 K) and figure of merit (0.702 at 1073 K) among the studied samples possessed the Na0.55Co0.9Bi0.1O2 compound, which also demonstrated the highest values of the Seebeck coefficient (666 μV/K at 1073 K). The obtained results show that the doping of layered sodium cobaltite by different metal oxides allows for improving its stability, microstructure, and functional properties, which proves the effectiveness of the doping strategy for developing new thermoelectric oxides with enhanced thermoelectric performance. [ABSTRACT FROM AUTHOR]

Transition metal dichalcogenides (TMDCs), represented by MX2 (where M = Mo, W and X = S, Se, and Te), and more recently, their moiré superlattices (i.e., formed by superimposing layers of TMDCs with different rotation angles) have attracted considerable interest due to their excellent physical properties and unique nanoscale functionalities. Compared to graphene, the literature indicates that TMDCs offer a competitive advantage in optoelectronic technologies, primarily owing to their compositionally controlled non-zero bandgap. These two-dimensional (2D) nanostructured single or multiple layers exhibit remarkable properties that differ from their bulk counterparts. Moreover, stacking different TMDC monolayers also forms heterostructures and introduces unique quantum effects and extraordinary electronic properties, which is particularly promising for next-generation optoelectronic devices and photo(electro)catalytic applications. Therefore, in this review, we also highlight the new possibilities in the formation of 2D/2D heterostructures of MX2-based materials with moiré patterns and discuss the main critical challenges related to the synthesis and large-scale applications of layered MX2 and MX2-based composites to spur significant advances in emerging optoelectronic and photo(electro)catalytic applications. [ABSTRACT FROM AUTHOR]

Objectives The purpose of a parallel-hole collimator in a scintillation camera system is to transmit only those photons that have an emission angle close to the direction of the hole. This makes it possible to receive spatial information about the origin of the emission, that is, radioactivity decay. The dimension, shape, and intrahole thickness determine the spatial resolution and, by a tradeoff, sensitivity. The composition of the collimator material also plays an important role in determining a proper collimator. In this study, we compared tungsten alloys as a potential collimator material replacement for the conventional lead antimony material used in most of the current camera systems. Materials and Methods Monte Carlo simulations of a commercial scintillation camera system with low energy high resolution (LEHR), medium-energy (ME), and high-energy (HE) collimators of lead, tungsten, and tungsten-based alloy were simulated for different I-131, Lu-177, I-123, and Tc-99m sources, and a Deluxe rod phantom using the SIMIND Monte Carlo code. Planar images were analyzed regarding spatial resolution, image contrast in a cold source case, and system sensitivity for each collimator configuration. The hole dimensions for the three collimators were those specified in the vendor's datasheet. Results Using Pb, W, and tungsten alloy (Wolfmet) as collimator materials, the full width at half maximum (FWHM) measures for total counts (T) for LEHR with Tc-99m source (6.9, 6.8, and 6.8 mm), for ME with Lu-177 source (11.7, 11.5, and 11.6 mm), and for HE with I-131 (6.2, 13.1, and 13.1 mm) were obtained, and the system sensitivities were calculated as 89.9, 86.1, and 89.8 cps T /MBq with Tc-99m source; 42.7, 17.4, and 20.9 cps T /MBq with Lu-177 source; and 40.1, 69.7, and 77.4 cps T /MBq with I-131 source. The collimators of tungsten and tungsten alloy (97.0% W, 1.5% Fe, 1.5% Ni) provided better spatial resolution and improved image contrast when compared with conventional lead-based collimators. This was due to lower septal penetration. Conclusion The results suggest that development of a new set of ME and HE tungsten and tungsten alloy collimators could improve imaging of I-131, Lu-177, and I-123. [ABSTRACT FROM AUTHOR]

Oxidation behavior at 800°C, 1000°C and 1200°C of nano-Cr2O3 dispersed W-Zr alloys fabricated using mechanical milling followed by conventional sintering at 1500°C in inert atmosphere is discussed. Three different alloys were designated as W-0.5Zr-1Cr2O3 (alloy A), W-0.5Zr-2Cr2O3 (alloy B), and W-1Zr-1Cr2O3 (alloy C) (in wt.%). The application range of W is greatly restricted by oxidation, necessitating the use of suitable alloying and dispersion techniques. Upon exposure to 800°C, alloy A exhibited the highest level of oxidation resistance, whereas alloy B demonstrated superior performance at 1000°C and 1200°C. This enhanced oxidation resistance in alloy B can be attributed to its microstructure, characterized by a fine and uniform distributed Cr2O3-rich and Zr-rich phase. At 800°C, protection against oxidation primarily resulted from improved densification, enhanced adhesion of oxide scale with the matrix phase, and decreased volatilization of WO3. However, at ≥ 1000°C, the development of Cr2WO6 seems to play a vital role. Higher activation energy was also observed in the current alloys compared to pure W, attributed to the combined influence of Cr2O3 and Zr dispersion. This study offers valuable insights into the development of oxidation-resistant alloys through Cr2O3 dispersion, particularly applicable for high-temperature applications. [ABSTRACT FROM AUTHOR]

In this study, the composition-dependent properties of a new type of NiTiCuW shape memory alloy were investigated. The martensite transformation temperature was measured by differential scanning calorimetry, crystal structure by XRD, microstructure analysis by microhardness measurement and scanning electron microscopy. The increase in Cu/W ratio in the composition decreased the transformation temperature below room temperature, and the alloys are in austenite phase at room temperature. X-ray results also supported the thermal measurement results. Moreover, a difference in the microhardness values of NiTiCuW alloys was observed, which exhibited martensite phase and austenite phase at room temperature. [ABSTRACT FROM AUTHOR]

With the continuous evolution and development, smelting technology has gradually matured. After the tungsten is extracted through the smelting process, a large amount of tungsten smelting slag is piled up, which has a negative impact on human production and life. The composition of tungsten smelting slag is complex, and there is leaching agent remaining on the surface, which is rich in valuable metals, so the selection of suitable process to recover the valuable metals in tungsten smelting slag can not only reduce the solid waste emission, reduce the pollution of soil and water resources, but also improve the resource utilization rate of valuable metals and reduce the cost of tungsten smelting slag treatment. The reduction, environmental protection and resource treatment of tungsten smelting slag are the key parts of carbon emission reduction in the tungsten industry. The recovery of metal tin out of a mixed tungsten smelting slag from treatment of wolframite and scheelite was experimentally studied. In this slag about 87.59% of the tin in the tungsten smelting slag was distributed in the -0.045 mm particle size, which was difficult to sort. The Knelsen vertical centrifugal separator was selected as the roughing equipment, and the optimal conditions for the roughing process were determined by step-by-step optimization experiments, which were 78.15% -0.038 mm of the grinding fineness, 15% of the feed concentration, 90 G/s of separation cone speed, and 2.60 L/min of backflush water flow. In order to further improve the tin grade of the rough concentrate, the four selection methods were compared and tested, and finally with the gravity separation process of "one roughing and one cleaning centrifugal separation, shaking table and centrifugal separation after classification", under the feed concentration 15%, the speed of the separation cone 90 G/s and the backflush water flow rate 2.75 L/min, the tin grade of tin concentrate was 4.03% and the tin recovery was 52.41%, which realized the effective recovery of valuable metal tin in tungsten smelting slag, and provided a certain reference for the reduction and resource utilization of the tungsten smelting slag. [ABSTRACT FROM AUTHOR]

Mechanical alloying is a preferred approach for producing tungsten (W)–zirconium (Zr)-based alloys due to their vast difference in melting point and insufficient synergic solubility. This study comprises fabrication of nano-chromium oxide (Cr2O3)-dispersed W-Zr alloys through mechanically alloying for 20 h followed by conventional sintering in inert (argon) atmosphere at 1400 and 1500 °C with a 2-h holding time. Alloys A, B, and C are designated as per the following compositions: 98.5W-0.5Zr-1(Cr2O3), 97.5W-0.5Zr-2(Cr2O3), and 98W-1Zr-1(Cr2O3), respectively. The effects of the Zr and Cr2O3 addition to W and sintering temperature have been discussed in relation to mechanical characteristics. The phase evaluation and microstructural behavior of the powders and sintered samples has been studied using x-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy, respectively. The powder characterization after 20 h of milling through SEM has depicted a homogeneous mixture of Zr and Cr2O3 with W. Combined addition of Zr and Cr2O3 has resulted in a bimodal grain size distribution. The enhanced grain refinement coarse/fine particle count ratio due to mechanical alloying was observed in alloy A after 20 h, which was 1.57 compared to 2.6 in alloy C. The alloy A sintered at 1500 °C exhibited the highest densification (91%), hardness (13 GPa), wear resistance, and compression strength (1.37 GPa) due to better fraction of fine grains, solid solution, and dispersion strengthening compared to other alloys in both sintering temperatures. [ABSTRACT FROM AUTHOR]

The present study deals with, nano-indentation, residual stress and oxidation study of mechanically alloyed powders sintered at 1100 °C and 1150 °C. Investigations were carried out using nanoindentation find elastic energy, nanohardness, elastic modulus (E), Fracture toughness of the alloy. The results of nano-indentation suggest that the sample experiences elastic and plastic deformation during the loading-unloading procedure, and the absence of discontinuity in the load-displacement curve proves that no cracks or brittle fractures are generated in the indents. W78Ni10Nb5Mo5Zr1(Y2O3)1 sintered at 1150 °C exhibits maximum microhardness and elastic modulus which were 19.74 GPa and 834.53 GPa, respectively, as compared to other alloys. There was improvement in fracture toughness with sintering at 1150 °C temperature. Compressive residual stresses generated in sample because of both pressure and temperature applied at same point of time. Reduction in residual stress observed at 1150 °C as compared to 1100 °C temperature of sintering. Oxidation analysis shows formation of oxides at 1000 °C. Each element in alloy forms their respective oxides on reaction with oxygen in air. Higher oxidation resistance shown by sample sintered at 1150 °C temperature. Addition of Y2O3 enhances oxidation resistance of alloys. Sintering at 1150 °C temperature improves oxidation resistance due to enhanced density. [ABSTRACT FROM AUTHOR]

Metal-ceramic composite coatings are produced on the surface of equipment components by laser cladding, improving the abrasive wear resistance of components and extending their service life. However, defects such as brittleness and cracks limit the wide application of metal-ceramic clad coatings in the field of construction machinery. In the present study, a dual-element (Ti/Nb) alloying method is innovatively adopted to regulate the microstructure and mechanical properties of tungsten carbide (WC)-reinforced clad coatings. Experimental results show that with the introduction of Ti/Nb, novel reinforcements are in-situ synthesized in the cladding coatings with two different kinds of morphologies: one is a core-shell carbide with the core of pure TiC and a shell of (Ti,Nb,W)C multiple carbide; the other is a (Ti,Nb,W)C multiple carbide. With 8 wt.% Ti/Nb addition, the newly formed multiple carbides with the appropriate content are well-dispersed and distributed in the clad coating, which effectively transfers load, inhibits the initiation and expansion of micro-cracks, and resists the wear damage of hard abrasive particles, solving the technical problems of the simultaneous improvement of toughness and abrasive wear resistance of metal-ceramic laser cladding coatings. [ABSTRACT FROM AUTHOR]