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Molecular dynamics (MD) simulations are performed to investigate the nanoscale tribology behavior of Ti-based FeCoNiTi High-entropy alloy (HEA) coating through nanoscratching. Three coating interface models, (001) HEA ||(0001) Ti , (001) HEA ||(11 2 ‾ 0) Ti , and (001) HEA ||(1 1 ‾ 00) Ti , are selected to explore the effects cutting depth (D) and cutting velocity (V) of abrasive particles during the nanoscratching process. The results show that the Ti-based HEA coating with the interface (001) HEA ||(0001) Ti has the smallest coefficient of friction (COF) making it most suitable as the coating interface. The increase in V resulted in the increase of the frictional force influenced by the Other structure composed of disordered atoms. Due to the existence of multiple phase structures in the limited area of the coating, dislocation nucleation is difficult and disordered atoms are formed. This is different from the strengthening caused by dislocation accumulation in the scratching region. The HEA coating plays an effective role in protecting the pure Ti substrate. With the protection of HEA coating, dislocation slip and deformation twinning were not observed in the pure Ti substrate. However, dislocation slip are the main plastic deformation mechanisms of uncoated pure Ti. These findings provide a theoretical reference for upgrading the wear resistance of pure Ti with HEA coating and expands the area of application of pure Ti. [Display omitted] • Cutting of depth and velocity affect the friction behavior of Ti-based HEA coating. • Other structure composed of disordered atoms strongly affects the frictional force. • With the protection of HEA coating, the Ti substrate has no plastic deformation. [ABSTRACT FROM AUTHOR]

The tensile deformation behavior is studied in pure titanium (Ti) nanopillars subjected to loading along the [0 0 0 1] orientation based on molecular dynamics (MD) simulations. The double yielding phenomenon is displayed in stress-strain curves when the deformation temperature is less than 380 K. One new type of deformation-induced phase transformation from the hexagonal close-packed (hcp) to face-centered cubic (fcc) phase has been predicted. The effects of temperature and strain rate on this type of phase transformation are systematically investigated. It is revealed that { 1 0 1 ¯ 2 } 〈 1 0 1 ¯ 1 〉 twinning plays an essential role in inducing the phase transformation, which is produced through dislocation glide of multiple Shockley partial dislocations inside the { 1 0 1 ¯ 2 } 〈 1 0 1 ¯ 1 〉 twin. A group of high-density stacking faults is accumulated though the continuous glide of multiple Shockley partial dislocations inside the twinning region, eventually leading to the allotropic phase transformation from the hcp to fcc phase. After twinning, two thermally activated dislocation slip processes compete with one another: Shockley partial dislocations and full dislocation slip. The deformation mechanism changes from phase transformation to dislocation slip when the temperature is higher than 380 K or the strain rate is lower than 10 8 s −1 . The dislocation slip on the { 1 0 1 ¯ 1 } pyramidal plane is clearly observed under tensile loading at higher temperatures. Furthermore, our simulations indicate that the nucleation rate has a strong effect on the deformation mechanism on the nanoscale. [ABSTRACT FROM AUTHOR]

The Charpy impact toughness of Ti–2.5Al–2Zr–1Fe alloy plate with a bimodal and normal grain size distribution was comparatively studied. The sample with the bimodal grain size structure exhibits the larger impact absorbed energy and lower anisotropy than that with the normal grain size structure, which is mainly attributed to the coordination of prismatic slips in the fine α grains and { 10 1 ‾ 2 } 10 1 ‾ 1 deformation twins in the coarse α grains. The current work provides a promising approach for improving impact toughness and reducing anisotropy through microstructure optimization in near-alpha Ti alloys. • An improved impact absorbed energy and decreased anisotropy were obtained in Ti–2.5Al–2Zr–1Fe alloy with bimodal grain size. • The improved impact absorbed energy was attributed to the prismatic slip associated with the twining inducing plasticity. • Microstructural optimization can improve the impact toughness and reduce anisotropy of near-alpha titanium alloys. [ABSTRACT FROM AUTHOR]

The Charpy impact absorbed energy of a hot-rolled Ti–6Al–3Nb–2Zr–1Mo alloy plate with different sampling and notching directions was investigated. Strong anisotropic variations occurred in impact absorption energies due to difference of the α phase crystal orientation and microstructural characteristics along different directions. The higher crack propagation energy of the sampling-notching direction sample (RD-ND) resulted in an impact absorption energy of approximately 2.5 times larger than that of the TD-ND, TD-RD and RD-TD samples. Based on the analysis of the α crystal orientation and the TEM microstructure after impact deformation, it was found that the higher absorption energy of the RD-ND sample was attributed to the activities of a large number of { 10 1 ‾ 0 } ⟨ 1 2 ‾ 10 ⟩ prismatic slips and the resistance created by grain boundaries against crack propagation, which also resulted in the delamination of the impact fracture surface. Finally, the coupling effect of crystallographic texture and microstructural characteristics on the impact deformation mechanisms of the hot-rolled Ti–6Al–3Nb–2Zr–1Mo alloy was described. • A strong anisotropy of the impact energy in A hot-rolled Ti6321 alloy plate is observed due to the coupling effect of the microstructural characteristics and the crystal orientation of the α grains. • The RD-ND orientation sample exhibits the highest impact absorbed energy due to the activity of a large number of { 10 1 ‾ 0 } 1 2 ‾ 10 prismatic slips and the barrier effect of grain boundary on crack propagation during impact loading. • The coupling effect of crystallographic texture and microstructural characteristics on the impact deformation mechanisms were established. [ABSTRACT FROM AUTHOR]

The fatigue crack growth (FCG) behaviors of a twin inducing plasticity (TWIP) Ti-5Al-1 V-Sn-1Zr-0.8Mo (Ti5111) alloy with three typical microstructures were investigated. Compared with the equiaxed and bimodal structures, the lamellar structure exhibited a higher resistance to the FCG rate, but it displayed a lower strength and elongation to failure. Many 10 1 ¯ 2 10 1 ¯ 1 deformation twins (DTs) spanning multiple α/β layers were observed in the lamellar structure near the FCG path. The same type of DT was also observed in the equiaxed structure, although its density was significantly lower than that of the lamellar structure, and no DTs were found in the bimodal structure. The higher resistance to FCG of the lamellar structure results from its large effective microstructural unit size (α colony), which is most favorable to deflecting cracks and increasing crack path tortuosity, and is associated with the blocking effect of deformation twin boundaries on crack propagation. • Compared with equiaxed and bimodal structure, the lamellar structure exhibits the highest resistance to FCG rate. • The high resistance to FCG of lamellar structure is due to the coupling effect of crack deflection and twin boundary barrier. • Deformation twins spanning multiple α/β layers were observed in lamellar structure near the fatigue crack propagation path. [ABSTRACT FROM AUTHOR]

Lexical bundles perform discourse functions and present differing levels of variability, with some slots replaceable by optional words. Incorporating both function and formulaicity perspectives is a promising approach to uncover certain features of these recurrent language patterns. Based on the variability measurement and functional taxonomy proposed by Biber (2009) and Biber et al. (2004), this study compared the extent to which the lexical bundles from research articles of applied linguistics and pharmaceutical sciences are fixed. Thereafter, the lexical bundles were examined across the discourse functions to explore the possible interaction between function and variability. The results indicate that variability shows disciplinary variation, with bundles from applied linguistics articles as a whole being relatively less fixed. In addition, discourse functions are found to be closely associated with variability. These findings shed light on the question of whether lexical bundles are prefabricated patterns and may facilitate the teaching of academic writing at the graduate level. [ABSTRACT FROM AUTHOR]

The influence of microstructure (bimodal and lamellar structure) on the fatigue crack growth (FCG) rate of Ti–6Al–3Nb–2Zr–1Mo alloy was investigated using compact-tension (CT) specimens. The da/dN curves showed that the FCG rate of lamellar structure was slower than that of bimodal structure, especially in the early stage of crack growth. The FCG paths in the early stage were observed by optical microscopy and scan electric microscopy. The results revealed that the FCG paths of lamellar structure were more tortuous than that of bimodal structure. The frequency of crack deflection and bifurcation of the lamellar structure is significantly higher than that of bimodal structure. The dominant mode of crack propagation for bimodal structure is crossing βtrans and αp, and for lamellar structure is crossing α colonies. Fatigue crack growth mechanisms at the early stage have been studied by observation of crystalline orientation near the crack propagation path at the crack tip, in combination with the slip trace analyzing. The results show that the fatigue crack growth directions in αp or βtrans for bimodal structure and α colony for lamellar structure are mostly consistent with that of prismatic or basal plane trace. This indicated that the cracks propagation modes of crossing αp or βtrans in bimodal structure and crossing α colonies in lamellar structure are resulting from the slip band cracking of the microstructure at crack tip, as the evidence of { 10 1 ‾ 0 } 11 2 ‾ 0 prismatic dislocation lines were observed in αp or βtrans for bimodal structure and α colony for lamellar structure by transmission electron microscope (TEM) near the fracture surface. • The da/dN curves showed that the FCG rate of lamellar structure was slower than that of bimodal structure, especially in the early stage of crack growth. • Cracks propagation modes were evaluated by EBSD-assisted slip trace analysis. [ABSTRACT FROM AUTHOR]

Electrochemical N 2 reduction reaction (NRR) has long been regarded as a promising process to generate NH 3 under ambient conditions. Therefore, developing cost-effective and high-performance non-noble-metal catalysts for NRR is highly desirable. Inspired by the biological nitrogenase structure, we here designed and synthesized a catalyst with iron-molybdenum sub-nanoclusters and single atoms on porous nitrogen-doped carbon (FeMo/NC). The catalyst features porous structure beneficial to active site exposure and accessibility to electrolyte as well as FeMo sub-nanoclusters and single atoms enabling to activate N 2 molecular. In situ near-ambient pressure X-ray photoelectron spectroscopy tests reveal that during the process from vacuum to nitrogen saturation, N 2 was close to, adsorbed on and interacted with Fe and Mo in FeMo/NC. The Fe and Mo through electron transfer play a key role in activating the N 2 molecules. Therefore, when tested for NRR, FeMo/NC achieves the maximum Faradaic efficiency (FE) of 11.8 ± 0.8% at −0.25 V and NH 3 yield rate of 26.5 ± 0.8 μg h−1 mg cat. −1 at −0.3 V in neutral electrolyte. Moreover, the catalyst exhibits ignorable variations in the FE and a slight decrease in current density for 100,000 s. This work develops a non-precious bimetallic electrocatalyst with synergetic effect capability for efficient NH 3 production and provides a guideline for the design of efficient and robust catalysts with coexistence of sub-nanoclusters and single atoms. Inspired by the biological nitrogenase, we have designed a novel catalyst composed of FeMo sub-nanoclusters/single atoms on N-doped carbon that can effectively catalyse electroreduction of N 2 to generate NH 3 in neutral media. Image 1 • FeMo sub-nanoclusters/single atoms are developed from the inspiration of biological nitrogenase. • The catalyst shows excellent activity toward neutral NH 3 electrosynthesis. • The catalyst also displays an outstanding stability during the electrolysis. • Near-ambient pressure X-ray photoelectron spectroscopy confirms that the coexistence of Fe and Mo activates the N 2 molecules. [ABSTRACT FROM AUTHOR]

As a novel two-dimensional nanomaterial, MXene is one of the most promising alternative electrode materials due to its large specific surface area, good electrical conductivity, excellent mechanical properties and tunable structure. This paper investigates the electrochemical performance of the MXene materials Zr 2 N and Zr 2 NS 2 as anode materials for lithium and sodium ion batteries. The results showed that on the Zr 2 N monolayer, lithium and sodium ions tended to adsorb at the C site, while on the Zr 2 NS 2 monolayer, lithium and sodium ions tended to adsorb at the B and A sites, respectively. The results of the Charge difference density diagram and Mulliken population analysis show that there is a significant electron transfer between the adsorbed metal ions and the material surface. This indicates that lithium and sodium ions form chemisorption on the Zr 2 N and Zr 2 NS 2 surfaces. The high theoretical specific capacity and low migration barrier suggest that Zr 2 N and Zr 2 NS 2 are promising anode materials for lithium and sodium ion batteries. • The electrochemical properties of Zr 2 N and Zr 2 NS 2 as anode materials for lithium and sodium ion batteries are analyzed and discussed. • The high theoretical specific capacity and low migration barrier suggest that Zr 2 N and Zr 2 NS 2 are promising anode materials for lithium and sodium ion batteries. • It provides positive theoretical guidance for the experiment. [ABSTRACT FROM AUTHOR]

The electronic structure and photocatalytic properties of two-dimensional GaSe/MoS 2 heterostructure are systematically studied by first-principles calculation. It is found that it could be used as a potential visible light catalyst to decompose water into H 2 and O 2. The lattice mismatch rate is 3.55%, and the binding energy was −0.446 eV, indicating that it has a stable configuration. An indirect band gap of 2.255 eV with hybrid HSE06 functional is observed, which falls into a wide range of visible light absorption. It exhibits II-type band alignment and this can promote the spatial separation of photogenerated carriers. In addition, the band edge spans the redox potential of water, indicating that heterostructure can produce hydrogen by photocatalytic decomposition H 2 O. The electrons transfer from GaSe to MoS 2 layer, while the holes do the opposite, thus improving the photocatalytic efficiency. Therefore, GaSe/MoS 2 heterostructure has broad application prospects in photocatalysis. • The GaSe/MoS 2 heterostructure is a very promising photocatalyst. • Work function of a material plays a momentous role in the band alignments. • The density of state can show the mechanism behind the orbital reconfiguration. • Semiconductor photocatalysis is considered as an ideal way to convert solar energy into chemical energy. [ABSTRACT FROM AUTHOR]

• Low-cycle multiaxial fatigue experiments of Q355D notched specimens under different loadings were carried out. • The important factors affecting fatigue life of notched specimens were analyzed by three correlation analysis methods. • A modified MGM (1, N) model was established by fine-tuning the time series of the GM (1, N) model. • A new fatigue life prediction method for notched specimens was proposed. The paper aims to analyze the stress–strain response of building steel under low-cycle multiaxial fatigue and to accurately evaluate the fatigue life of specimens by selecting the more important relevant factors that affect fatigue behavior. Based on this, low-cycle multiaxial fatigue experiments of Q355D notched specimens under different multiaxial loading are carried out. Firstly, the fatigue behavior of notched specimens under different loadings and the relationship between the biaxial strain amplitude ratio and fatigue life are analyzed. Secondly, Grey correlation analysis, Pearson correlation analysis, and Random Forest importance analysis are used to screen out the important factors affecting fatigue life. Finally, the grey MGM (1, N) model is used to predict the fatigue life of notched specimens, and the results show that the predicted life based on Random Forest importance analysis is in good agreement with the experimental life. In this paper, the multiaxial fatigue problem is decoupled into two sub-problems, i.e. screening out related factors and life prediction based on the related factors, which can be used as a reference for life prediction in structural design. [ABSTRACT FROM AUTHOR]

Interfacial segregation engineering is widely used as a means of regulating the strength and toughness of materials. In this paper, the effect of alloying elements on the interfacial segregation and interfacial bonding properties of fcc-Fe/NbC is investigated with the precipitated phase NbC in austenitic heat-resistant steel. The results show that there are eighteen interfacial configurations between the fcc-Fe and NbC phase, and the stability of the interface with Nb terminal is better than that of C terminal according to the calculation results of separation work and interface energy. Al atom is easy to segregate on the surface of austenite, while the alloy elements Mo, Nb, Cr, Ti, Mn, Y and Zr tend to segregate in the austenite matrix. The segregation of alloy elements Mo, Nb, Cr and Ti can enhance the hybridization between the d orbits of Fe and Nb atoms at the interface, thus promoting the bonding strength of the interface, while the segregation of Mn, Al, Y and Zr reduces the covalent interaction of the interface atoms, which weakens the bond strength at the interface. The above results have important practical significance for improving and regulating the composition and interfacial properties of heat-resistant steels. • Six fcc-Fe(111)/NbC(111) interfaces with different interface terminations are studied by first-principles. • The work of separation of the Nb-terminated interface is greater than that of the C-terminated interface. • The interface of the C-terminal is unstable. • Alloying elements affect the bonding strength of interfacial atoms. [ABSTRACT FROM AUTHOR]

In this effort, the influence of alloying element doping on fcc-Fe (111)/NbN (111) interface property is investigated by means of first principles. The interface structure combined with 5-layer fcc-Fe and 7-layer NbN is selected for investigation, because they exhibit characteristic consistent with the bulk counterpart. By calculating the interface energy, separation work and phonon spectra, the results show that interface 6 is stable. The alloying elements are more easily segregated at position 2 in the interface and it is chosen as the object of study. After Co and V doping, the separation work of the interface increases and the interfacial energy decreases. The degree of charge density consumption around them is greater than that of the intrinsic interface, indicating that the covalent bonds between atoms have been enhanced. This indicates that doping with Co and V atoms can improve the stability of the interface, which is consistent with the results towards population analysis and density of states. On the contrary, after doping with Zr, Sc, Y, and Ti atoms, the interatomic covalence weakens and the interface stability decreases. Especially for Y doping, the lowest electron consumption and the smallest electron cloud enrichment in the middle layer can be observed, demonstrating the worst interface stability. This insight has important guiding significance for the interface segregation behavior of alloying elements, and provides a theoretical basis for the development of next generation austenitic stainless steel. • Studied the effect of segregation of alloying elements Ti, Co, Zr, Y, V, Sc on fcc-Fe (111)/NbN (111). • After doping with Co and V atoms, the covalence between atoms is enhanced. • After doping with Co and V atoms, the interface stability can be improved. [ABSTRACT FROM AUTHOR]

Probabilistic fatigue evaluation is the key to ensure the service integrity of large-sized mechanical equipment, but in practical engineering, the probabilistic fatigue models coupled with multiaxial stress conditions and small sample information characteristics are still insufficient. Accordingly, the virtual subsample augmentation method is effectively coupled with the improved Bootstrap method to propose a general probabilistic fatigue evaluation process. Specifically, the random sample regeneration method is first used to expand the small sample fatigue data, and then life distribution information under different stress levels is fused based on the backwards statistical inference method, the P-S-N curve is fitted with the integrated life dispersion information. Secondly, a new fatigue damage parameter based on the inhibition function is proposed to modify the P-S-N curve and predict fatigue life. Meantime, the multiaxial fatigue test of Q355(D) alloy steel with different notch sizes is carried out, and the model is verified in conjunction with existing fatigue test data of TC4-DT alloy and TC4 alloy. The results show that the proposed model has a certain universality for notched specimens, the modified stress field intensity method can accurately characterize the impact of notch and size effects on fatigue damage of specimens. [ABSTRACT FROM AUTHOR]

How to improve the diffusion coefficient of Lithium ions in active materials is very necessary, which is responsible for the electrochemical performance. In this present contribution, LiFe 10/12 Co 1/12 Mn 1/12 P 11/12 S 1/12 O 4 (LF(CM)P(S)O) are designed and the stability, lithium ion diffusion rate, lithium intercalation potential, discharge curve, and electronic performances are systematically explored. The LF(CM)P(S)O shows the better stability with the formation energy of 2.01 eV. The lithium ion diffusion barrier of the system is reduced from 1.02 to 0.57 eV after doping, predicting that the lithium ion diffusion rate in LF(CM)P(S)O is 10 orders of magnitude faster than that of intrinsic system. The characteristic transition from p-type to n-type semiconductor is present due to the doping of S, and the doping of Mn and Co leads to the generation of impurity bands and the reduction of band gap from 3.78 to 0.737 eV. The effective mass of electrons in the doped system is 1.59m 0 , much greater than 1m 0 , which is conducive to the improvement of its conductivity. The charge density difference and electron localization function (ELF) demonstrates that the disappearance of electron enrichment and the decrease of the localization are responsible for the rapid migration of the lithium ion. The high operating voltage, charge-discharge platform of 4.7 V and the voltage difference contribute to the promotion of electrochemical performance, which open a window for the commercialization application of Li-ion battery. [ABSTRACT FROM AUTHOR]

The aim of present research was to investigate the hot tearing susceptibility (HTS) of SiC reinforced Al5Cu matrix composites. The HTS value of Al5Cu was 19.3, and the HTS values were 6.14, 16.05 and 44.98, corresponding to 0.5SiC/Al5Cu, 1SiC/Al5Cu and 2SiC/Al5Cu, respectively. The results indicated that the serious HTS of Al5Cu was obviously improved when the content of SiC particle was less than 1%, especially 0.5% SiC. Grain size and solidification temperature range were two significant factors for the HTS. For composites, SiC served as effective heterogeneous nucleation cores obviously increased the grain refining efficiency. The grain size was 55.24 μm for Al5Cu, the grain size of composites decreased to 42.77 μm (0.5SiC/Al5Cu), 36.19 μm (1SiC/Al5Cu) and 37.42 μm (2SiC/Al5Cu). Solidification temperature range of Al5Cu alloy was 110.49 °C. Compared with Al5Cu matrix alloy, the solidification temperature rang decreased for 0.5SiC/Al5Cu (108.54 °C) and 1SiC/Al5Cu (109.42 °C), but the 2SiC/Al5Cu had large solidification temperature range of 111.99 °C. The HTS improvement was mainly attributed to the refined grain and shortened solidification temperature range, which increased the residual liquid metal feeding property and decreased the shrinkage strain. In addition, the HTS mechanism of composites was discussed in detail. [ABSTRACT FROM AUTHOR]

Precipitated phases are generally considered to be beneficial to mechanical strengthening, while harmful to corrosion resistance. However, this study found that the Ti-induced precipitated Laves phase in FeCrVTi x medium-entropy alloys (MEAs) improves both corrosion resistance and mechanical properties than FeCrV MEA. Results reveal that the selective dissolution of precipitated phase enhances the corrosion resistance by the segregation of TiO 2 and increased V oxide content in the passive film. Only appropriate distribution, size, and content of the precipitated phase induced by specific Ti addition can achieve synergy between corrosion resistance and mechanical properties, suggesting potential reliable materials for nuclear systems. [Display omitted] • The precipitated phase make the synergy of corrosion resistance and mechanical properties in BCC+Laves structure MEAs. • The selective dissolution of the precipitated phase makes TiO 2 segregated at the surface of passive film. • The Ti addition increase the content of V oxides in the passive film to improve the corrosion resistance. • The Ti addition mainly induces precipitation strengthening, grain refinement strengthening to improve mechanical properties. [ABSTRACT FROM AUTHOR]

• The deformation mechanism of nanotwins under Hall-Petch enhancement effect was studied via MD simulation. • Excessive volume fraction of nano twins causes Hall-Petch effect breakdown. • Critical volume fraction nanotwins effectively inhibit grain rotation and stabilize grain boundaries. • Nanotwin layer inhibits dislocation nucleation and leads to deformation mechanism transformation. Grain boundary plasticity dominates the mechanical behavior of materials, and the introduction of intragranular nanotwins can achieve coordination between strength and ductility in metals and alloys. In this effort, nanotwins with different volume contents are introduced in NiCoAl alloys to explore the strengthening mechanism under the Hall-Petch effect from perspectives such as grain boundary energy, grain rotation angle, and grain coarsening. The results indicate that the introduction of nanotwins with critical volume fraction effectively inhibits grain boundary migration and grain combination, and improves the strength of the alloy by reducing grain boundary energy and hindering grain rotation. Meanwhile, it leads to a change in the strengthening mechanism from the combined effects of dislocation movement, grain boundary migration and deformation twinning to the dual strengthening of local movement of dislocations within the grain and Lomer-Cottrell locks. The latter hinders the slip of local dislocations within the grain and improves the mechanical property. In addition, based on the average grain size and atomic mean square displacement after high-temperature annealing, the stability mechanism of nanotwins in the alloy can obtain an insight from the aspect of atomic motion. This article explains the Hall-Petch strengthening mechanism from a more detailed and interesting point and provides insights into the strengthening mechanism of nanotwins under the Hall-Petch effect. [Display omitted] [ABSTRACT FROM AUTHOR]

FeCrVTi x medium-entropy alloys (MEAs) with BCC matrix and Laves precipitation have high yield strength (1097–1493 MPa), good fracture strain (27.1–47.7%) and excellent thermal conductivity (42.2–69.7 W/(m·K) at 673–1273 K), it is expected to be widely applied in the fields of advanced nuclear energy and aerospace. However, what is this kind of MEAs strengthening and high thermal conductivity mechanisms? According to the experimental results and theoretical calculations, a mixed-strengthening-mechanism model dominated by precipitation and fine-grain strengthening is proposed, it can well explain the increase in yield strength of FeCrV-based MEAs due to Ti-added. Meanwhile, the Laves-phase precipitation formed by adding Ti improves the compressive plastic deformation through grain refinement, crack bridging and crack deflection. Moreover, the high thermal conductivity of FeCrVTi x MEAs is primarily due to the inelastic scattering of phonons and electrons in the medium/high-temperature regions. Based on the above mechanisms, the mechanical and thermal properties of MEAs/HEAs can be regulated in the pre-design and post-treatment stages, which provide new ideas and methods for the design and performance-optimization of high-performance structural materials. [Display omitted] • The new criterion of Laves-phase formation in MEAs/HEAs is observed when δ ≥ 3.25% and ∆ χ Allen ≥ 6.957%. • A mixed-strengthening-mechanism model is proposed to explain well the strength increment of FeCrVTi x MEAs due to Ti-added. • Ti-added improves the compressive plastic deformation behavior of FeCrVTi x MEAs. • The high thermal conductivity in FeCrVTi x originates from inelastic scattering of phonons and electrons at 473–1273 K. [ABSTRACT FROM AUTHOR]

Precisely controlling grain boundary (GB) thermodynamic stability and strength is important for processing nanograined alloys. The segregation-induced stabilization and strengthening GB mechanisms of 20 transition metal elements in Ni Σ11 [110](113) STGB with low interfacial excess energy were clarified from first-principles total-energy calculations in this work. The results indicate that the segregation energy and GB energy are inversely related to the radius difference between TM and matrix Ni atoms. The segregation of 11 elements were identified to enable the Ni Σ11 [110](113) STGB to be stable according to Schuh criterion for GB stability. The electronic mechanism of GB stabilization through TM segregation is mainly due to the less anti-bonding states of Ni -X pairs than those of Ni–Ni pairs in unsegregated GB, from the analysis of crystal orbital Hamiltonian populations. The GB embrittlement resulted from TM segregation is mainly from the mechanical contribution caused by atomic size mismatch between segregation atom and matrix atom. The segregation caused GB strengthening comes from the chemical contribution, which is due to the fact that the segregation of X leads to the formation of stronger Ni -X covalent-like bonds instead of Ni–Ni metallic bonds. This work could provide better understanding on designing high-stable Ni nanograined alloys. • The elements that stabilize grain boundaries are screened by Schuh criterion. • The grain boundary's cohesion was characterized by first-principles tensile tests. • Stabilizing and strengthening mechanisms were uncovered at electronic level. [ABSTRACT FROM AUTHOR]

Constructing a novel van der Waals (vdW) heterostructure by integrating diverse two-dimensional (2D) materials is significant to generate the more fascinating performances. In this present contribution, the electronic and photocatalytic properties of ZnO/GaTe heterostructure have been explored using first-principles calculations. The results reveal that the interaction between layers is dominated by the vdW forces. It displays an intrinsic type-II band alignment and a direct band gap of 1.730 eV under hybrid HSE06 functional. The valence band top and conduction band bottom are located at ZnO and GaTe layers, respectively, which guarantees the spatial separation of photogenerated electron-hole pairs and improves the photocatalytic efficiency. Moreover, the band edges all span the energy levels of both the reduction and oxidation potentials of H 2 O, indicating that its better photocatalytic performance. The modulated photocatalytic properties under varied pH circumstances imply that an acid environment is more favorable to the water splitting process. Furthermore, the band edge alignment exhibits the significant adjustability through varying vertical and in-plane biaxial strains. These theoretical findings indicate that the ZnO/GaTe heterostructure can offer an alternative strategy to design the efficient photocatalysts for water splitting. [ABSTRACT FROM AUTHOR]

The thermodynamic stability and mechanical strength of grain boundaries (GBs) govern many key properties of nanocrystalline or polycrystalline metals. In order to design novel Cu-based alloys with extraordinary properties and broaden the application scopes of Cu alloys, it is essential to clarify the effects of GB structure and composition on the stability and cohesion of Cu GBs. Firstly, the GB energies and works of separation of 12 Cu symmetrical tilt GBs with various GB orientations were figured out by using first-principles calculations, to link the GB properties with structures. Our results shown that the GB energies and works of separation of 12 Cu GBs are notably anisotropic. The GB energies for these GBs have an inverted and linear relationship with their works of separation. As to GB composition, the segregation tendencies of 8 alloying elements (Mg, Ca, Cr, Ni, Zn, Zr, Ag and Sn) in the Cu Σ5 [001](210) symmetrical tilt GB and their cohesive and embrittling effects on the GB were studied. It was found that all considered solutes excluding the element Ni can segregate to the Cu GB and thus play stabilizing roles into the Cu GB. Among 8 solutes, only the Zr and Cr segregations can improve the thermodynamic stability and fracture strength of Cu GB simultaneously. The GB strengthening effects of Zr and Cr segregations was attributed to their significant chemical contributions to the embrittling potencies, i.e., the presence of covalent-like bonding features in newly-formed Cu–Zr/Cr bonds. The reduction/increase of anti-bonding/bonding states below the Fermi level in Cu–Zr/Cr atomic pairs should be responsible for the GB stabilizing effects of Zr and Cr segregations. [Display omitted] • Zr and Cr segregation can strengthen Cu Σ5 [001](210) symmetrical tilt grain boundary. • Zr and Cr segregation can stabilize Cu Σ5 [001](210) symmetrical tilt grain boundary. • Grain boundary energy present inverted linear relationship with work of separation. [ABSTRACT FROM AUTHOR]

Graphene-based van der Waals (vdW) heterostructures have currently emerged as a promising application in the construction of next-generation electronic and optoelectronic devices. In this present contribution, through the comprehensive first-principle calculations, the electronic characteristics along with the Schottky barrier of graphene/β-silicon nitride(0001) heterostructure are theoretically investigated, considering external strain and electric fields effects. The results concluded that the electronic performance of both the graphene monolayer and β-Si 3 N 4 (0001) surface are perfectly maintained in the heterostructure on account of a weak interlayer vdW force between them. Furthermore, the graphene/β-Si 3 N 4 (0001) heterostructure forms a p-type Schottky contact with the SBH of 0.72 eV, which can be modified by using normal strain or perpendicular electric field. It is found that the heterostructure still maintains a p-type Schottky contact when the interlayer spacing from 2.2 Å to 4.4 Å or when the applied positive electric field is smaller than 0.2 V/Å. Most importantly, a transformation from the p-type Schottky contact to Ohmic one is observed in the heterostructure at an electric field of +0.2 V/Å. The above results are expected to provide a practical guidance for designing and fabrication of the novel nanoelectronic devices based on graphene/β-Si 3 N 4 vdW heterostructure. • The n-type and p-type SBHs of 3.60 eV and 0.72 eV at the equilibrium state are obtained. • A p-type Schottky contact is present when the interlayer spacing is from 2.2 Å to 4.4 Å. • The schottky barrier of heterostructure with electric fields is investigated. • The transformation from p-type to Ohmic occurs at an electric field of 0.2 V/Å. [ABSTRACT FROM AUTHOR]

The research on electronic properties of graphene/β-Si 3 N 4 (0001) heterostructure are carried out by regulating the interlayer spacing employing DTF calculations. The calculated results show that all interfaces are bonded by van der Waals (vdW) force, the configuration of N t1 atom relative to the center of C ring is more stable with the equilibrium interlayer distance D 0 of 2.908 Å and binding energy per C atom of −0.531 eV. The energy band structure is similar to the superposition of two parts of heterojunction and retains the shape of the Dirac cone with a direct band gap of 67 meV. Combined with differential density map and population analysis, it is found that 0.03 e spontaneously flow from the graphene layer to the β-Si 3 N 4 (0001) layer, results in the presence of a built-in electric field, which is conducive to the separation of electrons and holes. It is noteworthy that the band gap decreases obviously when the layer spacing gradually increases from 2.0 Å to 3.2 Å. The present results are beneficial for the designing of microelectronic devices containing vdWhs and open a window for the applications of graphene-ceramic heterojunctions. • The electronic properties of graphene/β-Si 3 N 4 (0001) heterostructure are investigated. • The equilibrium distance D 0 is 2.908 Å and the binding energy of per C atom is −0.531 eV. • The energy band retains the shape of the Dirac cone with a direct band gap of 67 meV. • There is 0.03 e transfer between layers with the presence of a built-in electric field. • The band gap increases when the layer spacing decreases from 3.2 Å to 2.0 Å. [ABSTRACT FROM AUTHOR]

To reduce or even eliminate the negative effects of grain boundaries (GBs) in nickel-based superalloys, the GB-segregation behaviors of 14 main alloying elements X of superalloys and their effects on the stability and fracture strength of Ni Σ5 [001](210) GB were systematically investigated based on the concept of GB segregation engineering (GBSE), using first-principles calculations. We found that 10 alloying elements can segregate towards the GB. Their GB-segregation tendencies increase in the order of W < Mo < Al < Mn < Cu < Ti < Ru < Ta < Hf < Zr, due to the increase in atomic radius and electronegativity differences between X and host Ni atoms. The GB energies of X -segregated GBs depend linearly on the GB segregation energies of solutes X , the stronger segregation tendency of solute X could lower the GB energy and make the GB more stable. Except Cu, the segregations of the other 9 solutes increase the GB fracture strength. The segregation-induced GB stabilizing and strengthening mechanisms were further revealed on the electronic level. This work could be beneficial for manipulating the composition, structure and properties of Ni GBs and designing Ni-based superalloys with desired performances based on the GBSE. • The grain boundary segregation of alloying elements- X is affected by atomic radius and electronegativity differenc. • The distribution map of grain boundary energy and work of separation of X -segregated grain boundary is obtained. • The mechanism of grain boundary X -segregation induced stabilization is the reduction of anti-bonding states. • The strengthening mechanism of the grain boundary segregation of X is the increase in bond strength of Ni- X. [ABSTRACT FROM AUTHOR]