Transition metal borides(TMBs)are a new class of promising electrocatalysts for hydrogen generation by water splitting.However,the synthesis of robust all-in-one electrodes is challenging for practical applications.He...Transition metal borides(TMBs)are a new class of promising electrocatalysts for hydrogen generation by water splitting.However,the synthesis of robust all-in-one electrodes is challenging for practical applications.Herein,a facile solid-state boronization strategy is reported to synthesize a series of self-supported TMBs thin films(TMB-TFs)with large area and high catalytic activity.Among them,MoB thin film(MoB-TF)exhibits the highest activity toward electrocatalytic hydrogen evolution reaction(HER),displaying a low overpotential(η10=191 and 219 mV at 10 mA cm^(−2))and a small Tafel slope(60.25 and 61.91 mV dec^(−1))in 0.5M H_(2)SO_(4)and 1.0M KOH,respectively.Moreover,it outperforms the commercial Pt/C at the high current density region,demonstrating potential applications in industrially electrochemical water splitting.Theoretical study reveals that both surfaces terminated by TM and B atoms can serve as the active sites and the H*binding strength of TMBs is correlated with the p band center of B atoms.This work provides a new pathway for the potential application of TMBs in largescale hydrogen production.展开更多
Owing to the orbital hybridization between the transition metal and the B element and the electron-trapping effect of the B ele-ment,transition metal borides are considered very promising materials for energy catalysi...Owing to the orbital hybridization between the transition metal and the B element and the electron-trapping effect of the B ele-ment,transition metal borides are considered very promising materials for energy catalysis.In this work,an amorphous scaly high-entropy boride(HEB)with electron traps was designed and fabricated via a facile reduction method to improve the hydrogen storage properties of magnesium hydride(MgH_(2)).For dehydrogenation,the onset temperature of MgH_(2)+10wt%HEB was dropped to 187.4℃;be-sides,the composite exhibited superior isothermal kinetics and the activation energy of the composite was reduced from(212.78±3.93)to(65.04±2.81)kJ/mol.In addition,MgH_(2)+10wt%HEB could absorb hydrogen at 21.5℃,and 5.02wt%H_(2) was charged in 50 min at 75℃.For reversible hydrogen storage capacity tests,the composite maintained a retention rate of 97%with 6.47wt%hydrogen capacity after 30 cycles.Combining microstructure evidence with hydrogen storage performance,the catalytic mechanism was proposed.During ball milling,scaly high-entropy borides riveted a large number of heterogeneous active sites on the surface of MgH_(2).Driven by the cocktail effect as well as the orbital hybridization of metal borides,numerous active sites steadily enhanced the hydrogen storage reactions in MgH_(2).展开更多
Two novel out-of-plane ordered quaternary borides M'_(4)VSiB_(2) (M'=Nb and Mo) have been synthesized. The out-of-plane ordered characteristic has been confirmed by the X-ray diffraction, the neutron powder di...Two novel out-of-plane ordered quaternary borides M'_(4)VSiB_(2) (M'=Nb and Mo) have been synthesized. The out-of-plane ordered characteristic has been confirmed by the X-ray diffraction, the neutron powder diffraction and the scanning transmission electron microscopy with high-angle angular dark field images. By adjusting the stoichiometric ratio of Mo and V, the 16l site preferentially occupied by relatively larger atom and 4c site by relatively smaller atom have been confirmed. The further first-principle calculation demonstrates the dynamical and thermodynamical stability of Mo_(4)VSiB_(2) o-T2 phase. This work confirms the transition metal occupation strategy of o-T2 phase and enriches the out-of-plane ordered laminated borides family.展开更多
The first-principle calculations are performed to investigate the structural,mechanical and electronic properties of titanium borides （Ti2B,TiB and TiB2）.Those calculated lattice parameters are in good agreement wit...The first-principle calculations are performed to investigate the structural,mechanical and electronic properties of titanium borides （Ti2B,TiB and TiB2）.Those calculated lattice parameters are in good agreement with the experimental data and previous theoretical values.All these borides are found to be mechanically stable at ambient pressure.Compared with parent metal Ti （120 GPa）,the larger bulk modulus of these borides increase successively with the increase of the boron content in three borides,which may be due to direction bonding introduced by the boron atoms in the lattice and the strong covalent Ti-B bonds.Additionally,TiB can be regarded as a candidate of incompressible and hard material besides TiB2.Furthermore,the elastic anisotropy and Debye temperatures are also discussed by investigating the elastic constants and moduli.Electronic density of states and atomic Mulliken charges analysis show that chemical bonding in these titanium borides is a complex mixture of covalent,ionic,and metallic characters.展开更多
Electrochemical water splitting is a feasible method for producing environmental benignity energy of hydrogen,while high price and low availability on the earth of noble electrocatalysts constrain their global-scale a...Electrochemical water splitting is a feasible method for producing environmental benignity energy of hydrogen,while high price and low availability on the earth of noble electrocatalysts constrain their global-scale application.Transition metal borides(TMBs)have displayed unique metalloid characteristic and outstanding performance for oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)in the last few decades.Herein,recent developments of the TMBs for HER and OER are summarized.Initially,the impact factors and relevant evaluation of electrocatalytic performance are described,that is,overpotential,Tafel slope and exchange current density,stability,faradaic efficiency,turnover frequency,mass and specific activities.Moreover,the optimization strategies of borides are emphasized,which principally include coupling with effective substrates,elemental doping,phase modification,interfacial engineering,and morphology control.Finally,in order to reach the goal of application,the remaining challenges and perspectives are given to point out a direction for enhancing the performance of borides.展开更多
Lithium−sulfur batteries are one of the most competitive high-energy batteries due to their high theoretical energy density of _(2)600 W·h·kg^(−1).However,their commercialization is limited by poor cycle sta...Lithium−sulfur batteries are one of the most competitive high-energy batteries due to their high theoretical energy density of _(2)600 W·h·kg^(−1).However,their commercialization is limited by poor cycle stability mainly due to the low intrinsic electrical conductivity of sulfur and its discharged products(Li_(2)S_(2)/Li_(2)S),the sluggish reaction kinetics of sulfur cathode,and the“shuttle effect”of soluble intermediate lithi-um polysulfides in ether-based electrolyte.To address these challenges,catalytic hosts have recently been introduced in sulfur cathodes to en-hance the conversion of soluble polysulfides to the final solid products and thus prevent the dissolution and loss of active-sulfur material.In this review,we summarize the recent progress on the use of metal phosphides and borides of different dimensions as the catalytic host of sulfur cathodes and demonstrate the catalytic conversion mechanism of sulfur cathodes with the help of metal phosphides and borides for high-en-ergy and long-life lithium-sulfur batteries.Finally,future outlooks are proposed on developing advanced catalytic host materials to improve battery performance.展开更多
In recent years,transition metal borides(TMBs)have attracted much attention because they are considered as potential superhard materials and have more abundant crystal structures compared with traditional superhard ma...In recent years,transition metal borides(TMBs)have attracted much attention because they are considered as potential superhard materials and have more abundant crystal structures compared with traditional superhard materials.So far,however,no superhard materials have been found in TMBs.A large number of structures and potential new properties in TMBs are induced by the various hybridization ways of boron atoms and the high valence electrons of transition metals,which provide many possibilities for its application.And most TMBs have layered structures,which make TMBs have the potential to be a two-dimensional(2D)material.The 2D materials have novel properties,but the research on 2D TMBs is still nearly blank.In this paper,the research progress of TMBs is summarized involving structure,mechanical properties,and multifunctional properties.The strong covalent bonds of boron atoms in TMBs can form one-dimensional,twodimensional,and three-dimensional substructures,and the multiple electron transfer between transition metal and boron leads to a variety of chemical bonds in TMBs,which are the keys to obtain high hardness and multifunctional properties of TMBs.Further research on the multifunctional properties of TMBs,such as superconductors,catalysts,and high hardness ferromagnetic materials,is of great significance to the discovery of new multifunctional hard materials.展开更多
Easy machining into sharp lending edge, nose tip and complex shape components plays a pivotal role in the application of ultrahigh temperature ceramics in hypersonic vehicles, wherein low and controllable hardness is ...Easy machining into sharp lending edge, nose tip and complex shape components plays a pivotal role in the application of ultrahigh temperature ceramics in hypersonic vehicles, wherein low and controllable hardness is a necessary parameter to ensure the easy machinability. However, the mechanism that driving the hardness of metal hexaborides is not clear. Here, using a combination of the empirical hardness model for polycrystalline materials and density functional theory investigation, the hardness dependence on shear anisotropic factors of high temperature metal hexaborides has been established. It has come to light that through controlling the shear anisotropic factors the hardness of polycrystalline metal hexaborides can be tailored from soft and ductile to extremely hard and brittle, which is underpinned by the degree of chemical bonding anisotropy, i.e., the difference of B-B bond within the B;octahedron and that connecting the B;octahedra.展开更多
2D MBenes have been theoretically predicted to possess unique electronic structures and physicochemical properties,and thus shown great promise in various applications.However,the synthesis of individual single-layer ...2D MBenes have been theoretically predicted to possess unique electronic structures and physicochemical properties,and thus shown great promise in various applications.However,the synthesis of individual single-layer MBene remains a grand challenge due to its orthorhombic structure of MAB phases.Recently,scientists from Link?ping University have fabricated 2D monolayer Mo4/3B2-xTzwith ordered metal vacancies.Their results demonstrated the feasibility of top-down approach by chemical exfoliation of laminated compounds and provided the principle for further preparation of a wealth of MBenes.展开更多
Mixtures of W and B13C2 powders were mechanically milled and subsequently annealed at 900-1200℃.It is found that amorphous W-B-C alloy formed as the mixtures were milled for 20.80 h.After annealing the 80 h-milled mi...Mixtures of W and B13C2 powders were mechanically milled and subsequently annealed at 900-1200℃.It is found that amorphous W-B-C alloy formed as the mixtures were milled for 20.80 h.After annealing the 80 h-milled mixtures at 900-950℃,solid solutions of C and/or B in tungsten[W（B,C）],C in tungsten boride[W2B（C）or WB（C）]formed by the crystallization of amorphous W-B-C.The formation temperature of W2B（C）and WB（C）is lower than that of W2B and WB reported previously.As the 80 h-milled mixtures were annealed at 1200℃,W reacted with amorphous W-B-C completely to form WB and W2B5 or W2B5 instead of the solid solutions of C in tungsten borides,which is determined by the mole ratio of W to B13C2.The formation mechanisms of the W2B（C）and WB（C）solid solutions as well as phase transition rules of the mixtures at annealing temperature and mole ratio were also investigated using first-principle calculation.展开更多
In this paper, density functional computations have been applied to the structural, elastic and electronic properties of ternary transition metal diborides Re0.5Ir0.5B2, Re0.5Tc0.5B2, Os0.5W0.5B2 and Os0.5Ru0.5B2 in h...In this paper, density functional computations have been applied to the structural, elastic and electronic properties of ternary transition metal diborides Re0.5Ir0.5B2, Re0.5Tc0.5B2, Os0.5W0.5B2 and Os0.5Ru0.5B2 in hexagonal （P63/mmc） and orthorhombic （Pmmn） structures with both local density approximation and generalized gradient approximation. LDA gives smaller lattice parameters and larger elastic moduli than GGA. Both results show that the hexagonal ones are more stable than orthorhombic ones except Os0.5Ru0.5B2. Moreover, the hexagonal structure has superior elastic property than orthorhombic one. Generally speaking, the calculated elastic moduli of Re0.5Ir0.5B2 and Os0.5Ru0.5B2 are smaller than those values of Re0.5Tc0.5B2 and Os0.5W0.5B2 within the same structure because of the filling of antibonding states. The relativistic effects result in weaker bonds of Tc-B （Ru-B） than those of Re-B （Os-B）. All the diborides are ultra-incompressible. Re0.5Tc0.5B2 has the largest shear modulus and it is a promising superhard diboride like Os0.5W0.5B2. The elastic properties are in high correlation with the bond strength. The shear moduli are more sensitive than the bulk moduli to the bond strength.展开更多
Conditions of formation, structure and properties of boride iron layers on carbonaceous steels 3 and 45 at electron beam borating are investigated. New process to make layers of iron borides （Fe2B, FeB） using electr...Conditions of formation, structure and properties of boride iron layers on carbonaceous steels 3 and 45 at electron beam borating are investigated. New process to make layers of iron borides （Fe2B, FeB） using electron beam are reported. The microstructure and microhardness of boride layers are investigated and also are compared to layer properties obtained at solid phase borating. Formed layers were heterogeneous structure combining solid and weak components and resulting in to fragility reduction of boride layer.展开更多
The article presents experimental results on obtaining composites based on the systems TiB2-Al2O3,CrB2-Al2O3 and ZrB2-Al2O3 by a method combining SHS(self-propagating high-temperature synthesis)and MA(mechanical activ...The article presents experimental results on obtaining composites based on the systems TiB2-Al2O3,CrB2-Al2O3 and ZrB2-Al2O3 by a method combining SHS(self-propagating high-temperature synthesis)and MA(mechanical activation).Using the thermodynamic calculation program“THERMO”,the adiabatic temperature and the composition of the equilibrium combustion products are calculated.It is shown that the products of exothermic interaction are refractory compounds of metal borides and alumina,which in the ceramic composite form a dispersed phase and a ceramic binder.The effect of duration of the activated mixing on the morphology of the reaction mixture and formation of the microstructure of the ceramic composite was studied.The realization of solid-state SHS is due to the formation of the initial powder mixture of ultradisperse reagent sizes during mechanochemical activation.The SHS products were examined by X-ray diffraction analysis and a scanning electron microscope.High-temperature phases of borides of chromium,titanium,zirconium,aluminum oxide and their spinel are found in SHS products.The purpose of this work is to investigate the influence of regimes for preparing reaction mixtures on formation of the microstructure of a ceramic SHS composite based on titanium,chromium and zirconium borides.展开更多
Given increasing energy demands and environmental pollution,it is highly desirable to design new hydrogen evolution reaction(HER)catalysts.In this study,we have performed high throughput screening of transition-metal ...Given increasing energy demands and environmental pollution,it is highly desirable to design new hydrogen evolution reaction(HER)catalysts.In this study,we have performed high throughput screening of transition-metal borides(M2B)and Janus counterparts for appealing catalysts.The simulations showcase that the Pd_(2)B,PdPtB,PdIrB and PdAuB possess favorable HER performance with the different chemical nature and unique asymmetry structure.展开更多
On the basis of the current theoretical understanding of boron-based hard superconductors under ambient conditions,numerous studies have been conducted with the aim of developing superconducting materials with favorab...On the basis of the current theoretical understanding of boron-based hard superconductors under ambient conditions,numerous studies have been conducted with the aim of developing superconducting materials with favorable mechanical properties using boron-rich compounds.In this paper,first-principles calculations reveal the existence of an unprecedented family of tetragonal pentaborides MB_(5)(M=Na,K,Rb,Ca,Sr,Ba,Sc,and Y),comprising B_(20)cages and centered metal atoms acting as stabilizers and electron donors to the boron sublattice.These compounds exhibit both superconductivity and high hardness,with the maximum superconducting transition temperature T_(c)of 18.6 K being achieved in RbB5 and the peak Vickers hardness Hv of 35.1 GPa being achieved in KB_(5)at 1 atm.The combination of these properties is particularly evident in KB_(5),RbB5,and BaB5,with Tc values of∼14.7,18.6,and 16.3 K and H_(v)values of∼35.1,32.4,and 33.8 GPa,respectively.The results presented here reveal that pentaborides can provide a framework for exploring and designing novel superconducting materials with favorable hardness at achievable pressures and even under ambient conditions.展开更多
The morphology and growth mechanism of borides in Ti 48Al+(0.2%～0.8%)B (mole fraction) alloys were investigated. The results show that TiB 2 phase are all flakes with width <0.5 μm and aspect ratio >100 in all...The morphology and growth mechanism of borides in Ti 48Al+(0.2%～0.8%)B (mole fraction) alloys were investigated. The results show that TiB 2 phase are all flakes with width <0.5 μm and aspect ratio >100 in alloys containing 0.2% and 0.5%B, respectively, but there are a few hexagonal blocky borides with habit planes of (0001) and {1010} type besides flakes in the alloy containing 0.8%B. Flake borides are the products of irregular eutectic reactions growing coupled with matrix and blocky borides are primary TiB 2 phases growing unconstrained in melt.展开更多
Niobium boride powders having NbB, NbB2 and Nb3B4 phases in various amounts and single phase NbB powders were successfully synthesized by using powder metallurgy methods from related metal oxide raw materials in the p...Niobium boride powders having NbB, NbB2 and Nb3B4 phases in various amounts and single phase NbB powders were successfully synthesized by using powder metallurgy methods from related metal oxide raw materials in the presence of a strong reducing agent. Nb2O5, B2O3 and Mg powder blends were milled at room temperature by a high-energy ball mill for different time. Subsequently, undesired MgO phase was removed from the milled powders by HCl leaching to constitute NbB?NbB2?Nb3B4 as final products and they were subjected to an annealing process at 1500 °C for 4 h to observe probable boride transformation. Characterization was carried out by XRD, DSC, PSA, SEM/EDX, TEM and VSM. The effects of milling time (up to 9 h) on the formation, microstructure and thermal behavior of the final products were investigated. Reduction reaction took place after milling stoichiometric powder blends for 2 h. Nano-sized NbB?NbB2?Nb3B4 powders in high purity were obtained in the absence of any secondary phase and any impurity via mechanochemistry by milling for 5 h and leaching with 4 mol/L HCl. After annealing, pure and nano-sized NbB?NbB2?Nb3B4 powders transformed to a single NbB phase without leaving behind NbB2 and Nb3B4 phases.展开更多
Transition-metal borides have emerged as promising candidates for potential superhard materials due to their remarkable mechanical properties,favorable synthesis conditions and diverse physical properties.However,achi...Transition-metal borides have emerged as promising candidates for potential superhard materials due to their remarkable mechanical properties,favorable synthesis conditions and diverse physical properties.However,achieving the requisite hardness for classification as superhard materials in transition-metal borides remains a significant challenge.In this study,we employed a multicomponent strategy to optimize electron band filling,investigating the thermodynamic stability and mechanical properties of Scx Ta1−x B2(0≤x≤1)transition-metal diborides.Calculations predicted Sc0.5 Ta0.5 B2 as the most promising composition,with its Fermi level located near the pseudogap,resulting in the lowest thermodynamic energy and superior mechanical properties.Experimentally,Sc0.5 Ta0.5 B2 was successfully synthesized under ambient pressure,achieving a hardness of 31.5 GPa under a 4.9 N load,the highest hardness reported for single-phase transition-metal borides.Additionally,Sc0.5 Ta0.5 B2 shows an electrical resistivity of 104.9μΩ・cm at room temperature,indicating its excellent electrical conductivity.These findings provide critical insights for the design of novel superhard metal materials,achieved through electron filling modifications induced by multicomponent strategies.This approach expands the potential for developing cost-effective,superhard materials,with implications for advancing transition-metal diborides.展开更多
Structurally ordered intermetallic borides are a large family of inorganic solids with rich bonding schemes,and huge compositional and structural diversity.The family members possess high flexibility to modulate the l...Structurally ordered intermetallic borides are a large family of inorganic solids with rich bonding schemes,and huge compositional and structural diversity.The family members possess high flexibility to modulate the local electronic structures and surface adsorption properties,providing great opportunities for the development of advanced catalysts with superior activity and stability.In this review,we summarize the structural features of intermetallic borides,with emphasis on the covalent linkage patterns of boron atoms in them,and the research methods for understanding their electronic structures.We also present the recent developments in the synthesis of phase-pure,well-defined intermetallic borides,most of which are suitable for catalytic studies.We further highlight the theoretical and experimental advances in the emerging boride-catalyzed reactions and the important roles of boron in tuning electrocatalytic performances.Finally,we propose the remaining challenges and future developments of boride synthesis and catalytic applications.展开更多
Incorporating another metal into binary metal borides has emerged as a highly effective strategy for optimizing material properties.Herein,using high-throughput calculations,we systematically investigated the structur...Incorporating another metal into binary metal borides has emerged as a highly effective strategy for optimizing material properties.Herein,using high-throughput calculations,we systematically investigated the structural,electronic,and superconducting properties of Fm3m and F43m phases of Li_(2)MB(M=alkaline earth,3d,and 4d metals).Our analysis of 48 Li_(2)MB compounds at 0-60 GPa reveals that four of them are promising superconductors with TC≥10 K.It is further demonstrated that substitution of different M elements serves as an effective strategy for electron doping,enabling precise control of the band structure and density of states near the Fermi level for the F43m phase.This behavior is exemplified in Li_(2)Sc_(1-x)Ti_(x)B(x=0.05-0.25),which transforms from a semiconductor into a metal and further into a superconductor with increasing Ti doping concentration.For the Fm3m phase,Dirac points near the Fermi level are observed in the M=Sc and Y systems,suggesting unique electronic behavior.Our work provides deep insight into the superconducting mechanisms of lithium-based borides and offers guidance for the targeted design of novel boride superconductors.展开更多
基金National Natural Science Foundation of China,Grant/Award Number:52172058Outstanding Youth Fund of Natural Science Foundation of Inner Mongolia Autonomous Region,Grant/Award Number:2023JQ15+4 种基金Fundamental Research Funds for the Inner Mongolia Normal University,Grant/Award Numbers:2022JBBJ010,2022JBTD008Major Project Cultivation Fund for the Inner Mongolia Normal University,Grant/Award Number:2020ZD01Funds for Reform and Development of Local Universities Supported by The Central Government(Cultivation of First-Class Disciplines in Physics)Postdoctoral Fellowship Program of CPSF,Grant/Award Number:GZB20240101China Postdoctoral Science Foundation,Grant/Award Number:2024M750304.
文摘Transition metal borides(TMBs)are a new class of promising electrocatalysts for hydrogen generation by water splitting.However,the synthesis of robust all-in-one electrodes is challenging for practical applications.Herein,a facile solid-state boronization strategy is reported to synthesize a series of self-supported TMBs thin films(TMB-TFs)with large area and high catalytic activity.Among them,MoB thin film(MoB-TF)exhibits the highest activity toward electrocatalytic hydrogen evolution reaction(HER),displaying a low overpotential(η10=191 and 219 mV at 10 mA cm^(−2))and a small Tafel slope(60.25 and 61.91 mV dec^(−1))in 0.5M H_(2)SO_(4)and 1.0M KOH,respectively.Moreover,it outperforms the commercial Pt/C at the high current density region,demonstrating potential applications in industrially electrochemical water splitting.Theoretical study reveals that both surfaces terminated by TM and B atoms can serve as the active sites and the H*binding strength of TMBs is correlated with the p band center of B atoms.This work provides a new pathway for the potential application of TMBs in largescale hydrogen production.
基金supported by the National Natural Science Foundation of China(No.22179054)the Jiangsu Province Innovation Support Project,China(No.BZ2023010)+1 种基金the Project of Jiangsu University High-Tech Ship Collaborative Innovation Center(No.1174871801-11)the Ministry of Science and Technology of the People’s Republic of China(No.G2023014022L).
文摘Owing to the orbital hybridization between the transition metal and the B element and the electron-trapping effect of the B ele-ment,transition metal borides are considered very promising materials for energy catalysis.In this work,an amorphous scaly high-entropy boride(HEB)with electron traps was designed and fabricated via a facile reduction method to improve the hydrogen storage properties of magnesium hydride(MgH_(2)).For dehydrogenation,the onset temperature of MgH_(2)+10wt%HEB was dropped to 187.4℃;be-sides,the composite exhibited superior isothermal kinetics and the activation energy of the composite was reduced from(212.78±3.93)to(65.04±2.81)kJ/mol.In addition,MgH_(2)+10wt%HEB could absorb hydrogen at 21.5℃,and 5.02wt%H_(2) was charged in 50 min at 75℃.For reversible hydrogen storage capacity tests,the composite maintained a retention rate of 97%with 6.47wt%hydrogen capacity after 30 cycles.Combining microstructure evidence with hydrogen storage performance,the catalytic mechanism was proposed.During ball milling,scaly high-entropy borides riveted a large number of heterogeneous active sites on the surface of MgH_(2).Driven by the cocktail effect as well as the orbital hybridization of metal borides,numerous active sites steadily enhanced the hydrogen storage reactions in MgH_(2).
基金supported by the National Youth Talent Support Program(No.QNBJ-2022-03)the National Natu-ral Science Foundation of China(No.52371180)the Fundamental Research Funds for the Central Universities(Nos.N2209005 and N2309001).
文摘Two novel out-of-plane ordered quaternary borides M'_(4)VSiB_(2) (M'=Nb and Mo) have been synthesized. The out-of-plane ordered characteristic has been confirmed by the X-ray diffraction, the neutron powder diffraction and the scanning transmission electron microscopy with high-angle angular dark field images. By adjusting the stoichiometric ratio of Mo and V, the 16l site preferentially occupied by relatively larger atom and 4c site by relatively smaller atom have been confirmed. The further first-principle calculation demonstrates the dynamical and thermodynamical stability of Mo_(4)VSiB_(2) o-T2 phase. This work confirms the transition metal occupation strategy of o-T2 phase and enriches the out-of-plane ordered laminated borides family.
基金Project(2010JK404) supported by the Education Committee Natural Science Foundation of Shaanxi Province,ChinaProjects(ZK0918,ZK0915) supported by the Baoji University of Arts and Sciences Key Research,China
文摘The first-principle calculations are performed to investigate the structural,mechanical and electronic properties of titanium borides （Ti2B,TiB and TiB2）.Those calculated lattice parameters are in good agreement with the experimental data and previous theoretical values.All these borides are found to be mechanically stable at ambient pressure.Compared with parent metal Ti （120 GPa）,the larger bulk modulus of these borides increase successively with the increase of the boron content in three borides,which may be due to direction bonding introduced by the boron atoms in the lattice and the strong covalent Ti-B bonds.Additionally,TiB can be regarded as a candidate of incompressible and hard material besides TiB2.Furthermore,the elastic anisotropy and Debye temperatures are also discussed by investigating the elastic constants and moduli.Electronic density of states and atomic Mulliken charges analysis show that chemical bonding in these titanium borides is a complex mixture of covalent,ionic,and metallic characters.
基金supported by the National Natural Science Foundation of China(52025013,51622102)Ministry of Science and Technology of China MOST(2018YFB1502101)+1 种基金the 111 Project(B12015)the Fundamental Research Funds for the Central Universities.
文摘Electrochemical water splitting is a feasible method for producing environmental benignity energy of hydrogen,while high price and low availability on the earth of noble electrocatalysts constrain their global-scale application.Transition metal borides(TMBs)have displayed unique metalloid characteristic and outstanding performance for oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)in the last few decades.Herein,recent developments of the TMBs for HER and OER are summarized.Initially,the impact factors and relevant evaluation of electrocatalytic performance are described,that is,overpotential,Tafel slope and exchange current density,stability,faradaic efficiency,turnover frequency,mass and specific activities.Moreover,the optimization strategies of borides are emphasized,which principally include coupling with effective substrates,elemental doping,phase modification,interfacial engineering,and morphology control.Finally,in order to reach the goal of application,the remaining challenges and perspectives are given to point out a direction for enhancing the performance of borides.
基金financially supported by the National Natural Science Foundation of China (Nos. 51725401, 51904030, and 21935006)
文摘Lithium−sulfur batteries are one of the most competitive high-energy batteries due to their high theoretical energy density of _(2)600 W·h·kg^(−1).However,their commercialization is limited by poor cycle stability mainly due to the low intrinsic electrical conductivity of sulfur and its discharged products(Li_(2)S_(2)/Li_(2)S),the sluggish reaction kinetics of sulfur cathode,and the“shuttle effect”of soluble intermediate lithi-um polysulfides in ether-based electrolyte.To address these challenges,catalytic hosts have recently been introduced in sulfur cathodes to en-hance the conversion of soluble polysulfides to the final solid products and thus prevent the dissolution and loss of active-sulfur material.In this review,we summarize the recent progress on the use of metal phosphides and borides of different dimensions as the catalytic host of sulfur cathodes and demonstrate the catalytic conversion mechanism of sulfur cathodes with the help of metal phosphides and borides for high-en-ergy and long-life lithium-sulfur batteries.Finally,future outlooks are proposed on developing advanced catalytic host materials to improve battery performance.
基金supported by the National Key Research and Development Program of China(Grant Nos.2016YFA0401503 and 2018YFA0305700)the National Natural Science Foundation of China(Grant No.11575288)+1 种基金the Strategic Priority Research Program and Key Research Program of Frontier Sciences of the Chinese Academy of Sciences(Grant Nos.XDB33000000,XDB25000000,and QYZDBSSW-SLH013)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant No.Y202003)。
文摘In recent years,transition metal borides(TMBs)have attracted much attention because they are considered as potential superhard materials and have more abundant crystal structures compared with traditional superhard materials.So far,however,no superhard materials have been found in TMBs.A large number of structures and potential new properties in TMBs are induced by the various hybridization ways of boron atoms and the high valence electrons of transition metals,which provide many possibilities for its application.And most TMBs have layered structures,which make TMBs have the potential to be a two-dimensional(2D)material.The 2D materials have novel properties,but the research on 2D TMBs is still nearly blank.In this paper,the research progress of TMBs is summarized involving structure,mechanical properties,and multifunctional properties.The strong covalent bonds of boron atoms in TMBs can form one-dimensional,twodimensional,and three-dimensional substructures,and the multiple electron transfer between transition metal and boron leads to a variety of chemical bonds in TMBs,which are the keys to obtain high hardness and multifunctional properties of TMBs.Further research on the multifunctional properties of TMBs,such as superconductors,catalysts,and high hardness ferromagnetic materials,is of great significance to the discovery of new multifunctional hard materials.
基金pupported by the National Natural Science Foundation of China under Grant Nos. U1435206 and 51672064Beijing Municipal Science & Technology Commission under Grant Nos. Z151100003315012 and D16110000241600
文摘Easy machining into sharp lending edge, nose tip and complex shape components plays a pivotal role in the application of ultrahigh temperature ceramics in hypersonic vehicles, wherein low and controllable hardness is a necessary parameter to ensure the easy machinability. However, the mechanism that driving the hardness of metal hexaborides is not clear. Here, using a combination of the empirical hardness model for polycrystalline materials and density functional theory investigation, the hardness dependence on shear anisotropic factors of high temperature metal hexaborides has been established. It has come to light that through controlling the shear anisotropic factors the hardness of polycrystalline metal hexaborides can be tailored from soft and ductile to extremely hard and brittle, which is underpinned by the degree of chemical bonding anisotropy, i.e., the difference of B-B bond within the B;octahedron and that connecting the B;octahedra.
基金supported by the National Natural Science Foundation of China(Nos.52172205,11804166)the China Postdoctoral Science Foundation(No.2018M630587)Tianjin Natural Science Foundation(No.18JCQNJC77100)。
文摘2D MBenes have been theoretically predicted to possess unique electronic structures and physicochemical properties,and thus shown great promise in various applications.However,the synthesis of individual single-layer MBene remains a grand challenge due to its orthorhombic structure of MAB phases.Recently,scientists from Link?ping University have fabricated 2D monolayer Mo4/3B2-xTzwith ordered metal vacancies.Their results demonstrated the feasibility of top-down approach by chemical exfoliation of laminated compounds and provided the principle for further preparation of a wealth of MBenes.
基金supported by the National Natural Science Foundation of China(Grant Nos.11274135,11074093,61205038)the Specialized Research Fund for the Doctoral Program of Higher Education(Grant No.20130061130011)+2 种基金the Ph.D Programs Foundation of Ministry of Education of China(Grant No.20120061120011)the Science and Technology Development Project of Jilin Province,China(Grant No.20170101142JC)supported by High Performance Computing Center of Jilin University,China
文摘Mixtures of W and B13C2 powders were mechanically milled and subsequently annealed at 900-1200℃.It is found that amorphous W-B-C alloy formed as the mixtures were milled for 20.80 h.After annealing the 80 h-milled mixtures at 900-950℃,solid solutions of C and/or B in tungsten[W（B,C）],C in tungsten boride[W2B（C）or WB（C）]formed by the crystallization of amorphous W-B-C.The formation temperature of W2B（C）and WB（C）is lower than that of W2B and WB reported previously.As the 80 h-milled mixtures were annealed at 1200℃,W reacted with amorphous W-B-C completely to form WB and W2B5 or W2B5 instead of the solid solutions of C in tungsten borides,which is determined by the mole ratio of W to B13C2.The formation mechanisms of the W2B（C）and WB（C）solid solutions as well as phase transition rules of the mixtures at annealing temperature and mole ratio were also investigated using first-principle calculation.
基金supported by the National Natural Science Foundation of China (No. 20973174)973 Project (2007CB805307)
文摘In this paper, density functional computations have been applied to the structural, elastic and electronic properties of ternary transition metal diborides Re0.5Ir0.5B2, Re0.5Tc0.5B2, Os0.5W0.5B2 and Os0.5Ru0.5B2 in hexagonal （P63/mmc） and orthorhombic （Pmmn） structures with both local density approximation and generalized gradient approximation. LDA gives smaller lattice parameters and larger elastic moduli than GGA. Both results show that the hexagonal ones are more stable than orthorhombic ones except Os0.5Ru0.5B2. Moreover, the hexagonal structure has superior elastic property than orthorhombic one. Generally speaking, the calculated elastic moduli of Re0.5Ir0.5B2 and Os0.5Ru0.5B2 are smaller than those values of Re0.5Tc0.5B2 and Os0.5W0.5B2 within the same structure because of the filling of antibonding states. The relativistic effects result in weaker bonds of Tc-B （Ru-B） than those of Re-B （Os-B）. All the diborides are ultra-incompressible. Re0.5Tc0.5B2 has the largest shear modulus and it is a promising superhard diboride like Os0.5W0.5B2. The elastic properties are in high correlation with the bond strength. The shear moduli are more sensitive than the bulk moduli to the bond strength.
文摘Conditions of formation, structure and properties of boride iron layers on carbonaceous steels 3 and 45 at electron beam borating are investigated. New process to make layers of iron borides （Fe2B, FeB） using electron beam are reported. The microstructure and microhardness of boride layers are investigated and also are compared to layer properties obtained at solid phase borating. Formed layers were heterogeneous structure combining solid and weak components and resulting in to fragility reduction of boride layer.
文摘The article presents experimental results on obtaining composites based on the systems TiB2-Al2O3,CrB2-Al2O3 and ZrB2-Al2O3 by a method combining SHS(self-propagating high-temperature synthesis)and MA(mechanical activation).Using the thermodynamic calculation program“THERMO”,the adiabatic temperature and the composition of the equilibrium combustion products are calculated.It is shown that the products of exothermic interaction are refractory compounds of metal borides and alumina,which in the ceramic composite form a dispersed phase and a ceramic binder.The effect of duration of the activated mixing on the morphology of the reaction mixture and formation of the microstructure of the ceramic composite was studied.The realization of solid-state SHS is due to the formation of the initial powder mixture of ultradisperse reagent sizes during mechanochemical activation.The SHS products were examined by X-ray diffraction analysis and a scanning electron microscope.High-temperature phases of borides of chromium,titanium,zirconium,aluminum oxide and their spinel are found in SHS products.The purpose of this work is to investigate the influence of regimes for preparing reaction mixtures on formation of the microstructure of a ceramic SHS composite based on titanium,chromium and zirconium borides.
基金financially supported by the National Natural Science Foundation of China(Nos.52122308 and 51973200)the Project of China Postdoctoral Science Foundation(No.2022M712909)the National Supercomputing Center in Zhengzhou。
文摘Given increasing energy demands and environmental pollution,it is highly desirable to design new hydrogen evolution reaction(HER)catalysts.In this study,we have performed high throughput screening of transition-metal borides(M2B)and Janus counterparts for appealing catalysts.The simulations showcase that the Pd_(2)B,PdPtB,PdIrB and PdAuB possess favorable HER performance with the different chemical nature and unique asymmetry structure.
基金supported by the National Natural Science Foundation of China(Grant Nos.12104127 and 22131006)the Doctoral Starting Up Foundation of Hebei Normal University for Nationalities(Grant No.DR2020001)+1 种基金the Clean Energy(Carbon Peaking and Carbon Neutrality)Industry Research Institute of Chengde(Grant No.202205B090)the Natural Science Foundation of Shandong Province(Grant No.ZR2020QA060)。
文摘On the basis of the current theoretical understanding of boron-based hard superconductors under ambient conditions,numerous studies have been conducted with the aim of developing superconducting materials with favorable mechanical properties using boron-rich compounds.In this paper,first-principles calculations reveal the existence of an unprecedented family of tetragonal pentaborides MB_(5)(M=Na,K,Rb,Ca,Sr,Ba,Sc,and Y),comprising B_(20)cages and centered metal atoms acting as stabilizers and electron donors to the boron sublattice.These compounds exhibit both superconductivity and high hardness,with the maximum superconducting transition temperature T_(c)of 18.6 K being achieved in RbB5 and the peak Vickers hardness Hv of 35.1 GPa being achieved in KB_(5)at 1 atm.The combination of these properties is particularly evident in KB_(5),RbB5,and BaB5,with Tc values of∼14.7,18.6,and 16.3 K and H_(v)values of∼35.1,32.4,and 33.8 GPa,respectively.The results presented here reveal that pentaborides can provide a framework for exploring and designing novel superconducting materials with favorable hardness at achievable pressures and even under ambient conditions.
文摘The morphology and growth mechanism of borides in Ti 48Al+(0.2%～0.8%)B (mole fraction) alloys were investigated. The results show that TiB 2 phase are all flakes with width <0.5 μm and aspect ratio >100 in alloys containing 0.2% and 0.5%B, respectively, but there are a few hexagonal blocky borides with habit planes of (0001) and {1010} type besides flakes in the alloy containing 0.8%B. Flake borides are the products of irregular eutectic reactions growing coupled with matrix and blocky borides are primary TiB 2 phases growing unconstrained in melt.
基金financially supported by“The Scientific and Technological Research Council of Turkey(TUBITAK)”with the project title of“Synthesis of Refractory Metal Borides via Three Different Production Methods from Solid,Liquid and Gas Raw Materials for Various Application Areas,Sintering,Characterization,Comparison of Process and Final Products”and with the project number of 112M470
文摘Niobium boride powders having NbB, NbB2 and Nb3B4 phases in various amounts and single phase NbB powders were successfully synthesized by using powder metallurgy methods from related metal oxide raw materials in the presence of a strong reducing agent. Nb2O5, B2O3 and Mg powder blends were milled at room temperature by a high-energy ball mill for different time. Subsequently, undesired MgO phase was removed from the milled powders by HCl leaching to constitute NbB?NbB2?Nb3B4 as final products and they were subjected to an annealing process at 1500 °C for 4 h to observe probable boride transformation. Characterization was carried out by XRD, DSC, PSA, SEM/EDX, TEM and VSM. The effects of milling time (up to 9 h) on the formation, microstructure and thermal behavior of the final products were investigated. Reduction reaction took place after milling stoichiometric powder blends for 2 h. Nano-sized NbB?NbB2?Nb3B4 powders in high purity were obtained in the absence of any secondary phase and any impurity via mechanochemistry by milling for 5 h and leaching with 4 mol/L HCl. After annealing, pure and nano-sized NbB?NbB2?Nb3B4 powders transformed to a single NbB phase without leaving behind NbB2 and Nb3B4 phases.
基金supported by the National Key Research and Development Program of China(2021YFA1400503,2023YFA1608901 and 2021YFA400300)Natural Science Foundation of China(T2325013,52288102,12347162,12375304 and 12304268).
文摘Transition-metal borides have emerged as promising candidates for potential superhard materials due to their remarkable mechanical properties,favorable synthesis conditions and diverse physical properties.However,achieving the requisite hardness for classification as superhard materials in transition-metal borides remains a significant challenge.In this study,we employed a multicomponent strategy to optimize electron band filling,investigating the thermodynamic stability and mechanical properties of Scx Ta1−x B2(0≤x≤1)transition-metal diborides.Calculations predicted Sc0.5 Ta0.5 B2 as the most promising composition,with its Fermi level located near the pseudogap,resulting in the lowest thermodynamic energy and superior mechanical properties.Experimentally,Sc0.5 Ta0.5 B2 was successfully synthesized under ambient pressure,achieving a hardness of 31.5 GPa under a 4.9 N load,the highest hardness reported for single-phase transition-metal borides.Additionally,Sc0.5 Ta0.5 B2 shows an electrical resistivity of 104.9μΩ・cm at room temperature,indicating its excellent electrical conductivity.These findings provide critical insights for the design of novel superhard metal materials,achieved through electron filling modifications induced by multicomponent strategies.This approach expands the potential for developing cost-effective,superhard materials,with implications for advancing transition-metal diborides.
基金financial support from the National Natural Science Foundation of China(NSFC):Grant No.21922507 and 21771079the Fok Ying Tung Education Foundation:Grant No.161011+4 种基金financial support from the NSFC(Grant No.21901083)the Postdoctoral Innovative Talent Support Program(Grant No.BX20180120)the China Postdoctoral Science Foundation(Grant No.2018M641771)the National Natural Science Foundation of China(Grant No.21621001)the 111 Project(No.B17020)for financial support.
文摘Structurally ordered intermetallic borides are a large family of inorganic solids with rich bonding schemes,and huge compositional and structural diversity.The family members possess high flexibility to modulate the local electronic structures and surface adsorption properties,providing great opportunities for the development of advanced catalysts with superior activity and stability.In this review,we summarize the structural features of intermetallic borides,with emphasis on the covalent linkage patterns of boron atoms in them,and the research methods for understanding their electronic structures.We also present the recent developments in the synthesis of phase-pure,well-defined intermetallic borides,most of which are suitable for catalytic studies.We further highlight the theoretical and experimental advances in the emerging boride-catalyzed reactions and the important roles of boron in tuning electrocatalytic performances.Finally,we propose the remaining challenges and future developments of boride synthesis and catalytic applications.
基金supported by the National Natural Science Foundation of China(Grant Nos.11574109 and 91745203)。
文摘Incorporating another metal into binary metal borides has emerged as a highly effective strategy for optimizing material properties.Herein,using high-throughput calculations,we systematically investigated the structural,electronic,and superconducting properties of Fm3m and F43m phases of Li_(2)MB(M=alkaline earth,3d,and 4d metals).Our analysis of 48 Li_(2)MB compounds at 0-60 GPa reveals that four of them are promising superconductors with TC≥10 K.It is further demonstrated that substitution of different M elements serves as an effective strategy for electron doping,enabling precise control of the band structure and density of states near the Fermi level for the F43m phase.This behavior is exemplified in Li_(2)Sc_(1-x)Ti_(x)B(x=0.05-0.25),which transforms from a semiconductor into a metal and further into a superconductor with increasing Ti doping concentration.For the Fm3m phase,Dirac points near the Fermi level are observed in the M=Sc and Y systems,suggesting unique electronic behavior.Our work provides deep insight into the superconducting mechanisms of lithium-based borides and offers guidance for the targeted design of novel boride superconductors.
