Optimizing the oxygen reduction reaction(ORR)kinetics requires precise control of intermediate adsorption at active sites,which can be achieved through orbital engineering by regulating the electronic structure.This s...Optimizing the oxygen reduction reaction(ORR)kinetics requires precise control of intermediate adsorption at active sites,which can be achieved through orbital engineering by regulating the electronic structure.This study addresses the challenge by exploring how modulation of the 3d-orbital electronic structure of FeN_(4) active sites influences ORR electrocatalysis.To realize this,a catalyst composed of Fe_(3)C nanoparticles and FeN_(4) single atoms anchored on carbon black(Fe_(3)C-FeN_(4)/CB)was synthesized via a synergistic strategy of spatial confinement and atmosphere control.This unique heterostructure creates interfaces between Fe_(3)C and FeN_(4) that modulate the electronic configuration of the FeN_(4) center,transforming its geometry from square-planar to quasi-octahedral.Spectroscopic characterizations and theoretical calculations reveal that this orbital modulation results in a downward shift of the Fe dband center,altering the reaction pathway and lowering the energy barrier for ORR.Consequently,the Fe_(3)C-FeN_(4)/CB catalyst exhibits outstanding ORR activity,four-electron selectivity,excellent methanol tolerance,and remarkable electrochemical stability.When applied in a zinc-air battery,it achieves a peak power density of 178.4 mW cm^(-2)and superior cycling stability compared to commercial Pt/C catalysts.This work provides valuable insights into heterointerface-induced orbital modulation as a promising design principle for high-performance ORR electrocatalysts.展开更多
To overcome the limitations of traditional single-crystal X-ray diffraction(SCXRD)for microcrystalline materials and the peak-overlapping issue of powder X-ray diffraction(PXRD),this study employed cryogenic continuou...To overcome the limitations of traditional single-crystal X-ray diffraction(SCXRD)for microcrystalline materials and the peak-overlapping issue of powder X-ray diffraction(PXRD),this study employed cryogenic continuous rotation electron diffraction(cryo-cRED)with a low-dose strategy to determine the crystal structure of CL30,a novel silicogermanate framework.It is confirmed that CL30 crystallizes in the C2/m space group and has layered topology composed of discontinuous zigzag chains connected by double four-membered ring(d4r)units,with fluoride anions(F^(-))occluded in the d4r units.In CL30,charge balance involves organic structure-directing agent(OSDA)cations,occluded F^(-),and terminal oxygen sites whose protonation state cannot be established from the present three dimensional(3D)ED data.F^(-)encapsulated in the d4r units contributes to charge compensation as the counter-anion to OSDA cations,rather than only balancing the framework charge.Although the refinement indices(R_(1)=0.29,wR_(2)=0.71)exceeded typical small-molecule crystallography standards,the structural model remained highly reliable,as supported by geometric restraints and validation.In electron diffraction,elevated R_(1) values are commonly attributed to the intrinsic factors of the technique,such as dynamic scattering,detector noise from scintillator-based detectors,and TEM stage instability(large spheres of confusion).This study introduces a new structural prototype to the silicogermanate family and establishes a feasible workflow for determining the structures of radiation-sensitive microcrystalline porous materials.展开更多
The microstructural evolution and mechanical properties of a vacuum electron beam welded aerospace 5B70 aluminum alloy joint were studied.Quantitative analyses of the phase composition,microstructural evolution,grain ...The microstructural evolution and mechanical properties of a vacuum electron beam welded aerospace 5B70 aluminum alloy joint were studied.Quantitative analyses of the phase composition,microstructural evolution,grain size,grain boundary density,and texture changes were performed by X-ray diffraction,scanning electron microscopy,and electron backscatter diffraction.The fusion zone(FZ)comprises equiaxed cellular crystals,and a fine~20μm-thick crystal layer forms in the transition zone(TZ)between the FZ and heat affected zone(HAZ).The HAZ closely resembles the base material(BM),retaining the original rolling microstructure.Mechanical property testing shows that the fine-grained layer in the TZ exhibits the highest nanohardness,with the FZ corresponding to the lowest microhardness.The welded-joint sample has lower yield strength,ultimate tensile strength,and elongation after fracture than the BM.These reductions of mechanical properties are primarily influenced by the grain size and distribution of the precipitated phases.展开更多
Layered double hydroxides(LDHs)hold great promise as cathode materials for aqueous zinc-ion batteries(AZIBs).Nevertheless,they also face challenges of sluggish kinetics and rapid capacity loss.Herein,a conformational ...Layered double hydroxides(LDHs)hold great promise as cathode materials for aqueous zinc-ion batteries(AZIBs).Nevertheless,they also face challenges of sluggish kinetics and rapid capacity loss.Herein,a conformational entropy regulation strategy has been applied to surmount the shortcomings.A medium-entropy iron-based metal organic framework(MIL-88)derived NiCoFeInZnV-based layered double hydroxide with carbon loaded(ME-NiCoFeInZnV-LDH/C)has been first proposed and prepared with a designed method.The increased entropy optimizes electron conductivity and alleviates structure alteration and diffusion barrier during interactions with charge carriers,due to electron-induced effect and“cocktail”effect.Moreover,the nanosheet assembled hollow prismatic structures could homogenize flux distribution and electric field distribution.Therefore,the electrochemical kinetics,crystal structure stability,and activity could be dramatically improved.Leveraging the advantages of structure and composition regulation,Zn||ME-NiCoFeInZnV-LDH/C zinc battery delivers high specific capacities,rate performance,and cycling stability.This work proposes a novel and feasible medium-entropy strategy to prepare a high-performance cathode for advanced AZIBs,which is of prominent significance for the development of charge storage devices.展开更多
We report the discovery of bulk superconductivity in a new quinary intermetallic compound Th_(2)Mo_(2)Ru_(2)Si_(4)C,crystallized in a collapsed 22241-type structure.This structure is characterized by the intergrowth o...We report the discovery of bulk superconductivity in a new quinary intermetallic compound Th_(2)Mo_(2)Ru_(2)Si_(4)C,crystallized in a collapsed 22241-type structure.This structure is characterized by the intergrowth of ThMo_(2)Si_(2)C and ThRu_(2)Si_(2) units interconnected by equivalent Si-Si bonds that enhance inter-sublattice coupling.The refined lattice parameters are a=4.2212(1)Å and c=20.3899(7)Å.Electrical resistivity and magnetic susceptibility measurements of both polycrystalline and single-crystal samples consistently demonstrate bulk superconductivity with a transition temperature T_(c)∼6.0 K significantly higher than those of the constituent compound ThMo_(2)Si_(2)C and its related analogs.Under magnetic fields,the superconducting state exhibits a nearly isotropic behavior,which is attributed to strong covalent interlayer coupling.First-principles calculations reveal a substantial contribution from the Mo-d orbitals near the Fermi level,which exhibit several band-crossing points.The enhancement in T_(c) can be attributed to the synergistic combination of the valence electron concentration and the inter-sublattice self-doping effect between the[Ru_(2)Si_(2)]and[Mo_(2)Si_(2)C]layers.展开更多
La-Mg-Ni-based hydrogen storage alloys with superlattice structures are the new generation anode material for nickel metal hydride(Ni-MH)batteries owing to the advantages of high capacity and exceptional activation pr...La-Mg-Ni-based hydrogen storage alloys with superlattice structures are the new generation anode material for nickel metal hydride(Ni-MH)batteries owing to the advantages of high capacity and exceptional activation properties.However,the cycling stability is not currently satisfactory enough which plagues its application.Herein,a strategy of partially substituting La with the Y element is proposed to boost the capacity durability of La-Mg-Ni-based alloys.Furthermore,phase structure regulation is implemented simultaneously to obtain the A5 B19-type alloy with good crystal stability specifically.It is found that Y promotes the phase formation of the Pr5 Co19-type phase after annealing at 985℃.The alloy containing Y contributes to the superior rate capability resulting from the promoted hydrogen diffusion rate.Notably,Y substitution enables strengthening the anti-pulverization ability of the alloy in terms of increasing the volume match between[A_(2)B_(4)]and[AB5]subunits,and effectively enhances the anti-corrosion ability of the alloy due to high electronegativity,realizing improved long-term cycling stability of the alloy from 74.2%to 78.5%after cycling 300 times.The work is expected to shed light on the composition and structure design of the La-Mg-Ni-based hydrogen storage alloy for Ni-MH batteries.展开更多
From the perspective of revealing the theoretical foundation in structural protection and impact resistance,an elaborate discussion was provided on the room-and hightemperature deformation behaviors of novel B2-struct...From the perspective of revealing the theoretical foundation in structural protection and impact resistance,an elaborate discussion was provided on the room-and hightemperature deformation behaviors of novel B2-structured Al_(0.5)NbTi_(3)VZr_(0.5)lightweight high-entropy alloy(LHEA),which provided a kind of potential structural material in application to lightweight high-temperature instruments.展开更多
Proton exchange membrane fuel cells(PEMFCs)constitute a promising avenue for environmentally friendly power generation.However,the reliance on unsustainable platinum-based electrocatalysts used at the electrodes poses...Proton exchange membrane fuel cells(PEMFCs)constitute a promising avenue for environmentally friendly power generation.However,the reliance on unsustainable platinum-based electrocatalysts used at the electrodes poses challenges to the commercial viability of PEMFCs.Non-platinum group metal(non-PGM)alternatives,like nitrogen-coordinated transition metals in atomic dispersion(M–N–C catalysts),show significant potential.This work presents a comparative study of two distinct sets of Fe–N–C materials,prepared by pyrolyzing hybrid composites of polyaniline(PANI)and iron(Ⅱ)chloride on a hard template.One set uses bipyridine(BPy)as an additional nitrogen source and iron ligand,offering an innovative approach.The findings reveal that the choice of pyrolysis temperature and atmosphere influences the catalyst properties.The use of ammonia in pyrolysis emerges as a crucial parameter for promoting atomic dispersion of iron,as well as increasing surface area and porosity.The optimal catalyst,prepared using BPy and ammonia,exhibits a half-wave potential of 0.834 V in 0.5 M H_(2)SO_(4)(catalyst loading of 0.6 mg cm^(-2)),a mass activity exceeding 3 A g^(-1)and high stability in acidic electrolyte,positioning it as a promising non-PGM structure in the field.展开更多
Metallic glass matrix composites(BMGCs)with compositions of[(Zr_(0.5)Cu_(0.5))_(0.925)Al_(0.07)Sn_(0.005)]_(100-x)Ta_(x)(atomic fraction,%,x=3,5,7)were successfully prepared via dealloying in metallic melt.The reinfor...Metallic glass matrix composites(BMGCs)with compositions of[(Zr_(0.5)Cu_(0.5))_(0.925)Al_(0.07)Sn_(0.005)]_(100-x)Ta_(x)(atomic fraction,%,x=3,5,7)were successfully prepared via dealloying in metallic melt.The reinforcing phase in these alloys has core-shell hybrid structure with Ta-rich particles as core and B2-CuZr as shell.In this method,the dealloyed Ta from Zr-Ta pre-alloys maintained in solid state and aggregated to form the fine Ta-rich phase in the final products.This effectively decreases the size of Ta-rich phase compared with that prepared via conventional arc-melting,where the Ta-rich phase was formed through dissolving and precipitation.Among the three compositions,[(Zr_(0.5)Cu_(0.5))_(0.925)Al_(0.07)Sn_(0.005)]_(95)Ta_(5) showed the highest plastic strain of 11.2%,much higher than that of the arc-melted counterparts(4.3%).Such improvement in mechanical properties was related with the refined core-shell hybrid reinforcing structure,which could hinder the rapid propagation of main shear band more efficiently and cause them to branch and proliferate at the interface.展开更多
In order to ameliorate the electrochemical hydrogen storage performance of La-Mg-Ni system A2B7-type electrode alloys, a small amount of Si was added. The La0.8Mg0.2Ni3.3Co0.2Six （x=0-0.2） electrode alloys were prep...In order to ameliorate the electrochemical hydrogen storage performance of La-Mg-Ni system A2B7-type electrode alloys, a small amount of Si was added. The La0.8Mg0.2Ni3.3Co0.2Six （x=0-0.2） electrode alloys were prepared by casting and annealing. The effects of adding Si on the structure and electrochemical hydrogen storage characteristics of the alloys were investigated systematically. The results indicate that the as-cast and annealed alloys hold multiple structures, involving two major phases of （La, Mg）2Ni7 with a Ce2Ni7-type hexagonal structure and LaNi5 with a CaCu5-type hexagonal structure as well as one residual phase LaNi3. The addition of Si results in a decrease in （La, Mg）2Ni7 phase and an increase in LaNi5 phase without changing the phase structure of the alloys. What is more, it brings on an obvious effect on electrochemical hydrogen storage characteristics of the alloys. The discharge capacities of the as-cast and annealed alloys decline with the increase of Si content, but their cycle stabilities clearly grow under the same condition. Furthermore, the measurements of the high rate discharge ability, the limiting current density, hydrogen diffusion coefficient as well as electrochemical impedance spectra all indicate that the electrochemical kinetic properties of the electrode alloys first increase and then decrease with the rising of Si content.展开更多
Objective To examine the important roles of microRNAs （miRNAs） in regulating amphid structure and function, we performed a computational analysis for the genetic loci required for the sensory perception and their po...Objective To examine the important roles of microRNAs （miRNAs） in regulating amphid structure and function, we performed a computational analysis for the genetic loci required for the sensory perception and their possibly corresponding miRNAs in C. elegans. Methods Total 55 genetic loci required for the amphid structure and function were selected. Sequence alignment was combined with E value evaluation to investigate and identify the possible corresponding miRNAs. Results Total 30 genes among the 55 genetic loci selected have their possible corresponding regulatory miRNA（s）, and identified genes participate in the regulation of almost all aspects of amphid structure and function. In addition, our data suggest that both the amphid structure and the amphid functions might be regulated by a series of network signaling pathways. Moreover, the distribution of miRNAs along the 3＇ untranslated region （UTR） of these 30 genes exhibits different patterns. Conclusion We present the possible miRNA-mediated signaling pathways involved in the regulation of chemosensation and thermosensation by controlling the corresponding sensory neuron and interneuron functions. Our work will be useful for better understanding of the miRNA-mediated control of the chemotaxis and thermotaxis in C. elegans.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.22272105 and 22572118)Natural Science Foundation of Shanghai(Grant No.23ZR1423900)。
文摘Optimizing the oxygen reduction reaction(ORR)kinetics requires precise control of intermediate adsorption at active sites,which can be achieved through orbital engineering by regulating the electronic structure.This study addresses the challenge by exploring how modulation of the 3d-orbital electronic structure of FeN_(4) active sites influences ORR electrocatalysis.To realize this,a catalyst composed of Fe_(3)C nanoparticles and FeN_(4) single atoms anchored on carbon black(Fe_(3)C-FeN_(4)/CB)was synthesized via a synergistic strategy of spatial confinement and atmosphere control.This unique heterostructure creates interfaces between Fe_(3)C and FeN_(4) that modulate the electronic configuration of the FeN_(4) center,transforming its geometry from square-planar to quasi-octahedral.Spectroscopic characterizations and theoretical calculations reveal that this orbital modulation results in a downward shift of the Fe dband center,altering the reaction pathway and lowering the energy barrier for ORR.Consequently,the Fe_(3)C-FeN_(4)/CB catalyst exhibits outstanding ORR activity,four-electron selectivity,excellent methanol tolerance,and remarkable electrochemical stability.When applied in a zinc-air battery,it achieves a peak power density of 178.4 mW cm^(-2)and superior cycling stability compared to commercial Pt/C catalysts.This work provides valuable insights into heterointerface-induced orbital modulation as a promising design principle for high-performance ORR electrocatalysts.
基金supported by the National Natural Science Foundation of China (Grant No.12374021)Beijing Natural Science Foundation (Grant No.1252031)。
文摘To overcome the limitations of traditional single-crystal X-ray diffraction(SCXRD)for microcrystalline materials and the peak-overlapping issue of powder X-ray diffraction(PXRD),this study employed cryogenic continuous rotation electron diffraction(cryo-cRED)with a low-dose strategy to determine the crystal structure of CL30,a novel silicogermanate framework.It is confirmed that CL30 crystallizes in the C2/m space group and has layered topology composed of discontinuous zigzag chains connected by double four-membered ring(d4r)units,with fluoride anions(F^(-))occluded in the d4r units.In CL30,charge balance involves organic structure-directing agent(OSDA)cations,occluded F^(-),and terminal oxygen sites whose protonation state cannot be established from the present three dimensional(3D)ED data.F^(-)encapsulated in the d4r units contributes to charge compensation as the counter-anion to OSDA cations,rather than only balancing the framework charge.Although the refinement indices(R_(1)=0.29,wR_(2)=0.71)exceeded typical small-molecule crystallography standards,the structural model remained highly reliable,as supported by geometric restraints and validation.In electron diffraction,elevated R_(1) values are commonly attributed to the intrinsic factors of the technique,such as dynamic scattering,detector noise from scintillator-based detectors,and TEM stage instability(large spheres of confusion).This study introduces a new structural prototype to the silicogermanate family and establishes a feasible workflow for determining the structures of radiation-sensitive microcrystalline porous materials.
基金supported by the National Natural Science Foundation of China(Nos.52175206,52205187,52130509)the Science and Technology Planning Project of Guizhou Province,China(No.ZK[2022]013)。
文摘The microstructural evolution and mechanical properties of a vacuum electron beam welded aerospace 5B70 aluminum alloy joint were studied.Quantitative analyses of the phase composition,microstructural evolution,grain size,grain boundary density,and texture changes were performed by X-ray diffraction,scanning electron microscopy,and electron backscatter diffraction.The fusion zone(FZ)comprises equiaxed cellular crystals,and a fine~20μm-thick crystal layer forms in the transition zone(TZ)between the FZ and heat affected zone(HAZ).The HAZ closely resembles the base material(BM),retaining the original rolling microstructure.Mechanical property testing shows that the fine-grained layer in the TZ exhibits the highest nanohardness,with the FZ corresponding to the lowest microhardness.The welded-joint sample has lower yield strength,ultimate tensile strength,and elongation after fracture than the BM.These reductions of mechanical properties are primarily influenced by the grain size and distribution of the precipitated phases.
基金the funding support from the National Natural Science Foundation of China(Grant No.52202217,52471222)the Natural Science Foundation of Jilin Province(Grant No.YDZJ202201ZYTS375).
文摘Layered double hydroxides(LDHs)hold great promise as cathode materials for aqueous zinc-ion batteries(AZIBs).Nevertheless,they also face challenges of sluggish kinetics and rapid capacity loss.Herein,a conformational entropy regulation strategy has been applied to surmount the shortcomings.A medium-entropy iron-based metal organic framework(MIL-88)derived NiCoFeInZnV-based layered double hydroxide with carbon loaded(ME-NiCoFeInZnV-LDH/C)has been first proposed and prepared with a designed method.The increased entropy optimizes electron conductivity and alleviates structure alteration and diffusion barrier during interactions with charge carriers,due to electron-induced effect and“cocktail”effect.Moreover,the nanosheet assembled hollow prismatic structures could homogenize flux distribution and electric field distribution.Therefore,the electrochemical kinetics,crystal structure stability,and activity could be dramatically improved.Leveraging the advantages of structure and composition regulation,Zn||ME-NiCoFeInZnV-LDH/C zinc battery delivers high specific capacities,rate performance,and cycling stability.This work proposes a novel and feasible medium-entropy strategy to prepare a high-performance cathode for advanced AZIBs,which is of prominent significance for the development of charge storage devices.
基金supported by the National Key Research and Development Program of China (Grant Nos.2022YFA1403202 and 2023YFA1406101)the CAS Superconducting Research Project (Grant No.SCZX-0101)。
文摘We report the discovery of bulk superconductivity in a new quinary intermetallic compound Th_(2)Mo_(2)Ru_(2)Si_(4)C,crystallized in a collapsed 22241-type structure.This structure is characterized by the intergrowth of ThMo_(2)Si_(2)C and ThRu_(2)Si_(2) units interconnected by equivalent Si-Si bonds that enhance inter-sublattice coupling.The refined lattice parameters are a=4.2212(1)Å and c=20.3899(7)Å.Electrical resistivity and magnetic susceptibility measurements of both polycrystalline and single-crystal samples consistently demonstrate bulk superconductivity with a transition temperature T_(c)∼6.0 K significantly higher than those of the constituent compound ThMo_(2)Si_(2)C and its related analogs.Under magnetic fields,the superconducting state exhibits a nearly isotropic behavior,which is attributed to strong covalent interlayer coupling.First-principles calculations reveal a substantial contribution from the Mo-d orbitals near the Fermi level,which exhibit several band-crossing points.The enhancement in T_(c) can be attributed to the synergistic combination of the valence electron concentration and the inter-sublattice self-doping effect between the[Ru_(2)Si_(2)]and[Mo_(2)Si_(2)C]layers.
基金the financial support by the National Nat-ural Science Foundation of China(Nos.52201282,52071281,52371239)the China Postdoctoral Science Foundation(No.2023M742945)+4 种基金Hebei Provincial Postdoctoral Science Foundation(No.B2023003023)the Science Research Project of Hebei Education Department(No.BJK2022033)the Natural Science Foundation of Hebei Province(No.C2022203003)the Inner Mongolia Science and Technology Major Project(No.2020ZD0012)the Baotou Science and Technology Planning Project(No.XM2022BT09).
文摘La-Mg-Ni-based hydrogen storage alloys with superlattice structures are the new generation anode material for nickel metal hydride(Ni-MH)batteries owing to the advantages of high capacity and exceptional activation properties.However,the cycling stability is not currently satisfactory enough which plagues its application.Herein,a strategy of partially substituting La with the Y element is proposed to boost the capacity durability of La-Mg-Ni-based alloys.Furthermore,phase structure regulation is implemented simultaneously to obtain the A5 B19-type alloy with good crystal stability specifically.It is found that Y promotes the phase formation of the Pr5 Co19-type phase after annealing at 985℃.The alloy containing Y contributes to the superior rate capability resulting from the promoted hydrogen diffusion rate.Notably,Y substitution enables strengthening the anti-pulverization ability of the alloy in terms of increasing the volume match between[A_(2)B_(4)]and[AB5]subunits,and effectively enhances the anti-corrosion ability of the alloy due to high electronegativity,realizing improved long-term cycling stability of the alloy from 74.2%to 78.5%after cycling 300 times.The work is expected to shed light on the composition and structure design of the La-Mg-Ni-based hydrogen storage alloy for Ni-MH batteries.
基金financially supported by the Science and Technology Innovation Fund Project of GRIMAT Engineering Institute Co.,Ltd.,China and the National Key R&D Program of China(No.2023YFB3710403)
文摘From the perspective of revealing the theoretical foundation in structural protection and impact resistance,an elaborate discussion was provided on the room-and hightemperature deformation behaviors of novel B2-structured Al_(0.5)NbTi_(3)VZr_(0.5)lightweight high-entropy alloy(LHEA),which provided a kind of potential structural material in application to lightweight high-temperature instruments.
基金funding from the Hellenic Foundation for Research and Innovation(HFRI)under grant agreement No 3655.
文摘Proton exchange membrane fuel cells(PEMFCs)constitute a promising avenue for environmentally friendly power generation.However,the reliance on unsustainable platinum-based electrocatalysts used at the electrodes poses challenges to the commercial viability of PEMFCs.Non-platinum group metal(non-PGM)alternatives,like nitrogen-coordinated transition metals in atomic dispersion(M–N–C catalysts),show significant potential.This work presents a comparative study of two distinct sets of Fe–N–C materials,prepared by pyrolyzing hybrid composites of polyaniline(PANI)and iron(Ⅱ)chloride on a hard template.One set uses bipyridine(BPy)as an additional nitrogen source and iron ligand,offering an innovative approach.The findings reveal that the choice of pyrolysis temperature and atmosphere influences the catalyst properties.The use of ammonia in pyrolysis emerges as a crucial parameter for promoting atomic dispersion of iron,as well as increasing surface area and porosity.The optimal catalyst,prepared using BPy and ammonia,exhibits a half-wave potential of 0.834 V in 0.5 M H_(2)SO_(4)(catalyst loading of 0.6 mg cm^(-2)),a mass activity exceeding 3 A g^(-1)and high stability in acidic electrolyte,positioning it as a promising non-PGM structure in the field.
基金supported by the National Natural Science Foundation of China(Nos.52101138,52201075)Natural Science Foundation of Hubei Province,China(Nos.2023AFB798,2022CFB614)+3 种基金Shenzhen Science and Technology Program,China(No.JCYJ20220530160813032)State Key Laboratory of Solidification Processing in NWPU,China(Nos.SKLSP202309,SKLSP202308)Guangdong Basic and Applied Basic Research Foundation,China(No.2022A1515011227)State Key Laboratory of Powder Metallurgy of Central South University,China(No.Sklpm-KF-05).
文摘Metallic glass matrix composites(BMGCs)with compositions of[(Zr_(0.5)Cu_(0.5))_(0.925)Al_(0.07)Sn_(0.005)]_(100-x)Ta_(x)(atomic fraction,%,x=3,5,7)were successfully prepared via dealloying in metallic melt.The reinforcing phase in these alloys has core-shell hybrid structure with Ta-rich particles as core and B2-CuZr as shell.In this method,the dealloyed Ta from Zr-Ta pre-alloys maintained in solid state and aggregated to form the fine Ta-rich phase in the final products.This effectively decreases the size of Ta-rich phase compared with that prepared via conventional arc-melting,where the Ta-rich phase was formed through dissolving and precipitation.Among the three compositions,[(Zr_(0.5)Cu_(0.5))_(0.925)Al_(0.07)Sn_(0.005)]_(95)Ta_(5) showed the highest plastic strain of 11.2%,much higher than that of the arc-melted counterparts(4.3%).Such improvement in mechanical properties was related with the refined core-shell hybrid reinforcing structure,which could hinder the rapid propagation of main shear band more efficiently and cause them to branch and proliferate at the interface.
基金Projects(50961009,51161015)supported by the National Natural Science Foundation of ChinaProject(2011AA03A408)supported by the High-tech Research and Development Program of ChinaProjects(2011ZD10,2010ZD05)supported by the Natural Science Foundation of Inner Mongolia,China
文摘In order to ameliorate the electrochemical hydrogen storage performance of La-Mg-Ni system A2B7-type electrode alloys, a small amount of Si was added. The La0.8Mg0.2Ni3.3Co0.2Six （x=0-0.2） electrode alloys were prepared by casting and annealing. The effects of adding Si on the structure and electrochemical hydrogen storage characteristics of the alloys were investigated systematically. The results indicate that the as-cast and annealed alloys hold multiple structures, involving two major phases of （La, Mg）2Ni7 with a Ce2Ni7-type hexagonal structure and LaNi5 with a CaCu5-type hexagonal structure as well as one residual phase LaNi3. The addition of Si results in a decrease in （La, Mg）2Ni7 phase and an increase in LaNi5 phase without changing the phase structure of the alloys. What is more, it brings on an obvious effect on electrochemical hydrogen storage characteristics of the alloys. The discharge capacities of the as-cast and annealed alloys decline with the increase of Si content, but their cycle stabilities clearly grow under the same condition. Furthermore, the measurements of the high rate discharge ability, the limiting current density, hydrogen diffusion coefficient as well as electrochemical impedance spectra all indicate that the electrochemical kinetic properties of the electrode alloys first increase and then decrease with the rising of Si content.
文摘Objective To examine the important roles of microRNAs （miRNAs） in regulating amphid structure and function, we performed a computational analysis for the genetic loci required for the sensory perception and their possibly corresponding miRNAs in C. elegans. Methods Total 55 genetic loci required for the amphid structure and function were selected. Sequence alignment was combined with E value evaluation to investigate and identify the possible corresponding miRNAs. Results Total 30 genes among the 55 genetic loci selected have their possible corresponding regulatory miRNA（s）, and identified genes participate in the regulation of almost all aspects of amphid structure and function. In addition, our data suggest that both the amphid structure and the amphid functions might be regulated by a series of network signaling pathways. Moreover, the distribution of miRNAs along the 3＇ untranslated region （UTR） of these 30 genes exhibits different patterns. Conclusion We present the possible miRNA-mediated signaling pathways involved in the regulation of chemosensation and thermosensation by controlling the corresponding sensory neuron and interneuron functions. Our work will be useful for better understanding of the miRNA-mediated control of the chemotaxis and thermotaxis in C. elegans.
