The addition of hexagonal-close-packed(hcp)non-rare-earth elements Zr,Ti and Co,to the 10-component hep rare-earth-based high-entropy alloys(HEAs)with a composition of ScYLaNdGdTbDyHoErLuX(X=Zr,Co and Ti)was investiga...The addition of hexagonal-close-packed(hcp)non-rare-earth elements Zr,Ti and Co,to the 10-component hep rare-earth-based high-entropy alloys(HEAs)with a composition of ScYLaNdGdTbDyHoErLuX(X=Zr,Co and Ti)was investigated.The enthalpy of mixing between elements was found to have a significant effect on the formation of phases.The addition of Co combines with elements that had a strong chemical affinity to form intermetallic compounds by the effect of enthalpy.Ti was added with all elements with poor chemical affinity and exhibited rejection to form a phase alone.These were the two terminal manifestations of the role of enthalpy over entropy.Part of Zr was soluble in the matrix under the action of entropy,while the other part had a greater affinity for Sc than the other elements to form a precipitate under the action of enthalpy.This was the result of the local balance between the effect of enthalpy and entropy.The solid solution of the elements had different degrees of strengthening effect,among which Zr had the most excellent strengthening effect from 185 to 355 MPa,so the solid solution strengthening model and precipitation strengthening model were proposed to predict the strength of the alloy with the addition of Zr effectively.展开更多
Metallic hydrogen could be not only high-efficiency fuel for nuclear fusion and high explosive but also a high-temperature superconductor. The study of metallic hydrogen is of great help to solving some important prob...Metallic hydrogen could be not only high-efficiency fuel for nuclear fusion and high explosive but also a high-temperature superconductor. The study of metallic hydrogen is of great help to solving some important problems in the field of geophysics and astrophysics, such as the electronic and magnetic properties of the giant planets (Jupiter and Saturn) and their evolution, processes. So the study of metallic hydrogen is of momentous significance both theoretically and practically. In 1935 Wigner and Huntington pro-展开更多
The lattice parameters, elastic constants, cohesive energy, structural energy differences, as well as the properties of point defects and planar defects of hexagonal closepacked yttrium （hcpY） have been studied with...The lattice parameters, elastic constants, cohesive energy, structural energy differences, as well as the properties of point defects and planar defects of hexagonal closepacked yttrium （hcpY） have been studied with ab initio density functional theory for constructing an ex tensive database. Based on an analytical bondorder poial scheme, empirical manybody interatomic potential for hcpY has been developed. The model is fitted to some properties of Y, e.g., the lattice parameters, elastic constants, bulk modulus, cohesive energy, vacancy formation energy, and the structural energy differences. The present potential has ability to reproduce defect properties including the selfinterstitial atoms formation energies, vacancy formation energy, divacancy binding energy, as well as the bulk properties and the thermal dynamic properties.展开更多
In this paper, a new physically based constitutive model is developed for hexagonal close-packed metals, especially the Ti-6Al-4V alloy, subjected to high strain rate and different temperatures based on the microscopi...In this paper, a new physically based constitutive model is developed for hexagonal close-packed metals, especially the Ti-6Al-4V alloy, subjected to high strain rate and different temperatures based on the microscopic mechanism of plastic deformation and the theory of thermally activated dislocation motion. A global analysis of constitutive parameters based on the Latin Hypercube Sampling method and the Spearman＇s rank correlation method is adopted in order to improve the identification efficiency of parameters. Then, an optimal solution of constitutive parameters as a whole is obtained by using a global genetic algorithm composed of an improved niche genetic algorithm, a global peak determination strategy and the local accurate search techniques. It is concluded that the proposed constitutive modal can accurately describe the Ti-6Al-4V alloy＇s dynamic behavior because the prediction results of the model are in good agreement with the experimental data.展开更多
With the support by the National Natural Science Foundation of China and the Chinese Academy of Sciences,the research team led by Prof.Wang QiangBin(王强斌)at the CAS Key Laboratory of Nano-Bio Interface,Division of N...With the support by the National Natural Science Foundation of China and the Chinese Academy of Sciences,the research team led by Prof.Wang QiangBin(王强斌)at the CAS Key Laboratory of Nano-Bio Interface,Division of Nanobiomedicine and i-Lab,Suzhou Institute of Nano-Tech and Nano-Bionics,Chinese Academy of Sciences,revealed the role of metal alloy crystal structure in oxygen evolution reaction,which was recently published in Angew Chem Int Ed(2019,58(18):6099—6103).展开更多
High-pressure Raman scattering from hexagonal close-packed(HCP) metals Os and Re have been extended up to 200 GPa, and the pressure-dependent shear modulus C_(44)has been deduced from the Raman-active mode E_(28), whi...High-pressure Raman scattering from hexagonal close-packed(HCP) metals Os and Re have been extended up to 200 GPa, and the pressure-dependent shear modulus C_(44)has been deduced from the Raman-active mode E_(28), which is generated from the adjacent vibration of atoms in hexagonal planes, providing the valuable information about the elastic properties for HCP metals under high pressure. Combined with the available data of HCP metals from previous works,a further study indicates that the C_(44)/C_(44)ratio would be close to a constant value, 0.01, with increasing atomic number of metals. The results obtained from high-pressure Raman scattering will allow us to probe the elastic anisotropy of the HCP metals at very high pressure.展开更多
Recently,various topics on high-entropy alloys have been reported and great amounts of excellent properties have been investigated,including high strength,great corrosion resistance,great thermal stability,good fatigu...Recently,various topics on high-entropy alloys have been reported and great amounts of excellent properties have been investigated,including high strength,great corrosion resistance,great thermal stability,good fatigue and fracture properties,etc.Among all these research activities,high-entropy alloys tend to form face-centered-cubic(FCC)or body-centeredcubic(BCC)solid solutions due to their high-entropy stabilization effect,while the hexagonal structures are rarely reported.Up to now,the reported hexagonal high-entropy alloys are mainly composed of rare-earth elements and transitional elements.Their phase transformation and magnetic properties have also aroused wide concern.This study summarizes the above results and provides the forecast to the future.展开更多
A hybrid first-principles/Monte Carlo simulation is combined with experiments to study the structure and elastic properties of CoCrNi_x(x=1-0.5)alloys.The experimental X-ray diffraction patterns show that the structur...A hybrid first-principles/Monte Carlo simulation is combined with experiments to study the structure and elastic properties of CoCrNi_x(x=1-0.5)alloys.The experimental X-ray diffraction patterns show that the structures have changed from the single-phase face-centered cubic(FCC)structure at x=1-0.8 to the coexistence of FCC and the hexagonal close-packed structures at x=0.7-0.5,which is further confirmed by calculations on mixing energies.The elastic moduli by calculation are basically in agreement with experiments.Room-temperature tension shows that the six alloys have a certain plasticity,the strength and plasticity of the alloys have a linear decrease with the decrease in Ni contents,and the plasticity of the alloys drops from 84 to 23%.Furthermore,first-principles density function theory calculations were employed to reveal the electronic and magnetic structures of alloys.The electron density of states for all alloys is asymmetrical,which illustrates that the alloys are ferromagnetism.It is found that Cr atoms can suppress the ferromagnetism of alloys,since Cr atoms have both positive and negative magnetic moments in all alloys.展开更多
The inherent uncertainty of chain length in synthetic polymers casts doubt on the explicit understanding of fundamental principles.This study quantitatively assesses the critical role of chain-length distribution in t...The inherent uncertainty of chain length in synthetic polymers casts doubt on the explicit understanding of fundamental principles.This study quantitatively assesses the critical role of chain-length distribution in the self-assembly process,aiming to identify the point at which discernible discrepancies begin to emerge.By blending discrete diblock copolymers of varying sizes,chain-length nonuniformity can be precisely regulated while the average composition remains constant.Introducing a minor heterogeneity leads to an expansion of lattice dimension,while a phase transition occurs as the difference exceeds a threshold.Interestingly,a transition from the Frank–Kasperσphase to the body-centered cubic phase was triggered by enlarging the size difference of the corona block,while introducing heterogeneity in the core block stabilized the hexagonally close-packed spheres.A self-consistent field theory calculation reveals that the synergy between the long and short chains effectively releases packing frustration,leading to substantial changes in the free-energy landscape and stabilizing unconventional phases otherwise inaccessible.This work calls particular attention to the importance of chain-length heterogeneity and provides a robust approach to finely tuning the phase behavior and physical properties of block copolymers without altering their chemical composition.展开更多
Co nanowire arrays of different crystal struc-tures have been electrodeposited into self-assembled anodic aluminum oxide (AAO) templates by varying pH value of electrolyte. The XRD results show that crystal structure ...Co nanowire arrays of different crystal struc-tures have been electrodeposited into self-assembled anodic aluminum oxide (AAO) templates by varying pH value of electrolyte. The XRD results show that crystal structure of Co nanowires is fcc structure at pH = 2.5, a mixed structure of fcc and hcp at pH = 3.0 and 3.5, and hcp structure at pH = 5.0. Magnetic measurements indicate that Co nanowire ar-rays of different crystal structures exhibit different magnetic properties. The coercivity of Co nanowire array of fcc struc-ture is larger than that of hcp structure about 900×103/4p A·m-1 along wire axis, and its squareness is also larger than that of hcp structure.展开更多
基金financially supported by the Natural Science Foundation of Shanxi Province,China (Nos. 201901D111105 and 201901D111114)the Key Research and Development Program of Shanxi Province (No.202102050201008)+1 种基金the National Science Foundation,United States (Nos.DMR-1611180 and 1809640)the U.S.Army Research Office (Nos.W911NF-131-0438 and W911NF-19-2-0049)
文摘The addition of hexagonal-close-packed(hcp)non-rare-earth elements Zr,Ti and Co,to the 10-component hep rare-earth-based high-entropy alloys(HEAs)with a composition of ScYLaNdGdTbDyHoErLuX(X=Zr,Co and Ti)was investigated.The enthalpy of mixing between elements was found to have a significant effect on the formation of phases.The addition of Co combines with elements that had a strong chemical affinity to form intermetallic compounds by the effect of enthalpy.Ti was added with all elements with poor chemical affinity and exhibited rejection to form a phase alone.These were the two terminal manifestations of the role of enthalpy over entropy.Part of Zr was soluble in the matrix under the action of entropy,while the other part had a greater affinity for Sc than the other elements to form a precipitate under the action of enthalpy.This was the result of the local balance between the effect of enthalpy and entropy.The solid solution of the elements had different degrees of strengthening effect,among which Zr had the most excellent strengthening effect from 185 to 355 MPa,so the solid solution strengthening model and precipitation strengthening model were proposed to predict the strength of the alloy with the addition of Zr effectively.
文摘Metallic hydrogen could be not only high-efficiency fuel for nuclear fusion and high explosive but also a high-temperature superconductor. The study of metallic hydrogen is of great help to solving some important problems in the field of geophysics and astrophysics, such as the electronic and magnetic properties of the giant planets (Jupiter and Saturn) and their evolution, processes. So the study of metallic hydrogen is of momentous significance both theoretically and practically. In 1935 Wigner and Huntington pro-
文摘The lattice parameters, elastic constants, cohesive energy, structural energy differences, as well as the properties of point defects and planar defects of hexagonal closepacked yttrium （hcpY） have been studied with ab initio density functional theory for constructing an ex tensive database. Based on an analytical bondorder poial scheme, empirical manybody interatomic potential for hcpY has been developed. The model is fitted to some properties of Y, e.g., the lattice parameters, elastic constants, bulk modulus, cohesive energy, vacancy formation energy, and the structural energy differences. The present potential has ability to reproduce defect properties including the selfinterstitial atoms formation energies, vacancy formation energy, divacancy binding energy, as well as the bulk properties and the thermal dynamic properties.
基金the financial support by the National Natural Science Foundation of China Academy of Engineering Physicsthe jointly set-up"NSAF"joint fund under Contract No.U1430119
文摘In this paper, a new physically based constitutive model is developed for hexagonal close-packed metals, especially the Ti-6Al-4V alloy, subjected to high strain rate and different temperatures based on the microscopic mechanism of plastic deformation and the theory of thermally activated dislocation motion. A global analysis of constitutive parameters based on the Latin Hypercube Sampling method and the Spearman＇s rank correlation method is adopted in order to improve the identification efficiency of parameters. Then, an optimal solution of constitutive parameters as a whole is obtained by using a global genetic algorithm composed of an improved niche genetic algorithm, a global peak determination strategy and the local accurate search techniques. It is concluded that the proposed constitutive modal can accurately describe the Ti-6Al-4V alloy＇s dynamic behavior because the prediction results of the model are in good agreement with the experimental data.
文摘With the support by the National Natural Science Foundation of China and the Chinese Academy of Sciences,the research team led by Prof.Wang QiangBin(王强斌)at the CAS Key Laboratory of Nano-Bio Interface,Division of Nanobiomedicine and i-Lab,Suzhou Institute of Nano-Tech and Nano-Bionics,Chinese Academy of Sciences,revealed the role of metal alloy crystal structure in oxygen evolution reaction,which was recently published in Angew Chem Int Ed(2019,58(18):6099—6103).
基金financially supported by the National Natural Science Foundation of China (Grant Nos. 11774247 and U2030107)Sichuan University Innovation Research Program of China (Grant No. 2020SCUNL107)。
文摘High-pressure Raman scattering from hexagonal close-packed(HCP) metals Os and Re have been extended up to 200 GPa, and the pressure-dependent shear modulus C_(44)has been deduced from the Raman-active mode E_(28), which is generated from the adjacent vibration of atoms in hexagonal planes, providing the valuable information about the elastic properties for HCP metals under high pressure. Combined with the available data of HCP metals from previous works,a further study indicates that the C_(44)/C_(44)ratio would be close to a constant value, 0.01, with increasing atomic number of metals. The results obtained from high-pressure Raman scattering will allow us to probe the elastic anisotropy of the HCP metals at very high pressure.
基金financial support from the National Natural Science Foundation of China (No 51671020)Fundamental Research Funds for the Central Universities (No. FRF-MP-19-013)。
文摘Recently,various topics on high-entropy alloys have been reported and great amounts of excellent properties have been investigated,including high strength,great corrosion resistance,great thermal stability,good fatigue and fracture properties,etc.Among all these research activities,high-entropy alloys tend to form face-centered-cubic(FCC)or body-centeredcubic(BCC)solid solutions due to their high-entropy stabilization effect,while the hexagonal structures are rarely reported.Up to now,the reported hexagonal high-entropy alloys are mainly composed of rare-earth elements and transitional elements.Their phase transformation and magnetic properties have also aroused wide concern.This study summarizes the above results and provides the forecast to the future.
基金the National Key Laboratory for Remanufacturing(No.61420050204)Transformation of Scientific and Technological Achievements Programs of Higher Education Institutions in Shanxi(2019)+1 种基金opening project of the State Key Laboratory of Explosion Science and Technology(Beijing Institute of Technology,No.KFJJ20-13 M)Hua Tian would like to acknowledge the National Natural Science Foundation of China(No.51901152)。
文摘A hybrid first-principles/Monte Carlo simulation is combined with experiments to study the structure and elastic properties of CoCrNi_x(x=1-0.5)alloys.The experimental X-ray diffraction patterns show that the structures have changed from the single-phase face-centered cubic(FCC)structure at x=1-0.8 to the coexistence of FCC and the hexagonal close-packed structures at x=0.7-0.5,which is further confirmed by calculations on mixing energies.The elastic moduli by calculation are basically in agreement with experiments.Room-temperature tension shows that the six alloys have a certain plasticity,the strength and plasticity of the alloys have a linear decrease with the decrease in Ni contents,and the plasticity of the alloys drops from 84 to 23%.Furthermore,first-principles density function theory calculations were employed to reveal the electronic and magnetic structures of alloys.The electron density of states for all alloys is asymmetrical,which illustrates that the alloys are ferromagnetism.It is found that Cr atoms can suppress the ferromagnetism of alloys,since Cr atoms have both positive and negative magnetic moments in all alloys.
基金supported by the National Natural Science Foundation of China(grant no.22273026)the Recruitment Program of Guangdong(grant no.2016ZT06C322)+1 种基金the Research Funds from State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials,Soochow University(grant no.SDGC2109)the 111 Project(grant no.B18023).
文摘The inherent uncertainty of chain length in synthetic polymers casts doubt on the explicit understanding of fundamental principles.This study quantitatively assesses the critical role of chain-length distribution in the self-assembly process,aiming to identify the point at which discernible discrepancies begin to emerge.By blending discrete diblock copolymers of varying sizes,chain-length nonuniformity can be precisely regulated while the average composition remains constant.Introducing a minor heterogeneity leads to an expansion of lattice dimension,while a phase transition occurs as the difference exceeds a threshold.Interestingly,a transition from the Frank–Kasperσphase to the body-centered cubic phase was triggered by enlarging the size difference of the corona block,while introducing heterogeneity in the core block stabilized the hexagonally close-packed spheres.A self-consistent field theory calculation reveals that the synergy between the long and short chains effectively releases packing frustration,leading to substantial changes in the free-energy landscape and stabilizing unconventional phases otherwise inaccessible.This work calls particular attention to the importance of chain-length heterogeneity and provides a robust approach to finely tuning the phase behavior and physical properties of block copolymers without altering their chemical composition.
文摘Co nanowire arrays of different crystal struc-tures have been electrodeposited into self-assembled anodic aluminum oxide (AAO) templates by varying pH value of electrolyte. The XRD results show that crystal structure of Co nanowires is fcc structure at pH = 2.5, a mixed structure of fcc and hcp at pH = 3.0 and 3.5, and hcp structure at pH = 5.0. Magnetic measurements indicate that Co nanowire ar-rays of different crystal structures exhibit different magnetic properties. The coercivity of Co nanowire array of fcc struc-ture is larger than that of hcp structure about 900×103/4p A·m-1 along wire axis, and its squareness is also larger than that of hcp structure.
