The phase stability,elastic properties and electronic structures of three typical Mg-Y intermetallics including Mg_(24)Y_(5),Mg_(2)Y and MgY are systematically investigated using first-principles calculations based on...The phase stability,elastic properties and electronic structures of three typical Mg-Y intermetallics including Mg_(24)Y_(5),Mg_(2)Y and MgY are systematically investigated using first-principles calculations based on density functional theory.The optimized structural parameters including lattice constants and atomic coordinates are in good agreement with experimental values.The calculated cohesive energies and formation enthalpies show that either phase stability or alloying ability of the three intermetallics is gradually enhanced with increasing Y content.The single-crystal elastic constants C_(ij) of Mg-Y intermetallics are also calculated,and the bulk modulus B,shear modulus G,Young's modulus E,Poisson ratio v and anisotropy factor A of polycrystalline materials are derived.It is suggested that the resistances to volume and shear deformation as well as the stiffness of the three intermetallics are raised with increasing Y content.Besides,these intermetallics all exhibit ductile characteristics,and they are isotropic in compression but anisotropic to a certain degree in shear and stiffness.Comparatively,Mg_(24)Y_(5) presents a relatively higher ductility,while MgY has a relatively stronger anisotropy in shear and stiffness.Further analysis of electronic structures indicates that the phase stability of Mg-Y intermetallics is closely related with their bonding electrons numbers below Fermi level.Namely,the more bonding electrons number below Fermi level corresponds to the higher structural stability of Mg-Y intermetallics.展开更多
Al-Si alloy,a high temperature phase change material,has great potential in thermal management due to its advantages of high heat storage density and thermal conductivity.Microencapsulation of Al-Si alloy is one of th...Al-Si alloy,a high temperature phase change material,has great potential in thermal management due to its advantages of high heat storage density and thermal conductivity.Microencapsulation of Al-Si alloy is one of the effective techniques to solve high temperature leakage and corrosion.In this paper,commercial Al-10Si alloy micro powders were encapsulated with flexible ceramic shells whose total thickness is below 1μm by hydrothermal treatment and heat treatment in N_(2) atmosphere.The compositions and microstructures were characterized by XRD,SEM and TEM.The shell was composed of AlN fibers network structure embedded withα-Al_(2)O_(3)/AlN which prevented the alloy from leaking and oxidizing,as well as had excellent thermal stability.The latent heat of microcapsules was 351.8 J g^(-1)for absorption and 372.7 J g^(-1)for exothermic.The microcapsules showed near zero thermal performance loss with latent heat storage(LHS)/release(LHR)was 353.2/403.7 J g^(-1)after 3000 cycles.Compared with the published Al-Si alloy microcapsules,both high heat storage density and super thermal cycle stability were achieved,showing promising development prospects in high temperature thermal management.展开更多
基金This work was financially supported by the National Natural Science Foundation of China(No.51401036)the Hunan Provincial Natural Science Foundation of China(No.14JJ3086),the Research Foundation of Education Bureau of Hunan Province(No.12B001)the Key Laboratory of Efficient and Clean Energy Utilization,College of Hunan Province(No.2015NGQ005).
文摘The phase stability,elastic properties and electronic structures of three typical Mg-Y intermetallics including Mg_(24)Y_(5),Mg_(2)Y and MgY are systematically investigated using first-principles calculations based on density functional theory.The optimized structural parameters including lattice constants and atomic coordinates are in good agreement with experimental values.The calculated cohesive energies and formation enthalpies show that either phase stability or alloying ability of the three intermetallics is gradually enhanced with increasing Y content.The single-crystal elastic constants C_(ij) of Mg-Y intermetallics are also calculated,and the bulk modulus B,shear modulus G,Young's modulus E,Poisson ratio v and anisotropy factor A of polycrystalline materials are derived.It is suggested that the resistances to volume and shear deformation as well as the stiffness of the three intermetallics are raised with increasing Y content.Besides,these intermetallics all exhibit ductile characteristics,and they are isotropic in compression but anisotropic to a certain degree in shear and stiffness.Comparatively,Mg_(24)Y_(5) presents a relatively higher ductility,while MgY has a relatively stronger anisotropy in shear and stiffness.Further analysis of electronic structures indicates that the phase stability of Mg-Y intermetallics is closely related with their bonding electrons numbers below Fermi level.Namely,the more bonding electrons number below Fermi level corresponds to the higher structural stability of Mg-Y intermetallics.
基金financial support from the National Natural Science Foundation of China(No.52072276)Hubei Important Project on Science and Technology(No.2022BECO20).
文摘Al-Si alloy,a high temperature phase change material,has great potential in thermal management due to its advantages of high heat storage density and thermal conductivity.Microencapsulation of Al-Si alloy is one of the effective techniques to solve high temperature leakage and corrosion.In this paper,commercial Al-10Si alloy micro powders were encapsulated with flexible ceramic shells whose total thickness is below 1μm by hydrothermal treatment and heat treatment in N_(2) atmosphere.The compositions and microstructures were characterized by XRD,SEM and TEM.The shell was composed of AlN fibers network structure embedded withα-Al_(2)O_(3)/AlN which prevented the alloy from leaking and oxidizing,as well as had excellent thermal stability.The latent heat of microcapsules was 351.8 J g^(-1)for absorption and 372.7 J g^(-1)for exothermic.The microcapsules showed near zero thermal performance loss with latent heat storage(LHS)/release(LHR)was 353.2/403.7 J g^(-1)after 3000 cycles.Compared with the published Al-Si alloy microcapsules,both high heat storage density and super thermal cycle stability were achieved,showing promising development prospects in high temperature thermal management.
