A model has been developed to describe the microstructure evolution in the atomized droplets of Cu-Fe alloy during cooling through the metastable miscibility gap. Calculations have been performed for Cu85Fe15 alloy to...A model has been developed to describe the microstructure evolution in the atomized droplets of Cu-Fe alloy during cooling through the metastable miscibility gap. Calculations have been performed for Cu85Fe15 alloy to investigate the process of liquid-liquid phase transformation. The numerical results indicate that the minority phase droplets are nucleated in a temperature region around the peak of the supersaturation. The average radius of the Fe-rlch droplets decreases and the number density of the minority phase droplets increases with decreasing the atomized droplet size. The simulated results were compared with the experimental ones. The kinetic process of the liquid-liquid phase transformation was discussed in detail.展开更多
The metallic liquid with miscibility gap has been widely explored recently because of the increasing plastic deformation ability of phase-separated metallic glass. However, the poor glass-forming ability limits its ap...The metallic liquid with miscibility gap has been widely explored recently because of the increasing plastic deformation ability of phase-separated metallic glass. However, the poor glass-forming ability limits its application as the structural materials due to the positive mixing enthalpy of the two elements. Since high pressure is in favor of the formation of the glass, the effect of pressure on the structural and dynamical heterogeneity of phase-separated CusoAgso liquid is inves- tigated by molecular dynamics simulation in the pressure range of 0-16 GPa. The results clearly show that the pressure promotes the formation of metallic glass by increasing the number of fivefold symmetry cluster W and dynamical relaxation time; meanwhile, the liquid-liquid phase separation is also enhanced, and the homogenous atom pAlrs show stronger interaction than heterogeneous atom pAlrs with increasing pressure. The dynamical heterogeneity is related to the formation of fivefold symmetry clusters. The lower growing rate of W at higher pressure with decreasing temperature corresponds to the slow increase in dynamical heterogeneity. The pressured glass with miscibility gap may act as a candidate glass with improved plastic formation ability. The results explore the structural and dynamical heterogeneity of phase-separated liquid at atomic level.展开更多
The isothermal section of the Fe-Cu-Ni ternary system at 1173 K was determined by microprobe analysis and diffusion triple technique. The experimental results show that this isothermal section only contains a miscibil...The isothermal section of the Fe-Cu-Ni ternary system at 1173 K was determined by microprobe analysis and diffusion triple technique. The experimental results show that this isothermal section only contains a miscibility gap region,and the maximal Ni content in the miscibility gap is 44.7 at.-%Ni.展开更多
Powder metallurgy processes are suitable to produce form-stable solid−liquid phase change materials from miscibility gap alloys.They allow to obtain a composite metallic material with good dispersion of low-melting ac...Powder metallurgy processes are suitable to produce form-stable solid−liquid phase change materials from miscibility gap alloys.They allow to obtain a composite metallic material with good dispersion of low-melting active phase particles in a high-melting passive matrix,preventing leakage of the particles during phase transition and,therefore,increasing the stability of thermal response.Also,the matrix provides structural properties.The aim of this work is to combine conventional powder mixing techniques(simple mixing and ball milling)to improve active phase isolation and mechanical properties of an Al−Sn alloy.As matter of fact,ball milling of Sn powder allows to reduce hardness difference with Al powder;moreover,ball milling of the two powders together results in fine microstructure with improved mechanical properties.In addition,different routes applied showed that thermal response depends on the microstructure and,in particular,on the particle size of the active phase.In more detail,coarse active phase particles provide a fast heat release with small undercooling,while small particles solidify more slowly in a wide range of temperature.On the other hand,melting and,consequently,heat storage are independent of the particle size of the active phase.This potentially allows to“tailor”the thermal response by producing alloys with suitable microstructure.展开更多
Ag-Fe nanoparticles with a highly Ag rich average composition were synthesized by the sonochemical route.Silver-iron system exhibits a wide miscibility gap in the bulk materials.Interestingly,a graded compositional pr...Ag-Fe nanoparticles with a highly Ag rich average composition were synthesized by the sonochemical route.Silver-iron system exhibits a wide miscibility gap in the bulk materials.Interestingly,a graded compositional profile along the nanoparticle radius was observed.Regions at and near the surface of the nanoparticle contained both Ag and Fe atoms.The composition got relatively deficient Fe towards the center of the particle with particle core made up of pure Ag.Alloying of Ag and Fe is confirmed by the absence of diffraction signal corresponding to pure Fe phase and presence of a paramagnetic phase in nanoparticles containing a diamagnetic(Ag)and ferromagnetic(Fe)elements.展开更多
Development of high-performance phase transformation electrodes in lithium ion batteries requires comprehensive studies on stress-mediated lithiation involving migration of the phase interface. It brings out many coun...Development of high-performance phase transformation electrodes in lithium ion batteries requires comprehensive studies on stress-mediated lithiation involving migration of the phase interface. It brings out many counter-intuitive phenomena, especially in nanoscale electrodes, such as the slowing down migration of phase interface, the vanishing of miscibility gap under high charge rate, and the formation of surface crack during lithiation. However, it is still a challenge to simulate the evolution of stress in arbitrarily-shaped nanoscale electrodes, accompanied with phase transformation and concurrent plastic deformation. This article gives a brief review of our efforts devoted to address these issues by developing phase field model and simulation. We demonstrate that the miscibility gap of two-phase state is affected not only by stress but also by surface reaction rate and particle size. In addition, the migration of phase interface slows down due to stress. It reveals that the plastic deformation generates large radial expansion, which is responsible for the transition from surface hoop compression to surface hoop tension that may induce surface crack during lithiation. We hope our effort can make a contribution to the understanding of stress-coupled kinetics in phase transformation electrodes.展开更多
he expressions of the composition space and the dependent properties of the lattice constant, the energy bandgap and the Gibbs energy were presented for the (Ga,In)(As,Sb) quaternary compound semiconductor. On the bas...he expressions of the composition space and the dependent properties of the lattice constant, the energy bandgap and the Gibbs energy were presented for the (Ga,In)(As,Sb) quaternary compound semiconductor. On the basis of these expressions, a computer aided analysis system is set up for the design of ⅢⅤ compound semiconductor materials and growth processes. By using this system, a comprehensively optimized diagram is constructed through the projection of the optoelectronic properties (energy bandgap or wave length), in which the composition relations are matched to substrates and the miscibility gaps.展开更多
The experimental phase equilibria of the Mn-Si-Zn system available in the literature were critically evaluated.Thermodynamic assessment of the Mn-Si-Zn system was then performed in the framework of CALPHAD(CALculation...The experimental phase equilibria of the Mn-Si-Zn system available in the literature were critically evaluated.Thermodynamic assessment of the Mn-Si-Zn system was then performed in the framework of CALPHAD(CALculation of PHAse Diagram) method on the basis of the experimental data in the literature.The optimal thermodynamic parameters of the ternary system were then obtained,yielding a good agreement with most of the experimental data.The complete liquidus projection and reaction scheme was also presented for the Mn-Si-Zn system.It is noteworthy that a stable closed liquid miscibility gap appears in the computed ternary phase diagrams,even though it is metastable in three boundary binaries.The occurrence of such a closed miscibility gap can be predicted by a criterion considering the general thermodynamic rules and the features of the three constituent binary systems.展开更多
基金the finan cial supports from the National Natural Science Foundation of China(Grant Nos.50271076,50371092 , 50395104)the Sino-Germany Science Foundation(GZ032/1) the Natural Science Foundation of Liaoning Province of China.
文摘A model has been developed to describe the microstructure evolution in the atomized droplets of Cu-Fe alloy during cooling through the metastable miscibility gap. Calculations have been performed for Cu85Fe15 alloy to investigate the process of liquid-liquid phase transformation. The numerical results indicate that the minority phase droplets are nucleated in a temperature region around the peak of the supersaturation. The average radius of the Fe-rlch droplets decreases and the number density of the minority phase droplets increases with decreasing the atomized droplet size. The simulated results were compared with the experimental ones. The kinetic process of the liquid-liquid phase transformation was discussed in detail.
基金Financial support from the National Natural Science Foundation of China （Nos. 51371108, 51501104 and 51501103） and the Natural Science Foundation of Shandong Province （No. ZR2014EMM011） is gratefully acknowledged. A major part of the present computation was carried out using the HPC Cluster Supercomputer center at Shandong University （Weihai）.
文摘The metallic liquid with miscibility gap has been widely explored recently because of the increasing plastic deformation ability of phase-separated metallic glass. However, the poor glass-forming ability limits its application as the structural materials due to the positive mixing enthalpy of the two elements. Since high pressure is in favor of the formation of the glass, the effect of pressure on the structural and dynamical heterogeneity of phase-separated CusoAgso liquid is inves- tigated by molecular dynamics simulation in the pressure range of 0-16 GPa. The results clearly show that the pressure promotes the formation of metallic glass by increasing the number of fivefold symmetry cluster W and dynamical relaxation time; meanwhile, the liquid-liquid phase separation is also enhanced, and the homogenous atom pAlrs show stronger interaction than heterogeneous atom pAlrs with increasing pressure. The dynamical heterogeneity is related to the formation of fivefold symmetry clusters. The lower growing rate of W at higher pressure with decreasing temperature corresponds to the slow increase in dynamical heterogeneity. The pressured glass with miscibility gap may act as a candidate glass with improved plastic formation ability. The results explore the structural and dynamical heterogeneity of phase-separated liquid at atomic level.
文摘The isothermal section of the Fe-Cu-Ni ternary system at 1173 K was determined by microprobe analysis and diffusion triple technique. The experimental results show that this isothermal section only contains a miscibility gap region,and the maximal Ni content in the miscibility gap is 44.7 at.-%Ni.
文摘Powder metallurgy processes are suitable to produce form-stable solid−liquid phase change materials from miscibility gap alloys.They allow to obtain a composite metallic material with good dispersion of low-melting active phase particles in a high-melting passive matrix,preventing leakage of the particles during phase transition and,therefore,increasing the stability of thermal response.Also,the matrix provides structural properties.The aim of this work is to combine conventional powder mixing techniques(simple mixing and ball milling)to improve active phase isolation and mechanical properties of an Al−Sn alloy.As matter of fact,ball milling of Sn powder allows to reduce hardness difference with Al powder;moreover,ball milling of the two powders together results in fine microstructure with improved mechanical properties.In addition,different routes applied showed that thermal response depends on the microstructure and,in particular,on the particle size of the active phase.In more detail,coarse active phase particles provide a fast heat release with small undercooling,while small particles solidify more slowly in a wide range of temperature.On the other hand,melting and,consequently,heat storage are independent of the particle size of the active phase.This potentially allows to“tailor”the thermal response by producing alloys with suitable microstructure.
文摘Ag-Fe nanoparticles with a highly Ag rich average composition were synthesized by the sonochemical route.Silver-iron system exhibits a wide miscibility gap in the bulk materials.Interestingly,a graded compositional profile along the nanoparticle radius was observed.Regions at and near the surface of the nanoparticle contained both Ag and Fe atoms.The composition got relatively deficient Fe towards the center of the particle with particle core made up of pure Ag.Alloying of Ag and Fe is confirmed by the absence of diffraction signal corresponding to pure Fe phase and presence of a paramagnetic phase in nanoparticles containing a diamagnetic(Ag)and ferromagnetic(Fe)elements.
基金supported by the National Natural Science Foundation of China (Grant no. 11472262)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant no. XDB22040502)+1 种基金the Collaborative Innovation Center of Suzhou Nano Science and Technologythe Fundamental Research Funds for the Central Universities
文摘Development of high-performance phase transformation electrodes in lithium ion batteries requires comprehensive studies on stress-mediated lithiation involving migration of the phase interface. It brings out many counter-intuitive phenomena, especially in nanoscale electrodes, such as the slowing down migration of phase interface, the vanishing of miscibility gap under high charge rate, and the formation of surface crack during lithiation. However, it is still a challenge to simulate the evolution of stress in arbitrarily-shaped nanoscale electrodes, accompanied with phase transformation and concurrent plastic deformation. This article gives a brief review of our efforts devoted to address these issues by developing phase field model and simulation. We demonstrate that the miscibility gap of two-phase state is affected not only by stress but also by surface reaction rate and particle size. In addition, the migration of phase interface slows down due to stress. It reveals that the plastic deformation generates large radial expansion, which is responsible for the transition from surface hoop compression to surface hoop tension that may induce surface crack during lithiation. We hope our effort can make a contribution to the understanding of stress-coupled kinetics in phase transformation electrodes.
文摘he expressions of the composition space and the dependent properties of the lattice constant, the energy bandgap and the Gibbs energy were presented for the (Ga,In)(As,Sb) quaternary compound semiconductor. On the basis of these expressions, a computer aided analysis system is set up for the design of ⅢⅤ compound semiconductor materials and growth processes. By using this system, a comprehensively optimized diagram is constructed through the projection of the optoelectronic properties (energy bandgap or wave length), in which the composition relations are matched to substrates and the miscibility gaps.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50831007 and 51071179) National Basic Research Program of China (Grant No. 2011CB610401)
文摘The experimental phase equilibria of the Mn-Si-Zn system available in the literature were critically evaluated.Thermodynamic assessment of the Mn-Si-Zn system was then performed in the framework of CALPHAD(CALculation of PHAse Diagram) method on the basis of the experimental data in the literature.The optimal thermodynamic parameters of the ternary system were then obtained,yielding a good agreement with most of the experimental data.The complete liquidus projection and reaction scheme was also presented for the Mn-Si-Zn system.It is noteworthy that a stable closed liquid miscibility gap appears in the computed ternary phase diagrams,even though it is metastable in three boundary binaries.The occurrence of such a closed miscibility gap can be predicted by a criterion considering the general thermodynamic rules and the features of the three constituent binary systems.
