Solid-state electrolytes are critical for the development of next-generation high-energy and high-safety rechargeable batteries.Among all the candidates,sodium(Na)superionic conductors(NASICONs)are highly promising be...Solid-state electrolytes are critical for the development of next-generation high-energy and high-safety rechargeable batteries.Among all the candidates,sodium(Na)superionic conductors(NASICONs)are highly promising because of their evident advantages in high ionic conductivity and high chemical/electrochemical stability.The concept of NASICONs was proposed by Hong and Goodenough et al.in 1976 by reporting the synthesis and characterization of Na1+xZr2(SixP3−x)O12(0≤x≤3),which has attracted tremendous attention on the NASICONs-type solid-state electrolytes.In this review,we are committed to describing the development history of NASICONs-type solid-state electrolytes and elucidating the contribution of Goodenough as a tribute to him.We summarize the correlations and differences between lithium-based and sodium-based NASICONs electrolytes,such as their preparation methods,structures,ionic conductivities,and the mechanisms of ion transportation.Critical challenges of NASICONs-structured electrolytes are discussed,and several research directions are proposed to tackle the obstacles toward practical applications.展开更多
This paper investigates an efficient immersed boundary method(IBM)for multiple-core CPU machines with local grid refinement for the calculation of heat transfer between fluids and finite-sized particles.The fluid mome...This paper investigates an efficient immersed boundary method(IBM)for multiple-core CPU machines with local grid refinement for the calculation of heat transfer between fluids and finite-sized particles.The fluid momentum equations are solved by using the fractional step method,while the energy equation is solved by employing the second-order Adams-Bashforth method.For efficient load balancing between the CPU cores,the coupling between particles and fluid is obtained by applying the body force in the fluid equations,which depends on the solid volume fraction of particles contained in each grid cell,and then by linearly interpolating the particle temperature and velocity on the fluid grid cell(in place of the delta function commonly used in literature).Several test cases from the literature are studied,and good agreement is observed between the simulation results and the literature.Finally,a scaling study on multiple core machines is performed,demonstrating the proposed IBM's capabilities for a significant reduction in processing time.展开更多
The deformation mechanism of alloy in the semi-solid state has been investigated, with the compression of 2024 Al alloy in the semi-solid state as an example. Experimental results showed that the compressive deformati...The deformation mechanism of alloy in the semi-solid state has been investigated, with the compression of 2024 Al alloy in the semi-solid state as an example. Experimental results showed that the compressive deformation of 2024 Al alloy in the semi-solid state was mainly caused by the liquid flowing under the hydrostatic compressive stress, the grain boundary sliding under the shear stress and the plastic deformation of grain under the normal compressive stress. Among them, the grain boundary sliding was mainly accommodated by the nucleation and growth of cavity under the hydrostatic tensile stress.展开更多
Lithium metal solid-state batteries(LMSBs)have attracted extensive attention over the past decades,due to their fascinating advantages of safety and potential for high energy density.Solid-state electrolytes(SEs)with ...Lithium metal solid-state batteries(LMSBs)have attracted extensive attention over the past decades,due to their fascinating advantages of safety and potential for high energy density.Solid-state electrolytes(SEs)with fast ionic transport and excellent stability are indispensable components in LMSBs.Heretofore,a series of inorganic SEs have been extensively explored,such as sulfide-and oxide-based electrolytes.Unfortunately,they both have difficulty in achieving a satisfactory balance of conductivity and stability,and oxides suffer from a high impedance of grain boundaries,while sulfides encounter poor stability.Halide-based solid electrolytes are gradually emerging as one of the most promising candidates for LMSBs due to their advantages of decent room temperature ionic conductivity(>10^(−3)S cm^(−1)),good compatibility with oxide cathode materials,good chemical stability,and scalability.Herein,research and development of the widely studied metal halide SEs including fluorides,chlorides,bromides,and iodides are reviewed,mainly focusing on the structures and ionic conductivities as well as preparation methods and electrochemical/chemical stabilities.And then,based on typical metal halide solid electrolytes,we emphasize the interface issues(grain boundaries,cathode−electrolyte and electrolyte–anode interfaces)that exist in the corresponding LMSBs and summarize the related work on understanding and engineering these interfaces.Furthermore,the typical(or in situ)characterization tools widely used for solid-state interfaces are reviewed.Finally,a perspective on the future direction for developing high-performance LMSBs based on the halide electrolyte family is put out.展开更多
The role of Nd solid-solution and grain-boundary segregation in binary NiAl alloy was studied based on microhardness and compressive macrostrain. X-ray and Auger spectra studies indicate that Nd not only is soluble in...The role of Nd solid-solution and grain-boundary segregation in binary NiAl alloy was studied based on microhardness and compressive macrostrain. X-ray and Auger spectra studies indicate that Nd not only is soluble in grain interiors, but also segregates to the grain boundaries. Nd solid-solution induces an increase of the microhardness from 269 to 290 HV in grain interiors and segregation results in an enhancement of hardness from 252 to 342 HV on grain boundaries. Thus, the cohesion of grain boundaries is enhanced by Nd segregation, which make the alloy doped with 0.05 wt pct Nd exhibit more compressive microstrain, i.e. the higher the compressive ductility at room temperature, the better the final surface condition at elevated temperature. Finally, a discussion was made on the reason that Nd strengthens the grain boundaries in NiAl intermetallic alloy.展开更多
A new approach to model viscosity in the conservation of momentum equations is presented and discussed. Coefficient of viscosity is modeled in such a way that it reaches asymptotically to infinity at the solid boundar...A new approach to model viscosity in the conservation of momentum equations is presented and discussed. Coefficient of viscosity is modeled in such a way that it reaches asymptotically to infinity at the solid boundary but still yields a finite value for the shear stress at the solid wall. Basic objective of this research is to show that certain combinations of higher order normal velocity gradients become zero at the solid boundary. Malled solutions for the Couette flow and Poiseuille flow between two parallel plates are obtained by modeling the coefficient of viscosity in a novel way. Also, viscous drag computed by our model is expected to yield higher values than the values predicted by the existing models, which matches closely to the experimental data.展开更多
An advanced geometric modeler GEMS4.0 has been developed, in whichfeature representation is used at the highest level abstraction of a productmodel. Boundary representation is used at the bottom level, while CSG model...An advanced geometric modeler GEMS4.0 has been developed, in whichfeature representation is used at the highest level abstraction of a productmodel. Boundary representation is used at the bottom level, while CSG modelis adopted at the median level. A BRep data structure capable of modelingnon-manifold is adopted. NURBS representation is used for all curved surfaces.Quadric surfaces have dual representations consisting of their geometric datasuch as radius, center point, and center tals. Boundary representation of freeform surfaces is easily built by sweeping and skinning method with NURBSgeometry Set operations on curved solids with boundary representation areperformed by an evaluation process consisting of four steps. A file exchangefacility is provided for the conversion between product data described by STEPand product information generated by GEMS4.0展开更多
Boundary conditions are derived to represent the continuity requirements at the boundaries of a porous solid saturated with viscous fluid. They are derived from the physically grounded principles with a mathematical c...Boundary conditions are derived to represent the continuity requirements at the boundaries of a porous solid saturated with viscous fluid. They are derived from the physically grounded principles with a mathematical check on the conservation of energy. The poroelastic solid is a dissipative one for the presence of viscosity in the interstitial fluid. The dissipative stresses due to the viscosity of pore-fluid are well represented in the boundary conditions. The unequal particle motions of two constituents of porous aggre~ gate at a boundary between two solids are explained in terms of the drainage of pore-fluid leading to imperfect bonding. A mathematical model is derived for the partial connec- tion of surface pores at the porous-porous interface. At this interface, the loose-contact slipping and partial pore opening/connection may dissipate a part of strain energy. A numerical example shows that, at the interface between water and oil-saturated sandstone, the modified boundary conditions do affect the energies of the waves refracting into the isotropic porous medium.展开更多
With the development of vehicle gearbox to high-power-density and high-speed, how to predict and optimize the dynamic characteristics of vehicle gearbox becomes increasingly prominent. Aiming at the vehicle gearbox, t...With the development of vehicle gearbox to high-power-density and high-speed, how to predict and optimize the dynamic characteristics of vehicle gearbox becomes increasingly prominent. Aiming at the vehicle gearbox, this paper comprehensively and deeply studies the dynamic characteristics under the multi-boundary conditions. The generation mechanism of the multi-source excitations triggering the gearbox vibration is analyzed firstly. The vibration transfer path of the gearbox is explored. Secondly, the engine excitation, the gear meshing excitation and the bearing support load are numerically calculated. According to the finite element method,a fluid-solid coupling finite element model of the gearbox body is established to predict the gearbox dynamic responses based on the Galerkin method and the Hamiltonian variational principle. Finally, the effects of the excitation condition, oil height and reinforcement forms on the vibration responses of the gearbox body are thoroughly studied by simulation. The analysis indicates that it not only helps to modify and improve the method of forecasting the gearbox dynamic response, and also provides the theoretical and technical guidance for the gearbox design and optimization.展开更多
A solid electrolyte of LAGP[Li_(1.5)Al_(0.5)Ge_(1.5)(PO_(4))_(3)]contained 0.5 wt%Li F was prepared by using low-volatile raw materials.The effects of different heat treatment conditions(750–900°C,4–10 h)and ad...A solid electrolyte of LAGP[Li_(1.5)Al_(0.5)Ge_(1.5)(PO_(4))_(3)]contained 0.5 wt%Li F was prepared by using low-volatile raw materials.The effects of different heat treatment conditions(750–900°C,4–10 h)and additive(Li F)on the ionic conductivity,structural morphology,and crystal transformation process were investigated in detail.EIS(electrochemical impedance spectroscopies)showed that the ionic conductivity of LAGP contained 0.5 wt%Li F had a highest value of 3.17×10^(-4)S cm^(-1)with low activation energy(0.31 e V)after treating 825°C for 6 h,more than LAGP of 2.45×10^(-4)S cm^(-1).DSC analysis and SEM images indicated that adding a small amount of Li F to LAGP not only can lower the glass transition temperature(from 513°C to507°C)and crystallization temperature(from 622°C to 605°C),but also can modify the grain boundary and increase the relative density of LAGP(from 95.8%to 97.7%).展开更多
基金National Key Research and Development Program of China,Grant/Award Number:2020YFA0715000National Natural Science Foundation of China,Grant/Award Numbers:51902238,52127816,52172234Fundamental Research Funds for the Central Universities,Grant/Award Numbers:WUT:2020IVA069,2020IVB043,2021IVA020B。
文摘Solid-state electrolytes are critical for the development of next-generation high-energy and high-safety rechargeable batteries.Among all the candidates,sodium(Na)superionic conductors(NASICONs)are highly promising because of their evident advantages in high ionic conductivity and high chemical/electrochemical stability.The concept of NASICONs was proposed by Hong and Goodenough et al.in 1976 by reporting the synthesis and characterization of Na1+xZr2(SixP3−x)O12(0≤x≤3),which has attracted tremendous attention on the NASICONs-type solid-state electrolytes.In this review,we are committed to describing the development history of NASICONs-type solid-state electrolytes and elucidating the contribution of Goodenough as a tribute to him.We summarize the correlations and differences between lithium-based and sodium-based NASICONs electrolytes,such as their preparation methods,structures,ionic conductivities,and the mechanisms of ion transportation.Critical challenges of NASICONs-structured electrolytes are discussed,and several research directions are proposed to tackle the obstacles toward practical applications.
文摘This paper investigates an efficient immersed boundary method(IBM)for multiple-core CPU machines with local grid refinement for the calculation of heat transfer between fluids and finite-sized particles.The fluid momentum equations are solved by using the fractional step method,while the energy equation is solved by employing the second-order Adams-Bashforth method.For efficient load balancing between the CPU cores,the coupling between particles and fluid is obtained by applying the body force in the fluid equations,which depends on the solid volume fraction of particles contained in each grid cell,and then by linearly interpolating the particle temperature and velocity on the fluid grid cell(in place of the delta function commonly used in literature).Several test cases from the literature are studied,and good agreement is observed between the simulation results and the literature.Finally,a scaling study on multiple core machines is performed,demonstrating the proposed IBM's capabilities for a significant reduction in processing time.
文摘The deformation mechanism of alloy in the semi-solid state has been investigated, with the compression of 2024 Al alloy in the semi-solid state as an example. Experimental results showed that the compressive deformation of 2024 Al alloy in the semi-solid state was mainly caused by the liquid flowing under the hydrostatic compressive stress, the grain boundary sliding under the shear stress and the plastic deformation of grain under the normal compressive stress. Among them, the grain boundary sliding was mainly accommodated by the nucleation and growth of cavity under the hydrostatic tensile stress.
基金National Natural Science Foundation of China,Grant/Award Numbers:21975276,52102329Shanghai Science and Technology Committee,Grant/Award Number:20520710800Program of Shanghai Academic Research Leader,Grant/Award Number:21XD1424400。
文摘Lithium metal solid-state batteries(LMSBs)have attracted extensive attention over the past decades,due to their fascinating advantages of safety and potential for high energy density.Solid-state electrolytes(SEs)with fast ionic transport and excellent stability are indispensable components in LMSBs.Heretofore,a series of inorganic SEs have been extensively explored,such as sulfide-and oxide-based electrolytes.Unfortunately,they both have difficulty in achieving a satisfactory balance of conductivity and stability,and oxides suffer from a high impedance of grain boundaries,while sulfides encounter poor stability.Halide-based solid electrolytes are gradually emerging as one of the most promising candidates for LMSBs due to their advantages of decent room temperature ionic conductivity(>10^(−3)S cm^(−1)),good compatibility with oxide cathode materials,good chemical stability,and scalability.Herein,research and development of the widely studied metal halide SEs including fluorides,chlorides,bromides,and iodides are reviewed,mainly focusing on the structures and ionic conductivities as well as preparation methods and electrochemical/chemical stabilities.And then,based on typical metal halide solid electrolytes,we emphasize the interface issues(grain boundaries,cathode−electrolyte and electrolyte–anode interfaces)that exist in the corresponding LMSBs and summarize the related work on understanding and engineering these interfaces.Furthermore,the typical(or in situ)characterization tools widely used for solid-state interfaces are reviewed.Finally,a perspective on the future direction for developing high-performance LMSBs based on the halide electrolyte family is put out.
文摘The role of Nd solid-solution and grain-boundary segregation in binary NiAl alloy was studied based on microhardness and compressive macrostrain. X-ray and Auger spectra studies indicate that Nd not only is soluble in grain interiors, but also segregates to the grain boundaries. Nd solid-solution induces an increase of the microhardness from 269 to 290 HV in grain interiors and segregation results in an enhancement of hardness from 252 to 342 HV on grain boundaries. Thus, the cohesion of grain boundaries is enhanced by Nd segregation, which make the alloy doped with 0.05 wt pct Nd exhibit more compressive microstrain, i.e. the higher the compressive ductility at room temperature, the better the final surface condition at elevated temperature. Finally, a discussion was made on the reason that Nd strengthens the grain boundaries in NiAl intermetallic alloy.
文摘A new approach to model viscosity in the conservation of momentum equations is presented and discussed. Coefficient of viscosity is modeled in such a way that it reaches asymptotically to infinity at the solid boundary but still yields a finite value for the shear stress at the solid wall. Basic objective of this research is to show that certain combinations of higher order normal velocity gradients become zero at the solid boundary. Malled solutions for the Couette flow and Poiseuille flow between two parallel plates are obtained by modeling the coefficient of viscosity in a novel way. Also, viscous drag computed by our model is expected to yield higher values than the values predicted by the existing models, which matches closely to the experimental data.
文摘An advanced geometric modeler GEMS4.0 has been developed, in whichfeature representation is used at the highest level abstraction of a productmodel. Boundary representation is used at the bottom level, while CSG modelis adopted at the median level. A BRep data structure capable of modelingnon-manifold is adopted. NURBS representation is used for all curved surfaces.Quadric surfaces have dual representations consisting of their geometric datasuch as radius, center point, and center tals. Boundary representation of freeform surfaces is easily built by sweeping and skinning method with NURBSgeometry Set operations on curved solids with boundary representation areperformed by an evaluation process consisting of four steps. A file exchangefacility is provided for the conversion between product data described by STEPand product information generated by GEMS4.0
文摘Boundary conditions are derived to represent the continuity requirements at the boundaries of a porous solid saturated with viscous fluid. They are derived from the physically grounded principles with a mathematical check on the conservation of energy. The poroelastic solid is a dissipative one for the presence of viscosity in the interstitial fluid. The dissipative stresses due to the viscosity of pore-fluid are well represented in the boundary conditions. The unequal particle motions of two constituents of porous aggre~ gate at a boundary between two solids are explained in terms of the drainage of pore-fluid leading to imperfect bonding. A mathematical model is derived for the partial connec- tion of surface pores at the porous-porous interface. At this interface, the loose-contact slipping and partial pore opening/connection may dissipate a part of strain energy. A numerical example shows that, at the interface between water and oil-saturated sandstone, the modified boundary conditions do affect the energies of the waves refracting into the isotropic porous medium.
基金the National Natural Science Foundation of China(Nos.51505402 and 51405410)the Education and Scientific Research Projects of Young and Middle-Aged Teachers in Fujian Province in 2014(No.JA14245)
文摘With the development of vehicle gearbox to high-power-density and high-speed, how to predict and optimize the dynamic characteristics of vehicle gearbox becomes increasingly prominent. Aiming at the vehicle gearbox, this paper comprehensively and deeply studies the dynamic characteristics under the multi-boundary conditions. The generation mechanism of the multi-source excitations triggering the gearbox vibration is analyzed firstly. The vibration transfer path of the gearbox is explored. Secondly, the engine excitation, the gear meshing excitation and the bearing support load are numerically calculated. According to the finite element method,a fluid-solid coupling finite element model of the gearbox body is established to predict the gearbox dynamic responses based on the Galerkin method and the Hamiltonian variational principle. Finally, the effects of the excitation condition, oil height and reinforcement forms on the vibration responses of the gearbox body are thoroughly studied by simulation. The analysis indicates that it not only helps to modify and improve the method of forecasting the gearbox dynamic response, and also provides the theoretical and technical guidance for the gearbox design and optimization.
基金financially supported by the National Natural Science Foundation of China(Grant Nos 51503102)
文摘A solid electrolyte of LAGP[Li_(1.5)Al_(0.5)Ge_(1.5)(PO_(4))_(3)]contained 0.5 wt%Li F was prepared by using low-volatile raw materials.The effects of different heat treatment conditions(750–900°C,4–10 h)and additive(Li F)on the ionic conductivity,structural morphology,and crystal transformation process were investigated in detail.EIS(electrochemical impedance spectroscopies)showed that the ionic conductivity of LAGP contained 0.5 wt%Li F had a highest value of 3.17×10^(-4)S cm^(-1)with low activation energy(0.31 e V)after treating 825°C for 6 h,more than LAGP of 2.45×10^(-4)S cm^(-1).DSC analysis and SEM images indicated that adding a small amount of Li F to LAGP not only can lower the glass transition temperature(from 513°C to507°C)and crystallization temperature(from 622°C to 605°C),but also can modify the grain boundary and increase the relative density of LAGP(from 95.8%to 97.7%).
