Adopting the classical theory of hydrocodes,the constitutive relations of concretes are separated into an equation of state(EoS)which describes the volumetric behavior of concrete material and a strength model which d...Adopting the classical theory of hydrocodes,the constitutive relations of concretes are separated into an equation of state(EoS)which describes the volumetric behavior of concrete material and a strength model which depicts the shear properties of concrete.The experiments on the EoS of concrete is always challenging due to the technical difficulties and equipment limitations,especially for the specimen size effect on the EoS.Although some researchers investigate the shock properties of concretes by fly-plate impact tests,the specimens used in their tests are usually in one size.In this paper,the fly-plate impact tests on concrete specimens with different sizes are performed to investigate the size effect on the shock properties of concrete materials.The mechanical background of the size effect on the shock properties are revealed,which is related to the lateral rarefaction effect and the deviatoric stress produced in the specimen.According to the tests results,the modified EoS considering the size effect on the shock properties of concrete are proposed,which the bulk modulus of concrete is unpredicted by up to 20% if size effects are not accounted for.展开更多
The lattice doping has been widely used to improve the electrochemical performances of Li-rich cathode materials but the roles of the introduced foreign atoms are still not very clear.Herein,a series of Li2Ru1-xTixO3 ...The lattice doping has been widely used to improve the electrochemical performances of Li-rich cathode materials but the roles of the introduced foreign atoms are still not very clear.Herein,a series of Li2Ru1-xTixO3 solid solutions have been synthesized and the roles of Ti doping on the structural and electrochemical properties of Li2RuO3 have been comprehensively investigated.The Rietveld refinement exhibits that the interlayer spacing gradually shortens with increasing Ti content.This shrinkage is favorable to the layered structure stability but increases the lithium diffusion barrier.Galvanostatic measurements show that Li2Ru0.8Ti0.2O3 possesses the best cyclability with 196.9 and 196.1 m Ah g-1for charge and discharge capacity retaining after 90 cycles,respectively.Cyclic voltammetry scanning indicates that Ti dopant promotes the formation of more peroxo-or superoxo-like species but reduces the initial coulumbic efficiency.Results of electrochemical impedance spectroscopy display that Ti doping reduces the charge transfer impedance,which facilitates the lithium-ion diffusion across the electrolyteelectrode interface and improves the electronic conductivity.Li2Ru0.8Ti0.2O3exhibits the best electrochemical performance owing to the balance among all the factors discussed above.This study also offers some new insights into optimizing the electrochemical performances of Li-rich cathode materials through the lattice doping.展开更多
基金supported by the National Natural Science Foundation of China[Grant Nos.51938011 and 51908405]Australian Research Council。
文摘Adopting the classical theory of hydrocodes,the constitutive relations of concretes are separated into an equation of state(EoS)which describes the volumetric behavior of concrete material and a strength model which depicts the shear properties of concrete.The experiments on the EoS of concrete is always challenging due to the technical difficulties and equipment limitations,especially for the specimen size effect on the EoS.Although some researchers investigate the shock properties of concretes by fly-plate impact tests,the specimens used in their tests are usually in one size.In this paper,the fly-plate impact tests on concrete specimens with different sizes are performed to investigate the size effect on the shock properties of concrete materials.The mechanical background of the size effect on the shock properties are revealed,which is related to the lateral rarefaction effect and the deviatoric stress produced in the specimen.According to the tests results,the modified EoS considering the size effect on the shock properties of concrete are proposed,which the bulk modulus of concrete is unpredicted by up to 20% if size effects are not accounted for.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11575192 and 21403129)the Scientific Instrument Developing Project (Grant No. ZDKYYQ20170001)+2 种基金the International Partnership Program (Grant No. 211211KYSB20170060)“Hundred Talents Project” of the Chinese Academy of SciencesNatural Science Foundation of Beijing Municipality (Grant No. 2182082)
文摘The lattice doping has been widely used to improve the electrochemical performances of Li-rich cathode materials but the roles of the introduced foreign atoms are still not very clear.Herein,a series of Li2Ru1-xTixO3 solid solutions have been synthesized and the roles of Ti doping on the structural and electrochemical properties of Li2RuO3 have been comprehensively investigated.The Rietveld refinement exhibits that the interlayer spacing gradually shortens with increasing Ti content.This shrinkage is favorable to the layered structure stability but increases the lithium diffusion barrier.Galvanostatic measurements show that Li2Ru0.8Ti0.2O3 possesses the best cyclability with 196.9 and 196.1 m Ah g-1for charge and discharge capacity retaining after 90 cycles,respectively.Cyclic voltammetry scanning indicates that Ti dopant promotes the formation of more peroxo-or superoxo-like species but reduces the initial coulumbic efficiency.Results of electrochemical impedance spectroscopy display that Ti doping reduces the charge transfer impedance,which facilitates the lithium-ion diffusion across the electrolyteelectrode interface and improves the electronic conductivity.Li2Ru0.8Ti0.2O3exhibits the best electrochemical performance owing to the balance among all the factors discussed above.This study also offers some new insights into optimizing the electrochemical performances of Li-rich cathode materials through the lattice doping.