The main focus of this work is to study the effect of the ionic radius of different rare earth dopant cations RE^(3+)(RE=La,Sm,Dy,and Ho) on structural and various physical properties of sodium bismuth titanate(Na_(0....The main focus of this work is to study the effect of the ionic radius of different rare earth dopant cations RE^(3+)(RE=La,Sm,Dy,and Ho) on structural and various physical properties of sodium bismuth titanate(Na_(0.5)B_(0.5)TiO_(3),NBT) based perovskite nanomaterials.The X-ray diffraction data indicate the successful formation of the rhombohedral phase(space group R3c) of NBT nano perovskite incorporated with various rare earth ions in Bi-site.The lattice parameters were found to increase linearly with the ionic radius of the dopant cation.The ionic radii and atomic mass of rare earth dopants appear to be essential factors in the grain growth of the prepared compositions.The grain growth results in better crystallinity of the sample by reducing the microstrain with the increase of dopant ionic radius.Field emission scanning electron microscopy and energy-dispersive X-ray spectra confirm the prepared compositions' phase purity and stoichiometry.The UV-Vis spectra reveal that La-doped NBT composition exhibits the lowest optical band gap,which unfolds the application of NBT-based perovskite as photoactive material.The ac conductivity and complex impedance spectra unveil that the composition with the largest ionic radius,i.e.,La-doped NBT compound,exhibits the highest dc and bulk conductivity with the lowest activation energy.The frequency-dependent dielectric data follows Havriliak-Negami(HN) formalism and non-Debye type relaxation phenomena.Results also indicate that La-doped NBT composition exhibits the highest dielectric strength value.Thus,this study first elaborates that the increasing ionic radius of the rare earth dopant cation in the Bi-site of NBT perovskite improves its microstructural,optical,and electrical properties.展开更多
In the present investigation,an austenitic AISI 304 stainless steel was subjected to high strain rate surface deformation by Pipe Inner-Surface Grinding(PISG)technique.The depth-dependent deformation parameters(strain...In the present investigation,an austenitic AISI 304 stainless steel was subjected to high strain rate surface deformation by Pipe Inner-Surface Grinding(PISG)technique.The depth-dependent deformation parameters(strain,strain rate and strain gradient)were evaluated and the microstructures were systematically characterized.Microstructural evolution from millimeter-to nano-scale was explored,with special attention paid to the localized deformation.Microstructural evolution begins with the formation of planar dislocation arrays and the twin-matrix lamellae,which is followed by the localized deformation characterized by the initiation and the development of shear bands.A twinning-dominated process that was supplemented with dislocation slip-dominated one governed the microstructural evolution inside shear bands.The twin-matrix lamellae transform into extended/lamellar structure and finally the nanosized grains.Austenitic grains were substantially refined and martensitic transformation was effectively suppressed,of which the underlying mechanisms were analyzed.展开更多
A series of alkali halide doped chalcohalide glasses （100-x）（0.9GeS2-0.1Sb2S3）-xCsCl （x=5, 10, 15 and 20 mole fraction） were prepared. The absorption spectra and Raman scatting spectra of these glasses were meas...A series of alkali halide doped chalcohalide glasses （100-x）（0.9GeS2-0.1Sb2S3）-xCsCl （x=5, 10, 15 and 20 mole fraction） were prepared. The absorption spectra and Raman scatting spectra of these glasses were measured. The optical band gaps Eopt were obtained from ultraviolet absorption edges. Z-scan technique was utilized to investigate the third-order nonlinear optical properties of GeS2-Sb2S3-CsCl glasses. The value of Eopt increases and the third-order optical nonlinearity decreases with increasing CsCl content. Decreasing lone-pair electron and broadening the band-gap will provide less transition paths for nonlinear process, which play a key role in ultrafast third-order nonlinear optical responses of these chalcohalide glasses.展开更多
Closed-form analytical solutions of plastic shear strain and relative plastic shear displacement during shear band propagation are proposed under dynamic loadings based on gradient-dependent plasticity considering the...Closed-form analytical solutions of plastic shear strain and relative plastic shear displacement during shear band propagation are proposed under dynamic loadings based on gradient-dependent plasticity considering the effect of microstructures due to heterogeneous texture of Ti. According to the differences in shear stress levels, Ti specimen is divided into three regions: residual region, strain-softening region and elastic region. Well-developed shear band is formed in the residual region and the relative plastic shear displacement no longer increases. In the normal and tangential directions, the plastic strain and the displacement are nonuniform in the strain-softening region. At the tip of shear band, the shear stress acting on the band is increased to shear strength from the elastic state and the shear localization just occurs. Prior to the tip, Ti remains elastic. At higher strain rates, the extent of plastic strain concentration is greater than that under static loading. Higher strain rate increases the relative plastic shear displacement. The present analytical solution for evolution or propagation of shear localization under nonuniform shear stress can better reproduce the observed localized characteristics for many kinds of ductile metals.展开更多
基金Project supported by the Science and Engineering Research Board(SERB)(Govt.of India)(EMR/2017/000325)。
文摘The main focus of this work is to study the effect of the ionic radius of different rare earth dopant cations RE^(3+)(RE=La,Sm,Dy,and Ho) on structural and various physical properties of sodium bismuth titanate(Na_(0.5)B_(0.5)TiO_(3),NBT) based perovskite nanomaterials.The X-ray diffraction data indicate the successful formation of the rhombohedral phase(space group R3c) of NBT nano perovskite incorporated with various rare earth ions in Bi-site.The lattice parameters were found to increase linearly with the ionic radius of the dopant cation.The ionic radii and atomic mass of rare earth dopants appear to be essential factors in the grain growth of the prepared compositions.The grain growth results in better crystallinity of the sample by reducing the microstrain with the increase of dopant ionic radius.Field emission scanning electron microscopy and energy-dispersive X-ray spectra confirm the prepared compositions' phase purity and stoichiometry.The UV-Vis spectra reveal that La-doped NBT composition exhibits the lowest optical band gap,which unfolds the application of NBT-based perovskite as photoactive material.The ac conductivity and complex impedance spectra unveil that the composition with the largest ionic radius,i.e.,La-doped NBT compound,exhibits the highest dc and bulk conductivity with the lowest activation energy.The frequency-dependent dielectric data follows Havriliak-Negami(HN) formalism and non-Debye type relaxation phenomena.Results also indicate that La-doped NBT composition exhibits the highest dielectric strength value.Thus,this study first elaborates that the increasing ionic radius of the rare earth dopant cation in the Bi-site of NBT perovskite improves its microstructural,optical,and electrical properties.
基金the financial support of the Hundred Outstanding Creative Talents Projects in Hebei University,Chinathe Project Program of Heavy Machinery Collaborative Innovation Center,Chinathe National Natural Foundation of Hebei Province,China (Grant No. E2018203312)
文摘In the present investigation,an austenitic AISI 304 stainless steel was subjected to high strain rate surface deformation by Pipe Inner-Surface Grinding(PISG)technique.The depth-dependent deformation parameters(strain,strain rate and strain gradient)were evaluated and the microstructures were systematically characterized.Microstructural evolution from millimeter-to nano-scale was explored,with special attention paid to the localized deformation.Microstructural evolution begins with the formation of planar dislocation arrays and the twin-matrix lamellae,which is followed by the localized deformation characterized by the initiation and the development of shear bands.A twinning-dominated process that was supplemented with dislocation slip-dominated one governed the microstructural evolution inside shear bands.The twin-matrix lamellae transform into extended/lamellar structure and finally the nanosized grains.Austenitic grains were substantially refined and martensitic transformation was effectively suppressed,of which the underlying mechanisms were analyzed.
基金supported by the National Ba-sic Research Program of China ("973 Project", (No2006CB708607)the Science and Technology Department of Zhejiang Province, China (No 2006C11127)+1 种基金the Science and Technology Foundation of Ningbo, China (No2006B100068)the Natural Science Foundation of Ningbo, China (Nos 2006A610056, 2007A610004)
文摘A series of alkali halide doped chalcohalide glasses （100-x）（0.9GeS2-0.1Sb2S3）-xCsCl （x=5, 10, 15 and 20 mole fraction） were prepared. The absorption spectra and Raman scatting spectra of these glasses were measured. The optical band gaps Eopt were obtained from ultraviolet absorption edges. Z-scan technique was utilized to investigate the third-order nonlinear optical properties of GeS2-Sb2S3-CsCl glasses. The value of Eopt increases and the third-order optical nonlinearity decreases with increasing CsCl content. Decreasing lone-pair electron and broadening the band-gap will provide less transition paths for nonlinear process, which play a key role in ultrafast third-order nonlinear optical responses of these chalcohalide glasses.
文摘Closed-form analytical solutions of plastic shear strain and relative plastic shear displacement during shear band propagation are proposed under dynamic loadings based on gradient-dependent plasticity considering the effect of microstructures due to heterogeneous texture of Ti. According to the differences in shear stress levels, Ti specimen is divided into three regions: residual region, strain-softening region and elastic region. Well-developed shear band is formed in the residual region and the relative plastic shear displacement no longer increases. In the normal and tangential directions, the plastic strain and the displacement are nonuniform in the strain-softening region. At the tip of shear band, the shear stress acting on the band is increased to shear strength from the elastic state and the shear localization just occurs. Prior to the tip, Ti remains elastic. At higher strain rates, the extent of plastic strain concentration is greater than that under static loading. Higher strain rate increases the relative plastic shear displacement. The present analytical solution for evolution or propagation of shear localization under nonuniform shear stress can better reproduce the observed localized characteristics for many kinds of ductile metals.
