We report recent advances in the experimental and theoretical study of grain size(GS)effects on the thermal and mechanical properties of nanostructured NiTi polycrystalline shape memory alloy(SMA).It is shown that whe...We report recent advances in the experimental and theoretical study of grain size(GS)effects on the thermal and mechanical properties of nanostructured NiTi polycrystalline shape memory alloy(SMA).It is shown that when GS<60 nm,the superelastic stress-strain hysteresis loop area(H)of the polycrystal decreases rapidly with GS and tends to vanish as GS approaches 10 nanometers.At the same time,the temperature dependence of the transition stress also decreases with GS and eventually approaches zero,leading to a wide superelastic temperature window and breakdown of the Clausius-Claperyon relationship.Rate dependence of the stress-strain responses is significantly reduced and the cyclic stability of the material is improved by the nanocrystallization.It is proposed that the emergence of such significant changes in the behavior of the material with GS reduction originate from the large increase in the area-to-volume ratios of the nanometer-thick interfaces(grain boundary and Austenite-Martensite(A-M)interface)in the polycrystal.In particular,with GS reduction,interfacial energy terms will gradually become dominant over the bulk energy of the crystallite,eventually bring fundamental changes in the phase transition responses of the material.Modelling strategy leading to the establishment of quantitative relationships among GS,grain boundary,A-M interfaces and the macroscopic responses of the material are outlined.展开更多
Hybrid improper ferroelectricity has been extensively reported through theoretical prediction and experimental investigation in the oxides with Ruddlesden-Popper(R-P)structures.However,the experimentally reported ferr...Hybrid improper ferroelectricity has been extensively reported through theoretical prediction and experimental investigation in the oxides with Ruddlesden-Popper(R-P)structures.However,the experimentally reported ferroelectric materials based on triple-layer R-P structures are rare,and the weak ferroelectricity impedes its practical application.In the present work,the single-phase Li_(2)Nd_(2)Ti_(3)O_(10)ceramics with A-site cation ordered triple-layer R-P structure was obtained by spark plasma sintering technique,and the crystal structure of P2_(1)ab symmetry was revealed by neutron powder diffraction and transmission electron microscope analysis.Furthermore,the switchable ferroelectricity in Li_(2)Nd_(2)Ti_(3)O_(10)ceramics has been observed at room temperature,and the saturated polarization-electric field hysteresis loop was obtained with P_(r)=0.4μC/cm^(2)under the electric field of 250 kV/cm.The phase transition behavior of Li_(2)Nd_(2)Ti_(3)O_(10)oxides was revealed by the temperature-dependence Raman and dielectric spectra combined with the piezoelectric property.展开更多
The behavior of the solid phase in the upper zone of a circulating fluidized bed riser was studied using a phase Doppler anemometer. Glass particles of mean diameter 107μm and superficial gas velocities UE covering t...The behavior of the solid phase in the upper zone of a circulating fluidized bed riser was studied using a phase Doppler anemometer. Glass particles of mean diameter 107μm and superficial gas velocities UE covering the turbulent and the beginning of the fast fluidization regime were investigated. Three static bed heights were tested. Ascending and descending particles were found co-existing under all oper ating conditions tested, and at all measurement locations. Superficial gas velocity proved/happened to have a larger effect on descending particles at the wall and on ascending particles in the central region. Transversal particle velocities in both directions （toward the center and toward the wall） behaved rela- tively equivalently, with only slight difference observed at the wall. However, observation of the number of particles moving in either transversal direction showed a change in bed structure when increasing Ug. Furthermore, a balance was constantly observed between the core zone and the annulus zone where the mutual mass transfer between these two zones occurred continuously. Transition from a slow to a fast particle motion was accompanied by a transition to high levels of velocity fluctuations, and was found corresponding to the appearance of significant solid particle flow rate.展开更多
To further increase the energy density of lithium-ion batteries(LIBs),various researches have been conducted on high-voltage and high-capacity cathode materials.In this perspective,monoclinic Li_(3)V_(2)(PO_(4))_(3) i...To further increase the energy density of lithium-ion batteries(LIBs),various researches have been conducted on high-voltage and high-capacity cathode materials.In this perspective,monoclinic Li_(3)V_(2)(PO_(4))_(3) is a promising candidate due to its promising theoretical discharge capacity of 197 mAh/g with complex phase transition in the voltage range of 3.0 to 4.8 V.However,such asymmetric phase transition behavior with 3 Li^(+)ion extraction/insertion is highly irreversible,resulting in an initial discharge capacity of 163 mAh/g with deteriorated capacity retention.We suggest that cycling Li_(3)V_(2)(PO_(4))_(3) in the voltage range of 3.0 to 4.5 V suppresses the irreversible phase transition and elution of transition metal.Hence,Li_(3)V_(2)(PO_(4))_(3) in the voltage range of 3.0 to 4.5 V delivers an initial discharge capacity of about 142 mAh/g and exhibits extremely long cycle retention(78.70%2,000 cycles),as when cycling in the voltage range of 3.0 to 4.3 V(81.67%2,000 cycles).Furthermore,we present the possibility of a Li_(3)V_(2)(PO_(4))_(3)||Li_(3)V_(2)(PO_(4))_(3) symmetric all-solid-state battery based on an N/P ratio and a cutoff voltage design,which is demonstrated in liquid electrolyte half-cells and symmetric full cells.展开更多
基金supported by the Hong Kong Research Grant Council(RGC)(Grant No.619113)the National Natural Science Foundation of China(Grant No.11128204)the State Key Lab of Water Resources and Hydropower Engineering of WHU,China
文摘We report recent advances in the experimental and theoretical study of grain size(GS)effects on the thermal and mechanical properties of nanostructured NiTi polycrystalline shape memory alloy(SMA).It is shown that when GS<60 nm,the superelastic stress-strain hysteresis loop area(H)of the polycrystal decreases rapidly with GS and tends to vanish as GS approaches 10 nanometers.At the same time,the temperature dependence of the transition stress also decreases with GS and eventually approaches zero,leading to a wide superelastic temperature window and breakdown of the Clausius-Claperyon relationship.Rate dependence of the stress-strain responses is significantly reduced and the cyclic stability of the material is improved by the nanocrystallization.It is proposed that the emergence of such significant changes in the behavior of the material with GS reduction originate from the large increase in the area-to-volume ratios of the nanometer-thick interfaces(grain boundary and Austenite-Martensite(A-M)interface)in the polycrystal.In particular,with GS reduction,interfacial energy terms will gradually become dominant over the bulk energy of the crystallite,eventually bring fundamental changes in the phase transition responses of the material.Modelling strategy leading to the establishment of quantitative relationships among GS,grain boundary,A-M interfaces and the macroscopic responses of the material are outlined.
基金supported by the National Key R&D Program of China under Grant No.2022YFB3807602the National Natural Science Foundation of China under Grant No.52172131the outstanding doctoral dissertation funding of Zhejiang University under Grant No.422048A.
文摘Hybrid improper ferroelectricity has been extensively reported through theoretical prediction and experimental investigation in the oxides with Ruddlesden-Popper(R-P)structures.However,the experimentally reported ferroelectric materials based on triple-layer R-P structures are rare,and the weak ferroelectricity impedes its practical application.In the present work,the single-phase Li_(2)Nd_(2)Ti_(3)O_(10)ceramics with A-site cation ordered triple-layer R-P structure was obtained by spark plasma sintering technique,and the crystal structure of P2_(1)ab symmetry was revealed by neutron powder diffraction and transmission electron microscope analysis.Furthermore,the switchable ferroelectricity in Li_(2)Nd_(2)Ti_(3)O_(10)ceramics has been observed at room temperature,and the saturated polarization-electric field hysteresis loop was obtained with P_(r)=0.4μC/cm^(2)under the electric field of 250 kV/cm.The phase transition behavior of Li_(2)Nd_(2)Ti_(3)O_(10)oxides was revealed by the temperature-dependence Raman and dielectric spectra combined with the piezoelectric property.
文摘The behavior of the solid phase in the upper zone of a circulating fluidized bed riser was studied using a phase Doppler anemometer. Glass particles of mean diameter 107μm and superficial gas velocities UE covering the turbulent and the beginning of the fast fluidization regime were investigated. Three static bed heights were tested. Ascending and descending particles were found co-existing under all oper ating conditions tested, and at all measurement locations. Superficial gas velocity proved/happened to have a larger effect on descending particles at the wall and on ascending particles in the central region. Transversal particle velocities in both directions （toward the center and toward the wall） behaved rela- tively equivalently, with only slight difference observed at the wall. However, observation of the number of particles moving in either transversal direction showed a change in bed structure when increasing Ug. Furthermore, a balance was constantly observed between the core zone and the annulus zone where the mutual mass transfer between these two zones occurred continuously. Transition from a slow to a fast particle motion was accompanied by a transition to high levels of velocity fluctuations, and was found corresponding to the appearance of significant solid particle flow rate.
基金supported by the Technology Innovation Program(RS-2023-00256202,Development of MLCB design and manufacturing process technology for board mounting)funded by the Ministry of Trade,Industry and Energy(MOTIE,Korea)the Technology Innovation Program(or Industrial Strategic Technology Development Program-Public-Private joint investment semiconductor R&D program[K-CHIPS]to foster high-quality human resources)(RS-2023-00237003,High selectivity etching technology using cryoetch)funded by the Ministry of Trade,Industry and Energy(MOTIE,Korea)+1 种基金a 2022 Research Grant from Kangwon National University(No.202203080001)the National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIT)(RS-2023-00280367).
文摘To further increase the energy density of lithium-ion batteries(LIBs),various researches have been conducted on high-voltage and high-capacity cathode materials.In this perspective,monoclinic Li_(3)V_(2)(PO_(4))_(3) is a promising candidate due to its promising theoretical discharge capacity of 197 mAh/g with complex phase transition in the voltage range of 3.0 to 4.8 V.However,such asymmetric phase transition behavior with 3 Li^(+)ion extraction/insertion is highly irreversible,resulting in an initial discharge capacity of 163 mAh/g with deteriorated capacity retention.We suggest that cycling Li_(3)V_(2)(PO_(4))_(3) in the voltage range of 3.0 to 4.5 V suppresses the irreversible phase transition and elution of transition metal.Hence,Li_(3)V_(2)(PO_(4))_(3) in the voltage range of 3.0 to 4.5 V delivers an initial discharge capacity of about 142 mAh/g and exhibits extremely long cycle retention(78.70%2,000 cycles),as when cycling in the voltage range of 3.0 to 4.3 V(81.67%2,000 cycles).Furthermore,we present the possibility of a Li_(3)V_(2)(PO_(4))_(3)||Li_(3)V_(2)(PO_(4))_(3) symmetric all-solid-state battery based on an N/P ratio and a cutoff voltage design,which is demonstrated in liquid electrolyte half-cells and symmetric full cells.
