Vanadium pentoxide （V205） exhibits high theoretical capacities when used as a cathode in lithium ion batteries （LIBs）, but its application is limited by its structural instability as well as its low lithium and el...Vanadium pentoxide （V205） exhibits high theoretical capacities when used as a cathode in lithium ion batteries （LIBs）, but its application is limited by its structural instability as well as its low lithium and electronic conductivities. A porous composite of V2Os-SnO2/carbon nanotubes （CNTs） was prepared by a hydrothermal method and followed by thermal treatment. The small particles of V205, their porous structure and the coexistence of SnO2 and CNTs can all facilitate the diffusion rates of the electrons and lithium ions. Electrochemical impedance spectra indicated higher ionic and electric conductivities, as compared to commercial V205. The VzOs-SnOz/CNTs composite gave a reversible discharge capacity of 198 mAh.g- 1 at the voltage range of 2.05-4.0 V, measured at a current rate of 200 mA.g-1, while that of the commercial V205 was only 88 mAh.g-1, demonstrating that the porous V2Os-SnOz/CNTs composite is a promising candidate for high-performance lithium secondary batteries.展开更多
A novel and simple ion-exchange method was developed for the synthesis of nano-SnO/micro-C hybrid structure. The structure of the as prepared nano-SnO/micro-C was directly revealed by scanning electron microscopy （SE...A novel and simple ion-exchange method was developed for the synthesis of nano-SnO/micro-C hybrid structure. The structure of the as prepared nano-SnO/micro-C was directly revealed by scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. SnO particles with the size about 25 nm were well confined in amorphous carbon microparticles. Carbon matrix in micrometer scale not only acts as a protective buffer for the SnO nanoparticles during the battery cycling processes, but also avoids the shortcomings of nanostructures, such as low tap density and potential safety threats. Electrochemical behaviors of the nano-SnO/micro-C were tested as anode material in lithium ion batteries. The initial reversible capacity is 508 mA h g^-1, and the reversible capacity after 60 cycles is 511 mA h g^-1, indicating good capacity retention ability.展开更多
In this work,we present a new piezoelectric solid solution consisting of two typical alkali niobate-based materials,K_(0.5)Na_(0.5)NbO_(3)(KNN)and Li_(0.15)Na_(0.85)NbO_(3)(LNN).Although KNN and LNN have the same pero...In this work,we present a new piezoelectric solid solution consisting of two typical alkali niobate-based materials,K_(0.5)Na_(0.5)NbO_(3)(KNN)and Li_(0.15)Na_(0.85)NbO_(3)(LNN).Although KNN and LNN have the same perovskite structure,they exhibit extremely different electrical properties and mechanical behaviors.The phase structures,electrical and mechanical evolutions of the new lead-free piezoelectric materials with different ratios of KNN and LNN are comprehensively and theoretically investigated.According to the Xray diffraction patterns and curves of permittivity versus temperature,a series of complicated phase transitions can be found with varied LNN content.Rietveld refinement results based on XRD patterns reveal an oxygen octahedron tilting in the LNN-rich crystal structure,and simultaneously the reasons for octahedron tilting are discussed.The distorted crystal structure is accompanied by extremely decreased electric properties but increased mechanical properties,which reveals electrical and mechanical properties of alkali niobate-based piezoelectric ceramics strongly depend on their inner structures,and the enhancement of intrinsic hardness results in the deterioration of piezoelectric properties.Our work exhibits the detailed evolutions of structure,electrical and mechanical properties from KNN to LNN,which provides experimental and theoretical basis for development of new alkali niobate-based piezoelectric materials.展开更多
The BiAlO_(3)(BA)and(Bi_(0.5)Na_(0.5))ZrO_(3)(BNZ)are selected to form a solid solution with(K_(0.48)Na_(0.52))NbO_(3) via traditional solid state technique to optimize the electrical performance and temperature stabi...The BiAlO_(3)(BA)and(Bi_(0.5)Na_(0.5))ZrO_(3)(BNZ)are selected to form a solid solution with(K_(0.48)Na_(0.52))NbO_(3) via traditional solid state technique to optimize the electrical performance and temperature stability of KNNbased lead-free ceramics,simultaneously.Here we show that doped BA has a great influence on phase structure,morphologies,and electrical properties.The XRD patterns and dielectric constant versus temperature curves reveal that an increase in the BA content results in a transform of phase structures from a coexistence state of rhombohedral,orthorhombic and tetragonal phases to pseudocubic phase.Owing to the construction of R-O-T phase boundary,optimized performances(T_(C)~336℃,d_(33)~306 pC/N,kp=0.48)are obtained in 0.962(K_(0.48)Na_(0.52))NbO_(3)-0.003BiAlO_(3)-0.035(Bi_(0.5)Na_(0.5))ZrO_(3)(KNN-3)ceramics.Based on the sintered KNN-3 ceramic samples,high-frequency ultrasound imaging transducers are designed and fabricated,which exhibits a high center frequency of 24.5 MHz,a broad -6 dB bandwidth of 97% and a high-sensitivity.Finally,the imaging characteristic of the lead-free transducers is demonstrated via ex vivo imaging of biological tissue structure.As environment friendly materials,the excellent electrical and acoustic performance of developed KNN-based ceramics has great potential for practical applications.展开更多
Considerable clinical evidence has demonstrated that the prevalence and severity of many chronic pain syndromes differ across sex,and are more predominant in womenthan inmen[l]But most preclinical research on chronic ...Considerable clinical evidence has demonstrated that the prevalence and severity of many chronic pain syndromes differ across sex,and are more predominant in womenthan inmen[l]But most preclinical research on chronic pain mechanisms has been performed primarily in male animals.It is generally understood that inflammatory responses in the peripheral and central nervous systems are critical for chronic pain[2,3],Given that sex dimorphism influences immunity in various diseases[4].展开更多
Ga2O3 was doped into 0.95（K0.48Na0.52）NbO3-0.05LiTaO3 （KNN-LT） cera- mics and its influences on the sintering behavior, phase structure and electrical properties of ceramics were studied. Firstly, SEM observation ...Ga2O3 was doped into 0.95（K0.48Na0.52）NbO3-0.05LiTaO3 （KNN-LT） cera- mics and its influences on the sintering behavior, phase structure and electrical properties of ceramics were studied. Firstly, SEM observation exhibits that more and more glass phase appears in ceramics with the gradual addition of Ga2O3, which determines the continuous decrease in sintering temperatures. And the addition of Ga2O3 is also found to increase the orthorhombic-tetragonal transition temperature （To-T） of system to a higher level. Secondly, both the density and the coercive field （Ec） of ceramics increase firstly and then decrease with increasing the Ga2O3 content, and the KNN-LT-xGa sample at x = 0.004 shows a pinched P-E hysteresis loop. Finally, the impedance characteristics of KNN-LT-xGa ceramics were investigated at different temperatures, revealing a typical vacancy related conduction mechanism. This work demonstrates that Ga2O3 is a good sintering aid for KNN-based ceramics, and the vacancy plays an important role in the sintering and electrical behaviors of ceramics.展开更多
The development of rechargeable lithium-ion batteries (LIBs) is being driven by the ever-increasing demand for high energy density and excellent rate performance. Charge transfer kinetics and polarization theory, cons...The development of rechargeable lithium-ion batteries (LIBs) is being driven by the ever-increasing demand for high energy density and excellent rate performance. Charge transfer kinetics and polarization theory, considered as basic principles for charge regulation in the LIBs, indicate that the rapid transfer of both electrons and ions is vital to the electrochemical reaction process. Graphene, a promising candidate for charge regulation in high-performance LIBs, has received extensive investigations due to its excellent carrier mobility, large specific surface area and structure tunability, etc. Recent progresses on the structural design and interfacial modification of graphene to regulate the charge transport in LIBs have been summarized. Besides, the structure-performance relationships between the structure of the graphene and its dedicated applications for LIBs have also been clarified in detail. Taking graphene as a typical example to explore the mechanism of charge regulation will outline ways to further understand and improve carbon-based nanomaterials towards the next generation of electrochemical energy storage devices.展开更多
基金supported by the National Natural Science Foundation of China (No. 51001098)the Institute of Metal Research of CAS (No. 09NBA211A1)
文摘Vanadium pentoxide （V205） exhibits high theoretical capacities when used as a cathode in lithium ion batteries （LIBs）, but its application is limited by its structural instability as well as its low lithium and electronic conductivities. A porous composite of V2Os-SnO2/carbon nanotubes （CNTs） was prepared by a hydrothermal method and followed by thermal treatment. The small particles of V205, their porous structure and the coexistence of SnO2 and CNTs can all facilitate the diffusion rates of the electrons and lithium ions. Electrochemical impedance spectra indicated higher ionic and electric conductivities, as compared to commercial V205. The VzOs-SnOz/CNTs composite gave a reversible discharge capacity of 198 mAh.g- 1 at the voltage range of 2.05-4.0 V, measured at a current rate of 200 mA.g-1, while that of the commercial V205 was only 88 mAh.g-1, demonstrating that the porous V2Os-SnOz/CNTs composite is a promising candidate for high-performance lithium secondary batteries.
基金supported by the National Natural Science Foundation of China(No.51001098)the Natural Science Foundation of Liaoning Province(No.20102229)+1 种基金the Institute of Metal Research(No.09NBA211A1)the National Basic Research Program(973 Program,No.2011CBA00504)
文摘A novel and simple ion-exchange method was developed for the synthesis of nano-SnO/micro-C hybrid structure. The structure of the as prepared nano-SnO/micro-C was directly revealed by scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. SnO particles with the size about 25 nm were well confined in amorphous carbon microparticles. Carbon matrix in micrometer scale not only acts as a protective buffer for the SnO nanoparticles during the battery cycling processes, but also avoids the shortcomings of nanostructures, such as low tap density and potential safety threats. Electrochemical behaviors of the nano-SnO/micro-C were tested as anode material in lithium ion batteries. The initial reversible capacity is 508 mA h g^-1, and the reversible capacity after 60 cycles is 511 mA h g^-1, indicating good capacity retention ability.
基金supported by the National Natural Science Foundation of China(Grant No.51332003,No.11572057 and No.11702037)Program for Changjiang Scholars and Innovative Research Team(IRT14R37).
文摘In this work,we present a new piezoelectric solid solution consisting of two typical alkali niobate-based materials,K_(0.5)Na_(0.5)NbO_(3)(KNN)and Li_(0.15)Na_(0.85)NbO_(3)(LNN).Although KNN and LNN have the same perovskite structure,they exhibit extremely different electrical properties and mechanical behaviors.The phase structures,electrical and mechanical evolutions of the new lead-free piezoelectric materials with different ratios of KNN and LNN are comprehensively and theoretically investigated.According to the Xray diffraction patterns and curves of permittivity versus temperature,a series of complicated phase transitions can be found with varied LNN content.Rietveld refinement results based on XRD patterns reveal an oxygen octahedron tilting in the LNN-rich crystal structure,and simultaneously the reasons for octahedron tilting are discussed.The distorted crystal structure is accompanied by extremely decreased electric properties but increased mechanical properties,which reveals electrical and mechanical properties of alkali niobate-based piezoelectric ceramics strongly depend on their inner structures,and the enhancement of intrinsic hardness results in the deterioration of piezoelectric properties.Our work exhibits the detailed evolutions of structure,electrical and mechanical properties from KNN to LNN,which provides experimental and theoretical basis for development of new alkali niobate-based piezoelectric materials.
基金supported by the Supported by Sichuan Science and Technology Program(No.2019YJ0096)the National Natural Science Foundation of China(51932010,51332003)+1 种基金the Fundamental Research Funds for the Central Universities of Chinasupported by the China Scholarship Council(File no.:201706240056).
文摘The BiAlO_(3)(BA)and(Bi_(0.5)Na_(0.5))ZrO_(3)(BNZ)are selected to form a solid solution with(K_(0.48)Na_(0.52))NbO_(3) via traditional solid state technique to optimize the electrical performance and temperature stability of KNNbased lead-free ceramics,simultaneously.Here we show that doped BA has a great influence on phase structure,morphologies,and electrical properties.The XRD patterns and dielectric constant versus temperature curves reveal that an increase in the BA content results in a transform of phase structures from a coexistence state of rhombohedral,orthorhombic and tetragonal phases to pseudocubic phase.Owing to the construction of R-O-T phase boundary,optimized performances(T_(C)~336℃,d_(33)~306 pC/N,kp=0.48)are obtained in 0.962(K_(0.48)Na_(0.52))NbO_(3)-0.003BiAlO_(3)-0.035(Bi_(0.5)Na_(0.5))ZrO_(3)(KNN-3)ceramics.Based on the sintered KNN-3 ceramic samples,high-frequency ultrasound imaging transducers are designed and fabricated,which exhibits a high center frequency of 24.5 MHz,a broad -6 dB bandwidth of 97% and a high-sensitivity.Finally,the imaging characteristic of the lead-free transducers is demonstrated via ex vivo imaging of biological tissue structure.As environment friendly materials,the excellent electrical and acoustic performance of developed KNN-based ceramics has great potential for practical applications.
基金supported by National Natural Science Foundation of China(81771204)the Natural Science Foundation of Guangdong Province(2019A1515011838,2020A1515010204,2021A1515011742,and 2021A1515011742).
文摘Considerable clinical evidence has demonstrated that the prevalence and severity of many chronic pain syndromes differ across sex,and are more predominant in womenthan inmen[l]But most preclinical research on chronic pain mechanisms has been performed primarily in male animals.It is generally understood that inflammatory responses in the peripheral and central nervous systems are critical for chronic pain[2,3],Given that sex dimorphism influences immunity in various diseases[4].
基金This work was supported by the National Natural Science Foundation of China （Grant No. 51332003）.
文摘Ga2O3 was doped into 0.95（K0.48Na0.52）NbO3-0.05LiTaO3 （KNN-LT） cera- mics and its influences on the sintering behavior, phase structure and electrical properties of ceramics were studied. Firstly, SEM observation exhibits that more and more glass phase appears in ceramics with the gradual addition of Ga2O3, which determines the continuous decrease in sintering temperatures. And the addition of Ga2O3 is also found to increase the orthorhombic-tetragonal transition temperature （To-T） of system to a higher level. Secondly, both the density and the coercive field （Ec） of ceramics increase firstly and then decrease with increasing the Ga2O3 content, and the KNN-LT-xGa sample at x = 0.004 shows a pinched P-E hysteresis loop. Finally, the impedance characteristics of KNN-LT-xGa ceramics were investigated at different temperatures, revealing a typical vacancy related conduction mechanism. This work demonstrates that Ga2O3 is a good sintering aid for KNN-based ceramics, and the vacancy plays an important role in the sintering and electrical behaviors of ceramics.
基金This work was financially supported by the Ministry of Science and Technology of China(Nos.2016YFA0200100 and 2018YFA0703502)the National Natural Science Foundation of China(Nos.52021006,51720105003,21790052,and 21974004)+1 种基金the Strategic Priority Research Program of CAS(No.XDB36030100)the Beijing National Laboratory for Molecular Sciences(No.BNLMS-CXTD-202001).
文摘The development of rechargeable lithium-ion batteries (LIBs) is being driven by the ever-increasing demand for high energy density and excellent rate performance. Charge transfer kinetics and polarization theory, considered as basic principles for charge regulation in the LIBs, indicate that the rapid transfer of both electrons and ions is vital to the electrochemical reaction process. Graphene, a promising candidate for charge regulation in high-performance LIBs, has received extensive investigations due to its excellent carrier mobility, large specific surface area and structure tunability, etc. Recent progresses on the structural design and interfacial modification of graphene to regulate the charge transport in LIBs have been summarized. Besides, the structure-performance relationships between the structure of the graphene and its dedicated applications for LIBs have also been clarified in detail. Taking graphene as a typical example to explore the mechanism of charge regulation will outline ways to further understand and improve carbon-based nanomaterials towards the next generation of electrochemical energy storage devices.
