Future adaptive applications require lightweight and stiff materials with high active strain but low energy consumption.A suitable combination of these properties is offered by carbon nanotubebased actuators.Papers ma...Future adaptive applications require lightweight and stiff materials with high active strain but low energy consumption.A suitable combination of these properties is offered by carbon nanotubebased actuators.Papers made of carbon nanotubes(CNTs)are charged within an electrolyte,which results in an electrical field forming a double-layer of ions at their surfaces and a deflection of the papers can be detected.Until now,there is no generally accepted theory for the actuation mechanism.This study focuses on the actuation mechanism of CNT papers,which represent architectures of randomly oriented CNTs.The samples are tested electrochemically in an in-plane set-up to detect the free strain.The elastic modulus of the CNT papers is analyzed in a tensile test facility.The influence of various ion sizes of water-based electrolytes is investigated.During the tests,four parameters that have a significant influence on the mechanical performance of CNT papers were identified:the test conditions,the electrical charging,the microstructure and the ion size.All of these influencing factors point to the mechanically weak inter-tube linking at which the actuation seems to take place.Quadratic voltage-strain correlation suggests a combination of electrostatic and volumetric effects as the possible reason for CNT paper actuation.展开更多
Size-related properties of novel lithium battery materials, arising from kinetics, thermodynamics, and newly discov- ered lithium storage mechanisms, are reviewed. Complementary experimental and computational investig...Size-related properties of novel lithium battery materials, arising from kinetics, thermodynamics, and newly discov- ered lithium storage mechanisms, are reviewed. Complementary experimental and computational investigations of the use of the size effects to modify electrodes and electrolytes for lithium ion batteries are enumerated and discussed together. Size differences in the materials in lithium ion batteries lead to a variety of exciting phenomena. Smaller-particle materials with highly connective interfaces and reduced diffusion paths exhibit higher rate performance than the corresponding bulk materials. The thermodynamics is also changed by the higher surface energy of smaller particles, affecting, for example, secondary surface reactions, lattice parameter, voltage, and the phase transformation mechanism. Newly discovered lithium storage mechanisms that result in superior storage capacity are also briefly highlighted.展开更多
To investigate effect of metallic ion activation on different particle sizes of quartz in butyl xanthate solution,six common ions(Pb^(2+),Cu^(2+),Fe^(3+),Fe^(2+),Mg^(2+) and Ca^(2+)) were introduced as activators.The ...To investigate effect of metallic ion activation on different particle sizes of quartz in butyl xanthate solution,six common ions(Pb^(2+),Cu^(2+),Fe^(3+),Fe^(2+),Mg^(2+) and Ca^(2+)) were introduced as activators.The approaches of micro-flotation,adsorption test and zeta potential measurement were adopted to reveal the mechanism of ion activation.The results show that Pb^(2+),Cu^(2+) and Fe^(3+) are effective activators for the flotation of quartz in butyl xanthate solution because of their absorption on activated quartz surface.Average recoveries of fine particles(<37 μm) are greater than those of coarser particles(37-74 μm),suggesting that the former is easier to be activated and more likely to be floated and thus entrained in sulphide concentrate.From another perspective,addition of metallic ions(Pb^(2+),Cu^(2+) and Fe^(3+)) renders zeta potentials move positively,and addition of the same metallic ions and butyl xanthate makes zeta potential drop apparently,which support a mechanism where they adsorb onto quartz surface,resulting in an expected increase in butyl xanthate collector adsorption with a concomitant increase in the flotation recoveries.展开更多
Water Vapor Chemistry" as a new science was discovered and established from trace analysis in Gu’s laboratory(Gu, 1991; Gu et al., 1991). Gu’s Function shows that the trace metal ion concentration in water vapo...Water Vapor Chemistry" as a new science was discovered and established from trace analysis in Gu’s laboratory(Gu, 1991; Gu et al., 1991). Gu’s Function shows that the trace metal ion concentration in water vapor has positive correlation to"specific electron affinity constant"last ionization potential Iz/ion valence Z and negative correlation to ion volume V and coordination number N(Gu, 1994). Gu’s Func-tion C=f[(Iz/Z)/VN]of the bond parameter in water vapor chemistry corresponds to the potential energy function Z’ e2/r in the Schrodinger Equation of quantum chemistry. In different ions with the same 2+ charge, the ion concentration of water-water vapor transfer may be much different. This shows that the 2+ charge of different ions has different attractive force (hydration force). This different attractive force of the charge can be scaled with the relative energy or charge size from Gu’s Function.展开更多
The structural and the size evolution of embedded In nanoparticles in Al synthesized by ion implantation and subsequent annealing are experimentally investigated. The average radius r of In nanoparticles is determined...The structural and the size evolution of embedded In nanoparticles in Al synthesized by ion implantation and subsequent annealing are experimentally investigated. The average radius r of In nanoparticles is determined as a function of annealing time in a temperature range between 423 K and 453 K. The structural transition of In nanoparticles with the crystallographic orientation In (200)[002]||Al (200)[002] is observed to change into In (111)[110]||Al (002)[110] with a critical particle radius between 2.3 nm and 2.6 nm. In addition, the growth of In nanoparticles in the annealing process is evidently governed by the diffusion limited Ostwald ripening. By further analyzing the experimental data, values of diffusion coefficient and activation energy are obtained.展开更多
In this paper, a two-dimensional nanometer scale tip-plate discharge model has been employed to study nanoscale electrical discharge in atmospheric conditions. The field strength dis- tributions in a nanometer scale t...In this paper, a two-dimensional nanometer scale tip-plate discharge model has been employed to study nanoscale electrical discharge in atmospheric conditions. The field strength dis- tributions in a nanometer scale tip-to-plate electrode arrangement were calculated using the finite element analysis (FEA) method, and the influences of applied voltage amplitude and frequency as well as gas gap distance on the variation of effective discharge range (EDR) on the plate were also investigated and discussed. The simulation results show that the probe with a wide tip will cause a larger effective discharge range on the plate; the field strength in the gap is notably higher than that induced by the sharp tip probe; the effective discharge range will increase linearly with the rise of excitation voltage, and decrease nonlinearly with the rise of gap length. In addition, probe dimension, especially the width/height ratio, affects the effective discharge range in different manners. With the width/height ratio rising from 1 : 1 to 1 : 10, the effective discharge range will maintain stable when the excitation voltage is around 50 V. This will increase when the excitation voltage gets higher and decrease as the excitation voltage gets lower. Fhrthermore, when the gap length is 5 nm and the excitation voltage is below 20 V, the diameter of EDR in our simulation is about 150 nm, which is consistent with the experiment results reported by other research groups. Our work provides a preliminary understanding of nanometer scale discharges and establishes a predictive structure-behavior relationship.展开更多
Nano-sized powders of rare-earth ions added CdFe2O4 ferrites were synthesized by oxalate co-precipitation method.The influence of R ions(R = Sm3+, Y3+, and La3+) on the microstructure and magnetic properties of C...Nano-sized powders of rare-earth ions added CdFe2O4 ferrites were synthesized by oxalate co-precipitation method.The influence of R ions(R = Sm3+, Y3+, and La3+) on the microstructure and magnetic properties of CdFe2O4 ferrites was studied.XRD, SEM, FTIR, and magnetic hysteresis loops were used for analyzing the samples.The addition of R ions alters the structure of the powders and decreases the crystalline size, lattice constant, and grain size.The magnetic properties such as saturation magnetization, remanent magnetization, and magnetic moment increased due to addition of rare-earth ions in CdFe2O4 ferrite.The formation of secondary phase on the grain boundaries supports the abnormal growth.FTIR spectra show two absorption bands.Results suggest that the magnetic properties depend on the particular method of preparation and additives.展开更多
【目的】为研究混合锂离子超级电容器(hybrid lithium ion supercapacitor,HLIC)的性能,分析多种干扰因素对其电化学与热特性的影响。【方法】首先建立HLIC电化学热耦合模型;其次通过试验与数值模拟相互验证来证明模型的可靠性;最后分...【目的】为研究混合锂离子超级电容器(hybrid lithium ion supercapacitor,HLIC)的性能,分析多种干扰因素对其电化学与热特性的影响。【方法】首先建立HLIC电化学热耦合模型;其次通过试验与数值模拟相互验证来证明模型的可靠性;最后分析阳极活性材料颗粒粒径、充放电倍率、电芯结构状态对HLIC的电化学与热特性的影响,并通过建立核壳模型绘制核壳图,从微观的角度分析了阳极活性材料颗粒粒径对HLIC电化学性能的影响过程。【结果】HLIC在高倍率的条件下,减小粒径可使阳极活性材料颗粒锂化程度显著提高,10 C倍率下粒径15.5μm与0.5μm的单体相比,前者能量密度降低了63.14%,平均发热率增加了121.66%,最大温度上升了17.7 K;而在低倍率的条件下,粒径对HLIC的性能影响不大,无须增加成本过分减小粒径,并且电芯在层压方向导热性较差,需要在层压方向上增加散热以保证其工作性能良好。【结论】本研究对各个场景所需的HLIC性能参数的选取具有一定的参考意义。展开更多
An Al-doped spinel lithium manganese oxide was prepared by the adipic acid-assisted sol-gel method at 800℃, and the cathode materials (Liml0.05Mnl.9504) with different particle sizes were obtained through ball mill...An Al-doped spinel lithium manganese oxide was prepared by the adipic acid-assisted sol-gel method at 800℃, and the cathode materials (Liml0.05Mnl.9504) with different particle sizes were obtained through ball milling. The effects of particle size on the electrochemical performance of LiAl0.05Mnl.9504 samples were investigated by differential thermal analysis and thermogravimetry, X-ray diffraction, galvanostatic charge-discharge test, cyclic voltammetry, and electrochemical impedance spectroscopy. The results indicate that all samples with different particle sizes show the same pure spinel phase and good crystal structure; LiAlo.osMnl.9504 with Dso = 17.3 μm shows better capacity retention; LiAlo.osMnl.gsO4 cathode materials with small particle size have a bigger resistance of charge transfer than the large one, and the particle size has significant effects on the electrochemical performance of Al-doped spinel LiMn2O4 cathode materials.展开更多
The effect of spherical particle size on the surface morphology, electrochemical property and processability of lithium iron phosphate was systematically studied. Spherical lithium iron phosphate with different partic...The effect of spherical particle size on the surface morphology, electrochemical property and processability of lithium iron phosphate was systematically studied. Spherical lithium iron phosphate with different particle size distributions controlled with ball time of precursor slurry was prepared by spray drying method. The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), charge and discharge measurements and EIS. The electrochemical performances of the sample materials were measured by coin cells and 14500 batteries. XRD shows that the spherical lithium iron phosphate with different particle sizes all have good crystal structure due to the perfect mixing of the raw materials and rapid drying. The lithium iron phosphate microsphere with different particle sizes self-assembled with submicron primary particles has a core-shell structure. The longer ball time the precursors are, the smaller the active material particles are prepared. The electrode material with 6 h ball time of precursor slurry has the best physical properties and the processability. The composite has a uniform particle size and higher tap density of 1.46 g/cm3, which delivers a discharge capacity of 167.6 mAh/g at a discharge rate of 0.5 C. The results were confirmed by the 14 500 mA h cylindrical batteries, which delivers a discharge capacity of 579 mAh at 0.5 C. And low-temperature performance with capacity of 458.5 mA h at -20 °C under a discharge rate of 0.5 C is the 79.2% of the same discharge rate at 25 °C. Otherwise, the 14500 batteries also exhibit excellent cycling performance and the capacity maintains 93% after 2 000 cycles.展开更多
Magnesium ion-exchanged a-zirconium phosphates(Mg-α-ZrP) with particle sizes of 600 and 80 nm were prepared through the sealed ion-exchange and one-step hydrothermal synthesis methods, respectively. It was found that...Magnesium ion-exchanged a-zirconium phosphates(Mg-α-ZrP) with particle sizes of 600 and 80 nm were prepared through the sealed ion-exchange and one-step hydrothermal synthesis methods, respectively. It was found that larger particles of Mg-α-ZrP had a higher load-carrying capacity than that of smaller particles, whereas smaller Mg-α-ZrP particles had better anti-wear properties than that of larger Mg-α-ZrP particles under mild loads. The correlation between the particle size of the sample and the surface roughness of the friction pair thus seems to be a key factor influencing the performance.展开更多
Dynamics of ions in biological ion channels has been classically analyzed using several types of Poisson-Nernst Planck (PNP) equations. However, due to complex interaction between individual ions and ions with the cha...Dynamics of ions in biological ion channels has been classically analyzed using several types of Poisson-Nernst Planck (PNP) equations. However, due to complex interaction between individual ions and ions with the channel walls, minimal incorporation of these interaction factors in the models to describe the flow phenomena accurately has been done. In this paper, we aim at formulating a modified PNP equation which constitutes finite size effects to capture ions interactions in the channel using Lennard Jonnes (LJ) potential theory. Particularly, the study examines existence and uniqueness of the approximate analytical solutions of the mPNP equations, First, by obtaining the priori energy estimate and providing solution bounds, and finally constructing the approximate solutions and establishing its convergence in a finite dimensional subspace in <em>L</em><sup>2</sup>, the approximate solution of the linearized mPNP equations was found to converge to the analytical solution, hence proof of existence.展开更多
基金This work was supported by the German Federal Ministry of Education and Research(BMBF)[Aktu_Comp]and the German Research Foundation(DFG)[DFG PAK 355].
文摘Future adaptive applications require lightweight and stiff materials with high active strain but low energy consumption.A suitable combination of these properties is offered by carbon nanotubebased actuators.Papers made of carbon nanotubes(CNTs)are charged within an electrolyte,which results in an electrical field forming a double-layer of ions at their surfaces and a deflection of the papers can be detected.Until now,there is no generally accepted theory for the actuation mechanism.This study focuses on the actuation mechanism of CNT papers,which represent architectures of randomly oriented CNTs.The samples are tested electrochemically in an in-plane set-up to detect the free strain.The elastic modulus of the CNT papers is analyzed in a tensile test facility.The influence of various ion sizes of water-based electrolytes is investigated.During the tests,four parameters that have a significant influence on the mechanical performance of CNT papers were identified:the test conditions,the electrical charging,the microstructure and the ion size.All of these influencing factors point to the mechanically weak inter-tube linking at which the actuation seems to take place.Quadratic voltage-strain correlation suggests a combination of electrostatic and volumetric effects as the possible reason for CNT paper actuation.
基金supported by the National Natural Science Foundation of China(Grant Nos.51225204 and 21303222)the Shandong Taishan Scholarship,China+1 种基金the Ministry of Science and Technology,China(Grant No.2012CB932900)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA09010000)
文摘Size-related properties of novel lithium battery materials, arising from kinetics, thermodynamics, and newly discov- ered lithium storage mechanisms, are reviewed. Complementary experimental and computational investigations of the use of the size effects to modify electrodes and electrolytes for lithium ion batteries are enumerated and discussed together. Size differences in the materials in lithium ion batteries lead to a variety of exciting phenomena. Smaller-particle materials with highly connective interfaces and reduced diffusion paths exhibit higher rate performance than the corresponding bulk materials. The thermodynamics is also changed by the higher surface energy of smaller particles, affecting, for example, secondary surface reactions, lattice parameter, voltage, and the phase transformation mechanism. Newly discovered lithium storage mechanisms that result in superior storage capacity are also briefly highlighted.
基金Project(51274255)supported by the National Natural Science Foundation of ChinaProject(2015CX005)supported by Innovation Driven Plan of Central South University,China+1 种基金Project(2016RS2016)supported by Hunan Provincial Science and Technology Leader(Innovation Team of Interface Chemistry of Efficient and Clean Utilization of Complex Mineral Resources),ChinaProject supported by the Postdoctoral Research Station of Central South University,China
文摘To investigate effect of metallic ion activation on different particle sizes of quartz in butyl xanthate solution,six common ions(Pb^(2+),Cu^(2+),Fe^(3+),Fe^(2+),Mg^(2+) and Ca^(2+)) were introduced as activators.The approaches of micro-flotation,adsorption test and zeta potential measurement were adopted to reveal the mechanism of ion activation.The results show that Pb^(2+),Cu^(2+) and Fe^(3+) are effective activators for the flotation of quartz in butyl xanthate solution because of their absorption on activated quartz surface.Average recoveries of fine particles(<37 μm) are greater than those of coarser particles(37-74 μm),suggesting that the former is easier to be activated and more likely to be floated and thus entrained in sulphide concentrate.From another perspective,addition of metallic ions(Pb^(2+),Cu^(2+) and Fe^(3+)) renders zeta potentials move positively,and addition of the same metallic ions and butyl xanthate makes zeta potential drop apparently,which support a mechanism where they adsorb onto quartz surface,resulting in an expected increase in butyl xanthate collector adsorption with a concomitant increase in the flotation recoveries.
文摘Water Vapor Chemistry" as a new science was discovered and established from trace analysis in Gu’s laboratory(Gu, 1991; Gu et al., 1991). Gu’s Function shows that the trace metal ion concentration in water vapor has positive correlation to"specific electron affinity constant"last ionization potential Iz/ion valence Z and negative correlation to ion volume V and coordination number N(Gu, 1994). Gu’s Func-tion C=f[(Iz/Z)/VN]of the bond parameter in water vapor chemistry corresponds to the potential energy function Z’ e2/r in the Schrodinger Equation of quantum chemistry. In different ions with the same 2+ charge, the ion concentration of water-water vapor transfer may be much different. This shows that the 2+ charge of different ions has different attractive force (hydration force). This different attractive force of the charge can be scaled with the relative energy or charge size from Gu’s Function.
基金Project supported by the National Natural Science Foundation of China(Grant No.11505160)the Director Foundation of Institute of Materials,Chinese Academy of Engineering Physics(Grant No.SJZD201406)
文摘The structural and the size evolution of embedded In nanoparticles in Al synthesized by ion implantation and subsequent annealing are experimentally investigated. The average radius r of In nanoparticles is determined as a function of annealing time in a temperature range between 423 K and 453 K. The structural transition of In nanoparticles with the crystallographic orientation In (200)[002]||Al (200)[002] is observed to change into In (111)[110]||Al (002)[110] with a critical particle radius between 2.3 nm and 2.6 nm. In addition, the growth of In nanoparticles in the annealing process is evidently governed by the diffusion limited Ostwald ripening. By further analyzing the experimental data, values of diffusion coefficient and activation energy are obtained.
基金supported in part by External Cooperation Program of Chinese Academy of Sciences(No.GJHZ1218)National Natural Science Foundation of China(No.61004133)SSSTC JRP awards 2011(IZLCZ2 138953)
文摘In this paper, a two-dimensional nanometer scale tip-plate discharge model has been employed to study nanoscale electrical discharge in atmospheric conditions. The field strength dis- tributions in a nanometer scale tip-to-plate electrode arrangement were calculated using the finite element analysis (FEA) method, and the influences of applied voltage amplitude and frequency as well as gas gap distance on the variation of effective discharge range (EDR) on the plate were also investigated and discussed. The simulation results show that the probe with a wide tip will cause a larger effective discharge range on the plate; the field strength in the gap is notably higher than that induced by the sharp tip probe; the effective discharge range will increase linearly with the rise of excitation voltage, and decrease nonlinearly with the rise of gap length. In addition, probe dimension, especially the width/height ratio, affects the effective discharge range in different manners. With the width/height ratio rising from 1 : 1 to 1 : 10, the effective discharge range will maintain stable when the excitation voltage is around 50 V. This will increase when the excitation voltage gets higher and decrease as the excitation voltage gets lower. Fhrthermore, when the gap length is 5 nm and the excitation voltage is below 20 V, the diameter of EDR in our simulation is about 150 nm, which is consistent with the experiment results reported by other research groups. Our work provides a preliminary understanding of nanometer scale discharges and establishes a predictive structure-behavior relationship.
基金the University Grant Commission New Delhi for financial assistance through the Minor Research Project (No. 47-016/06)
文摘Nano-sized powders of rare-earth ions added CdFe2O4 ferrites were synthesized by oxalate co-precipitation method.The influence of R ions(R = Sm3+, Y3+, and La3+) on the microstructure and magnetic properties of CdFe2O4 ferrites was studied.XRD, SEM, FTIR, and magnetic hysteresis loops were used for analyzing the samples.The addition of R ions alters the structure of the powders and decreases the crystalline size, lattice constant, and grain size.The magnetic properties such as saturation magnetization, remanent magnetization, and magnetic moment increased due to addition of rare-earth ions in CdFe2O4 ferrite.The formation of secondary phase on the grain boundaries supports the abnormal growth.FTIR spectra show two absorption bands.Results suggest that the magnetic properties depend on the particular method of preparation and additives.
文摘An Al-doped spinel lithium manganese oxide was prepared by the adipic acid-assisted sol-gel method at 800℃, and the cathode materials (Liml0.05Mnl.9504) with different particle sizes were obtained through ball milling. The effects of particle size on the electrochemical performance of LiAl0.05Mnl.9504 samples were investigated by differential thermal analysis and thermogravimetry, X-ray diffraction, galvanostatic charge-discharge test, cyclic voltammetry, and electrochemical impedance spectroscopy. The results indicate that all samples with different particle sizes show the same pure spinel phase and good crystal structure; LiAlo.osMnl.9504 with Dso = 17.3 μm shows better capacity retention; LiAlo.osMnl.gsO4 cathode materials with small particle size have a bigger resistance of charge transfer than the large one, and the particle size has significant effects on the electrochemical performance of Al-doped spinel LiMn2O4 cathode materials.
文摘The effect of spherical particle size on the surface morphology, electrochemical property and processability of lithium iron phosphate was systematically studied. Spherical lithium iron phosphate with different particle size distributions controlled with ball time of precursor slurry was prepared by spray drying method. The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), charge and discharge measurements and EIS. The electrochemical performances of the sample materials were measured by coin cells and 14500 batteries. XRD shows that the spherical lithium iron phosphate with different particle sizes all have good crystal structure due to the perfect mixing of the raw materials and rapid drying. The lithium iron phosphate microsphere with different particle sizes self-assembled with submicron primary particles has a core-shell structure. The longer ball time the precursors are, the smaller the active material particles are prepared. The electrode material with 6 h ball time of precursor slurry has the best physical properties and the processability. The composite has a uniform particle size and higher tap density of 1.46 g/cm3, which delivers a discharge capacity of 167.6 mAh/g at a discharge rate of 0.5 C. The results were confirmed by the 14 500 mA h cylindrical batteries, which delivers a discharge capacity of 579 mAh at 0.5 C. And low-temperature performance with capacity of 458.5 mA h at -20 °C under a discharge rate of 0.5 C is the 79.2% of the same discharge rate at 25 °C. Otherwise, the 14500 batteries also exhibit excellent cycling performance and the capacity maintains 93% after 2 000 cycles.
基金Funded by the Key Program of National Natural Science Foundation of China(No.21436008)the General Program of National Natural Science Foundation of China(No.51372162)+1 种基金Young Scientists Fund of the National Natural Science Foundation of China(No.21506145)the Natural Science Foundation for Young Scientists of Shanxi Province,China(No.2015021032)
文摘Magnesium ion-exchanged a-zirconium phosphates(Mg-α-ZrP) with particle sizes of 600 and 80 nm were prepared through the sealed ion-exchange and one-step hydrothermal synthesis methods, respectively. It was found that larger particles of Mg-α-ZrP had a higher load-carrying capacity than that of smaller particles, whereas smaller Mg-α-ZrP particles had better anti-wear properties than that of larger Mg-α-ZrP particles under mild loads. The correlation between the particle size of the sample and the surface roughness of the friction pair thus seems to be a key factor influencing the performance.
文摘Dynamics of ions in biological ion channels has been classically analyzed using several types of Poisson-Nernst Planck (PNP) equations. However, due to complex interaction between individual ions and ions with the channel walls, minimal incorporation of these interaction factors in the models to describe the flow phenomena accurately has been done. In this paper, we aim at formulating a modified PNP equation which constitutes finite size effects to capture ions interactions in the channel using Lennard Jonnes (LJ) potential theory. Particularly, the study examines existence and uniqueness of the approximate analytical solutions of the mPNP equations, First, by obtaining the priori energy estimate and providing solution bounds, and finally constructing the approximate solutions and establishing its convergence in a finite dimensional subspace in <em>L</em><sup>2</sup>, the approximate solution of the linearized mPNP equations was found to converge to the analytical solution, hence proof of existence.