Bi0.5(Na0.85K0.15)0.5TiO3(BNKT15) thin films were synthesized by metal-organic decomposition(MOD) at annealing temperatures of 650,680,710 and 740℃,and the effects of annealing temperature on the microstructure,diele...Bi0.5(Na0.85K0.15)0.5TiO3(BNKT15) thin films were synthesized by metal-organic decomposition(MOD) at annealing temperatures of 650,680,710 and 740℃,and the effects of annealing temperature on the microstructure,dielectric properties,remnant polarization(2Pr) and leakage current density were studied with X-ray diffractometer,atomic force microscope,precision impedance analyzer,ferroelectric analysis station and semiconductor parameter tester.The results show that the thin film annealed at 710℃ exhibits a typical perovskite structure without predominant orientation and a smooth surface with evenly distributed grains.2Pr value(67.4 μC/cm2 under 830 kV/cm) and the leakage current density(1.6×10-6 A/cm2 at 170 kV/cm) for BNKT15 thin film annealed at 710℃ are better than those for thin films annealed at other temperatures.展开更多
The Li Ni1/3Co1/3Mn1/3O2 is first obtained by the controlled crystallization method and then coated with Ni3(PO4)2particles. The effects of the coating on rate capability and cycle life at high cut-off voltage are inv...The Li Ni1/3Co1/3Mn1/3O2 is first obtained by the controlled crystallization method and then coated with Ni3(PO4)2particles. The effects of the coating on rate capability and cycle life at high cut-off voltage are investigated by electrochemical impedance spectroscopy and galvanostatic measurements. The element ratio of Ni:Mn:Co is tested by inductively-coupled plasma spectrometer(ICP) analysis and it testified to be 1:1:1. It is indicated that Ni3(PO4)2-coated Li Ni1/3Co1/3Mn1/3O2 has an outstanding capacity retention, where 99% capacity retention is maintained after 10 cycles at 5C discharge rate between 2.7 V and 4.6 V. The electrochemical impedance spectroscopy(EIS) results show that the current exchange density i0 of the coated sample is higher than that of Li Ni1/3Co1/3Mn1/3O2, which is beneficial to its electrochemical performances. All the conclusions show that the Ni3(PO4)2coating can prominently enhance the high rate performance of the Li Ni1/3Co1/3Mn1/3O2, especially at high cut-off voltage.展开更多
The authors have investigated the pH and ionic strength response of self-assembled layers formed by adsorption of amphiphilic weak polyelectrolytes. Using the SFA （Surface Forces Apparatus） the authors measured forc...The authors have investigated the pH and ionic strength response of self-assembled layers formed by adsorption of amphiphilic weak polyelectrolytes. Using the SFA （Surface Forces Apparatus） the authors measured force-distance profiles of poly （isoprene）-poly （acrylic acid） block copolymers adsorbed on mica. Also by Atomic Force Microscopy the authors captured single polyelectrolyte molecule adsorbed on a surface. The effect of salt concentration （Cs） and pH upon the height of the brush layers was explored mainly by measuring the forces between two adsorbed polyelectrolyte brushes. At pH = 4 our results are in good agreement with the scaling prediction L0 ∝Cs-1/3 Changing the pH from 4 to 10 causes a remarkable swelling of the polymer layer, but only a weak dependence on salt concentration was detected at the higher pH. This can be attributed to the degree of dissociation, which depends on the local pH value. At low pH the polyelectrolyte chains have a low charge density, while on increasing the pH the degree of dissociation rises, and the increased charge density is followed by swelling of the adsorbed layer. The local concentration of ions in the brush is now greater than that of pH = 4 and approximately equivalent to 0.3 M. So the swelling is only weakly dependent on salt concentration in the range 0.01-1.0 M. The results demonstrate the tunable nature of such self-assembled polyelectroiyte brushes whose height and range of interactions, can be systematically controlled by adjusting the pH and ionic strength of the medium.展开更多
We report the experimental and theoretical investigation of the complete valence shell binding energy spectra and momentum profiles of naphthalene (C 10 H 8),using our high resolution electron momentum spectrometer,at...We report the experimental and theoretical investigation of the complete valence shell binding energy spectra and momentum profiles of naphthalene (C 10 H 8),using our high resolution electron momentum spectrometer,at impact energies of 1500 eV and 600 eV.The observed momentum profiles were compared with the Hartree-Fock (HF) and density functional theory (DFT) calculations,and the binding energy spectrum was compared with the Outer valence Green's function (OVGF) calculations.The impact energy dependent discrepancy between observed momentum distributions and calculations under the plane wave impulse approximation was ascribed to the distorted wave effects.展开更多
基金Projects(10672139, 10825209, 50872117) supported by the National Natural Science Foundation of ChinaProject(207079) supported by the Key Program of Ministry of Education of China+3 种基金Project(07JJ5002) supported by the Natural Science Foundation of Hunan Province, ChinaProject(08C862) supported by Scientific Research Fund of Hunan Provincial Education Department, ChinaProject([2008]101) supported by Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education MinistryProject([2007]362) supported by Hunan Prestigious Furong Scholar Award, China
文摘Bi0.5(Na0.85K0.15)0.5TiO3(BNKT15) thin films were synthesized by metal-organic decomposition(MOD) at annealing temperatures of 650,680,710 and 740℃,and the effects of annealing temperature on the microstructure,dielectric properties,remnant polarization(2Pr) and leakage current density were studied with X-ray diffractometer,atomic force microscope,precision impedance analyzer,ferroelectric analysis station and semiconductor parameter tester.The results show that the thin film annealed at 710℃ exhibits a typical perovskite structure without predominant orientation and a smooth surface with evenly distributed grains.2Pr value(67.4 μC/cm2 under 830 kV/cm) and the leakage current density(1.6×10-6 A/cm2 at 170 kV/cm) for BNKT15 thin film annealed at 710℃ are better than those for thin films annealed at other temperatures.
基金Supported by the National Natural Science Foundation of China(51074096)
文摘The Li Ni1/3Co1/3Mn1/3O2 is first obtained by the controlled crystallization method and then coated with Ni3(PO4)2particles. The effects of the coating on rate capability and cycle life at high cut-off voltage are investigated by electrochemical impedance spectroscopy and galvanostatic measurements. The element ratio of Ni:Mn:Co is tested by inductively-coupled plasma spectrometer(ICP) analysis and it testified to be 1:1:1. It is indicated that Ni3(PO4)2-coated Li Ni1/3Co1/3Mn1/3O2 has an outstanding capacity retention, where 99% capacity retention is maintained after 10 cycles at 5C discharge rate between 2.7 V and 4.6 V. The electrochemical impedance spectroscopy(EIS) results show that the current exchange density i0 of the coated sample is higher than that of Li Ni1/3Co1/3Mn1/3O2, which is beneficial to its electrochemical performances. All the conclusions show that the Ni3(PO4)2coating can prominently enhance the high rate performance of the Li Ni1/3Co1/3Mn1/3O2, especially at high cut-off voltage.
文摘The authors have investigated the pH and ionic strength response of self-assembled layers formed by adsorption of amphiphilic weak polyelectrolytes. Using the SFA （Surface Forces Apparatus） the authors measured force-distance profiles of poly （isoprene）-poly （acrylic acid） block copolymers adsorbed on mica. Also by Atomic Force Microscopy the authors captured single polyelectrolyte molecule adsorbed on a surface. The effect of salt concentration （Cs） and pH upon the height of the brush layers was explored mainly by measuring the forces between two adsorbed polyelectrolyte brushes. At pH = 4 our results are in good agreement with the scaling prediction L0 ∝Cs-1/3 Changing the pH from 4 to 10 causes a remarkable swelling of the polymer layer, but only a weak dependence on salt concentration was detected at the higher pH. This can be attributed to the degree of dissociation, which depends on the local pH value. At low pH the polyelectrolyte chains have a low charge density, while on increasing the pH the degree of dissociation rises, and the increased charge density is followed by swelling of the adsorbed layer. The local concentration of ions in the brush is now greater than that of pH = 4 and approximately equivalent to 0.3 M. So the swelling is only weakly dependent on salt concentration in the range 0.01-1.0 M. The results demonstrate the tunable nature of such self-assembled polyelectroiyte brushes whose height and range of interactions, can be systematically controlled by adjusting the pH and ionic strength of the medium.
基金supported by the National Natural Science Foundation of China (Grants Nos. 11074144,10874097 and 10704046)Specialized Research Fund for the Doctoral Program of Higher Education (Grant No. 20070003146)
文摘We report the experimental and theoretical investigation of the complete valence shell binding energy spectra and momentum profiles of naphthalene (C 10 H 8),using our high resolution electron momentum spectrometer,at impact energies of 1500 eV and 600 eV.The observed momentum profiles were compared with the Hartree-Fock (HF) and density functional theory (DFT) calculations,and the binding energy spectrum was compared with the Outer valence Green's function (OVGF) calculations.The impact energy dependent discrepancy between observed momentum distributions and calculations under the plane wave impulse approximation was ascribed to the distorted wave effects.
