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991.
992.
Fluorine substituted Li1.27Cr0.2Mn0.53O2 electrode, prepared by sol–gel method, was investigated in the present work. Thermal analysis was done on this cathode material
and found to be thermally stable with a loss of weight near 300 °C. Influence of fluorine substitution on the structural and
electrochemical properties of the Li1.27Cr0.2Mn0.53O2 electrode was studied by X-ray diffraction (XRD) and field emission scanning electron microscope. XRD pattern of the fluorine-doped
Li1.27Cr0.2Mn0.53O2 cathode material quenched at 900 °C indicates a phase pure material. The charge–discharge profile of the prepared cathode
material showed that the fluorine substitution for oxygen in the cathode material resulted in improved capacity retention.
Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, December 7–9,
2006. 相似文献
993.
R. Menegotto Costa L. Mendon?a Ferreira V. N. Vieira P. Pureur J. Schaf 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(2):107-113
We have studied experimentally the electrical magneto-conductivity near the
superconducting transition of YBa2Cu3O7-δ, YBa2
(Cu2.95Zn0.05)O7-δ and Y(Ba1.75Sr0.25)Cu3O7-δ polycrystalline samples. The measurements were performed in magnetic fields ranging from 0 to 400 Oe applied parallel to
the current orientation. The results show that the resistive transition of these systems proceeds in two stages. The pairing
transition occurs at the bulk critical temperature Tc, where superconductivity is stabilized within small and homogeneous regions of the
sample generically called grains. The regime of approach to the zero resistance state reveals the occurrence of a coherence
transition at a lower temperature Tc0. This transition is related to the connective nature of the granular samples and is controlled by fluctuations of the
order-parameter phase of individual grains. Our experiments show that the Zn-doping, besides depressing the pairing critical
temperature, strongly enlarges the temperature range dominated by effects related to the coherence transition. The substitution
of Ba by Sr causes only a small reduction of Tc, but also enhances significantly the effects related to the grain
coupling phenomenology. In general, our results indicate that these impurity substitutions in YBa2Cu3O7-δ produce or magnify the granularity at a microscopic level, enhancing the effects of phase fluctuations in the conductivity
near the transition. 相似文献
994.
A new type of combined magnetic focusing–electrostatic deflection systems whose orientation of deflection field is rotated synchronously with the beam electrons is proposed. This rotation deflection field can be formed by twistification of tube wall electrode (TWE) deflectors. Formulae are derived for the first-order optical properties, third-order geometrical aberrations and first-order chromatic aberrations of this system. A program was written in FORTRAN for numerical computation. An example is given; the computation results show that compared to the conventional systems, the proposed new system has lower deflection aberration coefficients. 相似文献
995.
A simple method was proposed to prepare nanosized Si composite anode materials for lithium-ion (Li-ion) batteries. The preparation
started with the shock-type ball milling of silicon in liquid media of polyacrylonitrile (PAN)/dimethylformamide (DMF) solution,
forming slurry where the nano-Si particles were uniformly dispersed, followed by the drying of the slurry to remove DMF. The
nanosized Si composite anode material was obtained after the pyrolysis of the mixture at 300 °C where the pyrolyzed PAN provided
a conductive matrix to relieve the morphological change of Si during cycling. As-prepared composite presented good cyclability
for lithium storage. The proposed process paves an effective way to prepare high performance Si, Sn, Sb and their alloys based
composite anode materials for Li-ion batteries. 相似文献
996.
Xueyu Qiu Yadong Han Xiuli Zhuang Xuesi Chen Yuesheng Li Xiabin Jing 《Journal of nanoparticle research》2007,9(5):901-908
Nano-hydroxyapatite (HA)/poly(l-lactide) (PLLA) composite microspheres with relatively uniform size distribution were prepared by a solid-in-oil-in-water
(s/o/w) emusion solvent evaporation method. The encapsulation of the HA nanopaticles in microshperes was significantly improved
by grafting PLLA on the surface of the HA nanoparticles (p-HA) during emulsion process. This procedure gave a possibility
to obtain p-HA/PLLA composite microspheres with uniform morphology and the encapsulated p-HA nanoparticle loading reached
up to 40 wt% (33 wt% of pure HA) in the p-HA/PLLA composite microspheres. The microstructure of composite microspheres from
core-shell to single phase changed with the variation of p-HA to PLLA ratios. p-HA/PLLA composite microspheres with the diameter
range of 2–3 μm were obtained. The entrapment efficiency of p-HA in microspheres could high up to 90 wt% and that of HA was
only 13 wt%. Surface and bulk characterizations of the composite microspheres were performed by measurements such as wide
angle X-ray diffraction (WAXD), thermal gravimetric analysis (TGA), environmental scanning electron microscope (ESEM) and
transmission electron microscopy (TEM). 相似文献
997.
I. V. Osipova I. A. Ryabkov N. G. Vnukova N. V. Bulina G. N. Churilov 《Journal of Applied Spectroscopy》2007,74(1):156-158
We present a design for a dual-jet arc plasmatron operating at a frequency of 66 kHz in an argon flow at atmospheric pressure.
We present the results of determination of the temperature, electron concentration, and electrode erosion obtained by atomic
emission spectral analysis. The proposed convenient design for a dualjet plasmatron and the low erosion of the copper electrodes
in the plasma make it possible to use it for medical purposes.
Report given at the Fifth International Conference on Plasma Physics and Plasma Technologies (PPPT-5), 18–22 September 2006,
Minsk, Belarus.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 139–140, January–February, 2007. 相似文献
998.
Gun Sang Jeon Chia-Chen Chang Jainendra K. Jain 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(3):271-282
We review and extend the composite fermion theory for semiconductor quantum dots in high magnetic fields. The mean-field model
of composite fermions is unsatisfactory for the qualitative physics at high angular momenta.
Extensive numerical calculations demonstrate that the microscopic CF theory,
which incorporates interactions between composite fermions, provides an excellent qualitative and quantitative account
of the quantum dot ground state down to the largest angular momenta studied,
and allows systematic improvements by inclusion of mixing between composite
fermion Landau levels (called Λ levels). 相似文献
999.
L. Qian Z. Xu F. Teng X.-X. Duan Z.-S. Jin Z.-L. Du F.-S. Li M.-J. Zheng Y.-S. Wang 《Journal of nanoparticle research》2007,9(3):523-527
Efficiency of polymer light-emitting diodes (PLEDs) with poly(2-methoxy-5-(2-ethyl hexyloxy)-p-phenylene vinylene) (MEH-PPV) as an emitting layer was improved if a dehydrated nanotubed titanic acid (DNTA) doped hole-buffer
layer polyethylene dioxythiophene (PEDOT) was used. Photoluminescence (PL) and Raman spectra indicated a stronger interaction
between DNTA and sulfur atom in thiophene of PEDOT, which suppresses the chemical interaction between vinylene of MEH-PPV
and thiophene of PEDOT. The interaction decreases the defect states in an interface region to result in enhancement in device
efficiency, even though the hole transporting ability of PEDOT was decreased. 相似文献
1000.
Christopher A. Paddon Farrah L. Bhatti Timothy J. Donohoe Richard G. Compton 《Journal of Physical Organic Chemistry》2007,20(2):115-121
Recent interest in the electrocatalytic activity of silver towards the reduction of alkyl iodides has led us to investigate whether the effect is observed in tetrahydrofuran (THF) at room temperature. Using platinum electrodes in THF for the reduction of alkyl halides at 298 K has been hampered by the solvent window, which ‘obscures’ the voltammetric signals of interest. In order to overcome these problems, voltammetry has been performed at low temperature and was shown to extend the voltammetric window, leading to accurate electrochemical analyses and even novel changes in mechanism(s) of the reactive species following electron‐transfer (ET). Herein, it is shown that for a primary and tertiary alkyl iodide in THF, electroreduction at silver leads to a significant shift in the reduction potential to more positive values compared to platinum. In addition, following reduction, a characteristic series of oxidation peaks are observed and are shown to be due to the specific activity of iodide ions towards silver following reductive cleavage of the parent alkyl iodide. This characteristic feature is not observed with other halide ions: bromide and chloride. Preparative electrolyses at controlled‐potential have suggested that the reduction of the above alkyl iodides is a one‐electron concerted process. The ‘free’ iodide ions act as a monitor of reaction progression, and the carbon‐centred radical either dimerises and/or abstracts a hydrogen atom from the electrolyte/solvent; 1‐iodoadamantane giving percentage yields of 58% adamantane and 39% 1,1'‐biadamantane, the primary alkyl iodide, prepared in‐house, giving 67% R‐H and 25% R‐R. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献