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[en] We have observed that molecular films of closo-1,2-dicarbadodecaborane (C2B10H12) decompose due to exposure to synchrotron light. Dissociation results in films that form a heterogeneous intermediate phase between associative molecular fragments and solid, thin film boron-carbide. This heterogeneous phase has an observed electronic structure that is an admixture of the electronic structure observed for molecularly condensed orthocarborane and the electronic structure anticipated for rhombohedral boron-carbide (based on the B12 icosahedral 'building block'). With the synchrotron radiation exposure at room temperature there is dissociative adsorption of this icosahedral molecule and the growth of boron-carbide film is enhanced. The composition of the growing film changes for very thin films on Si(111), as determined by the boron to carbon ratio. The boron concentration of the film increases with increasing film thickness until the boron to carbon ratio reaches 5 when the film thickness is approximately 12 A. After about 12 A of film growth the composition is constant, i.e. B5C. (author)
[en] While we welcome the attention paid to boron-rich semiconductor devices, several clarifications are indicated to a recent paper  modeling neutron capture in boron-rich semiconductor solid-state detectors
[en] Hard carbon-coated natural graphite materials have been prepared and evaluated as a negative electrode for high-energy and high-power lithium-ion capacitors. The graphite surface was coated with hard carbon by using polyacrylonitrile as a precursor, which was confirmed by X-ray diffraction, Raman spectroscopy, and transmission electron microscopy. The hard carbon coating on natural graphite particles significantly affects the electrochemical characteristics of lithium-ion capacitors. The full-cell using the hard carbon-coated graphite electrode showed much higher energy and power densities than those with pristine natural graphite and hard carbon electrodes, respectively. Furthermore, the hard carbon-coated graphite electrode exhibited an enhanced cycle performance with a capacity retention of 74.6% after 10,000 cycles, higher than those of pristine natural graphite (33.3%) and the mixture of hard carbon and natural graphite (51.4%). The results clearly indicate that the hard carbon-coated graphite electrode is suitable as a negative electrode material for high-energy and highpower lithium-ion capacitors
[en] Fluorine-doped tin oxide (SnOx:F) films on SUS 316 were prepared as a function of substrate temperature using electron cyclotron resonance-metal organic chemical vapor deposition (ECR-MOCVD) in order to achieve corrosion-resistant and low contact resistance bipolar plates for polymer electrolyte membrane fuel cells (PEMFCs). The SnOx:F films coated on SUS 316 substrate in the heating range from 200 to 500 0C were characterized by x-ray diffraction (XRD), Auger electron microscopy (AES) and field emission-scanning electron microscopy (FE-SEM). To simulate the aggressive PEMFC environment, all electrochemical experiments were conducted in 1 M H2SO4+2 ppm HF solution at 70 0C. With increases in the heat treatment temperature from 300 to 500 0C, it was shown that both corrosion resistance and interfacial contact resistance (ICR) substantially increase. The AES data revealed that the amount of fluorine decreases with increasing temperature in our experimental range. The deposition temperature appears to be one of the critical process parameters on the formation of the corrosion-protective layer for PEMFC bipolar plates. It is probably caused by microstructural evolution before/after potentiodynamic corrosion tests under the PEMFC environment.
[en] Carbon-coated Li4Ti5O12 anode materials for the lithium ion battery were synthesized by using sucrose to improve the electrochemical properties of Li4Ti5O12, and the carbon content was then tested. X-ray diffraction (XRD) showed that the coating of carbon does not influence the formation of Li4Ti5O12. Transmission electron microscopy (TEM) and Raman spectroscopy confirmed that carbon content exists on the surface of Li4Ti5O12. Electronic conductivity measurement indicated that the electronic conductivity of the carbon-coated Li4Ti5O12 material was 3.8x10-4 S cm-1, which is higher than that for the primary Li4Ti5O12 material (4.3x10-7 S cm-1). CV results show that carbon-coated Li4Ti5O12 shows a larger diffusion coefficient. Charge and discharge tests show that rate capability and cycle performance were improved because of the carbon coating.
[en] The growth of three-dimensional ZnO hybrid structures by metal-organic chemical vapor deposition was controlled through their growth pressure and temperature. Vertically aligned ZnO nanorods were grown on c-plane of sapphire substrate at 600 °C and 400 Torr. ZnO film was then formed in situ on the ZnO nanorods at 100, 600, and 700 °C and 10 Torr. High-resolution X-ray diffraction measurements showed that the ZnO film on the nanorods/sapphire grew epitaxially, and that the ZnO film/nanorods hybrid structures had well-ordered wurtzite structures. The hybrid ZnO structure was shown to be about 3–5 μm by field-emission scanning electron microscopy. The hybrid formed at 600 °C showed better crystalline quality those formed at 100 °C or 700 °C. These structures have potential applicability as nanobuilding blocks in nanodevices.
[en] Copper silicide-coated graphite as an anode material was prepared by the sequential employments of plasma enhanced chemical vapor deposition (PECVD) and radio frequency magnetron sputtering (RFMS) method at 300 deg. C. The silicon-coated graphite exhibited an initial discharge capacity of 540 mAh/g with 76% coulomb efficiency, and the discharge capacity was sharply decreased down to 50% of initial capacity after 30 cycles, probably due to large volume changes during the charge-discharge cycling. Copper silicide-coated graphite, however, exhibited an initial discharge capacity of 480 mAh/g with higher retention capacity of 87% even after 30 cycles, probably due to the enhanced interfacial conductivity. The copper silicide film on the graphite surface played as the active anode material of lithium secondary batteries via the reduction of interfacial resistance and mitigation of volume changes during repeated cycles
[en] Four kinds of synthetic graphite coated with silver and nickel for the anodes of lithium secondary batteries were prepared by a gas suspension spray coating method. The electrode coated with silver showed higher charge-discharge capacities due to a Ag-Li alloy, but rate capability decreased at higher charge-discharge rate. This result can be explained by the formation of an artificial Ag oxidation film with higher impedance, this lowered the rate capability at high charge-discharge rate due to its low electrical conductivity. Rate capability is improved, however, by coating nickel and silver together on the surface of synthetic graphite. The nickel which is inactive with oxidation reaction plays an important role as a conducting agent which enhanced the conductivity of the electrode
[en] The undoped and fluorine doped gallium tin oxide composite films are prepared by an electron cyclotron resonance metal organic chemical vapor deposition. Characteristics of structural, optical and electrical properties of the fluorine doped gallium tin oxide composite thin films are investigated. The four point probe method, atomic force microscopy and X-ray photoelectron spectroscopy are employed to characterize the composite thin films. UV-visible, X-ray diffraction, scanning electron microscope and Hall measurement performed on fluorine doped gallium tin oxide composite are films deposited on polyethylene terephthalate substrates. The diffraction pattern shows the presence of tetragonal structure with (112) special orientation for fluorine doped gallium tin oxide composite films. The doped composite film on F/Ga + Sn mole ratio of 0.35 is observed the lowest electrical resistivity of 3.35 x 10-4 Ω cm.
[en] Highlights: → Preparation of fluorine doped tin oxide (SnOx:F) and fluorine doped zinc tin oxide (ZnSnOx:F) coating layer on the surface of stainless steel 316 bipolar plate for PEMFCs (Proton Exchange Membrane Fuel Cells). → Evaluations of the corrosion resistance and the interfacial contact resistance of the bare, SnOx:F and ZnSnOx:F thin film coated stainless steel 316 bipolar plates. → Evaluation of single cell performance such as cell voltage and power density using bare stainless steel, SnOx:F and ZnSnOx:F film coated bipolar plates. - Abstract: The investigation of the electrochemical characteristics of the fluorine doped tin oxide (SnOx:F) and fluorine doped zinc tin oxide (ZnSnOx:F) was carried out in the simulated PEMFC environment and bare stainless steel 316 was used as a reference. The results showed that the ZnSnOx:F coating enhanced both the corrosion resistance and interfacial contact resistance (ICR). The corrosion current for ZnSnOx:F was 1.2 μA cm-2 which was much lower than that of bare stainless steel of 50.16 μA cm-2. The ZnSnOx:F coated film had the smallest corrosion current due to the formation of a tight surface morphology with very few pin-holes. The ZnSnOx:F coated film exhibited the highest values of the cell voltage and power density due to its having the lowest ICR values.