Gas flow sputtering is a novel method to perform sputtering at high pressure around 1 Torr. Titanium particles were sputtered, forcibly transferred by the gas flow, and heaped up on a substrate forming TiO2 film with the help of oxygen reaction gas. The photocatalytic activity and the crystal orientation of sputtered TiO2 changed with the flowing flux of oxygen gas and the temperature of substrate. The TiO2 synthesized at 0.3 seem O2 flow rate was polycrystallites of rutile and anatase phases with high photocatalytic activity.
We investigated the relation between the thermodynamic stability and crystal structure dependence of Li content for the substituted spinel, LixMn2-yMyO4 (M = Mg, Al, Cr, Mn). The enthalpy change per mole of atoms for the formation reaction, ΔHR, were calculated from the heat of dissolution. ΔHR increased with the decreasing Li content. ΔHR of the all amounts of Li content for LixMn2-yMyO4 (M = Mg, Al, Cr, Mn) decreased compared to that of LixMn2-yMyO4. The crystal structure analysis by powder neutron diffraction was examined for LixMn2-yMyO4 (M = Mg, Al, Cr, Mn). The Madelung energy increases with decreasing Li content for LixMn2O4, and it was associated with the thermodynamic data. From these results, the host structure is structurally and thermodynamically stable of the all amounts of Li content with the substitution of M for LixMn2-yMyO4.
The thermal property and heat-treatment products of the K-birnessite-type MnO2 were examined in the temperature range from 80 to 700℃ by means of TG-DTA, XRD, and TEM measurements. The birnessite phase was transformed gradually to the hollandite MnO2 phase on calcinating in the temperature range from 200 to 500℃, resulting in the formation of a single phase of high crystalline hollandite having a (2ﾗ2) tunnel structure at 550－600℃. The XRD and high-resolution TEM measurements have revealed that the nano-composite products consisting of the birnessite with scale-like crystals and the hollandite with needle-like crystals are formed at 300－400℃ in the course of calcinating the birnessite oxide. The electrochemical properties of the birnessite and its calcined products, including the discharge and cycling characteristics, were examined as cathodes for rechargeable lithium batteries. The birnessite/hollandite composite formed at around 300℃ showed a S-type smooth discharge curve with an average potential of 2.6 V vs. Li/LI+ and better performances with the initial discharge capacity of 210 mAh/g and the cycling capacity of about 170－200 mAh/g during 10 cyclings.
The electronic structure of TiO2 with brookite structure is calculated within the framework of the density functional theory (DFT). Calculated lattice constants are in excellent agreement with experimental values. Brookite is predicted to be a material with a direct band gap at the Γ point The valence band with the width ca. 4.8 eV is mainly constructed from O 2p orbitals, whereas the lower conduction band mainly Ti 3d orbitals.
In order to enhance the electrochemical performance of our solid-state metal hydride battery using an electrolyte of heteropolyacid hydrate, such as 12-molybdophosphoric acid hydrate (H3PMO12O40·20H2O), we tried to improve the total battery construction; the interface between electrode and electrolyte was increased and the electrolytic manganese dioxde was adapted as a positive electrode material instead of reagent grade manganese dioxide previously used. The resultant battery exhibited remarkablv longer cycle life performance, higher discharge efficiency, and lower po larization than the previous one. The high rate charge-discharge characteristics was improved significantly by optimiz ing electrolyte content in the positive electrode; the battery was able to operate over 200 cycles at 10 mA g (alloy)-1.
The anode products of a direct type polymer electrolyte membrane fuel cell, which uses ethanol as a fuel, are investigated. The cell is operated by circulating the fuel for 7 hours and anode liquid and gas products in the fuel are analyzed by gas chromatography. The main products are acetaldehyde for the liquid phase and carbon dioxide for the gas phase, indicating C-C bond of ethanol is decomposed by catalytic oxidation.
The high-pressure electric conductivity cell was newly developed for in-situ observations in multi-phasic solution systems. The conductivity of 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid in contact with CO2 was determined at 40ｰC as a function of CO2 pressure up to ~40 MPa. The conductivity of the ionic liquid exhibited a remarkable increase due to the dissolution of CO2 in the pressure range of 0.1 - 10 MPa.