For the purpose of clarifying the reason why the discharge capacity of a misch metal (Mm)-based hydrogen storage alloy negative electrode in nickel-metal hydride battery drastically decreases at relatively low temperatures, the activation energies for hydrogen diffusion in the alloy bulk, charge-transfer reaction on the electrode surface and the electric conductivity of KOH solution were evaluated in the temperature range of 25°C to −40°C. By comparing the activation energies with one another, it was clarified that both the hydrogen diffusion and the charge-transfer reaction significantly influenced the discharge process at relatively low temperatures. The addition of Mo to the MmNi3.6Mn0.4Al0.3Co0.7 alloy was found to be effective for the improvement of the high-rate dischargeability at relatively low temperatures.
The effects of reaction intermediates/products on gas-phase photocatalytic oxidation reaction of TCE with TiO2 were studied. A detailed investigation revealed that the chlorine molecules resulting from the photocatalytic oxidation reaction of trichloroethylene (TCE) and the intermediate, dichloroacetyl chloride (DCAC), are responsible for the very fast photocatalytic oxidation reaction of TCE. In the reactor containing chlorine molecules during the photocatalytic oxidation reaction of TCE with TiO2, the homogeneous photochemical oxidation reaction occurred simultaneously, resulting in an increase of the oxidation rate. The photocatalytic oxidation reaction of TCE with TiO2 progressed very fast, presumably also because the chlorine molecules adsorbed on TiO2 accelerated the net heterogeneous photocatalytic oxidation reaction of TCE.
It has been reported that RuO2 has a conductive nature like common metals despite its metal oxide character and has widely been used as a coating material for electric resistors etc. However, so far no report concerning the preparation of a transparent film has been found in the literature. We continued the efforts to prepare a transparent RuO2 film and developed a new method different from the conventional sol-gel method by preparing the precursor in a n-butanol-benzene system. To analyze the process of crystallization, the thermal behavior of RuO2 gel formed initially and the gases evolved during heat-treatment of the gel were investigated by TG-DTA-MS. The structure of the thin films after heat-treatment at 100, 250, and 450°C was measured by the X-ray diffraction method. n-Butanol and water were observed to evolve at a temperature range of 100-180°C beyond their boiling points. Transformation from the gel phase to the crystalline phase occurred at a temperature range of 100-250°C without any observation of the heat of crystallization upon DTA analysis. These results suggest the formation of an ordered gel network structure, which seems to arise from arrangement by the interaction among RuO2 precursors having both butoxy (hydrophobic) and hydroxy (hydrophilic) groups. Furthermore, it was presumed that the RuO2 gel crystallizes through the dehydration and dealcoholization reactions among these RuO2 precursors. The RuO2 thin films with thicknesses of 7.0 and 23.8 nm after heat-treatment at 450°C have transmittances of 59.6-75.8%, 36.2-59.0% in the wavelength range 380-780 nm, and electrical resistivities of 9.60 × 10−4 and 4.15 × 10−4 Ωcm, respectively. These thin films showed sufficient adhesion to a glass substrate.
Various kinds of fuels based on alcohols (methanol, ethanol, and isopropanol) and hydrocarbons (methane, ethane, and ethylene) were directly supplied to solid oxide fuel cells (SOFCs) to compare their power generation characteristics. The results on current-voltage characteristics and anodic polarization have revealed that methanol-, ethanol-, and methane-based fuels exhibited satisfactory electrochemical performance, whereas the use of other carbonaceous fuels with a higher carbon number resulted in carbon deposition and consequent degradation of power generation characteristics. Importance of decomposition and/or reforming reactions of fuel species at the electrodes is highlighted.
The water soluble sulfonated polyaniline, poly(2-methoxyaniline-5-sulfonic acid) (PMAS), was used as material for the modification of Au electrode surface in the electrochemical generation of superoxide ion (O2−•) in alkaline aqueous solution. The electrochemical generation of O2−• via one-electron reduction of O2 on PMAS-adsorbed Au electrode was confirmed using the specific reaction between O2−• and superoxide dismutase (SOD). PMAS adsorbed on Au electrode exhibited a reduction wave in the potential range of −0.4~−0.2 V (vs. Ag/AgCl (KC1 sat.)), in which the formal redox potential (E0’ = −0.31 V) of O2/O2−• redox couple is, and the electroreduced form of PMAS was oxidized by O2 molecule. It was concluded from these results that PMAS acts as a redox mediator for the reduction of O2 to O2−•. Moreover, based on the rotating disc experiments for O2 reduction, PMAS-poly(L-ysine)-modified Au electrode was found to effectively electrogenerate O2−• via the reduction of O2.
Silicon fibrous whiskers were grown by the thermal decomposition of SiH4 on a silicon substrate contaminated by dust in room air. The axial growth mechanism of the whisker is as follows. During the growth of the whisker, dislocations occur in the 〈110〉 direction inside the single crystalline pith of the whisker and the whisker grows in the 〈110〉 direction due to the growth mechanism involved with these dislocations.