Hajime Miyama

The function of metals in metal-compounded semiconductor photocatalysts

Abstract The effect of various metals on the photocatalytic activity of metal-compounded semiconductors was examined for the production of ammonia from azide ions and water. A correlation between the photocatalytic activity and the work function of the metals was found.

Heterogeneous photocatalytic synthesis of ammonia from water and nitrogen

Abstract Photocatalytic synthesis of ammonia from water and nitrogen was performed. Binary wafered catalysts prepared with semiconductor powder (TiO2, SrTiO3, CdS or GaP) and platinum black, where the copolymer of ethylene and vinylalcohol was used as a binder, were found to be more effective to yield ammonia than the semiconductor powders alone.

Preparation of hollow TiO2 fibers

Abstract Sol-gel processing was used to prepare hollow TiO 2 fibers. The growth of bubbles in the fibers, which were introduced through mechanical agitation of the sol, formed many hollow regions as the gel fiber solidified. The hollow fibers obtained were typically 2 mm in (hollow) length, with outside diameters of 50 to 200 μm, and wall thicjnesses from 5 to 50 μm. The hollow fibers were distortion-free.

Effect of surface compound formation on the photo-induced reaction at polycrystalline TiO2 semiconductor electrodes

Abstract The oxidation of methanol at the surface of illuminated polyerystalline TiO 2 semiconductor electrodes was investigated by measuring the current-doubling effect. Compounding TiO 2 with MoO 2 or MoS 2 increases the efficiency of alcohol oxidation. This compounding effect is discussed with reference to the electrode characteristics.

Kinetics of the photo-graft copolymerization of methoxypolyethyleneglycol methacrylate and N,N-dimethylaminoethyl methacrylate to dithiocarbamated poly(vinyl chloride)

Abstract Photo-graft copolymerization of methoxypolyethyleneglycol methacrylate (SM) and N,N-dimethylaminoethyl methacrylate (DAEM) to dithiocarbamated poly(vinyl chloride) (DTC-PVC) in cyclohexanone was carried out and the change of concentration of SM and DAEM with time were followed by thin-layer chromatography. Also, the change of concentration of DTC-groups during the photolysis of DTC-PVC was measured spectrophotometrically to determine the quantum yield of the photolysis. Simulation of the photo-graft copolymerization was carried out by substituting the quantum yield of the photolysis and other kinetic parameters such as monomer reactivity ratios, polymerization rate constants and φ factors, which were obtained separately, into equations for the photo-copolymerization. Agreement between experiment and calculation was very good. Moreover, experimental results concerning the degree of graft-polymerization and molecular weight change during the photo-copolymerization are discussed.

Behavior of titanate coupling agent on TiO2 particles

Abstract TiO 2 powder was treated with a series of titanate coupling agents containing caprate and various lower carboxylates. The corresponding carboxylic acids show different p K a values ranging from 0.6 to 4.9. These powders were dispersed in dioctylphthalate, an organic matrix, and their viscosities were measured. The lower the p K a of the carboxylic acid of titanate, the lower the viscosity of the corresponding dispersion. This result seems to be due to the difference in the amount of lipophilic group introduced onto the powder surface. Analysis with 1 H-NMR for the filtrate after treatment, however, revealed that there was no significant difference in the amount of introduced lipophilic group among these titanates. Results of FT-IR diffusive reflectance analysis of the treated TiO 2 powder suggested that the orientation of the titanate introduced onto the powder surface is important to an understanding of the viscosities of the dispersion.