Papers by Author: Takeshi Miki

Abstract: To obtain alumina powder with large surface area, the precursor sol was prepared by hydrolysis of aluminum isopropoxide and then mixing with trehalose dihydrate. The porous alumina powders were prepared by drying and calcination at 500-900 °C. The specific surface area went up to over 340 m²/g in the alumina powder calcined at 500 °C. The mean pore diameter of the alumina powder was increased by the addition of treahalose dihydrate. The porous alumina powder was successfully prepared by the addition of trehalose dihydrate to the precursor sol.

Abstract: Fe₂O₃/Al₂O₃ catalyst was prepared and the catalytic oxidation of toluene over the catalyst was investigated. The catalyst was prepared by wet impregnation of commercial alumina support. The support was impregnated with an aqueous solution of iron nitrate. The wet support was dried and calcined at 600-800 °C. The catalytic property of the catalyst was measured by the light-off curve of CO₂ yield. All these catalysts were active for total oxidation of toluene above 250 °C. The catalytic activity of catalyst calcined at 600 °C was better than those of catalysts calcined at 700 and 800 °C.

Abstract: To obtain porous TiO2 film, the precursor sol was prepared by hydrolysis of Ti isopropoxide and then complexed with trehalose dihydrate. The porous TiO2 film was fabricated by dip-coating method on quartz glass substrates using this sol. The TiO2 films were calcined at 500-900 °C. The photocatalytic activities of the films were evaluated by examining decomposition of methylene blue in aqueous solution under UV light irradiation. The photocatalytic activity of the porous TiO2 film showed a different tendency according to the irradiation wavelength of UV light. The activity of the film evaluated under UV light irradiation with a wavelength of 254 nm was not affected a great deal by the clacination temperature. In the case of UV light irradiation with a wavelength of 365 nm, the activity of the film increased with increasing calcination temperature and that of the film calcined at 800 °C was the highest.

Abstract: To obtain porous and thick TiO2 film, the precursor sol was prepared by hydrolysis of Ti isopropoxide and then complexed with trehalose dihydrate. The porous TiO2 film was fabricated by dip-coating technique on quartz glass substrates using this sol. The TiO2 films were calcined at 500-700 °C. The photocatalytic activity of the films was evaluated by examining decomposition of methylene blue in aqueous solution under UV light irradiation. The TiO2 film prepared from the sol with trehalose was more active than TiO2 film prepared from the sol without trehalose. The trehalose addition to the dip-coating solution was effective in improving the photocatalytic activity of the TiO2 film.

Abstract: Two types of titanium dioxide sol solutions were prepared using titanium tetra-isopropoxide, urea, 2-methoxyethanol and water. The prepared sol solutions were dip-coated onto fused silica plates. These as-prepared films were dried at 100 °C and then annealed at 650 °C. The annealed films were anatase type titanium dioxides. Visible light absorption by the films was observed in wavelengths longer than 400 nm. Also, photodegradation of methylene blue by visible light irradiation was accelerated in the presence of the films prepared by these methods.

Abstract: The influence of the titania photocatalyst nano-particles to the skin is to be doubted. We studied the influence of different titania photocatalyst nanoparticles shape to the artificial skin like the human body under the UV light irradiation conditions. The decomposition degree of the artificial skin was evaluated from the monitoring of the amount of carbon dioxide generated from them by the titania photocatalyst nanoparticle activity. When spreading their titania nanoparticles on the skin sample, the carbon dioxide generated from the skin was not detected in the apatite coating titania nano-particle sample through was detected the sample coating no apatite. The result was considered not to have existed the influence on the skin samples because the titania nano-particle was not to touch the skin sample directly.

Abstract: To obtain porous TiO2 film, the precursor sol was prepared by hydrolysis of Ti isopropoxide and then complexed with trehalose dihydrate. The porous TiO2 film was fabricated by dip-coating technique on glass substrates using this solution. The TiO2 film was calcined at 500 °C. The maximum thickness of the film by one–run dip-coating was ca. 740 nm. The film was composed of nanosized particle and pore. The porosity of the TiO2 film was increased by the addition of trehalose dihydrate to the sol. The porous TiO2 films were calcined at various temperatures. The effects of the calcination temperature on the microstructure of the porous TiO2 film were investigated. The porous film prepared from sol containing trehalose still kept the porous structure for calcination at 950 °C. The phase transition temperature from anatase to rutile of the film was shifted from 650 to 700 °C by trehalose addition to the sol.

Abstract: A novel photoresponsive zirconia (ZrO2) precursor solution was prepared using zirconium tetra-n-butoxide, 4-(phenylazo)benzoic acid and ethyleneglycol monomethylether. Two kinds of ZrO2 films were prepared using the photoresponsive ZrO2 precursor solution and by dip-coating while applying an electric field to the substrates: one was the film prepared with ultraviolet (UV) irradiation to the solution and as-deposited films; the other was the film prepared without UV irradiation. It was found that the surface roughness of films was greatly changed by UV irradiation. Furthermore, the photocatalytic activity of the rough film was greater than that of the smooth film.

Abstract: Nanoscale TiO2 is widely used in consumer products like sunscreen and cosmetics. The establishment of damage evaluation test method was attempted to examine the potential neurotoxicity of nanoscale TiO2 to human body skin in vitro model. The emergence amounts of carbon dioxide, which was expected one of the generation products from the skin according to the titania photocatalyst nanoparticles activity under UV / visible light radiation, were identified and measured by the gas analyzer. It was found that it could evaluate the degrees of damage to skin with the photocatalysts activity by using the new evaluation test method considered.

Abstract: A new photochromic ZrO2 precursor solution was prepared using zirconium tetra-n-butoxide, 4-(phenylazo)benzoic acid and ethyleneglycol monomethylether. The density functional theory (DFT) calculation has identified that the structure of the synthesized precursor molecule changed by UV irradiation. The two kinds of thin films were prepared using the photosensitive ZrO2 precursor solution without and with UV irradiation. The surface morphology of thin films changed by UV irradiation. It was found that the surface morphology of thin films is controlled by the difference of precursor structure introduced by UV irradiation.