Atsunori Matsuda

Weathering resistance of glass plates coated with sol-gel derived 9TiO2·91SiO2 films

Etude de verres de chaux sodee-silice recouverts de films de SiO 2 et de 9 TiO 2 •91 SiO 2

Pregrooving on glass disks by the sol-gel method (Part II): effects of the addition of organic polymers on the formation of glass films in the SiO2-TiO2 system

The effects of the addition of polyethylene glycol(PEG) on the formation of gel-derived glass films in the Si02-TiO2 system were studied, aimed at their application to the optical memory disks. The viscosity of the as-prepared sols increased almost linearly with increasing PEG content. The increase in viscosity of the sols during the storage was retarded with decreasing molecular weight of PEG added and with increasing amount of PEG added. The viscosity increase of the sols during the storage, however, showed a similar temperature dependence, i.e. almost the same apparent activation energy was obtained, in the sols containing different amounts of PEG. These findings indicate that PEG added to the SiO2-TiO2 sols scarcely reacts with the hydrolyzed inorganic species. The hardness of the resultant PEG-containing gel films greatly decreased with increasing PEG content. The gel films containing PEG of the smaller average molecular weight showed the higher hardness and the steeper increase in hardness with increasing the heat-treatment temperature than those containing PEG of the larger average molecular weight. For a high performance in the fine patterning process and densification of the resultant patterned films, PEG of the smaller amount and the smaller molecular weight is favorable, provided the PEG-containing gel films are initially soft enough to emboss fine patterns by pressing a stamper. Incorporated PEG in the Si02-Ti02 gel films decomposed completely at temperatures over 300 °C and had a very slight influence on chemical bondings in the resultant films.

Pregrooving on glass disks by the sol-gel method (Part I): formation and evaluation of pregrooved glass disks

Pregrooved glass disks were prepared by the application of the sol-gel coating technique; the soda-lime-silica glass disks were coated with polyethylene glycol(PEG)-containing Si02-Ti02 gel films, in which fine patterns were formed by pressing a stamper. The refractive index of the pregrooved layer was matched with that of the glass disks by adjusting the TiO2 content. When the weight ratio of PEG with the average molecular weight of 600 to SiO2-TiO oxides was unity, the pitch of the pregrooves formed was unchanged in comparison with that of the stamper used after the heat-treatment at 350°C, while the land height and the land width of the pregrooves were respectively reduced to 6O9 and 85 of those of the stamper after the heat-treatment. The noise level of the glass disks with the pregrooved SiO2-Ti02 layer was lower by 1-2 dB than that of the disks with pure 5i02 layer in the frequency range from 0.5 to 2.0 MHz. The lower noise level of the former can be ascribed to the agreement in the refractive index between the pregrooved layer and the glass disks.

Sol-gel technology for optical disk application

Fine patterning, pregrooved layer coatings, on glass disks by the sol-gel method has been successfully achieved. The pregrooving process, formation of a sol-gel film on a glass substrate, stamping the groove pattern on the gel film and heat treatment, is described. The specifications of the pregrooved glass disk of 130 mm in diameter are satisfactory for the requirements as an optical disk substrate in terms of dimensional and physical characteristics, mechanical characteristics, signals from grooves. It is noted that the sol-gel pregrooved optical disks substrates have such excellent features as small dynamic radial runout, very small tilt and much long life comparing with those of conventional plastic disk substrates. Cost- performance characteristics are discussed for suitable applications of the sol-gel pregrooved optical memory disks.

Cr(VI) removal on visible light active TiO2 nanotube arrays

Self-organized TiO2 nanotube (TNT) arrays were fabricated by anodic oxidation of titanium foil in three different fluoride electrolytes: ethylene glycol (EG), glycerol, and sodium sulfate (Na2SO4) at different voltage and anodization time. In these electrolytes, the TNTs were produced in ∼ 2 µm long, but at the different diameter. The size of inner diameter can be arranged from the largest to the smallest value in the order of glycerol > EG > Na2SO4. Crystallization of the TNTs by annealing was led to the formation of anatase-TiO2. The sample can be activated under natural sunlight for reduction of hexavalent chromium, Cr(VI) into trivalent chromium, Cr(III). The reduction was thought to occur via synergistic reactions between adsorption and photoreduction. The result demonstrates 100 % of Cr(VI) removal efficiency over the TNTs grown in EG after 120 min. Whereas, only 48 % and 45 % of Cr(VI) can be removed over the TNTs fabricated in glycerol and Na2SO4, respectively. High photocatalytic activity of the ...

Tailoring Parameters to Produce Nanowires on Metal Surface via Surface Oxidation Process

Thermal oxidation of iron, tungsten, titanium and copper was done in dry air to produce Fe2O3, WO3, TiO2 and CuO nanowires, respectively, at 500 ? 600 ?C. Whilst nanowires were observed on iron and copper, no nanowires were seen on titanium and tungsten. Keeping the temperature constant, oxidation of titanium and tungsten was continued but in the presence of water vapour. Through this method nanowires were successfully formed on titanium but not on tungsten. Potassium halide vapour was then introduced to the oxidation furnace for tungsten and after an hour of oxidation, nanowires were produced on the tungsten surface. Nevertheless, the growth mechanism of the nanowires on tungsten is thought to be very much different than iron, copper and titanium whereby on tungsten catalytic induced reaction is likely. Oxide nanowires on iron and titanium were further studied as oxide films on copper and tungsten were not well adhered to the substrate. Under sunlight radiation, ~ 90% of Cr(VI) was successfully removed on Fe2O3 nanowires compared to on TiO2 nanowires (~ 40 % removal) after an hour process. This is due to the smaller energy band gap of Fe2O3 compares to TiO2.