Papers by Author: Masahiro Yoshimura

Abstract: Apatite forming and bonding ability of Ti based bulk metallic glass ((Ti0.40Zr0.10Cu0.36Pd0.14)99Ca1: BMG) were investigated as a new type of biomaterials. Powder mixture of CaHPO4･2H2O and Ca(OH)2 and the BMG disks were treated with autoclave for hydrothermal hot-pressing simultaneously (150°C, 40MPa). And then the BMG disks were soaked in simulated body fluid (SBF, Kokubo solution). Apatite were deposited and covered on the surface of the BMG. It was firstly demonstrated that surface of Ti based bulk metallic glass could be revealed apatite forming ability.

Abstract: Photocatalyst materials were prepared as a hybrid between TiO2 /SiO2 via low temperature hydrothermal method (150oC) without further heat treatment. Porous silica from rice husk ash was used as a support for fine TiO2 particles which acted as a photocatalyst when radiated with a UV light. TiO2-deposited SiO2 was successfully prepared through hydrolysis of TiOSO4 solution by controlling synthesis parameters such as pH ,concentration of TiOSO4, temperature and time under hydrothermal treatment. The obtained products were characterized for physical and chemical properties by means of XRD, XRF, BET and TEM . It was found that pH had an influence on the crystallization of TiO2, and under an appropriated pH, only anatase presented along with amorphous phase. High crystallinity of nano-crystalline anatase ( about 5 nm) deposited on silica surface was observed through TEM. Adsorption and photocatalytic performances of the prepared catalyst were evaluated in methylene blue aqueous solution in the dark and under ultraviolet ray irradiation, respectively. Due to the synergetic functions of adsorption by porous substrate and decomposition by TiO2 photocatalyst, an enhancing of photocatalytic activity for decomposition of organic pollutants in water under UV rays was obtained.

Abstract: A finite difference method based on control volume methodology and interface-tracking technique for simulation of rapid solidification accompanied by melt undercooling will be described and applied to analyze the solidification of alumina sample on copper substrate.

Abstract: In this paper, we investigated numerically gravity induced skeletal settling during liquid phase sintering. The microstructural evolution will be simulated by simultaneous computation of displacement of the center of mass and mass transport due to dissolution and precipitation at the interfaces between solid-phase and liquid matrix. Common to this study based on domain methodology for definition of regular multi-domain model will be the need to relate some diffusional phenomena to essential geometric and topological attributes of the W-Ni porous microstructure influenced by skeletal settling combined with extrication of some solid-phase domains during liquid phase sintering.

Abstract: Highly crystalline titania nano-particles were synthesized by hydrothermal method using novel stable water-soluble titanium complexes. It was confirmed that single phase anatase, rutile and brookite, which can be rarely synthesized as a single phase, can be obtained by varying the ligand in the complex and pH of the aqueous solution. TEM observations and BET specific surface area measurements had shown that these samples consisted of nanosized particles of 5~200 nm and had high specific surface areas of 25~150 m2/g. According to UV-visible diffuse reflectance spectra, these titania samples absorbed light in the visible region (λ > 400 nm). Photocatalytic activities in NO oxidation reaction exhibited by synthesized titania powders under the irradiation by UV- visible light were higher than the activity of the commercial TiO2 photocatalyst P25 (Degussa). Especially, under illumination by only visible light of above 510 nm wavelength, photocatalytic activity of the obtained specimens exceeded that of P25 more than four times. We also clearly demonstrated that single phase brookite had high photocatalytic activity for NO oxidation.