Papers by Author: T. Asaoka

Abstract: It is recognized that TiO₂, the most popularly used photocatalyst, has a disadvantage that it only react with ultraviolet light. In this study, nitrogen-doped TiO₂ was selected as strategy for promoting the absorption of visible light, and SPS (spark plasma sintering) method was tried to fabricate a dense specimen without using binder materials. Preparation methods of specimen are as follows; yellow-colored N-doped TiO₂ powders were synthesized from a mixed aqueous solution containing TiCl₃ and NH₃. The precipitate was air-dried for 1 week. Then dried in a drying oven for 1day(50°C). And heat-treated for 1h(400°C).N-doped TiO₂ powder and non-doped TiO₂ powder were sintered by SPS at 400 or 700°C. N-doped TiO₂ fabricated by SPS showed a favorable crystal structure of anatase, and successful existence of doped nitrogen was confirmed by XPS analysis. UV-vis results showed that N-doped TiO₂ responded to visible light, which indicates an increasing possibility of this type of photocatalyst. Further study to extend the range of absorption wavelength is carrying out.

Abstract: Porous beads of bioactive ceramics such as HAp, TCP are considered to be promising as excellent scaffolds for cultivating bone cells. To realize this type of beads which maintains the function of scaffold with sufficient strength up to growth of new bone, and is expected to absorbed completely after the growth, a-TCP/ HAp functionally graded porous beads were fabricated. HAp is bioactive material which has both high strength and better tissue-adhesive properties, but that is not readily absorbed by the human body. On the contrary, a-TCP is highly bioabsorbable; it is quickly absorbed by the body, and, therefore, disappears before bone is completely replaced. Fabricated new beads are composed of a-TCP at the center and HAp at the surface, to control the solubility in living body. Bone cell adaptability of these beads were confirmed in vitro.