Papers by Author: Osamu Ohashi

Abstract: Specimens of aluminum (Al), austenitic stainless steel (SUS304L), pure iron (Fe) and Oxygen-free high conductivity copper (Cu) were treated by argon ion bombardment, and then were bonded by diffusion bonding method. The effects of argon ion bombardment on diffusion-bonded joints of four kinds of metallic materials were compared from the tensile strength at real bonded area and the fractographs. The results showed that bonding temperature was lowered by argon ion bombardment treatment for four kinds of materials. The effect of argon ion bombardment on diffusion-bonded joint depended strongly on the chemistry of the surface to be bonded, and increased in Al, SUS304L, Fe, and Cu in turn.

Abstract: In this paper, the effect of electric current on sintering of hydroxyapatite (HAp) in spark plasma sintering (SPS) process was investigated. The carbonate partially substituting hydroxyapatite was sintered up to 900 °C, and CO₂ evolved from HAp powder were measured in situ by using mass spectroscopy apparatus in the same time. The same gas analysis was performed in thermal analysis as comparison. In the thermal analysis, CO₂ gas was evolved at about 600 °C. On the other hand, in the SPS process, CO₂ gas was detected at lower temperature than that of thermal analysis. This result indicates that the surface of hydroxyapatite particles would be heated up locally in SPS process due to electric current.