Papers by Author: K. Maekawa

Abstract: Fabrication of variable porosity titanium foams through incorporation of sacrificial sodium chloride powder has been investigated. A three-dimensional solid foam pore skeleton containing macro- (200-400m), micro- (5-10m) and sub-micropores (< 1.5m) was formed during high temperature sintering of commercial purity titanium powder containing sacrificial sodium chloride particles, faceting of the interior pore powder surface being noted throughout. The largest macro-pores had a cubical topography representative of the sodium chloride powder that had been vaporized during heating to the sintering temperature. Formation of the smaller micro-pores appeared to have occurred during the compaction process these being retained in the specimen body due to incomplete sintering of the host powder. Finally formation of the smallest sub-micropores was associated with high temperature gas evolution and entrapment during sodium chloride vaporization.

Abstract: The present paper reports a microstructure inspection of powder fabrication of regulated structure Ti/Ti-based metal matrix composites (MMC) utilizing sacrificial NaCl particles. Blending, compaction and sintering of Ti and YSZ reinforced Ti compacts containing NaCl resulted in regulated foam structures with porosities between 45 and 70 pct. SEM observations indicated that three pore sizes and morphologies were formed while XRD analysis suggested that the yttria stabilized zirconia (YSZ) reinforcements are unstable at the high temperature sintering conditions considered in this study.

Abstract: Recent trends in bio technology have resulted in the need for accurate fabrication of pore structure of sophisticated porous materials used in advanced applications such as substrates for tissue growth, and various kinds of implants. Control of pore size is important for promoting growth of blood vessels and adequate fluid flow. In the present study, an attempt has been made to fabricate functionally porous structures using titanium, including an internally controlled three-dimensional (3-D) fractal structure. A novel 3-D modeling method that combines rapid prototyping with spark plasma sintering (SPS) is proposed, which enables us to control the internal porous structure. Titanium powder-tape or sheet is sintered or cut by a pulsed Nd:YAG laser to form 2-D fractal cross-sections. These 2-D layers are temporarily laminated in a carbon mold, being then jointed by the SPS method to maintain the internal porous structure. Process parameters for the sheet lamination method have extensively been investigated.