Preparation and Structural Control of Porous Hydroxyapatite with Unidirectionally Aligned Continuous Pores
Teisuke SATO, Tatsuo BESSHI, Takuo NAGAMACHI, Tatsuya KATO and Jyunji TAMATANI
Abstract:By using molten wax colloidal process with graphite powders as combustible pore-forming agents, a method for controlling the porosity and pore size of porous hydroxapatite ceramics has been developed. Porous hydroxyapatite with unidirectionally aligned continuous pores were fabricated by multistage extrusion of green billets. Starting billet of this multistage extrusion was made from stacking hydoxyapatite green disks of outer diameter 50mm and inner diameter 25mm filled with 100% graphite green disks of 25mm. In order to make the porous matrix, the mixture of hyroxyapatite and graphite was used instead of hydroxyapatite. By the primary extrusion, hexagonal rods with the graphite in the central part were extruded. These extruded hexagonal rods were bundled to make composite billets for the next stage extrusion. This process was repeated for several stages. Finally, the extruded rods of proper stage were sintered. Size of the continuous pore can be controlled by total extrusion ratio. The pore diameter obtained in the present work was from 350ƒÊm to 8ƒÊm. The porosity can be controlled by the billet structure. The mean flexural strength of the porous hydroxyapatite ceramics obtained in this work was from 32MPa to 56MPa. Key Words:Porous hydroxapatite, Continuous pore, Porous structure, Multistage extrusion, Flexural strength