Hydrothermal preparation of granular hydroxyapatite with controlled surface

Microstructure designed hydroxyapatite granules from about 50 mum to I mm in size were prepared by hydrothermal vapor exposure method at temperatures from 105degreesC to 250degreesC under the saturated vapor pressure of pure water. As starting materials, powder of alpha-tricalcium phosphate, gelatin and a vegetable oil were used. The size of granules, the shape of particles in the granules, and the microporosity of about 0.1 mum in size of the granules were controlled. The granular hydroxyapatite prepared at 200degreesC under the saturated vapor pressure of pure water for 20 h was composed of rod-shaped crystals of about 40 pin in length with mean aspect ratio of 50. Rod-shaped hydroxyapatite crystals were locked together to make micropores of about 0.1 mum in size. It was non-stoichiometric hydroxyapatite with calcium deficient composition. This granular hydroxyapatite should have the advantage of adsorptive activity, because it has large specific crystal surface and micropores.