Microstructure Designing of Hydroxyapatite Ceramics by Hip Post-Sintering

Abstract

Microstructure-designed hydroxyapatite ceramics were prepared by HIP post-sintering. Hydroxyapatite single crystals of about 25 nm x 90 nm in size synthesized hydrothermally at 200 °C under 2 MPa for 10 h were sintered normally in air for 3 h. The obtained ceramics were HIP′ed at the temperatire from 900° to 1100 °C under 200 MPa of Ar for 1 h without any capsules. This post-sintering brought about densification up to nearly 100% for the samples more than 90% dense having closed pores. The fully dense ceramics with a grain size of about 0.54 μm showed transparency. Furthermore, dense/porous layered hydroxyapatite ceramics could be prepared by the same technique from the fine crystals and coarse powders with relatively low sinterability.