Preparation of hydroxyapatite ceramics by hydrothermal hot-pressing method at 300 °C

Hydroxyapatite (HA) ceramics were prepared by a hydrothermal hot-pressing (HHP) method at a low temperature (300 degrees C). DCPD (CaHPO4 center dot 2H(2)O) + Ca(OH)(2), OCP (Ca8H2(PO4)(6)center dot 5H(2)O) + Ca (OH)(2), DCPD + NH3 center dot H2O, OCP + NH3 center dot H2O or alpha-TCP (Ca-3(PO4)(2)) + NH3 center dot H2O were used as the precursors. The mixture was treated by HHP under a condition of 300 degrees C/40 MPa. In sample DCPD + Ca (OH)(2) and OCP + Ca(OH)(2), the HA ceramics obtained showed a porous and homogenous microstructure, and the bending strength were 9.9 MPa and 10.9 MPa, respectively. In sample alpha-TCP+NH3 center dot H2O, rod-like HA crystals produced. When the starting materials were DCPD + NH3 center dot H2O, OCP + NH3 center dot H2O, the HA particles produced exhibited plate-like features. It appeared that the plate-like HA particles stacked into a lamellar structure. Tie formation of the lamellar structure leads to a noticeable improvement in fracture property of the HA ceramic. The bending strength and the fracture toughness of the sample prepared from OCP and ammonia water reach 90 MPa and 2.3 MPam(1/2), respectively.