Hydroxyapatite synthesized by a simplified hydrothermal method

Abstract

A simplified hydrothermal method of synthesizing hydroxyapatite powder is described. Heating powders of Ca(OH) 2, Ca(H 2PO 4) 2 · H 2O and distilled water in a pressurized pot at 109 °C for 1–3 h results in powders consisting of crystallized hydroxyapatite in a needle shape, 130–170 nm in length and 15–25 nm in width. The specific surface area is 31–43 m 2/g and the Ca P ratio is 1.640–1.643. The obtained HA powder can be sintered to a high density at 1200–1300 °C. No decomposition was identified by X-ray diffraction. The optimally sintered ceramic has a pore-free surface structure with a flexural strength of 120 MPa, a micro-Vickers hardness of 5.1 GPa and fracture toughness of 1.2 MPa · m 1 2 . The biocompatibility of the pulverized sintered-ceramic is excellent and comparable to that of a commercial grade hydroxyapatite by evaluating the implantation in a dog. The synthesis method is simple, economic, and results in a high quality powder which is useful in hard tissue reconstruction applications.