New processing method for hydroxyapatite coating by hydrothermal techniques

Abstract

Solidification of hydroxyapatite (HA) and its coating on titanium (Ti) rod was achieved simultaneously by utilizing a hydrothermal hot-pressing (HHP) method at a low temperature of 135°C. A mixture of calcium hydrogen phosphate dehydrate (DCPD) and calcium hydroxide was used as a starting powder material for HA coating. Ti rod was treated with the alkali solution before HHP treatment. The powder mixture and the Ti rod were placed into a double layered capsule. The capsule was put into a batch type autoclave for hydrothermal treatment. Pull-out tests were conducted to obtain an estimate of the interfacial property or the HA/Ti interface. The shear fracture strength obtained from the pull-out tests was approximately 4.0-5.5 MPa. In post-test observations after fracture tests, HA ceramics remained on Ti rod. It could be demonstrated that the fracture occurred into the HA ceramics, not into the HA/Ti interface. This observation suggests that the fracture property of the HA/Ti interface was close to or higher than that of the HA ceramics only.