Fabrication and Properties of Hydroxyapatite-Ti Network Composites

Hydroxyapatite (HA) powder was synthesized by a sol-gel method with Ca(OH)(2) and H3PO4 as reactants. The HA granules were then coated with TiH2 powder using a mechanical mixing method. The HA-TiH2 material system produced HA-Ti composites after hot-pressing at 1050 degrees C. The HA-Ti composites are mainly composed of HA and Ti, with small amounts of Ca2P2O7 and Ca-3(PO4)(2) phases. Fracture toughness and bending strength are 2.4 MPa.m(1/2) and 54.3 MPa, respectively for the HA-20vol%Ti composite, higher than those of the pure HA ceramic. The improvement in properties is because of the unique 3D network structure of Ti, which is an ideal reinforcement structure for the weak and brittle HA. According to ISO/TR 7405-1984, hemolysis test was performed to evaluate the blood compatibility of the material. The results show that the hemolysis rate of the HA-20vol%Ti composite is 0.56%. Relative growth rates (RGR) of L-929 cells soaked after 6 days in the HA-20vol%Ti group, pure Ti group, black group and pure Pb group were 132%, 100%, 90% and 6% respectively, while the level of cytotoxicity was grade 0 in HA-Ti composite group. These results imply that the HA-20vol%Ti composite has good biocompatibility and bioactivity.