Preparation Of Hydroxyapatite Particles And It's Coating On Titanium Substrate

Hydroxyapatite(Ca10(PO4)6(OH)2,HAP) bioceramic and its composites are widely used in bone prostheses and substitutions due to it's excellent bioactive properties.In this research, a co-precipitation process was used to synthesize the hydroxyapatite powders. The effects of pH, the Ca/P atomic ratio of raw materials, and the solvent selection on the resultant powders were studied. The heat treatment process was investigated. It was showed that the well-crystallized hydroxyapatite can be obtained by heat treatment at 700℃ for 2 hours. The resultant powders were composed of low-aggregated and well-dispersed particles with an average diameter of 40nm. Chemical analysis showed that the Ca/P atomic ratios of the sintered powders were very close to that of theoretical stoichiometric value (1.667).The hydroxyapatite coating on titanium substrate was the hotspot of the researches on the hydroxyapatite composites. The electro-deposited process used in this studies includes the following processes: electrochemical reaction, alkaline treatment at a low temperature and the heat treatment. The change of the electric current intensity and the mass of the coating with the time was investigated. The effect of cathode voltage on the coating morphology was also studied. The results showed that the mass of the coating can be controlled by adjusting the cathode voltage and the deposition time. As a result, the coating thickness can be controlled. At the same time, the well-crystallized, relative pure hydroxyapatite porous coatings were obtained. However, the adhesion strength between coating and substrate materials was so weak (5MPa) that the coated material can not meet with the mechanic requirement of human body to the implant materials.