THIN HYDROXYAPATITE LAYERS FORMED ON POROUS TITANIUM USING ELECTROCHEMICAL AND HYDROTHERMAL REACTION

In our previous study, it was found that hydroxyapatite (HA) microcrys tals were precipitated by hydrothermal treatment on an anodic titanium oxide film containing calcium and phosphorus (AOFCP) with an equivale nt Ca/P ratio to HA, which was formed on a titanium metal anode in an aqueous electrolytic solution of dissolved calcium acetate and beta-gl ycerophosphate. In this study, the formation mechanism of the AOFCP, h as been clarified. Spark discharges, which occur on titanium surface w ith a large amount of heat generation, cause crystallization of the Ti O2 matrix of the AOFCP and incorporation of calcium and phosphorus int o the matrix from these electrolytes simultaneously. The calcium and p hosphorus in the matrix seem to exist as ions rather than as calcium p hosphate. Also, thin HA layers consisting of the many precipitated mic rocrystals can be uniformly formed even on titanium with complex shape s or surface geometries such as the mesh, roughened surfaces and bead- coated porous coating by the present method.