Formation characterization of hydroxyapatite on titanium by microarc oxidation and hydrothermal treatment.

Microarc oxidation (MAO) was performed on titanium in an electrolyte containing calcium glycerphosphate (Ca-GP) and calcium acetate (CA) using a direct current power supply. It was found that the MAO method is suitable forming a ceramic coating containing Ca and P using titanium, and that films display a porous and rough structure on their surface. Samples with a Ca/P ratio of 1.71 were hydrothermally treated in water solution whose pH was adjusted to 7.0-11.0 by adding NaOH at 190 degrees C for 10 h in an autoclave. Hydroxyapatite crystals were precipitated on the film surface after the hydrothermal treatment, and the amount of hydroxyapatite precipitated increased with increasing pH of water solution. The oxide film composition was semiquantitatively analyzed with an electron probe microanalyzer. The microstructures on the sample surfaces were observed by scanning electron microscopy before and after the hydrothermal treatment. The topography of the oxide film was imaged with an atomic force microscope. Its cross section was observed by scanning electron microscopy after being coated with a thin Au film. The surface structures of the films were analyzed by X-ray diffraction.