Influence of Hydrothermal Treatment in Deionized Water on Surface Morphology and Structure of Titanium with Biomedical Application by Microarc Oxidation

Owing to the excellent biocompatibility and corrosion-resistance of titanium and bioactivity of hydroxyapatite, the titanium/hydroxyapatite composite material combining their advantages is a highlight with bright prospects in medical clinics. In the present paper, the microarc oxidation (MAO) was performed on commercial pure titanium at first. Furthermore, the hydrothermal treatment (HT)was given with media of deionized water at 200°C for 4h in an autoclave. The surface morphology of the samples was observed by scanning electron microscopy (SEM), and the detailed composition was analyzed with Energy-Dispersive X-Ray Spectroscopy (EDS). The X-ray diffraction analysis (XRD) was employed to characterize the crystal structure of composite. The results indicate that the titania film contains the Ca and P elements on titanium substrate after MAO, which converts into the hydroxyapatite crystals via hydrothermal treatment. The smaller size and amount of hydroxyapatite crystals are found when lower voltage is presented. But there are converse phenomena with higher voltage, especially, the differences can be neglected above 400V. It is shown that the micro-hole and hollow surface of titania film can induce the hydroxyapatite nucleation and growth as two different forming ways. The hydroxyapatite has a preference of forming in hollow surface with lower voltage, however, the presences of the micro-hole and hollow surface of titania film are occurring for higher voltage. The hydroxyapatite forming in micro-hole shows needle-like crystal and high bonding strength with surrounding titania film because of the mechanical restrict force from micro-hole wall. Also it is noted that hydroxyapatite crystals incline to precipitate on the film surface with high Ca and P concentrations after the hydrothermal treatment.