Titanium-based Surface Of Tio <sub> 2 </ Sub> / Ha Coating Preparation And Performance Research

Titanium and its alloys, due to its excellent biocompatibility, corrosion resistance and mechanical properties, are widely used as biomedical metal materials. However, they don't have bioactivity. On the contrary, Hydroxyapatite (HA) has excellent bioactivity and it can induce new bone formation because of the comparability of chemical composition between HA and bone tissue. But HA has bad toughness and low tensile strength. They limit the application of HA in the bearing position in human body. Therefore, the Ti/HA composite is prepared through the surface modification of titanium and its alloys, and its preparation methods have become a research focus.In this work, TA3 was etched in mixed acid in order to increase its surface roughness. Before the preparation of HA coating, a porous TiO₂ film was prepared on the surface of titanium by anodic oxidation method. The main compositions of electrolyte were H₃PO₄, Na₂HPO₄·12 H₂O and HF. Then the CaHPO₄·2H₂O coating which had been electrodeposited on the anodized surface of titanium was converted to HA by hydrothermal syntheses. In order to enhance the bonding strength between HA coating and titanium substrate, vacuum heat treatment of HA coating at 500℃, 600℃and 700℃was studied. Subsequently, comparative tests were used to analyze the influence of preparation process on bonding strength of coating. Surface and section morphology of HA coating and the porous TiO₂ film were observed by Scanning Electron Microscopy (SEM). The HA coating phase composition and functional groups were studied by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The bonding strength between coating and substrate was tested by using bond-tensile method and Scratch Tester.The results showed that the porous TiO₂ film could enhance the bonding strength of coating, which was two times than coating with no TiO₂ film. After vacuum heat treatment of HA coating at 500℃, 600℃and 700℃, the bonding strength of coating respectively increased by 34.7%, 39.6% and 27.2%. The HA coating compactness increased and binding improved when H₂O₂ was used during the electrodeposition.