Abstract
In order to further improve the corrosion resistance and bioactivity of NiTi alloy, TiO2-SiO2-HAP (hydroxyapatite) composite films with different composition were prepared on NiTi alloy substrate by a sol-gel method. The phase composition, surface morphology, interface adhesive strength and corrosion resistance were studied. The results indicated that the composite film heat-treated at 500°C showed amorphous state, and with increasing of heat-treatment temperature, crystals of CaSiO3, anatase TiO2 and hydroxyapatite (HAP) appeared. The composite film with higher (TiO2-SiO2) content was more uniform and smooth, and had higher interface adhesive strength with the substrate. With the decreasing of (TiO2-SiO2) content, the composite films tended to become irregular, and tiny crack clusters with ringy distribution appeared when the (Ti+Si)/Ca molar ratio was decreased to 25/75, which led to decrease of interface adhesive strength to some extent. The anodic polarization curves indicated that NiTi alloy coated with TiO2-SiO2-HAP composite films had an apparent improvement of corrosion resistance, with an obvious decrease of passivation current.
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