Hydroxyapatite/titania sol–gel coatings on titanium–zirconium alloy for biomedical applications

A simple sol–gel method was developed for hydroxyapatite/titania (HA/TiO₂) coatings on non-toxic titanium–zirconium (TiZr) alloy for biomedical applications. The HA/TiO₂-coated TiZr alloy displayed excellent bioactivity when soaked in a simulated body fluid (SBF) for an appropriate period. Differential scanning calorimetry, thermogravimetric analysis, X-ray diffraction and scanning electron microscopy-energy dispersive spectrometry were used to characterize the phase transformations and the surface structures and to assess the in vitro tests. The HA/TiO₂ layers were spin-coated on the surface of TiZr alloy at a speed of 3000 rpm for 15 s, followed by a heat treatment at 600 °C for 20 min in an argon atmosphere sequentially. The TiO₂ layer exhibited a cracked surface and an anatase structure and the HA layer displayed a uniform dense structure. Both the TiO₂ and HA layers were 25 μm thick, and the total thickness of the HA/TiO₂ coatings was 50 μm. The TiZr alloy after the above HA/TiO₂ coatings displayed excellent bone-like apatite-forming ability when soaked in SBF and can be anticipated to be a promising load-bearing implant material.