In situ composite coating of titania–hydroxyapatite on commercially pure titanium by microwave processing

Microwave (MW) processing has been studied as an alternative method of hydroxyapatite (HA) based composite coatings on commercially pure titanium (CPTi) to enhance the bioactivity for orthopaedic and dental implant applications. The coating was formed by processing CPTi metal packed in HA and at 800 W microwave power for 22 min. The composition of the coating was found to be TiO2 (rutile) as major phase along with HA as minor phase. The MW absorption of non-stoichiometric TiO2 layer, which was grown during the initial hybrid heating, resulted in sintering of apatite particles interfacing them. The non-stoichiometric nature of TiO2 was evident from the observed mid-gap bands in ultraviolet–visible diffusive reflectance (UV–VIS-DR) spectrum. The lamellar α structure of the substrate suggests that the processing temperature was above β transus of CPTi (1155 K). The oxygen stabilized α phase whose thickness increased with microwave processing time, was likely to be the reason for the increase in Youngʹs Modulus and hardness of the substrate. The coating induced apatite precipitation in bioactivity test. The osteoblast cell adhesion test demonstrated cell spreading which is considered favourable for cell proliferation and differentiation. Thus, in situ composite coating of titania and HA on CPTi was obtained by a simple one-step process.