Preparation, Microstructure and Bioactivity of Plasma-Sprayed TiO₂ Coating

In this paper, nano-structured TiO₂ coatings have been successfully deposited onto titanium alloy substrates by atmospheric plasma spraying technology using optimized plasma parameters. A chemical treatment method was employed to induce bioactivity on the TiO₂ surface. The bioactivity of as-sprayed and chemical treated TiO₂ coatings were evaluated by investigating the formation of apatite on their surface after they were soaked in simulated body fluids (SBF) for a period of time. Microstructure and the phase composition of the as-sprayed coating and apatite were analyzed by Field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy-dispersive X-ray spectrometry (EDS). The results obtained indicate that as-sprayed TiO₂ coating consists of rutile, anatase and suboxide such as Ti₃O₅. The surface of nano-TiO₂ coating is covered by nano particles of about 50nm in size. The bonding strength of TiO₂ coating with Ti alloy substrate is as high as 40 MPa. The corrosion resistance performance of nano-coating in SBF is better than that of Ti-6Al-4V alloy. The surface of as-sprayed TiO₂ coating can not induce bone-like apatite formation. Chemical treatment, such as acid and alkali, can improve bioactivity of TiO₂ coating surface.