Conformal coating containing Ca, P, Si and Na with double-level porous surface structure on titanium formed by a three-step microarc oxidation
Abstract
A bioactive coating containing Ca, P, Si and Na elements with a porous surface structure has been fabricated on a titanium (Ti) plate by a three-step microarc oxidation. Randomly distributed gouges (80–200 μm) have been observed from the conformal MAO coating (with micro-scale pore size of 0.6–2 μm in morphology) covered Ti surface which exhibits double-level porous structure. Meanwhile, it is noticed that Ca, P, Si and Na elements have been incorporated into the MAO coating but show different oxidation states of elements between the flat surface and gouge surface. The XPS results reveal that Ti–OH and SiO2 gel have only formed on the gouge surface because of the decreased microarc oxidizing ability in the local area. Besides, the bioactivity of the different MAO step prepared Ti plates has been examined by simulated body fluid (SBF) immersion. As expected, the three-step MAO prepared Ti with double-level porous surface structure exhibits the best apatite-inducing ability thanks to the as-introduced Ti–OH and Si–OH groups.