Effect of alkali treatments on apatite formation of microarc-oxidized coating on titanium alloy surface

Abstract Alkali treatments with three concentrations were used to modify a microarc-oxidized (MAO) coating on titanium alloy surface in order to further improve its surface bioactivity. Morphology, chemical compositions and phase constitues, roughness, contact angle and apatite induction of the alkali-treated coatings were studied and compared. Scanning electron microscope (SEM) was applied to observe the morphologies, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to detect the phase constitutes and chemical compositions, a surface topography profilometer was used to analyze the surface roughness, and contact angle was measured by liquid drop method. Alkali treatements result in the formation of Na₂Ti₆O₁₃ and Na₂Ti₃O₇ phase on the MAO coating, which leads to the increase of surface roughness and the decrease of contact angle. Experimental results showed that the apatite induction of the alkali-treated coatings was dependent on the applied alkali concentrations during treatments, and Na⁺ concentration can promote the formation of apatite phase.