MAO-derived hydroxyapatite/TiO2 nanostructured multi-layer coatings on titanium substrate

In this study, titanium substrates which previously oxidized through Micro arc oxidation method, was coated by Hydroxyapatite (HAp) coating once more by means of the same method. Morphology, topography and chemical properties as well as phase composition and thickness of layers were studied to reveal the effect of the electrolyte concentration on coating features. According to results, the obtained coatings are consisted of HAp and titania as the major phases along with minor amounts of calcium titanate and α-tri calcium phosphate. Ca and P are present on surface of obtained layers as well as predictable Ti and O based on the XPS results. Thickness profile of coatings figured out that by increasing the electrolyte concentration, especially by addition of more Calcium Acetate (CA) to electrolyte, the thickness of HAp layer would rise, consequently. However, the influence of coating time on thickness of obtained coatings would be more considerable than electrolyte concentration. High specific area coatings with nest morphology were obtained in Electrolyte containing 5 g/L β-Glycero Phosphate (β-GP) and 5 g/L CA. Increasing coating duration time in this kind of coatings would cause deduction of the nesting in their structure.

► HAp-TiO2 nanostructured porous multi-layer coatings were derived by MAO technique. ► The relation between electrolyte concentration and properties of coatings was studied. ► A specific electrolyte concentration resulted in producing coatings with nest morphology. ► By increasing the coating duration time the nesting amount would face a decrease. ► A increasing in electrolyte concentration led to thickening coatings.