Effect of electrolyte concentration on microstructure and properties of micro arc oxidized hydroxyapatite/titania nanostructured composite

Micro arc oxidation was employed to grow TiO2/hydroxyapatite composite layer on titanium substrate. The correlation between electrolyte concentration, diameter and density of the pores in fabricated layers was investigated. Therefore, the effect of electrolyte concentration on composition and morphology of grown layers was studied using SEM, EDX, XRD and XPS techniques. Samples were coated in electrolytes containing 5, 10 and 15 g/l calcium acetate and 1, 3 and 5 g/l β-glycerophosphate, at optimized voltage for 3 min. Pore size variations obey a similar pattern by the addition of both calcium acetate and β-glycerophosphatein various concentrations based on SEM observations. However, completely different volume fraction of porosities in as-obtained coatings was obtained as a result of these two components addition. Indeed, size and volume fraction of porosities in fabricated layers are directly affected by electrolyte concentration. The average crystallite size of TiO2 and hydroxyapatite was determined as 45 nm and 48.5 nm, respectively. Moreover, the biocompatibility of selected specimens has been proved by MTT test.