Preparation of Nano-porous Hydroxyapatite-Titania Coatings by Micro Arc Oxidation: Effect of Process Parameters

In the present work, TiO2/HAp nano-porous composite layers have been made by micro arc oxidation process in the electrolyte containing calcium acetate salts and β-glycerol phosphate with different concentrations and in various periods. Then the effects of these two variable parameters on phase structure, chemical composition, microstructures, and surface roughness of layers have been investigated. Studying the layers composition based on XRD and XPS techniques showed that they contain HAp phases, anatase, calcium titanate and α-tri-calcium phosphate. It was observed that the relative percentage of HAp reaches to its maximum amount in low levels of electrolyte concentration in small growth times but in high levels of electrolyte concentration in medium growth times. According to the observations of SEM and AFM, the layers with porous microstructures and rough surfaces were obtained whose pores sizes increased with time. Maximum amount of roughness was associated with the layers grown in higher concentrated electrolytes and medium process time, the layers presenting the best physical and chemical properties in order to be employed as bio-coatings. Based on XRD pattern, the average crystalline size of HAp was determined as