MAO-preparation of nanocrystalline hydroxyapatite–titania composite films: Formation stages and effect of the growth time

The HAp–TiO2 nanostructured layers with a porous morphology were fabricated through micro arc oxidation technique for different times, i.e. 3, 6, and 10 min. Compositional studies, performed by XRD and XPS techniques, showed that the layers consisted of hydroxyapatite, anatase, calcium titanate, and α-TCP phases. Based on the XRD results, it was observed that the hydroxyapatite relative content reached its maximum value at intermediate times. As an important achievement, it was figured out that the HAp phase gradually grows on a titania inner layer which forms within preliminary stages of the MAO treatment. Considering the XRD patterns, the hydroxyapatite crystalline size was determined as ∼48 nm which is favorable for bio-applications. Based on the SEM and AFM observations, the layers exhibited a porous morphology with a rough surface where the pores size increased with time. The highest porosity and roughness was achieved at intermediate times. The layers fabricated for intermediate growth times exhibited the most appropriate physical and chemical properties for bio-applications.