Micro arc oxidized HAp–TiO2 nanostructured hybrid layers-part I: Effect of voltage and growth time

Micro arc oxidation was employed to grow hydroxyapatite–TiO2 nanostructured porous composite layers. The layers were synthesized on the titanium substrates in the electrolytes consisting of calcium acetate and sodium β-glycerophosphate salts under different applied voltages for various times. SEM and AFM investigations revealed a porous structure and rough surface where the pores size and the surface roughness were respectively determined as 70–650 nm and 9.8–12.7 nm depending on the voltage and time. Chemical composition and phase structure of the layers were evaluated using EDX, XPS, and XRD methods. The layers consisted of the hydroxyapatite, anatase, α-TCP, and calcium titanatephases with a varying fraction depending on the growth conditions. The hydroxyapatite crystalline size was also determined as ∼42 nm. The sample fabricated under the voltage of 350 V for 3 min exhibited the most appropriate Ca/P ratio (∼1.60) as well as the highest amount of the hydroxyapatite phase. This sample had a fine surface morphology and a high pores density.