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 beta-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, alpha-TCP, and calcium titanatephases with a varying fraction depending on the growth conditions. The hydroxyapatite crystalline size was also determined as similar to 42 nm. The sample fabricated under the voltage of 350V for 3 min exhibited the most appropriate Ca/P ratio (similar to 1.60) as well as the highest amount of the hydroxyapatite phase. This sample had a fine surface morphology and a high pores density. (C) 2011 Elsevier B. V. All rights reserved.