Electrophoretic synthesis and characterization of bioactive HAp/TiO2 thin films coated on stainless steel

The aim of this study was to synthesize titanium dioxide (TiO2) thin films coated on 316L stainless steel (316L SS) and to characterize hydroxyapatite (HAp) growing onto TiO2 layer coated on the metallic substrate. These films were obtained by the electrophoretic synthesis (EPS) method using an acidic electrolyte containing H2SO4 and TiO2 nanoparticles. The growth of HAp on TiO2 thin films was achieved by immersion in simulated body fluid (SBF) during different periods of time in order to evaluate the bioactivity of structure in vitro study. The obtained coatings were characterized by XRD, SEM, AFM and EDX measurements. The XRD results reveal a crystalline phase (anatase) of TiO2 nanoparticles. The presence of TiO2 nanoparticles in the bath led to the preferential orientation of TiO2 crystallites after [101] crystallographic direction. During the coating EPS process, the presence of TiO2 provides more nucleation sites which are favourable to the adherence of nanoparticles on the metallic substrate. The surface morphology observed by SEEM analysis showed that TiO2 nanocrystals were attached on metallic surface. The appearance of the surface indicates porous structure and island-like cracked morphology with polygonal shapes. The roughness of the coating is in good agreement with standards for biomaterials which is proved by AFM measurements. The EDX spectra also confirm the presence of the Ca2+ and PO43- ions in the structure obtained by EPS method.