Synthesis of anodic titania nanotubes in Na2SO4/NaF electrolyte: A comparison between anodization time and specimens with biomaterial based approaches

Abstract

Surface modification of commercially pure titanium (cp-Ti) has been carried out by electrochemical anodic oxidation at constant voltage for different time periods (0.5, 1, 2 and 4.5h). Currents developed during the anodization indicate that the nanotubes are formed due to the competition of titania formation and dissolution under the assistance of electric field. Topologies of the anodized titanium change remarkably with time of oxidation. The morphology of the as-prepared nanotubes was characterized by scanning electron microscopy and atomic force microscopy while the chemistry and crystallinity were characterized by energy-dispersive X-ray spectroscopy and X-ray diffraction respectively. The as-anodized oxide was of amorphous but transformed to anatase and/or rutile crystal structure upon annealing for 3h at 600°C. The anatase structure showed excellent apatite-forming ability and produced a compact apatite layer covering the surface completely upon treatment in simulated body fluid (SBF) solution for 30h. Corrosion of anodized titanium samples was studied in a SBF solution using open circuit potential, polarization and electrochemical impedance measurements and compared with that of non-oxidized titanium. Among these samples, titanium anodized for 4.5h exhibited superior corrosion properties.