Preparation of hydroxyapatite-titanium dioxide coating on Ti6Al4V substrates using hydrothermal-electrochemical method

Abstract

Ti6Al4V substrates were anodized in a 0.5 mol/L H2SO4 solution at applied voltages of 90-140 V. A hydroxyapatite-titanium oxide (HA-TiO2) coating was then deposited on the anodized Ti6Al4V substrates via a hydrothermal-electrochemical method at a constant current. The obtained films and coatings were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier-transform infrared spectrometry. The microstructures of the porous films on the Ti6Al4V substrates were studied to investigate the effect of the anodizing voltage on the phase and morphology of the HA-TiO2 coating. The results indicated that both the phase composition and the morphology of the coatings were significantly influenced by changes in the anodizing voltage. HA-TiO2 was directly precipitated onto the surface of the substrate when the applied voltage was between 110 and 140 V. The coatings had a gradient structure and the HA exhibited both needle-like and cotton-like structures. The amount of cotton-like HA structures decreased with an increase in voltage from 90 to 120 V, and then increased slightly when the voltage was higher than 120 V. The orientation index of the (002) plane of the coating was at a minimum when the Ti6Al4V substrate was pretreated at 120 V.