Electrochemical and Sputtering Deposition of Hydroxyapatite Film on Nanotubular Ti-25Ta-xZr Alloys

The purpose of this study was to investigate the electrochemical and sputtering deposition of hydroxyapatite film on nanotubular Ti-25Ta-xZr alloys. The formation of nanotubular structures was achieved on the alloys by anodization in 1 M H3PO4 electrolyte containing 0.8 wt% NaF at room temperature. Electrochemical deposition was carried out using cyclic voltammetry at 80 degrees C in 5 mM Ca(NO3)(2)+3 mM NH4H2PO4 solution. Then, physical vapor deposition coating was obtained by radio frequency magnetron sputtering technique. The microstructures, phase transformation, and morphology of the hydroxyapatite film deposited on Ti-25Ta-xZr alloys were analyzed by optical microscopy, X-ray diffraction, and field emission scanning electron microscope. It was found that, as Zr content increased, precipitates of hydroxyapatite changed their leaf-like shape into a needle-like shape. For the alloy with the higher Zr content, the surface of the nanotubes was entirely covered with the radio frequency sputtered HA film. Wettability increased in the following order: bulk, nanotubular surface, and hydroxyapatite-coated nanotubular surface.