Morphology of hydroxyapatite coated nanotube surface of Ti-35Nb-xHf alloys for implant materials

The purpose of this research is to study the morphology of hydroxyapatite coated nanotube surface of Ti-35Nb-xHf for implant materials using various experiments. For this study, Ti-35Nb-xHf (x=0, 3, 7 and 15wt.%) alloys were prepared by arc melting and heat treated for 12 h at 1000 degrees C in an argon atmosphere and then water quenching. Nanotube formation on the Ti-35Nb-xHf alloys was achieved by anodizing in H(3)PO(4) electrolytes containing 0.8 wt.% NaF at room temperature. Anodization was carried out using an electrochemical method and all experiments were conducted at room temperature. Hydroxyapatite (HA) was deposited on the nanotubular Ti-35Nb-xHf alloys surface for the biomaterials by radio-frequency (RF) magnetron sputtering method. The morphologies of nanotubular and HA coated surface were characterized by X-ray diffractometer (XRD), opticalmicroscopy (OM), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy (STEM). The wettability of HA coated surface was measured by contact angle goniometer. The microstructure of Ti-35Nb-xHf alloys was transformed needle-like to equiaxed structure with Hf content and alpha '' phase decreased, whereas beta phase increased as Hf content increased. HA coating surface was affected by microstructure of bulk and morphology of nanotube formation. In case of low Hf content, tip of nanotube formed at beta phase was coated with HA film, whereas alpha '' phase was not coated with HA film. In case of high Hf content, nanotube surface was coated uniformly with HA film. The wettability of HA coated nanotubular surface was higher than that of non coated samples. (C) 2011 Elsevier B.V. All rights reserved.