Ultra-fine structural characterization and bioactivity evaluation of TiO ₂ nanotube layers

For an application as biomedical materials of high performance with a good biocompatibility, the TiO ₂ nanotube-type oxide film on Ti substrate has been fabricated by electrochemical method, and the effects of surface characteristics of TiO ₂ naotube layer have been investigated. The surface morphology of TiO ₂ nanotube layer depends on factors such as anodizing time, current density, and electrolyte temperature. Moreover, the cell and pore size gradually were increased with the passage of anodizing time. X-ray diffraction (XRD) results indicated that the TiO ₂ nanotube layer formed in acidic electrolytes was mainly composed of anatase structure containing rutile. From the analysis of chemical states of TiO ₂ nanotube layer using X-ray photoelectron spectroscopy (XPS), Ti2p, P2p and O1s were observed in the nanotubes layer, which were penetrated from the electrolyte into the oxide layer during anodic process. The incorporated phosphate species were found mostly in the forms of HPO ^- ₄, PO ^- ₄, and PO ^- ₃. From the result of biological evaluation in simulated body fluid (SBF) the TiO ₂ nanotube layer was effective for bioactive property.