Competition between phosphates and fluorides at anodic formation of titania nanotubes on titanium

Abstract

AbstractThe influence of phosphate (and its concentration) on the electrochemical properties of anodic porous oxide films formed on titanium surfaces in fluoride containing electrolyte was investigated by performing electrochemical measurements [potentiodynamic/potentiostatic polarization, open circuit potential (OCP), and capacitance measurements] for a titanium/oxide film/solution interface system in SBF solution. In previous work we demonstrated, that during anodizing titanium and titanium‐based implant materials in 2 M phosphoric acid solution the highly bioactive phosphate gel‐like layer can be formed over compact titania which can significantly stimulate apatite formation. In the present work, we report that anodizing titanium in the same solution with the addition of fluorides leads to formation of titanium oxide nanotubes rich in both phosphates and fluorides which makes the method highly suitable for additional promoting of apatite deposition into titania nanotubes. To study the effect of phosphates concentration, layers of titania nanotubes were produced in electrolytes of different phosphoric acid concentration. Their behavior as the future coatings on titanium for biomaterial applications was characterized by capacitance tests in simulated body fluids and by Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS) observations. Judging on the results of XPS analysis, the competition between fluorides and phosphates is observed during anodizing, and the higher concentration of the latter is responsible for higher bioactivity of nanotubes formed in 2M H3PO4 + 0.4% wt hydrofluoric acid (HF). Copyright © 2010 John Wiley & Sons, Ltd.