CHARACTERIZATION OF SURFACE-FILM FORMED ON TITANIUM IN ELECTROLYTE USING XPS

The surface film formed on titanium in a neutral electrolyte was characterized using XPS with an angular-dependent technique and argon-ion sputtering in order to predict the structure of the substance formed on titanium in a biological system. The results revealed that a calcium phosphate was naturally formed on titanium oxide, indicating that the surface layer of the titanium in the electrolyte consists of two parts: calcium phosphate and titanium oxide (essentially TiO2). The calcium phosphate contained phosphate in the form of PO4(3-), HPO4(2-) and H2PO4-. The proportion of PO4(3-) was the largest among the phosphates and approximately 60% of the phosphate was PO4(3-). The calcium phosphate also contained hydroxyl groups and bound water. The formation and growth of the calcium phosphate was caused by the adsorption of hydrated phosphate ions by the titanium surface, the release of protons from the phosphate ions, and the adsorption of calcium ions by the phosphate.