XPS characterization of surface modified titanium alloys for use as biomaterials

Three different Ti alloys of biomedical interest have been studied by means of X-ray photoelectron spectroscopy (XPS) to determine their surface chemical composition in both as-received condition and after oxidation at 750 °C in air for different times. Compositions of the investigated alloys were, in wt.%, Ti–7Nb–6Al, Ti–13Nb–13Zr and Ti–15Zr–4Nb. XPS analyses showed a behaviour of the Ti–7Nb–6Al alloy different from that of the two TiNbZr alloys, evidencing the role of the chemical composition of the alloys on the oxidation mechanisms. The oxidation process generates an aluminium-oxide rich surface on the Ti–7Nb–6Al, while in the case of the TiNbZr alloys a titanium-oxide rich layer is formed. The effect of the heat treatment on the contribution of the minority elements at the surface is also discussed.

► XPS surface analysis of Ti alloys, in as-received state and after heat treatment. ► In native oxide layers, presence of a mixture of oxides. ► The different alloying composition induces different thermal activated mechanisms. ► On oxidized Ti–7Nb–6Al, diffusion of Al towards the surface. ► Upon thermal oxidation, both TiNbZr alloys exhibit a titanium-oxide rich layer.