Thermal oxidation of vanadium-freeTi alloys: An X-ray photoelectron spectroscopy study

In the present work, X-rayphotoelectronspectroscopy (XPS) was used to study the surface chemical composition of three alloys for biomedical applications: Ti–7Nb–6Al, Ti–13Nb–13Zr and Ti–15Zr–4Nb. The surface of these alloys was modified by annealing in air at 750 °C for different times with the aim of developing an oxide thick layer on top. The evolution of surface composition with annealing time was studied by XPS, and compared with the composition of the native oxide layer present on the samples before annealing. Two different oxidation trends were observed depending on the alloying elements and their corresponding diffusion kinetics, which give rise to different chemical species at the topmost layers. These results were linked with an evaluation of the biological response of the alloys by bringing them in contact with human peripheral blood mononuclear cells (PBMC).
This work has been partially supported by the Spanish MEC under Projects MAT-2008-01497/NAN, MAT-2007-66719-C03-03, MAT-2006-13348 and CSD2007-00041, and by grants from Italian MIUR.