Surface characterization of new non-toxic titanium alloys for use as biomaterials M.F. L opez a, * , A. Guti errez b , J.A. Jim enez a a Dep. Ingenier õa de Materiales, Degradaci on y Durabilidad, Centro Nacional de Investigaciones Metal urgicas, CSIC, Avda Gregorio del Amo 8, E-28040 Madrid, Spain b Departamento de Ciencia y Tecnolog õa de Materiales, Universidad Miguel Hern andez, Avda Ferrocarril s/n, E-03202 Elche, Spain Abstract Thesurfaceoxidelayersformedspontaneouslythroughaircontactonthreenew,non-toxictitaniumalloyshavebeen investigated by X-ray photoelectron spectroscopy XPS). The alloys investigated were Ti±7Nb±6Al, Ti±13Nb±13Zr and Ti±15Zr±4Nb. The results show a large surface enrichment in Al oxides and Zr oxides, respectively, which indicates a considerable outwards diusion of these two elements. However, an analysis of the Nb 3d spectra reveals that the formation of Nb oxides at the surface is less favoured than in the case of the other alloying elements. The XPS data showforallthreeTialloysapassivelayerformedbyamixtureofTi,AlorZrandNboxides. Ó 2001 Elsevier Science B.V. All rights reserved. Keywords: X-ray photoelectron spectroscopy; Corrosion; Oxidation; Alloys; Polycrystalline surfaces 1. Introduction Corrosion of metallic biomaterials is a twofold problem. On the one side, it leads to material de- gradation. On the other side, it produces ion re- lease with harmful eects on the organism. The presence or absence of a protective surface oxide ®lm controls the corrosion behaviour of materi- als. Corrosion resistant materials react easily with oxygen from the atmosphere giving rise to a sur- face oxide layer, the so-called passive layer, which acts as a barrier against further oxidation [1±4]. Amongst conventional biomaterials, pure Ti as well as Ti±6Al±4V alloy exhibit excellent proper- ties for surgical implant applications [5,6]. The excellent corrosion resistance of pure Ti is attrib- utedtotheformationofaTiO 2 protective layer on its surface. By adding alloying elements to tita- nium, such as Al and V, its mechanical properties are improved [7±9]. However, for a better bio- compatibility it seems important to avoid in the composition the presence of V due to the toxic eects of V ion release [10]. Zr, Al, Nb, Ta and Pt are possible alloying elements that exhibit excel- lent biocompatibility, belonging to the non-toxic group in tissue interaction. Therefore, for appli- cationsinbiomedicineitiscrucialthedevelopment of new Ti alloys with good mechanical properties but with no V content. A detailed determination Surface Science 482±485 2001) 300±305 www.elsevier.nl/locate/susc * Corresponding author. Tel.: +34-915538900/+34-966658408; fax: +34-915347425. E-mail address: paquil@cenim.csic.es M.F. L opez). 0039-6028/01/$ - see front matter Ó 2001 Elsevier Science B.V. All rights reserved. PII:S0039-602800)01005-0