| AVS 62nd International Symposium & Exhibition | |
| Thin Film | Wednesday Sessions |
| Session TF+AS+BI-WeA |
| Session: | Thin Films for Biological and Biomedical Applications |
| Presenter: | Pedro Nascente, Federal University of Sao Carlos, Brazil |
| Authors: | D. Gonzalez, Federal University of Sao Carlos, Brazil T.C. Niemeyer, Federal University of Sao Carlos, Brazil C.R.M. Afonso, Federal University of Sao Carlos, Brazil P.A.P. Nascente, Federal University of Sao Carlos, Brazil |
| Correspondent: | Click to Email |
Metallic biomaterials such as AISI 316L stainless steel (SS), chromium-cobalt alloys, titanium and its alloys are commonly used in medical implants due to their interesting mechanical properties and thermal stability. However, 316L SS and Cr-Co alloys have much higher elastic modulus than bone, causing the loss after some years of implantation [1]. The elastic modulus of Ti-based alloys ranges from 55 to 110 GPa, being significantly lower than those for 316L SS (210 GPa) and Cr-Co alloys (240 GPa), making them more suitable for use in dental and orthopedic applications. Also Ti alloys present high strength, low density, high corrosion resistance, and good biocompatibility [1]. Pure Ti has two allotropic forms: hexagonal closest-packed (hcp), known as α phase, and body centered cubic (bcc), known as β phase, structures. Studies have shown that the addition of alloying β-stabilizing elements such as V, Mo, Nb, Zr, Mo, and Ta causes the decreasing of the modulus of elasticity of the β-Ti alloys without compromising the strength [1]. In this study, thin films of Ti-Nb alloys were deposited on AISI 316L stainless steel substrate by magnetron sputtering, and the structure, morphology, and composition of the films were analyzed by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). Thin films of three compositions were produced: Ti85Nb15 (Ti-26wt% Nb), Ti80Nb20 (Ti-33wt% Nb), and Ti70Nb30 (Ti-45wt% Nb). Structural characterization by XRD indicated that only the β phase was present in the thin films. XPS analysis showed a predominance of oxidized Ti and Nb on the film surfaces. TEM analyses were carried out in the following image modes: bright field (BF) images, selected area diffraction (SAD), scanning mode (STEM) BF and in annular dark field (ADF), and X-ray mapping using energy dispersive spectroscopy (EDS). For the Ti80Nb20 alloy film, TEM analysis showed columnar grains (~100 nm width) of -Ti phase, with a Nb-rich transition layer ranging from finer grains (in contact with SS substrate) to a coarser columnar grains. For the Ti75Nb25 alloy film, TEM analysis showed columnar grains (~50 nm width) of β-Ti phase, with a transition layer away from the SS substrate.
Acknowledgements: A.L. Gobbi, C.A. Silva, S.R. Araujo, and J. Bettini from the Brazilian Nanotechnology National Laboratory, for their assistance in the growth and characterization of the thin films; and CNPq and CNPEM ( Brazil ), for support.
[1] M. Geetha et al., Prog. Mater. Sci. 54 (2009) 397-425.