IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Applied Surface Analysis Tuesday Sessions
       Session AS-TuP

Paper AS-TuP9
Surface Oxidation of NiTi Shape Memory Alloy

Tuesday, October 30, 2001, 5:30 pm, Room 134/135

Session: Aspects of Applied Surface Analysis II Poster Session
Presenter: R.G. Vitchev, Katholieke Universiteit Leuven, Belgium
Authors: R.G. Vitchev, Katholieke Universiteit Leuven, Belgium
G.S. Firstov, On leave of absence from National Academy of Sciences of Ukraine
H. Kumar, Katholieke Universiteit Leuven, Belgium
B. Blanpain, Katholieke Universiteit Leuven, Belgium
J. Van Humbeeck, Katholieke Universiteit Leuven, Belgium
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NiTi shape memory alloys are often used as materials for medical implants. It is known that the biocompatibility of the implants fabricated from NiTi depends on their surface composition since nickel often causes allergic and toxic reactions. Protective titanium oxide layers on the NiTi surface are often created since they can prevent the contact of Ni with the body tissues. The purpose of this study is to determine the oxidation mechanism of the NiTi alloy. The samples were oxidised in air in the temperature range 473-1073 K. Scanning electron microscopy was used to study the morphology and composition of the oxidised surfaces. The kinetics of oxidation was investigated by means of thermo-gravimetry. X-ray photoelectron spectroscopy and Auger electron spectroscopy combined with sputter depth profiling were used to investigate the surface composition and chemical state of the constituent atoms and their depth distribution. Grazing incidence X-ray diffractometry and Raman spectroscopy were implemented to determine the phases formed in the oxide layers. Thermodynamic calculations were performed to explain the oxidation behaviour of the NiTi alloy.