Open Access
Article Number 05027
Number of page(s) 6
Section Applied Research and Applications: Engineering Materials with MT
Published online 01 September 2009
ESOMAT 2009, 05027 (2009)
DOI: 10.1051/esomat/200905027

TEM study of the mechanism of Ni ion release from Nitinol wires with original oxides

H. Tian1, D. Schryvers1, S. Shabalovskaya2, 3 and J. Van Humbeeck2

1  EMAT, University of Antwerp, Groenenborgerlaan 171. B-2020 Antwerp, Belgium
2  MTM, K. U. Leuven, Kasteelpark Arenberg 44, bus 2450, B-3001 Leuven, Belgium
3  Ames Laboratory – DOE, Ames, IA 50011, USA

Published online: 1 September 2009

The surface of commercial Nitinol wires with original oxides and a thickness in the 30-190 nm range was investigated by different state of art TEM techniques. The oxide surface layer was identified as a combination of TiO and TiO2 depending on the processing of the wire. Between the core of the wires and the oxidized surface, an interfacial Ni3Ti nanolayer was observed while Ni nanoparticles are found inside the original oxide. The particle sizes, their distribution in the surface and the Ti-O stoichiometry were deduced from the analysis of the obtained data. Molecular dynamics calculations performed for evaluation of the stability of Ni particles relative to the atomic state revealed that a pure Ni particle has a lower energy than free Ni atoms inside the TiO2 lattice. The obtained results are discussed with respect to surface stability and Ni release in the human body.

© Owned by the authors, published by EDP Sciences 2009