Abstract
The near-surface area of the commercial TiNi wire has been thinned by ion milling and investigated by transmission electron microscopy (TEM). The local chemical composition has been characterized by the combination of Energy-Dispersive-X-ray-Spectroscopy (EDX) and Electron-Energy-Loss-Spectroscopy (EELS) enabling us to measure simultaneously the content of heavy Ti, Ni, Cu and light O, C elements. It has been found that the wire mantle consists of the following consequent layers: 1. Austenitic TiNi with a small amount of fine martensitic plates. Lamellar shaped voids are observed near the edge of the TiNi phase. 2. Few distinct titanium oxide layers with the total thickness of about 5 μm and the thickness of the individual layers of 0.2-0.5 μm. The stoichiometry of titanium oxides is close to 50:50 but varies noticeably from layer to layer. EELS elemental mapping allows to visualize clearly the Ti and O distribution along the layers. 3. Outer TiO2 layer of I μm in thickness. The developed technique of ion milling and the combination of TEM,EDX and EELS has been shown to be suitable for characterization of commercial TiNi products and predicting the in-vivo release of Ni-ions from their surface.
Published Version
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