Regensburg 2004 – wissenschaftliches Programm

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DS: Dünne Schichten

DS 3: Ionenimplantation III

DS 3.4: Vortrag

Montag, 8. März 2004, 15:15–15:30, HS 31

Ni depletion of a NiTi surface by ion implantation for biomedical applications — •Natalia Shevchenko and Manfred Maitz — FZ Rossendorf, Postfach 510119, 01314 Dresden

The NiTi alloy is interesting for medical applications because of its either superelastic or memory shape properties. However, clinical acceptance of the alloy still is limited due to its high nickel content.

The aim of this work is to reduce the Ni concentration in a NiTi surface by ion implantation and study the influence on surface stability and biocompatibility.

Modification of the NiTi samples was performed by N or/ and Ar ion implantation at different parameters: ion energy (20 - 40 keV and 200 keV), fluence ( 10¹⁷ − 10¹⁸ cm⁻²), substrate temperature (RT - 400 C). The modified layers were examined by Auger electron spectroscopy, grazing incidence X-ray diffraction analysis and transmission electron microscopy. The corrosion resistance and biocompatibility were investigated by the electrochemical corrosion analysis and cell culture tests with bone forming cells, respectively.

Ion implantation could reduce the surface nickel content down to approx. 0.5 at %. Below the Ni depleted surface a Ni enriched zone is formed, which indicates an increased mobility either of Ni from the surface to the bulk or of Ti from the sub-surface to the surface. A reactive diffusion mechanism for the nickel depletion in this system is discussed. The corrosion stability increases by this treatment. In preliminary studies with bone forming cells no decrease in biocompatibility was seen by this treatment.