The effect of heating rate on the surface chemistry of NiTi |
| |
Authors: | Andreas Undisz Robert Hanke Katharina E Freiberg Volker Hoffmann Markus Rettenmayr |
| |
Institution: | 1. Otto Schott Institute of Materials Research, Friedrich Schiller University, Löbdergraben 32, 07743 Jena, Germany;2. IFW Dresden, Institute for Complex Materials, PO Box 270116, 01171 Dresden, Germany |
| |
Abstract: | The impact of the heating rate on the Ni content at the surface of the oxide layer of biomedical NiTi is explored. Heat treatment emulating common shape-setting procedures was performed by means of conventional and inductive heating for similar annealing time and temperature, applying various heating rates from ∼0.25 K s−1 to 250 K s−1. A glow discharge optical emission spectroscopy method was established and employed to evaluate concentration profiles of Ni, Ti and O in the near-surface region at high resolution. The Ni content at the surface of the differently treated samples varies significantly, with maximum surface Ni concentrations of ∼20 at.% at the lowest and ∼1.5 at.% at the highest heating rate, i.e. the total amount of Ni contained in the surface region of the oxide layer decreases by >15 times. Consequently, the heating rate is a determinant for the biomedical characteristics of NiTi, especially since Ni available at the surface of the oxide layer may affect the hemocompatibility and be released promptly after surgical application of a respective implant. Furthermore, apparently contradictory results presented in the literature reporting surface Ni concentrations of ∼3 at.% to >20 at.% after heat treatment are consistently explained considering the ascertained effect of the heating rate. |
| |
Keywords: | Nickel&ndash titanium alloy Surface characterization Heating rate effect Depth profiling Glow discharge optical emission spectroscopy |
本文献已被 ScienceDirect 等数据库收录! |
|