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The aim of this investigation was to enhance the biological behavior of NiTi shape memory alloy while preserving its super-elastic behavior in order to facilitate its compatibility for application in human body. The surfaces of NiTi samples were bombarded by three different nitrogen doses. Small-angle X-ray diffraction was employed for evaluating the generated phases on the bombarded surfaces. The electrochemical behaviors of the bare and surface-modified NiTi samples were studied in simulated body fluid (SBF) using electrochemical impedance and potentio-dynamic polarization tests. Ni ion release during a 2-month period of service in the SBF environment was evaluated using atomic absorption spectrometry. The cellular behavior of nitrogen-modified samples was studied using fibroblast cells. Furthermore, the effect of surface modification on super-elasticity was investigated by tensile test. The results showed the improvement of both corrosion and biological behaviors of the modified NiTi samples. However, no significant change in the super-elasticity was observed. Samples modified at 1.4E18 ion cm(-2) showed the highest corrosion resistance and the lowest Ni ion release.

In the present study, a nickel sulphate bath containing SiC particles between 0?5 and 5?0 mm has been used as the plating electrolyte to obtain Ni-SiC composites on copper surfaces with high hardness and wear resistance for using in antiwear applications such as dies, tools and working parts of automobiles. The influence of SiC concentration in the electrolyte on morphology, microhardness, friction coefficient and wear missing volume of coatings has been studied. The coatings were analysed with scanning electron microscopy as well as X-ray diffraction. The findings indicate that increasing the concentration of SiC particles in the Watts bath results in improving the microhardness of coatings and also decreasing the friction coefficient and wear missing volume. Increasing the presence of SiC particles not only decreases the grain size of Ni crystals but also changes the morphology and preference orientation of Ni crystals.