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XPS characterisation of surface modified Ni-Ti shape memory alloy

Research output: Contribution to journalJournal article


Journal publication date31/03/1997
JournalMaterials Science and Engineering: A
Number of pages6
Original languageEnglish


Ni-Ti shape memory alloy has been surface amorphised by N+ ion implantation and by controlled shot peening in order to improve surface mechanical properties. X-ray photoelectron spectroscopy (XPS) and surface wetting measurements have been used to characterise the surface modified Ni-Ti to provide a fuller understanding of the biomaterial potential of such a material. The results of this study show that both the modified and unmodified Ni-Ti surfaces were predominantly covered with TiO2 and the underlying substrate crystallography determined both the affinity for surface OH−/chemisorbed water and ultimately the wetting behaviour of distilled water. Additionally, N+ ion implanted Ni-Ti contained a TiN phase within the surface which reduced wetting, demonstrating a reduced interfacial energy. The surface concentrations of Ni were unaffected by the surface modifications, with all samples containing less than 3 at.% Ni. This study has shown that the surface TiO2 oxide layer was maintained despite the surface amorphisation treatments. It can be assumed that the TiO2 layer is almost identical in unimplanted and implanted surfaces and they will display the same biocompatibility.