Surface characterization of NiTi modified by plasma source ion implantation

Abstract This paper reports the novel application of an oxygen ion plasma for surface modification of a shape memory alloy. The surface characterization of oxygen ion implanted Ti–50.7 at% Ni alloy samples was performed with the assistance of Auger electron spectroscopy, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy techniques (TEM). TEM identified amorphous TiO 2 and crystalline phases of Ti 11 Ni 14 and Ti 4 Ni 2 O x . XPS results reveal that the surfaces of control samples are covered with predominantly TiO 2 and traces of TiO and NiTi, as well as NiO and Ni 2 O 3 . At the surface of oxygen-implanted samples, however, only TiO 2 and trace amounts of Ni 2 O 3 , NiO and NiTi were observed. TiO and NiO exist in much larger range than other oxides, and TiO extends to the oxide–metal interface. These results are especially noteworthy because of their implications for interpreting corrosion, wear, and biocompatibility behavior.