Photocatalytic Activity of the Oxide Layer Formed on NiTi Surface through Thermal Oxidation Process

Abstract

In the present study, we attempted to prepare a photocatalytic titanium dioxide (TiO2) layer on nickel-titanium (NiTi) alloy surface through a simple thermal oxidation process in air. At 723K, an amorphous TiO2 layer including a slight amount of Ni was formed on the surface. Above 873K, the TiO2 layer crystallized into a rutile phase. At 1023K, a complex oxide of NiTiO3 was also formed. The methylene blue degradation test for evaluating photocatalytic activity showed that the formed TiO2 layers act as photocatalyst under ultraviolet (UV) light illumination, and its activity is superior to that of the surface layer formed by oxidizing a pure Ti substrate. The adhesion strength of the surface layers formed at 723K on NiTi alloy was higher than that of a commercially available TiO2-coating. We conclude that thermal oxidation as a surface modification technique is expected to make NiTi alloys give photocatalytic activity. [doi:10.2320/matertrans.M2014114]