Please use this identifier to cite or link to this item: http://hdl.handle.net/10397/33696
Title: Microstructural characterization of oxide film formed on NiTi by anodization in acetic acid
Authors: Cheng, FT
Shi, P
Pang, GKH
Wong, MH
Man, HC 
Keywords: Anodization
NiTi
TEM
Titanium oxide
XPS
Issue Date: 2007
Publisher: Elsevier
Source: Journal of alloys and compounds, 2007, v. 438, no. 1-2, p. 238-242 How to cite?
Journal: Journal of alloys and compounds 
Abstract: NiTi was galvanostatically anodized in acetic acid aiming at forming an anodic film for improving corrosion resistance. While the corrosion behavior of anodized NiTi in Hanks' solution was reported elsewhere [P. Shi, F.T. Cheng, H.C. Man, Mater. Lett., submitted for publication], the present work reports the microstructural characterization of the anodic film formed. Bright-field image of the sample cross-section captured by transmission electron microscopy (TEM) revealed an oxide film of about 20 nm thick, which was smooth and free of defects. The surface roughness Ra of the film, determined by atomic force microscopy (AFM), was about 1.45 nm. Analysis by X-ray photoelectron spectroscopy (XPS) along the depth of the anodic film indicated that the oxidation state of Ti varied from +4 (corresponding to TiO2) at the surface to lower oxidation states (corresponding to Ti suboxides) beneath. A small amount of Ni in the metallic and oxidized states was also present. The Ni/Ti atomic ratio was about 0.04 at the surface of the anodic film, which was much lower than the corresponding value of 0.30 for the mechanically polished samples. Selected-area diffraction (SAD) patterns and high-resolution TEM image of the anodic film showed that the film was amorphous.
URI: http://hdl.handle.net/10397/33696
ISSN: 0925-8388
DOI: 10.1016/j.jallcom.2006.08.020
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