Microstructural characterization of oxide film formed on NiTi by anodization in acetic acid

被引:68
作者
Cheng, F. T. [1 ]
Shi, P.
Pang, G. K. H.
Wong, M. H.
Man, H. C.
机构
[1] Hong Kong Polytech Univ, Dept Appl Phys, Kowloon, Hong Kong, Peoples R China
[2] Liaoning Inst Technol, Dept Mat & Chem Engn, Liaoning, Peoples R China
[3] Hong Kong Polytech Univ, Dept Ind & Syst Engn, Kowloon, Hong Kong, Peoples R China
关键词
titanium oxide; anodization; NiTi; XPS; TEM;
D O I
10.1016/j.jallcom.2006.08.020
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
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 LR 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. (C) 2006 Elsevier B.V. All rights reserved.
引用
收藏
页码:238 / 242
页数:5
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