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论文类型：期刊论文
发表时间：2012-10-18
发表刊物：JOURNAL OF PHYSICAL CHEMISTRY C
收录刊物：SCIE、EI、Scopus
卷号：116
期号：41
页面范围：21771-21779
ISSN号：1932-7447
摘要：The formation of the passive oxide surface layer accounts for the superior biocompatibility of NiTi alloy based implant materials. However, the usage NiTi alloy is limited by the long-term release of biotoxic Ni ion from the bulk, facilitated by the formation of defects and vacancies in the surface oxide layer during conventional processing. To aid the improvement of the biocompatibility of NiTi alloys, extensive first-principles based calculations were performed to uncover the microscopic mechanism for the temperature controlled oxidation of NiTi alloy. We show that the oxygen adsorption and diffusion on the NiTi surface are the elementary steps for the formation of a surface oxide layer. Oxygen will bind strongly with the alloy surface and even induce surface reconstruction, and the adsorption energy can be as high as -6.14 eV. The requested surface diffusion for formation of TiO2 surface terminations is thermodynamics driven, but the corresponding kinetics is strongly affected by temperatures. These result in formation of TiO at low temperatures and TiO2 at elevated temperatures.