Indexed by:期刊论文

Date of Publication:2012-10-18

Journal:JOURNAL OF PHYSICAL CHEMISTRY C

Included Journals:SCIE、EI、Scopus

Volume:116

Issue:41

Page Number:21771-21779

ISSN No.:1932-7447

Abstract: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.