期刊
CHEMPHYSCHEM
卷 10, 期 1, 页码 226-235出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/cphc.200800528
关键词
alloys; density functional calculations; diffusion; kinetics; platinum
资金
- Air Force Office of Scientific Research
- Maui High Performance Computing Center
- Naval Oceanographic Office
- Engineering Research and Development Center Major Shared Resource Centers
Platinum is added to thermal barrier coatings (TBCs) as it is observed empirically to extend their lifetime, but the mechanism by which Pt acts is unknown. Since Pt has been proposed to alter diffusivities in NiAl, a key component of TBCs, we use first-principles quantum mechanics calculations to investigate atomic level diffusion mechanisms. Here, we examine the effect of Pt on five previously proposed mechanisms for Ni diffusion in NiAl: next-nearest-neighbor jumps, the triple defect mechanism, and three variants of the six jump cycle. We predict that Pt increases the rate of Ni diffusion by stabilizing point defects and defect clusters that ore diffusion intermediates. Previously, we predicted the triple defect mechanism to be a dominant Ni diffusion mechanism; it simultaneously results in long-range At diffusion in the opposite direction. Since Pt increases the rote of Ni diffusion, it also increases At diffusion in NiAl, which may be key to extending the coating lifetime.
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