期刊
SURFACE SCIENCE
卷 482, 期 -, 页码 254-259出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/S0039-6028(01)00910-4
关键词
auger electron spectroscopy; oxidation; surface segregation; nickel; aluminum; boron; grain boundaries
This paper focuses on local probe Auger spectroscopy studies of segregation and oxidation of in situ fractured Ni3Al specimens, both with and without B-doping. Although immediately after in situ fracture small amounts of segregated B at grain boundaries were observed occasionally in the B-doped specimens, the amount of B at the intergranular fracture surface drastically increased with time upon exposure to the ambient vacuum. After subsequent removal of B by depth profiling by in situ Ar+-bombardment (1 keV) at a rate of similar to3.3 nm/min, B again segregated to the Surface within several hours, accompanied by surface oxidation, under ultrahigh vacuum conditions at room temperature, Possible mechanisms of B surface segregation are related to the high binding energy between B and O and the fact that B lowers the surface energy of a Ni-enriched surface. Finally, prolonged exposure of the fracture Surface to the electron beam is shown to lead to enhanced Ni oxidation and to less B surface segregation. (C) 2001 Elsevier Science B.V. All rights reserved.
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