ISSN:
0142-2421
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Physics
Notes:
The oxidation behaviour of the alloys Fe-19 at.% Cr-9 at.% Ni and Ni-40 at.% Fe-20 at.% Cr was studied in situ at room temperature and oxygen pressures below 10-4 Pa by AES using low-energy M23VV transitions between 20 and 70 eV. Quantitative determination ofthe relevant components by factor analysis and least-squares fitting methods enabled a much more detailed analysis of the initial oxidation stages as compared to earlier studies. For all alloy elements, factor analysis revealed the presence of an intermediate chemical state before oxidation which is due to binding with chemisorbed oxygen. Least-squares fitting with standrd spectra of the pure elements in their metallic, oxidic and intermediate states disclosed the sequential oxidation of Cr, Fe and Ni with increasing oxygen exposure. Preferential oxygen chemisorption on Cr and oxidation of Cr is accompanied by oxygen-induced segregation and is followed by Fe and Ni oxidation on top of the previously formed oxide for the Ni-rich alloy. Nickel oxidation is drastically reduced in Fe-rich alloys. After exposure to 900 L of oxygen, oxidation results in a layered structure as confirmed by AES sputter depth profiles which can be resolved into oxide and pure metal components. Together with the small electron escape depth of only 2-4 atomic layers, this procedure gives well-resolved depth distributions within the total oxide thickness of ∼6-7 monolayers for NiFe40Cr20 and 11-12 monolayers for FeCr19Ni9.
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/sia.740190130
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