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Reactive element effects on the ionic transport processes in Cr2O3 scales

Liu, H. and Stack, M.M. and Lyon, S.B. (1998) Reactive element effects on the ionic transport processes in Cr2O3 scales. Solid State Ionics, 109 (3-4). pp. 247-257. ISSN 0167-2738

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Abstract

A study of the ionic and electronic partial conductivity of Cr2O3 scales selectively grown on Ni-20%Cr alloy with and without yttria additions in hydrogen water vapour at 900 degrees C, was carried out by the asymmetry polarisation technique. The results revealed that there were two main regions for the temperature dependence of conductivity in the range 300-900 degrees C. Above 700 degrees C, the Cr2O3 scale was an intrinsic electronic conductor with a corresponding activation energy of 1.7 eV. Below 700 degrees C, the Cr2O3 scale was a mixed ionic and electronic conductor. The activation energy was 0.6eV for electronic conductivity and 0.3 eV for ionic conductivity. The ionic transference number decreased as the temperature or applied voltage increased. The data strongly suggest that the presence of the reactive element in the scale reduces the concentration of mobile species, thus lowering the ionic transport number.

Item type: Article
ID code: 34384
Keywords: chromia scale, defects structure, ionic conductivity, ionic transport number, reactive elements effects, high temperature oxidation, electrical conductivity, defect structures, chromium, Mechanical engineering and machinery, Mining engineering. Metallurgy, Materials Science(all), Chemistry(all), Condensed Matter Physics
Subjects: Technology > Mechanical engineering and machinery
Technology > Mining engineering. Metallurgy
Department: Faculty of Engineering > Mechanical and Aerospace Engineering
Related URLs:
    Depositing user: Pure Administrator
    Date Deposited: 17 Oct 2011 15:26
    Last modified: 05 Sep 2014 11:54
    URI: http://strathprints.strath.ac.uk/id/eprint/34384

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