Oxygen Transport in Silica at High Temperatures: Implications of Oxidation Kinetics

Authors

  • C. Eric Ramberg,

    1. Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104–6272
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    • *

      Member, American Ceramic Society.

    • Now at Symyx Technologies, 3100 Central Expressway, Santa Clara, CA 95051.

  • Wayne L. Worrell

    1. Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104–6272
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      Member, American Ceramic Society.


  • N. S. Jacobson—contributing editor

  • Supported by the Department of Energy, Office of Naval Research, LRSM (Penn), Ashton Fellowship (Penn), and University Fellowship (Penn).

  • Based in part on the thesis submitted by author CER for the Ph.D. Degree in Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA, December 1997.

Abstract

The apparent change in activation energy describing the parabolic rate constant for the passive oxidation of SiC is examined. New data are combined with reevaluated previous results to determine the influences of crystallinity, impurity contamination, and multiple flux mechanisms. The results suggest that the high-temperature transition from interstitial-dominant to network-dominant oxygen transport is a property of amorphous SiO2 scales and does not exist for cristobalite. Highly crystalline scales do not show this transition. Agreement among various studies also suggests that, for high-purity SiO2 scales, there is no difference between the rates of interstitial oxygen transport in amorphous SiO2 and in β-cristobalite.

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