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Oxidation Studies of Si2N2O

  • J. Persson
  • P.-O. Käll
  • M. Nygren
  • R. Larker
Chapter

Abstract

Fully dense Si2N2O ceramics have been prepared using glass encapsulated HIP technique at a pressure of 200 MPa and at 1900 °C with a reaction time of 4 hours. The oxidation resistance of Si2N2O has been studied in the temperature range 1300–1600 °c by the thermogravimetric method. All weight gain curves do not follow the common parabolic rate law. Subsequent microstructural and X-ray diffraction studies have shown that the formed oxide scales consist of an amorphous siO2 phase and crystalline α-cristobalite implying that — to the extent that the crystalline products are formed during the oxidation experiment — the effective cross section area for diffusion of oxygen through the amorphous phase decreases during the experiment. An equation which describes how the effective area is reduced with time has been developed and incorporated into the common parabolic rate law, giving the following expression.
$$ \Delta {\text{W/}}{{\text{A}}_{\text{o}}} = {\text{a arctan }}{\left( {{\text{bt}}} \right)^{1/2}} + {\text{c}}{\left( {\text{t}} \right)^{1/2}} $$
with ΔW weight gain, Ao = the initial cross section area, t = time and a, b, and c = constants to be determined. All weight gain curves can be described by this equation, and the rate constant at different temperatures could thus be determined.

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References

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    Trigg, M. B and Jack, K. H Silicon oxynitride and O’-sialon ceramics. J. Mat. Sci. 1988, 23, 481.CrossRefGoogle Scholar
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Copyright information

© Elsevier Science Publishers Ltd and MPA Stuttgart 1992

Authors and Affiliations

  • J. Persson
    • 1
    • 2
  • P.-O. Käll
    • 1
    • 2
  • M. Nygren
    • 1
    • 2
  • R. Larker
    • 1
    • 2
  1. 1.Department of Inorganic Chemistry, Arrhenius Laboratory Stockholm UniversityStockholmSweden
  2. 2.Department of Engineering MaterialsLuleå University of TechnologyLuleåSweden

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