Thermodynamic Analysis of ZrB2–SiC Oxidation: Formation of a SiC-Depleted Region


  • William G. Fahrenholtz

    Corresponding author
    1. Department of Materials Science and Engineering, University of Missouri-Rolla, Rolla, Missouri
      †Author to whom correspondence should be addressed. e-mail:
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    • *Member, American Ceramic Society.

  • N. Jacobson—contributing editor

  • This work was supported by the Ceramics program in the Division of Materials Research at the National Science Foundation (DMR-0346800) and by the Ceramic and Non-Metallic Materials Program in the Air Force Office of Scientific Research (FA9550-06-1-0125).

†Author to whom correspondence should be addressed. e-mail:


A thermodynamic model was developed to explain the formation of a SiC-depleted layer during ZrB2–SiC oxidation in air at 1500°C. The proposed model suggests that a structure consisting of (1) a silica-rich layer, (2) a Zr-rich oxidized layer, and (3) a SiC-depleted zirconium diboride layer is thermodynamically stable. The SiC-depleted layer developed due to active oxidation of SiC. The oxygen partial pressure in the SiC-depleted layer was calculated to lie between 4.0 × 10−14 and 1.8 × 10−11 Pa. Even though SiC underwent active oxidation, the overall process was consistent with passive oxidation and the formation of a protective surface layer.