Title

The Effect of a Graphite Addition on Oxidation of ZrB₂–SiC in Air at 1500°C

Abstract

Dense ZrB2 containing 15 vol.% SiC and 15 vol.% graphite was exposed to flowing air at 1500 °C. A layered scale structure developed that consisted of (1) a uniform SiO2-rich layer on the surface, (2) a layer of ZrO2 and SiO2, (3) a layer of ZrO2 (4) a partially oxidized layer composed of porous ZrB2, ZrO2, and graphite, and (5) unaffected ZrB2–SiC–C. A thermodynamic model based on volatility diagrams and consistent with the experimental observations was constructed to explain the development of the layered structure. Oxidation behavior was consistent with passive oxidation and formation of a protective surface layer. Analysis indicated that it may not be possible to form a protective surface layer without actively oxidizing SiC and producing a porous partially oxidized layer between the outer protective layer and the underlying unoxidized material.

Department(s)

Materials Science and Engineering

Keywords and Phrases

ZrB2; SiC; Oxidation; Carbon; Thermodynamic Model

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2013 Elsevier, All rights reserved.


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