High-temperature oxidation of CVD silicon-based ceramics
- Tohoku Univ., Sendai (Japan); and others
Oxidation behavior of CVD SiC and CVD Si{sub 3}N{sub 4} was studied at 1773 to 2023 K in Ar-O{sub 2}, N{sub 2}-O{sub 2} and CO-CO{sub 2} atmospheres. In Ar-O{sub 2} and N{sub 2}-O{sub 2} atmospheres, the active oxidation rates for CVD SiC and CVD Si{sub 3}N{sub 4} were dominated by oxygen diffusion through a gas boundary layer. The active-to-passive transition oxygen partial pressures for CVD SiC were slightly greater than those for CVD Si{sub 3}N{sub 4}. In CO-CO{sub 2} atmospheres, at PCO{sub 2}/PCO < 10{sup -3} inward diffusion of CO{sub 2} gas controlled the active oxidation rates for CVD SiC; however, a chemical reaction controlled the rates for CVD Si{sub 3}N{sub 4}. At PCO{sub 2}/PCO > 10 {sup -2}, SiO{sub 2} particles or layers formed during the active oxidation; the decomposition of SiO{sub 2} could control the active oxidation rates. The Wagner model can be used to explain the active-to-passive transition in these atmospheres for both CVD SiC and CVD Si{sub 3}N{sub 4}. The volatility diagram and thermodynamic calculation, including mass balance relationship, were also useful to understand the transition behavior.
- OSTI ID:
- 518587
- Report Number(s):
- CONF-960367-; TRN: 97:003394-0016
- Resource Relation:
- Conference: Workshop on mass and charge transport in ceramics, Nagoya (Japan), 15-16 Mar 1996; Other Information: PBD: 1996; Related Information: Is Part Of Ceramic transactions: Mass and charge transport in ceramics. Volume 71; Koumoto, Kunihito; Sheppard, L.M.; Matsubara, Hideaki [eds.]; PB: 643 p.
- Country of Publication:
- United States
- Language:
- English
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