High-temperature mixed oxidation of nitride-bonded silicon carbide in oxidizing gas mixtures containing 2% Cl{sub 2}
- Univ. of Illinois, Chicago, IL (United States). Dept. of Civil Engineering, Mechanics, and Metallurgy
Nitride-bonded silicon carbide ceramics have lower processing costs than many other SiC-based ceramics and adequate properties for use as high-temperature heat exchangers in oxidizing environments. Silicon nitride has much better resistance to attack by chlorine at temperatures above 900 C than silicon carbide. When nitride bonded silicon carbide ceramics are exposed to gas mixtures containing 2% Cl{sub 2} and small amounts of oxygen in this temperature range, the SiC is selectively chlorinated, leaving behind a porous matrix of silicon nitride. The rate of corrosion is controlled by a combination of interfacial kinetics at the surfaces of the SiC grains and transport of volatile species through the silicon nitride skeleton. In more oxidizing environments, the rate of chlorination is suppressed by the formation of a protective SiO{sub 2} film. In more oxidizing environments at temperatures in excess of 1,200 C, the formation of volatile chloride reaction products at the interface between the SiC and the passivating SiO{sub 2} layer causes bubbles to form in the SiO{sub 2}, which accelerates the oxidation.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 82584
- Journal Information:
- Journal of the American Ceramic Society, Journal Name: Journal of the American Ceramic Society Journal Issue: 4 Vol. 78; ISSN 0002-7820; ISSN JACTAW
- Country of Publication:
- United States
- Language:
- English
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