High temperature corrosion of silicon based ceramics in environments containing halogens and alkali halides
Silicon carbide and other silicon-based ceramics obtain their oxidation resistance by the formation of protective silica films in oxygen containing environments. In the presence of chlorine or alkali chlorides, this film may not form, or may be unprotective, so that accelerated oxidation occurs. Chlorine and alkali halides may contribute to accelerated oxidation via three possible mechanisms. Active oxidation occurs at relatively low temperatures and high ratios of chlorine to oxygen, and is characterized by simultaneous formation of silicon chlorides and non-protective oxides. Silica film disruption occurs at higher temperatures when volatile chlorides format the interface between SiC and the Si0{sub 2} scale, and cause bubbles to form in the film. Alkali fluxing occurs in the presence of alkali chloride vapors. In alkali fluxing, a low melting glass is formed by the reaction between the alkali vapor species and silica rather than by reactions with chlorine itself.
- Research Organization:
- Univ. of Illinois at Chicago, IL (US)
- OSTI ID:
- 20002621
- Report Number(s):
- CONF-990401-; TRN: IM200002%%621
- Resource Relation:
- Conference: Corrosion NACExpo 99, 54th Annual Conference and Exposition, San Antonio, TX (US), 04/25/1999--04/30/1999; Other Information: 1 CD-ROM. Operating Systems: Windows 3.1, '95, '98 and NT; Macintosh; and UNIX; PBD: 1999; Related Information: In: Corrosion 99: Proceedings, [3500] pages.
- Country of Publication:
- United States
- Language:
- English
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