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CVD Mullite Coatings in High‐Temperature, High‐Pressure Air–H 2 O
Author(s) -
Haynes J. Allen,
Lance Michael J.,
Cooley Kevin M.,
Ferber Mattison K.,
Lowden Richard A.,
Stinton David P.
Publication year - 2000
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.2000.tb01250.x
Subject(s) - mullite , materials science , cristobalite , chemical vapor deposition , composite material , isothermal process , amorphous solid , layer (electronics) , volatility (finance) , porosity , ceramic , nanotechnology , chemistry , crystallography , quartz , physics , financial economics , economics , thermodynamics
Crystalline mullite was deposited by chemical vapor deposition (CVD) onto SiC/SiC composites overlaid with CVD SiC. Specimens were exposed to isothermal oxidation tests in high‐pressure air + H 2 O at 1200°C. Unprotected CVD SiC formed silica scales with a dense amorphous inner layer and a thick, porous, outer layer of cristobalite. Thin coatings (∼2 μm) of dense CVD mullite effectively suppressed the rapid oxidation of CVD SiC. No microstructural evidence of mullite volatility was observed under these temperature, pressure, and low‐flow‐rate conditions. Results of this preliminary study indicate that dense, crystalline, high‐purity CVD mullite is stable and protective in low‐velocity, high‐pressure, moisture‐containing environments.