Oxidation of SiC/BN/SiC ceramic matrix composites in dry and wet oxygen at intermediate temperatures

The oxidation behavior of SiC/BN/SiC ceramic matrix composites (CMCs) was evaluated from 400° to 800 °C in 100% O2 and 50% H2O/50% O2 gas mixtures. Thermogravimetric analysis (TGA) was utilized to measure weight change during controlled environment exposures at elevated temperatures for 1 and 50 hou...

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Bibliographic Details
Published in:Journal of the European Ceramic Society 2022-08, Vol.42 (10), p.4110-4120
Main Authors: Detwiler, K.N., Opila, E.J.
Format: Article
Language:English
Subjects:
Boron nitride
Focused ion beam (FIB)
Oxidation
SiC/SiC
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Summary:The oxidation behavior of SiC/BN/SiC ceramic matrix composites (CMCs) was evaluated from 400° to 800 °C in 100% O2 and 50% H2O/50% O2 gas mixtures. Thermogravimetric analysis (TGA) was utilized to measure weight change during controlled environment exposures at elevated temperatures for 1 and 50 hours. Oxidized CMCs and their oxides were studied post-exposure with scanning electron microscopy and energy dispersive spectroscopy. The oxidation onset and composition transition temperatures were evaluated. Key observations include oxide composition, oxide wetting, oxygen solubility in Hi-Nicalon SiC fibers and BN fiber coating oxidation and volatility behavior as a function of temperature. Degradation in wet environments at 600 °C was most extensive due to the formation of a non-wetting, non-protective surface oxide, allowing oxidant access to the BN fiber coatings followed by oxidation and volatilization. Implications of the CMC oxidation behavior are discussed for CMCs in service.
ISSN:0955-2219
1873-619X
DOI:10.1016/j.jeurceramsoc.2022.04.003