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Ractions of SiC with H 2 /H 2 O/Ar Mixtures at 1300°C
Author(s) -
Jacobson Nathan S.,
Eckel Andrew J.,
Misra Ajay K.,
Humphrey Donald L.
Publication year - 1990
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.1151-2916.1990.tb07596.x
Subject(s) - oxygen , impurity , thermogravimetric analysis , silicon , grain boundary , analytical chemistry (journal) , decomposition , microstructure , carbon fibers , materials science , phase (matter) , chemistry , metallurgy , environmental chemistry , organic chemistry , composite number , composite material
The reactions of a sintered α‐SiC with 5% H 2 /H 2 O/Ar at 1300°C were studied. Thermomchemical modeling indicates that three reaction regions are expected, depending on the initial water vapor or equivalently oxygen content of the gas stream. A high oxygen content ( P (O 2 ) > 10 −22 atm) leads to a SiO 2 formation. This generally forms as a protective film and limits consumption of the SiC (passive oxidation). An intermediate oxygen content (10 −22 atm > P (O 2 ) > 10 −26 atm) leads to SiO and CO formation. These gaseous products can lead to rapid consumption of the SiC (active oxidation). Thermogravimetric studies in this intermediate region gave reaction rates which appear to be controlled by H 2 O gas‐phase transport to the sample and reacted microstructures showed extensive grain‐boundary attack in this region. Finally, a very low oxygen content ( P (O 2 ) < 10 −26 atm) is thermochemically predicted to lead to selective removal of carbon and formation of free silicon. Experimentally low weight losses and iron silicides are observed in this region. The iron silicides are attributed to reaction of free silicon and iron impurities in the system.