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Thermochemical Studies in Selected Metal–Carbon–Oxygen Systems
Author(s) -
Wittmer Dale E.,
Temuri Maqsood Z.
Publication year - 1991
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.1151-2916.1991.tb04330.x
Subject(s) - oxidizing agent , carbide , carbon fibers , materials science , metal , oxygen , thermal expansion , chemical engineering , thermal stability , chemical stability , inorganic chemistry , metallurgy , composite material , chemistry , composite number , organic chemistry , engineering
Carbon–carbon composites have unique physical and chemical properties but are limited by poor oxidation resistance at elevated temperatures in an oxidizing environment. Coatings based on metal carbides and metal oxides are currently being used for limited oxidation protection at temperatures exceeding 1200°C. However, problems exist for all current coatings and potential future coatings because of thermochemical instability at elevated temperatures. Thermochemical equilibrium calculations for reactions between oxides and carbides of the same metal system were used to predict the stability of the associated interfaces. The systems examined were carbon and oxygen in combination with five metals (Si, Ti, Ta, Hf, and Zr). The SiO 2 /SiC system was determined to be the best choice up to about 1700°C, because of optimization of properties, while at higher temperatures, HfO 2 /HfC and ZrO 2 /ZrC systems appear to be more stable thermodynamically, although high thermal expansion coefficient and oxidation rate, for each carbide, may make them less physically compatible.