Review: Oxidation of SiC/SiC composites in low oxidising and high temperature environment

Abstract

Due to their thermal, mechanical, and nuclear properties, silicon carbide fiber reinforced, silicon carbide matrix (SiCf/SiCm) composites are promising candidate materials for fuel assembly in gas-cooled fast reactors (GFR), but their long term oxidation resistance must be evaluated under GFR relevant environments: high temperature, impure helium, yearlong in-core exposure. Experience from other high temperature applications shows that in an inert atmosphere SiC fibers may undergo a thermal decomposition. On the other hand at high P(O2), SiC based elements form surface silica that provides an outstanding corrosion resistance. However, oxidative volatilization of silica occurs at intermediate P(O2) and SiC suffers from active oxidation. Finally, the carbon layer at the fiber/matrix interface is highly sensitive to oxidation. The overall SiCf/SiCm behaviour is complex because it may involve degradation of several components and coupled interactions as well. A comprehensive R&D program is required to design a candidate composite material and to determine suitable environmental conditions. Fundamental as well as technical knowledge would be the basis of models for life time prediction. © 2008 Springer Science + Business Media B.V.