Chemical Corrosion of SiC by H2O

The system SiC – H2O is of great interest as a model system for the understanding of chemical corrosion of the new class of none-oxide ceramics.

  • What is the set of stable phases for an equi-molar closed system with variable temperature? 
  • What is the set of stable phases for an open system with fixed oxygen potential and variable temperature?
  • Figure 1 and Figure 2 show: In an equi-molar closed system SiC, SiO2 and carbon coexist over a wide temperature range until the formation of CO/G/ consumes the free carbon. At higher temperatures formation of SiO/G/ increases rapidly and only SiC will remain stable.
  • Figure 3 and Figure 4 show: When the oxygen potential is fixed (1×10-15) in addition to the input amounts of SiC and H2O the system behaves quite differently. There is a very wide temperature range in which the oxidation potential is large enough to render SiO2 as the only condensed phase. The gas composition will undergo quite drastic changes in this range. However, in a very small temperature range around 1900K SiO2 is completely transformed into SiC. A small amount of silicon will be transfered to the gas phase as SiO/G/.