Relationships between thermochemical and kinetic aspects of high temperature gas-solid reactions

Thermochemical diagrams are used to evaluate the stable condensed phases, the nature of the volatile species, the equilibrium pressures of the volatile species, and the mechanism of gas-solid reactions. For metal-oxygen systems that form condensed oxide phases and metal and oxide gaseous species, log p(Mesub(x)Osub(y)) vs. log p(Osub(2)) diagrams are used. For predicting the onset of the various oxidation processes, log p(Mesub(x)Osub(y)) vs. 1/T diagrams are used. Molybdenum oxidizes rapidly due to the formation of (MoO3)3(g) over the metal and MoO3(s,l) chromium oxidizes rapidly due to the formation of CrO3(g) at the Cr2O3(s) - O2 interface and Cr(g) at the Cr(s) - Cr2O3(s) interface. Silicon oxidizes rapidly at low oxygen pressures due to the formation of SiO(g) at te Si(s) - SiO2(s) interface