Dramatic influence of interface chemical potentials on the oxidation of silicon and carbon based compounds

At ultrahigh temperatures silicon and carbon based ceramics can either decompose vociferously by reacting with oxygen, or grow a passivation scale of silica, that prevents it. We show that this transition in silicon oxycarbonitride ceramics when heated to 1500 °C in variable oxygen pressure is tied to the interfacial chemical potential, or the virtual partial pressure of carbon-monoxide at the interface, which can be sustained only when the silica layer is growing.