Oxidation Inhibition Mechanisms in Coated Carbon–Carbon Composites

Abstract
The mechanism of oxidation resistance in SiC‐coated carbon‐carbon composites containing boron‐based inhibitors has been investigated using thermodynamic calculations, thermogravimetric analysis, and electron microscopy. A model is developed based on the formation of a volatile B2O2 sub‐oxide in the interior of the composite which condenses to B2O3 upon encountering a locally high oxygen partial pressure in coating cracks. The active‐to‐passive transition for the oxidation of elemental boron has been determined.