Analysis Solid State Chemical Reactions

Composite materials are, by definition, multi-phased. Quite often these phases are not distinguishable by optical microscopy. Raman analysis provides very rapid analysis that can differentiate phases, even closely related phases such as polymorphs of a given composition, or differing stoichiometries in a solid system. Recently a SiC conversion coating on a carbon-carbon composite used in the space shuttle was analyzed and various phases were mapped. The identification of phases, in combination with maps showing the physical proximity of the phases, provide insight into the solid state chemical reactions that produce the multi-phase coating.