3. Global view of reaction mechanisms in high-temperature solids

In all the foregoing ( [AF 3 688] and [AF 3 689]), the emphasis has been on the physico-chemical relationships of gases with solids, and on the elementary processes determining the rates of the corresponding reactions at high temperatures. The solid formed was assumed to be unique, unchanged throughout the duration of the reaction, and to constitute a dense, homogeneous layer, a physical barrier between the reactive solid and the reacting gas, at any temperature and pressure. The reactive substrate is also considered to be unchanging in composition and microstructure. This...