Transformations of Iron (III) Precursors in a Wave of Flameless RDX Combustion

Resumo

Flameless combustion of 40% Fe₂O₃ – 40% RDX – 20% HDI (mix I) and 30% CoCO₃ – 15% iron formate – 40% RDX – 15% HDI (mix II) systems was explored by time-resolved X-ray diffraction (TRXRD). In case of mix I, the reaction was found to proceed via the formation of FeO intermediate: Fe₂O₃ → FeO → Fe₃O₄. Variation in the extent of iron reduction was associated with dynamic temperature change and a reductant content of the reaction zone. The reduction proceeded as a solid-state reaction, without amorphization of the structure. The process in system II involved the formation of CoO and FeO intermediates. Further reduction – up to metals – takes place behind the combustion front and yields a mixture of nanosized Co, Fe, and Co_0.7Fe_0.3 particles. Exposure of hot reaction products – nano-sized Co and Fe – to the air leads to their self-ignition and formation of Co₃O₄ and Fe₃O₄, respectively.