Effect of Carbon Content on the Combustion and Chemical Conversion of Thermite Mixtures Based on Co3O4/Cr2O3/Nb2O5 with Al
V. I. Yukhvid, D. E. Andreev, K. V. Zakharov, A. S. Shchukin
Merzhanov Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences, Chernogolovka, 142432 Russia
Keywords: autowave synthesis, composite material, cobalt alloy, thermite mixture
Abstract
The combustion of highly exothermic multicomponent mixtures of Co3O4/Cr2O3/Nb2O5/Al with additives of MoO3, WO3, and carbon (graphite) under overload up to 200 g has been studied. It has been shown that the introduction of carbon into the initial mixture has a noticeable effect on the combustion, formation of chemical composition, and structure of combustion products. With an increase in the mass content of carbon in the initial mixture from 0 to 3.9 % the burning rate decreases by more than half, and the rate of dispersion of combustion products and the weight loss increase markedly. Under the action of overload, the two-phase melt of combustion products is stratified into two layers, which crystallize upon cooling. The lower metal layer contains Co, Nb, Cr, W, Mo, C, and impurity aluminum, and the upper layer contains mainly Al2O3. With an increase in carbon content above 4.0 %, the separation of the metal and oxide phases stops, and with a further increase, the flammability limit is reached. With an increase in carbon content in the mixture from 0 to 3.9 %, its concentration in the cast composite material reaches 5.4 %, the Al content is about 4.0 % and the content of Co, Nb, Cr, W, and Mo changes slightly. The combustion slag contains reducer metal oxide (Al2O3) and Cr2O3 impurity dissolved in it.
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