Extent of reaction in energetic particulate mixtures: Role of composition and particle size ratio

The extent of reaction in reactive solid mixtures, comprising two or more p articulate components, can be significantly affected by the presence of una voidable compositional fluctuations in these systems. This is particularly the case where the size of the reaction zone is of the order of a few parti cle diameters. Results of detailed computer simulations, aimed at investiga ting the influence of composition and particle size ratios, on the fluctuat ions and thus the extent of reaction in reactive solid mixtures, are report ed here. These data are complemented by analytical calculations performed f or systems in certain limiting cases. In accord with experimental observati ons on certain classes of such systems, namely pyrotechnics, both the simul ation and the analytical results show that the extent of reaction attains i ts maximum value at compositions, which compared to the stoichiometric rati o, are somewhat richer in the minor component. The deviation of the optimal composition from stoichiometry becomes more pronounced for small reaction zone sizes, where the relative compositional fluctuations are larger. The e ffect of altering the particle size ratio, for systems where the stoichiome tric volume ratio is different to 1:1, is found to be markedly asymmetric. Reducing the size of the particles of the minor component is seen to dramat ically improve the extent of reaction in the system. In contrast, any obser ved improvements, arising from a reduction in the size of the major compone nt, are found to be at best marginal. The analytical calculations allow an insight into these result to be gained. (C) 1999 American Institute of Phys ics. [S0021-9606(99)70115-7].