(694e) Flame Propagation of Al/PTFE Mechanically Activated Composites

The confined propagation velocity of nanoscale aluminum (nAl) and polytetrafluoroethylene (PTFE) metastable intermolecular composites (nAl/PTFE MICs) can be high due to convective heating that can occur at the reaction interface of discrete fuel/oxidizer particles. Unlike MICs, preheating of reactions in mechanically activated micron-sized Al/PTFE composites can occur through both inter-particle convection and intra-particle conduction. Preheating can be further dependent upon equivalence ratio, as for some ratios, reaction products are condensed-phase. The goal of this work is to determine the individual influences of conduction and convection on confined, mechanically activated Al/PTFE flame propagation by varying equivalence ratio, particle size, and intra-particle mixing (e.g. milling treatment). Instrumented tube combustion experiments are conducted in which optical and pressure wave propagation in mechanically activated Al/PTFE composites is observed using photodiodes and piezoelectric pressure transducers, respectively. Using similar packing densities while varying particle size, intra-particle mixing, and equivalence ratio, the effects of conduction and convection can be isolated.