Nano Aluminum Energetics: The Effect of Synthesis Method on Morphology and Combustion Performance

Nanoscale aluminum based energetic composites were prepared using polytetrafluoroethylene (PTFE) as an oxidizer, and optimized according to the maximum experimentally observed flame propagation rate in an instrumented burn tube. Optimization of the aluminum-based composites was performed using nanometric aluminum from two manufacturers, Argonide Corporation and Novacentrix, and the combustion results represent the first direct comparison of these two materials in a burn tube configuration. Argonide aluminum was found to consist of many fused spheres of nano aluminum mixed with some larger micron sized particles. Novacentrix aluminum consisted of spherical particles with a closer particle size distribution. The propagation rate optimized wt.-% aluminum powder values were 50 and 44.5 for Novacentrix and Argonide, respectively. At the optimized conditions, the time to steady propagation for both Argonide and Novacentrix were similar, however the startup time for the Novacentrix based mixtures was more sensitive to changes in the mixture ratio. The presence of micron sized aluminum and lower surface area, but higher active content in the Argonide mixtures resulted in lower propagation rates, pressurization rates and peak pressures but higher total impulse values. It was found that peak pressure is not the sole determining factor in propagation rate, but the highest pressurization rates correlate with propagation rate.