Gas vs. Condensed Phase Reactions in Nano-Thermites

Explosive formulations incorporating aluminum nano particles as a fuel has been extensively studied due to their low diffusion length scales and their high specific energy release compared to traditional organic formulations. In this work we evaluate the combustion product particle size distribution of nanothermites, and deduce some controlling combustion mechanisms. The results presented here show two distinct particle product distributions common to all fuel/oxidizer foumations evalauted. These two distribution contain a nanoparticle and supermicron product. From mass analysis we determine that ~90% of the product mass is comprised of the large particle population. Simple scaling arguments show that the large population cannot be formed from the vapor given the available residence time. This result implies that the majority of reaction and thus the energy release must occur in the condensed phase.