Kinetic study of thermal- and impact-initiated reactions in Al-Fe2O3 nanothermite

A study on the kinetics of thermal- and impact-initiated chemical reactions in Al-Fe2O3 nanothermites prepared using self-assembly and solvent-based mixing techniques was conducted in this work. Thermochemical initiation using ignition wire, dynamic pressure tests, and differential thermal analysis showed significant enhancement in reaction kinetics for the thermite prepared by self-assembly, in contrast to those prepared by simple physical mixing of nano- and micro-sized powder precursors. The intimate mixing using self-assembly increases the interfacial contact area between Al and Fe2O3, which influences the thermochemical reaction initiation characteristics more so than the particle size effects. On the other hand, results of impact-initiation of reactions at velocities up to 400 m s(-1) reveal that the reactant particle size plays a more dominant role in the case of such mechanochemical processes. It was found that micron-size thermite powder mixture system reacts at a lower impact energy threshold than the mixtures of nano-sized powders prepared either by solvent-mixing or self-assembly. The difference in the reaction threshold is associated with the higher localized strain resulting from fewer interparticle contacts in micro-sized powders in comparison to more distributed strain achieved during impact-initiation of nano-sized thermite particle. (C) 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.