High speed 2-dimensional temperature measurements of nanothermite composites: Probing thermal vs. Gas generation effects

This work investigates the reaction dynamics of metastable intermolecular composites through high speed spectrometry, pressure measurements, and high-speed color camera pyrometry. Eight mixtures including Al/CuO and Al/Fe₂O₃/xWO₃ (x being the oxidizer mol. %) were reacted in a constant volume pressure cell as a means of tuning gas release and adiabatic temperature. A direct correlation between gas release, peak pressure, and pressurization rate was observed, but it did not correlate with temperature. When WO₃ was varied as part of the stoichiometric oxidizer content, it was found that Al/Fe₂O₃/70% WO₃ achieved the highest pressures and shortest burn time despite a fairly constant temperature between mixtures, suggesting an interplay between the endothermic Fe₂O₃ decomposition and the higher adiabatic flame temperature sustained by the Al/WO₃ reaction in the composite. It is proposed that the lower ignition temperature of Al/WO₃ leads to the initiation of the composite and its higher flame temperature enhances the gasification of Fe₂O₃, thus improving advection and propagation as part of a feedback loop that drives the reaction. Direct evidence of such gas release promoting reactivity was obtained through high speed pyrometry videos of the reaction. These results set the stage for nanoenergetic materials that can be tuned for specific applications through carefully chosen oxidizer mixtures.