Reactive characterization of nanothermites

Conventional thermal analysis techniques (TG and DSC) give valuable information on the activation energy and the reactivity of energetic materials such as organic explosives. Here, we discuss the use of these methods for characterizing nanothermites, energetic compositions made of metallic oxides and a fuel (often a reducing metal). The experimental limitations of these analysis techniques are identified. It is difficult to ignite nanothermites with slow heating rates as those used in DSC. This is due to the inorganic nature of the thermite components and because the reaction involves interparticular heat and matter transfers. In addition, during the progressive decomposition of nanothermites, there is no change in mass, so it cannot be observed by thermogravimetric analysis. The use of laser ignition to prime the abrupt combustion of nanothermite pellets allows determining the ignition energy and analyzing the propagation of the combustion front. It also provides qualitative data that can be used to understand the combustion mechanism and to correlate it to the microstructure of the nanothermites. By analyzing several examples, we will show that the coupling of high speed video to existing thermal analysis techniques could significantly extend their utilization range for the characterization of new energetic materials.