Characterizing energy transfer using an infrared camera from a reacting nano-composite thermite embedded in a steel target

Abstract

A method to study energy transfer from a reacted thermite placed on a steel target substrate was presented as a function of thermite composition. A high speed infrared camera captured a temporally evolving thermal distribution through the substrate, while the thermite, which was placed in a v-notch, self propagated. Two thermite compositions were studied: Boron with Iron (III) Oxide (B-Fe2O3) and Aluminum with Iron (III) Oxide (Al-Fe2O3). A numerical model was developed to predict temperatures near the v-notch in order to estimate the amount of energy transferred into the steel by using a control volume energy balance. Results quantified the percent of the overall energy available from the chemical reaction that was conducted through the substrate and was compared to energy lost. The B-Fe2O3 reaction was more efficient in transferring energy into the steel, 46% of its heat of reaction, than Al-Fe2O3, 10% of its heat of reaction, based largely on the lower contribution of losses by radiation and convection. The Al-Fe2O3 reaction produced more gas by chemistry, 10% by mass, which transported more energy away from the v-notch region as compared to the non gas producing B-Fe2O3. The reaction times for Al-Fe2O3 propagation rate were roughly two to three times faster than the B-Fe2O3 which lowered the heating rate of the substrate. Much work had been performed that examine the combustion behaviors from a reacting thermite, but there are very few studies that attempt to quantify the energy transfer from a reacting thermite to a target. This diagnostic approach and numerical analysis was the first step towards quantifying energy transferred from a thermite into a target, and lost to the environment.