Simultaneous Pressure and Optical Measurements of Nanoaluminum Thermites: Investigating the Reaction Mechanism

This work investigates the reaction mechanism of metastable intermolecular composites by collecting simultaneous pressure and optical signals during combustion in a constant-volume pressure cell. Nanoaluminum and three different oxidizers are studied: CuO, SnO2, and Fe2O3. In addition, these mixtures are blended with varying amounts of WO3 as a means to perturb the gas release in the system. The mixtures with CuO and SnO2 exhibit pressure signals that peak on timescales faster than the optical signal, whereas the mixtures containing Fe2O3 do not show this behavior. The burn time is found to be relatively constant for both CuO and SnO2, even when a large amount of WO3 is added. For Fe2O3, the burn time decreases as WO3 is added, and the temperature increases. The results are consistent with the idea that oxidizers such as CuO and SnO2 decompose and release gaseous oxidizers fast, relative to the burning, and this is experimentally seen by an initial pressure rise followed by a prolonged optical emission. In this case, the burning is rate limited by the aluminum, and it is speculated to be similar to the burning of aluminum in a pressurized oxygenated environment. For the Fe2O3 system, the pressure and optical signals occur concurrently, indicating that the oxidizer decomposition is the rate-limiting step.