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

摘要

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, SnO_2, and Fe_2O_3. In addition, these mixtures are blended with varying amounts of WO_3 as a means to perturb the gas release in the system. The mixtures with CuO and SnO_2 exhibit pressure signals that peak on timescales faster than the optical signal, whereas the mixtures containing Fe_2O_3 do not show this behavior. The burn time is found to be relatively constant for both CuO and SnO_2, even when a large amount of WO_3 is added. For Fe_2O_3, the burn time decreases as WO_3 is added, and the temperature increases. The results are consistent with the idea that oxidizers such as CuO and SnO_2 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 Fe_2O_3 system, the pressure and optical signals occur concurrently, indicating that the oxidizer decomposition is the rate-limiting step.