Iron Oxides' Influence on the Thermal Decomposition of Pure Ammonium Perchlorate: A Comprehensive Review

The combustion of ammonium perchlorate (AP) has long been a focal point in the development of solid rocket propellants, with particular attention paid to the catalytic effects of iron oxides. Beginning in the 1950s, researchers have diligently studied the kinetics and mechanisms underlying AP combustion, with a focus on both micron-sized and nano-sized iron oxide catalysts due to their widespread application in rocket formulations worldwide. This research effort specifically excludes investigations involving alternative iron oxide-based catalysts, such as doped or mixed oxides, or supported iron oxides, as they are not commonly utilized in major rocket propellant formulations. Despite variations in specific parameters like activation energy and heat of dissociation, the fundamental understanding of AP decomposition with iron oxides remains consistent with earlier findings. Notably, micron-sized catalysts have minimal impact on the low-temperature decomposition (LTD) of AP but can influence high-temperature decomposition (HTD) by altering decomposition temperatures and reducing activation energy. In contrast, nano-sized catalysts tend to accelerate the reaction to such an extent that the LTD phase is often bypassed altogether due to the rapid consumption of NH3, a crucial component in the process. However, the transition to nano-sized particles presents a new challenge: the propensity for particle agglomeration. Current research endeavours are therefore dedicated to devising effective strategies to mitigate this issue and harness the full potential of nano-sized iron oxide catalysts in rocket propellant formulations.