Synthesis and mechanistic exploration of interfacial control and enhanced catalysis for improving thermal decomposition of AP in Al@AP-Fe2O3 composites

Abstract

Ammonium perchlorate (AP) is commonly used as an oxidant in composite solid propellants (CSPs). The thermal behavior of AP has a significant impact on CSP combustion. This study investigates the thermal behavior of Al-AP-Fe2O3 and Al@AP-Fe2O3 particles, which were produced using a recrystallization method, under various pressures. The ability of Fe2O3 to regulate the decomposition rate of AP and the reasons for the reduced ignition delay under enhanced Fe2O3 catalysis are also explored by using density functional theory (DFT) calculations. The results indicate that Fe2O3 with a large catalytic contact area has a strong ability to regulate the decomposition rate of AP. The decreasing trend of the temperature difference between low- and high-temperature decomposition peaks belonging to the Al@AP-Fe2O3 (32 °C (0.1 MPa) → 19 °C (1.0 MPa) → 14 °C (4.0 MPa)) is weaker than that of the Al-AP-Fe2O3 (60 °C (0.1 MPa) → 25 °C (1.0 MPa) → 0 °C (4.0 MPa)) under various pressures. Additionally, the low activation energy of ∗NH4ClO4 → ∗NH3 + ∗H (∗O3b) + ∗ClO4 (300 °C: 0.207 eV) is the main reason for the initial decomposition of AP to accelerate and the ignition delay to be reduced under the more adequate α-Fe2O3 catalysis. Furthermore, the catalysis of α-Fe2O3 with a large contact area can further facilitate or control the oxidation of NH3 under various pressures or temperatures, influencing the decomposition of AP and enabling its regulation. This study therefore highlights the importance of understanding the catalytic properties of Fe2O3 for improving the performance of CSPs and optimizing their combustion behavior.