Modulation of iron oxide-ammonium dinitramide (ADN) interface: enhancing catalytic decomposition and combustion for green propellants

Ammonium dinitramide (ADN), a promising green oxidizer for composite solid propellants, faces challenges like unstable low-pressure combustion and high burning rate pressure sensitivity. Introducing catalysts is an effective strategy to enhance the combustion performance of ADN propellants. In this study, iron oxide (Fe₂O₃) was incorporated into ADN particles to modulate their interface, effectively enhancing the contact area between them. Following the identification of its structural characteristics via morphological and elemental analysis, the ADN@Fe₂O₃ composite was incorporated into polyether binder-based propellant. Thermal decomposition tests indicated that the propellant containing ADN@Fe₂O₃ exhibited a lower decomposition temperature, a 10% increase in total heat release. Propellant combustion tests revealed the addition of ADN@Fe₂O₃ shortened the ignition delay time by 70%, increased the burning surface temperature from 450 to 550℃, enhanced the burning rate and lowered the pressure exponent from 0.86 to 0.68. Furthermore, the particle size of condensed combustion products decreased, while the α-Al₂O₃ content rose, indicating the more complete combustion of aluminum. Reaction path energy calculations showed that Fe₂O₃ reduced the energy barriers for rate-limiting steps during liquid-phase and gas-phase thermal decomposition of ADN by 28% and 75%, respectively. By modulation of interface, this study achieved highly efficient catalysis of the decomposition and combustion of ADN based propellant by Fe₂O₃. It also revealed the microscopic mechanism of the catalysis from theoretical perspective, providing new insights for controlling the thermal decomposition and combustion processes of energetic materials.