Encapsulation of micron-scale aluminum with pluralistic magnetic metallic nanoparticles and its combustion performance

Aluminum (Al) is often used as a metal fuel in solid propellants, whereas Co, Fe and Ni are used as combustion rate catalysts in solid propellants. However, owing to the oxide layer on the surface of Al powder, which hinders its energy release, and Co, Fe, and Ni, the nanometal particle catalysts are prone to agglomeration because of their high surface energy and magnetic properties. Therefore, in this study, a new composite material [Ternary]/µAl was formed by coating Al particles with Co, Fe and Ni by a displacement reaction. On the one hand, the nanoparticle interfacial layer reduces agglomeration between Al particles, and on the other hand, the nanoparticle interfacial layer facilitates oxygen transport through the established oxygen transport channels. As a result, [Ternary]/µAl has superior heat release and catalytic properties. The experimental results showed that [Ternary]/µAl, as a novel catalytic material, significantly reduced the main thermal decomposition temperature of the binary oxidant AN/NP-1, with an activation energy required for the reaction of 120.1 kJ/mol, and led to intense combustion, resulting in a combustion pressure of 1.29 MPa and a combustion rate of 2.86 MPa/s, releasing more combustion heat than the sample. The theoretical calculation results show that the propulsion efficiency of [Ternary]/µAl + AN/NP-1 is relatively high, and the proportion of the main thrust sources H2 and CO is increased to 67.8%. Based on the results of the thermal analyses and combustion tests, a possible combustion mechanism for [Ternary]/µAl + AN/NP-1 composites was proposed. In conclusion, improving the overall performance of metal fuel/oxidizer composites by the formation of interfacial layers through substitution reactions is expected to have wider applications in solid propellants.