Influence of Alumina Crystal Phases on the Combustion Dynamics of Al Particles

In this study, reactive molecular dynamics simulations based on the ReaxFF force field were employed to systematically investigate the microscopic regulatory effects of three major crystalline phases of alumina (αθ, and γ) on the combustion behavior of Al particles. By constructing Al core-shell models coated with different crystal forms of Al2O3 and simulating the combustion process in an oxygen-rich environment, we analyzed the evolution of several key indicators, including reactant diffusion, transition state formation time, the number of final agglomerated particles, and the composition of combustion products. The results show that γ-Al2O3, due to its loose structure, exhibits the best performance in promoting combustion reactions, characterized by the shortest transition state formation time (1346 ps) and the largest amount of final reaction products. In contrast, α-Al2O3, with its dense structure, significantly hin-ders oxygen permeation and Al atom mobility, thereby limiting the combustion process. Furthermore, experimental validation confirmed that Al particles coated with γ-Al2O3 produced larger and brighter flames during combustion, in good agreement with the simulation results. This study highlights the critical role of alumina crystalline phase in regulating Al combustion kinetics and provides theoretical insights and materials design guidance for the performance enhancement of A1-based propellants.