Inhibition mechanisms of CO2/Polydimethylsiloxane on ignition and combustion of nano-sized aluminum particles

Aluminum nanoparticles (ANPs) are promising energetic materials owing to their high energy density and advanced reactivity, but they are also prone to explosion. In this study, a polydimethylsiloxane-containing dry-water suppressant (PDMS@DW) is prepared, and the inhibitory effects of CO 2 and PDMS on ANP oxidation and explosion are evaluated using thermal analysis and dust-explosion experiments. The particle-surface reaction inhibition mechanism is elucidated by ReaxFF MD simulations. The experiments show that PDMS@DW significantly weakens oxidation heat release, increases the apparent activation energy, and delays the oxidation process, while the introduction of CO 2 or PDMS@DW markedly reduces both maximum explosion pressure and pressure rise rate. ReaxFF MD results reveal that CO 2 and PDMS suppress the formation of an oxygen-rich, negatively charged environment on the outer surface of the Al 2 O 3 -shell, thereby inhibiting the thermal diffusion of shell-O and core-Al atoms towards the inner shell interface, ultimately slowing down the melting of the Al-core. Based on the temperature rise rate, ANP combustion in O 2 /CO 2 atmospheres is partitioned into surface combustion, slow combustion and self-sustaining combustion. Surface combustion is identified as the dominant phase responsible for overpressure generation during ANP explosions. Atomic displacement analysis indicates surface combustion is governed primarily by reactions between external-O and both shell-Al and exposed core-Al atoms. CO 2 most effectively suppresses this critical stage. In contrast, PDMS promote the formation of a C/Si-containing coating on the particle surface, enabling inhibition throughout the entire combustion process; hence, ANPs in CO 2 /PDMS mixed systems do not enter the self-sustaining combustion stage within the same timescale. Novelty and significance statement This work employs ReaxFF MD simulations to investigate the ignition and combustion of ANP in CO 2 /PDMS atmosphere, revealing the critical stage and atomistic mechanisms associated with overpressure formation in nano-Al dust explosion. The simulation results are qualitatively supported by the experimental observations. The study clarifies the apparent dual behavior of CO 2 —enabling self-sustained combustion of ANP while simultaneously suppressing dust explosions—and, for the first time, reveals the suppression mechanisms of ANP ignition and combustion at the atomic scale. The research methodology and insights presented herein provide a theoretical foundation for the rational design of advanced dust explosion suppression materials.