Low-cost mesoporous SiO2 enables enhanced combustion and energy release in Al-Mg/AP energetic composites

Inert silica is repurposed as a potent modifier for Al-Mg/AP energetic composites. • 5 wt% SiO 2 reduces ignition delay by 35% and increases maximum flame area by 226%. • Optimal SiO 2 loading boosts pressurization rate by 126% in closed vessel tests. • 9 wt% SiO 2 reduces AP decomposition activation energy by 78 kJ/mol. Silica (SiO 2 ) is generally regarded as a chemically inert and low-cost material that is widely present in natural minerals and daily life. In conventional energetic formulations, SiO 2 is rarely considered an active component because of its high thermodynamic stability and low thermal conductivity. Herein, we demonstrate that mesoporous SiO 2 can serve as an effective reactive additive in Al-Mg/ammonium perchlorate (AP) energetic composites, participating in high-temperature aluminothermic reactions and regulating the overall energy-release behavior of the system. In this work, AP/SiO 2 precursor particles were prepared by spray drying, followed by solvent-assisted assembly with Al Mg alloy powder to obtain Al-Mg/(AP/SiO 2 ) composite energetic materials with different SiO 2 contents. The morphology, phase structure, combustion behavior, pressure output, thermal decomposition characteristics, evolved gaseous products, and post-combustion residues were systematically investigated using SEM, EDS, XRD, high-speed imaging, infrared thermography, closed-bomb pressure testing, TG-DSC, and TG-IR analyses. The results reveal that the introduction of mesoporous SiO 2 markedly alters the decomposition behavior of AP, promotes gas evolution, enhances ignition and combustion propagation, and modifies the condensed-phase reaction pathway of the Al-Mg/AP system. These effects are attributed to the combined roles of mesoporous confinement, surface silanol-assisted AP decomposition, local hotspot formation, and the participation of SiO 2 in aluminothermic reactions. This study provides new insight into the unconventional role of inert oxides in energetic combustion systems and offers a low-cost strategy for designing alternative multifunctional reactive additives and regulating energy-release mechanisms in metal-based energetic materials. Download: Download high-res image (182KB) Download: Download full-size image