Combustion characteristics and mechanisms of highly ignition-sensitive Al-Si-Li/PTFE energetic materials in low-pressure environments

As aerospace technologies advance globally, the application fields of energetic materials have expanded from ground and near-ground levels to high altitudes. The decrease in ambient pressure associated with increasing altitude significantly affects the ignition reliability and stable combustion of energetic materials. In this study, an Al-Si-Li/PTFE energetic material system was prepared via a film-coating process, and its ignition reliability and combustion characteristics under low-pressure environments were investigated. Its potential combustion mechanisms were analyzed using characterization techniques including TG-DSC, SEM, XRD, and XPS. The results demonstrate that the high-activity characteristic of Li effectively improves the ignition sensitivity of the alloy fuel. Compared to Al/PTFE and Al-Si/PTFE energetic systems, the ignition success rates of Al-Li/PTFE and Al-Si-Li/PTFE energetic systems reached 90% and 100%, respectively, under identical external stimulus conditions. At a pressure of 1 kPa, the mass ratio of the Al-Si-Li alloy to PTFE is also a critical factor affecting the combustion characteristics of the system. Compared with other Al-Si-Li/PTFE formulations, the sample with a 6:4 mass ratio exhibited the highest combustion temperature (1191 °C) and the largest flame area. Furthermore, ambient pressure significantly influences the combustion temperature and burning rate of the Al-Si-Li/PTFE energetic system. Under a 0.5 kPa condition, the system exhibited the lowest combustion temperature (982 °C) and the slowest linear burning rate (< 0.1854 cm/s). In low-pressure environments, the Al-Si-Li/PTFE energetic material system enhances its combustion performance primarily through solid-solid phase reactions, showing promising application potential in energetic material fields such as propellants, pyrotechnics, and thermites.