Fabrication and mechanistic study of AP/nAl/PTFE spherical encapsulated energetic materials with enhanced combustion performance

In this study, the evaporation induced self-assembly (EISA) method was used to encapsulate nano-sized aluminum (nAl)/polytetrafluoroethylene (PTFE) into ammonium perchlorate (AP) to form isolated encapsulated units with size distribution of 1–5 μm. The encapsulated AP/nAl/PTFE composites exhibited a higher combustion heat release (20109.2 J g⁻¹ in 3 MPa O₂ and 11137.2 J g⁻¹ in air), shorter ignition delay time (25.0 ms) and burning time (31.0 ms) than physically-mixed ones (18348.5 J g⁻¹ and 10595.6 J g⁻¹, 62.5 ms and 32.5 ms). Among all of the prepared composites, AP/nAl/PTFE with 15 wt% PTFE showed the optimum combustion performance. The Al₂O₃ shell of nAl could be efficiently etched by the in situ formed acid and F gases from AP and PTFE decomposition, which led to cracks and holes to release more active Al. The more intimate interaction, shorter diffusion length and more active Al release contributed to the enhanced combustion performance of AP/nAl/PTFE.