Novel interfacial antisolvent crystallization strategy to synthesize spherical ammonium perchlorate assemblies and investigate their thermal decomposition properties

Abstract

Ammonium perchlorate (AP) is an extensively used solid propellant oxidizer. Controlled synthesis of spherical AP microstructures has always been a significant challenge. In this work, a novel interfacial antisolvent crystallization strategy was described to regulate the AP morphology, and spherical AP assemblies were successfully achieved. In this study, N-methylpyrrolidone (NMP) served as the solvent, and oleic acid (OA) as the antisolvent whose high-viscosity can restrict the diffusion rate to temporally stabilize the AP–NMP microdroplets. Small AP cubes recrystallized at the surface of metastable NMP microdroplets, and ultimately self-assembled into spherical hollow AP assemblies. Under the optimized conditions, the obtained spherical hollow AP assemblies had a narrow particle size distribution in the size range of 20–30 μm, and were constructed from a monolayer of cubic AP subunits whose diameter is 1–2 μm. The low-temperature decomposition (LTD) temperature of the spherical AP assemblies increased by 5 °C, whereas the high-temperature decomposition (HTD) temperature decreased by 22 °C. The temperature difference (ΔT) between the LTD and HTD significantly decreased to 128 °C compared with that of the raw AP at 155 °C. The decomposition of the spherical AP assemblies shows a faster decomposition rate and more concentrated exothermic process. The proposed interfacial antisolvent crystallization strategy is an efficient method to synthesize spherical AP assemblies.