Influence of copper compounds on the exothermic reactions of an ammonium dinitramide-based energetic ionic liquids

We have been developing an ignition system for small satellites that uses energetic ionic liquid propellant (AMU) containing ammonium dinitramide (ADN), monomethylamine nitrate (MMAN), and urea. In this study, we investigated the effect of adding copper compounds to AMU in promoting the exothermic reaction of AMU in the condensed phase and increasing its ignitability by heating. We found that 2 wt% of basic copper nitrate (BCN) can dissolve in AMU. We used differential scanning calorimetry, thermogravimetry-differential thermal analysis, and a digital microscope to observe the condensed-phase reactions of ADN/BCN, MMAN/BCN, urea/BCN, and AMU/BCN mixtures, and we analyzed the thermal behavior to investigate the influence of BCN on their exothermic reactions. Although BCN dissolved by forming a complex with MMAN, it did not affect the initial exothermic reaction of AMU. BCN promoted the exothermic reaction at high temperatures, and the gross calorific value of the condensed-phase reaction was increased. Hence, adding BCN can potentially improve the ignitability of AMU. The promotion of exothermic reactions was attributed to the decomposition of the copper complex to copper oxide, which promotes the exothermic reaction of MMAN and ammonium nitrate, resulting from the decomposition of ADN.