Effect of Structure on the Initiation and Ignition Chemistry of Energetic Ionic Liquids

Abstract

Abstract : Ionic liquids are being explored in the search for advanced propellants that provide higher performance and lower environmental impact than traditional propellant systems. Because of the flexibility in designing ionic liquids, both mono-propellants and bi-propellants are being pursued. A family of bipropellant ionic liquids that react hypergolically with white fuming nitric acid was recently synthesized. The overall goal of this research program was to contribute to the fundamental understanding of the ignition of energetic ionic liquids by determining the effects of cation and anion structure on initiation reactions, and subsequent reactions leading to ignition, for representative compounds in three classes: amino-1,2,4 triazoles, amino-1,2,3-triazoles, and amino-tetrazoles. In order to achieve this objective, experiments were performed to determine the decomposition species and their temporal evolution over a range of temperatures. To gain further insight into the mechanism of decomposition, simplified kinetic models were formulated and overall kinetic parameters were derived. The second major research objective was to contribute to the understanding of the hypergolic reaction mechanism for the dicyanamide-based ionic liquids. Experimental results are reported for the species produced during hypergolic ignition as well as for the detection of a postulated key intermediate, dinitrobiuret.