Fourier transform infrared studies in hypergolic ignition of ionic liquids

A class of room-temperature ionic liquids (RTILs) that exhibit hypergolic activity toward fuming nitric acid is reported. Fast ignition of dicyanamide ionic liquids when mixed with nitric acid is contrasted with the reactivity of the ionic liquid azides, which show high reactivity with nitric acid, but do not ignite. The reactivity of other potential salt fuels is assessed here. Rapid-scan, Fourier transform infrared (FTIR) spectroscopy of the preignition phase indicates the evolution of N2O from both the dicyanamide and azide RTILs. Evidence for the evolution of CO2 and isocyanic acid (HNCO) with similar temporal behavior to N2O from reaction of the dicyanamide ionic liquids with nitric acid is presented. Evolution of HN3 is detected from the azides. No evolution of HCN from the dicyanamide reactions was detected. From the FTIR observations, biuret reaction tests, and initial ab initio calculations, a mechanism is proposed for the formation of N2O, CO2, and HNCO from the dicyanamide reactions during preignition.