Ignition Delay Reduction with Sodium Addition to Imidazolium-Based Dicyanamide Ionic Liquid.

A range of ionic liquids (ILs) have been synthesized and modeled to better understand the role of the cation in the ignition of hypergolic ionic liquids. Vogelhuber et al. have shown by density functional theory methods that the addition of sodium cations to an ionic liquid promotes ignition with white fuming nitric acid (WFNA) by lowering energy barriers. To validate this prediction, solid sodium dicyanamide (Na+DCA-) was added at various weight percents to 1-butyl-3-methylimidazolium dicyanamide (BMIM+DCA-). The ignition delay was measured for each mixture with WFNA. Overall, it was found that the Na+DCA- lowered the ignition delay by 11 ms at 7 wt %. The calculations done by Vogelhuber et al. appear to be consistent with this observation. The sodium cation may play a role by orienting the anion with the WFNA resulting in the favorable reaction energetics observed.