The development of green, high-performance hypergolic fuels as alternatives to toxic hydrazine derivatives remains a critical challenge for next-generation liquid propulsion systems. In this study, a low-cost synthesis of dicyanamide-based hypergolic ionic liquid (HIL) was developed via a metathesis reaction between 1-allyl-3-methylimidazolium chloride and sodium dicyanamide in acetonitrile, eliminating the need for expensive silver salts while maintaining high purity. The cost of raw materials was 95.47% lower than that of conventional synthetic route. A series of blend fuels comprising 1-allyl-3-methylimidazolium dicyanamide (AMImN(CN) 2 ) and triethylamine-borane complex (TEAB) with varying TEAB volume contents (5%, 10%, 15%, 20%, and 25%) were prepared, and their hypergolicity and combustion characteristics with white fuming nitric acid (WFNA) were systematically investigated using a self-developed dual-droplet test. The results revealed that increasing TEAB content progressively shortened the ignition delay time ( t id ), with a minimum of 20 vol% TEAB required to achieve t id < 50 ms for practical engine applications. TEAB’s combustion promoted AMImN(CN) 2 ’s sustained combustion, requiring at least 15 vol% TEAB for sufficient combustion of the AMImN(CN) 2 component. Taking into account hypergolicity, combustion characteristic, raw material cost, and physicochemical properties, the blend fuel containing 20 vol% TEAB was identified as the optimal formulation. Compared to unsymmetrical dimethylhydrazine (UDMH), this optimal blend fuel offered higher density (1.06 g/cm 3 ), wider liquid range (< −80 to 252°C), and superior density-specific impulse (357.95 s·g/cm 3 ), demonstrating its potential as a promising green alternative for hypergolic propellant fuels.
Guo et al. (Fri,) studied this question.