Ignition behavior of H2O2-based hypergolic ionic liquids promoted by non-metallic iodine-rich salts

The tunability of ionic liquids allows the cations and anions to play different roles, with the cations acting as fuel and the anions serving as catalysts. • Ionic liquid propellants are free of metals and can enhance the performance of the fuel. • The thermodynamic mechanism and ignition mechanism of ionic liquid iodine promoters were studied, providing a theoretical foundation for subsequent research. The H₂O₂-ILs spontaneous combustion propellant can solve the problems associated with traditional propellants, such as the toxicity, volatility and corrosive nature of oxidants. However, a long ignition delay time (IDT) has resulted in by the weak acidity and high latent heat of H₂O₂. This paper presents the synthesis of two non-metallic polyiodide promoters: 1,3-dimethyl-4,5-diiodoimidazolium iodide (P-1) and 1,3-dimethyl-4,5-diiodoimidazolium triiodide (P-2). The physical and chemical properties, as well as the combustion behaviour, of the two promoters when compounded with ionic liquid fuels (1-allyl-3-ethylcyanoammonium bromide ([AEIM][BH₃CN]) were studied. The IDT of the fuel system was reduced from 2870 ms to 90 ms (P-1, 15%) and 55 ms (P-2, 20%), respectively, after compounding the promoters. This improvement in ignition performance is primarily due to the promoter reducing the fuel's decomposition activation energy and the Gibbs free energy of the dehydrogenation reaction between hydrogen peroxide and H₃BCN anions in the fuel-H₂O₂ reaction. This study will inform the improvement of the performance of H₂O₂-ILs as spontaneous combustion propellants. Download: Download high-res image (141KB) Download: Download full-size image