Ultra-low ignition delay conjoined with high thermal stability borohydride hypergolic fuels: Synthesis, combustion characteristic, and decomposition mechanism

Hypergolic fuels are a research hotspot in rocket propellant studies. Among numerous hypergolic fuels, octahydrotriborate (B 3 H 8 − ) based salts exhibit outstanding ignition performance. This study proposes a novel synthetic route for B 3 H 8 − anion-based hypergolic salts. The samples were comprehensively characterized using NMR, infrared (IR) spectroscopy, and mass spectrometry, and their physicochemical properties, such as density and viscosity, were measured. All these salts showed good thermal stability and high specific impulse ( I sp ), the highest decomposition temperature and specific impulse are 235.2 °C and 298 s, respectively. Their combustion characteristics were investigated under multiple ignition modes, including chemical ignition method and laser ignition method, and all of them show superior low ignition delay times (< 3 ms) when connect with oxidant. Sample 1 demonstrated an extended combustion duration (1860 ms) in the laser ignition experiment. In addition, the decomposition mechanism of the sample under different working conditions was also studied using a combination of experimental and molecular dynamics (MD) simulation methods. Notably, certain samples achieved excellent performance in both chemical and laser ignition tests, indicating their adaptability to diverse ignition scenarios. • New synthesis method for [B 3 H 8 ] − based hypergolic fuels. • All samples have ultra-low ignition delay conjoined with good thermal-stability. • The combustion characteristics were investigated under multiple ignition modes. • The decomposition mechanism under different conditions was decoded.