Preparation and combustion properties of Al–Li alloy particles with enhanced stability and compatibility via in situ polymerization

Al–Li alloys are considered promising materials in solid propellants owing to their higher combustion efficiency than Al particles, which exhibit incomplete combustion. However, Al–Li alloy particles cannot be directly applied in propellant systems owing to their poor compatibility. Thus, in this work, an in situ polymerized film was formed via the pretreatment of Al–Li alloy followed by polymerization with trifluoroethyl methacrylate (TFEMA) and N,N′-methylene-bis-acrylamide (MBA). The hydrothermal stability of the coated samples was improved with a mass variation rate of 5.82% on treatment with TFEMA (30%) and MBA (10%), corresponding to 116.62% of Al–Li at 60 °C and 75% humidity for 30 days. Besides, the thermostability increased based on the 19° backward skewing of the high temperature exothermic peak. Meanwhile, there were no pores and cracks in the HTPB propellant, which proved the possibility of its practical application with the compatibility of level 1 with HTPB in solid rocket motors. In addition, the Al–Li propellant exhibited a better combustion performance of 0.53 s and 1309.33 °C than the Q3 Al propellant, with 1.34 s ignition delay time and 990.24 °C burning temperature. The combustion efficiency was also improved based on the observation of combustion phenomena and residue size. Besides, the combustion mechanism was analyzed based on the characteristics of Al–Li with the micro-explosion effect. Therefore, Al–Li alloy has the potential to be used as a new generation solid propellant.