Preparation of high-energy Al-Li alloy powders with enhanced compatibility and combustion performance by dense fluorosilane polymer composite coating

The superior combustion heat, lower ignition temperature, and enhanced combustion efficiency of aluminum–lithium (Al-Li) alloy powders have garnered significant research attention in relation to Al powders. However, the inadequate compatibility between Al-Li alloy powders (especially when Li > 3 wt%) and propellant components limits its application in the development of composite solid propellants. This study focuses on the surface-coating active Al-4.3Li (wt.%) alloy powder using a composite fluorosilane coupling agent to improve compatibility and combustion performance. A coating layer with a thickness of 30–40 nm was successfully formed on the surface of Al-4.3Li alloy powder through interactions involving Al-F, Al-O-Si, and Li-O-Si bonds, thereby achieving remarkable hydrophobicity. The heat release increased by 7.5 %, while the ignition delay time of the alloy powder decreased by nearly 200 ms, resulting in a significantly enhanced combustion performance in relation to that of the original Al-4.3Li alloy powder. Moreover, the modified Al-4.3Li alloy powder exhibited better compatibility, and no cracks or bubbles were observed in the cross-section of the propellant containing modified Al-4.3Li metal fuel. This study provides an effective approach for utilizing Al-Li alloy powders in solid propellants, which is of great significance for the development of high-energy propulsion systems.