The interface bonding strengthening enhancement of Al-Li alloy powders with dual-layer coating of composite fluorosilane polymers and PDA

Al-Li alloys are promising fuels for composite solid propellants due to their high energy density and favorable combustion characteristics. However, their application is limited by poor storage stability and inadequate interfacial adhesion. This study presents a novel dual-layer synergistic coating strategy using fluorinated alkylsilane (FAS) and polydopamine (PDA) to improve the interfacial stability of Al-Li alloys and the mechanical performance of Al-Li alloy-based propellants. The Sequential chemical deposition of FAS hydrophobic layer and PDA adhesive layer onto Al-5Li alloy particles was successfully accomplished and uniformly covered. The interfacial adhesion and wettability are increased by introducing catechol groups, which addresses the problems caused by FAS coating. Thermal analysis revealed negligible weight loss (≤0.191 %) from organic coating decomposition, indicating minimal impact on energy density. Mechanical testing showed that the fracture stress of propellants containing Al-5Li@FP particles was significantly improved to 1.593 MPa, and even surpassed those with pure aluminum, which was 1.263 MPa. Combustion experiments further showed a significant enhancement in the burning intensity of the modified alloy powders. This study achieves synergistic improvement of stability and interfacial adhesion in Al-Li alloys via a rationally designed PDA and FAS bilayer interface. Thereby offering an innovative pathway for developing high-performance solid propellants.