Low−temperature fabrication of highly reactive Al–Li alloy powders with enhanced HTPB compatibility and improved propellant combustion performance

Aluminum–lithium (Al–Li) alloy powders exhibiting the micro–explosion phenomenon are promising energetic additives for solid propellants. However, their high surface reactivity, particularly due to lithium (Li), leads to poor compatibility with binder components, thereby hindering practical application. Importantly, low−temperature reaction conditions slowed the reaction rate, helping to preserve the active components of Al–5Li powder during its modification with dichlorodimethylsilane (DCDMS) via a Li–induced low−temperature Wurtz–type reaction, which resulted in in–situ polymerization and formation of LiCl. Residual Si–Cl groups reacted with surface hydroxyls, generating trace HCl that removed native passivation layers (e.g., Li₂CO₃) and produced additional LiCl, while low–temperature enhanced DCDMS adsorption and limited surface species consumption, promoting formation of a dense chlorosilane coating encapsulating part of the LiCl. The modified Al–5Li@DCDMS powders showed good compatibility with hydroxyl–terminated polybutadiene (HTPB) and, compared with conventional Al–based HTPB propellants, exhibited pronounced micro–explosion behavior, with a 6.84 % higher burning rate and a 43.90 % shorter ignition delay. This work offers a viable surface passivation strategy and demonstrates the application potential of Al–Li alloy powders in advanced solid propellant systems.