Mechanochemical grafting polymerization of fluorinated thioctic acid towards high-performance aluminum fuels

Aluminum powder is widely used in solid propellants due to its high energy density, but the formation of the aluminum oxide layer on its surface limits its ignition and combustion efficiency. To address this issue, we designed and synthesized fluorinated lipoic acid monomers (FTA-3/7) and mechanically induced their in-situ polymerization to form a uniform coating on the surface of aluminum powder. The uniformly distributed and abundant F atoms within the FTA polymer, on one hand, contribute to the formation of Al-F coordination bond with the aluminum powder, further enhancing the adhesion between the polymer and the aluminum powder. On the other hand, the F atoms improve the ignition, combustion, and water resistance of the aluminum powder. The coated aluminum powder (Al@PFTA-3) exhibited 66.7% increase in emission spectral intensity and 399% increase in heat of combustion compared to pure aluminum. Additionally, the emission intensity of the solid propellant with Al@PFTA-3 increases by 2.4 times compared to the original, with a 20% reduction in self-sustaining combustion time, while its pressure index is lower than that of typical benchmark propellants. This method provides a simple and effective approach to improving the reactivity and stability of aluminum powder, while enhancing its performance in solid propellants.