Surface fluorination of n-Al particles with improved combustion performance and adjustable reaction kinetics

Abstract Surface composition plays a crucial role for the energy output performance of nanosized aluminum (n-Al) based metallic fuels. However, effective surface modification strategy with integrated functions and mild preparation conditions remains being exploited. Herein, a polydopamine fluoride (PF) coating was successfully constructed by covalent decoration of polydopamine (PDA) with thiol-terminated organic fluoride for surface engineering of n-Al under ambient conditions. The uniform coating of PF shell on the n-Al surface enabled the Al@PF composites optimized contact area between reactive components (Al and F). Concomitantly, the generation of fluoride gaseous species from PF coating facilitated the mass transport and self-activation of n-Al particles. It resulted in a substantially enhanced burning rate (196.4 mm s−1), which is 8.1 and 3.6 times than that of pristine n-Al (24.2 mm s−1) and physically mixed samples (54.7 mm s−1), respectively. Additionally, the reaction kinetics could be readily adjusted by tailoring the diffusion distance of reactants, as exhibited by varied heat release (0.24–1.43 kJ g−1), ignition delay (79–427 ms), and pressurization rate (6.3 × 101–2.3 × 103 kPa s−1). On this basis, the surface reaction mechanism was further clarified by combining theoretical simulation and experimental results. The current study provided a general approach for improving combustion performance and modulating reaction kinetics of advanced energy materials by elaborate surface design.