The reaction mechanism of Al NPs/PVDF high energy fuel: A ReaxFF MD and DFT study meshing together laser-ignition experimental verification

Aluminum nanoparticles (Al NPs) with the high energy can be used in rocket propulsion, but the propellant performance will be limited by the easy agglomeration property. The surface modification of Al NPs by polyvinylidene fluoride (PVDF) can inhibit their agglomeration and improve their combustion efficiency. However, there is a lack of essential understanding of the microscopic reaction mechanism of PVDF to promote the combustion of Al NPs. Hence, the oxidation and combustion processes of Al NPs/PVDF were investigated by using reactive molecular dynamics (RMD) simulations and density functional theory (DFT) calculations. Moreover, the combustion performance of Al NPs/PVDF was examined by laser ignition experiments. In the oxidation of Al NPs/PVDF, the PVDF is decomposed by the catalytic action of Al NPs. The dissociated F atoms react with the oxide shell to form AlxOyFz species, which elucidates the mechanism of the pre-ignition reaction of Al NPs with PVDF at the microscopic level. In the combustion of Al NPs/PVDF, the increase in PVDF content and temperature is favorable to the consumption of Al NPs. The experimental results also verify that the addition of PVDF can significantly enhance the combustion performance of Al NPs. These results reveal the promotion effects of PVDF on Al NPs in the ignition and combustion process at the atomic level and the macroscopic perspective, and lay the theoretical foundation for the early application of Al NPs/PVDF in propellants.