Mechanism study on enhancing the combustion performance of aluminum with polyvinylidene fluoride

Abstract

As a key metal fuel in high-energy solid propellants, the improvement of the combustion efficiency of aluminum (Al) is the focus of current research. In order to optimize the combustion performance of Al, polyvinylidene fluoride (PVDF) was used as a surface modifier in this study to modulate the combustion process of Al at the atomic scale by taking advantage of its unique high exothermicity and controllable fluorine-release properties. This study elucidates the molecular-level synergistic combustion mechanism in Al/PVDF systems using multiscale simulation approaches. By integrating quantum chemical calculations with reactive molecular dynamics, the interfacial reaction network between the PVDF thermal decomposition products and the Al oxide layer is systematically resolved. Specifically, Gaussian 16W calculations at the B3LYP/6-311+G(3d,2p) level demonstrate that PVDF-derived hydrogen fluoride (HF) molecules selectively capture the bridging oxygen atoms in Al₂O₃via a dual-step synergistic mechanism, resulting in a three-fold increase in the porosity of the oxide layer. Transition state theory analysis identified the rate-determining steps for the HF/AlO and HF/Al₂O₃ reactions, while bond order analysis quantitatively revealed the fluorine-induced Al–O bond cleavage mechanism. These insights facilitate in-depth analysis of the fluorine-catalyzed oxide stripping mechanism through thermodynamic parameter optimization. These findings not only establish a constitutive model for PVDF-modified Al combustion but also promote a research paradigm for tailoring metal combustion performance via molecular interfacial engineering.