Enhancing nano-thermite performance: Iron oxyfluoride (FeOF) as a novel oxidizer

Nano-thermite technology stands as a pivotal domain within the field of energetic material research. This study is to explore the innovative utilization of oxyfluorides as oxidants in thermites. High-purity FeOF was synthesized through a solvothermal approach and subsequently physically blended with aluminum (Al) to formulate a novel Al/FeOF nano-thermite. To shed light on the underlying reaction mechanisms, we conducted a comparative analysis of the thermal properties, activation energies, and combustion performances of the Al/FeOF nano-thermite against control samples, namely Al/Fe₂O₃, Al/FeF₃, and Al/Fe₂O₃/FeF₃. Under an air atmosphere, the heat release results revealed that the Al/Fe₂O₃ system released 2692.5 J·g⁻¹ of heat, while the Al/FeF₃ system released 1477.6 J·g⁻¹ . The heat release of the Al/Fe₂O₃/FeF₃ system further decreased to 1030.9 J·g⁻¹ . In stark contrast, the heat release of the Al/FeOF system significantly increased to 3011.9 J·g⁻¹ , highlighting a substantial difference among these systems. These findings imply that during the reaction process, there exists a competitive relationship between the independent metal oxide and metal fluoride. Conversely, when oxygen and fluorine coexist within the same material (FeOF), a distinct synergistic effect becomes evident. Analysis of the onset reaction temperatures demonstrated that the Al/Fe₂O₃ system initiated the reaction at 539.2 °C, the Al/FeF₃ system at 463.8 °C, the Al/Fe₂O₃/FeF₃ system at 572.6 °C, and the Al/FeOF system at 547.9 °C. These suggest that the co-presence of O and F reduces the competitive influence typically observed between fluorides and oxides. Moreover, the Al/FeOF system exhibited the lowest activation energy (170.57 kJ·mol⁻¹), the shortest ignition delay (15.3 ms), and the briefest combustion time (59.7 ms). These superior characteristics underscore its exceptional thermal stability and combustion performance.