Comprehensive study on nanosized NiF₂ in Al based energetic composites for enhanced reactive performance

Aluminum powder is widely used as a high-energy fuel in the domain of energetic materials, while the oxidation kinetics of Al is limited by the oxide shell on the particle surface which acts as a reaction barrier. Recently, transition metal fluorides have emerged as an intriguing type of fluorine-containing oxidizers which can improve reactivity of Al through interfacial fluorination. However, most previous research focused on micron-sized fluorides, while the reactivity of nanosized fluoride in energetic composite was rarely studied. In this work, nanosized NiF₂ (∼100 nm) was synthesized through a facile and safe approach, and it was coupled with nanosized and micron-sized Al powders to form energetic composites. Regardless of dimension of Al, Al/NiF₂ composite exhibited higher specific heat release, higher reaction efficiency, and lower reaction temperature than that of corresponding Al/NiO composite. Post-characterizations suggested that elemental Ni and AlF₃ were produced from the reaction of Al/NiF₂ composite at 710 °C, and AlF₃ was found to evaporate over 900 − 1050 °C. The long-term stability of energetic composites was evaluated through a real-time aging test for 12 months, and only slight energy degradation (<7.5 %) was founded in Al/NiF₂ composite. Concerning combustion behavior, Al/NiF₂ composite showed relatively low flame brightness but a comparable pressure generation compared to Al/NiO composite, which is presumably attributed by the endothermic evaporation of AlF₃. A notable finding is that hybrid Al/NiF₂/NiO composite exhibits superior pressure output, and this composite is rather explosive even for small charge amount, which shows the potential as a novel primary explosive. © 2024 Elsevier Ltd