Synthesis of trifluoroacetic acid encapsulated aluminium nanoparticles and reactivity characterisation via Al/CuO nanothermites.

This paper reports on the synthesis of aluminium nanoparticles (Al NPs) encapsulated with a trifluoroacetic acid (TFA) protective layer and the characterisation of their reactivity using Al/CuO nanothermite as a test platform. The Al NPs were synthesised via a wet chemistry process based on aluminium precursor reduction under oxygen-free conditions, and subsequently coated with TFA to prevent oxidation. The TFA-coated Al (Al@TFA) NPs were found to have an average diameter of 50 nm with a 2.5 nm thick protective coating, without detectable aluminium oxide by X-ray diffraction. Thermal analysis showed TFA decomposition below 500 °C and vigorous Al oxidation starting around 600 °C. To assess reactivity, Al@TFA/CuO nanothermite powder was prepared by physically mixing the Al@TFA NPs with CuO nanoparticles. Differential scanning calorimetry results exhibited the typical exothermic solid-solid thermite reaction peak at 617 °C as well as an additional exothermic peak shifting to a higher temperature of 844 °C, likely due to endothermic AlF3 sublimation. High-speed imaging of combustion in tubes showed initial slow reaction propagation at tens of m s-1 followed by an abrupt transition to over 100 m s-1, reaching 210 m s-1 at a thermite mixture equivalence ratio of 1.6. The results demonstrate TFA-encapsulation as a viable approach for producing aluminium nanoparticles with a fluorinated protective layer, and the nanothermite characterisation confirms their promising reactivity.