Thermal reaction properties of aluminum/iron fluoride nanothermites

The composite powders of nanoscale aluminum (n-Al) and iron fluoride (FeF3) were prepared by an ultrasonic mixing method. The microscopic morphology was examined by scanning electron microscopy, the crystalline phase structure was analyzed by X-ray diffractometer, and extensive thermal analysis of the single components and composites was carried out, focusing on the thermal reaction properties of n-Al/FeF3. The reaction process and pre-ignition reaction of the complexes were investigated by characterizing the reaction products of n-Al/FeF3 and Al2O3/FeF3 at certain temperatures. Finally, the apparent activation energy of the thermite reaction of n-Al/FeF3 was determined using the Ozawa method, the Flynn method, and the Starink method. Under an Ar environment, n-Al/FeF3 could react at a lower temperature (613.8 ℃) and give off more heat (1097.0 J g−1) compared with n-Al/Fe2O3. In the air environment, n-Al/FeF3 also showed a lower reaction temperature (509.7 ℃). N-Al could be totally oxidized at a lower temperature with a higher degree of reaction, although the reaction heat release (1477.6 J g−1) was lower than that of n-Al/Fe2O3 (2692.5 J g−1). A pre-ignition reaction occurred before the main reaction of n-Al/FeF3, but no evident exothermic peaks were found in the thermal analysis. The activation energies of exothermic peaks 1 and 2 for n-Al/FeF3 were 113.79 kJ mol−1 and 185.45 kJ mol−1, respectively, slightly higher than those of n-Al/Fe2O3. The study results reported in this work provide a certain reference for the in-depth research and application of the n-Al/fluoride thermite system, as well as fresh ideas for the development of novel nanothermite materials.