Enhancement of the ignition and combustion performance of nano-aluminum: the effect of cryolite

To study the effect of cryolite (Na₃AlF₆) on the ignition and combustion performance of nano-aluminum (n-Al), composites of n-Al with varying amounts of Na₃AlF₆ were prepared by physical mixing. By using TG–DSC–MS, TG–DTA, SEM–EDS, XRD, and a high-speed camera, the thermal characteristics, activation energy, ignition delay time, combustion phenomena, and reaction products of the materials were examined. The results show that there was a pre-ignition reaction between n-Al and Na₃AlF₆. The exotherm was roughly double that of n-Al after the addition of Na₃AlF₆. The n-Al gas–solid reaction had lower activation energy. The ignition and combustion tests reveal that Na₃AlF₆ decreased n-Al's ignition delay time to 50 ms, whereas an excess of Na₃AlF₆ had a negative effect. The n-Al with the Na₃AlF₆ addition displayed more violent combustion events during combustion. Analysis of the reaction products demonstrates that Na₃AlF₆ reacted with Al₂O₃ to generate aluminum oxyfluoride complex ions, which then reacted with Al₂O₃ to form Na₂Al_2xO_3x+1 (Na₂Al₂₂O₃₄) and AlF₃. The addition of Na₃AlF₆ effectively enhanced the ignition and combustion performance of n-Al, which is beneficial to the optimization of Al-based energetic nanocomposites. Graphical Abstract: Nano-aluminum with varying additions of cryolite was prepared by physical mixing, and the effect of cryolite on the ignition and combustion performance of nano-aluminum was analyzed [Figure not available: see fulltext.]