Wettability and flame retardancy of functionalized ionic liquids with magnesium powder

This study explored the effects of the following ionic liquids (ILs) on the wettability, flame retardancy, and explosion hazards of Mg particles: [EMIM]EtOSO₃ (EE), [BMIM]CF₃SO₃ (BC), and [BIM]BF₄ (BB). For 10 wt% BC, 20 wt% BC, and 20 wt% BB aqueous solutions, the contact angles of wetted Mg powder were 16 %, 44.2 %, and 29 % lower, respectively, than those for powder wetted with deionized water. The corresponding reductions in surface tension were 41.48 %, 47.5 %, and 32.9 %, respectively. The ILs enhanced water–Mg compatibility. Scanning electron microscopy and energy-dispersive X-ray spectroscopy revealed that the ILs caused substantial Mg particles agglomeration. Thermogravimetric, minimum ignition temperature, and X-ray diffraction tests showed that increasing the IL mass ratio resulted in better oxidation combustion suppression, confirming the high flame retardancy effect of the ILs. 20-L Apparatus with a Schlieren meter and high-speed camera were used to investigate Mg powder combustion; the addition of ILs greatly decreased the maximum explosion pressure (P_max) and maximum rate of pressure rise. P_max was 16.9 %, 64.8 %, and 43.7 % lower than that for untreated Mg. The Mg–IL mixtures exhibited irregular and discontinuous flames in early stage combustion. BC had the highest explosion suppression performance; at an Mg/BC mass ratio of 20:1, the explosion was completely suppressed. BB was superior to EE. The results indicate that BC is promising as a safe and efficient suppressant for Mg dust explosions.