Regulating magnesium combustion using surface chemistry and heating rate

The magnesium (Mg) particle surface can be used to regulate fluorination or oxidation reactions depending on the applied heating rate and Mg size. Magnesium particles are surrounded by a complex hydroxide shell composed of an inner layer oxide (MgO) outer (Mg(OH)2). As approach nanoscale, thick (e.g., 22 nm) becomes appreciable portion overall powder exploited reactivity. In this study, reactivity 800 nm (nMg) was compared 44 µm (µMg) when combined with Perfluoropolyethyer (PFPE), providing both fluorine oxygen for reactions. Experiments were performed at slow rates (10 °C/min) separate experiments fast (6.0 × 105 °C/min). studies differential scanning calorimeter (DSC) thermogravimetric (TG) analyzer examine reaction kinetics. faster hot wire ignite thermal run-away reaction. Powder X-ray diffraction (XRD) analysis recovered residue various temperatures corresponding exothermic events in DSC revealed pathways nMg + PFPE favoring For powders, Mg(OH)2 dehydrates low (313 °C) creating highly reactive sites condensed phase leading higher conversion MgO greater consumption through µMg, dehydration (498 stabilize µMg bulk occur elevated gas producing MgF2 concentrations. Under high conditions, formation is favored over sizes owing that promote formation. Theoretical using density functional theory (DFT) cluster models surfaces further show more species than MgO, especially temperatures. DFT results help explain pathway favors independent