Study on Al powder explosion suppression mechanism of MCA@ADP-MMT composite

Abstract

To investigate the effectiveness of nitrogen-phosphorus-silicon composite in suppressing Al powder explosions, a nitrogen-phosphorus-silicon synergistic explosion suppressant, MCA@ADP-MMT, was prepared using montmorillonite (MMT), melamine cyanurate (MCA), and aluminum diethylphosphinate (ADP) as the raw materials and its suppression effect and mechanism were investigated experimentally and numerically. Results show a strong correlation between suppression efficacy and suppressant concentration. At 300 %wt, MCA@ADP-MMT effectively quenches Al powder explosions, reducing maximum overpressure (P_max) by 96.3 %, maximum pressure rise rate (dP/dt_max) by 99.8 %, and the average flame propagation speed reduced from 2.26 m/s (α = 0.25) to 0.88 m/s (α = 1). The scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analyses reveal the physical suppression mechanism. The solid flame-retardant products, such as phosphates and silicates, produced from thermal decomposition of the composite coat the Al powder surface, which blocks heat and oxygen transfer and exerts a physical suppression effect. CHEMKIN simulations reveal the chemical mechanism. The nitrogen-, phosphorus-, and carbon-containing small molecules from explosion suppressant decomposition function through multiple mechanisms. They reduce the oxygen availability in the combustion zone by dilution, lower the combustion temperature by absorbing heat, scavenge reactive O radicals in the flame and inhibit the generation of AlO radicals, thereby terminating the chain reaction. In summary, MCA@ADP-MMT effectively mitigates Al powder explosions at elevated concentrations. This suppression performance is attributed to the synergistic effects of physical isolation-where the refractory coating impedes oxygen and heat transfer and gas phase chemical inhibition that involves dilution of oxygen, radical scavenge, and temperature reduction.