Combustion behavior and mechanism of levitated single MgB2 particles in air

Abstract

Abstract

Simultaneous decomposition and oxidation of MgB 2 strongly influence its combustion behavior and energy release efficiency, yet the detailed mechanism at the single-particle level remains insufficiently understood due to the lack of high-resolution diagnostics. In this work, the combustion of individual micrometer-sized MgB 2 particles was investigated using an electrodynamic levitator combined with high-speed microscopic imaging, with a calibrated object-plane sampling interval of 0.70 μm/pix. Results showed that MgB 2 particle combustion proceeds through three distinct stages associated with sequential decomposition and oxidation of Mg–B intermediate phases. Four combustion modes were identified: single-stage combustion, micro-explosion, and two types of three-stage combustion. Evaporation analysis further shows that the oxidation of boron-rich phases is diffusion-controlled. High-resolution observations reveal previously unobserved phenomena, including particle expansion, localized rupture and self-healing of the oxide layer, and a transient BO 2 -induced green flash marking the transition to the final combustion stage. These findings provide new insight into the role of magnesium in boron combustion, showing that magnesium improves the combustion process of boron, specifically through the promotion of the formation of a porous oxide layer and the exothermic oxidation.