Oxygen Index of Magnesium Powder

The combustion regimes were studied and the oxygen index for the bulk-density magnesium powder with a particle size of ~80 μm placed in a paper cup was determined in nitrogen–oxygen and argon–oxygen mixtures at pressures from 0.3 to 1 atm. It was shown that at a constant pressure of the mixture, there was a minimum concentration of oxygen at which sustained propagation of the combustion front was possible. The boundaries of the region of stable combustion of such a system in the pressure–oxygen concentration coordinates were determined. It was shown that, depending on the oxygen concentration, two combustion modes were possible: one-step mode far from the combustion limit and spin mode at the combustion limit. As the pressure or oxygen concentration in the mixture increased, the characteristic spin rotation time decreased and the propagation of the combustion front over the sample passed into a layer-by-layer mode. The dependence of the combustion front propagation velocity on the sample near the combustion limit on the mixture pressure and the oxygen concentration in its composition was determined.