An experimental study of ignition and combustion of a single boron particle with a nominal diameter of about 3 mum was conducted in the post-flame region of a flat-flame burner operated at one atmospheric pressure. Gas mixture temperatures and oxygen mole fractions were ranged from 1772-1993 K and 12.6-27.7percent, respectively. Two groups of boron particles (crystalline and amorphous boron) were used in this work. To study the effect of magnesium coating on ignition and combustion behavior of boron particles, the amorphous group of boron particles were coated with different weight percentages (0percent, 0.75percent, 1.26percent, 2.66percent, and 4.58percent) of Mg. The combustion of boron particles used in this study occurs in two continuous stages. During the first-stage combustion, the boron particle is still covered with a boron oxide layer. The second-stage combustion is associated with the full-fledged combustion of the bare boron particle. First-stage combustion times (t_1) of boron particles were found to decrease with increasing ambient gas temperature, but weakly dependent on ambient oxygen mole fraction. However, the increase of either ambient gas temperature or oxygen mole fraction led to a more pronounced decrease in second-stage combustion times (t_2). Considering the Mg coating, only the 0.75percent Mg-coated boron produced the effect of reducing the first-stage combustion time. The other Mg-coated boron samples, which appear to have too much coating, cause longer first-stage combustion times. For the test conditions studied, Mg coating showed nearly no effect on the second-stage combustion time.
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