Impacts of Particle Size and Pressure on Reactivity of Boron Oxidation

Thermogravimetric measurements were conducted on the oxidation of boron particles to elucidate the influence of particle size and pressure on the reaction process and mechanism. The experimental results showed that the initial temperature increased slightly as the particle size of boron powder increased and increased greatly as the total ambient pressure decreased. The boron oxide covering on the surface of the boron particles had a significant effect on the reactivity of the boron powder. For the particles in the studied size range, the reaction efficiency showed an incremental trend as the particle size increased. High pressure could decrease the reaction efficiency greatly because the evaporation rate of boron oxide would slow down as the ambient pressure increased. Furthermore, it was found that the effect O-2 partial pressure on the reaction efficiency was not only related to the total ambient pressure but also to the O-2 mole fraction. Both a higher O-2 mole fraction and smaller ambient pressure were favorable for oxidation efficiency. The experimental results also revealed that boron particles with a smaller size or at high pressure had relatively low effective activation energy.