Comparative Analysis of Boron Powders Obtained by Various Methods. I. Microstructure and Oxidation Parameters during Heating

This paper describes a study of boron powders and powder compounds, obtained by various methods, including metallothermal, electrolytic, and borane cracking methods. The crystal state, particle size and microstructure, presence and composition of impurities, and chemical composition of the oxide layer of boron particles are profoundly investigated. The effects of the above-mentioned characteristics on the particle oxidation parameters during heating with a constant rate are analyzed. The determining influence of chemical composition of the particle surface layer on the initial temperature of their intense oxidation is established. It is shown that the maximum increase in the mass and heat release value during oxidation of the boron powders is almost independent of microstructural features, crystal state, and chemical composition of and oxide layer thickness of the particles, and cannot serve as indicators of completeness of boron oxidation during heating.