The aluminothermic reduction of boric acid

The effect of metallic aluminium powder on the production of boron carbide–alumina composite was studied. Boric acid, carbon and aluminium powders were mixed in stoichiometric ratio, ball milled and heat treated at temperatures between 1300 and 1650 °C for 1–5 h in the presence of argon flow. Depending on the ratio of boron oxide to carbon, the formation of boron carbide by the carbothermal reduction, was possible at a temperature of around 1500 °C, but with the addition of metallic aluminium to the mixture of boric acid and carbon, the carbide formation temperature was reduced at least 300 °C. At 1300 °C, B₄C was the major phase with alumina in the reaction products. The liquid–solid reaction mechanism, which occurred during the aluminothermic process, had a specific influence on the formation of boron carbide.