A low cost, low energy, environmentally friendly process for producing high-purity boron carbide

Abstract

Boron carbide with purity levels higher than that achievable by traditional manufacturing processes using an electric arc furnace (EAF) was produced by a novel low cost, low energy, environmentally friendly process of carbothermic reduction of boric acid (H3BO3) with carbon using a self-designed temperature-controllable electric resistance furnace (ERF). The process is divided into three stages: the pelleting stage, the low-temperature pre-dehydration stage, and the high-temperature reduction stage. The optimal conditions are determined as a pelleting pressure of 20 MPa, pre-dehydration temperature of 400 °C, H3BO3/C ratio of 3.38, and reduction temperature of 1900–2300 °C. The formation of boron carbide changes from liquid-solid reactions to gas-solid reactions with increasing temperature. Furthermore, the decreasing CO partial pressure is verified to be beneficial for the synthesis of boron carbide. The proposed process circumvents the disadvantages caused by the evaporation of large quantities of water steam and unstable reduction temperature and B/C ratios exhibited by the traditional EAF process. Moreover, it provides a more stable and controllable reduction temperature for producing high-purity boron carbide that leads to improved energy consumption, product quality, and cost efficiency and reduces air pollution mainly caused by volatilization and condensation of boron oxides.