Effect of carbon source species on synthesis of CaB6 powders via induction heating

Abstract:

CaB₆ powders were prepared by the carbothermal reduction method in medium-frequency induction furnace, using CaCO₃ and B₂O₃ as raw materials, using pitch, activated carbon, ultrafine graphite, petroleum coke as reducing agent, respectively. The effects of the carbon source species on the phase composition, particle size distribution and microscopic morphology of CaB₆ powders synthesized by induction heating were studied. The results show that the reaction time is obviously shortened by using induction heating. When the pitch and activated carbon are used as the carbon source, high purity CaB₆ powders can be obtained at 1650 ℃ for 20 min. The grain size is approximately 10.9μm with a regular cubic shape when using the pitch as carbon source; However, when the ultrafine graphite and petroleum coke are used, the grain size of CaB₆ is relatively small, and lots of purity exist; When the petroleum coke is used, there has an obvious hard agglomeration between the CaB₆ grains; Appropriate excess carbon can improve the purity of CaB₆.

Key words:carbothermal reduction method; induction heating; CaB₆ powders; microscopic morphology;