Catalytic effect of cobalt on microwave synthesis of β-SiC powder

β-SiC was synthesized by a microwave reaction method in Ar, using silicon powder and phenolic resin as raw materials, and cobalt nitrate as a catalyst precursor. The effects of temperature, time, and catalyst content on the formation of SiC were investigated. When 1.0–2.0 wt% Co was used as a catalyst, phase pure β-SiC was formed after 30 min at 1150 °C. This synthesis temperature was 100 °C lower than that required by the conventional heating route catalyzed by with the identical amounts of catalyst. When a catalyst was absent, the synthesis temperature of β-SiC was as high as 1250 °C even in the case of using microwave heating. β-SiC particulates were formed, along with some whisker-shaped β-SiC of 30–100 nm in diameter and up to 20 μm in length. Density Functional Theory (DFT) calculations suggest that under the test conditions the formation of Co/Si alloy was energetically favorable, and played an important role in the Si–Si bond breaking and the subsequent SiC formation.