Preparation of cubic SiC from δ-Na₂Si₂O₅/carbon nanocomposite using cobalt catalyst

Silicon carbide (SiC) was prepared by carbothermal reduction of a crystalline-layered sodium silicate (δ-Na₂Si₂O₅)/carbon nanocomposite (LCN), which contained a stacked carbon film embedded with cobalt between the silicate layers. Subsequent sintering of this mixture for 3 h at 1000-1350°C resulted in the formation of graphitic carbon and SiC. Meanwhile, sintering without a cobalt catalyst resulted in the formation of graphitic carbon, regardless of the temperature. The use of a cobalt catalyst allowed the formation of a pure SiC phase at 1350°C. The formed SiC had an irregular worm-like morphology, with a particle size of ~5 µm. The Brunauer-Emmett-Teller surface areas of graphitic carbon and SiC were 28-150 and ~7.0 m²/g, respectively. We concluded that graphite and SiC were produced at this low sintering temperature because of the cobalt catalyst, which facilitated nanomixing of carbon and SiO₂ by sandwiching the carbon films between the silicate layers.