Influence of lanthanum on synthesis of SiC nanopowder

Low cost silicon carbide nanopowder, which used nanosized SiO2 and carbon as raw materials, was synthesised by a carbothermal reduction method. Thermogravimetry differential scanning calorimetry (TG-DSC) curves revealed that the SiC synthesis process had two steps for La was added. In the first step, after 0·3 wt-%La was added, the initial temperature for the formation of SiO(g) and CO(g) decreased from 1351·4 to 1250·9°C and the thermal activation energy decreased from 223·6 to 34·7 J g−. In the second step, the initial temperature for the formation of β-SiC decreased from 1526·5 to 1357·8°C and the thermal activation energy decreased from 693·7 to 295·7 J g−. Without La added, the optimum process for the formation of β-SiC was 1550°C for 120 min, meanwhile, the average powder diameter >150 nm. With La added, the optimum process was 1500°C for 120 min and the average powder diameter was ∼100 nm.