Synthesis of silicon carbide by carbothermal reduction of quartz in H2-Ar gas mixtures
This article examines the synthesis of silicon carbide by carbothermal reduction of quartz in H2, Ar and their mixtures. The quartz was crushed to less than 70 μm, uniformly mixed with graphite and pressed into pellets with carbon/silica molar ratio of 3.6. Reduction was studied in isothermal and temperature programmed experiments in a tube reactor in continuously flowing gas atmosphere. The reduction rate increased with increasing H2 partial pressure and temperature. Silicon carbide began to form at 1200 °C inreduction in H2. The conversion of quartz to silicon carbide at 1400 °C was completed in 270 minutes. This period was reduced to 140 minutes at 1500 °C and 70 minutes at 1600 °C. In the carbothermal reduction of quartz in Ar, the conversion of quartz to silicon carbide started at 1300 °C, and was incomplete after 270 minutes at 1500 °C. The faster reduction rate in H2 containing gas was attributed to the involvement of H2 in the reactions. At high temperatures, 1400-1600 °C, quartz was directly reduced by H2 to silicon monoxide.