The Influence of H₂ and CO Atmospheres on SiO Formation

Producing silicon with H₂ would be advantageous from an environmental viewpoint because it opens up a potentially CO₂-free process. This study investigated the interplay between atmosphere and the reaction between SiC and SiO₂ pellets. Process gasses containing Ar, H_2, and CO were examined at 1650 and 1750 °C. In pure Ar, the reaction was slow and found to be limited by mass transfer. The reaction was faster in the presence of H₂, and, in this case, it was instead slow reaction kinetics that was rate limiting. However, the effect disappeared when adding CO together with H₂. Both H₂ and CO produced SiC whiskers at 1650 °C, but H₂ to a greater degree than CO. The whiskers reinforced the pellets, which resulted in up to 20 times higher strength for a CO and H₂ containing process gas. Process gasses without of CO resulted in weaker pellets instead.