The Influence of H2 and CO Atmospheres on SiO Formation

Producing silicon with H-2 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 degrees C. In pure Ar, the reaction was slow and found to be limited by mass transfer. The reaction was faster in the presence of H-2, and, in this case, it was instead slow reaction kinetics that was rate limiting. However, the effect disappeared when adding CO together with H-2. Both H-2 and CO produced SiC whiskers at 1650 degrees C, but H-2 to a greater degree than CO. The whiskers reinforced the pellets, which resulted in up to 20 times higher strength for a CO and H-2 containing process gas. Process gasses without of CO resulted in weaker pellets instead.