The effects of transition metals on carbothermal synthesis of beta-SiC powder

Several transition metals were added in the carbothermal syntheses of beta-SiC powder from silica and phenolic resin at temperatures < 1500 degrees C. The effects of the transition metals on the yields of SiC and powder morphology were investigated. The results showed that by adding 1 wt.% of Fe, Co or Ni in the silica/phenolic resin mixtures, the synthesizing temperature of SiC decreased and the yields of SiC increased. But adding Mn, Pd or Cu has no favorable effects on the syntheses of beta-SiC powder. After reaction at 1400 degrees C, the highest yield was obtained by adding 1 wt.% Fe, which reaches 77%. Adding Co could result in 73% yield and adding Ni could only have 30% yield. The SiC powder obtained from mixtures with I wt.% Fe was agglomerated, while that from mixtures with I wt.% Co was mostly un-agglomerated particles of 100-300 nm in size. The positive effects of transition metals in SiC powder synthesis at temperatures < 1500 degrees C seems to be in the enhancement of SiO(g) formation. (c) 2006 Elsevier Ltd and Techna Group S.r.l. All rights reserved.