Conversion of raw rice husks to SiC by pyrolysis in nitrogen atmosphere

Raw rice husks without precoking were directly pyrolysed in a graphite resistance heating furnace at 1100-1400 degrees C in nitrogen atmosphere. The furnace chamber pressure was varied from atmospheric pressure (14.7 Psi or 101.3 KPa) to 24 Psi (165 KPa). Considerable quantities of SiC whiskers were formed at 1200-1400 degrees C. Small quantities of Si2N2O were also formed at 1100 and 1200 degrees C. No Si3N4 was formed. The increase in chamber pressure has resulted in (i) an increase in the crystallization of silica and carbon in rice husks, (ii) decrease in the formation of SiC whiskers. Pyrolysis in nitrogen atmosphere resulted in the formation of good quality (needle type) SiC whiskers. (C) 1997 Elsevier Science Limited.