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b-silicon carbide (SiC) porous ceramics were synthesized from pelletized powder mixtures of silicon (Si) and fullerene or Si and amorphous carbon (carbon black) at 1000 K for 24 h in sodium (Na) vapor. The relative density of the ceramics was 29%-34% of the theoretical density of SiC. Scanning electron microscopic observation of the fracture surface showed that the ceramics prepared with fullerene were agglomerates of submicrometersized SiC particles and open spaces. The samples prepared with carbon black had a smooth fracture surface with cavities and voids. Using transmission electron microscopy, grains of over 250 nm and a diffuse electron diffraction ring pattern of b-SiC were observed for the sample prepared with fullerene, and grains of 10-20 nm with a b-SiC spot ring pattern for the sample prepared with carbon black. A surface area of 11-17 m 2 /g and a mesopore size distribution in the range of 2-10 nm were shown by a nitrogen adsorption technique. Energy-dispersive X-ray analysis detected 1-5 at.% of Na against Si on the fracture surface of the ceramics.

Wood from balsa and Japanese cypress was transformed into carbonaceous preforms by pyrolysis and subsequently converted into cellular SiC ceramics by heating with Na and Si at 973 K for 86.4 ks. X-ray diffraction showed the structure of the formed SiC to be cubic b-type. Cellular structures similar to those of the preforms were observed for the resulting porous SiC ceramics by scanning electron microscopy.

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