Porous carbon/SiO2 composites were prepared by heating the compacts composed of the rice husk (RH) powders of small (<74 μm) (S) and medium (74-175 μm) (M) sizes. The packing density of the (S+M) mixture compact took a minimum value at S/ (S+M) (in weight) (R)=0.5. The RH compacts were heated at 600 and 800ºC in an alumina crucible covered with graphite granules to avoid the oxidation in air. The weight loss after the heat-treatment decreased with increasing R-value. The weight loss at 800ºC was larger than that at 600ºC. The carbon contents of the products at 800ºC were 49-67 wt%. The porosity of the carbon/SiO2 pellets decreased from 83% (R=0.3) to 51% (R=1) with increasing R-value. The macro-pore size in the products decreased from 33 μm to 7.5 μm with increasing R-value. The porosity and macro-pore size were not affected by the treatment temperature. The specific surface area (SSA) of the pellets heated at 800°C decreased from 262 to 207 m2g−1 with increasing R-value. The pellets heated at 600°C had 221 m2g−1 of SSA value at R=0.3, but those of R=0.5-1.0 showed very small SSA values, 16-45 m2g−1.

Keywords: rice husk, porous material, carbon, silica