Investigation of the effect of rice husk derived Si/SiC on the morphology and thermal stability of carbon composite aerogels

Highly porous carbon aerogels were prepared by pyrolyzing the novolac-silica aerogels. The silica phase was extracted from rice husk ash (RHA).The polymer aerogel was synthesized via the novel method of sol-gel polymerization in solvent vapor-saturated atmosphere. This method removes the need for supercritical drying and reduces the shrinkage of aerogels during drying stage and also has much lower process time compared to the conventional sol-gel method. In the next step, polymer composite aerogels become carbon/silica and carbon/silica/silicon carbide composites in pyrolysis (800 degrees C) and carbothermal reduction (1500 degrees C) stages, respectively. The characterization of the prepared composite aerogels was performed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analyses, respectively. Thermal and mechanical properties of the samples were investigated by differential scanning calorimetry (DSC) and compressive strength analysis. The resultant composite aerogels show a nanostructure with high porosity (above 82%) and low density (below 0.3 g cm(-3)).Si mapping images showed the good distribution of silica phase throughout the carbon matrix. Also the rate of oxidation for carbon composites decreased by silica incorporation and oxidation temperature increased about 20% by adding RHA silica. Compressive strength of composite samples increased about 25% by increasing RHA silica phase content. (C) 2015 Elsevier Ltd. All rights reserved.