Investigation of microstructure and mechanical properties of novolac/silica and C/SiO2/SiC aerogels using mercury porosimetry method

• Novolac/silica nanocomposite aerogels were prepared by using sol–gel polymerization.
• Sol–gel polymerizations were developed in the solvent saturated vapor atmosphere.
• The silica phase of initial aerogel sol was extracted from rice husk ash (RHA).
• Polymeric aerogels were successfully converted to carbon/silica and carbon/silica/silicon carbide aerogels.
• The buckling intrusion mechanism was observed for all aerogels below Pt.

Novolac/silica nanocomposite aerogels are prepared through the sol–gel polymerization process under a solvent saturated vapor atmosphere. The silica phase is extracted from rice husk ash in the form of silica xerogel powder. Nanocomposite aerogels are then fabricated through sol–gel polymerization of novolac resin in the presence of silica xerogel powder. These nanocomposite aerogels are then converted to carbon/silica and carbon/silica/silicon carbide nanocomposite aerogels using pyrolysis and carbothermal reduction processes at 800 and 1500 °C, respectively. Mercury porosimetry method is used for the evaluation of microstructure and mechanical properties of fabricated hybrid nanocomposite aerogels. Mercury porosimetry analysis and scanning electron microscopy results confirmed that the Pirard and Washburn theories are valid for the evaluation of aerogels' pore size distribution. The buckling intrusion mechanism is studied for all polymeric and carbon nanocomposite aerogels below transition pressure. The effect of heat treatment on the microstructural properties is also investigated by mercury porosimetry analysis. The Young's modulus values are determined using mercury porosimetry data and compression results. Based on our results, the Young's modulus of hybrid nanocomposite aerogels is not necessarily related to the density of aerogels.