Preparation of monolith SiC aerogel with high surface area and large pore volume and the structural evolution during the preparation

Resorcinol-formaldehyde/silica composite (RF/SiO₂) aerogel was synthesized by sol-gel process followed by supercritical drying (SCD). Monolithic SiC aerogel was obtained from RF/SiO₂ aerogel after carbothermal reduction. The evolution of physical property, crystal structure, morphology and pore structure from RF/SiO₂ to SiC aerogel was investigated by different methods, such as X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and N ₂ adsorption/desorption. The as-synthesized SiC aerogel presented typical mesoporous structure and possessed high porosity (91.8%), high surface area (328 m²/g) and large pore volume (2.28 cm³/g). Carbothermal reduction mechanism was also discussed based on the experiment and characterization results.