Effect of silica sources on nanostructures of resorcinol-formaldehyde/ silica and carbon/silicon carbide composite aerogels

The subject of this paper is the investigation of the effect of silica sources on microstructure of resorcinol-formaldehyde/silica composite (RF/SiO₂) and carbon/silicon carbide composite (C/SiC) aerogels. Hybrid silica sources (HSS) were composed of 3-(aminopropyl)triethoxysilane (APTES) and tetraethoxysilane (TEOS) with different molar ratio. RF/SiO ₂ aerogel was obtained by a single-step sol-gel process followed by supercritical fluid drying (SCFD). C/SiC aerogel was formed from RF/SiO ₂ aerogel after carbothermal reduction. Scanning electron microscopy (SEM) and N₂ adsorption/desorption were used to investigate the evolution of morphology and pore structures of aerogels. X-ray diffraction (XRD) and transmission electron microscopy (TEM) demonstrated that the as-prepared C/SiC aerogel was composed of carbon nanoparticle and α-SiC nanocrystal. The microstructure was hugely affected by the component of HSS. When the molar fraction of APTES in HSS was 60%, RF/SiO₂ and C/SiC aerogels possessed the highest surface area and pore volume and the lowest thermal conductivity.