Synthesis of monolithic carbon aerogels with high mechanical strength via ambient pressure drying without solvent exchange

A simple, fast and cost-effective method for monolithic carbon aerogels (CAs) preparation was proposed through sol-gel polycondensation of resorcinol with formaldehyde in a basic aqueous solution followed by ambient pressure drying without solvent exchange, and carbonization. The microstructure and network strength of CAs were tailored by adjusting the catalyst concentration ([resorcinol]/[sodium carbonate] in the range of 300–2000), water content ([deionized water]/[resorcinol] equals to 17 and 24, respectively), and gelation temperature (Tgel in the range of 30−90 °C). Resultantly, the CAs with a wide range of density (0.30–1.13 g/cm3), high specific surface area (465−616 m2/g), high compressive strength (6.5–147.4 MPa) and low thermal conductivity (0.065-0.120 Wm−1 K−1) were obtained in this work. Moreover, the large-sized CAs (100 × 100 × 20 mm3) can also be prepared by this method since the formed robust skeleton network can resist shrinkage/collapse of pore structure and prevent cracking during drying. The improved mechanical strength and monolithic forming abilities could be mainly attributed to the uniform arrangement of carbon particles and pores, fine particle size, abundant network structure and enhanced particle neck.