Synthesis of structure controllable carbon aerogel with low drying shrinkage and Scalable size as High-Temperature thermal insulator

Carbon aerogels, owing to the high-temperature durability and low thermal conductivity, are promising candidates for high-temperature thermal insulation used in inert atmospheres. However, significant drying shrinkage poses challenges in fabricating large-sized carbon aerogels and optimizing their thermal insulation properties. Herein, we report the synthesis of monolithic carbon aerogels with low drying shrinkage and controllable nanostructures by adding self-crosslinked chitosan to provide reaction sites and three-dimensional network support based on the traditional resorcinol-formaldehyde method in an acetic acid environment. Owing to the increased cross-linking degree of resorcinol-formaldehyde gel from the polymerization and hydrogen bonding between chitosan and resorcinol-formaldehyde oligomers, the skeleton of gel network is strengthened and the shrinkage during supercritical drying is as low as 1.51 %, resulting in a good monolithic shape of carbon aerogel (130 x 130 x 15 mm). Besides, they exhibit typical nanoporous characteristics with uniform and small particle size (9-130 nm) and low density (0.070-0.221 g center dot cm- 3), achieving a low thermal conductivity of 0.047 W center dot m- 1 center dot K- 1 at 1100 degrees C and high compressive strength of 1.80 MPa (density of 0.138 g center dot cm- 3). This method facilitates the production of carbon aerogels with low shrinkage, minimal defects, low density, and small pore size, rendering them suitable for applications requiring large dimensions and low defect levels, such as fiber-reinforced composites and high-performance thermal insulators.