Synthesis of Environmentally Friendly Nanoporous Monolithic Carbon Aerogels via Ambient Pressure Drying for High-Temperature Thermal Insulators

As a promising high-temperature thermal insulation, carbon aerogel is generally prepared by the carbonization of an organic aerogel. However, the preparation processes of solvent exchange and supercritical drying are complicated and contaminated, which hinder their large-scale production and application in the field of civil high-temperature thermal insulators. Herein, the nanoporous carbon aerogels were prepared by an environmentally friendly method of ambient pressure drying without solvent exchange with the usage of water as the solvent, acetic acid as an acid catalyst, and biopolymer chitosan as a cross-linking agent and supporting template. Through the polymerization and hydrogen bonds of chitosan with precursors to strengthen the gel network, carbon aerogels exhibit good monolithic shape (130 × 130 × 18 mm) with nanoparticle size (43–107 nm) and low density (0.187–0.395 g/cm³), leading to a low thermal conductivity (0.09592 W/m·K) and high compressive strength (11.50 MPa) at the density of 0.395 g/cm³. Notably, by the copyrolysis of organic fiber-reinforced organic aerogel composite, a crack-free carbon aerogel composite (0.244 g/cm³) was prepared with enhanced mechanical properties (compressive strength of 1.63 MPa at 10% strain and bending strength of 4.27 MPa) and low thermal conductivity (0.107 W/m·K at 1100 °C). This work may provide an environmentally friendly method for the industrialized preparation of reliable nanoporous carbon aerogels for high-temperature thermal protection components.