Morphology control of eco-friendly chitosan-derived carbon aerogels for efficient microwave absorption at thin thickness and thermal stealth

In the face of increasingly severe electromagnetic wave (EMW) pollution, the research of biomass-based carbon materials due to the advantages of being green, renewable, environment-friendly, porous and light has become one of the most attractive topics. However, there is little research on the microstructure control of biomass-based materials. Herein, two kinds of chitosan-derived carbon aerogels (CAs) were prepared by adjusting the amount of chitosan and changing the pre-freezing method. Two morphologies of bamboo tube structure (BTS) and isolated island structure (IIS) were controlled by the growth speed and direction of ice crystals in a refrigerator and freeze dryer differently. The obtained samples with very low densities of 0.075-0.174 g cm −3 can bear 400 times their own weight. Furthermore, the unique layer spacing and porous characteristics make the infrared emissivity of IIS aerogels possess 0.545-0.709 at 20-300 °C with greater thermal insulation. In particular, the effective absorption bandwidth (EAB) of the IIS aerogel nearly contains the entire Ku band within the thickness of 1.0-1.4 mm, and the minimum reflection loss (RL min ) peaks appear to shift to the left compared with the IIS aerogel. Besides, the simulation results of radar cross-section (RCS) show that the IIS with a thickness of 1.4 mm can reduce the RCS by ∼20.3 dB m 2 at 14.1 GHz. This study provides a reference for the study of eco-friendly chitosan-derived carbon absorbers. In the face of increasingly severe electromagnetic wave pollution, the research of biomass-based carbon materials due to the advantages of being green, renewable, environment-friendly, porous and light has become one of the most attractive topics.