Chitosan-derived carbon/chain-like CoNi composite aerogels for efficient electromagnetic absorption, radar stealth and thermal insulation.

With the increasingly severe problem of electromagnetic radiation pollution, pure carbon aerogels struggle to achieve a wide absorption bandwidth, strong absorption intensity and multifunctional integration at a low filler loading ratio. In this work, chitosan-derived carbon/chain-like CoNi composite aerogels with low bulk density (0.0949 ∼ 0.1019 g/cm3) were prepared by using biomass chitosan as carbon source through solvothermal reaction, solution blending and high-temperature carbonization. The introduction of the chain-like magnetic component not only optimized the impedance matching, but also constructed a dielectric-magnetic cooperative loss system, breaking through the performance limitations of pure carbon aerogels in terms of loss mechanism and structural design. When the content of CoNi alloy was 13.3 wt%, the binary composite aerogel exhibited the best electromagnetic wave absorption performance under the filler loading ratio of only 10 wt% in the paraffin matrix. Specifically, when the matching thickness was 2.75 mm, the minimum reflection loss reached -62.45 dB; when the thickness was 3.07 mm, the maximum absorption bandwidth of 8.08 GHz was achieved. Furthermore, the electromagnetic absorption mechanism of the prepared composite aerogels was clarified. Additionally, the binary composite aerogels possessed excellent thermal insulation performance and good simulated radar stealth performance, demonstrating its potential in various application scenarios. This work provides a new idea for the development of lightweight and multifunctional carbon-based electromagnetic wave absorbers derived from biomass sources.