Multiscale carbon-structured FeCoNi/C@CA for enhanced thermal insulation and microwave absorption

Although magnetic carbon composites enable efficient microwave attenuation, dense magnetic phases increase areal/volumetric mass, thereby challenging the concurrent realization of low density, thermal insulation, and electromagnetic attenuation in one architecture. Herein, we report a hierarchically engineered FeCoNi@C/lamellar carbon aerogel (FeCoNi@C/CA) fabricated for the first time via directional solidification of a resorcinol–formaldehyde gel followed by impregnation with FeCoNi-Prussian blue analogue and subsequent pyrolysis. The process yields a macroscale lamellar carbon framework uniformly decorated with hollow core–shell FeCoNi@C nanospheres. The continuous carbon lamellae construct long–range conductive networks that strengthen dielectric loss, whereas the magnetically coupled, hollow nanospheres introduce multiple scattering, interfacial polarization, and magnetic loss pathways. Notably, FeCoNi@C/CA-3 delivers an RL_min of −37.9 dB at 1.5 mm, and achieves a 5.8 GHz bandwidth spanning 12.2–18.0 GHz at 1.6 mm, underscoring its strong thin-layer and broadband absorption capability for low-density systems. Simultaneously, the aerogel architecture endows the composite with outstanding thermal insulation, delivering a maximum temperature drop of 121.5^°C between the hot stage and the exposed surface under the tested conditions. These findings establish a versatile strategy for integrating broadband EM absorption with thermal management in ultra-light, ultra-thin carbon-based architectures, expanding the design space for next-generation multifunctional shielding materials.