Improving the incompatibility between electromagnetic and thermal properties of CNF/Co composites via constructing 3D interconnected frameworks, double hot carriers, and multiple losses

To improve the incompatibility between thermal conduction and electromagnetic wave absorption properties, 3D interconnected CNF/Co composites as a multifunctional filler were fabricated with magnetic/dielectric dual loss and phonon/electron co-transfer via a straightforward sol-gel and annealing route. Results show that the CNF/Co composites produced at a high Co ²⁺ concentration ( c) exhibit low defects, small S _BET , large electrical conductivity, and high Co content. The optimal comprehensive properties of CNF/Co composites are achieved at c = 0.8 M. Besides, the CNF/Co composites bear a large thermal conductivity (3.61 W/mK) at a low load (15 wt%) due to the enhanced phonon/electron co-transfer in 3D interconnected CNF frameworks and decreased phonon scattering. Moreover, the CNF/Co composites demonstrate tunable electrical conductivity ( σ = 7.53 ×10 ⁻⁵ ∼ 1.22 ×10 ⁻² S/cm) and significant enhancements in electromagnetic wave absorption properties (4.53 GHz/mm, 2.4 mm thickness, 35% load), outperforming most other previously reported materials. The significant enhancements could be attributed to the high attenuation and excellent impedance matching caused by magnetic/dielectric dual-loss Co and 3D interconnected porous frameworks. The exceptional electromagnetic wave absorption properties and thermal conduction endow the 3D interconnected CNF/Co composites with prospective application as a multifunctional filler in modern electronics.