Construction of flower-like CoNi nanosheets/nitrogen-doped expanded graphite composites synergistically designed for efficient microwave absorption and excellent thermal conductivity

Electromagnetic pollution and device heat dissipation have become global issues. It is crucial to develop high-performance materials for microwave absorption with superior thermal conductivity. In this paper, three-dimensional porous network and flower-like CoNi nanosheets/nitrogen-doped expanded graphite (CoNi/N-EG) composites were successfully prepared with excellent microwave absorption properties. The effective absorption bandwidth (EAB) of the composites reaches up to 7 GHz and the minimum reflection loss (RL_min) reaches −59.98 dB with low content filling (5 wt%) and 2.9 mm thickness. The attributed enhancement is due to the CoNi/N-EG composites' rational microstructural design, synergistic interaction of dielectric and magnetic losses, and perfect impedance matching. In addition, the CoNi/N-EG composites exhibited excellent thermal stability and thermal conductivity, with an optimal thermal conductivity of 8.02 W m⁻¹ K⁻¹, which was enhanced by 18.3 % compared with EG. This paper is an inspiration for the study of designing high-performance carbon-based magnetic metal wave-absorbing materials with efficient thermal conductivity and unique morphology.