In Situ Growth of CoNi Alloy/N-Doped Hollow Carbon Foam for Electromagnetic Wave Absorption

To meet the demands for high-performance and cost-effective electromagnetic wave absorbers in practical applications, CoNi alloy/N-doped hollow carbon foam (CoNi/NCF) was synthesized using melamine foam as a precursor through a hydrothermal reaction. By introduction of appropriate CoNi alloys to form uniform magnetic metal nanoparticles on the surface of NCF, the electromagnetic wave absorption performance of NCF can be adjusted. These metal nanoparticles formed rich heterogeneous interfaces with the NCF, enhancing the interface polarization loss of the composite material to electromagnetic waves. The CoNi alloy increased the conductivity of composite materials, which was conducive to the formation of a three-dimensional conductive network and promoted the conduction loss of electromagnetic waves. As a magnetic metal, the CoNi alloy also brought magnetic losses to composite materials, increasing the ways to consume electromagnetic waves. Additionally, the doping of N atoms increased the dipole polarization loss of the NCF. The minimum reflection loss (RLmin) of CoNi/NCF reached −47.35 dB, and the maximum effective absorption bandwidth (EAB) reached 5.6 GHz (2.4 mm). CoNi/NCF effectively reduced the radar cross-section (RCS) signal on the surface of the electric conductor layer. This study provides a feasible strategy for developing magnetic composite carbon materials with an efficient electromagnetic wave absorption performance.