High-performance electromagnetic wave absorption of FeNi/N, S-codoped carbon composites in 2–40 GHz

An FeNi/nitrogen, sulfur-codoped carbon (FeNix/NS-C) composite was synthesized by a microwave-assisted method, polymerization of polypyrrole (PPy) and thermal decomposition. The FeNix/NS-C composite consisted of bimetallic FeNi, heteroatomic dopants (N, S) and (Fe/Ni)-Nx bonds. The FeNix/NS-C composites showed superior electromagnetic wave absorption (EMWA) performances, e.g., a strong reflection loss (RL) of −55.3 dB (21.4 GHz) and a broad effective absorption bandwidth of 32.46 GHz (3.92–17.08 and 18–37.3 GHz) by controlling the layer thickness (1.0–5.5 mm). The exceptional EMWA performances are attributed to the synergistic effect of magnetic loss that originated from the FeNi component, dielectric loss derived from the conduction loss (graphitic carbon), dipole polarization (heteroatoms (N and S), defective carbon, abundant functional groups (C–O, C–N, C–S, CO, etc.) and interfacial polarization (hierarchically porous features, numerous small core-shell configurations and heterojunctions among FeNi, "double-layer" carbon shells).