A heterojunction of high-entropy alloy and nitrogen-doped carbon nanospheres for efficient electromagnetic wave absorption†

FeCoNi-based high-entropy alloys (HEAs) with exceptional soft magnetic properties and electrical conductivity are utilized for electromagnetic wave (EMW) absorption. Nevertheless, these materials have limitations in terms of high density, susceptibility to oxidation, impedance mismatching, etc. Herein, a high-entropy alloy (HEA) of FeCoNiCuAl is prepared through a sol–gel process, and a heterojunction of this HEA and nitrogen-doped carbon (HEA/NC) is constructed by in situ polymerization and subsequent annealing treatment. The incorporation of NC with the defects induced by nitrogen atom doping not only optimizes the impedance matching, but also enhances dielectric loss properties of HEA/NC through dipole and interfacial polarization. The remarkable EMW absorption properties of HEA/NC are ascribed to the magnetic–dielectric synergistic loss. At a thickness of 1.80 mm, the minimum reflection loss (RL_min) is −56.38 dB and the maximum effective absorption bandwidth (EAB) is 5.69 GHz. Furthermore, the radar scattering cross-section (RCS) calculated using CST software can reach −19.05 dBm² in an actual environment, thereby confirming its excellent EMW absorption properties. In summary, this study offers new insights into the design and fabrication of HEAs as highly effective EMW absorption materials.