High-entropy alloy@air@Ni–NiO core-shell microspheres for electromagnetic absorption applications

Core-shell microspheres with high-entropy alloy (HEA: FeCoNiCrCuAl_0.3) as core and metal oxide (Ni–NiO) as shell have been successfully constructed via a two-step hydrothermal method. The chemical composition, microstructure, electromagnetic (EM) properties and EM wave absorption properties were characterized in detail. We find that the magnetic loss originated from high-entropy alloy and the dielectric loss caused by Ni–NiO can promote the consumption of EM energy through synergistic effect. The effective absorption bandwidth (f_E, RL < −10 dB) of HEA@air@Ni–NiO composites was 4.0 GHz with an ultra-thin matching thickness (d) of 1.3 mm. We believe that this HEA@air@Ni–NiO composite can be a new generation of high-efficiency high-entropy alloy based EM wave absorber because of its strong EM wave absorption capability under an ultra-thin matching thickness. In addition, the new preparation method of core-shell micro-/nanostructure also has important reference value.