Self-assembly of graphene hollow microspheres anchored with FeNi3/NiFe2O4 nanocrystal for highly efficient electromagnetic wave absorption

The graphene-based electromagnetic wave absorption materials have attracted extensive attention due to their lightweight, strong absorption, broadband, and thin thickness. In this work, graphene hollow microspheres anchored with FeNi-coupled nanocrystal (GHMs@FeNi3/NiFe2O4 ) were synthesized using water-in-oil (W/O) emulsification and high-temperature calcination. The GHMs@FeNi3/NiFe2O4 microspheres have a homogeneous spherical morphology and a pronounced hollow structure, and the FeNi-coupled nanocrystals are homogeneously embedded in a spongy shell assembled by rGO nanosheets. Owing to the optimized impedance matching and enhanced attenuation, the GHMs@FeNi3/NiFe2O4 composites exhibit outstanding microwave absorption ability, particularly in the Ku band. The minimum reflection loss (RLmin) value can reach -58.96 dB at 14.43 GHz with a matching thickness of 2.25 mm, and the effective absorption bandwidth (lower than -10 dB) is up to 6.29 GHz (11.71-18 GHz) covering the whole Ku band. We believe that our work provides an idea for the design of high-performance absorbing composite materials.