Facile design of 3D hierarchical NiFe2O4/N-GN/ZnO composite as a high performance electromagnetic wave absorber

•A novel hierarchical composite of NiFe2O4/N-GN/ZnO was fabricated successfully.•A strongest RL of −70.7 dB can be obtained with a filler content of 20 wt%.•The absorber exhibits superior microwave absorption properties.•The enhanced microwave absorption mechanisms are investigated in detail. Hierarchical composites containing both magnetic loss and dielectric loss materials prepared through rational structure design are highly popular for high-performance microwave absorbers due to their suitable impedance matching and strong attenuation constant. In this work, NiFe2O4/N-GN/ZnO hierarchical composite was synthesized by growing ZnO nanoflowers on magnetic graphene. The effects of this unique microstructure on the electromagnetic (EM) wave absorption performances of the composites were studied. The microstructure, compositions and EM parameters of the obtained samples were investigated by various techniques. Results showed that NiFe2O4/N-GN/ZnO composite showed enhanced EM wave absorption properties compared with NiFe2O4/N-GN. With a low filler loading of 20 wt%, the strongest reflection loss (RL) was as high as −70.7 dB at 13.5 GHz and the frequency bandwidth (RL over −10 dB) reached 3.5 GHz (11.7–15.2 GHz) with an absorber thickness of 2.7 mm. These results demonstrate that the NiFe2O4/N-GN/ZnO hierarchical composite is an ideal candidate for lessening EM wave interference with its advantages of light weight, strong absorption and broad frequency bandwidth.