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

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 (R_L) was as high as −70.7 dB at 13.5 GHz and the frequency bandwidth (R_L 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.