Synthesis of hierarchical core-shell NiFe2O4@MnO2 composite microspheres decorated graphene nanosheet for enhanced microwave absorption performance

A ternary functional composite NiFe2O4@MnO2@graphene was synthesized successfully via a facile method. The phase constitution, microstructures, morphologies and chemical compositions of the samples were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) and X-ray photoelectron spectroscopy (XPS). It was observed that the NiFe2O4 nanoparticles were coated by hierarchically MnO2 shells and distributed on the surface of graphene. Investigations of EM wave absorption indicated that NiFe2O4@MnO2@ graphene composite has the strongest reflection loss of −47.4 dB at 7.4 GHz at the matching thickness of 3 mm, compared to NiFe2O4 and NiFe2O4@MnO2, and its maximum absorption bandwidth (<−10 dB) is 4.3 GHz (from 5.1 to 9.4 GHz). The enhanced microwave absorption performance can be attributed to the hierarchical structure of MnO2, void space between MnO2 and graphene, and better impedance matching of ternary composite. The above results indicate that the novel hierarchical NiFe2O4@MnO2@graphene composite, with intense absorption and wide absorption bandwidth, would be a promising absorber with less EM wave interference.