Construction of a hollow nickel–magnesium ferrite decorated nitrogen-doped reduced graphene oxide composite aerogel for highly efficient and broadband microwave absorption

Abstract

Developing advanced microwave absorbing materials with wide absorption bandwidth, strong absorption strength, and low filling ratio remains a big challenge. In this paper, a nitrogen-doped reduced graphene oxide/hollow nickel–magnesium ferrite (NRGO/hollow Ni_0.5Mg_0.5Fe₂O₄) composite aerogel was prepared by a two-step method of solvothermal reaction and hydrothermal self-assembly. The results of microscopic morphology analysis showed that the as-prepared NRGO/hollow Ni_0.5Mg_0.5Fe₂O₄ composite aerogel had a three-dimensional (3D) porous network structure that was self-assembly by wrinkled NRGO flakes, and a large number of hollow Ni_0.5Mg_0.5Fe₂O₄ microspheres were almost evenly loaded on the crumpled surfaces of NRGO. Furthermore, the composition of spinel ferrite had a significant influence on the electromagnetic parameters and microwave absorption properties of NRGO-based composite aerogels. It is worth noting that when the filling ratio was only 10.0 wt%, the NRGO/hollow Ni_0.5Mg_0.5Fe₂O₄ composite aerogel showed the minimum reflection loss of −56.8 dB at a matching thickness of 3.6 mm, and the maximum effective absorption bandwidth of 6.1 GHz under a thin thickness of 2.3 mm. The obtained NRGO/hollow Ni_0.5Mg_0.5Fe₂O₄ composite aerogel had excellent microwave absorption performance, which was due to its special 3D porous and hollow structure, good impedance matching and synergistic effect of enhancing magnetic and dielectric loss. Therefore, our research results could provide a valuable reference for constructing 3D graphene-based composites as lightweight, broadband and high-efficiency microwave absorbers.