Air@rGO€Fe3O4 microspheres with spongy shells: self-assembly and microwave absorption performance
Hollow reduced graphene oxide microspheres embedded with Fe3O4 (Air@rGO€Fe3O4) were synthesized by a water-in-oil (W/O) emulsion technique followed by a calcination process. Their multicomponent hierarchical 3D microstructure was confirmed by XRD, XPS, SEM and TEM analysis methods. These Air@rGO€Fe3O4 microspheres are of low density (0.85–0.95 g cm−3) and possess excellent microwave absorption properties and corrosion resistance. Their minimum reflection loss (RLmin) value reaches −52 dB at 10 GHz with a thickness of 2.8 mm, and the absorption bandwidth (lower than −10 dB) is 7.2 GHz covering from 7.5 GHz to 14.7 GHz. After treatment in hydrochloric acid for five days, Air@rGO€Fe3O4 microspheres still exhibit an impressive microwave absorption performance and the RLmin value reaches up to −46 dB at 8.6 GHz with an absorption bandwidth (lower than −10 dB) of 6.0 GHz (6.3–12.3 GHz) with a matching thickness of 3.5 mm. These results demonstrate that the Air@rGO€Fe3O4 microspheres may be attractive candidate materials for microwave absorption applications.