Hollow Fe3O4 microspheres/graphene composites with adjustable electromagnetic absorption properties

Fe 3 O 4 @rGO composites, consisting of monodisperse hollow Fe 3 O 4 microspheres with an average particle size of 320 nm and reduced graphene oxide, were prepared by using a facile and efficient two-step solvothermal method. Compositions, microstructure and electromagnetic properties of the Fe 3 O 4 @rGO composites were systematically studied by using various analytical techniques. Compared with the hollow Fe 3 O 4 and bare rGO, the Fe 3 O 4 @rGO composites have significantly higher electromagnetic absorption performances. A maximum reflection loss ( RL ) of −49.8 dB was achieved at 8.48 GHz, with a wide bandwidth of 3.3 GHz from 6.6 GHz to 9.9 GHz, when the Fe 3 O 4 @rGO composites with a Fe 3 O 4 to rGO mass ratio of 2:1 were synthesized at 200 °C for 7 h by using ethylene glycol as the hydrothermal solvent. The absorption covered the mid-low frequency X-band, while the optimum match thickness was 3.0 mm. The peak position of the minimum reflectance of the Fe 3 O 4 @rGO composites shifted to lower frequencies with increasing content of Fe 3 O 4 . The electromagnetic absorption properties of the Fe 3 O 4 @rGO composites could be adjusted by controlling the mass ratio of the two components, reaction time and the sample thickness. SuchhHollow Fe 3 O 4 microspheres/graphene composites could be used as light-weight microwave absorption materials at the mid-low frequency bands. • The hollow Fe 3 O 4 microspheres are highly monodisperse. • Electromagnetic absorption characteristics have been significantly enhanced due to Fe 3 O 4 internal hollow structure and it's synergistic effect with rGO.