Synthesis of magnetic graphene aerogels for microwave absorption by in-situ pyrolysis

High-performance magnetic graphene aerogels nanocomposites with low density and enhanced microwave absorption properties have been developed firstly by a two-step strategy combining hydrothermal reaction and in situ pyrolysis. TEM images indicate that ultra-fine Ni nanocrystals with a relatively uniform size of 8 nm are anchored to the graphene nanosheets. Meanwhile, the resulting magnetic graphene aerogels possess superparamagnetism. The GA@Ni hybrids of paraffin mixed with an ultra-low filling content (<5 wt%) show superior capability of microwave absorption (MA) for practical application owing to their excellent impedance matching and synergistic effect. The minimum reflection loss (RLmin) reaches -52.3 dB at 11.9 GHz and the maximum effective absorption bandwidth (EAB) exceeding -10 dB is up to 6.5 GHz with an absorber layer thickness of 2.6 mm. Furthermore, the nanocomposites of epoxy resin mixed with 4.25 wt% GA@Ni exhibit an ultrawide EAB of 6.7 GHz with a thinner thickness of 2.52 mm. Interestingly, the electromagnetic parameters can be rationally regulated by adjusting the calcination temperature and filler contents to carry out highly efficient microwave absorption. Results indicate that magnetic graphene aerogels nanocomposites can be as superior microwave absorption materials and the two-step strategy will open an avenue for the fabrication of synergistic microwave absorbers. (c) 2019 Elsevier Ltd. All rights reserved.