A rapid, simple, and inexpensive process combining a microwave-assisted technique and a solvothermal method has been developed using graphene sheets and FeCl3 center dot 6H(2)O as the reactant to prepare graphene/Fe3O4 nanoparticle hybrids, which can be applied as an electromagnetic radiation absorbent. The experimental factors (i.e., composition ratio, microwave power, and irradiation time) on the products' characteristics were examined. Under optimal conditions, the morphological analysis revealed that the graphene sheet was homogeneously covered with Fe3O4 nanoparticles (similar to 50 nm). The electromagnetic parameters of the composites made from 20 wt% Fe3O4/graphene-epoxy were measured by a vector network analyzer. It was found that the 4- and 5 mm-thick composites could attain a reflection loss below -20 dB in the dual-ranges of 4-8 and 12-18 GHz. (C) 2015 Elsevier Ltd. All rights reserved.