Enhanced microwave absorption performance of highly dispersed CoNi nanostructures arrayed on graphene

Magnetic metals (Fe, Co, Ni) and alloys thereof are easily synthesized as nanoparticles, but obtaining highly dispersed graphene-based magnetic nanomaterials remains challenging. Here, three CoNi/graphene nanocomposites (CoNi/GN) are successfully assembled for the first time via a one-pot strategy without templating by manipulating the reaction time and solvents used for the same precursors. Moreover, the reduction of graphene oxide utilizing this method is more effective than that by conventional methods and the alloy particles are firmly embedded on the GN substrate. Compared to n- and p-CoNi/GN nanocomposites, o-CoNi/GN nanocomposites show the best electromagnetic wave absorption properties with the maximum reflection loss of-31.0 dB at 4.9 GHz for a thickness of 4 mm; the effective absorption bandwidth (< 10.0 dB) is 7.3 GHz (9.5–16.8 GHz) for a thickness of 2 mm. The structures and electromagnetic wave absorption mechanisms of the three composites were also investigated. This research provides a new platform for the development of magnetic alloy nanoparticles in the field of microwave-absorbing devices.