One-step self-triggered microwave-assisted fabrication of NiCo/graphene for microwave attenuation

Microwave-assisted reduction of graphene oxide (GO) has been reported to be very effective in producing high-quality reduced graphene oxide (rGO) and its composites. However, either pretreatment (e.g., heating) or an external trigger (e.g., copper wire) is required to initiate the process due to the poor microwave absorption ability of GO. In this work, we report a one-step self-triggered microwave-arcing approach for synthesizing rGO composites (NiCo/rGO) for the first time. Evidenced by permittivity value, the synergic microwave absorption between GO and the metal nitrate salts is found to play an important role in initiating the process. From XRD, Raman, XPS and TEM results, it is proposed that mildly reduced rGO is firstly formed after 10 s, which further enables stronger microwave absorption to facilitate the complete reduction of GO as well as formation of well-crystallized NiCo nanoparticles about 10 nm after 90 s. The as-synthesized product shows a minimum refection loss value of − 44.48 dB with an absorption bandwidth of 3.66 GHz at 4.5 mm.