Synthesis of reduced graphene oxides with magnetic Co nanocrystals coating for electromagnetic absorption properties

This paper reports a facile one-step reaction method to prepare rGo/Co hybrids with super-tiny Co nanocrystals coating on reduced graphene oxide, the rGo/Co hybrids have excellent electromagnetic wave absorption ability because of its good impedance matching and attenuation properties. The crystal structure, microtopography, and magnetic property of rGOs/Co hybrids were characterized by X-ray diffraction, transmission electron microscope, and vibrating sample magnetometer, respectively. Electromagnetic parameters were measured by vector network analyzer in the frequency range of 1-18 GHz using a coaxial line method. The rGOs can serve as perfect supports for dense coating of Co nanocrystals with an average size of 3.87 nm. Compared with pure rGOs and Co NPs, the rGO/Co hybrids exhibit excellent electromagnetic wave absorption properties with an optimal reflection loss (RL) value reaching up to - 52.73 dB at 14.34 GHz and a broad effective bandwidth (RL values lower than - 10 dB) of 6.2 GHz (11.8 to 18 GHz) at a thin thickness of 2.1 mm only. This work provides an efficient process to prepare a micro-nano composite absorber with strong and broadband electromagnetic wave absorption.