Porous Co nanospheres supported on nitrogen-doped graphene as high-efficiency electromagnetic wave absorbers with thin thickness

Abstract

The design of magnetic/dielectric composites with rational nanostructures can greatly determine the electromagnetic wave absorption performance of absorbers. Herein, the porous magnetic Co nanospheres supported on lightweight dielectric nitrogen-doped graphene (N-GN) were prepared through a simple one-pot solvothermal method as enhanced synergistic electromagnetic wave absorbers. The Co nanocrystals show porous spherical shape with hexagonal phase, which are supported uniformly on the crumpled N-GN without conglomeration. Even powerful ultrasound treatment cannot separate the Co nanospheres from N-GN, suggesting that the porous Co nanospheres are in-situ anchored on N-GN. Taking the combined advantages of magnetic porous Co nanospheres and dielectric lightweight N-GN, the Co/N-GN nanocomposites perform improved electromagnetic wave absorption abilities, such as high-efficiency absorption performance, thin matching thickness and broad effective absorption bandwidth. When the absorber thickness of nanocomposites is only 1.3 mm, the maximum reflection loss (RL) value can reach −24.3 dB at 17.7 GHz. And the effective absorption frequency with RL < −10 dB is ranging from 3.6 to 18 GHz, when the thickness of nanocomposites absorber is 1.2–4.0 mm. However, in the entire frequency range, the bare Co nanocrystals cannot exceed −10 dB. The improved absorption abilities for the Co/N-GN nanocomposites are mainly due to the combined effect of excellent magnetic and dielectric loss, which may result in better impedance matching condition and improved attenuation capacity. These results suggest that the porous Co/N-GN nanocomposites are attractive absorbents for electromagnetic wave absorption. Besides, decorating magnetic nanocrystals with nitrogen-doped graphene is believed to be a promising kind of magnetic/dielectric composites for high-efficiency electromagnetic wave absorption.