Nitrogen-Doped Graphene@Co/C Composite Aerogel Microspheres for Highly Efficient Electromagnetic Wave Absorption

In this study, high-strength graphene-based aerogel microspheres are used as a template to grow the metal–organic frameworks ZIF-67, and further, the mixtures are pyrolyzed to obtain the magnetic nitrogen-doped graphene@Co/C composite aerogel microspheres (N-rGOAMs@Co/C). The morphological observation shows that N-rGOAMs@Co/C are micrometer-scale aerogel microspheres with a three-dimensional network structure, where many porous magnetic Co/C nanoparticles with rough concave structures are loaded on the inner walls of the microspheres. By adjustment of the amount of ZIF-67 precursor, the shape and structure of the N-rGOAMs@Co/C can be controlled to match the impedance and electromagnetic parameters between the absorber and the air to precisely adjust the electromagnetic wave (EMW) absorption performance. Due to the hierarchical porous structure and nitrogen-doped cobalt–carbon hybrid components, the N-rGOAMs@Co/C exhibit strong and wide microwave absorption effects. When loading N-rGOAMs@Co/C-0.45 microspheres into the paraffin matrix at only 3.8 wt %, the minimum reflection loss (RLmin) value at a thickness of 2.3 mm is as high as −63.4 dB, and the maximum effective absorption bandwidth value at a thickness of 2.1 mm is up to 4.5 GHz (10.0–14.5 GHz). This work provides a simple and efficient method for preparing lightweight and high-efficiency EMW absorbers and has broad application prospects in the field of radar stealth protection.