Preparation of cauliflower shaped hp-Co/GNs composite microwave absorbing materials

In this work, the hollow porous cauliflower shaped cobalt spheres/graphite nanosheets (hp-Co/GNs) composites with brilliant absorbing performance have been successfully fabricated through a simple solvothermal method and a subsequent hydrothermal reduction process. When the filling amount of absorbing agent is 30 wt%, the composite exhibits excellent absorbing properties in the range of 4–7.92 GHz in S band and 16.24–18 GHz in Ku band. The optimum reflection loss value (RLmin) can be up to −52.1 dB at a thickness of 4.5 mm. By changing the time of the second step hydrothermal reduction reaction, the morphology of the composite changes and its microwave absorption properties are regulated. Its excellent microwave absorption performance benefits from the special hollow porous cauliflower shaped structure and the synergism of magnetic loss and dielectric loss. This study demonstrated that cauliflower shaped hp-Co/GNs composites can be applied as a better electromagnetic wave absorbing material.