Three-dimensional reduced graphene oxide foam modified with ZnO nanowires for enhanced microwave absorption properties

Flexible and high-performance electromagnetic absorbing materials of three-dimensional (3D) hierarchical reduced graphene oxide (RGO) foams decorated with in-situ grown ZnO nanowires (ZnO_nws) were realized by a direct freeze-drying and hydrothermal process. The unique structure not only effectively reduces agglomeration of RGO and the density of composites, but also makes great contributions to impedance match, dielectric loss and inner scattering, achieving enhanced microwave absorption performance. When RGO foam is 0.8 mg/mL, the ZnO_nws/RGO foam/PDMS composite with 3.3 wt% absorber loading attains a minimum reflection loss value of −27.8 dB at 9.57 GHz with a thickness of 4.8 mm, and a wide effective absorption bandwidth of 4.2 GHz covering the whole X band (8.2–12.4 GHz). The fundamental microwave absorption mechanism of the composites is discussed. These results demonstrate a promising method to fabricate an economical, lightweight, broadband and highly efficient microwave absorption material.