Light-weight, low-loading and large-sheet reduced graphene oxide for high-efficiency microwave absorber

Carbon materials are extensively used in lightweight and efficient microwave absorption (MA) due to their low density. However, the single carbon material has poor impedance matching and absorbing performance. Graphene oxide (GO) and reduced graphene oxide (rGO) are widely used as carbon materials with customizable dielectric properties, but there are still problems of poor MA and high loading. In this work, a series of large-sheet GO with different reduction degrees were prepared by a simple and controlled thermal reduction method, and their MA properties were investigated. The analysis of the composition, structure and MA performance of graphene showed that the MA performance of rGO was closely related to the reduction degree and the size of the sheet. Large sheet graphene was more likely to overlap each other to form a conductive network, reducing the filler loading. Meanwhile, after mixing rGO with different reduction degrees, the optimal reflection loss was −59.12 dB, which was 2.13 times and 1.59 times of the original single component. The effective absorption bandwidth was 3.54 GHz and the loading was only 1.5 wt%. This work provided a promising approach for constructing graphene-based composites with strong MA ability at low filler loadings.