A facile hydrothermal synthesis of MnO2 nanorod-reduced graphene oxide nanocomposites possessing excellent microwave absorption properties

Pure MnO2 nanorods and MnO2 nanorod/reduced graphene oxide (RGO) nanocomposites are prepared for microwave absorption by using a simple one-step hydrothermal method without using any toxic solvents. The results demonstrate that the MnO2 phases possess a high crystallization degree in both the pure nanorods and the nanocomposites but the nanocomposites exhibit two hybrid Mn phases, distinct from MnO2 in the pure nanorods. The electromagnetic characteristics and electromagnetic wave (EMW) absorption properties of the materials are investigated. The thickness dependent reflection loss shows that the peak frequency and effective absorption bandwidth all decrease with the increasing material thickness. Compared with the pure MnO2 nanorods, the introduction of RGO enhances the microwave absorbing intensity and effective absorption bandwidth. The maximum reflection loss value of the nanocomposites reaches -37 dB at 16.8 GHz with a thickness of 2.0 mm and the wide bandwidth corresponding to the reflection loss below -10 dB starts from 13 GHz until a value of -22 dB at 18 GHz. The enhanced microwave absorbing properties can be ascribed to the improved permittivity, dielectric loss and especially the synergistic effects between MnO2 nanorods and RGO nanosheets at their interfaces in the unique nanostructures of the MnO2/RGO nanocomposites.