Magnetic graphene for microwave absorbing application: Towards the lightest graphene-based absorber

Application of graphene derived nanomaterial in microwave absorption has been limited by the issue of excessively high dielectric loss. To address this issue, instead of resorting to burdensome compositing with metal and ceramic particles, we put forward the idea of approaching impedance match by transforming graphene from diamagnetic to ferromagnetic and meanwhile suppress the conductivity. In this study, we synthesized the Nitrogen-doped graphene (NG) by a facile hydrothermal method with graphene oxide (GO) and urea as precursors. In comparison with GO and reduced GO (rGO), the nitrogen doping along with reduction process boosted the magnetism via a Ruderman-Kittel-Kasuya-Yosida (RKKY) mechanism. Pyrrolic-N has been found to dominate the magnetic property induced, which cooperates with the suppression of conductivity to benefit the absorption performance. The reflection loss of nitrogen doped graphene can achieve - 11.3 dB absorption maximum at 12.7 GHz and an absorption bandwidth of 12.2-14.3 GHz (reflection loss < - 10 dB) at a thickness of 3 mm, which proves to be favourable with respective to the density as compared to existing graphene-based absorbers. (C) 2017 Elsevier Ltd. All rights reserved.