Layered NiCo alloy nanoparticles/nanoporous carbon composites derived from bimetallic MOFs with enhanced electromagnetic wave absorption performance

NiCo alloy nanoparticles/nanoporous carbon (NiCo/NPC) composites with multilayered structure were synthesized by in situ pyrolysis of the bimetallic NiCo-based metal-organic frameworks. Designable electromagnetic parameters accompanied with a low density, ultrathin thickness, wide absorption bandwidth and strong electromagnetic wave absorption were achieved in the NiCo/NPC composites. An optimum RL (reflection loss) value of -51 dB at 17.9 GHz with an effective absorbing bandwidth (RL < -10 dB) of 4.5 GHz (from 13.5 GHz to 18 GHz) and a thickness of 1.5 mm was obtained for the nanocomposite annealed at 600 degrees C. The nanoporous carbon with layered structure derived from the NiCo-MOFs contributed to the favorable impedance matching, polarization and multiple attenuations. In addition, the enhanced electromagnetic absorption performance was benefitted from the synergistic effects of the magnetic and dielectric loss among NiCo NPs, graphitized carbon layers and NPC, which was generated from natural and exchange resonance as well as multi-relaxation. This work not only offers a promising way for the development of high-performance electromagnetic wave absorbers, but also provides a valid fabricating concept for the bimetallic NPs/NPC composites. (C) 2019 Elsevier Ltd. All rights reserved.