3D Fe₃O₄ nanocrystals decorating carbon nanotubes to tune electromagnetic properties and enhance microwave absorption capacity

We fabricated a novel dielectric-magnetic nanostructure by hybridizing 3D Fe₃O₄ nanocrystals and multi-walled carbon nanotubes through a simple co-precipitation route. The 3D Fe₃O₄-MWCNTs composites demonstrate enhanced microwave absorption with tunable strong-absorption wavebands in the frequency range of 2-18 GHz. Double-band microwave absorption appears in the investigated frequency range and at various thicknesses. This depends on the loading concentration of 3D Fe₃O₄-MWCNTs. Minimum reflection loss values at 20 wt% loading of -23.0 dB and -52.8 dB are observed at 4.1 GHz and 12.8 GHz, respectively, which are superior to those of pure MWCNTs as well as other hybrids of Fe₃O₄. The improved absorption capacity arises from the synergy of dielectric loss and magnetic loss, as well as the enhancement of multiple interfaces among 3D Fe₃O₄ nanocrystals. All of these factors increase the flexibility of tuning microwave absorption. These results provide a new strategy to tune electromagnetic properties and enhance the capacity of high-efficient microwave absorbers.