The rambutan-like C@NiCo₂O₄ composites for enhanced microwave absorption performance

To obtain outstanding electromagnetic microwave absorption (EMWA) properties, the rambutan-like dielectric–magnetic C@NiCo₂O₄ material was successfully prepared by a simple hydrothermal method, followed by a carbonization process. Benefiting from the unique rambutan-like structure, the dielectric–magnetic C@NiCo₂O₄ composites showed excellent microwave attenuation ability: minimum reflection loss (RL_min) value of − 39.0 dB at 17.4 GHz and wide effective absorption bandwidth (EAB, reflection loss exceeding − 10 dB) of 4.16 GHz (> 13.84 GHz) with a matching thickness of only 1.5 mm, which were much better than those of pure C and NiCo₂O₄. The superior properties might be due to multiple synergistic effects: magnetic loss (NiCo₂O₄), dielectric loss (C, NiCo₂O₄), the multi-reflections, scattering and interface relaxation resulting from mesoporous rambutan-like structures, and the dipole polarization to get good electromagnetic matching and high attenuation efficiency.