Nitrogen-doped and Fe-filled CNTs/NiCo2O4 porous sponge with tunable microwave absorption performance

Lightweight, highly efficient, thermal stable microwave absorption materials are highly desirable but challenging for electromagnetic protection. Impedance matching and electromagnetic loss are two crucial factors for the microwave absorption materials design. Here, we successfully designed and synthesized a lightweight (31.5 mg/cm3) and porous NiCo2O4@carbon nanotubes (CNTs) hybrid sponge (NiCo2O4@CNTs) based on N-doped and Fe-filled CNTs. The as-prepared NiCo2O4@CNTs shows high thermal stability (>500 °C) and excellent microwave absorption properties with a minimum reflection loss value of - 45.1 dB at 9.0 GHz for absorber thickness of 2.5 mm. Moreover, the maximum absorption peak frequency and effective microwave absorption region (<10 dB) can be controlled in the range of 4.0–16.0 GHz by varying the thickness of the absorber. The highly efficient electromagnetic absorption performance of the sponge is mainly attributed to the high dipolar polarization, interfacial polarization loss and suitable impedance matching characteristic. These results indicate that the NiCo2O4@CNTs sponge can serve as the lightweight, highly efficient, and high temperature resistant microwave absorption materials.