Synthesis and electromagnetic wave absorption performance of NiCo2O4 nanomaterials with different nanostructures

Bayberry-like, needle array-like and urchin-like NiCo2O4 hierarchical structures were synthesized by simple hydrothermal reactions. The differences among the nanostructures and morphologies affecting their electromagnetic wave absorbing properties have been systematically studied. Benefiting from the unique hierarchical structures assembled by magnetic component units, all of these NiCo2O4 nanomaterials show satisfactory performances of absorbing microwave radiation. Remarkably, the urchin-like NiCo2O4 obtains an optimum reflection loss (RL) value of -40 dB when the matching thickness is only 1.4 mm. Moreover, the urchin-like NiCo2O4 reaches an effective absorbing bandwidth of about 15 GHz upon adjustment of the coating thickness. The outstanding electromagnetic wave absorbing properties are closely related to the strong interfacial polarization, dipole relaxation, eddy current loss and multiple reflections in its unique needle-like assembly.