Construction of sandwich-like NiCo2O4/Graphite nanosheets/NiCo2O4 heterostructures for a tunable microwave absorber

Abstract Currently, microwave absorbers have received much attention in the military and civil fields on account of electromagnetic radiation and stealth technology. Herein, NiCo2O4/Graphite nanosheets/NiCo2O4 (GNC) hybrid composites with sandwich-like heterostructures were carefully constructed using a hydrothermal method and subsequent annealing process. The morphology and microwave absorption performance are investigated by changing the additive amount of GNS to regulate the ratio of GNS/NiCo2O4. The results show that varying the ratio of GNS/NiCo2O4 has a tiny effect on its structure, nanoband-like NiCo2O4 with the width of 100 nm attaches to the surface of GNS, while it can well tune the microwave absorption properties. When the additive amount of GNS increases from 0.02 g to 0.04 g, the microwave absorption performance first improves and subsequently worsens, which is attributed to the effect of impedance matching and attenuation capacity that resulted from conductive loss, interface polarization, and charge polarization. When the additive amount of GNS is 0.03 g, the maximum reflection loss and effective absorption bandwidth of GNC-2 composites are −47.01 dB and 2.98 GHz (14.51–17.49 GHz) with a thickness of 1 mm. Our results can provide more information for the design and manufacture of composites based on graphite nanosheets as high-performance microwave absorbers.