Honeycomb-like NiCo2O4@MnO2 nanosheets array/3D porous expanded graphite hybrids for high-performance microwave absorber with hydrophobic and flame-retardant functions

To extend the service life of electronic devices in harsh working environments and protect human health from electromagnetic pollution, constructing high-performance microwave absorbers with multiple functions has become a hot spot. Herein, the honeycomb-like NiCo2O4@MnO2 nanosheets array was successfully assembled on the surface of expanded graphite (EG) via thermal treatment and hydrothermal process, realizing the integration of microwave absorption, hydrophobicity and flame resistance. Remarkably, the NiCo2O4@MnO2/EG exhibited a strong RLmin of −59.5 dB and an EAB of 4.6 GHz at the thickness of 1.68 mm, with a filling ratio of only 4%. It further confirmed that the carbon-based magnetic materials with multiple heterointerfaces can achieve better impedance matching and reflection loss from the synergistic effect of conductive loss, magnetic loss and polarization loss. In addition, the as-prepared hybrids also possess excellent hydrophobic and flame-retardant abilities due to the hierarchical nano-micro structure in which the high porosity of EG can dissipate heat rapidly during combustion and the intertwined nanosheets of NiCo2O4@MnO2 can enhance the surface roughness. This work opens up a new prospect for developing multifunctional and lightweight microwave absorbers to satisfy the practical application.