Microwave absorbing properties of graphene nanosheets/epoxy-cyanate ester resins composites

Microwave absorbing composites with epoxycyanate ester (EP-CE) as matrix and graphene nanosheets (GNSs) as absorbers were prepared, and their electromagnetic and microwave absorbing properties were investigated in the frequency range of 2.6-12.4 GHz. The microstructures of the composites showed a uniform dispersion of the GNSs in the matrix. The complex permittivity of the composites increased with increasing filler content. As absorbing materials, the GNSs/EP-CE composites possess excellent absorption properties. And the composites with 3 wt.% of GNSs exhibited high values of reflection loss (>10 dB) over a wide frequency range 5.8-6.6 GHz and maximum loss is 15.7 dB at 5.8 GHz at a thickness of 3 mm. The minimum reflection loss was found to move toward to the low frequency region (from 10.2 to 4.5 GHz) with increasing composites thickness. Especially, a minimum reflection loss value of -21.4 dB was obtained at 4.5 GHz for the composite thickness of 4 mm. Moreover, the thermal properties of the composites were also investigated in detail. It is observed that GNSs reinforced EP-CE composites demonstrated better thermal stability than that of EP-CE matrix, which make them suitable for use in aerospace applications and radar absorbing material (RAM).