Electromagnetic interference shielding and dielectric properties of graphene nanoplatelets/epoxy composites in the x-band frequency range

Materials with electromagnetic interference (EMI) shielding capabilities are crucial to reduce electromagnetic radiation pollution. This study investigates the EMI shielding and the dielectric properties of epoxy-based nanocomposites incorporating graphene nanoplatelets (GNPs) of varying surface area (750, 500 and 300 m(2)/g). Sonication during preparation and casting play significant roles in exfoliating and uniformly dispersing the GNPs in the epoxy matrix. EMI shielding properties are measured using the reflection-transmission method in the X-band frequency range, and dielectric properties are calculated using the Nicolson-Ross-Weir method. Complex permittivity, AC conductivity and EMI shielding performance increase with increasing GNP surface area and concentration, with maximum increase in properties over neat epoxy at 17 wt% 750 m(2)/g GNPs. The dominant observed shielding mechanism is reflection. However, at higher concentrations of the 750 m(2)/g GNPs, the material acts as a lossy medium with increasing absorptivity. The formation of conductive networks and interfacial polarization play a significant role in enhancing the real and imaginary parts of the permittivity and shielding performance.