The influence of ambient temperature and X-band frequency on EMI shielding performance of graphene/silica nanocomposites.

The electromagnetic interference (EMI) shielding devices fabricated by graphene-based nanocomposites are constantly exposed to high temperature and X-band frequency during service, but at present no theory can account for such environmental effects. In this work, a micromechanics-based theory is developed to address the influence of temperature and X-band frequency on EMI shielding of graphene/silica nanocomposites. First, the temperature-dependent electromagnetic constitutive relations are established for both graphene and silica, and then the temperature-dependent electromagnetic interface effects, including electron tunneling and hopping for the conductivity and dielectric polarization and relaxation for the permittivity, are introduced. With these constituent and interface properties, the effective complex permittivity and permeability of the nanocomposite are evaluated through the effective-medium approximation. The EMI shielding effectiveness (SE) in the X-band range is calculated from Maxwell's equations under the near-field wave source. The predicted complex permittivity and EMI SE are shown to agree with the experiments of rGO/silica nanocomposites over 320–480 K and 8–12 GHz. The X-band EMI SE enhances with the increase of temperature due to the increase of reflection loss, and the temperature influence increases with the sample thickness. Several other novel attributes are also discovered. • EMI SE for graphene-based nanocomposites is studied under near-field wave source. • Temperature-dependent electromagnetic properties of graphene, matrix, and interface are included. • It is demonstrated that the EMI SE is directly connected to microstructural parameters. • The results are validated with data of rGO/silica nanocomposites over 320–480 K and 8–12 GHz. [ABSTRACT FROM AUTHOR]