Dielectric properties and electromagnetic interference shielding effectiveness of Al2O3-based composites filled with FeSiAl and flaky graphite

Abstract Al2O3-based composites filled with FeSiAl and flaky graphite (FG) were prepared by hot-pressed sintering. The dielectric properties and electromagnetic interference shielding effectiveness were investigated. As the mass ratio of FeSiAl to FG decreases from 4:1 to 0:5, the real (e′) and imaginary (e″) parts of complex permittivity increase significantly. The increased e′ values are ascribed to the enhancement of interfacial polarization and electronic polarization, and the elevated conductance loss and relaxation loss lead to the increased e″ values. Due to the formation of conductive network and the increasing electrical conductivity, the electromagnetic shielding effectiveness is significantly improved with increasing the percentage of flaky graphite, and absorption plays a dominant role in the electromagnetic interference shielding mechanisms. The FeSiAl/FG-filled Al2O3 composite with the ratio of FeSiAl to FG 0:5 exhibits the maximum shielding effectiveness of 30.4 dB in the X-band, denoting the composites have wide potential application for large scale in military and commercial fields.