Investigation on microwave dielectric behavior of flaky carbonyl iron composites

The corresponding mechanism of high complex permittivity for micro flaky Fe-filled composites was still not apparent. In this letter, the dielectric behaviors of flaky carbonyl iron/epoxy resin composites within 2-18 GHz were studied experimentally and theoretically. Results show that an obvious increase both in real and imaginary part of permittivity can be observed as the volume fractions of FCI is up to the percolation threshold. Considering the influence of conduction current, a revised Debye model of permittivity has been proposed to reveal the mechanism of dielectric behavior in composites. The best fitting result demonstrate that conduction loss played an important role in increasing the permittivity after percolation. Fe3O4 was used as encapsulated shell on surface of the FCI to control the conduction and enhance the percolation threshold, resulting in better microwave absorption from better balance between the complex permittivity and permeability.