Multilayered absorber over K-and Ka-band based on graded concentration of carbon nanofillers: Modeling, Fabrication, and Experimental validation

In this paper, a thin wideband microwave absorber is modeled and validated experimentally between 18 and 40 GHz. The absorber is built by stacking conductive nanocomposite slabs having graded concentrations of conductive carbon nanofillers in order to achieve a reflectivity below-10 dB.These conductive composites are fabricated through blend compounding method using carbon nanotube (CNT) and graphene nanoplatelets (GNP) nanofillers loaded in a polycarbonate matrix. A systematic loading of nanofillers yields a hierarchical effect on nanocomposite permittivity and electrical conductivity, which are successfully modeled using Maxwell-Garnett formulation. It is shown that 1D and 2D geometry of nanofillers are individually and together influencing the real and imaginary parts of the permittivity and associated conductivity. This plays an important role to fabricate substrates having dedicated electromagnetic properties required for the design of efficient wideband absorbers, as demonstrated in this paper.