LAUSR

Abstract Dual-phase nanocomposites consisting of dielectric polyaniline (PA) of diameter ∼50 nm and semi-metallic expanded graphite (EG) were synthesized by in situ emulsion polymerization technique. This involved integrating EG in varied proportions of EG (0.00, 0.15, and 0.25 wt %) into PA and mixing with novolac phenolic resin (NPR) (10, 20, and 30 wt %) to tailor the microwave absorption properties ofrelative complex permittivity er(ω) = er′ – jer″, where er′ and er″ are real and imaginary parts of complex permittivity in the X-band frequency. The measured frequency-dependent er(ω) values showed significantly enhanced values for PA/EG–NPR nanocomposites with er′ ∼ 14.5 er″ ∼ 25.6, and (er″/er′) > 1.5 compared with PA–NPR nanocomposites with (er″/er′) > 0.25 and were analyzed using the principle of capacitance variation with filler concentration. Based on the Transmission Line Model, design optimization of single-layer microwave absorbers was performed for the developed nanocomposites. The fabricated absorber exhibited measured reflection loss RLm ∼32 dB at 9.7 GHz and RLm −17 dB at 10.9 GHz for 30 wt % PA/EGNPR (EG = 0.15) composite of thickness 3 mm and 20 wt % PA/EG–NPR (EG = 0.25) of thickness 2.5 mm, respectively, with −10 dB absorption bandwidth of 2.4 and 1.7 GHz in the X-band. A triangular-lattice perforated design for PA/EG composite was proposed to enhance the broad impedance matching and absorption bandwidth in the X-band.