Microwave scattering behaviour of carbon black/ molybdenum di sulphide /cobalt composite for electromagnetic interference shielding application

Abstract

Erasing signature of an object from an enemy's radar is, tactically, disruptive move achieved by the effective electromagnetic interference (EMI) shield. We report on the microwave scattering (2–18 GHz) behaviour of the nano-composite for architecting efficient shield composed of carbon black (CB), molybdenum di sulphide (MoS2) and cobalt (Co). Nano-composite, prepared by a facile, solid state synthesis route, are characterized using infrared, x-ray diffractometry, UV–visible, energy dispersive x-ray spectroscopic techniques including scanning electron microscopy. In infrared and Rayleigh analysis, formation of -C-Mo-C, OSO, Mo–O, and Co–O phases generated asymmetric polarization at low % CB content that gets transformed into a symmetric mode due to formation of Co–O and Co–S–C radicals at high CB % to cause maximum power losses. Possible polarization mechanism is discussed. In constitutive analysis, two-fold increase in the dielectric function, the dual behaviour (Debye and Jonscher) of the ac conductivity, and the synergistic magneto-dielectric coupling factor influenced the scattering performance of the composite. Broadly, at 18% composition, the shielding effectiveness is recorded to be > 97@14 GHz with 7.7 GHz of the bandwidth and the thickness ∼2.5 mm. The Dallenbach return loss is almost 75% revealing a high-performance shield design @18% CB/MoS2/Co nano-composite.