Characterization of Carbon-Based Epoxy Nanocomposite Shield for Broadband EMI Shielding Application in X and Ku Bands

Abstract

Electromagnetic interference (EMI) shielding in the X and Ku bands of electromagnetic spectrum are vital for communication and military applications. This work aims at developing and characterizing nanocomposite shield with two nano fillers- carbon nanotubes (CNT) and carbon nanofibers (CNF) dispersed at various weight combinations for shielding both X and Ku bands at minimum cost. DC conductivity of the prepared CNT-CNF based epoxy nanocomposites obey classical law of percolation theory. AC conductivity follows universal dynamic response (UDR) when CNT concentration is above 0.5wt.%. The rise in permittivity with filler concentration at a particular frequency is more prominent with the increase in CNF concentration. The measurement of shielding effectiveness of the prepared samples demonstrates that maximum shielding obtained is 24 dB and 30 dB in the X and Ku bands respectively and the optimum filler combination is 1wt.%CNT-5wt.%CNF agreeing with the results obtained from characterization. The nanocomposites with higher CNF content exhibit better shielding as compared with higher CNT content owing to the higher aspect ratio of CNF used. The shielding efficiency increases as the frequency band shifts from X to Ku. Absorption loss is the prominent mechanism of shielding in both bands, avoiding the chance for electromagnetic pollution.