Development of Cost-Effective Carbon Nanofiber Epoxy Nanocomposites for Lightweight Wideband EMI Shielding Application

• Published in: IEEE transactions on nanotechnology Vol. 20; pp. 627 - 634
• Main Authors: Mohan, Lekshmi, Kumar, Tanikonda Nishanth, Karakkad, Sunitha, Krishnan, Sindhu Thiruthi
• Format: Journal Article
• Language: English
• Published: New York IEEE 2021; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Broadband; Carbon fibers; Carbon nanofibers; characterization; Chemical composition; Chemicals; Conductivity; Dielectric loss; Dynamic response; Electromagnetic interference; electromagnetic parameters; Electromagnetic radiation; Electromagnetic shielding; Electron states; EMI shielding; epoxy; Ethanol; Fillers; High aspect ratio; Lightweight; Military applications; Molecular structure; Nanocomposites; Nanofibers; Percolation theory; Photoelectrons; polymer nanocomposites; Polymers; Raman scattering; shielding effectiveness; spectroscopy; Superhigh frequencies
• ISSN: 1536-125X; 1941-0085
• DOI: 10.1109/TNANO.2021.3103955

Electromagnetic interference (EMI) shielding is essential at minimizing cost in the X and Ku frequency bands utilized for radar and defense applications. Development and characterization of lightweight, cost-effective carbon nanofiber (CNF) based epoxy nanocomposites for wideband EMI shielding application is the primary focus of this work. CNF epoxy nanocomposites are prepared with a minimum thickness of 0.5 mm at various CNF concentrations from 0.1 to 8 wt.%. SEM analysis ensures uniform dispersion of fillers and spectroscopic measurements like Raman and X-ray photoelectron spectroscopy ensures the chemical composition, molecular structure, and electron states of the developed nanocomposite material. DC conductivity follows the classical law of percolation theory with a percolation threshold of 1.5 wt.%. The AC conductivity of prepared CNF-based nanocomposites follows the universal dynamic response when the filler content is beyond the percolation threshold. The variation of permittivity with varying filler concentration exhibits the various polarization mechanisms and dielectric loss in the nanocomposite material. The measured shielding effectiveness for 4 wt.% and 8 wt.% CNF content in the X and Ku bands confirms with 99% and 99.9% diminution of electromagnetic radiation, respectively, absorption is the dominant mechanism, thus lowering the chances for further electromagnetic interference. The high shielding effectiveness of the prepared nanocomposites is due to the inherent stacked cup structure of CNF, and the high aspect ratio of CNF used. The shielding efficiency of the prepared material increases with the frequency change from X-band to Ku-band.