Flexible PVA/Co Ferrite/MWCNT/AC Metacomposites: High Conductivity and Low Percolation Threshold

Abstract

Recently, metacomposites have emerged as a promising solution for electromagnetic wave absorption due to their extraordinary electromagnetic parameters. However, the underlying paradigm and regulation mechanism for the negative and near-zero responses of real permittivity are still not clearly understood. To address this gap, this study focuses on the development of metacomposites comprising poly(vinyl alcohol) (PVA), Co ferrite, multiwalled carbon nanotubes (MWCNT), and activated carbon (AC) using a cost-effective sol−gel method based on percolation theory. An in-depth analysis of the materials revealed that the combination of a porous structure and magnetic nanoparticles in the carbon matrix had a synergetic effect. This synergistic effect resulted in a remarkable improvement in the impedance matching conditions and attenuation ability of the metacomposites. Interestingly, as the frequency increased, the value of the real permittivity switched from positive to negative in PVA/Co ferrite/MWCNT/AC metacomposites. This phenomenon can be explained by the electrical dipole resonance of the interconnected MWCNTs. As a result, the metacomposites displayed excellent electromagnetic wave absorption performance, with the electromagnetic absorption capacity significantly enhanced to −28.1095 dB for a thickness of 1 mm. Such a high level of reflection loss (RL) indicates that these metacomposites have the capability to attenuate all incoming electromagnetic radiation. Consequently, these metacomposites hold great potential for various modern devices that require highly efficient, stable, adjustable, and lightweight absorption capabilities such as memristors, light-dependent resistances, and low-frequency reflectors.