Modified negative permittivity and X-band microwave absorption in polyvinyl Alcohol–MWCNT metacomposites

Abstract

Metacomposite films with modifiable negative permittivity are promising for wearable cloaking, sensing, electromagnetic interference shielding, and microwave absorption. The purpose of this study is to fabricate metacomposite films composed of polyvinyl alcohol (PVA) and multi-walled carbon nanotubes (MWCNTs) and demonstrate control of permittivity by varying MWCNT concentration. Drude-Lorentz and Drude models show negative permittivity behaviour as the MWCNT content increases. The Drude-Lorentz and Drude models confirm that at 1 wt% MWCNT loading, percolation occurs, leading to increased conductivity and a transition from positive to negative permittivity (−9 at 10 kHz and −200 at 34 kHz). Drude's model predicts negative permittivity across the entire frequency range of PVA with 3 wt% MWCNT. Metacomposite films exhibit electrical percolation, conductivity switching, permittivity shift, and capacitive-to-inductive transitions. These composites also demonstrate excellent X-band microwave absorption properties (up to −50 dB reflection loss) and a shielding efficiency of 22 dB, suggesting an absorption-dominated shielding mechanism.