Near–zero epsilon response and variable negative permittivity of flexible PVA-graphite metacomposites for absorption dominant electromagnetic interference shielding

Abstract

There is tremendous interest in intrinsic metamaterials exhibiting negative permittivity, due to their potential applications in the electromagnetic field. In this investigation, polyvinyl alcohol (PVA)–graphite flakes (G) metacomposites were fabricated using die-casting method, with varying graphite flake concentrations. Epsilon-near-zero behavior was observed in the composite containing 1 wt% graphite flakes (-0.71). A higher concentration of graphite particles maintained negative permittivity throughout the tested frequency range. 3 wt% graphite flake loading changes hopping conduction into metal-like conduction. These metacomposites offer a new framework for constructing materials with weakly and controllably negative permittivity, thereby simplifying their application in microwave absorption and electromagnetic interference (EMI) shielding. A high positive permittivity and minimal dielectric loss were observed in a double-layer composite structure, sandwiched between two layers exhibiting negative and positive permittivity. Furthermore, EMI shielding was thoroughly discussed in the X-band region with a shielding efficiency of –37 dB with 2.5 wt% graphite flakes.