Wide-Bandgap Silica Decorated Graphite Nanosheet for Decoupling Control of Dielectric Properties and Thermal Conductivity in Poly(Vinylidene Fluoride) Nanocomposites

Abstract

Flexible polymer dielectrics merging high dielectric constant (ε′) and breakdown strength (Eb) but low dielectric loss (tanδ) garnered a lot of interest in advanced electronic devices. To concurrently promote the ε′ and Eb and restrain the tanδ in graphite nanosheets (GNS)/poly (vinylidene fluoride, PVDF), a variety of core@shell structured GNS@SiO2 (silicon dioxide) nanofillers with diverse thicknesses were fabricated and then incorporated into PVDF. The results uncover that the presence of the SiO2 interlayer not only strengthens interface interactions between neat GNS and PVDF, but also effectively confines free carriers’ long-range migration resulting in decreased leakage conductivity and loss. Furthermore, it efficiently mitigates the intense dielectric mismatch between filler and host matrix, inhibiting local electric field distortion, introduces traps and raises the energy barrier height for de-trapping thus leading to much enhanced Eb. Moreover, the SiO2 shell also alleviates the phonon state density and phonon impedance mismatches between two components and facilitates the interfacial phonon transport resulting in meliorative thermal conductivity (TC) of the nanocomposites. The theoretical calculation uncovers the underlying mechanisms for both charge and phonon transport in the composites. Both dielectric parameters and TC of the GNS@SiO2/PVDF nanocomposites can be simultaneously modulated by optimizing the SiO2 shell thickness. Thus, the prepared GNS@SiO2/PVDF nanocomposites with simultaneously enhanced ε′, Eb and TC coupled with much suppressed tanδ present prospective applications in modern electronic instruments and power equipment.

Keywords: Graphite, Core-shell, Polymer composites, dielectric properties, thermal conductivity