Improved dielectric and electromagnetic interference shielding performance of materials by hybrid filler network design in three-dimensional nanocomposite films

A nanoscale stretching-induced one-dimensional (1D) nanofiller orientation in a three-dimensional (3D) film (the films form cell walls of foamed materials) is beneficial for improving the dielectric and electromagnetic interference (EMI) shielding properties of composite systems. However, nanoscale stretching may cause nanofiller separation, negatively impacting their properties. In this study, a two-dimensional (2D) nanofiller was introduced into a carbon nanofibre/poly(vinylidene fluoride) (CNF/PVDF) nanocomposite system to improve the nanoscale confined-space stretching effect. As a result, the degree of in-film orientation of the CNFs was significantly improved. Based on this effect, boron nitride was used as a 2D dielectric nanofiller to improve the degree of in-plane orientation of CNFs and to prepare 3D nanocomposite films with improved dielectric properties (improved by 54.3 %). Furthermore, 2D conductive nanofiller graphene nanoplatelets (GNPs) were employed to improve the degree of in-film orientation of CNFs for the preparation of CNF/GNP/PVDF nanocomposite foams with improved electrical conductivity and EMI shielding performance (increased by 89.4 %, from 18.8 to 35.6 dB·g−1·cm3 at 10 GHz). A Monte Carlo simulation was used to verify that the 2D nanofiller improved the 1D nanofiller orientation in the 3D nanocomposite film. This study provides a guide for the design of high-performance foamed nanocomposite materials.