Estimation of interface properties in epoxy-based barium titanate nanocomposites

Abstract

The study of the interface around a nanoparticle in a nanocomposite is crucial to understanding the performance of nanocomposites. In this work, an estimate of the interface thickness and interface permittivity is obtained based on the changes in dielectric properties in epoxy due to the introduction of nanofillers. Barium titanate (BaTiO3) nanofillers with an average diameter of 90 nm are used. Specimens with various filler loadings (1%–10% by volume) are used. Nanoparticles are used either as-received or surface-functionalized with 3-glycidoxypropyltrimethoxy-silane (GPS) before use. Fourier Transform Infra-red (FTIR) spectroscopy is used to study the surface chemistry of BaTiO3 nanofillers after GPS functionalization. Reasonable uniformity of dispersion is observed from Field Emission Scanning Electron Microscopy (FESEM) images. Complex permittivity is measured using Broadband Dielectric Spectroscopy over a wide frequency range (10−3 Hz to 10+6 Hz). A unit cell-based Finite Element model is used to compute the effective permittivity of a nanocomposite, for a given interface thickness and interface permittivity. This method combines the experimental data obtained from dielectric spectroscopy with a unit cell-based Finite Element Method (FEM) for electric field computation. A match between experimental and computational data indicates that the interfacial thickness around the nanoparticle is approximately 200 nm and interface permittivity is slightly higher than that of neat epoxy resin over the given frequency range.