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.

纳米复合材料中纳米颗粒周围界面的研究对于理解纳米复合材料的性能至关重要。在这项工作中，基于引入纳米填料导致环氧树脂介电性能的变化，获得了界面厚度和界面介电常数的估计值。使用平均直径为 90 nm 的钛酸钡 (BaTiO ₃ ) 纳米填料。使用具有不同填料填充量（按体积计 1%–10%）的样品。纳米颗粒可按原样使用，也可在使用前用 3-环氧丙氧基丙基三甲氧基硅烷 (GPS) 进行表面功能化。傅里叶变换红外 (FTIR) 光谱用于研究 BaTiO ₃的表面化学GPS功能化后的纳米填料。从场发射扫描电子显微镜 (FESEM) 图像观察到分散的合理均匀性。复介电常数是使用宽带介电光谱在宽频率范围（10 ^-3 Hz 至 10 ⁺⁶赫兹）。对于给定的界面厚度和界面介电常数，基于晶胞的有限元模型用于计算纳米复合材料的有效介电常数。该方法将从介电光谱获得的实验数据与基于晶胞的有限元方法 (FEM) 相结合，用于电场计算。实验和计算数据之间的匹配表明，纳米粒子周围的界面厚度约为 200 nm，并且界面介电常数在给定的频率范围内略高于纯环氧树脂。