Effect of shell-thickness on the dielectric properties of TiO2/SiO2 core-shell nanoparticles filled epoxy nanocomposites

The aim of this paper is to investigate the effect of shell thickness on the dielectric properties of epoxy nanocomposite systems and on the molecular dynamics. For this purpose, two core - shell nanoparticles were fabricated namely, TiO 2 /SiO 2 - 10 nm and TiO 2 /SiO 2 - 30 nm, where the number specifies the thickness of the shell. The nanoparticles were filled into the epoxy resin based on their specific surface area, where their total surface area was kept approximately equivalent in both the samples i.e ≃ 5.82 m2. To confirm the successful synthesis of both types of nanoparticles TEM images are presented. Further, these samples were characterized by dielectric spectroscopy (10−1 - 105 Hz). Both the type of epoxy nanocomposites show higher real permittivity than unfilled epoxy system. TiO 2 /SiO 2 - 30 nm being higher between both. A reduction in the β relaxation peak is reported as the size of the nanoparticles increases. The relation of β relaxation with the degree of cross linking is also discussed. No significant changes are observed between both the nanocomposite types in terms of interfacial losses at lower frequencies (10−1 - 1 Hz) even though the volume of nanoparticles in both samples is different. This is attributed to the fact that their surface interaction area, both between the core and shell as well as between the shell and the polymer, is approximately the same.