Impact of Particle Thermal Treatment on Dielectric Properties of Core-Shell Filled Epoxy Nano-composites

This paper presents the effect of Silica-Titania
$(\mathbf{SiO}_{2}{@}\mathbf{TiO}_{2})$
core-shell nano-particles added into amine-cured epoxy composites, under three different particle treatment conditions: untreated, calcined at 250
${}^{\circ}\mathbf{C}$
and 450
${}^{\circ}{\mathbf{C}}$
, on the dielectric and structural properties of the bulk composite. Characterization was conducted using a range of methods Transmission Electron Microscopy (TEM),
$\mathbf{Fourier}$
Transform Infra-Red Spectroscopy (FTIR), Raman Spectroscopy, Differential Scanning Calorimetry (DSC) and Broadband Dielectric Spectroscopy (BDS). TEM confirmed the synthesis of the core-shell architecture with denser shells at higher calcination temperatures. Raman spectroscopy showed an increase in the Ti-O-Ti network formation and orderliness with elevated temperature treatment. Incorporating untreated filler into epoxy reduces the bulk real permittivity, while the inclusion of calcined fillers leads to an increase. An additional
$\omega$
relaxation was observed in imaginary permittivity spectra of nano-composites pointing towards altered molecular dynamics within the epoxy due to nano-particle addition. These findings highlight the role of core-shell nano-particles in modifying the dielectric properties of epoxy composites, whilst differentiating them from conventional nano-particles.