Dynamic thermal-dielectric behavior of core-shell–structured aluminum particle-reinforced epoxy composites

Abstract

The broadband dielectric spectroscopy was carried out in the frequency range of 1–10⁷ Hz at the −20–200°C range to investigate the effect of temperature on the dynamic thermal–dielectric behavior of the aluminum (Al)/epoxy composite. The epoxy composites with core-shell–structured Al particles were prepared by solution method. The results show that the dielectric permittivity of the composites increased smoothly with a rise of filler content and reduced with an increase in frequency at room temperature. While the dielectric loss and conductivity still remained at low level owing to the nanoscale alumina insulating shell serving as a barrier layer to control the dielectric loss. The dielectric permittivity, dissipation factor, and conductivity of the composites increased with temperature and exhibited an abrupt rise around the glass transition temperature (T_g). A large increase in the dissipation factor and conductivity with temperature is attributed to the direct current conduction of thermal-activated charge carriers resulting from pure epoxy above T_g. The observed temperature-dependent dielectric relaxations of the composites indicated a thermally activated behavior of the relaxation time of epoxy chain segments.