Polymer composites filled with core@double-shell structured fillers: Effects of multiple shells on dielectric and thermal properties

Polymer dielectrics with a high dielectric constant (high ε), low dielectric loss and high thermal conductivity (k) are constantly pursued for advanced electrical power systems, driven by the continuous demands of device miniaturization and high operating temperature. In this paper, we present an effective approach to concurrently improve the dielectric properties and thermal conductivity of composites by tailoring filler interface. Core@double-shell structured aluminum particles are synthesized, with the metallic aluminum core encapsulated by a double-shell of amorphous and crystalline aluminum oxide. The double-shell filler structure enables a substantial increase in dielectric constant and reduction in dielectric loss for the corresponding composites, surpassing the performance of the unfilled polymer and the polymer composites containing the single-shell fillers. The improved dielectric properties can be attributed to the enhanced interfacial polarization. Furthermore, the thermal conductivity of the composites is also significantly improved when the low-k amorphous aluminum oxide shell is transformed into its crystalline phase with high thermal conductivity. © 2019 Elsevier Ltd