Enhanced thermal conductivity of aluminum oxide /Polyphenylmethyldimethylsiloxane composites via boron nitride-encapsulated graphene

Abstract

Polyphenylmethyldimethylsiloxane (PPMS) is rendered as an ideal thermal interface material matrix due to its superior electrical insulation properties and thermal stability. Nevertheless, the intrinsically low thermal conductivity (TC) poses challenges in meeting the heat dissipation demands of electronic components, necessitating the incorporation of thermally conductive fillers to achieve further enhancement. In this work, the TC of PPMS is synergistically enhanced by incorporating the graphene (Gr) encapsulated by boron nitride (BN) (BN@Gr) as well as aluminum oxide (Al₂O₃) coated with liquid metal gallium. Benefiting from the modified thermal conduction networks, the TC of the composite with 4.8 wt% BN@Gr and 79.2 wt% Al₂O₃ reaches 1.85 W/m·K, about 0.5 W/m·K higher than that of the composite containing 84 wt% Al₂O₃; this value is nearly 11 times greater than the TC of the PPMS matrix. Furthermore, the as-prepared composite exhibits high initial thermal decomposition temperature (519 °C), outstanding electrical insulation resistance (4.3 × 10¹² Ω cm) and good compressive strength (0.43 MPa at 20 % strain). This work provides a facile strategy to produce BN encapsulated Gr powders, which facilitates the rapid formation of thermal conduction pathways within the Al₂O₃/PPMS composites.