Interconnected 3-D networks of aluminum borate whiskers on Al2O3@h-BN core-shell particles enhancing thermal conductivity of polydimethylsiloxane composites

Abstract

Boron nitride-based core-shell spherical-structured fillers has been widely utilized to increase the thermal conductivity and thermal isotropy of polymer composites. However, conventional spherical-shaped particles have a proclivity for contacting single points between fillers, which limits enhancement of thermal conduction at the interfaces. Herein, we fabricated aluminum oxide (Al2O3)@hexagonal-boron nitride (h-BN) core-shell microspheres (ABC) using spray-drying technique and synthesized aluminum borate (Al18B4O33) whiskers on the surface of the particles via heat treatment process for achieving high quasi-isotropic thermally conductive fillers, which is attributed to the formation of multi-contacts among the interconnected Al18B4O33 whiskers. Polydimethylsiloxane (PDMS) composites containing Al2O3-Al18B4O33@h-BN microspheres (ABC-W) exhibited the highest through-plane thermal conductivity (8.8 W m-1 K-1). The composites exhibited a high thermal isotropy of 0.89. This study outlines a facile but straightforward strategy to enhance high quasi-isotropic thermal conductivity in polymer composites, holding immediate relevance for the development of composites utilized in versatile electronics to remove heat. © 2025