Preparation of quasi‐isotropic thermal conductive composites by interconnecting spherical alumina and 2D boron nitride flakes

Abstract Achieving thermal management composite material with isotropic thermal dissipation property by using an environmentally friendly and efficient method is one of the most challenging techniques as a traditional approach tending to form a horizontally arranged network within the polymer matrix or the preparation steps which are unduly cumbersome. What presented here is a close‐stack thermally conductive three‐dimensional (3D) hybrid network structure prepared by a simple and green strategy that intercalating the modified aluminum oxide (m‐Al 2 O 3 ) spheres of different sizes into the modified two‐dimensional (2D) boron nitride (m‐h‐BN) flakes. An effective 3D network is created by the multi‐dimensional fillers through volume exclusion and synergistic effects. The m‐h‐BN flakes facilitate in‐plane heat transfer, while the variously sized m‐Al 2 O 3 spheres insert into the gaps between adjacent m‐h‐BN flakes, which is conducive to the heat transfer in the out‐of‐plane direction. Additionally, strong interactions between the m‐Al 2 O 3 and m‐h‐BN promote the effective heat flux inside the 3D hybrid network structure. The 3D hybrid composite displays favorable quasi‐isotropic heat dissipation property (through‐plane thermal conductivity of 2.2 W·m −1 ·K −1 and in‐plane thermal conductivity of 11.6 W·m −1 ·K −1 ) in comparison with the single‐filler composites. Furthermore, the hybrid‐filler composite has excellent mechanical properties and thermal stability. The efficient heat dissipation capacity of the hybrid composite is further confirmed by a finite element simulation, which indicates that the sphere–flake hybrid structure possesses a higher thermal conductivity and faster thermal response performance than the single‐filler system. The composite material has great potential in meeting the needs of emerging and advancing power systems.