Spherical aggregated BN /AlN filled silicone composites with enhanced through-plane thermal conductivity assisted by vortex flow

[Display omitted] •h-BN assembles into spherical aggregated BN (A-BN) assisted by the vortex flow.•The mechanism and operating conditions of A-BN formation are systematically studied.•A through-plane TC of 6.56 W/(mK) is achieved due to the formation of A-BN.•A-BN/AlN/SR composite demonstrates excellent heat dissipation performance as TIMs. Thermal interface materials (TIMs) with high thermal conductivity and good insulation properties are in high demand for thermal management systems. Platelet-like materials such as BN and graphene usually orient horizontally in polymer composites, causing minor Through-plane thermal conductivity (TC) enhancement. Herein, aggregated BN (A-BN)/AlN/silicone rubber (SR) composites with enhanced through-plane TC are fabricated assisted by vortex flow during the planetary centrifugation process. It is found that BN platelets assembled into A-BN with spherical AlN as cores based on concentric vortex. Due to the formation of spherical A-BN, through-plane TC of as-prepared composites with 40 wt% BN and 45 wt% AlN is as high as 6.56 W/(m·K) while it is only 4.62 W/(m·K) for composites without A-BN. Such high TC should mainly be attributed to the large-sized spherical BN interconnected structure which constructs an efficient thermally conductive path in the through-plane direction. The heat dissipation evaluation test also demonstrates the excellent performance of the A-BN/AlN/SR composite. This work provides a facile strategy to produce large-sized BN agglomerates and gives insights into the vortex flow during the planetary centrifugation process.