Synergistic Enhanced Thermal Conductivity of Epoxy Composites with Boron Nitride Nanosheets and Microspheres

Herein, we report a new strategy to effectively enhance the thermal conductivity of epoxy composites by constructing a three-dimensional thermally conductive network with 2D boron nitride nanosheets (BNNSs) and 0D boron nitride microspheres (BNMSs). In the composites, the BNMSs serve as the principal building blocks for constructing the thermally conductive network because of their large sizes, while the BNNSs are embedded within the interspaces of the BNMSs to improve the thermal pathway density. Experimental and finite element analysis reveals that the combined BNNSs and BNMSs (BNNSs/BNMSs) outperform individual BNNSs and BNMSs in terms of thermal conductivity enhancement. Notably, the BNNSs/BNMSs/epoxy composite with a filler loading of 30 wt % shows a thermal conductivity of 1.148 W m–1 K–1, which is approximately 28.0 and 51.5% higher than the corresponding data for BNNSs/epoxy and BNMSs/epoxy composites, respectively, and five times that of pure epoxy. In addition, the BNNSs/BNMSs/epoxy composites exhibit favorable dielectric properties, dynamic mechanical properties, and thermal stability simultaneously. The strategy described in this study provides guidance for optimizing the design of high-performance epoxy composites to meet the requirements of thermal management in modern electronic devices.