The combustion synthesis of highly crystalline boron nitride nanosheets and their application in thermoconductive polymeric composites

Thermally conductive yet electrically insulating boron nitride nanosheets (BNNSs) are highly promising for thermal management applications in modern electrical devices and future energy systems. However, the large-scale and cost-effective synthesis of BNNSs is still challenging due to the complexity of BN binary compound growth. Here, we report the scalable fabrication of single crystalline BNNSs by a magnesiothermic reduction combustion synthesis method. Compact BNNS/epoxy resin (EP) composites were obtained by incorporating the as-synthesized BNNSs through a high-efficiency process using a planetary mixer, and the BNNS/EP composite exhibited 1150% and 632% thermal conductivity enhancement at cryogenic and room temperature, respectively. Moreover, remarkable coefficient of thermal expansion (CTE) reduction was achieved at the same time, and the strong heat transfer capability of the nanocomposites was demonstrated by infrared thermal imaging experiments. These desirable property enhancements are attributed to the high quality of the BNNS crystals, which not only reduced the CTE of the composites but also formed thermal conductive networks for the efficient diffusion of heat flow.