Ice‐Templated Three‐Dimensional Aligned Boron Nitride Nanosheets/Cellulose Nanofibers Network for High‐Performance Thermally Conductive Epoxy Composites

ABSTRACT The development of high‐performance thermally conductive polymer‐based composites is considered a crucial research direction in the field of thermal management. Boron nitride nanosheets (BNNS) are frequently utilized as thermally conductive fillers due to advantages including high intrinsic thermal conductivity and excellent electrical insulation. A three‐dimensional (3D) boron nitride nanosheets/cellulose nanofibers (BNNS/CNF) aerogel network was prepared utilizing BNNS and CNF as raw materials via a directional ice‐templating strategy. Epoxy resin/boron nitride nanosheets/cellulose nanofibers (EP/BNNS/CNF) composites were subsequently obtained through vacuum impregnation. BNNS are aligned directionally along the growth direction of ice crystals and bridged by CNF to form a continuous and stable 3D heat transfer pathway. The thermal conductivity of EP/BNNS/CNF composites is demonstrated to increase with the BNNS content from 0.28 W/(m K) (2.9 wt%) to 1.04 W/(m K) (7.2 wt%), which is superior to the thermal conductivity of the randomly distributed structure with the same composition (0.64 W/(m K)) and is measured to be 5.2 times that of pure EP (0.20 W/(m K)). Furthermore, infrared thermography and LED heat dissipation tests verify the rapid heat conduction capability of EP/BNNS/CNF composites. COMSOL simulations further demonstrate the crucial role of the oriented BNNS/CNF network in maintaining the continuity of the heat conduction pathways. The application potential of BNNS composites in thermal management devices and the effect of oriented structure design on thermal conductivity are thereby explored. Ultimately, a theoretical reference is provided for the development of high‐performance polymer‐based composites.