Thermal conductivity and electromagnetic shielding performance of three-dimensional anisotropic BN/MWCNT epoxy composites under low filling capacity

Traditional single-function composite materials cannot meet the developing requirements in modern electronics. To build a three-dimensional (3D) skeleton is an efficient solution for multifunctional composites. However, it is a challenge for polymeric composites to provide thermal conductivity and electromagnetic shielding while maintaining good mechanical properties. Herein, we propose an oriented 3D hexagonal boron nitride (h-BN)/multi-walled carbon nanotube (MWCNT) skeleton structure with thermal conduction and electromagnetic shielding pathways by using ice template and carbonization method, in which the h-BN was connected with MWCNT and cellulose nanofiber (CNF), and the hydrolyzedmethyltrimethoxy silane (MTMS) was added to reinforce the structure. When MWCNT is 1.5 wt% and h-BN is 5.7 wt%, the electromagnetic shielding efficiency (EMI SE) reaches 48 dB, the absorption parameter (A) is more than 50%, and the out-of-plane thermal conductivity (TC) is 1.17 W/m·K. Compared with the randomly distributed BN/MWCNT composite at same filling rate, the electromagnetic shielding of 3D BN/MWCNT skeleton structure is 639.6% high than that of randomly distributed BN/MWCNT composite, and the thermal conductivity increased by 290%. Dynamic mechanical analysis (DMA) results indicated that the storage modulus increased by 48%, and Tg shifted 10 ℃ higher than pure epoxy, which enhances the mechanical properties of the composites. This study provides a valuable guidance for preparing composite with high thermal conductivities, high mechanical properties and satisfactory EMI SE, which showed great potential as the next-generation high-performance EMI shielding materials.