Sandwich‐Like <scp>MXene</scp> @ <scp>BNNS</scp> Nanofillers for Enhanced Thermal Diffusion in Epoxy Resins

ABSTRACT Heat dissipation is of importance for modern microelectronic devices. However, it is still a great challenge for the composite to achieve eminent thermal, mechanical, electrical insulation, and thermal diffusion performance simultaneously. Negatively charged MXene and positively charged boron nitride nanosheets (BNNSs) self‐assembled into sandwich heterostructured MXene‐BNNSs (MXene@BNNS) fillers via electrostatic interactions. At a 50:1 BNNS‐to‐MXene mass ratio, the 2D MXene is well wrapped between the insulated BNNSs. The synergistic effect between the two nanosheets significantly improved the construction efficiency of thermal transport pathways. The in‐plane thermal conductivity of 25 wt% MXene@BNNS/epoxy is 0.912 W m −1 K −1 , which is increased by 404% and 98.1% compared to epoxy resins and BNNS/epoxy composites, respectively. Furthermore, the composite also has enhanced thermal stability with a temperature at 5% weight loss ( T d5% ) of 376.1°C and a char yield of 27.87%, good electrical insulation with a volume resistivity of 6.37 × 10 13 Ω cm and dielectric properties (dielectric constant &lt; 4.0), suggesting it is a promising thermal management material.