Lightweight composite BN/MWCNT/epoxy for electromagnetic wave absorption and thermal management

Optimizing polymeric material properties through composite filler incorporation has demonstrated effectiveness in enhancing both thermal conductivity and electromagnetic wave absorption. However, persistent challenges arise from filler incompatibility and the intrinsic trade-off between thermal conductivity and electromagnetic wave absorption performance. This study develops a facile fabrication method for epoxy-based composites containing boron nitride-coated multi-walled carbon nanotube (BN/MWCNT) composite fillers, designed for dual thermal management and microwave absorption applications. By controlling the BN coating extent on MWCNT surfaces, we facilitated precise regulation of dielectric properties and microstructural characteristics. Subsequent surfactant modification strengthened interfacial adhesion between fillers and matrix while suppressing particle agglomeration. The engineered coating architecture simultaneously reduced interfacial thermal resistance and established optimized conductive pathways. The composite achieved full X-band absorption (8.2–12.4 GHz) at 3.4 mm with merely 5 wt.% filler loading, demonstrating a minimum reflection loss of -39 dB at 9.7 GHz. Concurrently, the thermal conductivity increased by 104% compared to pure epoxy resin, confirming effective thermal network formation. This work establishes a practical approach for creating multifunctional electronic packaging composites through rational filler compounding and interface engineering.