Gamma Alumina@Boron Nitride Fiber‐Reinforced Functional Composites With Thermal Conductive Networks Exhibiting High Thermal Conductivity and Electrical Insulation

Functional composites with high thermal conductivity and insulating properties have emerged as a current research hotspot. This study fabricated a novel core–shell structured fiber filler (hexagonal boron nitride@gamma alumina (BN@AO)) using electrospinning technology and produced BN@AO/epoxy resin (EP) composites through hot pressing method. BN@AO filler can form thermal conductive (TC) network in the composites. Microscopically, h‐BN forms a continuous TC path in the BN@AO fibers, and macroscopically, the BN@AO fibers with high aspect ratios can form TC paths directly in the EP matrix. The results show that the optimal in‐plane and out‐of‐plane thermal conductivity ( λ ) of BN@AO/EP are 8.776 and 0.911 W·m ⁻¹ ·K ⁻¹ at 30 wt% filler loading, which are 3571.96% and 408.93% higher than EP, respectively. Furthermore, the BN@AO/EP composites retain excellent electrical insulation properties, with an AC breakdown field strength exceeding 50 kV·mm ⁻¹ . This research presents a fabrication method for high thermal conductivity insulating fillers, applicable to heat dissipation solutions in modern electric and electronic devices.