Interface engineering of AlN via phosphoric acid modification for enhanced thermal conduction, electrical insulation, and mechanical properties of epoxy composites

Abstract Epoxy resin (EP), widely employed as an insulating material in electrical and electronic devices, faces application challenges arising from its insufficient thermal conductivity. In this work, we report a phosphoric acid modification strategy for aluminum nitride (P-AlN) fillers to resolve interfacial compatibility issues at high loadings, realizing synergistic enhancement of thermal conductivity, electrical insulation, and mechanical properties in epoxy composites. The results demonstrate that at an optimal P-AlN loading of 35 wt%, the composite exhibits a thermal conductivity of 0.41 W·m −1 ·K −1 , representing a 78.3% improvement over the pristine. The surface flashover voltage reaches 16.2 kV, and the volume resistivity attains 4.1 × 10 14 Ω·m. Additionally, the tensile strength and Young’s modulus achieve 77.5 MPa and 4.7 GPa, respectively. In addition to the intrinsic contribution of AlN, the hydrogen bonding network formed between phosphate groups and the EP matrix plays a pivotal role in enhancing interfacial adhesion, reducing thermal resistance, and improving both insulation and mechanical properties. The underlying mechanism is revealed using molecular dynamics simulations. This work effectively alleviates the trade-off among thermal conductivity, electrical insulation, and mechanical properties at high filler loadings, offering theoretical guidance for the design of high-performance epoxy materials.