Surface modification and binary hybridization of alumina nanospheres for improving the fluidity, thermal conductivity and mechanical properties of epoxy composites

Abstract

Alumina (Al₂O₃) nanospheres were synthesized by homogeneous precipitation, during which their particle size and distribution could be facilely controlled by adding 2 wt% surfactants, resulting in two kinds of Al₂O₃ with average diameters of 230 and 700 nm. Then both of the Al₂O₃ were modified with silane coupling agent (KH560), and further hybridized into binary systems with different volume ratios to simultaneously enhance the fluidity, thermal conductivity (TC) and mechanical properties of epoxy composites. As expected, the surface modification of 4.0 wt% KH560 significantly decreased the particles agglomerates and viscosity of epoxy/Al₂O₃ composites, and improved their TC and tensile properties by enhanced interface interactions. While the binary hybridization system with 30 vol% small particles could not only construct more effective thermally conductive pathways within epoxy matrix, but also reduce the particle-particle friction by embedding small particles into the gaps of larger ones, leading to increased TC and fluidity of epoxy composites. Finally, the synergistic effect of surface modification and optimized hybridization ratio endowed epoxy/Al₂O₃ composites with low viscosity of 154 Pa·s at a shear rate of 1 s⁻¹, high TC of 2.96 W/m·K and tensile strength of 53 MPa, making them competitive in the fabrication of high-performance thermal interface materials.