Enhanced thermal conductivity of epoxy composites via bridged Al2O3 network with in situ formed silver nanoparticles

It is of great significance to achieve excellent thermal conduction for polymer composites in electrical insulation application. However, traditional polymer composites exhibit limited thermal conduction due to the absence of efficient heat transfer pathways. Herein, Al2O3 microspheres absorbed with silver acetate (AgAc) and 2‐ethyl‐4‐methylimidazole (2E4MI) complex were prepared as fillers for constructing heat transfer paths in epoxy composites. At a suitable temperature, 2E4MI was released from Ag(2E4MI)2Ac complex and initiated the curing reaction of epoxy. Simultaneously, nano silver ions were reduced, sintered in situ and then bridged separate Al2O3 microspheres to 3D filler network, which acted as thermal transport pathways in matrix. The thermal conductivity increased from 1.38 W/mK for Al2O3/epoxy composites to 2.62 W/mK for Al2O3@Ag(2E4MI)2Ac/epoxy composites at 60 vol% Al2O3 loading. Thanks to the 3D filler network, the tensile strength of Al2O3@Ag(2E4MI)2Ac/epoxy composites was obviously improved. Both the electrical resistivity and dielectric strength of the composites were basically preserved. Al2O3@Ag(2E4MI)2Ac/epoxy composites exhibit promising application in thermal management materials for advanced electric machinery and electronic devices. Schematic illustration of 3D thermal pathway in Al2O3@Ag(2E4MI)2Ac/epoxy composites.