Dual-curable emulsion enabled magnetic alignment of carbon fiber skeletons for thermally conductive epoxy composites

High power density electronic devices create an urgent demand for thermal interface materials with efficient through plane thermal conductivity. Carbon fibers are promising one dimensional thermally conductive fillers because of their high axial thermal conductivity, but direct magnetic alignment in viscous target matrices remains difficult because fiber rotation and rearrangement are hindered. To address this issue, a stepwise route combining preconstruction of an oriented framework with secondary infiltration is employed. Fe₃O₄ deposited on carbon fiber surfaces imparts magnetic responsiveness. A waterborne nanoemulsion with low viscosity (8.85 mPa⋅s) and photo and thermal dual curing capability serves as the dispersion and bridging medium. Under a vertical magnetic field, magnetized carbon fibers align into a vertical framework, and UV curing bridges neighboring fibers and fixes the oriented structure. After field removal, the framework remains stable, and thermal curing further improves its structural integrity. Secondary infiltration with liquid epoxy resin yields a composite with a through plane thermal conductivity of 53 W m⁻¹ K⁻¹ at 36 wt% filler loading, together with a better surface temperature response than a commercial carbon fiber pad. The pre oriented framework also adapts to other functional phases.