Fabrication of Fe3O4 coated boron nitride nanoplatelets by liquid-phase exfoliation for thermally enhanced epoxy composites via magnetic alignment

Abstract

Boron nitride nanoplatelets coated with Fe3O4 nanoparticles (BNNP/Fe3O4) were fabricated via a liquid-phase exfoliation method using an ultrasonicator, and a composite was prepared by incorporating the resultant filler into an epoxy matrix. This fabrication method not only provided efficient exfoliation assisted by additional shear force from added Fe3O4 but also simultaneously made BNNP reactive toward magnetic force because of the coating of Fe3O4, which has superparamagnetic character. During the curing process, an external magnetic field was applied to vertically align the filler in the epoxy matrix, which led to an increase in thermal conductivity because of the generation of 3-dimentional thermal transport channels. The obtained thermal conductivity of the anisotropically aligned BNNP/Fe3O4 composites with a filler fraction of 20 wt% was 1.07 W/mK, which is higher than that of the raw boron nitride composites with 20 wt% filler (0.62 W/mK) because of the uniform dispersion resulting from the exfoliation and the efficient heat conduction path via filler orientation. Moreover, an enhanced storage modulus was recorded using DMA after magnetic alignment.