Control of alignment of h-BN in polyetherimide composite by magnetic field and enhancement of its thermal conductivity

In this study, hexagonal boron nitride (h-BN) - polyetherimide (PEI) composites were prepared by a simple solution casting method, where the h-BN particles were aligned by an external magnetic field. Prior to the preparation of the composite samples, the h-BN platelets were firstly decorated by iron oxide nanoparticles (Fe3O4) to achieve the desired magnetic properties. Due to the alignment of h-BN particles, the composite exhibited greatly enhanced thermal conductivity along that direction. At a filler loading of 20 wt%, an enhancement of 166% was obtained, compared to that of the unaligned composite. Furthermore, the composite samples showed a low dielectric loss (~ 0.01) with the filling ratio below 20 wt% and a tensile modulus of up to 2.34 GPa. Bearing such thermal conductivity, electrical insulation properties, and mechanical properties, these composites with magnetically aligned h-BN particles show potentials for microelectronic packaging applications.