Boron nitride whisker @ graphene nanohybrid-filled epoxy composites with high thermal conductivities and low dielectric losses

Abstract In this work, we demonstrate boron nitride whisker @ graphene (BN@GE) nanohybrids with a unique morphology as a thermally conductive filler for improving the thermal conductivity of a polymer matrix. In this structure, GE sheets were applied to insulating hexagonal boron nitride (BN) whiskers via a simplified method to ensure the sheets were well separated when used in epoxy composites. The addition of GE to produce the BN@GE hybrids was found to reduce the length of the BN whiskers. In addition, separation of the sheets enhanced the three-dimensional thermally conductive networks within the composite, which improved the thermal conductivity and significantly enhanced the dielectric constant. Furthermore, the implanted insulating network of BN inhibited the charge carrier mobility on the well-separated sheets via GE fixation on the BN whiskers, and resulted in a low dielectric loss. As a result, the epoxy composite containing 40 wt% BN@GE-15 hybrid filler exhibited a thermal conductivity, dielectric constant, and ultra-low dielectric loss of 1.26 W m⁻¹ K⁻¹, 12.7, and 0.0051, respectively. We expect this uniquely structured hybrid filler will be suitable for the fabrication of thermal interface materials with high thermal conductivities and low dielectric losses.