3D boron nitride foam filled epoxy composites with significantly enhanced thermal conductivity by a facial and scalable approach

[Display omitted] •A 3D boron nitride foam was fabricated by the sacrifice of NH4HCO3 template.•The 3D boron nitride foam serves as a more effective heat transfer pathway.•Significantly enhanced thermal conductivity was achieved.•Finite element simulation revealed the reasons and strategies for improving thermal conductivity. Polymer composites with excellent thermal conductivity, low dielectric constant and low dielectric loss are urgently required for microelectronics and wireless communication systems. However, traditional thermal conductive polymer composites realized by simply adding inorganic fillers, cannot have high thermal conductivity and good electrical insulation concurrently, which greatly hinders the practical application. In this work, a facile and scalable assembly technique to construct a three-dimensional boron nitride foam (3D-BN) for the formation of 3D-BN/epoxy composites has been proposed to address this long-standing challenge. Herein we built a self-support and pressure reinforced 3D-BN foam composed of only bulk-BN microplates to serve as the thermal pathway. The obtained composite with greatly enhanced thermal conductivity enhancement (TCE) exhibits the highest through-plane thermal conductivity of 6.11 W m−1 K−1 ever reported for bulk-BN polymer composites. Further analysis by finite element simulation revealed that the high thermal conductivity is attributed to the polymer-free, pressure reinforced 3D-BN foam which serves as a more effective pathway for the phonons transmission. This work offers an easy approach and provides a new paradigm for the fabrication and design of thermal management polymers.