Highly thermally conductive flexible insulated PI/BNNS@rGO nanocomposite paper with a three-dimensional network bridge structure

The sharp increases in power consumption and heating capacity caused by the emergence of intelligent electronic devices necessitate the development of highly thermally conductive thermal interface materials (TIMs) with good heat dissipation properties. Boron nitride nanosheets (BNNS) are ideal materials with high thermal conductivity. Hence, it should be possible to produce flexible high thermal conductivity nanocomposites with a three-dimensional network containing ultrathin, large, and uniformly thick BNNS. In this study, large-scale (1–1.5 µm) fewer-layered (2 nm) BNNS with a high yield of 80% were prepared through the separation of a NaOH–LiCl aqueous solution by a hydrothermal method and in ball milling. Highly thermally conductive insulating nanocomposite paper with a three-dimensional bridging structure of two-component nanosheets filled with nanofibers was fabricated by a simple electrospinning–electrospraying technique. The mechanical properties of the polyimide (PI)/BNNS@reduced graphene oxide nancomposite paper were improved by 168% as compared with those of the PI/BNNS composite. With an increase in the BNNS content, a layered microstructure similar to that of natural nacre was produced, which resulted in a large in-plane thermal conductivity of 16.92 W/m·K. The described method can facilitate the design of TIMs with good electrical insulation properties, thermal stability, and flexibility.