An aqueous-only, green route to exfoliate boron nitride for preparation of high thermal conductive boron nitride nanosheet/cellulose nanofiber flexible film

With the rapid development of electronic device, thermal management material is currently in great demand. Therefore, to design material of efficient thermal management is of high significance. In this work, we report a green route that using only water exfoliate boron nitride (BN) powder and obtain hydroxylate boron nitride nanosheets (BNNS-OH) aqueous dispersion. The BNNS-OH as high thermally conductive nanofillers composited with cellulose nanofiber (CNF) is prepared a flexible film which has high thermal conductivity, superior mechanical properties and good thermal stability. In BNNS-OH/CNF film, BNNS-OH and CNF are stacked layer-by-layer to form a natural nacre structure, where CNF acted as the mortar filled in the interlayer space. The in-plane thermal conductivity of the 25 wt%BNNS-OH/CNF film is 22.67 W m−1 K−1, corresponding to thermal boundary resistance is 3.26 × 10−6 m2 kW−1 calculated by the Maxwell-Garnett effective medium theory (EMT) which is lower than that by previously reported methods. We demonstrate the potential usefulness of BNNS-OH/CNF film in electronic device-cooling application.