Effect of the addition of Al2O3 and h-BN fillers on the thermal conductivity of a cellulose nanofiber/nanodiamond composite film

To develop a highly thermally conductive composite film, two types of ceramic fillers with different shapes were bound with cellulose nanofiber (CNF) composite fibrils densely covered with nanodiamond (ND) particles. A hexagonal boron nitride (h-BN) filler with a plate-like structure was oriented in the in-plane direction of the CNF/ND nanosheets, increasing the in-plane thermal conductivity of the h-BN-based composite film by 38.7% from 4.45 to 6.17W/mK compared with the raw CNF/ND composite film. Conversely, the Al2O3 particles inflected the CNF/ND nanosheets and lowered the orientation of the nanosheets. The in-plane thermal conductivity of the Al2O3-based composite film was lower than that of the CNF/ND film. To develop a highly thermally conductive CNF/ND/ceramic composite film, the ceramic filler should be oriented in the plane direction, and h-BN with a high thermal conductivity is a suitable filler. [GRAPHICS] .