Nanofibrillated Cellulose/MgO@rGO composite films with highly anisotropic thermal conductivity and electrical insulation

Abstract

Abstract Graphene, an ideal two-dimensional material with high thermal conductivity, is widely used in the field of thermal management. However, its excellent electrical conductivity becomes an inevitable obstacle for applying in the electronic fields where electrical insulation materials are demanded. Herein, the reduced graphene oxide (rGO) decorated by magnesium oxide (MgO) particles was used as the hybrid thermal conducting filler to prepare the high thermal conductivity and electrical insulation nanofibrillated cellulose (NFC)-based composite films via a facile vacuum-assisted filtration and mechanical compression. In this way, MgO nano-particles not only reduced the interface thermal resistance between rGO and NFC but also cut the electric conductive pathways of rGO to enhance the thermal conductivity and maintain electrical insulation of the films. Simultaneously, mechanical compression caused the compacted layered structure formed by vacuum filtration along the in-plane direction. Thus, the obtained composite film exhibited high thermal conductivity and anisotropy. The in-plane and cross-plane thermal conductivity reached 7.45 W/(m·K) and 0.32 W/(m·K), respectively, when the filler content increased to 20 wt%, along with a high thermal conductivity anisotropy of 23 and superior electrical resistivity above 1011 Ω·m. Moreover, in the simulation test of the infrared camera, it has been demonstrated that the composite film dissipated heat quickly by the surface temperature variations of light-emitting-diode (LED) chips fixed on the composite film substrate with time. Therefore, the NFC-based composite films have great application prospects in the heat dissipation of electronic devices.