Highly flexible cellulose nanofiber/single-crystal nanodiamond flake heat spreader films for heat dissipation

Thermally conductive and electrically insulating polymer composites are ideal for applying in electrical or electronic fields as thermal management materials. Diamond nanomaterials have been used as an ideal thermal conductive filler due to their excellent intrinsic thermal conductivity. In this work, utilizing single-crystal nanodiamond (SCND) flakes as the thermally conductive filler, flexible cellulose nanofiber/single-crystal nanodiamond (CNF/SCND) flake composite films with high thermal conductivity were prepared by vacuum-assisted filtration. The strong hydrogen bonding interaction between CNF and SCND and the highly ordered stacking structure of SCND flake layers endowed the composite films with satisfactory flexibility and excellent heat dissipation performance. Compared with pure CNF film, a remarkable thermal conductivity enhancement of approximately 145.6 times and enhanced thermal conductivity (76.23 W m −1 K −1 ) was achieved in our CNF/SCND composite films. In addition, the enhanced thermal conductivity and excellent mechanical strength, accompanied with excellent flexibility, can be attributed to the CNF/SCND films with low and medium filling content of SCND. This demonstrates that the CNF/SCND composite films are a promising candidate as a heat spreader to rapidly cool LED lamps or electronic devices. A simple method was proposed to produce a flexible heat spreader with efficient thermal transportation performance.