Strong graphene-interlayered carbon nanotube films with high thermal conductivity

Fast growing flexible and wearable electronics and devices require thermal management materials having not only high thermal conductivity but also structural flexibility with mechanical robustness. However, most developed thermal management materials are relatively rigid and have low strength. Herein, we report a carbon nanotube/graphene hybrid film that combines high thermal conductivity (up to 1056 W/(mK)), extraordinary structural flexibility, and high mechanical strength (similar to 1 GPa). Such film consists of alternately stacked aligned, long and thin carbon nanotube sheets, which provide a mechanically strong and thermally conductive scaffold, and graphene sheets, which act as a highly conductive component. The hybrid film was prepared by in-situ spraying graphene oxide sheet solution onto an aligned, freestanding carbon nanotube aerogel sheet during winding the sheet on a rotating mandrel, followed by high-temperature annealing. Experimental and theoretical results suggested that the removal of defects of the hybrid films and the formation of covalent bonding between carbon nanotubes and graphene sheets resulted in improved thermal conductivities and mechanical strength. Application of such film as an orientational heat spreader has been demonstrated. (C) 2017 Elsevier Ltd. All rights reserved.