Preparation and characterization of high thermal conductive graphene films by improved reduction method

Abstract

Structural defects such as voids and air pockets in graphene films resulting in a lower density of graphene films reduced the thermal conductivity of graphene films. However, removing the structural defects of graphene films through traditional thermal reduction methods always conducted under extremely high temperature. The energy consumption becomes a severe and inevitable problem. Herein, an energy-saving step-by-step improved thermal reduction method was developed to manufacture the high thermal conductive graphene films. Effect of graphene oxide (GO) mixing ratios of different sheet sizes on the thermal properties of hybrid graphene films were investigated. In addition, mixed large and small size sheet graphene/carboxylated cellulose nanocrystals composite films (LS-G/CNC) composite films were prepared to further repair defects and further improve the thermal properties. Results showed that the in-surface thermal conductivity increased from 177 W/mK to 269 W/mK with an increase of approximately 52 % through step-by-step improved thermal reduction method. The mixed size sheet also increased the thermal conductivity of LS-G films to 607 W/mk. The small size sheet graphene oxide (SGO) filled the voids of the large size sheet graphene oxide (LGO). Finally, CNC was further used to fill the carbon atom vacancies in the thermal reduction process and improved the graphitization of the composite films. LS-G/CNC composite films without structural defects exhibited high thermal conductivity of 852 W/mk and electrical conductivity of 7.1 × 10⁴ S/m.