Abstract: Both high thermal conductivity (K) and large cross-sectional area are essential for thermal dissipation materials to maximize their heat transfer capability. However, the drastic decrease of K values with the increased thickness makes the existing graphite/graphene films less favored for practical applications. In this work, graphite film with both large thickness and high K value is produced based on an in-situ composition strategy between nanographene (G) and pyrocarbon (PyC) via chemical vapor deposition (CVD) using CH₃OH/C₂H₅OH mixed precursors. It's found that an optimized O/C ratio of precursors facilitates the construction of ordered G skeletons within the deposited G/PyC composites. Such G/PyC composites can be completely graphitized at a lower temperature than the existing products. After 2400 °C annealing, dense, thick, and highly aligned graphite films were prepared. Their K values reach 1350 and 1010 W m^-1 K^-1 at the thickness of 40 and 120 μm, respectively, surpassing the existing records with similar thicknesses. More importantly, the proposed method is insensitive to the deposition substrates, and the G/PyC can be infiltrated into large-size fiber preforms as a matrix for preparing centimeter-thick high K materials. Besides, the G/PyC also exhibits better mechanical and electromagnetic shielding performances than the existing products, indicating a promising multifunctional application prospect.

Key words: Graphene, Thermal management, Chemical vapor deposition