Synthesis of a Graphene Carbon Nanotube Hybrid Film by Joule Self-Heating CVD for Thermal Applications

TLDR: In this paper, a double-sided carbon nanotubes (CNT) hybrid film is used as a thermal pad for large scale roll-to-roll CNT synthesis.

Abstract: Hybrid films based on vertically aligned carbon nanotubes (CNTs) on graphene or graphite sheets have been proposed for application as thermal interface materials and micro heat sinks. However, the fabrication of these materials are limited to small scale, expensive and complicated chemical vapor deposition (CVD) for CNT synthesis. We present a new method for direct growth of CNTs on one or both sides of a thin graphene film (GF) using joule self-heating of the graphene film to provide the necessary heat for the thermal breakdown of carbon feedstock in a CVD process. The resulting CNT forests show good density and alignment consistent with regular CVD synthesis processes on silicon surfaces. The resulting double sided GF/CNT hybrid film is directly applicable as a thermal pad. The CNT forest has a thermal conductivity of 30 W/mK, measured by pulsed photothermal reflectance, and the total thermal interface resistance between aluminum blocks was measured to be 60 Kmm^2/W using an ASTM D5470 compliant 1-D measurement setup. This method of directly synthesizing CNTs on graphene films is more energy efficient and capable of larger volume production compared to traditional CVD methods. It is also compatible with scaling up towards continuous roll-to-roll production for large scale commercial production, one of the major limitations preventing CVD-grown CNTs from commercial applications.