Enhancing yield of carbon nanotube sheet synthesis: a comprehensive study of FC-CVD process parameters and their effects

The Floating Catalytic Chemical Vapor Deposition (FC-CVD) process, aimed at synthesizing carbon nanotube sheets (CNT sheets), has garnered considerable attention for its potential to transform a multitude of technological applications. This method enables the continuous production of flexible and self-supporting CNT sheets possessing exceptional mechanical and electrical properties, rendering them well-suited for a wide range of applications. Nonetheless, establishing a consistent and stable synthesis regime remains challenging due to the complex interplay among various process parameters. In this work, we analyzed the influence of catalyst activity and hydrocarbon precursors on CNT synthesis within the FC-CVD process. The main goal was to simultaneously increase the yield while reducing defects, an endeavor marked by an inverse correlation between the two objectives. We found a strong correlation between the mechanical and electrical properties of the CNT sheets and the precursor/catalyst feed rates. Additionally, we also examined the effects of carrier gas compositions and feed rate, highlighting the pivotal role played by precisely controlled gaseous environments in modulating the characteristics of the resultant CNT sheets. By finely adjusting these parameters, we successfully generated high-quality CNT sheets with an I_G/I_G ratio of more than 10, coupled with a yield exceeding 8%. The CNT sheets demonstrated higher tensile strength (> 20Pa) and electrical conductivity (> 4.5 MS/m). Furthermore, the stability of the synthesis process was confirmed through continuous CNT sheet production for four hours. By systematically exploring diverse process parameters, this study advances CNT sheet synthesis techniques, facilitating tailored properties for diverse applications. (author)