Gas phase pyrolysis synthesis of carbon nanotubes at high temperature

Publication date: 15 October 2017
Source:Materials & Design, Volume 132
Author(s): Guangfeng Hou, Devika Chauhan, Vianessa Ng, Chenhao Xu, Zhangzhang Yin, Michael Paine, Ruitao Su, Vesselin Shanov, David Mast, Mark Schulz, Yijun Liu
In this study, carbon nanotubes were synthesized at high temperature (1150–1500°C) using the substrate-free gas phase pyrolysis method. The CNT sock morphology, CNT structure, impurity, process yield and growth efficiency at high temperatures were investigated. It was found that the CNTs transform from single-walled to multi-walled nanotubes at elevated temperature. The amount of amorphous impurities increases with higher temperature, possibly due to an increased non-catalytic decomposition of hydrocarbons. However the CNT quality increases, as indicated by a higher Raman spectroscopy IG/ID ratio. The process yield increase by two folds at higher temperature (1500°C) compared to a lower temperature (1200°C), but the catalyst efficiency is highest at 1400°C with 1g Fe producing 5.1g CNT. The calculated carbon conversion rate is lower than 4%. The CNT growth is not limited by the availability of carbon around the catalyst, instead of by the availability of active catalyst particles. Based on a pristine CNT sheet, the measured electrical conductivity is highest at 1400°C, due to a balance between impurities and CNT quality. The tensile strength of the CNT sheet increases with the temperature, possibly because of the "gluing" effect of the carbonaceous impurities.

Graphical abstract

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