Growth Promotion and Etching of Carbon Nanotubes by Carbon Dioxide in Chemical Vapor Deposition using Methane Gas

Abstract

ABSTRACTWe report the effect of CO2 addition to CO4 gas on carbon nanotube (CNT) growth by chemical vapor deposition. CO2 gas was introduced during the growth of CNTs on Fe0.05Mo0.025MgO0.925 and Ni0.05Mo0.025MgO0.925 catalysts by CO4 gas at a temperature of 800–850°C, and its concentration in a fraction of the gas flow rate was varied from 5×10−3 to 50%. In the experimental condition of the preferential growth of multi-walled CNTs, the carbon yield and the G/D ratio in the Raman spectra of the CNTs grown in 10%-CO2/CO4 were slightly higher than that grown in CO4 only. However, CNTs hardly grew when the CO2 concentration was more than 10%. We then prepared CO2 gas diluted with Ar gas (CO2/Ar) and varied its flow rate between 0 and 10 sccm. As the CO2/Ar gas flow rate was increased, the number of RBM peaks decreased even though the G/D ratio gradually decreased. The decrease in the RBM intensities of CNTs on the FeMoMgO catalyst was more significant than that of NiMoMgO.