Abstract
As carbon nanotubes (CNTs) have properties superior to other carbon materials, a variety of applications, such as display devices, hydrogen storage materials and electrodes for electric double-layer capacitors, are anticipated. In order to compare the characteristics of CNTs synthesized by microwave plasma and pyrolysis techniques, CNTs were prepared using similar experimental conditions such as catalyst, temperature and pressure, and characterized using techniques such as SEM, TEM, and Raman spectroscopy. By comparing the results of carbon yield and SEM imaging of CNTs, it was noted that the carbon yield was same and CNTs yield was similar by the both method. CNTs obtained by microwave plasma were straight and helical, whereas CNTs obtained by pyrolysis were only straight. Also, TEM imaging revealed that the structures of CNTs formed by microwave plasma were multi-walled nanotubes and their outermost diameters (11 nm) were constantly independent of reaction time. Raman spectroscopy was used to determine that the ID/IG of CNTs formed by microwave plasma, using methane as the carbon source, was 0.68. In comparison, the ID/IG of CNTs synthesized by pyrolysis, using acetylene/hydrogen as the carbon source, was higher with a value of 0.81. It was suggested that the microwave plasma afforded higher quality CNTs due to the reactive effect of active species from methane formed by microwave plasma.
