Thermally controlled synthesis of single-wall carbon nanotubes with selective diameters

High quality single-wall carbon nanotubes were synthesized on a MgO supported Fe-Co catalyst system using an inductive radio frequency catalytic chemical vapor deposition method with methane utilized as the hydrocarbon source. The synthesis temperature was varied between 700-1000 degrees C, and major differences when it comes to the size controllability of the catalyst nano-particles and the nanotube morphology were noticed when the reaction temperature was set at 800 and at 1000 degrees C. The structural and morphological properties of the catalyst system were analyzed by microscopy, X-ray diffraction and surface area analysis. The electron microscopy analyses of the catalyst system showed that the Fe/Co active metal nano-clusters have a very narrow size distribution when the catalyst system is thermally treated at 800 degrees C. As a result, highly crystalline single-wall carbon nanotubes with a narrow diameter distribution were successfully synthesized. It was found that by increasing the reaction temperature from 800 to 1000 degrees C, the diameter distribution of Fe/Co nano-particles broadens and hence affects the nanotube diameters. At 1000 degrees C the nanotubes presented a wider diameter distribution when compared to the ones grown at lower temperatures, a fact correlated to the changes in the catalyst structural morphology. Furthermore, the nanotubes synthesized at different reaction temperatures were analyzed using several techniques such as electron microscopy, thermogravimetric analysis, Raman and UV-Vis-NIR spectroscopy.