Effect of organic additives in catalyst preparation on the growth of single-wall carbon nanotubes prepared by catalyst-assisted chemical vapour deposition
The effect of organic additives, including citric acid, PEG (2000) and PEG (200), on the yield and quality of single-wall carbon nanotubes (SWNTs) synthesized by a Fe-Mo catalyst dispersed on an alumina matrix prepared by the sol-gel process in assisted chemical vapour deposition (CVD) has been investigated by transmission electron microscopy (TEM), thermo-gravimetric analysis (TGA) and Raman spectroscopy. Different morphologies of catalyst including big flakes, spherical particles and porous supporting materials were obtained using citric acid, PEG (2000) and PEG (200) as dispersant, respectively. SWNT yields of 10 wt%, 16 wt% and 33 wt% were obtained using citric acid, PEG (2000) and PEG (200) as the dispersants, respectively, which implies that the PEG (200) is the most effective at improving the yield of SWNTs due to the effect of additives on the specific surface area of the catalyst. The as-grown SWNTs are mostly in large bundles with diameters of 0.5-2 nm, but in some cases, isolated tubes with much larger diameters can also be found. Finally a preliminary explanation for the increased SWNT yield using PEG (200) is presented.