S Mirershadi - Metallurgy Research Group, Material Research School, P.O. Box ۱۴۳۹۵-۸۳۶, Tehran, Iran
S.Z Mortazavi - Metallurgy Research Group, Material Research School, P.O. Box ۱۴۳۹۵-۸۳۶, Tehran, Iran
A Reyhani - Metallurgy Research Group, Material Research School, P.O. Box ۱۴۳۹۵-۸۳۶, Tehran, Iran
A.J Novinrooz - Material Research School, P.O. Box ۳۱۴۸۵-۴۹۸, Karaj, Iran

The multi-walled carbon nanotubes were synthesized on Fe-Ni bimetallic catalysts supported by MgO using thermal chemical vapor deposition. Purification processes to remove unwanted carbon structures and other metallic impurities carried out by boiling nitric and sulfuric acid solution. The studies revealed that molarity of acid and immersion duration of the carbon nanotubes in the acid solution is very crucial. It was found that 3 M of boiling nitric acid at 3 h treatment duration leads to the highest removal of the impurities with the least destructive effect. Various analytical techniques such as: TGA, Raman spectroscopy and HRTEM were employed to investigate the morphology, graphitization and quality of the carbon nanotubes.

multi-walled carbon nanotubes; nitric acid; purification; sulfuric acid