How is the Purification method for nanotubes?
Singlewall nanotube – SWNT Multiwall nanotube – MWNT When the material is made (as-produce) the nanotubes comes straight out of the reactor with the approximate concentration of 95% MWNT ( 90% in the case of SWNT) nanotube vs. non-nanotube material. These nanotubes are then processed and purified. This step yields an increase in purity of the tubes which are sold as “Purified Open Material”. This step uses a Heat and Acid Wash process, which removes the non-nanotubic material. (Non-Nanotubic material is usually comprised of amorphous and graphitic carbon, and metal catalyst, Nickel-Yttrium, Iron or other metals). Also process may shortens the nanotubes by “end eroding” during the acid wash which removes the ends of the nanotubes. A summary of the steps follows: Heat nanotubes in air to 300C to expose the carbon surface and oxidize the metal catalyst. Sonicate and wash in nitric acid and/or HCL to remove the metal catalyst, amorphous carbons and to open the ends of the nanotubes. Clean
