Purification of catalytically produced multi-wall nanotubes

Carbon nanotubes were produced in large amounts by catalytic decomposition of acetylene over a Co incorporated zeolite NaY support. Purification of mu lti-wall nanotubes was required in order to eliminate catalyst and amorphou s carbon produced by thermal decomposition of hydrocarbon. First, separatio n of nanotubes and catalyst particles was carried out by hydrofluoric acid treatment. Then, two ways of removing amorphous carbon were studied: perman ganate oxidation and air oxidation. The quality of nanotubes was characteri zed by means of transmission electron microscopy and the yield of pure nano tubes was quantitatively determined. Changes caused by treatment of the nan otubes were investigated by high resolution electron microscopy and a compa rison was made between the nanotubes produced by this method and those synt hesized by an are discharge process after oxidation treatment.