Abstract Submitted to the    NANOTUBE'04 Conference:

A scalable multi-step purification method is developed to remove metal catalysts and non-nanotube carbon from raw material produced by the High-Pressure CO (HiPco) process. In this study, the iron catalysts, coated by non-nanotube carbon, are exposed and oxidized by oxygen at successively higher temperatures. To avoid the catalytic effect of iron oxide on carbon nanotube oxidation, after each oxidation, the exposed and oxidized metal catalysts are inactivated by the reaction with C₂H₂F₄ or SF₆. Finally, inactivated iron compounds are removed by concentrated HCl soxhlet extraction. The purity and quality of each sample are documented by thermo-gravimetric analysis (TGA), Raman spectrometry, ultraviolet-visible-near-IR (UV-vis-near-IR) spectrometry, environmental scanning electron microscope (ESEM), and transmission electron microscope (TEM) spectroscopy. The purity (Fe < 1wt%) and yield (70%) are better than those of conventional met hods and little side wall damage is found.