Large-scale purification of laser and HiPco carbon nanotubes by soft-baking

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Olga Gorelik, olga.gorelik-1@nasa.gov1, Ed Sosa, edward.sosa-1@nasa.gov1, Pavel Nikolaev1, William Holmes1, Sivaram Arepalli1, and Leonard Yowell2. (1) ERC Inc. / NASA JSC, Mail Stop JE62, P. O. Box 58561, Houston, TX 77258, (2) NASA JSC, Mail Stop ES-4, P. O. Box 58561, houston, TX 77258
Current application development work at Johnson Space Center requires multi-gram quantities of well purified carbon nanotubes of consistent purity and quality. We have moved from HiPco carbon nanotubes purification in sub gram batches to 5 20 gram batches by soft-baking process1. It was noticed that large size batches of HiPco nanotubes behave differently when heated in humid air during the soft-bake step, producing temperature spikes and increased local oxidation. This in turn leads to inconsistency in the quality of the purified material. We have studied several techniques to improve consistency, including vacuum desorption and compaction before soft-bake. Soft-bake was also studied as an alternative to the traditional acid reflux for purification of pulsed laser produced nanotubes. We have determined correct temperature and timing of the soft-bake step and produced nanotubes with lower amount of the residual catalyst while significantly simplifying the overall process. Samples were characterized using JSC protocol2.

1. Journal of Physical Chemistry B, 105, 8297-8301 (2001). 2. Carbon 42, 8-9, 1783-1791 (2004)