Synthesis of high purity narrow-width carbon nanotubes

• Published in: Carbon (New York) 2012-08, Vol.50 (9), p.3200-3209
• Main Authors: Carneiro, O.C., Anderson, P.E., Rodriguez, N.M., Baker, R.T.K.
• Format: Article
• Language: English
• Subjects: Carbon; Carbon monoxide; Catalysis; Catalysts; Chemistry; Cross-disciplinary physics: materials science; rheology; Dispersing; Exact sciences and technology; Fullerenes and related materials; diamonds, graphite; General and physical chemistry; Granular materials; Inclusions; Materials science; Nanostructure; Physics; Purity; Specific materials; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
• ISSN: 0008-6223; 1873-3891
• DOI: 10.1016/j.carbon.2011.10.051

We have succeeded in controlling the width of multi-walled carbon nanotubes (MWCNT) by physical manipulation and pretreatment of the catalyst prior to reaction in a CO/H2 reactant mixture. Since the size of the metal catalyst particle determines the width of the nanotube, we have investigated the notion of introducing a dispersing agent into the catalyst formulation that facilitates fragmentation and prevents sintering of the granules during the reduction step. Inclusion of 5wt.% silica into a Fe–Ni (6:4) catalyst was found to reduce the average width of MWCNT from about 40 to 20nm, when the bimetallic was reacted in CO/H2 (1:4) at 670°C. On the other hand, when 5wt.% NaCl was used as the dispersant the average width of the MWCNT was decreased to about 11nm. The impact of both the catalyst pre-treatment and various post-treatment procedures on the width and purity of the final MWCNT product is discussed.