Effect of the reaction atmosphere on the diameter of single-walled carbon nanotubes produced by chemical vapor deposition

The influence of the reaction atmosphere on the type of single-walled carbon nanotubes (SWNT) grown during chemical vapor deposition (CVD) was investigated. Methane decomposition was catalyzed by Fe/MgO and Fe-Mo/MgO catalysts in argon, nitrogen and their mixtures. Nitrogen influences the carbon species significantly. The aggregation of iron nanoparticles in nitrogen results in the growth of N-doped carbon nanofibers on the Fe/MgO catalyst. A limited iron nanoparticle aggregation in nitrogen occurred on a Fe-Mo/MgO catalyst, on which there was an increase in the diameter of the SWNTs as the reaction atmosphere was more enriched in nitrogen, which was characterized by Raman spectroscopy. These results provide an experimental basis for the rational selection of the reaction atmosphere, and suggest an approach to control the size of the SWNTs in a CVD method. (C) 2006 Published by Elsevier Ltd.