Synthesis of branched carbon nanotubes using copper catalysts in a hydrogen-filled DC arc-discharger

Branched multi-walled carbon nanotubes (b-CNTs) were deposited in a collar around the cathode in a DC arc-discharger in the presence of hydrogen and copper catalysts. Irrespective of the gas pressure or oxidation state of the catalysts, common morphologies (compartmentalization/segmentation, branching, partial metal filling) were observed when raw samples from the collar were analyzed by TEM. EDX confirmed the presence of metallic copper in the tips, in the branches and in the partially filled b-CNTs. These features have led to the proposal of a common growth model, in which reactions between metallic copper nanoparticles and gaseous carbon species that were formed in hydrogen, were used to rationalize the various CNT structures synthesised. (C) 2008 Elsevier Ltd. All rights reserved.