The Influence of Hydrogen Treatment on Removal Degree of Iron Particles from CNTs

Abstract

Multi-walled carbon nanotubes were obtained by catalytic chemical vapor deposition. Ethylene was applied as the carbon source and nanocrystalline iron without support was used as the catalyst. In order to remove amorphous carbon, the samples were reduced under hydrogen atmosphere. As a result of this process cementite was decomposed to iron and carbon, and metal particles were separated from fibrous structures. This phenomenon facilitated further purification of carbon nanotubes from iron particles. The prepared material was refluxed in 1 or 5 M nitric and 1 or 5 M hydrochloric acid for 60 and 300 minutes. The metal amount decreased to ˜1wt% using HCl. The phase composition of the samples and the graphitization degree were determined using X-ray diffraction method. The morphology was characterized by high resolution transmission electron microscopy. The quantitative analysis of metal impurity content was evaluated using thermogravimetric analysis.

Keywords:

• Hydrogenation
• carbon nanotubes
• purification
• acid treatment

Acknowledgments

The author is grateful to Dr. E. Borowiak-Paleń (Institute of Chemical and Environmental Engineering, West Pomeranian University of Technology, Szczecin) for the measurements using High Resolution Transmission Electron Microscopy.

This study was carried out using the funds of Polish Ministry of Science and Higher Education (NN 205 112 135).