Studies of hydrogen interaction with carbon deposit containing carbon nanotubes

Nanocarbon materials were obtained by catalytic decomposition of ethylene on nanocrystalline iron at 500 and 550 °C. The increase in the carbon mass was controlled using the thermogravimetric method. After synthesis the samples were analyzed using the HRTEM and X-ray diffraction methods and contained iron carbide (cementite) and nanocarbon materials (carbon nanofibers, carbon nanotubes and amorphous carbon). Cementite crystallites were observed at the end of filamentous structures. In order to remove amorphous carbon and thick carbon nanofibers the samples were reduced under hydrogen atmosphere. As a result of the hydrogenation treatment, the cementite was decomposed into iron and carbon. The samples contained mainly multi-walled carbon nanotubes with open ends and had diameters in the range of approx. 10–30 nm.