Preparation and modification of carbon nanotubes

Carbon nanotubes (CNTs) were prepared by the catalytic decomposition of methane at 680 degrees C for 120 min, using nickel oxide-silica binary aerogels as the catalyst. The morphological structure of CNTs was investigated by transmission electron microscopy (TEM), X-ray Diffraction (XRD) and Raman spectroscopy. The results revealed that CNTs with diameter 40-60 nm showed high quality, uniform diameter and high length/diameter ratio, the wall structure of CNTs was similar with that of highly oriented pyrolytic graphite (HOPG), and some metal catalyst particles were encapsulated at the tip of CNTs. Different methods were compared to modify CNTs. Investigated by TEM, XRD, Raman spectroscopy and nitrogen adsorption/desorption for modified CNTs, it was confirmed that after modification treatment by immersion in diluted HNO3 solution with ultrasonic and then milling by ball at a high velocity, the metal catalyst particles at the tip of CNTs disappeared, the unique cylinder wall structure remained, the CNT length became short, the cap at the tip of nanotube was opened, and thus the internal surface area could be effectively used, leading to the increase of the specific surface area and pore volume. This technique is relatively simple and effective for modifying CNTs which can be scaled up for industrial applications. (C) 2005 Published by Elsevier B.V.