High-quality multi-wall carbon nanotubes （MCNTs） were prepared by CVD decomposing ethylene, using cobalt catalyst supported on multi-wall carbon nanotubes. Scanning electron microscopy（SEM） was used to characterize the catalyst, transmission electron microscope（TEM）, X-ray diffractometry（XRD） and TG-DTA technique were used to characterize the products. The morphologies and purity of CNTs obtained at different temperatures in the range of 700℃-850℃ were investigated. At the optimal decomposition temperature 770℃, the pure product show...
