Catalytic synthesis and purification of carbon nanotubes

Carbon deposition on a catalyst surface during decomposition of different carbon-containing compounds can be used for the synthesis of carbon nanotubes of graphitic structure. Different supported transition metal oxides were found to be active in the production of these nanotubes. The selectivity of the catalytic method is significantly higher than that of either the arc discharge or the flame method. The experiments were carried out in a flow system, at 700 °C, with various acetylene/nitrogen feeds. Deposited carbon was investigated by transition electron microscopy. The best samples were selected for further investigation and for the synthesis of carbon nanotubes in large amounts. For the purification, different methods were utilized. Separation of nanotubes from the catalyst (support and metal particles) and from other carbon products (soot, fibres) can be carried out only by the combination of ultrasound and various chemical treatments.