Growth of carbon nanotubes above the peritectic temperature of tungsten metal catalyst

The mechanism of formation of carbon nanotubes (CNTs) produced from the dissociation of tetrachloroethylene (TCE) and the co-injection of tungsten vapour in the nozzle of a DC thermal plasma torch is discussed. Tungsten and the dissociation of TCE form nanoparticles of tungsten carbide (WC), which provide the catalyst activity for the formation of CNTs. A new route for the mechanisms of formation is discussed following thermodynamic equilibrium calculations of the plasma torch system, energy dispersive spectroscopy and nano-diffraction analyses of the WC nanoparticles formed. These analyses provide an understanding of the dissociation pattern of TCE, evaluate the carbon concentration in the catalyst nanoparticles and determine the phase structure of these nanoparticles. We propose from these results a new mechanism of formation for CNT occurring above the peritectic temperature of the stoichiometric WC alloy.