A parametric study of carbon nanotubes production from tetrachloroethylene using a supersonic thermal plasma jet

Abstract

In this study we produce carbon nanotubes (CNT) using a DC non-transferred plasma torch operated at a power of 30 kW in argon and producing a supersonic jet. Tetrachloroethylene (TCE) is used as the carbon raw material. As an initial demonstration of the supersonic plasma jet approach and in an attempt to simplify the flow/nucleation fields of metal catalyst nanoparticles, the erosion of the torch tungsten electrodes is used as a source of metal vapours nucleating in situ into catalytic nanoparticles within the plasma jet. CNT mass yield values are based on thermogravimetry analysis correlated using electron microscopy and Raman spectroscopy. A parametric study is made to evaluate the influence of the different operating parameters on the yields of carbon nanotubes. The rapid quench generated by the supersonic jet, the high vapour pressures of carbon and a control of the temperature profile within the torch nozzle enable the rapid growth of CNT. Decreasing the reactor pressure from 0.66 to 0.26 atm leads to a CNT yield increase by 22%. High vapour pressure of carbon is obtained by increasing the TCE feed rate. From 0.05 to 0.15 mol/min, the yield of CNT is improved from 38.6 to 53.7 wt%. Beyond 0.15 mol TCE/min, the yield of CNT levels to around 50 wt%. In the start-up phase, the time of operation controls the temperature profile, which in turn drastically increases the yield of CNT from 0 to 8.2 wt% between the 3rd and the 4th minute of operation and to 53.7 wt% after the 5th minute.