Pressure effects on nanotubes formation using the submerged arc in water method

Synthesis of multi-walled carbon nanotubes (MWCNTs) by an arc discharge between two graphite electrodes submerged in water under controlled pressure (from 400 to 760 Torr) is reported. Transmission and scanning electron microscopy investigations of the arc discharge product collected from the bottom of the reactor revealed high concentrations of MWCNTs at all pressures. Dynamic light scattering (DLS) on suspensions containing MWCNTs showed that the mean diameter of the nanotubes increases with decreasing pressure. Raman spectroscopy analysis reveals that the relative amount of disordered carbon is significantly less in the low-pressure samples. Furthermore, the yield of the deposit was found to be independent of the pressure. These results suggest that the physical properties of MWCNTs formed by the submerged arc can be controlled by varying the pressure. (C) 2003 Elsevier B.V. All rights reserved.