Bulk synthesis of multi-walled carbon nanotubes by AC arc discharge method

Abstract

This work proposes the production of multi-walled carbon nanotubes by AC arc discharging of spectroscopically pure graphite electrodes of different shapes, that is, movable cylindrical and stationary rectangular electrode by manual metal arc welding setup. Continuous arc was generated by maintaining the gap of about 3 mm between the electrodes which in turn formed the plasma zone. Vaporization of carbon cations followed by sudden quenching paved the way for formation of carbon nantotubes. Nanotubes produced were deposited on the stationary graphite electrode in the form of soot. Further extraction of the nanoparticles from the soot was performed by conducting series of purification processes which will be discussed in upcoming chapters. Morphology and purity of the extracted nanotubes were investigated by X-ray diffraction, scanning electron microscopy, field-emission scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. Following the characterization process, it was observed that the so-produced nanotubes were of different shapes, that is, carbon cone nanotubes, nanocapsules, nanoparticles and branching type and randomly oriented. The length of the nanotubes varied from 231 to 561 nm, whereas diameter was found to be in the range of 14–55 nm.