Use of ohmic heating of cathode deposit filaments containing carbon nanotubers for admixtures’ extraction

Various methods of manufacturing carbon nanotubes have been developed lately. Purification of carbon nanotubes is a necessary stage of every method. In our research, cleaning of carbon nanotubes contained in a cathode deposit of argon arch discharge by means of the Ohmic heating is investigated. A direct current was sent into the deposit filament in conditions of atmospheric air. The registered volt-ampere characteristics have the form of the curve with a maximum that reaches 650-700 °С on the filament surface with subsequent current decrease at stable voltage. The surface morphology investigation shows that this process is accompanied by partial burning of amorphous and graphite-like carbon contained in filaments. The electrical resistance of specimens increases up to nearly 1-3 kOm. The X-ray diffraction comparison before and after cleaning confirms results of the experiment. It was also revealed that the increase of the specimen resistance leads to weak light micro-bursts moving across the specimen surface randomly. They appear at the voltage of 3-10 V and the current of 1-20 mkA. It is suggested that this effect is conditioned by electro-discharge of some micro- and nano-condensers from carbon nanotubes that have no contact. The discovered effect may be used to control purification quality of deposit filaments by flowing current.