Emission Processes at the Deposit in the Carbon Arc Discharge for Nanotube Synthesis
Authors: J. Ng and Y. Raitses
Abstract:
The atmospheric pressure carbon arc in helium is an important method for nanotube production.
Typical arcs operate in a dc mode between a graphite anode, which is consumed, and a cathode
which may be a lower melting point material. It is accepted that electrons from the cathode are
emitted by thermionic eld emission, requiring the cathode to be above the melting temperature
of its material. However, the cathode usually remains undamaged by the arc, raising the question
about how the electron current in the arc is supported. Our experiments with copper and graphite
cathodes have demonstrated that a suciently large area of the cathode is hot enough for thermionic
emission to be the source of most of the arc current, but emission is from the carbon deposit formed
on the cathode during arc operation. Due to its low heat conductivity, the cathode does not reach
its melting point and remains undamaged.
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Submitted to: Carbon (November, 2013)
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Download PPPL-4961 (pdf 275 KB 6 pp)
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