Carbon Arc Plasma Research Articles

Temperatures and C2 column densities in a carbon arc plasma

Diagnostic analyses were performed on a d.c. carbon arc discharge using optical emission spectroscopy. The influence of the self-absorption on intensity distribution in the rotational structure of the C2 (d g,v´ = 0 a u,v´´ = 0) emission band is discussed. The effect of the self-absorption was used in order to determine temperatures and column densities of C2 radicals in the a u,v´´ = 0 state in the arc zone. Temperatures within 3500-6500 K and column densities within (0.5-6) × 1015 cm-2 were found depending upon the arc current and plasma coordinates.

A Carbon Arc Process for Treatment of CF4 Emissions

Light perfluorocarbons, such as carbon tetrafluoride, are produced or emitted from a variety of processes, including manufacture of aluminum and processing of semiconductor devices. At the same time, the long atmospheric lifetime and high global warming potential of such compounds makes them an environmental concern. A new process for the abatement of perfluorocarbon emissions using a carbon arc plasma was investigated. In particular, the conversion of CF4 to C2F4 and higher fluorinated species, including poly(tetrafluoroethylene) (PTFE) was demonstrated. General features of the reaction chemistry are discussed, including primary reactions to form radicals and ions and secondary reactions to form C2F4 and higher compounds. The conversion efficiencies and products obtained in the reported experiments indicate potential applicability of the process for point source emission control of high global warming potential perfluorocarbons.

Influence of boron on carbon arc plasma and formation of fullerenes and nanotubes

Carbon–boron arc discharge was studied by emission spectroscopy during the formation of fullerenes and nanotubular structures. The presence of boron drastically suppresses the C 2 content in the plasma zone and the yield of fullerenes in the collected soot. It would suggest that there is a relationship between C 2 radicals and the formation of fullerenes. Novel complex nanostructures in the cathode deposits grown under those conditions were observed.

Patterns in the bulk growth of carbon nanotubes

The growth of nanotubes in carbon arc plasma is described in detail. The structure and organization of the nanotube deposits observed by SEM and AFM reveal a fractal-like pattern of growth. One of the key units of growth appears to be the micro-bundle composed of neatly packed and aligned nanotubes. The micro-bundle together with the field and current might explain the high formation yield of nanotubes.

Growth of carbon nanotubes

The production, morphologies and atomic structures of carbon nanotubes are reviewed, and a mechanism for tube growth is discussed on the basis of transmission electron microscopy observations. Capping of carbon nanotubes is explained nicely in terms of pentagons; distributions of pentagons in a hexagon network cause various cap morphologies. Heptagons, resulting in negative curvature into a graphitic plane, also provide a variety of graphitic structures. Pentagons and heptagons seem to play a key role in tube growth. On the basis of the consistency of various tube morphologies, we propose a model for tubule growth, in which the tubules are open at their ends while growing in the carbon arc plasma. To support this open-end growth mechanism, other evidence such as layer-by-layer growth on the tube surfacces and “over-shooting growth” on tube tips is given.

Anomalies in the Scattered Laser Light Spectra of a High Current Carbon Arc Plasma

The scattered light spectra of a high current carbon arc plasma have been studied. The temperature and density of the arc column were mapped using conventional scattering techniques. Small enhancements in the scattered light spectra were found at several wavelength shifts, including the shift corresponding to the plasma frequency. The dispersion relation of the anomalous waves was studied as a function of the plasma parameters. A theoretical model was constructed with a dispersion relation similar to that observed experimentally.