Electric Arc Methods to Synthesize Carbon Nanostructures

Abstract

The (mainly authors’) publications on the problems of electric arc synthesis (EAS) of different carbon nanostructures (CNS) are reviewed. EAS of CNS can be carried out in both gas and liquid environments. EAS in a gaseous environment has a number of advantages such as high productivity and speed of the condensation process as well as ease of mode control. However, this method of synthesis has also disadvantages; it requires complex vacuum and cooling systems, which make the installation bulky. In addition, this method does not solve the problem of agglomeration of synthesized CNS and has a synthesis by-product in the form of an incrustation (deposit) on the electrode. EAS in a liquid environment is characterized by more compact equipment, since it does not need vacuum (the process proceeds at atmospheric pressure) and cooling (the liquid environment plays the role of a heat sink) systems. With this method of synthesis, various types of dielectric liquids are used: from distilled water and liquid nitrogen to hydrocarbon solvents, which can serve as a source of carbon in the synthesis zone. By changing the composition of the liquid phase, it is possible to achieve the synthesis of various types of CNS. In addition, this method involves the use of metal electrodes, which, in addition to long service life, can act as catalysts. In this case, metal particles can be encapsulated with CNS, forming composites with different magnetic properties. In some works, it was shown that, when metal electrodes are used in the process of EAS in a liquid environment, the mixtures of metal carbides could form. The liquid environment after EAS of CNS is also of scientific interest. Probably, the liquid environment contains new modifications of soluble organic compounds, which are being searched by researchers all over the world. Thus, scientists found that, after EAS in a liquid environment using graphite electrodes, the working solution (С6Н6) changed its colour. This indicates the formation of soluble organic compounds in it. In the review, based on the literature data, a table of modes for the industrial synthesis of single-walled CNS was created, and a list of modes (regimes) for creating defective CNS as a method of increasing the adsorption area of nanoparticles is given. The solutions to important problems of the EAS method are fixed: agglomeration of CNS, the problem of deposit formation, and productivity improvement.

Keywords

• plasma-chemical synthesis
• electric arc discharge
• carbon nanostructures (cns)
• carbon nanoclusters (cnc)
• carbon nanotubes (сnt)
• cryogenic media
• liquid dielectrics