Continuous production of carbon nanotubes and fullerenes

Abstract

A method and a device for production of fullerene-related carbon nanotubes and fullerenes in direct current arc discharge between two graphite electrodes are disclosed. Two features distinctive from conventional arc discharge technique providing remarkably high productivity of the present method are introduced. The first feature comprises means for maintaining an optimal temperature of anode end surface to suppress formation of large carbon clusters and micro-crystallite carbon particles useless for synthesis of carbon nanotubes and fullerenes. The second one comprises means for maintaining an optimal concentration of carbon and catalyst vapor in vapor generation zone to ensure optimal yields of carbon nanotubes and fullerenes. Airtight plug-in cartridges are used to supply consumable electrodes and catalyst material inside closed-loop device without process being stopped. The means to perform automatic continuous feeding of consumable electrodes and catalyst, pneumatic transportation of condensables and their automatic continuous discharge are also described.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] Not Applicable STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT [0002] Not Applicable REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISK APPENDIX [0003] Not Applicable BACKGROUND OF THE INVENTION [0004] The present invention relates to such nanostructures as carbon nanotubes and fullerenes and a continuous method of their production. Fullerene C.sub.60, C.sub.70 and higher fullerenes were first produced in gram quantities in arc discharge between two graphite electrodes in 1990 [W. Kreatschmer et. al. “Solid C60: A new form of carbon”, Nature, 347, 354-357 (1990)]. It is still the major technique in commercial production of fullerenes, which is though characterized by limited productivity. [0005] Carbon nanotubes is a tubular form of carbon closely related to the C.sub.60 molecule, which can be also produced by the mentioned above arc discharge technique with addition of metal catalyst. Car...

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Benefits of technology

[0015]FIGS. 4A and 4B are detailed illustrations of catalyst feeding section for catalyst in a form of a metal wire or a fine metal powder correspondingly comprising automatic feeder and airtight plug-in cartr

Problems solved by technology

It is still the major technique in commercial production of fullerenes, which is though characterized by limited productivity.

Carbon nanotubes production by arc discharge technique possesses the same disadvantages as fullerene production—limited productivity and high final product cost.

That means that nanotube and fullerene yields are also functions of anode evaporation rate and productivity of existing arc discharge technique can't be scaled up in principle because any attempt to increase evaporation rate would increase carbon vapor concentration and promote primary formation of carbon black particles, which will dramatically reduce yield of the desired nanostructures.

The second reason of limited productivity of arc discharge technique constitutes the fact that temperature of anode surface rises with increase of electric current, which causes excessive formation of large carbon clusters and micro-crystallite carbon particles useless for synthesis of carbon nanotubes and fullerenes.

Both examples demonstrate that rise of anode surface temperature negatively affects carbon vapor composition and reduces yield of desired carbon nanostructures.

Since the method is easily scalable only economical considerations of the most appropriate scale and the largest size of graphite electrodes readily available could limit its utmost productivity.

Since carbon nanotubes are less mature then fullerenes we were not able to find out any explicit descriptions of their continuous production by arc discharge technique.

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