Chemistry of inorganic compounds – Carbon or compound thereof – Elemental carbon
Reexamination Certificate
2001-03-16
2004-12-28
Hendrickson, Stuart (Department: 1754)
Chemistry of inorganic compounds
Carbon or compound thereof
Elemental carbon
C423S447200, C423S460000
Reexamination Certificate
active
06835366
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is directed to making chemical derivatives of carbon nanotubes and to uses for the derivatized nanotubes, including making arrays as a basis for synthesis of carbon fibers.
2. Related Art
Fullerenes are closed-cage molecules composed entirely of sp
2
-hybridized carbons, arranged in hexagons and pentagons. Fullerenes (e.g., C
60
) were first identified as closed spheroidal cages produced by condensation from vaporized carbon.
Fullerene tubes are produced in carbon deposits on the cathode in carbon arc methods of producing spheroidal fullerenes from vaporized carbon. Ebbesen et al. (Ebbesen I), “Large-Scale Synthesis Of Carbon Nanotubes,”
Nature, Vol.
358, p. 220 (Jul. 16, 1992) and Ebbesen et al., (Ebbesen II), “Carbon Nanotubes,”
Annual Review of Materials Science,
Vol. 24, p. 235 (1994). Such tubes are referred to herein as carbon nanotubes. Many of the carbon nanotubes made by these processes were multi-wall nanotubes, i.e., the carbon nanotubes resembled concentric cylinders. Carbon nanotubes having up to seven walls have been described in the prior art. Ebbesen II; Iijima et al., “Helical Microtubules Of Graphitic Carbon,”
Nature, Vol.
354, p. 56 (Nov. 7, 1991).
Production of Single-wall Nanotubes
Single-wall carbon nanotubes (SWNT) have been made in a DC arc discharge apparatus of the typo used in fullerene production by simultaneously evaporating carbon and a small percentage of VII B transition metal from the anode of the arc discharge apparatus. See Iijima et al., “Single-Shell Carbon Nanotubes of 1 nm Diameter,”
Nature,
Vol. 363, p. 603 (1993); Bethune et al., “Cobalt Catalyzed Growth of Carbon Nanotubes with Single Atomic Layer Walls,”
Nature,
Vol. 63, p. 605 (1993); Ajayan et al., “Growth Morphologies During Cobalt Catalyzed Single-Shell Carbon Nanotube Synthesis,”
Chem. Phys. Lett.,
Vol. 215, p. 509 (1993); Zhou et al., “Single-Walled Carbon Nanotubes Growing Radially From YC
2
Particles,”
Appl. Phys. Lett.,
Vol. 65, p. 1593 (1994); Seraphin et al., “Single-Walled Tubes and Encapsulation of Nanocrystals Into Carbon Clusters,”
Electrochem. Soc,
Vol. 142, p. 290 (1995); Saito et al., “Carbon Nanocapsules Encaging Metals and Carbides,”
J. Phys. Chem. Solids,
Vol. 54, p. 1849 (1993); Saito et al., “Extrusion of Single-Wall Carbon Nanotubes Via Formation of Small Particles Condensed Near an Evaporation Source,”
Chem. Phys. Lett.,
Vol. 236, p. 419 (1995). It is also known that the use of mixtures of such transition metals can significantly enhance the yield of single-wall carbon nanotubes in the arc discharge apparatus. See Lambert et al., “Improving Conditions Toward Isolating Single-Shell Carbon Nanotubes,”
Chem. Phys. Lett.,
Vol. 226, p. 364 (1994). While the arc discharge process can produce single-wall nanotubes, the yield of nanotubes is low and the tubes exhibit significant variations in structure and size between individual tubes in the mixture. Individual carbon nanotubes are difficult to separate from the other reaction products and purify.
An improved method of producing single-wall nanotubes is described in U.S. Ser. No. 08/687,665, entitled “Ropes of Single-Walled Carbon Nanotubes” incorporated herein by reference in its entirety. This method uses, inter alia, laser vaporization of a graphite substrate doped with transition metal atoms, preferably nickel, cobalt, or a mixture thereof, to produce single-wall carbon nanotubes in yields of at least 50% of the condensed carbon, The single-wall nanotubes produced by this method tend to be formed in clusters, termed “ropes,” of 10 to 1000 single-wall carbon nanotubes in parallel alignment, held together by van der Waals forces in a closely packed triangular lattice. Nanotubes produced by this method vary in structure, although one structure tends to predominate.
A method of producing carbon fibers from single-wall carbon nanotubes is described in PCT Patent Application No. PCT/US98/04513, incorporated herein by reference in its entirety. The carbon fibers are produced using SWNT molecules in a substantially two-dimensional array made up of single-walled nanotubes aggregated (e.g., by van der Waals forces) in substantially parallel orientation to form a monolayer extending in directions substantially perpendicular to the orientation of the individual nanotubes. In this process the seed array tubes are opened at the top (free) end and a catalyst cluster is deposited at this free end. A gaseous carbon source is then provided to grow the nanotube assembly into a fiber. In various processes involving metal cluster catalysis, it is important to provide the proper number of metal atoms to give the optimum size cluster for single wall nanotube formation.
Derivatization of Single-wall Nanotubes
Since the discovery of single wall carbon nanotubes (SWNTs) in 1993 (Iijima, S. and Ichihashi, T.,
Nature
1993,363:603-605), researchers have been searching for ways to manipulate them chemically. While there have been many reports and review articles on the production and physical properties of carbon nanotubes, reports on chemical manipulation of nanotubes have been slow to emerge. There have been reports of functionalizing nanotube ends with carboxylic groups (Rao, et al.,
Chem. Commun.,
1996,1525-1526; Wong, et al.,
Nature,
1998,394:52-55), and then further manipulation to tether them to gold particles via thiol linkages (Liu, et al.,
Science,
1998, 280:1253-1256). Haddon and co-workers (Chen, et al.,
Science,
1998, 282:95-98) have reported solvating SWNTs by adding octadecylamine groups on the ends of the tubes and then adding dichlorocarbenes to the nanotube side wall, albeit in relatively low quantities (~2%). While theoretical results have suggested that functionalization of the nanotube side-wall is possible (Cahill, et al.,
Tetrahedron,
1996, 52 (14):5247-5256), experimental evidence confirming this theory has not been obtained.
SUMMARY OF THE INVENTION
Accordingly, it is an object of this invention to provide a method for derivatizing carbon nanotubes, especially the side walls of single-wall carbon nanotubes.
It is another object of this invention to provide a high yield, single step method for producing large quantities of continuous macroscopic carbon fiber from single-wall carbon nanotubes using inexpensive carbon feedstocks at moderate temperatures.
It is yet another object of this invention to provide macroscopic carbon fiber made by such a method. These and other objects of this invention are met by one or more of the following embodiments.
This invention provides single wall carbon nanotubes and/or tubular carbon molecules derivatized with substituents covalently bonded to carbon atoms of the side wall of the nanotube or molecule. The substituents may in principle be attached on the interior and/or exterior of the nanotube side wall, but the attachment will not be predominantly on the exterior wall. In particular, the single wall carbon nanotubes may have substituents selected from fluorine, alkyl and phenyl attached to the side wall. Such single wall carbon nanotubes having fluorine covalently bonded to the side wall of the nanotube demonstrate high electrical resistance.
This invention also provides a method for derivatizing carbon nanotubes comprising reacting carbon nanotubes with fluorine gas, the fluorine gas preferably being free of F
2
. Where the carbon nanotubes are single wall nanotubes, and the temperature is at least 500° C., the product may be multiple wall carbon nanotubes derivatized with fluorine. Where the carbon nanotubes are single wall nanotubes, and the temperature is between 250° C. and 500° C., the product is single wall carbon nanotubes having fluorine covalently bonded to carbon atoms of the side wall of the nanotube.
In one embodiment, this invention also provides a method for preparing single wall carbon nanotubes having substituents attached to the side wall of the nanotube by reacting single wall carbon nanotubes with fluorine gas and recovering fluorine derivatized carbon nanotub
Boul Peter
Colbert Daniel T.
Hauge Robert
Huffman Chad
Liu Jie
Hendrickson Stuart
Ross Spencer Garsson
Shaddox Robert C.
William Marsh Rice University
Winstead Sechrest & Minick P.C.
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