Method for growing continuous fiber

Details Method for growing continuous fiber Method for growing continuous fiber

2001-12-28

2004-06-15

Hendrickson, Stuart L. (Department: 1754)

Chemistry of inorganic compounds

Carbon or compound thereof

Elemental carbon

Reexamination Certificate

active

06749827

ABSTRACT:

BACKGROUND OF INVENTION
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).
Single-wall carbon nanotubes have been made in a DC arc discharge apparatus of the type used in fullerene production by simultaneously evaporating carbon and a small percentage of Group VIII 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 this 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.
Although the laser vaporization process produces improved single-wall nanotube preparations, the product is still heterogeneous, and the nanotubes are too tangled for many potential uses of these materials. In addition, the vaporization of carbon is a high energy process and is inherently costly. Therefore, there remains a need for improved methods of producing single-wall nanotubes of greater purity and homogeneity. Furthermore, many practical materials could make use of the properties of single-wall carbon nanotubes if only they were available as macroscopic components. However, such components have not been produced up to now.
SUMMARY OF THE INVENTION
Accordingly, it is an 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 another object of this invention to provide macroscopic carbon fiber made by such a method.
It is also an object of this invention to provide a molecular array of purified single-wall carbon nanotubes for use as a template in continuous growing of macroscopic carbon fiber.
It is another object of the present invention to provide a method for purifying single-wall carbon nanotubes from the amorphous carbon and other reaction products formed in methods for producing single-wall carbon nanotubes (e.g., by carbon vaporization).
It is also an object of the present invention to provide a new class of tubular carbon molecules, optionally derivatized with one or more functional groups, which are substantially free of amorphous carbon.
It is also an object of this invention to provide a number of devices employing the carbon fibers, nanotube molecular arrays and tubular carbon molecules of this invention.
It is an object of this invention to provide composite material containing carbon nanotubes.
It is another object of this invention to provide a composite material that is resistant to delamination.
A method for purifying a mixture comprising single-wall carbon nanotubes and amorphous carbon contaminate is disclosed. The method includes the steps of heating the mixture under oxidizing conditions sufficient to remove the amorphous carbon, followed by recovering a product comprising at least about 80% by weight of single-wall carbon nanotubes.
In another embodiment, a method for producing tubular carbon molecules of about 5 to 500 nm in length is also disclosed. The method includes the steps of cutting single-wall nanotube containing-material to form a mixture of tubular carbon molecules having lengths in the range of 5-500 nm and isolating a fraction of the molecules having substantially equal lengths. The nanotubes disclosed may be used, singularly or in multiples, in power transmission cables, in solar cells, in batteries, as antennas, as molecular electronics, as probes and manipulators, and in composites.
In another embodiment, a method for forming a macroscopic molecular array of tubular carbon molecules is disclosed. This method includes the steps of providing at least about 10
6
tubular carbon molecules of substantially similar length in the range of 50 to 500 nm; introducing a linking moiety onto at least one end of the tubular carbon molecules; providing a substrate coated with a material to which the linking moiety will attach; and contacting the tubular carbon molecules containing a linking moiety with the substrate.
In another embodiment, another method for forming a macroscopic molecular array of tubular carbon molecules is disclosed. First, a nanoscale array of microwells is provided on a substrate. Next, a metal catalyst is deposited in each microwells. Next, a stream of hydrocarbon or CO feedstock gas is directed at the substrate under conditions that effect growth of single-wall carbon nanotubes from each microwell.
In another embodiment, still another method for forming a macroscopic molecular array of tubular carbon molecules is disclosed. It includes the steps of providing surface containing purified but entangled and relatively endless single-wall carbon nanotube material; subjecting the surface to oxidizing conditions sufficient to cause short lengths of broken nanotubes to protrude up from the surface; and applying an electric field to the surface to cause the nanotubes protruding from the surface to align in an orientation generally perpendicular to the surface and coalesce into an array by van der Waals

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