Chemistry of inorganic compounds – Carbon or compound thereof – Elemental carbon
Reexamination Certificate
2002-01-11
2004-04-20
Hendrickson, Stuart L. (Department: 1754)
Chemistry of inorganic compounds
Carbon or compound thereof
Elemental carbon
C423S447200, C423S460000, C241S016000
Reexamination Certificate
active
06723299
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention is related to manipulating nanotubes, and more particularly to a system and method that utilize organic material, such as cyclodextrin, to manipulate nanotubes, such as carbon nanotubes, by, for example, dispersing and/or cutting the nanotubes.
2. Background
A carbon nanotube can be visualized as a sheet of hexagonal graph paper rolled up into a seamless tube and joined. Each line on the graph paper represents a carbon-carbon bond, and each intersection point represents a carbon atom.
In general, carbon nanotubes are elongated tubular bodies which are typically only a few atoms in circumference. The carbon nanotubes are hollow and have a linear fullerene structure. The length of the carbon nanotubes potentially may be millions of times greater than their molecular-sized diameter. Both single-walled carbon nanotubes (SWNTs), as well as multi-walled carbon nanotubes (MWNTs) have been recognized see “Nanotubes from Carbon” by P. M. Ajayan,
Chem. Rev.
1999, 99, 1787-1799, the disclosure of which is hereby incorporated herein by reference).
Carbon nanotubes are currently being proposed for a number of applications since they possess a very desirable and unique combination of physical properties relating to, for example, strength and weight. Carbon nanotubes have also demonstrated electrical conductivity. See Yakobson, B. I., et al.,
American Scientist,
85, (1997), 324-337; and Dresselhaus, M. S., et al., Science of Fullerenes and Carbon Nanotubes, 1996, San Diego: Academic Press, pp. 902-905. For example, carbon nanotubes conduct heat and electricity better than copper or gold and have 100 times the tensile strength of steel, with only a sixth of the weight of steel. Carbon nanotubes may be produced having extraordinarily small size. For example, carbon nanotubes are being produced that are approximately the size of a DNA double helix (or approximately {fraction (1/50,000)}
th
the width of a human hair).
Considering the excellent properties of carbon nanotubes, they are well suited for a variety of uses, from the building of computer circuits to the manufacturing of heat-reflective material, and even to the delivery of medicine. As a result of their properties, carbon nanotubes may be useful in microelectronic device applications, for example, which often demand high thermal conductivity, small dimensions, and light weight. Perhaps most promising is their potential to act as nano-wires and even tiny transistors in ultradense integrated circuits. One potential application of carbon nanotubes that has been recognized is their use in flat-panel Cd displays that use electron field-emission technology (as carbon nanotubes generally make excellent pipes for the high-energy electrons). Further potential applications that have been an~ recognized include electromagnetic shielding, such as for cellular telephones and laptop if computers, radar absorption for stealth aircraft, nano-electronics (including memories in new generations of computers), and use as high-strength, lightweight composites. Further, carbon nanotubes are potential candidates in the areas of electrochemical energy storage systems (e.g., lithium ion batteries) and gas storage systems.
Various techniques for producing carbon nanotubes have been developed. As examples, methods of forming carbon nanotubes are described in U.S. Pat. Nos. 5,753,088 and 5,482,601, the disclosures of which are hereby incorporated herein by reference. The three most common techniques for producing carbon nanotubes are: 1) laser vaporization technique, 2) electric arc technique, and 3) gas phase technique (e.g., HIPCO™ process), which are discussed further below.
In general, the “laser vaporizations” technique utilizes a pulsed laser to vaporize graphite in producing the carbon nanotubes. The laser vaporization technique is further described by A. G. Rinzler et al. in
Appl. Phys. A,
1998, 67, 29, the disclosure of which is hereby incorporated herein by reference. Generally, the laser vaporization technique produces carbon nanotubes that have a diameter of approximately 1.1 to 1.3 nanometers (nm). Such laser vaporization technique is generally a very low yield process, which requires a relatively long period of time to produce small quantities of carbon nanotubes. For instance, one hour of laser vaporization processing typically results in approximately 100 milligrams of carbon nanotubes.
Another technique for producing carbon nanotubes is the “electric arc” technique in which carbon nanotubes are synthesized utilizing an electric arc discharge. As an example, single-walled nanotubes (SWNTs) may be synthesized by an electric arc discharge under helium atmosphere with the graphite anode filled with a mixture of metallic catalysts and graphite powder (Ni:Y;C, as described more fully by C. Journey et al. in
Nature
(London), 388 (1997), 756. Typically, such SWNTs are produced as close-packed bundles (or “ropes”) with such bundles having diameters ranging from 5 to 20 nm. Generally, the SWNTs are well-aligned in a two-dimensional periodic triangular lattice bonded by van der Waals interactions. The electric arc technique of producing carbon nanotubes is further described by C. Journey and P. Bernier in
Appl. Phys. A,
67, 1, the disclosure of which is hereby incorporated herein by reference. Utilizing such an electric arc technique, the average carbon nanotube diameter is typically approximately 1.3 to 1.5 nm and the triangular lattice parameter is approximately 1.7 nm. As with the laser vaporization technique, the electric arc production technique is generally a very low yield process that requires a relatively long period of time to produce small quantities of carbon nanotubes. For instance, one hour of electric arc processing typically results in approximately 100 milligrams of carbon nanotubes.
Thus, both the laser vaporization technique and electric arc technique can only produce small quantities of SWNTs, See A. G. Rinzler et al,
Appl Phys. A,
1998, 67, 29-37; C. Journey and P. Bernier, ppl.
Phys. A,
1998, 67, 1-9. More recently, Richard Smalley and his colleagues at Rice University have discovered another process, the “gas phase” technique, which produces much greater quantities of carbon nanotubes than the laser vaporization and electric arc production techniques. The gas phase technique, which is referred to as the HIPCO process, produces carbon nanotubes utilizing a gas phase catalytic reaction. The HIPCO process uses basic industrial gas (carbon monoxide) under temperature and pressure conditions common in modem industrial plants to create relatively high quantities of high-purity carbon nanotubes that are essentially free of by-products. The HIPCO process is described in further detail by P. Nikolaev et al. in
Chem. Phys. Lett.,
1999, 313, 91, the disclosure of which is hereby incorporated herein by reference.
While daily quantities of carbon nanotubes produced using the above-described laser vaporization and electric arc techniques are approximately 1 gram per day, the HIPCO process may enable daily product of carbon nanotubes in quantities of a pound or more. Generally, the HIPCO technique produces carbon nanotubes that have relatively much smaller diameters than are typically produced in the laser vaporization or electric arc techniques. For instance, the nanotubes produced by the HIPCO technique generally have diameters of approximately 0.7 to 0.8 nanometer (nm).
Carbon nanotubes are commonly produced (e.g., using the above-described as techniques) in relatively long, highly tangled ropes. For example, SWNTs produced by the HIPCO process (which are available from Carbon Nanotechnologies, Inc.) generally comprise if relatively long (e.g., >4 micrometers (&mgr;m)) and relatively thick (e.g., 20-100 nm) ropes formed by a plurality of highly tangled carbon nanotubes.
A desire often exists for a nanotube structure that is shorter than the relatively long tubes commonly produced. Shortened single-walled carbon nanotubes (e.g., SWNTs having length ≦1 &mgr
Chen Jian
Dyer Mark J.
Haynes and Boone LLP
Hendrickson Stuart L.
Lish Peter J
Zyvex Corporation
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