Plastic and nonmetallic article shaping or treating: processes – Direct application of electrical or wave energy to work – Producing or treating inorganic material – not as pigments,...
Reexamination Certificate
1998-11-04
2001-08-28
Fiorilla, Christopher A. (Department: 1731)
Plastic and nonmetallic article shaping or treating: processes
Direct application of electrical or wave energy to work
Producing or treating inorganic material, not as pigments,...
C264S340000, C264S345000
Reexamination Certificate
active
06280677
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to processes involving nanotubes, and more specifically processes which are able to modify the physical properties of the nanotubes.
BACKGROUND OF THE INVENTION
Carbon nanotubes are known as elongated tubular bodies which are typically only a few atoms in circumference. Methods of forming carbon nanotubes are described, for example, in U.S. Pat. Nos. 5,753,088 and 5,482,601. The nanotubes are hollow and have a linear fullerene structure. Advantageously, the length of the nanotubes potentially may be millions of times greater than the molecular-sized diameter. 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. The 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. Investigative efforts regarding nanotubes have primarily focused on theoretical attempts to evaluate the nanotube molecular structure, and its potential relationship to physical properties.
Notwithstanding these efforts, there remains a need in art for a method to alter the physical properties of a nanotube such that it may be modified for various end use applications. For example, it would be particularly desirable to be able to alter the electrical properties within the nanotube such that the nanotube exhibits heterogeneous electrical behavior. As a result, the nanotube may be useful in microelectronic device applications which often demand high thermal conductivity, small dimensions, and light weight.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a method of modifying a physical property of a nanotube, such as an electrical property.
It is a further object of the invention to provide a nanotube having modified physical properties.
These and other objects and advantages are provide by the present invention. In one aspect, the invention provides a method of modifying a physical property of a nanotube. The method comprises subjecting a nanotube having a defined lattice structure orientation to stress conditions sufficient to disrupt the lattice structure orientation. A dipole of dislocation cores is formed therein, and the dipole of dislocation cores split and propagate in the nanotube in a manner such that the dipole of dislocation cores is separated by at least one domain of modified structure. As a result, at least one physical property of the nanotube is altered.
In one embodiment, the above method also includes exposing the nanotube to thermal conditions. In another embodiment, the method of the invention also includes the step of exposing the nanotube to radiation, preferably in the form of ultraviolet light or x-ray.
In a typical embodiment, the nanotube initially has a hexagonal core lattice structure and the application of stress disrupts this core lattice structure to form a dipole of pentagon-heptagon and heptagon-pentagon dislocation cores in the nanotube. These dislocation cores propagate throughout the nanotube such that a domain of modified lattice structure is formed between the dipole of dislocation cores as described herein.
In another aspect, the invention relates to a nanotube comprising: (1) a dipole of pentagon-heptagon dislocation cores located in an opposed spaced-apart relationship along a longitudinal axis of the nanotube; (2) a first region comprising a domain of modified lattice structure positioned between the dipole and formed by the dipole propagating throughout the nanotube as a result of stress being applied to the nanotube; and (3) second and third regions each positioned on opposite sides relative to the first region, the second and third regions comprising lattice structure domains which differ from the domain of modified lattice structure present in the first region such that the second and third regions possess a physical property different from the first region.
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Heyd et al. Uniaxial-stress effects on the electronic properties of carbon nanotubes, Mar. 15, 1997, Physical Review B, vol. 55, No. 11 pp. 6820-6823.*
Stephan et al., Curvature-induced bonding changed in carbon nanotubes investigated by electron energy-loss spectrometry, May 15, 1996, Physical Review B, vol. 53, No. 20, pp. 13824-13829.*
Charlier, J.-C., Ebbesen, T.W., and Lambin, P.; Structural and electronic properties of pentagon-heptagon pair defects in carbon nanotubes, Phys. Rev. B, 1996. 53(16): pp. 11108-11113.
Chico, L., et al.; Pure Carbon Nanoscale Devices: Nanotube Heterojunctions, Phys. Rev. Lett., 1996. 76(6): pp. 971-974.
Dunlap, B.I.; Connecting carbon tubules, Phys. Rev. B, 1992. 46(3): pp. 1933-1936.
Dresselhaus, M.S., Dresselhaus, G. and Eklund, P.C.;Science of Fullerenes and Carbon Nanotubes,1996, San Diego: Academic Press pp. 902-905.
Yakobson, B.I. and Smalley, R.E.; Fullerene Nanotubes: C1,000,000and Beyond, American Scientist, 1997. 85(4): pp. 324-337.
Yakobson, B.I.; Mechanical relaxation and “intramolecular plasticity” in carbon nanotubes, Appl. Phys. Lettl, 1998. 72(8): pp. 918-920.
Yakobson, B.I.; Dynamic Topology and Yield Strength of Carbon Nanotubes, Fullerenes, Electrochemical Society, 1997, Paris: ECS, Pennington., pp. 549-560.
Fiorilla Christopher A.
Myers Bigel Sibley & Sajovec P.A.
North Carolina State University
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