Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2001-08-23
2004-06-15
Yao, Sam Chuan (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C423S447200, C423S460000, C264S108000
Reexamination Certificate
active
06749712
ABSTRACT:
FIELD OF THE INVENTION
The Invention relates to the field of materials science and materials fabrication comprising carbon nanotubes.
BACKGROUND OF THE INVENTION
Carbon is a critical element of organic material, which makes up all living matter. Matter composed solely of carbon exists in the form of graphite, diamond and most recently the fullerenes. These forms are called allotropes and are chemically very stable. Allotropes of carbon can be used alone, or in combination with other materials to form composites, to make applicable materials such as industrial diamonds; for cutting tools and flat panel displays, carbon filaments; in the form of fibers for structural reinforcement and dielectrics, activated carbon; for filtration devices, electrode materials for the manufacturer of steel, construction materials; for insulation of nuclear reactors, and graphite rods; for high-temperature hearing elements.
With the discovery of the third allotrope of carbon, the fullerenes, carbon materials having a fine tubular structure within the order of a nanometer in diameter, have been discovered on a carbon rod after an arc discharge, a common way of producing carbon fullerenes (S. Iijima, Nature, Vol. 354, pp. 56-58, Nov. 7, 1991). These fibrilar carbon materials may be visualized by (a) providing benzene shell-like hexagonal molecules as a constituent unit which are formed by covalent bonding of carbon atoms, (b) placing the molecules tightly in a plane to form a carbon molecule sheet, (c) rolling the carbon molecule sheet into a cylindrical shape to form a cylindrical carbon tube as a unit or a high-molecular building block, (d) repeating the above steps (a)-(c) to form a plurality of cylindrical carbon tubes having different diameters, and thereafter (e) arranging their cylindrical carbon tubes in a concentric configuration to form a telescopic structure.
The above-mentioned cylindrical tubes have an extreme micro-diameter of the order of 1 nm at a minimum, and the spacing between a cylindrical tube and its inside cylindrical tube or its outside cylindrical tube is of the order of 0.34 nm which is approximately the same as the interlayer spacing of a graphite molecule. The interaction between tubes is van der Waals type, and electron transfer from tube to tube is very small. In the above-mentioned telescopic structure, there are various kinds of structure such as a double structure, triple structure, quadruple structure, quintuple structure.
The above fibrilar carbon material will be hereinafter referred to in some cases as a “(carbon) nanotube” or a “(carbon) tube”. Carbon nanotubes can take an almost infinite number of structures, which are characterized both by their diameter and their degree of helicity. The relation between the molecular structure and electronic band structure of the carbon nanotube has been taught in Japanese Patent Application No. 56306/1992 which was laid open on Sep. 7, 1993 under Japanese Unexamined Patent Publication No. 229809/1993, the disclosure of which is hereby incorporated by reference herein. In addition, a method of fabricating carbon tube devices having desired properties on the basis of the above relation has been proposed therein.
The above application No. 56306/1992 and N. Hamada et al., Phys. Rev. Lett., 68(10), pp. 1579-1581(1992) teach that the carbon nanotubes exhibit a variety of properties in electronic conduction from a metal to a semiconductor having various band gaps, depending on the radius of the cylindrical tube and the degree of helical arrangement of the six-membered carbon rings (i.e. the carbon hexagons), further, that the carbon nanotubes are useful as a material for use in functional devices utilizing such properties.
On the other hand, soccer ball-like spherical high-molecular weight carbon materials having benzene shell-like hexagonal molecules as a constituent unit or molecular building block are taught in S. Iijima et al., Nature, Vol. 356, pp. 776-778(1992). S. Iijima et al. have shown that a variety of complex variants of carbon nanotubes are obtained by introducing pentagons and heptagons into the hexagonal network. Also, it is known that the molecules such as C.60, C.70, C.78, C.82, can exist in a stable state. These soccer ball-like spherical carbon materials are in the solid state or in the form of a face-centered cubic lattice or any other crystal structures depending on van der Waals forces. If the crystal or solid material is doped with K, Rb, Cs or the like, the doped material exhibits the metal conduction and superconductivity at low temperature.
The above-mentioned carbon nanotube and soccer ball-like materials and high-molecular weight materials derived from either of them are thus well known. Carbon nanotubules have received a great attention as a new base material applicable to various industries. The teachings of U.S. Pat. No. 5,457,343, for example, discloses the use of a carbon nanotubule as an absorbent or complex enclosure for foreign materials.
Graphite is a layered material and is structured with the carbon hexagons spread out two dimensionally and repeated forming layers of graphite sheets. The methods of making graphite carbon materials have been well established and are being used by industry for mass production of graphite. The methods of making normal graphite materials are divided into three main types. There is a method of forming graphite using a liquid-phase carbonization process with ground coke and a bonding material as raw materials. There is a method which uses a solid-phase carbonization process using spun polyacrylonitrile, pitch and rayon filaments as they are, and there is a method which thermally decomposes hydrocarbon gases and then performs a gas-phase carbonization process.
Of the carbon materials with graphite type structure, graphite filaments could have been obtained by using the solid-phase carbonization method mentioned above, or could have been formed by thermal decomposition of hydrocarbon gases using metallic granules as a catalyst, or could have been obtained by forming amorphous carbon filaments using metallic granules as a catalyst and then heat-treating these filaments to make graphite. Also, a method is known of where needle shaped graphite could have been grown by applying a direct current discharge between two graphite electrodes in a rare gas atmosphere.
For example, one of the prior methods of growing the graphite filaments was proposed in 1960 by Roger Bacon of Union Carbide Co. (U.S.A.) (J. Appl. Phys., Vol. 31, p. 283 (1960)), and in this method direct current is discharged between two carbon-rod electrodes in an argon gas atmosphere at approximately 90 atmospheres, forming graphite filaments with a diameter of 1 to 5 .mu.m and length of 2 to 3 cm on the negative electrode. Using this method, the crystal structure of the resulting graphite filament is the same as that of normal graphite. In other words, each of the graphite filaments is structured with several oblong shaped single crystal graphite bundled around the filament axis, and each oblong graphite crystals bond together along the crystal boundaries to form a polycrystalline structure.
As mentioned above, the chemical and physical properties of carbon materials taking currently known graphitic structures as the main structural unit are well known. When considering more diverse industrial applications of carbon, a new carbon carbon-based material having a new structure is desired.
Carbon nanotubes have been refined so that they can be can be synthesized as single wall nanotubes (SWNTs.) SWNTs are micron long nanometer diameter tubes composed solely of carbon atoms. The geometrical arrangement of the carbon atoms in a SWNT is that of graphene (a single sheet of graphite). The overall configuration resembles a sheet of chicken wire, which is rolled to close seamlessly and capped with hemispheres on each end of the tube. In each vertice of the hypothetical chicken wire exists a carbon atom. This provides the graphene configuration. SWNTs are proposed to be 100 times stronger than steel at ⅙ the weight
Morgan & Lewis & Bockius, LLP
Nano Dynamics Inc.
Yao Sam Chuan
LandOfFree
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