Continuous carbon nanotube tape from a chemical vapor deposition system

Abstract

The present disclosure provides a carbon nanotube tape, a system for continuously producing the carbon nanotube tape and a process utilizing the system to produce the carbon nanotube tape. The process includes a chemical vapor deposition system and a tape forming system, comprising a housing, an air knife assembly, and a vacuum conveyor system.

Description

CONTINUOUS CARBON NANOTUBE TAPE FROM A CHEMICAL VAPOR DEPOSITION SYSTEMCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to US Pat. App. Ser. No. 63 / 528,498 filed July 24, 2023. The noted application is incorporated herein by reference.FIELD

[0002] The present disclosure in general relates to carbon nanotube tape and more particularly to systems and processes for producing carbon nanotube tape continuously from a chemical vapor deposition system and a tape forming system.BACKGROUND

[0003] Current processes for producing carbon nanotube tape are very labor intensive and costly. In general, such processes include: 1) producing 4 feet wide by 8 feet long raw carbon nanotube sheets in a chemical vapor deposition system; 2) harvesting the raw carbon nanotube sheets and inspecting the sheets to determine their suitability for use as carbon nanotube tape; 3) post processing the raw carbon nanotube sheets with a condensing chemical; 4) cutting the post processed sheets into 4 inch wide by 8 foot long lengths; 5) seaming the 4 inch wide by 8 foot long sections together via a hot glue process press; 6) rolling the seamed sheets up into spools 4 inches wide by 1000 to 2000 meters in length; 7) running the spools thru a slitting operation to produce a desired tape width, for e.g., from 5 / 16 inch to 1 inch; 8) optionally seaming the spooled tape together to produce longer finished width spools in 3000 to 4000 meter lengths; and 9) inspecting each completed spool for tape strength, width, tape thickness and seam thickness by continuously running the spooled tape over tension transducer rollers, digital non-contact width sensors, anddigital or manual thickness measuring devices. The finished spools of tape are then prepared for shipping.

[0004] It would be desirable to provide a new process capable of continuously producing carbon nanotube tape more efficiently and at a fraction of cost than current processes. The present disclosure provides such a process which eliminates several of the steps above, yet still produces carbon nanotube tape having a desired width and length and suitable for use in the aerospace, commercial wire and cable industries.SUMMARY

[0005] The present disclosure generally provides a system for continuously producing carbon nanotube tape that includes: (a) a chemical vapor deposition system operable to form a carbon nanotube material; and (b) a tape forming system comprising (i) a housing having an inlet coupled to an outlet of the chemical vapor deposition system, (ii) an air knife assembly positioned adjacent to the inlet and operable for receiving the carbon nanotube material, and (iii) a vacuum conveyor system operable to draw the carbon nanotube material from the air knife assembly and form the carbon nanotube tape.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIG. 1 illustrates a schematic diagram of a system for continuously producing carbon nanotube tape according to an embodiment of the present disclosure which generally includes a chemical vapor deposition system coupled to a tape forming system;

[0007] FIG. 2A is a schematic diagram of a floating catalyst chemical vapor deposition system for the production of carbon nanotube material which may be used in forming the carbon nanotube tape according to an embodiment of the present disclosure;

[0008] FIG. 2B is schematic illustration of an injector apparatus for use in connection with the system shown in FIG. 2A;

[0009] FIG. 2C illustrates a schematic diagram of a floating catalyst chemical vapor deposition system utilizing a plasma generator for production of carbon nanotube material in connection with an embodiment of the present disclosure;

[0010] FIG. 2D illustrates a schematic diagram of a plasma generator suitable for use in connection with the system of FIG. 2C;

[0011] FIG. 3 illustrates a schematic side view diagram of a tape forming system according to one embodiment of the present disclosure;

[0012] FIG. 4 is a front view of the tape forming system of FIG. 3;

[0013] FIG. 5 is a perspective view of the tape forming system of FIG. 3 receiving a carbon nanotube sock produced in a chemical vapor deposition system;

[0014] FIG. 6A is a perspective view of a vacuum conveyor system according to one embodiment of the present disclosure;

[0015] FIG. 6B is a perspective view of a deck in combination with a transmission mechanism and a guide mechanism of the vacuum conveyor system;

[0016] FIG. 6C is a top view of the deck in fluid connection with a vacuum source of the vacuum conveyor system;

[0017] FIG. 6D is a top view of a portion of a belt disposed on the deck of the vacuum conveyor system;

[0018] FIG. 6E is a perspective view of a continuous belt of the vacuum conveyor system;

[0019] FIG. 6F is a perspective view of a transmission mechanism of the vacuum conveyor system;

[0020] FIG. 6G is a perspective view of a guide mechanism of the vacuum conveyor system;

[0021] FIGS. 7A (in situ) and 7B (ex situ) are front views of a collection system of the tape forming system of FIG. 3 and the finished tape product; and

[0022] FIG. 8 is perspective view of a gas lock coupled to the tape forming system of FIG. 3.DETAILED DESCRIPTION

[0023] The present disclosure is generally directed to carbon nanotube tape and a system and a process for continuously producing the carbon nanotube tape. Referring to FIG. 1, in one embodiment the carbon nanotube tape is produced by a process that generally includes the following steps. First, a carbon nanotube material is produced in a chemical vapor deposition system 1000. The carbon nanotube material is then introduced into a tape forming system 1100 which is configured and operable to form the carbon nanotube tape. The tape forming system 1100 is coupled to the chemical vapor deposition 1000, in particular a synthesis chamber 1001 of the chemical vapor deposition system 1000. The synthesis chamber 1001, in general, includes an entrance end 1001a, into which reaction gases may be supplied, a hot zone 1002, where synthesis of extended length carbon nanotubes may occur, and an exit end 1001b from which the products of the reaction, namely the extended length carbon nanotubes (i.e., carbon nanotube material) and exhaust gases may exit. In some embodiments, synthesis chamber 1001 may include a quartz tube 1003, extending through the hot zone 1002. Although illustrated generally in FIG. 1, itshould be appreciated that other configurations may be employed in the design of synthesis chamber 1001.

[0024] The tape forming system 1100, in some embodiments, includes a housing 1105. The housing 1105, as illustrated in FIG. 1, may be substantially airtight to minimize the release of potentially hazardous airborne particulates from within the synthesis chamber 1001 to the environment, and to prevent oxygen from entering into the system 1100 and reaching the synthesis chamber 1001. In particular, the presence of oxygen within the synthesis chamber 1001 can affect the integrity and compromise the production of the carbon nanotubes.

[0025] The housing 1105 of the tape forming system 1100 also includes an inlet 1105a for engaging the exit end 1001b of the synthesis chamber 1001 in a substantially airtight manner. In some embodiments, as the carbon nanotubes exit the synthesis chamber 1001, the nanotubes entangle, bundle and otherwise coalesce into an extended network of interconnected and branching bundles and form a hollow carbon nanotube sock 1200 (i.e., the carbon nanotube material is a carbon nanotube sock) similar in shape to a windsock inflated by a breeze. An air knife assembly 1300 positioned adjacent to inlet 1105a is operable to guide and control the width of the carbon nanotube sock 1200 exiting the synthesis chamber 1001. The carbon nanotube sock 1200 is drawn onto a continuous conveying surface of a vacuum conveyor system 1400 positioned below air knife assembly 1300. The drawn down sock 1200 forms a thin film or tape 1250 on the continuous conveying surface (see FIG. 7B) and is transferred to a collection system positioned within the housing 1105, such as a receiving spool to form a roll, or alternatively, is transferred from the housing 1105 to ambient conditions via a gas lock (shown in FIG. 8) for eitherrolling onto a receiving spool to form a roll or for transfer to other equipment for post processing.

[0026] The surprising advantages to the systems and processes of the present disclosure are that the width of the carbon nanotube sock exiting the synthesis chamber may be controlled by the air knife assembly without the sock sticking to components of the tape forming system. While the air knife assembly is operable to control the carbon nanotube sock’s width, the carbon nanotube sock exiting the chemical vapor deposition system is filled with hydrogen and must be degassed. The air knife assembly works in conjunction with the vacuum conveyor system drawing the controlled width carbon nanotube sock onto the continuous conveying belt to produce the carbon nanotube tape. The carbon nanotube tube tape’s width and thickness may both be controlled by: the production rate of the carbon nanotube tube material in the chemical vapor deposition system; operation of the air knife assembly, the speed of the conveying belt; and, the vacuum draw down rate of the carbon nanotube sock from the air knife assembly. In some embodiments, the production rate of the carbon nanotube tube material may range from about 5-50 grams / hour, the speed of the conveying belt may range from about 10-100 feet / minute and the vacuum draw down rate of the carbon nanotube sock may range from about 20-60 hertz. The carbon nanotube tape produced according to the present disclosure may have a width ranging from about 5 / 16-3 inches (and having substantially straight edges as shown in FIGS. 7A and 7B). In still other embodiments, the carbon nanotube tape produced according to the process of the present disclosure may have a density ranging from about (1-10 grams / meter2).

[0027] As discussed above, the carbon nanotube tape according to the present disclosure is formed from carbon nanotube material. According to one embodiment, the carbonnanotube material includes entangled carbon nanotubes having the particular characteristics: (i) a diameter of between about 10-100 nm, or between about 12-90 nm, or between about 15-80 nm, or between about 17-60 nm, or between about 20-50 nm, or between about 25-30 nm (ii) a length of between about 0.1-10 mm, or between about 0.2- 9 mm, or between about 0.3-8 mm, or between about 0.44-7 mm, or between about 5-6 mm (iii) a density of between about 0.3-1.9 g / cm3, or between about 0.35-1.8 g / cm3, or between about 0.5-1.7 g / cm3, or between about 0.1-1 g / cm3, or between about 0.3-1.1 g / cm3, (iv) an aspect ratio of at least about 250,000, or at least about 350,000, or at least about 500,000, or at least about 600,000 (v) a strain to failure of between about 1.8-7%, or between about 2-6.5% or between about 3-5%, (vi) and a surface area from about 100-300 m2 / g, or from about 125-275 m2 / g, or from about 150-250 m2 / g or from about 175-225 m2 / g. In further embodiments, in addition to the characteristics above, the entangled carbon nanotubes may also be characterized as having a tensile strength of between about 0.2-3.2 GPa, or between about 0.3-3 GPa, or between about 0.3-2.8 GPa and / or a specific strength of between about 1800-2900 kN-M / kg, or between about 2000-2700 kN-M / kg or between about 2200-2600 kN-M / kg.

[0028] Presently, there exist multiple processes and variations thereof for growing nanotubes useful in the present disclosure. These processes include: (1) Chemical Vapor Deposition, a common process that can occur at near ambient or at high pressures, and at temperatures above about 400°C, (2) Arc Discharge, a high temperature process that can give rise to tubes having a high degree of perfection, and (3) Laser ablation.

[0029] As discussed above, a Chemical Vapor Deposition process or similar gas phase pyrolysis procedure known in the industry may be used to grow the appropriate carbonnanotubes. Growth temperatures for a Chemical Vapor Deposition process may be comparatively low ranging, for instance, from about 400°C to about 1350°C. Carbon nanotubes, both single wall carbon nanotubes (SWNT) or multiwall carbon nanotubes (MWNT), may be grown, in some embodiments, by exposing nanoscaled catalyst particles in the presence of reagent carbon-containing gases (i.e., a gaseous carbon source). In particular, the nanoscaled catalyst particles may be introduced into the reagent carbon- containing gases, either by the addition of existing particles or by in situ synthesis of the particles from a metal-organic precursor, or even non-metallic catalysts. Although both SWNT and MWNT may be grown, in certain instances, SWNT may be selected due to their relatively higher growth rate and tendency to form rope-like structures which may offer advantages in handling, thermal conductivity, electronic properties and strength.

[0030] The carbon nanotubes utilized in this disclosure may be described as bare, pristine, unpurified or purified. The terms “bare” and / or “pristine” and / or “unpurified” describe carbon nanotubes that have had little or no treatment since their chemical synthesis. Carbon nanotubes of these types are primarily, but not limited to, materials that are available directly from the synthesis process. The term “purified” carbon nanotubes are primarily defined as carbon nanotubes that have been treated either chemically and / or thermally and / or physically to impart improved properties to the carbon nanotubes. Examples of such treatments include, but are not limited to, acid treatment to remove catalyst or amorphous carbon and thermally annealing to remove amorphous carbon and / or reduce the number of carbon defect sites. Additionally, carbon nanotubes may be media milled to break down carbon nanotube aggregates to assist in carbon nanotube dispersing and processing. Various methods and approaches to purify carbon nanotubes are knownto those skilled in the art and described in the literature and the materials prepared by any such techniques can be utilized in this disclosure.

[0031] It should be noted that although reference is made throughout the application to nanotubes synthesized from carbon, other compound(s), such as boron nitride, MoS2, or a combination thereof may be used in the synthesis of nanotubes in connection with the present disclosure.

[0032] In one embodiment, the present disclosure employs a floating catalyst chemical vapor deposition (“CVD”) system and process to generate the carbon nanotubes. Since growth temperatures for the floating catalyst CVD process may be comparatively low ranging, for instance, from about 400°C to about 1400°C, carbon nanotubes, single wall carbon nanotubes (SWNT), multiwall carbon nanotubes (MWNT) or both, may be grown. Although both SWNT and MWNT may be grown, in certain instances, SWNT may be preferred because of their higher growth rate and tendency to form ropes which may offer handling, safety and strength advantages.

[0033] FIG. 2A represents an embodiment of the present disclosure in which an essentially horizontal CVD system 20 is depicted in which the carbon nanotubes can be grown. CVD system 20 includes a housing 21 (i.e., furnace) having opposite ends 211 and 212, and a passageway 213 extending between ends 211 and 212. A tube 22 (i.e., reactor) having a proximal portion and a distal portion within which the elongated non-entangled carbon nanotube filaments may be generated may be situated within the passageway 213 of housing 21. Tube 22 is filled with a pre-heated dense gas, such as, but not limited to, argon, sulfur hexafluoride (SFe), carbon monoxide or mixtures thereof. These dense gases have been pre-heated to a temperature of at least about 100°C, or at least about 200°C, or at leastabout 300°C or at least about 400°C, or at least about 500°C, or at least about 600°C or at least about 700°C, or at least about 800°C, or at least about 900°C or at least about 1000°C so that they are denser than the incoming injected CVD gases (i.e., fluid mixture) which enter at end 222 (or lower end of tube 22). The concentration of the dense gases within tube 22 may be at least about 10 mole % or at least about 20 mole % or at least about 30 mole% or at least about 40 mole % or at least about 50 mole% or at least about 60 mole % or at least about 70 mole % or at least about 80 mole % or at least about 90 mole % or at least about 99.9 mole %. On injection of the incoming fluid mixture, heat is transferred from the pre-heated dense gas within tube 22 to the light incoming fluid mixture feedstock by conduct! on / convecti on and from the walls of tube 22 by radiation.

[0034] Ends 221 and 222 of tube 22 may be positioned so that they extend from ends 211 and 212 respectively of housing 21. Housing 21 may include heating elements or other mechanisms (such as a slot furnace) to generate temperatures ranging between about 1000°C to about 1500°C, which are necessary for the growth of carbon nanotubes within tube 22. As the heating elements or other mechanisms must maintain the temperature environment within tube 22 to within a specified range during the synthesis of the elongated non-entangled carbon nanotube filaments, although not illustrated, the system 20 may include a thermocouple on the exterior of tube 22 to monitor the temperature environment within tube 22. The maintenance of the temperature range within tube 22, for e.g., from about 1 100°C to about 1400°C, may be optimized by the use of an insulating structure 223. Insulating structure 223 as shown in FIG. 2C. may be made from, for e.g., zirconia ceramic fibers (e.g., zirconia-stabilized boron nitride). Other insulating materials may also be used.

[0035] As the housing 21 and tube 22 must withstand variations in temperature and gas- reactive environments, housing 21 and tube 22 may be manufactured from a strong, substantially gas-impermeable material that is substantially resistant to corrosion. The housing 21 and tube 22 may be made from a quartz or ceramic material, such as, for e.g., Macor® machinable glass ceramic, to provide enhanced shock absorption. Of course, other materials may also be used, so long as the housing 21 and tube 22 can remain impermeable to gas and maintain their non-corrosive character. Also, although illustrated as being cylindrical in shape, housing 21 and tube 22 may be provided with any geometric cross-section.

[0036] CVD system 20 is coupled to tape forming system 23 at its distal portion. Tape forming system 23 is in fluid communication with end 221 of tube 22 enabling it to receive carbon nanotube material generated within tube 22. At opposite end 222 of tube 22, CVD system 20 may include an injector apparatus 24 (i.e., nebulizer) in fluid communication with tube 22. Injector 24 may be designed to receive from a reservoir 25 a fluid mixture of components necessary for the growth of nanotube filaments within tube 22. Injector 24 may also be designed to vaporize or fluidize the mixture (i.e., generating small droplets) before directing the mixture into tube 22 for the generation and growth of the carbon nanotubes. In some embodiments, multiple filaments could be produced from an injector array (not shown), such as a device similar to a spinneret commonly used in gel spinning.

[0037] The fluid mixture entering at end 222, in one embodiment, can include, among other things, (a) a metal catalyst precursor from which a metal catalyst particle can be generated for subsequent growth of the nanotubes thereon, (b) a conditioner compound for controlling size distribution of metal catalyst particles generated from the metal catalystprecursor, and thus the diameter of the nanotubes, and (c) a carbon source for depositing carbon atoms onto the metal catalyst particle in order to grow the elongated non-entangled nanotubes.

[0038] Examples of the metal catalyst precursor from which metal catalyst particles may be generated include ferrocene materials such as iron or iron alloy, nickel, cobalt, their oxides, or their alloys (or compounds with other metals or ceramics). Alternatively, the metal catalyst particles may be made from metal oxides, such as Fest , Fe2C>4, or FeO, similar oxides of cobalt or nickel, or a combination thereof.

[0039] Examples of the conditioner compound for use in connection with the fluid mixture of the present disclosure include thiophene, EES, other sulfur containing compounds, or a combination thereof.

[0040] Examples of the carbon source for use in connection with the fluid mixture of the present disclosure include, but are not limited to, ethanol, methyl formate, propanol, acetic acid, hexane, methanol, or blends of methanol with ethanol. Other liquid carbon source may also be used, including C2H2, CH3, and CH4.

[0041] With reference now to FIG. 2B, there is shown a detailed illustration of injector 24. Injector 24 includes a substantially tubular chamber 241 defining a pathway 242 along which the vaporized fluid mixture may be generated and directed into reactor tube 22. To vaporize or fluidize the mixture, injector 24 may include a nebulizing tube 26 designed to impart a venturi effect in order to generate small droplets from the fluid mixture being introduced from reservoir 25. It should be appreciated that the vaporizing or fluidizing of the fluid mixture may occur substantially as the fluid exits through distal end 261 of nebulizing tube 26. The droplets being generated may range from nanoscale in size tomicroscale in size. To direct the vaporized fluid mixture along the nebulizing tube 26 into the reactor tube 22, a volume of gas, such as H2, He or any other inert gas(es), may be used to push or propel the vaporized fluid toward the reactor tube 22.

[0042] Although illustrated as substantially tubular, it should be appreciated that injector 24 may be provided with any geometric designs, so long as the injector can accommodate the nebulizing tube 26, and provide a pathway along which the vaporized fluid mixture can be directed into reactor tube 22.

[0043] In addition, it should be noted that the injector 24 may be designed to permit introduction of individual components of the fluid mixture into the injector 24 rather than providing them as part of the fluid mixture. In such an embodiment, each component may be individually vaporized, through a nebulizing tube similar to tube 26, and introduced into the injector 24, where they may be allowed to mix and subsequently be directed along the injector 24 in a similar manner to that described above.

[0044] As injector 24 is situated within a portion of reactor tube 22 and furnace 21, the heat being generated within tube 22 and furnace 21 may have a negative effect on the temperature environment within injector 24. In order to shield injector 24 from the heat in reactor tube 22 and furnace 21, an insulation package 27 may be provided about injector 24. In particular, insulation package 27 may act to preserve the temperature environment along the length of injector 24.

[0045] With the presence of insulation package 27, the temperature environment within injector 24 may be lowered to a range which can affect the various reactions necessary for growing the carbon nanotubes. To that end, injector 24 may also include a heating zone A situated downstream from the nebulizing tube 26 to provide a temperature range sufficientto permit the formation of metal catalyst particles from the metal catalyst precursors. The heating zone A may include a first heater 28 situated downstream of the distal end 261 of nebulizing tube 26. Heater 28 may be provided to maintain a temperature range at, for instance, Tpinecessary to decompose the metal catalyst precursor into its constituent atoms, and which atoms may thereafter cluster into metal catalyst particles on which nanostructures may subsequently be grown. In order to maintain the temperature range at Tpiat a level necessary to decompose the metal catalyst precursor, heater 28, in one embodiment, may be situated slightly downstream of Tpi. In an embodiment where ferrocene is used as a precursor, its constituent atoms (i.e., iron particles), substantially nanoscaled in size, may be generated when the temperature at Tpican be maintained in a range of from about 200°C to about 300°C.

[0046] Heating zone A may further include a second heater 29 positioned downstream of first heater 28, and within furnace 21. Heater 29 may be provided to maintain a temperature range at, for example, TP2 necessary to decompose the conditioner compound into its constituent atoms. These atoms, in the presence of the clusters of metal catalyst particles, can interact with the clusters to control the size distribution of the metal catalyst particles, and hence the diameter of the nanostructures being generated. In an embodiment where thiophene is used as a conditioning compound, sulfur may be released upon decomposition of the thiophene to interact with the clusters of metal catalyst particles. Heater 29, in an embodiment, may be designed to maintain a temperature range at TP2 from about 700°C to about 950°C and to maintain such a range at a location slightly downstream of the heater29.

[0047] In accordance with one embodiment, TP2 may be located at a desired distance from Tpi. As various parameters can be come into play, the distance from Tpito TP2 should be such that the flow of fluid mixture from Tpi, where decomposition of the metal catalyst precursor occurs, to TP2 can optimize the amount of decomposition of the conditioning compound, in order to optimize the size distribution of the metal catalyst particles.

[0048] It should be appreciated that in addition to the particular temperature zones generated by first heater 28 and second heater 29 within injector 24, the temperature at the distal end 261 of nebulizing tube 26 may also need to be maintained within a particular range in the injector 24 in order to avoid either condensation of the vaporized fluid mixture or uneven flow of the fluid mixture as it exits through distal end 261 of nebulizing tube 26. In an embodiment, the temperature at the distal end 261 may need to be maintained between about 100°C and about 250°C. If, for example, the temperature is below the indicated range, condensation of the fluid mixture may occur along a wall surface of the injector 26. Consequently, the fluid mixture that is directed from the injector 26 into the reactor tube 22 may be substantially different from that of the mixture introduced from reservoir 25. If, for example, the temperature is above the indicated range, boiling of the fluid mixture may occur at the distal end 261, resulting in sputtering and uneven flow of the fluid into the injector 24.

[0049] As injector 24 may need to maintain a temperature gradient along its length, whether to minimize condensation of the distal end 261 of the nebulizing tube 26, to maintain the necessary temperature at Tpito permit decomposition of the metal catalyst precursor, or at TP2 to permit decomposition of the conditioning compound, insulationpackage 27, in addition to shielding heat from the reactor tube 22 and furnace 21, can act to maintain the desired temperature gradient along injector 24 at each critical location.

[0050] In one embodiment, the insulation package 27 may be made from quartz or similar materials, or from a porous ceramic material, such as zirconia ceramic fibers (for e.g., zirconia-stabilized boron nitride). Other insulating materials may also, of course, be used.

[0051] With continued reference to FIG. 2B, system 20 may include at least one inlet 291 through which a carrier gas may be introduced into reactor tube 22. The introduction of a carrier gas into tube 22 may assist in moving the fluid mixture along tube 22 subsequent to its exit from injector 24. In addition, as it may be desirable to minimize turbulent flow or vortex flow associated with the fluid mixture as it exits injector 24, the carrier gas may be permitted to flow along the reactor tube 22 and along an exterior surface of injector 24. In an embodiment the carrier gas may be permitted to flow at a speed substantially similar to that of the fluid mixture, as the mixture exits the injector 24, to permit the fluid mixture to maintain a substantially laminar flow. By maintaining a substantially laminar flow, growth and strength of the nanotubes being produced may be optimized. In an embodiment, the carrier gas may be H2, He or any other inert gas.

[0052] To further minimize turbulent flow or vortex flow as the fluid mixture exits the injector 24, insulation package 27 may be provided with a substantially tapered design about distal end of injector 24. Alternatively, or in addition, an extension (not shown) may be situated about distal end of injector 24 to expand the flow of the fluid mixture substantially radially away from the center of the injector 24 as the fluid mixture exits the distal end of the injector. The presence of such an extension can slow down flow velocity of the fluid mixture and allow the flow pattern to remain substantially laminar.

[0053] It should be appreciated that the injector 24 may be designed to decompose the metal catalyst precursor at Tpiand the conditioning compound at TP2 as the fluid mixture moves along injector 24. However, the carbon source necessary for nanostructured growth does not get decomposed and may remain substantially chemically unchanged as the fluid mixture moves along injector 24.

[0054] However, since the distal end of injector 24 protrudes into furnace 21, as seen in FIGS. 2-2A, its proximity to a substantially higher temperature range within the furnace 21, and thus reactor tube 22, can expose the carbon source immediately to a temperature range necessary to decompose the carbon source, upon its exiting through the distal end of the injector 24, for subsequent nanotube growth. In an embodiment, the temperature range at interface 242 between distal end of the injector and furnace 21 may be from about 1000°C to about 1250°C.

[0055] With reference to FIG. 2C, a plasma generator 230 may be disposed about the distal end of the injector 24. In this manner, the fluid mixture may be passed through a plasma flame 232 of the plasma generator 230 before entering the reactor tube 22. In an embodiment, there may be provided hermetic seals or fluid tight seals around the junctions between the plasma generator 230 and the injector 24, as well as between the plasma generator 230 and the reactor tube 22 to prevent gases and particles in the fluid mixture from escaping from the system 20. In one embodiment, the plasma generator 230 may be in an axial or linear alignment with the tubular chamber 241 of the injector 24 to provide an efficient flow path for the fluid mixture from the injector 24 and through the plasma generator 230. In an embodiment, the alignment of the plasma generator 230 with the injector 24 is such that the fluid mixture is allowed to pass substantially through the middleof the plasma generator 230. In some embodiments, this may lead to the fluid mixture passing through the middle region of the plasma flame 232, which may have a more uniform temperature profile than the outer regions of the plasma flame 230. The plasma generator 230 may also be in an axial or linear alignment with the reactor tube 22.

[0056] In an embodiment, the plasma generator 230 may provide concentrated energy, in the form of the plasma flame 232, to increase the temperature of the fluid mixture to a temperature higher than the temperature range in the injector 24. In an embodiment, the plasma generator 230 can increase the temperature of the fluid mixture to a level sufficient to decompose the carbon source into its constituent atoms for activation of nanostructure growth. In an embodiment, the plasma generator 230 may operate between about 1200°C and about 1700°C. Because the temperature of the plasma flame 232 is substantially higher than the temperature in the injector 24, the heat generated by the plasma flame 232 may have a negative effect on the temperature environment within the injector 24. To that end, the plasma generator may be provided with a heat shield 260 situated between the region of the plasma generator 230 where the plasma flame 232 is generated and the injector 24 to preserve the temperature environment along the length of injector 24. In one embodiment, the heat shield 260 may be made from a porous ceramic material, such as zirconia ceramic fibers (e.g., zirconia-stabilized boron nitride). Other insulating materials may, of course, also be used.

[0057] Because the plasma generator 230 may provide concentrated energy to the fluid mixture thereby initiating quicker decomposition of the carbon source, in one embodiment, a shorter reactor tube 22, the furnace 21, or both may be used and still generate nanotubes of sufficient length. Of course, to the extent desired, reactor tube 22, the furnace 21, orboth may be provided with similar or longer lengths than in systems without a plasma generator. In an embodiment, utilizing the plasma generator 230 in the process may enable production of longer carbon nanotubes.

[0058] It should also be noted that in some embodiments, the injector 24 and plasma generator 230 may be utilized with minimal heat or without additional heat in the reaction tube 22. It should also be noted that multiple plasma generators may be utilized in the system 20 to provide a desired temperature gradient over a travel distance of the fluid mixture.

[0059] FIG. 2D illustrates one embodiment of the plasma generator 230. In an embodiment, the plasma generator 230 may be a direct current (DC) power generator. The plasma generator 230 may include an anode 252 and a cathode 254, which can be cooled by water or another cooling fluid or another material that may act as a heat sink to transfer the heat away from the electrodes 252, 254. In an embodiment, the electrodes 252, 254 may be high diffusivity-metal electrodes, such as typically made of copper or silver. Plasma gas may flow around the anode 252 and cathode 254 and may be ionized by an electric arc 256 initiated between the anode 252 and cathode 254 to create plasma flame 232. Suitable plasma gasses may be either reactive or non-reactive and may include, but are not limited, argon oxygen, nitrogen, helium, hydrogen or another gas. In an embodiment, the plasma generator 230 may include one or more Helmholtz coils 258 or another device for producing magnetic field for rotating the arc 256. In such an embodiment, the anode 252 and cathode 254 may be provided with an annular shape to facilitate rotation of the arc 256. While FIG. 2D illustrates one suitable embodiment of aplasma generator, other designs and types of plasma generators (i.e., radio frequency, alternating current and other discharges plasma generators) may be implemented.

[0060] In an embodiment, the Helmholtz coils 258 can be used to generate an electromagnetic or electrostatic field for in situ alignment of the nanotubes downstream of the plasma generator 230 in the reactor chamber 22. Additionally, or alternatively, the electromagnetic field created by the plasma generator 230 can act to deflect the carbon nanotubes towards the axis of the reaction tube 22 by generating a torque on the carbon nanotubes, packing the carbon nanotubes towards such axis. In an embodiment the plasma generator 230 can also be designed to push or focus the cloud of carbon nanotubes into a smaller radial volume as the cloud of carbon nanotubes proceeds through the reaction tube 22. In an embodiment, particles from which carbon nanotubes grow can be charged by a particle charger so that the particles can respond to electrostatic forces.

[0061] To the extent more than one plasma generator 230 is used, the plasma generators field strength and position can be optimized to align the carbon nanotubes. Additionally, or alternatively, the power generators may be in linear alignment with one another, and each successive downstream plasma generator may be configured to generate a stronger electrostatic field, so as to force or condense the flowing cloud of carbon nanotubes toward a smaller radial volume, while moving the carbon nanotubes in a substantial axial alignment with the reaction tube 22. In some embodiments, the successive plasma generators can also be used to control the flow acceleration or deceleration, allowing the nanotubes to radially condense toward a filament like shape. Such an approach toward condensing the flow of carbon nanotubes can force the carbon nanotubes to be in closer proximity to enhance contact between adjacent nanotubes. Contacts between adjacentcarbon nanotubes can be further enhanced via non-covalent interactions between the carbon nanotubes, such as London dispersion forces or van der Waals forces.

[0062] In operation, a number of processes may be occurring in a region between the nebulizing tube 26 and the main furnace 21 of system 20. For instance, initially, the fluid mixture of metal catalyst precursor, conditioning compound and carbon source may be introduced from reservoir 25 into injector 24 by way of nebulizing tube 26. To assist in directing the fluid mixture along the nebulizing tube 26, an inert gas, such as H2 or He may be used. As the fluid mixture moves along the nebulizing tube 26 and exits therefrom, tube 26 can impart a venturi effect to vaporize the fluid mixture (i.e., generate droplets from the fluid mixture). To minimize any occurrences of condensation or boiling as the fluid mixture exits the nebulizing tube 26, such an area within the injector 24 may be maintained at a temperature level ranging from about 100°C to about 250°C.

[0063] In an embodiment, an additive for the carbon source may be included in the fluid mixture to optimize growth conditions, as well as enhancing the strength of carbon nanotube material made from the carbon nanotubes being produced. Examples of additives include, but are not limited to, Ceo, C70, C72, Cs4, and C100.

[0064] The vaporized fluid mixture may then proceed along the injector 24 toward the first heater 28 where the temperature may be maintained at Tpiat levels ranging from about 200°C to about 300°C, the metal catalyst precursor within the fluid mixture may be decomposed, releasing its constituent atoms. The decomposition temperature of the metal catalyst precursor, in an embodiment, can be dependent on the carrier gas (for e.g., H2 or He), and may depend on the presence of other species. The constituent atoms may subsequently cluster into metal catalyst particles of a characteristic size distribution. Thissize distribution of the metal catalyst particles can, in general, evolve during migration through the injector 24 and into the furnace 21.

[0065] Next, the fluid mixture may proceed further downstream along the injector 24 toward the second heater 29. The second heater 29, in an embodiment, may maintain the temperature at TP2 at a level ranging from about 700°C to about 950°C where the conditioning compound may decompose into its constituent atoms. The constituent atoms of the conditioning compound may then react with the clusters of metal catalyst particles to effectuate the size distribution of the clusters of metal catalyst particles. In particular, the constituent atoms of the conditioning compound can act to stop the growth and / or inhibit evaporation of the metal catalyst particles. In an embodiment, the constituent atoms of the conditioning compounds along with H2 in the injector 24 may interact with the clusters of metal catalyst particles to affect size distribution of the metal catalyst particles.

[0066] It should be appreciated that the carbon source within the fluid mixture may remain chemically unchanged or otherwise not decomposed within injector 24, as the fluid mixture travels along the entire length of the injector 24.

[0067] The conditioned metal catalyst particles once moved beyond the second heater 29 may thereafter move across interface 242 between distal end 241 of injector 24 and furnace 21 to enter into the main portion of reactor tube 12 filled with the pre-heated dense gas. Upon exiting the injector 24, the conditioned metal catalyst particles, along with the carbon source, may maintain a substantially laminar flow in the presence of a carrier gas, such as H2 or He. In the presence of the carrier gas, the conditioned metal catalyst particles may be diluted by the volume of carrier gas.

[0068] In addition, upon entry into the main portion of the reactor tube 22, where the temperature range within the reactor tube 22 may be maintained at a level sufficient to decompose the carbon source into its constituent carbon atoms, the presence of the carbon atoms can activate nanotube growth. In an embodiment, the temperature range may be from about 1000°C to about 1250°C. In general, growth occurs when the carbon atoms attach themselves substantially sequentially upon the metal catalyst particles to form a nanotube, such as a carbon nanotube.

[0069] In an embodiment, the fluid mixture from the injector 24 may be passed through the plasma generator 230 before entering the reactor tube 22.

[0070] As described above, upon entering the main portion of the reactor tube 22, heat is transferred from the dense gas to the light fluid mixture by conduct! on / conv ection and from the walls of the reactor tube 22 by radiation such that elongated non-entangled nanotubes are produced. In addition, the flow of the fluid mixture within the main portion of the reactor tube 22 is such that minimal or substantially no nanotubes contact the walls of the reactor tube 22.

[0071] Growth of the nanotubes may end when the metal catalyst particles become inactive, the concentration of constituent carbon atoms near the metal catalyst particles is reduced to a relatively low value, or the temperature drops as the mixture moves beyond an area within the reactor tube 22 where the temperature range is maintained at a sufficient level for growth.

[0072] FIG. 3 schematically illustrates an exemplary tape forming system 23 the present disclosure. The depicted tape forming system 23 is just one example of a tape forming system 23 that can suitably incorporate the principles of the present disclosure. Indeed,many alternative designs and configurations of the tape forming system 23 may be employed, without departing from the scope of this disclosure. In one embodiment, the tape forming system 23 is coupled to the distal end of the CVD system 20 and generally includes a substantially air tight housing 31 and an inlet 33 of the housing 31 for engaging the exit end 221 of the reactor tube 22 in a substantially airtight manner.

[0073] Referring now to FIGS. 3-6G, the tape forming system 23 also includes: an air knife assembly 35 positioned adjacent to the exit end 221 of reactor tube 22, the air knife assembly being operable to guide and control the width of the carbon nanotube sock 50 as it exits reactor tube 22; and, a vacuum conveyor assembly 36 positioned below the air knife assembly 35, the vacuum conveyor assembly being operable to draw the carbon nanotube sock 50 from the air knife assembly 35 onto a conveying surface or belt 37 to form a carbon nanotube tape or thin film 60 and to transfer the carbon nanotube tape 60 distally from the air knife assembly 35. In a further embodiment, tape forming system 23 also includes a collection assembly 38 positioned distally from air knife assembly 35 and operable to collect the carbon nanotube tape 60 from the vacuum conveyor assembly 36.

[0074] The air knife assembly 35 includes a first gas guide 40a supported by vacuum conveyor assembly 36. Gas guide mounting brackets 42 are secured to the discharge conveyor assembly 36 and support the first gas guide 40a. A gas supply line 44a extends from the first gas guide 40a and communicates with a source of pressurized gas 41.

[0075] The air knife assembly 35 further includes a second gas guide 40b. The second gas guide is positioned on an opposite side of the first gas guide 40a and is supported by vacuum conveyor assembly 36. Gas guide mounting brackets 42 are secured to vacuum conveyor assembly 36 and support the second gas guide 40b. The second gas guide 40b issubstantially identical to the first gas guide 40a and also includes a gas supply line 44b extending from the second gas guide 40b and communicating with a source of pressurized gas 41. In one embodiment, the brackets 42 for at least one of the gas guides 40a and 40b can be configured to be adjustable, such that the position of the gas guides 40a and 40b may be adjusted with respect to a conveying surface 37 of the vacuum conveyor assembly 36. For example, the gas guides 40a and 40b may be adjusted such that the distance between their lower ends (“C”) ranges from about 0.25-3.5 inches.

[0076] While the specific construction, configuration and operation of the gas guides may vary, the gas guides 40a and 40b are generally configured to provide a substantially uninterrupted thin layer of highly concentrated moving gas sufficient to control the width of the carbon nanotube sock. Since gas guide 40b is identical to gas guide 40a, only gas guide 40a will now be further described (with such description also applicable to gas guide 40b).

[0077] Gas guide 40a includes converging section 45 having an outer wall 46 and a gas permeable inner wall 47 spaced from the outer wall 46. The outer wall 46 may be made of a gas impermeable metal such as stainless steel, carbon steel (with or without a coating) or aluminum, or other gas impermeable material.

[0078] The gas permeable inner wall 47 may be made of a porous plate, such as a porous graphite plate, a porous metal plate, a porous stainless steel plate, a porous aluminum plate, a porous brass plate, a porous ceramic plate, a porous resin plate, or a porous composite plate, for e.g., carbon, KEVLAR aramid, and boron. In some embodiments, the gas permeable inner wall 47 may be comprised of two or more layers of the same or different material above. In one particular embodiment, the gas permeable inner wall 47comprises a porous graphite plate. As will be discussed further below, fluidization and / or suspension of the carbon nanotube sock 50 above the porous surface of the gas permeable inner wall can enable the carbon nanotube sock 50 to pass over the inner wall with very little friction and without sticking to the wall, in a manner comparable to an air hockey style surface.

[0079] Alternatively, instead of using a porous plate, the gas permeable inner wall 47 may be, for example, a screen, or screen material. In still another alternative, the gas permeable inner wall 47 may be a fluidizing plate made (for e.g., machined, drilled, water jetted, laser cut) to have multiple holes, slots, passageways and / or jets or passageways extending through the fluidizing plate. The holes, slots, passageways and / or jets can be in a particular pattern (for e.g., matrix, radii, star, concentric circles). Further, the configuration of the holes, slots, passageways, and / or jets (for e.g., different size, different profile, different cross-sectional shape, tapering, particular surface roughness and / or surface finish in holes, slots, passageways, and / or jets or outer surfaces) can be tailored to create various fluidizing effects.

[0080] Various methods may be utilized to secure the gas permeable inner wall 47 on the interior surface of the converging section 45. For example, one or more connecting structures may be provided on the interior surface of the converging section 45 and the gas permeable inner wall 47 may be attached to such structures via welding, bolting or other known methods of attachment.

[0081] As illustrated, the air knife assembly 35 has a longitudinal axis “L” parallel to a normal vector “N.” As shown in FIG. 4, the converging section 45 has a horizontal slope angle a that is relative to a horizontal plane transverse to the longitudinal axis L and thevector N. Accordingly, as the horizontal slope angle a from the horizontal plane increases, the steepness of the slope of the outer wall 46 increases.

[0082] FIG. 4 also shows a vertical slope angle 0 that is relative to vertical vector N parallel to the longitudinal axis L and is measurable between the sloping outer wall 46 of converging section 45 and the normal (or perpendicular) vector N of the air knife assembly 35. The vertical slope angle 0 equals 90° minus the horizontal slope angle a. In the illustrated example, the sloping outer wall 46 of the converging section 45 becomes steeper as the value of the slope angle 0 approaches zero degrees (0°).

[0083] Although other slope angles are contemplated, according to one embodiment, a typical range of the horizontal slope angle a may be about 25°-65°, or about 40°-50° or about 45°. Similarly, while other angles are contemplated, in another embodiment, a typical range of vertical slope angle 0 may be about 20°-60°, or about 30°-55° or about 45°.

[0084] In the tape forming system shown in FIG. 4, the gas permeable inner wall 47 follows the slope of the outer wall 46. Thus, the outer wall 46 and the gas permeable inner wall 47 may have the same slope angles a and 0. However, the present disclosure also contemplates the gas permeable inner wall 47 not following the slope of the outer wall 46. Regardless of whether the gas permeable inner wall 47 follows the slope of the outer wall, the gas permeable inner wall 47 may be oriented at slope angles in the ranges of slope angles a and 0 discussed above. Thus, while other angles are contemplated, in one embodiment, the gas permeable inner wall 47 is oriented at the horizontal slope angle a in the range from about 25°-65°, or about 40°-50° or about 45°. Also, while other angles arecontemplated, the gas permeable inner wall 47 is oriented at the slope angle in a range of about 20°-60°, or about 30°-55° or about 45°.

[0085] As discussed above, the air knife assembly 35 includes a converging section 45 which has an outer wall 46 and a gas permeable inner wall 47 spaced from the outer wall section. The air knife assembly 35 also includes a gas supply line 44 A and B intercommunicating with the gas supply 41 and the space between the outer and inner wall sections 46 and 47. Flow in the gas supply line may be controlled by valve V.

[0086] Thus, the air knife assembly 35 includes the gas permeable inner wall 47 on, but spaced from the interior surface of the converging section 45 to define a space between the gas permeable inner wall 47 and the sloping outer wall 46 of converging section 45. Gas from gas supply line 44 A and B intercommunicating with gas supply 41 is interjected into the space between the gas permeable inner wall 47 and the sloping outer wall 46 of converging section 45 and passes through the gas permeable inner wall 47. This forms a layer of gas between the gas permeable inner wall 47 and the carbon nanotube sock to fluidize the carbon nanotube sock in the air knife assembly 35 above the gas permeable inner wall 47. This enhances flow of the carbon nanotube sock therein such that the carbon nanotube sock has sufficient fluid flow within the converging section 45 to be guided without sticking to the gas guide(s).

[0087] A gas supply system comprised of the gas supply and gas supply line may further include piping, pressure regulator(s), manifolds, valves, nozzles (e.g., adjustable nozzles), connections (e.g., pipe couplings), etc. for routing or piping air or other suitable gas (for e.g., argon, hydrogen or any gas under pressure) into gas guide 40a. The gas may be supplied / injected into the space between the outer wall 46 and the gas permeable inner wall47 at a controlled pressure and at a controlled flow rate. The valve(s) V may assist in controlling the gas rate.

[0088] The tape forming system 23 also includes a vacuum conveyor assembly 36. The vacuum conveyor assembly 36 is operable to draw the carbon nanotube sock 50 (see FIG. 5) from the air knife assembly 35 onto a conveying surface to form carbon nanotube tape and transfer the carbon nanotube tape away from the air knife assembly 35. In certain embodiments, the conveyor belt may be controlled by a simple drive in which the drive speed is controlled with a motor.

[0089] FIG. 6 A illustrates an embodiment of the vacuum conveyor assembly 36 that may be used in the present disclosure. As shown, the vacuum conveyor assembly 36 includes a vacuum source 602. The vacuum source 602 may be in fluid connection with a deck 604. Thus, the vacuum source 602 may be configured to pull air away from the deck 604. The deck 604 has a first deck end 662 and a second deck end 664 opposite the first deck end 662 defining a length therebetween that extends in the direction MD. Further, the deck 604 has a width extending in the cross direction CD. The deck 604 may comprise one or more channels 626, as shown in FIG. 6B, extending in the direction MD and located on the deck surface 606. With continued reference to FIG. 6A, the belt 608 may be adjacent the deck surface 606. The belt 608 has a length extending in the direction MD and a width extending in the cross direction CD. Further, the belt 608 may include a first surface 610, a second surface 612 opposite the first surface 610, a first edge 636, and a second edge 638 opposite the first edge 636. The second surface 612 of the belt 608 may be in facing relationship with the deck surface 606 and the first surface 610 may be exposed to the carbon nanotube sock. The belt 608 may also include one or moreapertures 614 disposed between the first edge 636 and the second edge 638. Further, each aperture 614 defined by the belt 608 may be aligned with at least one channel 626 on the deck 604. Thus, air can be drawn through the apertures 614 and subsequently through the channels 626 into the deck 604 and out to the vacuum source 602.

[0090] The belt 608 may further comprise a first row of teeth and a second row of teeth disposed on the second surface 612 of the belt 608. In one embodiment, a first row of teeth and a second row of teeth attached to the belt 608 may be used by the transmission mechanism 615 to move the belt. The transmission mechanism 615 may be adjacent to the first deck end 662 and configured to engage and drive the belt. More specifically, the first row of teeth may engage a first gear member 616 and the second row of teeth may engage a second gear member 618. The first gear member 616 and the second gear member 618 may be positioned on an axle member 620 that is driven by a drive mechanism 622, such as a rotary motor. Thus, as the axle member 620 rotates, the first gear member 616 and the second gear member 618 rotate about the longitudinal axle axis 624 of the axle member 620. The rotation of the first gear member 616 and the second gear member 618 may move the belt 608 across the deck surface 606 in the direction MD.

[0091] As shown in FIG. 6A, a guide mechanism 646 may be positioned opposite the transmission mechanism 615 and adjacent to the second deck end 664. The guide mechanism 646 may be configured to guide the belt 608 during operation of the vacuum conveyor system 36. For example, for a vacuum conveyor system comprising a continuous-loop belt, the belt would be required to be directed back over the deck surface during operation. The guide mechanism 646 may comprise a shaft 666 that may rotateabout a longitudinal shaft axis 668. The shaft 666 may be adapted to support the belt 608. In an alternative embodiment, not shown, it is believed that the drive mechanism 622 may also operatively engage the shaft 666 such that the drive mechanism 622 causes the shaft 666 to rotate about the longitudinal shaft axis 668. The rotation of the shaft 666 may move the belt 608 in the direction MD.

[0092] Referring to FIGS. 6B and 6C, as stated above, the vacuum source 602 may be connected to the deck 604 such that air can be drawn from the deck 604 to the vacuum source 602. The deck 604 has a deck length DL extending in the direction MD and a deck width DW extending in the cross direction CD. The deck surface 606 may define one or more channels 626. The channels 626 may extend through the deck surface 606 so that each channel 626 is in fluid connection with the vacuum source 602. Each channel 626 may have a size and a shape. The size and shape of each channel 626 may be different than or the same as the size and shape of another channel 626. However, the size and shape of the channel 626 should be sufficient to provide the desired suction either alone or in combination with the belt 608. In one example embodiment, as shown in FIG. 6C, the channels 626 may be an elongated, oval shape. Further, the channel 626 may be positioned on the deck surface 606 such that the apertures 614 in the belt 608 undergo a substantially constant vacuum when disposed on the deck surface 606. The deck 604 may be made from any material that has sufficient strength to withstand the load of the belt and articles to be conveyed and sufficient structural rigidity to withstand one more channels 626 that may extend through the deck surface 606. For example, the deck 604 may be made from steel, aluminum, ceramic, phenolic plate, and / or polymer elements, including but not limited to UHMW polymer,Teflon, phenolic polymer, and / or delrin. The deck surface 606 may also be anodized, electroplated, vapor deposition coated, polymer coated, or ceramic coated to reduce the coefficient of friction and to reduce wear.

[0093] As shown in FIG. 6D, the belt 608 may extend across at least a portion of the deck surface 606. More specifically, the belt 608 may be positioned on the deck surface 606 such that the entire belt width BW is supported by the deck surface 606. Stated another way, in one embodiment, the belt width BW may be less than or equal to the deck width DW. The belt 608 may comprise a first edge 636 and a second edge 638 opposite the first edge 636. Further, the belt may comprise one or more apertures 614 located within the first edge 636 and the second edge 638. In one embodiment, the one or more apertures 614 may be positioned in rows. Further, the belt 608 may be positioned on the deck surface 606 such that the rows of apertures 214 are in fluid connection with the one or more channels 626 on the deck surface 606. If the belt 608 remains in proper alignment such that the apertures 614 are in fluid connection with the channels 626, the apertures 614 may be designed to have a smaller cross section. Stated another way, if a manufacturer knew that the apertures 614 on the belt 608 would not become misaligned with the channels 626, the manufacturer could design the apertures 614 to have a smaller cross section and / or a cross section that corresponds to the cross section of the channel and, thus, require less energy to obtain a greater suction.

[0094] Alternatively, if it was known that the apertures 614 on the belt 608 could become misaligned, also referred to as mistrack, during processing, the apertures 614 would have to be designed to have a larger cross section so that at least some portion of the aperture may remain in fluid connectivity with the channel 626 when the belt was misaligned.Having to design a larger aperture 614 may result in higher energy to obtain and / or maintain the desired suction on the carbon nanotube tape. The vacuum source 602 would be required to pull more air through the aperture 614 to maintain the desired suction over the carbon nanotube tape. Thus, reducing the mistrack of belt 608 allows a smaller CD dimension of channels 626 for a given CD width of apertures 614 and a smaller CD dimension of apertures 614 in the belt 608, which may result in increased strength of the belt 608. It is important that the belt 608 maintain its orientation in the CD such that the one or more apertures 614 remain substantially aligned with the one or more channels 626.

[0095] The one or more apertures 614 may be placed in any number of configurations on the belt 608. The one or more apertures 614 may be sized to generate the desired suction on the carbon nanotube tape given the configuration of the channels 626 and the capability of the vacuum source 602 to draw in air. Each aperture 614 may be shaped to maximize the ability to control the carbon nanotube tape. For example, in one embodiment, as shown in FIG. 6E, the apertures 614 may be circular in shape. In an alternate embodiment, not shown, the apertures may be elongated ovals, to maximize the cross section area of apertures 614 in fluid communication with the carbon nanotube tape for a given CD width of channels 626. Further to the above, placement of the one or more apertures 614 should be designed in view of the placement of the channels 626 on the deck surface 606 and / or size of the carbon nanotube tape to be acted on. The apertures 614 should be placed on the belt 608 such that when the belt 608 overlays the deck surface 606 the one or more apertures 614 are in fluid contact withthe channels 626. Fluid contact means that the vacuum source may pull air through the aperture 614 and the adjacent channel 626 and into the deck 604.

[0096] A belt 608, as shown in FIG. 6E, may be configured such that it forms a continuous loop. To form the continuous loop, the belt 608 may comprise a seam 628. The seam 628 may be the location at which the two ends of the belt are joined. The seam 628 should be strong enough to withstand the stresses exerted on the belt 608 during the manufacturing process. Due to the configuration of the belt as a continuous loop, the second surface 612 of the belt may maintain engagement with the transmission mechanism 615 and the guide mechanism 646 during the manufacture of the carbon nanotube tape. Thus, the second surface 612 of the belt 608 may be connected to one or more rows of teeth to interact with the transmission mechanism 615 and the guide mechanism 646.

[0097] As previously disclosed, the belt 608 may be driven in the direction MD by a tracking mechanism 615, as shown in FIG. 6F. The belt 608 may comprise a first row of teeth and a second row of teeth that may be used by the transmission mechanism 615 to move the belt. The first row of teeth may engage a first gear member 616 and the second row of teeth may engage a second gear member 618. The surface profile of the first gear member 616 may match that of the first row of teeth and the surface profile of the second gear member 618 may match that of the second row of teeth. Thus, as the axle member 620 rotates, the first gear member 616 and the second gear member 618 rotate about the longitudinal axle axis 624 of the axle member 620. As the first gear member 616 and the second gear member 618 rotate, the first gear member 616 and the second gear member 618 mesh with a portion of the first row of teeth and the secondrow of teeth, respectively, to cause movement of the belt 608 across the deck surface 606 in the direction MD. By “mesh” is meant that the gear teeth of the gear member interlink with the row of teeth such that the gear teeth may exert a force on the row of teeth to move the belt.

[0098] As illustrated in FIG. 6F, the transmission mechanism 615 may comprise an axle member 620 having a first end portion 648 and a second end portion 650, opposite the first end portion 648, and an axle length 652 extending in the cross direction CD. The axle member 620 may be adapted to rotate about the longitudinal axle axis 624. The axle member 620 may be connected to a roller 644 disposed between the first end portion 648 and the second end portion 650 of the axle member 620. The roller 644 engages the axle member such that when the axle member rotates, the roller also rotates about the longitudinal axle axis 624. The roller 644 has an outer surface 654 having a circumference and may be configured to support the belt 608 as it moves. Further, the roller 644 includes a first roller end 656 and a second roller end 658 opposite the first roller end. The first roller end 656 may be adjacent to the first gear member 616. Similarly, the second roller end 658 may be adjacent to the second gear member 618. More specifically, the second gear member 618 may be removably attached to the second roller end 658. For example, the second gear member 618 may be screwed to the second roller end 658. Further, at least one of the roller 644 and the second gear member 618 may be fixedly attached to the axle member 620 such that as the axle member rotates, the roller 644 and the second gear member 618 may also rotate about the longitudinal axle axis 624.

[0099] As illustrated in FIG. 6F, the first gear member 616 can be adjacent to the first roller end 656 and the first end portion of the axle member 648. The first gear member 616 may slidably engage the axle member 620 such that the first gear member 616 may move along the axle length 652. Stated another way, the first gear member 616 may be movably connected with the first end portion 648 of the axle member 620 such that the second gear member is movable in the cross direction CD along the length 652 of the axle member 620. Thus, the first gear member 616 can slide along the surface of the axle member 620 in the cross direction CD. Limits may be put on the cross directional movement of the first gear member 616 such that a stopper, not shown, can be placed between the first gear member 616 and the first end portion 648 of the axle member 620. Further, the interaction of splines located on each of the first gear member 616 and the axle member 620 may allow the first gear member 616 to rotate about the longitudinal axis 624 of the axle member 620 as the axle member 620 rotates. It is believed that the configuration of the first gear member 616 may also be applied to the second gear member 618 such that second gear member 618 may be slidably engaged with the axle member. By having at least one of the first gear member 616 and the second gear member 618 slidably engaged with the axle member 624, the belt 608 may move in the cross direction CD. This cross directional movement may alleviate the cross directional forces that act on the belt 608 resulting in improved belt life and increased productivity.

[0100] As previously stated, opposite the transmission mechanism 615 and adjacent to the second deck end 664 may be the guide mechanism 646, as shown in FIG. 6A. The guide mechanism 646 may comprise a shaft 666 that may rotate about a longitudinal shaft axis 668, as illustrated in detail in FIG. 6G. The shaft 666 may be configured tointeract with the second surface 612 of the belt 608 and to guide and / or drive the belt 608 during operation of the vacuum conveyor system 36. The shaft 666 includes an external surface 670 having a circumference and a shaft length 676 extending between a first shaft end 672 and a second shaft end 674, opposite the first shaft end 672. For example, in one embodiment, the shaft 666 may have an external surface 670 having a uniform circumference extending along the shaft length 676 from the first shaft end 672 to the second shaft end 674, not shown. In another alternative embodiment, the shaft 666 may have an external surface 670 having a circumference that varies along the shaft length 676.

[0101] It is believed that the belt 608 can be advanced by either or both axle member 622 and the shaft 666. More specifically, a drive mechanism 622 may be operatively connected to at least one of the axle member 620 and the shaft 666. For example, in one embodiment, the drive mechanism 622 may be operatively connected to the axle member 620 such that the axle member 622 may be forced to rotate about the longitudinal axis 624, which in turn advanced the belt 608. In an alternative embodiment, the drive mechanism 622 may be operatively connected to the shaft 666 such that the shaft 666 may be driven to rotate around the longitudinal shaft axis 668, which in turn advances the belt 608.

[0102] The carbon nanotube sock may be drawn down to form the carbon nanotube tape and transferred away from the air knife assembly according to the following steps. A conveyor assembly 36 such as that shown in FIGS. 5 and 6A, is positioned below the air knife assembly 35. The vacuum conveyor assembly 36 may comprise a deck 604 and a belt 608. The deck may include a channel 626. The belt 608 may include a firstsurface 610, a second surface 612 opposite the first surface, and a row of apertures 614. The second surface 612 of the belt 608 may be in a facing relationship with the deck 604. Air may be drawn through the channel 626 with a vacuum source 602. The air being drawn through the row of apertures 614 and the channel 626 may create suction on the carbon nanotube sock 50 within the gas guides of the air knife assembly 35 to draw the carbon nanotube sock 50 onto the first surface 610 of the belt 608 to form the carbon nanotube tape 60 (see FIG. 7). The carbon nanotube tape 60 is held against the first surface 610 of the belt 608. The belt 608 may be advanced in the direction MD. To aid in advancing the belt 608 and / or maintaining alignment of the belt 608, the angled teeth of a first gear member 616 may mesh with a first row of angled teeth connected with the second surface 612 of the belt 608, and the angled teeth of a second gear member 618 may mesh with a second row of angled teeth connected with the second surface 612 of the belt 608. At least one of the first gear member 616 and the second gear member 618 may be connected with an axle member 620. The axle member may rotate about a longitudinal axle axis, and the first gear member and the second gear member may rotate with the axle member. The row of apertures 614 may align with the channel 626 by moving the belt 608 in a cross direction CD. Further, the belt 608 may be guided in the direction MD by supporting the second surface 612 of the belt 608 with a shaft 666.

[0103] According to one embodiment, the tape forming system 23 may further include a collection assembly. Referring to FIGS. 3 and 7, the collection assembly 38 includes a rolling device 62 spaced from the air knife assembly 35 and positioned at the end of vacuum conveyor assembly 36. The rolling device 62 collects the carbon nanotube tape 60 from vacuum conveyor assembly 36 into at least one spool 63. The rolling device62 includes a pair of towers 64 for supporting the spool 63. The spool 63 is removable from the towers 64.

[0104] Referring now to FIG. 8, in an alternative embodiment, the tape forming mechanism 23 may be coupled to a gas lock 72. By "gas lock" is meant any enclosure or chamber which is provided with two opening / closing mechanisms, such as a physical barrier for e.g., a flap, or a gas barrier, which are substantially gas tight in the closed state. Accordingly, the gas lock 72 is provided with a first or inside opening / closing mechanism 73, which is located between the tape forming mechanism 23 and the gas lock 72. The gas lock 72 is further provided with a second or outside opening / closing mechanism 74, such as physical barrier, for e.g., a flap or gas barrier which serves as a separation between the gas lock 72 and the environment 75 outside the tape forming mechanism 23. Although only one gas lock is shown, two or more gas locks may also be used. The gas lock is operable in forming an effective barrier which prevents the gas (i.e., hydrogen) from the tape forming mechanism 23 from escaping during the introduction of the carbon nanotube tape 60 into the chamber and its withdrawal. Thus, the gas lock allows the passage of a continuous conveyor 76 carrying carbon nanotube tape 60 into and out of a chamber while preventing the exit of hydrogen gas from the chamber. The gas lock 72 further includes an outlet 77 for removing a gaseous vapor / air mixture within the chamber originating from carbon nanotube tape 60 being not completely hydrogen-free and / or from the gas exchange between the tape forming mechanism 23 and the gas lock 72 when the first opening / closing mechanism located between the gas lock and the tape forming mechanism is open. The degassed carbon nanotube tape 76 exiting the gas lock may then be transferred by theconveyor to a collection system similar to that describe above or to other equipment or systems for post processing.

[0105] According to another embodiment, there is provided a system for continuously producing carbon nanotube tape that generally includes: (i) the horizontally oriented chemical vapor deposition system as described herein; and (ii) a tape forming system as described herein coupled to the horizontally oriented chemical vapor deposition system.

[0106] Thus, in one embodiment, the chemical vapor deposition includes (a) a reactor having a proximal end, a distal upper end and an inner cavity configured for holding a dense gas; (b) an injector positioned at the proximal end of the reactor configured for propelling a fluid mixture into the reactor, the fluid mixture comprising a metal catalyst precursor from which a metal catalyst particle can be generated for subsequent growth of elongated non-entangled carbon nanotubes thereon, a conditioner compound for controlling size distribution of metal catalyst particles generated from the metal catalyst precursor, and a carbon source for depositing carbon atoms onto the metal catalyst particle in order to grow the elongated non-entangled carbon nanotubes, and (c) a furnace surrounding the reactor configured to heat the reactor to a temperature sufficient to generate metal catalyst particles from the metal catalyst precursor and carbon atoms from the carbon source. The chemical vapor deposition system is thus operable to produce a carbon nanotube sock from the elongated non-entangled carbon nanotubes.

[0107] The tape forming system includes (a) a housing having an inlet for engaging an exit end of the reactor of the chemical vapor deposition system in a substantially airtight manner, (b) an air knife assembly including opposing guides operable to control the width of the carbon nanotube sock, (c) a vacuum conveyor system operable to draw the carbonnanotube sock from the air knife assembly down onto a conveying surface to form the carbon nanotube tape and transfer the carbon nanotube distally from the air knife assembly. In some embodiments, the tape forming system further includes a collection system for collecting the carbon nanotube tape from the conveying surface of the vacuum conveyor assembly.

[0108] In an alternative embodiment, the system further includes a gas lock coupled to an outlet of the vacuum conveyor system operable to degas the carbon nanotube tape and transfer the carbon nanotube tape to the ambient environment for collection onto a spool as described above or to equipment for post processing.

[0109] In still another embodiment, there is provided a method for continuously producing carbon nanotube tape generally including the steps of: (i) producing a carbon nanotube material in a horizontally orientated chemical vapor deposition system as described herein; and (ii) introducing the carbon nanotube material into a tape forming system as described herein coupled to the chemical vapor deposition system, the tape forming system operable to produce the carbon nanotube tape.

[0110] Although making and using various embodiments of the present invention have been described in detail above, it should be appreciated that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention, and do not delimit the scope of the invention.

Claims

CLAIMSWhat is claimed is:

1. A system for continuously producing carbon nanotube tape comprising: (a) a chemical vapor deposition system operable to form a carbon nanotube material; and (b) a tape forming system comprising (i) a housing having an inlet coupled to an outlet of the chemical vapor deposition system, (ii) an air knife assembly positioned adjacent to the inlet and operable for receiving the carbon nanotube material, and (iii) a vacuum conveyor system operable to draw the carbon nanotube material from the air knife assembly and form the carbon nanotube tape.

2. The system of claim 1, wherein the air knife assembly comprises opposing gas guides operable to control the width of the carbon nanotube material.

3. The system of claim 2, wherein the carbon nanotube material is a carbon nanotube sock.

4. The system of claim 1, wherein the vacuum conveyor system comprises a vacuum source fluidly connected to a continuous conveying surface.

5. The system of claim 1, further comprising a collection system for collecting the carbon nanotube tape.

6. The system of claim 5, wherein the collection system is positioned within the housing of tape forming system.

7. The system of claim 5, wherein the collection system is positioned outside of the housing of the tape forming system.

8. The system of claim 7, further comprising an air lock positioned between the tape forming system and the collection system.

9. The system of claim 1, wherein the chemical vapor deposition system is a floating catalyst chemical vapor deposition system.

10. A method for continuously producing carbon nanotube tape comprising (a) producing extended length carbon nanotubes in a chemical vapor deposition system, the chemical vapor deposition system comprising a synthesis chamber having an entrance end into which reaction gases are supplied, a hot zone where the extended length carbon nanotubes are synthesized from the reaction gases and an exit end where the extended length carbon nanotubes exit, and (b) introducing the non-entangled carbon nanotubes into a tape forming system wherein the tape forming system comprises a housing having an inlet engaging the exit of the synthesis chamber, an air knife assembly adjacent to the inlet of the tape forming system for providing a layer of uninterrupted gas to prevent the nonentangled elongated carbon nanotubes from adhering to the inlet and the air knife assembly and a vacuum conveyor system positioned below the air knife assembly for providing a vacuum to degas and draw the non-entangled elongated carbon nanotubes down and form the carbon nanotube tape.

11. The method of claim 10, wherein the non-entangled elongated carbon nanotubes exiting the synthesis chamber entangle, bundle and otherwise coalesce into an extended network of interconnected and branching bundles to form a hollow carbon nanotube sock.

12. The method of claim 10, wherein the air knife assembly guides control the width of the carbon nanotube sock.

13. The method of claim 12, wherein the vacuum conveyor system draws the carbon nanotube sock onto a conveying surface to form the carbon nanotube tape.

14. The method of claim 13, wherein the vacuum conveyor system transfers the carbon nanotube tape on the conveying surface distally from the air knife assembly.

15. The method of claim 14, wherein the carbon nanotube tape is transferred to a collection system and rolled onto a spool.

16. The method of claim 14, wherein the carbon nanotube tape is transferred to a gas lock and further degassed to form a degassed carbon nanotube tape.

17. The method of claim 16, wherein the degassed carbon nanotube tape is transferred to a collection system and rolled onto a spool.

18. A carbon nanotube tape produced according to the method of claim 10.

19. The carbon nanotube tape of claim 18, wherein the carbon nanotube tape has a width of about 5 / 16 - 3 inches and a length of greater than 650 feet.

20. The carbon nanotube tape of claim 19, wherein the carbon nanotube tape has substantially straight edges.[Add claims regarding use of variable belt speed and vacuum draw to control density ] [Add description and claims related to CBC injector and furnace tube size to vary density from 1-100 gms]

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