WO2010036405A1

WO2010036405A1 - Nanostructure composite sheets and methods of use

Info

Publication number: WO2010036405A1
Application number: PCT/US2009/043209
Authority: WO
Inventors: Jennifer Mann; David S. Lashmore; Brian White; Peter L. Antoinette
Original assignee: Nanocomp Technologies, Inc.
Priority date: 2008-05-07
Filing date: 2009-05-07
Publication date: 2010-04-01
Also published as: EP2279512A1; EP2279512B1; CA2723486A1; JP2011524604A; US8847074B2; ES2753901T3; US20100000754A1; AU2009244149A1; JP6182176B2; JP2011524323A; CA2723599A1; JP5674642B2; US20120177926A1; EP2279512A4; JP2016074594A; JP5864253B2; EP2274464A1; WO2009137722A1; US20150107890A1; AU2009297067A1

Abstract

A nanostructured sheet that can include a substantially planar body, a plurality of nanotubes defining a matrix within the body, and a protonation agent that can be dispersed throughout the matrix of nanotubes for enhancing proximity of adjacent nanotubes to one another. A method of making such a nanostructured sheet is also disclosed.

Description

NANOSTRUCTURE COMPOSITE SHEETS AND METHODS OF USE

TECHNICAL FIELD

[0001] The present invention relates to the formation of composite material, and more particularly, to composite material made from nanostructure composite sheets designed to promote shielding, absorption, and increased conductivity.

BACKGROUND ART

[0002] Carbon nanotubes are known to have extraordinary tensile strength, including high strain to failure and relatively high tensile modulus. Carbon nanotubes may also be highly resistant to fatigue, radiation damage, and heat. To this end, the addition of carbon nanotubes to composite materials can increase tensile strength and stiffness of the composite materials.

[0003] Within the last fifteen (15) years, as the properties of carbon nanotubes have been better understood, interests in carbon nanotubes have greatly increased within and outside of the research community. One key to making use of these properties is the synthesis of nanotubes in sufficient quantities for them to be broadly deployed. For example, large quantities of carbon nanotubes may be needed if they are to be used as high strength components of composites in macroscale structures (i.e., structures having dimensions greater than 1 cm.)

[0004] One common route to nanotube synthesis can be through the use of gas phase pyrolysis, such as that employed in connection with chemical vapor deposition. In this process, a nanotube may be formed from the surface of a catalytic nanoparticle. Specifically, the catalytic nanoparticle may be exposed to a gas mixture containing carbon compounds serving as feedstock for the generation of a nanotube from the surface of the nanoparticle. [0005] Recently, one promising route to high-volume nanotube production has been to employ a chemical vapor deposition system that grows nanotubes from catalyst particles that "float" in the reaction gas. Such a system typically runs a mixture of reaction gases through a heated chamber within which the nanotubes may be generated from nanoparticles that have precipitated from the reaction gas. Numerous other variations may be possible, including ones where the catalyst particles may be pre-supplied.

[0006] In cases where large volumes of carbon nanotubes may be generated, however, the nanotubes may attach to the walls of a reaction chamber, resulting in the blockage of nanomaterials from exiting the chamber. Furthermore, these blockages may induce a pressure buildup in the reaction chamber, which can result in the modification of the overall reaction kinetics. A modification of the kinetics can lead to a reduction in the uniformity of the material produced.

[0007] An additional concern with nanomaterials may be that they need to be handled and processed without generating large quantities of airborne particulates, since the hazards associated with nanoscale materials are not yet well understood.

[0008] The processing of nanotubes or nanoscale materials for macroscale applications has steadily increased in recent years. The use of nanoscale materials in textile fibers and related materials has also been increasing. In the textile art, fibers that are of fixed length and that have been processed in a large mass may be referred to as staple fibers. Technology for handling staple fibers, such as flax, wool, and cotton has long been established. To make use of staple fibers in fabrics or other structural elements, the staple fibers may first be formed into bulk structures such as yarns, tows, or sheets, which then can be processed into the appropriate materials.

[0009] Accordingly, it would be desirable to provide a material that can take advantage of the characteristics and properties of carbon nanotubes, so that a sheet made of carbon nanotubes can be processed for end use applications, including (i) structural systems, such as fabrics, armor, composite reinforcements, antennas, electrical or thermal conductors, and electrodes, (ii) mechanical structural elements, such as plates and I- beams, and (iii) cabling or ropes.

SUMMARY OF THE INVENTION

[00010] The present invention provides, in accordance with one embodiment, a nanostructured sheet. The sheet includes a substantially planar body, a plurality of nanotubes defining a matrix within the body, and a protonation agent dispersed throughout the matrix of nanotubes for enhancing proximity of adjacent nanotubes to one another.

[00011] The present invention provides, in accordance with another embodiment, a method of forming a nanostructured sheet. The method includes generating a substantially planar body defined by a matrix of nanotubes, applying a protonation agent throughout the matrix of nanotubes, and allowing the presence of the protonation agent to bring adjacent nanotubes in closer proximity with one another.

BRIEF DESCRIPTION OF DRAWINGS

[00012] Fig. 1 illustrates electrical properties of carbon nanotubes made in accordance with one embodiment of the present invention.

[00013] Fig. 2 illustrates resistivity versus temperature characteristics of carbon nanotubes made in accordance with one embodiment of the present invention.

[00014] Fig. 3 illustrates resistivity versus temperature characteristics of carbon nanotubes in (and out of) the presence of a magnetic field.

[00015] Fig. 4 illustrates an embodiment of the present invention. [00016] Fig. 5 illustrates an alternative embodiment of the present invention.

[00017] Fig. 6 illustrates a Chemical Vapor Deposition system for fabricating nanotubes, in accordance with one embodiment of the present invention.

[00018] Fig. 7 illustrates a system of the present invention for formation and harvesting of nanofibrous materials.

[00019] Fig. 8 illustrates a system of the present invention for formation and harvesting of nanofibrous materials.

[00020] Fig. 9 illustrates a system of the present invention for treating nanostructured sheets post formation.

[00021] Fig. 10 illustrates insertion loss from nanostructured sheets made in accordance with an embodiment of the present invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS

[00022] The present invention provides, in an embodiment, a composite material made from nanostructured sheets designed to promote, for instance, electromagnetic interference shielding, absorption of signals or electromagnetic waves, and increased conductivity. In an embodiment, the sheet material may include a substantially planar body in the form of a composite sheet. A plurality of nanotubes may define a matrix within the planar body. As there may exist openings between adjacent nanotubes in the matrix, a protonation agent may be applied. A plurality of composite sheets may be then layered on one another.

[00023] Presently, there exist multiple processes and variations thereof for growing nanotubes, and forming yarns, sheets or cable structures made from these nanotubes. These include: (1) Chemical Vapor Deposition (CVD), 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.

[00024] The present invention, in one embodiment, employs a CVD process or similar gas phase pyrolysis procedures known in the industry to generate the appropriate nanostructures, including carbon nanotubes. Growth temperatures for a CVD process can be comparatively low ranging, for instance, from about 400° C to about 1350° C. Carbon nanotubes, both single wall (SWNT) or multiwall (MWNT), may be grown, in an embodiment of the present invention, by exposing nanoscaled catalyst particles in the presence of reagent carbon-containing gases (i.e., gaseous carbon source). In particular, the nanoscaled catalyst particles may be introduced into the reagent carbon-containing gases, either by 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.

[00025] The strength of the individual carbon nanotubes generated in connection with the present invention may be about 30 GPa or more. Strength, as should be noted, is sensitive to defects. However, the elastic modulus of the carbon nanotubes fabricated in the present invention may not be sensitive to defects and can vary from about 1 to about 1.2 TPa. Moreover, the strain to failure of these nanotubes, which generally can be a structure sensitive parameter, may range from a about 10% to a maximum of about 25% in the present invention.

[00026] Furthermore, the nanotubes of the present invention can be provided with relatively small diameter. In an embodiment of the present invention, the nanotubes fabricated in the present invention can be provided with a diameter in a range of from less than 1 nm to about 10 nm. [00027] The nanotubes of the present invention can also be used as a conducting member to carry relatively high current similar to a Litz wire or cable. However, unlike a Litz wire or cable soldered to a connector portion, the nanotube conducting member of the present invention can exhibit relatively lower impedance in comparison. In particular, it has been observed in the present invention that the shorter the current pulses, the better the nanotube-based wire cable or ribbon would perform when compared with a copper ribbon or Litz wire. One reason for the observed better performance may be that the effective frequency content of the pulse, which can be calculated from the Fourier Transform of the waveform for current pulses that are square and short, e.g., about 100 ms to less than about 1 ms, can be very high. Specifically, individual carbon nanotubes of the present invention can serve as conducting pathways, and due to their small size, when bulk structures are made from these nanotubes, the bulk structures can contain extraordinarily large number of conducting elements, for instance, on the order of 10¹⁴/cm² or greater.

[00028] Carbon nanotubes of the present invention can also demonstrate ballistic conduction as a fundamental means of conductivity. Thus, materials made from nanotubes of the present invention can represent a significant advance over copper and other metallic conducting members under AC current conditions. However, joining this type of conducting member to an external circuit requires that essentially each nanotube be electrically or thermally contacted to avoid contact resistance at the junction.

[00029] Carbon nanotubes of the present invention can exhibit certain characteristics which are shown in Figs. 1-3. Fig. 1 illustrates the electrical properties of carbon nanotubes made in accordance with one embodiment of the present invention. Fig. 2 illustrates the resistivity of these carbon nanotubes in relation to temperature. Fig. 3 illustrates characteristics of carbon nanotube resistivity versus temperature in (and out of) the presence of a magnetic field. [00030] It should be noted that although reference is made throughout the application to nanotubes synthesized from carbon, other compound(s), such as boron, M0S₂, or a combination thereof may be used in the synthesis of nanotubes in connection with the present invention. For instance, it should be understood that boron nanotubes may also be grown, but with different chemical precursors. In addition, it should be noted that boron may also be used to reduce resistivity in individual carbon nanotubes. Furthermore, other methods, such as plasma CVD or the like can also be used to fabricate the nanotubes of the present invention.

[00031] The present invention provides, in an embodiment, a composite material made from nanostructured composite sheets designed to increase conductivity of the carbon nanotubes within the sheet. As shown in Fig. 4, the composite material 10 may include a substantially planar body in the form of a composite sheet 12. A plurality of nanotubes 14 may define the planar body. As there may be openings between adjacent carbon nanotubes, in order to enable efficient conduction between a nanoscale environment and a traditional electrical and/or thermal circuit system, the proximity of adjacent nanotubes within the planar body may be brought closer to one another. To enhance the proximity between adjacent nanotubes, a protonation agent may be applied. In an embodiment, the composite material may be a single layer as shown in Fig. 4, or may be a plurality of layers on top of one another as shown in Fig. 5.

System for Fabricating Sheets

[00032] With reference now to Fig. 6, there is illustrated a system 30, similar to that disclosed in U.S. Patent Application Serial No. 11/488,387 (incorporated herein by reference), for use in the fabrication of nanotubes. System 30, in an embodiment, may be coupled to a synthesis chamber 31. The synthesis chamber 31, in general, includes an entrance end 311, into which reaction gases (i.e., gaseous carbon source) may be supplied, a hot zone 312, where synthesis of extended length nanotubes 313 may occur, and an exit end 314 from which the products of the reaction, namely the nanotubes and exhaust gases, may exit and be collected. The synthesis chamber 31, in an embodiment, may include a quartz tube 315 extending through a furnace 316. The nanotubes generated by system 30, on the other hand, may be individual single- walled nanotubes, bundles of such nanotubes, and/or intertwined single- walled nanotubes (e.g., ropes of nanotubes).

[00033] System 30, in one embodiment of the present invention, may also include a housing 32 designed to be substantially airtight, so as to minimize the release of potentially hazardous airborne particulates from within the synthesis chamber 31 into the environment. The housing 32 may also act to prevent oxygen from entering into the system 30 and reaching the synthesis chamber 31. In particular, the presence of oxygen within the synthesis chamber 31 can affect the integrity and compromise the production of the nanotubes 313.

[00034] System 30 may also include a moving belt 320, positioned within housing 32, designed for collecting synthesized nanotubes 313 made from a CVD process within synthesis chamber 31 of system 30. In particular, belt 320 may be used to permit nanotubes collected thereon to subsequently form a substantially continuous extensible structure 321, for instance, a non-woven or woven sheet. Such a sheet may be generated from compacted, substantially non-aligned, and intermingled nanotubes 313, bundles of nanotubes, or intertwined nanotubes (e.g., ropes of nanotubes), with sufficient structural integrity to be handled as a sheet.

[00035] To collect the fabricated nanotubes 313, belt 320 may be positioned adjacent the exit end 314 of the synthesis chamber 31 to permit the nanotubes to be deposited on to belt 320. In one embodiment, belt 320 may be positioned substantially parallel to the flow of gas from the exit end 314, as illustrated in Fig. 6. Alternatively, belt 320 may be positioned substantially perpendicular to the flow of gas from the exit end 314 and may be porous in nature to allow the flow of gas carrying the nanomaterials to pass therethrough. Belt 320 may be designed as a continuous loop, similar to a conventional conveyor belt. To that end, belt 320, in an embodiment, may be looped about opposing rotating elements 322 (e.g., rollers) and may be driven by a mechanical device, such as an electric motor. Alternatively, belt 320 may be a rigid cylinder. In one embodiment, the motor may be controlled through the use of a control system, such as a computer or microprocessor, so that tension and velocity can be optimized. The collected nanotubes may then be removed manually or by any other means off the belt 320 for subsequent use.

[00036] Looking at Fig. 7, system 40 may include a pressure applicator, such as roller 45, situated adjacent belt 44, that may be positioned substantially perpendicular to the flow of gas, so as to apply a compacting force (i.e., pressure) onto the collected nanomaterials. In particular, as the nanomaterials get transported toward roller 45, the nanomaterials on belt 44 may be forced to move under and against roller 45, such that a pressure may be applied to the intermingled nanomaterials while the nanomaterials get compacted between belt 44 and roller 45 into a coherent substantially-bonded sheet 46. To enhance the pressure against the nanomaterials on belt 44, a plate 444 may be positioned behind belt 44 to provide a hard surface against which pressure from roller 45 can be applied. It should be noted that the use of roller 45 may not be necessary should the collected nanomaterials be ample in amount and sufficiently intermingled, such that an adequate number of contact sites exists to provide the necessary bonding strength to generate the sheet 46.

[00037] To disengage the sheet 46 of intermingled nanomaterials from belt 44 for subsequent removal from housing 42, a scalpel or blade 47 may be provided downstream of the roller 45 with its edge against surface 445 of belt 44. In this manner, as sheet 46 moves downstream past roller 45, blade 47 may act to lift the sheet 46 from surface 445 of belt 44. In an alternate embodiment, a blade does not have to be in use to remove the sheet 46. Rather, removal of the sheet 46 may be manually by hand or by other known methods in the art.

[00038] Additionally, a spool or roller 48 may be provided downstream of blade 47, so that the disengaged sheet 46 may subsequently be directed thereonto and wound about roller 48 for harvesting. As the sheet 46 is wound about roller 48, a plurality of layers may be formed. Of course, other mechanisms may be used, so long as the sheet 46 can be collected for removal from the housing 42 thereafter. Roller 48, like belt 44, may be driven, in an embodiment, by a mechanical drive, such as an electric motor 481, so that its axis of rotation may be substantially transverse to the direction of movement of the sheet 46.

[00039] In order to minimize bonding of the sheet 46 to itself as it is being wound about roller 48, a separation material 49 (see Fig. 8) may be applied onto one side of the sheet 46 prior to the sheet 46 being wound about roller 48. The separation material 49 for use in connection with the present invention may be one of various commercially available metal sheets or polymers that can be supplied in a continuous roll 491. To that end, the separation material 49 may be pulled along with the sheet 46 onto roller 48 as sheet 46 is being wound about roller 48. It should be noted that the polymer comprising the separation material 49 may be provided in a sheet, liquid, or any other form, so long as it can be applied to one side of sheet 46. Moreover, since the intermingled nanotubes within the sheet 46 may contain catalytic nanoparticles of a ferromagnetic material, such as Fe, Co, Ni, etc., the separation material 49, in one embodiment, may be a non-magnetic material, e.g., conducting or otherwise, so as to prevent the sheet 46 from sticking strongly to the separation material 49. In an alternate embodiment, a separation material may not be necessary. [00040] After the sheet 46 is generated, it may be left as a sheet 46 or it may be cut into smaller segments, such as strips. In an embodiment, a laser may be used to cut the sheet 46 into strips. The laser beam may, in an embodiment, be situated adjacent the housing such that the laser may be directed at the sheet 46 as it exits the housing. A computer or program may be employed to control the operation of the laser beam and also the cutting of the strip. In an alternative embodiment, any mechanical means or other means known in the art may be used to cut the sheet 46 into strips.

Treatment Process

[00041] Once a sheet 46 is generated, the sheet 46 may undergo treatment to enhance conductivity and productivity of the nanotubes in the sheet. If strips are generated, the strips may also undergo a treatment processes to enhance conductivity and productivity of the nanotubes in the strip. Treatment of a sheet 46 after formation may, in an embodiment, include subjecting the sheet 46 to a protonation agent. One feature of the protonation agent may be to bring the carbon nanotubes in closer proximity with one another. By bringing the carbon nanotubes closer together, the protonation agent may act to reduce surface tension, reduce resistivity, and increase conductivity of the sheet. Examples of a protonation agent may include an acid such as hydronium ion, hydrochloric acid, hydrobromic acid, hydrofluoric acid, hydroiodic acid, carbonic acid, sulfuric acid, nitric acid, fluorosulfuric acid, chlorosulfonic acid, methane sulfonic acid, trifluoromethane sulfonic acid, oleum, an agent thereof, or a combination thereof, or other materials capable of being electrically and/or thermally conductive.

[00042] The protonation agent may be applied, in an embodiment, through the use of an apparatus 60, such as that shown in Fig. 9. The apparatus may, in an embodiment, include a plurality of rollers for guiding the sheet through the application process. As shown, a first roller 64 and second roller 65 may be situated adjacent one another with the second roller 65 being positioned downstream from roller 64. A tub 61 having a first end 62 and a second end 63 and containing the protonation agent may be situated underneath the first roller 64 and the second roller 65. The first roller may act to force the sheet through the tub 61 and onto the second roller 65. The second roller 65 may pull the sheet from the first roller 64 and may wring excess protonation agent fluid from the sheet. A third roller 66 may be positioned above the first end 62 of the tub near the first roller 64, while the fourth roller 67 may be positioned above the second end 63 of the tub near the second roller 65. Rollers 64, 65, 66, and 67 may be situated in series to allow the sheet 68 to move smoothly through the rollers. Of course, although shown in Fig. 9 as having four rollers, an apparatus for post treatment of sheets 68 may include a fewer number or a greater number of rollers. To the extent necessary, a hood may be situated in such a manner as to prevent fumes from the protonation agent to escape. In one embodiment, the apparatus 60 may include a hood such as a polypropylene hood.

[00043] Treating the sheet 68 with a protonation agent may involve positioning a bobbin or roll of sheet 68 on the third roller 66. The sheet 68 may then move downstream, passing from the third roller 66, through the first roller 64, into the tub 61 containing the protonation agent, and onto the second roller 65 and across the fourth roller 67.

[00044] In certain circumstances after treatment, the resulting sheet 68 may be acidic or basic. To bring the pH of the resulting sheet 68 to approximately neutral, a rinsing solution may be applied to the sheet 68. The rinsing solution may, in an embodiment, be applied continuously with the protonation agent or it may be applied independently of the protonation agent.

[00045] In another embodiment, treatment of the sheet 68 may further include spraying the sheet 68 with a second solution as it exits the furnace and is collected on the belt 320. The solution may contain a mixture of compounds that cover the outer surface of the nanotubes in such a manner as to enhance alignment of the carbon nanotubes and allow the carbon nanotubes to come into closer proximity with one another.

[00046] In an embodiment, the mixture of the second solution may include a solvent, a polymer, a metal, or a combination thereof. The solvent used in connection with the solution of the present invention can be used to lubricate the sheet in order to gain better alignment and enhancement in the properties of the carbon nanotubes. Examples of a solvent that can be used in connection with the solution include toluene, kerosene, benzene, hexanes, any alcohol including but not limited to ethanol, methanol, butanol, isopropanol, as well as tetrahydrofuran, 1- methyl-2-pyrrolidinone, dimethyl formamide, methylene chloride, acetone or any other solvent as the present invention is not intended to be limited in this manner. In an embodiment, the solvent may be used as a carrier for a polymer, monomer, inorganic salt, or metal oxide to.

[00047] Examples of a polymer that can be used in connection with the solution include a small molecule or polymer matrix (thermoset or thermoplastic) including, but not limited to, polyurethane, polyethylene, poly(styrene butadiene), polychloroprene, poly(vinyl alcohol), poly(vinyl pyrrolidone), poly(acrylonitrile-co-butadiene-co-styrene), epoxy, polyureasilazane, bismaleimide, polyamide, polyimide, polycarbonate, or any monomer including styrene, divinyl benzene, methyl acrylate, and tert-butyl acrylate. In an embodiment, the polymer may include polymer particles, that are difficult to obtain in liquid form.

[00048] Examples of a metal that can be used in connection with the solution include a salt (any transition metal, alkali metal, or alkali earth metal salt or mixture thereof including, but not limited to, nickel hydroxide, cadmium hydroxide, nickel chloride, copper chloride, calcium zincate (CaZn2(OH)6)), or metal oxide (any transition metal, alkali metal, or alkali earth metal oxide or mixture thereof, including but not limited to: zinc oxide, iron oxide, silver oxide, copper oxide, manganese oxide, LiCoO2, LiNiO2, LiMxCo l-xO2, LiMn2O4). In an embodiment, the metal may include polymers or volatile solvents to create a carbon nanotube metal matrix composite. Examples of such polymers or volatile solvents include powdered forms of aluminum or its alloys, nickel, superalloys, copper, silver, tin, cobalt, iron, iron alloys, or any element that can be produced in a powdered form including complex binary and ternary alloys or even superconductors.

[00049] To disperse the solution, a spraying apparatus may be used. The spraying apparatus may be any apparatus that is commercially available. In an embodiment, at one end of the spraying apparatus, there may be a spray head, through which the solution may be sprayed onto the sheet 46. In an embodiment, the spray head may be flat, round, or any other shape so long as it can permit solution to exit therethrough. To the extent desired, the spray head may emit a solution in a continuous manner or in a preprogrammed manner.

[00050] Once the sheet 68 has been treated, the treated sheet 68 may be subject to a heat source for processing of the sheet. For example, the sheet may be subject to sintering, hot isostatic pressing, hot pressing, cold isostatic pressing so as to yield a composite sheet or the desired form of the final product.

[00051 ] Treatment of the composite sheet may, in another embodiment, further include infusing the composite sheet with a glassy carbon material so as to increase the structural integrity of the sheet and provide substantially low resistance coupling. Glassy carbon, in general, may be a form of carbon related to carbon nanotubes and can contain a significant amount of graphene like ribbons comprising a matrix of amorphous carbon. These ribbons include sp bonded ribbons that can be substantially similar to the sp² bonded nanotubes. As a result, they can have relatively good thermal and electrical conductivity. Examples of precursor materials from which glassy carbon can be made include furfuryl alcohol, RESOL resin (i.e., catalyzed alkyl-phenyl formaldehyde), PVA, or liquid resin or any material known to form glassy carbon when heat treated. Of course, other commercially available glassy carbon materials or precursor materials can be used.

Applications

[00052] The systems and methods of the present invention can provide bulk nanomaterials of high strength, lower or similar weight, in a composite sheet. By providing the nanomaterials in a composite sheet, the bulk nanomaterials can be easily handled and subsequently processed for end use applications, including (i) structural systems, such as fabrics, armor, composite reinforcements, antennas, electrical or thermal conductors, heaters, and electrodes, (ii) mechanical structural elements, such as plates and I-beams, and (iii) cabling or ropes. Other applications can include hydrogen storage, batteries, or capacitor components.

[00053] Moreover, the composite sheet may be incorporated into composite structures for additional end use applications, such as sporting goods products, helmets, antenna, morphing applications, aerospace, lightning protectionm flame proofing, etc. Composite sheets may further be nickel free, meaning they may be less toxic than standard products. Additionally, composite sheets may be repairable to eliminate the need to replace the composite sheets entirely or in part. In one embodiment, a composite material may be formed by impregnating the composite sheet with a matrix precursor, such as Krayton, vinyl ester, PEEK, bispolyamide, BMI (bismaleimide), epoxies, or polyamides, and subsequently allowing the matrix to polymerize or thermally cure.

[00054] Composite sheets of carbon nanotubes made from the present invention can have a wide variety of applications. Examples of specific applications include electromagnetic interference shielding (EMI shielding) which may either absorb, reflect, or transmit electromagnetic waves. Shielding may be beneficial to prevent interference from surrounding equipment and may be found in stereo systems, telephones, mobile phones, televisions, medical devices, computers, and many other appliances. For these and similar applications, it may be important that the glassy carbon precursor be provided in a substantially thin layer, so that infiltration into the carbon nanotube sheet can be minimized to prevent degradation to the properties of the sheet.

[00055] EMI shielding may further be useful in minimizing insertion loss from sheets of carbon nanotubes. Insertion loss represents the difference in power reception prior to and after the use of a composite sheet. As illustrated in Fig. 10, there is an almost immediate drop in power reception followed by a stabilization.

[00056] Composite sheets of carbon nanotubes can have additional applications, such as utilizing the resulting assembly in the absorption of radar signal (EMI shielding) or to provide other desirable properties, such as lighting protection, heat sinks, or actuators. For such applications, it may not be critical if the bonding agent penetrates the carbon nanotube sheet. Accordingly, the glassy carbon material can be coated with less care than for that carried out in capacitor, battery or fuel cell applications. In one embodiment, the substrate for applications in this example can be a graphite epoxy, e-glass epoxy, or combinations with other types of matrices.

[00057] While the present invention has been described with reference to certain embodiments thereof, it should be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt to a particular situation, indication, material and composition of matter, process step or steps, without departing from the spirit and scope of the present invention. All such modifications are intended to be within the scope of the claims appended hereto.

Claims

What is claimed is:

1. A nanostructured sheet comprising: a substantially planar body; a plurality of nanotubes defining a matrix within the body; and a protonation agent dispersed throughout the matrix of nanotubes for enhancing proximity of adjacent nanotubes to one another.

2. A nanostructured sheet as set forth in claim 1, wherein the planar body can be of any geometric shape.

3. A nanostructured sheet as set forth in claim 1, wherein each nanotube includes a catalytic nanoparticle of a ferromagnetic material.

4. A nanostructured sheet as set forth in claim 3, wherein the ferromagnetic material includes one of Fe, Co, Ni, an alloy thereof, a combination thereof, or related materials.

5. A nanostructured sheet as set forth in claim 1, wherein the proximity of adjacent nanotubes acts to enhances conductivity of the sheet.

6. A nanostructured sheet as set forth in claim 1, wherein the protonation agent includes one of hydronium ion, hydrochloric acid, hydrobromic acid, hydrofluoric acid, hydroiodic acid, carbonic acid, sulfuric acid, nitric acid, fluorosulfuric acid, chlorosulfonic acid, methane sulfonic acid, trifluoromethane sulfonic acid, oleum, an agent thereof, a combination thereof, or related materials.

7. A nanostructured sheet as set forth in claim 1, designed for use in one of RF applications, EMI applications, EMP applications, high current transmission, or lightning strike resistance.

8. A nanostructured sheet as set forth in claim 1, designed for use in one of thermal conduction, electrical conduction, pulsed applications, thermo-electric applications, or power generation.

9. A nanostructured sheet as set forth in claim 1, designed for use in one of sensor applications, space antennae, tunable antennae, solar cell, radar, aerospace, flat panel displays, heat sinks or other similar applications.

10. A nanostructured sheet as set forth in claim 1, further including a solution of a mixture of compounds to enhance alignment.

11. A nanostructured sheet as set forth in claim 10, wherein the mixture of compounds also promotes conductivity by enhancing proximity of adjacent nanotubes to one another.

12. A nanostructured sheet as set forth in claim 10, wherein the mixture includes a solvent, a polymer, a metal, or a combination thereof.

13. A nanostructured sheet as set forth in claim 12, wherein the solvent includes toluene, kerosene, benzene, hexanes, any alcohol including but not limited to ethanol, methanol, butanol, isopropanol, as well as tetrahydrofuran, l-methyl-2-pyrrolidinone, dimethyl formamide, methylene chloride, acetone, or a combination thereof.

14. A nanostructured sheet as set forth in claim 12, wherein the polymer includes polyurethane, polyethylene, poly(styrene butadiene), polychloroprene, poly(vinyl alcohol), poly(vinyl pyrrolidone), poly(acrylonitrile-co-butadiene-co-styrene), epoxy, polyureasilazane, bismaleimide, polyamide, polyimide, polycarbonate, or any monomer including styrene, divinyl benzene, methyl acrylate, tert-butyl acrylate, or a combination thereof.

15. A nanostructured sheet as set forth in claim 12, wherein the metal includes salt (any transition metal, alkali metal, or alkali earth metal salt or mixture thereof including, but not limited to, nickel hydroxide, cadmium hydroxide, nickel chloride, copper chloride, calcium zincate (CaZn2(OH)6)), or metal oxide (any transition metal, alkali metal, or alkali earth metal oxide or mixture thereof, including but not limited to: zinc oxide, iron oxide, silver oxide, copper oxide, manganese oxide, LiCoO2, LiNiO2, LiMxCo l-xO2, LiMn2O4), or combination thereof.

16. A method for forming a nanostructured sheet comprising: generating a substantially planar body defined by a matrix of nanotubes; applying a protonation agent throughout the matrix of nanotubes; and allowing the presence of the protonation agent to bring adjacent nanotubes in closer proximity with one another.

17. A method of claim 16, wherein the protonation agent further enhances conductivity.

18. A method of claim 16, further including treating the sheet with a solution of a mixture of compounds to enhance alignment.

19. A method of claim 16, further including treating the sheet with a solution of a mixture of compounds to enhance proximity of adjacent nanotubes to one another.

20. A method of claim 19, wherein treating includes utilizing a solvent, a polymer, a metal, or a combination thereof.