Title:
CARBON NANOTUBE NETWORK-BASED NANO-COMPOSITES
Kind Code:
A1


Abstract:
Techniques for manufacturing carbon nanotube network-based nano-composites are provided. In some embodiments, a nano-composite manufacturing method includes forming a carbon nanotube (CNT) network, immersing the CNT network into an electroplating solution, applying electrical energy, and relaying the electrical energy flow to produce a nano-composite having uniform conductive bridges on the CNT network.



Inventors:
Kim, Yong Hyup (Seoul, KR)
Kang, Tae June (Seoul, KR)
Application Number:
12/192016
Publication Date:
02/18/2010
Filing Date:
08/14/2008
Assignee:
SNU R&DB FOUNDATION (Seoul, KR)
Primary Class:
Other Classes:
204/230.5, 204/242, 205/96, 204/229.8
International Classes:
C25D5/00; C25D17/00; C25D17/10
View Patent Images:



Primary Examiner:
RIPA, BRYAN D
Attorney, Agent or Firm:
KNOBBE MARTENS OLSON & BEAR LLP (2040 MAIN STREET, FOURTEENTH FLOOR, IRVINE, CA, 92614, US)
Claims:
What is claimed is:

1. An electroplating apparatus for manufacturing a nano-composite comprising: a power supply configured to generate electrical energy; a carbon nanotube network; an electroplating solution comprising any one selected from the group consisting of metal ion, conductive polymer, and a combination thereof; an anode coupled to the power supply and immersed in the electroplating solution; two or more electrodes attached to the carbon nanotube network at predetermined intervals and immersed in the electroplating solution; and a relay coupled to the power supply and the two or more electrodes and configured to switch over the electrical energy flow from a portion of the two or more electrodes to another portion of the two or more electrodes.

2. The apparatus of claim 1, wherein the anode is selected from the group consisting of Al, Cr, Co, Ni, Cu, Zn, Rh, Pd, Ag, Sn, W, Pt, Au, Ti, Mn, Cd and Pb.

3. The apparatus of claim 1 further comprising: one or more detectors positioned to measure the electrical value between the anode and the two or more electrodes.

4. The apparatus of claim 1 further comprising: a controller coupled to the power supply and/or the relay.

5. An electroplating apparatus for manufacturing a nano-composite comprising: a power supply configured to generate electrical energy; an electroplating solution comprising any one selected from the group consisting of metal ions, conductive polymers, and a combination thereof; an anode coupled to the power supply and immersed in the electroplating solution; a carbon nanotube network coupled to the power supply through two or more parts thereof at predetermined intervals and immersed in the electroplating solution; and a relay coupled to the power supply and the two or more parts of the carbon nanotube network and configured to switch over the electrical energy flow from a portion of the two or more parts of the carbon nanotube network to another portion of the two or more parts of the carbon nanotube network.

6. The apparatus of claim 5, wherein the anode is selected from the group consisting of Al, Cr, Co, Ni, Cu, Zn, Rh, Pd, Ag, Sn, W, Pt, Au, Ti, Mn, Cd and Pb.

7. The apparatus of claim 5 further comprising: one or more detectors positioned to measure the electrical value between the anode and the carbon nanotube network.

8. The apparatus of claim 5 further comprising: a controller coupled to the power supply and/or the relay.

9. A method for manufacturing a nano-composite using electroplating comprising: forming a carbon nanotube (CNT) network having one or more intertube junctions between different carbon nanotubes; immersing the carbon nanotube network attached to two or more electrodes which are arranged at predetermined intervals into an electroplating solution; applying an electrical energy among an anode and a portion of the two or more electrodes for applying an electroplating substance of the electroplating solution to the carbon nanotube network; and relaying the electrical energy flow from a portion of the two or more electrodes to another portion of the two or more electrodes under conditions effective to produce a nano-composite having uniform conductive bridges of the electroplating substance at the one or more intertube junctions.

10. The method of claim 9, wherein the time period and frequency of relaying the electrical energy flow is adjusted to reduce the contact resistance of the CNT network.

11. The method of claim 9, wherein the anode is selected from the group consisting of Al, Cr, Co, Ni, Cu, Zn, Rh, Pd, Ag, Sn, W, Pt, Au, Ti, Mn, Cd and Pb.

12. The method of claim 9, wherein the applying of electrical energy and the relaying of the electrical energy flow is performed with an electrical current density ranging from about 1 nA/cm2 to about 1000 mA/cm2.

13. The method of claim 9, wherein the electroplating substance comprises any one selected from the group consisting of metal, conductive polymer, and a combination thereof.

14. The method of claim 13, wherein the metal is at least one selected from the group consisting of Al, Cr, Co, Ni, Cu, Zn, Rh, Pd, Ag, Sn, W, Pt, Au, Ti, Mn, Cd and Pb.

15. The method of claim 13, wherein the conductive polymer comprises at least one selected from the group consisting of polyaniline, polyimide, polyester, polyacetylene, polypyrrole, polythiophene, poly-p-phenylenevynilene, polyepoxide, polydimethylsiloxane, polyacrylate, poly methyl methacrylate, cellulose acetate, polystyrene, polyolefin, polymethacrylate, polycarbonate polysulphone, polyethersulphone, and polyvinyl acetate.

16. The method of claim 9, wherein the size of the conductive bridges ranges from about 0.5 nm to about 10 nm when the electroplating substance is metal.

17. The method of claim 9, wherein the forming of the carbon nanotube network is carried out by any one selected from the group consisting of dip-coating, spin coating, bar coating, spraying, self-assembly, Langmuir-Blodgett deposition, and vacuum filtration.

18. The method of claim 9 further comprising: measuring the electrical value between the anode and the two or more electrodes.

19. A method for manufacturing a nano-composite using electroplating comprising: forming a carbon nanotube (CNT) network having one or more intertube junctions between different carbon nanotubes; immersing the carbon nanotube network into an electroplating solution, wherein the carbon nanotube network is coupled to a power supply through two or more parts thereof at predetermined intervals; applying an electrical energy among an anode and a portion of the two or more parts of the carbon nanotube network for applying an electroplating substance of the electroplating solution to the carbon nanotube network; and relaying the electrical energy flow from a portion of the two or more parts of the carbon nanotube network to another portion of the two or more parts of the carbon nanotube network under conditions effective to produce a nano-composite having uniform conductive bridges of the electroplating substance at the one or more intertube junctions.

20. The method of claim 19, wherein the time period and frequency of relaying the electrical energy flow is adjusted to reduce the contact resistance of the CNT network.

21. The method of claim 19, wherein the anode is selected from the group consisting of Al, Cr, Co, Ni, Cu, Zn, Rh, Pd, Ag, Sn, W, Pt, Au, Ti, Mn, Cd and Pb.

22. The method of claim 19, wherein the applying of electrical energy and the relaying of the electrical energy flow is performed with an electrical current density ranging from about 1 nA/cm2 to about 1000 mA/cm2.

23. The method of claim 19, wherein the electroplating substance comprises any one selected from the group consisting of metal, conductive polymer, and a combination thereof.

24. The method of claim 23, wherein the metal is at least one selected from the group consisting of Al, Cr, Co, Ni, Cu, Zn, Rh, Pd, Ag, Sn, W, Pt, Au, Ti, Mn, Cd and Pb.

25. The method of claim 23, wherein the conductive polymer comprises at least one selected from the group consisting of polyaniline, polyimide, polyester, polyacetylene, polypyrrole, polythiophene, poly-p-phenylenevynilene, polyepoxide, polydimethylsiloxane, polyacrylate, poly methyl methacrylate, cellulose acetate, polystyrene, polyolefin, polymethacrylate, polycarbonate polysulphone, polyethersulphone, and polyvinyl acetate.

26. The method of claim 19, wherein the size of the conductive bridges ranges from about 0.5 nm to about 10 nm when the electroplating substance is metal.

27. The method of claim 19, wherein the forming of the carbon nanotube network is carried out by any one selected from the group consisting of dip-coating, spin coating, bar coating, spraying, self-assembly, Langmuir-Blodgett deposition, and vacuum filtration.

28. The method of claim 19 further comprising: measuring the electrical value between the anode and the carbon nanotube network.

Description:

TECHNICAL FIELD

The present disclosure relates generally to nano-composites and, more particularly, to carbon nanotube (CNT) network-based nano-composites.

BACKGROUND

Recently, CNTs have attracted great attention in many research areas due to their superior mechanical, thermal and electrical properties that make them potentially useful in various applications in nanotechnology, electronics, optics and other fields.

CNTs are generally synthesized by chemical vapor deposition (CVD), laser ablation or arc discharge, and are categorized as single-walled nanotubes (SWNTs) and multi-walled nanotubes (MWNTs). MWNTs include concentric cylinders with the smallest cylinder in the middle immediately surrounded by a larger cylinder which in turn is immediately surrounded by an even larger cylinder. Here, each cylinder represents a “wall” of CNTs, hence the name “multi-walled” nanotubes.

Although CNTs have been extensively utilized in many applications due to their extraordinary physical properties, a major drawback of CNT-based applications is irreproducibility. It is difficult to reproduce single CNT devices consistently due to the variations in chirality and geometry of CNTs. However, such individual variation is suppressed in the CNT network by an ensemble averaging over a large number of CNTs. CNT networks are reproducible and fabricated at low cost with high efficiency by using the processes of dip-coating, spraying, vacuum filtration, and so on. These characteristics make them ideal candidates for various applications. For example, CNT networks have been studied for thin-film transistors, diodes, strain and chemical sensors, field emission devices, and transparent conductive electrodes. Especially, CNT transparent conducting electrodes (CNT-TCE) may provide a critical component of next generation flexible displays due to their excellent electrical properties and mechanical flexibility.

TCE is used for various applications such as liquid crystal display (LCD), plasma display panel (PDP), and touchpads. Indium tin oxide (ITO) is a general TCE material suitable for most applications, but indium is a rare material currently produced only in Russia. As demand for TCE continues to increase, the price of indium has rapidly increased. TCE is generally made by coating the ITO layer on a glass substrate or a flexible polymer substrate. A drawback is that, since ITO is a brittle material, it is not suitable for flexible display which has become of great interest recently. Therefore, it is necessary to develop a low price TCE with enough flexibility.

Another drawback is that, even though individual CNTs have high electrical conductivity, the resistances at the junctions between one CNT to another are considered as a dominant bottleneck to commercializing CNT-TCE with low resistivity. Still another drawback is the complex and inefficient synthesis techniques which are presently required to utilize the outstanding physical properties of CNTs.

SUMMARY

Nano-composites, methods, and apparatus for manufacturing a nano-composite are provided. In one embodiment, an electroplating apparatus includes a power supply, a CNT network, an electroplating solution, an anode, and a relay.

In another embodiment, a method for manufacturing a nano-composite includes forming a CNT network, immersing the CNT network into an electroplating solution, applying an electrical energy, and relaying the electrical energy flow to produce a nano-composite having uniform conductive bridges on the CNT network.

In still another embodiment, the present disclosure provides a CNT network-based nano-composite.

The Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an illustrative embodiment of an electroplating apparatus for manufacturing a nano-composite.

FIG. 2 shows an illustrative embodiment of a Scanning Electron Microscopy (SEM) image of a portion of the nano-composite electroplated with metal using the apparatus of FIG. 1.

FIG. 3 an illustrative embodiment of a SEM image of another portion of the nano-composite electroplated with metal using the apparatus of FIG. 1.

FIG. 4 shows another illustrative embodiment of an electroplating apparatus for manufacturing a nano-composite.

FIG. 5 shows still another illustrative embodiment of an electroplating apparatus for manufacturing a nano-composite.

FIG. 6 is a schematic diagram of an illustrative embodiment of a CNT network with metal bridges.

FIG. 7 is a schematic diagram of an illustrative embodiment of a CNT network with conductive polymer bridges.

FIG. 8 is a flow chart of an illustrative embodiment for manufacturing a CNT network-based nano-composite.

DETAILED DESCRIPTION

In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the components of the present disclosure, as generally described herein, and illustrated in the Figures, may be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure.

As used herein, a “junction” generally means a place where CNTs join or cross one another. The term “junction” also encompasses a situation where CNTs are adjacent to one another with narrow gaps so as to be bridged by a conductive substance, wherein the size and density of the conductive bridge is within the range to not seriously undermine the transparency of the manufactured nano-composite for its various uses. The size and density of the conductive bridges are also within the range to reduce the resistance between the CNTs within the CNT network.

FIG. 1 shows an illustrative embodiment of an electroplating apparatus 100 for manufacturing a nano-composite. As depicted, the electroplating apparatus 100 includes a power supply 102, a container 104, an anode 106, an electrode 108, a CNT network 110, a substrate 112, and an electroplating solution 114. The power supply 102 is electrically coupled to the anode 106 and the electrode 108.

The CNT network 110 attached to the electrode 108 is immersed into the electroplating solution 114 to perform electroplating thereon. Electrical energy is applied across the anode 106 and the electrode 108 immersed in the electroplating solution 114, causing the CNT network 110 to be deposited with the electroplating substance, for example metal (indicated by the symbol “M”) in the electroplating solution 114 to produce a nano-composite. Various types of metals or conductive polymers may be used for forming the electroplating solution 114. In this way, electroplating substance may work as bridges between CNTs, thereby reducing resistance between crossover CNTs within the CNT network 110.

FIGS. 2 and 3 show illustrative embodiments of SEM images of different portions of the nano-composite manufactured by using the apparatus 100 of FIG. 1. As depicted in FIG. 2, the portion of the nano-composite, which is near the electrode 108 has a high density of electroplating substance (e.g., Cu) on the CNT network 110. On the other hand, the other portion of the nano-composite, which is far from the electrode 108, has a low density of electroplating substance, as illustrated in FIG. 3, although the density distribution of the CNTs on the CNT network 110 is uniform. With respect to FIGS. 2 and 3, the CNT network 110 was electroplated in the electroplating solution 114 over a long period of time and thus a good deal of the electroplating substance was deposited on the CNT network 110, especially on the portion of the CNT network 110 near the electrode 108, to make the CNTs of FIG. 2 more opaque than those of FIG. 3. Considering that the electroplating substance such as metals or conductive polymers tends to gather around the electrode 108, for the nano-composite manufactured by using the apparatus 100 of FIG. 1, the density distribution of the electroplating substance is not uniform over the CNT network 110, resulting in the non-uniform electrical resistance and transparency according to the region of the manufactured nano-composite.

FIG. 4 shows another illustrative embodiment of an electroplating apparatus 400 for manufacturing a nano-composite. As depicted, the electroplating apparatus 400 includes a power supply 402, a container 404, an anode 406, two electrodes 408, 410, a CNT network 412, a substrate 414, an electroplating solution 416, and a relay 418. The power supply 402 is electrically coupled to the anode 406 and the relay 418. The relay 418 is electrically coupled to the two electrodes 408, 410.

The relay 418 may be changeover switches having two switch positions. The relay 418 allows one electrical circuit between the electrode 408 and the anode 406 to switch a second electrical circuit between the electrode 410 and the anode 406, which can be separated from the first.

The electroplating solution 416 may comprise metal ion, conductive polymer or a combination thereof. Various types of metals or conductive polymer for the electroplating solution 416 may be used to form conductive bridges among the CNTs at intertube junctions. The electroplating solution 416 may have a composition suitable for electroplating a particular conductive material.

The electroplating substance (indicated by the symbol “ES”) of the electroplating solution 416 comprises metal, conductive polymer, or a combination thereof. This means that the metal ion and/or conductive polymer of the electroplating solution 416 work as the electroplating substance. When the electroplating substance, which forms conductive bridges among the different CNTs at intertube junctions, comprises metal, the metal as an electroplating substance is at least one selected from the group consisting of Al, Cr, Co, Ni, Cu, Zn, Rh, Pd, Ag, Sn, W, Pt, Au, Ti, Mn, Cd and Pb. In some embodiments, the metal bridges are made from the above-described process by using Cu, Au, Ni and the like. For example, Cu may be used as the electroplating substance, and a sulfuric acid bath (0.75M of CuSO4.5H2O+74 g/L of H2SO4+0.2 g/L of gelatin) may be prepared as the electroplating solution 416. In other embodiments, Au may be used as the electroplating substance and an Au-bath (12 g/L of KAu(CN)2+90 g/L of C6H5Na3O7.2H2O) may be prepared as the electroplating solution 416. According to alternative embodiments, Ni may be used as the electroplating substance, and a sulfamate-chloride bath (600 g/L of Ni(SO3NH2)2.4H2O+5 g/L of NiCl2.6H2O+45 g/L of H3BO3) may be prepared as the electroplating solution 416.

When the electroplating substance comprises a conductive polymer, the conductive polymer is at least one selected from the group consisting of polyaniline, polyimide, polyester, polyacetylene, polypyrrole, polythiophene, poly-p-phenylenevynilene, polyepoxide, polydimethylsiloxane, polyacrylate, poly methyl methacrylate, cellulose acetate, polystyrene, polyolefin, polymethacrylate, polycarbonate polysulphone, polyethersulphone, and polyvinyl acetate.

The anode 406 is selected from the group consisting of Al, Cr, Co, Ni, Cu, Zn, Rh, Pd, Ag, Sn, W, Pt, Au, Ti, Mn, Cd and Pb. In the electroplating process, the same type of metal used as the electroplating substance may be used as the anode 406. If the electroplating substance is conductive polymers, by way of non-limiting example, Pt, Ag, Cu or Ni may be used as the anode 406.

Any metal having good conductivity may be used as a material for the electrodes 408, 410. By way of non-limiting example, stainless, Cu, Ni or Al may be used as the electrodes 408, 410.

The substrate 414 may be selected, but is not limited to, from the group consisting of glass, glass wafer, silicon wafer, quartz, plastic, and transparent polymer.

In operation, the CNT network 412 attached to the two electrodes 408, 410 is immersed into the electroplating solution 416 contained in the container 404. In further embodiments, the CNT network 412 attached to the two or more electrodes 408, 410 may be supported in the electroplating solution 416 by a support mechanism (not shown in FIG. 4).

An electrical potential generated by the power supply 402 is applied across the anode 406 and one of the two electrodes 408, 410 immersed in the container 404, causing the CNT network 412 to be electroplated with the electroplating substance. According to an alternative embodiment, the CNT network 412 itself may work as an electrode without the need for any other electrode. In this case, the power supply 402 can be directly coupled to the two opposite ends of the CNT network 412.

The power supply settings can be voltage settings or current settings. Further, one or more rectifiers (not shown in FIG. 4) can be interposed between the power supply 402 and the relay 418 and/or between the power supply 402 and the anode 406. The density, shape and size of conductive bridges that is electroplated on the CNT network 412 may be controlled by the voltage level, the current level, the content of the electroplating substance or the combination thereof. In operation, the electrical current density may range from about 1 nA/cm2 to about 1000 mA/cm2.

When an electrical potential is applied to the CNT network 412, an electrical potential drop can be generated at junctions among the different CNTs, causing a temperature difference in the CNT network 412. That is, the temperature around the junctions between the different CNTs can be higher than that of other regions of the CNT network 412. Owing to the potential drop and/or the temperature difference, the electroplating substance such as metal or conductive polymer is selectively attracted to the position of junctions among the different CNTs and predominately electroplated thereon, bridging the different CNTs to each other.

After a predetermined time period, the relay 418 is switched to supply electrical energy from one electrode, for example, electrode 408, to the other electrode, for example, electrode 410. The electroplating is further conducted under conditions effective to form uniform conductive bridges between different CNTs through one or more relays of the electrical circuit. The length of the relay time period and the frequency of the relay can be determined by routine experimentation. As a result, contact resistances between different CNTs can be significantly reduced. The transparency of the produced nano-composite can be controlled within the range of being useful for its uses by adjusting electroplating conditions.

In certain embodiments, one or more detectors, for example detectors 420, 422 in FIG. 4, may be coupled between the anode 406 and the two electrodes 408, 410 in order to measure electrical values such as voltage and electric current. Resistance value and/or transparency value can be calculated from the measured electrical value and used for adjusting electroplating conditions. Further, resistance value and/or transparency values can be used for checking whether the electroplating is conducted to have targeted physical properties and/or for determining the completion time of the electroplating.

In certain embodiments, the electroplating apparatus 400 may comprise a controller 424 such as, by way of example and not a limitation, a computer. The controller 424 may operate under the control of a computer program stored on the hard disk drive or through other computer programs, such as programs stored on a removable disk. In some embodiments, the controller 424 may be a programmable logic computer (PLC), such as an Allen-Bradley Controllogix Processor or a Modicon PLC. The controller 424 can receive input signals from various components of the apparatus 400 and control a particular parameter of the apparatus 400 based on these signals. For example, the controller 424 is electrically coupled to the power supply 402 and/or the relay 418 and optionally the detectors 420, 422 for controlling the electroplating conditions such as voltage, electric current, electroplating time, switching period. In this manner, relatively instantaneous adjustments can be made regarding the electroplating conditions within the electroplating apparatus 400.

The electroplating apparatus 400 is able to prevent conductive bridges from being dominantly formed at certain regions of the CNT network 412 since the direction of electrical energy flow is alternately changed from one electric circuit to the other electric circuit through the two electrodes 408, 410. In this way, it is possible to produce a nano-composite having uniform conductive bridges over the CNT network 412 in a simple and efficient fashion without damaging physical properties such as resistance and transparency.

Depending on the design requirements and/or the application field, the number and arrangement of electrodes may have various types. For example, another illustrative embodiment of an electroplating apparatus 500 for manufacturing a nano-composite may have four electrodes 508, 510, 512, 514 attached to a CNT network 516 as illustrated in FIG. 5. As depicted, the electroplating apparatus 500 includes a power supply 502, a container 504, an anode 506, the four electrodes 508, 510, 512, 514, the CNT network 516, a substrate 518, an electroplating solution 520, and a relay 522. The power supply 502 is electrically coupled to the anode 506 and the relay 522. The relay 522 is electrically coupled to the four electrodes 508, 510, 512, 514.

The relay 522 may be changeover switches having four switch positions. The relay 522 may allow one electrical circuit between one of the four electrodes 508, 510, 512, 514 and the anode 506 to alternatively switch another electrical circuit between another of the four electrodes 508, 510, 512, 514 and the anode 506, which can be separated from one another. Any one of many approaches for relaying an electrical energy flow among the plurality of electrodes 508, 510, 512, 514 can be employed. The relay 522 may allow two electrical circuits to be on at the same time and then to be switched to the other two electrical circuits. For example, at the commencement of the electroplating, the relay 522 is set to electrically connect the anode 506 with the two electrodes 508, 512 at the same time for generating two electrical circuits. After a predetermined period of time, the relay 522 is switched to the positions to connect the anode 506 with the other two electrodes 510, 514.

The types of materials used for the electroplating substance (indicated by the symbol “ES”), the anode 506, the electrodes 508, 510, 512, 514, and the substrate 518 of the electroplating apparatus 500 may be the same with those described regarding FIG. 4. The electroplating apparatus 500 may also further comprise a support mechanism and/or one or more rectifiers.

The power supply settings can be voltage settings or current settings. The voltage level, the current level or the concentration of the electroplating substance is adjusted to control density and size of the electroplating substance that is electroplated on the CNT network 516.

In certain embodiments, one or more detectors (524, 526, 528, and 530 in FIG. 5) may be coupled between the anode 506 and the four electrodes 508, 510, 512, 514 in order to measure the electrical value such as voltage and electric current. In further embodiments, the electroplating apparatus 500 may comprise a controller 532. The controller 532 may be electrically coupled to the power supply 502 and/or the relay 522 and, optionally, the detectors 524, 526, 528, 530 for controlling the electroplating conditions such as voltage, electric current, electroplating time, switching period. In some embodiments, two of more power supplies can be used instead of only one power supply 502.

The density, shape and size of conductive bridges that is electroplated on the CNT network 516 is controlled by the voltage level, the current level, the content of the electroplating substance or the combination thereof.

According to alternative embodiments, the relay 522 may have many more sets of switch contacts, and the direction, order, and number of relaying the electrical energy flow can be varied as necessary.

In some embodiments, to further enhance the properties of the nano-composite according to its uses, various post-treatments may be employed, including UV-irradiation, thermal annealing, electroplating, and the like.

FIG. 6 shows a schematic diagram of an illustrative embodiment of the CNT network 412 with metal (indicated by the symbol “M”) bridges. The size of the metal bridges ranges, but is not limited to, from about 0.5 nm to about 10 nm.

FIG. 7 illustrates a schematic diagram of an illustrative embodiment of the CNT network 412 with conductive polymer (indicated by the symbol “CP”) bridges. As illustrated in FIG. 7, the conductive polymer easily penetrates into the narrow space among CNTs at the junctions due to capillary action. The conductive polymer inserts into or wraps around the junctions among the different CNTs to produce the nano-composite having conductive bridges.

As depicted in FIGS. 6 and 7, the nano-composite include the CNT network 412 having one or more intertube junctions among the two or more CNTs and electroplating substance associated with the CNT network 412, where a predominant amount of the electroplating substance is present at the one or more intertube junctions, and where the electroplating substance provides one or more conductive bridges among the two or more CNTs. About 70 to about 100% of the electroplating substance associated with the CNT network may be present at intertube junctions among different CNTs.

According to the present disclosure, it is possible to evenly deposit electroplating substance at junctions between CNTs by changing the position of the working electrodes through a relay and thus improve erosion of the electroplating coating to provide uniform distribution of the conductive bridges on the CNT network. Contact resistances among different CNTs can also be regular over the nano-composite. The nano-composite of the present disclosure may have a sheet resistance of from about 1 Ω/sq to about 1000 Ω/sq depending on its uses. Further, the transparency of the produced nano-composite can be controlled to have a narrow standard deviation.

FIG. 8 is a flow chart of an illustrative embodiment for manufacturing a CNT network-based nano-composite. At block 820, a CNT network may be prepared by using various techniques such as dip-coating, spin coating, bar coating, spraying, self-assembly, Langmuir-Blodgett deposition, vacuum filtration, and the like.

In order to form a CNT network, the CNT colloidal solution may be prepared by dispersing purified CNTs in a solvent, such as deionized water or an organic solvent, for example, 1,2-dichlorobenzene, dimethyl formamide, benzene, methanol, and the like. Since the CNTs produced by the currently available methods may contain impurities, they may need to be purified before being dispersed into the solution. The purification may be performed by wet oxidation in an acid solution or dry oxidation. A suitable purification method may comprise refluxing CNTs in a nitric acid solution (e.g., about 2.5 M), re-suspending the CNTs in water with a surfactant (e.g., sodium lauryl sulfate, sodium cholate) at pH 10, and then filtering the CNTs using a cross-flow filtration system. The resulting purified CNT suspension may then be passed through a filter, such as a polytetrafluoroethylene filter. Alternatively, purified CNTs can be purchased directly.

The purified CNTs may be in a powder form that can be dispersed into the solvent. In certain embodiments, an ultrasonic wave or microwave treatment can be carried out to facilitate the dispersion of the purified CNTs throughout the solvent. The dispersing may be carried out in the presence of a surfactant. Various types of surfactants may be used including, but not limited to, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, sodium dodecylsulfonate, sodium n-lauroylsarcosinate, sodium alkyl allyl sulfosuccinate, polystyrene sulfonate, dodecyltrimethylammonium bromide, cetyltrimethylammonium bromide, Brij, Tween, Triton X, and poly(vinylpyrrolidone). In this way, a well-dispersed and stable CNT colloidal solution is prepared.

A substrate can be prepared with surface treatment for high wettability. Considering that a post-wet-process is required after a CNT network is formed, a hydrophilic SAM (self assembled monolayer) coating or piranha (H2SO4:H2O2=4:1)-treatment may be adopted to increase the adhesion force between CNTs and the substrate. CNTs can be coated on the substrate with the prepared colloidal solution by various methods including dip coating, spraying, spin coating and so on. Then a CNT network is formed on the substrate.

At block 840, the CNT network is immersed into an electroplating solution to perform electroplating. The CNT network can be attached to two or more electrodes arranged at predetermined intervals or work as an electrode itself to which a power supply is electronically coupled through two or more parts thereof at predetermined intervals. The electroplating solution comprises metal ions, conductive polymers, or a combination thereof.

At block 860, electrical energy is applied across an anode and a portion of two or more electrodes that are immersed in the electroplating solution, and then the electroplating substance of the electroplating solution is applied to the CNT network.

At block 880, the electrical energy flow is relayed from a portion of two or more electrodes to another portion of two or more electrodes under conditions effective to produce a nano-composite having uniform conductive bridges of the electroplating substance at junctions between the different CNTs.

In this way, electroplated metals or conductive polymers may work as bridges between different CNTs, thereby reducing the electrical resistance of the CNT network and increasing adhesion between the CNT network and a substrate. Further, the transparency of the nano-composite can be adjusted to the desired level based on the amount, density, shape and size of conductive bridges, which can be controlled by varying electroplating conditions such as voltage level, current level, the concentration of the electroplating substance, or the combination thereof.

In accordance with the present disclosure, a TCE is provided comprising the nano-composite described above, which can replace brittle and expensive ITO electrodes. Further, a nano-composite of the present disclosure can be applied to various fields such as flexible displays, Electromagnetic-interference (EMI) shielding material, and Organic Light Emitting Diodes (OLED).

The following examples are provided for illustration of some of the illustrative embodiments of the present disclosure but are by no means intended to limit their scope.

Example 1

Preparation of a Nano-Composite

Preparation of a CNT Network

Sonication is conducted for about 30 min in nitric acid to purify CNTs (product number: ASP-100F, Iljin Nanotech). The CNTs are neutralized using D.I. water after wet-oxidization and then passed through vacuum filtration. The purified CNTs are dispersed in 1,2-dichlorobenzene. An ultrasonication treatment is carried out for about 10 hr to facilitate dispersion of the purified CNTs throughout the solvent. In this way, the well-dispersed and stable CNT colloidal solution is prepared. A soda lime glass is used as a substrate. Piranha (H2SO4:H2O2=4:1)-treatment is adopted to remove impurities on the surface of the substrate and modify the surface of the substrate so as to have polarity, thereby increasing the adhesion force between CNTs and the substrate. The glass substrate is immersed vertically into the CNT colloidal solution and dip-coating is performed with the withdrawal velocity of 3 mm/min at room temperature to produce a CNT network.

Preparation of a Nano-Composite Using Electroplating

A nano-composite having conductive bridges on the CNT network is prepared by the following process. Cu is used as an anode and a sulfuric acid bath (0.75M of CuSO4.5H2O+74 g/L of H2SO4+0.2 g/L of gelatin) is prepared as an electroplating solution. The CNT network attached to two electrodes at opposite ends thereof is immersed into the electroplating solution. Electrical energy is applied between the anode and one of the electrodes and then the electrical energy flow is switched to the circuit between the anode and the other electrode, producing a nano-composite having uniform Cu bridges at junctions among the different CNTs. Electroplating is performed with a current density of 10 mA/cm2 at room temperature. Electrical resistance is measured using a 4-point probe (model: CMT-SR2000N, AIT) and transparency is observed using an ultraviolet-visible spectrophotometer (model: Lambda-20, Perkin Elmer). The nano-composite has 90 Ω/sq of resistance and about 85% of transparency.

Those skilled in the art will appreciate that, for this and other processes and methods disclosed herein, the functions performed in the processes and methods may be implemented in differing order. Furthermore, the outlined steps and operations are only provided as examples, and some of the steps and operations may be optional, combined into fewer steps and operations, or expanded into additional steps and operations without detracting from the essence of the disclosed embodiments.

The herein described subject matter sometimes illustrates different components contained within, or connected with, other different components. It is to be understood that such depicted architectures are merely exemplary, and many other architectures can be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively “associated” such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as “associated with” each other such that the desired functionality is achieved, irrespective of the architectures or intermediate components. Likewise, any two components so associated can also be viewed as being “operably connected”, or “operably coupled”, to each other to achieve the desired functionality, and any two components capable of being so associated can also be viewed as being “operably coupled”, to each other to achieve the desired functionality. Specific examples of being operably coupled include but are not limited to physically matching and/or physically interacting components and/or wirelessly interacting and/or wirelessly interacting components and/or logically interacting and/or logically interacting components.

With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.

It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, to gain a better understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense wherein one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense wherein one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.”

From the foregoing, it will be appreciated that various embodiments of the present disclosure have been described herein for purposes of illustration, and that various modifications may be made without departing from the scope and spirit of the present disclosure. Accordingly, the various embodiments disclosed herein are not intended to be limiting, with the true scope and spirit being indicated by the following claims.