Carbon nanotube fluid matrix

Abstract

Carbon nanotube fluid matrix, a method for producing the carbon fluid matrix, and the use of the carbon fluid matrix for printing. According to certain embodiments, the carbon fluid matrix is ​​free of surfactants, polymers and additives typically required for a stable formulation.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of and priority to U.S. Provisional Patent Application No. 63 / 277910, filed November 10, 2021, the entire disclosure of which is incorporated herein by reference.

[0002] Technical Field The present application relates to carbon nanotube fluid matrices. In particular, the present application is directed to carbon nanotube fluid matrices, methods for preparing carbon nanotube fluid matrices, and uses of such matrices. [Background technology]

[0003] Nanotubes are members of the fullerene structure family, which also includes spherical buckybowls; both ends of a nanotube may be capped with a hemisphere of the buckybowl structure. They get their name from the fact that they are long, hollow structures whose walls are made of atomically thick carbon sheets called graphene. These sheets are rolled at specific, discrete angles ("chiral"), and the combination of the rolling angle and the radius determines the properties of the nanotube (for example, whether the nanotube behaves as a metal or a semiconductor). Nanotubes are classified as single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). While single-walled carbon nanotubes contain a single folded graphene sheet, multi-walled carbon nanotubes contain multiple wrapped layers (concentric tubes) of graphite.

[0004] Single-walled carbon nanotubes are characterized by their unique mechanical, electrical and optical properties. The tensile strength of single-walled carbon nanotubes is well above 30 GPa, and the electrical conductivity of metallic single-walled carbon nanotubes is 10 6S / m. The SWNT network formed after deposition of the SWNT dispersion also allows the transmission of visible and infrared light perpendicular to the plane of the film. This property is due to the extremely small diameter of SWNTs (<1.5 nm on average) and their enormous aspect ratio (i.e. length to diameter) with typical values ​​of 1000-1500. Thus, the formation of transparent conductive networks is possible. This combination of properties in a single material makes it an outstanding candidate for a large number of laboratory-proven applications, including field-effect transistors, non-volatile memories, displays, touch screens, battery electrodes, supercapacitors, and filtration membranes.

[0005] Once formed, such carbon nanotube dispersions can be mixed with other materials, such as a solution of a polymer whose conductivity needs to be improved, or can be deposited onto a substrate using established coating techniques such as dip coating, spray coating or inkjet printing.

[0006] The raw carbon nanotube soot produced generally contains the desired carbon nanotube product as well as extraneous impurities such as transition metal catalysts, graphitic carbon, amorphous carbon nanoparticles, fullerenes, carboanions, polycyclic aromatic hydrocarbons, etc. The nature and level of electronic impurities present in a given feedstock varies depending on the synthesis method used, e.g. laser, arc, high pressure carbon monoxide conversion (HiPco), chemical vapor deposition (CVD), combustion, etc.

[0007] Known purification protocols generally include steps of common unit operations such as pre-oxidation, acid reflux, mechanical mixing, sonication, filtration, neutralization, and centrifugation. Choosing the appropriate combination depends on the method of carbon nanotube production and the specific impurities of interest. Foreign impurities such as catalytic metal particles, fullerenic carbon, amorphous carbon, graphitic carbon, and carbon onions are present to varying degrees in the raw carbon nanotube samples prepared. Oxidative chemical treatments as part of the purification protocol and multiple acid treatments as part of the general purification process can yield reasonably clean carbon nanotubes (less than 0.5 wt% relative to metal residues). However, aggressive chemical purification leads to loss of conductive pathways, significantly reducing the electrical conductance of single tubes, as well as vanishing interband optical transitions arising from van Hove singularities. Therefore, for many applications, especially those requiring a combination of optical and electrical properties, preserving the electronic structure of the carbon nanotubes substantially intact is a key aspect of the formation of single-walled carbon nanotube inks.

[0008] In one purification procedure, carbon nanotubes are purified with a combination of sulfuric and nitric acids. This process produces a highly flowable, highly debundled, and concentrated "wet paste." In another purification procedure, carbon nanotubes are purified with a combination of phosphoric and nitric acids. The practical benefits and theoretical performance enhancements of carbon nanotubes in applications are generally best realized when the purified, debundled carbon nanotube material is maintained in a debundled state throughout the device / product / process application.

[0009] Dispersions of carbon nanotubes (CNTs) in water and other common solvents are generally thermodynamically unstable; that is, the carbon nanotube bundles can grow in diameter or aggregate, ultimately resulting in a non-stabilized dispersion. If the CNT bundles aggregate and grow in size or assemble in the coating solution (i.e., before a film is formed), the assembly of the film is further impaired and the resulting dry coating exhibits a higher surface resistance for a given mass deposition per unit area. Furthermore, small particle and CNT dispersions are typically formed from solvents and dispersing aids such as surfactants or other additives such as polymers. However, the additives can also precipitate in the coating as the solvent evaporates, preventing the formation of a conductive network. This results in suboptimal electronic performance of the thin film.

[0010] What is needed is a stable carbon nanotube fluid matrix with CNTs uniformly dispersed in a solvent, where the CNTs do not aggregate for periods of 12 to 24 hours or longer. Additionally, what is needed is a carbon nanotube fluid matrix that does not contain surfactants, polymers, or other additives that may interfere with the desired properties of the coating or printed film. Summary of the Invention [Means for solving the problem]

[0011] The present application is directed to a carbon nanotube fluid matrix, a method for making the carbon fluid matrix, and the use of the carbon fluid matrix for printing. According to certain embodiments, the carbon fluid matrix is ​​free of surfactants, polymers, and additives that are typically required for a stable formulation.

[0012] In some aspects, a stable carbon nanotube fluid matrix is ​​disclosed that includes carbon nanotubes dispersed in a solvent mixture. The solvent mixture includes a first solvent and a second solvent; (a) the first solvent has a boiling point below 100° C. and the second solvent has a boiling point above 100° C.; or (b) the first solvent is a monohydric alcohol and the second solvent is a diol.

[0013] In some embodiments, the stable carbon nanotube fluid matrix is ​​stable over a concentration range from about 1 mg / L to about 3000 mg / L.

[0014] In some embodiments, the first solvent is selected from the group consisting of hexane, isopropanol, n-propanol, methanol, ethanol, benzene, acetonitrile, tetrahydrofuran, and mixtures thereof.

[0015] In some embodiments, the second solvent is selected from the group consisting of propylene glycol methyl ether, dimethylformamide, n-methylpyrrolidone, dimethylacetamide, dimethylsulfoxide, silane, butanol, toluene, xylene, chlorobenzene, dichlorobenzene, ethylene glycol, propylene glycol, glycerol, methyl lactate, cyclohexanol, and mixtures thereof.

[0016] In some embodiments, the first solvent is selected from isopropyl alcohol, ethanol, n-propanol, methanol, or a mixture thereof.

[0017] In some embodiments, the second solvent is cyclohexanol, ethylene glycol, or propylene glycol.

[0018] In some embodiments, the solvent mixture comprises at least one monohydric alcohol and at least one diol.

[0019] In some embodiments, the solvent mixture includes cyclohexanol, isopropyl alcohol, and ethylene glycol.

[0020] In some embodiments, the stable carbon nanotube fluid matrix is ​​free of surfactants, dispersing aids and polymers.

[0021] In some embodiments, the solvent mixture consists essentially of water, a first solvent, and a second solvent.

[0022] In some embodiments, the carbon nanotubes are functionalized. In some embodiments, the carbon nanotubes are functionalized with a plurality of oxygen-containing functional groups.

[0023] In some embodiments, the carbon nanotubes comprise single-walled carbon nanotubes, multi-walled carbon nanotubes, or a mixture thereof.

[0024] In some embodiments, the solvent mixture includes ethylene glycol, cyclohexanol, and propylene glycol.

[0025] In some embodiments, the solvent mixture includes silane.

[0026] According to another aspect, a stable carbon nanotube fluid matrix is ​​disclosed comprising functionalized carbon nanotubes dispersed in a solvent mixture, wherein the stable carbon nanotube fluid matrix is ​​free of surfactants, dispersing aids and polymers, and wherein the stable carbon nanotube fluid matrix is ​​stable up to a concentration of about 3000 mg / L.

[0027] According to another aspect, a method of making a stable carbon nanotube fluid matrix includes providing a carbon nanotube composition comprising oxidized carbon nanotubes; and dispersing the carbon nanotube composition in a solvent mixture comprising a first solvent and a second solvent, to provide a stable carbon nanotube fluid matrix. (a) the first solvent has a boiling point below 100° C. and the second solvent has a boiling point above 100° C.; or (b) the first solvent is a monohydric alcohol and the second solvent is a diol.

[0028] In some embodiments, the first solvent is removed from the carbon nanotube fluid matrix to produce a concentrated carbon nanotube fluid matrix.

[0029] According to another aspect, a method of coating or printing on a substrate includes providing a concentrated carbon nanotube fluid matrix and printing or coating the concentrated carbon nanotube fluid matrix on a substrate.

[0030] In some embodiments, the concentrated carbon nanotube fluid matrix is ​​screen printed onto a substrate.

[0031] In some embodiments, the solvent mixture includes ethylene glycol, cyclohexanol, and propylene glycol.

[0032] According to another aspect, a stable graphene fluid matrix is ​​disclosed, the matrix comprising graphene dispersed in a solvent mixture comprising a first solvent and a second solvent; (a) the first solvent has a boiling point below 100° C. and the second solvent has a boiling point above 100° C.; or (b) the first solvent is a monohydric alcohol and the second solvent is a diol. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] It should be noted that the produced carbon nanotube feedstock, purified carbon nanotube material, fullerenes, and / or any other fullerene material can be synthesized and / or processed by approaches described, for example, in U.S. Pat. No. 5,273,729 to Howard et al., filed May 24, 1991, U.S. Pat. No. 5,985,232 to Howard et al., filed September 11, 1996, U.S. Pat. No. 7,335,344 and U.S. Pat. No. 7,887,775 B2 to Height et al., filed March 14, 2003, U.S. Pat. No. 7,435,403 to Kronholm et al., filed July 3, 2003, and U.S. Pat. Nos. 7,396,520 and 7,771,692 to Howard et al., filed January 21, 2005, which are incorporated herein by reference in their entireties.

[0034] In some embodiments, the carbon nanotubes are single-walled carbon nanotubes. In other embodiments, the carbon nanotubes are multi-walled carbon nanotubes. For example, in some non-limiting embodiments, the nanotubes have at least two walls (i.e., double-walled). In other embodiments, the nanotubes have between 3 and 12 walls. In further embodiments, the nanotubes have 12 or fewer walls. In yet other embodiments, the nanotubes have 2-6 walls. In some embodiments, the carbon nanotubes have 2-8 walls. In further embodiments, the carbon nanotubes have 2-10 walls. In exemplary non-limiting embodiments, the carbon nanotubes have 2, 4, 6, 8, 10, or 12 walls.

[0035] In another embodiment, a mixture of single-walled and multi-walled carbon nanotubes is provided. For example, in some embodiments, a mixture of single-walled and double-walled nanotubes is provided. In a further embodiment, a mixture of single-walled and multi-walled nanotubes is provided. In another embodiment, a mixture of multi-walled carbon nanotubes is provided, the mixture including nanotubes with various wall configurations. The compositions and matrices disclosed herein can also be used with graphene, as well as CNTs and combinations thereof.

[0036] As used herein, the term "stable" as used with respect to a CNT or graphene formulation or fluid matrix means one that can withstand centrifugation at at least 10,000 g for at least 30 minutes and provide an optical density at 550 nm of at least about 0.1.

[0037] The term "surfactant" as used herein refers to a compound that reduces the interfacial tension between carbon nanotubes and a fluid. Surfactants may be attached to the carbon nanotube surface by covalent or ionic bonds, or by pi-stacking, or may wrap around the carbon nanotube.

[0038] As used herein, the term "dispersing aid / stabilizing additive" refers to a non-nanotube component that is present in the fluid matrix along with the carbon nanotubes to provide stabilization, and that remains in the carbon nanotube matrix after the fluid matrix has evaporated.

[0039] As used herein, the term "fluid" refers to a liquid having a viscosity of less than about 3 poise at 25°C.

[0040] As used herein, the term "functionalized carbon nanotubes" refers to carbon nanotubes having an atom or group of atoms attached to the sidewall or end cap of the carbon nanotube. 2The hybrid structure is disrupted through covalent bonds and through non-covalent bonds such as pi-stacking, dipole-dipole forces, and van der Waals interactions.

[0041] As used herein, the term "oxidized carbon nanotubes" refers to functionalized carbon nanotubes having oxygen-containing functional surface groups, such as carboxylic acid, ketone, lactone, anhydride, or hydroxyl functional groups.

[0042] Discrete oxidized carbon nanotubes can be obtained from the as-produced bundled carbon nanotubes by various methods. One such method includes oxidation using a combination of concentrated acids such as phosphoric acid, sulfuric acid, and / or nitric acid. The techniques disclosed in PCT / US09 / 68781 and PCT / US2021 / 053319, the disclosures of which are incorporated herein by reference, are particularly useful for producing discrete carbon nanotubes for use in certain embodiments of the present invention. Bundled carbon nanotubes can be made by known means, such as chemical vapor deposition, laser ablation, and high pressure carbon monoxide synthesis. Bundled carbon nanotubes can exist in various forms, such as soot, powder, fibers, and buckypaper. Furthermore, bundled carbon nanotubes can be of any length, diameter, or chirality. Carbon nanotubes can be metallic, semi-metallic, semiconducting, or non-metallic, depending on their chirality and number of walls.

[0043] CNT pastes prepared as described in PCT / US2021 / 053319 are particularly useful in that the CNT pastes can be dispersed at relatively high concentrations in a wide variety of solvents, particularly due to the paste feedstock produced by the disclosed phosphoric acid process. According to some embodiments, the CNT matrices disclosed herein can be produced without the use of dispersing aids or stability-promoting additives.

[0044] The discrete oxidized carbon nanotubes can include, for example, single-walled carbon nanotubes, double-walled carbon nanotubes, or multi-walled carbon nanotubes, and combinations thereof.

[0045] Carbon nanotubes purified by the oxidation process can be incorporated into water, aqueous / mixed solvent systems, and purely organic systems, but also allow other possibilities such as high viscosity solvents, monomers, and polymers, where dispersion stability can be aided and promoted by the high viscosity vehicle rather than being solely determined by solubility parameters / surface tension.

[0046] Sprayable and rod-coatable inks are useful in many ink application processes, with screen printing being another common process application. Screen-printable inks have significant morphological differences from rod-coatable and sprayable inks, particularly in viscosity, and generally utilize high viscosity solvents such as cyclohexanol.

[0047] According to certain aspects of the invention, carbon nanotubes can form stable matrices in various solvents by combining a low boiling point solvent with a high boiling point solvent. A low boiling point solvent is typically a solvent with a boiling point of about 100° C. or less, more particularly about 80° C. or less. A high boiling point solvent is typically a solvent with a boiling point of about 100° C. or more, particularly about 130° C. or more, and more particularly about 150° C. or more. Particularly useful solvents are those with a boiling point of about 150° C. or more and a surface tension of about 30 dines / cm or more. In some embodiments, water may be used in place of the low boiling point solvent. Without being bound by theory, it is believed that the use of a high boiling point solvent in the dual boiling range is beneficial in that the high boiling point solvent acts as a film former to prepare a stable wet film such that the dual composition can be applied in a roll-to-roll ("R2R") ready process such as slot die, gravure, or flexographic printing.

[0048] According to some embodiments, the one or more first solvents comprise between about 5% and 95% by weight of the total formulation, and the one or more second solvents comprise between about 5% and 95% by weight of the total formulation, or the one or more first solvents comprise between about 15% and 80% by weight of the total formulation, and the one or more second solvents comprise between about 15% and 85% by weight of the total formulation, or the one or more first solvents comprise between about 20% and about 70% by weight of the total formulation, and the one or more second solvents comprise between about 20% and about 70% by weight of the total formulation, or the one or more first solvents comprise between about 25% and about 50% by weight of the total formulation, and the one or more second solvents comprise between about 50% and about 65% by weight of the total formulation. The compositions disclosed herein may also include water in addition to the first and second solvents.

[0049] Solvent combinations can be tested for miscibility, which provides an indication of whether the solvent mixture provides stability in accordance with the present disclosure. Representative miscibility test results are shown below:

[0050] [Table 1]

[0051] According to certain embodiments, the processes disclosed herein can provide stable carbon nanotube dispersions having carbon nanotube content between about 0.01 absorbance units and about 40 absorbance units, more specifically between about 0.1 absorbance units and about 20 absorbance units, as determined by optical density at 550 nm. In a typical optical density measurement, the high concentration dispersion is diluted with a 10:1 or similar dilution ratio to allow measurement in the operating range of the UV-Vis or UV-Vis monochromator (typically about 0.1 to about 2 absorbance units). Depending on the desired coating method and substrate, the final concentration optical density of the ultrasonically spray coatable ink is about 0.1 to 5 absorbance units, and the final concentration optical density of the slot-die or rod coatable ink is about 5 to about 20 absorbance units. A mass balance method determined a carbon nanotube concentration of 315 mg / L at an optical density of 14 absorbance units for one of the carbon nanotube compositions.

[0052] According to some embodiments, the carbon nanotube fluid matrix is ​​stable up to a concentration of about 3000 mg / L, about 2000 mg / L, about 1000 mg / L, about 750 mg / L, or about 500 mg / L.

[0053] According to some embodiments, a stable carbon nanotube fluid matrix is ​​provided, the fluid matrix being stable over a concentration range of about 1 mg / L to about 3000 mg / L, over a concentration range of about 10 mg / L to about 500 mg / L, over a concentration range of about 20 mg / L to about 400 mg / L, or over a concentration range of about 30 mg / L to about 300 mg / L.

[0054] According to one aspect, the present invention provides neat CNT concentrations at concentrations of up to about 3000 mg / L, up to about 2000 mg / L, up to about 1000 mg / L, up to about 750 mg / L, up to about 600 mg / L, or up to about 500 mg / L without the need for dispersing aids, surfactants, binders, stabilizing polymers or other compounds to facilitate dispersion, such as graphene oxide (GO), acetylene glycol, or imidazolidinone compounds. According to certain embodiments, the stable formulations provided herein consist essentially of or consist of the solvent in the solvent mixture used to prepare the finished composition from a paste comprised of oxidized CNTs. According to certain embodiments, the present invention provides stable CNT compositions that do not require post-processing of the film to be formed, since all non-nanotube components are water / organic solvents and are all removed upon evaporation of the wet film. Furthermore, in some cases, the heat treatment required to remove the solvent is typically at or below about 80° C., making it suitable for plastic substrate (and therefore R2R) processing.

[0055] According to some embodiments of the present invention, carbon nanotubes can be combined with one or more monohydric alcohols and one or more diols to form stable matrices in a variety of solvents. According to some embodiments, the one or more first solvents comprise between about 5-95% and the one or more second solvents comprise between about 5-95% by weight of the total formulation, or the one or more first solvents comprise between about 20-95% and the one or more second solvents comprise between about 5-80% by weight of the total formulation, or the one or more first solvents comprise between about 40% and about 95% by weight of the total formulation and the one or more second solvents comprise between about 5% and about 60% by weight of the total formulation, or the one or more first solvents comprise between about 50% and about 80% by weight of the total formulation and the one or more second solvents comprise between about 15% and about 50% by weight of the total formulation, or the one or more first solvents comprise between about 55% and about 75% by weight of the total formulation and the one or more second solvents comprise between about 15% and about 35% by weight of the total formulation. The compositions disclosed herein can also include water in addition to the first and second solvents.

[0056] Table 1 provides boiling point data for various monohydric alcohols and diols that may be used in accordance with certain embodiments of the present invention.

[0057] [Table 2] EXAMPLES

[0058] Example 1 – Slot die coating test The following fluid matrices were prepared using purified carbon nanotube paste (approximately 0.18% solids as determined by TGA): Cyclohexanol 30.32% Ethylene glycol 29.22% Water 12.9% Isopropanol 27.57%

[0059] The composition was mixed in a planetary centrifugal mixer followed by probe sonication. A stable supernatant composition was obtained / recovered after ultracentrifugation. The optical density (absorbance at 550 nm) of the matrix carbon nanotube composition was measured to be 14 and the concentration by mass balance was determined to be about 310 mg / L. The liquid was applied to a wet film of about 50 microns thickness on a slot die coater and the solvent was evaporated to give a dry film of about 2000 Ω / sq with a film transmittance of about 90% in a single application.

[0060] Example 2 - Dimatix Inkjet Printing The composition of Example 1 was diluted to approximately 20-70% solids using the described solvent blend and optimized inkjet parameters to promote stable jetting performance. Subsequent Dimatix inkjet printing produced transparent conductive traces with minimal passes.

[0061] Example 3 - Pattern transfer The pattern to be transferred was placed under the film to be printed. In the test case, the pattern to be transferred was a perforated sheet with mm-scale holes. A metal porous sheet was covered with a thin silicone film, on which the substrate film to be printed was placed, a "bird bar" of coating was placed on top of the film (with a gap of 1 mil or 4 mil depending on the test), beads of a flowable matrix of the composition described in Example 1 were deposited, and the wet film was cast on the fixed substrate film. Immediately observable was the pattern of the perforated sheet underneath that was transferred. Once the low viscosity, high boiling point solvent had evaporated, the wet substrate was removed from the silicone sheet and the wet film was held vertically to observe that the pattern remained fixed and did not run off. After evaporating the remaining solvent in an oven at about 80°C, it was observed that the pattern was indeed completely transferred to the dry film.

[0062] Example 4 - Screen Printing A second solvent blend formulation was prepared by combining the same purified carbon nanotube paste to obtain the following final solvent composition: Cyclohexanol 68.36% 1,2 Propanediol 20.36% Ethylene glycol 11.28%

[0063] The viscous carbon nanotube liquid was pipetted onto a 305 mesh screen, printed, and allowed to evaporate the solvent, followed by a single screen printing onto an ST504 polyester substrate, yielding a film with approximately 600 Ω / sq and a film transmittance of approximately 86%. This example shows that it is possible to produce a surfactant-, polymer-, and additive-free solvent mixture suitable for screen printing.

[0064] Example 5 - Neat NMP CNT dispersion The purified carbon nanotube paste used in Example 1 was added to neat n-methylpyrrolidone (NMP) and probe sonicated, then purified by ultracentrifugation to yield a dark ink with an optical density (absorbance measurement) of 38 at 550 nm.

[0065] Example 6 - Neat·Silene·CNT Dispersion The purified carbon nanotube paste used in Example 1 was added to Silene and probe sonicated, then purified by ultracentrifugation to yield a dark ink with an optical density (absorbance measurement) of 33 at 550 nm.

[0066] Example 7 – Silene-Solvent-Blend CNT Dispersion In the formulation described in Example 1, cyclohexanol was replaced with silane to provide a stable ink that could be slot-die coated.

[0067] Examples based on monohydric alcohols and diols Inks were prepared according to the following general formulation:

[0068] [Table 3]

[0069] The resulting ink was slot-die coated using a 1 mil bar on an 80 °C stage.

[0070] [Table 4]

[0071] Non-alcoholic ink An ink sample was prepared as shown in Ink Formulation B, using non-alcohol in place of the monohydric alcohol and diol in Ink Formulation A.

[0072] [Table 5]

[0073] The resulting ink was slot die coated using a 1 mil bar at a stage of 80° C. The test results obtained are shown in Table 3 below.

[0074] [Table 6]

[0075] The low boiling point solvents (IPA and water) in the ink were removed using a rotary evaporator (rotovap) to give a high concentration ink, which was then probe sonicated at 60% amplitude for 20 seconds. The resulting concentrated ink was recoated using a 1 mil bar at an 80° C. stage, and the test results obtained are shown in Table 4 below.

[0076] [Table 7]

[0077] The samples were prepared and tested according to the following procedure: The substrate (Melinex ST504) is a high gloss, heat stabilized polyester film and was used as received without any pretreatment such as corona treatment or rinsing.

[0078] The ink was coated using a Bird bar with a gap thickness of 1 micron, with the ink applied to a fixed substrate on a platen preheated to a surface temperature of 80° C., and a coating speed of about 200 mm / s. The ink liquid evaporated on the heated stage, and upon evaporation, only the carbon nanotube film composition remained on the ST504 substrate. No post-processing was performed except for further heating in the oven at about 90° C. to ensure complete evaporation of the solvent.

[0079] Film properties were measured including sheet resistance using an eddy current meter, stack transmittance and stack haze using a haze meter. Each sample was prepared once and four locations were measured across the film to determine sheet resistance, and two locations were measured to determine stack transmittance and haze. The ST504 substrate alone measured T at 89.5% and H at 0.3%.

[0080] To prepare the ink, a CNT paste composition is used that is comprised of carbon nanotube material functionalized with a plurality of oxygen-containing functional groups, the paste containing about 0.1% to 2.5% by weight of carbon nanotubes. According to certain embodiments, the CNT paste may be prepared according to the process disclosed in PCT / US2021 / 053319 or a similar process. A solvent blend consisting of water and / or a polar solvent is probe sonicated in the presence of the prepared ink-liquid blend for a total of about 0.5 seconds per mL of ink, followed by centrifugation.

[0081] According to a particular embodiment, the composition of the functionalized carbon nanotube material in the final fluid matrix is ​​from about 50 mg / L to about 1000 mg / L.

[0082] In a similar manner, the paste composition and fluid matrix prepared above can be transferred to a rotary evaporator to remove the low boiling point solvent components, and the fluid matrix can be concentrated to only the high boiling point components. Such compositions are useful for applications requiring viscosities of about 20 cP to about 500-3,000 cP or more, such as screen printing.

[0083] Upon reviewing the description and embodiments of the present invention, those skilled in the art will understand that modifications and equivalent substitutions can be made in implementing the present invention without departing from the essence of the present invention. Therefore, the present invention is not limited by the embodiments expressly described above, but only by the following claims.

Claims

1. A stable carbon nanotube fluid matrix comprising carbon nanotubes dispersed in a solvent mixture comprising a first solvent and a second solvent, (a) the first solvent has a boiling point below 100°C and the second solvent has a boiling point above 100°C; or (b) the first solvent is a monohydric alcohol and the second solvent is a diol; Stable carbon nanotube fluid matrix.

2. 10. The stable carbon nanotube fluid matrix of claim 1, which is stable over a concentration range of about 1 mg / L to about 3000 mg / L.

3. 3. The stable carbon nanotube fluid matrix of claim 1 or 2, wherein the first solvent is selected from the group consisting of hexane, isopropanol, n-propanol, methanol, ethanol, benzene, acetonitrile, tetrahydrofuran, cyclohexanol, and mixtures thereof.

4. 2. The stable carbon nanotube fluid matrix of claim 1, wherein the second solvent is selected from the group consisting of propylene glycol methyl ether, dimethylformamide, n-methylpyrrolidone, dimethylacetamide, dimethylsulfoxide, silane, butanol, toluene, xylene, chlorobenzene, dichlorobenzene, ethylene glycol, propylene glycol, glycerol, methyl lactate, cyclohexanol, and mixtures thereof.

5. 5. The stable carbon nanotube fluid matrix of claim 4, wherein the first solvent is selected from the group consisting of isopropyl alcohol, ethanol, n-propanol, methanol, and mixtures thereof.

6. 5. The stable carbon nanotube fluid matrix of claim 4, wherein the second solvent is cyclohexanol, ethylene glycol, or propylene glycol.

7. 10. The stable carbon nanotube fluid matrix of claim 1, wherein the solvent mixture comprises at least one monohydric alcohol and at least one diol.

8. 10. The stable carbon nanotube fluid matrix of claim 1, wherein the solvent mixture comprises cyclohexanol, isopropyl alcohol, and ethylene glycol.

9. 10. The stable carbon nanotube fluid matrix of claim 1, wherein the stable carbon nanotube fluid matrix is ​​free of surfactants, dispersing aids, and polymers.

10. 10. The stable carbon nanotube fluid matrix of claim 1, wherein the solvent mixture consists essentially of water, a first solvent, and a second solvent.

11. 10. The stable carbon nanotube fluid matrix of claim 1, wherein the carbon nanotubes are functionalized.

12. 10. The stable carbon nanotube fluid matrix of claim 1, wherein the carbon nanotubes are functionalized with a plurality of oxygen-containing functional groups.

13. 10. The stable carbon nanotube fluid matrix of claim 1, wherein the carbon nanotubes are selected from the group consisting of single-walled carbon nanotubes, multi-walled carbon nanotubes, and mixtures thereof.

14. 10. The stable carbon nanotube fluid matrix of claim 1, wherein the solvent mixture comprises ethylene glycol, cyclohexanol, and propylene glycol.

15. The stable carbon nanotube fluid matrix of claim 1 , wherein the solvent mixture comprises silene.

16. A stable carbon nanotube fluid matrix comprising functionalized carbon nanotubes dispersed in a solvent mixture, comprising: The stable carbon nanotube fluid matrix is ​​free of surfactants, dispersing aids, and polymers; The stable carbon nanotube fluid matrix is ​​stable up to a concentration of about 3000 mg / L.

17. 1. A method for producing a stable carbon nanotube fluid matrix, comprising: providing a carbon nanotube composition comprising oxidized carbon nanotubes; dispersing the carbon nanotube composition in a solvent mixture comprising a first solvent and a second solvent; Including, (a) the first solvent has a boiling point below 100°C and the second solvent has a boiling point above 100°C; or (b) the first solvent is a monohydric alcohol and the second solvent is a diol, providing a stable carbon nanotube fluid matrix; method.

18. 20. The method of claim 17, further comprising removing the first solvent from the carbon nanotube fluid matrix to produce a concentrated carbon nanotube fluid matrix.

19. The method of claim 17 or 18, wherein the first solvent is selected from the group consisting of hexane, isopropanol, n-propanol, methanol, ethanol, benzene, acetonitrile, tetrahydrofuran, cyclohexanol, and mixtures thereof.

20. The method of claim 17, wherein the second solvent is selected from the group consisting of propylene glycol methyl ether, dimethylformamide, n-methylpyrrolidone, dimethylacetamide, dimethyl sulfoxide, silane, butanol, toluene, xylene, chlorobenzene, dichlorobenzene, ethylene glycol, propylene glycol, glycerol, methyl lactate, cyclohexanol, and mixtures thereof.

21. 1. A method of coating or printing on a substrate, comprising: providing a carbon nanotube-rich fluid matrix according to claim 18; printing or coating the high concentration carbon nanotube fluid matrix onto a substrate.

22. 22. The method of claim 21, wherein the concentrated carbon nanotube fluid matrix is ​​screen printed onto the substrate.

23. 23. The method of claim 21 or 22, wherein the solvent mixture comprises ethylene glycol, cyclohexanol, and propylene glycol.

24. A stable graphene fluid matrix comprising graphene dispersed in a solvent mixture comprising a first solvent and a second solvent, (a) the first solvent has a boiling point below 100°C and the second solvent has a boiling point above 100°C; or (b) the first solvent is a monohydric alcohol and the second solvent is a diol; Graphene fluid matrix.