CN115651449A

CN115651449A - Conductive composite material, conductive ink and application

Info

Publication number: CN115651449A
Application number: CN202211378403.0A
Authority: CN
Inventors: 张好斌; 邓志明; 汤萍萍; 李禄禄; 于中振
Original assignee: Beijing University of Chemical Technology
Current assignee: Beijing University of Chemical Technology
Priority date: 2022-11-04
Filing date: 2022-11-04
Publication date: 2023-01-31

Abstract

The invention provides a conductive composite material, conductive ink and application, wherein the conductive composite material comprises: an inner core portion and an outer layer portion; the inner core portion includes a two-dimensional transition metal carbon/nitrogen compound represented by the general formula: m _n+1 X _n T, wherein n is an integer of 1 to 3; m is selected from Sc, ti, zr, V, nb, cr or Mo; x represents a C or N element; t represents one or more reactive functional groups; the outer layer section includes a polymer of an aromatic polyphenol having two or more phenolic hydroxyl groups.

Description

Conductive composite material, conductive ink and application

Technical Field

The invention relates to the field of materials, relates to a conductive composite material, and more particularly relates to an MXene/poly-polyphenol based conductive material and a preparation method thereof.

Background

In recent years, rapid development of new electronic technologies such as 5G communication technology and internet of things has led to the development of high integration, miniaturization and light weight of various high-performance portable electronic devices, and has also posed a greater challenge to the preparation of flexible, thin and designable conductive wires, films and patterned materials, such as electromagnetic materials like antennas, electromagnetic interference (EMI) shielding films and coatings, filters, and the like.

It is clear that high density, difficult to process metallic materials are difficult to meet the fabrication of these highly integrated, thin, programmable conductive materials. Conductive inks are important for thin, programmable, conformal EMI shielding and have wide applications in many fields such as radio frequency identification (FRID), conductive electrodes, smart packaging, anti-counterfeiting, biosensing, etc., and therefore, the development of high performance conductive inks has great significance and economic value.

Further, it is known that two-dimensional transition metal carbon/nitrides (MXenes) have great potential in the fields of energy, sensing, water treatment, biology, particularly EMI shielding, etc. due to their excellent electrical conductivity, unique nano-layered structure and surface polarity. Researchers have thus far prepared various MXene-based conductive fibers, films, aerogels, and composites with EMI shielding properties comparable to or even superior to metal and graphene materials, and also focused on the study of other properties of these materials, such as mechanical properties, etc. For example, cited document 1 provides a stretchable two-dimensional nano conductive material (MXene) -based composite material excellent in stability, which has excellent electrical conductivity and electromagnetic shielding property, while having improved stability of electrical conductivity upon dynamic deformation such as stretching. The cited document 2 provides an improved fiber having a core-sheath composite structure based on a two-dimensional nanomaterial, particularly on an MXene material, having a core formed of a two-dimensional nanomaterial and a sheath of a polyamide having an aromatic structure, and having not only excellent electromagnetic shielding properties but also ultrahigh tensile properties and toughness as well as excellent electrical conductivity of the resulting fiber.

Although the study of the electromagnetic shielding property and mechanical property of the MXene-based composite material has been greatly progressed, the study of the MXene conductive ink is being made. Unlike graphene, MXene, which has surface polarity, is generally considered more favorable for the formation of well-dispersed high-performance polar inks, and thus, for the design and fabrication of functional electronics and patterned coatings.

Citation 3 discloses an MXene/ink high sensitivity sensor (strain or temperature sensor) containing no high-valent metal ions, which is a composite structure of an MXene material and an ink, and which is capable of improving the sensor sensitivity because the MXene material has a small size and a small number of layers so as not to contain high-valent metal ions.

Citation 4 provides a highly efficient thermally conductive UV-LED ink comprising a modified MXene material, which polymerizes a melamine-formaldehyde prepolymer in situ with exfoliated MXene to obtain a melamine-formaldehyde modified MXene.

Reference 5 discloses a water-based MXene-based energy storage electrode material 3D printing ink, wherein the 3D printing ink includes oxygen-free water, MXene, an auxiliary agent, and an energy storage electrode active material.

Further, it is known that knife coating is advantageous to achieve large area application of ink, while screen printing and extrusion printing techniques facilitate the design of fine patterned conductive coatings. These processing methods have high requirements on the viscosity and rheological properties of the ink. In the prior art, thickening of an MXene ink is generally achieved by adding a thickener such as nanopowder or polymer, for example, cited document 6 discloses an MXene-based electrothermal ink comprising MXene nanosheets, an aqueous thickener xanthan gum and water, wherein: the mass fraction of MXene is 5-35%, and the mass ratio of MXene to xanthan gum is (300-200) to (1-10). Citation 7 discloses a water-based MXene nanocellulose-based functional ink, which is characterized in that: comprises the following components in a mass ratio of 10-90: as the MXene nanosheets and nanocelluloses of 10 to 90, water-soluble polymers and the like can be used.

Although the use of thickening components can adjust the viscosity of the ink to the requirements of the printing mode, the conductivity of the MXene ink is reduced, and the quality and density of the coating are increased.

In addition, other applications of the MXene ink include gel materials suitable for 3D printing (forming electrodes), applications of infrared characteristics thereof, and the like, and for example, reference 8 discloses a 3D aerogel base based on MXene and having a double camouflage function of infrared stealth and visible light.

Therefore, inks based on two-dimensional conductive nanomaterials, particularly on MXene materials, have not been said to be entirely sufficient, despite the above-mentioned research.

Cited documents:

cited document 1: CN 113096853A

Citation 2: CN 114438618A

Citation 3: CN111595363A

Cited document 4: CN 114163867A

Cited document 5: CN 114621633A

Cited document 6: CN113372765A

Cited document 7: CN 114958094A

Cited document 8: CN 114705082A

Disclosure of Invention

Problems to be solved by the invention

As described above, inks based on two-dimensional conductive nanomaterials, particularly MXene materials, have been studied to some extent in terms of properties such as electrical/thermal conductivity, dispersibility, and the like.

However, another challenging problem is that MXene-containing materials have poor rheology due to weak interlayer interaction, e.g. MXene-containing inks typically do not have high ink viscosity in the required amount range, which is why MXene inks are processed with more applications.

Other techniques requiring high ink viscosity, such as silk-screen printing, extrusion printing, gravure printing, blade coating, etc., are rarely reported, and thus, the application approaches of high-quality printing using MXene-based ink are also severely limited.

Further, more importantly, the problem of easy oxidation of MXene ink is not effectively solved. And the MXene conductive coating developed by the method still has the problems of low concentration of a conductor, limited infrared emissivity, short service life, unsuitability for long-term use and the like.

In addition, although an infrared stealth product is produced by utilizing the properties of MXene that the heat conduction is high and the infrared emission is low, such as in cited document 8. But it is for this reason that MXene has limited infrared security applications.

Only, based on the above-mentioned current state and problems of the prior art, the present invention provides an ink based on two-dimensional conductive nanomaterial, especially MXene material, which greatly improves the rheological properties thereof without significantly damaging the electrical properties thereof, and can realize higher system viscosity to be suitable for a wide range of printing scenarios (screen printing, extrusion printing, gravure printing, blade coating, etc.) even though the amount of the two-dimensional conductive nanomaterial is reduced and no additional thickening component is used.

Furthermore, the invention can obtain the material with the changed infrared emission characteristic by flexibly adjusting the thickness of the coating layer and the like by coating the surface of the two-dimensional conductive nano material, so that the infrared emission rate is obviously enhanced, the adjustable infrared emission characteristic can be realized, and the material has practical application value in the aspects of infrared anti-counterfeiting and the like.

Means for solving the problems

After long-term research, the inventor finds that the technical problems can be solved through implementation of the following technical scheme:

[1] the present invention first provides a conductive composite, wherein the conductive composite comprises:

an inner core part and an outer layer part;

the inner core portion includes a transition metal carbon/nitrogen compound represented by the general formula:

M _n+1 X _n T

wherein n is an integer of 1 to 3; m is selected from Sc, ti, zr, V, nb, cr or Mo; x represents a C or N element; t represents one or more reactive functional groups,

the outer layer section includes a polymer of an aromatic polyphenol having two or more phenolic hydroxyl groups.

[2] The conductive composite according to [1], wherein the conductive composite has a conductivity of 0.1 to 3000S/cm.

[3] The conductive composite according to [1] or [2], wherein M of the two-dimensional transition metal carbon/nitrogen compound includes Ti, and the two-dimensional transition metal carbon/nitrogen compound has a layered structure of 1 to 5 layers.

[4] The conductive composite according to any one of [1] to [3], wherein the two-dimensional transition metal carbon/nitrogen compound has an average size of 2000nm or less.

[5] The conductive composite material according to any one of [1] to [4], wherein the aromatic polyphenol further has one or more carboxyl groups or lactone groups formed by the carboxyl groups.

[6] The conductive composite according to any one of [1] to [5], wherein the aromatic polyphenol is selected from one or more of tannic acid, ellagic acid, 3, 4-dihydroxyphenylalanine, or a derivative thereof.

[7] The conductive composite according to any one of [1] to [6], wherein the average thickness of the outer layer portion is 0.5 to 8nm.

[8] Further, the present invention also provides a conductive ink, wherein it comprises the conductive composite according to any one of [1] to [7].

[9] The ink according to [8], wherein the content of the conductive composite material is 10 to 100g/L.

[10] In addition, the present invention provides an electromagnetic wave regulating conductive micro-grid, wherein it comprises a raw material derived from the conductive composite material according to any one of claims [1] to [7] or is obtained by printing using the ink according to claim [8] or [9], wherein the pitch of the conductive micro-grid is 75 to 1000 μm.

[11] In addition, the invention also provides an infrared anti-counterfeiting pattern, wherein the infrared anti-counterfeiting pattern comprises raw materials derived from the conductive composite material as described in any one of the items [1] to [7] or is obtained by printing the anti-counterfeiting pattern by using the ink as described in the item [8] or the item [9], wherein optionally, the ink comprises at least two different conductive composite materials.

[12] The electromagnetic wave regulating conductive micro-grid or anti-counterfeiting pattern according to [10] or [11], wherein the printing is selected from screen printing, offset printing, gravure printing, extrusion printing or blade coating printing.

ADVANTAGEOUS EFFECTS OF INVENTION

Through the use of the technical scheme, the invention can obtain the following technical effects:

1) By carrying out surface wrapping on the aromatic polyphenol on the two-dimensional conductive nano material, the rheological property of the material can be greatly improved while the conductivity of the material is not obviously damaged, and particularly, in the formula of the conductive ink, the requirement of high-viscosity printing can be met by using the reduced conductive composite material.

2) By the surface coating of the aromatic polyphenol, the infrared emission of the two-dimensional conductive nano material can be improved, and the obtained printed pattern can obtain an infrared anti-counterfeiting effect.

3) The ink provided by the invention can meet the requirements of low solid content and high viscosity without using thickening or thickening auxiliary agent components in the prior art, thereby avoiding the performance reduction of conductivity and the like caused by the use of the auxiliary agent components in the prior art.

4) The surface of the aromatic polyphenol is wrapped on the two-dimensional conductive nano material, so that the problem of oxidation of the two-dimensional conductive nano material in preparation of conductive ink and practical application can be greatly improved.

Drawings

FIG. 1: comparison of morphology/antioxidant Properties of inventive example 1 and comparative example 1

FIG. 2: comparison of the viscosity of the systems of inventive example 1 and comparative example 1

FIG. 3: comparison of morphology/antioxidant Properties of inventive example 2 with comparative example 1

FIG. 4 is a schematic view of: polyester fabric treated in embodiment 4 of the invention

FIG. 5 is a schematic view of: electromagnetic shielding Properties of polyimide film treated in example 5 of the present invention

FIG. 6: characteristics of electromagnetic shielding device production in embodiment 6 of the present invention

FIG. 7: design, preparation and identification demonstration of preparing infrared anti-counterfeiting coating in embodiment 7 of the invention

Detailed Description

The present invention will be described in detail below. The technical features described below are explained based on typical embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples. It should be noted that:

in the present specification, the unit names used are international standard unit names unless otherwise specified.

In the present specification, "%" is used to mean weight or mass percent unless otherwise specified.

In the present specification, the numerical range represented by "numerical value a to numerical value B" means a range including the end points of numerical values a and B.

In the present specification, the numerical ranges indicated by "above" or "below" refer to numerical ranges including the number.

In the present specification, the term "may" includes both the case where a certain process is performed and the case where no process is performed.

In the present specification, the expression "substantially" or "substantially" is used to indicate that the error from the reference is within 1%.

In the present specification, the term "room temperature" refers to a temperature condition of 25 ℃.

Reference in the specification to "some specific/preferred embodiments," "other specific/preferred embodiments," "embodiments," and so forth, means that a particular element (e.g., feature, structure, property, and/or characteristic) described in connection with the embodiment is included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it is to be understood that the described elements may be combined in any suitable manner in the various embodiments.

The invention mainly provides a conductive composite material based on a two-dimensional conductive nano material, which is subjected to surface modification, in particular to surface coating. The present invention is obtained mainly based on the following findings:

the existing two-dimensional transition metal carbon/nitrogen compound has the characteristics of weak viscosity characteristic and low infrared emission efficiency. It has been found that inclusion by using a polymer of an aromatic polyphenol externally thereof greatly improves rheological properties and oxidation resistance of the conductive composite, particularly, when the conductive composite is used in an ink, particularly a water-based ink, it not only has good dispersibility, but also causes a large increase in viscosity of the entire system even at a low amount, which may be due to surface characteristics of the aromatic polyphenol and a certain conductivity based on a conjugated system. On the other hand, through the wrapping treatment, the conductive composite material and the pure two-dimensional transition metal carbon/nitrogen compound are well combined, so that the infrared emission efficiency of the conductive composite material is obviously improved compared with that of the pure two-dimensional transition metal carbon/nitrogen compound, the infrared emission efficiency can be adjusted through the thickness of the outer layer part of the wrapping material and the like, the good infrared emission characteristic of the transition metal carbon/nitrogen compound material which is originally considered to be an infrared shielding material is given, and the conductive composite material can be used for preparing infrared anti-counterfeiting patterns. And the oxidation resistance of the conductive composite material is improved, so that the quality stability of the obtained printed product is correspondingly and greatly improved.

< first aspect >

In a first aspect of the invention, a conductive composite is provided, wherein the conductive composite is particularly suitable for use in the preparation of conductive inks.

The conductive composite material has a core-shell structure, and specifically, the conductive composite material has an inner core part and an outer layer part; the inner core portion includes a two-dimensional transition metal carbon/nitrogen compound represented by the general formula:

M _n+1 X _n T

Transition metal carbon/nitrogen compound

The two-dimensional conductive nano material in the inner core part of the invention can be selected from one or more two-dimensional transition metal carbon/nitrogen compounds, and more preferably, a two-dimensional transition metal carbon/nitrogen compound with hydrophilicity or modified by hydrophilicity can be used.

In some particular embodiments the transition metal is selected from early transition metals. Therefore, in the present invention, the two-dimensional nano conductive material is preferably a material having the following general formula:

M _n+1 X _n T

wherein n is an integer of 1 to 3; m is selected from Sc, ti, zr, V, nb, cr or Mo; x represents a C or N element; t represents one or more reactive functional groups, the type of which is not particularly limited and may be selected from-OH, -COOH, -F, O ^2- 、-NH ₄ ⁺ Or NH ₃ One or more of the groups. It should be noted that some of the prior arts use the above "T" as "T" too _x "means, but those skilled in the art will understand that the two expressions have equivalent physical and chemical meanings.

Further, in the present invention, for the two-dimensional conductive nanomaterial, in some exemplary embodiments, a two-dimensional conductive nanosheet typified by MXene(s) may be selected. MXene(s) are obtained by etching weakly bonded A site elements (such as Al atoms) in the MAX phase mainly through HF acid or a mixed solution of hydrochloric acid and fluoride. The graphene nano-film has the characteristics of high specific surface area and high conductivity of graphene, and has the advantages of flexible and adjustable components, controllable minimum nano-layer thickness, hydrophilicity and the like, so that the graphene nano-film is preferable. The present invention is not particularly limited with respect to a specific method for synthesizing the above-described two-dimensional conductive nanomaterial, and a synthesis or preparation method that is conventional in the art may be used.

More specifically, in some embodiments of the invention, M is selected from Ti, X is selected from C, and T is Q _y Wherein Q represents-OH, -COOH, -F, or O ^2- 、-NH ⁴⁺ Or NH ₃ One or more of the groups, and the total number y of these groups is not particularly limited, in relation to the preparation method for obtaining MXene(s).

Further, for the two-dimensional conductive nanomaterial of the present invention to be a multilayered sheet having a certain size in general, in some preferred embodiments, it may be adjusted by a synthetic process or a processing method so as to have a suitable number of layers, for example, the two-dimensional conductive nanomaterial of the present invention, particularly MXene, which may have a layered structure of 10 layers or less, preferably 1 to 5 layers, and more preferably 1 to 3 layers.

Further, there is no particular limitation in principle on the size of the two-dimensional conductive nanomaterial of the present invention, but from the viewpoint of economy of manufacture and convenience of subsequent coating treatment and dispersion in ink, in some specific embodiments, the two-dimensional conductive nanomaterial may have an average size of not more than 2000nm, preferably 200 to 1800nm, more preferably 300 to 1500nm or 350 to 1400nm. The size of the two-dimensional conductive nanomaterial in the present invention refers to the length of the widest portion in the major plane of the two-dimensional material.

Furthermore, the core part of the invention can also use other conductive/electromagnetic shielding materials besides the two-dimensional conductive nano material without affecting the effect of the invention.

The other conductive material is not particularly limited, and may be selected from one-dimensional nano conductive materials, other two-dimensional nano materials other than the two-dimensional transition metal carbon/nitrogen compound, and optional three-dimensional nano conductive materials. Examples of such materials include metal nanowires, metal nanoparticles, carbon nanomaterials (carbon nanotubes, graphene), and the like.

In some specific embodiments of the present invention, the content of the two-dimensional transition metal carbon/nitrogen compound in the core portion of the present invention is 80% or more, preferably 85% or more, further preferably 90% or more, and more preferably 95% or more, based on the total mass of the conductive material.

Aromatic polyphenol compound

In the present invention, the outer layer portion for covering the inner core portion includes a polymer formed of an aromatic polyphenol compound.

The aromatic polyphenol compound of the present invention has two or more hydroxyl groups and at least two phenolic hydroxyl groups directly bonded to an aromatic ring. In some preferred embodiments of the present invention, the phenolic hydroxyl groups have 2 to 30, more preferably 3 to 20, and still more preferably 4 to 15. The presence of a plurality of phenolic hydroxyl groups on the one hand can impart good surface hydrophilicity to the polymer after polymerization, and on the other hand, the plurality of phenolic hydroxyl groups also contributes to the polymerization activity requirements.

Further, the aromatic ring of the present invention may be any of carbocyclic rings having aromaticity, aromatic rings having hetero atoms (N, S, O, or the like), and the like in some specific embodiments. And in some preferred embodiments such aromatic rings are carbocyclic aromatic rings having 6 to 14 carbon atoms in the aromatic ring, such as benzene rings, naphthalene rings, and the like.

Further, each of the aromatic polyphenol compounds may have one or more of the aromatic ring structures. In the present invention, since a large conjugation effect can be formed due to the presence of the aromatic structure, the obtained polymer is also imparted with a certain conductivity.

The aromatic polyphenol compound of the present invention may further have one or more carboxyl groups, and in some specific embodiments, it may have 1 to 15 carboxyl groups, preferably 2 to 10 carboxyl groups, from the viewpoint of polymerizability. These carboxyl groups may be present in the form of free or free carboxyl groups or may be present in the form of (endo) esters with the surrounding hydroxyl groups. In addition, in some embodiments of the present invention, the aromatic polyphenol compound may not contain an amino group or a nitrogen-containing group, so as not to reduce the polymerization reactivity by the salt formation effect.

Further, as the aromatic polyphenol compound which may be used in some preferred embodiments of the present invention, one or more of tannic acid, ellagic acid, 3, 4-dihydroxyphenylalanine or derivatives thereof may be exemplified. The derivatives include salts of these, alkyl-substituted compounds having 1 to 10 carbon atoms, halogen-substituted compounds, and compounds obtained by oxidizing (a part of) hydroxyl groups thereof.

Aromatic polyphenol polymer

The aromatic polyphenol polymer of the present invention is obtained by self-polymerization of the aromatic polyphenol compound, and such self-polymerization can be usually carried out under an appropriate pH condition. For the suitable pH values, alkaline conditions are generally possible, for example pH values above 7 and below 10.

The method for adjusting the pH is not particularly limited in the present invention, and the pH can be adjusted by using an alkaline substance or a buffer system. In some preferred embodiments, the method for adjusting pH according to the present invention may use a TAPS buffer solution, a Bicine buffer solution or a Tris-HCl buffer solution, preferably a Tris-HCl buffer solution having a pH of 7.5 to 10.

In some specific embodiments of the present invention, the aromatic polyphenol compound may be dissolved in an aqueous solution system with the pH adjusted, and then reacted at room temperature for 0.2 to 10 hours, preferably 0.5 to 6 hours, preferably under stirring, to obtain an aromatic polyphenol polymer.

Further, such a polymer is usually mainly composed of an oligomer, and for example, a polymer composed of 2 to 20 monomers, preferably 2 to 10 monomers, and more preferably 3 to 5 monomers is used as a main component. In addition, a crosslinked structure through a hydrogen bond or a chemical bond may also be present in these polymers.

In addition, optionally, a catalyst may be used in the above polymerization reaction to promote the progress of the polymerization, if necessary, and a typical catalyst that can be used is a metal-based catalyst, for example, a copper-based catalyst or the like.

Conductive composite material

The conductive composite material is obtained by wrapping the aromatic polyphenol polymer outside the inner core layer comprising the transition metal carbon/nitrogen compound.

There is no particular limitation on the manner of coating in principle.

In some specific embodiments of the present invention, the material for forming the core part may be put into an aqueous solution, and then the aromatic polyphenol compound is polymerized under the pH condition described above, and thus, the inclusion of the core part by the polymer is also completed at the same time of the polymerization.

In other embodiments of the present invention, the aromatic polyphenol compound may be polymerized, and the material forming the core portion may be added later in the polymerization or after the polymerization is completed, so that the polymer wraps the surface of the material forming the core portion, and optionally, the polymerization system may be diluted before the material forming the core portion is added, so as to obtain a suitable system viscosity for facilitating the compounding of the polymer and the material forming the core portion. At this time, the material for forming the core portion may be added in the form of a suspension at the time of the above addition, and further, may be reacted at room temperature for 18 to 36 hours to complete the inclusion of the core portion.

For the product after the coating, the conductive composite material can be finally separated by the methods of centrifugation, cleaning, drying and the like.

The amount of the aromatic polyphenol compound (polymer) used in the above coating process may be, in some specific embodiments, 1 to 50 mass%, preferably 3 to 40 mass%, more preferably 5 to 30 mass%, and still more preferably 7 to 20 mass% of the total mass of the material forming the core portion.

The thickness of the outer layer portion of the conductive composite material can be adjusted by adjusting the amount ratio of the aromatic polyphenol compound (polymer) to the core-forming material, and in some specific embodiments of the present invention, the average thickness of the outer layer portion may be 0.5 to 8nm, preferably 0.8 to 6nm, more preferably 1 to 4nm or 1.2 to 3nm, or the like.

Further, the conductive composite material according to the present invention is mainly or entirely formed by coating a surface of a single sheet of the two-dimensional transition metal carbon/nitrogen compound, or may be formed by aggregating several of the single particles by adsorption or electrostatic interaction to form secondary particles, and the secondary particles may be newly dispersed into the single particles by mechanical force or the like.

In addition, the conductive composite material obtained by the present invention still has good conductivity, which may be related to the proper thickness of the outer layer part of the conductive composite material and the certain conductivity due to the electron conjugation. In some specific embodiments of the invention, the electrically conductive, electro-composite material of the present invention has an electrical conductivity of 0.1 to 3000S/cm, preferably 0.2 to 2800S/cm, 0.3 to 2500S/cm, 0.4 to 2000S/cm, 0.5 to 1800S/cm, 0.6 to 1500S/cm, 0.7 to 1300S/cm, 0.8 to 1000S/cm and the like, including 1, 5, 10, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 1200, 1600, 2100S/cm and the like, as examples.

< second aspect >

In a second aspect of the present invention, there is provided a conductive ink comprising the conductive composite provided in the first aspect above.

For the conductive ink, it may further include a dispersant, an optional assistant, and the like, in addition to the above-described conductive composite material.

In some specific embodiments of the present invention, the dispersant may be a water-based dispersant, and the water-washing dispersant may be water or a mixed system of water and a water-soluble alcohol. As such alcohols, methanol, ethanol and the like are included by way of example. In some preferred embodiments of the present invention, the water content in the aqueous dispersant may be 85% by volume or more, and more preferably 90% by volume or more.

Other auxiliaries in the ink of the present invention are not particularly limited, and may generally include pigments, surfactants, film-forming aids, viscosity modifiers (aqueous thickeners), and the like. It should be noted that the conductive ink of the present invention can obtain a desired high viscosity at a low content even without using a thickener.

With respect to the content of the conductive composite in the conductive ink of the present invention, in some specific embodiments, the content of the conductive composite is 10 to 100g/L, preferably 15 to 70g/L, and more preferably 20 to 60g/L, based on the total mass of the conductive ink.

In addition, the amount of the above-mentioned other additives that can be used is not particularly limited and may be adjusted according to the actual printing process or the requirements of the target product, and in some preferred embodiments, the amount of the other additives may be 10 mass% or less, preferably 8 mass% or less, and more preferably 5 mass% or less, based on the total mass of the conductive ink.

< third aspect >

In a third aspect of the present invention, there is provided a method of printing the conductive ink of the second aspect described above, and a printed pattern and effects of the pattern obtained thereby.

As described above, the conductive composite material according to the present invention or the ink containing the same may be applied to a printing method having a wide viscosity range, and particularly, the conductive ink according to the present invention may have a high viscosity even if a two-dimensional conductive nanomaterial is contained in a smaller amount than that of the prior art, even without additionally using a thickener.

Printing methods suitable for the conductive ink of the present invention include screen printing, extrusion printing, gravure printing, blade coating, and the like.

In addition, the printing substrate to which the conductive ink of the present invention is applied is not particularly limited, and may include: paper substrates, polymer (film) substrates, textile substrates, semiconductor substrates, metal substrates, wood substrates, and the like.

For the pattern of the present invention, it may include a raw material derived from one or more of the conductive composites or be formed of the above-described conductive ink. In some embodiments, the printing of the conductive ink described above can be to a pattern having a striped grid, which optionally can be applied as an electromagnetic wave-modulating conductive micro-grid element, through the use of which an adjustment of the direction of propagation and/or intensity of the electromagnetic wave can be achieved. In addition, in some preferred embodiments of the invention, the spacing between the stripes in the element may be controlled to be 1000 μm or less, preferably 75 μm or more, typically, for example, 100 to 900 μm, 200 to 800 μm, and the like. In addition, the width of the stripe is not particularly limited in principle, and may be adjusted according to the adjustment routine in the art and the target requirement.

In other specific embodiments of the present invention, the pattern of the present invention, which may include a raw material derived from one or more of the conductive composites, may have a difference in thickness of the outer layer therebetween. And these patterns may be designed in advance by, for example, drawing software (CAD).

In a preferred embodiment, the pattern of the present invention may be a series of patterns or a set of patterns, and when they occur together, the conductive composite may be different in different patterns. In some preferred embodiments, such a pattern may be a dot-matrix or array-like pattern.

In another preferred embodiment, the pattern of the present invention may be such that in one overall pattern, different regions use different said conductive composites.

For the patterns obtained based on the conductive composite material, the outer layer part provided by the invention exists, so that the infrared emission efficiency of the material is greatly improved, and further, the infrared emission efficiency of different materials is different due to different outer layer part thicknesses, so that the infrared characteristic identification and anti-counterfeiting application are realized. Therefore, the conductive composite material changes the cognition that the conventional transition metal carbon/nitrogen compound is only used for infrared shielding (infrared stealth) or a temperature sensor, maintains good conductivity and electromagnetic shielding property, and can be used for infrared emission, particularly for an anti-counterfeiting scene of infrared emission characteristic identification.

For the infrared security device of the present invention, in some embodiments, it may be present in the topmost layer of the security article, or in a functional layer below the topmost layer, which further increases security and concealment. More specifically, the infrared anti-counterfeiting pattern of the invention is used for one or more of (valuable) commodities, securities, certificates, stamps, printed matters with limited issue characteristics, calligraphy and painting, and the like.

Examples

The invention will be further illustrated by the following specific examples:

example 1

The embodiment provides MXene/poly-polyphenol conductive ink and a preparation method thereof, wherein the preparation method of the MXene/poly-polyphenol conductive ink comprises the following steps:

(1) First, 5g of Ti ₃ AlC ₂ Type MAX was put into complex solvent of hydrochloric acid (9M, 100mL)/lithium fluoride (99%, 8 g) in portions, and reacted for 48 hours with stirring (300 rpm) at 35 ℃.

(2) After the reaction is completed, the reaction solution is poured into 1200mL of deionized water to terminate the reaction, and the reaction solution is washed with water for many times and centrifuged until the pH value is about 6. And dispersing the centrifugally collected slurry in 300ml of deionized water, and carrying out ultrasonic treatment at 10 ℃ and 40kHz for 1h to obtain a few layers of MXene by stripping. Centrifuging the ultrasonically stripped mixed solution at 3500rpm for 60min to obtain an upper suspension to remove the non-etched MAX residues, and collecting lower slurry at 9000rpm for 45min to remove the small MXene nanosheets with low conductivity. The MXene nano-sheet has a diameter range of 100-1500nm, and an average diameter of 450nm. The MXene film is subjected to suction filtration, and the conductivity of the MXene is measured to be 5000S cm ^-1 。

(3) 40mg of tannic acid was put into Tris-HCl buffer (pH =7.5, 200 mL) and kept stirring at 400 rpm.

(4) 5mL of a 40mg/mL MXene dispersion was slowly added to the tris solution, and the reaction was continued for 16 hours. The reaction was then centrifuged at 9000rpm for 30min and multiple water washes were centrifuged until the supernatant had a pH of 5-7. And pouring out the supernatant to obtain MXene slurry with the lower layer being modified by polyphenol.

(5) Extruding 1mL of slurry by adopting a single-channel injection pump, calculating the solid content of the slurry after freeze drying, and then diluting and stirring the slurry by adding rated deionized water to obtain the titanium carbide MXene/polyphenol conductive ink with specific solid content.

Also, the ink can be stored at room temperature for 1 month without severe oxidation (fig. 1). The ink achieved a large adjustment of viscosity between 0.5 and 14000pa.s depending on the concentration change (figure 2). The conductivity of the MXene/polyphenol film was measured to be about 800S/cm. The mid-infrared emissivity is about 25%.

Example 2

(1) First, 2g of Ti ₃ AlC ₂ Type MAX was put into complex solvent of hydrochloric acid (9M, 40mL)/lithium fluoride (99%, 3.2 g) in portions, and reacted at 35 ℃ with stirring (300 rpm) for 24 hours.

(2) After the reaction was complete, the reaction solution was poured into 400mL of deionized water to terminate the reaction, washed with water several times and centrifuged to a pH of about 6. And dispersing the centrifugally collected slurry in 100ml of deionized water, and carrying out ultrasonic treatment at 10 ℃ and 40kHz for 1h to obtain a few layers of MXene by stripping. Centrifuging the ultrasonically stripped mixed solution at 3500rpm for 90min to obtain an upper suspension to remove the non-etched MAX residues, and collecting lower slurry at 9000rpm for 40min to remove the small MXene nanosheets with low conductivity.

(3) 100mg of tannic acid was put into Tris-HCl buffer (pH =7.5, 200 mL) and continuously stirred at 400 rpm.

(4) 5mL of a 40mg/mL MXene dispersion was slowly added to the tris solution, and the reaction was continued for 20 hours. The reaction solution was then centrifuged at 9000rpm for 30min, washed with water several times and centrifuged until the supernatant had a pH of 5-7. And pouring out the supernatant to obtain MXene slurry with the lower layer being modified by polyphenol.

(5) Extruding 1mL of slurry by adopting a single-channel injection pump, calculating the solid content of the slurry after freeze drying, and then diluting and stirring the slurry by using rated deionized water to obtain the titanium carbide MXene/polyphenol conductive ink with specific solid content. Also, the ink can be stored at room temperature for 1 month without severe oxidation (fig. 3). The conductivity of the MXene/polyphenol film was measured to be about 0.9S/cm. The mid-infrared emissivity is about 42%.

Example 3

(1) First, 5g of Ti3AlC2 type MAX was put in portions into a complex solvent of hydrochloric acid (9M, 100mL)/lithium fluoride (99%, 8 g), and reacted at 35 ℃ with stirring (300 rpm) for 48 hours.

(2) After the reaction was complete, the reaction mixture was poured into 1200mL of deionized water to terminate the reaction, washed with water several times and centrifuged to a pH of about 6. And dispersing the centrifugally collected slurry in 300ml of deionized water, and carrying out ultrasonic treatment at 10 ℃ and 40kHz for 1h to obtain a few layers of MXene by stripping. Centrifuging the ultrasonically stripped mixed solution at 3500rpm for 60min to obtain an upper suspension to remove the non-etched MAX residues, and collecting lower slurry at 9000rpm for 45min to remove the small MXene nanosheets with low conductivity. The MXene nano-sheet has a diameter range of 100-1500nm, and an average diameter of 450nm. The MXene film is subjected to suction filtration, and the conductivity of the MXene is measured to be 5000S cm ^-1 。

(3) 60mg of dopamine hydrochloride is put into a Tris-HCl buffer solution (pH =10, 200 mL), the continuous stirring reaction is carried out for 1h under the condition of keeping 400rpm, and the dopamine is subjected to oxidative self-polymerization to eliminate partial positively charged amino groups so as to avoid the coagulation after MXene dispersion liquid is added.

(4) 5mL of 40mg/mL MXene dispersion was slowly poured into the above Tris-HCl solution, and the reaction was continued for 16 hours. The reaction was then centrifuged at 9000rpm for 30min and multiple water washes were centrifuged until the supernatant had a pH of 5-7. And pouring out the supernatant to obtain MXene slurry with the lower layer being modified by polydopamine.

(5) Extruding 1mL of slurry by adopting a single-channel injection pump, calculating the solid content of the slurry after freeze drying, and then diluting and stirring the slurry by adding rated deionized water to obtain the titanium carbide MXene/polydopamine conductive ink with specific solid content.

The ink achieves a large adjustment of the viscosity in the range of 1-20000pa.s depending on the concentration change. The conductivity of the filtered MXene/polydopamine film was determined to be about 300S/cm. The mid-infrared emissivity is 28%.

Example 4

The embodiment provides an MXene/polyphenol conductive fabric and a preparation method thereof, wherein the preparation method of the MXene/polyphenol conductive fabric comprises the following steps:

(1) Adding deionized water into the MXene/polyphenol conductive ink obtained in the example 1 for dilution to obtain MXene/polyphenol conductive ink with the concentration of 5 mg/mL;

(2) Selecting polyester fabric (110 g/m) of 4cm x 10cm ² ) Immersing the mixed solution in 20ml of the MXene/polyphenol conductive ink for 1 hour, taking out the mixed solution, draining the excessive ink on the surface (figure 4), and drying the mixed solution in an oven at the temperature of 60 ℃ for 4 hours. Thus obtaining the MXene/poly-polyphenol conductive fabric. The conductivity of the fabric is 20S/m, and the electromagnetic shielding effectiveness of the double-layer fabric (300 micrometers) in an X wave band is 20dB.

Example 5

The embodiment provides an MXene/poly-polyphenol conductive coating and a preparation method thereof, wherein the preparation method of the MXene/poly-polyphenol conductive coating comprises the following steps:

(1) Adding deionized water into the MXene/polyphenol conductive ink obtained in the example 1 for dilution to obtain MXene/polyphenol conductive ink with the concentration of 20 mg/mL;

(2) The polyimide film subjected to hydrophilic treatment is selected as a substrate, and the height of the scraper is 500 micrometers. The draw-down speed was 120mm/s. The drying temperature was 40 degrees celsius. After drying, a conductive MXene/polyphenol coating with a thickness of about 3 μm and an electromagnetic shielding performance of about 36dB in the X-band was obtained (FIG. 5).

Example 6

The invention also provides a method for preparing the electromagnetic shielding device based on the MXene/polyphenol coating or pattern preparation method, which comprises the following steps:

a pattern with a slit interval of 200 microns is designed by CAD, and is printed on paper and a polymer film by using 60mg/mL MXene/poly polyphenol ink in example 1, and after drying, the conductive micro-grid (a in fig. 6) is obtained. When the slit of the conductive micro-grid is parallel to the electric field direction of the X-waveband electromagnetic wave, the shielding effectiveness is 18.2dB; while vertically, the shielding effectiveness is 0.62dB (b in fig. 6). The electromagnetic wave shielding switch and the electromagnetic wave transmission regulation and control can be realized by rotating the conductive micro-grid.

Example 7

The invention also provides a method for printing the infrared anti-counterfeiting patterns spliced by the MXene/poly-polyphenol coatings with different infrared emissivities by using the MXene/poly-polyphenol ink prepared from different feeding amounts of polyphenol and MXene and by using the concept of multicolor printing.

The ink with lower infrared emissivity adopts 60mg/mL MXene/polyphenol ink in example 1, and the infrared emissivity of the obtained coating is 25%. The feed ratio of polyphenol to MXene of the ink with medium infrared emissivity is 3: the rest of the synthesis was identical to example 1. The feeding ratio of polyphenol to MXene of the ink with higher infrared emissivity is 1:1, the rest of the synthesis method is identical to example 1. Printing the designed multi-element pattern on a substrate at one time, wherein the substrate is a polymer film, a fabric, a wood board and the like, and drying to obtain the MXene/polyphenol infrared anti-counterfeiting pattern (a in figure 7). After the infrared anti-counterfeiting pattern can be heated, the anti-counterfeiting pattern can be identified and decoded by an infrared camera (b of figure 7).

Comparative example 1

The comparative example provides an MXene conductive ink and a preparation method thereof, wherein the preparation method of the MXene conductive ink comprises the following steps:

(2) After the reaction was complete, the reaction mixture was poured into 400mL of deionized water to terminate the reaction, washed with water several times and centrifuged to a pH of about 6. And dispersing the centrifugally collected slurry in 100ml of deionized water, and carrying out ultrasonic treatment at 10 ℃ and 40kHz for 1h to obtain a few layers of MXene by stripping. Centrifuging the ultrasonically stripped mixed solution at 3500rpm for 90min to obtain an upper suspension to remove the non-etched MAX residues, and collecting lower slurry at 9000rpm for 40min to remove the small MXene nanosheets with low conductivity. It was then concentrated to different concentrations for use.

The inks prepared in example 1 and comparative example 1 were diluted to 15mL/mL and left under room temperature and air conditions for 1 month, and their X-ray diffraction patterns and transmission electron microscope images were characterized. As can be seen from the X-ray diffraction pattern in fig. 1a, MXene in comparative example 1 undergoes significant oxidation and the rutile phase of titanium dioxide occurs. Further observing the morphology of the nanosheets by a transmission electron microscope, the nanosheets have a large number of titanium dioxide particles and obvious breakage and holes (b in fig. 1). Whereas the ink of example 1 did not undergo significant oxidation (a in fig. 1). The nanosheet structure was intact (c in fig. 1).

The inks prepared in example 1 and comparative example 1 were concentrated to 40mL/mL, and the viscosities of both were measured (fig. 2), and both comparative example 1 and example 1 exhibited shear thinning characteristics. The viscosity of comparative example 1 is only 2Pa · s, whereas the viscosity of example 1 is as high as 130Pa · s, up to about 14000Pa · s when the concentration of example 1 is increased to 60mL/mL, to meet the high viscosity requirements of processing such as screen printing, direct write printing, etc.

It should be noted that, although the technical solutions of the present invention are described by specific examples, those skilled in the art can understand that the present invention should not be limited thereto.

While embodiments of the present invention have been described above, the above description is illustrative, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen in order to best explain the principles of the embodiments, the practical application, or improvements made to the technology in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

Industrial applicability

The conductive composite and the conductive ink of the present invention can be industrially prepared and applied.

Claims

1. An electrically conductive composite, comprising:

an inner core portion and an outer layer portion;

the inner core portion includes a two-dimensional transition metal carbon/nitrogen compound represented by the general formula:

M _n+1 X _n T

2. The composite of claim 1, wherein the conductive composite has an electrical conductivity of 0.1 to 3000S/cm.

3. The composite material according to claim 1 or 2, wherein M of the two-dimensional transition metal carbon/nitrogen compound comprises Ti, and the two-dimensional transition metal carbon/nitrogen compound has a layered structure of 1 to 5 layers.

4. The composite material according to any one of claims 1 to 3, characterized in that the two-dimensional transition metal carbon/nitrogen compound has an average size of 2000nm or less.

5. The composite material according to any one of claims 1 to 4, wherein the aromatic polyphenol further has one or more carboxyl groups or lactone groups formed from the carboxyl groups.

6. Composite material according to any one of claims 1 to 5, characterized in that said aromatic polyphenol is selected from one or more of tannic acid, ellagic acid, 3, 4-dihydroxyphenylalanine or their derivatives.

7. The composite material according to any one of claims 1 to 6, wherein the average thickness of the outer layer portion is 0.5 to 8nm.

8. Conductive ink, characterized in that it comprises a conductive composite according to any one of claims 1 to 7.

9. The ink according to claim 8, wherein the content of the conductive composite material is 10 to 100g/L.

10. An electromagnetic wave regulating conductive micro-grid, comprising a raw material derived from the conductive composite material according to any one of claims 1 to 7 or obtained by printing using the ink according to claim 8 or 9, wherein the pitch of the conductive micro-grid is 75 to 1000 μm.

11. An infrared security device comprising a raw material derived from the conductive composite material according to any one of claims 1 to 7 or a printed security device obtained by using the ink according to claim 8 or 9, wherein optionally the ink comprises at least two different conductive composite materials.

12. The electromagnetic wave modulating conductive micro-grid according to claim 10 or the infrared anti-counterfeiting pattern according to claim 11, wherein the printing is selected from screen printing, offset printing, gravure printing, extrusion printing or blade coating printing.