Conductive two-dimensional particles, method for producing same, conductive film, conductive paste, and conductive composite material

Abstract

The conductive two-dimensional particle is a conductive two-dimensional particle of a layered material comprising one or more layers, the layer includes a layer host represented by the following formula: TimXn (in the formula, X is a carbon atom, a nitrogen atom, or a combination thereof, n is 1-4, and m is greater than n and 5 or less), and a modification or terminal T (T is at least one selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom, and a hydrogen atom) present on the surface of the layer host. The atomic ratio of Al to Ti (Al / Ti) is 0 at% or more and 0.10 at% or less.

Description

Technical Field

[0001] The present disclosure relates to a conductive two-dimensional particle and a method for manufacturing the same, a conductive film, a conductive paste, and a conductive composite material. Background Art

[0002] In recent years, MXene has attracted attention as a new material with electrical conductivity. MXene is a type of so-called two-dimensional material, and as described later, is a layered material having one or more layers. Generally speaking, MXene has the form of particles (including powder, flakes, nanosheets, etc.) of such layered materials.

[0003] Currently, various studies are being conducted on the application of MXene in various electrical devices. For example, in non-patent document 1, it is shown that since two-dimensional titanium carbide MXene is basically not mass-produced, in the case of changing the amount of a single reaction to synthesize two-dimensional titanium carbide MXene and mass production, scanning electron microscopy, X-ray diffraction, dynamic light scattering, Raman spectroscopy, X-ray photoelectron spectroscopy, ultraviolet visible spectroscopy, conductivity measurement, etc. are used to confirm whether this situation affects the structure and composition of two-dimensional titanium carbide MXene flakes. In addition, in non-patent document 2, it is shown that the reflectivity of the MXene antenna formed by the secondary (2D) titanium carbide (MXene), which is a material useful in the production of thin and lightweight flexible antennas, is small, and the conductivity and water dispersibility can be further ensured.

[0004] Prior art literature

[0005] Non-patent literature

[0006] Non-patent literature :Scalable Synthesis of Ti3C2Tx MXene, Christopher E. Shucket al., ADVANCED ENGINEERING MATERIALS 2020

[0007] Non-patent literature :2D Titanium carbide (MXene) for wireless communication,SCIENCE ADVANCES, 21 Sep 2018, Vol 4, Issue 9 Summary of the invention

[0008] Problems to be solved by the invention

[0009] However, the electrical conductivity of the MXene antenna disclosed in Non-Patent Document 1 and Non-Patent Document 2 cannot be said to be high, and it is necessary to improve it in order to achieve a conductive film with higher conductivity. The present disclosure is completed in view of the above situation, and its purpose is to provide a conductive two-dimensional particle capable of forming a highly conductive conductive film, etc., a method for manufacturing the conductive two-dimensional particle, and a conductive film, a conductive paste, and a conductive composite material using the conductive two-dimensional particle.

[0010] Means for solving problems

[0011] According to one aspect of the present disclosure, there is provided:

[0012] A conductive two-dimensional particle, which is a conductive two-dimensional particle comprising one or more layers of a layered material,

[0013] The above layer comprises the following formula:

[0014] Ti m X n

[0015] (wherein X is a carbon atom, a nitrogen atom or a combination thereof,

[0016] n is greater than or equal to 1 and less than or equal to 4,

[0017] m is greater than n and less than 5)

[0018] The layer body shown, and the modification or terminal T (T is at least one selected from a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom and a hydrogen atom) present on the surface of the layer body,

[0019] Furthermore, the atomic ratio of Al to Ti (Al / Ti) is greater than or equal to 0 atomic % and less than or equal to 0.10 atomic %.

[0020] According to another aspect of the present disclosure, there is provided:

[0021] A method for producing conductive two-dimensional particles, comprising:

[0022] (a) Prepare the following formula:

[0023] Ti m AlX n

[0024] (wherein X is a carbon atom, a nitrogen atom or a combination thereof,

[0025] n is greater than or equal to 1 and less than or equal to 4,

[0026] m is greater than n and less than 5)

[0027] Precursors shown;

[0028] (b1) contacting the precursor with an etching solution to perform etching to remove at least a portion of Al from the precursor;

[0029] (c) cleaning the etched product obtained by etching to obtain a cleaned product;

[0030] (d) performing an intercalation treatment of an interlayer inserting compound, the intercalation treatment comprising the step of stirring a mixed solution containing the cleaning material and the interlayer inserting compound of the cleaning material; and

[0031] (e1) using the intercalation product obtained by the above intercalation treatment to perform delamination to obtain conductive two-dimensional particles,

[0032] An atomic ratio of Al to Ti (Al / Ti) in the conductive two-dimensional particles is 0 atomic % or more and 0.10 atomic % or less.

[0033] Effects of the Invention

[0034] According to the present disclosure, conductive two-dimensional particles are formed of a specified layered material (also referred to as "MXene" in this specification), and further, the atomic ratio of Al to Ti (Al / Ti) is greater than 0 atomic % and less than 0.10 atomic %, thereby providing conductive two-dimensional particles that contain MXene and are capable of forming a conductive film exhibiting high conductivity.

[0035] In addition, according to the present disclosure, conductive two-dimensional particles can be manufactured by the following method: (a) preparing a specified precursor; (b1) making the above-mentioned precursor contact with an etching solution to perform etching to remove at least a portion of Al from the above-mentioned precursor; (c) cleaning the etched product obtained by etching to obtain a cleaned product; (d) performing an intercalation treatment of an interlayer insertion compound, and the above-mentioned intercalation treatment includes the step of stirring a mixed solution containing the above-mentioned cleaned product and the interlayer insertion compound of the cleaned product; and (e1) using the intercalation treated product obtained by the above-mentioned intercalation treatment to perform delamination, thereby manufacturing conductive two-dimensional particles in which the atomic ratio of Al to Ti (Al / Ti) is greater than 0 atomic % and less than 0.10 atomic %. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 1 and 2 are schematic cross-sectional views showing MXene as a layered material that can be used for a conductive film in one embodiment of the present disclosure, wherein (a) shows a single-layer MXene and (b) shows a multi-layer (two-layer) MXene.

[0037] Figure 2 These are diagrams for explaining a conductive film in one embodiment of the present disclosure, wherein (a) is a schematic cross-sectional view of the conductive film, and (b) is a schematic perspective view of MXene particles in the conductive film.

[0038] Figure 3 The precipitates (AlF 3 ·3H 2 O) is a graph showing the XRD measurement results. DETAILED DESCRIPTION

[0039] (Embodiment 1: Conductive Two-Dimensional Particles)

[0040] Hereinafter, the conductive two-dimensional particles in one embodiment of the present disclosure will be described in detail, but the present disclosure is not limited to such an embodiment.

[0041] The conductive two-dimensional particles in this embodiment are

[0042] Conductive two-dimensional particles comprising one or more layers of layered material,

[0043] The above layer comprises the following formula:

[0044] Ti m X n

[0045] (wherein X is a carbon atom, a nitrogen atom or a combination thereof,

[0046] n is greater than or equal to 1 and less than or equal to 4,

[0047] m is greater than n and less than 5)

[0048] The layer body shown, and the modification or terminal T (T is at least one selected from a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom and a hydrogen atom) present on the surface of the layer body,

[0049] Furthermore, the atomic ratio of Al to Ti (Al / Ti) is greater than or equal to 0 atomic % and less than or equal to 0.10 atomic %.

[0050] The above-mentioned layered materials can be understood as layered compounds, which can also be expressed as "Ti m X n T s ", s is an arbitrary number. In the past, x or z was sometimes used instead of s. Typically, n can be 1, 2, 3 or 4, but is not limited thereto.

[0051] For MXene, it is known that the above formula can be converted into: Ti m X n It manifests itself in the following form.

[0052] Ti 2 C. Ti 2 N、Ti 3 C 2 、Ti 3 N2 、Ti 3 (CN), Ti 4 N 3

[0053] Typically, for example, the MAX phase is Ti 3 AlC 2 MXene is Ti 3 C 2 T s (In other words, X is C, n is 2, and m is 3).

[0054] It should be noted that in the present embodiment, MXene may also contain residual Al in a relatively small amount, for example, 6% by mass or less relative to the original Al. The residual amount of Al may preferably be 5% by mass or less. However, even if the residual amount of Al exceeds 6% by mass, there may be no problem depending on the purpose and use conditions of the conductive two-dimensional particles.

[0055] The conductive two-dimensional particles of this embodiment include Figure 1 (a) shows an aggregate of one layer of MXene 10a (single-layer MXene). More specifically, MXene 10a has Ti m X n The layer body shown (Ti m X n The MXene layer 7a includes a modified or terminal MXene layer T3a, 5a present on the surface of the layer body 1a (more specifically, at least one of the two surfaces facing each other in each layer). Therefore, the MXene layer 7a is also represented as "Ti m X n T s ", s is an arbitrary number.

[0056] The conductive two-dimensional particles of this embodiment may include one layer and a plurality of layers. As a plurality of layers of MXene (multilayer MXene), such as Figure 1 As schematically shown in (b), two layers of MXene 10b can be exemplified, but the present invention is not limited to these examples. Figure 1 1b, 3b, 5b, 7b in (b) are similar to the above Figure 1 (a) 1a, 3a, 5a, 7a are the same. Two adjacent MXene layers (e.g., 7a and 7b) of a multilayer MXene are not necessarily completely separated, but may be partially in contact. The above-mentioned MXene10a is a mixture of the above-mentioned single-layer MXene10a and the multilayer MXene10b, in which the above-mentioned multilayer MXene10b is separated from each other and exists in the form of one layer, and sometimes the multilayer MXene10b that has not been separated remains.

[0057] The present embodiment is not limited thereto, but the thickness of each layer of MXene (corresponding to the above-mentioned MXene layers 7a and 7b) may be, for example, 0.8 nm to 10 nm, further 0.8 nm to 5 nm, and particularly 0.8 nm to 3 nm (may vary mainly depending on the number of Ti layers contained in each layer). For each stack of multilayer MXene that may be included, the interlayer distance (or gap size, in Figure 1 The thickness (represented by Δd in (b)) may be, for example, 0.8 nm to 10 nm, particularly 0.8 nm to 5 nm, and particularly about 1 nm. The total number of layers may be 2 to 20,000.

[0058] The conductive two-dimensional particles of the present embodiment can be a MXene with a small number of layers obtained by interlayer exfoliation treatment of the multilayer MXene that can be included. The above-mentioned "small number of layers" means, for example, that the number of layers of MXene is less than 10 layers, and further, it can be less than 6 layers. Hereinafter, the "multilayer MXene with a small number of layers" is sometimes referred to as "few-layer MXene". In addition, a single-layer MXene and a few-layer MXene are sometimes combined and referred to as "single-layer·few-layer MXene".

[0059] The conductive two-dimensional particles of the present embodiment preferably contain a single-layer MXene and a few-layer MXene, i.e., a single-layer·few-layer MXene. In the above-mentioned conductive two-dimensional particles, the proportion of single-layer·few-layer MXene can be 50% by volume or more, or the proportion of multilayer MXene can be 50% by volume or more. Preferably, the proportion of single-layer·few-layer MXene is 50% by volume or more. In the conductive two-dimensional particles of the present embodiment, it is more preferred that the proportion of single-layer·few-layer MXene with a thickness of less than 10 nm accounts for more than 90% by volume of all MXene, and more preferably more than 95% by volume.

[0060] In the above-mentioned conductive two-dimensional particles, the volume ratio of the single-layer and few-layer MXene is preferably large, and the average thickness of the above-mentioned conductive two-dimensional particles is preferably 15nm or less. More preferably, the average thickness is 10nm or less. On the other hand, the lower limit of the average thickness of the conductive two-dimensional particles can be, for example, 0.5nm.

[0061] The average value of the thickness of the conductive two-dimensional particles is obtained as a number average size (for example, a number average of at least 40 particles) based on an atomic force microscope (AFM) photograph.

[0062] The conductive two-dimensional particles of the present embodiment are MXene two-dimensional particles with a low Al concentration in which the atomic ratio of Al to Ti (Al / Ti) is greater than 0 atomic % and less than 0.10 atomic %. That is, Al may not be contained, and even if Al is contained, it may be suppressed within the above atomic ratio range. The conductive two-dimensional particles of the present embodiment are MXene two-dimensional particles that can be obtained through subsequent steps by sufficiently removing Al by controlling the etching conditions, for example, as described below, in the etching of a precursor such as a MAX phase. The atomic ratio of Al to Ti (Al / Ti) can be obtained by analyzing the contents of Al and Ti using ICP emission spectrometry, as shown in the examples described below.

[0063] (Embodiment 2: Method for producing conductive two-dimensional particles)

[0064] Hereinafter, the method for producing the conductive two-dimensional particles in this embodiment will be described in detail, but the present disclosure is not limited to this embodiment.

[0065] A method for producing a conductive two-dimensional particle (first production method) according to the present embodiment is a method for producing a conductive two-dimensional particle including the following steps:

[0066] (a) Prepare the following formula:

[0067] Ti m AlX n

[0068] (wherein X is a carbon atom, a nitrogen atom or a combination thereof,

[0069] n is greater than or equal to 1 and less than or equal to 4,

[0070] m is greater than n and less than 5)

[0071] Precursors shown;

[0072] (b1) contacting the precursor with an etching solution to perform etching to remove at least a portion of Al from the precursor;

[0073] (c) cleaning the etched product obtained by etching to obtain a cleaned product;

[0074] (d) performing an intercalation treatment of an interlayer inserting compound, the intercalation treatment comprising the step of stirring a mixed solution containing the cleaning material and the interlayer inserting compound of the cleaning material; and

[0075] (e1) using the intercalation product obtained by the above intercalation treatment to perform delamination to obtain conductive two-dimensional particles,

[0076] An atomic ratio of Al to Ti (Al / Ti) in the conductive two-dimensional particles is 0 atomic % or more and 0.10 atomic % or less.

[0077] Another method for producing conductive two-dimensional particles (second production method) according to the present embodiment is a method for producing conductive two-dimensional particles comprising the following steps:

[0078] (a) Prepare the following formula:

[0079] Ti m AlX n

[0080] (wherein X is a carbon atom, a nitrogen atom or a combination thereof,

[0081] n is greater than or equal to 1 and less than or equal to 4,

[0082] m is greater than n and less than 5)

[0083] Precursors shown;

[0084] (b2) contacting the precursor with an etching solution containing an interlayer insertion compound to perform etching to remove at least a portion of Al from the precursor and to perform intercalation treatment of the interlayer insertion compound;

[0085] (e2) using the (etching + intercalation) product obtained by the above-mentioned etching and intercalation treatment, delamination is performed to obtain conductive two-dimensional particles,

[0086] An atomic ratio of Al to Ti (Al / Ti) in the conductive two-dimensional particles is 0 atomic % or more and 0.10 atomic % or less.

[0087] Hereinafter, each step of the first manufacturing method and the second manufacturing method will be described in detail.

[0088] Process (a)

[0089] In both the first and second manufacturing methods, a predetermined precursor is first prepared. The predetermined precursor that can be used in this embodiment is a MAX phase as a precursor of MXene, which is represented by the following formula:

[0090] Ti m AlX n

[0091] (wherein X is a carbon atom, a nitrogen atom or a combination thereof,

[0092] n is greater than or equal to 1 and less than or equal to 4,

[0093] m is greater than n and less than 5)

[0094] The above X, n and m are as described in the case of MXene.

[0095] The MAX phase has a layer composed of Al located between Ti m X n The MAX phase typically has a repeating unit in which one layer of X atoms is arranged between each of the n+1 layers of Ti (these layers are collectively referred to as "Ti m X n layer"), and an Al layer ("Al layer") is arranged as a layer next to the Ti layer of the n+1th layer, but the present invention is not limited to this.

[0096] The MAX phase can be produced by a known method. For example, TiC powder, Ti powder and Al powder are mixed by a ball mill, and the obtained mixed powder is fired in an Ar atmosphere to obtain a fired body (massive MAX phase). Thereafter, the obtained fired body is crushed by an end mill to obtain a powdered MAX phase for subsequent steps.

[0097] Process (b1)

[0098] In the first manufacturing method, the precursor is brought into contact with an etching solution to perform etching to remove at least a portion of Al from the precursor. The etching conditions are not limited as long as the atomic ratio of Al to Ti (Al / Ti) in the conductive two-dimensional particles finally obtained is greater than 0 atomic % and less than 0.10 atomic %. It is preferred to use an etching solution containing HF. HF can also be mixed with other acids as auxiliary acids. As other acids, hydrochloric acid, phosphoric acid, hydroiodic acid, etc. can be cited. For example, pure water can also be mixed as a solvent. The etching solution preferably contains HF and the HF concentration is greater than 7.0 M. The HF concentration is more preferably greater than 8.0 M. It should be noted that the upper limit of the HF concentration can be, for example, 30 M. From the viewpoint of etching in a short time and a high yield of conductive two-dimensional particles, it is preferred to increase the HF concentration of the etching solution.

[0099] The contact time with the etching solution (hereinafter referred to as "etching time") is preferably 8 hours or less. By shortening the etching time to preferably 8 hours or less, the AlF as an Al impurity in MXene, which is mainly insulating, can be suppressed. 3 ·3H 2 O is formed, and MXene two-dimensional particles suitable for forming a film with high electrical conductivity can be obtained. The etching time is more preferably 6 hours or less. On the other hand, from the viewpoint of sufficiently removing Al from the MAX phase, the etching time is preferably set to, for example, 0.5 hours or more.

[0100] As a method of bringing the precursor into contact with the etching solution, there can be cited a method of immersing the precursor in the etching solution, etc. Other preferred conditions for the etching treatment are not particularly limited, and known conditions can be adopted. As an etched product obtained by the above etching treatment, there can be cited, for example, a slurry.

[0101] Process (c)

[0102] In the first manufacturing method, the etched product obtained by the above-mentioned etching is cleaned. By cleaning, the acid used in the above-mentioned etching can be fully removed. It should be noted that it has been confirmed that even if the above-mentioned etching conditions are inappropriate and Al impurities are formed in the form of precipitates during etching, the precipitates cannot be fully removed by the cleaning. The cleaning medium mixed with the etched product is not limited as long as it can fully remove the above-mentioned acid, etc. For example, in addition to water (pure water), it can also be cleaned by a solution containing substances other than water such as dilute hydrochloric acid. The amount of the cleaning medium and the cleaning method are not particularly limited. For example, stirring with water, centrifugal separation, etc. can be cited. As a stirring method, stirring using hand shaking, automatic shaking table, shear mixer, pot mill, etc. can be cited. The degree of stirring such as stirring speed and stirring time can be adjusted according to the amount and concentration of the object to be processed. The above-mentioned cleaning can be performed more than once. It is preferred to perform multiple cleanings. For example, specifically, the following steps (i) to (iv) can be performed within a range of not less than 2 times and not more than 15 times: (i) adding a cleaning medium (to the etched product or the residual precipitate obtained in the following (iv)), (ii) stirring, (iii) centrifuging the stirred product, and (iv) discarding the supernatant after centrifugation to recover the residual precipitate.

[0103] Process (d)

[0104] In the first manufacturing method, an intercalation treatment of an interlayer inserting compound is performed, and the treatment includes a step of stirring a mixed solution containing the above-mentioned cleaning material and a compound for interlayer inserting of the cleaning material (abbreviated as "interlayer inserting compound").

[0105] The interlayer insertion compound can be inserted between the layers of the cleaned material, and the specific type is not limited as long as it is a compound that can separate the layers in the delamination of the subsequent process (e1). As the above-mentioned interlayer insertion compound, alkali metal compounds and alkaline earth metal compounds are preferred. More preferably, it is a Li-containing compound. As the Li-containing compound, an ionic compound formed by the bond of Li ions and cations can be used. For example, Li chloride, Li phosphate, Li sulfate, Li nitrate, Li carboxylate can be mentioned. LiCl as a Li chloride is preferred.

[0106] There are no particular restrictions on other conditions of the intercalation treatment. There are no particular restrictions on the liquid properties of the mixed solution containing the cleaned material and the compound for intercalation of the cleaned material. The mixed solution containing the cleaned material and the compound for intercalation of the cleaned material is preferably acidic with a pH of 6 or less.

[0107] The content of the interlayer insertion compound in the interlayer complex is preferably set to 0.001% by mass or more. The above content is more preferably 0.01% by mass or more, and further preferably 0.1% by mass or more. On the other hand, from the perspective of dispersibility in the solution, the content of the interlayer insertion compound is preferably set to 10% by mass or less, and more preferably 1% by mass or less.

[0108] The specific method of intercalation is not particularly limited. For example, for the water medium clay of the above-mentioned MXene as a water-treated product, the above-mentioned interlayer intercalation compound can be mixed and stirred, or it can be left to stand. For example, stirring at room temperature can be cited. For the above-mentioned stirring method, for example, a method using a stirring bar such as a stirrer, a method using a stirring blade, a method using a mixer, and a method using a centrifugal device can be cited. The stirring time can be set according to the manufacturing scale of the conductive two-dimensional particles, and can be set, for example, between 12 and 24 hours.

[0109] Process (b2)

[0110] In the second manufacturing method, the precursor is brought into contact with an etching solution containing an interlayer insertion compound to perform etching to remove at least a portion of Al from the precursor (removal and layer separation as needed), while simultaneously performing intercalation treatment of the interlayer insertion compound.

[0111] In this embodiment, when etching is performed to remove at least a portion of Al from the MAX phase (removal and layer separation as appropriate), the Ti m X n The interlayer insertion of the layers (including the case where Al partially remains) is performed by intercalation treatment of an interlayer insertion compound including Li, etc. As the interlayer insertion compound, the same compound as the interlayer insertion compound shown in step (b1) can be used. As the interlayer insertion compound, lithium fluoride can be used.

[0112] The content of the interlayer insertion compound in the etching solution is preferably set to 0.001 mass % or more. The above content is more preferably 0.01 mass % or more, and further preferably 0.1 mass % or more. On the other hand, from the viewpoint of ensuring dispersibility in the solution, the content of the interlayer insertion compound in the etching solution is preferably set to 10 mass % or less, and more preferably 1 mass % or less.

[0113] The etching solution in step (b2) is not limited as long as it contains the above-mentioned interlayer insertion compound and the atomic ratio of Al to Ti (Al / Ti) in the finally obtained conductive two-dimensional particles is greater than 0 atomic % and less than 0.10 atomic %. It is preferred to use an etching solution containing HF. It is more preferred that the etching solution is contacted with an HF concentration of 7.0M or more for less than 8 hours as shown in the above step (b1). Other preferred conditions are not limited, and examples include methods using a mixed solution of lithium fluoride and hydrochloric acid. Among these methods, a method using a mixed solution with, for example, pure water as a solvent can be cited. As an etched product obtained by the above-mentioned etching process, a slurry can be cited, for example.

[0114] Of the first production method and the second production method, the production method divided into the step (b1) etching treatment and the step (c) intercalation treatment like the first production method is preferred because it is easier to form a single layer of MXene.

[0115] ·Process (e1), Process (e2)

[0116] In the first manufacturing method, the intercalation product obtained by the intercalation treatment is used, and in the second manufacturing method, the (etching + intercalation) product obtained by the etching and intercalation treatment is used, and delamination is performed respectively to obtain conductive two-dimensional particles in which the atomic ratio of Al to Ti in the particles (Al / Ti) is greater than 0 atomic % and less than 0.10 atomic %. The conditions for the delamination treatment are not particularly limited and can be performed by known methods. For example, it can be performed by the method shown below.

[0117] For example, the following delamination treatment may be performed, which includes a step of washing the remaining precipitate after centrifuging the above-mentioned intercalation treatment product and discarding the supernatant. For example, after the slurry-like intercalation treatment product or (etching + intercalation) treatment product is centrifuged and the supernatant is discarded, the process of washing the remaining precipitate with a washing medium such as water or a solution containing a substance other than water may include: (i) adding a washing medium to the remaining precipitate after discarding the supernatant and stirring; (ii) centrifuging; (iii) recovering the supernatant. The operations (i) to (iii) may be repeated more than once, preferably more than twice and less than 10 times, to obtain conductive two-dimensional particles in the form of a delamination treatment product. Alternatively, the supernatant may be centrifuged, the supernatant after centrifugation may be discarded, and conductive two-dimensional particles may be obtained in the form of a delamination treatment product.

[0118] In the manufacturing method of this embodiment, ultrasonic treatment as delamination is not performed after etching. As described above, since ultrasonic treatment is not performed, the particles are difficult to be damaged, and conductive two-dimensional particles containing single-layer and few-layer MXene with a large two-dimensional surface can be obtained. Conductive two-dimensional particles containing single-layer and few-layer MXene with a large two-dimensional surface can form a film without using a binder, and the obtained film exhibits high conductivity.

[0119] (Embodiment 3: Conductive film (conductive film))

[0120] The conductive film of this embodiment may include a conductive film containing the conductive two-dimensional particles of this embodiment. Figure 2 The conductive film 30 of this embodiment includes Figure 2 (a) is a conductive two-dimensional particle 10 made of a predetermined layered material. Figure 2 (b) is a schematic perspective view of MXene particles included in the conductive film 30. The conductive film of the present embodiment may be a film in which only the conductive two-dimensional particles 10 are stacked.

[0121] The conductive film may also be a conductive composite material film (conductive composite material film) further comprising a polymer (resin). For the above-mentioned polymer, for example, it may be included as an additive such as an adhesive added when forming the film, or it may be added to give the film strength or flexibility. In the case of the above-mentioned conductive composite material film, the proportion of the above-mentioned polymer in the conductive composite material film (when dry) may exceed 0 volume%, and may preferably be set to 30 volume% or less. The proportion of the above-mentioned polymer may also be further set to 10 volume% or less, and may further be set to 5 volume% or less. In other words, the proportion of conductive two-dimensional particles (particles of layered materials) in the conductive composite material film (when dry) is preferably set to 70 volume% or more, and may further be set to 90 volume% or more, and may further be set to 95 volume% or more. The conductive film may also be a laminated film of two or more conductive composite materials having different proportions of the above-mentioned conductive two-dimensional particles.

[0122] Examples of the polymer include hydrophilic polymers (including polymers obtained by mixing a hydrophilic auxiliary agent with a hydrophobic polymer to render it hydrophilic, and polymers obtained by subjecting a hydrophobic polymer or the like to a surface hydrophilization treatment). The hydrophilic polymer is preferably a polymer containing at least one selected from the group consisting of polysulfone, cellulose acetate, regenerated cellulose, polyethersulfone, water-soluble polyurethane, polyvinyl alcohol, sodium alginate, acrylic acid-based water-soluble polymers, polyacrylamide, polyaniline sulfonic acid, and nylon.

[0123] The hydrophilic polymer is a hydrophilic polymer having a polar group, and the polar group is more preferably a group that forms a hydrogen bond with the modification of the layer or the terminal T. As the polymer, for example, one or more polymers selected from water-soluble polyurethane, polyvinyl alcohol, sodium alginate, acrylic acid-based water-soluble polymers, polyacrylamide, polyaniline sulfonic acid and nylon can be preferably used.

[0124] Among them, more preferably one or more polymers selected from water-soluble polyurethane, polyvinyl alcohol, and sodium alginate. As the above-mentioned polymer, preferably a polymer having a urethane bond having both hydrogen bond donor and hydrogen bond acceptor properties, from this viewpoint, the above-mentioned water-soluble polyurethane is particularly preferred.

[0125] The thickness of the conductive film is preferably 0.5 μm or more and 20 μm or less. Since the contact resistance of the grain boundary decreases and the conductivity tends to increase by increasing the thickness of the conductive film, it is preferably set to 0.5 μm or more. The film thickness is more preferably 1.0 μm or more. From the point of view of conductivity, the thicker the film thickness, the better. However, when flexibility is sought, the film thickness is preferably 20 μm or less, and more preferably 15 μm or less. The thickness of the conductive film can be measured, for example, by measurement using a micrometer, cross-sectional observation based on a scanning electron microscope (SEM), a microscope, or a laser microscope.

[0126] For the conductive film formed by the conductive two-dimensional particles of this embodiment, the conductivity obtained by substituting the thickness of the conductive film measured by the aforementioned method, for example, the thickness of the conductive film measured by the method described in the examples, and the surface resistivity of the conductive film into the following formula can preferably reach 7000 S / cm or more.

[0127] Conductivity [S / cm] = 1 / (thickness of conductive film [cm] × surface resistivity of conductive film [Ω / □])

[0128] (Method for producing conductive film (conductive film))

[0129] The method for producing the conductive film of the present embodiment using the MXene particles (conductive two-dimensional particles) produced as described above is not particularly limited. For example, the conductive film can be formed as exemplified below.

[0130] First, a MXene dispersion is prepared in which the MXene particles prepared as described above are present in a medium liquid. Examples of the medium liquid include an aqueous medium liquid and an organic medium liquid. The medium liquid of the MXene dispersion is typically water, and depending on the circumstances, other liquid substances may be contained in a small amount (based on the whole, for example, 30% by mass or less, preferably 20% by mass or less) in addition to water.

[0131] Before drying, the MXene dispersion may be used to form a precursor of a conductive film (also referred to as a "precursor film"). The method for forming the precursor film is not particularly limited, and for example, suction filtration, coating, spraying, etc. may be used.

[0132] In more detail, as a MXene dispersion, for example, the supernatant containing the conductive two-dimensional particles can be appropriately adjusted (for example, diluted with an aqueous medium liquid), and filtered through a filter (which can constitute a specified component together with the conductive film, or can be finally separated from the conductive film) provided in a suction filter (Nutsche) or the like, and at least a portion of the aqueous medium liquid is removed, thereby forming a precursor film on the filter. The filter is not particularly limited, and a membrane filter can be used. By performing the above-mentioned filtration, a conductive film can be made without using the above-mentioned adhesive, etc. If the conductive two-dimensional particles of the present embodiment are used, a conductive film can be made like this without using an adhesive, etc.

[0133] Alternatively, the MXene dispersion can be directly applied to the substrate, or appropriately adjusted (for example, diluted with an aqueous medium or added with an adhesive) and applied to the substrate. As the coating method, for example: a method of spraying using a nozzle such as a single-fluid nozzle, a two-fluid nozzle, a spray gun, etc.; a method of slit coating, screen printing, metal mask printing, etc. using a desktop coater, a comma coater, a rod coater; spin coating, dip coating, dripping, etc. As the above-mentioned substrate, for example, a substrate formed of a metal material, resin, etc. suitable for a biosignal sensing electrode can be appropriately used. By coating on any suitable substrate (which can constitute a prescribed component together with the conductive film, or can be ultimately separated from the conductive film), a precursor film can be formed on the substrate.

[0134] Next, the precursor film formed in the above step is dried to obtain, for example, Figure 2 Such a conductive film 30 is schematically shown in FIG. In the present embodiment, “drying” means removing the aqueous medium liquid that may be present in the precursor.

[0135] Drying can be carried out under mild conditions such as natural drying (typically, placing in an air atmosphere at normal temperature and pressure), air drying (blowing air), or under relatively intense conditions such as warm air drying (blowing heated air), heat drying, and / or vacuum drying. The above drying can be carried out, for example, at a temperature of 400 degrees or less using a normal pressure oven or a vacuum oven.

[0136] The formation and drying of the precursor film may be repeated as appropriate until a conductive film of a desired thickness is obtained. For example, a combination of spray coating and drying may be repeated a plurality of times.

[0137] When the conductive composite material of the present embodiment has a sheet-like form, for example, the conductive two-dimensional particles and a polymer may be mixed to form a coating film as exemplified below.

[0138] First, the conductive two-dimensional particles (MXene particles) are mixed with a MXene dispersion or MXene powder in a medium liquid (aqueous medium liquid or organic medium liquid), and a polymer. The medium liquid of the MXene dispersion is typically water, and depending on the circumstances, other liquid substances may be contained in a small amount (based on the whole, for example, 30% by mass or less, preferably 20% by mass or less).

[0139] The conductive two-dimensional particles (MXene particles) and the polymer may be stirred using a dispersing device such as a homogenizer, a propeller stirrer, a thin film gyratory stirrer, a planetary stirrer, a mechanical oscillator, or a vortex mixer.

[0140] The slurry of the mixture of the above-mentioned MXene particles and the polymer can be applied to a substrate (e.g., a substrate), and the coating method is not limited. For example, there can be cited: a method of spraying using a nozzle such as a single-fluid nozzle, a two-fluid nozzle, a spray gun, etc.; a method of slit coating using a table coater, a comma coater, a rod coater, screen printing, metal mask printing, etc.; a coating method based on spin coating, dip coating, and dripping. As described above, the above-mentioned substrate can be appropriately formed of a metal material, resin, etc. suitable for a biosignal sensing electrode.

[0141] The coating and drying can be repeated as many times as necessary until a film of a desired thickness is obtained. Drying and curing can be performed, for example, in a normal pressure oven or a vacuum oven at a temperature of 400 degrees or less.

[0142] (Embodiment 4: Conductive paste)

[0143] As other uses of the conductive two-dimensional particles of this embodiment, a conductive paste containing the conductive two-dimensional particles can be cited. As the conductive paste, for example, a mixture of conductive two-dimensional particles (particles of a predetermined layered material) and a medium can be cited. As the above-mentioned medium, an aqueous medium liquid, an organic medium liquid, a polymer, metal particles, ceramic particles, etc. can be cited, and a medium containing one or more of them can also be cited. The mass ratio of the conductive two-dimensional particles (particles of a layered material) in the conductive paste can be, for example, 50% or more.

[0144] As an example of the application, the conductive paste is applied to a substrate or the like and dried to form a conductive film.

[0145] (Embodiment 5: Conductive composite material)

[0146] As other uses of the conductive two-dimensional particles of this embodiment, a conductive composite material containing the conductive two-dimensional particles and a polymer can be cited. The conductive composite material is not limited to the shape of the conductive composite film (conductive composite film) described above. In addition to the shape of the film described above, the shape of the conductive composite material can also be a cuboid, a sphere, a polygon, etc. having a thickness.

[0147] As the above-mentioned polymer, the same polymer as that used in the above-mentioned conductive composite material film (conductive composite material film) can be used. For example, it can be included as an additive such as an adhesive for forming, or it can be added for strength or flexibility. The above-mentioned polymer can be set to more than 0% by volume, and preferably to less than 30% by volume, based on the proportion of the above-mentioned polymer in the conductive composite material (when dry). The proportion of the above-mentioned polymer can also be further set to less than 10% by volume, and can also be further set to less than 5% by volume. In other words, the proportion of the particles of the layered material in the conductive composite material (when dry) is preferably set to more than 70% by volume, and can also be further set to more than 90% by volume, and can also be further set to more than 95% by volume.

[0148] Examples of the polymer include hydrophilic polymers (including polymers obtained by mixing a hydrophilic auxiliary agent with a hydrophobic polymer to make it hydrophilic, and polymers obtained by subjecting the surface of a hydrophobic polymer to a hydrophilic treatment). Examples of the hydrophilic polymer include more preferably polymers containing one or more selected from the group consisting of polysulfone, cellulose acetate, regenerated cellulose, polyethersulfone, water-soluble polyurethane, polyvinyl alcohol, sodium alginate, acrylic acid-based water-soluble polymers, polyacrylamide, polyaniline sulfonic acid, and nylon.

[0149] The hydrophilic polymer is a hydrophilic polymer having a polar group, and more preferably a hydrophilic polymer having a polar group that forms a hydrogen bond with the modification of the layer or the terminal T. As the polymer, for example, one or more polymers selected from water-soluble polyurethane, polyvinyl alcohol, sodium alginate, acrylic acid-based water-soluble polymers, polyacrylamide, polyaniline sulfonic acid and nylon can be preferably used.

[0150] Among them, more preferably one or more polymers selected from water-soluble polyurethane, polyvinyl alcohol, and sodium alginate. As the above-mentioned polymer, preferably a polymer having a urethane bond having both hydrogen bond donor and hydrogen bond acceptor properties, from this viewpoint, the above-mentioned water-soluble polyurethane is particularly preferred.

[0151] The conductive two-dimensional particles, the method for producing the conductive two-dimensional particles, the conductive film, the conductive paste, and the conductive composite material in the present embodiment are described in detail above, but various changes can be made. It should be noted that the conductive two-dimensional particles in the present embodiment can also be produced by a method different from the production method in the above-mentioned embodiment, and it should also be noted that the production method of the conductive two-dimensional particles in the present embodiment is not limited to providing the conductive two-dimensional particles in the above-mentioned embodiment.

[0152] Example

[0153] [Production of single-layer and few-layer MXene]

[0154] [Examples 1 to 3, Comparative Examples 1 to 3]

[0155] In Examples 1 to 4, the following steps are performed in sequence: (1) preparation of a precursor (MAX), (2) etching of the precursor, (3) cleaning after etching, (4) Li intercalation, and (5) delamination to produce a sample containing a single-layer or few-layer MXene.

[0156] (1) Preparation of precursor (MAX)

[0157] TiC powder, Ti powder and Al powder (all manufactured by Kojundo Chemical Laboratory Co., Ltd.) were put into a ball mill with zirconium oxide balls at a molar ratio of 2:1:1 and mixed for 24 hours. The obtained mixed powder was fired at 1350°C for 2 hours in an Ar atmosphere. The fired body (block MAX) thus obtained was crushed with an end mill to a maximum size of less than 40 μm. Thus, Ti as a precursor (powdered MAX) was obtained. 3 AlC 2 particle.

[0158] (2) Etching of precursor

[0159] Using the Ti prepared by the above method 3 AlC 2 The particles (powder) were etched under the following etching conditions to obtain 3 AlC 2 A solid-liquid mixture (slurry) of the solid components of a powder.

[0160] (Etching conditions)

[0161] Precursor: Ti 3 AlC 2 (Sieve with mesh size 45μm)

[0162] Etching solution composition: HF concentration is as shown in Table 1 below

[0163] HCl concentration: 7.4M

[0164] Etching liquid volume: 60mL

[0165] Precursor (Ti 3 AlC 2 )Input amount: 3.0g

[0166] Etching container: 100mL Iboy

[0167] Etching temperature: 35°C

[0168] Etching time: as shown in Table 1 below

[0169] Stirrer speed: 400rpm

[0170] (3) Cleaning after etching

[0171] The slurry was divided into two parts, each of which was put into two 50 mL centrifuge tubes. After centrifugation at 3500G using a centrifuge, the supernatant was discarded. 40 mL of pure water was added to the precipitate remaining in each centrifuge tube, and the supernatant was separated and removed by centrifugation at 3500G again. This operation was repeated 11 times. After the final centrifugation, the supernatant was discarded to obtain Ti 3 C 2 T s - Water medium clay It should be noted that in this embodiment, although the cleaning is performed with pure water, it is not limited to this, and for example, it can also be cleaned with dilute hydrochloric acid or the like.

[0172] (4) Li intercalation

[0173] For Ti prepared by the above method 3 C 2 T s -water medium clay, Li intercalation was carried out under the following conditions.

[0174] (Conditions for Li intercalation)

[0175] ·Ti 3 C 2 T s -Moisture medium clay (MXene after washing): solid content 0.75g

[0176] LiCl: 0.75g

[0177] Intercalation container: 100mL Iboy

[0178] Temperature: 20°C or higher and 25°C or lower (room temperature)

[0179] Time: 18h

[0180] Stirrer speed: 800rpm

[0181] (5) Delamination

[0182] The slurry obtained by intercalation of Li is placed in a 50 mL centrifuge tube, centrifuged at 3500G using a centrifuge, and the supernatant is discarded. Next, (i) 40 mL of pure water is added to the remaining precipitate, and then stirred on a shaker for 15 minutes, (ii) centrifuged at 3500G, and (iii) the supernatant is recovered as a liquid containing a single layer and a few layers of MXene. The operations (i) to (iii) are repeated 4 times in total to obtain a supernatant containing a single layer and a few layers of MXene. Furthermore, the supernatant is centrifuged at 4500G for 2 hours using a centrifuge, and the supernatant is discarded to obtain clay containing a single layer and a few layers of MXene.

[0183] [surface ]

[0184]

[0185] 〔evaluate〕

[0186] [Atomic ratio of Al to Ti (Al / Ti)]

[0187] The samples containing single-layer and few-layer MXene (clay containing single-layer and few-layer MXene) obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were freeze-dried to produce powders, which were dissolved by alkali fusion method, and the contents of Al and Ti were analyzed by ICP emission spectrometry to determine the atomic ratio of Al to Ti. For the above analysis, iCAP6300 manufactured by ThermoFisher Scientific Inc. was used. The results are also recorded in Table 1 above.

[0188] [Electrical conductivity of membrane]

[0189] (Method of producing film)

[0190] The clay containing a single layer and a few layers of MXene obtained by delamination (solid content 0.0375 g) was mixed with 25 mL of pure water to form a slurry and filtered to produce a MXene film. A membrane filter (Merck Co., Ltd., Durapore, pore size 0.65 μm) was used as the filter for the filtration. After filtration, vacuum drying was performed at 80°C for more than 8 hours to obtain a MXene film.

[0191] (Method for determining film density)

[0192] The film was punched out into a disc shape with a diameter of 12 mm using a punch press, and the weight was measured using an electronic balance and the thickness was measured using a height gauge. The film density was then calculated based on these measured values.

[0193] (Method for determining membrane conductivity)

[0194] Calculate the conductivity of the obtained MXene film. The conductivity is the average of three conductivities obtained in the following manner: measure the resistivity (Ω) and thickness (μm) at three locations of a sample, and calculate the conductivity (S / cm) based on these measured values. Use a simple low resistivity meter Loresta AX MCP-T370 (manufactured by Mitsubishi Chemical Analysis) to measure the surface resistance of the film using the 4-terminal method. Then, the volume resistivity is calculated based on the obtained surface resistance and the film thickness measured using a micrometer, and the conductivity is calculated by taking the reciprocal of this value. The conductivity is obtained by standardizing the film density obtained above to: 2g / cm 3 The results are also recorded in the above Table 1.

[0195] The following conclusions can be drawn from Table 1 above. In Examples 1 to 3, MXene films were obtained by etching under conditions where the HF concentration of the etching solution was high and the etching time was shorter than before. The obtained MXene film is a conductive film in which Al / Ti is suppressed to less than 0.10 atomic % and exhibits a high electrical conductivity of more than 7000 S / cm. On the other hand, in Comparative Examples 1 to 3, MXene films were obtained by the conventional method, i.e., etching was performed under conditions where the HF concentration of the etching solution was various and the etching time was as long as 24 hours. The Al / Ti of the obtained MXene film exceeded 0.10 atomic % and the electrical conductivity was less than 7000 S / cm. The present embodiment is not subject to any theoretical constraints, but it can be considered that the reason why the MXene films of Examples 1 to 3 exhibit higher electrical conductivity than the MXene films of Comparative Examples 1 to 3 is as follows. That is, it can be considered that: when the etching time becomes longer, AlF 3 ·3H 2 O precipitation, due to the AlF 3 ·3H 2 O is insoluble in water, so it does not decrease even if it is washed with pure water, and remains on the surface and between layers of MXene. As a result, it is believed that AlF contained in MXene, which is an insulator, 3 On the other hand, it is believed that in Examples 1 to 3, by using an etching solution containing HF at a certain concentration or more and shortening the etching time to a certain time or less, the electrical conductivity of the insulator AlF 3 It should be noted that the above AlF 3 It is a trihydrate, but the presence or absence of hydration water and the amount of hydration water are not limited.

[0196] In order to verify the above-mentioned embodiment, the following Experiment 1 and Experiment 2 were also carried out.

[0197] (Experiment 1)

[0198] 0.42 g of pure aluminum powder was added to 60 mL of etching solution (HF: 2.8 M, HCl: 7.4 M) and dissolved, and then left for various periods of time as shown in Table 2 below, and then the amount of precipitate precipitated in the etching solution was determined. The results are also shown in Table 2.

[0199] [surface ]

[0200]

[0201] In addition, the XRD measurement of the above precipitate was carried out under the following conditions. The XRD curve as the measurement result is shown in Figure 3 According to the Figure 3 It was confirmed that the above precipitate was AlF 3 ·3H 2 O.

[0202] (XRD measurement conditions)

[0203] ·Using device: MiniFlex600 manufactured by Rigaku Co., Ltd.

[0204] ·Measurement conditions

[0205] Light source: Cu lamp

[0206] Characteristic X-ray: CuKα=1.54Å

[0207] Measuring range: 3 degrees - 20 degrees

[0208] Step length: 50 steps / degree

[0209] From the above Table 2 and the results of XRD measurement, it was confirmed that the longer the etching time corresponding to the standing time, the greater the amount of AlF 3 ·3H 2 The more O can be precipitated.

[0210] (Experiment 2)

[0211] Etching was performed for 1, 3, or 6 hours using etching solutions with different HF concentrations (except for HF, the same etching solution as used in the examples). Then, the etching rate of the etched product was determined. For the etching rate, the Al content (atomic %) was determined by washing with water after the above etching and analyzing by ICP emission spectrometry. Then, it was assumed that the detected Al originated from Ti. 3AlC 2 , according to [(compose Ti 3 AlC 2 Al-detected Al) / (constituting Ti 3 AlC 2 The results are shown in Table 3.

[0212] [surface ]

[0213]

[0214] According to the results in Table 3, it can be considered that when the HF concentration of the etching solution is lower than 2.8M, even if the etching time is 6 hours, the etching rate is only 32.1%, and the yield of MXene particles obtained by further intercalation after etching is originally low. Therefore, it can be considered that it is difficult to shorten the etching time when the HF concentration of the etching solution is low. On the other hand, it is known that when the HF concentration of the etching solution is 9.9M, the etching rate is 89.3% under the condition of an etching time of 6 hours. Etching can be performed in a short time, and the etching time can be shortened. In addition, it can be considered that if the etching time is short, AlF 3 ·3H 2 The amount of O precipitation is small, and most of the detected Al comes from Ti 3 AlC 2 .

[0215] Industrial Applicability

[0216] The conductive two-dimensional particles, conductive film, conductive paste, and conductive composite material disclosed herein can be used in any appropriate application, and can be preferably used as electrodes in electric devices, for example.

[0217] The disclosure of this specification may include the following aspects.

[0218] <1> A conductive two-dimensional particle, which is a conductive two-dimensional particle comprising one or more layers of a layered material,

[0219] The above layer comprises the following formula:

[0220] Ti m X n

[0221] (wherein X is a carbon atom, a nitrogen atom or a combination thereof,

[0222] n is greater than or equal to 1 and less than or equal to 4,

[0223] m is greater than n and less than 5)

[0224] The layer body shown, and the modification or terminal T (T is at least one selected from a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom and a hydrogen atom) present on the surface of the layer body,

[0225] Furthermore, the atomic ratio of Al to Ti (Al / Ti) is greater than or equal to 0 atomic % and less than or equal to 0.10 atomic %.

[0226] <2> according to <1> The conductive two-dimensional particles described above have an average thickness of 15 nm or less.

[0227] <3> according to <1> or <2> The conductive two-dimensional particles, wherein the Ti m X n Ti 3 C 2 .

[0228] <4> A method for producing conductive two-dimensional particles, comprising:

[0229] (a) Prepare the following formula:

[0230] Ti m AlX n

[0231] (wherein X is a carbon atom, a nitrogen atom or a combination thereof,

[0232] n is greater than or equal to 1 and less than or equal to 4,

[0233] m is greater than n and less than 5)

[0234] Precursors shown;

[0235] (b1) contacting the precursor with an etching solution to perform etching to remove at least a portion of Al from the precursor;

[0236] (c) cleaning the etched product obtained by etching to obtain a cleaned product;

[0237] (d) performing an intercalation treatment of an interlayer inserting compound, the intercalation treatment comprising the step of stirring a mixed solution containing the cleaning material and the interlayer inserting compound of the cleaning material; and

[0238] (e1) using the intercalation product obtained by the above intercalation treatment to perform delamination to obtain conductive two-dimensional particles,

[0239] An atomic ratio of Al to Ti (Al / Ti) in the conductive two-dimensional particles is 0 atomic % or more and 0.10 atomic % or less.

[0240] <5> A method for producing conductive two-dimensional particles, comprising:

[0241] (a) Prepare the following formula:

[0242] Ti m AlX n

[0243] (wherein X is a carbon atom, a nitrogen atom or a combination thereof,

[0244] n is greater than or equal to 1 and less than or equal to 4,

[0245] m is greater than n and less than 5)

[0246] Precursors shown;

[0247] (b2) contacting the precursor with an etching solution containing an interlayer insertion compound to perform etching to remove at least a portion of Al from the precursor and to perform intercalation treatment of the interlayer insertion compound;

[0248] (e2) using the (etching + intercalation) product obtained by the above-mentioned etching and intercalation treatment, delamination is performed to obtain conductive two-dimensional particles,

[0249] An atomic ratio of Al to Ti (Al / Ti) in the conductive two-dimensional particles is 0 atomic % or more and 0.10 atomic % or less.

[0250] <6> according to <4> or <5> In the method for producing the conductive two-dimensional particles, the HF concentration of the etching solution is 7.0 M or more, and the time for which the precursor is in contact with the etching solution is 8 hours or less.

[0251] <7> according to <4> ~ <6> The method for producing conductive two-dimensional particles described in any one of the above, wherein the time for which the precursor is in contact with the etching solution is 0.5 hours or longer.

[0252] <8> according to <4> ~ <7> The method for producing conductive two-dimensional particles according to any one of the preceding claims, wherein the Ti m AlX n Ti 3 AlC 2 .

[0253] <9> A conductive film comprising <1> ~ <3> The conductive two-dimensional particle according to any one of the above.

[0254] <10> according to <9> The conductive film is a conductive film formed of the conductive two-dimensional particles, and has an electrical conductivity of 7000 S / cm or more as determined by the following formula.

[0255] Conductivity [S / cm] = 1 / (thickness of conductive film [cm] × surface resistivity of conductive film [Ω / □])

[0256] <11> A conductive paste comprising <1> ~ <3> The conductive two-dimensional particle according to any one of the above.

[0257] <12> A conductive composite material comprising <1> ~ <3> The conductive two-dimensional particles and polymer described above.

[0258] The present application claims priority based on Japanese Patent Application No. 2022-080357, which is a Japanese patent application. Japanese Patent Application No. 2022-080357 is incorporated into the present specification by reference.

[0259] Description of Reference Numerals

[0260] 1a, 1b layer main body (M m X n layer)

[0261] 3a, 5a, 3b, 5b modified or terminal T

[0262] 7a, 7b MXene layer

[0263] 10, 10a, 10b MXene particles (conductive two-dimensional particles, particles of layered materials)

[0264] 30 Conductive film (conductive thin film)

Claims

1. A conductive two-dimensional particle, which is a conductive two-dimensional particle comprising one or more layers of a layered material, The layer comprises the formula: You m X n The layer body shown, and the modification or terminal T present on the surface of the layer body, wherein, T is at least one selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom and a hydrogen atom, Formula Ti m X n In which X is a carbon atom, a nitrogen atom or a combination thereof, n is greater than or equal to 1 and less than or equal to 4, m is greater than n and less than 5, Furthermore, the atomic ratio of Al to Ti (Al / Ti) is greater than or equal to 0 atomic % and less than or equal to 0.10 atomic %.

2. The conductive two-dimensional particle according to claim 1, wherein The average thickness of the conductive two-dimensional particles is 15 nm or less.

3. The conductive two-dimensional particle according to claim 1 or 2, wherein The Ti m X n It is Ti3C2.

4. A method for producing conductive two-dimensional particles, comprising: (a) Prepare the following formula: Of m AlX n The precursor shown, Formula Ti m AlX n In which X is a carbon atom, a nitrogen atom or a combination thereof, n is greater than or equal to 1 and less than or equal to 4, m is greater than n and less than 5; (b1) contacting the precursor with an etching solution to perform etching to remove at least a portion of Al from the precursor; (c) cleaning the etched product obtained by etching to obtain a cleaned product; (d) performing an intercalation treatment of an interlayer inserting compound, the intercalation treatment comprising the step of stirring a mixed solution containing the cleaning material and the interlayer inserting compound of the cleaning material; as well as (e1) using the intercalation product obtained by the intercalation treatment and performing delamination to obtain conductive two-dimensional particles, An atomic ratio of Al to Ti (Al / Ti) in the conductive two-dimensional particles is greater than or equal to 0 atomic % and less than or equal to 0.10 atomic %.

5. A method for producing conductive two-dimensional particles, comprising: (a) Prepare the following formula: Of m AlX n The precursor shown, Formula Ti m AlX n In which X is a carbon atom, a nitrogen atom or a combination thereof, n is greater than or equal to 1 and less than or equal to 4, m is greater than n and less than 5; (b2) contacting the precursor with an etching solution containing an interlayer insertion compound to perform etching to remove at least a portion of Al from the precursor and to perform intercalation treatment of the interlayer insertion compound; (e2) using the "etching + intercalation" treated product obtained by performing the etching and intercalation treatments as described above to perform delamination to obtain conductive two-dimensional particles, An atomic ratio of Al to Ti (Al / Ti) in the conductive two-dimensional particles is greater than or equal to 0 atomic % and less than or equal to 0.10 atomic %.

6. The method for producing conductive two-dimensional particles according to claim 4 or 5, wherein: The HF concentration of the etching solution is 7.0 M or more, and the precursor is in contact with the etching solution for 8 hours or less.

7. The method for producing conductive two-dimensional particles according to any one of claims 4 to 6, wherein: The precursor is in contact with the etching solution for 0.5 hours or more.

8. The method for producing conductive two-dimensional particles according to any one of claims 4 to 7, wherein: The Ti m AlX n It is Ti3AlC2. 9 . A conductive film comprising the conductive two-dimensional particles according to claim 1 .

10. The conductive film according to claim 9, which is a conductive film formed of the conductive two-dimensional particles, and has a conductivity of 7000 S / cm or more as determined by the following formula: Electrical conductivity [S / cm] = 1 / (thickness of the conductive film [cm] × surface resistivity of the conductive film [Ω / □]). 11 . A conductive paste comprising the conductive two-dimensional particles according to claim 1 . 12 . A conductive composite material comprising the conductive two-dimensional particles according to claim 1 and a polymer.

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