Nanosheet structure and method for producing a nanosheet structure

Abstract

The present invention provides a nanosheet structure and a method for producing a nanosheet structure. [Solution] The nanosheet structure is formed by the aggregation of nanosheets, and has a porosity of 32% to 65%.

Description

[Technical Field]

[0001] The present invention relates to a nanosheet structure and a method for producing a nanosheet structure. [Background technology]

[0002] Patent Document 1 describes a method for producing a thin film consisting of a nanosheet monolayer, comprising: preparing a colloidal aqueous solution in which a nanosheet obtained by peeling off a single layer of an inorganic layered material is dispersed in a dispersion medium containing water and a lower alcohol having 5 or fewer carbon atoms; dropping the colloidal aqueous solution onto a substrate; and aspirating the dropped colloidal aqueous solution from the substrate. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-49062 [Overview of the Initiative]

[0004] One aspect of the present invention is a nanosheet structure formed by the aggregation of nanosheets, wherein the porosity is 32% or more and 65% or less. Another aspect of the present invention is a nanosheet structure formed by the aggregation of nanosheets, with a BET specific surface area of ​​1 m². 2 / g~5m 2 It is / g. Another aspect of the present invention is a nanosheet structure in which the amount of Kr adsorbed when the relative pressure is 0.08 to 0.59 is 0.24 cm³ under standard conditions. 3 / g~0.9cm 3 It is / g.

[0005] Another aspect of the present invention is a method for producing a nanosheet structure, comprising: dispersing nanosheets in a dispersion medium to produce a nanosheet dispersion liquid; atomizing the nanosheet dispersion liquid to generate a mist; and attaching the mist to an object to obtain a nanosheet structure. Another aspect of the present invention is a method for producing a nanosheet structure, comprising: dispersing nanosheets in a dispersion medium to produce a nanosheet dispersion liquid; atomizing the nanosheet dispersion liquid to generate a mist; and attaching the mist to an object to produce a nanosheet structure with a BET specific surface area of ​​1 m². 2 / g~5m 2 This includes obtaining a nanosheet structure that is / g. Another aspect of the present invention is a method for producing a nanosheet structure, comprising: dispersing nanosheets in a dispersion medium to produce a nanosheet dispersion liquid; atomizing the nanosheet dispersion liquid to generate a mist; and attaching the mist to an object, wherein the amount of Kr adsorbed at a relative pressure of 0.08 to 0.59 is 0.24 cm³ under standard conditions. 3 / g~0.9cm 3 This includes obtaining a nanosheet structure that is / g. [Brief explanation of the drawing]

[0006] [Figure 1] This figure illustrates the procedure for producing the nanosheet dispersion in this embodiment. [Figure 2] This figure shows an example of a nanosheet structure generating apparatus according to this embodiment. [Figure 3] Figure 3(A) is an AFM (Atomic Force Microscopy) image of the nanosheets in the nanosheet dispersion 14 in this embodiment, and Figure 3(B) is a TEM (Transmission Electron Microscopy) image. [Figure 4] This graph shows the thickness of the nanosheet in this embodiment. Figure 4(A) shows the cross-sectional thickness of the nanosheet along line A1 in Figure 3(A), and Figure 4(B) shows the cross-sectional thickness of the nanosheet along line A2 in Figure 3(A). [Figure 5] This is a Scanning Electron Microscope (SEM) image of a cross-section of the nanosheet structure of Example 1. [Figure 6] This is an SEM image of a cross-section of the nanosheet structure of Example 2. [Figure 7]SEM image of the cross-section of the nanosheet structure of Example 3. [Figure 8] A diagram for explaining the film thickness. [Figure 9] SEM image of the cross-section of the nanosheet structure of Comparative Example 1. [Figure 10] SEM image of the cross-section of the nanosheet structure of Comparative Example 2. [Figure 11] SEM image of the cross-section of the nanosheet structure of Comparative Example 3. [Figure 12] SEM image of the cross-section of the nanosheet structure of Comparative Example 4. [Figure 13] SEM image of the cross-section of the nanosheet structure of Comparative Example 5. [Figure 14] SEM image of the cross-section of the nanosheet structure of Comparative Example 6. [Figure 15] Graph showing the Kr adsorption isotherms of Example 4 and Comparative Example 7.

Mode for Carrying Out the Invention

[0007] Hereinafter, embodiments according to the present invention (hereinafter referred to as "the present embodiments") will be described. The following present embodiments are examples for explaining the present invention and are not intended to limit the present invention to the following contents. The present invention can be appropriately modified and implemented within the scope of its gist.

[0008] In the drawings, the same reference numerals are given to the same elements, and redundant explanations are omitted. Also, the positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to the illustrated ratios. Also, the "cross-section" in the "cross-sectional view" or "cross-sectional perspective" refers to a cross-section perpendicular to the horizontal plane.

[0009] Recently, nanosheets have been utilized in various fields due to their excellent properties. The porous nanosheet structure obtained by the present embodiments is expected to be applied in a wide range of fields because it has a high specific surface area.

[0010] FIG. 1 is a diagram for explaining the production procedure of the nanosheet dispersion liquid 14 in the present embodiment. The layered substance 11 used in the present embodiment is any one or more of, for example, metal oxides, metal sulfides, metal hydroxides, or clay minerals. More specifically, the layered substance 11 is, for example, any one or more of metal oxides, metal sulfides, metal hydroxides, or clay minerals such as niobium, ruthenium, titanium, vanadium, manganese, cobalt, iron, zinc, molybdenum, tungsten, zirconium, or aluminum. Further, the layered substance 11 may be a compound containing any one or more of carbon, nitrogen, boron, silicon, phosphorus, arsenic, antimony, bismuth, hafnium, tantalum, sulfur, selenium, tellurium, gallium, indium, germanium, tin, lead, oxygen, strontium, copper, fluorine, magnesium, cadmium, iodine, chlorine, silver, calcium. Further, the layered substance 11 may also be a salt with ions of alkali metals such as lithium, potassium, sodium, or ions of group 2 metals such as magnesium, calcium, strontium, barium. These are also referred to as inorganic layered compounds. Specifically, the layered substance 11 is, for example, K4Nb6O 17 ·3H2O or the like.

[0011] First, an interlayer expansion process of the layered substance 11 is performed (step S01). In this process, by mixing the layered substance 11 with bulky organic molecules, ions, polymers, etc., a first intermediate 12 in which guest molecules are intercalated into the layered substance 11 is obtained. As the bulky organic molecules, ions, polymers, for example, any one or more of alkylammonium salts such as dodecylammonium chloride, octylammonium bromide, tetradecylammonium hydroxide; alkylsulfonates such as sodium dodecylbenzenesulfonate, sodium lauryl sulfate; organic acids such as terephthalic acid, oleic acid; polymers such as polyethylene glycol, polyacrylic acid can be used.

[0012] Next, a modification step of the first intermediate 12 is performed (step S02). In this step, the first intermediate 12 and a surface modifier are combined to obtain a second intermediate 13 in which the compound has been modified from the first intermediate 12. More specifically, when the first intermediate 12 and the surface modifier are combined, a graft reaction occurs, causing the surface of each layer of the layered material 11 to become hydrophilic and the interlayers of the layered material 11 to peel off. Phosphoric acid, organophosphorus compounds having a POH group, phosphorus coupling agents, silane coupling agents, alcohols, carboxylic acids, etc., can be used as surface modifiers.

[0013] Next, the second intermediate 13 is subjected to an ultrasonic treatment process (step S03). In this process, the second intermediate 13 and water or a predetermined dispersion medium are placed in a container 31, and ultrasonic treatment is performed using an ultrasonic homogenizer 32. As a result, a nanosheet dispersion liquid 14 is obtained in which nanosheets peeled off from the layered material 11 are dispersed in the dispersion medium. The ultrasonic frequency and output in the ultrasonic treatment process can be set as appropriate. For example, the ultrasonic frequency can be 28kHz to 40kHz. For example, the ultrasonic output can be 100W to 550W. The average thickness of the nanosheets is usually in the range of 0.1nm to 5nm, preferably 0.5nm to 3.5nm.

[0014] The procedure for producing the nanosheet dispersion 14 is not limited to the example shown in this figure, and the appropriate method can be selected depending on the nanosheet material used. Furthermore, in the procedure for producing the nanosheet dispersion 14 shown in Figure 1, the nanosheet dispersion may be prepared by omitting at least one of steps S01, S02, and S03, and any of the steps may be replaced with other steps. When obtaining nanosheets by peeling off the layered material 11, it is sufficient to peel off at least the layered material 11, and as a method of peeling, in addition to the intercalation and sonication treatment described above, methods such as surface modification, oxidation, and swelling may be used.

[0015] Furthermore, nanosheets may be fabricated without using the method of exfoliating the layered material 11 described above. In that case, methods such as CVD (Chemical Vapor Deposition), sol-gel method, and precipitation of metals or metal oxides between lamellar micelles may be used as the method for fabricating the nanosheets. A nanosheet dispersion can be prepared by dispersing the fabricated nanosheets in a dispersion medium. As specific methods for fabricating nanosheets other than those of this embodiment, for example, methods described in the papers "Janus Polymer Single Crystal Nanosheet via Evaporative Crystallization" (dx.doi.org / 10.1021 / mz5002806 | ACS Macro Lett. 2014, 3, 675-678) and "Janus Nanodisc of Diblock Copolymers" (Adv. Mater. 2014, 26, 4469-4472) may be used.

[0016] Furthermore, in this embodiment, the nanosheet may be made from, for example, clay minerals, layered silicates, layered double hydroxides, layered transition metal oxyacids, layered perovskites, layered metal oxides, layered nitrides, graphite, transition metal dichalcogenides, or MXene. Alternatively, the nanosheet may be any of clay nanosheets, silica nanosheets, metal oxide nanosheets, or graphene.

[0017] Furthermore, the nanosheet may contain one or more of the following: niobium, ruthenium, titanium, vanadium, manganese, cobalt, iron, zinc, molybdenum, tungsten, and zirconium. Additionally, the nanosheet may contain one or more of the following: carbon, nitrogen, boron, silicon, aluminum, phosphorus, arsenic, antimony, bismuth, hafnium, tantalum, sulfur, selenium, tellurium, gallium, indium, germanium, tin, lead, oxygen, strontium, copper, fluorine, magnesium, cadmium, iodine, chlorine, silver, and calcium.

[0018] Figure 2 shows an example of a nanosheet structure generating apparatus 1 in this embodiment. The nanosheet structure generating apparatus 1 comprises a mist generating unit 110 and a film formation unit 120. The mist generating unit 110 atomizes the nanosheet dispersion liquid 14. The film formation unit 120 deposits the mist of the nanosheet dispersion liquid 14 onto the object to be film-formed 21. The mist generating unit 110 and the film formation unit 120 are connected via piping 116.

[0019] The mist generating unit 110 includes an outer container 111, an inner container 112, a lid 113, a gas supply pipe 114, and an ultrasonic transducer 115. The outer container 111 is a container that houses the propagating liquid, the inner container 112, and the ultrasonic transducer 115. The outer container 111 houses the inner container 112 and the propagating liquid such that at least a portion of the inner container 112 is in contact with the propagating liquid.

[0020] The inner container 112 contains a nanosheet dispersion liquid 14, which is the material for the mist. The lid 113 is installed at the opening at the top of the inner container 112. The mist generating unit 110 does not necessarily have to have a lid 113.

[0021] The gas supply pipe 114 delivers carrier gas for transporting mist to the inner container 112. The gas supply pipe 114 is attached to the top or lid 113 of the inner container 112. The position and configuration of the gas supply pipe 114 are not particularly limited, and it is sufficient if it is configured to supply carrier gas into the inner container 112.

[0022] The ultrasonic transducer 115 generates vibrations. The vibrations generated by the ultrasonic transducer 115 are transmitted to the nanosheet dispersion 14 in the inner container 112 by the propagation liquid. The installation position of the ultrasonic transducer 115 is not limited; any structure that allows the vibrations of the ultrasonic transducer 115 to be transmitted to the nanosheet dispersion 14 is acceptable. When the vibrations of the ultrasonic transducer 115 are transmitted to the nanosheet dispersion 14, the mist generating unit 110 does not need to have an outer container 111 and a propagation liquid. In addition, any transducer that generates mist 50 can be used as the ultrasonic transducer 115, and it may not even be an ultrasonic transducer. As a result, ultrasonic vibrations are applied to the nanosheet dispersion 14 by the vibrations of the ultrasonic transducer 115.

[0023] The output and frequency of the ultrasonic transducer 115 that generates the mist can be set as appropriate. The frequency can be, for example, 1.0 MHz to several MHz. The output can be, for example, 10 W to 200 W.

[0024] The film deposition unit 120 comprises a housing 121, a temperature control device 122, and a stage 123. The housing 121 is a wall separating the film deposition unit 120 from the outside. The temperature control device 122 adjusts the temperature of the object to be deposited 21. The stage 123 holds the object to be deposited 21. The object to be deposited 21 can be a glass substrate, a plastic substrate, a metal substrate, etc., and the material is not particularly limited. Furthermore, for example, the object to be deposited 21 can be a film or an object with a shape other than a flat plate, and the shape is not particularly limited.

[0025] In this embodiment, mist generated in the mist generation unit 110 is supplied to the film deposition unit 120 via the piping 116. More specifically, vibrations from the ultrasonic transducer 115 are transmitted to the nanosheet dispersion liquid 14 in the internal container 112 via the propagation liquid. The vibrations cause the nanosheet dispersion liquid 14 to be atomized into mist. The generated mist is sent to the piping 116. Carrier gas supplied from the gas supply pipe 114 is also sent to the piping 116. The piping 116 transports the mist and carrier gas from the mist generation unit 110 to the film deposition unit 120.

[0026] The mist that reaches the film deposition section 120 via the piping 116 arrives at the object to be deposited 21 and forms a nanosheet structure 22. In this embodiment, the nanosheet structure 22 is a porous material having multiple pores separated by a thin film. This embodiment makes it possible to obtain a nanosheet structure 22 with a suitable porosity.

[0027] Furthermore, it is preferable that the temperature control device 122 heats the object to be deposited on 21 at least until the mist reaches it. If the temperature of the object to be deposited on 21 is low when the mist reaches it, new mist will arrive before the mist on the object to be deposited on 21 has dried properly. As a result, the nanosheets that have been peeled off by the ultrasonic treatment process (step S03) may be re-laminated or aggregated, leading to thickening of the thin film contained in the nanosheet structure 22. Also, if the temperature of the object to be deposited on 21 is high when the mist reaches it, it may dry before reaching the object to be deposited on 21, which could reduce the adhesion between the mist and the object to be deposited on 21. In addition, high temperatures may also reduce the adhesion rate of the mist to the object to be deposited on 21 due to the generation of upward gas flow and other factors.

[0028] At least the temperature of the object to be deposited on 21 when the mist reaches it is preferably 45°C or higher, more preferably 47°C or higher, and even more preferably 50°C or higher, when water is used as the dispersion medium. Furthermore, at least the temperature of the object to be deposited on 21 when the mist reaches it is preferably 57°C or lower, more preferably 55°C or lower, and even more preferably 53°C or lower.

[0029] Furthermore, when ethanol is used as the dispersion medium, the temperature of the object to be filmed 21 is preferably 28°C or higher, more preferably 30°C or higher, and even more preferably 33°C or higher. In addition, the temperature of the object to be filmed 21 at least when the mist reaches the object to be filmed 21 is preferably 40°C or lower, more preferably 37°C or lower, and even more preferably 35°C or lower.

[0030] Furthermore, when calculating the vapor pressure from the aforementioned temperature, the vapor pressure of the dispersion medium when the mist reaches the film-forming object 21 is preferably 72 mmHg or higher, more preferably 80 mmHg or higher, and even more preferably 92 mmHg or higher. Also, the vapor pressure of the dispersion medium when the mist reaches the film-forming object 21 is preferably 130 mmHg or lower, more preferably 118 mmHg or lower, and even more preferably 107 mmHg or lower. When using solvents other than water and ethanol as described above, the temperature can be calculated from these vapor pressure values ​​and set to an appropriate substrate temperature.

[0031] Furthermore, the configuration of the nanosheet structure generating apparatus 1 is not limited to the example shown in Figure 2. For example, a mist containment tank for capturing excess mist may be provided between the mist generating unit 110 and the film formation unit 120, or a sensor for detecting the flow rate of mist passing through the piping 116 may be provided.

[0032] The nanosheet structure 22 obtained by this embodiment has multiple pores, and if the porosity, which is the ratio of the volume of pores to the volume of the nanosheet structure 22, is large, it exhibits high performance, for example, when the nanosheet structure 22 is used as an absorbent material. Furthermore, because the nanosheet structure 22 has a large specific surface area, catalytic performance can be improved by obtaining a nanosheet structure 22 having the structure of this embodiment using a catalytic nanosheet material. In addition, because the nanosheet structure 22 has a high porosity, it has a low refractive index and is expected to be applicable to anti-reflective coatings and the like. The porosity of the nanosheet structure 22 in this embodiment is preferably 32% or more, more preferably 35% or more, and even more preferably 40% or more. The porosity of the nanosheet structure 22 in this embodiment is more preferably 65% ​​or less, even more preferably 60% or less, and even more preferably 55% or less.

[0033] Furthermore, if the average thickness of the thin film between adjacent pores (also called the "average wall thickness") is thin, the pores are formed to be larger or finer, resulting in high performance as a porous material. The average thickness is preferably 7 times or less the thickness of a single layer of the nanosheet used, more preferably 5 times or less the thickness of a single layer of the nanosheet, and even more preferably 4 times or less the thickness of a single layer of the nanosheet. The thin film contains at least one nanosheet.

[0034] In the nanosheet dispersion 14, nanosheets are dispersed in a single layer. When this nanosheet dispersion 14 is atomized to form a film, the mist containing dispersed nanosheets and the dispersion medium reaches the substrate 21, which is the object to be deposited. When the mist adheres to the substrate, the dispersion medium contained in the mist volatilizes. By continuing to supply the mist for a predetermined time, a nanosheet structure 22 with voids is formed. If the amount of volatilization of the dispersion medium is small, the substrate may be heated to actively dry the dispersion medium. Since the drying rate of the dispersion medium affects the size of the voids, the size of the voids can also be controlled by appropriately setting the mist supply rate to the substrate and the substrate temperature.

[0035] When attempting to form the nanosheet structure 22 using other deposition methods such as spin coating or drop casting, a large amount of nanosheet dispersion 14 is supplied to the substrate at once, causing the nanosheets to re-layer or aggregate on the substrate. As a result, the supplied nanosheets become thicker, and the average thickness of the thin film between adjacent pores becomes larger compared to when deposition is performed by mist. In other words, the large average thickness between adjacent pores prevents the acquisition of a structure with a large porosity.

[0036] The nanosheet structure 22 has a large specific surface area, enabling applications in a wide range of fields. The nanosheet structure 22 has a BET specific surface area of ​​1.0 m². 2 It is preferable that it be 1.5m or more per gram. 2 It is more preferable that it be 2.0m or more per gram. 2 It is even more preferable that the amount is greater than or equal to / g. Furthermore, the nanosheet structure 22 may, for example, have a BET specific surface area of ​​10.0 m².2 It is less than / g, and another example is 5.0m 2 It is less than / g, and another example is 3.0m 2 It is less than / g.

[0037] The BET specific surface area can be determined from the adsorption isotherm using Kr as the adsorbed gas.

[0038] Furthermore, the nanosheet structure 22 has a Kr adsorption capacity of 0.24 cm³ under standard conditions when the relative pressure is 0.08 to 0.59. 3 / g~0.9cm 3 It is preferable that the value be / g. Relative pressure refers to the value obtained by dividing the atmospheric pressure at the time of measurement by the saturated vapor pressure. Standard conditions refer to conditions of 0°C and 1 atmosphere.

[0039] <Examples> Next, examples and comparative examples of the present invention will be described. However, the present invention is not limited to these examples.

[0040] <Generation of nanosheet dispersion 14> The ampoule contains layered hexaniobate (K4Nb6O 17 3.0 g of (3H2O) and 4.05 g of dodecylammonium chloride dissolved in 40 mL of pure water were added and heated at 80°C for 4 days. Then, the mixture was centrifuged at 4500 rpm for 5 minutes, the solid was washed twice with pure water and twice with acetone, and dried. This yielded the first intermediate 12, in which the interlayers of the layered hexaniobate were expanded.

[0041] Next, 122.4 g of the first intermediate, 417.6 μL g of phosphoric acid, and 50 mL of anhydrous 2-butanone were placed in a Schlenk flask and heated at 80°C for 4 days under a nitrogen atmosphere. After that, the mixture was centrifuged at 4500 rpm for 5 minutes, the solid was washed twice with acetone, and dried. This yielded the second intermediate 13, in which the layered surface of the hexaniobate was modified with phosphoric acid.

[0042] Next, 100 mg of the second product was added to 100 mL of pure water and stirred for 1 day. Then, sonication was performed for 30 minutes using an ultrasonic homogenizer while cooling in an ice bath. A Branson sonicator MODEL SFX250 was used, and the amplitude was set to 40%. The sonication was performed intermittently, with a 10-second interval followed by a 5-second rest period. The treated liquid was centrifuged at 4500 rpm for 10 minutes, and the supernatant was collected. This liquid is nanosheet dispersion 14. The solid content concentration of the dispersion was 4 mg / mL.

[0043] Figure 3(A) is an AFM (Atomic Force Microscopy) image of nanosheets in the nanosheet dispersion 14 in this embodiment, and Figure 3(B) is a TEM (Transmission Electron Microscopy) image. According to Figure 3(A), nanosheets with a lateral size of 200 nm or more and less than 300 nm were observed.

[0044] Figure 4 is a graph showing the thickness of the nanosheet in Figure 3. Figure 4(A) shows the cross-sectional thickness of the nanosheet along line A1 in Figure 3(A), and Figure 4(B) shows the cross-sectional thickness of the nanosheet along line A2 in Figure 3(A). It was found that the nanosheet in Figure 3(A) has a thickness of approximately 2 nm.

[0045] <Examples 1-3> 80 mL of nanosheet dispersion 14 was placed in the internal container 112 of the nanosheet structure generation apparatus 1. An ultrasonic transducer 115 was placed in an external container 111 containing ice water, and the internal container 112 containing the nanosheet dispersion 14 was placed inside it. A lid 113 was placed over the internal container 112, and a gas supply pipe 114 was inserted through one of the two holes in the lid 113, and N2, which would serve as a carrier gas, was supplied from the gas supply pipe 114 at a rate of 4 L / min. A pipe 116 was inserted through the other hole, and mist was transported to the film formation section 120.

[0046] During mist transport, the object to be deposited 21, placed on stage 123, was temperature-controlled by placing it on a temperature control device, a Cool Stirrer (Cynics Corporation, Cool Stirrer CPS-300). The temperature control device controlled the temperature of the object to be deposited 21 to 50°C. The mist transported to the deposition section 120 was blown onto the object to be deposited 21 on stage 123, and a nanosheet structure 22 was deposited. After the mist was generated, the deposition of the nanosheet structure 22 continued for 120 minutes from the time the carrier gas was inflow, and a total of three nanosheet structures 22 were produced.

[0047] Figure 5 shows an SEM (Scanning Electron Microscope) image of a cross-section of the nanosheet structure 22 of Example 1. Figure 6 shows an SEM image of a cross-section of the nanosheet structure 22 of Example 2. Figure 7 shows an SEM image of a cross-section of the nanosheet structure 22 of Example 3. For each example, the nanosheet structure 22 was processed by ion milling to obtain a cross-section perpendicular to the film deposition target 21, and an SEM image at 100,000x magnification was observed. For each example, the nanosheet structure 22 was observed in areas with a film thickness of 100 nm or more and a width of 1 μm or more.

[0048] As shown in Figure 5, the nanosheet structure 22 had multiple pores separated by thin films. Since the pores are randomly distributed, the volumetric porosity can be said to be equal to the area porosity in the cross-section. That is, in each SEM image shown in Figure 5, the area occupied by the nanosheet structure 22 (area including pores) was calculated and defined as the "structure area". In addition, the area of ​​the thin film between each pore was calculated and defined as the "thin film area". The pore area was obtained by subtracting the "thin film area" from the "structure area". The "porosity" was calculated by dividing the pore area by the "structure area" and expressing it as a percentage. Porosity = (Structure area - Thin film area) / Structure area × 100 = void area / structure area ×100

[0049] Figure 8 is a diagram illustrating the thin film thickness. The portion sandwiched between the two arrows is the thin film portion between adjacent pores. The thickness of the thin film was measured by determining the distance between the arrows. For each nanosheet structure 22 in Examples 1 to 3, 10 dispersed locations were selected from the SEM image of a single cross-section, and the thickness of the thin film (wall thickness) was measured and the average value was calculated and referred to as the "average wall thickness". The thin film portion sandwiched between the two arrows may be a single layer or may be a state in which multiple nanosheets are stacked on top of each other.

[0050] <Comparative Examples 1-3> A nanosheet dispersion 14, similar to that used in Examples 1-3, was dropped onto a film-forming object 21 to obtain a nanosheet structure 22. During film formation, the film-forming object 21 was heated to 50°C using a temperature control device 122. Subsequently, the structure area, thin film area, porosity, and average wall thickness were measured in the same manner as in Examples 1-3.

[0051] Figures 9-11 show SEM images of cross-sections of the nanosheet structures 22 of Comparative Examples 1-3. Figure 9 is an SEM image of the cross-section of the nanosheet structure 22 of Comparative Example 1, Figure 10 is an SEM image of the cross-section of the nanosheet structure 22 of Comparative Example 2, and Figure 11 is an SEM image of the cross-section of the nanosheet structure 22 of Comparative Example 3. The objects observed in the SEM images are the same as those in Examples 1-3 shown in Figure 5.

[0052] <Comparative Examples 4-6> During film formation, the object to be filmed 21 was not heated, and the nanosheet structure 22 was formed at room temperature. Other than this, the procedure was the same as in Comparative Examples 1-3.

[0053] Figures 12-14 show SEM images of cross-sections of the nanosheet structures 22 of Comparative Examples 4-6. Figure 12 is an SEM image of the cross-section of the nanosheet structure 22 of Comparative Example 4, Figure 13 is an SEM image of the cross-section of the nanosheet structure 22 of Comparative Example 5, and Figure 14 is an SEM image of the cross-section of the nanosheet structure 22 of Comparative Example 6. The objects observed in the SEM images are the same as those in Examples 1-3 shown in Figure 5.

[0054] The measurement results for each example and each comparative example are shown below.

[0055]

Table 1

[0056]

Table 2

[0057] <Evaluation> According to each of the examples and comparative examples, by using the mist deposition method in which the mist is generated using the nanosheet dispersion liquid 14 and the nanosheet structure 22 is deposited on the film formation target object 21, it was confirmed that the nanosheet structure 22 having an appropriate porosity can be obtained. Further, it was confirmed that by using the mist deposition method, the nanosheet structure 22 having an appropriate wall thickness can be obtained.

[0058] <Example 4, Comparative Example 7> As Example 4, ethanol was used instead of water as the dispersion medium for dispersing the second product, and the nanosheet structure 22 was produced. Other conditions are the same as in Example 1 except that the temperature of the film formation target object is 33°C. When the dispersion medium is water, the temperature of the film formation target object is 50°C and the vapor pressure is 92 mmHg, and in the case of ethanol, the temperature is 33°C and the vapor pressure is 92 mmHg.

[0059] As Comparative Example 7, similar to Example 4, ethanol was used as the dispersion medium to obtain the nanosheet dispersion liquid 14. Then, similar to Comparative Example 1, the nanosheet dispersion liquid 14 was dropped onto the film formation target object 21 to produce the nanosheet structure 22.

[0060] <Evaluation of Kr adsorption amount> Figure 15 is a graph showing the Kr adsorption isotherms for Example 4 and Comparative Example 7. Kr was used as the adsorption gas. Using BELSORP MAX from Microtrac-Bel, the amount of Kr adsorbed under standard conditions was measured for each of the nanosheet structures 22 of Example 4 and Comparative Example 7 when the relative pressure was varied. Furthermore, for Example 4 and Comparative Example 7, the BET specific surface area and pore volume were obtained by BET analysis using the measurement results related to the Kr adsorption isotherms.

[0061] The measurement results for Example 4 and Comparative Example 7 are shown below.

[0062] [Table 3]

[0063] In Example 4, the amount of Kr adsorbed at a relative pressure of 0.08 to 0.59 was 0.24 cm³ under standard conditions. 3 / g~0.9cm 3 The value was found to be / g, indicating higher adsorption performance compared to Comparative Example 7. Furthermore, it was found that the nanosheet structure 22 according to Example 4 has a larger BET specific surface area than that of Comparative Example 7.

[0064] Based on the above, it was confirmed that a nanosheet structure 22 with a high specific surface area and high adsorption performance, enabling applications in a wide range of fields, was produced. [Explanation of Symbols]

[0065] 1: Nanosheet structure generation device, 11: Layered material, 12: First intermediate, 13: Second intermediate, 14: Nanosheet dispersion, 21: Film deposition target, 22: Nanosheet structure, 31: Container, 32: Ultrasonic homogenizer, 110: Mist generation unit, 111: Outer container, 112: Inner container, 113: Lid, 114: Gas supply pipe, 115: Ultrasonic transducer, 116: Piping, 120: Film deposition unit, 121: Housing, 122: Temperature control device, 123: Stage, A1·A2: Parts

Claims

1. A nanosheet structure formed by the aggregation of nanosheets, with a porosity of 32% to 65%.

2. Nanosheets are assembled to form a structure with a BET specific surface area of ​​1 m². ２ / g to 5m ２ A nanosheet structure that is / g.

3. When nanosheets aggregate to form a structure, the amount of Kr adsorbed under a relative pressure of 0.08 to 0.59 is 0.24 cm³ under standard conditions. ３ / g ~ 0.9cm ３ A nanosheet structure with a density of / g.

4. A nanosheet structure according to any one of claims 1 to 3, Multiple holes, A thin film located between adjacent holes and forming the holes, The nanosheet structure comprises at least one nanosheet, wherein the thin film has an average thickness of seven times or less that of a single layer of the nanosheet.

5. A nanosheet structure according to any one of claims 1 to 3, The nanosheet is a nanosheet structure containing one or more of the following: niobium, ruthenium, titanium, vanadium, manganese, cobalt, iron, zinc, molybdenum, tungsten, and zirconium.

6. A nanosheet structure according to any one of claims 1 to 3, The nanosheet structure is one of the following: clay nanosheets, silica nanosheets, metal oxide nanosheets, or graphene.

7. A nanosheet structure according to any one of claims 1 to 3, The nanosheet is a nanosheet structure made from one or more of the following: clay mineral, layered silicate, layered double hydroxide, layered transition metal oxyacid, layered perovskite, layered metal oxide, layered nitride, graphite, transition metal dichalcogenide, and MXene.

8. Dispersing nanosheets in a dispersion medium to produce a nanosheet dispersion liquid, The nanosheet dispersion is atomized to generate a mist, A method for producing a nanosheet structure, comprising attaching the aforementioned mist to an object to obtain a nanosheet structure.

9. Dispersing nanosheets in a dispersion medium to produce a nanosheet dispersion liquid, The nanosheet dispersion is atomized to generate a mist, The mist is applied to an object, and the BET specific surface area is 1 m². ２ / g to 5m ２ A method for producing a nanosheet structure, comprising obtaining a nanosheet structure that is / g.

10. Dispersing nanosheets in a dispersion medium to produce a nanosheet dispersion liquid, The nanosheet dispersion is atomized to generate a mist, When the aforementioned mist is applied to an object, the amount of Kr adsorbed at a relative pressure of 0.08 to 0.59 is 0.24 cm³ under standard conditions. ３ / g ~ 0.9cm ３ A method for producing a nanosheet structure, comprising obtaining a nanosheet structure that is / g.

11. A method for producing a nanosheet structure according to any one of claims 8 to 10, The nanosheet structure is a nanosheet structure having a porosity of 32% or more, and is a method for producing a nanosheet structure.

12. A method for producing a nanosheet structure according to any one of claims 8 to 10, The aforementioned nanosheet structure is Multiple holes, A thin film located between adjacent holes and forming the holes, A method for producing a nanosheet structure, wherein the thin film contains at least one nanosheet, and the average thickness of the thin film is seven times or less the thickness of a single layer of the nanosheet.

13. A method for producing a nanosheet structure according to any one of claims 8 to 10, A method for producing a nanosheet structure, comprising preparing the nanosheet by one of the following methods: CVD, sol-gel method, precipitation between lamellar micelles, or exfoliation of a layered material.

14. A method for producing a nanosheet structure according to any one of claims 8 to 10, A method for producing a nanosheet structure, comprising the step of generating the mist, which includes an ultrasonic treatment in which ultrasonic vibrations are applied to the nanosheet dispersion.

15. A method for producing a nanosheet structure according to any one of claims 8 to 10, The procedure for generating the aforementioned nanosheet dispersion includes an ultrasonic treatment in which ultrasonic vibrations are applied to the dispersion medium, and is a method for generating a nanosheet structure.

16. A method for producing a nanosheet structure according to any one of claims 8 to 10, The procedure for producing the aforementioned nanosheet dispersion includes a process in which one or more bulky organic molecules, ions, or polymers are reacted with a layered material, followed by a graft reaction, to produce a nanosheet structure.

17. A method for producing a nanosheet structure according to claim 16, A method for producing a nanosheet structure, wherein the bulky organic molecule, ion, or polymer is one or more of alkylammonium salts, alkyl sulfonates, organic acids, and polymers.

18. A method for producing a nanosheet structure according to any one of claims 8 to 10, A method for producing a nanosheet structure, wherein the object is heated in the procedure for obtaining the nanosheet structure.

19. A method for generating a nanosheet structure according to claim 18, A method for producing a nanosheet structure, wherein the temperature of the object in the procedure for obtaining the nanosheet structure is 28°C to 57°C.

20. A method for producing a nanosheet structure according to any one of claims 8 to 10, A method for producing a nanosheet structure, wherein, in the procedure for obtaining the nanosheet structure, the vapor pressure of the dispersion medium when the mist reaches the object is 72 mHg to 130 mHg.

21. A method for producing a nanosheet structure according to claim 13, The nanosheet is fabricated by peeling off the layered material. The layered material is a metal oxide, metal sulfide, metal hydroxide, or clay mineral. Method for generating nanosheet structures.

22. A method for producing a nanosheet structure according to any one of claims 8 to 10, A method for producing a nanosheet structure, wherein the nanosheet contains one or more of the following: niobium, ruthenium, titanium, vanadium, manganese, cobalt, iron, zinc, molybdenum, tungsten, and zirconium.

23. A method for producing a nanosheet structure according to any one of claims 8 to 10, A method for producing a nanosheet structure, wherein the nanosheet is one of clay nanosheets, silica nanosheets, metal oxide nanosheets, or graphene.

24. A method for producing a nanosheet structure according to any one of claims 8 to 10, A method for producing a nanosheet structure, wherein the nanosheet is made from one or more of the following: clay mineral, layered silicate, layered double hydroxide, layered transition metal oxyacid, layered perovskite, layered metal oxide, layered nitride, graphite, transition metal dichalcogenide, and MXene.

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