A method for dispersing clay mineral monolayers based on staged alcohol molecule intercalation and exfoliation

Abstract

The present application relates to the technical field of mineral material microcharacterization, and in particular to a method for dispersing clay mineral monolayer suitable for transmission electron microscope observation. The method for dispersing clay mineral monolayer based on stage alcohol intercalation and exfoliation comprises the following steps: dispersing clay mineral in deionized water to obtain a clay mineral suspension system by stirring; adding small molecule alcohol to the suspension system first and then adding macromolecular alcohol, and stirring to obtain a dilute dispersion system; performing ultrasonic treatment to make the clay mineral form a dispersion system mainly in monolayer or few-layer structure; dropping onto a carrier film for transmission electron microscope to make the lamella spread on the surface of the carrier film; and observing by using a transmission electron microscope. The present application is conducive to obtaining clay mineral monolayer samples with good dispersion and complete structure, and is suitable for morphology and structure characterization under transmission electron microscope.

Description

Technical Field

[0001] This invention relates to the field of mineral material microstructure characterization technology, specifically to a method for single-layer dispersion of clay minerals suitable for observation by transmission electron microscopy. Background Technology

[0002] Saponite is a typical 2:1 type montmorillonite clay mineral. Its crystal structure consists of two layers of silicon-oxygen tetrahedra sandwiching a layer of metallic-oxygen octahedra, with exchangeable cations and water molecules in the interlayer. Because saponite is easier to synthesize in the laboratory than montmorillonite, it is often used as an important model mineral for studying and simulating the nucleation, growth, and lamellar evolution of montmorillonite clay minerals. The physicochemical properties of clay minerals are closely related to their layered structure, especially in monolayer or few-layered dispersions. Their surface structure, edge characteristics, interfacial reactivity, and elemental distribution characteristics can more directly reflect the mineral crystal growth process. Therefore, obtaining well-dispersed, structurally complete saponite monolayer samples and accurately characterizing their monolayer morphology, size, and elemental spatial distribution is of great significance for revealing the formation and growth mechanism of saponite. Currently, how to effectively obtain and characterize the monolayer structure of saponite remains one of the key technical issues in the study of saponite mineral growth mechanisms.

[0003] Transmission electron microscopy (TEM) is an important technique for observing the morphology and monolayer structure of saponite sheets due to its high spatial resolution. However, the electrostatic forces, van der Waals forces, and hydrogen bonds between saponite layers cause them to easily aggregate and recombine in liquid systems. During TEM sample preparation, this often results in multilayered overlapping structures, leading to decreased electron beam transmittance, blurred sheet boundaries, and difficulty in identifying monolayer regions, thus affecting the accurate observation of monolayer morphology. Furthermore, the thin and flexible nature of saponite sheets makes them prone to curling, collapse, or localized aggregation during sample preparation and drying, further increasing the difficulty of monolayer observation.

[0004] Currently, methods such as mechanical stirring, high-power ultrasound, or organic solvent-assisted dispersion are commonly used to improve the exfoliation degree of soapstone sheets. While high-intensity ultrasound can promote interlayer exfoliation, it can easily lead to edge breakage, size reduction, and even lattice structure damage, making it difficult to balance exfoliation efficiency and sheet integrity. On the other hand, using only a single alcohol solvent for dispersion, although it can reduce liquid surface tension and improve sheet spreadability, has limited effect on weakening interlayer forces. The exfoliated sheets are still prone to re-aggregation during settling, resulting in poor dispersion stability. Existing methods typically lack effective control over the gradual interlayer intercalation and stable exfoliation process, making it difficult to consistently obtain soapstone samples with a high proportion of monolayers and intact structures.

[0005] Therefore, there is an urgent need to provide a mild, efficient and stable monolayer dispersion method for clay minerals (especially soapstone) that can reduce the aggregation and overlap of lamellae, increase the proportion of monolayer lamellae and the stability of the dispersion system, and maintain the integrity of the lamellae structure as much as possible. This would allow for the acquisition of high-quality soapstone monolayer samples suitable for transmission electron microscopy observation, providing a reliable sample preparation method for the study of soapstone micromorphology and lamellae structure. Summary of the Invention

[0006] To address the problems of unstable saponite monolayers, easy overlap and aggregation of layers, and difficulty in obtaining structurally intact monolayer morphology under transmission electron microscopy (TEM), this invention provides a saponite monolayer dispersion method based on staged alcohol molecule intercalation and exfoliation. This method systematically designs the processes of saponite dispersion, dilution, intercalation and exfoliation, loading, and imaging observation, establishing a saponite monolayer sample preparation process suitable for TEM. This method can improve the dispersibility and monolayer ratio of saponite layers while maintaining the structural integrity of the saponite layers as much as possible, reducing layer overlap and aggregation, thereby obtaining saponite monolayer samples suitable for TEM observation.

[0007] In a first aspect, the present invention provides a method for monolayer dispersion of clay minerals based on staged alcohol molecule intercalation and exfoliation, comprising the following steps:

[0008] a. Dispersion treatment: Clay minerals are added to deionized water and stirred to obtain a clay mineral suspension system.

[0009] Furthermore, the clay mineral is a montmorillonite-type clay mineral, preferably montmorillonite.

[0010] Furthermore, in the clay mineral suspension system, the mass-volume concentration of clay minerals is 0.05-0.2 mg / mL.

[0011] Furthermore, the stirring speed is 50-200 rpm, and the stirring time is 2-6 hours.

[0012] In this step, deionized water is used as the liquid medium for dispersion treatment. Its low impurity ion content helps reduce the impact of exogenous ions on the interlayer forces and dispersion state of clay minerals. Low-shear stirring promotes pre-dispersion of lamellar layers without introducing strong mechanical stress, thereby reducing the formation of large agglomerates.

[0013] b. Dilution treatment: First, add a first alcohol solvent to the suspension system, then add a second alcohol solvent, stir, and obtain a diluted dispersion system.

[0014] Furthermore, the first alcohol solvent is a monoalcohol solvent.

[0015] Furthermore, the first alcohol solvent is selected from methanol or ethanol.

[0016] Furthermore, the second alcohol solvent is a polyol solvent.

[0017] Furthermore, the second alcohol solvent is selected from one or more of glycerol, ethylene glycol, and polyethylene glycol.

[0018] Furthermore, the molecular weight of the polyethylene glycol is 200-600.

[0019] Furthermore, the total amount of alcohol solvent (first alcohol solvent + second alcohol solvent) added is such that the mass-volume concentration of clay minerals in the diluted dispersion system is 0.01-0.05 mg / mL.

[0020] Furthermore, the amount of the first alcohol solvent added is 1 / 3 to 1 / 2 of the total volume of the alcohol solvent (first alcohol solvent + second alcohol solvent).

[0021] Furthermore, the stirring speed is 50-200 rpm.

[0022] Furthermore, the stirring time is 30-90 minutes.

[0023] Further, after adding the first alcohol solvent, stir for 30-60 minutes; then add the second alcohol solvent and stir for 30-90 minutes to promote the full interaction between the alcohol solvent and the film.

[0024] Optionally, after the second alcohol solvent is added, the system can be allowed to stand for 2-12 hours to further improve the stability of the dispersion system.

[0025] This invention employs a method of "first adding small-molecule single-unit alcohols, then adding large-molecule polyols." The small-molecule single-unit alcohols (such as methanol and ethanol) have smaller molecular sizes, which facilitates their entry into the interlayer of clay minerals and promotes the replacement of water molecules between layers, thereby weakening interlayer interactions and increasing interlayer spacing. Subsequently, the added large-molecule polyols (such as ethylene glycol, glycerol, and low-molecular-weight polyethylene glycol) have larger molecular sizes and contain multiple hydroxyl groups, providing multi-point hydrogen bonding to form a more stable adsorption layer on the sheet surface and offering stronger steric hindrance, effectively preventing the sheets from recombining or collapsing during subsequent drying. If only small-molecule single-unit alcohols are used, although they can successfully enter the interlayer, their small molecular size results in weak adsorption capacity, and rapid solvent evaporation during drying may still lead to sheet collapse or recombination. If only large-molecule polyols are used, their larger molecular size results in greater kinetic resistance to entry into the interlayer, limiting the initial exfoliation effect. By using two alcohol solvents in stages, a synergistic effect is achieved, complementing each other to a certain extent.

[0026] c. Ultrasonic exfoliation: The diluted dispersion system is subjected to ultrasonic treatment to obtain the dispersion system.

[0027] In the dispersion system, clay minerals are mainly formed in single-layer or few-layer structures.

[0028] Furthermore, the ultrasonic power is 100-300 W, and the duration is 5-30 minutes.

[0029] Ultrasonic treatment can generate instantaneous shearing through the liquid phase cavitation effect, thereby promoting further separation of the partially expanded sheets.

[0030] Optionally, a pulse mode can be used to reduce the possibility of sheet fragmentation caused by continuous ultrasound, with a pulse period of 2-5 seconds and an interval of 1-3 seconds.

[0031] d. Loading and spreading: The dispersion system is dropped onto a transmission electron microscope carrier film, so that the sheets spread on the surface of the carrier film.

[0032] Furthermore, after adding the solution, allow it to stand and dry.

[0033] Furthermore, the dropping speed is 1-5 μL / time, the dropping volume is 5-15 μL, and after dropping, it is allowed to stand for 1-5 minutes to allow it to spread naturally.

[0034] Furthermore, the carrier film is an ultrathin film material with high electronic transparency, selected from amorphous carbon films, silicon nitride films, or graphene films.

[0035] Furthermore, the thickness of the carrier film is 5-20 nm.

[0036] Furthermore, the drying process is either natural drying or vacuum drying, and the drying time is 10-60 minutes.

[0037] e. Cleaning treatment: Plasma cleaning is performed on the carrier membrane loaded with the sample.

[0038] Furthermore, the cleaning gas is selected from argon or an argon-oxygen mixture, with a cleaning power of 30-100 W, a cleaning time of 10-60 seconds, and a gas flow rate of 10-50 sccm. This step helps reduce organic contaminants and residual solvents on the surface of the carrier membrane, thereby reducing background contamination and improving the observation effect of transmission electron microscopy.

[0039] f. Imaging observation: The morphology of clay mineral lamellae was observed using a transmission electron microscope.

[0040] Specifically, the processed samples were observed using transmission electron microscopy, and lamellar regions with relatively uniform thickness, less overlap, and more complete structure were selected for morphological characterization.

[0041] Furthermore, the accelerating voltage of the transmission electron microscope is 80-200 kV.

[0042] The beneficial effects of this invention are:

[0043] 1. This invention employs low-shear stirring in a liquid system to pre-disperse clay minerals, reducing the formation of large agglomerates while avoiding the introduction of strong mechanical stress. Furthermore, dilution with alcohol solvents and controlled ultrasonic treatment further weaken the interactions between the lamellar layers, making it easier for clay minerals to disperse in the system in a monolayer or few-layer state. Compared to direct high-intensity ultrasonic dispersion methods, this invention improves lamellar dispersibility while maintaining the integrity of the lamellar structure.

[0044] 2. This invention introduces an alcohol solvent dilution step before sample loading. This reduces the concentration of clay mineral sheets per unit volume, thereby decreasing collisions and recombination between sheets. Furthermore, it improves the wettability and interfacial environment of the dispersion system, making it easier for the sheets to spread uniformly after being dropped onto the surface of the transmission electron microscope carrier film. This reduces the formation of localized thick areas and overlapping multilayers, facilitating the acquisition of single-layer regions suitable for transmission electron microscopy observation.

[0045] 3. This invention employs a staged alcohol molecule interaction mechanism. The initial addition of small-molecule single alcohols (such as methanol and ethanol) facilitates entry into the interlayer spaces of clay minerals and promotes the replacement of water molecules within these layers, thereby weakening interlayer forces and increasing interlayer spacing. Subsequently added large-molecule polyols (such as ethylene glycol, glycerol, and polyethylene glycol) further act on the expanded interlayer regions, forming a relatively stable adsorption layer on the sheet surface. Through hydrogen bonding and steric hindrance, this reduces the tendency for sheet recombination. This staged treatment method facilitates gentle and gradual exfoliation between layers, reduces the potential damage to the sheet structure caused by rapid action of a single alcohol, and improves the stability of the dispersion system.

[0046] 4. In this invention, after the sample is loaded onto the carrier membrane, a low-energy plasma cleaning step is used to reduce organic contaminants and residual solvents on the surface of the carrier membrane. After cleaning, background contamination during transmission electron microscopy observation is reduced, thereby improving the clarity of sheet edges and morphological details, which is beneficial for the observation and identification of single-layer regions.

[0047] 5. This invention, through synergistic control of steps such as dispersion, intercalation, ultrasonic exfoliation, and load spreading, makes it easier for soapstone sheets to form a more uniform dispersion with less overlap on the surface of the transmission electron microscope carrier film. Compared with traditional direct dispersion methods, this invention can increase the probability of obtaining single-layer or few-layer regions, thereby improving the stability and repeatability of transmission electron microscopy observations.

[0048] 6. This invention optimizes several key aspects, including sample dispersion, loading, and imaging observation, enabling soapstone sheets to be observed in a relatively dispersed and structurally intact state under transmission electron microscopy. Therefore, this invention facilitates the acquisition of soapstone monolayer morphology images with clear edges and minimal overlap, providing a stable sample preparation method for the study of soapstone sheet structure and morphology. Attached Figure Description

[0049] Figure 1 The Mg-Ni soapstone powder samples used in the examples and comparative examples are shown.

[0050] Figure 2 The XRD patterns of the soapstone samples used in the examples and comparative examples are shown.

[0051] Figure 3 The image shows a STEM image of soapstone sheets in Example 1, with the left and right images showing the morphology of soapstone sheets in different regions.

[0052] Figure 4 The image shows a STEM image of soapstone sheets in Example 2, where the left and right images show the morphology of soapstone sheets in different regions.

[0053] Figure 5 The image shows a STEM image of soapstone sheets in Example 3, where the left and right images show the morphology of soapstone sheets in different regions.

[0054] Figure 6 The image shows a STEM image of soapstone lamellae in Comparative Example 1, where the left and right images show the morphology of soapstone lamellae in different regions.

[0055] Figure 7 The image shows a STEM image of soapstone lamellae in Comparative Example 2, where the left and right images show the morphology of soapstone lamellae in different regions.

[0056] Figure 8 The image shows a STEM image of soapstone lamellae in Comparative Example 3, where the left and right images show the morphology of soapstone lamellae in different regions. Detailed Implementation

[0057] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and therefore should not be considered as a limitation on the scope of protection of the present invention. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0058] The soapstone of this invention can be natural soapstone or artificially synthesized soapstone. Artificially synthesized soapstone can be produced using methods commonly used in the art, such as hydrothermal synthesis and microwave synthesis.

[0059] This invention employs a hydrothermal method commonly used in the art to synthesize soapstone: first, mixed solutions containing sodium silicate, aluminum chloride, and magnesium chloride are prepared separately to obtain a theoretical composition of Na... + 0.3 [Si 3.7 Al 0.3 [M3]O 10 The coprecipitated gel of (OH)₂·nH₂O (M=Mg, Ni) was filtered and washed. The Mg gel was then hydrothermally treated at 220℃ for 1 day, and the Ni gel at 25℃ for 1 day. After washing, filtration, and drying at 45℃ for 1 week, Mg saponite precursor pMg₂₂₀ and Ni saponite precursor pNi₂₅ were obtained, respectively. Equimolar amounts of the two precursors were then mixed and added to deionized water, followed by hydrothermal treatment at 220℃ for 60 days to obtain the final Mg-Ni saponite sample. Figure 1 As shown.

[0060] Furthermore, the characteristic diffraction peaks of the XRD pattern of the synthesized sample were compared with those of the standard card for saponite. The two were consistent, with no other impurity peaks, indicating the synthesis of pure-phase saponite. The XRD pattern is shown below. Figure 2 .

[0061] All alcohol solvents used in this invention are commercially available.

[0062] Example 1

[0063] A method for monolayer dispersion of clay minerals based on staged alcohol molecule intercalation and exfoliation includes the following steps:

[0064] Step a. Dispersion treatment: Take the soapstone raw material to be tested and add it to deionized water at a mass-volume ratio of 1 mg:10 mL to prepare a soapstone-water suspension with a mass concentration of 0.1 mg / mL. Place the suspension in a container and use a stirrer to perform low-shear stirring treatment on the suspension at a stirring speed of 100 rpm for 4 hours.

[0065] Step b. Dilution treatment: Take 5 mL of the soapstone-water suspension obtained in step a, add 2 mL of anhydrous ethanol, stir for 30 minutes, then add 3 mL of ethylene glycol, and continue stirring for 30 minutes to dilute the final soapstone concentration in the system to 0.05 mg / mL.

[0066] Step c. Ultrasonic exfoliation: The soapstone dispersion diluted in step b is placed in an ultrasonic device for ultrasonic treatment. The ultrasonic power is 200 W and the ultrasonic time is 15 minutes. The pulse mode is used (2 seconds working / 1 second interval).

[0067] Step d. Loading and spreading: Take 10 μL of the soapstone dispersion after ultrasonic treatment in step c, and drop it onto the ultrathin carbon film carrier for transmission electron microscopy at a rate of 2 μL / drop and a volume of 8 μL. After dropping, let it stand for 2 minutes, and then let it air dry at room temperature for 30 minutes to allow the soapstone flakes to adhere to and spread on the surface of the ultrathin carbon film.

[0068] Step e. Cleaning treatment: After the soapstone loading is completed, the ultrathin carbon film carrier membrane is placed in a plasma cleaner and cleaned with low-energy plasma under an argon atmosphere. The cleaning power is 50 W, the cleaning time is 30 seconds, and the gas flow rate is 30 sccm.

[0069] Step f. Imaging and Acquisition: The sample cleaned in step e was placed in a transmission electron microscope, and the saponite was observed using scanning transmission electron microscopy. The accelerating voltage was set to 200 kV, and the beam spot size was 1 nm. By adjusting the imaging parameters, the saponite sheets on the carrier were screened, and areas with relatively uniform thickness and intact structure were selected for observation. The results show that the saponite sheets processed by the method in this embodiment are relatively uniformly dispersed on the carrier film surface, and single-layer or few-layer structures with clear edges and no overlap can be observed.

[0070] like Figure 3 As shown (left and right images represent different regions), after further treatment with ethylene glycol on the basis of ethanol pre-dispersion, the aggregation of the sample was significantly reduced, the overlap and edge connections between layers were significantly decreased, and the dispersibility of the layers was further improved, allowing for clear observation of the morphological characteristics of the soapstone layers. This is because the initial addition of ethanol molecules has good diffusion and wettability, which facilitates entry into the soapstone interlayer and promotes the replacement of interlayer water molecules, thereby weakening interlayer interactions and promoting the expansion of interlayer spacing. The subsequent addition of ethylene glycol, as a dihydroxy alcohol macromolecule, can further act on the expanded interlayer region, improving the dispersion stability of the layers in the liquid phase through strong hydrogen bonding, and reducing the tendency of layer recombination by utilizing steric hindrance. The staged alcohol molecule treatment method is beneficial for promoting the gradual exfoliation of soapstone layers and increasing the stable proportion of monolayer or few-layer structures in the dispersion system.

[0071] Example 2

[0072] All other steps are the same as in Example 1, the only difference being:

[0073] Step b. Dilution treatment: Take 5 mL of the soapstone-water suspension obtained in step a, add 2 mL of anhydrous ethanol to dilute it, and stir for 30 minutes; then add 3 mL of glycerol and continue stirring for 30 minutes to dilute the final soapstone concentration in the system to 0.05 mg / mL.

[0074] Saponite was observed using scanning transmission electron microscopy, such as... Figure 4 As shown (left and right images represent different regions). After stepwise dispersion treatment with ethanol and glycerol, the soapstone sheets exhibited good dispersion, with almost no overlap between sheets and no multi-particle edge connections. Relatively independent and dispersed single-sheet structures could be observed, allowing for a more intuitive characterization of the size and morphology of the single sheets.

[0075] Example 3

[0076] A method for monolayer dispersion of clay minerals based on staged alcohol molecule intercalation and exfoliation includes the following steps:

[0077] Step a. Dispersion treatment: Take the soapstone raw material to be tested and add it to deionized water at a mass-to-volume ratio of 1 mg:10 mL to prepare a soapstone-water suspension with a mass concentration of 0.1 mg / mL. The stirring speed is 100 rpm and the stirring time is 3 hours.

[0078] Step b. Dilution: Take 5 mL of the soapstone-water suspension obtained in step a, add 2.5 mL of methanol, and stir for 30 minutes; then add 2.5 mL of glycerol and continue stirring for 30 minutes. The final soapstone concentration in the system is diluted to 0.05 mg / mL.

[0079] Step c. Ultrasonic exfoliation: The soapstone dispersion diluted in step b is placed in an ultrasonic device for ultrasonic treatment under relatively mild conditions: ultrasonic power of 100 W, ultrasonic time of 15 minutes, and pulse mode (2 seconds working / 1 second interval).

[0080] The remaining steps d, e, and f are the same as in Example 1.

[0081] like Figure 5 As shown (left and right images represent different regions), the soapstone samples processed by the method in this embodiment show no significant overlap between soapstone layers, with only a few small-scale layer edges connected, but this does not affect the morphological observation of individual layers. This demonstrates that the method of the present invention has good adaptability to different types of small molecule alcohols and different process parameters.

[0082] Comparative Example 1

[0083] Step a. Dispersion treatment: Take the soapstone raw material to be tested and add it to deionized water at a mass-volume ratio of 1 mg:10 mL to prepare a soapstone-water suspension with a mass concentration of 0.1 mg / mL. Place the suspension in a container and use a stirrer to perform low-shear stirring treatment on the suspension at a stirring speed of 100 rpm for 4 hours.

[0084] Step b. Ultrasonic exfoliation: Place 5 mL of the soapstone dispersion obtained in step a into an ultrasonic device for ultrasonic treatment. The ultrasonic power is 200 W and the ultrasonic time is 15 minutes. The pulse mode is used (2 seconds working / 1 second interval).

[0085] Step c. Loading and spreading: Take 10 μL of the ultrasonically treated soapstone dispersion and drop it onto the ultrathin carbon film carrier for transmission electron microscopy at a rate of 2 μL / drop and a volume of 8 μL. After dropping, let it stand for 2 minutes, and then let it air dry at room temperature for 30 minutes to allow the soapstone flakes to adhere to and spread on the surface of the ultrathin carbon film.

[0086] Step d. Cleaning treatment: After the soapstone loading is completed, the ultrathin carbon film carrier membrane is placed in a plasma cleaner and cleaned with low-energy plasma under an argon atmosphere. The cleaning power is 50 W, the cleaning time is 30 seconds, and the gas flow rate is 30 sccm.

[0087] Step e. Imaging and acquisition: Same as step f in Example 1.

[0088] STEM images of soapstone as follows Figure 6 As shown (left and right images represent different regions), when soapstone is dispersed only in ultrapure water without dilution with alcohol solvents, the sample tends to agglomerate significantly during drying. Most of the sheets overlap, forming only a small number of monolayer structures, and there are obvious edge connections between the sheets. This indicates that relying solely on water dispersion and ultrasonic treatment is insufficient to effectively obtain well-dispersed monolayer soapstone sheets.

[0089] Comparative Example 2

[0090] A method for monolayer dispersion of clay minerals based on ethanol molecular intercalation exfoliation includes the following steps:

[0091] Step a. Dispersion treatment: Take the soapstone raw material to be tested and add it to deionized water at a mass-volume ratio of 1 mg:10 mL to prepare a soapstone-water suspension with a mass concentration of 0.1 mg / mL. Place the suspension in a container and perform low-shear stirring treatment on the suspension using a stirrer at a speed of 100 rpm for 4 hours.

[0092] Step b. Dilution treatment: Take 5 mL of the soapstone-water suspension obtained in step a and add ethanol to dilute it so that the volume concentration of ethanol in the system reaches 50% (5 mL), and the mass concentration of soapstone is diluted to 0.05 mg / mL. After adding ethanol, continue stirring for 60 minutes to allow the ethanol and soapstone to react fully.

[0093] Step c. Ultrasonic exfoliation: The soapstone dispersion diluted in step b is placed in an ultrasonic device for ultrasonic treatment. The ultrasonic power is 200 W and the ultrasonic time is 15 minutes. The pulse mode is used (2 seconds working / 1 second interval).

[0094] Step d. Loading and spreading: Take 10 μL of the soapstone dispersion after ultrasonic treatment in step c, and drop it onto the ultrathin carbon film carrier for transmission electron microscopy at a rate of 2 μL / drop and a volume of 8 μL. After dropping, let it stand for 2 minutes and then air dry at room temperature for 30 minutes to allow the soapstone flakes to adhere to and spread on the surface of the ultrathin carbon film.

[0095] Step e. Cleaning treatment: After the soapstone loading is completed, the ultrathin carbon film carrier membrane is placed in a plasma cleaner and cleaned with low-energy plasma under an argon atmosphere. The cleaning power is 50 W, the cleaning time is 30 seconds, and the gas flow rate is 30 sccm.

[0096] Step f. Imaging and Acquisition: The sample cleaned in step e was placed in a transmission electron microscope, and the saponite was observed using scanning transmission electron microscopy (STEM) imaging mode. The accelerating voltage was set to 200 kV, and the beam spot size was 1 nm. By adjusting the imaging parameters, the saponite sheets on the support were screened, and areas with relatively uniform thickness, intact structure, and minimal overlap were selected for observation. The results are shown in [Figure number missing]. Figure 7 (The left and right images represent different regions.)

[0097] pass Figure 7 It can be seen that the soapstone sample diluted with anhydrous ethanol can, to some extent, inhibit the aggregation of lamellar sheets and form more dispersed soapstone sheets. However, compared with Example 1, the single-layer dispersion effect is still inferior. A small amount of lamellar aggregation and overlap still exist in the sample, and some lamellar edges are connected to each other, failing to form a completely independent and dispersed lamellar structure. This indicates that although ethanol alone can improve wetting and spreading, its effect on inhibiting lamellar recombination is still limited.

[0098] Comparative Example 3

[0099] The other steps are basically the same as in Example 1, with the only difference being:

[0100] Take 5 mL of the soapstone-water suspension obtained in step a, pre-mix 2 mL of anhydrous ethanol and 3 mL of ethylene glycol evenly, and then add them to the suspension all at once, stirring for 60 minutes. The remaining steps of dispersion, sonication, loading, washing, and imaging are exactly the same as in Example 1.

[0101] The results are as follows Figure 8As shown (left and right images represent different regions). After treatment with simultaneous addition of alcohol solvent, the dispersion effect of the soapstone sheets was worse than in Example 1, with some degree of interconnection and local overlap still existing between the sheets. This is because, under the same ultrasonic conditions, simultaneous addition of large-molecule ethylene glycol may hinder the rapid intercalation of small-molecule ethanol, resulting in a slightly lower exfoliation efficiency than the staged addition method.

[0102] The above results show that, compared with the method of using only water dispersion or only a single small molecule alcohol, the present invention adopts a staged treatment method of first adding a small molecule single alcohol and then adding a large molecule polyol, which significantly improves the area ratio of the single layer region of soapstone sheets and the stability of the dispersion system, while maintaining a high degree of sheet integrity, thus verifying the effectiveness and superiority of the method of the present invention.

Claims

1. A method for single-layer dispersion of clay minerals based on staged alcohol molecular intercalation and exfoliation, characterized in that, Includes the following steps: a. Dispersion treatment: Clay minerals are added to deionized water and stirred to obtain a clay mineral suspension system; b. Dilution treatment: First, add a first alcohol solvent to the suspension system, then add a second alcohol solvent, stir, and obtain a diluted dispersion system; The first alcohol solvent is a monool solvent; the second alcohol solvent is a polyol solvent. c. Ultrasonic exfoliation: The diluted dispersion system is subjected to ultrasonic treatment to obtain the dispersion system; d. Loading and spreading: The dispersion system is dropped onto a transmission electron microscope carrier film, allowing the sheets to spread on the surface of the carrier film; e. Cleaning process: Plasma cleaning is performed on the carrier membrane loaded with the sample; The clay mineral is soapstone.

2. The method according to claim 1, characterized in that, In step a, the mass-volume concentration of clay minerals in the clay mineral suspension system is 0.05-0.2 mg / mL; the stirring speed is 50-200 rpm, and the stirring time is 2-6 hours.

3. The method according to claim 1, characterized in that, In step b, the mass-volume concentration of clay minerals in the diluted dispersion system is 0.01-0.05 mg / mL; the stirring speed is 50-200 rpm.

4. The method according to claim 1, characterized in that, In step b, the first alcohol solvent is selected from methanol or ethanol; the second alcohol solvent is selected from one or more of glycerol, ethylene glycol, and polyethylene glycol.

5. The method according to claim 4, characterized in that, In step b, the amount of the first alcohol solvent added is 1 / 3 to 1 / 2 of the total volume of the alcohol solvent.

6. The method according to claim 1, characterized in that, In step b, after adding the first alcohol solvent, stir for 30-60 minutes, then add the second alcohol solvent and stir for 30-90 minutes.

7. The method according to claim 1, characterized in that, In step c, the power of the ultrasonic treatment is 100-300W, and the time is 5-30 minutes.

8. The method according to claim 1, characterized in that, In step d, the carrier film is selected from amorphous carbon film, silicon nitride film or graphene film, with a thickness of 5-20 nm; after drop addition, it is allowed to stand and dry.

9. The method according to claim 1, characterized in that, In step e, the gas used for plasma cleaning is selected from argon or an argon-oxygen mixture, the cleaning power is 30-100 W, the cleaning time is 10-60 seconds, and the gas flow rate is 10-50 sccm.

10. The method according to claim 1, characterized in that, It also includes step f. observing clay mineral lamellae using a transmission electron microscope; the accelerating voltage of the transmission electron microscope is 80-200 kV.

Images