A few-layer graphene dispersion and method of making same

Abstract

The present application belongs to the technical field of graphene preparation, and particularly relates to a few-layer graphene dispersion liquid and a preparation method thereof. The preparation method of the few-layer graphene dispersion liquid comprises the following steps: (1) pre-impregnation treatment: expandable graphite is impregnated in a mixed solution containing hydrogen silicone oil and tetraethyl orthosilicate; (2) microwave expansion: the expandable graphite obtained by the pre-impregnation treatment in step (1) is subjected to microwave treatment to obtain expanded graphite; (3) the expanded graphite is added into a peeling solution, and is sheared and dispersed to obtain a few-layer graphene dispersion liquid; components of the peeling solution include an alkali catalyst, a silane coupling agent and a solvent. The preparation method of the few-layer graphene dispersion liquid is simple in process, controllable in cost and friendly to the environment, and the prepared few-layer graphene dispersion liquid has excellent dispersion stability and application performance.

Description

Technical Field

[0001] This invention belongs to the field of graphene preparation technology, specifically relating to a few-layer graphene dispersion and its preparation method. Background Technology

[0002] Graphene, a two-dimensional carbon nanomaterial with excellent electrical, thermal, and mechanical properties, has broad application prospects in composite materials, coatings, energy storage devices, and electronic devices. However, the industrial application of graphene is mainly limited by its high preparation cost, low yield, and poor dispersion stability in application media.

[0003] Currently, the main methods for preparing graphene include mechanical exfoliation, chemical vapor deposition, redox methods, and liquid-phase exfoliation. While redox methods can achieve large-scale production, the resulting graphene oxide has numerous defects, affecting its intrinsic properties. Chemical vapor deposition produces high-quality graphene, but its high cost makes industrial production difficult. Liquid-phase exfoliation offers advantages such as simple processing and relatively low cost, but suffers from low exfoliation efficiency and poor product dispersion stability.

[0004] Liquid phase exfoliation typically uses high-energy-density ultrasound or high shear force to physically exfoliate graphite, but this method has the following problems: low yield, usually only 1%-5% of graphite can be effectively exfoliated; the prepared graphene is prone to re-agglomeration in solvents, resulting in poor dispersion stability; it requires the use of large amounts of organic solvents, which is not environmentally friendly; and it is difficult to achieve continuous and large-scale production.

[0005] To improve exfoliation efficiency and product stability, researchers have attempted to add surfactants or functionalized molecules during the exfoliation process. However, these methods often introduce impurities, affecting the intrinsic properties of graphene. Therefore, developing an efficient, environmentally friendly, and scalable method for graphene preparation is of significant scientific and practical value.

[0006] Therefore, there is a need to provide an improved technical solution that addresses the shortcomings of the existing technology. Summary of the Invention

[0007] The purpose of this invention is to provide a few-layer graphene dispersion and its preparation method, so as to help solve or improve at least one of the problems of low efficiency, poor dispersion stability and difficulty in large-scale production in the prior art graphene preparation methods.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a few-layer graphene dispersion, comprising the following steps: (1) pre-impregnation treatment: impregnating expandable graphite in a mixed solution of hydrogen-containing silicone oil and tetraethyl orthosilicate; (2) microwave expansion: subjecting the expandable graphite obtained by the pre-impregnation treatment in step (1) to microwave treatment to obtain expanded graphite; (3) adding the expanded graphite to a stripping solution and shearing and dispersing it to obtain a few-layer graphene dispersion; wherein the components of the stripping solution include an alkaline catalyst, a silane coupling agent and a solvent.

[0009] Preferably, in step (1), the mass ratio of tetraethyl orthosilicate to hydrogen-containing silicone oil is 1:(0.5-3); the hydrogen-containing silicone oil is a polymethylhydrosiloxane containing Si-H bonds or a copolymer of polymethylhydrosiloxane and polydimethylsiloxane, with a molecular weight of 1000-10000.

[0010] Preferably, the alkaline catalyst is at least one selected from calcium hydroxide, sodium hydroxide, potassium hydroxide, and tetramethylammonium hydroxide; and the silane coupling agent is an amino-containing silane coupling agent.

[0011] Preferably, the silane coupling agent is at least one selected from 3-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane.

[0012] Preferably, the stripping solution comprises the following components in parts by weight: 0.1-5 parts of alkaline catalyst, 1-10 parts of silane coupling agent, 10-50 parts of ethanol, and 50-200 parts of water.

[0013] Preferably, in step (3), the mass ratio of the expanded graphite to the stripping solution is 1:(10-100).

[0014] Preferably, in step (1), the soaking time is 0.5-4 hours.

[0015] Preferably, in step (2), the power of the microwave treatment is 800-1200W, and the microwave treatment time is 5-60s; the microwave treatment is carried out under inert gas protection.

[0016] Preferably, in step (3), the rotation speed is 5000-20000 rpm and the shearing dispersion time is 30-120 min; the shearing dispersion is carried out in a shearing emulsifier.

[0017] Preferably, in step (3), after shearing and dispersion, the step further includes centrifugation to remove unpeeled graphite agglomerates; the centrifugation speed is 2000-8000 rpm and the centrifugation time is 30-90 min.

[0018] The present invention also provides a few-layer graphene dispersion, which adopts the following technical solution: a few-layer graphene dispersion, wherein the few-layer graphene dispersion is prepared by the method described above.

[0019] Beneficial effects:

[0020] The method for preparing few-layer graphene in this invention, compared to existing technologies, is as follows:

[0021] (1) Significantly improves the peeling efficiency: Through pre-impregnation treatment and microwave rapid expansion, the interlayer spacing of graphite is greatly increased, creating favorable conditions for subsequent peeling; combined with the synergistic effect of mechanical peeling and hydrogen chemical peeling, graphene peeling can be achieved better; the graphene yield can reach more than 10% (or even about 35%), which is much higher than the 1%-5% of the traditional liquid phase peeling method.

[0022] (2) Excellent product dispersion stability: The silane coupling agent hydrolyzes and condenses under alkaline conditions to form a polysiloxane network structure that coats the graphene surface. Through the dual mechanisms of electrostatic stability and steric hindrance stability, the graphene sheets are prevented from re-aggregating, so that the graphene remains stably dispersed in the aqueous medium.

[0023] (3) Outstanding environmental friendliness: The entire preparation process uses water and ethanol as the main solvents, avoiding the use of toxic organic solvents; the generation of hydrogen is an in-situ reaction, requiring no external gas; the reaction conditions are mild and the energy consumption is low.

[0024] (4) Excellent product quality: The number of layers of the prepared few-layer graphene is mainly distributed in 3-14 layers, with an average thickness of 3-5 layers; Raman spectroscopy shows that the ID / IG ratio is less than 0.3, indicating a low defect density; the electrical conductivity can reach 1000-3000 S / m, maintaining the excellent intrinsic properties of graphene.

[0025] (5) High industrialization potential: The process of this invention is simple, requires low equipment, and is easy to operate continuously; the raw material cost is low. Its comprehensive production cost is about RMB 800-1,500 / kg, which is significantly lower than that of chemical vapor deposition (RMB 50,000-200,000 / kg) and traditional ultrasonic liquid phase exfoliation (RMB 3,000-8,000 / kg), and comparable to that of redox method (RMB 1,000-3,000 / kg), but the product quality is significantly better (ID / IG < 0.3 in this invention, while ID / IG in redox method is usually > 1.0), which has significant cost benefits and market competitiveness.

[0026] (6) Excellent application performance: The few-layer graphene dispersion prepared by this invention can be directly used in composite materials, coatings, conductive films and other fields. Since the graphene surface is coated with a siloxane network, it has good compatibility with the resin matrix. It can improve the mechanical properties, electrical conductivity and barrier properties of the matrix material at a low addition amount, and has good application prospects. Attached Figure Description

[0027] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. Wherein:

[0028] Figure 1 This is a TEM image of few-layer graphene provided in Embodiment 1 of the present invention.

[0029] Figure 2 This is a TEM image of few-layer graphene provided in Embodiment 4 of the present invention.

[0030] Figure 3 This is a TEM image of the graphene sample in Comparative Example 7. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0032] The present invention will now be described in detail with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other.

[0033] This invention addresses at least one of the problems in existing graphene preparation methods, namely low efficiency, poor dispersion stability, and difficulty in large-scale production, by providing a method for preparing a few-layer graphene dispersion.

[0034] The method for preparing a few-layer graphene dispersion according to an embodiment of the present invention includes the following steps: (1) pre-impregnation treatment: impregnating expandable graphite in a mixed solution containing hydrogen silicone oil and tetraethyl orthosilicate; (2) microwave expansion: microwave treatment of the expandable graphite obtained by the pre-impregnation treatment in step (1) to obtain expanded graphite; (3) adding the expanded graphite to a stripping solution and shearing and dispersing it to obtain a few-layer graphene dispersion; the components of the stripping solution include an alkaline catalyst, a silane coupling agent and a solvent.

[0035] During the pre-impregnation process, due to the viscosity of tetraethyl orthosilicate (TEOS) (approximately 0.6 μm), ) is much lower than that of hydrogen-containing silicone oil (10-50 m The two are mixed to significantly reduce the viscosity of the mixed solution (relative to hydrogen-containing silicone oil), improve permeability, and make the mixed solution easier to penetrate into the interlayer of expandable graphite. In the microwave expansion stage, the gas generated by the pyrolysis / gasification of TEOS and the rapid vaporization of water adsorbed between graphite layers expands the interlayer spacing. At the same time, the SiO2 generated by hydrolysis condensation is deposited on the graphite surface to play a supporting role and prevent the interlayer spacing from shrinking. In the peeling and dispersion stage (step (3)), TEOS and silane coupling agent co-condense to form an inorganic-organic hybrid siloxane network. TEOS provides inorganic SiO2 components to enhance the rigidity and stability of the coating layer.

[0036] The alkaline catalyst plays two main roles in this invention. Firstly, it catalyzes the decomposition of hydrogen-containing silicone oil to produce hydrogen gas: the Si-H bonds in the hydrogen-containing silicone oil undergo hydrolysis under alkaline conditions (…). The generated hydrogen gas inserts into the graphite layers, assisting in mechanical exfoliation and achieving chemically assisted exfoliation; secondly, it catalyzes the hydrolysis and condensation of silane coupling agents: silane coupling agents hydrolyze under alkaline conditions to generate silanol groups ( The polysiloxane network then condenses to form a polysiloxane network that coats the graphene surface, preventing the graphene sheets from re-aggregating through electrostatic stabilization (protonation of amino groups provides positive charge) and steric stabilization (organic chains provide steric hindrance).

[0037] In this invention, the silane coupling agent mainly plays a role in stabilizing dispersion and surface modification: the silane coupling agent molecule contains alkoxy groups that can react with inorganic materials (graphene). ) and organic functional groups compatible with organic matter (such as amino-NH2); under alkaline conditions, alkoxy groups hydrolyze to generate silanol groups ( The amino functional groups then co-condense with the oxygen-containing groups on the graphene surface or with tetraethyl orthosilicate to form a stable siloxane coating layer on the graphene surface; the amino functional groups are protonated and carry a positive charge, providing electrostatic stability through electrostatic repulsion; the organic chains provide steric hindrance to prevent graphene sheets from approaching and agglomerating.

[0038] The method for preparing the few-layer graphene dispersion of the present invention can significantly increase the interlayer spacing of graphite through pre-impregnation treatment and microwave rapid expansion, creating favorable conditions for subsequent exfoliation. In addition, the exfoliation solution in step (3) allows the silane coupling agent to hydrolyze and condense under alkaline conditions, forming a polysiloxane network structure that coats the graphene surface. Through the dual mechanisms of electrostatic stability and steric hindrance stability, the graphene sheets are prevented from re-aggregating, and the graphene remains stably dispersed in the aqueous medium. The method for preparing the few-layer graphene dispersion of the present invention is environmentally friendly and has great industrial potential. The prepared product has excellent quality and excellent application performance.

[0039] In a preferred embodiment of the method for preparing the few-layer graphene dispersion of the present invention, the hydrogen-containing silicone oil is a... The molecular weight of the hydrosilicone oil is 1000-10000. If the molecular weight of the hydrosilicone oil is too small (<1000), its volatility increases, making it easily lost during impregnation and microwave treatment, and its interaction with the graphite surface is weak. A low absolute number of bonds results in insufficient hydrogen production, leading to weakened expansion and exfoliation effects and poor dispersion stability of the final product. Furthermore, if the molecular weight of the hydrogen-containing silicone oil is too large (>10000), its viscosity will be too high (typically >100m). Even when mixed with tetraethyl orthosilicate, the viscosity remains high, the penetration rate is slow, the impregnation is insufficient, and it is difficult to decompose under microwave conditions. Furthermore, the hydrogen production rate is slow, the expansion motive force is insufficient, and the residual large-molecule silicone oil increases dispersion resistance, reduces peeling efficiency, and leads to increased costs. Hydrogen-containing silicone oils with a molecular weight of 1000-10000 achieve a good balance between viscosity, penetration, hydrogen production capacity, and economy.

[0040] In a preferred embodiment of the method for preparing the few-layer graphene dispersion of the present invention, in step (1), the mass ratio of tetraethyl orthosilicate to hydrogen-containing silicone oil is 1:(0.5-3) (e.g., 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, or 1:3). If the proportion of tetraethyl orthosilicate is too low, its viscosity reduction effect is limited, the coating layer is weak, and stability decreases; if the proportion of tetraethyl orthosilicate is too high, it will lead to a reduction in the hydrogen production of the hydrogen-containing silicone oil and may form an excessively thick SiO2 layer, affecting the graphene performance and also causing a decrease in exfoliation efficiency.

[0041] In a preferred embodiment of the method for preparing the few-layer graphene dispersion of the present invention, the alkaline catalyst is at least one of calcium hydroxide, sodium hydroxide, potassium hydroxide and tetramethylammonium hydroxide; the silane coupling agent is an amino-containing silane coupling agent.

[0042] When calcium hydroxide is used as a base catalyst, calcium ions can react with those in the siloxane network. The groups and amino groups form coordination bonds, acting as crosslinking agents to connect multiple siloxane units, forming a dense three-dimensional network structure. This significantly enhances the mechanical strength and chemical stability of the coating layer, resulting in no significant precipitation in the dispersion after standing at room temperature for 6 months, with a concentration retention rate greater than or equal to 90%. When sodium hydroxide or potassium hydroxide is used, the coordination ability of alkali metal ions is relatively weak, and they mainly rely on... Catalytic silane condensation forms a siloxane network. The degree of crosslinking in this network is slightly lower than that in the calcium hydroxide system, but it still provides good dispersion stability. When tetramethylammonium hydroxide is used, since it does not contain metal ions, it mainly forms linear or weakly crosslinked siloxane structures, resulting in good short-term dispersion stability. This invention preferably uses aminosilane coupling agents because amino groups are strongly basic and easily protonated in aqueous media, providing better electrostatic stability than other functional groups.

[0043] Preferably, the silane coupling agent is at least one selected from 3-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane.

[0044] In a preferred embodiment of the method for preparing the few-layer graphene dispersion of the present invention, the exfoliation solution comprises the following components in parts by weight: 0.1-5 parts of an alkaline catalyst (e.g., 0.1, 0.5, 1, 2, 3, 4, or 5 parts), 1-10 parts of a silane coupling agent (e.g., 1, 3, 5, 8, or 10 parts), 10-50 parts of ethanol (e.g., 10, 15, 20, 25, 30, 35, 40, 45, or 50 parts), and 50-200 parts of water (e.g., 50, 80, 100, 130, 160, 180, or 200 parts). If the amount of alkaline catalyst is too small, it will not be able to effectively catalyze the hydrogen-containing silicone oil to generate sufficient hydrogen gas for efficient chemical exfoliation. At the same time, it will be difficult to provide enough calcium ions to form a stable polysilsesquioxane coating layer, resulting in a sharp drop in both exfoliation efficiency and product stability. Conversely, if the amount of alkaline catalyst is too large, it will cause excessive hydrogen gas generation, damaging the graphene sheets and increasing their defect density. At the same time, the excessively high ionic strength may disrupt the electrostatic stability of the dispersion system, causing agglomeration and introducing too many impurities. If the amount of silane coupling agent is too small, it will not be enough to form a complete protective layer on the exfoliated graphene surface, and it will not be able to provide effective steric hindrance to overcome van der Waals forces, causing the graphene to rapidly re-agglomerate, and the stability and yield of the dispersion will drop sharply. Conversely, if the amount of silane coupling agent is too large, it will cause over-coating. This excessively thick insulating siloxane shell will severely degrade the intrinsic electrical and thermal conductivity of graphene, and the excessive molecules may cause "bridging flocculation" or form impurities, which will also have an adverse effect on dispersion stability and product purity.

[0045] In a preferred embodiment of the method for preparing the few-layer graphene dispersion of the present invention, in step (3), the mass ratio of expanded graphite to exfoliation solution is 1:(10-100) (e.g., 1:10, 1:30, 1:50, 1:70, 1:90 or 1:100). If the mass ratio of expanded graphite to the exfoliation solution is too small, it means that the graphite raw material input in the reaction system is insufficient. Although it can ensure sufficient exfoliation and stability, it will significantly reduce the yield of a single batch and the final concentration of the dispersion, resulting in a decrease in equipment and energy utilization and poor production efficiency and economy. Conversely, if the ratio is too large, two major problems will arise: First, the effective components (alkali catalyst, silane coupling agent) in the exfoliation solution are relatively insufficient, which cannot provide sufficient chemical exfoliation power and sufficient stabilization coating for all graphene sheets, resulting in a simultaneous decrease in exfoliation efficiency and product stability. Second, the excessively high solid content will make the system viscosity too high, which will seriously hinder the effective transfer of mechanical shear force and heat dissipation. This will not only worsen the exfoliation effect, but may also lead to excessive equipment load, which is also not conducive to large-scale production.

[0046] In a preferred embodiment of the method for preparing the few-layer graphene dispersion of the present invention, in step (2), the power of the microwave treatment is 800-1200W (e.g., 800W, 900W, 1000W, 1100W, or 1200W), and the microwave treatment time is 5-60s (e.g., 5s, 10s, 20s, 30s, 40s, 50s, or 60s); the microwave treatment is carried out under inert gas protection. In contrast, the prior art typically performs microwave expansion of expandable graphite in an air environment; the present invention, by performing microwave treatment of expandable graphite under inert gas (e.g., nitrogen, argon, or other rare gases), helps the intercalating agent (containing hydrogen-silicone oil) to react efficiently and controllably according to the designed mechanism under microwave conditions, thereby stably achieving high exfoliation efficiency and high product quality.

[0047] In a preferred embodiment of the method for preparing the few-layer graphene dispersion of the present invention, in step (4), the rotation speed during shear dispersion is 5000-20000 rpm (e.g., 5000 rpm, 7000 rpm, 10000 rpm, 13000 rpm, 16000 rpm, 18000 rpm or 20000 rpm), and the shear dispersion time is 30-120 min (e.g., 30 min, 50 min, 70 min, 90 min, 110 min or 120 min); the shear dispersion is carried out in a shear emulsifier.

[0048] In a preferred embodiment of the method for preparing the few-layer graphene dispersion of the present invention, step (4) further includes a step of centrifugation to remove unexfoliated graphite agglomerates after shear dispersion; the centrifugation speed is 2000-8000 rpm (e.g., 2000 rpm, 4000 rpm, 6000 rpm or 8000 rpm), and the centrifugation time is 30-90 min (e.g., 30 min, 40 min, 50 min, 60 min, 70 min, 80 min or 90 min).

[0049] This invention also proposes a few-layer graphene dispersion, which is prepared by the method described above in the embodiments of this invention.

[0050] The few-layer graphene dispersion and its preparation method of the present invention will be described in detail below through specific embodiments.

[0051] The main raw materials used in the following examples are sourced as follows: Expandable graphite is flake graphite, 80 mesh, with an expansion ratio of 300 times; Hydrogen-containing silicone oil is polymethylhydrosiloxane containing Si-H bonds, with a molecular weight of 2000 and a brand name of HMS-301; Tetraethyl orthosilicate is an analytical grade reagent; Alkali catalysts are calcium hydroxide, sodium hydroxide, potassium hydroxide, or tetramethylammonium hydroxide, all of which are analytical grade reagents; Silane coupling agents are 3-aminopropyltriethoxysilane (brand name KH-550), N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (brand name KH-602), or N-phenyl-3-aminopropyltrimethoxysilane, all of which are analytical grade reagents; Ethanol is an analytical grade reagent; Deionized water is prepared in the laboratory.

[0052] The performance testing methods involved in the following embodiments are as follows:

[0053] (1) Concentration and yield determination: Take 10 mL of the dispersion in a petri dish of known mass, dry it under vacuum at 80 °C for 24 hours until constant weight, weigh the solid mass and calculate the concentration. Yield = (final graphene mass / initial expandable graphite mass) × 100%.

[0054] (2) Layer number distribution determination: Observation was performed using a transmission electron microscope (TEM). The dispersion was diluted and dropped onto a copper grid to dry naturally. The number of layers was counted by observing the edge wrinkles, and 200 layers were randomly counted.

[0055] (3) Raman spectroscopy test: Raman spectrometer (laser wavelength 532nm) was used for characterization. After the dispersed droplets were dried on the silicon wafer to form a film, the test was performed. Ten points were randomly selected and the average value was taken. The ID / IG ratio was calculated to evaluate the defect density.

[0056] (4) Conductivity determination: The dispersion was vacuum filtered to form a film and dried using the four-probe method. The sheet resistance was measured using a four-probe tester. and film thickness t (μm, converted to [value] during calculation] ),according to Calculate the conductivity (unit: S / m).

[0057] (5) Dispersion stability test: Let the dispersion stand at room temperature, observe the appearance periodically and take samples to measure the concentration change.

[0058] Example 1

[0059] The preparation method of the few-layer graphene dispersion in this embodiment includes the following steps:

[0060] (1) Pre-impregnation treatment: Take 10g of expandable graphite (flake graphite, 80 mesh, expandable ratio 300 times), add it to a mixed solution of 5g of hydrogen-containing silicone oil (polymethylhydrosiloxane, molecular weight 2000) and 2.5g of tetraethyl orthosilicate, impregnate at room temperature for 2 hours, stirring once every 30 minutes to ensure that the mixed solution fully penetrates into the graphite layers.

[0061] (2) Microwave expansion: The pre-impregnated expandable graphite is placed in a microwave oven and heated at 1000W for 30 seconds to obtain expanded graphite with a volume expansion of about 200 times.

[0062] (3) Preparation of stripping solution: Prepare stripping solution by weight: 2 parts calcium hydroxide, 5 parts 3-aminopropyltriethoxysilane, 30 parts ethanol, and 100 parts deionized water. Stir and mix thoroughly.

[0063] (4) Exfoliation and dispersion: 5g of expanded graphite obtained in step (2) was added to 500mL of exfoliation solution and dispersed for 60 minutes using a high-speed shear emulsifier (IKA T25) at 15000rpm. During this process, the hydrogen-containing silicone oil decomposed under the catalysis of calcium hydroxide to generate hydrogen gas, which was then inserted into the graphite layers to achieve chemical exfoliation; at the same time, 3-aminopropyltriethoxysilane and calcium ions formed a polysilsesquioxane network structure, which stabilized the exfoliated graphene sheets.

[0064] (5) Separation and purification: The dispersion was centrifuged at 5000 rpm for 60 minutes to remove the unpeeled graphite agglomerates and obtain the few-layer graphene dispersion of this embodiment.

[0065] The performance test results of the few-layer graphene dispersion in this embodiment show that:

[0066] (1) Concentration and yield: Following the concentration determination method described above, the graphene mass was measured in three parallel experiments to be 35.3 mg, 35.2 mg, and 35.1 mg (corresponding to 10 mL of dispersion), with an average value of 35.2 mg. The concentration of the dispersion was calculated to be 3.52 mg / mL. The total volume of the dispersion was 500 mL, the total mass of graphene was 1.760 g, and the yield was 35.2% (relative to the 5 g of expanded graphite added for exfoliation).

[0067] (2) Layer distribution: After processing by the method of the present invention, few-layer graphene with fewer layers (mainly distributed in 3-8 layers) and uniform dispersion was successfully obtained. Figure 1 ).

[0068] (3) Raman spectrum: The ID / IG ratio is 0.25±0.03, indicating that the defect density is low and the crystal structure is well preserved.

[0069] (4) Conductivity: The dispersion was filtered to form a film (with a film thickness of about 9.8 μm). The sheet resistance was measured to be 40 Ω / sq using the four-probe method, and the conductivity was calculated to be 2550 S / m, indicating that graphene has excellent electrical conductivity.

[0070] (5) Dispersion stability: After standing at room temperature, the concentration of the dispersion was 3.48 mg / mL after 1 week (sedimentation rate 1.2%), 3.43 mg / mL after 1 month (sedimentation rate 2.4%), and 3.35 mg / mL after 3 months (sedimentation rate 4.9%). The dispersion was uniform in appearance and there was no obvious stratification. After 6 months, the concentration of the upper layer was 3.18 mg / mL (sedimentation rate 9.8%). There was a small amount of sediment at the bottom, but the overall dispersion remained good, showing excellent long-term stability.

[0071] Example 2

[0072] The only difference between this embodiment and Example 1 is that a different stripping solution was used (by mass, the stripping solution in this embodiment includes: 1 part sodium hydroxide, 8 parts N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, 25 parts ethanol, and 120 parts deionized water), while the rest are the same as in Example 1.

[0073] The performance test results of the few-layer graphene dispersion in this embodiment show that:

[0074] (1) Concentration and yield: According to the above concentration determination method, the graphene mass was measured in three parallel experiments to be 22.7 mg, 22.5 mg, and 22.4 mg (corresponding to 10 mL of dispersion), with an average value of 22.5 mg. The concentration of the dispersion was calculated to be 2.25 mg / mL. The total volume of the dispersion was 500 mL, the total mass of graphene was 1.125 g, and the yield was 22.5% (relative to the 5 g of expanded graphite added for exfoliation).

[0075] (2) Layer distribution: The number of graphene layers is mainly distributed in 4-10 layers, and the layers are evenly dispersed.

[0076] (3) Raman spectroscopy: The ID / IG ratio is 0.28±0.04, indicating that the defect density is very low and the graphene is of excellent quality.

[0077] (4) Conductivity: The dispersion was filtered to form a film (with a film thickness of about 10.2 μm). The sheet resistance was measured to be 54 Ω / sq using the four-probe method, and the conductivity was calculated to be 1815 S / m.

[0078] (5) Dispersion stability: After standing at room temperature, the concentration of the dispersion was 2.21 mg / mL after 1 week (sedimentation rate 1.7%), 2.13 mg / mL after 1 month (sedimentation rate 5.2%), and 2.06 mg / mL after 3 months (sedimentation rate 8.6%), showing good dispersion stability.

[0079] Example 3

[0080] The only difference between this embodiment and Example 1 is that the amount of each raw material is scaled up proportionally to examine the feasibility of large-scale preparation of few-layer graphene dispersion.

[0081] Specifically, the amount of expandable graphite was increased to 1 kg (containing 500 g of hydrosilicone oil and 250 g of tetraethyl orthosilicate), and the amounts of other raw materials were increased in the same proportion (200 g of calcium hydroxide, 500 g of 3-aminopropyltriethoxysilane, 3 kg of ethanol, and 10 kg of deionized water); exfoliation and dispersion were performed using an industrial high-speed disperser (10,000 rpm) for 90 minutes; centrifugation was performed using an industrial centrifuge at 5,000 rpm for 60 minutes. All other procedures remained the same as in Example 1.

[0082] The performance test results of the few-layer graphene dispersion in this embodiment show that:

[0083] (1) Concentration and yield: Following the concentration determination method described above, the graphene mass was measured in three parallel experiments to be 24.2 mg, 24.1 mg, and 24.0 mg (corresponding to 10 mL of dispersion), with an average value of 24.1 mg. The concentration of the dispersion was calculated to be 2.41 mg / mL. The total volume of the dispersion was approximately 80 L, the total mass of graphene was approximately 193 g, and the yield was 19.3% (relative to the initial 1.00 kg of expandable graphite).

[0084] (2) Layer distribution: The number of graphene layers is mainly distributed in 3-9 layers.

[0085] (3) Raman spectrum: The ID / IG ratio is 0.27±0.03, indicating that the defect density is very low, which reproduces the excellent results of the small-scale experiment.

[0086] (4) Conductivity: The dispersion was filtered to form a film (with a film thickness of about 10.5 μm). The sheet resistance was measured to be 46 Ω / sq using the four-probe method, and the conductivity was calculated to be 2070 S / m. The conductivity was stable.

[0087] (5) Dispersion stability: After standing at room temperature, the concentration of the dispersion was 2.36 mg / mL (sedimentation rate 1.9%) after 1 week, 2.32 mg / mL (sedimentation rate 3.8%) after 1 month, and 2.23 mg / mL (sedimentation rate 7.7%) after 3 months. The dispersion had a uniform appearance, no obvious stratification, and good long-term stability.

[0088] Example 4

[0089] The difference between this embodiment and Example 1 is as follows: 10g of expandable graphite, 2.5g of hydrogen-containing silicone oil, and 5g of tetraethyl orthosilicate (TEOS:silicone oil mass ratio 1:0.5); the exfoliation solution composition is: 0.1 parts calcium hydroxide, 1 part 3-aminopropyltriethoxysilane, 10 parts ethanol, and 50 parts deionized water; 5g of expanded graphite is added to 50mL of exfoliation solution (expanded graphite:exfoliation solution mass ratio 1:10); microwave power is 800W for 5s; shearing speed is 5000rpm for 30min; centrifugation speed is 2000rpm for 30min.

[0090] The performance test results of the few-layer graphene dispersion in this embodiment show that:

[0091] (1) Concentration and Yield: Following the concentration determination method described above, the graphene mass was measured in three parallel experiments to be 123.2 mg, 123.0 mg, and 122.8 mg (corresponding to 10 mL of dispersion), with an average value of 123.0 mg. The concentration of the dispersion was calculated to be 12.3 mg / mL. The total volume of the dispersion was 50 mL, the total mass of graphene was 0.615 g, and the yield was 12.3% (relative to the 5 g of expanded graphite added for exfoliation).

[0092] (2) Layer number distribution: The graphene layers are mainly distributed between 5 and 14. The graphene prepared in this example has a relatively wide layer number distribution range, indicating that the uniformity of the product layer number has decreased. Figure 2 What is shown is the morphology of a layer with a relatively large number of layers (14 layers).

[0093] (3) Raman spectrum: The ID / IG ratio is 0.32±0.05, indicating that the defect density has increased compared to the optimal conditions, but still remains at a low level.

[0094] (4) Conductivity: The dispersion was filtered to form a film (with a film thickness of about 10.8 μm). The sheet resistance was measured to be 48 Ω / sq using the four-probe method, and the conductivity was calculated to be 1,930 S / m.

[0095] (5) Dispersion stability: After standing at room temperature, the concentration of the dispersion was 12.0 mg / mL after 1 week (sedimentation rate 2.5%), 11.5 mg / mL after 1 month (sedimentation rate 6.5%), and 10.8 mg / mL after 3 months (sedimentation rate 12.0%). The dispersion had a uniform appearance, no obvious stratification, and good long-term stability.

[0096] Example 5

[0097] The difference between this embodiment and Example 1 is as follows: 10g of expandable graphite, 15g of hydrogen-containing silicone oil, and 5g of tetraethyl orthosilicate (TEOS:silicone oil mass ratio 1:3); the exfoliation solution composition: 5 parts calcium hydroxide, 10 parts 3-aminopropyltriethoxysilane, 50 parts ethanol, and 200 parts deionized water; 5g of expanded graphite was added to 500mL of exfoliation solution (expanded graphite:exfoliation solution mass ratio 1:100); microwave power 1200W, time 60s; shearing speed 20000rpm, time 120min; centrifugation speed 8000rpm, time 90min.

[0098] The performance test results of the few-layer graphene dispersion in this embodiment show that:

[0099] (1) Concentration and yield: According to the above concentration determination method, the graphene mass was measured in three parallel experiments to be 11.9 mg, 11.7 mg and 11.65 mg (corresponding to 10 mL of dispersion), with an average value of 11.7 mg. The concentration of the dispersion was calculated to be 1.17 mg / mL. The total volume of the dispersion was 500 mL, the total mass of graphene was 0.585 g, and the yield was 11.7% (relative to the 5 g of expanded graphite added for exfoliation).

[0100] (2) Layer distribution: The number of graphene layers is mainly distributed in 3-9 layers.

[0101] (3) Raman spectroscopy: The ID / IG ratio is 0.31±0.04, indicating that the defect density has increased slightly, but the product still has good structural integrity.

[0102] (4) Conductivity: The dispersion was filtered to form a film (with a film thickness of about 9.5 μm). The sheet resistance was measured to be 58 Ω / sq using the four-probe method, and the conductivity was calculated to be 1,815 S / m.

[0103] (5) Dispersion stability: After standing at room temperature, the concentration of the dispersion was 1.15 mg / mL after 1 week (sedimentation rate 1.7%), 1.13 mg / mL after 1 month (sedimentation rate 3.4%), and 1.05 mg / mL after 3 months (sedimentation rate 10.3%). The dispersion had a uniform appearance, no obvious stratification, and good long-term stability.

[0104] Example 6

[0105] The difference between this embodiment and Example 1 is as follows: 10g of expandable graphite, 7.5g of hydrogen-containing silicone oil, and 5g of tetraethyl orthosilicate (TEOS:silicone oil mass ratio 1:1.5); the exfoliation solution composition is: 2.5 parts calcium hydroxide, 5.5 parts 3-aminopropyltriethoxysilane, 30 parts ethanol, and 125 parts deionized water; 5g of expanded graphite is added to 250mL of exfoliation solution (the mass ratio of expanded graphite to exfoliation solution is 1:50); microwave power is 1000W for 30s; shearing speed is 12000rpm for 75min; centrifugation speed is 5000rpm for 60min.

[0106] The performance test results of the few-layer graphene dispersion in this embodiment show that:

[0107] (1) Concentration and yield: According to the above concentration determination method, the graphene mass was measured in three parallel experiments to be 49.8 mg, 49.6 mg, and 49.4 mg (corresponding to 10 mL of dispersion), with an average value of 49.6 mg. The concentration of the dispersion was calculated to be 4.96 mg / mL. The total volume of the dispersion was 250 mL, the total mass of graphene was 1.240 g, and the yield was 24.8% (relative to the 5 g of expanded graphite added for exfoliation; the mass ratio of expanded graphite to exfoliation solution was 1:50).

[0108] (2) Layer distribution: The number of graphene layers is mainly distributed in 3-9 layers.

[0109] (3) Raman spectrum: The ID / IG ratio is 0.26±0.03, indicating low defect density and good lattice integrity.

[0110] (4) Conductivity: The dispersion was filtered to form a film (with a film thickness of about 10.0 μm). The sheet resistance was measured to be 45 Ω / sq using the four-probe method, and the conductivity was calculated to be 2,220 S / m.

[0111] (5) Dispersion stability: After standing at room temperature, the concentration of the dispersion was 4.88 mg / mL after 1 week (sedimentation rate 1.6%), 4.79 mg / mL after 1 month (sedimentation rate 3.4%), and 4.62 mg / mL after 3 months (sedimentation rate 6.9%). The dispersion had a uniform appearance, no obvious stratification, and good long-term stability.

[0112] Example 7

[0113] The only difference between this embodiment and Example 1 is that the alkaline catalyst used is 1.5 parts of potassium hydroxide; all other aspects are the same as in Example 1.

[0114] The performance test results of the few-layer graphene dispersion in this embodiment show that:

[0115] (1) Concentration and yield: Following the concentration determination method described above, the graphene mass was measured in three parallel experiments to be 27.7 mg, 27.6 mg, and 27.5 mg (corresponding to 10 mL of dispersion), with an average value of 27.6 mg. The concentration of the dispersion was calculated to be 2.76 mg / mL. The total volume of the dispersion was 500 mL, the total mass of graphene was 1.380 g, and the yield was 27.6% (relative to the 5 g of expanded graphite added for exfoliation).

[0116] (2) Layer distribution: The number of graphene layers is mainly distributed in 4-10 layers.

[0117] (3) Raman spectroscopy: The ID / IG ratio is 0.29±0.04, indicating that the defect density is low, but slightly higher than that of the calcium hydroxide catalytic system.

[0118] (4) Conductivity: The dispersion was filtered to form a film (with a film thickness of about 10.0 μm). The sheet resistance was measured to be 46 Ω / sq using the four-probe method, and the conductivity was calculated to be 2,180 S / m.

[0119] (5) Dispersion stability: After standing at room temperature, the concentration of the dispersion was 2.71 mg / mL after 1 week (sedimentation rate 1.8%), 2.62 mg / mL after 1 month (sedimentation rate 5.0%), and 2.46 mg / mL after 3 months (sedimentation rate 10.8%). The dispersion exhibited a uniform appearance with no obvious stratification, demonstrating good long-term stability. The dispersion stability was slightly lower than that of the calcium hydroxide system, mainly due to the presence of potassium. + Cannot be like Ca 2+ That way, a stable polysilsesquioxane network structure can be formed with the silane coupling agent.

[0120] Example 8

[0121] The only difference between this embodiment and Example 1 is that 6 parts of N-phenyl-3-aminopropyltrimethoxysilane are used instead of 5 parts of 3-aminopropyltriethoxysilane as the silane coupling agent; all other aspects remain the same as in Example 1.

[0122] The performance test results of the few-layer graphene dispersion in this embodiment show that:

[0123] (1) Concentration and yield: According to the above concentration determination method, the graphene mass was measured in three parallel experiments to be 31.1 mg, 31.0 mg and 30.9 mg (corresponding to 10 mL of dispersion), with an average value of 31.0 mg. The concentration of the dispersion was calculated to be 3.10 mg / mL. The total volume of the dispersion was 500 mL, the total mass of graphene was 1.550 g, and the yield was 31.0% (relative to the 5 g of expanded graphite added for exfoliation).

[0124] (2) Layer distribution: The number of graphene layers is mainly distributed in 3-9 layers.

[0125] (3) Raman spectroscopy: The ID / IG ratio is 0.27±0.03, indicating that the defect density is very low and the phenylsilane coupling agent does not introduce obvious defects.

[0126] (4) Conductivity: The dispersion was filtered to form a film (with a film thickness of about 9.9 μm). The sheet resistance was measured to be 44 Ω / sq using the four-probe method, and the conductivity was calculated to be 2,296 S / m.

[0127] (5) Dispersion stability: After standing at room temperature, the concentration of the dispersion was 3.06 mg / mL (sedimentation rate 1.4%) after 1 week, 2.97 mg / mL (sedimentation rate 4.2%) after 1 month, and 2.89 mg / mL (sedimentation rate 6.9%) after 3 months. The dispersion had a uniform appearance and no obvious stratification, indicating good long-term stability. The presence of phenyl groups enhanced the π-π interaction with graphene, providing stronger adsorption force and steric hindrance effect.

[0128] Example 9

[0129] The only difference between this embodiment and Embodiment 1 is that the pre-impregnation time in step (1) is shortened to 10 minutes. Everything else remains the same as in Embodiment 1.

[0130] The performance test results of the few-layer graphene dispersion in this embodiment show that:

[0131] (1) Concentration and yield: According to the above concentration determination method, the graphene mass was measured in three parallel experiments to be 29.5 mg, 29.4 mg, and 29.3 mg (corresponding to 10 mL of dispersion), with an average value of 29.4 mg. The concentration of the dispersion was calculated to be 2.94 mg / mL. The total volume of the dispersion was 500 mL, the total mass of graphene was 1.470 g, and the yield was 29.4% (relative to the 5 g of expanded graphite added for exfoliation).

[0132] (2) Layer distribution: The number of graphene layers is mainly distributed in 3–9 layers, with the proportion of fewer layers being slightly lower than in Example 1 (due to insufficient peeling caused by shortened pre-impregnation time).

[0133] (3) Raman spectrum: The ID / IG ratio was 0.30±0.03, which was slightly higher than that of Example 1 (0.25±0.03), indicating that insufficient pre-impregnation led to a slight increase in defects, but the overall lattice integrity was still good.

[0134] (4) Conductivity: The dispersion was filtered to form a film (with a film thickness of about 9.8 μm). The sheet resistance was measured to be 52 Ω / sq using the four-probe method, and the conductivity was calculated to be 1,960 S / m.

[0135] (5) Dispersion stability: After standing at room temperature, the concentration of the dispersion was 2.89 mg / mL after 1 week (sedimentation rate 1.8%), 2.83 mg / mL after 1 month (sedimentation rate 3.8%), 2.72 mg / mL after 3 months (sedimentation rate 7.6%), and 2.55 mg / mL after 6 months (sedimentation rate 13.5%). The dispersion had a uniform appearance, no obvious stratification, and good long-term stability.

[0136] Example 10

[0137] The only difference between this embodiment and embodiment 1 is that the shearing speed in step (4) is 25,000 rpm, while the rest are the same as in embodiment 1.

[0138] The performance test results of the few-layer graphene dispersion in this embodiment show that:

[0139] (1) Concentration and yield: According to the above concentration determination method, the graphene mass was measured in three parallel experiments to be 31.9 mg, 31.8 mg, and 31.7 mg (corresponding to 10 mL of dispersion), with an average value of 31.8 mg. The concentration of the dispersion was calculated to be 3.18 mg / mL. The total volume of the dispersion was 500 mL, the total mass of graphene was 1.590 g, and the yield was 31.8% (relative to the 5 g of expanded graphite added for exfoliation).

[0140] (2) Layer distribution: The number of graphene layers is mainly distributed in 3–9 layers, which is similar to Example 1, but the average size of the sheets is slightly reduced (high shear can easily cause further breakage of the sheets).

[0141] (3) Raman spectrum: The ID / IG ratio was 0.33±0.03, which was slightly higher than that of Example 1 (0.25±0.03), indicating that the excessively high shear rate introduced more edge defects and microstructure damage.

[0142] (4) Conductivity: The dispersion was filtered to form a film (with a film thickness of about 9.8 μm). The sheet resistance was measured to be 55 Ω / sq using the four-probe method, and the conductivity was calculated to be 1,860 S / m.

[0143] (5) Dispersion stability: After standing at room temperature, the concentration of the dispersion was 3.12 mg / mL after 1 week (sedimentation rate 1.9%), 3.03 mg / mL after 1 month (sedimentation rate 4.7%), 2.92 mg / mL after 3 months (sedimentation rate 8.2%), and 2.72 mg / mL after 6 months (sedimentation rate 14.5%). The overall dispersion stability was slightly worse than that of Example 1.

[0144] Example 11

[0145] The only difference between this embodiment and Example 1 is that the amount of calcium hydroxide used in step (3) is 6 parts, while the rest are the same as in Example 1.

[0146] The performance test results of the few-layer graphene dispersion in this embodiment show that:

[0147] (1) Concentration and yield: According to the above concentration determination method, the graphene mass was measured in three parallel experiments to be 21.1 mg, 21.0 mg and 20.9 mg (corresponding to 10 mL of dispersion), with an average value of 21.0 mg. The concentration of the dispersion was calculated to be 2.10 mg / mL. The total volume of the dispersion was 500 mL, the total mass of graphene was 1.050 g, and the yield was 21.0% (relative to the 5 g of expanded graphite added for exfoliation).

[0148] (2) Layer distribution: The number of graphene layers is mainly distributed in 4–11 layers. The number of fewer layers is slightly lower than that in Example 1, and slight agglomeration can be seen.

[0149] (3) Raman spectroscopy: The ID / IG ratio was 0.33±0.04, which was higher than that of Example 1 (0.25±0.03), indicating that there was excess Ca. 2+ This leads to excessive ionic strength in the system, excessively rapid condensation, and an increase in edge defects and microcracks.

[0150] (4) Conductivity: The dispersion was filtered to form a film (with a film thickness of about 10.0 μm). The sheet resistance was measured to be 52 Ω / sq using the four-probe method, and the conductivity was calculated to be 1,920 S / m.

[0151] (5) Dispersion stability: After standing at room temperature, the concentration of the dispersion was 2.04 mg / mL after 1 week (sedimentation rate 2.9%), 1.96 mg / mL after 1 month (sedimentation rate 6.7%), and 1.82 mg / mL after 3 months (sedimentation rate 13.3%), showing more obvious supernatant clarification and bottom sedimentation than in Example 1.

[0152] Comparative Example 1

[0153] In this comparative example, a graphene dispersion was prepared using the traditional ultrasonic exfoliation method: 5g of expanded graphite was dispersed in 500mL of N-methylpyrrolidone, ultrasonically treated (power 400W) for 8 hours, and then separated by centrifugation.

[0154] The performance test results of the few-layer graphene dispersion in this comparative example show that:

[0155] (1) Concentration and yield: According to the above concentration determination method, the graphene mass was measured in three parallel experiments to be 2.02 mg, 2.00 mg and 1.98 mg (corresponding to 10 mL of dispersion), with an average value of 2.00 mg. The concentration of the dispersion was calculated to be 0.20 mg / mL. The total volume of the dispersion was 500 mL, the total mass of graphene was 0.100 g, and the yield was 2.0% (relative to the 5 g of expanded graphite added for exfoliation).

[0156] (2) Layer distribution: The number of graphene layers is mainly distributed between 6 and 15, with fewer layers (≤5 layers) accounting for a relatively low proportion. At the same time, local aggregates are visible.

[0157] (3) Raman spectrum: The ID / IG ratio is 0.55±0.08, which is significantly higher than that of the embodiment of the present invention, indicating that the ultrasonic liquid phase method introduces more defects and poorer lattice integrity.

[0158] (4) Conductivity: The dispersion was filtered to form a film (with a film thickness of about 10.0 μm). The sheet resistance was measured to be 180 Ω / sq using the four-probe method, and the conductivity was calculated to be 555 S / m.

[0159] (5) Dispersion stability: After standing at room temperature, the concentration of the dispersion was 0.14 mg / mL after 1 week (sedimentation rate 30.0%), 0.10 mg / mL after 1 month (sedimentation rate 50.0%), and 0.07 mg / mL after 3 months (sedimentation rate 65.0%). Obvious stratification and sedimentation were observed, indicating poor stability.

[0160] Comparative Example 2

[0161] The only difference between this comparative example and Example 1 is that: no pre-impregnation treatment is used, and ordinary flake graphite is directly subjected to microwave treatment and exfoliation dispersion (i.e., step (1) is omitted), while the rest is consistent with Example 1.

[0162] The performance test results of the few-layer graphene dispersion in this comparative example show that:

[0163] (1) Concentration and yield: According to the above concentration determination method, the graphene mass was measured in three parallel experiments to be 1.02 mg, 1.00 mg and 0.98 mg (corresponding to 10 mL of dispersion), with an average value of 1.00 mg. The concentration of the dispersion was calculated to be 0.10 mg / mL. The total volume of the dispersion was 500 mL, the total mass of graphene was 0.050 g, and the yield was 1.0% (relative to the 5 g of expanded graphite added for exfoliation).

[0164] (2) Layer distribution: The number of graphene layers is mainly distributed in 10–25 layers. The proportion of multilayers and agglomerates is relatively high, while the proportion of few-layer sheets is relatively low (corresponding to insufficient microwave expansion and insufficient interlayer spacing).

[0165] (3) Raman spectrum: The ID / IG ratio is 0.62±0.09, which is significantly higher than that of the embodiment of the present invention, indicating that the defects are increased and the lattice integrity is poor due to the lack of pre-impregnation-co-expansion.

[0166] (4) Conductivity: The dispersion was filtered to form a film (with a film thickness of 10.0 μm). The sheet resistance was measured to be 238 Ω / sq using the four-probe method, and the conductivity was calculated to be 420 S / m.

[0167] (5) Dispersion stability: After standing at room temperature, the concentration of the dispersion was 0.06 mg / mL after 1 week (sedimentation rate 40.0%), 0.04 mg / mL after 1 month (sedimentation rate 60.0%), and 0.02 mg / mL after 3 months (sedimentation rate 80.0%). Obvious stratification and sedimentation were observed, indicating poor stability.

[0168] Comparative Example 3

[0169] The only difference between this comparative example and Example 1 is that no hydrogen-containing silicone oil is added to the pre-impregnation mixture in step (1), and only 5g of tetraethyl orthosilicate is used. All other aspects are the same as in Example 1.

[0170] The performance test results of the few-layer graphene dispersion in this comparative example show that:

[0171] (1) Concentration and yield: According to the above concentration determination method, the graphene mass was measured in three parallel experiments to be 1.52 mg, 1.50 mg and 1.48 mg (corresponding to 10 mL of dispersion), with an average value of 1.50 mg. The concentration of the dispersion was calculated to be 0.15 mg / mL. The total volume of the dispersion was 500 mL, the total mass of graphene was 0.075 g, and the yield was 1.5% (relative to the 5 g of expanded graphite added for exfoliation).

[0172] (2) Layer distribution: The number of graphene layers is mainly distributed in 8–18 layers, with a low proportion of fewer layers and local aggregates.

[0173] (3) Raman spectrum: ID / IG ratio is 0.52±0.07.

[0174] (4) Conductivity: The dispersion was filtered to form a film (with a film thickness of about 10.0 μm). The sheet resistance was measured to be 200 Ω / sq using the four-probe method, and the conductivity was calculated to be 500 S / m.

[0175] (5) Dispersion stability: After standing at room temperature, the concentration of the dispersion was 0.11 mg / mL (sedimentation rate 26.7%) after 1 week, 0.09 mg / mL (sedimentation rate 40.0%) after 1 month, and 0.06 mg / mL (sedimentation rate 60.0%) after 3 months, showing stratification and sedimentation, indicating generally low stability. This is mainly due to the lack of hydrogen generated from the hydrogen-containing silicone oil for chemical stripping; relying solely on mechanical shearing force results in extremely low stripping efficiency. This comparison demonstrates that hydrogen-containing silicone oil, as an "in-situ hydrogen source," is indispensable for achieving efficient chemical stripping.

[0176] Comparative Example 4

[0177] The only difference between this comparative example and Example 1 is that tetraethyl orthosilicate is not added to the pre-impregnation mixture in step (1), and only 5g of hydrogen-containing silicone oil is used. All other aspects are consistent with Example 1.

[0178] The performance test results of the few-layer graphene dispersion in this comparative example show that:

[0179] (1) Concentration and yield: According to the above concentration determination method, the graphene mass was measured in three parallel experiments to be 3.6 mg, 3.5 mg, and 3.4 mg (corresponding to 10 mL of dispersion), with an average value of 3.5 mg. The concentration of the dispersion was calculated to be 0.35 mg / mL. The total volume of the dispersion was 500 mL, the total mass of graphene was 0.175 g, and the yield was 3.5% (relative to the 5 g of expanded graphite added for exfoliation).

[0180] (2) Layer distribution: The graphene layers are mainly distributed in 6–14 layers, with a certain proportion of multilayer sheets and local agglomerates. The proportion of fewer layers is lower than in the example.

[0181] (3) Raman spectroscopy: The ID / IG ratio was 0.50±0.06, which was significantly higher than that of the example, indicating that the structural defects were increased due to the high viscosity of the pre-impregnation liquid, insufficient penetration and uneven expansion.

[0182] (4) Conductivity: The dispersion was filtered to form a film (with a film thickness of about 10.0 μm). The sheet resistance was measured to be 90 Ω / sq using the four-probe method, and the conductivity was calculated to be 1,110 S / m.

[0183] (5) Dispersion stability: After standing at room temperature, the concentration of the dispersion was 0.24 mg / mL after 1 week (sedimentation rate 31%), 0.20 mg / mL after 1 month (sedimentation rate 43%), and 0.15 mg / mL after 3 months (sedimentation rate 57%). Obvious stratification and sedimentation were observed, indicating poor stability.

[0184] Comparative Example 5

[0185] The only difference between this comparative example and Example 1 is that calcium hydroxide is not added to the stripping solution in step (3). Everything else is the same as in Example 1.

[0186] The performance test results of the few-layer graphene dispersion in this comparative example show that:

[0187] (1) Concentration and yield: According to the above concentration determination method, the graphene mass was measured in three parallel experiments to be 1.82 mg, 1.80 mg and 1.78 mg (corresponding to 10 mL of dispersion), with an average value of 1.80 mg. The concentration of the dispersion was calculated to be 0.18 mg / mL. The total volume of the dispersion was 500 mL, the total mass of graphene was 0.090 g, and the yield was 1.8% (relative to the 5 g of expanded graphite added for exfoliation).

[0188] (2) Layer distribution: The number of graphene layers is mainly distributed in 10–22 layers, with a low proportion of few layers and obvious agglomerates.

[0189] (3) Raman spectrum: The ID / IG ratio is 0.60±0.08, which is significantly higher than that of the embodiment of the present invention, indicating that there are more defects and poor lattice integrity.

[0190] (4) Conductivity: The dispersion was filtered to form a film (with a film thickness of about 10.0 μm). The sheet resistance was measured to be 265 Ω / sq using the four-probe method, and the conductivity was calculated to be 377 S / m.

[0191] (5) Dispersion stability: After standing at room temperature, the concentration of the dispersion was 0.09 mg / mL (sedimentation rate 50.0%) after 1 week, 0.05 mg / mL (sedimentation rate 72.2%) after 1 month, and 0.02 mg / mL (sedimentation rate 88.9%) after 3 months, showing obvious stratification and sedimentation, indicating poor stability. Comparing this comparative example with Example 1 shows that the alkaline catalyst is a necessary condition for driving the two core processes of "hydrogen chemical stripping" and "in-situ stabilization reaction".

[0192] Comparative Example 6

[0193] The only difference between this comparative example and Example 1 is that the amount of silane coupling agent (3-aminopropyltriethoxysilane) used in the stripping solution in step (3) is 0.5 parts. All other aspects are the same as in Example 1.

[0194] The performance test results of the few-layer graphene dispersion in this comparative example show that:

[0195] (1) Concentration and yield: According to the above concentration determination method, the graphene mass was measured in three parallel experiments to be 2.41 mg, 2.40 mg and 2.39 mg (corresponding to 10 mL of dispersion), with an average value of 2.40 mg. The concentration of the dispersion was calculated to be 0.24 mg / mL. The total volume of the dispersion was 500 mL, the total mass of graphene was 0.120 g, and the yield was 2.4% (relative to the 5 g of expanded graphite added for exfoliation).

[0196] (2) Layer distribution: The number of graphene layers is mainly distributed in 8–20 layers, with a low proportion of fewer layers and visible local aggregation.

[0197] (3) Raman spectrum: ID / IG ratio is 0.58±0.07.

[0198] (4) Conductivity: The dispersion was filtered to form a film (with a film thickness of about 10.0 μm). The sheet resistance was measured to be 167 Ω / sq using the four-probe method, and the conductivity was calculated to be 600 S / m.

[0199] (5) Dispersion stability: After standing at room temperature, the concentration of the dispersion was 0.20 mg / mL after 1 week (sedimentation rate 16.7%), 0.16 mg / mL after 1 month (sedimentation rate 33.3%), and 0.11 mg / mL after 3 months (sedimentation rate 54.2%), showing stratification and sedimentation, indicating poor stability. This shows that sufficient silane coupling agent is the fundamental guarantee for forming a complete and stable coating layer and preventing graphene re-agglomeration.

[0200] Comparative Example 7

[0201] The only difference between this comparative example and Example 1 is that steps (1)-(2) are omitted, and expandable graphite (the same as in Example 1) without pre-impregnation and microwave expansion treatment is used instead of the expanded graphite in step (4) of Example 1. All other aspects are consistent with Example 1.

[0202] TEM images of the graphene prepared in this comparative example are as follows: Figure 3 As shown; by Figure 3 It can be seen that: in this comparative example, mechanical shearing of expandable graphite alone is insufficient to achieve effective exfoliation of graphene, and the product is a multilayer agglomerate, which cannot produce few-layer graphene.

[0203] In summary, the method for preparing the few-layer graphene dispersion of the present invention is significantly superior to the prior art in terms of exfoliation efficiency, product concentration, and dispersion stability.

[0204] The method for preparing the few-layer graphene dispersion of the present invention is simple, cost-controllable, and environmentally friendly. The prepared few-layer graphene dispersion has excellent dispersion stability and application performance, and is suitable for large-scale industrial production. It has broad application prospects in composite materials, coatings, conductive materials and other fields.

[0205] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a few-layer graphene dispersion, characterized in that, Includes the following steps: (1) Pre-impregnation treatment: Expandable graphite is impregnated in a mixed solution containing hydrosilicone oil and tetraethyl orthosilicate; (2) Microwave expansion: The expandable graphite obtained by the pre-impregnation treatment in step (1) is subjected to microwave treatment to obtain expanded graphite; (3) The expanded graphite is added to the exfoliation solution and sheared and dispersed to obtain a few-layer graphene dispersion; The stripping solution comprises the following components in parts by weight: 0.1-5 parts of alkaline catalyst, 1-10 parts of silane coupling agent, 10-50 parts of ethanol, and 50-200 parts of water.

2. The method for preparing the few-layer graphene dispersion as described in claim 1, characterized in that, In step (1), the mass ratio of tetraethyl orthosilicate to hydrogen-containing silicone oil is 1:(0.5-3); The hydrogen-containing silicone oil is a polymethylhydrosiloxane containing Si-H bonds or a copolymer of polymethylhydrosiloxane and polydimethylsiloxane, with a molecular weight of 1000-10000.

3. The method for preparing the few-layer graphene dispersion as described in claim 1, characterized in that, The alkaline catalyst is at least one of calcium hydroxide, sodium hydroxide, potassium hydroxide, and tetramethylammonium hydroxide; The silane coupling agent is an amino-containing silane coupling agent.

4. The method for preparing the few-layer graphene dispersion as described in claim 3, characterized in that, The silane coupling agent is at least one selected from 3-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane.

5. The method for preparing the few-layer graphene dispersion as described in claim 1, characterized in that, In step (3), the mass ratio of the expanded graphite to the stripping solution is 1:(10-100).

6. The method for preparing the few-layer graphene dispersion as described in claim 1, characterized in that, In step (1), the soaking time is 0.5-4 hours.

7. The method for preparing the few-layer graphene dispersion as described in claim 1, characterized in that, In step (2), the power of the microwave treatment is 800-1200W, and the microwave treatment time is 5-60s; The microwave processing is performed under inert gas protection.

8. The method for preparing the few-layer graphene dispersion as described in claim 1, characterized in that, In step (3), the rotation speed during shearing and dispersion is 5000-20000 rpm, and the shearing and dispersion time is 30-120 min; The shear dispersion is carried out in a shear emulsifier.

9. The method for preparing the few-layer graphene dispersion as described in claim 1, characterized in that, In step (3), the shearing and dispersion process further includes a centrifugation step to remove unpeeled graphite agglomerates; The centrifugation speed is 2000-8000 rpm, and the centrifugation time is 30-90 min.

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