Preparation method of antistatic stainless steel lining paper

Abstract

The preparation method of the anti-static stainless steel lining paper comprises the steps of base paper preparation, surface treatment, anti-static coating preparation, coating, drying and the like, and further comprises calendaring treatment. The base paper is prepared from softwood pulp and hardwood pulp in proportion, and the binding force of the base paper and a coating is enhanced through plasma activation; the antistatic coating contains a carbon nanotube and graphene compounded conductive filler, is matched with a binder and a dispersant, and is coated and dried by an optimized process. According to the method, through cooperation of all links, the lining paper is good and stable in antistatic performance, base paper and a coating are firmly combined, the surface is smooth and wear-resistant, the performance is stable in a humid environment, the stainless steel surface is effectively protected, and the method is suitable for stainless steel processing, transportation and storage scenes.

Description

Technical Field

[0001] This invention relates to the field of paper lining technology, specifically to a method for preparing antistatic stainless steel paper lining. Background Technology

[0002] During the processing, transportation, and storage of stainless steel, lining paper is used to protect its surface from scratches, contamination, and other damage.

[0003] Traditional stainless steel liner paper often suffers from poor antistatic properties, easily attracting dust and impurities due to static electricity, thus affecting the surface quality of stainless steel. Simultaneously, the base paper of traditional liner paper lacks sufficient strength, resulting in poor adhesion to the coating. During use, issues such as coating peeling and base paper damage easily occur, making it difficult to meet the long-term and complex environmental requirements for stainless steel protection. Furthermore, some antistatic liner papers use unevenly dispersed conductive materials, leading to unstable antistatic performance. Moreover, performance deteriorates significantly in humid environments or after prolonged use, further limiting their application range. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing antistatic stainless steel liner paper, so as to solve the technical problems of insufficient strength of the base paper, poor coating adhesion, and easy coating peeling and base paper damage during use.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for preparing antistatic stainless steel liner paper includes the following steps:

[0007] (1) Preparation of base paper: Softwood pulp and hardwood pulp are mixed at a mass ratio of 3:1-5:1, and then pulped and formed into base paper. The basis weight of the base paper is 40-60 g / m².

[0008] (2) Surface treatment of base paper: Atmospheric pressure plasma is used to activate the surface of base paper. The treatment power is 80-120W and the treatment time is 15-30s.

[0009] (3) Preparation of antistatic coating: The conductive filler, binder, dispersant and deionized water are mixed and ultrasonically dispersed for 15-30 min to prepare antistatic coating. The conductive filler is a composite system of carbon nanotubes and graphene, wherein the mass ratio of carbon nanotubes to graphene is 1:0.5-1:2, and the mass fraction of the conductive filler in the coating is 5%-15%.

[0010] (4) Coating: Apply the antistatic coating to the surface of the base paper treated in step (2) by using a doctor blade coating method. The coating amount is 8-15 g / m².

[0011] (5) Drying: Dry the coated base paper at 60-80℃ for 1-3 minutes to obtain antistatic stainless steel backing paper.

[0012] The above-mentioned technical solution describes a method for preparing antistatic stainless steel liner paper. The method involves preparing base paper by mixing appropriate proportions of pulps, combining plasma surface activation treatment, and then using conductive fillers composed of carbon nanotubes and graphene to form an antistatic coating. After coating and drying, the liner paper acquires good antistatic properties, and the base paper and coating are firmly bonded together, meeting the basic usage requirements of stainless steel liner paper and demonstrating good performance in protecting the surface of stainless steel.

[0013] As a preferred embodiment of the present invention, in step (1), the beating degree of softwood pulp is 30-40°SR, and the beating degree of hardwood pulp is 20-30°SR. By adopting the above technical solution and limiting the beating degree of softwood pulp and hardwood pulp, the two pulp fibers can form a more reasonable interwoven structure, improve the strength and uniformity of the base paper, provide a stable substrate for subsequent coating adhesion, and enhance the overall structural stability of the liner paper.

[0014] As a preferred embodiment of the present invention, in step (2), the working gas for plasma treatment is a mixture of argon and oxygen, wherein the volume ratio of argon to oxygen is 5:1-10:1. By adopting the above technical solution, plasma treatment using a mixture of argon and oxygen can more effectively activate the surface of the base paper, increase the surface polar groups, further improve the adhesion between the base paper and the subsequent antistatic coating, and reduce coating peeling.

[0015] As a preferred embodiment of the present invention, in step (3), the binder is a mixture of waterborne polyurethane and polyvinyl alcohol, wherein the mass ratio of waterborne polyurethane to polyvinyl alcohol is 3:1-5:1, and the mass fraction of the binder in the coating is 20% to 30%. Using the above technical solution, the mixture of waterborne polyurethane and polyvinyl alcohol as a binder not only leverages the good flexibility and adhesion of waterborne polyurethane but also utilizes the film-forming properties of polyvinyl alcohol to form a continuous and firm film layer on the base paper, thereby improving the mechanical properties of the coating and its bonding effect with the base paper.

[0016] As a preferred embodiment of the present invention, in step (3), the dispersant is sodium dodecylbenzenesulfonate, and its mass fraction in the coating is 0.5% to 2%. By adopting the above technical solution, sodium dodecylbenzenesulfonate, as a dispersant, can promote the uniform dispersion of conductive fillers in the coating, avoid the agglomeration of conductive fillers, ensure the consistent performance of the antistatic coating, and make the antistatic effect of the backing paper uniform and stable.

[0017] As a preferred embodiment of the present invention, in step (4), the doctor blade angle for doctor blade coating is 30-45°, and the coating speed is 50-100 m / min. By adopting the above technical solution, the specific doctor blade angle and coating speed can ensure that the antistatic coating is uniformly coated on the base paper, control the consistency of the coating thickness, avoid local over-thickness or under-thinness, and help stabilize the antistatic performance and appearance quality of the backing paper.

[0018] As a preferred embodiment of the present invention, in step (5), the drying process adopts segmented heating, sequentially passing through three temperature segments of 60℃, 70℃, and 80℃, with each temperature segment having a processing time of 20-40s. By adopting the above technical solution, segmented heating and drying can gradually dehydrate the coated base paper, avoiding coating cracking or base paper deformation caused by rapid drying, which helps to maintain the integrity of the coating and the original properties of the base paper, and improves the overall quality of the lining paper.

[0019] As a further aspect of the present invention, the present invention also includes step (6) calendering: the dried backing paper is calendered at 80-100℃ and 5-10MPa for 5-10s, and the linear speed of the calendering roller is 30-50m / min. Using the above technical solution, the calendering process can make the backing paper surface smoother, reduce surface roughness, and further enhance the bonding tightness between the coating and the base paper, improve the gloss and wear resistance of the backing paper, and better protect the stainless steel surface from scratches.

[0020] As a preferred embodiment of the present invention, the antistatic coating in step (3) further includes an antioxidant, which is a hindered phenolic antioxidant with a mass fraction of 0.1% to 0.5%. By adopting the above technical solution, adding an antioxidant to the antistatic coating can inhibit the oxidative aging of conductive fillers during long-term use, maintain the stability of the conductive network, and extend the effective period of the antistatic performance of the backing paper.

[0021] As a preferred embodiment of the present invention, a wet strength agent is also added to the base paper in step (1). The wet strength agent is polyamide polyamine epichlorohydrin, and the amount added is 1% to 3% of the oven-dry pulp mass. By adopting the above technical solution, adding a wet strength agent to the base paper can improve the strength of the base paper in a humid environment, reduce the damage of the base paper caused by moisture, enhance the reliability of the liner paper under humid conditions, and extend its service life.

[0022] As a preferred embodiment of the present invention, in step (3), the carbon nanotubes have a diameter of 10-50 nm and a length of 1-5 μm; the graphene is a single-layer graphene with a sheet diameter of 5-20 μm. By adopting the above technical solution, the specific morphological parameters of the carbon nanotubes and graphene are defined, which is conducive to the formation of a more complete conductive network in the coating by the two conductive fillers, thereby synergistically improving the conductivity of the antistatic coating and enhancing the antistatic effect of the backing paper.

[0023] Compared with existing technologies, the method for preparing antistatic stainless steel liner paper of the present invention has the following beneficial effects:

[0024] In the preparation of the base paper, a specific ratio of softwood pulp and hardwood pulp is mixed, along with an appropriate beating degree, to form a well-structured fiber interwoven structure in the base paper, resulting in excellent strength and uniformity, providing a stable substrate for subsequent coating adhesion. After atmospheric pressure plasma activation treatment, the surface polar groups of the base paper increase, significantly improving the adhesion to the antistatic coating and effectively preventing coating peeling.

[0025] In the antistatic coating, the conductive filler composed of carbon nanotubes and graphene is uniformly dispersed under the action of a dispersant to form a stable conductive network, giving the backing paper good and stable antistatic properties.

[0026] The proper selection and formulation of the adhesive ensures strong adhesion and good mechanical properties of the coating. Optimization of processes such as coating, drying, and calendering results in uniform coating thickness, a smooth and wear-resistant backing paper surface, and further enhances the protective effect on stainless steel surfaces.

[0027] The addition of antioxidants extends the effective period of antistatic properties, and the introduction of wet strength agents enhances the strength of the base paper in humid environments, significantly improving the reliability and service life of the liner paper in complex environments. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are merely specific examples of embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a flowchart of an embodiment of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0031] In the description of the embodiments of the present invention, it should be understood that the terms "upper", "lower", "front", "rear", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of the present invention.

[0032] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, an integral connection, or a detachable connection; they can refer to the internal connection of two components; they can refer to a direct connection or an indirect connection through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the embodiments of the present invention should be understood according to the specific circumstances.

[0033] Reference Figure 1 As shown, the present invention provides the following five embodiments:

[0034] Example 1:

[0035] Preparation method: Softwood pulp and hardwood pulp were mixed at a mass ratio of 3:1, with a freeness of 30°SR for the softwood pulp and 20°SR for the hardwood pulp. After beating and papermaking, a base paper with a basis weight of 40 g / m² was produced. Atmospheric pressure plasma was used, with a mixture of argon and oxygen at a volume ratio of 5:1 as the working gas, and the surface of the base paper was treated with 80W power for 15 seconds. Carbon nanotubes and graphene at a mass ratio of 1:0.5 were used as conductive fillers, accounting for 5% of the coating mass fraction. This was combined with 20% by mass of a waterborne polyurethane and polyvinyl alcohol composite binder (mass ratio of 3:1), 0.5% sodium dodecylbenzenesulfonate dispersant, and deionized water, and ultrasonically dispersed for 15 minutes to prepare an antistatic coating. The coating was applied using a doctor blade at a 30° angle and a speed of 50 m / min, with a coating amount of 8 g / m². It was dried at 60℃ for 1 minute and finally calendered at 80℃ and 5 MPa for 5 seconds, with a calendering roller linear speed of 30 m / min.

[0036] Technical effects: The base paper, with its mixed pulp types and specific beating degree forming a well-interwoven structure, exhibits good strength and uniformity. Plasma activation ensures a strong bond between the base paper and the coating. A well-formulated combination of conductive fillers, binders, and other additives, along with appropriate coating, drying, and calendering processes, endows the liner paper with excellent antistatic properties, a smooth and wear-resistant surface, and effective protection for stainless steel surfaces.

[0037] Working principle: Mixing pulps with different beating degrees allows for better fiber interweaving. Plasma treatment increases the polar groups on the base paper surface. In the antistatic coating, conductive fillers form a conductive network, binders ensure coating adhesion, and dispersants guarantee uniform dispersion. The coating process ensures uniform coating, drying cures the coating, and calendering improves surface quality.

[0038] Experimental data: Tests showed that the tensile strength of the base paper increased by 20%, and the surface resistivity decreased to 10. 8 The coating strength is below Ω, meeting antistatic requirements. The coating adhesion test achieved a 5B grade, and the coating showed no significant damage after the abrasion resistance test.

[0039] Example 2:

[0040] Preparation method: Softwood pulp and hardwood pulp were mixed in a 4:1 mass ratio, with a softwood pulp freeness of 35°SR and a hardwood pulp freeness of 25°SR, to produce a base paper with a basis weight of 50 g / m². Atmospheric pressure plasma was used to treat the base paper surface with an argon-oxygen mixture of 8:1 volume ratio at 100W for 20 seconds. The conductive filler consisted of carbon nanotubes and graphene in a 1:1 mass ratio, accounting for 10% of the coating mass. The binder was a 25% (mass fraction) waterborne polyurethane and polyvinyl alcohol compound (mass ratio 4:1), and the dispersant was 1% sodium dodecylbenzenesulfonate. Ultrasonic dispersion was performed for 20 minutes. Doctor blade coating was applied at a 35° angle and a speed of 70 m / min, with a coating weight of 12 g / m². Drying was carried out at 70℃ for 2 minutes, followed by calendering at 90℃ and 7 MPa for 8 seconds at a calendering roller linear speed of 40 m / min.

[0041] Technical benefits: Optimized pulp ratio and beating degree result in superior base paper performance. Plasma treatment enhances coating adhesion. The antistatic coating formulation and application process stabilize the antistatic properties of the liner paper, further improving overall strength and surface quality, making it better suited for stainless steel liner applications.

[0042] Working principle: Appropriate pulp ratio and beating degree optimize the base paper structure. Plasma more fully activates the base paper. The adjusted antistatic coating components work synergistically, and coating and subsequent processes ensure coating quality and performance.

[0043] Experimental data: The tensile strength of the base paper is increased by 30% compared with ordinary base paper, and the surface resistivity is stabilized at 10. 7 Approximately Ω. The coating exhibits good flexibility, showing no cracks during bending tests, and its gloss is improved by 30%.

[0044] Example 3:

[0045] Preparation method: Softwood pulp and hardwood pulp were mixed at a mass ratio of 5:1, with a freeness of 40°SR for the softwood pulp and 30°SR for the hardwood pulp, to produce a base paper with a basis weight of 60 g / m². Atmospheric pressure plasma was used to treat the base paper surface for 30 seconds using an argon-oxygen mixture at a volume ratio of 10:1 and a power of 120W. The antistatic coating consisted of carbon nanotubes and graphene at a mass ratio of 1:2, accounting for 15% of the coating mass. The binder was a 30% (mass fraction) waterborne polyurethane and polyvinyl alcohol compound (mass ratio 5:1), and the dispersant was 2% sodium dodecylbenzenesulfonate. The mixture was ultrasonically dispersed for 30 minutes. Doctor blade coating was applied at a 45° angle and a speed of 100 m / min, with a coating amount of 15 g / m². The coating was dried at 80°C for 3 minutes, followed by calendering at 100°C and 10 MPa for 10 seconds, with a calendering roller linear speed of 50 m / min.

[0046] Technical benefits: A specific pulp ratio and high freeness impart high stability to the base paper. Thorough plasma treatment ensures excellent coating adhesion. High content of conductive fillers and other additives enhance the antistatic properties of the liner paper, while high strength and surface quality effectively protect stainless steel and adapt to complex operating environments.

[0047] Working principle: High freeness and a suitable pulp ratio allow the base paper fibers to interweave tightly. Intense plasma treatment greatly increases the surface activity of the base paper. High-content conductive fillers form a dense conductive network, and the synergistic effects of these processes ensure the overall performance of the liner paper.

[0048] Experimental data: The burst strength of the base paper increased by 40%, and the surface resistivity was as low as 10. 6 Ω. The coating exhibits excellent abrasion resistance; after 1000 simulated uses, the coating remains intact, with a gloss retention rate of 90%.

[0049] Example 4:

[0050] Preparation method: Based on Example 2, 0.1% hindered phenolic antioxidant was added to the antistatic coating, and 1% polyamide polyamine epichlorohydrin wet strength agent was added to the base paper.

[0051] Technical effects: Antioxidants inhibit the oxidation of conductive fillers, extending the effective period of antistatic properties. Wet strength agents significantly improve the strength of the base paper in humid environments, reduce moisture damage, and enhance the reliability and service life of the liner paper in complex environments.

[0052] Working principle: Antioxidants capture free radicals and prevent the conductive filler from oxidizing. Wet strength agents form covalent bonds with fibers, enhancing the bonding force between fibers and improving wet strength.

[0053] Experimental data: Accelerated aging tests showed that the antistatic properties of the liner paper with added antioxidants were maintained for 50% longer. In humid environments, the tensile strength retention rate of the base paper with added wet strength agent reached 80%, while that of the unadded agent was only 50%.

[0054] Example 5:

[0055] Preparation method: Based on Example 3, carbon nanotubes with a diameter of 10 nm and a length of 1 μm and single-layer graphene with a sheet diameter of 5 μm were used as conductive fillers. 0.3% hindered phenolic antioxidant was added to the antistatic coating, and 2% polyamide polyamine epichlorohydrin wet strength agent was added to the base paper.

[0056] Technical benefits: The specific morphology of conductive filler forms a superior conductive network, significantly enhancing antistatic properties. Antioxidants and wet strength agents further improve the performance of the liner paper in long-term use and humid environments, resulting in superior overall performance.

[0057] Working principle: Small-diameter and short-length carbon nanotubes and small-diameter graphene flakes more easily form a uniform conductive network. Antioxidants and wet strength agents play roles in anti-oxidation and moisture resistance, respectively, improving the overall performance of the liner paper.

[0058] Experimental data: Surface resistivity decreased to 10 5 Ω, which is further reduced compared to Example 3. After aging test, the antistatic performance retention rate reached 80%, and the strength loss of the base paper in humid environment was less than 20%, demonstrating excellent comprehensive performance.

[0059] In summary, the working principle of the method for preparing antistatic stainless steel liner paper provided in this embodiment of the invention is as follows:

[0060] Firstly, in the base paper preparation stage, the mixing and beating of different pulp types utilize the characteristics of different fibers to ensure thorough interweaving between them, forming a structurally stable base paper that provides a solid foundation for subsequent processing. Atmospheric pressure plasma treatment bombards the base paper surface with high-energy particles, breaking surface molecular bonds and introducing polar functional groups, thereby improving the wettability and chemical reactivity of the base paper surface and enhancing its adhesion to the coating. In the preparation of the antistatic coating, conductive fillers carbon nanotubes and graphene, with their excellent conductivity, interconnect in the coating to form conductive pathways, achieving the antistatic function; dispersants prevent the conductive fillers from agglomerating through charge repulsion or steric hindrance, ensuring their uniform distribution; binders tightly bind the conductive fillers to the base paper through intermolecular forces, ensuring a firm coating adhesion. The coating process controls parameters such as the doctor blade angle and speed to ensure uniform coating of the base paper surface; the drying process evaporates the solvent in the coating, allowing the coating to solidify and take shape; calendering, through high temperature and high pressure, makes the surface of the backing paper denser and smoother, improving surface quality and the tightness of the coating's adhesion to the base paper. Antioxidants inhibit the oxidation reaction of conductive fillers by capturing free radicals, thus maintaining the stability of the conductive network; wet strength agents form covalent bonds with the base paper fibers, enhancing the bonding strength between fibers and improving the tensile strength of the base paper in humid environments.

[0061] The antistatic stainless steel liner paper is easy to use. After the stainless steel is processed, cut the prepared antistatic stainless steel liner paper to a size that matches the stainless steel sheet. Place the liner paper with the antistatic coating side facing the stainless steel surface, smoothly covering the stainless steel sheet, ensuring a tight fit between the liner paper and the stainless steel surface to avoid scratches or contamination caused by air residue. When stacking stainless steel sheets, place one sheet of this liner paper between every two layers for isolation and protection. During transportation and storage, the liner paper effectively prevents the stainless steel surface from attracting dust and impurities due to static electricity generated by friction, while also preventing scratches caused by direct contact between stainless steel sheets. When the stainless steel sheet needs to be used, simply peel the liner paper off the stainless steel surface; no coating residue will remain during the peeling process, and it will not damage the stainless steel surface.

[0062] The foregoing has shown and described the basic principles of the present invention. The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. The above embodiments and descriptions in the specification are only illustrative of the principles of the present invention. Any modifications, equivalent substitutions, and improvements made within the scope of the present invention without departing from the scope of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for producing an anti-static stainless steel liner paper, characterized by The method comprises the following steps: (1) base paper preparation: mixing coniferous wood pulp and broadleaf wood pulp at a mass ratio of 3:1-5:1, and preparing base paper through beating and papermaking, wherein the basis weight of the base paper is 40-60 g / m²; (2) base paper surface treatment: activating the surface of the base paper by using atmospheric pressure plasma, the treatment power is 80-120 W, and the treatment time is 15-30 s; (3) antistatic coating preparation: mixing conductive fillers, binders, dispersants and deionized water, and preparing antistatic coating through ultrasonic dispersion for 15-30 min, wherein the conductive fillers are a compounded system of carbon nanotubes and graphene, the mass ratio of carbon nanotubes to graphene is 1:0.5-1:2, and the mass fraction of the conductive fillers in the coating is 5%-15%; (4) coating: coating the antistatic coating on the surface of the base paper treated in step (2) by using a doctor blade coating method, and the coating amount is 8-15 g / m²; (5) drying: drying the coated base paper at 60-80°C for 1-3 min to obtain the antistatic stainless steel lining paper.

2. The method for preparing antistatic stainless steel liner paper according to claim 1, characterized in that: In step (1), the beating degree of the coniferous wood pulp is 30-40°SR, and the beating degree of the broadleaf wood pulp is 20-30°SR.

3. The method for preparing antistatic stainless steel liner paper according to claim 1, characterized in that: In step (2), the working gas of the plasma treatment is a mixed gas of argon and oxygen, wherein the volume ratio of argon to oxygen is 5:1-10:

1.

4. The method for preparing an antistatic stainless steel liner paper according to claim 1, characterized in that: In step (3), the binder is a compounded product of water-based polyurethane and polyvinyl alcohol, wherein the mass ratio of water-based polyurethane to polyvinyl alcohol is 3:1-5:1, and the mass fraction of the binder in the coating is 20%-30%.

5. The method for preparing an antistatic stainless steel liner paper according to claim 1, characterized in that: In step (3), the dispersant is sodium dodecyl benzene sulfonate, and the mass fraction of the dispersant in the coating is 0.5%-2%.

6. The method for preparing an antistatic stainless steel liner paper according to claim 1, characterized in that: In step (4), the doctor blade angle of the doctor blade coating is 30-45°, and the coating speed is 50-100 m / min.

7. The method for preparing antistatic stainless steel liner paper according to claim 1, characterized in that: In step (5), the drying process adopts a segmented heating, and the paper is sequentially subjected to three temperature sections of 60°C, 70°C and 80°C, and the treatment time of each temperature section is 20-40 s.

8. The method for preparing an antistatic stainless steel liner paper according to claim 1, characterized in that: It also comprises step (6) calendering treatment: calendering the dried lining paper at 80-100°C and 5-10 MPa for 5-10 s, and the linear speed of the calendering roller is 30-50 m / min.

9. The method for preparing an antistatic stainless steel liner paper according to claim 1, characterized in that: The antistatic coating of step (3) further comprises an antioxidant, wherein the antioxidant is a hindered phenolic antioxidant, and the mass fraction of the antioxidant is 0.1%-0.5%.

10. A method of producing an anti-static stainless steel backing paper according to any one of claims 1 to 9, characterized in that: The base paper of step (1) further comprises a wet strength agent, wherein the wet strength agent is polyamide polyamine epichlorohydrin, and the addition amount of the wet strength agent is 1%-3% of the mass of the dry pulp; in step (3), the diameter of the carbon nanotubes is 10-50 nm, and the length is 1-5 μm; and the graphene is single-layer graphene, and the flake diameter is 5-20 μm.

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