CN110255549B - Preparation method of graphene and stripping method of two-dimensional nano material - Google Patents
Preparation method of graphene and stripping method of two-dimensional nano material Download PDFInfo
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Abstract
The application relates to a preparation method of graphene and a stripping method of a two-dimensional nano material, belonging to the technical field of nano materials. A method for preparing graphene, comprising: mixing the alkali solution dispersed with the graphite powder with soluble salt for reaction to obtain a mixed solution containing the grinding aid, wherein the grinding aid is in a supersaturated state in the mixed solution, so that part of the grinding aid is precipitated and dispersed in the mixed solution. And stirring the mixed solution in which the graphite powder and the solid particles precipitated by the grinding aid are dispersed to obtain the graphene dispersion liquid. And (4) washing and drying the graphene dispersion liquid. The grinding aid with small particle size prepared by the in-situ generation method can uniformly enter the graphite layers, efficiently peel the graphite layers apart, and can obtain graphene with small size and uniform layer structure. The preparation method is a one-step method, does not need additional intercalation, does not need stripping under an acidic condition, can avoid pollution and corrosion of acid to the environment and equipment, and is environment-friendly.
Description
Technical Field
The application relates to the technical field of nano materials, in particular to a preparation method of graphene and a stripping method of a two-dimensional nano material.
Background
The existing method for preparing graphene powder in a large scale has various characteristics and certain defects. A large amount of strong oxidant and strong concentrated acid are needed in the preparation process, so that the preparation method is not environment-friendly; the preparation energy consumption is high, and the preparation efficiency is low; the prepared graphene sheet layer is thick and has structural defects.
Disclosure of Invention
In view of the defects of the prior art, an object of the embodiments of the present application includes providing a method for preparing graphene and a method for peeling a two-dimensional nanomaterial, so as to solve the technical problem that a preparation process of small-sized graphene is complicated.
In a first aspect, an embodiment of the present application provides a method for preparing graphene, including: mixing the alkali solution dispersed with the graphite powder with soluble salt for reaction to obtain a mixed solution containing the grinding aid, wherein the grinding aid is in a supersaturated state in the mixed solution, so that part of the grinding aid is precipitated and dispersed in the mixed solution. And stirring the mixed solution in which the graphite powder and the solid particles precipitated by the grinding aid are dispersed to obtain the graphene dispersion liquid. And (4) washing and drying the graphene dispersion liquid.
Because of the close spacing between graphite layers, it is currently difficult to produce small particle size materials that can be sized to close the spacing between graphite layers for exfoliation of graphite. Even if small-particle substances are prepared by a complex process, the dispersibility of the small-particle substances cannot be guaranteed in the stripping process, and graphene with a uniform layer structure cannot be obtained.
The inventor of the application obtains a preparation method of graphene through research, and a grinding aid with small particle size is directly generated by reacting soluble salt with alkali on the surface of a graphite flake and in a flake layer by adopting an in-situ generation method. Because the grinding aid is in a supersaturated state in a mixed solution, namely the grinding aid is dissolved and precipitated in a dynamic equilibrium state, solid particles with the size close to the graphite interlamellar spacing of 0.334nm can be precipitated, and the dynamic equilibrium state can ensure that the solid particles are uniformly dispersed. Under the effect of stirring, solid particle can evenly enter into between the graphite layer, peels off the graphite flake layer high-efficiently, carries out the water washing drying again and can obtain the even graphite alkene of small-size, layer structure. The preparation method is a one-step method, does not need additional intercalation, can be stripped under the condition of no acid, can avoid the pollution and corrosion of acid to the environment and equipment, and is environment-friendly.
In some examples of this application, the grinding aid has a solubility of 2X 10 at 0 deg.C-9-0.2。
The grinding aid with dissolving property is easier to reach a supersaturated state in the preparation process, and is easier to repeatedly dissolve and separate out in a mixed solution.
In some embodiments of the present application, the soluble salt comprises a soluble inorganic salt. Optionally, the soluble inorganic salt comprises at least one of a calcium salt, a copper salt, and an iron salt. More optionally, the inorganic salt comprises at least one of calcium chloride, calcium acetate, copper chloride, copper sulfate, ferric chloride, and ferrous sulfate.
Calcium salt, copper salt and iron salt can react with alkali in an alkali solution to generate a grinding aid which is slightly soluble or not soluble in water, the grinding aid is small in size, and graphite can be stripped under the action of mechanical stirring.
In some embodiments of the present application, the grinding aid is at least one of calcium hydroxide, calcium carbonate, copper hydroxide, copper carbonate, iron hydroxide, and iron carbonate.
The grinding aid can reach a dynamic equilibrium state of dissolution and precipitation in a solution, and can enter into a graphite layer to gradually peel off the graphite layer under the drive of external high-speed energy.
In some examples of the present application, the mixed solution was sanded for 5 to 7 hours using a sand mill.
The sand mill is adopted for mechanical stirring as an implementation mode, has better mechanical action and meets the action force of stripping the graphite sheet layer.
In some embodiments of the present application, the step of stirring comprises mechanical stirring at 2000-.
Through the research of the inventor of the application, the mechanical stirring under the conditions can meet the requirement of external acting force for graphite sheet stripping.
In some embodiments of the present disclosure, the alkali in the alkali solution is 7% to 15% by mass, and optionally, the alkali is strong alkali.
The alkali is added to stir in an alkaline environment to cause micro-curling of the sheet layer, and reacts with soluble salts to generate grinding aid. In order to meet the graphite sheet curling requirement and obtain enough grinding aid, the mass percentage of the alkali is 7-15%.
In some embodiments of the present application, before mixing the alkali solution with the graphite powder dispersed therein with the soluble salt, the method further comprises: and (3) grinding and emulsifying the alkali solution dispersed with the graphite powder for 0.5-1.5 h.
In order to enable the graphite sheet layer to be slightly curled and the interlayer spacing of the edge of the sheet layer to be gradually increased, one implementation mode is to sand and emulsify the alkali solution dispersed with the graphite powder for 0.5 to 1.5 hours by a sand mill.
In some embodiments of the present application, the graphite powder has a particle size of no greater than 8000 mesh.
The grinding aid adopted by the application is small in size, and can be used for stripping small-size graphite powder, so that small-size graphene is obtained.
In a second aspect, the present application also provides a method for peeling off a two-dimensional nanomaterial, comprising: and mixing and reacting the aqueous alkali in which the two-dimensional material is dispersed with soluble salt to obtain a mixed solution containing the grinding aid, wherein the grinding aid is in a supersaturated state in the mixed solution, so that part of the grinding aid is precipitated and dispersed in the mixed solution. The mixed solution in which the two-dimensional material and the solid particles precipitated from the grinding aid were dispersed was stirred. The two-dimensional material comprises: graphite, BN, MoS2、WSe2、WTe2、MoO3、Fe3GeTe2。
The method adopts an in-situ generation method to enable soluble salt to react with alkali on the surface of the two-dimensional material and in the structure of the two-dimensional material to directly generate the grinding aid with small particle size. Because the grinding aid is in a supersaturated state, namely a dynamic equilibrium state of dissolution and precipitation in a mixed solution, the size of the precipitated solid particles is small, and the dynamic equilibrium state can ensure that the solid particles are uniformly dispersed. Under the action of stirring, solid particles can uniformly enter between the two-dimensional materials, and the two-dimensional materials are efficiently peeled.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.
Fig. 1 is a schematic diagram of a graphene peeling process provided in an embodiment of the present application;
fig. 2 is a scanning electron microscope image of graphene powder provided in example 1 of the present application;
fig. 3 is a scanning electron microscope image of graphene sheet diameter provided in example 1 of the present application;
fig. 4 is a scanning electron microscope image of graphene powder provided in example 3 of the present application;
fig. 5 is a scanning electron microscope image of graphene powder provided in example 5 of the present application;
fig. 6 is a scanning electron microscope image of graphene powder provided in example 6 of the present application;
fig. 7 is an XPS carbon peak spectrum of graphene provided in example 1 of the present application;
fig. 8 is a raman spectrum of graphene provided in example 1 of the present application;
fig. 9 is a scanning electron microscope image of boron nitride nanosheet powder provided in example 9 of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
Graphene has gained significant practical application in a variety of fields due to its unique structure and excellent properties. The method for preparing graphene powder in a large scale at present comprises the following steps: many methods, such as redox method, liquid phase stripping method, jet milling method, intercalation dissociation method, etc., all of which have certain disadvantages.
In the redox method preparation process, a large amount of strong oxidant and strong concentrated acid are inevitably needed, the method is extremely unfriendly to the environment, the graphene lamellar structure is greatly damaged due to the strong oxidation effect of the prepared graphene, and the electrical conductivity and the heat conductivity are rapidly reduced.
The mechanism of the liquid phase stripping method is mainly that a graphite sheet layer is opened by utilizing high-speed shearing liquid to prepare the thin graphene.
The jet milling is mainly to add the expanded graphite into a jet mill and strip the expanded graphite by using the force of air flow, and the method can obtain a large amount of graphene nanosheet powder, but the raw material generally adopts the expanded graphite which is stripped to be thinner, and under the action of strong air flow, although the graphene lamellar layer can be stripped, the graphene lamellar layer is inevitably re-stacked, so that the graphene lamellar layer prepared by the method is usually thicker.
The intercalation dissociation method is generally to open a graphite sheet layer through weak oxidation at the edge, then insert a small molecular intercalator into the graphite sheet layer by means of strong acidity or high temperature and high pressure and the like to form a new graphene intercalation compound, and then strip the graphite sheet layer by means of physicochemical characteristics of small molecules to finally obtain the graphene nanosheet with relatively thin layer number, but the chemical intercalation is a dynamic process, the method is almost difficult to strip graphene with extremely small size, and the method needs oxidation to be used for intercalation, and the intercalator is generally strong acid or metal halide and is not environment-friendly; and a graphene intercalation compound is formed after intercalation, and intercalation and cleavage usually need to be carried out step by step under different chemical conditions, so that the process is complex.
There are also currently some manufacturing methods that are combinations of these methods. There is a research that graphite is put into an oxidizing strong acid solution for acidification treatment, so that a certain amount of acid is inserted between graphite sheets, and then the graphite sheets intercalated with the acid are put into an alkaline aqueous solution or an organic solution for intense ultrasound. Although the method can obtain the thin-layer graphene, nitric acid and potassium permanganate are needed for intercalation in the early stage of the preparation process, the influence of strong oxidizing property and volatility on the environment is large, and the preparation process is not environment-friendly. Later exfoliation requires high power sonication, the ultrasonic energy is limited and the uniformity of the product produced can be affected. And the preparation also needs to be carried out step by step, the intercalation and the later stripping need to be carried out step by step, and the preparation efficiency is relatively low.
Further studies have disclosed ultrasonic exfoliation in aqueous alkali solutions after intercalation using acid treatment. The preparation process is complex, and the intercalation of concentrated acid also brings a series of environmental problems. By the preparation methods, the small-size thin-layer non-oxidized graphene nanosheet is difficult to obtain.
In the research process, the inventor of the application finds that the graphite layers are relatively close to each other, so that the material with small particle size is difficult to prepare at present, and the size of the material can be close to the graphite layer spacing so as to strip the graphite. Even if small-particle substances are prepared by a complex process, the small-particle substances are easy to aggregate in the stripping process, the dispersibility of the small-particle substances cannot be guaranteed, and graphene with a uniform layer structure cannot be obtained.
The inventor of the present application proposes a simple method for preparing graphene, which is particularly suitable for preparing small-layer thin-layer graphene.
The following describes a method for preparing graphene and a method for peeling a two-dimensional nanomaterial in an embodiment of the present application.
Referring to fig. 1, an embodiment of the present application provides a method for preparing graphene, including:
and fully mixing a certain amount of graphite powder with water to ensure that no solid dry powder of graphite powder exists in the water. Optionally, the mixed solution is added to a high speed dispersant to continue the dispersion. In the present application, the dispersant may be a high speed shear, an emulsifying machine, a colloid mill, or a sand mill.
In some embodiments of the present application, in order to obtain small-sized graphene, the particle size of the graphite powder is not greater than 8000 mesh. Optionally, the particle size of the graphite powder is 9000 meshes or 10000 meshes.
And adding a certain amount of alkali into the mixed solution to ensure that the mass concentration (mass percentage content) of the alkali in the alkali solution dispersed with the graphite powder is 7-15%. In some embodiments of the present application, the base is a strong base, such as sodium hydroxide, potassium hydroxide. In other embodiments herein, the base comprises sodium carbonate, potassium carbonate. Stirring sufficiently to disperse the mixed alkali solution, so that graphite in the alkaline environment has sheet layer micro-curling and the distance between the edge layers of the sheet layers is gradually increased. The structure is beneficial to the grinding aid to enter a graphite sheet layer, and then the graphite is stripped. Wherein, the stirring and mixing can be carried out by adopting a high-speed shearing machine, an emulsifying machine, a colloid mill or a sand mill. In a possible embodiment, a certain amount of alkali solution is added to the mixed solution to make the alkali dispersed more uniformly, i.e. the alkali is dissolved in the aqueous solution first and then added to the aqueous graphite solution. Optionally, the alkali is 8%, 10%, 12% or 13% by mass.
And (2) performing sand grinding and emulsification on the aqueous alkali dispersed with the graphite powder for 0.5-1.5h, fully mixing the aqueous alkali with the graphite powder and infiltrating the graphite powder by the step, so that the graphite sheet layer is slowly curled, and meanwhile, hydroxide ions are tightly attached to the graphite sheet layer and enter the graphite sheet layer along with the solution. Facilitating subsequent in situ generation of grinding aid. Optionally, the sanding emulsification time can be 0.8h, 1h and 1.2 h.
Adding soluble salt into the fully mixed graphite alkali solution, and reacting the soluble salt with alkali to directly generate hydroxide, namely the grinding aid. As hydroxyl ions are distributed on the graphite sheet layer, the hydroxyl ions react with soluble salt to directly generate the grinding aid in the graphite sheet layer structure. In the embodiment of the application, the grinding aid is in a supersaturated state in the mixed solution. The grinding aid is in a dynamic equilibrium state of dissolution and precipitation in the mixed solution, so that the grinding aid is repeatedly dissolved and precipitated in the mixed solution to form small crystals with a single molecular size, and the size of the small crystals is close to that of graphite interlamellar spacing of 0.334 nm. Under the drive of external high-speed energy, the small crystals can enter into the graphite layers, the graphite layers are gradually peeled off, the peeling efficiency is very high, and the grinding aid is in a dynamic balance state, so that the solid particles can be uniformly dispersed, and the prepared graphene is uniform in thickness and small in size. Small crystals which are slightly soluble in water can be removed by adding water in a sufficient amount during the cleaning process.
In some examples of this application, the grinding aid has a solubility of 2X 10 at 0 deg.C-9-0.2. Grinding aids of this nature are slightly or poorly soluble in water and are more readily available in mixed solutionsRepeatedly dissolving and separating out. Meanwhile, the hardness of the grinding aid is lower than 4, so that the grinding aid is prevented from wearing a graphite cavity.
In some embodiments of the present disclosure, the soluble salt comprises a soluble inorganic salt, and optionally, the soluble inorganic salt comprises at least one of a calcium salt, a copper salt, and an iron salt. Further, the soluble inorganic salt includes at least one of calcium chloride, calcium acetate, copper chloride, copper sulfate, ferric chloride, and ferrous sulfate. The grinding aid comprises calcium hydroxide and/or calcium carbonate when the soluble salt comprises a calcium salt, copper hydroxide and/or copper carbonate when the soluble salt comprises a copper salt, and iron hydroxide and/or iron carbonate when the soluble salt comprises an iron salt. Wherein the solubility of calcium hydroxide is 0.189 and the solubility of copper hydroxide is 1.722 × 10 at 0 deg.C-6The solubility of copper carbonate is 1.462X 10-4The solubility of ferric hydroxide is 2.097X 10-9Solubility of calcium carbonate is 4X 10-3。
And stirring the mixed solution containing the graphite and the grinding aid. The stirring in the embodiment of the application is high-energy-density stirring, so that the grinding aid peels away graphite flakes to form a thin graphene aqueous dispersion. In some embodiments of the present application, the mechanical agitation is by high speed shearing, emulsifying, colloid or sand milling. In a possible embodiment, the stirring conditions are mechanical stirring at 2000-. Optionally, the stirring speed is 5000r/min, 8000r/min, 10000r/min, 120000r/min and 150000r/min, and the stirring time is 5.5h, 6h and 6.5 h.
And washing the obtained graphene aqueous dispersion with water. In some examples of the present application, the aqueous graphene dispersion was washed with water and a weak acid to remove grinding aids and alkali. And then repeatedly washing the graphene dispersion system with water to a deionized state, and removing most of water in the graphene dispersion system in a centrifugal mode to obtain the graphene aqueous slurry with a certain concentration.
And drying the graphene water-based slurry to obtain the graphene nano powder.
The preparation method of the graphene provided by the application is a one-step method, does not need additional intercalation, can be stripped under the condition of no acid addition, can avoid pollution and corrosion of acid to environment and equipment, and is environment-friendly.
The graphene prepared by the preparation method of the graphene is thin in thickness, uniform in size, high in edge defect and almost free of oxygen-containing functional groups in the graphene, the structure is kept complete, and the electrical and thermal properties are basically not damaged. Because the graphene has very high edge defects, can be modified and grafted by functional groups, has good hydrophilicity, can form a stable graphene water dispersion system under the condition of no additive in water, and the concentration of the dispersion system can stably exist from 1ppm to 10 percent.
In some embodiments of the present application, the particle size of the graphite powder is small, and graphene with a size not greater than 2 microns can be obtained.
The application also provides a stripping method of the two-dimensional nano material, which comprises the following steps:
and fully mixing a certain amount of two-dimensional nano material with water to ensure that the two-dimensional nano material in a solid dry powder state does not exist in the water. Optionally, the mixed solution is added to a high speed dispersant to continue the dispersion. In the present application, the dispersant may be a high speed shear, an emulsifying machine, a colloid mill, or a sand mill. Two-dimensional materials in this application include graphite, BN, MoS2、WSe2、WTe2、MoO3And Fe3GeTe2At least one of (1). In some embodiments of the present application, the two-dimensional material is selected from one of the materials.
And adding a certain amount of alkali into the mixed solution to ensure that the mass concentration (mass percentage content) of the alkali in the alkali solution dispersed with the two-dimensional nano material is 7-15%. In some embodiments of the present application, the base is a strong base, such as sodium hydroxide, potassium hydroxide. In other embodiments herein, the base comprises sodium carbonate, potassium carbonate.
And (2) sanding and emulsifying the aqueous alkali dispersed with the two-dimensional nano material for 0.5-1.5h, so that the aqueous alkali is fully mixed with the two-dimensional nano material and infiltrates the two-dimensional nano material, the two-dimensional nano material is slowly curled, and meanwhile, hydroxide ions are tightly attached to the two-dimensional nano material and enter the two-dimensional nano material along with the solution. Facilitating subsequent in situ generation of grinding aid.
And adding soluble salt into the fully mixed alkali solution, and reacting the soluble salt with the alkali to directly generate hydroxide, namely the grinding aid. As hydroxyl ions are distributed on the two-dimensional nano material, the two-dimensional nano material reacts with soluble salt to directly generate the grinding aid on the surface or in the structure of the two-dimensional nano material. In the embodiment of the application, the grinding aid is in a supersaturated state in the mixed solution. The grinding aid is in a dynamic equilibrium state of dissolution and precipitation in the mixed solution, so that the grinding aid is repeatedly dissolved and precipitated in the mixed solution to form small crystals with single molecular size, the small crystals can enter the middle of the two-dimensional nanomaterial structure under the drive of external high-speed energy to gradually strip the two-dimensional nanomaterial, the stripping efficiency is high, and the grinding aid is in the dynamic equilibrium state, so that the solid particles can be uniformly dispersed,
and stirring the mixed solution containing the two-dimensional nano material and the grinding aid. The stirring in the embodiment of the application is high-energy-density stirring, so that the grinding aid peels off the two-dimensional nano material. In some embodiments of the present application, the mechanical agitation is by high speed shearing, emulsifying, colloid or sand milling.
The features and properties of the present application are described in further detail below with reference to examples.
Example 1
The embodiment provides a preparation method of graphene, which includes:
adding 5 parts of graphite powder into 95 parts of water in parts by weight, fully stirring and uniformly mixing until no dry powder is formed, and adding into a sand mill for sand milling and emulsification. Wherein the particle size of the graphite powder is 8000 meshes.
7.5 parts of sodium hydroxide solid is weighed, dissolved by a small amount of water, slowly added into a sand mill, and is subjected to sand milling and emulsification together with graphite for about 1 hour.
Adding 7.5 parts of calcium chloride into a small amount of water, fully dissolving, slowly adding into a sand mill for multiple times, wherein calcium hydroxide slightly soluble in water is generated in the sand mill, dissolving and separating out in the high-speed sand mill are a dynamic balance process by utilizing the characteristic that the calcium hydroxide is slightly soluble in water, and stripping is finished after sanding for 5 hours.
Taking out the graphene slurry, adding a slight excess of dilute hydrochloric acid solution, neutralizing to remove calcium hydroxide, repeatedly washing with water to a deionized state, centrifuging at 2000r/min for 2 minutes to remove excessive water in the slurry, and drying to obtain graphene nanosheet powder.
The graphene nanosheets are very uniform in size and are smaller than 2 microns in size.
Example 2
The present embodiment provides a method for preparing graphene, which is different from embodiment 1 in that:
the graphite powder is 12000 meshes, and the obtained graphene nanosheets are very uniform in size and smaller than 1 micron in size.
Example 3
The present embodiment provides a method for preparing graphene, which is different from embodiment 1 in that:
7.5 parts of calcium chloride is changed into 10 parts of calcium acetate, the sanding stripping time is prolonged from 5 hours to 7 hours, and acid adopted in the graphene slurry cleaning process is dilute acetic acid solution.
Example 4
The present embodiment provides a method for preparing graphene, which is different from embodiment 1 in that:
7.5 parts of sodium hydroxide is changed into 7.5 parts of sodium carbonate, and the sodium carbonate is added into dilute hydrochloric acid to be quickly stirred and discharged to generate carbon dioxide gas in the cleaning process.
Example 5
The present embodiment provides a method for preparing graphene, which is different from embodiment 1 in that:
the high-speed dispersion equipment is changed into a high-speed shearing machine.
Example 6
The embodiment provides a preparation method of graphene, which includes:
adding 1 part of graphite powder into 99 parts of water by weight, fully stirring and uniformly mixing until no dry powder is formed, adding the mixture into a sand mill for sand milling emulsification, weighing 15 parts of sodium hydroxide solid, dissolving the sodium hydroxide solid with a small amount of water, slowly adding the sodium hydroxide solid into the sand mill, carrying out sand milling emulsification together with graphite for about 1 hour, adding 15 parts of calcium chloride into a small amount of water, fully dissolving, slowly adding the calcium chloride into the sand mill for multiple times, generating calcium hydroxide slightly soluble in water in the sand mill, utilizing the characteristic that the calcium hydroxide is slightly soluble in water, carrying out a dynamic balance process of dissolution and precipitation in a high-speed sand mill, after 5 hours of sand milling, finishing stripping, taking out graphene slurry, adding a slight excess dilute hydrochloric acid solution, neutralizing and reacting to remove the calcium hydroxide, repeatedly cleaning the slurry with water to a deionized state, centrifuging the slurry for 2 minutes at 2000r/min, removing excess water in the slurry, and then drying to obtain the thin-layer graphene nanosheet powder.
Example 7
The present embodiment provides a method for preparing graphene, which is different from embodiment 1 in that:
7.5 parts of calcium chloride is changed into 5 parts of copper sulfate, and the washing process is carried out by adopting dilute sulfuric acid.
Example 8
The present embodiment provides a method for preparing graphene, which is different from embodiment 1 in that:
7.5 parts of calcium chloride is changed into 5 parts of ferrous chloride, and the sanding time is prolonged to 10 hours.
Example 9
The embodiment provides a preparation method of two-dimensional nano boron nitride, which comprises the following steps:
adding 5 parts by weight of boron nitride powder into 90 parts by weight of water and 5 parts by weight of ethanol mixed solution, fully stirring and uniformly mixing until no dry powder state exists, and adding into a sand mill for sand milling and emulsification.
Weighing 10 parts of sodium hydroxide solid, dissolving with a small amount of water, slowly adding into a sand mill, and carrying out sand milling emulsification together with graphite for about 1 hour.
Adding 7.5 parts of calcium chloride into a small amount of water, fully dissolving, slowly adding into a sand mill for multiple times, wherein calcium hydroxide slightly soluble in water is generated in the sand mill, dissolving and separating out in the high-speed sand mill are a dynamic balance process by utilizing the characteristic that the calcium hydroxide is slightly soluble in water, and stripping is finished after sanding for 5 hours.
And taking out the boron nitride slurry, adding a slight excess of dilute hydrochloric acid solution, neutralizing to remove calcium hydroxide, repeatedly washing with water to a deionized state, centrifuging at 2000r/min for 2 minutes to remove excessive water in the slurry, and drying to obtain the boron nitride nanosheet powder.
Test examples
Microstructure detection of the graphene powder and graphene sheet prepared in example 1 was performed by a scanning electron microscope, and the results are shown in fig. 2 and 3. Fig. 2 is a scanning electron microscope image of graphene powder, and it can be seen from the image that the graphene powder obtained by the preparation method provided in example 1 has a uniform size. Fig. 3 is a scanning electron microscope image of graphene sheet diameter, and it can be seen that the size of the graphene is less than 2 microns. The preparation method provided by the application can be used for preparing small-size graphene.
The graphene powder obtained in example 1 was examined by an X-ray spectrometer, and the results are shown in fig. 7. The graphene powder prepared in example 1 was detected by a raman spectrometer, and the result is shown in fig. 8. As can be seen from fig. 7, the oxygen peak is very low, and the carbon peak structure is complete, indicating that graphene contains almost no carbon-oxygen, carbon-dioxy, and carbon-epoxy bonds. As can be seen from fig. 8, the defect peak of the prepared graphene is high, and the XPS confirms that the oxygen-containing functional group is low, so that the high defect peak is mostly derived from the defect with high edge. The graphene structure prepared by the method provided by the application is kept relatively complete, and the electrical and thermal properties are basically not damaged.
The microstructure of the graphene powder prepared in example 3 was examined by a scanning electron microscope, and the results are shown in fig. 4, which shows that the graphene has a thin lamellar structure, a curled shape, a complete structure, and high edge defects.
The microstructure of the graphene powder prepared in example 5 was examined by a scanning electron microscope, and the results are shown in fig. 5, which shows that the graphene powder prepared by mechanical stirring with a high-speed shearing machine has a small particle size and a thin lamellar structure.
The microstructure of the graphene prepared in example 6 was examined by a scanning electron microscope, and the result is shown in fig. 6, which shows that the graphene has a thin lamellar structure.
The microstructure of the boron nitride obtained in example 9 was examined by a scanning electron microscope, and the result is shown in fig. 9, which shows that the boron nitride has a thin lamellar structure.
The embodiments described above are some, but not all embodiments of the present application. The detailed description of the embodiments of the present application is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Claims (12)
1. A method for preparing graphene, comprising:
mixing and reacting an alkali solution dispersed with graphite powder with a soluble salt to obtain a mixed solution containing a grinding aid, wherein the grinding aid is in a supersaturated state in the mixed solution, so that part of the grinding aid is precipitated and dispersed in the mixed solution;
stirring the mixed solution in which the graphite powder and the solid particles precipitated by the grinding aid are dispersed to obtain graphene dispersion liquid;
washing and drying the graphene dispersion liquid;
the grinding aid is at least one of calcium hydroxide, calcium carbonate, copper hydroxide, copper carbonate, ferric hydroxide and ferric carbonate.
2. The method for preparing graphene according to claim 1, wherein the grinding aid has a solubility of 2 x 10 in water at 0 ℃-9-0.2。
3. The method according to claim 1, wherein the soluble salt comprises a soluble inorganic salt.
4. The method according to claim 3, wherein the soluble inorganic salt includes at least one of a calcium salt, a copper salt, and an iron salt.
5. The method according to claim 4, wherein the soluble inorganic salt includes at least one of calcium chloride, calcium acetate, copper chloride, copper sulfate, ferric chloride, and ferrous sulfate.
6. The method for preparing graphene according to claim 1, wherein the mixed solution is sanded for 5 to 7 hours by using a sand mill.
7. The method for preparing graphene according to claim 1, wherein the stirring step comprises mechanical stirring at 2000-20000r/min for 5-7 h.
8. The method for preparing graphene according to claim 1, wherein before the mixing of the alkali solution in which the graphite powder is dispersed with the soluble salt, the method further comprises: and (3) sanding and emulsifying the alkali solution dispersed with the graphite powder for 0.5-1.5 h.
9. The preparation method of graphene according to claim 1 or 8, wherein the alkali in the alkali solution is 7-15% by mass.
10. The method for producing graphene according to claim 9, wherein the base is a strong base.
11. The method according to claim 1, wherein the particle size of the graphite powder is not more than 8000 mesh.
12. A method for peeling off two-dimensional nano-materials is characterized by comprising the following steps: mixing and reacting an alkali solution dispersed with a two-dimensional material with a soluble salt to obtain a mixed solution containing a grinding aid, wherein the grinding aid is in a supersaturated state in the mixed solution, so that part of the grinding aid is precipitated and dispersed in the mixed solution;
stirring the mixed solution in which the two-dimensional material and the solid particles precipitated from the grinding aid are dispersed;
the two-dimensional material comprises graphite, BN and MoS2、WSe2、WTe2、MoO3And Fe3GeTe2At least one of;
the grinding aid is at least one of calcium hydroxide, calcium carbonate, copper hydroxide, copper carbonate, ferric hydroxide and ferric carbonate.
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