A grinding device and graphene and a method for preparing the same

Abstract

The application discloses a kind of grinding device and graphene and its preparation method.The grinding device includes: cauldron, grinding component in the cauldron interior, fan, and upper rotating component and lower rotating component, wherein the upper rotating component is used to drive the grinding component to rotate;The lower rotating component is used to drive the fan to rotate;The fan is brought into the grinding component interior by rotation;The grinding component grinds raw materials by rotation.The grinding device of the application is simple in structure, easy to use, high in grinding efficiency, and the grinding disc runs at low speed, thereby greatly reducing the wear of the grinding disc;The preparation method of the application is green and environmentally friendly, no post-treatment, and low in cost, suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention relates to a grinding apparatus and graphene, and a method for preparing the same. Background Technology

[0002] Graphene is a carbon material with a thickness of only 0.335 nm. It possesses extremely high strength, excellent electrical conductivity, is a semiconductor with zero bandgap, exhibits good thermal conductivity, and unique properties such as the room-temperature quantum Hall effect and room-temperature ferromagnetism. Researchers generally predict that graphene has significant application prospects in electronics, information, energy, materials, and biomedicine. How to prepare high-quality graphene at low cost has always been a hot research topic in this field.

[0003] Currently, the main methods for preparing graphene include redox methods, liquid-phase exfoliation, and chemical vapor deposition. Redox methods use graphite as a raw material, oxidizing it with strong oxidants such as concentrated sulfuric acid or potassium permanganate to obtain graphene oxide, which is then reduced back to graphene through high temperatures or chemical methods. This method is the most common and widely used in industrial production. However, graphene obtained after oxidation with strong oxidants has many defects, and even after reduction, its physical and chemical properties are still somewhat compromised. Furthermore, the preparation process uses large amounts of strong oxidants and acids, causing serious environmental pollution. Liquid-phase exfoliation mainly uses ultrasonic exfoliation, i.e., prolonged ultrasonication in an organic solvent. This method produces graphene with fewer defects, but the use of organic solvents is harmful to human health, and it suffers from low yield and small graphene size. Chemical vapor deposition (CVD) uses carbon-containing compounds such as methane as raw materials, growing graphene through high-temperature decomposition on the surface of a substrate such as a metal. This is currently the main method for preparing graphene films. However, the immaturity and high cost of the CVD process limit its large-scale application. Therefore, the preparation of graphene remains a key focus in the field of graphene research.

[0004] Disc mixers first appeared in the mid-20th century. In July 1948, Elmer S. Scott disclosed a "Disk Grinder and Mixer," which uses a conveying screw to push material between two grinding discs, where the material is mixed under the relative motion of the two discs. This equipment is suitable for grinding low-viscosity fluids or solid particles. In 1995, Xu Xi et al. developed a disc-shaped mechanochemical reactor, which can grind materials through the shearing and extrusion action of the grinding discs. CN105800594B discloses a graphene material based on this solid-phase mechanochemical reactor and its preparation method. It utilizes the three-dimensional strong shear structure of the solid-phase mechanochemical reactor to introduce a grinding aid during the grinding of graphite. The three-dimensional shear force induced by the three-dimensional shear structure causes the grinding aid and graphite to generate strong mutual friction, exfoliating the graphite and thus preparing single-layer or few-layer graphene. Furthermore, CN106044761B discloses a high-shear-force wear-resistant rubber grinding disc for preparing graphene, its preparation method, and its application. This method utilizes the high frictional force of the upper and lower surfaces of the wear-resistant rubber disc, resulting in high graphene peeling efficiency and thin graphene thickness. The upper and lower surfaces of the wear-resistant rubber disc primarily exert pure shear force with low impact force, effectively avoiding damage to the graphite lattice, reducing structural defects in the graphene, and producing high-quality graphene. However, this equipment cannot be self-circulated and is not a closed system, making it unsuitable for applications involving volatile substances or requiring specific temperatures and pressures. CN109382167A discloses a self-circulating grinding disc device for high-pressure environments, and CN110817853A discloses a method for preparing edge-carboxylated graphene based on this grinding disc device; however, the efficiency of this grinding disc is too low. CN202011091971.3 improves the graphene yield by modifying the grinding disc structure, but due to the high-speed operation of the grinding disc, severe wear occurs, which is detrimental to production use. Summary of the Invention

[0005] To address the aforementioned problems in existing technologies, this invention provides a novel grinding apparatus and a method for preparing graphene using this apparatus. The grinding apparatus of this invention is a graphene grinding apparatus with forced circulation within a reactor, specifically a novel graphene grinding apparatus and graphene preparation method that can be used under supercritical carbon dioxide conditions. Because supercritical carbon dioxide possesses gas-like diffusivity and liquid-like solubility, while also exhibiting low viscosity and low surface tension, it can rapidly penetrate into graphite, thereby reducing the π-π interactions between graphite flakes. Through the shearing action of the grinding disc (grinding component), graphite is exfoliated into graphene. Simultaneously, the shearing action of the grinding disc also breaks down the graphite or graphene, and the newly generated highly active edges react with carbon dioxide, resulting in the modification of carboxyl groups at the edges of the graphene. The grinding apparatus of this application has a simple structure, is easy to use, has high grinding efficiency, and operates at low speed, thus greatly reducing grinding disc wear. The preparation method of this invention is green and environmentally friendly, requires no post-processing, and is low-cost, making it suitable for large-scale industrial production.

[0006] The first aspect of the present invention provides a grinding apparatus, comprising: a vessel, a grinding component inside the vessel, a fan 10, an upper rotating component, and a lower rotating component, wherein the upper rotating component is used to drive the grinding component to rotate; the lower rotating component is used to drive the fan to rotate; the fan brings raw materials into the grinding component by rotating; and the grinding component grinds the raw materials by rotating.

[0007] According to some embodiments of the device of the present invention, preferably, the vessel is a sealable vessel, including a vessel lid 1 and a vessel body 2.

[0008] According to some embodiments of the device of the present invention, preferably, the upper rotating component includes a power input shaft 3, a grinding disc drive shaft 4, a drive disk 6, and a drive pin 7, wherein the power input shaft 3 transmits rotational power to the grinding disc drive shaft 4; the grinding disc drive shaft 4 is connected to the drive disk 6; and the drive pin 7 is used to drive the grinding component.

[0009] According to some embodiments of the device described in this invention, preferably, the rotating component further includes a locking nut 5, and the grinding disc drive shaft 4 and the drive disc 6 are connected via the locking nut 5. A schematic diagram of the drive disc is shown, for example but not limited to... Figure 6 As shown.

[0010] According to some embodiments of the device of the present invention, preferably, a spring is provided on the drive pin 7, the spring being used to adjust the contact force of the grinding components. That is, the spring is used to adjust the contact force between the moving plate 8 and the fixed plate 9.

[0011] According to some embodiments of the device described in this invention, preferably, the power input shaft 3 transmits rotational power from the vessel cover 1 of the vessel to the grinding disc drive shaft 4 via a coupling.

[0012] According to some embodiments of the apparatus of the present invention, preferably, the grinding component includes a moving disc 8 and a fixed disc 9. Moving disc structure - front view, for example but not limited to... Figure 7 As shown.

[0013] According to some embodiments of the device of the present invention, preferably, a feed inlet is provided on the upper surface of the moving disk 8, and the raw material enters between the moving disk 8 and the fixed disk 9 from the feed inlet of the grinding disk.

[0014] According to some embodiments of the device of the present invention, preferably, the grinding surface of the moving disk 8 has an eccentric parallel straight groove structure, more preferably 4-8 sets of eccentric parallel straight groove structures. A schematic diagram of the grinding surface of the moving disk 8 is provided, for example but not limited to... Figure 2 As shown.

[0015] According to some embodiments of the device described in this invention, preferably, the grinding surface of the fixed disk 9 has an eccentric parallel straight groove structure, more preferably 4-8 sets of eccentric parallel straight groove structures. A schematic diagram of the fixed disk structure is provided, for example but not limited to... Figure 4 As shown.

[0016] According to some embodiments of the device of the present invention, preferably, the lower surface of the moving disk 8 is provided with a material settling groove for diverting the raw material and allowing the raw material to enter the interior of the grinding component.

[0017] According to some embodiments of the device described in this invention, preferably, the depth of the material settling trench is no greater than 1 mm.

[0018] According to some embodiments of the device of the present invention, preferably, the cross-section of the material settling channel is a sloping shape; more preferably, the cross-section of the material settling channel is a 10°-30° sloping shape, with the included angle between the two sides of the cross-section being 90°. Preferably, the bottom has been rounded. A schematic diagram of the cross-section of the material settling channel is provided, for example, but not limited to... Figure 3 As shown.

[0019] According to some embodiments of the device described in this invention, preferably, the grinding device further includes a grinding disc fixing bracket 12 for connecting the grinding component to the lid 1 of the vessel.

[0020] According to some embodiments of the device described in this invention, preferably, the grinding component further includes an airflow guide pipe 13 and the grinding disc drive shaft 4 has a hollow hole structure, through which carbon dioxide airflow returns to the lower half of the reactor via the airflow guide pipe 13 from the hollow hole of the grinding disc drive shaft 4.

[0021] According to some embodiments of the device described in this invention, preferably, the grinding device further includes a baffle 11, wherein the baffle 11 is used in conjunction with the rotation of the fan 10 to return the raw material that has settled to the lower half of the pot to the upper half of the pot so that it can enter the interior of the grinding component.

[0022] According to some embodiments of the device of the present invention, preferably, the angle between the baffle and the bottom surface is 40°-60°.

[0023] The grinding apparatus according to the present invention includes, for example but not limited to, the following: Figure 1 As shown. The grinding device of the present invention adopts a dual transmission system. The transmission system above the vessel drives the moving disc to rotate slowly, while the transmission system below the vessel drives the fan to rotate rapidly. The raw material enters from the top of the grinding discs between the two grinding discs by the high-speed rotation of the fan, and is then ground to finally produce high-quality graphene. The grinding device includes a sealed high-pressure vessel, grinding components and a fan arranged inside the vessel, and upper and lower rotating components for driving the grinding components and the fan to rotate respectively. The grinding components include a moving disc 8 and a fixed disc 9 with a feed inlet. The grinding device also includes a grinding disc fixing bracket, an airflow guide pipe, and a baffle.

[0024] In this invention, the grinding force of the grinding mixer is achieved through the relative motion of a pair of grinding discs (moving disc 8 and fixed disc 9, also referred to as grinding components). For example... Figure 2 The provided moving disc pattern employs a six-set eccentric parallel straight groove structure, providing sufficient grinding and conveying capacity while facilitating manufacturing. Material settling grooves are also incorporated into the grinding disc. When raw material enters the lower surface of the moving disc (the surfaces where the moving and fixed discs rub against each other are grooved), it is diverted in these grooves, allowing for more efficient entry into the grinding components (between the two grinding discs). For graphite grinding, the groove depth must be controlled to within 1mm. Furthermore, the groove cross-section features a 20° slope, with a 90° included angle on both sides to prevent material accumulation at the groove root, and a rounded bottom. The specific groove cross-section is shown below. Figure 3 As shown. The structure of the fixed plate is similar to that of the moving plate. The pattern shape of the moving plate is as follows. Figure 4 As shown. Figure 5 Figures (1), (2), (3), and (4) illustrate the relative motion of the raw material within the groove cross-section during the mutual grinding of the moving and fixed discs. The figure depicts the process of a groove from complete overlap to final separation. Under the action of friction on the groove surface, the raw material undergoes interlayer shearing and is also sheared by the two screw grooves.

[0025] In this invention, the raw materials are forcibly circulated within the vessel. The overall structure of the grinding device is as follows: Figure 1As shown in the diagram. The vessel lid 1 and vessel body 2 form a closed reaction vessel space. The power input shaft 3 transmits rotational power from the vessel lid 1 to the grinding disc drive shaft 4 via a coupling. The drive disc 6 is mounted to the grinding disc drive shaft 4 via a locking nut 5. The structure of the drive disc 6 is as follows... Figure 6 As shown, for example, but not limited to, it has three holes for driving the drive pin 7 mounted on the moving disc 8. The diameter of the holes is slightly larger than the diameter of the drive pin 7, which can effectively ensure that the grinding surface of the moving disc 8 and the grinding surface of the fixed disc 9 are in close contact. If necessary, a spring can be installed on the drive pin to adjust the contact force between the moving disc and the fixed disc, thereby adjusting the grinding force. An independently driven fan 10 is installed at the bottom of the vessel. When the fan 10 rotates, it cooperates with the baffle 11 to allow the raw material that has settled into the lower half of the vessel to return to the upper half of the vessel. The entire grinding component is installed with the vessel cover 1 through the grinding disc fixing bracket 12. During installation, the verticality and coaxiality of each system must be ensured. Furthermore, when the fan 10 rotates, the air force drags the raw material upward into the upper half of the vessel. The airflow will return to the lower half of the vessel through the hollow hole of the grinding disc drive shaft 4 and the airflow guide pipe 13. Since the raw material has a relatively large specific gravity, it will settle in the upper half of the vessel and fall onto the moving disc 8 (see details of the structure). Figure 7 The raw material enters the grinding area through the settling grooves on the driven disc 8. During the design of the grinding components, to achieve effective raw material circulation in a supercritical carbon dioxide environment, the rotational speed of the bottom-mounted fan 10 needs to be adjusted according to the specific gravity and particle size range of the raw material. Insufficient rotational speed results in particle settling; excessive rotational speed causes the raw material to either return to the bottom of the vessel via the guide pipe after reaching the upper part of the vessel through the backflow baffle, or fail to settle effectively in the grinding disc area. Simultaneously, for applications requiring high fan speeds, the sealing of the fan drive shaft in high-pressure vessel conditions must be further considered. Higher rotational speeds increase the difficulty of the drive structure. Therefore, precise computer simulation is needed to determine the fan speed. Figure 8 This is a schematic diagram of the raw material flow state (the suspended flow state of the material inside the vessel) under fluid-structure interaction calculation conditions. Taking a 0.5mm particle size raw material as an example, based on 2500 kg / m³... 3 The required optimal rotational speed is 1200 r / min for the given density.

[0026] A second aspect of the present invention provides a method for preparing graphene using the above-described apparatus, comprising: adding raw materials and supercritical carbon dioxide into a reactor; driving a fan to rotate via a lower rotating component to bring the raw materials into a grinding component; driving the grinding component to rotate via an upper rotating component; and grinding the raw materials inside the grinding component.

[0027] According to some embodiments of the method described in this invention, preferably, the method further includes: reducing the pressure to atmospheric pressure within 5-20 seconds after grinding.

[0028] According to some preferred embodiments of the method described according to the present invention, the method includes:

[0029] Step 1: Add the raw materials to the pot;

[0030] Step 2: Introduce carbon dioxide into the reactor, control the temperature and pressure, and keep the carbon dioxide in a supercritical state to form a mixture of graphite powder and supercritical carbon dioxide. Grind the mixture in the reactor.

[0031] Step 3: After grinding, the pressure inside the reactor is quickly reduced to atmospheric pressure to obtain the graphene product.

[0032] According to some embodiments of the method described in this invention, preferably, the raw material is flake graphite powder and / or expanded graphite powder.

[0033] According to some embodiments of the method described in this invention, preferably, the particle size of the raw material is 10-325 mesh, more preferably 32-100 mesh.

[0034] According to some embodiments of the method described in this invention, preferably, the temperature of the supercritical carbon dioxide is greater than 31.26°C and the pressure is greater than 7.29 MPa.

[0035] According to some embodiments of the method described in this invention, preferably, the weight ratio of raw materials to carbon dioxide is 1:5-1:40, more preferably 1:5-1:25.

[0036] According to some embodiments of the method described in this invention, preferably, the rotational speed of the moving disc inside the vessel is 100-300 r / min.

[0037] According to some embodiments of the method described in this invention, preferably, the fan speed is 800-1500 r / min.

[0038] According to some embodiments of the method described in this invention, preferably, the temperature inside the vessel is 35-200°C, more preferably 35-100°C, and even more preferably 34-70°C.

[0039] According to some embodiments of the method described in this invention, preferably, the pressure inside the vessel is 75-300 atm, more preferably 75-200 atm, and even more preferably 75-160 atm.

[0040] A third aspect of the present invention provides graphene prepared according to the method described above.

[0041] According to some embodiments of the graphene described in this invention, in a preferred embodiment, the proportion of graphene layers with 10 or fewer layers can reach 91% or more. This proportion can be calculated by observing the ratio of the number of graphene layers with 10 or fewer layers to the total number of graphene layers in a TEM.

[0042] According to some embodiments of the graphene described in this invention, preferably, the edges of the graphene are modified with carboxyl groups.

[0043] The beneficial effects of this invention are:

[0044] (1) The device of the present invention does not require an external circulation system and can realize the circulation and grinding of raw materials in the device. The present invention uses a downward drive to drive the fan to rotate rapidly, and the graphite is guided by the baffle and settles into the grinding component (grinding disc); supercritical carbon dioxide flows through the airflow guide pipe after stirring, realizing the circulation of the air path.

[0045] (2) The grinding device of the present invention has a simple structure and is easy to use. The slow rotation of the moving disc can extend the grinding time of the raw material on the grinding disc, improve the grinding efficiency, reduce the wear of the grinding disc, and extend the service life of the grinding disc, making it suitable for large-scale industrial production.

[0046] (3) The preparation method of the present invention uses supercritical carbon dioxide as solvent, the process is green and environmentally friendly, there is no post-processing, and the cost is low, which is conducive to the development of downstream products. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the grinding device provided in Embodiment 1 of the present invention;

[0048] Figure 2 This is a schematic diagram of the structure of the moving disc grinding surface provided in Embodiment 1 of the present invention;

[0049] Figure 3 This is a cross-sectional schematic diagram of the material settling trench provided in Embodiment 1 of the present invention;

[0050] Figure 4 This is a schematic diagram of the stabilizing structure provided in Embodiment 1 of the present invention;

[0051] Figure 5 This is a schematic diagram of the relative motion of the moving plate and the fixed plate and the grinding of the screw groove provided in Embodiment 1 of the present invention;

[0052] Figure 6 This is a schematic diagram of the drive disk structure provided in Embodiment 1 of the present invention;

[0053] Figure 7 This is a front view of the moving disk structure provided in Embodiment 1 of the present invention;

[0054] Figure 8This is a schematic diagram of the suspended flow state of the raw materials in the reactor provided in Embodiment 1 of the present invention;

[0055] Figure 9 This is a SEM image of graphene provided in Embodiment 2 of the present invention;

[0056] Figure 10 This is a TEM image of graphene provided in Embodiment 2 of the present invention;

[0057] Figure 11 The graphene Raman spectrum provided in Embodiment 2 of the present invention.

[0058] Explanation of reference numerals in the attached figures

[0059] 1. Lid; 2. Body; 3. Power input shaft; 4. Grinding disc drive shaft; 5. Locking nut; 6. Drive disc; 7. Drive pin; 8. Moving disc; 9. Fixed disc; 10. Fan; 11. Baffle; 12. Grinding disc fixing bracket; 13. Airflow guide pipe. Detailed Implementation

[0060] To make the present invention easier to understand, the present invention will be described in detail below with reference to embodiments. These embodiments are for illustrative purposes only and are not limited to the scope of application of the present invention.

[0061] The testing method and equipment used in this invention are as follows:

[0062] To make the present invention easier to understand, the present invention will be described in detail below with reference to embodiments. These embodiments are for illustrative purposes only and are not limited to the scope of application of the present invention.

[0063] The testing method and equipment used in this invention are as follows:

[0064] (1) The SEM (scanning electron microscope) was purchased from FEI Company, model XL-30.

[0065] (2) The TEM (transmission electron microscope) was purchased from Philips, model TECNAL 20.

[0066] (3) The Raman spectrometer was purchased from Renishaw, model inVia Qontor, and the excitation source was selected as 532nm.

[0067] (4) The oxygen element was determined using an XPS instrument, which was purchased from Thermo Fisher Scientific, model ESCALAB250.

[0068] (5) The conductivity was measured using a powder resistivity and conductivity tester, which was purchased from Ningbo Ruike Weiye Instrument Co., Ltd., model FT-300.

[0069]

Example 1

[0070] use Figure 1 The grinding apparatus shown has a closed reaction vessel space formed by the vessel lid 1 and vessel body 2. The power input shaft 3 transmits rotational power from the vessel lid 1 to the grinding disc drive shaft 4 via a coupling. The drive disc 6 is mounted on the grinding disc drive shaft 4 via a locking nut 5. Three holes on the drive disc are used to drive the drive pin 7 mounted on the moving disc 8. The diameter of the holes is slightly larger than the diameter of the drive pin 7, effectively ensuring a tight fit between the grinding surface of the moving disc 8 and the grinding surface of the fixed disc 9. Springs can be installed on the drive pins as needed to adjust the contact force between the moving and fixed discs, thereby adjusting the grinding force.

[0071] A feed inlet is provided on the upper surface of the moving disc 8. The raw material enters the area between the moving disc 8 and the fixed disc 9 through the feed inlet. The grinding surfaces of both the moving disc 8 and the fixed disc 9 have a pattern of 6 sets of eccentric parallel straight grooves. A material settling groove is provided on the lower surface of the moving disc 8 to divert the raw material and allow it to enter the grinding components. The depth of the material settling groove is no more than 1 mm, and the cross-section of the material settling groove adopts a 20° slope shape with an included angle of 90° on both sides. The bottom has been rounded.

[0072] An independently driven fan 10 is installed at the bottom of the reactor. When the fan 10 rotates, it works in conjunction with a baffle 11 to allow raw materials settling in the lower reactor to return to the upper reactor and enter the grinding components. The baffle 11 forms a 50° angle with the bottom surface. The entire grinding component is installed on the reactor lid 1 via a grinding disc mounting bracket 12. During installation, the verticality and coaxiality of each component are ensured. Furthermore, when the fan 10 rotates, the airflow pulls the raw materials upwards into the upper reactor area. The airflow returns to the lower reactor through the hollow hole of the drive shaft 4 and the airflow guide pipe 13. Because the raw materials have a relatively high specific gravity, they settle in the upper reactor, falling onto the upper surface of the moving disc 8. The raw materials then enter the grinding area through the settling grooves on the moving disc 8, thus achieving the grinding of the raw materials.

[0073] The process of preparing graphene using the above-mentioned apparatus is as follows:

[0074] Graphite powder (raw material) is placed on the moving plate 8, and the reactor body 2 is sealed. Carbon dioxide gas is injected into the reactor via a filling pump. The temperature inside the jacket is controlled by an external circulating heating pump. Once the carbon dioxide inside the reactor reaches a supercritical state, the upper and lower rotating components are activated. The moving plate 8 and fan 10 rotate accordingly, and the graphite powder circulates within the reactor. After grinding for a certain period of time, the pressure inside the reactor is rapidly reduced to atmospheric pressure to obtain the graphene product.

[0075]

Example 2

[0076] This embodiment provides a method for preparing graphene using the grinding apparatus of Example 1.

[0077] 100g of 32-mesh flake graphite powder (purchased from Qingdao Jintao Graphite Co., Ltd.) was placed on a rotating disc, and the reactor was sealed. 2.5kg of carbon dioxide was injected into the reactor via a pump, bringing the internal pressure to 60 atm. The temperature inside the reactor was increased to 55℃ and the pressure to 120 atm by adding more carbon through the jacket. The rotating disc was set to 100 rpm, and the fan speed to 1000 rpm. Both the upper and lower rotating components were activated. The experiment was stopped after 24 hours. The pressure inside the reactor was reduced to 1 atm within 10 seconds, and the material was released from the bottom of the reactor, yielding graphene.

[0078] The prepared graphene was analyzed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the results are as follows: Figure 9 and Figure 10 As shown, the graphene sheet diameter is 5-10 micrometers. Statistical analysis of the number of layers revealed that 91% of the prepared graphene had fewer than 10 layers. The electrical conductivity of this graphene, measured using a powder conductivity meter, was 500 S / m. XPS results showed an oxygen content of 5.3%, and Raman spectroscopy results were as follows. Figure 11 As shown, I D / I G =0.12. After 1440 hours of operation, the grinding disc showed signs of wear.

[0079]

Example 3

[0080] This embodiment provides a method for preparing graphene using the grinding apparatus of Example 1.

[0081] 50g of 32-mesh expanded graphite powder was placed on a rotating disc, and the reactor was sealed. 2.5kg of carbon dioxide was injected into the reactor via a pump, bringing the internal pressure to 60 atm. The temperature inside the reactor was increased to 60℃ and the pressure to 160 atm by adding material through the jacket. The rotating disc was set to 300 rpm, and the fan speed to 800 rpm. Both the upper and lower rotating components were activated. The experiment was stopped after 20 hours. The pressure inside the reactor was reduced to 1 atm within 10 seconds, and the material was released from the bottom of the reactor, yielding graphene.

[0082] The prepared graphene was analyzed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), revealing sheet diameters of 5-10 micrometers. Statistical analysis of the number of layers showed that approximately 93% of the prepared graphene had fewer than 10 layers. The electrical conductivity of the graphene, measured using a powder conductivity meter, was 720 S / m. XPS results indicated an oxygen content of 7.8%, and Raman spectroscopy results showed... D / I G =0.16.

[0083]

Example 4

[0084] The grinding apparatus is the same as in Example 1, except that the fan speed is 600 r / min.

[0085] Graphene was prepared according to the raw materials and methods of Example 2.

[0086] The obtained graphene was analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the graphene sheet diameter was 150 micrometers. Statistical analysis of the number of layers showed that approximately 30% of the obtained graphene had fewer than 10 layers. The electrical conductivity of the graphene was measured to be 1800 S / m using a powder conductivity meter. XPS results showed an oxygen content of 0%, and Raman spectroscopy results showed ID / IG = 0.

[0087]

Example 5

[0088] The grinding apparatus is the same as in Example 1, except that the fan speed is 2000 r / min.

[0089] Graphene was prepared according to the raw materials and methods of Example 2.

[0090] The prepared graphene was analyzed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), revealing a sheet diameter of 10-20 micrometers. Statistical analysis of the number of layers showed that approximately 30% of the prepared graphene had fewer than 10 layers. The electrical conductivity of the graphene was measured to be 810 S / m using a powder conductivity meter. XPS results showed an oxygen content of 3.5%, and Raman spectroscopy results showed an ID / IG ratio of 0.11.

[0091]

Example 6

[0092] The grinding apparatus according to Example 1 differs in that the angle between the baffle and the bottom surface is 90°.

[0093] Graphene was prepared according to the raw materials and methods of Example 2.

[0094] The prepared graphene was analyzed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), revealing a sheet diameter of 10-20 micrometers. Statistical analysis of the number of layers showed that approximately 35% of the prepared graphene had fewer than 10 layers. The electrical conductivity of the graphene was measured to be 830 S / m using a powder conductivity meter. XPS results showed an oxygen content of 3.2%, and Raman spectroscopy results showed an ID / IG ratio of 0.12.

[0095]

Example 7

[0096] The grinding apparatus according to Example 1 differs in that it lacks an airflow guide tube 13.

[0097] Graphene was prepared according to the raw materials and methods of Example 2.

[0098] The obtained graphene was analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the graphene sheet diameter was 5-10 micrometers. Statistical analysis of the number of layers showed that approximately 60% of the graphene prepared in Comparative Example 5 had fewer than 10 layers. The electrical conductivity of this graphene was measured to be 530 S / m using a powder conductivity meter. XPS results showed an oxygen content of 5.6%, and Raman spectroscopy results showed an ID / IG ratio of 0.10.

[0099] Comparative Example 1

[0100] The self-circulating grinding disc device for high-pressure environments described in sections

[0034] -

[0048] of the CN109382167A specification was used. Under the same experimental conditions as in Example 2, 100g of 32-mesh flake graphite powder was placed on the moving disc. 2.5kg of carbon dioxide was injected into the reactor via a pump, bringing the reactor pressure to 60 atm. The temperature inside the reactor was increased to 55°C and the pressure to 120 atm by adding material through the jacket. The grinding disc rotation speed was set to 1000 r / min, and the magnetic rotation component was activated. The experiment was stopped after 24 hours. The pressure inside the reactor was reduced to 1 atm within 10 seconds, and the material was released from the bottom of the reactor, yielding graphene.

[0101] The obtained graphene was analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the graphene sheet diameter was 5-10 micrometers. Statistical analysis of the number of layers showed that approximately 13% of the graphene prepared in Comparative Example 1 had fewer than 10 layers. The conductivity of this graphene was measured to be 87 S / m using a powder conductivity meter. XPS results showed an oxygen content of 13.4%, and Raman spectroscopy results showed an ID / IG ratio of 0.22.

[0102] Comparative Example 2

[0103] The grinding apparatus according to Embodiment 1 differs in that both the grinding component and the fan are driven by the same rotating component.

[0104] Graphene was prepared according to the raw materials and methods of Example 2.

[0105] The obtained graphene was analyzed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the graphene sheet diameter was 5-10 micrometers. Statistical analysis of the number of layers showed that approximately 36% of the graphene prepared in Comparative Example 5 had fewer than 10 layers. The electrical conductivity of this graphene was measured to be 870 S / m using a powder conductivity meter. XPS results showed an oxygen content of 5.3%, and Raman spectroscopy results showed an ID / IG ratio of 0.12. After 240 hours of operation, the grinding disc showed severe wear.

[0106] The above description is merely a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, based on the technical teachings provided by the present invention and as common knowledge in the field, other equivalent modifications and improvements can be made, and these should also be considered within the scope of protection of the present invention.

Claims

1. A grinding apparatus, comprising: The vessel, the grinding component inside the vessel, the fan (10), and the upper and lower rotating components, wherein, The vessel is a sealed vessel, including a lid (1) and a body (2). The upper rotating component is used to drive the grinding component to rotate; The lower rotating component is used to drive the fan to rotate; The fan draws the raw material into the grinding component by rotating; The grinding component grinds the raw material by rotating; The grinding device also includes a baffle (11), which is used to return the raw material that has settled to the lower half of the pot to the upper half of the pot by the rotation of the fan (10) and the baffle (11) to the inside of the grinding component; The angle between the baffle and the bottom surface is 40°-60°; The upper rotating component includes a power input shaft (3), a grinding disc drive shaft (4), a drive disc (6), and a drive pin (7), wherein, The power input shaft (3) transmits the rotational power to the grinding disc drive shaft (4). The grinding wheel drive shaft (4) is connected to the drive disk (6), and the drive disk (6) is used to drive the drive pin (7) to rotate; The drive pin (7) is used to drive the grinding component; The grinding component also includes an airflow guide pipe (13) and the grinding disc drive shaft (4) has a hollow hole structure. The carbon dioxide airflow returns to the lower half of the reactor through the airflow guide pipe (13) from the hollow hole of the grinding disc drive shaft (4).

2. The apparatus according to claim 1, characterized in that, The upper rotating component also includes a locking nut (5), and the grinding disc drive shaft (4) and the drive disc (6) are connected by the locking nut (5); And / or, a spring is provided on the drive pin (7), the spring being used to adjust the contact force of the grinding component; And / or, the power input shaft (3) transmits rotational power from the vessel cover (1) to the grinding disc drive shaft (4) via a coupling.

3. The apparatus according to claim 1 or 2, characterized in that, The grinding components include a moving disc (8) and a fixed disc (9); The upper surface of the moving disk (8) has a feed inlet, and the raw material enters between the moving disk (8) and the fixed disk (9) from the feed inlet of the grinding disk.

4. The apparatus according to claim 3, characterized in that, The grinding surface of the moving disk (8) has an eccentric parallel straight groove structure.

5. The apparatus according to claim 4, characterized in that, The grinding surface of the fixed plate (9) has an eccentric parallel straight groove structure.

6. The apparatus according to claim 5, characterized in that, The lower surface of the moving disk (8) is provided with a material settling groove for diverting the raw material and allowing it to enter the grinding component; the depth of the material settling groove is no more than 1 mm.

7. The apparatus according to claim 6, characterized in that, The cross-section of the material settling trench is sloping.

8. The apparatus according to claim 7, characterized in that, The grinding surface of the moving disk (8) has a pattern of 4-8 sets of eccentric parallel straight grooves; And / or, the grinding surface of the fixed plate (9) has a pattern of 4-8 sets of eccentric parallel straight grooves; And / or, the cross-section of the material settling ditch adopts a 10°-30° slope shape, and the included angle between the two sides of the cross-section is 90°.

9. The apparatus according to claim 1 or 2, characterized in that, The grinding device also includes a grinding disc fixing bracket (12) for connecting the grinding component to the lid (1) of the vessel.

10. A method for preparing graphene using the apparatus according to any one of claims 1-9, comprising: The raw materials and supercritical carbon dioxide are added into the reactor. The rotating part at the bottom drives the fan to rotate, and the fan rotation brings the raw materials into the grinding part. The rotating part at the top drives the grinding part to rotate, and the raw materials are ground inside the grinding part.

11. The method for preparing graphene using the apparatus according to claim 10, characterized in that, The method further includes: after grinding, reducing the pressure to atmospheric pressure within 5-20 seconds.

12. The method according to claim 11, characterized in that, The method includes: Step 1: Add the raw materials to the pot; Step 2: Introduce carbon dioxide into the reactor, control the temperature and pressure, and keep the carbon dioxide in a supercritical state to form a mixture of graphite powder and supercritical carbon dioxide. Grind the mixture in the reactor. Step 3: After grinding, the pressure inside the reactor is quickly reduced to atmospheric pressure to obtain the graphene product.

13. The method according to claim 12, characterized in that, The raw material is flake graphite powder and / or expanded graphite powder; And / or, the particle size of the raw material is 10-325 mesh; And / or, the temperature of supercritical carbon dioxide is greater than 31.26℃ and the pressure is greater than 7.29MPa; And / or, the weight ratio of raw materials to carbon dioxide is 1:5 to 1:40; And / or, the rotational speed of the moving plate inside the vessel is 100-300 r / min; And / or, the fan speed is 800-1500 r / min; And / or, the temperature inside the vessel is 35-200℃; And / or, the pressure inside the vessel is 75-300 atm.

14. The method according to claim 13, characterized in that, The particle size of the raw material is 32-100 mesh; And / or, the weight ratio of raw materials to carbon dioxide is 1:5 to 1:25; And / or, the temperature inside the vessel is 35-100℃; And / or, the pressure inside the vessel is 75-200 atm.

15. The method according to claim 14, characterized in that, The pressure inside the vessel is 75-160 atm.

16. Graphene prepared by the method according to any one of claims 10 to 15.

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