CN116462191B - Method for preparing graphene - Google Patents
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- CN116462191B CN116462191B CN202310097014.9A CN202310097014A CN116462191B CN 116462191 B CN116462191 B CN 116462191B CN 202310097014 A CN202310097014 A CN 202310097014A CN 116462191 B CN116462191 B CN 116462191B
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- 229910021389 graphene Inorganic materials 0.000 title claims abstract description 187
- 238000000034 method Methods 0.000 title claims abstract description 77
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- 239000010439 graphite Substances 0.000 claims abstract description 216
- 239000007787 solid Substances 0.000 claims abstract description 128
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- 230000002687 intercalation Effects 0.000 claims abstract description 48
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- 239000002904 solvent Substances 0.000 claims description 35
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- 239000002798 polar solvent Substances 0.000 claims description 24
- 238000006243 chemical reaction Methods 0.000 claims description 18
- 238000001069 Raman spectroscopy Methods 0.000 claims description 16
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- 229910052794 bromium Inorganic materials 0.000 claims description 13
- 239000007789 gas Substances 0.000 claims description 13
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- 238000001237 Raman spectrum Methods 0.000 claims description 7
- 229910021382 natural graphite Inorganic materials 0.000 claims description 7
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- 239000007858 starting material Substances 0.000 claims description 5
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- 229910052801 chlorine Inorganic materials 0.000 claims description 4
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- 238000009529 body temperature measurement Methods 0.000 claims description 3
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- PNDPGZBMCMUPRI-UHFFFAOYSA-N iodine Chemical compound II PNDPGZBMCMUPRI-UHFFFAOYSA-N 0.000 claims description 3
- 230000001681 protective effect Effects 0.000 claims description 3
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- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
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Classifications
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/15—Nano-sized carbon materials
- C01B32/182—Graphene
- C01B32/184—Preparation
- C01B32/19—Preparation by exfoliation
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B2204/00—Structure or properties of graphene
- C01B2204/04—Specific amount of layers or specific thickness
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Nanotechnology (AREA)
- Inorganic Chemistry (AREA)
- Carbon And Carbon Compounds (AREA)
Abstract
The application discloses a method for preparing graphene, which comprises the following steps: a) Mixing graphite raw materials with an intercalation agent, and standing to obtain colloid dispersion liquid; b) Filtering the colloid dispersion liquid, and drying filtrate to obtain modified solid graphite; c) And expanding the modified solid graphite in a microwave field to obtain graphene. According to the application, the graphite raw material fully pretreated in the method is poured into a high-power continuous microwave system, and the rapid dry microwave expansion in the air is realized by monitoring and controlling the microwave power and the temperature, so that a defect-free ton-level graphene product is directly obtained. The graphene product can be directly used without subsequent treatment.
Description
Technical Field
The application belongs to the field of new graphene materials, and particularly relates to a method for preparing graphene and a system for implementing the method.
Background
Graphene exhibits excellent electron transport ability, heat conduction ability, and mechanical properties due to its two-dimensional, few-layer crystal structure. The excellent characteristics enable the graphene to show wide application prospects in the fields of flexible electronics, energy storage materials and devices, fuel cells, anticorrosive coatings and the like. Along with the discovery of graphene, low-cost and large-scale preparation of graphene is also one of main research directions of the industry.
Currently mainstream graphene preparation methods include a graphite oxide reduction method (Hummers method) and a chemical vapor deposition method (Chemical vapor deposition, CVD method). The Hummers method is to oxidize graphite into graphite oxide by strong oxidant concentrated sulfuric acid, concentrated nitric acid, potassium permanganate and the like, then to form graphene oxide by ultrasonic treatment, and then to obtain graphene powder by reduction. The method has long process period and serious pollution, and the obtained graphene has a plurality of defects and low quality, and the defects limit the application of the graphene in high-end scenes such as high thermal conductivity, high electrical conductivity, excellent mechanical strength and the like. The graphene prepared by the CVD method has higher quality, but has complex process, higher cost and uneven layer number, and is difficult to realize large-scale industrialized production at present.
The method for preparing graphene by microwave stripping refers to preparing graphene by stripping a solid graphite sheet layer by utilizing huge energy released by the rapid heating effect of microwaves on a carbon material. The method has the advantages of high efficiency, green and the like, and has great potential in the field of large-scale rapid preparation of graphene.
Microwaves have been used to assist in the production of expanded graphite and graphene. For example, zhu et al use microwave-assisted puffing and reduction of dried graphite oxide powder (Yanwu Zhu et al, "Microwave assisted exfoliation and reduction of graphite oxide for ultracapacitors", carbon, volume 48, phase 7, month 6 of 2010, page 2118 2122). The process oxidizes and intercalates natural graphite to produce a graphite oxide/graphite intercalation compound, the resulting product being as incompletely separated/isolated graphene sheets and microwave reduced graphite oxide.
Khavrel et al, which are incorporated herein by reference, relate to the same problems (Khavrel et al, ,"Fluorinated microwave exfoliated graphite oxide:structural features and double layer capacitance",Fullerenes,Nanotubes and Carbon Nanostructures,, volume 24, stage 4, month 3 of 2016, pages 266-272). The method oxidizes natural graphite to graphite oxide, then expands the graphite oxide to prepare expanded graphite oxide, and then changes the expanded graphite oxide into fluorinated graphite oxide.
Similarly, voiry et al prepared graphite oxide powder from natural graphite, then dispersed the graphite oxide in a liquid to form a solution (e.g., graphite oxide + water), and then puffed the solution with ultrasound to produce graphene oxide flakes, which were finally dried and thermally reduced using a microwave oven to obtain reduced graphene oxide (d.voir et al, "High quality GRAPHENE VIA microwave reduction of solution exfoliated graphene oxide", science, volume 353, stage 6306, 2016, 9, pages 1413 1416). Notably, the microwaves in the method are not used to expand the graphite oxide, but rather to thermally reduce the dried, ultrasonically expanded graphene oxide sheets.
Matsumoto et al used a combination of microwaves and a specific set of oligomeric ionic liquids to directly utilize natural graphite dispersed in the ionic liquid to produce graphene (M.Matsumoto et al ,"Ultrahigh throughput exfoliation of graphite into pristine'single layer'graphene using microwaves and molecularly engineered ionic liquids",Nature Chemistry,, vol.7, 9, month 2015, p. 730 735). However, this ionic liquid is difficult to produce and very expensive, which is disadvantageous for mass production. Meanwhile, the ionic liquid can cause chemical defects on the surface of the graphene.
Lin Yijun et al (CN 110662600B) treat graphite with a dielectric heating promoter selected from polar organic molecules, inorganic dielectric materials, or combinations thereof and prepare graphene by a microwave expansion process. However, in the case of using a polar solvent (hydrophilic solvent), the graphite surface has poor hydrophilicity, and the treatment process of this technique has an essential disadvantage of insufficient effect according to the similar compatibility principle, and thus the resultant product cannot ensure uniformity of quality. The starting graphite or graphitic carbon material of this technique needs to be less than 50 μm in length and the smaller the size the better, with a significant limitation on the starting material. The focusing microwave system of the technology is a double microwave source, has high power and high reaction temperature, needs inert gas to protect and cool products, and otherwise has explosion risk. Because the temperature of the graphene product before discharging is high, the graphene product is required to be collected after being cooled. In addition, the microwave reaction equipment disclosed in the document lacks a process temperature measurement module, the control of the production process is not guaranteed, and the product quality is uncontrollable; the strip-shaped transmission device is easy to spill graphite raw materials and graphene products on microwave reaction equipment and an operation workshop, so that equipment damage or dust pollution is caused; the horizontal absorbing device is easy to absorb the intercalated graphite which is not completely reacted into the receiving container, so that the quality of the graphene product is reduced.
Therefore, there is an urgent need to develop a new graphene production method that can controllably produce high quality graphene products, and can be mass-produced, green, and low-energy-consumption, while being implemented in an air environment to meet the needs of large-scale industrial applications.
Disclosure of Invention
In view of the above, the application aims to provide a method for preparing high-quality graphene and continuous microwave equipment for mass production of graphene, and the method adopts green and safe reagents, has mild reaction conditions, and has simple and controllable technical process and strong practicability, so that ton-level controllable production of high-quality graphene products can be realized.
According to one aspect of the present application, there is provided a method of preparing graphene, comprising:
a) Mixing graphite raw materials with an intercalation agent, and standing to obtain colloid dispersion liquid;
b) Filtering the colloid dispersion liquid, and drying filtrate to obtain modified solid graphite;
c) And expanding the modified solid graphite in a microwave field to obtain graphene.
Optionally, in step a), the time of standing is 0.5-120h.
Alternatively, the time of the standing is independently any value or a range of values between any two selected from 0.5h、1h、2h、3h、5h、8h、10h、12h、15h、17h、20h、22h、24h、27h、30h、35h、40h、45h、50h、55h、60h、65h、70h、75h、80h、85h、90h、95h、100h、105h、110h、115h、120h.
Preferably, the time of the standing is 2-24 hours.
More preferably, the time of the standing is 2 to 10 hours.
Optionally, in step a), the mixing is followed by ultrasonic dispersion to reduce the time of the standing.
Optionally, the time of the ultrasonic treatment is 10-120min.
Optionally, the time of the ultrasound is independently any value or a range of values between any two selected from 10min, 20min, 30min, 40min, 50min, 60min, 70min, 80min, 90min, 100min, 110min, 120 min.
Optionally, the intercalating agent is at least one selected from the group consisting of non-polar molecules iodine, bromine, chlorine, sulfur, argon, or a mixture of two or more thereof.
According to the application, the nonpolar molecular iodine can be elemental iodine; the nonpolar molecular bromine can be elemental bromine, such as liquid bromine; the nonpolar molecular chlorine can be elemental chlorine, such as chlorine gas; the nonpolar molecular sulfur may be elemental sulfur.
Optionally, the intercalating agent is used in the form of an intercalating agent solution comprising the intercalating agent and a solvent, the solvent comprising at least one of a non-polar solvent, a polar solvent.
According to the application, the intercalating agent may be used in the presence or absence of a solvent. That is, the intercalating agent and the solvent may be mixed with the graphite raw material after being prepared into a solution, or the intercalating agent may be directly mixed with the graphite raw material.
Optionally, the nonpolar solvent is at least one selected from cyclohexane, n-hexane, petroleum ether, chloroform, and carbon tetrachloride.
Optionally, the polar solvent is at least one selected from water and alcohol.
Alternatively, the alcohol includes methanol, ethanol, propanol, isopropanol, ethylene glycol, glycerol, or any other alcohol commonly used.
Optionally, the polar solvent is at least one selected from water, methanol, ethanol, isopropanol.
According to the present application, the solvent in the intercalating agent solution comprises a non-polar solvent, a polar solvent or a combination of both.
Optionally, the solvent is a non-polar solvent.
Optionally, the solvent is a polar solvent.
Alternatively, the solvent is a mixture of a nonpolar solvent and a polar solvent.
Optionally, the solvent comprises the nonpolar solvent and the polar solvent, and the volume ratio of the nonpolar solvent to the polar solvent is 10:0.001-0.001:10.
Alternatively, the volume ratio of the nonpolar solvent to the polar solvent is independently any value or range between any two values selected from 10:0.001、9.5:0.001、9:0.001、8.5:0.001、8:0.001、7.5:0.001、7:0.001、6.5:0.001、6:0.001、5.5:0.001、5:0.001、4.5:0.001、4:0.001、3.5:0.001、3:0.001、2.5:0.001、2:0.001、1.5:0.001、1:0.001、0.9:0.001、0.8:0.001、0.7:0.001、0.6:0.001、0.5:0.001、0.4:0.001、0.3:0.001、0.2:0.001、0.1:0.001、0.09:0.001、0.08:0.001、0.07:0.001、0.06:0.001、0.05:0.001、0.04:0.001、0.03:0.001、0.02:0.001、0.01:0.001、0.009:0.001、0.008:0.001、0.007:0.001、0.006:0.001、0.005:0.001、0.004:0.001、0.003:0.001、0.002:0.001、0.001:0.001、0.001:0.002、0.001:0.003、0.001:0.004、0.001:0.005、0.001:0.006、0.001:0.007、0.001:0.008、0.001:0.009、0.001:0.01、0.001:0.02、0.001:0.03、0.001:0.04、0.001:0.05、0.001:0.06、0.001:0.07、0.001:0.08、0.001:0.09、0.001:0.1、0.001:0.2、0.001:0.3、0.001:0.4、0.001:0.5、0.001:0.6、0.001:0.7、0.001:0.8、0.001:0.9、0.001:1、0.001:1.5、0.001:2、0.001:2.5、0.001:3、0.001:3.5、0.001:4、0.001:4.5、0.001:5、0.001:5.5、0.001:6、0.001:6.5、0.001:7、0.001:7.5、0.001:8、0.001:8.5、0.001:9、0.001:9.5、0.001:10.
Preferably, the volume ratio of the nonpolar solvent to the polar solvent is 4:0.001-0.001:4.
Optionally, the volume ratio of the intercalating agent to the solvent is 1:0.001-0.001:1.
Alternatively, the volume ratio of the intercalating agent to the solvent is independently any value or range between any two selected from 1:0.001、0.9:0.001、0.8:0.001、0.7:0.001、0.6:0.001、0.5:0.001、0.4:0.001、0.3:0.001、0.2:0.001、0.1:0.001、0.09:0.001、0.08:0.001、0.07:0.001、0.06:0.001、0.05:0.001、0.04:0.001、0.03:0.001、0.02:0.001、0.01:0.001、0.009:0.001、0.008:0.001、0.007:0.001、0.006:0.001、0.005:0.001、0.004:0.001、0.003:0.001、0.002:0.001、0.001:0.001、0.001:0.002、0.001:0.003、0.001:0.004、0.001:0.005、0.001:0.006、0.001:0.007、0.001:0.008、0.001:0.009、0.001:0.01、0.001:0.02、0.001:0.03、0.001:0.04、0.001:0.05、0.001:0.06、0.001:0.07、0.001:0.08、0.001:0.09、0.001:0.1、0.001:0.2、0.001:0.3、0.001:0.4、0.001:0.5、0.001:0.6、0.001:0.7、0.001:0.8、0.001:0.9、0.001:1.
Preferably, the volume ratio of the intercalating agent to the solvent is 1:1-1:9.
Optionally, in step a), the graphite raw material is at least one selected from natural graphite (including flake graphite and soil graphite) and synthetic graphite.
Preferably, the graphite raw material is natural crystalline flake graphite, and the grain diameter is more than or equal to 10 mu m.
More preferably, the particle size of the natural crystalline flake graphite is more than or equal to 50 μm.
Optionally, in step a), the volume ratio of the intercalating agent or the intercalating agent solution to the graphite raw material is 1:1-10:1.
Optionally, the volume ratio of the intercalating agent to the graphite starting material is independently any value selected from 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1, 10:1 or a range of values between any two.
Optionally, the volume ratio of the intercalation solution to the graphite feedstock is independently any value selected from 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1, 10:1, or a range of values between any two.
Preferably, the volume ratio of the intercalation agent or the intercalation agent solution to the graphite raw material is 2:1-5:1.
More preferably, the volume ratio of the intercalating agent or the intercalating agent solution to the graphite raw material is 3:1.
Optionally, in step b), the drying is performed at a controlled and adjustable temperature and wind speed such that the filtrate is air-dried uniformly.
Optionally, the controlled and adjustable temperature is 10-90 ℃, and the controlled and adjustable wind speed is 1-10L/min.m 2.
Preferably, the controlled and adjustable temperature is 30-60 ℃, and the controlled and adjustable wind speed is 4-6L/min.m 2.
Optionally, in step b), the modified solid graphite has a solids content of 30 to 99wt%.
Alternatively, the solid content of the modified solid graphite is independently any value or a range between any two values selected from 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, 90wt%, 95wt%, 99 wt%.
Preferably, the modified solid graphite has a solids content of 40 to 95wt%.
Optionally, step c) comprises: and expanding the modified solid graphite in a tiled state through a microwave irradiation area in the microwave field to obtain the graphene.
Optionally, in step c), the modified solid graphite has a flat thickness of 0.1 to 50mm.
Alternatively, the tiling thickness of the modified solid graphite is independently any value or a range of values between any two selected from 0.1mm、0.3mm、0.5mm、0.7mm、0.9mm、1mm、1.5mm、2mm、2.5mm、3mm、3.5mm、4mm、4.5mm、5mm、5.5mm、6mm、6.5mm、7mm、7.5mm、8mm、8.5mm、9mm、9.5mm、10mm、15mm、20mm、25mm、30mm、35mm、40mm、45mm、50mm.
Preferably, the tiling thickness of the modified solid graphite is 1-30mm.
Optionally, in step c), the modified solid graphite passes at a rate of 0.1 to 20m/min.
Alternatively, the rate of passage of the modified solid graphite is independently any value or range of values between any two selected from 0.1m/min、0.3m/min、0.5m/min、0.7m/min、1.0m/min、1.2m/min、1.4m/min、1.6m/min、1.8m/min、1.9m/min、2.0m/min、2.5m/min、3.0m/min、3.5m/min、4.0m/min、4.5m/min、5.0m/min、5.5m/min、6.0m/min、6.5m/min、7.0m/min、7.5m/min、8.0m/min、8.5m/min、9.0m/min、9.5m/min、10.0m/min、10.5m/min、11.0m/min、12.0m/min、13.0m/min、14.0m/min、15.0m/min、16.0m/min、17.0m/min、18.0m/min、19.0m/min、20.0m/min.
Preferably, the modified solid graphite has a passing rate of 2-10m/min.
Optionally, in step c), the power of the microwaves is 1-50kW.
Alternatively, the power of the microwaves is independently any value selected from 1kW, 2kW, 3kW, 4kW, 5kW, 8kW, 10kW, 15kW, 20kW, 25kW, 30kW, 35kW, 40kW, 45kW, 50kW or a range between any two.
Preferably, the power of the microwaves is 8-25kW.
Optionally, the method further comprises: and monitoring the expansion temperature of the modified solid graphite in the microwave field in real time, and adjusting the input power of microwaves to ensure that the microwave field is uniformly distributed in a reaction zone.
According to the present application, the temperature at which the modified solid graphite expands under microwave irradiation can be monitored using a variety of techniques (e.g., optical fiber or infrared) to facilitate monitoring the stability of the process.
Optionally, the method further comprises: water vapor and exhaust gas generated by expansion of the modified solid graphite in the microwave field are removed so that the surface oxygen content and defects of the graphene are reduced.
According to the present application, water vapor and exhaust gas may be removed in a variety of ways, such as by directing the exhaust gas out or capturing the exhaust gas.
Optionally, in step c), the volume expansion of the graphene with respect to the graphite raw material is 30-200 times.
Optionally, the expansion ratio of the graphene relative to the graphite raw material is more than or equal to 60.
Preferably, the expansion ratio of the graphene relative to the graphite raw material is more than or equal to 80.
Optionally, in step c), the number of layers of the graphene is less than or equal to 5 as measured by, for example, transmission electron microscopy or raman spectroscopy.
Preferably, the number of layers of the graphene is less than or equal to 3.
More preferably, the number of layers of the graphene is 1-3.
Optionally, in step c), the ratio of the D peak intensity to the G peak intensity of the graphene in the Raman spectrum is I D/IG less than or equal to 0.2.
Preferably, I D/IG of the graphene in the Raman spectrum is less than or equal to 0.05.
More preferably, the graphene has an I D/IG =0 in raman spectrum.
Optionally, the method further comprises: the graphene is collected in a vertically derived manner.
According to the application, the discharging mode of the graphene can be set as vertical suction. Compared with the horizontal suction material, the vertical suction material is beneficial to avoiding the suction of unreacted modified solid graphite.
According to another aspect of the present application, there is provided a system for carrying out the method as described above, comprising a feeding module, a conveying module, a microwave module, a control feedback module and a discharge module, wherein:
the feed module is configured such that the modified solid graphite is input onto the delivery module in a continuous quantitative state;
The conveying module is configured to enable the modified solid graphite to stably and uniformly pass through the microwave module to reach the discharging module;
the microwave module is configured to provide a power-controllable microwave input such that the microwave field is formed in a reaction zone and such that the modified solid graphite expands rapidly as it passes through a microwave irradiation zone in the microwave field;
the control feedback module is configured to provide real-time temperature measurement and feedback, and adjust microwave power so that the microwave field is uniformly distributed in a reaction zone;
the discharge module is configured to continuously collect the graphene.
Optionally, the feeding module comprises an automatic feeder.
Optionally, the automatic feeder comprises a vibratory feeder, a gravimetric feeder, a volumetric auger type feeder, an injector, a compressed air auxiliary feeder, a vacuum auxiliary feeder, a gravity feeder, a drum type feeder, a wheel type feeder, a slide rail, a chute, a conveyor type feeder, or a combination thereof.
Optionally, the conveying module comprises a drive link plate, which is composed of a plurality of interconnected segments.
Optionally, the segments are configured to bend inwardly in a groove shape in a natural state to provide a receiving space for expansion of the modified solid graphite, and to expand in a stressed state to fit in or out of the material.
According to the application, the above-described arrangement of segments can be realized in different ways. In one embodiment, the drive link plate is cyclically driven around two drive shafts, the microwave module is disposed between the two drive shafts, and the feed module and the discharge module are disposed adjacent to the two drive shafts, respectively. For each segment, when the segment is close to any transmission shaft, the back surface of the segment is unfolded due to the acting force from the transmission shaft, so that the modified solid graphite is convenient to feed or the graphene product is convenient to discharge; when the modified solid graphite is far away from the two transmission shafts, the modified solid graphite is bent inwards naturally, so that a reactor type accommodating space is conveniently provided for the expansion of the modified solid graphite when the modified solid graphite is irradiated by microwaves, and the effect of combining the transmission chain plate and the reactor is achieved. In this case, the modified solid graphite can be made easier to uniformly absorb microwave irradiation, and dust (from, for example, modified solid graphite or graphene, etc.) scattering phenomenon is not generated, resulting in damage to equipment or dust pollution to workshops.
Optionally, the microwave module further comprises a degassing device configured to remove water vapor and adsorbed exhaust gas generated by expansion of the modified solid graphite in the microwave field.
Preferably, the degassing means comprises means for allowing water vapour and exhaust gases to leave or scrubbing means for capturing water vapour and exhaust gases.
Optionally, the discharge module is configured to collect the graphene in a vertically derived manner.
Preferably, the discharging module comprises a aspirator configured to direct graphene out in a vertical discharging manner. Compared with the horizontal suction, the vertical suction is beneficial to avoiding suction of unreacted modified solid graphite.
Optionally, the length of the microwave field is 0.5-6m.
Alternatively, the length of the microwave field is independently any value or range between any two values selected from 0.5m, 0.6m, 0.7m, 0.8m, 0.9m, 1.0m, 1.5m, 2.0m, 2.5m, 3.0m, 3.5m, 4.0m, 4.5m, 5.0m, 5.5m, 6.0 m.
Preferably, the length of the microwave field is 1-3m.
Alternatively, the microwave field is carried out directly in air without a protective atmosphere.
According to the application, the expansion of the modified solid graphite in the microwave field does not need to be carried out under a protective atmosphere, but can be carried out directly in air.
In the context of the present application, the terms "reaction" and "expansion" are not strictly distinguished, and both may in most cases be understood and used interchangeably.
The application has the following beneficial effects:
1) According to the method for preparing graphene, disclosed by the application, the non-polar solvent in the intercalation agent solution can promote the intercalation modification of the graphite raw material to be more thorough and sufficient, so that the quality of a graphene product is improved.
2) According to the method for preparing graphene, disclosed by the application, the core parameter of the temperature of the modified solid graphite expanding under microwaves is monitored, so that the real-time control of a technological process can be effectively realized, and the uniformity of the product quality is ensured.
3) According to the method for preparing graphene, the reagent is green and safe, the reaction condition is mild, the operation is performed in an air environment, the process is simple and controllable, and the industrial practicability is high.
Drawings
Fig. 1 is a schematic diagram of the overall structure of a graphene preparation system according to an embodiment of the present application.
Fig. 2 is a schematic view of a drive link plate and a single segment according to an embodiment of the present application, wherein (a) is a schematic view of the working principle of the drive link plate and (B) is a schematic view of a section of the single segment.
Fig. 3 is a transmission electron micrograph of graphene prepared according to one embodiment of the present application, wherein (a) is a transmission electron micrograph showing the size of graphene, and (B), (C) and (D) are transmission electron micrographs of 5, 4 and 3 layers of graphene, respectively.
Fig. 4 is a raman spectrum of graphene prepared according to one embodiment of the present application, wherein (a) is a raman spectrum in the range of 200-3250cm -1 and (B) is a raman spectrum fitted to 2D peak-splitting of graphene in the range of 2550-2850cm -1.
Detailed Description
The method for preparing the graphene and the system for implementing the method have the advantages of high quality of graphene products, controllable technological process and the like. The reason for the high quality of graphene products is mainly the following five points: 1) The formula of the intercalation agent contains nonpolar material components, so that intercalation modification of the graphite raw material is more thorough and sufficient, the surface of the graphene is not damaged, and defect-free high quality is ensured; 2) The air speed and the temperature of the drying process are controlled and regulated, so that the intercalation agent is uniformly distributed among graphite layers, and uniform expansion power is provided for graphite in a microwave field; 3) The temperature control of the microwave reaction equipment is critical, and the high quality of mass-produced products is ensured through the coupling with the speed of the chain plate; 4) The design of combining the transmission chain plate and the reactor can lead the modified solid graphite to be easier to uniformly absorb microwaves, and has no dust (from the modified solid graphite, the graphene and the like) scattering phenomenon to cause damage to equipment or dust pollution to workshops; 5) The blanking module is arranged to vertically suck materials instead of horizontally suck materials, so that the unreacted modified solid graphite can be effectively prevented from being sucked into the receiving container. The reason for controllable quality of graphene products is mainly the following two points: 1) The non-polar substance component is added in the formula of the intercalation agent, so that intercalation modification of the graphite raw material is more thorough and sufficient; 2) In the process of expanding and stripping the modified solid graphite into graphene, the most core technological parameter is the reaction temperature, and the reaction temperature curve of the modified solid graphite under microwave irradiation can be monitored in real time by arranging a temperature-regulating feedback module in a microwave reaction cavity, so that the process parameter control is effectively realized, and the uniformity and reliability of the mass-produced product quality are ensured.
The graphene prepared according to the present application may be an ultrathin graphene sheet mainly comprising a single layer of graphene or a mixture of single and few layers of graphene.
The method for preparing graphene and the system for implementing the method can realize continuous, controllable and mass production of high-quality graphene, and are determined for various reasons. On one hand, the intercalation agent solution containing nonpolar substances is used for preprocessing the graphite, so that the expansion of the graphite under microwaves is quicker, more thorough and more sufficient, thereby having the premise of high-quality mass production; on the other hand, the advantages brought by the full pretreatment of the graphite raw material are furthest exerted by improving various aspects of the production process (including real-time monitoring feedback of the reaction temperature, matching of microwave power and the speed of the chain plate, design of combining the transmission chain plate and the reactor, controllable drying, vertical discharging and the like). Under the combined action of the factors, continuous, controllable and mass production of high-quality graphene is finally realized.
In practical application, the graphite raw material subjected to the full pretreatment can be directly poured into a high-power continuous microwave system, and the rapid dry microwave expansion in the air is realized by monitoring and controlling the microwave power and the temperature, so that the defect-free and ton-grade graphene product is directly obtained. The graphene product can be directly used without subsequent treatment.
In addition, the microwave system for mass production of graphene can realize accurate control of the temperature and the microwave field distribution of the microwave reaction zone, so that the controllable and mass preparation of high-quality graphene with about 3 layers is realized.
The application is further illustrated below with reference to examples. It is to be understood that these examples are illustrative of the present application and are not intended to limit the scope of the present application.
The experimental procedures, which are not specified in the following examples, are generally carried out under conventional conditions or under conditions recommended by the manufacturer.
Unless otherwise indicated, the raw materials and reagents used in the examples of the present application were purchased commercially and used as received. Wherein the particle size of the flake graphite powder is more than 30 mu m, and other raw materials and reagents are all analytically pure.
The analytical instrument used in the examples of the present application is as follows:
transmission electron microscope, JEM-F200, available from Japanese electronics Co; the main parameters are as follows: the dot resolution is 0.19nm and the working voltage is 200kV.
Raman spectrometer, inVia basic, available from ranishao company, england; the main parameters are as follows: the laser wavelength is 532nm, the scanning range is 100-4000cm -1, the laser power is 10%, and the exposure time is 10s.
The graphene preparation processes in the following examples are all carried out by the graphene preparation systems as shown in fig. 1 and 2. Fig. 1 shows a schematic diagram of the overall structure of a graphene preparation system 1. The graphene preparation system 1 consists of a feeding module, a conveying module, a microwave module, a control feedback module and a discharging module. The feed module comprises a vibratory feeder 11; the conveying module comprises a transmission chain plate 21; the microwave module includes: a microwave generator 31 and an exhaust gas outlet 32, the microwave generator 31 providing a microwave irradiation region 311; the control feedback module comprises a control feedback device 51; the outfeed module comprises a suction device 41.
Fig. 2 (a) shows a schematic diagram of the working principle of the drive link plate 21, and fig. 2 (B) shows a schematic perspective diagram of the segment 211 and its constituent drive link plate 21. As shown in fig. 2 (B), the segment 211 may be deformed, which is bent inward in a groove shape in a natural state, and is unfolded in a stressed state. As shown in fig. 2 (a), the driving link plate 21 is circularly driven around two driving shafts 22 and 23, the microwave generator 31 is disposed between the driving shafts 22 and 23, and the vibration feeder 11 and the suction device 41 are disposed near the driving shafts 22 and 23, respectively. When the joint 211 approaches the transmission shaft 22 or 23, the back surface is unfolded due to the acting force from the transmission shaft 22 or 23, so that the modified solid graphite is convenient to be fed through the vibration feeder 11 or the graphene product is convenient to be discharged through the aspirator 41; and the segments 211 are naturally bent inward as they move away from the drive shafts 22 and 23, thereby facilitating the provision of a reactor-type accommodation space for the modified solid graphite to expand as it passes through the microwave generator 31.
Referring to fig. 1 and 2, the vibratory feeder 11 feeds the modified solid graphite onto the drive link plate 21 in a flat state having a thickness of about 5 mm. The drive link plate 21 conveys the modified solid graphite through the microwave irradiation zone 311 generated by the microwave generator 31. The control feedback device 51 monitors the expansion temperature of the modified solid graphite under the irradiation of microwaves in real time, and feeds back the input power of the microwaves to the microwave generator 31 to discharge the generated water vapor and the generated exhaust gas from the exhaust gas outlet 32. The high quality graphene product is fluffy and is finally guided out and collected by the aspirator 41 in the vertical direction.
Example 1
(1) Preparation of modified solid graphite
Chloroform as a nonpolar solvent and ethanol as a polar solvent were mixed at a volume ratio of 1:0.25 at room temperature to obtain a complex solvent. Bromine is used as an intercalator, and the intercalator solution is obtained by mixing the intercalator with the obtained composite solvent in a volume ratio of 4:6.
The resulting intercalation solution is used to pretreat the graphite feedstock. And immersing graphite in the intercalation agent solution according to the volume ratio of the intercalation agent solution to the graphite raw material of 3:1 to obtain a dispersion liquid. The dispersion is filtered and air-dried, wherein the air-dried temperature is 35 ℃ and the air speed is 5L/min.m 2, so as to obtain the modified solid graphite. The solid content of the obtained modified solid graphite was 60% by weight.
(2) Preparation of high quality graphene
The modified solid graphite obtained as described above was sent to the graphene preparation system 1, and the graphene preparation process was performed according to the procedure described above. Wherein the tiling thickness of the modified solid graphite is 1.0mm, the irradiation power of the microwave generator 31 is 18kW, and the transmission speed of the transmission chain plate 21 is 1.0m/min. The graphene product prepared by the method is off-white and fluffy. The expansion ratio of the graphene product is 110 times compared with that of a graphite raw material. The number of layers of the graphene product is 3 as measured by transmission electron microscope characterization. The graphene product has an I D/IG of 0 as measured by raman spectroscopy characterization.
Example 2
(1) Preparation of modified solid graphite
Carbon tetrachloride as a nonpolar solvent and methanol as a polar solvent were mixed at a volume ratio of 1:0.33 at room temperature to obtain a composite solvent. Iodine is used as an intercalation agent, and the intercalation agent solution is obtained by mixing the iodine and the obtained composite solvent in a volume ratio of 3:7.
The resulting intercalation solution is used to pretreat the graphite feedstock. And immersing graphite in the intercalation agent solution according to the volume ratio of the intercalation agent solution to the graphite raw material of 3:1 to obtain a dispersion liquid. The dispersion is filtered and air-dried, wherein the air-dried temperature is 30 ℃ and the air speed is 6L/min.m 2, and the modified solid graphite is obtained. The solid content of the obtained modified solid graphite was 60% by weight.
(2) Preparation of high quality graphene
The modified solid graphite obtained as described above was sent to the graphene preparation system 1, and the graphene preparation process was performed according to the procedure described above. Wherein the tiling thickness of the modified solid graphite is 2.0mm, the irradiation power of the microwave generator 31 is 16kW, and the transmission speed of the transmission chain plate 21 is 3.0m/min. The graphene product prepared by the method is off-white and fluffy. The expansion ratio of the graphene product is 90 times compared with that of a graphite raw material. The number of layers of the graphene product is 3 as measured by transmission electron microscope characterization. The graphene product has an I D/IG of 0 as measured by raman spectroscopy characterization.
Example 3
(1) Preparation of modified solid graphite
Cyclohexane as a nonpolar solvent and water as a polar solvent were mixed at a volume ratio of 1:0.25 at room temperature to obtain a composite solvent. And mixing chlorine serving as an intercalator with the obtained composite solvent in a volume ratio of 1:9 to obtain an intercalator solution.
The resulting intercalation solution is used to pretreat the graphite feedstock. And immersing graphite in the intercalation agent solution according to the volume ratio of the intercalation agent solution to the graphite raw material of 3:1 to obtain a dispersion liquid. The dispersion is filtered and air-dried, wherein the air-dried temperature is 50 ℃ and the air speed is 4L/min.m 2, and the modified solid graphite is obtained. The solid content of the obtained modified solid graphite was 50% by weight.
(2) Preparation of high quality graphene
The modified solid graphite obtained as described above was sent to the graphene preparation system 1, and the graphene preparation process was performed according to the procedure described above. Wherein the tiling thickness of the modified solid graphite is 2.0mm, the irradiation power of the microwave generator 31 is 20kW, and the transmission speed of the transmission chain plate 21 is 3.0m/min. The graphene product prepared by the method is gray black and fluffy. The expansion ratio of the graphene product is 80 times compared with that of a graphite raw material. The number of layers of the graphene product is 4 as measured by transmission electron microscope characterization. The graphene product was found to have an I D/IG of 0.03 as determined by raman spectroscopy characterization.
Example 4
(1) Preparation of modified solid graphite
At room temperature, n-hexane as a nonpolar solvent and propanol as a polar solvent are mixed in a volume ratio of 1:0.1 to obtain a composite solvent. And mixing sulfur serving as an intercalator with the obtained composite solvent in a volume ratio of 1:9 to obtain an intercalator solution.
The resulting intercalation solution is used to pretreat the graphite feedstock. And immersing graphite in the intercalation agent solution according to the volume ratio of the intercalation agent solution to the graphite raw material of 3:1 to obtain a dispersion liquid. The dispersion is filtered and air-dried, wherein the air-dried temperature is 35 ℃ and the air speed is 5L/min.m 2, so as to obtain the modified solid graphite. The solid content of the obtained modified solid graphite was 60% by weight.
(2) Preparation of high quality graphene
The modified solid graphite obtained as described above was sent to the graphene preparation system 1, and the graphene preparation process was performed according to the procedure described above. Wherein the tiling thickness of the modified solid graphite is 30mm, the irradiation power of the microwave generator 31 is 35kW, and the transmission speed of the transmission chain plate 21 is 1.0m/min. The graphene product prepared by the method is gray black and fluffy. The expansion ratio of the graphene product is 70 times compared with that of a graphite raw material. The number of layers of the graphene product is 5 as measured by transmission electron microscopy characterization. The graphene product was found to have an I D/IG of 0.05 as determined by raman spectroscopy characterization.
Example 5
(1) Preparation of modified solid graphite
Petroleum ether as a nonpolar solvent and isopropanol as a polar solvent are mixed at room temperature in a volume ratio of 1:0.25 to obtain a composite solvent. Bromine is used as an intercalating agent, and the intercalating agent solution is obtained by mixing the bromine with the obtained composite solvent in a volume ratio of 9:1.
The resulting intercalation solution is used to pretreat the graphite feedstock. And immersing graphite in the intercalation agent solution according to the volume ratio of the intercalation agent solution to the graphite raw material of 9:1 to obtain a dispersion liquid. The dispersion is filtered and air-dried, wherein the air-dried temperature is 60 ℃ and the air speed is 5L/min.m 2, so as to obtain the modified solid graphite. The solid content of the obtained modified solid graphite was 80% by weight.
(2) Preparation of high quality graphene
The modified solid graphite obtained as described above was sent to the graphene preparation system 1, and the graphene preparation process was performed according to the procedure described above. Wherein the tiling thickness of the modified solid graphite is 50mm, the irradiation power of the microwave generator 31 is 50kW, and the transmission speed of the transmission chain plate 21 is 0.1m/min. The graphene product prepared by the method is off-white and fluffy. The expansion ratio of the graphene product is 90 times compared with that of a graphite raw material. The number of layers of the graphene product is 3 as measured by transmission electron microscope characterization. The graphene product has an I D/IG of 0 as measured by raman spectroscopy characterization.
Example 6
(1) Preparation of modified solid graphite
Chloroform as a nonpolar solvent and ethanol as a polar solvent were mixed at a volume ratio of 1:0.33 at room temperature to obtain a complex solvent. Bromine is used as an intercalating agent, and the intercalating agent solution is obtained by mixing the bromine with the obtained composite solvent in a volume ratio of 9:1.
The resulting intercalation solution is used to pretreat the graphite feedstock. And immersing graphite in the intercalation agent solution according to the volume ratio of the intercalation agent solution to the graphite raw material of 5:1 to obtain a dispersion liquid. The dispersion is filtered and air-dried, wherein the air-dried temperature is 35 ℃ and the air speed is 5L/min.m 2, so as to obtain the modified solid graphite. The solid content of the obtained modified solid graphite was 80% by weight.
(2) Preparation of high quality graphene
The modified solid graphite obtained as described above was sent to the graphene preparation system 1, and the graphene preparation process was performed according to the procedure described above. Wherein the tiling thickness of the modified solid graphite is 20mm, the irradiation power of the microwave generator 31 is 45kW, and the transmission speed of the transmission chain plate 21 is 10m/min. The graphene product prepared by the method is gray black and fluffy. The expansion ratio of the graphene product is 70 times compared with that of a graphite raw material. The number of layers of the graphene product is 5 as measured by transmission electron microscopy characterization. The graphene product was found to have an I D/IG of 0.04 as determined by raman spectroscopy characterization.
Example 7
(1) Preparation of modified solid graphite
Carbon tetrachloride as a nonpolar solvent and water as a polar solvent are mixed at a volume ratio of 1:0.33 at room temperature to obtain a composite solvent. Bromine is used as an intercalator, and the intercalator solution is obtained by mixing the intercalator with the obtained composite solvent in a volume ratio of 1:10.
The resulting intercalation solution is used to pretreat the graphite feedstock. And immersing graphite in the intercalation agent solution according to the volume ratio of the intercalation agent solution to the graphite raw material of 10:1 to obtain a dispersion liquid. The dispersion is filtered and air-dried, wherein the air-dried temperature is 35 ℃ and the air speed is 5L/min.m 2, so as to obtain the modified solid graphite. The solid content of the obtained modified solid graphite was 40% by weight.
(2) Preparation of high quality graphene
The modified solid graphite obtained as described above was sent to the graphene preparation system 1, and the graphene preparation process was performed according to the procedure described above. Wherein the tiling thickness of the modified solid graphite is 15mm, the irradiation power of the microwave generator 31 is 25kW, and the transmission speed of the transmission chain plate 21 is 8.0m/min. The graphene product prepared by the method is off-white and fluffy. The expansion ratio of the graphene product is 100 times compared with that of a graphite raw material. The number of layers of the graphene product is 3 as measured by transmission electron microscope characterization. The graphene product has an I D/IG of 0 as measured by raman spectroscopy characterization.
Example 8
(1) Preparation of modified solid graphite
Petroleum ether as a nonpolar solvent and methanol as a polar solvent are mixed at a volume ratio of 1:0.25 at room temperature to obtain a composite solvent. Mixing iodine and bromine serving as intercalators with the obtained composite solvent in a volume ratio of 2:8 to obtain an intercalator solution.
The resulting intercalation solution is used to pretreat the graphite feedstock. And immersing graphite in the intercalation agent solution according to the volume ratio of the intercalation agent solution to the graphite raw material of 3:1 to obtain a dispersion liquid. The dispersion is filtered and air-dried, wherein the air-dried temperature is 35 ℃ and the air speed is 5L/min.m 2, so as to obtain the modified solid graphite. The solid content of the obtained modified solid graphite was 60% by weight.
(2) Preparation of high quality graphene
The modified solid graphite obtained as described above was sent to the graphene preparation system 1, and the graphene preparation process was performed according to the procedure described above. Wherein the tiling thickness of the modified solid graphite is 0.1mm, the irradiation power of the microwave generator 31 is 13kW, and the transmission speed of the transmission chain plate 21 is 6.0m/min. The graphene product prepared by the method is off-white and fluffy. The expansion ratio of the graphene product is 100 times compared with that of a graphite raw material. The number of layers of the graphene product is 3 as measured by transmission electron microscope characterization. The graphene product has an I D/IG of 0 as measured by raman spectroscopy characterization.
Example 9
(1) Preparation of modified solid graphite
Chloroform was used as a nonpolar solvent as a single solvent at room temperature. Bromine is used as an intercalating agent, and chloroform, which is a nonpolar solvent, is mixed in a volume ratio of 2:8 to obtain an intercalating agent solution.
The resulting intercalation solution is used to pretreat the graphite feedstock. And immersing graphite in the intercalation agent solution according to the volume ratio of the intercalation agent solution to the graphite raw material of 6:1 to obtain a dispersion liquid. The dispersion is filtered and air-dried, wherein the air-dried temperature is 35 ℃ and the air speed is 5L/min.m 2, so as to obtain the modified solid graphite. The solid content of the obtained modified solid graphite was 60% by weight.
(2) Preparation of high quality graphene
The modified solid graphite obtained as described above was sent to the graphene preparation system 1, and the graphene preparation process was performed according to the procedure described above. Wherein the tiling thickness of the modified solid graphite is 1.0mm, the irradiation power of the microwave generator 31 is 18kW, and the transmission speed of the transmission chain plate 21 is 1.0m/min. The graphene product prepared by the method is off-white and fluffy. The expansion ratio of the graphene product is 110 times compared with that of a graphite raw material. The number of layers of the graphene product is 3 as measured by transmission electron microscope characterization. The graphene product has an I D/IG of 0 as measured by raman spectroscopy characterization.
Example 10
(1) Preparation of modified solid graphite
Bromine was used as an intercalating agent at room temperature, and was used as it is without mixing with a solvent.
The graphite raw material is pretreated with bromine as an intercalating agent. And immersing graphite in the intercalating agent bromine according to the volume ratio of the intercalating agent to the graphite raw material of 2:1 to obtain a dispersion liquid. The dispersion is filtered and air-dried, wherein the air-dried temperature is 35 ℃ and the air speed is 5L/min.m 2, so as to obtain the modified solid graphite. The solid content of the obtained modified solid graphite was 60% by weight.
(2) Preparation of high quality graphene
The modified solid graphite obtained as described above was sent to the graphene preparation system 1, and the graphene preparation process was performed according to the procedure described above. Wherein the tiling thickness of the modified solid graphite is 1.0mm, the irradiation power of the microwave generator 31 is 20kW, and the transmission speed of the transmission chain plate 21 is 1.0m/min. The graphene product prepared by the method is off-white and fluffy. The expansion ratio of the graphene product is 108 times compared with that of a graphite raw material. The number of layers of the graphene product is 3 as measured by transmission electron microscope characterization. The graphene product has an I D/IG of 0 as measured by raman spectroscopy characterization.
Comparative example 1
Samples were prepared according to the same procedure as in example 1, except that the intercalation solution was mixed with the graphite starting material at a volume ratio of 1:9, the resulting modified solid graphite had a solids content of 98wt%, the resulting graphene product had an expansion ratio of 30 times as compared to the graphite starting material, the number of layers of the graphene product was 10 or more as determined by transmission electron microscopy characterization, and the I D/IG of the graphene product was 0.46 as determined by raman spectroscopy characterization.
Comparative example 2
Samples were prepared according to the same procedure as in example 1, except that the lay-flat thickness of the modified solid graphite was 60mm, the expansion ratio of the obtained graphene product was 40 times as compared with the graphite raw material, the number of layers of the graphene product was 10 as measured by transmission electron microscopy characterization, and the I D/IG of the graphene product was 0.14 as measured by raman spectroscopy characterization.
Comparative example 3
Samples were prepared in the same manner as in example 1, except that the air-drying temperature was 105℃and the air speed was 20L/min.m 2, the solid content of the obtained modified solid graphite was 95% by weight, the expansion ratio of the obtained graphene product was 25 times as compared with the graphite raw material, the number of layers of the graphene product was 10 or more as determined by transmission electron microscopy characterization, and the I D/IG of the graphene product was 0.68 as determined by Raman spectroscopy.
Comparative example 4
Samples were prepared in the same manner as in example 1, except that the air-dried temperature was 20℃and the air speed was 0.5L/min.m 2, the solid content of the obtained modified solid graphite was 93% by weight, the expansion ratio of the obtained graphene product was 28 times as compared with the graphite raw material, the number of layers of the graphene product was 10 or more as determined by transmission electron microscopy characterization, and the I D/IG of the graphene product was 0.61 as determined by Raman spectroscopy characterization.
The above description is only a few examples of the present application and is not intended to limit the present application in any way. While the application has been described in terms of preferred embodiments, these embodiments are not intended to limit the application. Any person skilled in the art, using the disclosure of the present application, may make some changes or modifications equivalent to the equivalent embodiments without departing from the scope of the present application.
Claims (9)
1. A method of preparing graphene, comprising:
a) Mixing graphite raw materials with an intercalator solution, performing ultrasonic dispersion and standing to obtain a colloid dispersion;
the graphite raw material is selected from natural graphite;
the natural graphite comprises natural crystalline flake graphite and soil-like graphite;
the grain diameter of the natural crystalline flake graphite is more than or equal to 10 mu m;
The intercalating agent solution comprises an intercalating agent and a solvent;
The volume ratio of the intercalation agent solution to the graphite raw material is 1:1-10:1;
The volume ratio of the intercalation agent to the solvent is 1:1-1:9;
the intercalation agent is at least one of nonpolar simple substance molecular iodine, bromine and chlorine;
the solvent comprises a nonpolar solvent and a polar solvent;
The nonpolar solvent is at least one selected from cyclohexane, n-hexane, petroleum ether, chloroform and carbon tetrachloride;
the polar solvent is at least one selected from water, methanol, ethanol and isopropanol;
the volume ratio of the nonpolar solvent to the polar solvent is 1:0.001-0.33;
The standing time is 2-10 h; the ultrasonic time is 10-120 min;
b) Filtering the colloid dispersion liquid, and drying filtrate to obtain modified solid graphite;
The solid content of the modified solid graphite is 40-80 wt%;
The drying is performed at a controlled and adjustable temperature and wind speed;
the controlled and adjustable temperature is 30-60 ℃, and the controlled and adjustable wind speed is 4-6L/min m 2;
c) Expanding the modified solid graphite in a tiled state through a microwave irradiation region in a microwave field to obtain the graphene;
The tiling thickness of the modified solid graphite is 0.1-50 mm;
the passing rate of the modified solid graphite is 0.1-10 m/min;
The power of the microwaves is 4-25 kW;
Monitoring the expansion temperature of the modified solid graphite in the microwave field in real time, and adjusting the input power of microwaves to ensure that the microwave field is uniformly distributed in a reaction zone;
Removing water vapor and exhaust gas generated by expansion of the modified solid graphite in the microwave field so as to reduce the surface oxygen content and defects of the graphene;
the volume expansion of the graphene relative to the graphite raw material is 70-110 times;
The number of layers of the graphene is less than or equal to 5;
the ratio I D/IG of the intensity of the D peak to the intensity of the G peak of the graphene in the Raman spectrum is less than or equal to 0.03;
The method is implemented by a system comprising a feeding module, a conveying module, a microwave module, a control feedback module and a discharging module; wherein:
the feed module is configured such that the modified solid graphite is input onto the delivery module in a continuous quantitative state; the feeding module comprises an automatic feeding machine;
The conveying module is configured to enable the modified solid graphite to stably and uniformly pass through the microwave module to reach the discharging module; the conveying module comprises a transmission chain plate, wherein the transmission chain plate consists of a plurality of mutually connected joint blocks; the segments are configured to bend inwards to be groove-shaped in a natural state to provide an accommodating space for the expansion of the modified solid graphite, and to be unfolded to match with feeding or discharging in a stress state;
the microwave module is configured to provide a power-controllable microwave input such that the microwave field is formed in a reaction zone and such that the modified solid graphite expands rapidly as it passes through a microwave irradiation zone in the microwave field;
the microwave module further comprises a degassing device comprising means for allowing water vapor and exhaust gases to leave or a scrubbing device for capturing water vapor and exhaust gases;
the control feedback module is configured to provide real-time temperature measurement and feedback, and adjust microwave power so that the microwave field is uniformly distributed in a reaction zone;
The discharging module comprises a sucker, wherein the sucker is configured to collect graphene in a vertical guiding-out manner;
The length of the microwave field is 1-3 m;
the microwave field is carried out directly in air without setting a protective atmosphere.
2. The method of claim 1, wherein the step of determining the position of the substrate comprises,
The number of layers of the graphene is 1-3;
the volume expansion of the graphene relative to the graphite raw material is 90-110 times.
3. The method according to claim 1, wherein the graphene has a D-peak to G-peak intensity ratio I D/IG = 0 in raman spectroscopy.
4. The method of claim 1, wherein the volume ratio of the non-polar solvent to the polar solvent is 1:0.001-0.25.
5. The method of claim 1, wherein the volume ratio of the non-polar solvent to the polar solvent is 1:0.001-0.1.
6. The method of claim 1, wherein the volume ratio of the intercalating agent to the solvent is 1:4-9.
7. The method of claim 1, wherein the volume ratio of the intercalation solution to the graphite starting material is 3-9:1;
The grain diameter of the natural crystalline flake graphite is more than or equal to 50 mu m.
8. The method of claim 1, wherein the controlled and adjustable temperature is 35-60 ℃ and the controlled and adjustable wind speed is 4-5L/min-m 2.
9. The method of claim 1, wherein the modified solid graphite has a flat thickness of 1.0 to 30 mm a; the passing rate of the modified solid graphite is 1.0-6.0 m/min; the power of the microwaves is 10-25 kW.
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