Method and device for preparing graphene based on chemical bubble coupling ultrasonic efficient stripping

Abstract

The invention discloses a method and device for preparing graphene based on chemical bubble coupling ultrasonic efficient stripping, and relates to the technical field of graphene preparation. Hydrogen peroxide is heated, chemical nano bubbles are generated through chemical reaction, and the multi-physical-field synergistic effect of the ultrasonic cavitation effect is coupled, so that the graphene is prepared. After bubble expansion intercalation and pre-stripping are carried out on flake graphite layers through bubbles, local high-pressure shock waves are generated through ultrasonic cavitation, Van der Waals force of graphite molecular bonds is destroyed through cavitation force, and the graphene stripping efficiency is remarkably improved through chemical-multi-physical field cooperation and cyclic stripping. Efficient stripping and controllable layer number of graphene are realized, continuous production can be realized, and the method has important significance on continuous production of graphene preparation and development of a large-scale technology.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of graphene preparation, and particularly relates to a method for preparing graphene by high-efficiency exfoliation based on chemical bubble coupling ultrasonic waves and a device thereof. BACKGROUND

[0002] At present, graphene is mainly prepared by exfoliation technology, and the existing graphene exfoliation technology mainly has the following defects and technical problems: ① the traditional mechanical exfoliation method has the problems of low exfoliation efficiency and uneven layer number; ② the traditional Hummers chemical oxidation method uses strong acid and strong base, and has the problems of serious environmental pollution, many product defects, and difficult layer number control; ③ the chemical vapor deposition method has the problems of complex process and high energy consumption; ④ the pure ultrasonic exfoliation method has the problems of high energy consumption, low exfoliation efficiency, and easy structure damage; and the existing single physical exfoliation technology cannot effectively destroy the van der Waals force between the graphite layers, resulting in unsatisfactory exfoliation effect, low yield, and high difficulty in continuous production. Therefore, it is necessary to improve the existing graphene exfoliation technology, and develop a graphene exfoliation technology with high exfoliation efficiency, low energy consumption, green and pollution-free, and continuous production. SUMMARY

[0003] Therefore, based on the above background, the present application provides a method for preparing graphene by high-efficiency exfoliation based on chemical bubble coupling ultrasonic waves and a device thereof. The present application generates chemical nanobubbles by heating hydrogen peroxide solution, and uses the multi-physical field synergy of chemical reaction and coupling ultrasonic cavitation effect. The interlayer of flake graphite is expanded and intercalated by the nanobubbles generated by the heated hydrogen peroxide solution, and then the graphite molecular bond van der Waals force is destroyed by the cavitation force generated by the local high pressure shock wave generated by the multi-stage cavitation of ultrasonic waves. The graphene exfoliation efficiency is significantly improved by chemical-multiple physical field synergy and multiple cycle exfoliation, the graphene is efficiently exfoliated and the layer number is controllable, and the continuous production can be realized. The present application has important significance for the development of continuous production and large-scale technology of graphene preparation.

[0004] The technical scheme provided by the present application is as follows: A method for preparing graphene by high-efficiency exfoliation based on chemical bubble coupling ultrasonic waves, comprising the following steps: S1: configuring a slurry with flake graphite, hydrogen peroxide solution and hydrophilic dispersant; S2: heating the slurry of step S1 to decompose hydrogen peroxide to generate micro-nano O2 / H2O bubbles; S3: sequentially treating the slurry containing O2 / H2O bubbles in step S2 with ultrasonic waves of different frequencies; S4: performing secondary mechanical exfoliation on the slurry after ultrasonic treatment in step S3 by high-pressure homogenization.

[0005] Further, it further comprises a step S5: performing at least one cycle of steps S2 to S4 on the slurry after the secondary mechanical stripping of step S4.

[0006] Further, the mass concentration of the hydrogen peroxide in step S1 is 3% to 30%.

[0007] Further, the flake graphite in step S1 is selected from flake graphite with a particle size of 200 to 6000 mesh and a purity of 4N, and the mass ratio of the flake graphite to the hydrogen peroxide is 1: (25-60).

[0008] Further, the temperature of the slurry in step S2 is controlled at 40-90℃.

[0009] Further, step S3 is sequentially subjected to ultrasonic treatment of 3-6 different frequencies, and the ultrasonic frequencies are sequentially from large to small, and the frequency difference of adjacent ultrasonic frequencies is greater than or equal to 10 kHz.

[0010] Based on the same inventive concept, the application further provides a graphene preparation device, which comprises a batching tank, a reaction kettle, one or more ultrasonic reaction kettles, a high-pressure homogenizer, a heat exchanger and a circulating slurry buffer tank, and the ultrasonic reaction kettles are connected in series through pipelines. The batching tank is connected with the reaction kettle through a pipeline, and the materials in the batching tank are transported to the reaction kettle through the pipeline for treatment. The reaction kettle is connected with the first ultrasonic reaction kettle through a pipeline, and the materials in the reaction kettle are transported to the first ultrasonic reaction kettle through the pipeline for treatment. The last ultrasonic reaction kettle is connected with the high-pressure homogenizer through a pipeline, and the materials in the last ultrasonic reaction kettle are transported to the high-pressure homogenizer for treatment. The high-pressure homogenizer is connected with the heat exchanger, and the heat exchanger is connected with the circulating slurry buffer tank.

[0011] Further, a first return pipe is arranged between the circulating slurry buffer tank and the batching tank, and the materials in the circulating slurry buffer tank are transported to the batching tank through the first return pipe.

[0012] Further, a second return pipe is arranged on the first return pipe, one end of the second return pipe is connected with the reaction kettle, and the materials in the circulating slurry buffer tank are transported to the reaction kettle through the second return pipe for treatment.

[0013] Further, the ultrasonic reaction kettle comprises a kettle body, and an ultrasonic vibration rod is arranged in the kettle cavity of the kettle body.

[0014] The application has the following beneficial effects: The present application first constructs a chemical-physical field synergistic peeling mechanism, uses micro-bubbles generated by the thermal decomposition of hydrogen peroxide and the cavitation explosion effect in the ultrasonic field to realize the directional intercalation and tearing of graphite interlayers and achieve the effect of efficient peeling of graphene: the present application first uses the bubbles generated by the chemical decomposition reaction of hydrogen peroxide to swell and intercalate and pre-peel the flake graphite in the slurry, then combines the vibration cavitation effect of multi-stage ultrasonic waves to cavitate and explode the flake graphite, uses the swelling intercalation and cavitation force to effectively destroy the van der Waals force of the graphite molecular bond, constructs the synergistic mechanism of bubble swelling-explosion and ultrasonic cavitation shock wave to generate high-frequency shear force, significantly improves the peeling efficiency of graphene through chemical-multiple physical field synergy and cyclic peeling, compared with the peeling by using ultrasonic waves alone, not only has high yield, but also has low defect rate of the prepared graphene and low energy consumption. The present application realizes the controllable number of layers of graphene by using a cyclic treatment process to perform controllable cyclic peeling treatment on the slurry, and the slurry is subjected to swelling intercalation and cavitation explosion peeling for multiple times.

[0015] The peeling preparation process of the graphene of the present application is carried out under low-temperature and normal-pressure conditions, the conditions are easy to control, the cost is low, and the whole process uses hydrogen peroxide as an environmentally friendly solvent, no strong acid or strong base is added, and the COD value of the wastewater is very low, which is green, environmentally friendly, low-carbon and energy-saving.

[0016] The graphene prepared by the present application has high quality, and after the slurry is subjected to 5 cycles, the proportion of the prepared graphene with 1-5 layers is ≥80%, and the defect density is ≤5%.

[0017] The device of the present application can realize continuous production, and further improve the production efficiency of graphene. BRIEF DESCRIPTION OF DRAWINGS

[0018] ATTACHMENT Figure 1 The left drawing is the untreated flake graphite raw material, which has a two-dimensional multi-layer tight molecular structure; the right drawing is the graphite after being treated by the chemical bubble coupling ultrasonic wave, the bubble particles are intercalated into the two-dimensional graphene intermolecular loose molecular structure, and the blue beads are the intercalated bubble particles, which are intercalated into the graphene intermolecular and coupled with the molecular covalent bond to support the intercalation force to peel the two-dimensional graphene layers.

[0019] ATTACHMENT Figure 2 The drawing is the device structure diagram of the present application for efficiently preparing graphene based on chemical bubble coupling ultrasonic wave.

[0020] ATTACHMENT Figure 3 The drawing is the structure diagram of the ultrasonic reaction kettle of the present application.

[0021] ATTACHMENT Figure 4Microstructure electron microscope images of graphene prepared for different cycle times of the embodiment of the present application, wherein Figure 4 A is 5000 mesh raw material flake graphite; Figure 4 B is graphene prepared for 3 cycles; Figure 4 C is graphene prepared for 5 cycles; Figure 4 D is graphene prepared for 7 cycles.

[0022] In the drawing, 1 is a batching tank; 2 is a reaction kettle; 3 is an ultrasonic reaction kettle; 4 is a high-pressure homogenizer; 5 is a heat exchanger; 6 is a circulating slurry buffer tank; 7 is a homogenizer; 8 is a diaphragm pump; 9 is a first return pipe; 10 is a second return pipe; 110 is a product buffer tank. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical scheme and advantages of the embodiment of the present application clearer, the technical scheme in the embodiment of the present application will be described clearly and completely below in combination with the embodiment of the present application. Obviously, the described embodiment is a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiment in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0024] The materials, reagents and the like used in the following embodiments can be obtained from commercial channels unless otherwise specified.

[0025] In combination with Figure 1 the principle diagram, the technical scheme of the present application is as follows: A method for preparing graphene based on chemical bubble coupling ultrasonic high-efficiency peeling, comprising the following steps: S1: stirring and configuring slurry in a batching tank with 4N purity flake graphite, hydrogen peroxide solution and hydrophilic dispersant; The concentration of hydrogen peroxide used in this step is 3% to 30%, and the particle size of flake graphite is 200 to 6000 mesh; the mass ratio of flake graphite to hydrogen peroxide is 1: (25-60).

[0026] The hydrophilic dispersant uses 0.3wt% hydroxypropyl cellulose water dispersion, and the amount of addition is 0.5-1.5wt% of the amount of slurry.

[0027] S2: heating the slurry of step S1 to promote the decomposition of hydrogen peroxide to produce micro-nano O2 / H2O bubbles; Specifically, the stirring speed can be controlled by a stirrer to make the decomposition of hydrogen peroxide to produce micro-nano O2 / H2O bubbles; The temperature of the slurry in this step is controlled at 40-90℃.

[0028] S3: The slurry containing O2 / H2O bubbles in step S2 is sequentially subjected to ultrasonic treatment at 3-6 different frequencies; The ultrasonic frequencies are sequentially from large to small, and the frequency difference of adjacent ultrasonic frequencies is ≥10 kHz.

[0029] S4: The slurry after ultrasonic treatment in step S3 is subjected to high-pressure homogenization treatment at 50-200 MPa, secondary mechanical exfoliation, and cooling of the slurry, with the temperature of the slurry controlled at 40℃±1℃.

[0030] S5: The cooled slurry after secondary mechanical exfoliation in step S4 is subjected to steps S2-S4 for 3-6 cycles.

[0031] Example 1: A graphene preparation device, comprising a batching tank 1, a reaction kettle 2, four ultrasonic reaction kettles 3, a high-pressure homogenizer 4, a heat exchanger 5, and a circulating slurry buffer tank 6, wherein the ultrasonic reaction kettles 3 are connected in series through pipes; the batching tank is provided with a stirrer, and the reaction kettle is provided with a stirrer.

[0032] The batching tank 1 is connected to the reaction kettle 2 through a pipe, and the material in the batching tank 1 is transported to the reaction kettle 2 for treatment; specifically, there can be another embodiment as shown in Figure 2 The batching tank 1 and the reaction kettle 2 are provided with a homogenizer 7, and the slurry in the batching tank is transported to the homogenizer 7 for homogenization and emulsification pretreatment, and then transported to the reaction kettle for treatment.

[0033] The reaction kettle is provided with an electromagnetic heating coil, and the reaction kettle is provided with a PID temperature control module, which controls the temperature accuracy of the slurry in the reaction kettle to be within 2℃ by controlling the electromagnetic heating coil.

[0034] The reaction kettle 2 is connected to the first ultrasonic reaction kettle 3 through a pipe, and the material in the reaction kettle 2 is transported to the first ultrasonic reaction kettle 3 for treatment; the material in the first ultrasonic reaction kettle 3 is transported to the second ultrasonic reaction kettle 3 through a pipe, and so on, until the material is transported to the last ultrasonic reaction kettle 3; the last ultrasonic reaction kettle 3 is connected to the high-pressure homogenizer 4 through a pipe, and the material in the last ultrasonic reaction kettle 3 is transported to the high-pressure homogenizer 4 for treatment; The high-pressure homogenizer 4 is connected to the heat exchanger 5, and the heat exchanger 5 is connected to the circulating slurry buffer tank 6. Specifically, the heat exchanger 5 is a plate heat exchanger, and the refrigerant is chilled water with a temperature of 5℃±1℃.

[0035] The first return pipe 9 is arranged between the circulating slurry buffer tank 6 and the batching tank 1, and the material in the circulating slurry buffer tank 6 is transported to the batching tank 1 through the first return pipe 9. The circulating slurry buffer tank is connected with the product buffer tank 110 through a pipeline, and the material in the circulating slurry buffer tank 6 can be transported to the product buffer tank for buffering.

[0036] The second return pipe 100 is arranged on the first return pipe 9, one end of the second return pipe 100 is connected with the reaction kettle 2, and the material in the circulating slurry buffer tank 6 is transported to the reaction kettle 2 for treatment through the second return pipe 100.

[0037] The ultrasonic reaction kettle 3 comprises a kettle body 31, an ultrasonic vibration rod 32 is arranged in the kettle cavity of the kettle body 31, and an electromagnetic heating coil 33 is additionally arranged outside the kettle body 31. The ultrasonic vibration rod can control ultrasonic waves of 20-100 kHz.

[0038] In specific application, the pipeline between the reaction kettle, the ultrasonic reaction kettle and each material tank can be installed with a diaphragm pump 8 for material transportation, which is a conventional technology and will not be described here.

[0039] Example 2: combined with the principle of Figure 1 the device of example 1 based on chemical bubble coupling ultrasonic high-efficiency stripping to prepare graphene, comprising the following steps: S1: 20 kg of flake graphite with an average particle size of 5000 mesh and 3 wt% hydrogen peroxide solution are put into the batching tank according to a mass ratio of 1:25 to prepare slurry, 0.3 wt% hydroxypropyl cellulose aqueous dispersion is added to the batching tank at a total amount of 1.5 wt%, and then the slurry is stirred and configured, and then the slurry is transported to the homogenizer for homogenization and emulsification pretreatment at 6000 rpm through the pneumatic diaphragm pump; The hydroxypropyl cellulose used in this example and the following examples and comparative examples has a CAS number of 9004-64-2; S2: The slurry after homogenization and emulsification pretreatment is transported to the reaction kettle with an electromagnetic heating coil, the temperature of the slurry in the reaction kettle is controlled at 65±0.5℃ through heating, and maintained for 30 min to promote the decomposition of hydrogen peroxide to generate micro-nano O2 / H2O bubbles; in specific application, the air pressure power of the diaphragm pump for transporting the material in this step is (0.2-0.5) MPa.

[0040] S3: The slurry containing O2 / H2O bubbles in step S2 is sequentially delivered into four ultrasonic reaction kettles (four-stage reaction kettles) for treatment. After the treatment of four-stage different frequency ultrasonic waves, the four ultrasonic reaction kettles control the frequency of the ultrasonic waves by ultrasonic heating rods in turn as 80 kHz, 60 kHz, 40 kHz and 20 kHz, and the ultrasonic power density is 5 W / cm³. The total treatment time of the four ultrasonic reaction kettles is 45 min. Specifically, for example, 80 KZ ultrasonic treatment for 10 min, 60 KZ ultrasonic treatment for 10 min, 40 KZ ultrasonic treatment for 10 min, and 20 KZ ultrasonic treatment for 15 min.

[0041] S4: The slurry after the ultrasonic treatment in step S3 is delivered to a high-pressure homogenizer for high-pressure homogenization treatment at a pressure of 120 MPa for secondary mechanical exfoliation. The slurry after the high-pressure homogenizer treatment is cooled to 35°C by a heat exchanger. S5: The slurry after the secondary mechanical exfoliation and cooling in step S4 is subjected to steps S2 to S4 for 4 cycles to obtain a graphene dispersion liquid. Specifically: The slurry after the secondary mechanical exfoliation and cooling in step S4 is heated, and the temperature of the slurry is controlled at 65±0.5°C for 30 min to promote the decomposition of hydrogen peroxide to generate micro-nano O2 / H2O bubbles. Then the slurry is sequentially delivered into four ultrasonic reaction kettles (four-stage reaction kettles) for treatment. After the treatment of four-stage different frequency ultrasonic waves, the four ultrasonic reaction kettles control the frequency of the ultrasonic waves by ultrasonic heating rods in turn as 80 kHz, 60 kHz, 40 kHz and 20 kHz, and the ultrasonic power density is 5 W / cm³. The total treatment time of the four ultrasonic reaction kettles is 45 min. Then the slurry after the ultrasonic treatment is delivered to a high-pressure homogenizer for high-pressure homogenization treatment at a pressure of 120 MPa for secondary mechanical exfoliation. This is a first cycle, and the cycle is continued for 4 times. A total of 5 heating bubble pre-exfoliation, 5 ultrasonic exfoliation and 5 secondary mechanical exfoliation are carried out. A total of 5 cycles are carried out to finally prepare a graphene dispersion liquid.

[0042] Example 3: Based on the principle of Figure 1 Example 1, this embodiment uses the device to prepare graphene based on chemical bubble coupling ultrasonic high-efficiency exfoliation, including the following steps: S1: According to the mass ratio of 1:25, 20 kg of flake graphite with an average particle size of 5000 mesh and 3 wt% hydrogen peroxide solution are put into a batching tank. After adding 0.3 wt% hydroxypropyl cellulose water dispersion solution accounting for 1.5 wt% of the total slurry amount in the batching tank, the slurry is stirred and configured. Then the slurry is delivered to a homogenizer for homogenization and emulsification pretreatment at 6000 rpm by a pneumatic diaphragm pump. S2: The slurry after the homogenization and emulsification pretreatment is transported to a reaction kettle with an electromagnetic heating coil. The temperature of the slurry is controlled at 65±0.5℃ by heating the slurry in the reaction kettle for 30 min, so as to promote the decomposition of hydrogen peroxide to generate micro-nano O2 / H2O bubbles. In this step, the air pressure power (0.2-0.5 MPa) of the diaphragm pump for transporting the material.

[0043] S3: The slurry containing O2 / H2O bubbles in step S2 is sequentially transported to four ultrasonic reaction kettles (four-stage reaction kettles) for treatment. After the treatment of ultrasonic waves with different frequencies in four stages, the frequencies of the ultrasonic waves in the four ultrasonic reaction kettles are controlled by an ultrasonic heating rod to be 80 kHz, 60 kHz, 40 kHz and 20 kHz in sequence, and the ultrasonic power density is 5 W / cm³. The total treatment time of the four ultrasonic reaction kettles is 45 min. Specifically, for example, the treatment time of 80KZ ultrasonic wave is 10 min, the treatment time of 60KZ ultrasonic wave is 10 min, the treatment time of 40KZ ultrasonic wave is 10 min, and the treatment time of 20KZ ultrasonic wave is 15 min.

[0044] S4: The slurry after the ultrasonic treatment in step S3 is transported to a high-pressure homogenizer for high-pressure homogenization treatment under a pressure of 120 MPa for secondary mechanical exfoliation. The slurry after the treatment of the high-pressure homogenizer is cooled to 35℃ by a heat exchanger. S5: The slurry after the secondary mechanical exfoliation and cooling in step S4 is subjected to steps S2 to S4 for 2 cycles to obtain a graphene dispersion liquid. Specifically: The slurry after the secondary mechanical exfoliation and cooling in step S4 is heated, and the temperature of the slurry is controlled at 65±0.5℃ for 30 min to promote the decomposition of hydrogen peroxide to generate micro-nano O2 / H2O bubbles. Then, the slurry is sequentially transported to four ultrasonic reaction kettles (four-stage reaction kettles) for treatment. After the treatment of ultrasonic waves with different frequencies in four stages, the frequencies of the ultrasonic waves in the four ultrasonic reaction kettles are controlled by an ultrasonic heating rod to be 80 kHz, 60 kHz, 40 kHz and 20 kHz in sequence, and the ultrasonic power density is 5 W / cm³. The total treatment time of the four ultrasonic reaction kettles is 45 min. Then, the slurry after the ultrasonic treatment is transported to a high-pressure homogenizer for high-pressure homogenization treatment under a pressure of 120 MPa for secondary mechanical exfoliation. The above is a first cycle. The cycle is continued for 2 times. A total of 3 heating bubble pre-exfoliation, 3 ultrasonic exfoliation and 3 secondary mechanical exfoliation are carried out. A total of 3 cycles are carried out. Finally, a graphene dispersion liquid is prepared.

[0045] Example 4: Based on the principle of Figure 1 , this embodiment uses the device of Example 1 to prepare graphene by chemical bubble coupling ultrasonic wave high-efficiency exfoliation, which includes the following steps: S1: 20 kg of flake graphite with an average particle size of 5000 mesh and 3 wt% hydrogen peroxide solution were put into a batching tank according to a mass ratio of 1:25. After adding 0.3 wt% hydroxypropyl cellulose water dispersion solution to the batching tank at a total amount of 1.5 wt% of the slurry, the slurry was stirred and configured, and then the slurry was transported to a homogenizer by a pneumatic diaphragm pump for homogenization and emulsification pretreatment at 6000 rpm; S2: The slurry after homogenization and emulsification pretreatment was transported to a reaction kettle with an electromagnetic heating coil. The temperature of the slurry was controlled at 65±0.5℃ by heating the slurry in the reaction kettle, and maintained for 30 min to promote the decomposition of hydrogen peroxide to generate micro-nano O2 / H2O bubbles. In this step, the air pressure power of the diaphragm pump for transporting the material was 0.2-0.5 MPa.

[0046] S3: The slurry containing O2 / H2O bubbles in step S2 was sequentially transported to four ultrasonic reaction kettles (four-stage reaction kettle) for treatment. After treatment by four-stage ultrasonic waves with different frequencies, the four ultrasonic reaction kettles controlled the ultrasonic wave frequency by ultrasonic heating rods in the order of 20 kHz, 40 kHz, 60 kHz, and 80 kHz, with an ultrasonic power density of 5 W / cm³. The total treatment time of the four ultrasonic reaction kettles was 45 min. Specifically, for example, 80KZ ultrasonic treatment for 10 min, 60KZ ultrasonic treatment for 10 min, 40KZ ultrasonic treatment for 10 min, and 20KZ ultrasonic treatment for 15 min.

[0047] S4: The slurry after ultrasonic treatment in step S3 was transported to a high-pressure homogenizer for high-pressure homogenization treatment at a pressure of 120 MPa for secondary mechanical exfoliation. The slurry after high-pressure homogenizer treatment was cooled to 35℃ by a heat exchanger; S5: The cooled slurry after secondary mechanical exfoliation in step S4 was subjected to steps S2 to S4 for 6 cycles to obtain a graphene dispersion liquid, i.e., specifically: The slurry after secondary mechanical peeling of step S4 is heated, the temperature of the slurry is controlled at 65±0.5℃ for 30 min to promote the decomposition of hydrogen peroxide to generate micro-nano O2 / H2O bubbles; then the slurry is sequentially sent to four ultrasonic reaction kettles (four-stage reaction kettles) for treatment, the four ultrasonic reaction kettles control the frequency of the ultrasonic waves by ultrasonic heating rods in turn as 80 kHz, 60 kHz, 40 kHz and 20 kHz, the ultrasonic power density is 5 W / cm³, and the total treatment time of the four ultrasonic reaction kettles is 45 min; then the slurry after ultrasonic treatment is sent to a high-pressure homogenizer for high-pressure homogenization treatment at a pressure of 120 MPa, secondary mechanical peeling is performed, and one cycle is completed, and the cycle is continued for 6 times, that is, the slurry is heated, bubbled, peeled, and mechanically peeled for 7 times, and the cycle is completed for 7 times, to finally prepare the graphene dispersion liquid.

[0048] Comparative Example 1: A method for preparing graphene, comprising the following steps: S1: 20 kg of flake graphite with an average particle size of 5000 mesh and 3 wt% hydrogen peroxide solution are put into a batching tank according to a mass ratio of 1:25, 0.3 wt% hydroxypropyl cellulose water dispersion solution is added into the batching tank at 1.5 wt% of the total amount of the slurry, and then the slurry is stirred and configured, and then the slurry is sent to a homogenizer for 6000 rpm homogenization and emulsification pretreatment by a pneumatic diaphragm pump; S2: The slurry after homogenization and emulsification pretreatment is sent to a reaction kettle with an electromagnetic heating coil, the temperature of the slurry is controlled at 65±0.5℃ by heating the slurry in the reaction kettle for 30 min to promote the decomposition of hydrogen peroxide to generate micro-nano O2 / H2O bubbles; in this step, the air pressure power of the diaphragm pump for delivering the material is 0.2-0.5 MPa.

[0049] S3: The slurry containing O2 / H2O bubbles in step S2 is sequentially sent to four ultrasonic reaction kettles (four-stage reaction kettles) for treatment, the four ultrasonic reaction kettles control the frequency of the ultrasonic waves by ultrasonic heating rods in turn as 20 kHz, 40 kHz, 60 kHz and 80 kHz, the ultrasonic power density is 5 W / cm³, and the total treatment time of the four ultrasonic reaction kettles is 45 min. Specifically, for example, 80KZ ultrasonic treatment for 10 min, 60KZ ultrasonic treatment for 10 min, 40KZ ultrasonic treatment for 10 min, and 20KZ ultrasonic treatment for 15 min.

[0050] S4: The slurry after the ultrasonic treatment in step S3 is transported to a high-pressure homogenizer for high-pressure homogenization treatment at a pressure of 120 MPa, and secondary mechanical peeling is performed; the slurry after the high-pressure homogenizer treatment is cooled to 35°C through a heat exchanger; S5: The slurry after the secondary mechanical peeling and cooling in step S4 is subjected to the steps S2 to S4 for 4 times, and a graphene dispersion liquid is obtained, specifically: The slurry after the secondary mechanical peeling and cooling in step S4 is heated, and the temperature of the slurry is controlled at 65±0.5°C for 30 min to promote the decomposition of hydrogen peroxide to generate micro-nano-sized O2 / H2O bubbles; then the slurry is sequentially transported to four ultrasonic reaction kettles (four-stage reaction kettles) for treatment, and the four ultrasonic reaction kettles control the ultrasonic frequency through ultrasonic heating rods, and the frequency is 20 kHz, 40 kHz, 60 kHz and 80 kHz in sequence, and the ultrasonic power density is 5 W / cm³, and the total treatment time of the four ultrasonic reaction kettles is 45 min; then the slurry after the ultrasonic treatment is transported to a high-pressure homogenizer for high-pressure homogenization treatment at a pressure of 120 MPa, and secondary mechanical peeling is performed, which is a first cycle, and the cycle is continued for 4 times, and a total of 5 heating bubble pre-peeling, 5 ultrasonic peeling and 5 secondary mechanical peeling are performed, and a total of 5 cycles are performed, and finally a graphene dispersion liquid is prepared.

[0051] The comparative example can be implemented by the device of example 1.

[0052] Compared with example 2, the ultrasonic frequency of the comparative example is increased from low to high with the same frequency difference.

[0053] Comparative example 2: a method for preparing graphene, comprising the following steps: S1: 20 kg of flake graphite with an average particle size of 5000 mesh and 3 wt% hydrogen peroxide solution are put into a batching tank according to a mass ratio of 1:25, 0.3 wt% hydroxypropyl cellulose water dispersion solution is added to the batching tank at 1.5 wt% of the total amount of the slurry, and then the slurry is stirred and configured, and then the slurry is transported to a homogenizer for homogenization and emulsification pretreatment at 6000 rpm through a pneumatic diaphragm pump; S2: The slurry after the homogenization and emulsification pretreatment is transported to a reaction kettle with an electromagnetic heating coil, the temperature of the slurry is controlled at 65±0.5°C through heating the slurry in the reaction kettle, and maintained for 30 min to promote the decomposition of hydrogen peroxide to generate micro-nano-sized O2 / H2O bubbles; in this step, the air pressure power of the diaphragm pump for transporting the material is 0.2-0.5 MPa.

[0054] S3: The slurry containing O2 / H2O bubbles in step S2 is treated with ultrasonic waves (ultrasonic reactor of Example 1), and the frequency of the ultrasonic waves is controlled at 50 kHz, and the total treatment time in the reactor is 45 min.

[0055] S4: The slurry after ultrasonic treatment in step S3 is transported to a high-pressure homogenizer for high-pressure homogenization treatment at a pressure of 120 MPa, and secondary mechanical exfoliation is performed; the slurry after high-pressure homogenizer treatment is cooled to 35°C by a heat exchanger; S5: The cooled slurry after secondary mechanical exfoliation in step S4 is subjected to steps S2 to S4 for 4 cycles to obtain a graphene dispersion liquid, namely specifically: The cooled slurry after secondary mechanical exfoliation in step S4 is heated, and the temperature of the slurry is controlled at 65±0.5°C for 30 min to promote the decomposition of hydrogen peroxide to generate micro-nano O2 / H2O bubbles; then the slurry is sequentially transported into one or four ultrasonic reactors (four-stage reactor) for treatment, and the ultrasonic frequency is set to 50 kHz, and the total treatment time in the ultrasonic reactor is 45 min; then the slurry after ultrasonic treatment is transported to a high-pressure homogenizer for high-pressure homogenization treatment at a pressure of 120 MPa, and secondary mechanical exfoliation is performed, which is one cycle, and the cycle is continued for 4 times, a total of 5 times of heating bubble pre-exfoliation, 5 times of ultrasonic exfoliation and 5 times of secondary mechanical exfoliation, and a total of 5 cycles are performed, and finally a graphene dispersion liquid is prepared.

[0056] The comparative example can be performed by the device of Example 1.

[0057] Compared with Example 2, the ultrasonic wave in the comparative example is changed to the same frequency.

[0058] Comparative Example 3: A method for preparing graphene, comprising the following steps: S1: 20 kg of flake graphite with an average particle size of 5000 mesh and ionized water are put into a batching tank according to a mass ratio of 1:25, 0.3wt% hydroxypropyl cellulose water dispersion liquid is added to the batching tank at 1.5wt% of the total amount of the slurry, and then the slurry is stirred and configured, and then the slurry is transported to a homogenizer for homogenization and emulsification pretreatment at 6000 rpm by a pneumatic diaphragm pump; S2: The slurry after homogenization and emulsification pretreatment is transported to a reactor with an electromagnetic heating coil, and the temperature of the slurry is controlled at 65±0.5°C by heating the slurry in the reactor for 30 min; in this step, the air pressure power of the diaphragm pump for transporting the material is 0.2-0.5 MPa.

[0059] S3: The slurry in step S2 is sequentially delivered into four ultrasonic reaction kettles (four-stage reaction kettles) for treatment. After four-stage treatment with different frequency ultrasonic waves, the four ultrasonic reaction kettles control the frequency of the ultrasonic waves by ultrasonic heating rods in sequence as 20 kHz, 40 kHz, 60 kHz and 80 kHz, and the ultrasonic power density is 5 W / cm³. The total treatment time of the four ultrasonic reaction kettles is 45 min. Specifically, for example, 80 KZ ultrasonic treatment for 10 min, 60 KZ ultrasonic treatment for 10 min, 40 KZ ultrasonic treatment for 10 min and 20 KZ ultrasonic treatment for 15 min.

[0060] S4: The slurry after ultrasonic treatment in step S3 is delivered into a high-pressure homogenizer for high-pressure homogenization treatment at a pressure of 120 MPa for secondary mechanical exfoliation. The slurry after high-pressure homogenizer treatment is cooled to 35 °C by a heat exchanger. S5: The slurry after secondary mechanical exfoliation and cooling in step S4 is subjected to steps S2 to S4 for 4 cycles to obtain a graphene dispersion liquid. Specifically: The slurry after secondary mechanical exfoliation and cooling in step S4 is heated, and the temperature of the slurry is controlled at 65 ± 0.5 °C for 30 min to promote the decomposition of hydrogen peroxide to generate micro-nano O2 / H2O bubbles. Then, the slurry is sequentially delivered into four ultrasonic reaction kettles (four-stage reaction kettles) for treatment. After four-stage treatment with different frequency ultrasonic waves, the four ultrasonic reaction kettles control the frequency of the ultrasonic waves by ultrasonic heating rods in sequence as 80 kHz, 60 kHz, 40 kHz and 20 kHz, and the ultrasonic power density is 5 W / cm³. The total treatment time of the four ultrasonic reaction kettles is 45 min. Then, the slurry after ultrasonic treatment is delivered into a high-pressure homogenizer for high-pressure homogenization treatment at a pressure of 120 MPa for secondary mechanical exfoliation. This is one cycle. The above process is repeated for 4 cycles. In total, the slurry is subjected to 5 times of heating and bubble pre-exfoliation, 5 times of ultrasonic exfoliation and 5 times of secondary mechanical exfoliation. In total, the slurry is subjected to 5 cycles. Finally, a graphene dispersion liquid is prepared.

[0061] In the slurry of the present comparative example, no hydrogen peroxide solution is added.

[0062] The raw material flake graphite, the graphene prepared by exfoliation in Example 2, Example 3 and Example 4 are respectively characterized by electron microscopy, and the results are shown in FIG. 1. Figure 4 .

[0063] The yield of graphene, the yield of graphene with less than 3 layers and the defect rate of graphene in the graphene dispersion liquid prepared in Example 2 to Example 4, Comparative Example 1 to Comparative Example 3 are counted, and the results are shown in Table 1.

[0064] Table 1: Yield of graphene and defect rate thereof Graphene yield (%) Graphene yield (%) Defect rate (%) Example 2 92 81 5 Example 3 67 42 2 Example 4 95 85 9 Comparative Example 1 88 73 11 Comparative Example 2 72 60 14 Comparative Example 3 30 14 17 Note: Yield and defect rate calculation reference as follows: ① Yield calculation (calculated yield of graphene of 10 layers and below as product): Mass concentration method: After centrifugal separation, the mass concentration of graphene in the supernatant (such as mg / mL) is measured, and the yield is calculated by comparing with the initial graphite input. For example, a dispersion of 0.01 mg / mL corresponds to a monolayer yield of 1 wt%, and Raman spectroscopy assisted: The proportion of monolayer is evaluated by the ratio of D peak and G peak intensity (I_D / I_G), and the yield is calculated in combination with the total mass.

[0065] ② Defect rate evaluation Using Raman spectroscopy analysis: D peak (~1350 cm -1 ) reflects structural defects, and G peak (~1580 cm -1 ) represents the integrity of graphene. The defect rate is positively correlated with the I_D / I_G ratio.

[0066] As can be seen from Table 1, through Examples 2 to 4, with the increase of the number of cycles, the yield of graphene and the yield of graphene below 3 layers are increased, but when the number of cycles exceeds 5, at the 7th or more than 7 times, the defect rate of graphene is relatively high, so in specific application, the number of cycles is controlled at 5, which is the best. As can be seen from Example 2 and Comparative Example 2, the recovery rate and defect rate of graphene treated by hetero-frequency ultrasonic treatment of the slurry are better than those treated by ultrasonic treatment of the same frequency, and by comparing Example 2 and Comparative Example 1, it can be seen that although both of them use hetero-frequency to exfoliate graphene, compared with the ultrasonic treatment of the slurry, the frequency from large to small is more conducive to improving the yield of graphene and reducing the defect rate.

[0067] The above describes the present application and its embodiments, which is not restrictive, and the examples shown are only one of the embodiments of the present application, and the actual structure is not limited thereto. In general, if a person skilled in the art is inspired thereby, without departing from the spirit of the present application, without creative design, similar structure and embodiments of the technical solutions can be designed, which shall belong to the protection scope of the present application.

Claims

1. A method for preparing graphene by high-efficiency exfoliation based on chemical bubble coupling with ultrasonic waves, characterized in that, Includes the following steps: S1: A slurry is prepared using flake graphite, hydrogen peroxide solution, and a hydrophilic dispersant; S2: The slurry from step S1 is heated to promote the decomposition of hydrogen peroxide and generate micro / nano-sized O2 / H2O bubbles. S3: The slurry containing O2 / H2O bubbles from step S2 is subjected to ultrasonic treatment at different frequencies in sequence. S4: The slurry after ultrasonic treatment in step S3 is subjected to secondary mechanical stripping through high-pressure homogenization.

2. The method for preparing graphene based on chemical bubble coupled ultrasonic exfoliation according to claim 1, characterized in that, It also includes step S5: the slurry after the second mechanical stripping in step S4 is cycled at least once from step S2 to S4.

3. The method for preparing graphene based on chemical bubble coupled ultrasonic exfoliation according to claim 1, characterized in that, The mass concentration of hydrogen peroxide in step S1 is 3% to 30%.

4. The method for preparing graphene based on chemical bubble coupled ultrasonic exfoliation according to claim 3, characterized in that, In step S1, the flake graphite is selected from flake graphite with a particle size of 200 to 6000 mesh, and the mass ratio of the flake graphite to hydrogen peroxide is 1:(25-60).

5. The method for preparing graphene based on chemical bubble coupled ultrasonic exfoliation according to claim 1, characterized in that, In step S2, the heating temperature of the slurry is controlled between 40-90℃.

6. The method for preparing graphene based on chemical bubble coupled ultrasonic exfoliation according to claim 1, characterized in that, Step S3 involves sequentially processing with 3-6 different ultrasonic frequencies, with the ultrasonic frequencies decreasing sequentially and the frequency difference between adjacent ultrasonic waves being ≥10kHz.

7. A graphene preparation apparatus for implementing the method for efficient exfoliation of graphene based on chemical bubble coupling with ultrasonic waves as described in any one of claims 1 to 6, characterized in that, It includes a batching tank, a reaction vessel, an ultrasonic reaction vessel, a high-pressure homogenizer, a heat exchanger, and a circulating slurry buffer tank. The number of ultrasonic reaction vessels is one or more, and the ultrasonic reaction vessels are connected in series through pipelines. The mixing tank is connected to the reaction vessel via a pipeline, and the materials in the mixing tank are transported to the reaction vessel for processing via the pipeline; The reactor is connected to the first ultrasonic reactor via a pipeline, and the material in the reactor is transported to the first ultrasonic reactor for processing via the pipeline. The last ultrasonic reactor is connected to a high-pressure homogenizer via a pipeline, and the material from the last ultrasonic reactor is transported to the high-pressure homogenizer for processing. The high-pressure homogenizer is connected to a heat exchanger, and the heat exchanger is connected to a circulating slurry buffer tank.

8. The graphene preparation apparatus according to claim 7, characterized in that, A first return pipe is provided between the circulating slurry buffer tank and the batching tank, and the material in the circulating slurry buffer tank is transported to the batching tank through the first return pipe.

9. The graphene preparation apparatus according to claim 8, characterized in that, A second return pipe is provided on the first return pipe, and one end of the second return pipe is connected to the reactor. The material in the circulating slurry buffer tank is transported to the reactor for processing through the second return pipe.

10. A graphene preparation apparatus according to any one of claims 7 to 9, characterized in that, The ultrasonic reactor includes a reactor body, and an ultrasonic vibrating rod is inserted into the reactor body cavity.

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