A method for preparing graphene based on chemical bubble coupling ultrasonic wave and a device thereof

Abstract

The application discloses a method for preparing graphene based on chemical bubble coupling ultrasonic wave high-efficiency stripping and a device thereof, and relates to the technical field of graphene preparation. The method is characterized in that: hydrogen peroxide is heated to generate chemical nanobubbles through chemical reaction, and the chemical nanobubbles are coupled with the multi-physical field synergy of ultrasonic cavitation effect. After the interlayer of flake graphite is expanded and intercalated by the bubbles and pre-stripped, a local high-pressure shock wave is generated by ultrasonic cavitation, the van der Waals force of graphite molecular bonds is destroyed by cavitation force, the graphene stripping efficiency is significantly improved through chemical-multiple physical field synergy and cyclic stripping, the graphene high-efficiency stripping and layer number control are realized, and continuous production can be realized. The method has important significance for the development of continuous production and large-scale technology of graphene preparation.

Description

TECHNICAL FIELD

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

[0002] At present, graphene is mainly prepared by a peeling technology, and the existing graphene peeling technology mainly has the following defects and technical problems: ① the traditional mechanical peeling method has the problems of low peeling 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 peeling method has the problems of high energy consumption, low peeling efficiency and easy structure damage; and the existing single physical peeling technology cannot effectively destroy the van der Waals force between the graphite layers, resulting in unsatisfactory peeling effect, low yield and high difficulty in continuous production. Therefore, it is necessary to improve the existing peeling preparation technology of graphene, and develop a peeling preparation technology of graphene with high peeling efficiency, low energy consumption, green and no pollution, and continuous production. SUMMARY

[0003] Therefore, based on the above background, the present application provides a method for preparing graphene based on chemical bubble coupling ultrasonic wave and a device thereof. The present application generates chemical nanobubbles by heating hydrogen peroxide solution, and couples the multi-physical field synergy of ultrasonic cavitation effect. The interlayer of flake graphite is expanded and intercalated by the nanobubbles generated by the heated hydrogen peroxide solution, and then a local high-pressure shock wave is generated by the multi-stage cavitation of ultrasonic waves. The van der Waals force of the graphite molecular bond is destroyed by the cavitation force. The graphene peeling efficiency is significantly improved by chemical-multiple physical field synergy and multiple cycle peeling, the graphene is efficiently peeled 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:

[0005] A method for preparing graphene based on chemical bubble coupling ultrasonic wave, comprising the following steps:

[0006] S1: configuring a slurry with flake graphite, hydrogen peroxide solution and hydrophilic dispersant;

[0007] S2: heating the slurry of step S1 to decompose hydrogen peroxide to generate micro-nano O2 / H2O bubbles;

[0008] S3: sequentially treating the slurry containing O2 / H2O bubbles in step S2 with ultrasonic waves of different frequencies;

[0009] S4: the slurry after the ultrasonic treatment in step S3 is subjected to secondary mechanical exfoliation by high-pressure homogenization.

[0010] Further, it further comprises step S5: the slurry after the secondary mechanical exfoliation in step S4 is subjected to at least one cycle of steps S2 to S4.

[0011] Further, the mass concentration of hydrogen peroxide in step S1 is 3% to 30%.

[0012] 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 hydrogen peroxide is 1: (25-60).

[0013] Further, the temperature of the slurry in step S2 is controlled at 40-90℃.

[0014] Further, step S3 is subjected to ultrasonic treatment of 3-6 different frequencies in sequence, the ultrasonic frequencies are in sequence from large to small, and the frequency difference of adjacent ultrasonic frequencies is ≥10 kHz.

[0015] Based on the same inventive concept, the application also 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, the ultrasonic reaction kettles are connected in sequence through pipelines;

[0016] 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.

[0017] 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.

[0018] 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.

[0019] The high-pressure homogenizer is connected with the heat exchanger, and the heat exchanger is connected with the circulating slurry buffer tank.

[0020] 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.

[0021] 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.

[0022] Further, the ultrasonic reaction kettle comprises a kettle body, and an ultrasonic vibration rod is arranged in a kettle cavity of the kettle body.

[0023] The present application realizes the following beneficial effects:

[0024] The present application first constructs a chemical-physical field synergistic exfoliation 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 achieves the effect of efficient exfoliation of graphene.

[0025] The present application realizes the following beneficial effects:

[0026] The present application realizes the following beneficial effects:

[0027] The present application realizes the following beneficial effects:

[0028] The present application realizes the following beneficial effects: BRIEF DESCRIPTION OF DRAWINGS

[0029] ATTACHMENT Figure 1 The left drawing is the untreated flake graphite raw material, which is a two-dimensional multi-layer tight molecular structure; the right drawing is the chemical bubble coupling ultrasonic treatment, in which the bubble particle is inserted into the two-dimensional graphene intermolecular loose molecular structure, and the blue beads are the cavitation intercalation bubble particles, which have been inserted into the graphene intermolecular and coupled with the molecular covalent bond to support the intercalation force to exfoliate the two-dimensional graphene sheet.

[0030] ATTACHMENT Figure 2 The present application realizes the following beneficial effects: The present application realizes the following beneficial effects:

[0031] Figure 1 is a structural schematic diagram of the ultrasonic reactor of the present application. Figure 3 Figure 2 is a structural schematic diagram of the ultrasonic reactor of the present application.

[0032] Figure 3 is a structural schematic diagram of the ultrasonic reactor of the present application. Figure 4 Figure 4 is a microstructure electron microscope image of graphene prepared by 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 by 3 cycles; Figure 4 C is graphene prepared by 5 cycles; Figure 4 D is graphene prepared by 7 cycles.

[0033] Figure 1, a batching tank; 2, a reactor; 3, an ultrasonic reactor; 4, a high-pressure homogenizer; 5, a heat exchanger; 6, a circulating slurry buffer tank; 7, a homogenizer; 8, a diaphragm pump; 9, a first return pipe; 10, a second return pipe; 110, a product buffer tank. DETAILED DESCRIPTION

[0034] 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.

[0035] In the following examples, the materials, reagents, etc. used, unless otherwise specified, can be obtained from commercial channels.

[0036] In combination with Figure 1 the principle diagram, the technical scheme of the present application is as follows:

[0037] A method for preparing graphene based on chemical bubble coupling ultrasonic high-efficiency peeling, comprising the following steps:

[0038] S1: In a batching tank, 4N purity flake graphite, hydrogen peroxide solution and hydrophilic dispersant are stirred to configure slurry;

[0039] 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).

[0040] 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.

[0041] S2: heating the slurry of step S1 to cause decomposition of hydrogen peroxide to generate micro-nano-sized O2 / H2O bubbles;

[0042] Specifically, the stirring speed can be controlled by the stirrer to cause decomposition of hydrogen peroxide to generate micro-nano-sized O2 / H2O bubbles.

[0043] The temperature of the slurry in this step is controlled at 40-90℃.

[0044] S3: the slurry containing O2 / H2O bubbles in step S2 is sequentially subjected to ultrasonic treatment at 3-6 different frequencies.

[0045] The ultrasonic frequencies are sequentially from large to small, and the frequency difference between adjacent ultrasonic frequencies is ≥10 kHz.

[0046] S4: the slurry after ultrasonic treatment in step S3 is subjected to high-pressure homogenization treatment at 50-200 MPa for secondary mechanical exfoliation, and the slurry is cooled, with the temperature of the slurry controlled at 40℃±1℃.

[0047] S5: the cooled slurry after secondary mechanical exfoliation in step S4 is subjected to steps S2 to S4 for 3-6 cycles.

[0048] 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, 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.

[0049] The batching tank 1 is connected to the reaction kettle 2 through a pipe, and the materials in the batching tank 1 are 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.

[0050] 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 of the slurry in the reaction kettle to within 2℃ by controlling the electromagnetic heating coil.

[0051] The reaction kettle 2 is connected with the first ultrasonic reaction kettle 3 through a pipeline, and the material in the reaction kettle 2 is transported to the first ultrasonic reaction kettle 3 through the pipeline for treatment; the material in the first ultrasonic reaction kettle 3 is transported to the second ultrasonic reaction kettle 3 through the pipeline, and so on, until the material is transported to the last ultrasonic reaction kettle 3, and the last ultrasonic reaction kettle 3 is connected with the high-pressure homogenizer 4 through a pipeline, and the material in the last ultrasonic reaction kettle 3 is transported to the high-pressure homogenizer 4 for treatment;

[0052] The high-pressure homogenizer 4 is connected with the heat exchanger 5, and the heat exchanger 5 is connected with 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℃.

[0053] 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.

[0054] 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 through the second return pipe 100 for treatment.

[0055] 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.

[0056] In specific application, the pipeline between the reaction kettle, the ultrasonic reaction kettle and each material tank can be appropriately installed with a diaphragm pump 8 for material transportation, which is a conventional technology and will not be described here.

[0057] Embodiment 2: Based on the principle of Figure 1 Embodiment 1, this embodiment uses the device of Embodiment 1 to prepare graphene based on chemical bubble coupling ultrasonic high-efficiency stripping, which comprises the following steps:

[0058] S1: 20kg of flake graphite with an average particle size of 5000 mesh and 3wt% hydrogen peroxide solution are put into the batching tank according to a mass ratio of 1:25 to prepare slurry, 0.3wt% hydroxypropyl cellulose water dispersion solution is added into the batching tank at a total amount of 1.5wt%, and then the slurry is stirred and configured, and then the slurry is transported to the homogenizer for homogenization and emulsification pretreatment at 6000rpm through a pneumatic diaphragm pump;

[0059] The hydroxypropyl cellulose used in this example and the following examples and comparative examples has CAS No. 9004-64-2;

[0060] 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, and maintained for 30 min to promote the decomposition of hydrogen peroxide to generate micro-nano O2 / H2O bubbles; in specific applications, the air pressure power of the diaphragm pump for transporting the material is (0.2-0.5) MPa.

[0061] S3: The slurry containing O2 / H2O bubbles in step S2 is transported into four ultrasonic reaction kettles (four-stage reaction kettles) in sequence for treatment, and the four-stage ultrasonic waves with different frequencies are controlled by the ultrasonic heating rods in the four ultrasonic reaction kettles in sequence as 80 kHz, 60 kHz, 40 kHz and 20 kHz, and 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.

[0062] 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 for secondary mechanical exfoliation; and the slurry after the high-pressure homogenizer treatment is cooled to 35℃ by a heat exchanger.

[0063] S5: The cooled slurry after the secondary mechanical exfoliation in step S4 is subjected to the cycle of steps S2 to S4 for 4 times to obtain a graphene dispersion liquid, i.e.

[0064] The cooled slurry after the secondary mechanical exfoliation in step S4 is heated, and the temperature of the slurry is controlled at 65±0.5℃, and maintained for 30 min to promote the decomposition of hydrogen peroxide to generate micro-nano O2 / H2O bubbles; then the slurry is transported into four ultrasonic reaction kettles (four-stage reaction kettles) in sequence for treatment, and the four-stage ultrasonic waves with different frequencies are controlled by the ultrasonic heating rods in the four ultrasonic reaction kettles in sequence as 80 kHz, 60 kHz, 40 kHz and 20 kHz, 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 for secondary mechanical exfoliation, which is a first 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 times of cycle, and finally a graphene dispersion liquid is prepared.

[0065] Example 3: Combination Figure 1 Based on the principle of Example 1, this embodiment uses the device to prepare graphene based on chemical bubble coupling ultrasonic high-efficiency stripping, including the following steps:

[0066] S1: Put 20 kg of flake graphite with an average particle size of 5000 mesh and 3 wt% hydrogen peroxide solution into the 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, stir and configure the slurry, and then deliver the slurry to the homogenizer for homogenization and emulsification pretreatment at 6000 rpm through the pneumatic diaphragm pump;

[0067] S2: Deliver the slurry after homogenization and emulsification pretreatment to the reaction kettle with an electromagnetic heating coil. Heat the slurry in the reaction kettle to control the temperature of the slurry at 65±0.5℃ 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.

[0068] S3: Deliver the slurry containing O2 / H2O bubbles in step S2 to four ultrasonic reaction kettles (four-stage reaction kettle) in sequence for treatment. After treatment by ultrasonic waves of different frequencies in four stages, the four ultrasonic reaction kettles control the frequency of the ultrasonic waves through ultrasonic heating rods in sequence as 80 kHz, 60 kHz, 40 kHz, and 20 kHz, with an ultrasonic power density of 5 W / cm³. 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.

[0069] S4: Deliver the slurry after ultrasonic treatment in step S3 to the high-pressure homogenizer for high-pressure homogenization treatment at a pressure of 120 MPa for secondary mechanical stripping. The slurry after treatment by the high-pressure homogenizer is cooled to 35℃ by the heat exchanger;

[0070] S5: Cycle the slurry after secondary mechanical stripping and cooling in step S4 for 2 times according to steps S2 to S4 to obtain a graphene dispersion liquid, i.e., specifically:

[0071] 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, and the four ultrasonic reaction kettles control the frequency of the ultrasonic waves to be 80 kHz, 60 kHz, 40 kHz and 20 kHz in sequence through ultrasonic heating rods, 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 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 2 times, that is, the slurry is heated, bubbled, peeled and mechanically peeled for 3 times, and the cycle is completed for 3 times, to finally prepare the graphene dispersion liquid.

[0072] Example 4: Combination Figure 1 The principle of the present application is based on the principle of the device of Example 1, and the graphene is prepared by chemical bubble coupling ultrasonic high-efficiency peeling, which comprises the following steps:

[0073] 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 is added to the batching tank at a total amount of 1.5 wt% of the slurry, and then the slurry is stirred and configured, and then the slurry is sent to a homogenizer for homogenization and emulsification pretreatment at 6000 rpm through a pneumatic diaphragm pump;

[0074] 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℃ for 30 min by heating the slurry in the reaction kettle 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.

[0075] S3: The slurry containing O2 / H2O bubbles in step S2 is sequentially sent to four ultrasonic reaction kettles (four-stage reaction kettles) for treatment, and the four ultrasonic reaction kettles control the frequency of the ultrasonic waves to be 20 kHz, 40 kHz, 60 kHz and 80 kHz in sequence through ultrasonic heating rods, and 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.

[0076] 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;

[0077] S5: The slurry after the secondary mechanical peeling and cooling in step S4 is subjected to the steps S2 to S4 for 6 times, and a graphene dispersion liquid is obtained, specifically:

[0078] 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, which are 80 kHz, 60 kHz, 40 kHz and 20 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 6 times, a total of 7 times of heating bubble pre-peeling, 7 times of ultrasonic peeling and 7 times of secondary mechanical peeling, and a total of 7 times of circulation, and finally a graphene dispersion liquid is prepared.

[0079] Comparative Example 1: A method for preparing graphene, comprising the following steps:

[0080] 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 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 a homogenizer for homogenization and emulsification pretreatment at 6000 rpm through a pneumatic diaphragm pump;

[0081] 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 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.

[0082] 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 ultrasonic waves of different frequencies in four stages, the frequencies of the ultrasonic waves of the four ultrasonic reaction kettles are controlled by ultrasonic heating rods to be 20 kHz, 40 kHz, 60 kHz and 80 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 ultrasonic wave treatment is 80 KZ for 10 min, 60 KZ for 10 min, 40 KZ for 10 min and 20 KZ for 15 min.

[0083] 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, and secondary mechanical peeling is performed. The slurry after the treatment of the high-pressure homogenizer is cooled to 35°C by a heat exchanger.

[0084] S5: The slurry after the secondary mechanical peeling and cooling in step S4 is subjected to the cycle of steps S2 to S4 for 4 times to obtain a graphene dispersion liquid. Specifically, for example:

[0085] 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 O2 / H2O bubbles. Then, the slurry is sequentially delivered into four ultrasonic reaction kettles (four-stage reaction kettles) for treatment. After the treatment of ultrasonic waves of different frequencies in four stages, the frequencies of the ultrasonic waves of the four ultrasonic reaction kettles are controlled by ultrasonic heating rods to be 20 kHz, 40 kHz, 60 kHz and 80 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 delivered to a high-pressure homogenizer for high-pressure homogenization treatment at a pressure of 120 MPa, and secondary mechanical peeling is performed. This is a first cycle. The above cycle is continued for 4 times. In total, the slurry is subjected to 5 times of heating and bubble pre-peeling, 5 times of ultrasonic peeling and 5 times of secondary mechanical peeling. In total, the slurry is subjected to 5 cycles. Finally, a graphene dispersion liquid is prepared.

[0086] The comparative example can be implemented by the device of example 1.

[0087] Compared with example 2, the ultrasonic frequency of the comparative example is increased from low to high at the same frequency difference.

[0088] Comparative example 2: A method for preparing graphene, comprising the following steps:

[0089] 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, 0.3 wt% hydroxypropyl cellulose water dispersion was added to the batching tank at 1.5 wt% of the total amount of the slurry, and then 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;

[0090] 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; the air pressure power of the diaphragm pump for transporting the material in this step was 0.2-0.5 MPa.

[0091] S3: The slurry containing O2 / H2O bubbles in step S2 was treated by ultrasonic wave (ultrasonic reaction kettle of Example 1), and the frequency of the ultrasonic wave was controlled at 50 kHz, and the total treatment time in the kettle was 45 min.

[0092] 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 peeling; the slurry after high-pressure homogenizer treatment was cooled to 35℃ by a heat exchanger;

[0093] S5: The slurry after secondary mechanical peeling and cooling in step S4 was subjected to steps S2 to S4 for 4 times to obtain a graphene dispersion liquid, namely specifically:

[0094] The slurry after secondary mechanical peeling and cooling in step S4 was heated, the temperature of the slurry was controlled at 65±0.5℃, and maintained for 30 min to promote the decomposition of hydrogen peroxide to generate micro-nano O2 / H2O bubbles; then the slurry was transported to one or four ultrasonic reaction kettles (four-stage reaction kettle) in sequence for treatment, the ultrasonic frequency was set to 50 kHz, and the total ultrasonic reaction kettle treatment time was 45 min; then the slurry after ultrasonic treatment was transported to a high-pressure homogenizer for high-pressure homogenization treatment at a pressure of 120 MPa for secondary mechanical peeling, which was a first cycle, and the cycle was continued for 4 times, a total of 5 times of heating bubble pre-peeling and 5 times of ultrasonic peeling and 5 times of secondary mechanical peeling, a total of 5 times of cycle, and finally a graphene dispersion liquid was prepared.

[0095] The comparative example can be carried out by the device of Example 1.

[0096] In the comparative example, the ultrasonic wave is replaced by the same frequency as in Example 2.

[0097] Comparative Example 3: A method for preparing graphene, comprising the following steps:

[0098] S1: Put 20 kg of flake graphite with an average particle size of 5000 mesh and ionized water into the batching tank at a mass ratio of 1:25. Add 0.3 wt% of a hydroxypropyl cellulose water dispersion to the total amount of 1.5 wt% of the slurry in the batching tank, stir to prepare the slurry, and then deliver the slurry to the homogenizer for 6000 rpm homogenization and emulsification pretreatment through the pneumatic diaphragm pump;

[0099] S2: Deliver the slurry after homogenization and emulsification pretreatment to the reaction kettle with an electromagnetic heating coil, heat the slurry in the reaction kettle, control the temperature of the slurry at 65±0.5℃, and maintain for 30 min; In this step, the air pressure power of the diaphragm pump for delivering the material is 0.2-0.5 MPa.

[0100] S3: Deliver the slurry in step S2 to four ultrasonic reaction kettles (four-stage reaction kettle) in turn for treatment. After four-stage treatment of different frequency ultrasonic waves, the four ultrasonic reaction kettles control the frequency of the ultrasonic waves through ultrasonic heating rods in turn 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, 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.

[0101] S4: Deliver the slurry after ultrasonic treatment in step S3 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 is cooled to 35℃ through a heat exchanger;

[0102] S5: The cooled slurry after secondary mechanical exfoliation in step S4 is cycled 4 times through steps S2 to S4 to obtain a graphene dispersion, i.e.

[0103] The slurry after secondary mechanical exfoliation 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-sized 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 to be 80 kHz, 60 kHz, 40 kHz and 20 kHz, respectively, by means of ultrasonic heating rods, 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 sent to a high-pressure homogenizer for high-pressure homogenization treatment at a pressure of 120 MPa. The slurry is subjected to secondary mechanical exfoliation, and one cycle is completed. This cycle is repeated four times, and a total of five cycles are completed. Finally, the graphene dispersion liquid is prepared.

[0104] The hydrogen peroxide solution is not added to the slurry of the present comparative example.

[0105] 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 FIGS. 1-4. Figure 4 .

[0106] The yield of graphene, the yield of graphene with 3 layers or less 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.

[0107] Table 1: Yield of graphene and defect rate thereof

[0108] 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

[0109] Note: The yield and defect rate are calculated as follows:

[0110] ① Yield calculation (calculated based on graphene with 10 layers or less as product): mass concentration method: the mass concentration of graphene in the supernatant after centrifugal separation is measured (such as mg / mL), and the yield is calculated by comparison with the initial graphite input. For example, a dispersion of 0.01 mg / mL corresponds to a single-layer yield of 1 wt%, and Raman spectroscopy is used for auxiliary evaluation: the proportion of single-layer is evaluated by the intensity ratio of D peak to G peak (I_D / I_G), and the yield is calculated in combination with the total mass.

[0111] ② Defect rate evaluation

[0112] Raman spectroscopy is used for 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 I_D / I_G ratio.

[0113] As can be seen from Table 1, it can be seen from Examples 2 to 4 that as the number of cycles increases, both the graphene yield and the graphene yield below 3 layers increase, 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 times, and the effect is optimal. 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 as can be seen from Example 2 and Comparative Example 1, although both use hetero-frequency to peel graphene, compared with the frequency of ultrasonic treatment of the slurry from large to small, it is more conducive to improve the graphene yield and reduce the defect rate.

[0114] The above describes the present application and its embodiments, which are 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 summary, if a person skilled in the art is inspired thereby, without departing from the purpose of the present application, without creative design, similar structure and embodiments of the technical solution, which should belong to the protection scope of the present application.

Claims

1. A method for preparing graphene based on chemical bubble coupling ultrasonic wave high-efficiency exfoliation, characterized in that, It comprises the following steps: S1: preparing slurry with flake graphite, hydrogen peroxide solution and hydrophilic dispersant; S2: heating the slurry of step S1 to promote the decomposition of hydrogen peroxide to generate micro-nano O2 / H2O bubbles; S3: the slurry containing O2 / H2O bubbles in step S2 is sequentially subjected to ultrasonic treatment of different frequencies; S4: the slurry after ultrasonic treatment in step S3 is subjected to secondary mechanical exfoliation by high-pressure homogenization; The device for preparing graphene based on chemical bubble coupling ultrasonic high-efficiency exfoliation comprises a batching tank, a reaction kettle, an ultrasonic reaction kettle, a high-pressure homogenizer, a heat exchanger and a circulating slurry buffer tank, the number of the ultrasonic reaction kettles is more than one, 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.

2. The method according to claim 1, wherein, It further comprises step S5: circulating the slurry after secondary mechanical exfoliation in step S4 at least once through steps S2 to S4. 3.The method of claim 1, wherein the method is characterized by, The mass concentration of hydrogen peroxide in step S1 is 3% to 30%.

4. The method according to claim 3, wherein the method is characterized by, The flake graphite in step S1 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 according to claim 1, wherein the method is characterized by, The heating temperature of the slurry in step S2 is controlled at 40-90℃. 6.The method of claim 1, wherein the method is characterized by, Step S3 is sequentially subjected to ultrasonic treatment of 3-6 different frequencies, and the frequencies of the ultrasonic waves decrease in turn, and the frequency difference between adjacent ultrasonic waves is ≥10 kHz. 7.The method of claim 1, wherein the method is characterized by, 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.

8. The method for preparing graphene based on chemical bubble coupled ultrasonic exfoliation according to claim 7, characterized in that, 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.

9. The method according to claim 7 or 8, wherein the method is characterized by, The ultrasonic reaction kettle comprises a kettle body, and an ultrasonic vibration rod is arranged in the kettle cavity of the kettle body.

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