Preparation method of spherical closed-cell graphene foam and graphene foam

Abstract

The invention belongs to the technical field of graphene materials, and particularly relates to a spherical closed-cell graphene foam preparation method and graphene foam, and the spherical closed-cell graphene foam preparation method comprises the following steps: S1, preparing a high-concentration graphene oxide solution; step S2, preparing a graphene oxide-acrylamide-N, N '-methylene bisacrylamide sol; s3, mixing the sol with PMMA (polymethyl methacrylate) microspheres to prepare a PMMA microsphere suspension; step S4, carrying out gelation treatment on the PMMA microsphere suspension liquid to obtain a gel body; step S5, dehydrating and curing the gel in a drying box to obtain a graphene oxide-PMMA microsphere composite material block; and step S6, performing high-temperature carbonization on the composite material block obtained in the step S5 to obtain the spherical closed-cell graphene foam.

Description

Technical Field

[0001] The invention belongs to the technical field of graphene materials, and in particular relates to a method for preparing spherical closed-cell graphene foam and the graphene foam. Background Art

[0002] Graphene foam is a porous material with a wide range of applications, and is often used in the fields of load-bearing, adsorption, energy storage, etc. The pore-making process of graphene foam in the preparation process is particularly important, which is usually reflected in the hard template method, soft template method and template-free method. For graphene foam used in the field of load-bearing, the pore structure is extremely important. Spherical pores can eliminate stress concentration to the greatest extent, while closed pores can minimize defects on the pore walls of graphene foam. Spherical pores mainly depend on the template of the pore-making process, while closed pores mainly depend on the wrapping performance of graphene oxide on the pore-making template.

[0003] Commonly used templates are metal and polymer materials. Graphene foam prepared by metal templates has excellent strength, but the cost is high and the process cycle is long. The use of polymer templates has the advantages of low cost and short process cycle, but the prepared graphene oxide wraps the polymer template only by physical adsorption, resulting in poor wrapping. A large number of open pores will be formed during the heat treatment process, making it difficult to form a closed-cell structure.

[0004] Therefore, how to provide a spherical closed-cell graphene foam with good encapsulation and load-bearing properties is a technical problem that urgently needs to be solved in this field.

[0005] It should be noted that the above information disclosed in this background technology section is only used to understand the background technology of the present application concept, and therefore, the above description is not considered to constitute information of the prior art. Summary of the invention

[0006] The embodiments of the present disclosure at least provide a spherical closed-cell graphene foam and a preparation method thereof.

[0007] In a first aspect, the present disclosure provides a method for preparing a spherical closed-cell graphene foam, comprising the following steps: step S1, preparing a high-concentration graphene oxide aqueous solution, namely, mixing concentrated sulfuric acid with potassium permanganate and sodium nitrate, heating to prepare a manganese anhydride solution, mixing flake graphite with the manganese anhydride solution, heating and stirring, and sequentially adding an aqueous hydrogen peroxide solution and dilute hydrochloric acid, and after the reaction is completed, standing to remove the supernatant to obtain a high-concentration graphene oxide aqueous solution; step S2, preparing a graphene oxide-acrylamide-N-N'methylenebisacrylamide sol, namely, mixing N-N'methylenebisacrylamide and deionized water, and adding after the complete dissolution. The high concentration graphene oxide aqueous solution prepared in step S1 is added, and acrylamide is added after it is completely dissolved, and the mixture is mixed evenly to obtain a graphene oxide-acrylamide-N-N'methylenebisacrylamide sol; step S3, the graphene oxide-acrylamide-N-N'methylenebisacrylamide sol is added to PMMA microspheres to obtain a PMMA microsphere suspension; step S4, the PMMA microsphere suspension is subjected to gelation treatment to obtain a gel; step S5, the gel is dehydrated and solidified to obtain a graphene oxide-PMMA microsphere composite material block; step S6, the composite material block obtained in step S5 is subjected to high temperature carbonization to obtain a spherical closed-cell graphene foam.

[0008] In an optional embodiment, in step S1, the mass ratio of concentrated sulfuric acid to potassium permanganate is 30:1-70:1, and the mass ratio of concentrated sulfuric acid to sodium nitrate is 90:1-450:1.

[0009] In an optional embodiment, the particle size of the flake graphite in step S1 is 2-5 mm, and the mass ratio of flake graphite to concentrated sulfuric acid is 1:100-1:10.

[0010] In an optional embodiment, in step S1, the concentration of the aqueous hydrogen peroxide solution is 10%-30%, and the concentration of the dilute hydrochloric acid is 2%-5%.

[0011] In an optional embodiment, the heating and stirring temperature in step S1 is 60-80° C. and the stirring time is 24-48 h.

[0012] In an optional embodiment, the mass ratio of acrylamide, N-N'methylenebisacrylamide, and high concentration graphene oxide aqueous solution in step S2 is (10-90): (0.7-1): (130-170).

[0013] In an optional embodiment, the particle size of the PMMA microspheres in step S3 is 1 micron-50 microns; and the mass ratio of the PMMA microspheres to the high concentration graphene oxide aqueous solution is 1:10-1:100.

[0014] In an optional embodiment, the temperature of the gelation treatment in step S4 is 60-80° C. and the time is 8-10 h.

[0015] In an optional embodiment, the temperature of the dehydration and curing in step S5 is 100-200° C., and the duration of the heat preservation treatment is 24-48 hours.

[0016] In an optional embodiment, in step S6, the temperature of the high-temperature carbonization is 800-1200° C.; and the duration of the heat preservation treatment is 2-10 h.

[0017] In a second aspect, the embodiments of the present disclosure also provide a spherical closed-cell graphene foam prepared by the method described above.

[0018] The beneficial effect of the present invention is that the preparation method of the spherical closed-cell graphene foam proposes a scheme of combining a high-concentration graphene oxide aqueous solution and PMMA microspheres to prepare graphene foam. On the one hand, by introducing acrylamide-N-N'methylenebisacrylamide sol into the high-concentration graphene oxide aqueous solution, the acrylamide-N-N'methylenebisacrylamide sol will be carbonized and fix the graphene oxide during the heat treatment process, so that the high-concentration graphene oxide has good encapsulation of the PMMA microspheres and can form a closed-cell structure; on the other hand, compared with PU microspheres, PMMA microspheres have good dimensional ability in the gel body, so that the closed cells present a spherical morphology, thereby improving the load-bearing performance of the graphene foam.

[0019] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings.

[0020] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 A physical picture of a block of graphene oxide-PMMA microsphere composite material prepared in Example 1 provided in the embodiments of the present disclosure; Figure 2 This is a SEM image of a bulk of a graphene oxide-PMMA microsphere composite material prepared in Example 1 provided in the embodiments of the present disclosure; Figure 3 A physical picture of the closed-cell spherical graphene foam prepared in Example 1 provided in the embodiments of the present disclosure; Figure 4 This is an SEM image of the closed-cell spherical graphene foam prepared in Example 1 provided in the embodiments of the present disclosure. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] As used herein, the phrases "in one embodiment," "according to one embodiment," "in some embodiments," and the like generally refer to the fact that the particular feature, structure, or characteristic following the phrase may be included in at least one embodiment of the present disclosure. Therefore, a particular feature, structure, or characteristic may be included in more than one embodiment of the present disclosure, so that these phrases do not necessarily refer to the same embodiment. As used herein, the terms "example," "exemplary," and the like are used to "serve as an example, instance, or illustration." Any implementation, aspect, or design described herein as "example" or "exemplary" is not necessarily to be construed as preferred or superior to other implementations, aspects, or designs. On the contrary, the use of the terms "example," "exemplary," and the like is intended to present concepts in a concrete manner.

[0025] Herein, example embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. As used herein, expressions such as "at least one of..." modify the entire list of elements when following a list of elements, rather than modifying individual elements in the list. For example, the expression "at least one of a, b, and c" should be understood to include only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c.

[0026] The terms used herein are only used to describe specific exemplary configurations and are not intended to be limited. As used herein, the singular articles "one", "an" and "the" may also be intended to include plural forms, unless it is clearly indicated above that this is not the case. The terms "include", "comprise" and "have" are inclusive, and therefore specify the presence of features, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components and / or combinations thereof. The method steps, processes and operations described herein should not be interpreted as necessarily requiring them to be performed in the specific order discussed or shown, unless specifically identified as an execution order. Additional or alternative steps may be adopted.

[0027] At present, the templates commonly used in the preparation of graphene foam are metal and polymer materials. Among them, the graphene foam prepared by metal template has excellent strength, but the cost is high and the process cycle is long. The use of polymer material template has the advantages of low cost and short process cycle, but the prepared graphene oxide wraps the polymer template only by physical adsorption, resulting in poor wrapping. A large number of open pores will be formed during the heat treatment process, making it difficult to form a closed-cell structure.

[0028] The defects existing in the above solutions are the results obtained by the inventor after practice and careful research. Therefore, the discovery process of the above problems and the solutions proposed by the present disclosure for the above problems below should be the contributions made by the inventor to the present disclosure during the disclosure process.

[0029] The present disclosure provides a method for preparing a spherical closed-cell graphene foam, comprising the following steps: step S1, preparing a high-concentration graphene oxide aqueous solution, namely, mixing concentrated sulfuric acid with potassium permanganate and sodium nitrate, heating to prepare a manganese anhydride solution, mixing flake graphite with the manganese anhydride solution, heating and stirring, sequentially adding an aqueous hydrogen peroxide solution and dilute hydrochloric acid, and standing to remove the supernatant after the reaction is completed to obtain a high-concentration graphene oxide aqueous solution; step S2, preparing a graphene oxide-acrylamide-N-N'methylenebisacrylamide sol, namely, mixing N-N'methylenebisacrylamide and deionized water, and adding step S3 after the N-N'methylenebisacrylamide is completely dissolved. The high-concentration graphene oxide aqueous solution prepared in S1 is completely dissolved, and then acrylamide is added and mixed evenly to obtain a graphene oxide-acrylamide-N-N'methylenebisacrylamide sol; step S3, adding the graphene oxide-acrylamide-N-N'methylenebisacrylamide sol to PMMA microspheres to obtain a PMMA microsphere suspension; step S4, gelling the PMMA microsphere suspension to obtain a gel; step S5, dehydrating and curing the gel to obtain a graphene oxide-PMMA microsphere composite material block; step S6, high-temperature carbonizing the composite material block obtained in S5 to obtain a spherical closed-cell graphene foam.

[0030] In some embodiments, specifically, the mass ratio of concentrated sulfuric acid to potassium permanganate in step S1 is 30:1-70:1, and the mass ratio of concentrated sulfuric acid to sodium nitrate is 90:1-450:1.

[0031] In some embodiments, specifically, the particle size of the flake graphite in step S1 is 2-5 mm, and the mass ratio of flake graphite to concentrated sulfuric acid is 1:100-1:10.

[0032] In some embodiments, specifically, the concentration of the aqueous hydrogen peroxide solution in step S1 is 10%-30%, and the concentration of the dilute hydrochloric acid is 2%-5%.

[0033] In some embodiments, specifically, the heating and stirring temperature in step S1 is 60-80° C., and the stirring time is 24-48 hours.

[0034] In some embodiments, specifically, the mass ratio of acrylamide, N-N'methylenebisacrylamide, and high concentration graphene oxide aqueous solution in step S2 is (10-90): (0.7-1): (130-170).

[0035] In some embodiments, specifically, the particle size of the PMMA microspheres in step S3 is 1 micron-50 microns; and the mass ratio of the PMMA microspheres to the high concentration graphene oxide aqueous solution is 1:10-1:100.

[0036] In some embodiments, specifically, the temperature of the gelation treatment in step S4 is 60-80° C. and the time is 8-10 hours.

[0037] In some embodiments, specifically, the temperature of the dehydration and curing in step S5 is 100-200° C., and the duration of the heat preservation treatment is 24-48 hours.

[0038] In some embodiments, specifically, in step S6, the temperature of the high-temperature carbonization is 800-1200° C.; and the duration of the heat preservation treatment is 2-10 hours.

[0039] The disclosed embodiment also provides a spherical closed-cell graphene foam prepared by the above method. Some embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. The following embodiments and features in the embodiments can be combined with each other if there is no conflict.

[0040] Embodiment 1, the preparation method of this embodiment is as follows: Preparation of high-concentration graphene oxide aqueous solution: Mix concentrated sulfuric acid, potassium permanganate, and sodium nitrate solution in a mass ratio of 180:6:2, stir at 80°C, and the total mass of the solution is 188 g. Then, take 2 g of flake graphite with a particle size of 5 mm and mix it with the above solution. Add 10 ml each of 30% aqueous hydrogen peroxide solution and 5% dilute hydrochloric acid, and stir for 24 hours.

[0041] Preparation of graphene oxide-N-N'acrylamide-methylenebisacrylamide sol: Take 13g of high-concentration graphene oxide aqueous solution, 0.1g of N-N'methylenebisacrylamide and 3g of acrylamide and stir evenly.

[0042] Preparation of microsphere suspension: Take 1 g of PMMA microspheres with a particle size of 10 μm and mix them evenly with the above sol.

[0043] Gelation treatment: The stirred microsphere suspension was placed in a vacuum drying oven at 70 °C for 10 h to complete the gelation.

[0044] Drying treatment: After gelation, the gel was dried in a vacuum drying oven at 140°C for 24 hours. Figure 1 As shown, its SEM picture is as follows Figure 2 shown.

[0045] Carbonization treatment: Carbonization treatment was then performed at 1200 °C for 2 h to complete the carbonization treatment. Figure 3 As shown, its SEM picture is as follows Figure 4 As shown, it can be seen that the graphene foam obtained in Example 1 has a spherical closed-cell structure.

[0046] Embodiment 2, the preparation method of this embodiment is as follows: Preparation of high-concentration graphene oxide aqueous solution: Mix concentrated sulfuric acid, potassium permanganate, and sodium nitrate solution in a mass ratio of 200:4:1, stir at 75°C, and the total mass of the solution is 205 g. Then, take 4 g of flake graphite with a particle size of 3 mm and mix it with the above solution. Add 10 ml of 20% aqueous hydrogen peroxide solution and 10 ml of 4% dilute hydrochloric acid, and stir for 36 hours.

[0047] Preparation of graphene oxide-N-N'acrylamide-methylenebisacrylamide sol: Take 150g of high-concentration graphene oxide aqueous solution, 0.8g of N-N'methylenebisacrylamide and 50g of acrylamide and stir evenly.

[0048] Preparation of microsphere suspension: Take 2 g of PMMA microspheres with a particle size of 10 μm and mix them evenly with the above sol.

[0049] Gelation treatment: The stirred microsphere suspension was placed in a vacuum drying oven at 80 °C for 10 h to complete the gelation.

[0050] Drying treatment: After gelation, the gel was dried in a vacuum drying oven at 130 °C for 24 h.

[0051] Carbonization treatment: The carbonization treatment was then completed at 1100 °C for 3 h.

[0052] In summary, the preparation method of the spherical closed-cell graphene foam proposes a scheme of combining a high-concentration graphene oxide aqueous solution and PMMA microspheres to prepare graphene foam. On the one hand, by introducing acrylamide-N-N'methylenebisacrylamide sol into the high-concentration graphene oxide aqueous solution, the acrylamide-N-N'methylenebisacrylamide sol will be carbonized and fix the graphene oxide during the heat treatment process, so that the high-concentration graphene oxide has good encapsulation of the PMMA microspheres and can form a closed-cell structure; on the other hand, compared with PU microspheres, PMMA microspheres have good shaping ability in the gel, so that the closed cells present a spherical morphology, thereby improving the load-bearing performance of the graphene foam.

[0053] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A method for preparing spherical closed-cell graphene foam, characterized in that: The steps include: Step S1, preparing a high-concentration graphene oxide aqueous solution, that is, mixing concentrated sulfuric acid with potassium permanganate and sodium nitrate, heating to prepare a manganese anhydride solution, mixing flake graphite with the manganese anhydride solution, heating and stirring, and then sequentially adding a hydrogen peroxide aqueous solution and dilute hydrochloric acid, and after the reaction is completed, standing and removing the supernatant to obtain a high-concentration graphene oxide aqueous solution; Step S2, preparing graphene oxide-acrylamide-N-N'methylenebisacrylamide sol, that is, mixing N-N'methylenebisacrylamide and deionized water, adding the high-concentration graphene oxide aqueous solution prepared in step S1 after the N-N'methylenebisacrylamide is completely dissolved, adding acrylamide after the graphene oxide is completely dissolved, and mixing evenly to obtain graphene oxide-acrylamide-N-N'methylenebisacrylamide sol; Step S3, adding graphene oxide-acrylamide-N-N'methylenebisacrylamide sol to PMMA microspheres to obtain a PMMA microsphere suspension; Step S4, gelling the PMMA microsphere suspension to obtain a gel; Step S5, dehydrating and solidifying the gel to obtain a graphene oxide-PMMA microsphere composite material block; Step S6, carbonizing the graphene oxide-PMMA microsphere composite material block obtained in S5 at high temperature to obtain spherical closed-cell graphene foam.

2. The preparation method according to claim 1, characterized in that In step S1 The mass ratio of the concentrated sulfuric acid to potassium permanganate is 30:1-70:1, and the mass ratio of the concentrated sulfuric acid to sodium nitrate is 90:1-450:

1.

3. The preparation method according to claim 1, characterized in that: In step S1 The particle size of the flake graphite is 2-5 mm, and the mass ratio of the flake graphite to concentrated sulfuric acid is 1:100-1:

10.

4. The preparation method according to claim 1, characterized in that: In step S1 The concentration of the aqueous hydrogen peroxide solution is 10%-30%, and the concentration of the dilute hydrochloric acid is 2%-5%.

5. The preparation method according to claim 1, characterized in that: In step S1 The heating and stirring temperature is 60-80° C. and the stirring time is 24-48 hours.

6. The preparation method according to claim 1, characterized in that: In step S2 The mass ratio of acrylamide, N-N'methylenebisacrylamide and high-concentration graphene oxide aqueous solution is (10-90): (0.7-1): (130-170).

7. The preparation method according to claim 1, characterized in that: In step S3 The PMMA microspheres have a particle size of 1 μm to 50 μm; and The mass ratio of the PMMA microspheres to the high-concentration graphene oxide aqueous solution is 1:10-1:

100.

8. The preparation method according to claim 1, characterized in that: In step S4 The gelation treatment is carried out at a temperature of 60-80°C and for a time of 8-10 hours.

9. The preparation method according to claim 1, characterized in that: In step S5 The dehydration and curing temperature is 100-200°C, and the insulation treatment time is 24-48h.

10. The preparation method according to claim 1, characterized in that: In step S6, The temperature of the high-temperature carbonization is 800-1200°C; the duration of the heat preservation treatment is 2-10h.

11. A spherical closed-cell graphene foam prepared by the preparation method according to any one of claims 1 to 10.

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