Graphene-based aerogel as well as rapid preparation method and application thereof

Abstract

The invention discloses graphene-based aerogel and a rapid preparation method and application thereof, and the rapid preparation method comprises the following steps: carrying out solvothermal reaction on ferric salt and an organic ligand to prepare a precursor; the precursor is calcined in an inert atmosphere, and the MOF-derived Fe3O4 (at) C nanorod is obtained; the preparation method comprises the following steps: uniformly mixing graphene oxide, ascorbic acid and Fe3O4 (at) C nanorods according to a mass ratio of (1-7): (2-14): (2-5), and then carrying out hydrothermal reaction to prepare rGO hydrogel; completely freezing the rGO hydrogel, and then unfreezing the rGO hydrogel; and drying the unfrozen rGO hydrogel, so as to obtain the rGO aerogel. The preparation process of the material simultaneously has the characteristics of rapid gelling and rapid drying, and the speed can be increased in the two key processes of aerogel preparation, so that the production efficiency is improved and the production cost is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of aerogel preparation, and particularly relates to a graphene-based aerogel, a rapid preparation method thereof, and an application thereof. Background Art

[0002] The statements herein only provide background art related to the present invention and do not necessarily constitute prior art.

[0003] An aerogel refers to a nano-porous solid material formed by replacing the liquid phase in a gel with a gas through a sol-gel method, having an extremely high porosity and specific surface area, and being widely used in fields such as adsorption, catalysis, thermal management, and electromagnetic wave absorption, with broad application prospects. Current aerogel manufacturing methods, such as freeze drying and supercritical drying, require a large amount of energy, harsh process parameters, and a long synthesis time (at least 24 hours).

[0004] In addition, the strength and toughness of aerogels are very low, and they are easily damaged by external forces in the form of vibration, pressure, and impact. When an aerogel is frozen, the water molecules in it will crystallize and release heat, which may cause stress accumulation inside the aerogel and further damage its structure. Therefore, to avoid the fragmentation of aerogels, various factors, including temperature, humidity, and vibration, need to be controlled during the preparation, storage, and use processes, and collisions also need to be avoided, and the conditions are relatively harsh. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a graphene-based aerogel, a rapid preparation method thereof, and an application thereof. The preparation process of this material has the characteristics of rapid gelation and rapid drying at the same time, can accelerate the speed in two key processes of aerogel preparation, thereby improving production efficiency and reducing production costs.

[0006] To achieve the above purpose, the present invention is realized through the following technical solutions:

[0007] In a first aspect, the present invention provides a rapid preparation method of a graphene-based aerogel, comprising the following steps:

[0008] Performing a solvothermal reaction on an iron salt and an organic ligand in a mass ratio of 2 - 3:1 to obtain a precursor;

[0009] Calcining the precursor in an inert atmosphere to obtain MOF-derived Fe 3 O 4 @C nanorods;

[0010] Mixing graphene oxide, ascorbic acid, and Fe 3 O 4@C nanorods are uniformly mixed in a mass ratio of 1-7:2-14:2-5, and then rGO hydrogel is prepared through a hydrothermal reaction.

[0011] After the rGO hydrogel is completely frozen, it is thawed again.

[0012] The thawed rGO hydrogel is dried to obtain rGO aerogel.

[0013] The process of complete freezing and then thawing mainly relies on the freezing process to create a macroporous structure, thereby reducing the capillary force by expanding the pores and avoiding the collapse of the pore structure due to excessive capillary force during atmospheric pressure drying.

[0014] In some embodiments, the iron salt is ferric chloride, ferric nitrate or ferric sulfate.

[0015] In some embodiments, the organic ligand is fumaric acid. Only fumaric acid can be used, otherwise the state of the synthesized MOF will change and it will be difficult to meet the requirements.

[0016] In some embodiments, the temperature of the solvothermal reaction is 80-120 °C, and the reaction time is 2-6 h. For example, the temperature of the solvothermal reaction can be 80 °C, 81 °C, 82 °C, 83 °C, 84 °C, 85 °C, 86 °C, 87 °C, 88 °C, 89 °C, 90 °C, 91 °C, 92 °C, 93 °C, 94 °C, 95 °C, 96 °C, 97 °C, 98 °C, 99 °C, 100 °C, 101 °C, 102 °C, 103 °C, 104 °C, 105 °C, 106 °C, 107 °C, 108 °C, 109 °C, 111 °C, 111 °C, 112 °C, 113 °C, 114 °C, 115 °C, 116 °C, 117 °C, 118 °C, 119 °C, 120 °C.

[0017] Preferably, the temperature of the solvothermal reaction is 90-110 °C, and more preferably 95-100 °C.

[0018] In some embodiments, the calcination temperature is 400-800 °C, the calcination time is 1-3 h, and the heating rate is 1-3 °C / min. For example, it can be 400 °C, 450 °C, 500 °C, 550 °C, 600 °C, 650 °C, 700 °C, 750 °C or 800 °C. The calcination time can be 1 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h, 2 h, 2.1 h, 2.2 h, 2.3 h, 2.4 h, 2.5 h, 2.6 h, 2.7 h, 2.8 h, 2.9 h or 3 h.

[0019] Preferably, the calcination temperature is 400-800 °C, preferably 500-700 °C, and more preferably 550-650 °C.

[0020] In some embodiments, the temperature of the hydrothermal reaction is 75-100°C, and the reaction time is 20-60 min. For example, the temperature can be 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C, 90°C, 91°C, 92°C, 93°C, 94°C, 95°C, 95°C, 97°C, 98°C, 99°C, 100°C.

[0021] The reaction time can be 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min.

[0022] Preferably, the temperature of the hydrothermal reaction is 80-100° C., and the reaction time is 20-40 min; further preferably, the temperature of the hydrothermal reaction is 90-95° C., and the reaction time is 25-35 min.

[0023] In some embodiments, the freezing temperature is -60 to -20°C, such as -60°C, -55°C, -50°C, -45°C, -40°C, -35°C, -30°C, -25°C or -20°C.

[0024] Preferably, the freezing temperature is -40 to -20°C; more preferably, the freezing temperature is -25 to -20°C.

[0025] In some embodiments, Fe 3 O 4 @C The mass ratio of nanorods and graphene oxide GO is 5:2-6.

[0026] In a second aspect, the present invention provides a graphene-based aerogel prepared by the preparation method.

[0027] In a third aspect, the present invention provides the use of the graphene-based aerogel in preparing an electromagnetic wave absorbing device.

[0028] The beneficial effects achieved by one or more embodiments of the present invention are as follows:

[0029] (1) The rapid preparation method of rGO aerogel material proposed in the present invention comprises the following steps: 3 O 4 Fe@C nanorod surface 3 O 4 The particles undergo etching reaction to generate iron ions to cross-link GO, which accelerates the gelation of GO. This process accelerates the synthesis of rGO hydrogel. On the other hand, the rigid Fe 3 O 4The @C nanorods are embedded in the pore walls of the rGO hydrogel, which can improve the mechanical properties of the pore walls of the hydrogel and stabilize the structure of the hydrogel; Thirdly, Fe 3 O 4 The Fe 3 O 4 particles inside the @C nanorods will not undergo an etching reaction with ascorbic acid under the protection of graphite carbon. Therefore, the entire sample still retains its magnetism in the end. Under the multiple loss mechanisms of the dielectric loss of rGO and the magnetic loss of magnetic Fe 3 O 4 , the rapidly synthesized rGO aerogel has excellent electromagnetic wave absorption characteristics.

[0030] (2) Compared with the prior art, the preparation process adopted in the present invention can rapidly form an rGO hydrogel within 25 minutes and be stabilized by metal-organic framework derivatives. Subsequently, a nanostructured aerogel is produced by drying under atmospheric pressure within 4.5 hours, and the synthesis speed is 3 times faster than the previous benchmark. It is worth noting that the obtained aerogel can maintain its pore structure even under strong wet-dry cycles and atmospheric pressure.

[0031] (3) The reflection loss of the rGO aerogel prepared under atmospheric pressure and rapidly to electromagnetic waves reaches -66.91 dB at a frequency of 12.16 GHz, the matching thickness is only 3.57 mm, and the best effective absorption bandwidth reaches 6.65 GHz. The rGO aerogel prepared under atmospheric pressure and rapidly has certain wave absorption performance and has wide application value.

[0032] (4) The process method for rapidly and efficiently preparing rGO aerogel proposed in the present invention can promote their large-scale application in the field of electromagnetic wave absorption due to its low cost and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The specification drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0034] Figure 1 SEM image of the MOF-derived Fe 3 O 4 @C nanorods prepared in Example 1.

[0035] Figure 2 TEM image of the GO used in Example 1.

[0036] Figure 3 Optical photographs of the rGO hydrogel formed during the preparation processes of Example 1 and Comparative Example 1.

[0037] Figure 4The storage modulus and loss modulus of the rGO hydrogel formed during the preparation processes of Example 1 and Comparative Example 1.

[0038] Figure 5 The drying process data and optical photos of the rGO aerogel formed during the preparation processes of Example 1 and Comparative Example 1.

[0039] Figure 6 The XRD patterns of the rGO aerogel formed during the preparation processes of Example 1 and Comparative Example 1.

[0040] Figure 7 The optical photos of the large-sized rGO aerogel formed during the preparation process of Example 1.

[0041] Figure 8 The SEM images of the large-sized rGO aerogel formed during the preparation process of Example 1.

[0042] Figure 9 The "dry-wet" cycle data of the rGO aerogel formed during the preparation process of Example 1.

[0043] Figure 10 The dielectric constant of the rGO aerogel formed during the preparation process of Example 1.

[0044] Figure 11 The magnetic permeability of the rGO aerogel formed during the preparation process of Example 1.

[0045] Figure 12 The reflection loss diagrams of the rGO aerogel formed during the preparation process of Example 1. Detailed implementation manners

[0046] It should be noted that the following detailed descriptions are all illustrative and are intended to provide further explanations of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0047] The present invention will be further described below in conjunction with examples.

[0048] Example 1

[0049] (1) Dissolve 2.168 g of ferric chloride hexahydrate and 0.9288 g of fumaric acid in 70 mL of deionized water. After stirring for 30 min, a homogeneous solution is obtained, which is then transferred to a 100 ml hydrothermal reactor and reacted at 100 °C for 4 h. After cooling to room temperature, the product is separated by centrifugation, washed three times with water and ethanol, and dried overnight at 60 °C to obtain the MIL88A precursor.

[0050] (2) The MIL88A precursor obtained in (1) was annealed at 600 °C for 2 h in a nitrogen atmosphere to obtain the MOF-derived Fe 3 O 4 @CNanorods.

[0051] (3) Pour the GO aqueous solution into a beaker, and then add ascorbic acid to the beaker with a mass ratio of GO to ascorbic acid of 1:2 while stirring. 3 O 4 The mass ratio of @C is 5:4. Take the Fe obtained in (2) 3 O 4 @C nanorods were introduced into the above solution. The resulting solution was then heated to 95°C for 25 min to obtain rGO hydrogel. These hydrogels were completely frozen and thawed at -20°C and finally dried in an oven to obtain ambient pressure dried rGO aerogel.

[0052] (4) The rGO aerogel obtained in (3) was subjected to electromagnetic parameter testing using an Agilent Technologies E8363A electromagnetic wave vector network analyzer, and the wave absorption performance of the material was calculated based on the electromagnetic parameters to obtain the following: Figure 12 Results shown.

[0053] from Figure 1 It can be seen that the three elements Fe, C, and O are evenly distributed in the MOF-derived Fe 3 O 4 @CNanorods.

[0054] from Figure 2 It can be seen that the GO used in the experiment is in a large-sized monolithic state.

[0055] from Figure 3 It can be seen that compared with the hydrogel without adding MOF derivatives, the volume of the hydrogel is significantly reduced after adding MOF derivatives, indicating that MOF derivatives can promote gelation.

[0056] from Figure 4 It can be seen that compared with the hydrogel without adding MOF derivatives, the storage modulus of the hydrogel increased significantly after adding MOF derivatives, indicating that MOF derivatives can strengthen the skeleton of the hydrogel and ensure that the volume does not shrink during normal pressure drying.

[0057] from Figure 5 It can be seen that under the same drying conditions, the hydrogel with added MOF derivatives can be completely dried within 4.5 hours without structural collapse, while the hydrogel without MOF derivatives suffers from severe structural collapse during the drying process.

[0058] from Figure 6It can be seen that after the hydrogel containing MOF derivatives is dried, Fe exists in the aerogel 3 O 4 phase, indicating that the magnetic particles inside the MOF derivatives are retained, and the whole sample still exhibits good magnetism.

[0059] From Figure 7 it can be seen that based on the characteristics of atmospheric drying, the sample preparation is not limited by the size of the instrument, so it is very suitable for the large-scale preparation of aerogels.

[0060] From Figure 8 it can be seen that after drying, the obtained aerogel still exhibits the characteristics of a porous structure, and the pore structure does not shrink and collapse due to the existence of capillary force.

[0061] From Figure 9 it can be seen that the obtained rGO aerogel can be cycled multiple times in wet and dry environments without structural collapse.

[0062] From Figure 10 and Figure 11 it can be seen that the obtained rGO aerogel has good electromagnetic parameters and has the potential to be an excellent electromagnetic wave absorption material.

[0063] From Figure 12 it can be seen that the rGO aerogel absorbing material has excellent electromagnetic wave absorption performance. The reflection loss of electromagnetic waves reaches -66.91 dB at a frequency of 12.16 GHz, the matching thickness is only 3.57 mm, and the best effective absorption bandwidth reaches 6.65 GHz.

[0064] Comparative Example 1

[0065] (1) Dissolve 2.168 g of ferric chloride hexahydrate and 0.9288 g of fumaric acid in 70 mL of deionized water. After stirring for 30 min, a homogeneous solution is obtained, and then it is transferred to a 100 ml hydrothermal reactor and reacted at 100 °C for 4 h. After cooling to room temperature, the product is separated by centrifugation, washed three times with water and ethanol, and dried at 60 °C overnight to obtain the MIL88A precursor.

[0066] (2) Take the MIL88A precursor obtained in (1) and anneal it at 600 °C for 2 hours in a nitrogen atmosphere to obtain MOF-derived Fe 3 O 4 @C nanorods.

[0067] (3) Pour the aqueous solution of GO into a beaker, and then add ascorbic acid to the beaker while stirring according to the mass ratio of GO to ascorbic acid of 1:2. Then heat the resulting solution to 95 °C and react for 25 min to obtain rGO hydrogel. These hydrogels were completely frozen and thawed at -20 °C, and finally dried in an oven to obtain ambient pressure dried rGO aerogel.

[0068] The difference from Example 1 is that in the third step of the preparation process, MOF-derived Fe 3 O 4 @C nanorods were not added, only the mixed solution of GO and ascorbic acid.

[0069] Example 2

[0070] (1) Dissolve 2.154 g of ferric chloride hexahydrate and 0.9123 g of fumaric acid in 70 mL of deionized water. After stirring for 30 min to obtain a homogeneous solution, then transfer it to a 100 ml hydrothermal reactor and react at 120 °C for 2 h. After cooling to room temperature, centrifuge to separate the product, wash it three times with water and ethanol, and dry it at 60 °C overnight to obtain the MIL88A precursor.

[0071] (2) Take the MIL88A precursor obtained in (1) and anneal it at 800 °C for 2 h in a nitrogen atmosphere to obtain MOF-derived Fe 3 O 4 @C nanorods.

[0072] (3) Pour the aqueous solution of GO into a beaker, and then add ascorbic acid to the beaker while stirring according to the mass ratio of GO to ascorbic acid of 1:2. Subsequently, under ultrasonic treatment, take the Fe 3 O 4 @C obtained in (2) according to the mass ratio of GO to Fe 3 O 4 @C of 5:2 and introduce it into the above solution.

[0073] Then heat the resulting solution to 90 °C and react for 35 min to obtain rGO hydrogel.

[0074] The rGO hydrogel was completely frozen and thawed at -20 °C, and finally dried in an oven to obtain ambient pressure dried rGO aerogel.

[0075] Example 3

[0076] (1) Dissolve 2.026 g of ferric chloride hexahydrate and 0.9034 g of fumaric acid in 70 mL of deionized water. After stirring for 30 min, a homogeneous solution is obtained, which is then transferred to a 100 mL hydrothermal autoclave and reacted at 80 °C for 6 h. After cooling to room temperature, the product is separated by centrifugation, washed three times with water and ethanol, and dried at 60 °C overnight to obtain the MIL88A precursor.

[0077] (2) Take the MIL88A precursor obtained in (1) and anneal it at 400 °C for 3 h in a nitrogen atmosphere to obtain the MOF-derived Fe 3 O 4 @C nanorods.

[0078] (3) Pour the aqueous solution of GO into a beaker, and then add ascorbic acid to the beaker according to the mass ratio of GO to ascorbic acid of 1:2 while stirring. Subsequently, take the Fe 3 O 4 @C obtained in (2) and introduce it into the above solution according to the mass ratio of GO to Fe 3 O 4 @C of 5:6 under ultrasonic treatment.

[0079] Then heat the resulting solution to 100 °C and react for 40 min to obtain the rGO hydrogel.

[0080] Freeze the rGO hydrogel completely at -40 °C, thaw it, and finally dry it in an oven to obtain the environmentally pressure-dried rGO aerogel.

[0081] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for rapidly preparing graphene-based aerogel, characterized in that: The steps include: The iron salt and the organic ligand are subjected to a solvothermal reaction at a mass ratio of 2-3:1 to obtain a precursor; The precursor was calcined in an inert atmosphere to obtain MOF-derived Fe3O4@C nanorods; Graphene oxide, ascorbic acid and Fe3O4@C nanorods were uniformly mixed in a mass ratio of 1-7:2-14:2-5, and then subjected to a hydrothermal reaction to prepare rGO hydrogel; After the rGO hydrogel is completely frozen, it is thawed; The thawed rGO hydrogel is dried to obtain rGO aerogel.

2. The method for rapidly preparing graphene-based aerogel according to claim 1, characterized in that: The iron salt is ferric chloride, ferric nitrate or ferric sulfate.

3. The method for rapidly preparing graphene-based aerogel according to claim 1, characterized in that: The organic ligand is fumaric acid.

4. The method for rapidly preparing graphene-based aerogel according to claim 1, characterized in that: The temperature of the solvent thermal reaction is 80-120°C and the reaction time is 2-6h; Preferably, the temperature of the solvothermal reaction is 90-110°C, more preferably 95-100°C.

5. The method for rapid preparation of graphene-based aerogel according to claim 1, characterized in that: The calcination temperature is 400-800°C and the calcination time is 1-3h; Preferably, the calcination temperature is 400-800°C, preferably 500-700°C, and more preferably 550-650°C.

6. The method for rapidly preparing graphene-based aerogel according to claim 1, characterized in that: The temperature of the hydrothermal reaction is 75-100°C and the reaction time is 20-60min; Preferably, the temperature of the hydrothermal reaction is 80-100° C., and the reaction time is 20-40 min; further preferably, the temperature of the hydrothermal reaction is 90-95° C., and the reaction time is 25-35 min.

7. The method for rapidly preparing graphene-based aerogel according to claim 1, characterized in that: The freezing temperature is -60 to -20°C; Preferably, the freezing temperature is -40 to -20°C; more preferably, the freezing temperature is -25 to -20°C.

8. The method for rapidly preparing graphene-based aerogel according to claim 1, characterized in that: The mass ratio of Fe3O4@C nanorods and graphene oxide GO is 5:2-6.

9. A graphene-based aerogel, characterized in that: Prepared by the rapid preparation method according to any one of claims 1 to 8.

10. Use of the graphene-based aerogel according to claim 9 in preparing an electromagnetic wave absorbing device.

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