Multi-scale structure graphene macroscopic body, preparation method thereof and application of multi-scale structure graphene macroscopic body as electromagnetic shielding material

Abstract

The invention relates to a preparation method of a graphene macroscopic body with a multi-scale structure, which comprises the following steps: (1) preparing a few stripped lamellar graphene oxide by adopting a chemical oxidation method to obtain a graphene oxide aqueous dispersion; (2) adding a surfactant into the graphene oxide aqueous dispersion obtained in the step (1), and stirring to obtain a bubble group filled graphene oxide slurry, namely a printing foaming slurry; (3) filling the foaming slurry obtained in the step (2) into an injector for direct writing and printing to obtain a three-dimensional macroscopic body with a specific shape; and (4) carrying out drying molding and reduction treatment on the three-dimensional macroscopic body obtained in the step (3) to obtain the graphene macroscopic body with the multi-scale structure. The graphene macroscopic body with the multi-scale structure prepared by the invention has the advantages of individualized customization, ultra-low density, super-strong elasticity and excellent electromagnetic shielding performance, and is an electromagnetic shielding material with good application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of electromagnetic shielding materials, and specifically relates to a multi-scale structured graphene macrobody, a preparation method thereof, and an application thereof as an electromagnetic shielding material. Background Art

[0002] The rapid development of modern electronic information technology has improved people's quality of life, but the electromagnetic interference and radiation pollution caused by it have an increasingly significant impact on the operation of electronic devices, human life and health. The development of a lightweight, strong and high-performance electromagnetic shielding material is an important means to alleviate harmful electromagnetic radiation pollution. With the continuous development of portable and implantable devices, new demands have been put forward for the customization of electromagnetic shielding material structures. Graphene macro-bodies, due to their ultra-low density, rich porosity, large specific surface area, high electrical conductivity, high thermal and chemical stability, and excellent electromagnetic shielding performance, are an electromagnetic shielding material with good application prospects. However, similar to other conventional electromagnetic shielding materials (such as one-dimensional carbon nanotubes, two-dimensional MXene, etc.), although graphene macro-bodies have excellent electromagnetic shielding capabilities, due to the poor processability of the material and the inability to achieve controllable customization using conventional graphene powders or aqueous dispersions, it is difficult to meet the current personalized customization needs of shielding material shapes for different electronic devices. This has greatly restricted the development and application of electromagnetic shielding materials.

[0003] Direct ink writing and printing is a technology that uses electromagnetic shielding material powder and thickeners to mix and prepare viscoelastic ink, and prints three-dimensional macroscopic bodies by stacking and accumulating layer by layer. It can produce complex, fine, and personalized structural devices that are difficult to manufacture with traditional processing methods, and achieve one-time molding from materials to devices. Obtaining shielding material slurry or precursor with a certain viscosity and rheology is the key to achieving direct writing and printing of three-dimensional electromagnetic shielding material macroscopic bodies. In order to improve the rheology of electromagnetic shielding material slurry, supplement and enhance the viscosity of the material, and obtain excellent printability, the electromagnetic shielding material content in the slurry is usually increased or various fillers are introduced to give the electromagnetic shielding material slurry printability. For example, to improve the rheological properties of MXene slurry, the content of MXene is increased to 28.9wt% (Orangi, et al. ACS Nano 2020, 14, 640-650); cellulose is used as a functional filler and added to the graphene oxide slurry (1.7wt%) to improve the viscosity and rheological properties of the shielding material slurry, realize continuous extrusion of the slurry, and improve the stability of the printed three-dimensional structure (Erfanian, et al. Carbon 2023, 210, 118037); or high-concentration shielding powders (15-30wt% carbon nanotubes, graphene nanosheets, metal wires, etc.) and high-concentration fillers (65-84wt% polymers) are used simultaneously to realize direct writing and printing of three-dimensional electromagnetic shielding materials (CN113561473B). However, improving the rheological properties of electromagnetic shielding slurry by the above methods will inevitably lead to a high macroscopic density and a hard structure of the final printed electromagnetic shielding material. At the same time, the introduction of fillers will have adverse effects on its mechanical and conductive properties. In addition, the existing methods only focus on improving the rheological properties of electromagnetic shielding slurries, preparing stable printable inks, and realizing personalized customization of the macroscopic shape of three-dimensional electromagnetic shielding materials, while there are few reports on the microstructural design of materials. The performance of materials is always determined by their microstructures. Under the premise of realizing personalized customization of the macrostructure of electromagnetic shielding materials, designing and controlling the microstructure of materials is of great significance and application value for realizing customized electromagnetic shielding materials with excellent performance. It is still a huge challenge to use direct writing to print lightweight and tough three-dimensional electromagnetic shielding macrobodies, realize the controllable design of the macro and microstructures of electromagnetic shielding materials, and construct electromagnetic shielding devices with excellent comprehensive performance.

[0004] The present invention uses a foaming strategy to introduce a bubble group into the slurry, improves the viscosity and rheology of the electromagnetic shielding material slurry, combines direct writing printing technology, designs a lightweight porous graphene macro-body with a specific macroscopic shape, and uses the bubble group as a template to realize the controllable regulation of the microstructure of the printed graphene macro-body. On the one hand, the introduction of the bubble group forms a large number of gas-liquid interfaces in the slurry, and the nanosheets in the slurry are evenly imprisoned in the thin film between the gas-liquid interface, thereby limiting their movement and improving the rheology of the slurry; on the other hand, the bubble group serves as a template for the self-assembly of the nanosheet layer, guiding it to cross-link with each other in the thin film at the gas-liquid interface, inhibiting its face-to-face stacking, and constructing a spherical closed porous structure wrapped by a few nanosheet layers, increasing the passage path and reflection interface of electromagnetic waves in the graphene macro-body, strengthening the capture, interference and attenuation of incident electromagnetic waves, and thereby simultaneously improving the total electromagnetic shielding performance and the proportion of absorbed electromagnetic waves. At present, there is no report on the preparation of graphene electromagnetic shielding macro-bodies by introducing bubble groups and combining 3D printing technology to simultaneously realize multi-scale regulation of macro and micro structures. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a multi-scale structured graphene macro-body and its electromagnetic shielding material in view of the key difficulties in the existing electromagnetic shielding material preparation technology. The method only uses a bubble group to adjust the rheological properties of the graphene oxide aqueous dispersion, which not only realizes the direct writing and printing of low-concentration graphene oxide slurry without adding any filler, but also provides a bubble template for the self-assembly of nanosheets, guides the orderly arrangement of two-dimensional nanosheets, inhibits the stacking of nanosheets, and constructs a spherical closed porous structure wrapped by a few nanosheets, giving full play to the reflection and dissipation effect of the nanosheets on electromagnetic waves, and strengthening the interference and attenuation of electromagnetic waves inside the material.

[0006] One of the purposes of the present invention is to provide a method for preparing a multi-scale structured graphene macro-body, characterized in that it comprises the following steps:

[0007] Obtaining graphene oxide dispersion: preparing a few exfoliated graphene oxide sheets by chemical oxidation method, and obtaining graphene oxide aqueous dispersion as initial slurry;

[0008] Obtaining printable foaming ink: adding a surfactant to the graphene oxide aqueous dispersion, stirring to obtain a graphene oxide slurry filled with bubble groups, and obtaining a foaming slurry, i.e., printable foaming ink;

[0009] Obtaining a three-dimensional macroscopic body of a specific shape by direct writing and printing: the obtained foaming slurry is loaded into a syringe with a needle, and the slurry is continuously and smoothly extruded onto a low-temperature aluminum plate for direct writing and printing to obtain a three-dimensional macroscopic body of a specific shape;

[0010] Obtaining a multi-scale structured graphene macrobody: placing the obtained three-dimensional macrobody in a -20°C refrigerator for 30 minutes, then drying it into shape, removing the internal ice crystals, preferably drying it for 24 to 48 hours, and then performing high-temperature heat treatment or chemical reduction under the protection of an inert atmosphere to finally obtain a 3D printed multi-scale structured graphene macrobody.

[0011] Furthermore, in the step of obtaining the graphene oxide dispersion, the graphene oxide in the graphene oxide aqueous solution is obtained by chemical oxidation methods including Hummers method, modified Hummers method, Brodie method and Staudenmaier method;

[0012] Preferably, the concentration of the graphene oxide aqueous solution is 0.5wt% to 2wt%;

[0013] Furthermore, in the step of obtaining the printable foaming ink, the added surfactant is any one of alkyl glucoside, sodium dodecylbenzene sulfonate, and stearic acid;

[0014] Preferably, the mass ratio of the surfactant to graphene oxide is 1:2 to 2:1;

[0015] Furthermore, in the step of obtaining the printable foaming ink, cellulose, polyethylene glycol or polyvinyl alcohol or the like may be added as a foam stabilizer to improve the stability of the foaming ink at room temperature;

[0016] Furthermore, in the step of obtaining the printable foamable ink, the stirring method includes any one or more combinations of mechanical stirring, magnetic stirring, and vortex oscillation;

[0017] Preferably, the stirring is mechanical stirring, the stirring rate is 500 to 5000 rpm, and the stirring time is 2 to 10 minutes; more preferably, the mechanical stirring rate is 1000 to 3000 rpm, and the stirring time is 4 to 6 minutes;

[0018] Furthermore, in the step of obtaining a three-dimensional macroscopic body of a specific shape by direct writing and printing, the inner diameter of the syringe needle is 200 to 1000 μm, the extrusion printing moving speed is 1 to 10 mm / s, the extrusion pressure is 30 to 300 kPa, and the surface temperature of the aluminum plate is -10 to 0°C;

[0019] Furthermore, in the step of obtaining the multi-scale structured graphene macro-body, the drying and molding method includes vacuum freeze drying and CO2 supercritical drying;

[0020] Furthermore, in the step of obtaining the multi-scale structured graphene macro-body, the reduction method includes any one of thermal reduction and chemical reduction;

[0021] Preferably, the temperature of the thermal reduction treatment is 400-1500°C, the heat treatment time is 20-120 minutes, the heating rate is 5-30°C / min, and the inert gas protection includes nitrogen atmosphere and argon atmosphere; more preferably, the temperature of the high temperature heat treatment is 500-1000°C, and the heat treatment time is 20-60 minutes;

[0022] The second object of the present invention is to provide a multi-scale structured graphene macrobody, which is prepared by the method described in one of the objects. The multi-scale structured graphene macrobody has the characteristics of personalized customizable macroscopic shape, ultra-low density, and super elasticity. Nanosheets are orderly assembled on a microscopic scale to form a spherical closed porous structure wrapped by a regular small number of sheets.

[0023] The third object of the present invention is to provide an electromagnetic shielding material, which is a multi-scale structured graphene macrobody prepared by the method described in one of the objects.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention uses graphene oxide aqueous dispersion as the initial slurry, introduces bubble groups by stirring method, improves the viscoelasticity of graphene oxide aqueous dispersion, prepares printable graphene oxide foaming ink, and realizes 3D printing of macro structures of specific shapes; at the same time, the bubble groups are used as templates to guide the orderly self-assembly of nanosheets to construct a spherical closed porous network structure wrapped by a few nanosheets; finally, a 3D printed multi-scale structured graphene macro-body is obtained by drying, molding and reduction treatment. The present invention chooses to introduce bubble groups into the graphene oxide aqueous dispersion as viscosity regulators, without adding additional fillers or increasing the content of electromagnetic shielding materials, to achieve controllable customization of the three-dimensional structure of the graphene electromagnetic shielding macro-body; and uses bubble groups to guide the orderly self-assembly of nanosheets to complete the design of the microstructure. The multi-scale structured graphene electromagnetic shielding macro-body after reduction treatment has good inter-lamellar connection, rich internal pores, and can withstand thousands of compression-rebound cycle tests, showing characteristics such as rapid custom printing, ultra-low density, super elasticity and excellent electromagnetic shielding performance, as follows:

[0026] (1) Quick custom printing

[0027] The graphene oxide foaming ink based on bubble groups provided by the present invention uses only the number of bubble groups to adjust its viscoelasticity, and the viscosity range can be controlled within 1 to 2000 Pa·s, with excellent rheological properties and room temperature stability. The foaming ink can adapt to extrusion writing and printing with needles of different inner diameters, ensuring continuous and smooth extrusion from the needle, while maintaining the formed shape after extrusion, and finally drying, forming and reducing to obtain a high-precision three-dimensional customized macroscopic body.

[0028] This method can bring out the functionality of the prepared material without removing the filler.

[0029] (2) Ultra-low density

[0030] The preparation method of the present invention directly uses the bubble group as a viscosity regulator, without increasing the content of functional materials or adding additional fillers, which greatly reduces the amount of materials used; the bubble group is used as a template to construct a rich porous structure inside the material, which further reduces the density of the electromagnetic shielding material. Therefore, the graphene electromagnetic shielding macroscopic body finally obtained exhibits an ultra-low density characteristic, and its density is only 0.001-0.010 g / cm 3 .

[0031] (3) Super elasticity

[0032] It has been verified through experiments that the multi-scale structured graphene electromagnetic shielding macro-body obtained by the preparation method of the present invention can still maintain its good structure after 1000 compression cycle tests, and can immediately (within 1 s) return to its original height after the external force is removed.

[0033] (4) Excellent electromagnetic shielding performance

[0034] The multi-scale structured graphene electromagnetic shielding macro-body obtained by the preparation method of the present invention has an electromagnetic shielding performance of up to 103.2dB when the thickness is 1cm, and the surface reflection is only 4.8dB. When the thickness and density of the shielding material are comprehensively considered, its specific electromagnetic shielding performance can reach up to 52252dB·cm 2 / g, which is the largest value among the foam materials reported so far. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a macroscopic morphology image of the 3D printed multi-scale structured graphene electromagnetic shielding macroscopic body prepared in Example 1.

[0036] Figure 2 This is a scanning electron microscope image of the multi-scale structured graphene electromagnetic shielding macrostructure prepared in Example 1.

[0037] Figure 3 This is a scanning electron microscope image of the conventional graphene macrostructure prepared in Comparative Example 1.

[0038] Figure 4 This is a cyclic compression test diagram of the multi-scale structured graphene electromagnetic shielding macroscopic body in Example 1.

[0039] Figure 5 This is a cyclic compression test diagram of the conventional graphene macrobody prepared in Comparative Example 1.

[0040] Figure 6This is a comparison chart of the electromagnetic shielding performance of the graphene macro-bodies prepared in Examples 1-3 and Comparative Example 1. DETAILED DESCRIPTION

[0041] Embodiments of the present invention are described in detail below, and the examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions from beginning to end. The embodiments described below by reference to the accompanying drawings are exemplary, are intended to be used to explain the present invention, and are not to be construed as limitations of the present invention. Those who do not indicate specific techniques or conditions in the embodiments are carried out according to the techniques or conditions described in the literature in this area or according to the product specification. Those who do not indicate the manufacturer of reagents or instruments used are all conventional products that can be obtained commercially.

[0042] Example 1

[0043] Step 1: preparing a few exfoliated graphene oxide sheets by conventional modified Hummers chemical oxidation method, and dialysis purification to obtain a graphene oxide aqueous dispersion with a concentration of 0.8 wt%;

[0044] Step 2: Take 60 mL of the graphene oxide aqueous dispersion in step 1, add 0.45 g of alkyl glycoside, introduce a large number of bubbles by mechanical stirring, the mechanical stirring rate is 2000 rpm, and the stirring time is 5 min to obtain a graphene oxide slurry filled with bubble groups, which is a printable foaming ink;

[0045] Step 3: The graphene oxide foaming slurry in step 2 is loaded into a syringe with a needle having an inner diameter of 400 μm, and then the syringe is fixed on an operating table, and the moving speed and extrusion pressure are set to 4 mm / s and 140 kPa, and the ink is continuously and smoothly extruded onto a low-temperature aluminum plate, and the surface temperature of the aluminum plate is set to -4°C, and a specific grid-shaped three-dimensional macroscopic body is prepared by direct ink writing layer by layer printing;

[0046] Step 4: Place the three-dimensional grid-like macrobody in step 3 in a -20°C refrigerator for 30 minutes, then freeze-dry it to form, remove the internal ice crystals, and freeze-dry it for 24 hours. Then, heat treat it at 500°C for 1 hour under argon atmosphere protection, with a heating rate of 20°C / min, and finally obtain a 3D printed multi-scale structured graphene macrobody.

[0047] The obtained graphene oxide foaming slurry has a maximum viscosity of 1500Pa·s, and its viscosity and rheological properties are significantly improved, showing non-Newtonian fluid characteristics; the density of the obtained 3D printed multi-scale structured graphene electromagnetic shielding macro-body is 0.0045g / cm 3 (<0.01g / cm 3, that is, an ultra-light structure); the electrical conductivity can reach 36.9S / m; after 1000 compression cycle tests, it can still maintain its good structure, and can rebound to its original height immediately (within 1 second) after the external force is removed. When the compression amount is 90%, its compression modulus reaches 78.3kPa; when the thickness is 0.6cm, its total electromagnetic shielding performance can reach 76.4dB, of which the surface reflection is 4.5dB and the internal absorption is 70.9dB.

[0048] Example 2

[0049] Compared with Example 1, the only difference between this embodiment is that the mechanical stirring rate in step 2 is increased to 3000 rpm, and the rest are the same, that is, a 3D printed multi-scale structured graphene electromagnetic shielding macroscopic body with ultra-lightness, ultra-strong elasticity and high electromagnetic shielding performance is obtained.

[0050] The viscosity and rheological properties of the obtained graphene oxide foaming slurry are improved, showing non-Newtonian fluid characteristics; the density of the obtained multi-scale structured graphene electromagnetic shielding macrobody is only 0.0033g / cm 3 ; The electrical conductivity is 23.2S / m; It exhibits more excellent resilience performance, and almost no performance degradation occurs during repeated compression, but when the compression amount is 90%, its compression modulus is reduced to 39.6kPa; when the thickness is 0.6cm, its total electromagnetic shielding performance can reach 64.0dB, of which the surface reflection is 4.1dB and the internal absorption is 59.9dB.

[0051] Example 3

[0052] Compared with Example 1, the difference between this embodiment is that the mechanical stirring rate in step 2 is reduced to 1000 rpm, and the rest are the same, that is, a 3D printed multi-scale structured graphene electromagnetic shielding macroscopic body with ultra-lightness, ultra-strong elasticity and high electromagnetic shielding performance is obtained.

[0053] The obtained graphene oxide foaming slurry exhibits non-Newtonian fluid properties; the density of the obtained multi-scale structured graphene electromagnetic shielding macrobody is 0.0056g / cm 3 ; The electrical conductivity is 46.5S / m; It exhibits good resilience performance, and its compression modulus is 55.9kPa when the compression amount is 90%; When the thickness is 0.6cm, its total electromagnetic shielding performance can reach 65.7dB, of which the surface reflection is 4.7dB and the internal absorption is 61.0dB.

[0054] Example 4

[0055] Compared with Example 1, the only difference between this embodiment and Example 1 is that the concentration of graphene oxide in step 1 is changed to 1.0wt%, and the rest are the same, that is, a multi-scale structured graphene electromagnetic shielding macro-body with ultra-lightness, ultra-strong elasticity and high electromagnetic shielding performance is obtained. The density of the multi-scale structured graphene electromagnetic shielding macro-body obtained by this method is slightly increased, and the elasticity, Young's modulus, electrical conductivity and electromagnetic shielding capability are all increased.

[0056] The obtained graphene oxide foaming slurry exhibits non-Newtonian fluid properties; the density of the obtained multi-scale structured graphene electromagnetic shielding macrobody is 0.0051g / cm 3 ; The electrical conductivity is 40.2S / m; It exhibits good resilience performance, and its compression modulus is 85.4kPa when the compression amount is 90%; When the thickness is 0.6cm, its total electromagnetic shielding performance can reach 79.5dB, of which the surface reflection is 4.6dB and the internal absorption is 74.9dB.

[0057] Example 5

[0058] Compared with Example 1, the difference between this embodiment is that the alkyl glycoside in step 2 is changed to sodium dodecylbenzene sulfonate, and the addition amount of sodium dodecylbenzene sulfonate is kept at 0.45g. The rest are the same, that is, a multi-scale structured graphene electromagnetic shielding macrobody with ultra-lightness, ultra-elasticity and high electromagnetic shielding performance is obtained.

[0059] The obtained graphene oxide foaming slurry exhibits non-Newtonian fluid properties and is printable; the density of the obtained multi-scale structured graphene electromagnetic shielding macrobody is 0.0046 g / cm 3 ; The electrical conductivity can reach 37.5S / m; It also exhibits good resilience and can immediately (within 1 second) recover to its original height after hundreds of compression cycles; When the thickness is 0.6cm, its total electromagnetic shielding performance can reach 77.6dB, of which the surface reflection is 4.5dB and the internal absorption is 73.1dB.

[0060] Example 6

[0061] The present embodiment is different from the embodiment 1 in that 0.48 g of cellulose is additionally added as a foam stabilizer in step 2, thereby obtaining a multi-scale structured graphene electromagnetic shielding macro-body with ultra-lightness, ultra-strong elasticity and high electromagnetic shielding performance.

[0062] The density of the obtained multi-scale graphene electromagnetic shielding macrobody is increased to 0.0098g / cm 3 , the electrical conductivity, mechanical properties and electromagnetic shielding properties all decreased slightly.

[0063] Comparative Example 1

[0064] Step 1: preparing a few exfoliated graphene oxide sheets by conventional modified Hummers chemical oxidation method, and dialysis purification to obtain a graphene oxide aqueous dispersion with a concentration of 0.8 wt%;

[0065] Step 2: Place 60 mL of the mixed solution from step 1 into a mold and directly freeze it in a -20°C refrigerator for 1 hour;

[0066] Step 3: Freeze-dry the frozen material in step 2 to remove the internal ice crystals. The freeze-drying time is 24 hours. Then, heat treat it at 500°C for 1 hour under argon atmosphere protection with a heating rate of 5°C / min to finally obtain a conventional graphene macrobody with well-preserved morphology.

[0067] Due to the introduction of no bubble groups, the initial graphene oxide dispersion cannot be directly used for extrusion printing and can only be formed with the help of a mold; the density of the conventional graphene macrobody obtained is 0.0071g / cm 3 ; The electrical conductivity can reach 74.4S / m; but its mechanical properties are poor. After several cycles of compression, it produces irreversible deformation of more than 50% of the original height; when the thickness is 0.6cm, its total electromagnetic shielding performance is 58.8dB, of which the surface reflection is 4.9dB and the internal absorption is 53.9dB.

[0068] Comparative Example 2

[0069] The only difference between this comparative example and comparative example 1 is that the heating rate in step 3 is adjusted to 20°C / min, which ultimately leads to structural disintegration of the material during the high-temperature heat treatment process and the inability to maintain a stable macroscopic structure, and has no testing and application value.

[0070] Comparative Example 3

[0071] Compared with Example 1, the only difference between this comparative example and Example 1 is that the concentration of the graphene oxide dispersion in step 1 is controlled to 0.4wt%, and the rest are the same. The graphene oxide foaming slurry obtained by this method has a low viscosity and still exhibits a certain fluidity, and the bubble group has poor stability at room temperature, and cannot effectively maintain a three-dimensional structure after extrusion, so it cannot be used as a printing ink to achieve extrusion printing of customized shapes.

[0072] Combination Figure 1 It can be seen that the 3D printed multi-scale structure grid-like graphene macro-body prepared by Example 1 of the present invention can maintain the shape originally printed, and has a complete structure and a good shape.

[0073] Combination Figure 2It can be seen that inside the multi-scale structured graphene electromagnetic shielding macrobody prepared in Example 1, the nanosheets self-assemble with the bubble group as a template to form a spherical closed porous structure wrapped by a small number of sheets in an orderly and regular manner. The face-to-face stacking between the sheets is effectively suppressed, and at the same time, the sheets maintain good connection, thereby having excellent mechanical properties.

[0074] Combination Figure 3 It can be seen that the conventional graphene macrobody prepared in Comparative Example 1 has disordered and chaotic arrangement of the sheets, serious stacking of the sheets, and weak connections between the sheets. Therefore, after multiple compressions, obvious collapse occurs.

[0075] Combination Figure 4 It can be seen that when the compression amount is 50%, the multi-scale structured graphene electromagnetic shielding macro-body prepared by Example 1 can still completely recover to its original height after 1000 compression cycles without obvious irreversible deformation, showing good resilience.

[0076] Combination Figure 5 It can be seen that the conventional graphene macrobody prepared in Comparative Example 1 undergoes obvious irreversible deformation after several compression cycles, and its deformation exceeds 50% of the original height.

[0077] Combination Figure 6 It can be seen that the conventional graphene macrobody prepared by comparative example 1 has the lowest electromagnetic shielding efficiency in the X-band. With the introduction of bubble groups (Examples 1-3), a spherical closed porous structure wrapped by a small number of interconnected nanosheet layers is formed inside the multi-scale structured graphene electromagnetic shielding macrobody, which strengthens the multiple scattering and interference loss of the incident electromagnetic wave, improves the absorption of the incident electromagnetic wave, and finally makes it show a more excellent electromagnetic wave shielding effect.

Claims

1. A method for preparing a multi-scale structured graphene macrobody, characterized in that: The preparation method comprises the following steps: (1) preparing a few exfoliated graphene oxide sheets by chemical oxidation to obtain a graphene oxide aqueous dispersion as an initial slurry; (2) adding a surfactant to the graphene oxide aqueous dispersion described in step (1), stirring to obtain a graphene oxide slurry filled with bubble groups, and obtaining a foaming slurry, i.e., a printable foaming ink; (3) The foamed slurry obtained in step (2) is loaded into a syringe with a needle, and the slurry is continuously and smoothly extruded onto a low-temperature aluminum plate for direct writing and printing to obtain a three-dimensional macroscopic body with a characteristic shape; (4) Drying, forming and reducing the three-dimensional macroscopic body described in step (3) to obtain a multi-scale structured graphene macroscopic body.

2. The preparation method according to claim 1, characterized in that The chemical oxidation method in step (1) includes Hummers method, modified Hummers method, Brodie method and Staudenmaier method; The concentration of the graphene oxide dispersion is 0.5wt% to 2wt%.

3. The preparation method according to claim 1, characterized in that: The surfactant added in step (2) is any one of alkyl glycoside, sodium dodecylbenzene sulfonate, and stearic acid; The mass ratio of the surfactant to graphene oxide in step (2) is 1:2 to 2:

1.

4. The preparation method according to claim 1, characterized in that: The stirring method in step (2) includes any one or more combinations of mechanical stirring, magnetic stirring, and vortex oscillation; The stirring is mechanical stirring, the stirring rate is 500 to 5000 rpm, and the stirring time is 2 to 10 minutes.

5. The preparation method according to claim 1, characterized in that: In step (3), the inner diameter of the needle of the syringe is 200 to 1000 μm, the extrusion printing moving speed is 1 to 10 mm / s, the extrusion pressure is 30 to 300 kPa, and the surface temperature of the aluminum plate is -10 to 0°C.

6. The preparation method according to claim 1, characterized in that: The drying and molding method in step (4) includes freeze drying and CO2 supercritical drying.

7. The preparation method according to claim 1, characterized in that: The reduction method in step (4) includes any one of thermal reduction and chemical reduction; The temperature of the thermal reduction treatment is 400-1500° C., the heat treatment time is 20-120 minutes, the heating rate is 5-30° C. / min, and the inert gas protection includes nitrogen atmosphere and argon atmosphere. More preferably, the heat treatment temperature is 500-1000° C., and the heat treatment time is 20-60 minutes.

8. The preparation method according to claim 1, characterized in that: The preparation method comprises the following steps: (1) chemically oxidizing, exfoliating and centrifuging flake graphite to obtain a graphene oxide dispersion; (2) mixing 0.5 wt% to 2 wt% of the graphene oxide dispersion with a surfactant in a mass ratio of 1:2 to 2:1, and mechanically stirring at a speed of 1000 to 3000 rpm for 4 to 6 minutes to obtain a foaming slurry; (3) The foaming slurry described in step (2) is loaded into a syringe, and the slurry is continuously extruded onto a low-temperature aluminum plate, the inner diameter of the syringe needle is 200 to 1000 μm, the extrusion printing moving speed is 1 to 10 mm / s, the extrusion pressure is 30 to 300 kPa, and the surface temperature of the aluminum plate is -10 to 0°C, to obtain a three-dimensional macroscopic body of a specific shape; (4) freeze-drying and thermally reducing the three-dimensional macroscopic body described in step (3) to obtain a multi-scale structured graphene macroscopic body.

9. A multi-scale graphene macrostructure, characterized in that: The multi-scale structured graphene macrobody is prepared by the method described in claim 1, and the multi-scale structured graphene macrobody has the characteristics of being customizable, ultra-low density, super-strong elasticity and excellent electromagnetic shielding performance.

10. A use of the multi-scale structured graphene macro-body as claimed in claim 9, characterized in that: The multi-scale structured graphene macrobody is applied in the field of electromagnetic shielding materials.

Images