Metamaterial foam wave absorber based on reduced graphene oxide / porous carbon material, preparation method and application

Abstract

The invention relates to the technical field of microwave absorbing materials, and discloses a metamaterial foam wave absorber based on a reduced graphene oxide / porous carbon material, a preparation method and application. Comprising the following steps: step 1, fully mixing a sodium carboxymethyl cellulose CMCNa solution with a graphene oxide GO dispersion liquid to obtain a GO-CMCNa solution; 2, the GO-CMCNa solution in the step 1 is printed into a preset porous structure through a 3D printing method, and the reduced graphene oxide / porous carbon material can be obtained after directional freeze drying; and step 3, preparing a metamaterial structure from the reduced graphene oxide / porous carbon material obtained in the step 2 to obtain the required wave absorber. By adopting the combination of the resonance pattern layer, the lossy dielectric layer and the wave-transparent layer, the obtained microwave absorber can effectively reduce the intensity of a thermal radiation signal, and has infrared stealth capability.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave absorption materials, and particularly relates to a metamaterial foam absorber based on reduced graphene oxide / porous carbon materials, a preparation method and an application thereof. Background Art

[0002] With the rapid development of multi-band radar detection technology and the popularization of electronic instruments, there is an urgent need for a high-performance microwave absorption (MA) material with a wide absorption band to effectively resist multi-band detection radars and electromagnetic pollution. These materials are crucial for effectively countering multi-band detection radars and reducing electromagnetic pollution. Currently, MA materials usually rely on composition design and microstructure regulation to improve their reflection loss (RL). This method usually can only obtain superior performance within a single band, and the less-than-ideal effective absorption bandwidth (EAB) is still a bottleneck restricting their wide application. This design relies more on empirical material compounding processes, requires a large number of cross-experiments, and does not have theoretical and regular experimental guidance. Summary of the Invention

[0003] The present invention provides a metamaterial foam absorber based on reduced graphene oxide / porous carbon materials, a preparation method and an application thereof for the problems existing in the prior art.

[0004] The technical solution adopted by the present invention is: a preparation method of a metamaterial foam absorber based on reduced graphene oxide / porous carbon, comprising the following steps:

[0005] Step 1: Fully mix a sodium carboxymethyl cellulose (CMCNa) solution with a graphene oxide (GO) dispersion to obtain a GO-CMCNa solution; wherein the mass ratio of CMCNa to GO is 2.4:1 to 10.

[0006] Step 2: Print the GO-CMCNa solution in Step 1 into a preset porous structure by 3D printing, and then obtain reduced graphene oxide / porous carbon materials after directional freeze-drying.

[0007] Step 3: Prepare the reduced graphene oxide / porous carbon materials obtained in Step 2 into a metamaterial structure to obtain the required absorber.

[0008] Further, the absorber is composed of three layers stacked, which are a metal pattern layer, a lossy dielectric layer and a wave-transmitting layer from top to bottom; the lossy dielectric layer is a reduced graphene oxide / porous carbon material.

[0009] Further, the lossy dielectric layer is composed of two concentric layers with different thicknesses stacked; from bottom to top, they are the first layer and the second layer, and the length of the second layer is less than that of the first layer; the first layer is a zigzag structure, and the second layer is a cuboid structure with a square cross-section.

[0010] Further, the lossy dielectric layer is formed by stacking two concentric structures with different thicknesses; from bottom to top are the first layer and the second layer, and the length of the second layer is less than that of the first layer; the first layer is composed of four cuboid structures with the same size and rectangular cross-sections, arranged in two rows, and the outer connections form a square; the second layer is a cuboid structure with a square cross-section.

[0011] Further, the lossy dielectric layer is formed by stacking two concentric structures with different thicknesses; from bottom to top are the first layer and the second layer, and the length of the second layer is less than that of the first layer; the second layer is a zigzag structure, and the first layer is a cuboid structure with a square cross-section.

[0012] Further, the metal pattern layer is an open resonator ring.

[0013] Further, during the 3D printing process in step 2, layer-by-layer printing is performed with a layer thickness of 0.2 mm and a spacing of 1.8 mm.

[0014] Further, in step 3, the carbonization temperature is 500 °C and the carbonization time is 2 h.

[0015] A metamaterial foam absorber based on reduced graphene oxide / porous carbon.

[0016] An application of a metamaterial foam absorber based on reduced graphene oxide / porous carbon, wherein the absorber is used to prepare a microwave absorber, and the microwave absorber is composed of an array arrangement of absorbers.

[0017] The beneficial effects of the present invention are as follows:

[0018] (1) The reduced graphene oxide / porous carbon foam prepared by the present invention has a good grid structure. Through directional freezing, the growth direction of ice crystals is consistent with the printing direction, forming a layered porous structure;

[0019] (2) The present invention combines a resonant pattern layer, a lossy dielectric layer, and a wave-transmitting layer, and the obtained microwave absorber can effectively reduce the intensity of thermal radiation signals and has infrared stealth capabilities. Description of the Drawings

[0020] Figure 1 The structure of the absorber obtained in Example 1 of the present invention.

[0021] Figure 2 The schematic diagram of the structure of the lossy dielectric layer in the present invention.

[0022] Figure 3 The schematic diagram of the lossy dielectric layer in Example 1 of the present invention, and a - d are the results at different magnification levels.

[0023] Figure 4 Schematic diagrams of the tests of Example 1 and Comparative Example of the present invention and the simulation results of Example 1. a is a physical diagram, and b is a result curve diagram.

[0024] Figure 5 Infrared stealth performance test results of the microwave absorber obtained from Example 1 and Comparative Example 2 of the present invention. a is the temperature-time curve; b is the infrared emissivity. Specific embodiments

[0025] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0026] A preparation method of a metamaterial foam absorber based on reduced graphene oxide / porous carbon includes the following steps:

[0027] Step 1: Thoroughly mix a sodium carboxymethylcellulose (CMCNa) solution with a graphene oxide (GO) dispersion to obtain a GO-CMCNa solution; the mass ratio of CMCNa to GO is 2.4:1 to 10; the graphene oxide dispersion is a high-concentration slurry obtained by centrifugation-ultrasonic cycling purification three times.

[0028] Step 2: Inject the GO-CMCNa solution in Step 1 into a direct-write 3D printer, set the extrusion air pressure to 0.1 MPa, the printing speed to 3 mm / s, and the platform temperature to -10 °C. Layer by layer forming is carried out according to a preset porous structure (layer thickness 0.2 mm, spacing 1.8 mm). After forming, it is directionally freeze-dried at -50 °C for 48 h, and then carbonized at 500 °C for 2 h in an argon atmosphere to obtain a reduced graphene oxide / porous carbon material.

[0029] Step 3: Prepare the reduced graphene oxide / porous carbon material obtained in Step 2 into a metamaterial structure to obtain the required absorber.

[0030] The absorber is composed of three layers stacked on top of each other, which are a metal pattern layer, a lossy dielectric layer, and a wave-transmitting layer from top to bottom; the lossy dielectric layer is a reduced graphene oxide / porous carbon material. The metal in the metal pattern layer generally uses Al and is set as an open resonator ring structure. The wave-transmitting layer uses PDMS with a thickness of 1 to 4 mm. The metal pattern layer is as Figure 2 shown, the width of the opening is 2y, the range of y is 3 to 9 mm, the width of the circular ring is 2x, the range of x is 1 to 5 mm, and the thickness of the metal pattern layer is 0.05 to 0.2 mm.

[0031] The lossy dielectric layer can be designed as a gradient structure or a combination of a gradient and a resonant structure, as Figure 2 shown. The combination of the gradient structure and the resonant structure includes:

[0032] 1) The absorber is composed of two concentric layers with different thicknesses stacked on top of each other; from bottom to top are the first layer and the second layer, and the length of the second layer is less than that of the first layer; the first layer is a meandering structure, and the second layer is a cuboid structure with a square cross-section.

[0033] The length and width of the first layer are both 60 mm, and the thickness is D / 2; the length and width of the second layer are both 60×x mm, and the thickness is D / 2; the width of the square ring is b, and the shortest distance from the inner side to the center is a; the value ranges of both a and b are 1 to 14 mm. D is 3 to 10 mm, and x is 0.2 to 0.8.

[0034] 2) The absorber is composed of two concentric layers with different thicknesses stacked on top of each other; from bottom to top are the first layer and the second layer, and the length of the second layer is less than that of the first layer; the first layer consists of four cuboid structures with the same size and rectangular cross-sections, arranged in two rows in an array, and the outer edges are connected to form a square (a cross-shaped resonant cavity is formed in the middle); the second layer is a cuboid structure with a square cross-section. The length and width of the first layer are both 60 mm, and the thickness is (1 - A)D; the length and width of the second layer are both 60×x mm, and the thickness is AD, where A is 0.2 to 0.8.

[0035] The cross-shaped resonance width of the first layer is 2a, and the range of a is 9.5 to 29.5 mm.

[0036] 3) The absorber is composed of two concentric layers with different thicknesses stacked on top of each other; from bottom to top are the first layer and the second layer, and the length of the second layer is less than that of the first layer; the second layer is a meandering structure, and the first layer is a cuboid structure with a square cross-section.

[0037] The length and width of the first layer are both 60 mm, and the thickness is (1 - A)D; the length and width of the second layer are both 60×x mm, and the thickness is AD. D is 3 to 10 mm, x is 0.2 to 0.8, and A is 0.2 to 0.8.

[0038] The width of the square ring is b, and the shortest distance from the inner side to the center is a; the value ranges of both a and b are 1 to 14 mm.

[0039] Arranging the absorbers in an array can obtain a microwave absorber.

[0040] Example 1

[0041] A preparation method of a metamaterial foam absorber based on reduced graphene oxide / porous carbon, comprising the following steps:

[0042] Step 1: Centrifuge 100 mL of a graphene oxide (GO) dispersion with a concentration of 10 mg / mL at 10,000 rpm for 30 minutes. After discarding the supernatant, retain the precipitate. Ultrasonically treat the concentrated GO dispersion (power 10%, time 10 minutes), and repeat the centrifugation - ultrasonication cycle 3 times to obtain a high-purity concentrated GO slurry.

[0043] Prepare sodium carboxymethyl cellulose (CMCNa) with a mass concentration of 1 wt.%. Mix 24 g of the sodium carboxymethyl cellulose solution with the high-purity concentrated GO slurry and ultrasonically treat for 10 minutes to homogenize the system.

[0044] Step 2: Load the GO-CMCNa solution from Step 1 into the syringe of a direct ink writing (DIW) 3D printer and perform printing according to the following parameters. First, perform model design and slicing: Construct a three-dimensional structure model based on 3D MAX 2019, export the STL file to the slicing software Cura, generate a G-code program, and plan a printing path with a layer thickness of 0.2 mm and a filling density of 30%. Secondly, control the printing parameters at an extrusion air pressure of 0.1 MPa; a printing speed of 3 mm / s; a needle gauge of 21G (inner diameter 0.4 mm); a printing pitch of 1.8 mm; and a platform temperature of -10°C.

[0045] Place the printed material in a freeze dryer and treat it at -50°C for 48 h to remove moisture and retain the porous structure. Subsequently, place the dried sample in a tubular furnace, heat it to 500°C at a rate of 5°C / min under argon protection, and hold for 2 h to obtain 3D printed reduced graphene oxide / porous carbon.

[0046] Step 3: Prepare the absorber as Figure 1 shown. The absorber is composed of three layers stacked on top of each other, which are a metal pattern layer, a lossy dielectric layer, and a transmitting layer from top to bottom; the lossy dielectric layer is a reduced graphene oxide / porous carbon material. The metal pattern layer is a square split-ring resonator structure; and the three-layer structure is concentrically arranged. The obtained microwave absorber is abbreviated as the P-L-T structure.

[0047] The lossy dielectric layer (L layer) selects the structure as the 3rd structure above. The first layer is a cube structure with the same length and width, and the second layer is a meandering structure. Where D is 6 mm, the length and width of the first layer are both 60 mm, and the thickness is 1 mm; the length and width of the second layer are 30 mm, and the thickness is 5 mm; a = 5 mm, b = 2 mm.

[0048] The transmitting layer is PDMS (T layer), and its length and width are the same as those of the first layer in the lossy dielectric layer, and the thickness h is 3 mm.

[0049] The metal pattern layer (P layer) is prepared from Al material, with a square loop structure, smaller than the outer ring structure of the second layer, x is 2 mm, y is 4 mm, and the thickness d is 0.1 mm.

[0050] By arranging the absorber structures in an array, the microwave absorber can be obtained.

[0051] Example 2

[0052] Other steps in this example are the same as those in Example 1, except that in step 3, the lossy dielectric layer adopts the above-mentioned 1) structure.

[0053] Example 3

[0054] Other steps in this example are the same as those in Example 1, except that in step 3, the lossy dielectric layer adopts the above-mentioned 2) structure.

[0055] Example 4

[0056] Other steps in this example are the same as those in Example 1, except that in step 1, the concentration of the graphene oxide solution is 1 mg / L.

[0057] Example 5

[0058] Other steps in this example are the same as those in Example 1, except that in step 1, the concentration of the graphene oxide solution is 3 mg / L.

[0059] Example 6

[0060] Other steps in this example are the same as those in Example 1, except that in step 1, the concentration of the graphene oxide solution is 5 mg / L.

[0061] Example 7

[0062] Other steps in this example are the same as those in Example 1, except that in step 1, the concentration of the graphene oxide solution is 7 mg / L.

[0063] Comparative Example 1

[0064] Other steps in this example are the same as those in Example 1, except that in step 3, the absorber only includes a lossy dielectric layer.

[0065] Comparative Example 2

[0066] Other steps in this example are the same as those in Example 1, except that in step 3, the absorber includes a lossy dielectric layer and a transmitting layer, and does not include a metal pattern layer.

[0067] Figure 3SEM image of the lossy dielectric layer obtained in Example 1 of the present invention. As can be seen from the figure, a good grid structure is maintained, the pore distribution is uniform, the pore size is 1 mm, and the printing wire diameter is 0.4 mm. This shows that the macroscopic structure of the material is precisely controlled by 3D printing technology. After magnification, it can be seen from b, c, and d that the material exhibits a layered multi-macroscopic pore structure, and the printing wire exhibits a porous structure with regularly distributed voids formed by ice crystals. This is mainly attributed to the combination of 3D printing and directional freeze-drying processes. During 3D printing, the graphene-based ink forms a preliminary grid structure by extrusion, and then is further solidified by directional freezing. During the freezing process, the growth direction of the ice crystals is consistent with the printing direction, forming a layered porous structure. This structure is more beneficial to the mechanical properties of the material.

[0068] Figure 4 Measured and simulated results of the microwave absorber obtained in Example 1 of the present invention. The simulation was carried out using a frequency-domain simulator, the simulation frequency was between 2 and 18 GHz, the boundary condition was set as a periodic structure, the top was set as free space, and the bottom was set as an ideal conductor. Figure 4 In b, the Al-rGO / C-PDMS curve is the measured result of Example 1, and rGO / C represents the measured curve of Comparative Example 2. Al-rGO / C-PDMS (simulation) represents the simulation curve of Example 1.

[0069] Measured results of the microwave absorber obtained in Comparative Example 1. As can be seen from the figure, the structure of Example 1 exhibits an EAB of 13.37 GHz, almost completely covering the C band, and completely covering the X band and Ku band. In addition, in the C band, the RLMAX of the P-L-T structure reaches -41.77 dB, indicating that it has extremely strong wave absorption ability in the low-frequency region. This excellent performance has greatly improved the absorption ability of the graphene-based material in the C band. The excellent performance is mainly attributed to the collaborative design of the resonant pattern layer and the wave-transmitting layer. The resonant pattern layer enhances the loss ability of the material to electromagnetic waves through the coupling effect of electric resonance and magnetic resonance, especially the wave absorption performance in the low-frequency region has been significantly improved. At the same time, the wave-transmitting layer optimizes the absorption performance of the material in a specific frequency band by adjusting the reflection characteristics of electromagnetic waves. This dual optimization mechanism enables the structure of Example 1 to exhibit excellent wave absorption performance in a wide frequency range.

[0070] It can be seen from the measured results of Example 1 and Comparative Example 1 that, compared with Comparative Example 1, the EAB in Example 1 has been significantly expanded from 2.93 GHz to 13.37 GHz, thus achieving full coverage of the X and Ku bands, and the RLMAX in the C band reaches -41.77 dB. It not only optimizes the RL performance, but also significantly broadens the absorption bandwidth, providing a more excellent solution for electromagnetic wave absorption applications.

[0071] Figure 5 Infrared stealth ability results of the microwave absorbers obtained in Example 1 and Comparative Example 2. a is the temperature-time curve; b is the infrared emissivity. (Al-rGO / C-PDMS is the result of Example 1, and rGO / C-PDMS is the result of Comparative Example 2)

[0072] As can be seen from the figure, when the temperature of the heating stage is stable at 80 °C, the rGO / C-PDMS sample shows a certain heat insulation effect due to the presence of PDMS as a heat insulation layer and air in the rGO / C porous structure, and its temperature is stable at about 50 °C, far lower than the temperature of the heating stage. For the P-L-T structure, due to the introduction of aluminum (Al) as the resonant pattern layer, its temperature can be maintained at about 40 °C. This result fully demonstrates the significant advantage of the P-L-T structure in terms of heat insulation performance. By reducing the surface temperature of the material, the P-L-T structure can effectively reduce the intensity of the thermal radiation signal, thereby improving the infrared stealth performance.

[0073] The microwave absorber obtained by combining a resonant pattern layer, a lossy dielectric layer, and a wave-transparent layer in the present invention can effectively reduce the intensity of the thermal radiation signal and has infrared stealth ability. The introduction of the metamaterial not only increases the internal reflection and loss but also changes the resonant frequency, resulting in double absorption peaks in the radar frequency band, effectively broadening the effective absorption bandwidth (EAB). By adjusting the metamaterial parameters, its performance can be adjusted. The special structure design successfully broadens the EAB from 2.93 GHz to 13.37 GHz, almost completely covering the C-band, X-band, and Ku-band, and the RLMAX in the C-band reaches -41.77 dB, significantly improving the wave absorption ability in the low-frequency region.

Claims

1. A preparation method of a metamaterial foam absorber based on reduced graphene oxide / porous carbon, characterized in that, It includes the following steps: Step 1: Thoroughly mix the sodium carboxymethyl cellulose (CMCNa) solution with the graphene oxide (GO) dispersion to obtain the GO-CMCNa solution; wherein the mass ratio of CMCNa to GO is 2.4:1 to 10; Step 2: Print the GO-CMCNa solution obtained in Step 1 into a preset porous structure by 3D printing, and after directional freeze-drying, the reduced graphene oxide / porous carbon material can be obtained; Step 3: Prepare the reduced graphene oxide / porous carbon material obtained in Step 2 into a metamaterial structure to obtain the required absorber.

2. The preparation method of a metamaterial foam absorber based on reduced graphene oxide / porous carbon according to claim 1, characterized in that the absorber is composed of three layers stacked on top of each other, which are a metal pattern layer, a lossy dielectric layer, and a wave-transmitting layer from top to bottom; the lossy dielectric layer is a reduced graphene oxide / porous carbon material.

3. The preparation method of a metamaterial foam absorber based on reduced graphene oxide / porous carbon according to claim 2, characterized in that, The lossy dielectric layer is composed of two concentric structures with different thicknesses stacked on top of each other; from bottom to top are the first layer and the second layer, and the length of the second layer is less than that of the first layer; the first layer is a meandering structure, and the second layer is a cuboid structure with a square cross-section.

4. The preparation method of a metamaterial foam absorber based on reduced graphene oxide / porous carbon according to claim 2, characterized in that, The lossy dielectric layer is composed of two concentric structures with different thicknesses stacked on top of each other; from bottom to top are the first layer and the second layer, and the length of the second layer is less than that of the first layer; the first layer is composed of four cuboid structures with the same size and rectangular cross-sections, arranged in two rows in an array, and the outer connection lines form a square; the second layer is a cuboid structure with a square cross-section.

5. The preparation method of a metamaterial foam absorber based on reduced graphene oxide / porous carbon according to claim 2, characterized in that the lossy dielectric layer is composed of two concentric structures with different thicknesses stacked on top of each other; from bottom to top are the first layer and the second layer, and the length of the second layer is less than that of the first layer; the second layer is a meandering structure, and the first layer is a cuboid structure with a square cross-section.

6. The preparation method of a metamaterial foam absorber based on reduced graphene oxide / porous carbon according to claim 2, characterized in that, The metal pattern layer is an open resonator ring.

7. The preparation method of a metamaterial foam absorber based on reduced graphene oxide / porous carbon according to claim 1, characterized in that, During the 3D printing process in Step 2, it is printed layer by layer with a layer thickness of 0.2 mm and a spacing of 1.8 mm.

8. The preparation method of a metamaterial foam absorber based on reduced graphene oxide / porous carbon according to claim 1, characterized in that, In Step 3, the carbonization temperature is 500 °C and the carbonization time is 2 h.

9. A metamaterial foam absorber based on reduced graphene oxide / porous carbon obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the metamaterial foam absorber based on reduced graphene oxide / porous carbon as described in claim 9, characterized in that, The absorber is used to prepare a microwave absorber, and the microwave absorber is composed of an array of absorbers.

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