Carbon-based metamaterial electromagnetic wave absorber and preparation method and application thereof

Abstract

The invention discloses a carbon-based metamaterial electromagnetic wave absorber and a preparation method and application thereof. The wave absorbing body adopts a three-layer composite structure, wherein the bottom layer is a copper plate reflecting layer; the lower layer is of a honeycomb-like structure and is formed by periodically arranging regular octagons and square hollow quadrangular prisms externally connected with the regular octagons, and the adjustable wave absorbing frequency band is achieved by adjusting and controlling the width and height of the hollow cores; the upper layer is of a pointed cone structure, and the impedance matching characteristic is enhanced by optimizing the vertex angle of the regular rectangular pyramid. The wave absorber is made of photosensitive resin, based on the photocuring 3D printing technology, honeycomb-like and pointed cone structures are printed step by step and bonded and combined, and high-precision forming is achieved in combination with parameterized regulation and control. The wave absorber has the advantages of light weight, broadband absorption and adjustable mechanical performance, can be applied to the fields of EMI shielding of electronic equipment, military radar stealth, high-frequency communication protection, electromagnetic environment protection and the like, and remarkably improves the electromagnetic wave absorption and shielding effectiveness through the metamaterial structure design and a multi-component cooperative loss mechanism.

Description

Technical Field

[0001] The present invention relates to the field of additive manufacturing of electromagnetic wave absorbers, and particularly to a carbon-based metamaterial electromagnetic wave absorber, a preparation method thereof, and an application thereof. Background Art

[0002] Traditional wave-absorbing materials usually have problems such as a single resonance peak, a narrow effective absorption bandwidth, and low wave-absorbing intensity due to being restricted by preparation technologies and material properties, and it is difficult to meet the actual requirements of broadband and high-efficiency absorption. In recent years, the emergence of metamaterials has provided new ideas for the development of wave-absorbing materials. Metamaterial electromagnetic wave absorbers have the advantages of simple structure, light weight, and high absorption rate. Through the design of periodic precise geometric structures, the absorption behavior of electromagnetic waves can be effectively regulated. Additive manufacturing technology has become an important breakthrough in the preparation of wave-absorbing materials due to its unique advantages of high-precision forming and flexibility in material selection. The wave-absorbing performance of metamaterial electromagnetic wave absorbers is mainly affected by the absorption of wave-absorbing agents and the resonant absorption of special structures. In terms of wave-absorbing agents, the introduction of carbon-based materials such as graphene and carbon nanotubes can significantly improve the electromagnetic loss performance of wave-absorbing materials. These carbon-based materials not only have excellent electrical conductivity but also can adjust the electronic structure at the nanoscale, thereby greatly enhancing the absorption ability of electromagnetic waves. In terms of wave-absorbing structures, by optimizing the structure design, the broadband wave-absorbing ability and adaptability to multi-angle incidence of materials can be significantly improved, and the characteristics of high-efficiency absorption and light weight can also be achieved, but its complex shape poses higher requirements for preparation precision and efficiency.

[0003] Among many additive manufacturing technologies, the stereolithography additive manufacturing technology uses ultraviolet light to irradiate photosensitive resin to undergo a cross-linking curing reaction, which has the characteristics of rapid prototyping and high resolution, and has great potential in the preparation of wave-absorbing materials. Although the stereolithography additive manufacturing technology has demonstrated its application advantages in the preparation of wave-absorbing materials, in practical applications, it still faces some challenges, such as the treatment of high-absorbance slurries and the stable forming of complex structures. The curing efficiency in traditional technologies is limited. Especially when printing large-size or high-fill-rate structures, there is often insufficient internal curing. How to combine the metamaterial structure resonance and the electromagnetic loss mechanism of wave-absorbing agents to further improve the performance of wave absorbers is still a technical bottleneck that needs to be solved urgently.

[0004] Chinese Patent CN118119170A proposes a pyramidal honeycomb structure wave-absorbing material, which is composed of a honeycomb structure flat plate layer and a pyramidal array layer. The pyramidal geometric structure effectively reduces electromagnetic wave reflection through gradual impedance and improves the wave-absorbing performance through multiple scattering. The reflection loss of the traditional single honeycomb structure wave-absorbing material is less than -10 dB in the range of 12 - 16 GHz; the wave-absorbing bandwidth of the traditional single pyramidal structure wave-absorbing material covers 8 - 18 GHz, and the reflection loss in the range of 15 - 18 GHz is less than -20 dB. The reflection loss of the pyramidal honeycomb structure wave-absorbing material is less than -15 dB in the entire 8 - 18 GHz band.

[0005] Chinese Patent CN112134024A discloses a three-dimensional broadband metamaterial absorber based on all-graphite. Through the design of sunken polyhedrons and the combination of highly symmetric geometric structures, broadband wave absorption and large-angle oblique incidence performance are achieved, and it has polarization-insensitive characteristics. Its broadband absorption frequency covers 13.6 THz to 33 THz, and the relative bandwidth is 83.3%; in the range of 15 - 35 THz, the oblique incidence performance: the absorption rate is higher than 0.9 when the incident angle is 30°; the absorption rate is higher than 0.72 when the incident angle is 45°.

[0006] The above patents are either difficult to prepare, rely on traditional high-temperature melting processing methods, have low efficiency and high requirements for materials and processes, and are difficult to achieve lightweight; or have limited wave absorption performance regulation, are insufficient in realizing multi-loss mechanisms and impedance matching, resulting in narrow wave absorption bandwidth and low efficiency. Therefore, a new additive manufacturing method for electromagnetic absorbers is needed to prepare electromagnetic absorbers with lightweight, simple structure, strong controllability, and broadband electromagnetic wave absorption. Summary of the Invention

[0007] Aiming at the problems of high preparation difficulty, difficulty in achieving lightweight, poor controllability, and narrow absorption bandwidth of current electromagnetic absorbers, the present invention combines stereolithography additive manufacturing technology and special structure design, and proposes a carbon-based metamaterial electromagnetic absorber, its preparation method and application.

[0008] The present invention can be realized through the following technical solutions:

[0009] One of the technical solutions of the present invention provides a carbon-based metamaterial electromagnetic absorber; the structure of the carbon-based metamaterial electromagnetic absorber is divided into an upper layer, a lower layer, and a bottom layer: the lower layer is composed of several structural units with the same shape arranged in a honeycomb-like structure as the base layer; the upper layer is composed of several structural units with the same shape arranged in a tapered structure as the functional layer; the bottom layer is a complete copper plate as the reflection layer;

[0010] Furthermore, the structural unit of the honeycomb-like structure is composed of a hollow quadrangular prism with a regular octagon cross-section circumscribed by a square; among the four non-adjacent sides of the regular octagon, each side coincides with one side of the square, and the remaining four sides respectively form gaps with the square; in each two adjacent structural units, the squares share one side; the wall thickness of each structural unit in the honeycomb-like structure is 0.9 - 1.1 mm, preferably 1 mm; the side length of the square circumscribing the regular octagon is 8.45 - 8.5 mm, preferably 8.485 mm; the height of the honeycomb-like structure is 5 - 15 mm, preferably 10 mm.

[0011] Furthermore, the structural unit of the tapered structure is composed of a regular square pyramid, and the size of the square at the bottom of the regular square pyramid is the same as that of the square cross-section of the hollow quadrangular prism in the structural unit of the honeycomb-like structure; the tapered structure is pasted on the top of the honeycomb-like structure, that is, on the opposite side of the copper plate; the apex angle of the regular square pyramid in the structural unit of the tapered structure is 30-35°, preferably 32°; the height of the tapered part of the regular square pyramid is 13.5-15.8 mm, preferably 14.8 mm.

[0012] Furthermore, a complete copper plate is attached to the bottom of the honeycomb-like structure as the bottom layer for reflecting the dissipated electromagnetic waves; the thickness of the copper plate is 1-1.2 mm, preferably 1 mm.

[0013] Furthermore, the honeycomb-like base layer improves the dielectric loss and magnetic loss effects through multi-interface actions. The upper tapered structure realizes impedance gradient matching, reduces the reflection of electromagnetic waves at the interface between the absorber and air; increases the multiple reflections and scattering of electromagnetic waves between the tapered parts, and improves the broadband absorption performance. The copper plate at the bottom further reflects the dissipated electromagnetic waves, making them return to the inside of the absorber for secondary loss, thereby increasing the energy dissipation rate.

[0014] Furthermore, the carbon-based metamaterial electromagnetic absorber is made of a photosensitive resin without absorber doping as the matrix, and the surface is coated with a composite photosensitive resin doped with an absorber.

[0015] The composite photosensitive resin material doped with an absorber, by weight, is: 40-50 parts of photosensitive resin without absorber doping, 0.1-0.8 parts of carbon nanotubes, 50-60 parts of carbonyl iron powder, and 8-12 parts of diluent; preferably: 44.5 parts of photosensitive resin without absorber doping, 0.5 parts of carbon nanotubes, 55 parts of carbonyl iron powder, and 10 parts of diluent.

[0016] Furthermore, the diluent is one or more of polyethylene glycol diacrylate, propylene glycol diacrylate, or methyl methacrylate.

[0017] The material of the photosensitive resin without absorber doping, by weight, is: 70-90 parts of oligomer, 18-25 parts of monomer, 3-5 parts of photoinitiator, and 0.02-0.04 parts of dispersant; preferably: 80 parts of oligomer, 20 parts of monomer, 5 parts of photoinitiator, and 0.03 parts of dispersant.

[0018] Furthermore, the oligomer includes one or more of polyurethane acrylate, epoxy acrylate, aliphatic epoxy resin, polyester acrylate, or fluorine-modified acrylate.

[0019] Furthermore, the monomer includes one or more of monofunctional acrylate monomers, difunctional acrylate monomers, or polyfunctional acrylate monomers.

[0020] Further, the photoinitiator includes one or more of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, benzil, 2-methyl-1-(4-methylthiophenyl)-2-morpholin-1-propanone, 2,4,6-trimethylbenzoyl-ethoxy-phenylphosphine oxide, and 2-isopropylthioxanthone.

[0021] Further, the dispersant is one or more of BYKP-115, N,N-dimethylformamide, and Disper711.

[0022] The second technical solution of the present invention provides an operation method for preparing the above-mentioned carbon-based metamaterial electromagnetic absorber by photo-thermal assisted in-situ curing additive manufacturing. This operation method is based on the photo-curing 3D printing additive manufacturing technology and includes the following steps:

[0023] S1. Model and slice the honeycomb-like structure and the conical structure of the carbon-based metamaterial electromagnetic absorber in the above technical solution respectively, import the model file into a photo-curing printer, and set the printing parameters; mix the materials according to the material ratio in the above technical solution to obtain a photosensitive resin slurry without absorber doping.

[0024] S2. Print the lower honeycomb-like structure: First, add the photosensitive resin slurry without absorber doping, select the lower structure slice file, and print until the end to obtain a complete lower honeycomb-like structure.

[0025] S3. Print the upper conical structure: First, add the photosensitive resin slurry without absorber doping, select the upper structure slice file, and print until the end to obtain a complete upper conical structure.

[0026] S4. Bond the upper conical structure and the lower honeycomb-like structure together to obtain a bonded absorber.

[0027] S5. Mix the materials according to the material ratio in the above technical solution to obtain a composite photosensitive resin doped with an absorber; coat the composite photosensitive resin doped with an absorber on the bonded absorber obtained in S4, in small amounts and multiple times to make the coating uniform.

[0028] S6. Paste a thick copper plate on the bottom of the lower honeycomb-like structure to obtain a complete carbon-based metamaterial electromagnetic absorber.

[0029] In an embodiment of the present invention, in step S1, Rhino software is used for modeling. After the modeling is completed, it is respectively imported into Chitubox for slicing.

[0030] In an embodiment of the present invention, the printing parameters in step S1 are as follows: layer thickness 0.020 mm, number of bottom layers 5, exposure time 40 s, bottom layer exposure time 50 s, number of transition layers 15, and transition type linear.

[0031] In an embodiment of the present invention, the model of the stereolithography printer in step S1 is: Elegoo SaturnS. In some other unspecified embodiments, the model of the stereolithography printer can be changed.

[0032] In an embodiment of the present invention, the bonding method in step S4 is any one of: epoxy resin bonding, polyurethane glue bonding, acrylic glue bonding, phenolic resin bonding, polyimide resin bonding; in some specific embodiments of the present invention, epoxy resin bonding is used, and the binder used for the epoxy resin bonding is: epoxy resin.

[0033] In an embodiment of the present invention, the bonding method in step S6 is any one of: epoxy resin bonding, polyurethane glue bonding, acrylic glue bonding, phenolic resin bonding, polyimide resin bonding; the binder used for the epoxy resin bonding is: epoxy resin; in some specific embodiments of the present invention, epoxy resin bonding is used, and the binder used for the epoxy resin bonding is: epoxy resin.

[0034] The third technical solution of the present invention provides an application of a carbon-based metamaterial electromagnetic absorber. The carbon-based metamaterial electromagnetic absorber is used as a functional material or structural component for electromagnetic wave absorption and shielding. Through its dielectric / magnetic loss characteristics and metamaterial microstructure design, efficient absorption, scattering suppression, or reflection attenuation of electromagnetic waves is achieved; the fields of the application at least include the following:

[0035] (1) The carbon-based metamaterial electromagnetic absorber is used for electronic devices and electromagnetic interference (EMI) shielding to reduce electromagnetic interference between devices and ensure the normal operation of the devices;

[0036] (2) The carbon-based metamaterial electromagnetic absorber is used for radar stealth technology in the military field to reduce the radar reflection of targets such as aircraft, unmanned aerial vehicles, and missiles and improve the stealth ability;

[0037] (3) The carbon-based metamaterial electromagnetic absorber is used in high-frequency communication systems, such as satellite communication and microwave communication, to absorb or shield high-frequency signals and avoid signal leakage or external signal interference;

[0038] (4) The carbon-based metamaterial electromagnetic absorber is used for radio frequency (RF) shielding and absorption to reduce the influence of radio frequency electromagnetic waves on precision instruments and electronic devices;

[0039] (5) The carbon-based metamaterial electromagnetic absorber is used for electromagnetic environmental protection to avoid potential hazards caused by electromagnetic radiation to human health, and is widely applied to medical devices, power facilities, etc.

[0040] Compared with the prior art, the beneficial effects of the present invention are embodied in the following aspects:

[0041] (1) Based on the photothermal-assisted in-situ curing additive manufacturing process, the present invention forms a functional material system by compounding an absorbent with a photosensitive resin, and regulates the component ratios of a photoinitiator, an oligomer, a monomer, a dispersant and the absorbent to realize the synergistic optimization of the mechanical strength and electromagnetic loss performance of the absorber.

[0042] (2) The present application uses the photothermal-assisted in-situ curing additive manufacturing technology to utilize ultraviolet light irradiation to cause a crosslinking curing reaction of the photosensitive resin, and this technology has the characteristics of rapid prototyping and high resolution.

[0043] (3) The hollow honeycomb-like structure design and the application of carbon-based metamaterials endow the present invention with superior lightweight characteristics and broadband absorption characteristics.

[0044] (4) The lower-layer honeycomb-like structure design enables the present invention to flexibly regulate the absorption range by regulating the width and height of the honeycomb-like hollow core.

[0045] (5) The upper-layer tapered structure design enables the present invention to flexibly regulate the absorption range by regulating the apex angle. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for description in the embodiments.

[0047] Figure 1 It is a schematic diagram of the 4×4 array (excluding the bottom copper plate) of the absorber structure in the embodiment of the present invention;

[0048] Figure 2 It is a schematic diagram of the 4×4 array of the honeycomb-like bottom plate structure of the absorber structure in the embodiment of the present invention;

[0049] Figure 3 It is a schematic diagram of the 4×4 array of the tapered upper layer structure of the absorber structure in the embodiment of the present invention;

[0050] Figure 4 It is a front view of the 4×4 array of the absorber structure in the embodiment of the present invention;

[0051] Figure 5 It is a left view of the 4×4 array of the absorber structure in the embodiment of the present invention;

[0052] Figure 6 It is a top view of the 4×4 array of the absorber structure in the embodiment of the present invention;

[0053] Figure 7 This is the flow chart for preparing the photosensitive resin slurry doped with microwave absorbing agent in the embodiments of the present invention;

[0054] Figure 8 This is the front view of the physical object of the microwave absorber prepared under the specific embodiment of the present invention;

[0055] Figure 9 This is the top view of the physical object of the microwave absorber prepared under the specific embodiment of the present invention;

[0056] Figure 10 This is the bottom view of the physical object of the microwave absorber prepared under the specific embodiment of the present invention;

[0057] Figure 11 This is the frequency-reflection loss graph of the microwave absorber prepared under the specific embodiment of the present invention. Specific Embodiment

[0058] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be described in detail below with reference to specific embodiments. It should be noted that the following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made. These all fall within the protection scope of the present invention.

[0059] For all raw materials of the present invention, there is no special limitation on their sources, and those purchased on the market or prepared by conventional methods well-known to those skilled in the art can be used, and all the raw materials can be obtained through commercial channels.

[0060] Example 1 A Carbon-based Metamaterial Electromagnetic Wave Absorber Prepared by Photo-thermal Assisted In-situ Curing Additive Manufacturing

[0061] This example combines Figures 1 to 7 to provide a detailed description of a three-dimensional structure microwave absorber of carbon-based metamaterials prepared by photo-thermal assisted in-situ curing additive manufacturing according to the present invention. Specifically, the preparation of the composite photosensitive resin adopts the Figure 7 shown process, and the overall structure is as Figure 1 shown, and the specific steps are as follows:

[0062] A. In a 250 mL three-necked flask, add 80 g of difunctional aliphatic polyurethane acrylate (oligomer), 20 g of triethylene glycol acrylate (monomer), 5 g of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (photoinitiator), and 0.03 g of dispersant BYKP-115. Under the condition of room temperature and avoiding light, stir for 30 min to obtain a transparent and homogeneous liquid, that is, the photosensitive resin slurry without doping microwave absorbing agent; all the reagents in this step are produced by Zhuhai Sanlv Industrial Co., Ltd.;

[0063] B. Immediately place the photosensitive resin slurry without absorber doping obtained in step A into the material tank until the liquid level reaches two-thirds of the material tank; slice the lower layer model on the computer with the following parameters set: layer thickness 0.020 mm, number of bottom layers 5, exposure time 40 s, bottom layer exposure time 50 s, number of transition layers 15, and transition type linear.

[0064] C. After slicing is completed, print the lower layer structure (such as Figure 2 ) and the upper layer structure (such as Figure 3 ). After printing is completed, remove the protective cover, disassemble the material tank and the printing platform, clean them, and after ensuring they are dry, reinstall the printing platform and the material tank;

[0065] D. Prepare an appropriate amount of epoxy resin to ensure good bonding performance during the curing process. Align the prepared upper layer conical structure with the lower layer honeycomb-like structure to ensure accurate docking of their contact surfaces. Coat an appropriate amount of epoxy resin on their contact surfaces to ensure that the resin evenly covers the entire bonding area. Bond the two layers tightly to ensure complete contact of the contact surfaces without gaps. Then, use a fixture or a pressing tool to fix the two layers to ensure no displacement or misalignment during the bonding process. After the epoxy resin is initially cured at room temperature, perform post-curing treatment at 80 °C according to the requirements in the resin instruction manual to ensure that the bonding strength reaches the expected value;

[0066] E. Take 44.5 mL of the photosensitive resin slurry without absorber doping obtained in step A, add 0.5 g of carbon nanotubes (electric loss absorber), 55 g of carbonyl iron powder (magnetic loss absorber), and 10 g of polyethylene glycol diacrylate (diluent), and mechanically stir for 30 min to obtain a composite photosensitive resin slurry doped with absorbers. The carbon nanotubes in this step are produced by Dongguan Kelude Innovation Technology Co., Ltd.; the carbonyl iron powder is produced by Qinghe Hengbei Metal Materials Co., Ltd.; and the polyethylene glycol diacrylate is produced by Shanghai Yinchang New Materials Co., Ltd.

[0067] F. Prepare the composite photosensitive resin slurry doped with absorbers to ensure that the absorbers are evenly dispersed in the resin. Use a soft brush to quickly and evenly coat the composite photosensitive resin slurry doped with absorbers on the surface of the printed structure, and control the coating amount each time. After each coating, wait for partial curing of the resin surface. After ensuring that the coating is flat and bubble-free, perform the next coating. The coating process should maintain a consistent coating thickness, gradually increase the coating thickness, and avoid excessive one-time coating. After coating is completed, place the coated structure in an appropriate light-curing environment and irradiate the resin layer with ultraviolet light to cure it into a shape;

[0068] G. Prepare an appropriate amount of epoxy resin. Place the lower structure (honeycomb-like structure) on a stable workbench, ensuring that the bottom is clean and free of impurities. Cut a 1-mm-thick copper plate into appropriate dimensions so that it can completely cover the bottom contact surface of the lower structure. Quickly and evenly coat a layer of epoxy resin on the back of the copper plate, ensuring that the resin layer is evenly covered and there is no missed coating. Quickly attach the resin-coated copper plate to the bottom of the lower structure, ensuring good contact between the two and aligning the positions. Use a clamp or heavy object to firmly press the copper plate to ensure no displacement or warping during the bonding process. After the epoxy resin is initially cured at room temperature, perform a post-curing treatment at 80 °C to ensure that the bonding strength of the epoxy resin reaches the maximum, and finally form a stable composite structure to obtain a complete carbon-based metamaterial electromagnetic wave absorber. The physical diagram of this carbon-based metamaterial electromagnetic wave absorber is as shown in Figures 8 to 10 shown.

[0069] Example 2 Performance Characterization of a Carbon-Based Metamaterial Electromagnetic Wave Absorber Prepared by Photo-Thermal Assisted In-Situ Curing and Additive Manufacturing

[0070] The inventor also used a vector network analyzer to test the frequency-reflection loss curve of the finished carbon-based metamaterial electromagnetic wave absorber prepared in Example 1 to evaluate its absorption ability in different frequency ranges. The model of the vector network analyzer is 3672B-S, manufactured by Sinyee Technologies Co., Ltd.

[0071] Figure 11 In the figure, the X coordinate is the frequency, with the unit of GHz, and the Y coordinate is the reflection loss, with the unit of dB. It can be seen from the data analysis that the minimum reflection loss RLmin is -32.28 dB, and excellent wave absorption ability is exhibited throughout the 23-40 GHz band. The lower the minimum reflection loss value, the better the wave absorption effect, which means that the material can effectively absorb electromagnetic waves and reduce reflection; the wide coverage frequency band can meet the absorption requirements of different frequency electromagnetic waves in various scenarios. For example, in the fields of communication, radar, etc., this material can well suppress electromagnetic interference in specific frequency bands. Considering the previously published patent data of carbon-based wave absorption materials, such an absorption bandwidth and the lowest reflection loss are at a relatively high level in the industry.

[0072] The above description of the embodiments is to enable those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative labor. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A carbon-based metamaterial electromagnetic absorber, characterized in that: The structure of the carbon-based metamaterial electromagnetic absorber is divided into an upper layer, a lower layer and a bottom layer: The lower layer is composed of several structural units of the same shape arranged into a honeycomb-like structure, serving as the base layer; The upper layer is composed of several structural units of the same shape arranged into a pointed cone structure, serving as a functional layer; The bottom layer is a complete copper plate, which serves as a reflective layer.

2. The carbon-based metamaterial electromagnetic absorber according to claim 1, characterized in that: The structural unit of the honeycomb-like structure is composed of a hollow quadrangular prism with a cross section of a regular octagon circumscribing a square; four non-adjacent sides of the regular octagon overlap with four sides of the square, and the remaining four sides form gaps with the squares; in every two adjacent structural units, the squares share one side; The wall thickness of each structural unit in the honeycomb-like structure is 0.9-1.1 mm; the side length of the circumscribed square of the regular octagon is 8.45-8.5 mm; and the height of the honeycomb-like structure is 5-15 mm.

3. The carbon-based metamaterial electromagnetic absorber according to claim 1, characterized in that: The structural unit of the pointed cone structure is composed of a regular tetrahedron, and the size of the square of the bottom surface of the regular tetrahedron is consistent with the square of the cross section of the hollow tetrahedron in the structural unit of the honeycomb-like structure; the pointed cone structure is pasted on the top of the honeycomb-like structure, that is, on the opposite side of the copper plate; The top angle of the regular quadrangular prism of the structural unit of the pointed cone structure is 30-35°; the height of the pointed cone of the regular quadrangular prism is 13.5-15.8 mm.

4. The carbon-based metamaterial electromagnetic absorber according to claim 1, characterized in that: A complete copper plate is attached to the bottom of the honeycomb-like structure as a bottom layer for reflecting the stray electromagnetic waves; The copper plate has a thickness of 1 to 1.2 mm.

5. The carbon-based metamaterial electromagnetic absorber according to claim 1, characterized in that: The carbon-based metamaterial electromagnetic absorber is made of a non-absorbent doped photosensitive resin as a matrix, and the surface is coated with a composite photosensitive resin doped with an absorbent.

6. The carbon-based metamaterial electromagnetic absorber according to claim 5, characterized in that: The composite photosensitive resin material doped with an absorber comprises, by weight: 40 to 50 parts of a photosensitive resin doped with no absorber, 0.1 to 0.8 parts of carbon nanotubes, 50 to 60 parts of carbonyl iron powder, and 8 to 12 parts of a diluent; The material of the non-absorbent doped photosensitive resin comprises, by weight: 70-90 parts of oligomer, 18-25 parts of monomer, 3-5 parts of photoinitiator, and 0.02-0.04 parts of dispersant.

7. The carbon-based metamaterial electromagnetic absorber according to claim 6, characterized in that: The diluent is one or more of polyethylene glycol diacrylate, propylene glycol diacrylate or methyl methacrylate; The oligomer includes one or more of polyurethane acrylate, epoxy acrylate, aliphatic epoxy resin, polyester acrylate or fluorine-modified acrylate; The monomers include one or more of monofunctional acrylate monomers, difunctional acrylate monomers or multifunctional acrylate monomers; The photoinitiator includes one or more of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, diphenyl glycol ketone, 2-methyl-1-(4-methylthiophenyl)-2-morpholine-1-propanone, 2,4,6-trimethylbenzoyl-ethoxy-phenylphosphine oxide, and 2-isopropylthioxanthone; The dispersant is one or more of BYKP-115, N,N-dimethylformamide, and Disper711.

8. A method for preparing a carbon-based metamaterial electromagnetic absorber according to any one of claims 1 to 7 by photothermal assisted in-situ curing and additive manufacturing, characterized in that: Based on the light-curing 3D printing additive preparation technology, the following steps are included: S1. Model and slice the honeycomb-like structure and the pointed cone structure of the carbon-based metamaterial electromagnetic absorber described in any one of claims 1 to 7, import the model file into a light-curing printer, and set printing parameters; prepare the materials according to the material ratio described in any one of claims 5 to 7 to obtain a photosensitive resin slurry doped with an absorber; S2. Printing the lower honeycomb structure: first add a non-absorbent doped photosensitive resin slurry, select the lower structure slice file, and print until the end to obtain a complete lower honeycomb structure; S3. Printing the upper conical structure: first add the photosensitive resin slurry without absorber, select the upper structure slice file, and print until the end to obtain a complete upper conical structure; S4. The upper conical structure is bonded to the lower honeycomb structure to obtain a bonded absorber; S5. Prepare the materials according to any one of claims 5 to 7 to obtain a composite photosensitive resin doped with an absorbent; apply the composite photosensitive resin doped with an absorbent to the bonded absorber obtained in S4 in small amounts and multiple times to make the coating uniform; S6. Paste a thick copper plate to the bottom of the lower honeycomb-like structure to obtain a complete carbon-based metamaterial electromagnetic absorber.

9. The method for preparing a carbon-based metamaterial electromagnetic absorber by photothermal-assisted in-situ curing additive according to claim 8, characterized in that: The printing parameters in step S1 are: layer thickness 0.020 mm, number of bottom layers 5, exposure time 40 s, bottom layer exposure time 50 s, number of transition layers 15, and transition type linear; The bonding method in step S4 or S6 is any one of epoxy resin bonding, polyurethane adhesive bonding, acrylic adhesive bonding, phenolic resin bonding, and polyimide resin bonding; the adhesive used in the epoxy resin bonding is epoxy resin.

10. An application of a carbon-based metamaterial electromagnetic absorber, characterized in that: The carbon-based metamaterial electromagnetic absorber serves as a functional material or structural component for electromagnetic wave absorption and shielding, and achieves efficient absorption, scattering suppression or reflection attenuation of electromagnetic waves through its dielectric / magnetic loss characteristics and metamaterial microstructure design.

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