A multilayer heterostructure rGO / (C-SiC) n Electromagnetic shielding materials and their preparation methods

Abstract

This invention discloses a multilayer heterostructure rGO / (C-SiC) interface. n This invention relates to electromagnetic shielding materials and their preparation methods, belonging to the technical field of carbon-based composite materials and electromagnetic functional materials. The method employs a combination of vacuum impregnation and heat treatment to alternately impregnate a reduced graphene oxide (rGO) aerogel framework with carbon and silicon carbide precursors, constructing a C-SiC multilayer heterogeneous interface structure with controllable layer count. This invention utilizes a combination of vacuum impregnation and heat treatment to alternately generate pyrolytic carbon and silicon carbide layers in situ on a three-dimensional rGO aerogel framework, constructing a C-SiC multilayer heterogeneous interface structure with controllable layer count. This structure simultaneously introduces electromagnetic loss mechanisms such as conductive loss, interface polarization, and multiple scattering within a lightweight porous framework, effectively improving the impedance matching characteristics of the material. This allows for the designable control of the electromagnetic wave absorption peak position and effective absorption bandwidth; simultaneously, it considers the material's heat resistance and environmental stability, meeting the requirements of high-frequency electromagnetic wave absorption applications.

Description

Technical Field

[0001] This invention belongs to the technical field of carbon-based composite materials and electromagnetic functional materials, specifically relating to a multilayer heterogeneous interface rGO / (C-SiC). n Electromagnetic shielding materials and their preparation methods are discussed, along with the application of this composite material in fields such as electromagnetic wave absorption / electromagnetic protection. Background Technology

[0002] With the significant improvement in the collaborative strike capabilities of space exploration and strategic defense systems, multi-temperature, broadband absorbing technology has shown great application potential in the field of "radar stealth" technology. At the same time, the rapid development of modern electronic information technology, 5G / 6G high-frequency communication, and aerospace technology has led to electromagnetic radiation pollution that not only seriously interferes with the stable operation of precision electronic equipment but also poses a potential threat to human health. Therefore, the development of high-performance lightweight electromagnetic wave absorbing materials with the characteristics of "thin, light, wide, and strong" has become a core need that urgently needs to be addressed.

[0003] Carbon-based materials, including graphene, carbon nanotubes, and carbon fibers, have attracted increasing attention as electromagnetic wave absorbing materials due to their low density, good chemical stability, and considerable dielectric properties. Among these, graphene, with its unique two-dimensional (2D) layer structure composed of hexagonal honeycomb lattices, large specific surface area and aspect ratio, and excellent conductivity, offers great potential for constructing lightweight, porous aerogel-based electromagnetic wave absorbing materials. The abundant pores in aerogels not only reduce mass density but also improve the impedance matching characteristics of the electromagnetic wave absorber. Furthermore, the high porosity effectively increases the multiple reflections of incident electromagnetic waves, which, combined with the high electromagnetic wave loss capacity of the graphene aerogel tube walls, ensures the high electromagnetic wave absorption performance of graphene-based aerogels. Therefore, graphene aerogels, with their ultra-low density, huge specific surface area, and continuous three-dimensional porous network, can generate extremely strong conductive loss and are considered a highly promising next-generation lightweight absorbing framework material. However, the highly continuous carbon network inside pure graphene often leads to excessively high overall electrical conductivity of the material, causing severe impedance mismatch. A large number of incident electromagnetic waves are reflected the moment they come into contact with the material surface and are difficult to penetrate into the interior and be effectively attenuated.

[0004] Besides designing porous structures, additional components such as magnetic particles, metal oxides, or polymers can be effectively incorporated to modulate the dielectric and electromagnetic wave absorption properties of graphene-based aerogels. These components not only help reduce the aggregation of graphene layers and improve the mechanical strength of the aerogel, but also contribute to the generation of new heterogeneous interfaces, enhancing the polarization loss capability of incident electromagnetic waves. Metal oxides and magnetic particles can effectively modulate electromagnetic parameters and improve impedance matching, thereby enhancing the electromagnetic wave absorption of graphene-based aerogels. However, the high density, difficulty in dispersibility, or poor oxidative stability of these magnetic components or metal oxides limit the further development of lightweight, durable, and high-performance graphene aerogel-based electromagnetic wave absorbing materials. Polymers such as cellulose nanofibers, polypyrrole, and aramid nanofibers, with their low density, easy processability, and chemical stability, have been widely used to improve the dispersibility of graphene nanosheets and adjust electromagnetic parameters to optimize the electromagnetic wave absorption of graphene-based aerogels. However, the poor temperature resistance, low mechanical strength, and unsustainable properties of most petrochemical polymers hinder the construction of low-density but robust and durable graphene-based aerogels. To overcome this bottleneck, introducing dielectric semiconductor materials silicon carbide (SiC) and pyrolytic carbon (PyC) to construct a composite microwave absorbing system has become a key path for optimizing electromagnetic parameters. The introduction of SiC not only reduces the overall conductivity of the system and significantly improves impedance matching, but also provides abundant dipole polarization losses; while PyC can be used as a modification layer to finely control the microscopic conductive network. When the three are combined, the attenuation of electromagnetic waves inside the material will be upgraded from a single conductive loss to a perfect synergy of conductive loss, strong interfacial polarization loss caused by heterogeneous interfaces, and multiple reflection and scattering losses within the three-dimensional channels. Although constructing a rGO / SiC / PyC multilayer composite system has significant microwave absorption advantages in theory, existing conventional physical blending, hydrothermal methods, or atmospheric pressure impregnation processes have significant technical bottlenecks. Due to the complex micro- and nano-scale pores within aerogels, precursors are highly susceptible to capillary resistance and strong obstruction from residual air within the pores under normal pressure. This results in SiC precursors or carbon sources often only adhering to the surface of the aerogel, failing to penetrate deep into the pores to form a uniform coating. Simultaneously, existing methods cannot precisely control component distribution at the microscale, easily leading to component aggregation and making it impossible to construct regular alternating multilayer (e.g., ABA-type) microstructures. This disorder and inhomogeneity in the microstructure severely reduces the number of heterogeneous interfaces within the composite system, failing to fully stimulate interfacial polarization effects and hindering the progressive attenuation effect of the multilayer structure. Therefore, overcoming the mass transfer limitations of existing impregnation processes and developing a novel preparation method that can overcome pore resistance, allow precursors to penetrate deep into the aerogel, and precisely construct alternating rGO / SiC / PyC multilayer microstructures to maximize the synergistic effect of impedance matching and multiple loss mechanisms has become a pressing technical challenge. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a multilayer heterogeneous interface rGO / (C-SiC). n Electromagnetic shielding materials and their preparation methods address the technical problems in existing technologies where conventional physical blending, hydrothermal methods, or atmospheric pressure impregnation processes are limited by the capillary resistance effect and residual air resistance in the micro-nano channels within the aerogel. This results in the precursors being unable to uniformly penetrate deep into the channels and only adhering to the surface. Furthermore, it is impossible to precisely control the component distribution at the microscale to construct a regular alternating multilayer structure. Consequently, component agglomeration, insufficient number of heterogeneous interfaces, and failure to fully utilize interfacial polarization loss and progressive attenuation effects are caused, ultimately severely restricting the synergistic effect of impedance matching and multiple loss mechanisms.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A multilayer heterostructure rGO / (C-SiC) n A method for preparing electromagnetic shielding materials, comprising: alternately impregnating a reduced graphene oxide aerogel framework with carbon precursors and silicon carbide precursors by combining vacuum impregnation and heat treatment to construct a carbon-silicon carbide multilayer heterogeneous interface structure with controllable number of layers.

[0007] Specifically, the method includes the following steps: Step 1, Preparation of graphene oxide (GO): Step 1.1, Pre-oxidation: Mix concentrated sulfuric acid and phosphoric acid, add graphite and potassium persulfate and stir to react; after the reaction is complete, cool and then pour into water and let stand overnight; after standing, filter, wash with water, centrifuge and dry in sequence to obtain pre-oxidized graphite.

[0008] Step 1.2, Oxidation: Add the pre-oxidized graphite obtained in Step 1.1 to sulfuric acid and stir. After cooling, add potassium permanganate and stir at low temperature, then stir at constant temperature. After the constant temperature stirring is completed, add ice water and hydrogen peroxide dropwise to terminate the reaction. Pour the reaction solution into water, stir and let stand overnight. After standing, wash with acid and centrifuge to obtain graphene oxide, which is then freeze-dried for later use.

[0009] Step 2, constructing graphene oxide (GO) aerogel: The graphene oxide obtained in Step 1 is prepared into a GO dispersion, stirred and then frozen, and then freeze-dried to obtain a three-dimensional GO sponge skeleton.

[0010] Step 3, Preparation of reduced graphene oxide (rGO) aerogel framework: The GO sponge three-dimensional framework obtained in step 2 is subjected to high-temperature heat treatment in a protective atmosphere to obtain the rGO aerogel framework.

[0011] Step 4, in-situ generation of pyrolytic carbon (PyC) layer: The rGO aerogel framework obtained in step 3 is immersed in carbon precursor solution under vacuum environment for vacuum impregnation; then solidification and high-temperature pyrolysis are performed sequentially to obtain pyrolytic carbon / reduced graphene oxide (PyC / rGO) composite aerogel.

[0012] Step 5, in-situ generation of silicon carbide (β-SiC) layer: The PyC / rGO composite aerogel obtained in step 4 is immersed in silicon carbide precursor solution under vacuum environment for vacuum impregnation; then drying and ceramic heat treatment are performed in sequence to generate silicon carbide (β-SiC) layer on the skeleton in situ.

[0013] Step Six: Repeat steps four and five alternately n times each to finally obtain rGO / (C-SiC). n Composite aerogel; the value of n ranges from 1 to 8.

[0014] This invention also protects a multilayer heterostructure rGO / (C-SiC) prepared by the method described above. n The electromagnetic shielding material uses a three-dimensional interconnected reduced graphene oxide aerogel as a framework, with pyrolytic carbon layers and silicon carbide distributed in the pore walls and inside the framework.

[0015] The present invention also has the following technical features: Specifically, in step 1.1, the stirring reaction is carried out at a temperature of 80°C for 4.5 hours.

[0016] Specifically, in step 1.2, the temperature for low-temperature stirring is -3℃, and the time is 0.5 to 1 h.

[0017] Specifically, in step 1.2, the constant temperature stirring temperature is 35℃ and the time is 2 hours.

[0018] Specifically, in step two, a GO dispersion is prepared by stirring for 3 to 5 hours.

[0019] Optionally, in step two, dimethyl sulfoxide (DMSO) or anhydrous ethanol is added as a structure regulating agent when preparing the GO dispersion. The volume ratio of DMSO to solvent is 1:(25-100), and the volume ratio of anhydrous ethanol to solvent is 1:(10-40).

[0020] Specifically, in step two, the solvent for the GO dispersion is water, with a concentration of 5–25 mg / mL.

[0021] Specifically, in step two, the stirring temperature is 20℃~30℃ and the time is 2.5~3.5h.

[0022] Specifically, in step two, the freezing temperature is -18℃ to -24℃, and the freezing time is 20 to 30 hours.

[0023] Specifically, in step two, the freeze-drying temperature is -50℃ to 0℃, and the time is 40 to 52 hours.

[0024] Specifically, in step three, the high-temperature heat treatment temperature is 900–1100℃, and the time is 1.5–2.5 hours.

[0025] Specifically, in step four, the carbon precursor is phenolic resin, the solvent for the carbon precursor solution is ethanol, and the mass fraction of the carbon precursor is 30% to 50%.

[0026] Specifically, in step four, the conditions for vacuum impregnation are: vacuum degree of -0.1MPa to -0.06MPa, and impregnation time of 0.5 to 1h.

[0027] Specifically, in step four, the curing temperature is 120℃ and the time is 2.5 to 3.5 hours.

[0028] Specifically, in step four, the conditions for high-temperature pyrolysis are: pyrolysis at 800–1100℃ for 1.5–2.5 h in a protective atmosphere.

[0029] Specifically, in step five, the carboalkyl precursor is polycarbosilane, the solvent of the carboalkyl precursor solution is xylene, and the mass fraction of the carboalkyl precursor is 30% to 50%.

[0030] Specifically, in step five, the conditions for vacuum impregnation are: vacuum degree of -0.1MPa to -0.06MPa, and impregnation time of 0.5 to 1h.

[0031] Specifically, in step five, the drying temperature is 80–120℃ and the time is 0.5–1 hour.

[0032] Specifically, in step five, the conditions for the ceramization heat treatment are: pyrolysis at 800–1100℃ for 1.5–2.5 h in a protective atmosphere.

[0033] Compared with the prior art, the present invention has the following technical effects: (I) This invention utilizes a combination of vacuum impregnation and heat treatment to alternately generate pyrolytic carbon layers and silicon carbide layers in situ on a three-dimensional rGO aerogel framework, constructing a C-SiC multilayer heterogeneous interface structure with controllable layer count. This structure simultaneously introduces electromagnetic loss mechanisms such as conductive loss, interface polarization, and multiple scattering within a lightweight porous framework, effectively improving the impedance matching characteristics of the material. This allows for the designable control of the electromagnetic wave absorption peak position and effective absorption bandwidth. Simultaneously, it considers the material's heat resistance and environmental stability, meeting the requirements of high-frequency electromagnetic wave absorption applications.

[0034] (II) The material prepared by this invention possesses a three-dimensional interconnected conductive network and multi-level channels, with abundant interfaces. Through the synergistic effect of multiple mechanisms such as conductive loss, interface polarization / dipole polarization loss, and multiple scattering, it exhibits excellent electromagnetic wave shielding capability. Significant electromagnetic absorption performance can be obtained in the X-band (8.2–12.4 GHz), with the optimal sample reflection loss reduced to approximately [missing value]. The absorption peak position and effective bandwidth can be adjusted by changing the material thickness and the number of C-SiC layers; the total electromagnetic shielding effectiveness (SET) in the X-band reaches more than 30 dB.

[0035] (III) The material prepared by this invention introduces the β-SiC phase, which endows the material with excellent heat resistance and environmental stability, making it suitable for high temperature or complex service conditions and broadening the application range of the material.

[0036] (IV) The rGO / (C-SiC) prepared in this invention n The composite material has a unique microstructure, in which graphene has a layered porous structure, and pyrolytic carbon and silicon carbide are alternately impregnated on the porous structure to form a large number of heterojunction interfaces. The addition of silicon carbide and pyrolytic carbon not only greatly improves the electromagnetic shielding and wave absorption performance of the material, but also effectively enhances the mechanical properties of the material, giving it better overall performance. Attached Figure Description

[0037] Figure 1 The rGO / (C-SiC) prepared in Example 1 (from left to right) n Photograph of the aerogel of the composite material.

[0038] Figure 2 The image shows a SEM image of the rGO / (C-SiC)1 composite material prepared in Example 1.

[0039] Figure 3 The image shows a SEM image of the rGO / (C-SiC)2 composite material prepared in Example 2.

[0040] Figure 4 The image shows a SEM image of the rGO / (C-SiC)3 composite material prepared in Example 3.

[0041] Figure 5 The image shows a SEM image of the rGO / (C-SiC)4 composite material prepared in Example 4.

[0042] Figure 6 The rGO / (C-SiC) samples obtained in Examples 1 to 4 are examples. n XRD pattern of composite material.

[0043] Figure 7This is a 3D RL image of the rGO / (C-SiC)2 composite material prepared in Example 2.

[0044] Figure 8 This is a 2D RL image of the rGO / (C-SiC)2 composite material prepared in Example 2.

[0045] Figure 9 The image shows the Cole-Cole curve of the rGO / (C-SiC)2 composite material prepared in Example 2.

[0046] Figure 10 This is a normalized impedance matching image of the rGO / (C-SiC)2 composite material prepared in Example 2.

[0047] Figure 11 The rGO / (C-SiC) samples obtained in Examples 1 and 4 are examples of this study. n Images related to the electromagnetic shielding performance of composite materials.

[0048] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0049] It should be noted that all raw materials used in this invention, unless otherwise specified, are those known in the art. For example: Polycarbosilanes are polycarbosilanes with molecular weights of 800-2500 g / mol known in the prior art.

[0050] Phenolic resin is a thermosetting (7%-9% hexamethylenetetramine) phenolic resin known in the prior art. The technical approach of this invention is as follows: First, graphene oxide (GO) hydrogel is prepared. By controlling the concentration of graphene oxide (GO) hydrogel, an aerogel precursor with controllable pore structure and good connectivity is obtained. A small amount of DMSO can be introduced to regulate gel nucleation and pore structure. GO aerogel is obtained through freeze-drying and then reduced at high temperature under an inert atmosphere to form a three-dimensional rGO aerogel framework. Based on this, a combination of vacuum impregnation and heat treatment is used to vacuum impregnate the framework with phenolic resin, allowing the phenolic resin to be shaped within the framework and form a continuous filling phase. Then, through curing / pyrolysis, the phenolic resin is transformed and a pyrolytic carbon (PyC) layer is generated in situ. The resulting carbon composite structure of rGO framework and PyC serves as the carbon phase base layer for subsequent construction of heterogeneous interfaces. Next, a polycarbosilane (PCS) precursor is vacuum impregnated, transforming PCS into a silicon carbide phase, preferably generating β-SiC. This forms a heterogeneous interface between the carbon phase and the SiC phase, and a SiC layer or distributed phase is formed within the pore walls / framework. Finally, by repeating the alternating cycle of "PyC deposition-SiC generation", a multilayer heterogeneous interface structure with controllable number of layers (C-SiC) is constructed. Following the above technical approach, specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0051] Example 1 This embodiment presents a multilayer heterostructure rGO / (C-SiC) n The preparation method of electromagnetic shielding material includes the following steps: Step 1: Prepare graphene oxide (GO) using the modified Hummers method: Step 1.1, Pre-oxidation: Mix 20 mL of concentrated sulfuric acid with 10 mL of phosphoric acid, add 3 g of 400 mesh graphite and 2.5 g of potassium persulfate (K2S2O8) and stir. Then stir at a constant temperature of 80℃ in a water bath for 4.5 h. After cooling to room temperature, pour into 1 L of deionized water and let stand overnight. Filter and repeatedly wash / centrifuge with water until the supernatant is close to neutral. Dry to obtain pre-oxidized graphite.

[0052] Step 1.2, Oxidation: Pre-oxidized graphite was added to sulfuric acid and mechanically stirred. After cooling to -3°C, potassium permanganate was slowly added at low temperature and stirring continued for 1 h. Then, the mixture was transferred to a 35°C water bath and stirred for 2 h. Ice water was then slowly added dropwise, followed by the addition of 30% hydrogen peroxide (20 mL) to terminate the reaction. The reaction solution was poured into approximately 1200 mL of water, stirred, and allowed to stand overnight. After adding hydrochloric acid, the mixture was centrifuged in batches at 4°C until the pH of the supernatant reached 5–7, yielding GO, which was then freeze-dried for later use.

[0053] Step 2, constructing graphene oxide (GO) aerogel: The prepared graphene oxide was mixed with water to prepare a dispersion with a concentration of 16 mg / mL without adding any auxiliary solution. The mixture was stirred at room temperature for 3 hours, then frozen for 24 hours, and then freeze-dried at -50℃ to 0℃ for 48 hours to obtain the GO sponge three-dimensional skeleton.

[0054] Step 3, preparation of reduced graphene oxide (rGO) aerogel framework: The GO sponge three-dimensional framework obtained in step 2 is placed in a tube furnace, and the temperature is raised to 1000℃ under nitrogen protection for high-temperature heat treatment for 120 min to obtain a three-dimensional connected rGO aerogel framework.

[0055] Step 4, in-situ generation of pyrolytic carbon (PyC) layer: The rGO aerogel framework obtained in step 3 is immersed in an ethanol solution of phenolic resin (with a mass fraction of 30%) under vacuum (vacuum degree of -0.1MPa to -0.06MPa) for 30 min, followed by curing at 120℃ for 3 h, and finally high-temperature pyrolysis at 900℃ under nitrogen atmosphere for 2 h to obtain pyrolytic carbon / reduced graphene oxide (PyC / rGO) composite aerogel.

[0056] Step 5, in-situ generation of silicon carbide (β-SiC) layer: Under vacuum conditions (vacuum degree of -0.1MPa to -0.06MPa), the PyC / rGO composite aerogel prepared in step 4 is immersed in a xylene solution of polycarbosilane (where the mass fraction of polycarbosilane is 30%) for 30 min; then vacuum dried at 80℃ until the xylene is completely volatilized, and then pyrolyzed at 1000℃ in a nitrogen atmosphere for 2 h, so that a silicon carbide (β-SiC) layer is generated in-situ on the framework.

[0057] Step Six: Repeat steps Four and Five once each to finally obtain the rGO / (C-SiC)1 composite aerogel, as shown in the figure below. Figure 1 As shown, the micromorphological characterization is as follows Figure 2 As shown in the figure and XRD pattern Figure 6 As shown.

[0058] In this embodiment, a vector network analyzer was used to test the rGO / (C-SiC)1 composite aerogel. The testing process was as follows: the sample was ground into powder, and a test sample was prepared by adding 50% paraffin wax. The electromagnetic wave frequency range for the sample test was 8.2–12.4 GHz. According to conventional evaluation methods for absorbing materials, the test results showed that the rGO / (C-SiC)1 material achieved a minimum reflection loss of -22.43 dB at a frequency of 11.749 GHz within the 8.2–12.4 GHz range, an effective absorption bandwidth of 3.24 GHz at a thickness of 2.8 mm, and an electromagnetic shielding effectiveness of over 30 dB in the X-band.

[0059] Example 2: This embodiment provides a method for preparing a multilayer heterogeneous interface rGO(C-SiC)n electromagnetic shielding material. The method is basically the same as in Embodiment 1, except that in this embodiment, step six is ​​a repeated cycle of steps four and five, performed twice each, ultimately yielding an rGO / (C-SiC)2 composite aerogel. Its physical image is shown below. Figure 1 As shown, the characterization is as follows Figure 3 and Figure 6 As shown.

[0060] In this embodiment, a vector network analyzer was used to test the rGO / (C-SiC)2 composite aerogel. The testing process was as follows: the sample was ground into powder, and a test sample was prepared by adding 50% paraffin wax. The electromagnetic wave frequency range for sample testing was 1–18 GHz. According to conventional evaluation methods for absorbing materials, the test results showed that the rGO / (C-SiC)2 material achieved a minimum reflection loss of -43.64 dB at a frequency of 13.6543 GHz within the 1–18 GHz range, and an effective absorption bandwidth of 3.44 GHz at a thickness of 1.3 mm.

[0061] Example 3: This embodiment presents a multilayer heterostructure rGO / (C-SiC) n The method for preparing electromagnetic shielding materials is basically the same as in Example 1, except that step six involves repeating steps four and five three times each, ultimately yielding rGO / (C-SiC)3 composite aerogel, as shown in the figure below. Figure 1 As shown, the characterization is as follows Figure 4 and Figure 6 As shown.

[0062] In this embodiment, a vector network analyzer was used to test the rGO / (C-SiC)3 composite aerogel. The testing process was as follows: the sample was ground into powder, and a test sample was prepared by adding 50% paraffin wax. The electromagnetic wave frequency range for sample testing was 1–18 GHz. According to conventional evaluation methods for absorbing materials, the test results showed that the rGO / (C-SiC)3 material achieved a minimum reflection loss of -38.22 dB at a frequency of 11.4231 GHz within the 1–18 GHz range, and an effective absorption bandwidth of 4.08 GHz at a thickness of 1.3 mm.

[0063] Example 4: This embodiment presents a multilayer heterostructure rGO / (C-SiC) n The method for preparing electromagnetic shielding materials is basically the same as in Example 1, except that in this example, step six is ​​a cycle of steps four and five, each performed four times, ultimately yielding rGO / (C-SiC)4 composite aerogel, as shown in the figure below. Figure 1 As shown, the characterization is as follows Figure 5 and Figure 6 As shown.

[0064] In this embodiment, a vector network analyzer was used to test the rGO / (C-SiC)4 composite aerogel. The testing process was as follows: the sample was ground into powder, and a test sample was prepared by adding 50% paraffin wax. The electromagnetic wave frequency range for the sample test was 8.2–12.4 GHz. According to conventional evaluation methods for microwave absorbing and electromagnetic shielding materials, the test results showed that the minimum reflection loss of the rGO / (C-SiC)4 material within the 8.2–12.4 GHz range at a frequency of 11.224 GHz reached -7.03 dB, and the electromagnetic shielding effectiveness in the X-band reached over 70 dB.

Claims

1. A multilayer heterogeneous interface rGO / (C-SiC) n The method for preparing electromagnetic shielding materials is characterized by, This method includes: using a combination of vacuum impregnation and heat treatment to alternately impregnate a reduced graphene oxide aerogel framework with carbon precursors and silicon carbide precursors, thereby constructing a carbon-silicon carbide multilayer heterostructure with a controllable number of layers.

2. The multilayer heterostructure rGO / (C-SiC) as described in claim 1 n The method for preparing electromagnetic shielding materials is characterized by, The method specifically includes the following steps: Step 1: Prepare graphene oxide; Step 2: Construct graphene oxide aerogel; Step 3: Prepare the reduced graphene oxide aerogel framework; Step 4, in-situ generation of pyrolytic carbon layer: The reduced graphene oxide aerogel framework obtained in step 3 is immersed in carbon precursor solution under vacuum environment for vacuum impregnation. Subsequently, solidification and high-temperature pyrolysis were carried out sequentially to obtain pyrolytic carbon / reduced graphene oxide composite aerogel; Step 5, in-situ generation of silicon carbide layer: The pyrolytic carbon / reduced graphene oxide composite aerogel obtained in step 4 is immersed in a carbide precursor solution under vacuum environment for vacuum impregnation. Subsequently, drying and ceramic heat treatment are performed sequentially to generate a silicon carbide layer in situ on the skeleton. Step Six: Repeat steps four and five alternately n times each to finally produce a multilayer heterogeneous interface rGO / (C-SiC). n Electromagnetic shielding materials.

3. The multilayer heterostructure rGO / (C-SiC) as described in claim 2 n The method for preparing electromagnetic shielding materials is characterized by, In step four, the carbon precursor is phenolic resin, the solvent for the carbon precursor solution is ethanol, and the mass fraction of the carbon precursor is 30%–50%. In step four, the vacuum impregnation conditions are: vacuum degree of -0.1MPa to -0.06MPa, and impregnation time of 0.5 to 1h; In step four, the curing temperature is 120℃ and the time is 2.5–3.5 h; In step four, the conditions for high-temperature pyrolysis are: pyrolysis at 800–1100℃ for 1.5–2.5 h in a protective atmosphere.

4. The multilayer heterostructure rGO / (C-SiC) as described in claim 2 n The method for preparing electromagnetic shielding materials is characterized by, In step five, the carboalkyl precursor is polycarbosilane, the solvent for the carboalkyl precursor solution is xylene, and the mass fraction of the carboalkyl precursor is 30%–50%. In step five, the vacuum impregnation conditions are: vacuum degree of -0.1MPa to -0.06MPa, and impregnation time of 0.5 to 1h; In step five, the drying temperature is 80–120℃, and the time is 0.5–1 hour; In step five, the conditions for the ceramic heat treatment are: pyrolysis at 800–1100℃ for 1.5–2.5 h in a protective atmosphere.

5. The multilayer heterostructure rGO / (C-SiC) as described in claim 2 n The method for preparing electromagnetic shielding materials is characterized by, Step one includes the following steps: Step 1.1, Pre-oxidation: Mix concentrated sulfuric acid and phosphoric acid, add graphite and potassium persulfate and stir to react; after the reaction is complete, cool and then pour into water and let stand overnight; after standing, filter, wash with water, centrifuge and dry in sequence to obtain pre-oxidized graphite; Step 1.2, Oxidation: Add the pre-oxidized graphite obtained in Step 1.1 to sulfuric acid and stir. After cooling, add potassium permanganate and stir at low temperature, then stir at constant temperature. After the constant temperature stirring is completed, add ice water and hydrogen peroxide dropwise to terminate the reaction. Pour the reaction solution into water, stir and let stand overnight. After standing, wash with acid and centrifuge to obtain graphene oxide, which is then freeze-dried for later use.

6. The multilayer heterostructure rGO / (C-SiC) as described in claim 5 n The method for preparing electromagnetic shielding materials is characterized by, In step 1.1, the stirring reaction was carried out at a temperature of 80°C for 4.5 hours. In step 1.2, the low-temperature stirring temperature is -3℃ and the time is 0.5 to 1 h; the constant-temperature stirring temperature is 35℃ and the time is 2 h.

7. The multilayer heterostructure rGO / (C-SiC) as described in claim 2 n The method for preparing electromagnetic shielding materials is characterized by, The second step is as follows: the graphene oxide obtained in the first step is prepared into a graphene oxide dispersion, stirred and then frozen, and then freeze-dried to obtain a three-dimensional skeleton of graphene oxide sponge. In step two, a graphene oxide dispersion is prepared by stirring for 3 to 5 hours. In step two, the solvent for the graphene oxide dispersion is water, with a concentration of 5–25 mg / mL. In step two, the stirring temperature is 20℃~30℃, and the time is 2.5~3.5h; In step two, the freezing temperature is -18℃ to -24℃, and the freezing time is 20 to 30 hours. In step two, the freeze-drying temperature is -50℃ to 0℃, and the time is 40 to 52 hours.

8. The multilayer heterostructure rGO / (C-SiC) as described in claim 2 n The method for preparing electromagnetic shielding materials is characterized by, The third step is as follows: The three-dimensional skeleton of graphene oxide sponge obtained in the second step is subjected to high-temperature heat treatment in a protective atmosphere to obtain a reduced graphene oxide aerogel skeleton. In step three, the high-temperature heat treatment is carried out at a temperature of 900–1100℃ for 1.5–2.5 hours.

9. The multilayer heterostructure rGO / (C-SiC) as described in claim 2 n The method for preparing electromagnetic shielding materials is characterized by, In step six, the value of n ranges from 1 to 8.

10. A multilayer heterostructure rGO / (C-SiC) prepared by the method according to any one of claims 1 to 9 n Electromagnetic shielding material, characterized in that, The material uses a three-dimensionally connected reduced graphene oxide aerogel as a framework, with pyrolytic carbon layers and silicon carbide layers distributed on the pore walls and inside the framework.

Images