Lightweight heat-insulating multifunctional electromagnetic wave absorbing material with one-dimensional silicon carbide nanowires grown on two-dimensional reduced graphene oxide and preparation method of lightweight heat-insulating multifunctional electromagnetic wave absorbing material

Abstract

The invention discloses a lightweight heat-insulating multifunctional electromagnetic wave absorbing material with one-dimensional silicon carbide nanowires grown on two-dimensional reduced graphene oxide and a preparation method of the lightweight heat-insulating multifunctional electromagnetic wave absorbing material, and belongs to the technical field of preparation of wave absorbing composite materials, the preparation method comprises the following steps: preparing silicon-containing foamed graphene oxide, preparing a precursor, and carrying out heat treatment in a low-oxygen environment. The preparation of the silicon-containing foamed graphene oxide comprises the following steps: dissolving Tween 80 in absolute ethyl alcohol, and stirring to prepare a foaming agent; mixing the graphene oxide slurry with a foaming agent and metal silicon powder, and stirring at a high speed to obtain silicon-containing foamed graphene oxide; the heat treatment in the low-oxygen environment comprises the following steps: putting the precursor into a graphite crucible, and sintering by a carbon burying method to obtain the lightweight heat-insulating multifunctional electromagnetic wave absorbing material with one-dimensional silicon carbide nanowires grown on two-dimensional reduced graphene oxide. Through reasonable design of the material composition and the preparation method, the material is ultra-light, has excellent electromagnetic wave absorption capability, and can be kept stable in a complex environment.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of microwave absorbing composite materials, and particularly to a lightweight heat-insulating and multifunctional electromagnetic wave absorbing material for growing one-dimensional silicon carbide nanowires on two-dimensional reduced graphene oxide and a preparation method thereof. Background Art

[0002] With the rapid development of modern electronic technology, the problems of electromagnetic wave radiation and interference have become increasingly serious, and the demand for high-performance electromagnetic wave absorbing materials is becoming more and more urgent. Traditional electromagnetic wave absorbing materials often have problems such as high density, narrow absorption bandwidth, and unsatisfactory absorption effect. In the fields of aerospace, miniaturization of electronic devices, and military stealth, there is an urgent need to develop a material that has both ultra-light characteristics and excellent electromagnetic wave absorption performance. Silicon carbide nanowires have advantages such as high strength, high melting point, and good chemical stability, and have potential in enhancing material strength and electromagnetic wave absorption; reduced graphene oxide has a unique two-dimensional sheet structure and excellent electrical properties, and can effectively convert electromagnetic wave energy into heat energy for dissipation, and has been widely used in the field of electromagnetic wave absorbing materials. However, the research on compounding these two materials into a composite material remains to be further explored, and how to optimize the proportion of each component and the preparation process to achieve synergistic effects is the current challenge.

[0003] Chinese Patent CN118851162A discloses a preparation method of a nitrogen-doped reduced graphene oxide / zinc ferrite@nitrogen-doped carbon nanocomposite microwave absorbing material. In this patent, ferric chloride hexahydrate and zinc chloride are used as precursors, and zinc ferrite is synthesized by a solvothermal reaction. Then, dopamine self-polymerization and carbonization treatment are used to obtain a zinc ferrite@nitrogen-doped carbon composite, and finally, graphene oxide is used as a template for hydrothermal synthesis of the target composite material. The absorption intensity of this material reaches -61.1 dB at a thickness of 3.06 mm, and the effective absorption bandwidth reaches 6 GHz (covering the Ku band); at a thickness of 2.61 mm, the widest effective absorption bandwidth reaches 7.2 GHz, covering the Ku band and part of the X band, and the filling ratio is low (16.5 wt.%). However, when using ferric chloride hexahydrate and zinc chloride as precursors to synthesize zinc ferrite in the preparation, it needs to be carried out in a high-temperature environment, and the magnetic structure of metal elements may change in the high-temperature environment, resulting in magnetic loss.

[0004] Chinese Patent CN117596858A discloses a Ni / NiO-rGO nanocomposite with excellent electromagnetic wave absorption performance, its preparation method and application. In this patent, a soluble nickel salt is stirred and mixed with a graphene oxide aqueous suspension, followed by a hydrothermal reaction. The obtained hydrogel is soaked in a urea solution, dried, and then subjected to high-temperature thermal carbon reduction in a tubular furnace to obtain the composite material. When the filling amount of this material in the paraffin dispersion system is 5wt%, the minimum reflection loss value reaches -35.6 dB at a matching thickness of 1.8 mm, and the effective absorption bandwidth is 5.04 GHz. The nanoparticles are uniformly dispersed on the graphene sheets and have a mesoporous structure. However, this patent lacks sufficient research on the performance stability of this material in complex environments (such as high temperature, high humidity, etc.). From the perspective of the preparation method and composition, this patent stirs and mixes a soluble nickel salt with a graphene oxide aqueous suspension and then performs a hydrothermal reaction, and then obtains the composite material through a series of treatments. From the perspective of the material composition, nickel elements and their compounds may undergo chemical reactions such as oxidation and corrosion in high-temperature and high-humidity environments, affecting the microstructure and electromagnetic properties of the material.

[0005] Generally speaking, when reduced graphene oxide is combined with traditional magnetic materials for the preparation of electromagnetic wave absorption materials, the main problem is that the prepared electromagnetic wave absorption materials are unstable in complex environments. Through experiments, when a semiconductor ceramic material, silicon carbide nanowires, and reduced graphene oxide are compounded to prepare an electromagnetic wave absorption material, not only can the above problems be solved to a certain extent, but also the advantages of the two materials can be fully utilized, resulting in an enhanced electromagnetic wave absorption ability of the prepared electromagnetic wave absorption material. Summary of the Invention

[0006] Aiming at the deficiencies of the existing technology, the present invention provides a lightweight heat-insulating multifunctional electromagnetic wave absorption material with one-dimensional silicon carbide nanowires grown on two-dimensional reduced graphene oxide and its preparation method. By reasonably designing the material composition and preparation method, the material is ultra-light and has excellent electromagnetic wave absorption ability, and can also remain stable in complex environments.

[0007] To solve the above technical problems, the technical solutions adopted by the present invention are as follows: A lightweight heat-insulating multifunctional electromagnetic wave absorption material with one-dimensional silicon carbide nanowires grown on two-dimensional reduced graphene oxide and its preparation method, including: preparing silicon-containing foamed graphene oxide, preparing a precursor, and heat treatment in a low-oxygen environment; For the preparation of the silicon-containing foamed graphene oxide, Tween 80 is dissolved in absolute ethanol and stirred to prepare a foaming agent; the graphene oxide slurry is mixed with the foaming agent and metal silicon powder and stirred at high speed to obtain the silicon-containing foamed graphene oxide; In the preparation of the silicon-containing foamed graphene oxide, the dosage ratio of Tween 80 to absolute ethanol is 7-8 g:50-60 mL; Preferably, the dosage ratio of Tween 80 to absolute ethanol is 7.5 g:55 mL; The dosage ratio of graphene oxide slurry, foaming agent, and metal silicon powder is 7-8 g:4-6 mL:0.2-2 g; Preferably, the dosage ratio of graphene oxide slurry, foaming agent, and metal silicon powder is 7.5 g:5 mL:0.2-2 g; The stirring is magnetic stirring, and the stirring time is 10-15 min; Preferably, the stirring time is 10 min; The stirring speed of the high-speed stirring is 950-1100 rpm, and the time is 15-25 min; Preferably, the stirring speed of the high-speed stirring is 1000 rpm, and the time is 20 min; The concentration of graphene oxide in the graphene oxide slurry is 2.8-3.2%, and the sheet diameter of graphene oxide is 100-500 nm; The purity of the Tween 80 ≥ 99.5%; the purity of the metal silicon powder ≥ 99%, and the particle size ≤ 800 mesh; For the preparation of the precursor, the silicon-containing foamed graphene oxide is subjected to freezing treatment and then vacuum freeze-drying treatment to obtain the precursor; In the preparation of the precursor, the temperature of the freezing treatment is -65°C to -55°C, and the time is 12-36 h; Preferably, the temperature of the freezing treatment is -60°C, and the time is 24 h; The temperature of the vacuum freeze-drying treatment is -65°C to -55°C, and the time is 36-54 h; Preferably, the temperature of the vacuum freeze-drying treatment is -60°C, and the time is 48 h; For the heat treatment in a low-oxygen environment, the precursor is placed in a graphite crucible and sintered by the carbon burial method to obtain a lightweight heat-insulating and multifunctional electromagnetic wave absorption material for the growth of one-dimensional silicon carbide nanowires on two-dimensional reduced graphene oxide; In the heat treatment in a low-oxygen environment, the temperature of the carbon burial method sintering is 1500-1600°C, and the time is 2-3 h; Preferably, the temperature of the carbon burial method sintering is 1500°C, and the time is 2 h.

[0008] A lightweight heat-insulating and multifunctional electromagnetic wave absorption material for the growth of one-dimensional silicon carbide nanowires on two-dimensional reduced graphene oxide prepared by the aforementioned preparation method.

[0009] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The lightweight heat-insulating and multifunctional electromagnetic wave absorption material prepared by the present invention has the characteristics of low density and light weight, and its density can be as low as 0.2124-0.5382 g / cm3 ; Using the coaxial method of a vector network analyzer (detection standard GJB5239-2004), when the addition amount of the microwave absorbing material is 15% of the total mass of the test microwave absorbing ring, the specific reflection loss RL min value can reach -51.59 dB (8.32 GHz), and the effective absorption bandwidth EAB max is 4.0 GHz, and the thickness is 2.9 mm; (2) The lightweight heat-insulating and multifunctional electromagnetic wave absorbing material prepared by the present invention has a certain mechanical strength, can adapt to different usage environments and processing requirements, and also has certain heat-insulating and temperature-resistant properties; Place the lightweight heat-insulating and multifunctional electromagnetic wave absorbing material with a thickness of 5 mm on an alcohol lamp, then place a cotton ball on the lightweight heat-insulating and multifunctional electromagnetic wave absorbing material, and then continuously burn. At the 300th second of burning, the cotton ball has not yet carbonized; (3) The preparation method of the lightweight heat-insulating and multifunctional electromagnetic wave absorbing material of the present invention, compared with traditional electromagnetic absorbing materials, has a simple preparation process, low cost, can be mass-produced, and has broad application prospects. For example, in the fields of aerospace, electronic equipment protection, communication base stations, etc., it can effectively solve problems such as electromagnetic interference and electromagnetic radiation; (4) The preparation method of the lightweight heat-insulating and multifunctional electromagnetic wave absorbing material of the present invention optimizes the impedance matching of the composite material by regulating the introduction amount of graphene oxide, and adjusts the impedance matching and enhances the matrix strength with the help of silicon carbide nanowires, thereby overcoming the problems of single material or poor synergistic effect in existing patents, and preparing a super-light composite material with excellent electromagnetic wave absorption ability, filling the gap in this field. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0011] Figure 1 It is a 3D schematic diagram of the electromagnetic wave absorption performance of the lightweight heat-insulating and multifunctional electromagnetic wave absorbing material with two-dimensional reduced graphene oxide growing one-dimensional silicon carbide nanowires prepared in Example 1; Figure 2 It is a 3D schematic diagram of the electromagnetic wave absorption performance of the lightweight heat-insulating and multifunctional electromagnetic wave absorbing material with two-dimensional reduced graphene oxide growing one-dimensional silicon carbide nanowires prepared in Example 2; Figure 3 It is a 3D schematic diagram of the electromagnetic wave absorption performance of the lightweight heat-insulating and multifunctional electromagnetic wave absorbing material with two-dimensional reduced graphene oxide growing one-dimensional silicon carbide nanowires prepared in Example 3; Figure 4 3D schematic diagram of the electromagnetic wave absorption performance of the lightweight thermal insulation and multifunctional electromagnetic wave absorption material prepared by growing one-dimensional silicon carbide nanowires on two-dimensional reduced graphene oxide in Example 4; Figure 5 3D schematic diagram of the electromagnetic wave absorption performance of the lightweight thermal insulation and multifunctional electromagnetic wave absorption material prepared by growing one-dimensional silicon carbide nanowires on two-dimensional reduced graphene oxide in Example 5; Figure 6 Test result diagram of the thermal insulation performance of the lightweight thermal insulation and multifunctional electromagnetic wave absorption material prepared by growing one-dimensional silicon carbide nanowires on two-dimensional reduced graphene oxide in Example 5; Figure 7 Scanning electron microscope analysis diagrams at different preparation stages of the product prepared in Example 5; In the figure, Figure 7 a- Figure 7 c are the scanning electron microscope analysis diagrams of the prepared precursor; Figure 7 d- Figure 7 f are the scanning electron microscope analysis diagrams in the middle stage of heat treatment in a low-oxygen environment; Figure 7 g- Figure 7 i are the scanning electron microscope analysis diagrams of the obtained lightweight thermal insulation and multifunctional electromagnetic wave absorption material; Figure 8 3D schematic diagram of the electromagnetic wave absorption performance of the lightweight thermal insulation and multifunctional electromagnetic wave absorption material prepared by growing one-dimensional silicon carbide nanowires on two-dimensional reduced graphene oxide in Example 6; Detailed implementation manners

[0012] The various exemplary implementation manners of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0013] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0014] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific implementation manners of the specification of the present invention, which are obvious to those skilled in the art. Other implementation manners obtained from the specification of the present invention are obvious to those skilled in the art. The specification and examples of the present invention are only exemplary.

[0015] Terms such as "comprising", "including", "having", "containing", etc. used in this text are all open-ended terms, meaning including but not limited to.

[0016] Unless otherwise specified, the "parts" in the embodiments of the present invention refer to parts by weight.

[0017] Normal temperature in the embodiments of the present invention refers to 25 ± 2 °C.

[0018] The technical solutions of the present invention will be further described in detail below through specific embodiments, but the protection scope of the present invention is not limited thereto.

[0019] Example 1 A preparation method of a lightweight heat-insulating and multifunctional electromagnetic wave absorbing material for growing one-dimensional silicon carbide nanowires on two-dimensional reduced graphene oxide is specifically as follows: 1. Prepare silicon-containing foamed graphene oxide: Weigh 7.5 g of Tween 80 and dissolve it in 50 ml of absolute ethanol, stir magnetically for 10 min to prepare a foaming agent; weigh 7 g of graphene oxide (GO) slurry, add 5 mL of the foaming agent, and then add 0.2 g of metallic silicon powder. After high-speed stirring for 20 min, silicon-containing foamed graphene oxide is obtained; The purity of the Tween 80 ≥ 99.5%; The concentration of graphene oxide in the graphene oxide slurry is 3%, and the sheet diameter of the graphene oxide is 100 - 500 nm; The purity of the metallic silicon powder ≥ 99%, and the particle size is 800 mesh; The stirring speed during the high-speed stirring is 1000 rpm; 2. Prepare a precursor: Carefully take out the silicon-containing foamed graphene oxide in step 1, put it into the cold trap of a freeze dryer, freeze it at -60 °C for 24 h, then take it out and perform vacuum freeze-drying treatment. After 48 h, a precursor is obtained; The temperature of the vacuum freeze-drying treatment is -60 °C; 3. Heat treatment in a low-oxygen environment: Put the precursor in step 2 into a graphite crucible, perform sintering by the carbon burial method, and keep it at 1500 °C for 2 h to obtain a three-dimensional porous structure composed of two-dimensional sheet-like reduced graphene oxide, that is, a lightweight heat-insulating and multifunctional electromagnetic wave absorbing material for growing one-dimensional silicon carbide nanowires on two-dimensional reduced graphene oxide.

[0020] This example also provides a lightweight heat-insulating and multifunctional electromagnetic wave absorbing material for growing one-dimensional silicon carbide nanowires on two-dimensional reduced graphene oxide prepared by the foregoing preparation method.

[0021] When the reflection loss RLmin value of the material is < 10 dB in the frequency range of 2 - 18 GHz, it means that the material has achieved a 90% loss of electromagnetic wave energy. Using the coaxial method of a vector network analyzer (detection standard GJB5239 - 2004), when the test frequency is 2 - 18 GHz, the 3D schematic diagram of the electromagnetic wave absorption performance of the lightweight thermal insulation and multifunctional electromagnetic wave absorption material prepared in this embodiment, where two-dimensional reduced graphene oxide grows one-dimensional silicon carbide nanowires, is shown in Figure 1 as shown, from Figure 1 it can be seen that when the addition amount of the wave-absorbing material is 15% of the total mass of the test wave-absorbing ring, the measured reflection loss RL of the lightweight thermal insulation and multifunctional electromagnetic wave absorption material prepared in this embodiment min value is -25.81 dB (17.84 GHz), and the effective absorption bandwidth EAB max is 2.08 GHz, and the thickness is 5.5 mm; using the Archimedes drainage method to measure its volume density is 0.2124 g / cm 3 .

[0022] Example 2 A preparation method of a lightweight thermal insulation and multifunctional electromagnetic wave absorption material where two-dimensional reduced graphene oxide grows one-dimensional silicon carbide nanowires. On the basis of the preparation method of Example 1, in the first step of preparing silicon-containing foamed graphene oxide, the dosage of metal silicon powder is changed to 0.4 g.

[0023] The remaining operations are the same as those in Example 1.

[0024] Using the coaxial method of a vector network analyzer (detection standard GJB5239 - 2004), when the addition amount of the wave-absorbing material is 15% of the total mass of the test wave-absorbing ring and the test frequency is 2 - 18 GHz, the 3D schematic diagram of the electromagnetic wave absorption performance of the lightweight thermal insulation and multifunctional electromagnetic wave absorption material prepared in this embodiment, where two-dimensional reduced graphene oxide grows one-dimensional silicon carbide nanowires, is shown in Figure 2 as shown, from Figure 2 it can be seen that the reflection loss RL of the lightweight thermal insulation and multifunctional electromagnetic wave absorption material prepared in this embodiment min value is -13.55 dB (14.16 GHz), and the effective absorption bandwidth EAB max is 3.92 GHz, and the thickness is 1.5 mm; using the Archimedes drainage method to measure its volume density is 0.2568 g / cm 3 .

[0025] Example 3 A preparation method of a lightweight thermal insulation and multifunctional electromagnetic wave absorption material where two-dimensional reduced graphene oxide grows one-dimensional silicon carbide nanowires. On the basis of the preparation method of Example 1, in the first step of preparing silicon-containing foamed graphene oxide, the dosage of metal silicon powder is changed to 0.6 g.

[0026] The remaining operations are the same as those in Example 1.

[0027] Using the coaxial method of a vector network analyzer (detection standard GJB5239-2004), when the addition amount of the wave-absorbing material is 15% of the total mass of the test wave-absorbing ring and the test frequency is 2-18 GHz, the 3D schematic diagram of the electromagnetic wave absorption performance of the lightweight heat-insulating and multifunctional electromagnetic wave absorption material prepared in this example, which is two-dimensional reduced graphene oxide growing one-dimensional silicon carbide nanowires, is shown in Figure 3 as shown, from Figure 3 it can be seen that the reflection loss RL min value of the lightweight heat-insulating and multifunctional electromagnetic wave absorption material prepared in this example is -14.55 dB (17.76 GHz), and the effective absorption bandwidth EAB max is 3.6 GHz, and the thickness is 1.0 mm; the volume density is measured to be 0.3125 g / cm 3 .

[0028] Example 4 A preparation method of a lightweight heat-insulating and multifunctional electromagnetic wave absorption material in which two-dimensional reduced graphene oxide grows one-dimensional silicon carbide nanowires. On the basis of the preparation method of Example 1, in the first step of preparing silicon-containing foamed graphene oxide, the dosage of metal silicon powder is changed to 0.8 g.

[0029] The remaining operations are the same as those in Example 1.

[0030] Using the coaxial method of a vector network analyzer (detection standard GJB5239-2004), when the addition amount of the wave-absorbing material is 15% of the total mass of the test wave-absorbing ring and the test frequency is 2-18 GHz, the 3D schematic diagram of the electromagnetic wave absorption performance of the lightweight heat-insulating and multifunctional electromagnetic wave absorption material prepared in this example, which is two-dimensional reduced graphene oxide growing one-dimensional silicon carbide nanowires, is shown in Figure 4 as shown, from Figure 4 it can be seen that the minimum reflection loss RLmin value of the lightweight heat-insulating and multifunctional electromagnetic wave absorption material prepared in this example is -20.14 dB (17.76 GHz), the maximum effective absorption bandwidth EABmax is 4.08 GHz, and the thickness is 1.2 mm; the volume density is measured to be 0.3891 g / cm 3 .

[0031] Example 5 A preparation method of a lightweight heat-insulating and multifunctional electromagnetic wave absorption material in which two-dimensional reduced graphene oxide grows one-dimensional silicon carbide nanowires. On the basis of the preparation method of Example 1, in the first step of preparing silicon-containing foamed graphene oxide, the dosage of metal silicon powder is changed to 1.0 g.

[0032] The remaining operations are the same as those in Example 1.

[0033] Using the coaxial method of a vector network analyzer (detection standard GJB5239-2004), when the addition amount of the microwave absorbing material is 15% of the total mass of the test microwave absorbing ring and the test frequency is 2-18 GHz, the 3D schematic diagram of the electromagnetic wave absorption performance of the lightweight thermal insulation multifunctional electromagnetic wave absorbing material prepared in this example, in which two-dimensional reduced graphene oxide grows one-dimensional silicon carbide nanowires, is shown in Figure 5 as follows. It can be seen from Figure 5 that the reflection loss RL of the lightweight thermal insulation multifunctional electromagnetic wave absorbing material prepared in this example min is -51.59 dB (8.32 GHz), the effective absorption bandwidth EAB max is 4.0 GHz, and the thickness is 2.9 mm. The volume density is measured to be 0.4568 g / cm 3 .

[0034] The thermal insulation performance of the lightweight thermal insulation multifunctional electromagnetic wave absorbing material prepared in this example, in which two-dimensional reduced graphene oxide grows one-dimensional silicon carbide nanowires, is tested as follows: As a control group, cotton balls are placed on an alcohol lamp respectively; as an experimental group, a lightweight thermal insulation multifunctional electromagnetic wave absorbing material with a thickness of 5 mm is placed on the alcohol lamp, and then cotton balls are placed on the lightweight thermal insulation multifunctional electromagnetic wave absorbing material, and then continuous combustion is carried out. The specific test result diagram is shown in Figure 6 as follows. It can be seen from Figure 6 that in the control group, the cotton balls had become carbon at the 90th second of combustion, while in the experimental group, the cotton balls had not become carbon at the 300th second of combustion. It shows that the lightweight thermal insulation multifunctional electromagnetic wave absorbing material prepared in this example has excellent thermal insulation performance.

[0035] Scanning electron microscopy analysis is carried out at different preparation stages of the product prepared in this example. The specific scanning electron microscopy analysis results are shown in Figure 7 , Figure 7 a- Figure 7 c are the prepared precursors. It can be seen from Figure 7 a-7b that the precursors are porous matrices. Figure 7 d- Figure 7 f are the middle stage of heat treatment in a low-oxygen environment. It can be seen from Figure 7 d- Figure 7 f that silicon carbide nanowires have been in-situ grown. Figure 7 g- Figure 7 i is the obtained lightweight thermal insulation multifunctional electromagnetic wave absorbing material. It can be seen from 7g- Figure 7It can be seen that the two-dimensional sheet structure of reduced graphene oxide and the one-dimensional structure of silicon carbide nanowires have grown. The reduced graphene oxide and silicon carbide nanowires form complex heat conduction paths inside the material, increasing phonon scattering and reducing the thermal conductivity, thereby enhancing the heat insulation effect.

[0036] It can be seen from Figure 6 and Figure 7 that the lightweight heat-insulating and multifunctional electromagnetic wave absorbing material prepared in this embodiment has an obvious porous structure with relatively uniform pore distribution. This porous structure helps to reduce the density of the material, thus achieving the lightweight characteristic. The porous structure can also increase the specific surface area of the material, which is beneficial to the heat exchange with the external environment and the interaction of electromagnetic waves. And this uniform porous structure plays an important role in the heat insulation performance because air can play a good heat insulation effect in the pores, reducing heat conduction.

[0037] Figure 7 The diameter of the in-situ grown silicon carbide nanowires in is relatively uniform, the length is relatively long, and there is a certain degree of dispersion among them. The one-dimensional nanowire structure can increase the aspect ratio of the material, which has a positive effect on the absorption and scattering of electromagnetic waves and can improve the electromagnetic wave absorption performance of the material. The nanowires are embedded or attached to the matrix, and this structure is beneficial to enhancing the mechanical properties of the material. At the same time, the presence of the nanowires may also further improve the electrical conductivity of the material, thereby affecting the electromagnetic wave absorption characteristics. The reduced graphene oxide sheets and the silicon carbide nanowires are intertwined with each other to form a complex network structure. This structure combines the advantages of two-dimensional materials and one-dimensional materials. Two-dimensional reduced graphene oxide has a large specific surface area and good flexibility, while one-dimensional silicon carbide nanowires provide a high aspect ratio and good electrical conductivity. The two work together, promising to significantly improve the comprehensive performance of the material, such as electromagnetic wave absorption, heat insulation, and mechanical properties, etc.

[0038] Example 6 A preparation method of a lightweight heat-insulating and multifunctional electromagnetic wave absorbing material with two-dimensional reduced graphene oxide growing one-dimensional silicon carbide nanowires. On the basis of the preparation method of Example 1, in the first step of preparing silicon-containing foamed graphene oxide, the dosage of metal silicon powder is changed to 2.0 g.

[0039] The remaining operations are the same as those in Example 1.

[0040] Using the coaxial method of a vector network analyzer (detection standard GJB5239-2004), when the addition amount of the wave-absorbing material is 15% of the total mass of the test wave-absorbing ring and the test frequency is 2-18 GHz, the 3D schematic diagram of the electromagnetic wave absorption performance of the lightweight heat-insulating and multifunctional electromagnetic wave absorbing material with two-dimensional reduced graphene oxide growing one-dimensional silicon carbide nanowires prepared in this embodiment is shown in Figure 8 as shown, it can be seen from Figure 8It can be seen that the reflection loss RL of the lightweight thermal insulation and multifunctional electromagnetic wave absorbing material prepared in this embodiment min is -17.16 dB (18 GHz), the effective absorption bandwidth EAB max is 1.52 GHz, and the thickness is 5.1 mm; its volume density is measured to be 0.5382 g / cm by the Archimedes drainage method 3 .

[0041] It can be seen from Examples 1-6 that as the addition amount of metal silicon powder gradually increases from 0.2 g to 2.0 g, the reflection loss RL min value shows a trend of first decreasing, then increasing, and then decreasing again, and the effective absorption bandwidth EAB max and density also change accordingly, indicating that the content of metal silicon powder has a significant impact on the material properties.

[0042] Comparative Example 1 A preparation method of a lightweight thermal insulation and multifunctional electromagnetic wave absorbing material for growing one-dimensional silicon carbide nanowires on two-dimensional reduced graphene oxide. On the basis of the preparation method of Example 1, in the low-oxygen environment heat treatment step of the third step, the graphite crucible is changed to an ordinary crucible made of alumina.

[0043] The remaining operations are the same as those in Example 1.

[0044] In the low-oxygen environment heat treatment of the third step, the appearance of the material becomes completely white, and there is basically no carbon residue, indicating that the material is oxidized in the low-oxygen environment heat treatment of the third step.

[0045] Comparative Example 2 A preparation method of a lightweight thermal insulation and multifunctional electromagnetic wave absorbing material for growing one-dimensional silicon carbide nanowires on two-dimensional reduced graphene oxide. On the basis of the preparation method of Example 1, in the precursor preparation step of the second step, omitting the freezing of the silicon-containing foamed graphene oxide in the cold trap of the freeze dryer.

[0046] The three-dimensional porous structure of the precursor obtained in the precursor preparation step of the second step collapses.

[0047] Comparative Example 3 A preparation method of a lightweight thermal insulation and multifunctional electromagnetic wave absorbing material for growing one-dimensional silicon carbide nanowires on two-dimensional reduced graphene oxide. On the basis of the preparation method of Example 1, in the step of preparing silicon-containing foamed graphene oxide in the first step, the preparation of the foaming agent is omitted.

[0048] The remaining operations are the same as those in Example 1.

[0049] The obtained lightweight thermal insulation and multifunctional electromagnetic wave absorbing material does not have a porous structure.

[0050] From the results of the examples and comparative examples, it can be seen that metallic silicon powder is the key raw material for generating silicon carbide nanowires, and different addition amounts will significantly change the growth quantity and morphology of silicon carbide nanowires. When the added amount of silicon powder is small, the generated silicon carbide nanowires are less, and its effect on adjusting impedance matching and enhancing electromagnetic wave absorption is limited. As the added amount of silicon powder increases, a large number of grown silicon carbide nanowires can better regulate the impedance, enhancing the absorption and scattering of electromagnetic waves within the material. At the same time, as the added amount of metallic silicon powder increases, the generated silicon carbide nanowires and the possibly remaining silicon components increase, resulting in an increase in the material quality and density.

[0051] The porous structure of the material is determined by the foaming process, and its porosity, pore size, and distribution have a significant impact on the performance. If the parameters of each step in the preparation process are not well controlled, such as inappropriate freeze-drying temperature and time, it may lead to the collapse or non-uniformity of the porous structure. In Comparative Example 3, no foaming agent was added, and the obtained lightweight heat-insulating multifunctional electromagnetic wave absorbing material had no porous structure, unable to achieve multiple reflections and scattering of electromagnetic waves and good heat-insulating effects; in Comparative Example 2, the three-dimensional porous structure collapsed without freeze treatment, also reducing the material performance. In the examples, a uniform and stable porous structure helps to reduce the density, increase the specific surface area, and enhance the electromagnetic wave absorption and heat-insulating performance.

[0052] The above results further illustrate that the lightweight heat-insulating multifunctional electromagnetic wave absorbing material prepared in the examples has stable performance under high temperature and high humidity. The main reasons are as follows: First, its unique three-dimensional porous structure is composed of two-dimensional reduced graphene oxide and one-dimensional silicon carbide nanowires. This structure is very stable. At high temperatures, the characteristics of high melting point and good chemical stability of silicon carbide nanowires can maintain the overall structure stability of the material, prevent the structure from collapsing due to high temperature, and ensure the stability of electromagnetic wave absorption and heat-insulating performance; Second, the high conductivity of reduced graphene oxide is less affected within a certain temperature range and can continue to effectively dissipate the energy of electromagnetic waves; Third, in a high-humidity environment, the porous structure of the material makes it difficult for a large amount of water to accumulate and damage the internal structure, and silicon carbide nanowires and reduced graphene oxide themselves are not easily chemically reacted with water, reducing the performance deterioration caused by humidity. Therefore, the lightweight heat-insulating multifunctional electromagnetic wave absorbing material prepared in the examples can maintain good performance stability in complex environments.

Claims

1. A method for preparing a lightweight, heat-insulating, multifunctional electromagnetic wave absorbing material by growing one-dimensional silicon carbide nanowires from two-dimensional reduced graphene oxide, characterized in that: include: Preparation of silicon-containing foamed graphene oxide, preparation of precursor, and heat treatment in a low-oxygen environment.

2. The method for preparing a lightweight, heat-insulating, multifunctional electromagnetic wave absorbing material of one-dimensional silicon carbide nanowires grown from two-dimensional reduced graphene oxide according to claim 1, characterized in that: The method for preparing silicon-containing foamed graphene oxide comprises dissolving Tween 80 in anhydrous ethanol and stirring to prepare a foaming agent; mixing graphene oxide slurry with the foaming agent and metallic silicon powder and stirring at high speed to obtain silicon-containing foamed graphene oxide.

3. The method for preparing a lightweight, heat-insulating, multifunctional electromagnetic wave absorbing material of one-dimensional silicon carbide nanowires grown from two-dimensional reduced graphene oxide according to claim 2, characterized in that: In the preparation of silicon-containing foamed graphene oxide, the usage ratio of Tween 80 to anhydrous ethanol is 7-8 g:50-60 mL; The usage ratio of graphene oxide slurry, foaming agent and metal silicon powder is 7-8g:4-6mL:0.2-2g.

4. The method for preparing a lightweight, heat-insulating, multifunctional electromagnetic wave absorbing material of one-dimensional silicon carbide nanowires grown from two-dimensional reduced graphene oxide according to claim 2, characterized in that: In the preparation of silicon-containing foamed graphene oxide, the stirring is magnetic stirring, and the stirring time is 10-15 minutes; The high-speed stirring has a stirring speed of 950-1100 rpm and a time of 15-25 min.

5. The method for preparing a lightweight, heat-insulating, multifunctional electromagnetic wave absorbing material of one-dimensional silicon carbide nanowires grown from two-dimensional reduced graphene oxide according to claim 2, characterized in that: In the preparation of silicon-containing foamed graphene oxide, the concentration of graphene oxide in the graphene oxide slurry is 2.8-3.2%, and the diameter of the graphene oxide flakes is 100-500 nm; The purity of the Tween 80 is ≥99.5%; the purity of the metallic silicon powder is ≥99%, and the particle size is ≤800 meshes.

6. The method for preparing a lightweight, heat-insulating, multifunctional electromagnetic wave absorbing material of one-dimensional silicon carbide nanowires grown from two-dimensional reduced graphene oxide according to claim 1, characterized in that: In the preparation of the precursor, the silicon-containing foamed graphene oxide is subjected to a freezing treatment and then subjected to a vacuum freeze-drying treatment to obtain the precursor.

7. The method for preparing a lightweight, heat-insulating, multifunctional electromagnetic wave absorbing material of one-dimensional silicon carbide nanowires grown from two-dimensional reduced graphene oxide according to claim 6, characterized in that: In the preparation of the precursor, the freezing treatment temperature is -65°C to -55°C, and the time is 12-36h; The vacuum freeze-drying treatment is performed at a temperature of -65°C to -55°C and for a time of 36-54 hours.

8. The method for preparing a lightweight, heat-insulating, multifunctional electromagnetic wave absorbing material of one-dimensional silicon carbide nanowires grown on two-dimensional reduced graphene oxide according to claim 1, characterized in that: The low-oxygen environment heat treatment is to place the precursor in a graphite crucible and perform carbon embedding sintering to obtain a lightweight, heat-insulating, multifunctional electromagnetic wave absorbing material in which two-dimensional reduced graphene oxide grows one-dimensional silicon carbide nanowires.

9. The method for preparing a lightweight, heat-insulating, multifunctional electromagnetic wave absorbing material of one-dimensional silicon carbide nanowires grown on two-dimensional reduced graphene oxide according to claim 8, characterized in that: In the low oxygen environment heat treatment, the temperature of the carbon embedding sintering method is 1500-1600° C. and the time is 2-3 hours.

10. A lightweight, heat-insulating, multifunctional electromagnetic wave absorbing material comprising one-dimensional silicon carbide nanowires grown from two-dimensional reduced graphene oxide prepared by the preparation method according to any one of claims 1 to 9.

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