Carbon-rich SiC@Si3N4 double-network aerogel and preparation method thereof

Abstract

The present application relates to aerogel material technical field, more specifically, it relates to a kind of carbon-rich SiC@Si3N4 double network aerogel and preparation method.The double network aerogel includes inner skeleton and outer skeleton, inner skeleton is SiC network, outer skeleton is Si3N4 network, double network aerogel is formed by SiC network and Si3N4 network interlacing, SiC network and Si3N4 network are rich in situ carbon, the content of in situ carbon in Si3N4 network is far less than the content of in situ carbon in SiC network.The aerogel of the application successfully integrates multiple key performances: high porosity and low thermal conductivity ensure excellent heat insulation capacity;Reflection loss of minimum-60dB, effective absorption bandwidth reaches 5GHz, which proves its excellent broadband wave-absorbing performance;Material compressive strength can reach more than 14MPa, which shows excellent mechanical reliability, and provides an ideal solution for electromagnetic protection and thermal management of high-end equipment.

Description

Technical Field

[0001] This invention relates to the field of aerogel materials technology, and more specifically, to a carbon-rich SiC@Si3N4 dual-network aerogel and its preparation method. Background Technology

[0002] With the rapid development of modern aerospace and high-speed aircraft technology, equipment faces the dual challenges of thermal management and electromagnetic protection in extreme environments. During high-speed flight, aerodynamic heating causes surfaces to withstand extremely high temperatures, while the internal electronic equipment bays require effective thermal insulation to ensure normal operation. Simultaneously, as significant sources and reflectors of electromagnetic radiation, the radar stealth performance of aircraft is crucial. Therefore, developing an integrated material that combines superior high-temperature thermal insulation with efficient broadband radar wave absorption capabilities has become an urgent need in the field of new materials.

[0003] Traditionally, a stacked structure of "wave-absorbing layer + heat insulation layer" is used, which has problems such as weak interfacial bonding, overall bulkiness, and easy delamination under thermal stress. It is difficult to meet the requirements of lightweight, integrated and high reliability of equipment. Three-dimensional porous aerogel materials are regarded as ideal lightweight heat insulation carriers due to their extremely low density, high porosity and excellent heat insulation performance. However, single-component aerogels such as silica are "transparent" to electromagnetic waves and do not have wave-absorbing function, which cannot meet the integrated requirements.

[0004] The research focus then shifted to high-temperature resistant ceramic materials with intrinsic wave absorption characteristics. Among them, silicon carbide (SiC), as a dielectric loss type wave absorbing material, has adjustable resistivity and is resistant to high temperature and oxidation. However, its wave absorption mechanism is simple, its impedance matching is poor, and it is prone to sintering and shrinkage at high temperatures. Silicon nitride (Si3N4), on the other hand, has excellent mechanical properties, low dielectric constant, and resistance to high temperature creep, and can be used as a stable structural framework. However, its wave absorption capability is limited.

[0005] By constructing multi-component composite ceramic aerogels of SiC and Si3N4, it is hoped that interfacial polarization and multiple scattering induced by heterogeneous interfaces can be utilized to enhance dielectric loss and synergistically optimize impedance matching, making it easier for electromagnetic waves to enter the material interior and be dissipated. However, existing composite technologies (such as physical mixing or surface coating) are difficult to achieve uniform composite and stable bonding at the nanoscale, resulting in poor interfacial effects, phase separation at high temperatures, and performance degradation.

[0006] Specifically, regarding the SiC and Si3N4 composite system, existing research has mostly focused on high-density, heavy-weight dense multiphase ceramic bulks or coatings, which are difficult to meet the requirements of lightweight applications. Even though some porous composite ceramics have been reported, they are mostly simple mixtures or discontinuous structures with distinct primary and secondary phases, failing to form a three-dimensional continuous dual network in which the two phases intertwine and support each other, thus limiting the full utilization of material properties. Summary of the Invention

[0007] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, one aspect of the present invention is to provide a carbon-rich SiC@Si3N4 dual-network aerogel, the dual-network aerogel comprising an inner framework and an outer framework, the inner framework being a SiC network and the outer framework being a Si3N4 network, the dual-network aerogel being formed by interweaving the SiC network and the Si3N4 network, wherein the SiC network and the Si3N4 network contain 5% to 30% by mass of in-situ carbon, and the mass ratio of the in-situ carbon content in the Si3N4 network to the in-situ carbon content in the SiC network is 1:1 to 1:30.

[0008] Another objective of this invention is to provide a method for preparing carbon-rich SiC@Si3N4 dual-network aerogel, the specific steps of which are as follows:

[0009] S1. Measure out deionized water, anhydrous ethanol, N,N-dimethylformamide, hexadecyltrimethylammonium chloride and vinyltriethoxysilane in sequence, mix them, and stir until homogeneous;

[0010] S2. Add glacial acetic acid dropwise to the mixed solution I in S1 to adjust the pH value and obtain the H value of the mixed solution I. Continue stirring and hydrolyzing to obtain vinyltriethoxysilane sol.

[0011] S3. While stirring, add concentrated ammonia dropwise to the vinyltriethoxysilane sol in S2. After the addition is complete, continue stirring and then let stand to obtain a vinyltriethoxysilane wet gel.

[0012] S4. The vinyltriethoxysilane wet gel obtained in S3 is soaked in anhydrous ethanol for aging, then transferred to n-hexane for solvent replacement, and dried in an atmospheric pressure environment to obtain vinyltriethoxysilane aerogel.

[0013] S5. The vinyltriethoxysilane aerogel obtained in S4 was subjected to high-temperature treatment in an inert gas atmosphere to obtain carbon-rich SiC aerogel.

[0014] S6. Sequentially measure and mix deionized water, anhydrous ethanol, N,N-dimethylformamide, hexadecyltrimethylammonium chloride, methyltrimethoxysilane and vinyltriethoxysilane to obtain mixed solution II;

[0015] S7. Add glacial acetic acid dropwise to the mixed solution II in S6 to adjust the pH value, and then continue to stir and hydrolyze while adding concentrated ammonia dropwise. After the concentrated ammonia is added, continue stirring to obtain methyltrimethoxysilane / vinyltriethoxysilane composite sol.

[0016] S8. The methyltrimethoxysilane / vinyltriethoxysilane composite sol obtained in S7 is immersed into the pores of the carbon-rich SiC aerogel obtained in S5 by high vacuum impregnation method, and in-situ gelation is completed at the same time. After aging in anhydrous ethanol, it is transferred to n-hexane for solvent replacement and dried in an ambient pressure environment to obtain carbon-rich SiC / methyltrimethoxysilane / vinyltriethoxysilane composite aerogel.

[0017] S9. The carbon-rich SiC / methyltrimethoxysilane / vinyltriethoxysilane composite aerogel obtained in S8 was subjected to high-temperature treatment in an inert gas atmosphere to obtain a carbon-rich SiC@Si3N4 double-network aerogel.

[0018] Preferably, the volume ratio of deionized water, anhydrous ethanol, N,N-dimethylformamide, hexadecyltrimethylammonium chloride and vinyltriethoxysilane in S1 is 1-30:1-50:1-5:1-5:1-30.

[0019] Preferably, in step S2, the pH value is adjusted to 4-6, and then the mixture is continuously stirred and hydrolyzed at 20-60°C for 6-48 hours.

[0020] Preferably, in step S3, the volume ratio of vinyltriethoxysilane sol to concentrated ammonia is 1:0.5 to 1:1.5, and the mixture is stirred for 1 to 30 minutes.

[0021] Preferably, in step S4, the aging process lasts 12 to 48 hours, followed by drying at 30 to 60°C under normal pressure for 1 to 24 hours. In step S5, the inert gas is argon (Ar), and the process involves high-temperature treatment at 1500 to 1600°C.

[0022] Preferably, the volume ratio of deionized water, anhydrous ethanol, N,N-dimethylformamide, hexadecyltrimethylammonium chloride, methyltrimethoxysilane and vinyltriethoxysilane in S6 is 1-30:1-50:1-5:1-5:1-60:1-30.

[0023] Preferably, in step S7, the pH value is adjusted to 4-6, and then the mixture is continuously stirred and hydrolyzed at 20-60°C for 6-48 hours. The volume ratio of mixed solution II to concentrated ammonia is 1:0.5-1:1.5. After the concentrated ammonia is added, stirring is continued for 1-5 minutes.

[0024] Preferably, the S8 process involves aging for 12 to 48 hours and drying at 30 to 60°C under normal pressure for 1 to 24 hours.

[0025] Preferably, the inert gas in S9 is nitrogen (N2) at a high temperature of 1350–1450°C.

[0026] The beneficial effects of this invention are as follows:

[0027] By constructing a dual "wave-transmitting and wave-absorbing" network in situ, gradient impedance matching from the surface to the interior is achieved. The outer layer is composed of a Si3N4 network with a low dielectric constant, which has an impedance similar to that of the air interface. This effectively reduces the initial reflection of electromagnetic waves and promotes the maximum entry of wave energy into the material. The inner SiC network serves as the main absorber. The continuous structure formed by the interweaving of the two at the microscale naturally constitutes a channel with gradually changing impedance, perfectly balancing the "penetration" and "dissipation" requirements of electromagnetic waves, and laying the structural foundation for efficient wave absorption.

[0028] The spatial coupling of the gradient carbon enrichment strategy and the dual-network structure synergistically enhances the multiple loss mechanism. Through precise composition design, carbon elements are gradient-enriched in the inner SiC network, while the outer Si3N4 network maintains a low carbon content to preserve its wave transmission function. This design ensures that after electromagnetic waves successfully penetrate, they encounter a powerful dissipation system inside the material. The highly carbon-enriched SiC network not only enhances the electrical conductivity loss but also optimizes its dielectric loss capability. At the same time, the numerous heterogeneous interfaces between SiC and Si3N4 induce significant interfacial polarization. This multiple dissipation mechanism, constructed by electrical conductivity loss, dielectric loss, and interfacial polarization, ensures that electromagnetic wave energy can be rapidly and efficiently converted into heat energy, ultimately enabling the material to achieve strong absorption effects over a wide frequency range.

[0029] Additional aspects and advantages of the invention will become apparent from the description which follows, or may be learned by practice of the invention. Attached Figure Description

[0030] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0031] Figure 1 This is a schematic diagram of the structure of the carbon-rich SiC@Si3N4 dual-network aerogel according to an embodiment of the present invention;

[0032] Figure 2 This is the mercury intrusion curve of carbon-rich SiC@Si3N4 dual-network aerogel according to an embodiment of the present invention;

[0033] Figure 3 This is the XRD pattern of the carbon-rich SiC@Si3N4 dual-network aerogel of this invention.

[0034] Figure 4 These are scanning electron microscope images of carbon-rich SiC@Si3N4 dual-network aerogels according to embodiments of the present invention;

[0035] Figure 5 This is a stress-strain curve of the carbon-rich SiC@Si3N4 dual-network aerogel according to an embodiment of the present invention. Detailed Implementation

[0036] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0037] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0038] Example 1

[0039] S1. Measure 20 ml of deionized water, 10 ml of anhydrous ethanol, 2.5 ml of N,N-dimethylformamide, 1 ml of hexadecyltrimethylammonium chloride and 20 ml of vinyltriethoxysilane in sequence, mix them, and stir well to prepare mixed solution I;

[0040] S2. Add glacial acetic acid dropwise to the mixed solution I in S1 to make the pH of the mixed solution 5, and then continue to stir and hydrolyze for 24 hours at 30°C to obtain vinyltriethoxysilane sol;

[0041] S3. While stirring, add 15 ml of concentrated ammonia dropwise to the vinyltriethoxysilane sol in S2. After the concentrated ammonia is added, continue stirring for 15 minutes, and then let it stand to obtain a vinyltriethoxysilane wet gel.

[0042] S4. The vinyltriethoxysilane wet gel obtained in S3 was soaked in anhydrous ethanol for 48 hours and then transferred to n-hexane for solvent replacement. Finally, it was dried at 60°C and atmospheric pressure for 12 hours to obtain vinyltriethoxysilane aerogel.

[0043] S5. The vinyltriethoxysilane aerogel obtained in S4 was subjected to high-temperature treatment at 1550℃ in an argon (Ar) atmosphere to obtain carbon-rich SiC aerogel.

[0044] S6. Measure 20 ml of deionized water, 30 ml of anhydrous ethanol, 1.5 ml of N,N-dimethylformamide, 1.5 ml of hexadecyltrimethylammonium chloride, 40 ml of methyltrimethoxysilane, and 20 ml of vinyltriethoxysilane in sequence, mix them, and stir well to prepare mixed solution II;

[0045] S7. Add glacial acetic acid dropwise to the mixed solution II in S6 to make the pH of the mixed solution 5. Then, stir and hydrolyze continuously at 40°C for 36 hours. Then, add 15 ml of concentrated ammonia dropwise while stirring. After the concentrated ammonia is added, continue stirring for 3 minutes to obtain methyltrimethoxysilane / vinyltriethoxysilane composite sol.

[0046] S8. The methyltrimethoxysilane / vinyltriethoxysilane composite sol obtained in S7 is immersed into the pores of the carbon-rich SiC aerogel obtained in S5 by high vacuum impregnation method, and in-situ gelation is completed at the same time. After aging in anhydrous ethanol for 24 hours, it is transferred to n-hexane for solvent replacement. Finally, it is dried at 45°C and atmospheric pressure for 24 hours to obtain carbon-rich SiC / methyltrimethoxysilane / vinyltriethoxysilane composite aerogel.

[0047] S9. The carbon-rich SiC / methyltrimethoxysilane / vinyltriethoxysilane composite aerogel obtained in S8 was subjected to high-temperature treatment at 1400℃ in a nitrogen (N2) atmosphere to obtain a carbon-rich SiC@Si3N4 double-network aerogel, the structural schematic diagram of which is shown below. Figure 1 As shown.

[0048] Example 2

[0049] S1. Measure 10 ml of deionized water, 20 ml of anhydrous ethanol, 2 ml of N,N-dimethylformamide, 2 ml of hexadecyltrimethylammonium chloride and 25 ml of vinyltriethoxysilane in sequence, mix them, and stir well to prepare mixed solution I;

[0050] S2. Add glacial acetic acid dropwise to the mixed solution I in S1 to make the pH of the mixed solution 4.5, and then continue to stir and hydrolyze at 30°C for 36 hours to obtain vinyltriethoxysilane sol;

[0051] S3. While stirring, add 18 ml of concentrated ammonia dropwise to the vinyltriethoxysilane sol in S2. After the concentrated ammonia is added, continue stirring for 18 minutes, and then let it stand to obtain a vinyltriethoxysilane wet gel.

[0052] S4. The vinyltriethoxysilane wet gel obtained in S3 was soaked in anhydrous ethanol for 24 hours and then transferred to n-hexane for solvent replacement. Finally, it was dried at 50°C and atmospheric pressure for 16 hours to obtain vinyltriethoxysilane aerogel.

[0053] S5. The vinyltriethoxysilane aerogel obtained in S4 was subjected to high-temperature treatment at 1500℃ in an argon (Ar) atmosphere to obtain carbon-rich SiC aerogel.

[0054] S6. Measure 25 ml of deionized water, 25 ml of anhydrous ethanol, 2 ml of N,N-dimethylformamide, 1.5 ml of hexadecyltrimethylammonium chloride, 60 ml of methyltrimethoxysilane and 30 ml of vinyltriethoxysilane in sequence, mix them, and stir well to prepare mixed solution II;

[0055] S7. Add glacial acetic acid dropwise to the mixed solution II in S6 to make the pH of the mixed solution 5. Then, stir and hydrolyze continuously at 60°C for 10 hours. Then, add 10 ml of concentrated ammonia dropwise while stirring. After the concentrated ammonia is added, continue stirring for 2 minutes to obtain methyltrimethoxysilane / vinyltriethoxysilane composite sol.

[0056] S8. The methyltrimethoxysilane / vinyltriethoxysilane composite sol obtained in S7 is immersed into the pores of the carbon-rich SiC aerogel obtained in S5 by high vacuum impregnation method, and in-situ gelation is completed at the same time. After aging in anhydrous ethanol for 24 hours, it is transferred to n-hexane for solvent replacement. Finally, it is dried at 60°C and atmospheric pressure for 12 hours to obtain carbon-rich SiC / methyltrimethoxysilane / vinyltriethoxysilane composite aerogel.

[0057] S9. The carbon-rich SiC / methyltrimethoxysilane / vinyltriethoxysilane composite aerogel obtained in S8 was subjected to high-temperature treatment at 1450℃ in a nitrogen (N2) atmosphere to obtain a carbon-rich SiC@Si3N4 double network aerogel.

[0058] Example 3

[0059] S1. Measure 15 ml of deionized water, 20 ml of anhydrous ethanol, 1.5 ml of N,N-dimethylformamide, 2 ml of hexadecyltrimethylammonium chloride and 25 ml of vinyltriethoxysilane in sequence, mix them, and stir well to prepare mixed solution I;

[0060] S2. Add glacial acetic acid dropwise to the mixed solution I in S1 to make the pH of the mixed solution 6, and then continue to stir and hydrolyze at 60°C for 28 hours to obtain vinyltriethoxysilane sol;

[0061] S3. While stirring, add 20 ml of concentrated ammonia dropwise to the vinyltriethoxysilane sol in S2. After the concentrated ammonia is added, continue stirring for 5 minutes, and then let it stand to obtain a vinyltriethoxysilane wet gel.

[0062] S4. The vinyltriethoxysilane wet gel obtained in S3 was soaked in anhydrous ethanol for 18 hours and then transferred to n-hexane for solvent replacement. Finally, it was dried at 50°C and atmospheric pressure for 20 hours to obtain vinyltriethoxysilane aerogel.

[0063] S5. The vinyltriethoxysilane aerogel obtained in S4 was subjected to high-temperature treatment at 1500℃ in an argon (Ar) atmosphere to obtain carbon-rich SiC aerogel.

[0064] S6. Measure 30 ml of deionized water, 50 ml of anhydrous ethanol, 5 ml of N,N-dimethylformamide, 1 ml of hexadecyltrimethylammonium chloride, 40 ml of methyltrimethoxysilane and 20 ml of vinyltriethoxysilane in sequence, mix them, and stir well to prepare mixed solution II;

[0065] S7. Add glacial acetic acid dropwise to the mixed solution II in S6 to make the pH of the mixed solution 5.5. Then, continue to stir and hydrolyze for 48 hours at 30°C. Then, add 10 ml of concentrated ammonia dropwise while stirring. After the concentrated ammonia is added, continue stirring for 3 minutes to obtain methyltrimethoxysilane / vinyltriethoxysilane composite sol.

[0066] S8. The methyltrimethoxysilane / vinyltriethoxysilane composite sol obtained in S7 is immersed into the pores of the carbon-rich SiC aerogel obtained in S5 by high vacuum impregnation method, and in-situ gelation is completed at the same time. After aging in anhydrous ethanol for 48 hours, it is transferred to n-hexane for solvent replacement. Finally, it is dried at 60°C and atmospheric pressure for 10 hours to obtain carbon-rich SiC / methyltrimethoxysilane / vinyltriethoxysilane composite aerogel.

[0067] S9. The carbon-rich SiC / methyltrimethoxysilane / vinyltriethoxysilane composite aerogel obtained in S8 was subjected to high-temperature treatment at 1400℃ in a nitrogen (N2) atmosphere to obtain a carbon-rich SiC@Si3N4 double network aerogel.

[0068] Testing and Experiment

[0069] Thermal conductivity tests were performed on embodiments one to three of the present invention. The test results showed that the thermal conductivity of the SiC@Si3N4 dual-network aerogel was 0.592 W / (m·K).

[0070] Electromagnetic parameters were tested and reflectivity was calculated for embodiments one to three of the present invention. The results showed that the reflection loss was as low as -60dB and the effective absorption bandwidth was 5GHz.

[0071] Mercury porosimetry analysis was performed on embodiments one to three of the present invention, and the mercury porosimetry curves are shown below. Figure 2 As shown;

[0072] XRD analysis was performed on embodiments one to three of the present invention, and the results are as follows: Figure 3 As shown;

[0073] Scanning electron microscopy analysis was performed on embodiments one to three of the present invention, and the results are as follows: Figure 4 As shown;

[0074] The compressive strength of embodiments one to three of the present invention was tested, and the test results are as follows: Figure 5 As shown;

[0075] In summary, thanks to the unique SiC@Si3N4 dual-network structure and gradient carbon-rich design, the aerogel of this invention successfully integrates multiple key properties: high porosity (>85%) and low thermal conductivity (0.592 W / (m·K)) ensure excellent thermal insulation capabilities; a reflection loss as low as -60 dB and an effective absorption bandwidth of 5 GHz demonstrate its superior broadband absorption performance; at the same time, the material's compressive strength can reach over 14 MPa, exhibiting excellent mechanical reliability, providing an ideal solution for electromagnetic protection and thermal management of high-end equipment.

[0076] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing carbon-rich SiC@Si3N4 dual-network aerogel, characterized in that: The dual-network aerogel includes an inner framework and an outer framework. The inner framework is a SiC network, and the outer framework is a Si3N4 network. The dual-network aerogel is formed by interweaving SiC and Si3N4 networks. The SiC and Si3N4 networks contain 5% to 30% by mass of in-situ carbon, and the mass ratio of the in-situ carbon content in the Si3N4 network to the in-situ carbon content in the SiC network is 1:1 to 1:

30. The specific steps of the preparation method are as follows: S1. Deionized water, anhydrous ethanol, N,N-dimethylformamide, hexadecyltrimethylammonium chloride and vinyltriethoxysilane were measured and mixed in sequence, and stirred evenly to prepare mixed solution I; S2. Add glacial acetic acid dropwise to the mixed solution I in S1, adjust the pH value, and continue stirring to hydrolyze and obtain vinyltriethoxysilane sol; S3. While stirring, add concentrated ammonia dropwise to the vinyltriethoxysilane sol in S2. After the addition is complete, continue stirring and then let stand to obtain a vinyltriethoxysilane wet gel. S4. The vinyltriethoxysilane wet gel obtained in S3 is soaked in anhydrous ethanol for aging, then transferred to n-hexane for solvent replacement, and dried in an atmospheric pressure environment to obtain vinyltriethoxysilane aerogel. S5. The vinyltriethoxysilane aerogel obtained in S4 was subjected to high-temperature treatment in an inert gas atmosphere to obtain carbon-rich SiC aerogel. S6. Sequentially measure and mix deionized water, anhydrous ethanol, N,N-dimethylformamide, hexadecyltrimethylammonium chloride, methyltrimethoxysilane and vinyltriethoxysilane to obtain mixed solution II; S7. Add glacial acetic acid dropwise to the mixed solution II in S6 to adjust the pH value, and then continue to stir and hydrolyze while adding concentrated ammonia dropwise. After the concentrated ammonia is added, continue stirring to obtain methyltrimethoxysilane / vinyltriethoxysilane composite sol. S8. The methyltrimethoxysilane / vinyltriethoxysilane composite sol obtained in S7 is immersed into the pores of the carbon-rich SiC aerogel obtained in S5 by high vacuum impregnation method, and in-situ gelation is completed at the same time. After aging in anhydrous ethanol, it is transferred to n-hexane for solvent replacement and dried in an ambient pressure environment to obtain carbon-rich SiC / methyltrimethoxysilane / vinyltriethoxysilane composite aerogel. S9. The carbon-rich SiC / methyltrimethoxysilane / vinyltriethoxysilane composite aerogel obtained in S8 was subjected to high-temperature treatment in an inert gas atmosphere to obtain carbon-rich SiC@Si3N4 double network aerogel. The volume ratio of deionized water, anhydrous ethanol, N,N-dimethylformamide, hexadecyltrimethylammonium chloride and vinyltriethoxysilane in S1 is 1-30:1-50:1-5:1-5:1-30; The S4 process involves aging for 12–48 hours and drying at 30–60°C under normal pressure for 1–24 hours. The S5 process involves using argon as the inert gas and treating at 1500–1600°C. The volume ratio of deionized water, anhydrous ethanol, N,N-dimethylformamide, hexadecyltrimethylammonium chloride, methyltrimethoxysilane and vinyltriethoxysilane in S6 is 1-30:1-50:1-5:1-5:1-60:1-30. The inert gas in S9 is nitrogen, and the temperature is 1350-1450℃.

2. The method for preparing a carbon-rich SiC@Si3N4 dual-network aerogel according to claim 1, characterized in that: The pH value in S2 is adjusted to 4-6, and then the mixture is continuously stirred and hydrolyzed at 20-60°C for 6-48 hours.

3. The method for preparing a carbon-rich SiC@Si3N4 dual-network aerogel according to claim 1, characterized in that: In the S3 mixture, the volume ratio of vinyltriethoxysilane sol to concentrated ammonia is 1:0.5 to 1:1.5, and the mixture is stirred for 1 to 30 minutes.

4. The method for preparing a carbon-rich SiC@Si3N4 dual-network aerogel according to claim 1, characterized in that: In step S7, the pH value is adjusted to 4-6, and then the mixture is continuously stirred and hydrolyzed at 20-60℃ for 6-48 hours. The volume ratio of mixed solution II to concentrated ammonia is 1:0.5-1:1.

5. After the concentrated ammonia is added, stirring is continued for 1-5 minutes.

5. The method for preparing a carbon-rich SiC@Si3N4 dual-network aerogel according to claim 1, characterized in that: The S8 is aged for 12 to 48 hours and then dried in an ambient pressure environment at 30 to 60°C for 1 to 24 hours.

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