Composite aerogel bridge fireproof material reinforced by SiC-coated SiO2 core-shell structure and preparation method of composite aerogel bridge fireproof material
The composite aerogel material reinforced by the SiC@SiO2 core-shell structure solves the problem of insufficient stability of fireproof materials at high temperatures, and achieves efficient infrared shielding and high-temperature stability. The material can effectively block the spread of fire at high temperatures.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIANGSU ZHIQIAO TECHNOLOGY CO LTD
- Filing Date
- 2026-01-07
- Publication Date
- 2026-04-14
AI Technical Summary
Existing fireproof materials lack stability at high temperatures and cannot effectively prevent the spread of fire. Furthermore, multi-functional designs are costly or complex to construct, and traditional sealing materials are prone to producing molten droplets and toxic gases at high temperatures.
A composite aerogel material reinforced with a SiC@SiO2 core-shell structure is prepared by encapsulating a silica shell with SiC aerogel nanoparticles, combining it with Al(OH)3 gel sol and high-silica fiber felt to form a core-shell structure, and then combining chemical vapor deposition and supercritical drying technology.
It achieves efficient infrared shielding and high-temperature stability, increases the oxidation resistance temperature of the SiC core, reduces the thermal conductivity between SiC particles, and has excellent mechanical properties, enabling it to stably block the spread of fire at high temperatures.
Smart Images
Figure CN121850472A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of bridge fireproof materials, specifically relating to SiC@SiO2 core-shell structure reinforced composite aerogel bridge fireproof materials and their preparation methods. Background Technology
[0002] While existing fire-resistant materials can maintain a certain level of stability at high temperatures, their temperature resistance typically does not exceed 300℃. Above this temperature, some materials soften, deform, or even fail, becoming ineffective in preventing the spread of fire. For example, fire-resistant putty is prone to moisture absorption and failure in high-temperature environments, requiring additional waterproofing measures.
[0003] Existing fire-resistant materials are mostly designed for a single function. For example, while multi-layer coated lenses can improve infrared shielding, these optical materials are expensive and complex to install. In scenarios such as cable ducts, traditional fire-resistant sealing materials (such as organic sealants) are prone to producing molten droplets and toxic gases at high temperatures, which may exacerbate the spread of fire.
[0004] Therefore, in order to address the above-mentioned technical problems, it is necessary to provide a fireproof bridge material with SiC@SiO2 core-shell structure reinforcement and its preparation method.
[0005] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention
[0006] The purpose of this invention is to provide a SiC@SiO2 core-shell structure reinforced composite aerogel bridge fireproof material and its preparation method, which can solve the above-mentioned problems.
[0007] To achieve the above objectives, a specific embodiment of the present invention provides the following technical solution: The SiC@SiO2 core-shell structure reinforced composite aerogel bridge fireproof material includes a SiC@SiO2 unit layer and a composite layer. The SiC@SiO2 unit layer has SiC aerogel nanoparticles as the core and a silica coating layer grown on its surface as the shell. The composite layer includes Al(OH)3 gel sol and high silica fiber felt.
[0008] In one or more embodiments of the present invention, the thickness of the silicon dioxide coating layer is 30~50 nm.
[0009] In one or more embodiments of the present invention, the Al(OH)3 gel sol is mixed with the SiC@SiO2 unit layer at a volume ratio of 1:1 to 1:3.
[0010] In one or more embodiments of the present invention, the fiber diameter of the high silica fiber felt is 10~20 μm, the porosity is >80%, and the volume ratio to the core-shell unit is 1:2~1:4.
[0011] The preparation method of SiC@SiO2 core-shell structure reinforced composite aerogel bridge fireproof material includes the following steps: Preparation of S1 and SiC aerogels: Organic / SiO2 aerogel precursors were prepared by sol-gel method, and then carbonized to obtain C / SiO2 composite aerogels. The C / SiO2 composite aerogels were then subjected to high-temperature carbothermic reduction to obtain SiC aerogels. S2. Using chemical vapor deposition or controlled sol-gel method, a layer of amorphous silica is uniformly coated on the surface of SiC aerogel framework. S3. The above-mentioned core-shell powder is dispersed in a silica sol containing an aluminum source, impregnated with high-silica fiber felt, and finally dried by supercritical drying to obtain the final product.
[0012] In one or more embodiments of the present invention, the specific steps of S1 include: S11. Preparation of organic / SiO2 aerogel precursor: Sol preparation: Mix organic polymer monomers with SiO2 source, add catalyst, and magnetically stir at 50-70℃ for 2-4 hours to hydrolyze and condense SiO2 source to form SiO2 sol, while organic polymer undergoes condensation reaction to form organic-inorganic hybrid sol. Gel formation: Pour the hybrid sol into a mold, seal it, and age it at 60-80℃ for 2-3 days to allow the molecules in the sol to further cross-link and form a wet gel with a three-dimensional network structure. Solvent replacement: Replace the water in the wet gel with ethanol or acetone for 12-24 hours, and change the solvent every 6-8 hours. Drying: Supercritical CO2 drying or atmospheric pressure drying is used to remove the solvent while preserving the porous structure of the aerogel; S12. Carbonization: Inert gas is used for protection. The carbonization temperature is set to 600-1000℃, the heating rate is 1-5℃ / min, and the holding time is 2-4 hours for carbonization operation. S13. Formation of granular SiC: Carbon in C / SiO2 composite aerogel undergoes a carbothermic reduction reaction with SiO2 at high temperature to form SiC particles. During the reaction, the temperature is set to 1400-1800℃, the heating rate is 5-10℃ / min, and the holding time is 2-5 hours. Inert gas or reducing gas is used for protection during the reaction. S14. Post-processing: Acid washing and purification: Immerse the SiC aerogel in a mixed solution of hydrofluoric acid and nitric acid at a ratio of 1:3, soak at 60-80℃ for 2-4 hours, and then rinse with deionized water until neutral. Supercritical drying: The acid-washed SiC aerogel is placed in an autoclave, CO2 is introduced to supercritical conditions, and the conditions are maintained for 2-4 hours. Then, the CO2 is slowly released to obtain the dried SiC aerogel. The supercritical conditions are: CO2 critical temperature 31.1℃, critical pressure 7.38MPa.
[0013] In one or more embodiments of the present invention, the organic polymer monomer in S11 includes phenol or formaldehyde, and the SiO source includes TEOS.
[0014] In one or more embodiments of the present invention, the inert gas in steps S12 and S13 includes argon and nitrogen, and the reducing gas in step S13 includes hydrogen.
[0015] In one or more embodiments of the present invention, the specific steps of S3 include: S31. Pretreatment of high-silica felt: Gently rinse the high-silica felt with deionized water, then ultrasonically clean it with anhydrous ethanol for 5-10 minutes. After taking it out, place it in an oven to dry, or air dry it at room temperature until there is no ethanol residue. Then cut it to the required size and record the initial mass. S32. Impregnation of mixed gel and high silica felt: Place the pretreated high silica felt into a vacuum impregnation tank, pour in an appropriate amount of mixed gel, then close the tank, turn on the vacuum pump to evacuate to a vacuum degree ≤10 Pa, maintain for 30-60 minutes, then slowly release the vacuum, let it stand for 2-4 hours to impregnate, and gently shake the tank during this period to help distribute it evenly. S33, CO2 supercritical drying: S331. Sample loading: Place the impregnated and displaced gel-high silica felt composite into the sample rack of the supercritical drying autoclave, ensuring no compression or deformation. S332. Adding CO2: Close the vessel and inject liquid CO2 into the vessel until the pressure inside the vessel reaches 5-6 MPa; S333, Circulation and replacement: Turn on the CO2 circulation pump to continuously introduce fresh CO2 and discharge old CO2, circulate 3-5 times to ensure that the solvent is completely replaced by CO2; S334, Increase pressure and temperature to the supercritical state; S335, maintain the cycle state, slowly increase the temperature to 35-45℃, and at the same time slowly increase the pressure to 8-12 MPa, and maintain this supercritical condition for at least 12-24 hours; S336. Pressure Reduction: After supercritical drying is completed, the pressure is slowly reduced, first to below 7 MPa, and then further reduced to atmospheric pressure. At the same time, the temperature can be naturally cooled to room temperature or assisted to be cooled to below 30°C.
[0016] In one or more embodiments of the present invention, the injection of liquid CO2 into the reactor in step S332 requires controlling the temperature to below the CO2 critical point using a low-temperature bath, with the temperature set to 15-20°C.
[0017] Compared with the prior art, the SiC@SiO2 core-shell structure reinforced composite aerogel bridge fireproof material and its preparation method of the present invention have the following advantages: 1) Perfect infrared shielding: SiC nuclei can efficiently scatter, reflect and absorb infrared radiation of 2-5μm, fundamentally blocking the radiation heat transfer path.
[0018] 2) Dual protection mechanism: The SiO2 shell first isolates the SiC core from direct contact with oxygen, significantly improving the oxidation resistance temperature of SiC; secondly, this shell also eliminates direct contact between highly thermally conductive SiC particles, reducing the increase in solid-state thermal conductivity caused by the introduction of SiC, and ensuring stability even at high temperatures.
[0019] 3) Strong interfacial bonding: The SiC-SiO2 core-shell structure unit is chemically bonded to the surrounding SiO2 / Al(OH)3 aerogel matrix through the SiO2 shell, resulting in low interfacial thermal resistance, strong bonding force, and superior material mechanical properties. Attached Figure Description
[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0021] Figure 1 This is a schematic diagram of the core-shell structure of the SiC@SiO2 core-shell structure in one embodiment of the present invention; Figure 2 This is a schematic diagram comparing the infrared shielding efficiency of ordinary SiO2 aerogel with that of the embodiments of this application; Figure 3 This is a schematic diagram comparing the high-temperature stability and thermal management capabilities of ordinary pure SiC particles with those of the embodiments in this application.
[0022] Explanation of key figure labels: 1-SiC aerogel nanoparticles, 2-silica coating layer. Detailed Implementation
[0023] To enable those skilled in the art to better understand the technical solutions in this disclosure, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this disclosure.
[0024] like Figure 1 As shown, the SiC@SiO2 core-shell structure-enhanced composite aerogel bridge fireproof material and its preparation method in one embodiment of the present invention solve the problems of infrared shielding and high-temperature stability at the same time by constructing special "core-shell" structured nanocomposite units.
[0025] A SiC@SiO2 core-shell structure-reinforced composite aerogel bridge fireproof material comprises a SiC@SiO2 unit layer and a composite layer. The SiC@SiO2 unit layer has SiC aerogel nanoparticles 1 as the core, with a silica coating layer 2 grown on its surface as the shell. The composite layer includes Al(OH)3 gel sol and high-silica fiber felt. In other words, SiC aerogel nanoparticles 1 serve as the "core," and a dense, amorphous silica coating layer 2 is grown in situ on its surface as the "shell," forming the basic building block of the "SiC@SiO2" core-shell structure. These units are then combined with Al(OH)3 gel sol and high-silica fiber felt to construct a composite aerogel.
[0026] Furthermore, the thickness of the silica coating layer 2 is 30-50 nm. Al(OH)3 gel sol is mixed with the SiC@SiO2 unit layer at a volume ratio of 1:1 to 1:3. The high-silica fiber felt has a fiber diameter of 10-20 μm, a porosity >80%, and a volume ratio of 1:2 to 1:4 with the core-shell unit.
[0027] The preparation method of SiC@SiO2 core-shell structure reinforced composite aerogel bridge fireproof material includes the following steps: Preparation of S1 and SiC aerogels: Organic / SiO2 aerogel precursors were prepared by sol-gel method, and then carbonized to obtain C / SiO2 composite aerogels. The C / SiO2 composite aerogels were then subjected to high-temperature carbothermic reduction to obtain SiC aerogels. S2. An amorphous silica coating layer 2 is uniformly coated on the surface of the SiC aerogel framework using chemical vapor deposition or a controlled sol-gel method. S3. The above-mentioned core-shell powder is dispersed in a silica sol containing an aluminum source, impregnated with high-silica fiber felt, and finally dried by supercritical drying to obtain the final product.
[0028] S31, High-Silica Felt Pretreatment Objective: To remove surface dust / impurities and improve the uniformity of gel impregnation.
[0029] Gently rinse the high-silica felt with deionized water (if the surface is obviously oily), then ultrasonically clean it with anhydrous ethanol for 5-10 minutes (frequency 40 kHz, power 200 W).
[0030] After removal, place in a 60℃ oven to dry for 12 hours (or air dry at room temperature until there is no ethanol residue), cut to the required size (e.g., 10×10×2 cm3), and record the initial mass (m0).
[0031] S32, Impregnation of mixed gel with high-silica felt; Objective: To enable the composite gel to fully fill the gaps between the fibers of the high-silica felt, forming a uniform aerogel-fiber composite structure.
[0032] Place the pretreated high-silica felt into a vacuum impregnation tank and pour in an appropriate amount of mixed gel (ensure that the gel completely covers the felt, with a volume of about 1.5-2 times the volume of the felt).
[0033] Close the tank and turn on the vacuum pump to evacuate the air to a vacuum level of ≤10 Pa, and maintain it for 30-60 minutes (to remove the air from the pores of the felt fibers and promote gel penetration).
[0034] Slowly release the vacuum (to avoid violent flow of the gel), and let it stand for 2-4 hours. During this time, you can gently shake the container to help distribute the gel evenly.
[0035] S33, CO2 supercritical drying S331. Sample loading: Place the impregnated and displaced gel-high silica felt composite into the sample rack of the supercritical drying autoclave, ensuring no compression deformation (avoiding damage to the fiber structure).
[0036] S332. Adding CO2: Close the vessel and inject liquid CO2 into it (control the temperature to below the CO2 critical point, such as 15-20℃, using a low-temperature bath) until the pressure inside the vessel reaches 5-6 MPa (the space is filled with liquid CO2).
[0037] S333, Circulation and Displacement: Turn on the CO2 circulation pump to continuously introduce fresh CO2 and discharge old CO2. 2， To replace the residual solvent inside, cycle 3-5 times (each cycle lasting 30-60 minutes) to ensure that the solvent (such as ethanol) is completely replaced with CO2.
[0038] S334, Increase pressure and temperature to the supercritical state: S335. Maintain the circulation state, slowly increase the temperature to 35-45℃ (exceeding the CO2 critical temperature of 31.1℃), and at the same time slowly increase the pressure to 8-12 MPa (exceeding the CO2 critical pressure of 7.38 MPa). Maintain these supercritical conditions (temperature 35-45℃, pressure 10±1MPa) for at least 12-24 hours to ensure that all liquid CO2 is converted into supercritical fluid and fully removes solvent molecules.
[0039] S336. Pressure Reduction: After supercritical drying is completed, the pressure is reduced slowly, and the pressure reduction rate is controlled to be ≤0.1 MPa / min. First, the pressure is reduced to below 7 MPa, and then further reduced to atmospheric pressure to avoid rapid pressure reduction causing the aerogel structure to collapse. At the same time, the temperature can be naturally cooled to room temperature or assisted to be cooled to below 30℃.
[0040] It is worth noting that the specific steps of S1 are as follows: Preparation of S11, organic / SiO2 composite aerogel precursor; 1. Raw material preparation; Organic polymers: Phenolic resins (RF, which are formed by the condensation polymerization of phenol and formaldehyde) are commonly used.
[0041] SiO2 source: Tetraethyl orthosilicate (TEOS).
[0042] Catalysts: Acids (such as hydrochloric acid and oxalic acid) or bases (such as ammonia and sodium hydroxide) are used to regulate the hydrolysis and polycondensation rate of SiO2 sol. Under acid catalysis, SiO2 sol forms a linear or branched structure, which easily forms a rigid framework after drying; base catalysis promotes the rapid formation of a three-dimensional network structure and increases the specific surface area of the aerogel.
[0043] 2. Preparation process; Sol preparation: Organic polymer monomers (such as phenol and formaldehyde) are mixed with SiO2 source (such as TEOS) in a certain molar ratio (such as phenol: formaldehyde: TEOS = 1:2:3), and a catalyst (such as ammonia water to adjust the pH to 8-9) is added. The mixture is magnetically stirred at 50-70℃ for 2-4 hours to allow TEOS to hydrolyze and condense to form SiO2 sol. At the same time, the organic polymer undergoes a condensation reaction to form an organic-inorganic hybrid sol.
[0044] Gel formation: Pour the hybrid sol into a mold, seal it, and age it at 60-80℃ for 2-3 days to allow the molecules in the sol to further cross-link and form a three-dimensional network structure wet gel (i.e., organic / SiO2 composite wet gel).
[0045] Solvent replacement: To remove water from the wet gel and prevent the skeleton from collapsing due to water evaporation during the drying process, the water in the wet gel needs to be replaced with ethanol or acetone. The replacement time is about 12-24 hours, and the solvent should be changed every 6-8 hours.
[0046] Drying: Supercritical CO2 drying or atmospheric pressure drying is used to remove the solvent while preserving the porous structure of the aerogel.
[0047] It should be noted that supercritical CO2 drying is a classic method for preparing organic / SiO2 composite aerogels. Its principle is that under supercritical conditions (critical temperature of CO2 31.1℃, critical pressure 7.38MPa), the diffusion coefficient of CO2 is similar to that of liquids, allowing it to rapidly displace the solvent in the gel and avoid skeletal shrinkage caused by capillary forces. Atmospheric pressure drying, on the other hand, requires solvent displacement (e.g., ethanol → n-hexane → carbon dioxide) to reduce the surface tension of the gel and minimize drying shrinkage.
[0048] S12, carbonization treatment: forming C / SiO2 composite aerogel; 1. Carbonization conditions; Atmosphere: An inert gas is used for protection to prevent organic components from reacting with oxygen at high temperatures to produce CO2 or H2O, which would reduce carbon production.
[0049] Among them, inert gases include argon and nitrogen. Argon is a commonly used protective gas due to its high chemical inertness.
[0050] Temperature: The carbonization temperature is usually 600-1000℃, and the heating rate is 1-5℃ / min. If the temperature is too low (<600℃), the organic components cannot be completely removed; if the temperature is too high (>1000℃), it will cause the crystal form transformation of SiO2 (such as quartz → tridymite), causing the framework structure to collapse. At the same time, carbon will graphitize, reducing its reactivity with SiO2.
[0051] Time: The heat preservation time is 2-4 hours to ensure that the organic components are completely carbonized.
[0052] 2. Reaction mechanism; During carbonization, organic polymers (such as phenolic resins) undergo pyrolysis, generating carbon and volatile products (such as H2O, CO2, phenol, etc.).
[0053] Furthermore, the pyrolysis reaction is divided into three stages; Dehydration stage (100-200℃): The water in the wet gel evaporates, and the organic polymer begins to dehydroxylate.
[0054] Thermolysis stage (200-600℃): Organic polymers undergo chain scission and cross-linking, generating a large number of volatile products (such as phenol and formaldehyde), while forming the initial carbon skeleton.
[0055] Graphitization stage (600-1000℃): The carbon skeleton is further rearranged to form a denser graphite structure, but the temperature needs to be controlled to avoid excessive graphitization.
[0056] S13, Carbothermic reduction reaction: produces particulate SiC; In C / SiO2 composite aerogels, carbon undergoes a carbothermic reduction reaction with SiO2 at high temperatures to generate SiC particles. This is the core step in the preparation of SiC aerogels. The reaction process requires control of temperature, atmosphere, and time to regulate the crystal form (such as α-SiC, β-SiC), particle size, and morphology of SiC.
[0057] 1. Reaction principle; The chemical equation for the carbothermic reduction reaction is:
[0058] This reaction is endothermic and requires high temperatures (>1300℃). During the reaction, SiO2 reacts with carbon to first form intermediate products (such as SiC2), which then further react to form SiC particles.
[0059] 2. Process parameters; Atmosphere: Use inert or reducing gas for protection to prevent SiC from being oxidized at high temperatures.
[0060] The inert gases include argon and nitrogen. Argon is a commonly used protective gas due to its low cost and easy availability. The reducing gas includes hydrogen. Hydrogen can promote the reduction of intermediate products and increase the yield of SiC.
[0061] Temperature: The carbothermic reduction temperature is typically 1400-1800℃, with a heating rate of 5-10℃ / min. Too low a temperature (<1400℃) results in a slow reaction rate and low SiC yield; too high a temperature (>1800℃) leads to SiC particle growth (>1μm), reducing the specific surface area.
[0062] Time: Keep warm for 2-5 hours to ensure the reaction is complete.
[0063] 3. Crystal form regulation; SiC exists in various crystal forms, including α-SiC and β-SiC. Among them, β-SiC (cubic crystal system) has higher hardness and thermal stability, making it the first choice for preparing high-performance SiC aerogels.
[0064] Crystal form control can be achieved in the following ways; α-SiC crystal form regulation: α-SiC gradually forms above 1600℃.
[0065] β-SiC crystal form regulation: β-SiC is stable at 1400-1600℃. Therefore, by controlling the carbothermic reduction temperature at 1400-1600℃, granular SiC with β-SiC as the main component can be obtained.
[0066] Furthermore, adding small amounts of metal oxides or carbides can promote the nucleation and growth of β-SiC. For example, adding 5% Al2O3 can increase the β-SiC content from 70% to 90%.
[0067] Among them, metal oxides include Al2O3 and TiO2, and carbides include SiC seed crystals.
[0068] S14. Post-processing: Purification and performance optimization; The SiC aerogel obtained after carbothermic reduction may contain free carbon, unreacted SiO2, and metal impurities, which need to be removed through post-processing to improve the purity and performance of the product.
[0069] 1. Acid washing and purification; Objective: To remove unreacted SiO2 (reacting with HF) and free carbon (reacting with HNO3).
[0070] Process: Immerse the SiC aerogel in a mixed solution of hydrofluoric acid (HF) and nitric acid (HNO3) (HF:HNO3=1:3) at 60-80℃ for 2-4 hours, and then rinse with deionized water until neutral.
[0071] Principle: HF reacts with SiO2 to generate SiF4 gas (SiO2 + 4HF = SiF4↑ + 2H2O), thus removing unreacted SiO2; HNO3 reacts with free carbon to produce CO2 gas (C + 4HNO3 = CO2↑ + 4NO2↑ + 2H2O), thus removing the free carbon.
[0072] 2. Supercritical drying; Objective: To preserve the porous structure of SiC aerogel and prevent particle aggregation.
[0073] Process: Place the acid-washed SiC aerogel in an autoclave, introduce CO2 to supercritical conditions, maintain for 2-4 hours, and then slowly release CO2 to obtain dry SiC aerogel.
[0074] Advantages: Supercritical drying avoids particle agglomeration caused by capillary forces, preserving the high specific surface area and porous structure of aerogels.
[0075] like Figure 2 As shown, the columnar shape of existing ordinary SiO2 aerogels is very high, indicating that most of the 2-5μm infrared radiation can penetrate it, resulting in a large amount of heat being transferred in the form of radiation at high temperatures. The radiation thermal resistance is very low, which confirms its poor radiation shielding ability. In contrast, this application shows its perfect infrared shielding ability, blocking most of the radiation and exhibiting extremely strong resistance to radiation heat transfer, which is 5-6 times that of ordinary aerogels.
[0076] like Figure 3 As shown, existing pure SiC particles have low oxidation resistance and high thermal conductivity. This application, however, uses a SiO2 shell as a physical barrier, significantly delaying the oxidation process of the SiC core, thus giving the material a higher operating temperature limit. Furthermore, it successfully prevents the formation of a continuous network between the highly thermally conductive SiC particles, thereby suppressing the increase in the overall solid-state thermal conductivity of the material. It will be apparent to those skilled in the art that this disclosure is not limited to the details of the exemplary embodiments described above, and that this disclosure can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of this disclosure is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this disclosure. No reference numerals in the claims should be construed as limiting the scope of the claims.
[0077] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.
Claims
1. A SiC@SiO2 core-shell structure reinforced composite aerogel bridge fireproof material, characterized in that, It includes a SiC@SiO2 unit layer and a composite layer. The SiC@SiO2 unit layer has SiC aerogel nanoparticles as the core and a silica coating layer grown on its surface as the shell. The composite layer includes Al(OH)3 gel sol and high silica fiber felt.
2. The SiC@SiO2 core-shell structure reinforced composite aerogel bridge fireproof material according to claim 1, characterized in that, The thickness of the silica coating layer is 30~50 nm.
3. The SiC@SiO2 core-shell structure reinforced composite aerogel bridge fireproof material according to claim 1 or 2, characterized in that, The Al(OH)3 gel sol is mixed with the SiC@SiO2 unit layer at a volume ratio of 1:1 to 1:
3.
4. The SiC@SiO2 core-shell structure reinforced composite aerogel bridge fireproof material according to claim 1, characterized in that, The high-silica fiber felt has a fiber diameter of 10~20 μm, a porosity of >80%, and a volume ratio of 1:2~1:4 to the core-shell unit.
5. A method for preparing a SiC@SiO2 core-shell structure reinforced composite aerogel bridge fireproof material, used to prepare the SiC@SiO2 core-shell structure reinforced composite aerogel bridge fireproof material according to any one of claims 1-4, characterized in that, Includes the following steps: Preparation of S1 and SiC aerogels: Organic / SiO2 aerogel precursors were prepared by sol-gel method, and then carbonized to obtain C / SiO2 composite aerogels. The C / SiO2 composite aerogels were then subjected to high-temperature carbothermic reduction to obtain SiC aerogels. S2. Using chemical vapor deposition or controlled sol-gel method, a layer of amorphous silica is uniformly coated on the surface of SiC aerogel framework. S3. The above-mentioned core-shell powder is dispersed in a silica sol containing an aluminum source, impregnated with high-silica fiber felt, and finally dried by supercritical drying to obtain the final product.
6. The preparation method of the SiC@SiO2 core-shell structure reinforced composite aerogel bridge fireproof material according to claim 5, characterized in that, The specific steps of S1 include: S11. Preparation of organic / SiO2 aerogel precursor: Sol preparation: Mix organic polymer monomers with SiO2 source, add catalyst, and magnetically stir at 50-70℃ for 2-4 hours to hydrolyze and condense SiO2 source to form SiO2 sol, while organic polymer undergoes condensation reaction to form organic-inorganic hybrid sol. Gel formation: Pour the hybrid sol into a mold, seal it, and age it at 60-80℃ for 2-3 days to allow the molecules in the sol to further cross-link and form a wet gel with a three-dimensional network structure. Solvent replacement: Replace the water in the wet gel with ethanol or acetone for 12-24 hours, and change the solvent every 6-8 hours. Drying: Supercritical CO2 drying or atmospheric pressure drying is used to remove the solvent while preserving the porous structure of the aerogel; S12. Carbonization: Inert gas is used for protection. The carbonization temperature is set to 600-1000℃, the heating rate is 1-5℃ / min, and the holding time is 2-4 hours for carbonization operation. S13. Formation of granular SiC: Carbon in C / SiO2 composite aerogel undergoes a carbothermic reduction reaction with SiO2 at high temperature to form SiC particles. During the reaction, the temperature is set to 1400-1800℃, the heating rate is 5-10℃ / min, and the holding time is 2-5 hours. Inert gas or reducing gas is used for protection during the reaction. S14. Post-processing: Acid washing and purification: Immerse the SiC aerogel in a mixed solution of hydrofluoric acid and nitric acid at a ratio of 1:3, soak at 60-80℃ for 2-4 hours, and then rinse with deionized water until neutral. Supercritical drying: The acid-washed SiC aerogel is placed in an autoclave, CO2 is introduced to supercritical conditions, and the conditions are maintained for 2-4 hours. Then, the CO2 is slowly released to obtain the dried SiC aerogel. The supercritical conditions are: CO2 critical temperature 31.1℃, critical pressure 7.38MPa.
7. The preparation method of the SiC@SiO2 core-shell structure reinforced composite aerogel bridge fireproof material according to claim 6, characterized in that, The organic polymer monomer in S11 includes phenol or formaldehyde, and the SiO source includes TEOS.
8. The preparation method of the SiC@SiO2 core-shell structure reinforced composite aerogel bridge fireproof material according to claim 7, characterized in that, The inert gases in steps S12 and S13 both include argon and nitrogen, and the reducing gas in step S13 includes hydrogen.
9. The preparation method of the SiC@SiO2 core-shell structure reinforced composite aerogel bridge fireproof material according to claim 7 or 8, characterized in that, The specific steps of S3 include: S31. Pretreatment of high-silica felt: Gently rinse the high-silica felt with deionized water, then ultrasonically clean it with anhydrous ethanol for 5-10 minutes. After taking it out, place it in an oven to dry, or air dry it at room temperature until there is no ethanol residue. Then cut it to the required size and record the initial mass. S32. Impregnation of mixed gel and high silica felt: Place the pretreated high silica felt into a vacuum impregnation tank, pour in an appropriate amount of mixed gel, then close the tank, turn on the vacuum pump to evacuate to a vacuum degree ≤10 Pa, maintain for 30-60 minutes, then slowly release the vacuum, let it stand for 2-4 hours to impregnate, and gently shake the tank during this period to help distribute it evenly. S33, CO2 supercritical drying: S331. Sample loading: Place the impregnated and displaced gel-high silica felt composite into the sample rack of the supercritical drying autoclave, ensuring no compression or deformation. S332. Adding CO2: Close the vessel and inject liquid CO2 into the vessel until the pressure inside the vessel reaches 5-6 MPa; S333, Circulation and replacement: Turn on the CO2 circulation pump to continuously introduce fresh CO2 and discharge old CO2, circulate 3-5 times to ensure that the solvent is completely replaced by CO2; S334, Increase pressure and temperature to the supercritical state; S335, maintain the cycle state, slowly increase the temperature to 35-45℃, and at the same time slowly increase the pressure to 8-12 MPa, and maintain this supercritical condition for at least 12-24 hours; S336. Pressure Reduction: After supercritical drying is completed, the pressure is slowly reduced, first to below 7 MPa, and then further reduced to atmospheric pressure. At the same time, the temperature can be naturally cooled to room temperature or assisted to be cooled to below 30°C.
10. The preparation method of the SiC@SiO2 core-shell structure reinforced composite aerogel bridge fireproof material according to claim 9, characterized in that, In step S332, the injection of liquid CO2 into the reactor requires controlling the temperature to below the CO2 critical point using a low-temperature bath, with the temperature set to 15-20℃.