High-temperature-resistant ablative thermal-insulation aerogel and preparation method and application thereof

Abstract

The application provides a preparation method of a high-temperature-resistant ablation-resistant heat-insulating aerogel, plasticizer polyethylene glycol is introduced into a graphene and silica dispersion solution to be compounded and laid up a film, and then a solvent plasticizing foaming technology is used to prepare a composite aerogel, the prepared aerogel has the advantages of ablation resistance and excellent heat-insulating function, light weight, good compression resilience and the like, and can maintain the original shape and performance at high temperature to be repeatedly used. The scheme has the advantages of simple process, controllable process, low reaction condition and suitability for industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional materials, and in particular relates to a high-temperature ablation-resistant thermal insulation aerogel and a preparation method and application thereof. Background Art

[0002] With the rapid development of hypersonic aircraft and space shuttles, thermal protection materials are needed to resist high-temperature oxidation and ablation caused by combustion airflow while also having good thermal insulation properties to prevent excessive temperature rise from affecting the normal operation of aircraft electronic components. Graphene aerogel has attracted widespread attention due to its low density, high specific surface area, low thermal conductivity, good processability, and ease of preparation of bulk materials. However, graphene-based materials are easily oxidized in oxygen-containing environments above 600°C. Secondly, when faced with the ablation impact brought by high-temperature airflow, the porous carbonized layer formed is easily oxidized, leading to oxidative corrosion and mechanical erosion, seriously affecting its service reliability and stability. Therefore, it is crucial to solve the ablation failure problem of graphene aerogel materials to adapt to harsh operating environments. Summary of the Invention

[0003] To overcome the above technical deficiencies, the present invention proposes a high-temperature ablation-resistant thermal insulation aerogel and its preparation method. The composite aerogel is prepared by combining graphene and silica dispersions with a plasticizer, polyethylene glycol, and using solvent plasticization and foaming technology. The aerogel is then heat-treated at high temperatures to produce a silicon carbide / carbon composite aerogel.

[0004] This invention incorporates silicon carbide into the pore walls of the aerogel as an ablation-resistant protective layer. During high-temperature ablation, the silicon carbide first transforms into a dense oxide, thereby preventing further ablation. A two-dimensional graphene carbon skeleton provides curved connections for the silicon carbide, which, combined with foaming, forms an anisotropic structure that reduces vertical heat transfer. The resulting aerogel combines ablation resistance with excellent thermal insulation, while also being lightweight and exhibiting good compression resilience. It can also maintain its original shape and performance even at high temperatures.

[0005] One of the technical solutions of the present invention is to provide a high-temperature ablation-resistant thermal insulation aerogel. The aerogel pore wall has a three-layer structure, the middle layer is a graphene skeleton, and the outer layer is silicon carbide grown in situ on the graphene. The silicon carbide and the graphene skeleton are tightly combined. In a high-temperature oxygen-containing environment, dense silicon dioxide can be generated to protect the internal graphene skeleton.

[0006] The second technical solution of the present invention is to provide a method for preparing a high-temperature ablation-resistant thermal insulation aerogel, which specifically includes the following steps:

[0007] (1) uniformly mixing polyethylene glycol, graphene oxide aqueous dispersion, and silicon dioxide aqueous dispersion, coating to form a film, and drying at room temperature to obtain a composite film;

[0008] (2) placing the composite film in a foaming agent solution for foaming, and drying after foaming to obtain a composite aerogel;

[0009] (3) The composite aerogel is heat-treated to obtain a high-temperature ablation-resistant thermal insulation aerogel.

[0010] Furthermore, the molecular weight of the polyethylene glycol in step 1 is 800-10000. The mass ratio of polyethylene glycol to graphene oxide is 1:1.

[0011] Furthermore, the concentration of the graphene oxide aqueous dispersion in step 1 is 0.1-50 mg / g, the concentration of the silicon dioxide aqueous dispersion is 10 mg / g, and the solid content of silicon dioxide accounts for 50-90 wt% of the total solid content of silicon dioxide and graphene oxide.

[0012] Furthermore, the foaming agent solution in step 2 is one of hydrazine hydrate solution, sodium borohydride solution, sodium bicarbonate solution and sodium carbonate solution.

[0013] Furthermore, the heat treatment in step 3 is carried out at 1500-1700° C. in an argon atmosphere for 2 hours.

[0014] When applied to silica materials, PEG can effectively increase the surface tension of the silica. This property is particularly important for resisting stress damage generated within the material during the drying process. During the material's transition from a wet to a dry state, the evaporation of water causes internal tensile stress. If this stress is too great, it can cause cracks on the surface or within the material. PEG, by increasing the elasticity and strength of the surface, can effectively alleviate this stress concentration, thereby reducing or even preventing the possibility of cracking in the silica material during drying. In the foaming solution, the PEG molecular chains exhibit excellent plasticity, enabling them to effectively drive the orderly migration of silica particles during bubble growth. This orderly migration allows the silica particles to be evenly distributed within the bubbles, forming a uniform and stable pore wall structure. This uniform pore wall not only enhances the material's mechanical properties but also improves its thermal insulation and other physical properties to a certain extent, opening up a wider range of application possibilities for foaming materials.

[0015] Introducing silicon dioxide between graphene oxide layers can weaken the interlayer forces, causing it to quickly peel off at the silicon dioxide interface during the foaming process and form a silicon dioxide surface. Further, during the heat treatment process, this silicon dioxide is carbonized to form a silicon carbide protective layer, thereby obtaining an ABA pore wall structure of silicon carbide-coated carbon, which effectively avoids the problem of ablation and oxidation.

[0016] A third technical solution of the present invention provides a thermal insulation application for the aforementioned high-temperature ablation-resistant aerogel. The aerogel produced by this invention has a vertical thermal conductivity as low as 15 mW / mK, and its weight retention after heat treatment at 800°C for 30 minutes is no less than 70%. It exhibits excellent thermal insulation and resistance to high-temperature ablation. Furthermore, the aerogel produced by this invention exhibits deformation retention exceeding 90% after compression by 60%.

[0017] Beneficial effects of the present invention:

[0018] (1) Polyethylene glycol plasticizer is added to the silica and graphene oxide solution to improve the plasticity of the film so as to obtain a large-sized complete composite film, which is then plasticized and foamed into aerogel by solvent. The size of the film and aerogel can be controlled. The solvent plasticization and foaming process is relatively simple and does not require a special drying process, so it is more conducive to industrial development.

[0019] (2) Silicon carbide is introduced into the outer layer of the graphene carbon wall, and is converted into oxide in a high-temperature oxygen atmosphere to form a protective layer, which prevents oxygen from entering the inner layer of the pore wall, effectively inhibits the thermal decomposition of the carbon skeleton, and achieves the effect of ablation resistance. In addition, a large number of -Si-C bonds and -Si-O bonds are introduced into the surface layer of the graphene skeleton, which improves the thermal stability and residual carbon rate of the aerogel. After heat treatment at 800℃ for 30 minutes, the residual weight is not less than 70%.

[0020] (3) The aerogel prepared by the solvent plasticization foaming technology has an anisotropic structure, which reduces the heat transfer in the vertical direction and has low thermal conductivity in the vertical direction. At the same time, the nano-silicon carbide particles have a large number of nanopores, which reduce the heat conduction of the gas. The thermal conductivity in the vertical direction can be as low as 15mW / mK.

[0021] (4) The solvent plasticization and foaming technology used supports the silica particles through two-dimensional graphene sheets to form curved pore units. The prepared aerogel blocks have low density, high porosity and excellent mechanical properties. They can withstand different deformations and maintain their original shape and performance at high temperatures. The aerogel retains more than 90% of its deformation after being compressed by 60%. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 SEM image of silica composite aerogel

[0023] Figure 2 This is the SEM image of the high-temperature ablation-resistant thermal insulation aerogel of Example 1. DETAILED DESCRIPTION

[0024] The following examples are used to further illustrate the present invention. Their purpose is to illustrate the present invention and should not be construed as limiting the scope of the present invention. Unless otherwise specified, all references are by weight and weight percentage.

[0025] Unless otherwise specified, the raw materials used in the present invention are conventional commercial products; the methods used in the present invention are conventional methods in the art unless otherwise specified.

[0026] The embodiments of the present invention are further described below with reference to a number of embodiments.

[0027] It should be clear that the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0028] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The singular forms "a", "an", "the" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0029] The molecular weight referred to in the present invention generally refers to the weight average molecular weight.

[0030] Example 1

[0031] Polyethylene glycol (800 molecular weight) was added to a mixture of a 10 mg / ml aqueous graphene oxide dispersion (purchased from Hangzhou Gaoxin Technology Co., Ltd., with an average size of 20 μm) and a 10 mg / g nano-silica microsphere dispersion. The polyethylene glycol, graphene oxide, and silica were mixed in a solid content weight ratio of 1:1:1. The film was then laid, dried naturally, and then foamed in 80% hydrazine hydrate for 4 hours. The film was then replaced with ethanol and then n-hexane, and dried at atmospheric pressure to obtain a composite aerogel. Figure 1 As shown in the figure, it can be seen that the silicon dioxide particles are evenly dispersed on the surface of the pore wall. Subsequently, a high-temperature ablation-resistant thermal insulation aerogel was obtained by heating at 1500℃ in an argon atmosphere for 2 hours. Figure 2 As shown in the figure, after high-temperature treatment, the uniform silicon dioxide particles are carbonized into silicon carbide, forming a dense network on the surface of the pore wall. The silicon carbide is located on the surface of the pore wall, further enhancing the material's high-temperature stability and thermal insulation properties, laying the foundation for its application in high-temperature environments.

[0032] In high-temperature environments, silicon carbide transforms into a dense oxide during ablation, preventing further ablation while also providing elasticity through the curved pore walls. The aerogel has a vertical thermal conductivity of 20mW / mK and a density of 10mg / cm³. Testing of its ablation resistance at 800°C revealed a 70% weight retention after 30 minutes of heat treatment, and 95% deformation retention after 60% compression.

[0033] Example 2

[0034] Polyethylene glycol (800 molecular weight) was added to a 0.1 mg / ml aqueous dispersion of graphene oxide (purchased from Hangzhou Gaoxin Technology Co., Ltd., with an average size of 20 μm) and a 10 mg / g dispersion of nano-silica microspheres. The polyethylene glycol, graphene oxide, and silica were mixed in a solid content weight ratio of 1:1:9. The film was then naturally dried and foamed in 80% hydrazine hydrate for 4 hours. The composite aerogel was then replaced with ethanol and n-hexane, and dried at atmospheric pressure. Figure 1 As shown in the figure, it can be seen that the silica particles are evenly dispersed on the surface of the pore wall. Subsequently, a high-temperature ablation-resistant thermal insulation aerogel was obtained by heating it at 1700°C in an argon atmosphere for 2 hours. The aerogel has a vertical thermal conductivity of 15mW / mK and a density of 20mg / cm 3 ,, the ablation resistance effect was tested at a high temperature of 800℃. The residual weight was 78% after 30 minutes of heat treatment, and the deformation retention was 92% after compression of 60%.

[0035] Example 3

[0036] Same as Example 1, except that the molecular weight of polyethylene glycol is replaced by 1w, the obtained high temperature ablation resistant material has a vertical thermal conductivity of 15mW / mK and a density of 20mg / cm 3 ,After heat treatment at 800℃ for 30 minutes, the residual weight is 70%, and after compression by 60%, the deformation retention is 90%.

[0037] Example 4

[0038] Polyethylene glycol with a molecular weight of 10,000 was added to 50 mg / ml aqueous graphene oxide (purchased from Hangzhou Gaoxin Technology Co., Ltd., with an average size of 20um) and 10 mg / g nano-silica microsphere dispersion. Polyethylene glycol, graphene oxide, and silica were mixed in a solid content mass ratio of 1:1:4. The membrane was laid, and then the naturally dried membrane was placed in 80% hydrazine hydrate for foaming for 4 hours. It was then replaced with ethanol and n-hexane and dried at normal pressure to obtain a composite aerogel. Subsequently, it was heated at 1700°C in an argon atmosphere for 2 hours to obtain a high-temperature resistant ablation insulation aerogel. The thermal conductivity of the aerogel in the vertical direction is 15 mW / mK, and the density is 17 mg / cm 3 The ablation resistance test was carried out at a high temperature of 800℃. The residual weight was 77% after 30 minutes of heat treatment, and the deformation retention was 95% after 60% compression.

[0039] Comparative Example 1

[0040] 10mg / ml of aqueous graphene oxide (purchased from Hangzhou Gaoxin Technology Co., Ltd., with an average size of 20μm) was compounded with 10mg / g of a dispersion of nano-silica microspheres, with a silica solid content of 60%. The mixture was then freeze-dried and then heat-treated in argon at 2000°C. The resulting aerogel has a vertical thermal conductivity of 30mW / mK and a density of 10mg / cm 3 The ablation resistance test was carried out at a high temperature of 800°C. After 30 minutes of heat treatment, the residual weight was 65%, and after 60% compression, the deformation retention was 67%.

[0041] In this embodiment, since there is no foaming to expose the SiO2, ABA cannot be formed and the effect is not good.

[0042] Comparative Example 2

[0043] 10mg / ml aqueous graphene oxide (purchased from Hangzhou Gaoxin Technology Co., Ltd., with an average size of 20um) was compounded with 10mg / g of nano-silica microsphere dispersion and then laid as a film. After natural drying, due to the brittleness of the silica particles and the weak interaction between the particles, a complete composite film could not be obtained during the film drying process due to the large surface tension.

[0044] The above embodiments describe in detail the structure, features and effects of the present invention. The above are only preferred embodiments of the present invention. Any changes made in accordance with the concept of the present invention, or modifications to equivalent embodiments with equivalent changes, which do not exceed the scope covered by the specification, should be within the scope of protection of the present invention.

Claims

1. A method for preparing a high-temperature ablation-resistant thermal insulation aerogel, characterized in that: The following steps are involved: (1) Polyethylene glycol, graphene oxide aqueous dispersion, and silicon dioxide aqueous dispersion are uniformly mixed, coated into a film, and dried at room temperature to obtain a composite film; wherein the solid content of silicon dioxide accounts for 50-90wt% of the total solid content of silicon dioxide and graphene oxide; and the mass ratio of polyethylene glycol to graphene oxide is 1:1; (2) placing the composite film in a foaming agent solution for foaming, and drying after foaming to obtain a composite aerogel; the foaming agent solution is one of hydrazine hydrate solution, sodium borohydride solution, sodium bicarbonate solution and sodium carbonate solution; (3) The composite aerogel is heat-treated to obtain a high-temperature ablation-resistant thermal insulation aerogel.

2. The preparation method according to claim 1, characterized in that The molecular weight of the polyethylene glycol is 800-10000.

3. The preparation method according to claim 1, characterized in that The concentration of the graphene oxide aqueous dispersion in step 1 is 0.1-50 mg / g, and the concentration of the silicon dioxide aqueous dispersion is 10 mg / g.

4. The preparation method according to claim 1, characterized in that The heat treatment in step 3 is performed at 1500-1700° C. in an argon atmosphere for 2 hours.

5. A high temperature ablation resistant thermal insulation aerogel prepared by the method according to claim 1, characterized in that: The aerogel pore wall has a three-layer structure, with the middle layer being a graphene skeleton and the outer layer being silicon carbide grown in situ on the graphene.

6. A thermal insulation application of the high-temperature ablation-resistant thermal insulation aerogel prepared by the preparation method according to claim 1.

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