High-temperature oxidation-resistant ceramic aerogel and preparation method thereof

Abstract

The application discloses a high-temperature oxidation-resistant ceramic aerogel and a preparation method thereof, and belongs to the technical field of ceramic aerogels.The main body of the high-temperature oxidation-resistant ceramic aerogel is a silicon nitride aerogel, the nanostructure of the silicon nitride aerogel is one of one-dimensional silicon nitride nanowires and two-dimensional silicon nitride nanobands or a combination of the two nanostructures, and the nanostructure of the silicon nitride aerogel is sequentially coated with a silicon carbide precursor coating and a zirconium carbide precursor coating from inside to outside.The application can solve the defects that traditional ceramic aerogels are prone to oxidation failure under superhigh temperature and are difficult to be prepared at low cost and in large scale.

Description

Technical Field

[0001] This invention belongs to the field of ceramic aerogel technology, specifically relating to a high-temperature antioxidant ceramic aerogel and its preparation method. Background Technology

[0002] Ceramic aerogels are novel materials with extremely low density, high porosity, low thermal conductivity, and high-temperature resistance, and are widely considered to be potential revolutionary materials in the future field of thermal insulation. Currently, based on their chemical composition, ceramic aerogels can be mainly divided into two categories: oxide ceramic aerogels and non-oxide ceramic aerogels. Oxide ceramic aerogels are prone to crystallization embrittlement and structural collapse under high-temperature conditions, thus their operating temperature is significantly limited, rarely exceeding 1000℃. In contrast, non-oxide ceramic aerogels exhibit better high-temperature stability, with silicon nitride aerogels being particularly outstanding, demonstrating excellent mechanical flexibility and high-temperature resistance. However, current silicon nitride aerogel preparation technologies are costly and difficult to scale up, and they are prone to oxidation failure in aerobic environments above 1100℃, making long-term stable use difficult. For example, the journal *Materials Research Express* (2019, 1250c4) reported the research results of Yang et al., indicating that silicon nitride nanowires rapidly oxidize and fail in aerobic environments above 1100℃, completely transforming into silicon dioxide at 1500℃. Solving the problems of preparation cost and thermal stability in high-temperature oxygen environments will help to achieve large-scale preparation of silicon nitride ceramic aerogels with higher temperature resistance, thereby promoting the application of this material in the field of high-temperature thermal insulation.

[0003] Currently, there are few reported patents and papers on simultaneously achieving low-cost, large-scale preparation of silicon nitride aerogels and improving their antioxidant properties. For example, Chinese invention patent CN 114956858 A, "A Layered Elastic-Plastic Silicon Nitride Ceramic Aerogel and Its Preparation Method," uses siloxane as a raw material. First, a silicon nitride nanowire film is prepared on graphite paper. After peeling the film off the graphite paper, it is then layered with silicon nitride ceramic sheets to form a silicon nitride aerogel. This method is not suitable for large-scale aerogel preparation. Another example is Chinese invention patent CN 113929470A, "A Silicon Nitride Nanoribbon Aerogel and Its Preparation Method," which mixes and solidifies short-cut carbon fibers and polysiloxane, then heats it in nitrogen to prepare silicon nitride nanofiber aerogel. This method is suitable for large-scale preparation of silicon nitride aerogels, but the prepared aerogel will undergo oxidation failure in an oxygen-rich environment at 1100℃. Chinese invention patent CN 110028048 A, entitled "A Method for Preparing High-Temperature Resistant Lightweight Silicon Nitride Aerogel Material," utilizes a sol-gel method to obtain a precursor wet gel, followed by supercritical drying and high-temperature heat treatment to obtain bulk silicon nitride aerogel. While this method enables large-scale aerogel preparation, the supercritical drying process consumes a large amount of energy, resulting in high preparation costs. Furthermore, the aerogel prepared cannot be used in an aerobic environment at temperatures not exceeding 1100℃. Chinese invention patent CN 112047742 A, entitled "A Low-Cost Method for Preparing Large-Size Silicon Nitride Nanoribbon Aerogels," directly synthesizes silicon nitride using low-cost silicon powder and nitrogen as raw materials. Although this method achieves low-cost preparation, the oxidation resistance temperature of the prepared aerogel is only 1000℃. For example, Chinese invention patent CN 111205106 A, "A Silicon Nitride@Carbon Microwave Absorbing Foam and Its Preparation Method and Application," and the journal *ACS Nano* (2024, 4c03816) report methods for coating pyrolytic carbon onto the surface of silicon nitride aerogel using hydrothermal and chemical vapor deposition methods. While these two methods improve the heat resistance temperature of silicon nitride aerogel to some extent in an inert atmosphere, the pyrolytic carbon coating layer is rapidly oxidized in an oxygen-rich environment above 400°C. Chinese invention patent CN 113999015A, "A Lightweight and High-Strength Elastic Ceramics and Its Preparation Method," involves high-temperature pre-oxidation treatment of silicon nitride aerogel to form an oxide film on the surface of silicon nitride nanowires. While this method improves the elasticity and plasticity of the aerogel, it cannot be used for extended periods in an oxygen-rich environment at 1100°C.

[0004] In summary, research on the low-cost, large-scale preparation of silicon nitride ceramic aerogels that can stably operate in high-temperature and oxygen-rich environments is still in a technological gap stage. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a high-temperature antioxidant ceramic aerogel and its preparation method, so as to solve the problems of traditional ceramic aerogel being prone to oxidation failure at ultra-high temperature and difficult to prepare on a large scale at low cost, which makes it difficult to apply traditional ceramic aerogel to thermal insulation fields such as aerospace, high-temperature kilns and fire-fighting equipment.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention provides a high-temperature antioxidant ceramic aerogel, the main body of which is silicon nitride aerogel, and the nanostructure of which is one of the nanostructures of one-dimensional silicon nitride nanowires and two-dimensional silicon nitride nanoribbons or a combination of two nanostructures.

[0008] The nanostructure of the silicon nitride aerogel is coated with a silicon carbide precursor coating and a zirconium carbide precursor coating from the inside out.

[0009] In one embodiment, the high-temperature antioxidant ceramic aerogel is composed of nitrogen, silicon, carbon, and zirconium.

[0010] In one embodiment, under an aerobic environment, the silicon carbide precursor coating and the zirconium carbide precursor coating undergo in-situ ceramicization and oxidation as the temperature increases; the silicon carbide precursor coating and the zirconium carbide precursor coating are transformed into a silicon dioxide coating and a zirconium dioxide coating.

[0011] In one embodiment, after the silicon dioxide melting temperature is reached, the silicon dioxide coating forms a flowing molten silicon dioxide liquid, and the zirconium dioxide nanoparticles in the zirconium dioxide coating dissolve in the molten silicon dioxide liquid to jointly form a binary eutectic liquid film.

[0012] This invention also provides a method for preparing high-temperature antioxidant ceramic aerogel, comprising the following steps:

[0013] S1: Add a metal catalyst to the polysiloxane sol, stir evenly to obtain a mixed sol, impregnate the polymer foam skeleton in the mixed sol, dry to form a mixed dry gel foam, and then perform high-temperature heat treatment to obtain silicon nitride aerogel.

[0014] S2: Prepare polycarbosilane sol, immerse silicon nitride aerogel in polycarbosilane sol, remove and perform first curing treatment to obtain silicon carbide precursor / silicon nitride composite ceramic aerogel.

[0015] S3: Prepare polyzirconium carbide sol, immerse silicon carbide precursor / silicon nitride composite ceramic aerogel in polyzirconium carbide sol, remove and perform a second curing treatment to obtain zirconium carbide precursor / silicon carbide precursor / silicon nitride composite ceramic aerogel.

[0016] In one embodiment, in S1, the mass ratio of the polysiloxane sol, the metal catalyst, and the polymer foam skeleton is (1-30):(1-5):(1-30).

[0017] In one embodiment, in S1, the metal catalyst is one or a combination of platinum catalyst, palladium catalyst, copper catalyst, and nickel catalyst; the polymer foam skeleton is one or a combination of polyurethane foam, polystyrene foam, polypropylene foam, polyethylene foam, polystyrene copolymer foam, polymethyl methacrylate foam, polyphenylene sulfide foam, and melamine foam.

[0018] In one embodiment, in step S2, the polycarbosilane sol is prepared by uniformly mixing a carbon source, a silicon source, an organic solvent, and water.

[0019] The mass ratio of the carbon source, silicon source, organic solvent and water is (1-50):(1-50):(1-200):(1-200).

[0020] In one embodiment, in step S3, the polyzirconium carbide sol is prepared by uniformly mixing a carbon source, a zirconium source, an organic solvent, and water.

[0021] The mass ratio of the carbon source, zirconium source, organic solvent and water is (1-50):(1-50):(1-200):(1-200).

[0022] In one embodiment, in step S1, the drying temperature is 30–150°C; the high-temperature heat treatment temperature is 1350–1650°C, and the high-temperature heat treatment is carried out in a nitrogen-containing atmosphere.

[0023] In S2 and S3, the temperature of the first curing treatment and the second curing treatment is 150-300°C, and the first curing treatment and the second curing treatment are carried out under an inert atmosphere.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] This invention provides a high-temperature antioxidant ceramic aerogel. The structural components of the silicon nitride aerogel are one-dimensional silicon nitride nanowires and two-dimensional silicon nitride nanoribbons. Compared with granular and nanosheet structural components, these nanowires and nanoribbons with a large aspect ratio have higher mechanical deformation capacity, endowing the silicon nitride aerogel with excellent compression resilience and bending resistance. A binary antioxidant coating of silicon carbide precursor and zirconium carbide precursor is coated on the surface of the silicon nitride aerogel nanostructure. The antioxidant coating formed by the nanoparticles undergoes in-situ ceramicization during heating. This process absorbs a large amount of heat energy, playing a role in active thermal protection and effectively reducing the direct damage of high temperature to the aerogel structure.

[0026] Furthermore, in a high-temperature, oxygen-rich environment, the silicon carbide and zirconium carbide ceramics formed will oxidize and transform into silicon dioxide and zirconium dioxide due to the presence of oxygen. The nano-zirconia particles dissolve in the molten silicon dioxide, forming a dense binary eutectic liquid film. This film effectively blocks oxygen from contacting silicon nitride, preventing oxidation and performance degradation, thus significantly improving the high-temperature oxidation resistance of the aerogel. Simultaneously, the nano-zirconia particles increase the viscosity of the molten silicon dioxide, providing a stronger anchoring effect and enhancing its resistance to high-temperature airflow or flame impact. Additionally, the molten liquid film can weld silicon nitride nanocomponents, limiting their positional displacement after compression, thereby effectively improving the aerogel's elasticity and plasticity. Therefore, the antioxidant composite ceramic aerogel prepared by this invention possesses higher temperature resistance, oxidation resistance, and elasticity and plasticity, and can be widely used in thermal insulation fields such as aerospace, high-temperature kilns, and fire-fighting equipment.

[0027] This invention provides a method for preparing high-temperature antioxidant ceramic aerogels. It utilizes readily available polymer foam frameworks as the carbon source and template for synthesizing silicon nitride aerogels, forming the aerogels in one step via a carbothermal reduction reaction, thus achieving efficient aerogel preparation. Furthermore, the high porosity of the prepared aerogels allows for excellent adsorption of the precursor sol for coatings, facilitating the efficient coating of the silicon nitride aerogel nanostructure with a binary antioxidant coating of silicon carbide and zirconium carbide precursors. Therefore, this preparation method offers advantages such as low cost and suitability for large-scale production. Attached Figure Description

[0028] Figure 1 An optical photograph of the high-temperature antioxidant ceramic aerogel prepared in Example 1 of the present invention;

[0029] Figure 2 This is an EDS energy dispersive spectroscopy (EDS) analysis diagram of the high-temperature antioxidant ceramic aerogel prepared in Example 1 of the present invention;

[0030] Figure 3 Infrared thermal imaging images of the high-temperature antioxidant ceramic aerogel prepared in Example 1 of the present invention under butane spray gun (approximately 1300°C); wherein, Figures a, b, c, and d represent infrared thermal images at 5, 10, 15, and 30 min, respectively.

[0031] Figure 4 The images show SEM comparisons of the high-temperature antioxidant ceramic aerogel prepared in Example 1 of the present invention before and after oxidation treatment at 1500℃ for 1 hour; wherein, Figure a is a schematic diagram before heat treatment, and Figure b is a schematic diagram after heat treatment. Detailed Implementation

[0032] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0033] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0034] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0035] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0036] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0037] This invention provides a high-temperature antioxidant ceramic aerogel and its preparation method.

[0038] The present invention provides a high-temperature antioxidant ceramic aerogel, wherein the main body of the high-temperature antioxidant ceramic aerogel is silicon nitride aerogel, and the nanostructure of the silicon nitride aerogel is one of the following nanostructures: one-dimensional silicon nitride nanowires and two-dimensional silicon nitride nanoribbons, or a combination of the two nanostructures; the nanostructure of the silicon nitride aerogel is coated with a silicon carbide precursor coating and a zirconium carbide precursor coating from the inside to the outside.

[0039] More importantly, in an aerobic environment, the aforementioned silicon carbide precursor coating and zirconium carbide precursor coating undergo in-situ ceramicization and oxidation as the temperature increases; the aforementioned silicon carbide precursor coating and zirconium carbide precursor coating form silicon carbide and zirconium carbide ceramics, which are further oxidized and transformed into silicon dioxide coating and zirconium dioxide coating.

[0040] Based on the above, after reaching the melting temperature of silicon dioxide, the silicon dioxide coating forms a flowing molten silicon dioxide liquid, and the zirconium dioxide nanoparticles in the zirconium dioxide coating dissolve in the molten silicon dioxide liquid to jointly form a binary eutectic liquid film.

[0041] like Figure 1 As shown, the high-temperature antioxidant ceramic aerogel provided in one embodiment is a light yellow three-dimensional block with a density of 20-80 mg / cm³. 3 The main component of the high-temperature antioxidant ceramic aerogel is silicon nitride, and the structural components constituting the silicon nitride aerogel are one-dimensional silicon nitride nanowires and two-dimensional silicon nitride nanoribbons.

[0042] In the high-temperature antioxidant ceramic aerogel, the silicon carbide precursor and zirconium carbide precursor binary antioxidant coating are uniformly coated on the surface of the silicon nitride nanostructure; the main elemental composition of the high-temperature antioxidant ceramic aerogel is nitrogen, silicon, carbon and zirconium.

[0043] The high-temperature antioxidant ceramic aerogel has extremely low thermal conductivity, ranging from 0.032 to 0.058 W / mk; the high-temperature antioxidant ceramic aerogel also exhibits excellent antioxidant properties, and its microstructure does not change significantly after being treated in an aerobic environment at 1500℃ for 1 hour.

[0044] Another aspect of the present invention provides a method for preparing high-temperature antioxidant ceramic aerogel, the method comprising the following steps: preparing a polysiloxane sol and adding a metal catalyst, stirring evenly to obtain a mixed sol, immersing a polymer foam skeleton in the sol, drying to form a mixed dry gel foam, and then heat-treating at high temperature in a nitrogen-containing atmosphere to obtain a silicon nitride aerogel; immersing the prepared silicon nitride aerogel in a polycarbosilane sol, removing it after adsorption saturation, and curing it to obtain a silicon carbide precursor / silicon nitride composite ceramic aerogel, the curing process being carried out in an oven, which can also be understood as heating to achieve curing; immersing the silicon carbide precursor / silicon nitride composite ceramic aerogel in a polyzirconium carbide sol, removing it after adsorption saturation, and curing it to obtain a zirconium carbide precursor / silicon carbide precursor / silicon nitride composite ceramic aerogel, i.e., a high-temperature antioxidant ceramic aerogel, the curing process also being carried out in an oven, which can also be understood as heating to achieve curing.

[0045] The specific steps of the above preparation method are as follows:

[0046] Step 1) Prepare a polysiloxane sol and add a metal catalyst. Stir until homogeneous to obtain a mixed sol. Immerse the polymer foam skeleton in the sol for 30-120 minutes and dry it at 30-150°C to form a mixed dry gel foam. Then, heat-treat it at high temperature in a nitrogen atmosphere to obtain silicon nitride aerogel.

[0047] Step 2) Prepare a polycarbosilane sol, immerse the silicon nitride aerogel prepared in S1 in the sol, remove it after adsorption saturation, and cure it in an inert atmosphere at 150-300℃ to obtain a silicon carbide precursor / silicon nitride composite ceramic aerogel.

[0048] Step 3) Prepare a polyzirconium carbide sol, immerse the silicon carbide precursor / silicon nitride composite ceramic aerogel prepared in S2 in the sol, remove it after adsorption saturation, and cure it in an inert atmosphere at 150-300℃ to obtain the zirconium carbide precursor / silicon carbide precursor / silicon nitride composite ceramic aerogel, i.e., high-temperature antioxidant ceramic aerogel.

[0049] The specific dosage and process conditions are as follows:

[0050] In step 1), the process of preparing the polysiloxane sol is as follows: silicone resin, ethanol and water are mixed evenly in a mass ratio of 3:10:8 to obtain the polysiloxane sol.

[0051] In step 1), the mass ratio of the polysiloxane sol, the metal catalyst, and the polymer foam skeleton is (1-30):(1-5):(1-30); the metal catalyst can be one or a combination of platinum catalyst, palladium catalyst, copper catalyst, and nickel catalyst; the polymer foam skeleton can be one or a combination of polyurethane foam, polystyrene foam, polypropylene foam, polyethylene foam, polystyrene copolymer foam, polymethyl methacrylate foam, polyphenylene sulfide foam, and melamine foam; the nitrogen-containing atmosphere can be one or a combination of nitrogen and ammonia; the high-temperature heat treatment temperature is 1350-1650℃.

[0052] In step 2), the preparation method of the polycarbosilane is as follows: the carbon source, silicon source, organic solvent and water are mixed in a mass ratio of (1-50):(1-50):(1-200):(1-200), and after stirring evenly, a polycarbosilane sol is obtained.

[0053] In step 3), the preparation method of the polyzirconium carbide is as follows: the carbon source, zirconium source, organic solvent and water are mixed in a mass ratio of (1-50):(1-50):(1-200):(1-200), and after stirring evenly, polyzirconium carbide sol is obtained.

[0054] The aforementioned organic solvents include, but are not limited to, solvents such as ethanol, ethylene glycol, acetone, xylene, and tert-butanol.

[0055] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0056] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0057] Example 1:

[0058] Step 1) Prepare a polysiloxane sol and add a platinum catalyst. Stir until homogeneous to obtain a mixed sol. Immerse the melamine foam skeleton in the sol for 60 minutes. Dry at 100°C to form a mixed dry gel foam. Then, heat-treat at 1500°C in a nitrogen atmosphere to obtain a silicon nitride aerogel.

[0059] Step 2) Weigh 1g of furfuryl alcohol, 5g of tetraethyl orthosilicate, 10g of acetone and 20g of water, mix them and stir evenly to obtain polycarbosilane sol. Immerse the silicon nitride aerogel prepared in Step 1 in the sol. After adsorption saturation, take it out and cure it at 200℃ in an inert atmosphere to obtain silicon carbide precursor / silicon nitride composite ceramic aerogel.

[0060] Step 3) Weigh 1g of furfuryl alcohol, 5g of zirconium oxynitrate, 10g of ethanol and 20g of water, mix them and stir evenly to obtain polyzirconium carbide sol. Immerse the silicon carbide precursor / silicon nitride composite ceramic aerogel prepared in step 2 into the sol. After adsorption saturation, take it out and cure it at 180℃ in an inert atmosphere to obtain zirconium carbide precursor / silicon carbide precursor / silicon nitride composite ceramic aerogel, that is, high temperature antioxidant ceramic aerogel.

[0061] The prepared high-temperature antioxidant ceramic aerogel had a density of 40 mg / cm³ and a thermal conductivity of 0.042 W / mK at room temperature. Figure 1 As can be seen, the high-temperature antioxidant ceramic aerogel appears as a light yellow, three-dimensional block. (The last sentence appears to be incomplete and possibly refers to a different material.) Figure 2 It is evident that the main elements of antioxidant composite ceramic aerogels are nitrogen, silicon, carbon, and zirconium. (From...) Figure 3 It is evident that the high-temperature antioxidant ceramic aerogel maintains excellent thermal insulation performance even after being irradiated by a butane flame at 1300℃, with the back temperature of the aerogel stabilizing at 95℃ after 30 minutes of irradiation. Figure 4It is evident that the microstructure of the antioxidant composite ceramic aerogel remains essentially unchanged after treatment in an aerobic environment at 1500℃ for 1 hour, demonstrating that the aerogel possesses excellent high-temperature antioxidant properties.

[0062] Example 2:

[0063] Step 1) Prepare a polysiloxane sol and add a copper catalyst. Stir until homogeneous to obtain a mixed sol. Immerse the polymethyl methacrylate foam skeleton in the sol for 80 minutes. Dry at 60°C to form a mixed dry gel foam. Then, heat-treat at 1450°C in a nitrogen atmosphere to obtain a silicon nitride aerogel.

[0064] Step 2) Weigh 2g of furfuryl alcohol, 5g of tetraethyl orthosilicate, 20g of acetone and 40g of water, mix them and stir evenly to obtain polycarbosilane sol. Immerse the silicon nitride aerogel prepared in Step 1 in the sol. After adsorption saturation, take it out and cure it at 260℃ in an inert atmosphere to obtain silicon carbide precursor / silicon nitride composite ceramic aerogel.

[0065] Step 3) Weigh 2g of furfuryl alcohol, 5g of zirconium oxynitrate, 20g of ethanol and 40g of water, mix them and stir evenly to obtain polyzirconium carbide sol. Immerse the silicon carbide precursor / silicon nitride composite ceramic aerogel prepared in step 2 into the sol. After adsorption saturation, take it out and cure it at 180℃ in an inert atmosphere to obtain zirconium carbide precursor / silicon carbide precursor / silicon nitride composite ceramic aerogel, that is, high temperature antioxidant ceramic aerogel.

[0066] Example 3:

[0067] Step 1) Prepare a polysiloxane sol and add a platinum catalyst. Stir until homogeneous to obtain a mixed sol. Immerse the polyurethane foam skeleton in the sol for 120 min. Dry at 60°C to form a mixed dry gel foam. Then, heat-treat at 1400°C in a nitrogen atmosphere to obtain a silicon nitride aerogel.

[0068] Step 2) Weigh 2g of furfuryl alcohol, 10g of tetraethyl orthosilicate, 30g of acetone and 20g of water, mix them and stir evenly to obtain polycarbosilane sol. Immerse the silicon nitride aerogel prepared in step 1 in the sol. After adsorption saturation, take it out and cure it at 300℃ in an inert atmosphere to obtain silicon carbide precursor / silicon nitride composite ceramic aerogel.

[0069] Step 3) Weigh 1g of furfuryl alcohol, 10g of zirconium oxynitrate, 20g of ethanol and 30g of water, mix them and stir evenly to obtain polyzirconium carbide sol. Immerse the silicon carbide precursor / silicon nitride composite ceramic aerogel prepared in step 2 into the sol. After adsorption saturation, take it out and cure it at 150℃ in an inert atmosphere to obtain zirconium carbide precursor / silicon carbide precursor / silicon nitride composite ceramic aerogel, that is, high temperature antioxidant ceramic aerogel.

[0070] Example 4:

[0071] Step 1) Prepare a polysiloxane sol and add a nickel catalyst. Stir until homogeneous to obtain a mixed sol. Immerse a polyethylene foam skeleton in the sol for 80 minutes. Dry at 150°C to form a mixed dry gel foam. Then, heat-treat at 1600°C in a nitrogen atmosphere to obtain a silicon nitride aerogel.

[0072] Step 2) Weigh 4g of furfuryl alcohol, 8g of tetraethyl orthosilicate, 30g of acetone and 40g of water, mix them and stir evenly to obtain polycarbosilane sol. Immerse the silicon nitride aerogel prepared in Step 1 in the sol. After adsorption saturation, take it out and cure it at 180℃ in an inert atmosphere to obtain silicon carbide precursor / silicon nitride composite ceramic aerogel.

[0073] Step 3) Weigh 4g of furfuryl alcohol, 7g of zirconium oxynitrate, 20g of ethanol and 30g of water, mix them and stir evenly to obtain polyzirconium carbide sol. Immerse the silicon carbide precursor / silicon nitride composite ceramic aerogel prepared in step 2 into the sol. After adsorption saturation, take it out and cure it at 200℃ in an inert atmosphere to obtain zirconium carbide precursor / silicon carbide precursor / silicon nitride composite ceramic aerogel, that is, high temperature antioxidant ceramic aerogel.

[0074] Example 5:

[0075] Step 1) Prepare a polysiloxane sol and add a palladium catalyst. Stir until homogeneous to obtain a mixed sol. Immerse the polypropylene foam skeleton in the sol for 80 minutes. Dry at 30°C to form a mixed dry gel foam. Then, heat-treat at 1650°C in a nitrogen atmosphere to obtain a silicon nitride aerogel.

[0076] Step 2) Weigh 1g of furfuryl alcohol, 1g of tetraethyl orthosilicate, 1g of acetone and 1g of water, mix them and stir evenly to obtain polycarbosilane sol. Immerse the silicon nitride aerogel prepared in step 1 in the sol. After adsorption saturation, take it out and cure it at 300℃ in an inert atmosphere to obtain silicon carbide precursor / silicon nitride composite ceramic aerogel.

[0077] Step 3) Weigh 1g of furfuryl alcohol, 1g of zirconium oxynitrate, 1g of ethanol and 1g of water, mix them and stir evenly to obtain polyzirconium carbide sol. Immerse the silicon carbide precursor / silicon nitride composite ceramic aerogel prepared in step 2 into the sol. After adsorption saturation, take it out and cure it at 150℃ in an inert atmosphere to obtain zirconium carbide precursor / silicon carbide precursor / silicon nitride composite ceramic aerogel, that is, high temperature antioxidant ceramic aerogel.

[0078] Example 6:

[0079] Step 1) Prepare a polysiloxane sol and add a palladium catalyst. Stir until homogeneous to obtain a mixed sol. Immerse the polystyrene copolymer foam skeleton in the sol for 80 minutes. Dry at 150°C to form a mixed dry gel foam. Then, heat-treat at 1350°C in a nitrogen atmosphere to obtain a silicon nitride aerogel.

[0080] Step 2) Weigh 50g of furfuryl alcohol, 50g of tetraethyl orthosilicate, 200g of acetone and 200g of water, mix them and stir evenly to obtain polycarbosilane sol. Immerse the silicon nitride aerogel prepared in Step 1 in the sol. After adsorption saturation, take it out and cure it at 150℃ in an inert atmosphere to obtain silicon carbide precursor / silicon nitride composite ceramic aerogel.

[0081] Step 3) Weigh 2g of furfuryl alcohol, 5g of zirconium oxynitrate, 20g of ethanol and 40g of water, mix them and stir evenly to obtain polyzirconium carbide sol. Immerse the silicon carbide precursor / silicon nitride composite ceramic aerogel prepared in step 2 into the sol. After adsorption saturation, take it out and cure it at 300℃ in an inert atmosphere to obtain zirconium carbide precursor / silicon carbide precursor / silicon nitride composite ceramic aerogel, that is, high temperature antioxidant ceramic aerogel.

[0082] Example 7:

[0083] Step 1) Prepare a polysiloxane sol and add a palladium catalyst. Stir until homogeneous to obtain a mixed sol. Immerse the polystyrene foam skeleton in the sol for 80 minutes. Dry at 150°C to form a mixed dry gel foam. Then, heat-treat at 1350°C in a nitrogen atmosphere to obtain a silicon nitride aerogel.

[0084] Step 2) Weigh 2g of furfuryl alcohol, 5g of tetraethyl orthosilicate, 20g of acetone and 40g of water, mix them and stir evenly to obtain polycarbosilane sol. Immerse the silicon nitride aerogel prepared in Step 1 in the sol. After adsorption saturation, take it out and cure it at 150℃ in an inert atmosphere to obtain silicon carbide precursor / silicon nitride composite ceramic aerogel.

[0085] Step 3) Weigh 50g of furfuryl alcohol, 50g of zirconium oxynitrate, 200g of ethanol and 400g of water, mix them and stir evenly to obtain polyzirconium carbide sol. Immerse the silicon carbide precursor / silicon nitride composite ceramic aerogel prepared in step 2 into the sol. After adsorption saturation, take it out and cure it at 300℃ in an inert atmosphere to obtain zirconium carbide precursor / silicon carbide precursor / silicon nitride composite ceramic aerogel, that is, high temperature antioxidant ceramic aerogel.

[0086] Example 8:

[0087] Step 1) Prepare a polysiloxane sol and add a palladium catalyst. Stir until homogeneous to obtain a mixed sol. Immerse the polyphenylene sulfide foam skeleton in the sol for 80 minutes. Dry at 150°C to form a mixed dry gel foam. Then, heat-treat at 1350°C in a nitrogen atmosphere to obtain a silicon nitride aerogel.

[0088] Step 2) Weigh 2g of furfuryl alcohol, 5g of tetraethyl orthosilicate, 20g of acetone and 40g of water, mix them and stir evenly to obtain polycarbosilane sol. Immerse the silicon nitride aerogel prepared in Step 1 in the sol. After adsorption saturation, take it out and cure it at 150℃ in an inert atmosphere to obtain silicon carbide precursor / silicon nitride composite ceramic aerogel.

[0089] Step 3) Weigh 2g of furfuryl alcohol, 5g of zirconium oxynitrate, 20g of ethanol and 40g of water, mix them and stir evenly to obtain polyzirconium carbide sol. Immerse the silicon carbide precursor / silicon nitride composite ceramic aerogel prepared in step 2 into the sol. After adsorption saturation, take it out and cure it at 300℃ in an inert atmosphere to obtain zirconium carbide precursor / silicon carbide precursor / silicon nitride composite ceramic aerogel, that is, high temperature antioxidant ceramic aerogel.

[0090] In summary, the high-temperature antioxidant ceramic aerogel prepared by this invention has excellent flexibility, thermal insulation and antioxidant properties, and can be prepared at low cost and on a large scale, and has great application potential in thermal insulation fields such as aerospace, high-temperature kilns and fire protection engineering.

[0091] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A high-temperature antioxidant ceramic aerogel, characterized in that, The main body of the high-temperature antioxidant ceramic aerogel is silicon nitride aerogel, and the nanostructure of the silicon nitride aerogel is one of the following nanostructures: one-dimensional silicon nitride nanowires and two-dimensional silicon nitride nanoribbons, or a combination of the two nanostructures. The nanostructure of the silicon nitride aerogel is coated with a silicon carbide precursor coating and a zirconium carbide precursor coating from the inside out. The preparation method of the high-temperature antioxidant ceramic aerogel includes the following steps: S1: Add a metal catalyst to the polysiloxane sol, stir evenly to obtain a mixed sol, impregnate the polymer foam skeleton in the mixed sol, dry to form a mixed dry gel foam, and then perform high-temperature heat treatment to obtain silicon nitride aerogel. S2: Prepare polycarbosilane sol, immerse silicon nitride aerogel in polycarbosilane sol, remove and perform first curing treatment to obtain silicon carbide precursor / silicon nitride composite ceramic aerogel. S3: Prepare polyzirconium carbide sol, immerse silicon carbide precursor / silicon nitride composite ceramic aerogel in polyzirconium carbide sol, remove and perform a second curing treatment to obtain zirconium carbide precursor / silicon carbide precursor / silicon nitride composite ceramic aerogel.

2. A method for preparing high-temperature antioxidant ceramic aerogel according to claim 1, characterized in that, Includes the following steps: S1: Add a metal catalyst to the polysiloxane sol, stir evenly to obtain a mixed sol, impregnate the polymer foam skeleton in the mixed sol, dry to form a mixed dry gel foam, and then perform high-temperature heat treatment to obtain silicon nitride aerogel. S2: Prepare polycarbosilane sol, immerse silicon nitride aerogel in polycarbosilane sol, remove and perform first curing treatment to obtain silicon carbide precursor / silicon nitride composite ceramic aerogel. S3: Prepare polyzirconium carbide sol, immerse silicon carbide precursor / silicon nitride composite ceramic aerogel in polyzirconium carbide sol, remove and perform a second curing treatment to obtain zirconium carbide precursor / silicon carbide precursor / silicon nitride composite ceramic aerogel.

3. The method for preparing high-temperature antioxidant ceramic aerogel according to claim 2, characterized in that, In S1, the mass ratio of the polysiloxane sol, the metal catalyst, and the polymer foam skeleton is (1~30):(1~5):(1~30).

4. The method for preparing high-temperature antioxidant ceramic aerogel according to claim 2, characterized in that, In S1, the metal catalyst is one or a combination of platinum catalyst, palladium catalyst, copper catalyst, and nickel catalyst; the polymer foam skeleton is one or a combination of polyurethane foam, polystyrene foam, polypropylene foam, polyethylene foam, polystyrene copolymer foam, polymethyl methacrylate foam, polyphenylene sulfide foam, and melamine foam.

5. The method for preparing high-temperature antioxidant ceramic aerogel according to claim 2, characterized in that, In step S2, the polycarbosilane sol is prepared by uniformly mixing a carbon source, a silicon source, an organic solvent, and water. The mass ratio of the carbon source, silicon source, organic solvent and water is (1~50):(1~50):(1~200):(1~200).

6. The method for preparing high-temperature antioxidant ceramic aerogel according to claim 2, characterized in that, In step S3, the polyzirconium carbide sol is prepared by uniformly mixing a carbon source, a zirconium source, an organic solvent, and water. The mass ratio of the carbon source, zirconium source, organic solvent and water is (1~50):(1~50):(1~200):(1~200).

7. The method for preparing high-temperature antioxidant ceramic aerogel according to claim 2, characterized in that, In step S1, the drying temperature is 30~150 ℃; the high-temperature heat treatment temperature is 1350~1650 ℃, and the high-temperature heat treatment is carried out in a nitrogen-containing atmosphere; In S2 and S3, the temperature of the first curing treatment and the second curing treatment is 150~300 ℃, and the first curing treatment and the second curing treatment are carried out under an inert atmosphere.

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