A multi-dimensional assembled nanometer thermal insulation material and a preparation method thereof

Abstract

The application relates to a multi-dimensional assembled nanometer thermal insulation material and a preparation method thereof. The method comprises the following steps: uniformly dispersing nanometer fibers with high length-diameter ratio, magnesium-aluminum spinel nano powder and nanometer silicon carbide in water to obtain a dispersion slurry; adding a high-temperature adhesive into the dispersion slurry and uniformly dispersing, and then aging to obtain a wet gel; the high-temperature adhesive is one or more of a calcium aluminate cement gelling agent, a zirconium oxide-calcium phosphate composite sol gelling agent and a calcium silico-aluminate cement gelling agent; and the wet gel is sequentially subjected to solvent replacement and supercritical drying to prepare the multi-dimensional assembled nanometer thermal insulation material. The application improves the macropore structure of the nanometer fibers, limits the internal gas phase heat transfer of the thermal insulation material, can effectively solve the problem of insufficient mechanical strength of the nanometer fiber material, and can comprehensively improve the mechanical and thermal properties of the nanometer fiber thermal insulation material.

Description

Technical Field

[0001] This invention belongs to the field of nanofiber thermal insulation materials technology, and particularly relates to a multidimensional assembled nano-thermal insulation material and its preparation method. Background Technology

[0002] Nanofiber insulation materials, characterized by their lightweight, high-temperature resistance, and low thermal conductivity, have become a research hotspot in the field of nanofiber insulation materials. However, current nanofiber insulation materials are all assembled using nanofibers as a framework. The micron-sized macroporous structure inside the material cannot effectively restrict heat transfer from the gas, resulting in severely inadequate insulation performance.

[0003] Existing technologies have reported methods for improving pore structure by doping with aerogel nanoparticles, resulting in effective enhancements to the thermal insulation performance of materials. However, current methods all use silica aerogel particles as the skeletal thermal insulation filler. Silica aerogels suffer from insufficient temperature resistance, and the preparation process requires a sol-gel process, making the entire composite material preparation cumbersome. Furthermore, the preparation of nanofibers typically employs freeze-drying, a process difficult to scale up. Therefore, there is an urgent need to develop a simple and effective method for preparing high-temperature resistant nanofiber aerogel composite thermal insulation materials.

[0004] In summary, it is essential to provide a multidimensional assembled nano-insulating material and its preparation method. Summary of the Invention

[0005] To address one or more technical problems existing in the prior art, this invention provides a multidimensional assembled nano-thermal insulation material and its preparation method.

[0006] The present invention provides a method for preparing a multidimensional assembled nanomaterial for thermal insulation, the method comprising the following steps:

[0007] (1) Use water to uniformly disperse high aspect ratio nanofibers, magnesium aluminum spinel nanopowder and nano silicon carbide to obtain a dispersion slurry.

[0008] (2) A high-temperature binder is added to the dispersion slurry and dispersed evenly, and then aged to obtain a wet gel; the high-temperature binder is one or more of calcium aluminate cement binder, zirconia-calcium phosphate binder and calcium aluminosilicate cement binder;

[0009] (3) The wet gel was subjected to solvent replacement and supercritical drying in sequence to prepare a multidimensional assembled nano-insulating material.

[0010] Preferably, the nanofibers are one or more of the following: zirconia nanofibers, magnesium aluminum spinel nanofibers, zirconium silicate nanofibers, mullite nanofibers, and alumina nanofibers.

[0011] Preferably, the aspect ratio of the nanofiber is (200-10000):1; and / or the particle size of the magnesium aluminum spinel nanopowder is 20nm-200nm.

[0012] Preferably, the mass ratio of the nanofibers to the magnesium aluminum spinel nanopowder is (1-9):1; and / or the mass amount of the nano silicon carbide is 4-8% of the sum of the mass amounts of the nanofibers and the magnesium aluminum spinel nanopowder.

[0013] Preferably, the total mass percentage of nanofibers and magnesium aluminum spinel nanopowder in the dispersion slurry is 10-20%; and / or the mass amount of the high-temperature adhesive in step (2) is 5-20% of the mass amount of nanofibers in step (1).

[0014] Preferably, the aging temperature is 60℃~90℃, and the aging time is 12h~48h.

[0015] Preferably, the solvent replacement is performed 3 to 5 times; the solvent replacement is performed using a cyclohexane / ethanol mixed solvent, preferably, the cyclohexane / ethanol mixed solvent is a mixture of n-hexane and ethanol in a volume ratio of 1:(1 to 3); and / or the supercritical drying time is 48 to 96 hours.

[0016] Preferably, in step (1), rare earth high-entropy ceramic nanofibers are also added, and the mass ratio of the rare earth high-entropy ceramic nanofibers to magnesium aluminum spinel nanopowder is 1:(1-2).

[0017] Preferably, the rare earth high-entropy ceramic nanofibers are rare earth zirconate high-entropy ceramic nanofibers A2Zr2O7 and / or rare earth hafnium salt high-entropy ceramic nanofibers B2Hf2O7; A is any five rare earth elements La, Sr, Ce, Er, Y and Yb, and the sum of the atomic molar percentages of each rare earth element is 100%, and the atomic molar percentages of each rare earth element are equal, or the difference in atomic molar percentages does not exceed 1-3%; B is any five rare earth elements Nd, Sm, Eu, Gd, Dy and Er, and the sum of the atomic molar percentages of each rare earth element is 100%, and the atomic molar percentages of each rare earth element are equal, or the difference in atomic molar percentages does not exceed 1-3%.

[0018] In a second aspect, the present invention provides a multidimensionally assembled nano-thermal insulating material prepared by the preparation method described in the first aspect of the present invention.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects:

[0020] This invention uses high-temperature resistant magnesium aluminum spinel nanopowder as a pore structure regulator to improve the macroporous structure of nanofibers, limiting gas-phase heat transfer within the insulation material. The direct introduction of the nanopore regulator avoids the cumbersome sol-gel process, making material preparation more convenient. Furthermore, this invention uses high-temperature resistant, high aspect ratio nanofibers as the framework structural component, utilizing the entanglement effect of the aspect ratio fibers to form a high-strength nanofiber framework with a bird's nest-like structure, effectively solving the problem of insufficient mechanical strength in nanofiber materials. In addition, this invention introduces a high-temperature inorganic gelling agent as a high-temperature binder, avoiding the secondary high-temperature treatment process in the traditional nanofiber aerogel material molding process, thus comprehensively improving the mechanical and thermal properties of the nanofiber insulation material. The multi-dimensional assembled nano-insulation material prepared by this invention can withstand temperatures up to 1400℃. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments thereof. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0022] The present invention provides a method for preparing a multidimensional assembled nanomaterial for thermal insulation, the method comprising the following steps:

[0023] (1) High aspect ratio nanofibers, magnesium aluminum spinel nanopowder and nano silicon carbide (also referred to as silicon carbide nanopowder) are uniformly dispersed in water to obtain a dispersion slurry; in this invention, the particle size (average particle size) of the nano silicon carbide is 50-100 nm; in this invention, magnesium aluminum spinel nanopowder is also referred to as nano magnesium aluminum spinel; in this invention, specifically, for example, a certain ratio of high aspect ratio nanofibers, magnesium aluminum spinel nanopowder and nano silicon carbide are stirred and dispersed in water to obtain a dispersion slurry, which is a raw material for assembling and forming a multidimensional nanofiber thermal insulation skeleton; this invention does not specifically limit the stirring and dispersion method, nor does it specifically limit the amount of silicon carbide added, which can be conventionally selected by those skilled in the art.

[0024] (2) A high-temperature binder is added to the dispersion slurry and dispersed evenly, and then aged to obtain a wet gel; the high-temperature binder is one or more of calcium aluminate cement gelling agent (i.e., calcium aluminate cement), zirconia-calcium phosphate composite sol gelling agent, and calcium aluminosilicate cement gelling agent (i.e., calcium aluminosilicate cement); the present invention does not specifically limit calcium aluminate cement and calcium aluminosilicate cement, and any directly purchased products can be used; in the present invention, calcium aluminosilicate cement refers to aluminosilicate cement with calcium aluminosilicate as the main component; in the present invention, the zirconia-calcium phosphate composite sol gelling agent is composed of zirconia sol and calcium phosphate sol mixed at a mass ratio of 1:1, the solid content of the zirconia sol is 20-25 wt%, and the solid content of the calcium phosphate sol is 20-25 wt%; in the present invention, a high-temperature binder is added to the dispersion slurry and stirred and dispersed evenly, and then aged at high temperature to obtain a wet gel.

[0025] (3) The wet gel is subjected to solvent replacement and supercritical drying in sequence to prepare a multidimensional assembled nano-insulating material; In this invention, supercritical drying is carried out in a supercritical drying kettle, for example, supercritical carbon dioxide drying. This invention does not specifically limit the conditions of supercritical drying, which is a conventional technique in the field; This invention provides a method for preparing a composite insulation material based on magnesium aluminum spinel nanofiber reinforcement, and the obtained multidimensional assembled nano-insulating material is also referred to as high temperature resistant composite insulation material or high temperature resistant nanofiber aerogel composite insulation material.

[0026] This invention uses high-temperature resistant magnesium aluminum spinel nanopowder as a pore structure regulator to improve the macroporous structure of nanofibers, limiting gas-phase heat transfer within the insulation material. The direct introduction of the nanopore regulator avoids the cumbersome sol-gel process, making material preparation more convenient. Furthermore, this invention uses high-temperature resistant, high aspect ratio nanofibers as the framework structural component, utilizing the entanglement effect of the aspect ratio fibers to form a high-strength nanofiber framework with a bird's nest-like structure, effectively solving the problem of insufficient mechanical strength in nanofiber materials. In addition, this invention introduces high-temperature inorganic binders (calcium aluminate cement binder, zirconium oxide-calcium phosphate composite sol binder, and / or calcium aluminosilicate cement binder) as high-temperature adhesives, avoiding the secondary high-temperature treatment process in the traditional nanofiber aerogel material molding process. This comprehensively improves the mechanical and thermal properties of nanofiber insulation materials because this invention discovers that these inorganic binders can enable the dispersion slurry described in this invention to form a strong gel at relatively low temperatures. This invention achieves material molding and strength enhancement without the need for a secondary high-temperature treatment. Furthermore, it reveals that these inorganic gelling agents possess high temperature resistance and low thermal conductivity, further reducing the overall thermal conductivity of the material and thus improving its thermal insulation performance. In contrast, traditional high-temperature adhesives such as silica sol and aluminum dihydrogen phosphate have weak hydration resistance and typically require the addition of organic gelling agents and / or high-temperature treatment to solidify and enhance material properties. This increases production costs and process complexity. Silica sol has limited temperature resistance, and aluminum dihydrogen phosphate tends to expand during high-temperature curing, creating an uneven macroporous structure, which reduces the overall mechanical and thermal properties of the material. Additionally, secondary high-temperature treatment can cause partial collapse or shrinkage of the fine pore structure in nanofiber aerogel materials, reducing porosity. Reduced porosity leads to increased thermal conductivity and decreased thermal insulation performance. The multidimensional assembled nano-insulation material prepared by this invention can withstand temperatures up to 1400℃.

[0027] According to some preferred embodiments, the nanofibers are one or more of zirconia nanofibers, magnesium aluminum spinel nanofibers, zirconium silicate nanofibers, mullite nanofibers, and alumina nanofibers. Preferably, the nanofibers are mullite nanofibers, magnesium aluminum spinel nanofibers, alumina nanofibers, zirconium silicate nanofibers, and zirconia fibers, etc. These nanofibers have excellent temperature resistance, all not lower than 1300℃. The present invention does not specifically limit the source of these nanofibers, and products that can be purchased directly or products prepared by existing methods can be used.

[0028] According to some preferred embodiments, the aspect ratio (average aspect ratio) of the nanofibers is (200-10000):1 (e.g., 200:1, 1000:1, 2000:1, 3000:1, 4000:1, 5000:1, 6000:1, 7000:1, 8000:1, 9000:1, or 10000:1); and / or the particle size (average particle size) of the magnesium aluminum spinel nanopowder is 20nm-200nm (e.g., 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 1...). (90 or 200 nm); In this invention, preferably, the aspect ratio of the nanofibers is 200:1 to 10000:1. This invention has found that if the aspect ratio of the nanofibers is too small, it is difficult to form a framework structure, while if the aspect ratio is too large, the pore structure size is difficult to control, resulting in a large number of micron-sized pores. In this invention, magnesium aluminum spinel has a stable crystal structure and good temperature resistance. As a high-temperature pore structure regulator, preferably, the particle size is 20 to 200 nm. This invention has found that if the particle size of magnesium aluminum spinel nanopowder is too small, it is difficult to effectively support the pore structure, and the framework structure is unstable. If the particle size of magnesium aluminum spinel nanopowder is too large, it will lead to low pore structure regulation efficiency.

[0029] According to some preferred embodiments, the mass ratio of the nanofibers to the magnesium aluminum spinel nanopowder is (1-9):1 (e.g., 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1 or 9:1); and / or the mass amount of the nano silicon carbide is 4-8% (e.g., 4%, 5%, 6% or 8%) of the sum of the mass amounts of the nanofibers and the magnesium aluminum spinel nanopowder.

[0030] According to some preferred embodiments, the total mass percentage of nanofibers and magnesium aluminum spinel nanopowder in the dispersion slurry is 10-20% (e.g., 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%); and / or the mass amount of the high-temperature adhesive in step (2) is 5-20% (e.g., 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%) of the mass amount of nanofibers in step (1). (13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%); In this invention, the amount of the high-temperature adhesive is preferably 5-20%. If the amount of the high-temperature adhesive is too large, it will cause the high-temperature adhesive to form its own cluster structure, reduce the surface energy of the nano-components, make the material prone to shrinkage at high temperatures, and reduce the temperature resistance of the material. At the same time, if the amount of the high-temperature adhesive is too large, it will cause the solid phase thermal conductivity of the material to increase, and the nanofibers will also undergo local agglomeration, resulting in a significant increase in the macroscopic equivalent thermal conductivity of the material.

[0031] According to some preferred embodiments, the aging temperature is 60℃~90℃ (e.g., 60℃, 70℃, 80℃ or 90℃), and the aging time is 12h~48h (e.g. 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46 or 48h). In this invention, the preferred aging temperature for forming a wet gel is 60-90℃. If aging is carried out at a low temperature below 60℃, the aging efficiency will be low and the skeleton will be difficult to strengthen effectively. If aging is carried out at a high temperature above 90℃, the temperature will be too high and will generate air pressure, which will destroy the structural stability of the material.

[0032] According to some preferred embodiments, the solvent replacement is performed 3 to 5 times (e.g., 3, 4, or 5 times) to ensure that the aqueous solution is completely replaced. In this invention, it is preferred that each solvent replacement takes 18 to 30 hours. The solvent replacement uses a cyclohexane / ethanol mixed solvent as the solvent. Preferably, the cyclohexane / ethanol mixed solvent is a mixture of n-hexane and ethanol with a volume ratio of 1:(1 to 3) (e.g., 1:1, 1:1.5, 1:2, 1:2.5, or 1:3). In this invention, it is preferred to use a cyclohexane / ethanol mixed solvent as the solvent for solvent replacement. The use of both can protect the nanostructure while ensuring the uniformity and thoroughness of solvent replacement. Furthermore, using a cyclohexane and ethanol mixed solvent with a volume ratio of 1:(1 to 3) for solvent replacement can effectively prevent cracking of the internal structure during the replacement process, and can better control the porosity and pore size distribution of the material, thereby improving the mechanical and thermal properties of the nano-insulating material.

[0033] According to some preferred embodiments, the supercritical drying time is 48 to 96 hours (e.g., 48, 60, 72, 84 or 96 hours), which ensures that the material is completely dried and avoids damage to the skeleton.

[0034] According to some preferred embodiments, in step (1), rare earth high-entropy ceramic nanofibers are also added, wherein the mass ratio of the rare earth high-entropy ceramic nanofibers to magnesium aluminum spinel nanopowder is 1:(1-2) (e.g., 1:1, 1:1.5, or 1:2), that is, step (1) is: dispersing the high aspect ratio nanofibers, rare earth high-entropy ceramic nanofibers, magnesium aluminum spinel nanopowder, and nano-silicon carbide uniformly with water to obtain a dispersion slurry; in this invention, when the dispersion slurry contains rare earth high-entropy ceramic nanofibers, it is preferred that the dispersion slurry contains the high aspect ratio nanofibers. The total mass percentage of nanofibers with a diameter ratio, rare earth high-entropy ceramic nanofibers, and magnesium aluminum spinel nanopowder is 10-20%. In this invention, preferably, the dispersion slurry also contains rare earth high-entropy ceramic nanofibers. This invention has found that introducing them into nano-insulation materials can effectively improve the overall strength of the material, making it more robust and durable when subjected to external pressure and mechanical stress. It can also increase the multiple scattering and reflection effects of heat radiation, thereby improving the insulation performance. This can further enhance the mechanical and insulation properties of multi-dimensional assembled nano-insulation materials.

[0035] According to some preferred embodiments, the aspect ratio (average aspect ratio) of the rare earth high-entropy ceramic nanofibers is (50-100):1. Unlike high aspect ratio nanofibers used as the main raw material for nanofiber thermal insulation skeletons, this invention preferably uses rare earth high-entropy ceramic nanofibers with an aspect ratio of (50-100):1. This invention has found that two nanofibers with different aspect ratios can form a multi-scale reinforcement effect. The rare earth high-entropy ceramic nanofibers with a smaller aspect ratio can fill the gaps between high aspect ratio nanofibers, forming a more compact and uniform structure. This multi-scale structure can more effectively transfer and disperse stress, improving the overall mechanical properties of the material. Furthermore, the mixing of two nanofibers with different aspect ratios can form pore structures with different sizes and shapes, optimizing the pore structure. This multi-scale pore structure can effectively block heat conduction paths, reduce heat conduction efficiency, and thus improve the thermal insulation performance of the material. This invention is more preferably an improvement in the mechanical and thermal insulation performance of nano-thermal insulation materials by adding rare earth high-entropy ceramic nanofibers with an aspect ratio of (50-100):1.

[0036] According to some preferred embodiments, the rare earth high-entropy ceramic nanofibers are rare earth zirconate high-entropy ceramic nanofibers A2Zr2O7 and / or rare earth hafnium salt high-entropy ceramic nanofibers B2Hf2O7; A is any five of the rare earth elements La (lanthanum), Sr (strontium), Ce (cerium), Er (erbium), Y (yttrium), and Yb (ytterbium), and the sum of the atomic molar percentages of each rare earth element is 100%, and the atomic molar percentages of each rare earth element are equal, or the difference in atomic molar percentages does not exceed 1-3%; B is any five of the rare earth elements Nd (neodymium), Sm (samarium), Eu (eurypium), Gd (gadolinium), Dy (dysprosium), and Er (erbium), and the sum of the atomic molar percentages of each rare earth element is 100%, and the atomic molar percentages of each rare earth element are equal, or the difference in atomic molar percentages does not exceed 1-3%.

[0037] According to some preferred embodiments, the rare-earth high-entropy ceramic nanofibers are (La 0.2 Sr 0.2 Ce 0.2 Er 0.2 Yb 0.2 )2Zr2O7 high-entropy ceramic nanofibers, (La 0.2 Sr 0.2 Ce 0.2 Er 0.2 Y 0.2 )2Zr2O7 high-entropy ceramic nanofibers, (Sm 0.2 Eu 0.2 Gd 0.2 Dy 0.2 Er 0.2 )2Hf2O7 high-entropy ceramic nanofibers or (Nd 0.2 Eu 0.2 Gd 0.2 Dy 0.2 Er 0.2 This invention relates to 2Hf2O7 high-entropy ceramic nanofibers. These high-entropy ceramic nanofibers exhibit superior performance compared to other high-entropy ceramic nanofibers in terms of high-temperature stability, thermal conductivity, and optical reflection properties. This allows for the preparation of multi-dimensionally assembled nano-insulation materials with superior performance. The rational combination of rare earth elements provides various beneficial physical and chemical properties, such as excellent optical properties, thermal stability, and chemical stability. The rational combination of these elements significantly improves the overall performance of the material. Furthermore, the rational combination of rare earth elements in these high-entropy ceramic nanofibers results in lower thermal conductivity, effectively blocking heat conduction and thus further enhancing the insulation performance of the nano-insulation material.

[0038] This invention does not specifically limit the source of rare earth zirconate high-entropy ceramic nanofibers A2Zr2O7 and / or rare earth hafnium salt high-entropy ceramic nanofibers B2Hf2O7. For example, they can be directly purchased products or products prepared by existing methods. In this invention, specifically, the source of (La) high-entropy ceramic nanofibers B2Hf2O7 is used to prepare... 0.2 Sr 0.2 Ce 0.2 Er 0.2 Yb 0.2 Taking Zr2O7 high-entropy ceramic nanofibers as an example, the preparation steps can be as follows:

[0039] ①Prepared by sol-gel method (La 0.2 Sr 0.2 Ce 0.2 Er 0.2 Yb 0.2 )2Zr2O7 high-entropy ceramic dispersion: Lanthanum acetate, Strontium acetate, Cerium acetate, Erbium acetate, and basic zirconium carbonate are used as raw materials, and aqueous acetic acid solution is used as solvent; according to (La 0.2 Sr 0.2 Ce 0.2 Er 0.2 Yb 0.2 The molar ratio of each element in 2Zr2O7 was determined by adding the raw material to an aqueous acetic acid solution (acetic acid to water mass ratio of 1:1) and stirring for 0.5 h to obtain (La) 0.2 Sr 0.2 Ce 0.2 Er 0.2 Yb 0.2 )2Zr2O7 high-entropy ceramic dispersion, making (La 0.2 Sr 0.2 Ce 0.2 Er 0.2 Yb 0.2 The solid content (concentration) of the Zr2O7 high-entropy ceramic dispersion is 15 wt%.

[0040] ② Add polyethylene oxide to the (La) obtained in step ① 0.2 Sr 0.2 Ce 0.2 Er 0.2 Yb 0.2 In a high-entropy ceramic dispersion of 2Zr2O7, the mixture is stirred evenly to prepare a spinning solution, such that the spinning solution contains 2% polyethylene oxide by mass.

[0041] ③ The prepared spinning solution is drawn into the syringe of the electrospinning equipment. The electrospinning parameters are set as follows: voltage 20kV, injection speed 0.4mm / min, and distance 15cm. After setting the parameters, the spinning solution is electrospinned, then dried in a 70℃ forced-air drying oven for 12 hours, and finally calcined at 1200℃ in air atmosphere for 2 hours to obtain (La). 0.2 Sr 0.2 Ce 0.2 Er 0.2 Yb 0.2 )2Zr2O7 high-entropy ceramic nanofibers.

[0042] In this invention, (Sm) is prepared 0.2 Eu 0.2 Gd 0.2 Dy 0.2 Er 0.2 Taking 2Hf2O7 high-entropy ceramic nanofibers as an example, the preparation steps can be as follows:

[0043] ①Prepared by sol-gel method (Sm 0.2 Eu 0.2 Gd 0.2 Dy 0.2 Er 0.2 )2Hf2O7 high-entropy ceramic dispersion: samarium acetate, europium acetate, gadolinium acetate, dysprosium acetate, erbium acetate, and hafnium chloride are used as raw materials, and an aqueous acetic acid solution is used as the solvent; according to (Sm 0.2 Eu 0.2 Gd 0.2 Dy 0.2 Er 0.2 The molar ratio of each element in 2Hf₂O₇ was determined by adding the raw material to an aqueous acetic acid solution (acetic acid to water mass ratio of 1:1) and stirring for 0.5 h to obtain (Sm 0.2 Eu 0.2 Gd 0.2 Dy 0.2 Er 0.2 The high-entropy ceramic dispersion of 2Hf2O7 makes (Sm 0.2 Eu 0.2 Gd 0.2 Dy 0.2 Er 0.2 The solid content (concentration) of the 2Hf2O7 high-entropy ceramic dispersion is 15wt%.

[0044] ② Add polyethylene oxide to the (Sm) obtained in step ① 0.2 Eu 0.2 Gd 0.2 Dy 0.2 Er 0.2In a high-entropy ceramic dispersion of 2Hf2O7, the mixture is stirred evenly to prepare a spinning solution, such that the spinning solution contains 2% polyethylene oxide by mass.

[0045] ③ The prepared spinning solution is drawn into the syringe of the electrospinning equipment. The electrospinning parameters are set as follows: voltage 20kV, injection speed 0.4mm / min, and distance 15cm. After setting the parameters, the spinning solution is electrospun, then dried in a 70℃ forced-air drying oven for 12 hours. Following this, it is calcined at 1200℃ in air atmosphere for 2 hours to obtain (Sm... 0.2 Eu 0.2 Gd 0.2 Dy 0.2 Er 0.2 )2Hf2O7 high-entropy ceramic nanofibers.

[0046] In a second aspect, the present invention provides a multidimensionally assembled nano-thermal insulating material prepared by the preparation method described in the first aspect of the present invention.

[0047] The present invention will be further described below by way of examples, but the scope of protection of the present invention is not limited to these embodiments.

[0048] Example 1

[0049] (1) Alumina nanofibers with an aspect ratio of 200:1, magnesium aluminum spinel nanopowder with a particle size of 20 nm, and silicon carbide nanopowder with a particle size of 50 nm are placed in water and stirred to disperse them to obtain a dispersion slurry; wherein, the mass ratio of alumina nanofibers to magnesium aluminum spinel nanopowders is 9:1, and the mass of silicon carbide nanopowders is 5% of the sum of the masses of alumina nanofibers and magnesium aluminum spinel nanopowders; the total mass percentage of alumina nanofibers and magnesium aluminum spinel nanopowders in the dispersion slurry is 10%.

[0050] (2) Add calcium aluminate cement to the dispersion slurry obtained in step (1), stir and disperse evenly, and then age at 90°C for 48 hours to obtain wet gel; in step (2), the mass amount of calcium aluminate cement is 5% of the mass amount of alumina nanofibers in step (1).

[0051] (3) The wet gel obtained in step (2) is placed in a cyclohexane / ethanol mixed solvent (the volume ratio of cyclohexane to ethanol is 1:2) for solvent replacement 3 times, and the solvent replacement time is 24h each time. Then it is sent to a supercritical drying kettle for supercritical carbon dioxide drying for 48h to prepare a multidimensional assembled nano heat insulation material.

[0052] Example 2

[0053] (1) Alumina nanofibers with an aspect ratio of 1000:1, magnesium aluminum spinel nanopowder with a particle size of 200 nm, and silicon carbide nanopowder with a particle size of 50 nm are placed in water and stirred and dispersed to obtain a dispersion slurry; wherein, the mass ratio of alumina nanofibers to magnesium aluminum spinel nanopowders is 1:1, and the mass of silicon carbide nanopowders is 5% of the sum of the masses of alumina nanofibers and magnesium aluminum spinel nanopowders; the dispersion slurry contains a total mass percentage of 20% alumina nanofibers and magnesium aluminum spinel nanopowders.

[0054] (2) Add calcium aluminate cement to the dispersion slurry obtained in step (1), stir and disperse evenly, and then age at 60°C for 24 hours to obtain wet gel; in step (2), the mass amount of calcium aluminate cement is 15% of the mass amount of alumina nanofibers in step (1).

[0055] (3) The wet gel obtained in step (2) was placed in a cyclohexane / ethanol mixed solvent (the volume ratio of cyclohexane to ethanol was 1:2) for solvent replacement 5 times, and the solvent replacement time was 24h each time. Then it was sent to a supercritical drying kettle for supercritical carbon dioxide drying for 72h to prepare a multidimensional assembled nano-thermal insulation material.

[0056] Example 3

[0057] (1) Zirconia nanofibers with an aspect ratio of 2000:1, magnesium aluminum spinel nanopowder with a particle size of 50 nm, and silicon carbide nanopowder with a particle size of 50 nm are placed in water and stirred and dispersed to obtain a dispersion slurry; wherein, the mass ratio of zirconia nanofibers to magnesium aluminum spinel nanopowder is 4:1, and the mass of silicon carbide nanopowder is 5% of the sum of the masses of zirconia nanofibers and magnesium aluminum spinel nanopowder; the total mass percentage of zirconia nanofibers and magnesium aluminum spinel nanopowder in the dispersion slurry is 15%.

[0058] (2) Add zirconium oxide-calcium phosphate composite sol gelling agent to the dispersion slurry obtained in step (1), stir and disperse evenly, and then age at 80°C for 48 hours to obtain wet gel; in step (2), the mass amount of zirconium oxide-calcium phosphate composite sol gelling agent is 20% of the mass amount of zirconium oxide nanofibers in step (1).

[0059] (3) The wet gel obtained in step (2) was placed in a cyclohexane / ethanol mixed solvent (the volume ratio of cyclohexane to ethanol was 1:2) for solvent replacement 4 times, and the solvent replacement time was 24h each time. Then it was sent to a supercritical drying kettle for supercritical carbon dioxide drying for 96h to prepare a multidimensional assembled nano heat insulation material.

[0060] Example 4

[0061] (1) Zirconium silicate nanofibers with an aspect ratio of 2000:1, magnesium aluminum spinel nanopowder with a particle size of 50 nm, and silicon carbide nanopowder with a particle size of 50 nm are placed in water and stirred and dispersed to obtain a dispersion slurry; wherein, the mass ratio of zirconium silicate nanofibers to magnesium aluminum spinel nanopowder is 4:1, and the mass of silicon carbide nanopowder is 5% of the sum of the masses of zirconium silicate nanofibers and magnesium aluminum spinel nanopowder; the dispersion slurry contains a total mass percentage of zirconium silicate nanofibers and magnesium aluminum spinel nanopowder of 15%.

[0062] (2) Add calcium aluminosilicate cement to the dispersion slurry obtained in step (1), stir and disperse, and then age at 80°C for 48 hours to obtain wet gel; in step (2), the mass amount of calcium aluminosilicate cement is 20% of the mass amount of zirconium silicate nanofibers in step (1).

[0063] (3) The wet gel obtained in step (2) was placed in a cyclohexane / ethanol mixed solvent (the volume ratio of cyclohexane to ethanol is 1:2) for solvent replacement 4 times, and the solvent replacement time was 24h each time. Then it was sent to a supercritical drying kettle for supercritical carbon dioxide drying for 96h to prepare a multidimensional assembled nano heat insulation material.

[0064] Example 5

[0065] (1) Mullite nanofibers with an aspect ratio of 2000:1, magnesium aluminum spinel nanopowder with a particle size of 50 nm, and silicon carbide nanopowder with a particle size of 50 nm are placed in water and stirred and dispersed to obtain a dispersion slurry; wherein, the mass ratio of mullite nanofibers to magnesium aluminum spinel nanopowders is 4:1, and the mass of silicon carbide nanopowders is 5% of the sum of the masses of mullite nanofibers and magnesium aluminum spinel nanopowders; the total mass percentage of mullite nanofibers and magnesium aluminum spinel nanopowders in the dispersion slurry is 15%.

[0066] (2) Add calcium aluminate cement to the dispersion slurry obtained in step (1), stir and disperse evenly, and then age at 80°C for 48 hours to obtain wet gel; in step (2), the mass amount of calcium aluminate cement is 20% of the mass amount of mullite nanofiber in step (1).

[0067] (3) The wet gel obtained in step (2) was placed in a cyclohexane / ethanol mixed solvent (the volume ratio of cyclohexane to ethanol was 1:2) for solvent replacement 4 times, and the solvent replacement time was 24h each time. Then it was sent to a supercritical drying kettle for supercritical carbon dioxide drying for 96h to prepare a multidimensional assembled nano heat insulation material.

[0068] Example 6

[0069] (1) Magnesium aluminum spinel nanofibers with an aspect ratio of 2000:1, magnesium aluminum spinel nanopowder with a particle size of 50 nm, and silicon carbide nanoparticles with a particle size of 50 nm are placed in water and stirred and dispersed to obtain a dispersion slurry; wherein, the mass ratio of magnesium aluminum spinel nanofibers to magnesium aluminum spinel nanopowders is 4:1, and the mass of silicon carbide is 5% of the sum of the masses of magnesium aluminum spinel nanofibers and magnesium aluminum spinel nanopowders; the total mass percentage of magnesium aluminum spinel nanofibers and magnesium aluminum spinel nanopowders in the dispersion slurry is 15%.

[0070] (2) Add calcium aluminate cement to the dispersion slurry obtained in step (1), stir and disperse, and then age at 80°C for 48 hours to obtain wet gel; in step (2), the mass amount of calcium aluminate cement is 20% of the mass amount of magnesium aluminum spinel nanofiber in step (1).

[0071] (3) The wet gel obtained in step (2) was placed in a cyclohexane / ethanol mixed solvent (the volume ratio of cyclohexane to ethanol was 1:2) for solvent replacement 4 times, and the solvent replacement time was 24h each time. Then it was sent to a supercritical drying kettle for supercritical carbon dioxide drying for 96h to prepare a multidimensional assembled nano heat insulation material.

[0072] Example 7

[0073] Example 7 is basically the same as Example 5, except that:

[0074] (1) Mullite nanofibers with an aspect ratio of 2000:1 and (La) nanofibers with an aspect ratio of 80:1 were combined. 0.2 Sr 0.2 Ce 0.2 Er 0.2 Yb 0.2 )2Zr2O7 high-entropy ceramic nanofibers, magnesium aluminum spinel nanopowder with a particle size of 50nm, and nano-silicon carbide with a particle size of 50nm were placed in water and stirred to disperse them, obtaining a dispersion slurry; wherein, the mass ratio of mullite nanofibers to magnesium aluminum spinel nanopowder was 4:1, (La 0.2 Sr 0.2 Ce 0.2 Er 0.2 Yb 0.2 The mass ratio of 2Zr2O7 high-entropy ceramic nanofibers to magnesium aluminum spinel nanopowder is 1:1.5, and the mass of nano-silicon carbide is 5% of the sum of the mass of mullite nanofibers (high aspect ratio nanofibers) and magnesium aluminum spinel nanopowder; the dispersion slurry contains mullite nanofibers, (La... 0.2 Sr 0.2 Ce 0.2 Er 0.2 Yb 0.2The sum of the mass percentages of Zr2O7 high-entropy ceramic nanofibers and magnesium aluminum spinel nanopowder is 15%.

[0075] Example 8

[0076] Example 8 is basically the same as Example 5, except that:

[0077] (1) Mullite nanofibers with an aspect ratio of 2000:1 and (Sm) nanofibers with an aspect ratio of 80:1 are combined. 0.2 Eu 0.2 Gd 0.2 Dy 0.2 Er 0.2 High-entropy ceramic nanofibers (2Hf₂O₇), magnesium aluminum spinel nanopowder with a particle size of 50 nm, and nano-silicon carbide with a particle size of 50 nm were placed in water and stirred to disperse them, obtaining a dispersion slurry; wherein the mass ratio of mullite nanofibers to magnesium aluminum spinel nanopowder was 4:1, (Sm 0.2 Eu 0.2 Gd 0.2 Dy 0.2 Er 0.2 The mass ratio of high-entropy ceramic nanofibers (Hf₂O₇) to magnesium aluminum spinel nanopowder is 1:1.5, and the mass of nano-silicon carbide is 5% of the sum of the masses of mullite nanofibers (high aspect ratio nanofibers) and magnesium aluminum spinel nanopowder; the dispersion slurry contains mullite nanofibers, (Sm 0.2 Eu 0.2 Gd 0.2 Dy 0.2 Er 0.2 The sum of the mass percentages of 2Hf2O7 high-entropy ceramic nanofibers and magnesium aluminum spinel nanopowder is 15%.

[0078] Example 9

[0079] Example 9 is basically the same as Example 5, except that:

[0080] (3) The wet gel obtained in step (2) was placed in ethanol for solvent replacement 4 times, with each solvent replacement lasting 24 hours. Then it was sent to a supercritical drying kettle for supercritical carbon dioxide drying for 96 hours to prepare a multidimensional assembled nano-insulating material.

[0081] Comparative Example 1

[0082] Comparative Example 1 is basically the same as Example 5, except that:

[0083] (1) Mullite nanofibers with an aspect ratio of 50:1, magnesium aluminum spinel nanopowder with a particle size of 50 nm and silicon carbide nanopowder with a particle size of 50 nm are placed in water and stirred and dispersed to obtain a dispersion slurry; wherein, the mass ratio of mullite nanofibers to magnesium aluminum spinel nanopowders is 4:1, the mass of silicon carbide nanopowders is 5% of the sum of the mass of mullite nanofibers and magnesium aluminum spinel nanopowders, and the mass percentage of mullite nanofibers and magnesium aluminum spinel nanopowders in the dispersion slurry is 15%.

[0084] The mullite nanofibers used in this comparative example have too small an aspect ratio, making it difficult to form a skeleton structure during the preparation process and thus failing to obtain nano-insulating materials.

[0085] Comparative Example 2

[0086] (1) Mullite nanofibers with an aspect ratio of 20000:1, magnesium aluminum spinel nanopowder with a particle size of 50 nm, and silicon carbide nanopowder with a particle size of 50 nm are placed in water and stirred and dispersed to obtain a dispersion slurry; wherein, the mass ratio of mullite nanofibers to magnesium aluminum spinel nanopowders is 4:1, and the mass of silicon carbide nanopowders is 5% of the sum of the masses of mullite nanofibers and magnesium aluminum spinel nanopowders; the total mass percentage of mullite nanofibers and magnesium aluminum spinel nanopowders in the dispersion slurry is 15%.

[0087] (2) Add calcium aluminate cement to the dispersion slurry obtained in step (1), stir and disperse evenly, and then age at 80°C for 48 hours to obtain wet gel; in step (2), the mass amount of calcium aluminate cement is 20% of the mass amount of mullite nanofiber in step (1).

[0088] (3) The wet gel obtained in step (2) was placed in a cyclohexane / ethanol mixed solvent (the volume ratio of cyclohexane to ethanol was 1:2) for solvent replacement 4 times, and the solvent replacement time was 24h each time. Then it was sent to a supercritical drying kettle for supercritical carbon dioxide drying for 96h to obtain nano heat insulation material.

[0089] Comparative Example 3

[0090] (1) Mullite nanofibers with an aspect ratio of 2000:1, magnesium aluminum spinel nanopowder with a particle size of 50 nm, and silicon carbide nanoparticles with a particle size of 50 nm are placed in water and stirred and dispersed to obtain a dispersion slurry; wherein, the mass ratio of mullite nanofibers to magnesium aluminum spinel nanopowders is 4:1, and the mass of silicon carbide is 5% of the sum of the masses of mullite nanofibers and magnesium aluminum spinel nanopowders; the mass percentage of mullite nanofibers and magnesium aluminum spinel nanopowders in the dispersion slurry is 15%.

[0091] (2) Add calcium aluminate cement to the dispersion slurry obtained in step (1), stir and disperse evenly, and then age at 80°C for 48 hours to obtain wet gel; in step (2), the mass amount of calcium aluminate cement is 41.67% of the mass amount of mullite nanofiber in step (1).

[0092] (3) The wet gel obtained in step (2) was placed in a cyclohexane / ethanol mixed solvent (the volume ratio of cyclohexane to ethanol was 1:2) for solvent replacement 4 times, and the solvent replacement time was 24h each time. Then it was sent to a supercritical drying kettle for supercritical carbon dioxide drying for 96h to obtain nano heat insulation material.

[0093] Comparative Example 4

[0094] (1) Mullite nanofibers with an aspect ratio of 2000:1, magnesium aluminum spinel powder with a particle size of 5 μm, and nano-silicon carbide with a particle size of 50 nm are placed in water and stirred and dispersed to obtain a dispersion slurry; wherein, the mass ratio of mullite nanofibers to magnesium aluminum spinel powder is 4:1, and the mass of nano-silicon carbide is 5% of the sum of the mass of mullite nanofibers and magnesium aluminum spinel powder; the mass percentage of mullite nanofibers and magnesium aluminum spinel powder in the dispersion slurry is 15%.

[0095] (2) Add calcium aluminate cement to the dispersion slurry obtained in step (1), stir and disperse evenly, and then age at 80°C for 48 hours to obtain wet gel; in step (2), the mass amount of calcium aluminate cement is 20% of the mass amount of mullite nanofiber in step (1).

[0096] (3) The wet gel obtained in step (2) was placed in a cyclohexane / ethanol mixed solvent (the volume ratio of cyclohexane to ethanol was 1:2) for solvent replacement 4 times, and the solvent replacement time was 24h each time. Then it was sent to a supercritical drying kettle for supercritical carbon dioxide drying for 96h to obtain nano heat insulation material.

[0097] Comparative Example 5

[0098] (1) Mullite nanofibers with an aspect ratio of 2000:1 and nano-silicon carbide with a particle size of 50 nm are placed in water and stirred and dispersed to obtain a dispersion slurry; wherein, the mass of nano-silicon carbide is 5% of the mass of mullite nanofibers, and the mass percentage of mullite nanofibers in the dispersion slurry is 15%.

[0099] (2) Add calcium aluminate cement to the dispersion slurry obtained in step (1), stir and disperse evenly, and then age at 80°C for 48 hours to obtain wet gel; in step (2), the mass amount of calcium aluminate cement is 20% of the mass amount of mullite nanofiber in step (1).

[0100] (3) The wet gel obtained in step (2) was placed in a cyclohexane / ethanol mixed solvent (the volume ratio of cyclohexane to ethanol was 1:2) for solvent replacement 4 times, and the solvent replacement time was 24h each time. Then it was sent to a supercritical drying kettle for supercritical carbon dioxide drying for 96h to obtain nano heat insulation material.

[0101] Comparative Example 6

[0102] Comparative Example 6 is basically the same as Example 5, except that:

[0103] (2) Add silica sol (the solid content of silica sol is 30wt%) and polyethylene oxide (PEO) to the dispersion slurry obtained in step (1), stir and disperse to obtain a mixture; wherein, the mass of silica sol is 10% of the mass of mullite nanofibers in step (1), and the mass of polyethylene oxide is 2% of the mass of mullite nanofibers in step (1).

[0104] (3) The mixture was rapidly frozen with liquid nitrogen for 30 min, and then freeze-dried at -10℃ for 72 h and calcined at 600℃ for 2 h to obtain nano-insulation material.

[0105] Comparative Example 7

[0106] Comparative Example 7 is basically the same as Example 5, except that:

[0107] (2) Add aluminum dihydrogen phosphate aqueous solution (the solid content of aluminum dihydrogen phosphate aqueous solution is 40wt%) and polyethylene oxide (PEO) to the dispersion slurry obtained in step (1), stir and disperse to obtain a mixture; wherein, the mass of aluminum dihydrogen phosphate aqueous solution is 10% of the mass of mullite nanofibers in step (1), and the mass of polyethylene oxide is 2% of the mass of mullite nanofibers in step (1).

[0108] (3) The mixture was rapidly frozen with liquid nitrogen for 30 min, and then freeze-dried at -10℃ for 72 h and calcined at 600℃ for 2 h to obtain nano-insulation material.

[0109] The thermal conductivity and compressive strength at 10% deformation of the materials prepared in each embodiment and comparative example of the present invention were measured, and the results are shown in Table 1. As can be seen from Table 1, the materials prepared in the preferred embodiments of the present invention have low thermal conductivity and high compressive strength at high temperatures.

[0110] Table 1

[0111]

[0112]

[0113] In Table 1, the symbol "-" indicates that the performance metric does not exist.

[0114] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a multidimensionally assembled nanomaterial for thermal insulation, characterized in that, The method includes the following steps: (1) High aspect ratio nanofibers, magnesium aluminum spinel nanopowder and nano silicon carbide are uniformly dispersed in water to obtain a dispersion slurry; the aspect ratio of the nanofibers is (200~10000):1; the particle size of the magnesium aluminum spinel nanopowder is 20nm~200nm; the particle size of the nano silicon carbide is 50~100nm; the nanofibers are one or more of zirconium oxide nanofibers, magnesium aluminum spinel nanofibers, zirconium silicate nanofibers, mullite nanofibers and alumina nanofibers; in step (1), rare earth high entropy ceramic nanofibers are also added, and the mass ratio of the rare earth high entropy ceramic nanofibers to the magnesium aluminum spinel nanopowder is 1:(1~2); (2) Add a high-temperature binder to the dispersion slurry and disperse it evenly, then age it to obtain a wet gel; the high-temperature binder is one or more of calcium aluminate cement gelling agent, zirconia-calcium phosphate composite sol gelling agent and calcium aluminosilicate cement gelling agent; the mass amount of the high-temperature binder in step (2) is 5~20% of the mass amount of the nanofibers in step (1); (3) The wet gel is subjected to solvent replacement and supercritical drying in sequence to prepare a multidimensional assembled nano-thermal insulation material; the solvent replacement is a cyclohexane / ethanol mixed solvent, which is a mixture of cyclohexane and ethanol in a volume ratio of 1: (1~3).

2. The preparation method according to claim 1, characterized in that: The mass ratio of the nanofibers to the magnesium aluminum spinel nanopowder is (1~9):1; and / or The mass of the nano-silicon carbide is 4 to 8% of the sum of the mass of the nanofibers and the magnesium aluminum spinel nanopowder.

3. The preparation method according to claim 1, characterized in that: The dispersion slurry contains 10-20% by mass of nanofibers and magnesium aluminum spinel nanopowder.

4. The preparation method according to claim 1, characterized in that: The aging temperature is 60℃~90℃, and the aging time is 12h~48h.

5. The preparation method according to claim 1, characterized in that: The number of solvent replacements is 3 to 5 times; and / or The supercritical drying time is 48~96 hours.

6. The preparation method according to claim 1, characterized in that: The rare earth high-entropy ceramic nanofibers are rare earth zirconate high-entropy ceramic nanofibers A2Zr2O7 and / or rare earth hafnium salt high-entropy ceramic nanofibers B2Hf2O7. A is any five rare earth elements selected from La, Sr, Ce, Er, Y, and Yb, and the sum of the atomic molar percentages of each rare earth element is 100%, and the atomic molar percentages of each rare earth element are equal, or the difference in atomic molar percentages does not exceed 1-3%. B is any five of the rare earth elements Nd, Sm, Eu, Gd, Dy and Er, and the sum of the atomic molar percentages of each rare earth element is 100%, and the atomic molar percentages of each rare earth element are equal, or the difference in atomic molar percentages does not exceed 1 to 3%.

7. A multidimensionally assembled nano-thermal insulation material prepared by any one of claims 1 to 6.

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