Preparation method of aerogel modified silicon mullite brick with high strength and low heat-conducting property

Abstract

The invention belongs to the technical field of refractory materials, and particularly discloses a preparation method of an aerogel modified silicon mullite brick with high strength and low heat-conducting property. Comprising 5-15 parts of silicon carbide particles, 50-70 parts of bauxite A, 19-29 parts of bauxite B, 5-10 parts of bauxite fine powder, 1-2 parts of unmodified aerogel powder, 1 part of a solvent and 3-6 parts of alcohol. The preparation method comprises the following steps: 1, mechanically stirring and mixing silicon carbide particles, bauxite A, bauxite B, bauxite fine powder and a solvent to obtain a mixed raw material; 2, adding the aerogel powder into the mixed raw material, and continuously stirring and mixing to form aggregate; step 3, processing the aggregate through a brick press to obtain a green brick; and 4, placing the green brick in a tunnel kiln, carrying out gradient heating sintering, and discharging the green brick out of the kiln to obtain the aerogel modified silicon mullite brick. The refractory material has low heat conductivity, high strength and good fire resistance, and has remarkable economic benefits and environmental protection values.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of refractory materials, and particularly relates to a preparation method of aerogel modified silica-mullite bricks with high strength and low thermal conductivity. BACKGROUND

[0002] Refractory bricks are usually used in high-temperature environments, such as industrial kiln fields (metallurgy, cement, ceramics, glass, building, etc.), and the main performance requirements include high-temperature resistance, corrosion resistance, heat insulation, etc. However, traditional refractory bricks mainly focus on the strength and the needs of the environment on the brick body, and ignore the influence of heat insulation on energy consumption, environmental protection and CO2 emission. According to the improvement of various demands and technical standards in recent years, the product with low thermal conductivity, high thermal shock resistance and high strength becomes the focus of research and development.

[0003] The existing research results are more methods of using a "sandwich" structure (such as a working layer / pouring layer / heat insulation layer) to construct a new type of refractory brick (such as the technical solution disclosed in patent No. CN202111329008.9), and to realize the synergy of high strength and low thermal conductivity through interface optimization. However, in complex working conditions, there is a potential risk of collapse at the interface due to the difference in material properties. Although some technologies have made preliminary attempts on low-thermal-conductivity refractory bricks (such as the technical solutions disclosed in patent Nos. CN202121981927.X and CN202010257526.3), they all sacrifice strength, wear resistance or quality to achieve low thermal conductivity of refractory products through porosity or lightness, which has great safety hazards in industrial kilns, especially large-scale metallurgical and cement kilns. Therefore, how to balance the strength, thermal shock stability and wear resistance of refractory materials while reducing the thermal conductivity of the products has become a problem that needs to be solved in the refractory materials industry.

[0004] Aerogel, as the most potential full-pore new material, has ultra-low thermal conductivity due to its light weight, high specific surface area and small pore size, which can effectively reduce heat loss. However, the existing aerogel material has a heat-resistant temperature of only 650℃, which cannot meet the application scenarios of high-temperature heat insulation. In addition, in the sintering process of refractory materials, the performance of conventional aerogel materials may be affected by high temperature, especially the collapse of its nanostructure, which affects its heat insulation and mechanical properties. In addition, under high temperature, different materials of aerogel may also have chemical or physical reactions with other substances in the refractory material. Therefore, the technology of using aerogel to enhance the heat insulation performance of refractory materials is not mature, and there are defects that the heat insulation performance and the strength of the refractory material do not meet the expectations. SUMMARY

[0005] The application aims to provide aerogel modified silicon-mullite bricks with high strength and low thermal conductivity, so as to solve the technical problems of the prior art that the thermal insulation performance of refractory materials is strengthened by aerogel, but there are still deficiencies in the thermal insulation performance and material strength.

[0006] The preparation method of the aerogel modified silicon-mullite brick with high strength and low thermal conductivity, wherein the aerogel modified silicon-mullite brick comprises, in terms of weight parts, 5-15 parts of silicon carbide particles, 50-70 parts of bauxite A, 19-29 parts of bauxite B, 5-10 parts of bauxite fine powder, 1-2 parts of unmodified aerogel powder, 1 part of solvent and 3-6 parts of alcohol; wherein the particle size range of the bauxite A is 3-5 mm, the particle size range of the bauxite B is 1-3 mm, the particle size range of the bauxite fine powder is 0-0.5 mm, the aerogel powder is silica aerogel powder, and the solvent is anhydrous ethanol; the preparation method comprises the following steps:

[0007] Step one, the silicon carbide particles, the bauxite A, the bauxite B, the bauxite fine powder and the solvent are mixed by mechanical stirring until color uniformity is achieved, to obtain mixed raw materials;

[0008] Step two, the aerogel powder is added to the mixed raw materials and continues to be stirred and mixed until color uniformity is achieved, and the mixing state presents a "porridge-like" state, to form aggregates;

[0009] Step three, the aggregates are processed by a brick press to obtain green bricks;

[0010] Step four, the green bricks are placed in a tunnel kiln, gradient temperature sintering is performed, and the aerogel modified silicon-mullite bricks are obtained after being taken out of the kiln.

[0011] Preferably, the porosity of the silica aerogel powder is > 90%, the bulk density is 60-120 kg / m 3 , the pore size is 1-15 nm, and the thermal conductivity is 0.017-0.023 W / (m.K).

[0012] Preferably, the aerogel modified silicon-mullite brick further comprises modified aerogel powder, the addition amount of the modified aerogel powder is 0.5-1 parts by weight, and the modified aerogel powder is obtained by modifying the silica aerogel powder with a silane coupling agent and an aluminum nitrate solution.

[0013] Preferably, the bauxite A, the bauxite B and the bauxite fine powder all adopt the same type of bauxite, the mass percentage of Al2O3 is 80-85%, the mass percentage of Fe2O3 is 1-2%, and the volume density of the bauxite is 2.9 g / cm3; in the silicon carbide particles, the mass percentage of SiC is 92-96%, and the particle size is ≤0.074 mm.

[0014] Preferably, only using unmodified aerogel powder, step two gradually adds unmodified aerogel powder to the mixed raw materials, sprays alcohol during mixing, and mixes until the color is uniform to form the aggregate.

[0015] Preferably, only using unmodified aerogel powder, step two treats the unmodified aerogel powder with alcohol, weighs a certain amount of unmodified aerogel powder in a container, weighs a certain amount of alcohol, adds alcohol while stirring the aerogel powder, uses intermittent spraying, stirs the aerogel powder material until it is uniform, thereby obtaining a mixture containing aerogel powder; then, the mixture containing aerogel powder is added to the mixed raw materials, alcohol is sprayed during mixing, and mixing is performed until the color is uniform to form the aggregate.

[0016] Preferably, step two mixes the unmodified aerogel powder and the modified aerogel powder together by stirring and sprays alcohol during stirring until the color is uniform to form a mixture containing aerogel powder; larger agglomerates are removed by hand kneading during mixing; then, the mixture containing aerogel powder is added to the mixed raw materials, alcohol is sprayed during mixing, and mixing is performed until the color is uniform to form the aggregate.

[0017] Preferably, the modified aerogel powder is prepared by the following method: preparing 2%-5% silane coupling agent, adding the above-mentioned silane coupling agent to the aerogel solution, stirring for 20-40 minutes; after homogenization, adding aluminum nitrate solution for treatment, stirring for 30 minutes, adding the treated modified mixed solution to the gelling agent to promote the transition of the solution to the gel, placing the gel in a drying device after 24 hours to dry into powder, and finally placing it in a 500℃ muffle furnace to obtain the modified aerogel powder.

[0018] Preferably, in step four, the sintering temperature reaches 1000-1400℃.

[0019] The present application has the following advantages:

[0020] 1. The present application uses silica as the aerogel material, and the nanoporous structure of the aerogel matrix material is SiO2, which is consistent with part of the main components of silica mullite bricks. During the sintering process, part of the aerogel is sintered with bauxite to form mullite phase. The structure size of the aerogel powder (~ 30 nm) is small, which can be embedded in the mineral crystal gap of the refractory brick matrix to form a "physical anchoring" effect, and an interfacial reinforcement layer is formed during the sintering process, as shown in the figure. Figure 1 The present application enhances the mechanical stability of "aerogel bricks" through an interlocking network composite structure, solving the defect of large loss of mechanical properties of traditional low thermal conductivity refractory bricks.

[0021] 2. Refractory bricks generally have a macroporous structure with a porosity of approximately 15-18% (taking silica-mullite bricks as an example), while aerogel materials have a pearl-chain-like nanoporous structure with closed pores and a porosity of over 99%, effectively suppressing thermal convection of air molecules. Therefore, this invention utilizes aerogel adhesion and a surface-modified protective layer to retain the aerogel framework and nanoporous structure, forming a gradient pore distribution with the macropores of the refractory brick, creating a "heat flow barrier" and improving the low thermal conductivity of the "aerogel brick." This invention provides a novel energy-saving material for high-temperature industrial kilns that combines low thermal conductivity, high strength, and good refractory performance, reducing heat loss by more than 20%, and has significant economic and environmental benefits.

[0022] 3. During sintering, a high-temperature resistant ceramic transition layer is formed on the surface of the partially modified aerogel. By optimizing the sintering regime (gradual heating from 1000 to 1400℃) and synergistically combining it with aerogel surface modification technology, the problem of performance degradation caused by nanostructure collapse in traditional aerogels at high temperatures (>800℃) is solved. Furthermore, during high-temperature sintering, the aerogel forms a stable phase with Al2O3 in bauxite, thus preventing crystal transformation and significantly enhancing high-temperature stability. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the interlocking network composite structure formed by the preparation method of aerogel-modified silica-mullite brick with high strength and low thermal conductivity according to the present invention.

[0024] Figure 2 This is a comparison image of the aerogel-modified silica-mullite brick obtained in Example 1 of the present invention and a sample of a standard refractory brick in the prior art. The integrated composite brick is the aerogel-modified silica-mullite brick obtained in Example 1.

[0025] Figure 3 The graph shows the temperature of the outer surface of the brick under an internal furnace temperature of 1100℃ during the experimental test of this invention, which lasted for 3 hours. Detailed Implementation

[0026] The following description of the embodiments will provide a more detailed explanation of the specific implementation of the present invention, in order to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention.

[0027] like Figure 1As shown, this invention provides a method for preparing aerogel-modified silica-molybdenum bricks with both high strength and low thermal conductivity. The aerogel-modified silica-molybdenum bricks, by weight, comprise: 5-15 parts silicon carbide particles, 50-70 parts bauxite A, 19-29 parts bauxite B, 5-10 parts fine bauxite powder, 1-2 parts unmodified aerogel powder, 1 part solvent, and 3-6 parts alcohol for mixing. The particle size ranges as follows: bauxite A is 3-5 mm, bauxite B is 1-3 mm, fine bauxite powder is 0-0.5 mm, the solvent is anhydrous ethanol, and the aerogel powder is silica aerogel powder.

[0028] The porosity of silica aerogel powder is >90%, and the bulk density is 60-120 kg / m³. 3 The pore size is 1–15 nm, and the thermal conductivity is 0.017–0.023 W / (mK).

[0029] The aerogel-modified silica brick also includes modified aerogel powder, which is added in an amount of 0.5-1 parts by weight. The modified aerogel powder is obtained by modifying silica aerogel powder with silane coupling agent and aluminum nitrate solution.

[0030] Bauxite A, Bauxite B, and fine bauxite powder all use the same type of bauxite, with Al2O3 accounting for 80-85% of the mass and Fe2O3 accounting for 1-2% of the mass. The bulk density of the bauxite is 2.9 g / cm3. In the silicon carbide particles, SiC accounts for 92-96% of the mass, and the particle size is ≤0.074 mm.

[0031] The preparation method of the above-mentioned aerogel-modified silica-mullite bricks includes the following steps.

[0032] Step 1: Mix silicon carbide particles, bauxite A, bauxite B, bauxite powder and solvent by mechanical stirring until the color is uniform, and obtain mixed raw materials.

[0033] Step 2: Add the aerogel powder to the mixed raw materials and continue stirring until the color is uniform and the mixture has a "porridge-like" consistency, forming aggregate.

[0034] When the present invention uses only unmodified aerogel powder, this step can be to gradually add the unmodified aerogel powder to the mixed raw materials, spray alcohol with a spray bottle during the mixing process, and mix until the color is uniform and aggregate is formed.

[0035] The mixture containing the aerogel powder can also be prepared first: a certain amount of unmodified aerogel powder is weighed in a container (such as a beaker or a sealed stirrer), and a certain amount of alcohol is weighed, and the alcohol is added while stirring the aerogel powder, which can be added in the form of intermittent spraying, and the aerogel powder is stirred until uniform. Thus, a mixture containing the aerogel powder is obtained. Then, the mixture containing the aerogel powder is added to the mixed raw materials, and alcohol is sprayed (using a spray bottle) during the mixing process, and the mixture is mixed until the color is uniform to form the aggregate, and the state of the mixture presents a "porridge-like" state.

[0036] When the modified aerogel powder is used in the present application, the unmodified aerogel powder and the modified aerogel powder can be mixed together by stirring, and alcohol is sprayed during the stirring process until a mixture containing the aerogel powder is formed. During the mixing process, larger agglomerates are removed by hand kneading. Then, the mixture containing the aerogel powder is added to the mixed raw materials, and alcohol is sprayed (using a spray bottle) during the mixing process, and the mixture is mixed until the color is uniform to form the aggregate, and the state of the mixture presents a "porridge-like" state.

[0037] The modified aerogel powder is prepared by the following method: 2%-5% of a silane coupling agent (such as methyltrimethoxysilane) is prepared, the silane coupling agent is added dropwise into the aerogel solution, and stirred for 20-40 minutes; after homogenization, an aluminum nitrate solution is added for treatment, and stirred for 30 minutes; the modified mixture solution after complete treatment is added to a gelling agent to promote the conversion of the solution to a gel, and the gel is placed in a drying device after 24 hours to dry into a powder, and finally placed in a 500℃ muffle furnace for calcination to obtain the modified aerogel powder.

[0038] The above several methods consume all the alcohol in the components of the aerogel modified silica brick when the aggregate is prepared.

[0039] Step three, the aggregate is processed through a brick press to obtain a green brick.

[0040] In this step, the aggregate is pressed and formed by a brick press, and then demolded and pre-dried to remove the water from the brick body, to obtain a green brick.

[0041] Step four, the green brick is placed in a tunnel kiln, and sintered at a gradient temperature of 1000-1400℃ to obtain the aerogel modified silica brick.

[0042] The key innovation of the present application is to improve the interfacial bonding force of the surface modified aerogel with the refractory matrix, and to optimize the sintering system to avoid the collapse of the aerogel nanostructure at high temperature. The refractory brick prepared by the scheme has a thermal conductivity of 0.8-1.2 W / (m.K) (more than 40% lower than that of traditional refractory bricks), while maintaining an excellent mechanical property of compressive strength > 80 MPa.

[0043] The specific implementation of the present application is as follows:

[0044] Example 1:

[0045] The aerogel modified silicon-mullite brick includes, by weight fraction, 5 parts of silicon carbide particles, 60 parts of bauxite A, 22 parts of bauxite B, 7 parts of bauxite fine powder, 1 part of unmodified aerogel powder, 1 part of modified aerogel powder, 1 part of solvent, and 3 parts of alcohol.

[0046] The particle size range of the bauxite A is 3-5 mm, the particle size range of the bauxite B is 1-3 mm, the particle size range of the bauxite fine powder is 0-0.5 mm, the solvent is anhydrous ethanol, and the aerogel powder is a silica aerogel powder. The porosity of the silica aerogel powder is >90%, the bulk density is 60-120 kg / m 3 , the pore size is ~ 15 nm, and the thermal conductivity is 0.017-0.023 W / (m.K).

[0047] The bauxite A, the bauxite B, and the bauxite fine powder all use the same type of bauxite, in which the mass percentage of Al2O3 is in the range of 80-85%, the mass percentage of Fe2O3 is in the range of 1-2%, and the volume density of the bauxite is 2.9 g / cm3. In the silicon carbide particles, the mass percentage of SiC is 92-96%, and the particle size is ≤0.074 mm.

[0048] The preparation method of the aerogel modified silicon-mullite brick includes the following steps:

[0049] Step one, the silicon carbide particles, the bauxite A, the bauxite B, the bauxite fine powder, and the solvent are mixed by mechanical stirring until the color is uniform to obtain a mixed raw material.

[0050] Step two, the aerogel powder is added to the mixed raw material and continues to be stirred and mixed until the color is uniform, and the mixed state presents a "porridge-like" state to form the aggregate.

[0051] In a container (such as a beaker or a sealed stirrer), 1 part of unmodified aerogel powder and 1 part of modified aerogel powder are weighed, and 3 parts of alcohol are weighed. The alcohol is added while the two kinds of aerogel powders are being stirred and mixed, and the addition method can be intermittent spraying. The aerogel powder material is stirred until it is uniform. Thus, a mixture containing aerogel powder is obtained. Then, the mixture containing the aerogel powder is added to the mixed raw material, and alcohol is sprayed (using a watering can) during the mixing process. The mixture is mixed until the color is uniform to form the aggregate, and the mixed state presents a "porridge-like" state. The entire mixing process consumes 3 parts of alcohol, and 1 part of unmodified aerogel powder and 1 part of modified aerogel powder are added and mixed in the mixed raw material.

[0052] Step three, the aggregate is processed by the brick press to obtain the green brick. In this step, the aggregate is pressed by the brick press to form, and then is demolded and pre-dried to remove the water of the brick body to obtain the green brick.

[0053] Step four, the green brick is placed in a tunnel kiln, and is sintered at a gradient temperature of 1000-1400°C to obtain the aerogel modified silicon mullite brick.

[0054] Example 2:

[0055] Compared with Example 1, the component ratio and the preparation method of the aerogel modified silicon mullite brick in this example are basically the same as those of Example 1, and the differences are as follows:

[0056] In the aerogel modified silicon mullite brick, the components include, in mass parts, 10 parts of silicon carbide particles, 57 parts of bauxite A, 22 parts of bauxite B, 10 parts of bauxite fine powder, 1.5 parts of unmodified aerogel powder, 0.5 part of modified aerogel powder, and 4.5 parts of alcohol.

[0057] Example 3:

[0058] Compared with Example 1, the component ratio and the preparation method of the aerogel modified silicon mullite brick in this example are basically the same as those of Example 1, and the differences are as follows: 15 parts of silicon carbide particles, 50 parts of bauxite A, 29 parts of bauxite B, 5 parts of bauxite fine powder, 1.3 parts of unmodified aerogel powder, and 0.7 part of modified aerogel powder.

[0059] Example 4:

[0060] Compared with Example 1, the component ratio and the preparation method of the aerogel modified silicon mullite brick in this example are basically the same as those of Example 1, and the differences are as follows: 70 parts of bauxite A, 19 parts of bauxite B, 5 parts of bauxite fine powder, 2 parts of unmodified aerogel powder, 0 part of modified aerogel powder, and 6 parts of alcohol.

[0061] In the container, 2 parts of unmodified aerogel powder is weighed, and alcohol is added while stirring the unmodified aerogel powder to obtain a mixture containing aerogel powder; then, the mixture containing aerogel powder is added to the mixed raw materials, and alcohol is sprayed (using a watering can) during the mixing process until the color is uniform to form the aggregate, and the state of the mixed materials presents a "porridge-like" state. The whole mixing process consumes 6 parts of alcohol, and the mixing of the mixed raw materials and 2 parts of unmodified aerogel powder is completed.

[0062] The mixing process can also gradually add 2 parts of unmodified aerogel powder to the mixed raw materials, and spray alcohol using a watering can during the mixing process until the color is uniform to form the aggregate.

[0063] Comparative Example:

[0064] As the comparative example, the refractory bricks, in mass parts: 10 parts of silicon carbide; 60 parts of bauxite A; 25 parts of bauxite B; and 5 parts of fine powder. The process flow of the refractory bricks includes mixing the raw materials except the aerogel and alcohol to form mixed raw materials, and mechanical stirring is performed during the mixing until the color is uniform and the mixing state presents "porridge-like".

[0065] The various aspects of performance are tested by the experimental examples 1-4 and the comparative example (see Figure 2 and Figure 3 ), and the test performance results are shown in Table 1.

[0066] Table 1: Test results of various aspects of performance of examples 1-4 and the comparative example

[0067]

[0068] From the above table, it can be seen that the aerogel modified silicon-magnesia brick generated by the example has less strength loss compared to the ordinary refractory brick and is far greater than the national standard critical value, the thermal conductivity is reduced by >30%, the actual temperature measurement insulation effect is significant, and the temperature drop is >40℃. Therefore, the aerogel modified silicon-magnesia brick has both mechanical properties and insulation effect, and has great application value in the field of industrial kiln.

[0069] The above has exemplarily described the present application, and it is obvious that the specific implementation of the present application is not limited by the above-mentioned manner, as long as various non-essential improvements are made by using the inventive concept and technical solution of the present application, or the inventive concept and technical solution of the present application is directly applied to other occasions without improvement, all of which are within the protection scope of the present application.

Claims

1. A method for preparing aerogel-modified silica-mullite bricks with both high strength and low thermal conductivity, characterized in that: The aerogel-modified silica-molybdenum brick, by weight, comprises: 5-15 parts silicon carbide particles, 50-70 parts bauxite A, 19-29 parts bauxite B, 5-10 parts fine bauxite powder, 1-2 parts unmodified aerogel powder, 1 part solvent, and 3-6 parts alcohol; wherein the particle size range of bauxite A is 3-5 mm, the particle size range of bauxite B is 1-3 mm, the particle size range of fine bauxite powder is 0-0.5 mm, the aerogel powder is silica aerogel powder, and the solvent is anhydrous ethanol; the preparation method includes the following steps: Step 1: Mix silicon carbide particles, bauxite A, bauxite B, bauxite powder and solvent by mechanical stirring until the color is uniform, and obtain mixed raw materials; Step 2: Add the aerogel powder to the mixed raw materials and continue stirring and mixing until the color is uniform and the mixture has a "porridge-like" consistency, forming aggregate; Step 3: Process the aggregate into brick blanks using a brick press; Step 4: Place the brick blanks in a tunnel kiln and sinter them by gradient heating. The bricks are then removed from the kiln to obtain aerogel-modified silica-molybdenum bricks.

2. The method for preparing aerogel-modified silica-molybdenum bricks with high strength and low thermal conductivity according to claim 1, characterized in that: The porosity of silica aerogel powder is >90%, and the bulk density is 60-120 kg / m³. 3 The pore size is 1–15 nm, and the thermal conductivity is 0.017–0.023 W / (mK).

3. The method for preparing aerogel-modified silica-molybdenum bricks with high strength and low thermal conductivity according to claim 1, characterized in that: Aerogel-modified silica bricks also include modified aerogel powder, which is added in an amount of 0.5-1 parts by weight. The modified aerogel powder is obtained by modifying silica aerogel powder with silane coupling agent and aluminum nitrate solution.

4. The method for preparing aerogel-modified silica-molybdenum bricks with high strength and low thermal conductivity according to claim 1, characterized in that: Bauxite A, Bauxite B, and fine bauxite powder all use the same type of bauxite, with Al2O3 ranging from 80-85% by mass, Fe2O3 ranging from 1-2% by mass, and the bulk density of the bauxite being 2.9 g / cm3; in the silicon carbide particles, the mass percentage of SiC is 92-96%, and the particle size is ≤0.074 mm.

5. A method for preparing an aerogel-modified silica-mullite brick with high strength and low thermal conductivity according to claims 1, 2, and 4, characterized in that: When using only unmodified aerogel powder, in step two, the unmodified aerogel powder is gradually added to the mixed raw materials, and alcohol is sprayed during the mixing process until the color is uniform and aggregate is formed.

6. The method for preparing an aerogel-modified silica-mullite brick with high strength and low thermal conductivity according to claims 1, 2 and 4, characterized in that: When using only unmodified aerogel powder, step two involves treating the unmodified aerogel powder with alcohol. A certain amount of unmodified aerogel powder is weighed into a container, and then a certain amount of alcohol is weighed. The alcohol is added while stirring the aerogel powder, using an intermittent spraying method. The aerogel powder material is stirred until it becomes uniform, thus obtaining a mixture containing aerogel powder. Then, the mixture containing aerogel powder is added to the mixing raw materials, and alcohol is sprayed during the mixing process until the color is uniform and aggregate is formed.

7. The method for preparing aerogel-modified silica-mullite bricks with high strength and low thermal conductivity according to claim 3, characterized in that: Step 2: Mix the unmodified aerogel powder and the modified aerogel powder together by stirring, and spray alcohol during the stirring process until a uniform color is formed to form a mixture containing aerogel powder; remove larger agglomerates by hand during the mixing process; then, add the mixture containing aerogel powder to the mixing raw materials, spray alcohol during the mixing process, and mix until a uniform color is formed to form aggregate.

8. The method for preparing an aerogel-modified silica-mullite brick with high strength and low thermal conductivity according to claim 3, characterized in that: Modified aerogel powder is prepared by the following method: 2%-5% silane coupling agent is prepared, and the silane coupling agent is added dropwise to the aerogel solution and stirred for 20-40 minutes; after homogenization, aluminum nitrate solution is added for treatment and stirred for 30 minutes; the completely treated modified mixed solution is added to a gelling agent to promote the transformation of the solution into a gel; after gelling for 24 hours, it is placed in a drying device to dry into powder, and finally placed in a muffle furnace at 500℃ to calcine to obtain modified aerogel powder.

9. The method for preparing aerogel-modified silica-mullite bricks with high strength and low thermal conductivity according to claim 1, characterized in that: In step four, the sintering temperature reaches 1000-1400℃.

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