Preparation method of ceramic aerogel / ceramic fiber / MXene composite thermal insulation material

Abstract

The present invention relates to the field of composite materials and discloses a method for preparing a ceramic aerogel / ceramic fiber / MXene composite thermal insulation material, comprising: 1) preparing an aqueous dispersion of a MXene two-dimensional nanomaterial; 2) mixing cellulose and the aqueous dispersion of the MXene two-dimensional nanomaterial to obtain a mixed slurry A; 3) mixing cellulose, ceramic fiber, a silicon source, an aluminum source, and water to obtain a mixed slurry B; 4) mixing mixed slurry B, mixed slurry A, and citric acid, and heating the mixture to obtain a mixed slurry C; and 5) directionally freezing the mixed slurry C, freeze-drying it, and finally calcining it to obtain the ceramic aerogel / ceramic fiber / MXene composite thermal insulation material. The ceramic aerogel / ceramic fiber / MXene composite thermal insulation material prepared according to the present invention has a relatively regular hexagonal honeycomb pore structure and has the advantages of low high-temperature thermal conductivity and good compression resilience.

Description

Technical Field

[0001] The present invention relates to the field of composite materials, and in particular to a method for preparing a ceramic aerogel / ceramic fiber / MXene composite thermal insulation material. Background Art

[0002] Ceramic aerogel has many unique advantages such as low density, large specific surface area, low thermal conductivity, and good fire resistance. It has broad application prospects in the fields of thermal insulation and fire resistance, thermal / acoustic / electrical insulation, sound absorption and vibration reduction, energy storage materials, etc. However, traditional silica ceramic aerogel cannot withstand high temperature conditions greater than 900°C, which will cause structural collapse and volume shrinkage. Alumina ceramic aerogel is resistant to high temperatures but has a high thermal conductivity of more than 20W / mK and a density of up to 3.6g / cm 3 Therefore, when alumina ceramics are used as functional materials (non-structural materials), their thermal insulation and weight reduction effects are very weak. Therefore, the development of new ceramic aerogels that are ultra-light and can withstand temperatures above 1300°C is of great practical significance.

[0003] In view of the requirements for higher mechanical resilience and lower high-temperature thermal conductivity, there is an urgent need to propose a preparation method for ceramic aerogel / ceramic fiber composite insulation materials with novel structure and excellent performance to achieve the goals of simple process, short preparation cycle and low cost, give full play to the advantages of ceramic aerogel composite materials, push the application of ceramic aerogel to a new level, and thus meet the social development needs for multifunctional integrated new materials. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a method for preparing a ceramic aerogel / ceramic fiber / MXene composite thermal insulation material. The ceramic aerogel / ceramic fiber / MXene composite thermal insulation material prepared according to the method of the present invention has a relatively regular hexagonal honeycomb pore structure inside, and has the advantages of low high-temperature thermal conductivity and good compression resilience.

[0005] The specific technical solutions of the present invention are:

[0006] In a first aspect, the present invention provides a method for preparing a ceramic aerogel / ceramic fiber / MXene composite thermal insulation material, comprising the following steps:

[0007] 1) Preparation of MXene two-dimensional nanomaterial aqueous dispersion.

[0008] 2) The cellulose and MXene two-dimensional nanomaterial aqueous dispersions are uniformly mixed to prepare a mixed slurry A.

[0009] 3) The cellulose, ceramic fiber, silicon source, aluminum source and water are mixed uniformly to prepare a mixed slurry B.

[0010] 4) Mixing the mixed slurry B, the mixed slurry A and citric acid uniformly, adjusting the pH to 8.5-11.0, heating for reaction, and cooling to obtain a mixed slurry C.

[0011] 5) The mixed slurry C is first transferred to a directional freezing device for directional freezing, then freeze-dried, and calcined to obtain a ceramic aerogel / ceramic fiber / MXene composite thermal insulation material.

[0012] MXene two-dimensional nanomaterials, ceramic fibers, and ceramic aerogels all have a high abundance of hydroxyl groups on their surfaces, and the formation of composite thermal insulation materials relies primarily on the interaction of these surface hydroxyl groups. The present inventors found that this hinders the formation of relatively regular hexagonal honeycomb pores in the mixed slurry after freeze-drying, resulting in an irregular porous structure. Furthermore, the MXene two-dimensional nanosheets in the resulting composite thermal insulation material are also disordered, resulting in poor high-temperature radiation protection and low compression resilience.

[0013] To this end, the present invention uses cellulose to modify the surface of MXene two-dimensional nanomaterials and ceramic fibers respectively, and through the strong hydrogen bonding effect of the rich hydroxyl groups on the surfaces of the two, the above-mentioned substances are cross-linked by in-situ generation of ceramic aerogel and the addition of citric acid to form covalent bonds. After the mixed slurry is freeze-dried, it can not only form relatively regular hexagonal honeycomb holes, but also its micro-cross-linked structure is conducive to the orientation of the layered structure, thereby achieving efficient suppression of high-temperature radiation and reducing thermal conductivity. At the same time, this microstructure also makes the composite insulation material exhibit excellent mechanical resilience. The present invention found that if cellulose modification is not performed, but MXene and ceramic fibers are directly cross-linked by citric acid, this will reduce the movable space around the MXene, which is not conducive to the orientation of the MXene during the directional freezing process.

[0014] The present invention adopts a directional freezing process to obtain a vertically oriented structure by controlling the longitudinal growth of ice crystals formed by water during the pre-freezing process, and the mixed slurry forms a skeleton at the gaps between the ice crystals during the directional freezing process, and phase separation forms a honeycomb structure.

[0015] Preferably, in step 1), the MXene two-dimensional nanomaterial is Ti3C2Tx MXene two-dimensional nanomaterial.

[0016] As a preferred method for preparing the Ti3C2Tx MXene two-dimensional nanomaterial, the TiAlC2 ceramic particles are etched by a chemical etchant, and Ti3C2Tx is obtained by washing and peeling. x MXene two-dimensional nanomaterial aqueous dispersion.

[0017] Furthermore, the chemical etchant is a mixed solution of acid and lithium fluoride in a ratio of 10 mL: 1-5 g; the acid is hydrochloric acid or hydrofluoric acid.

[0018] Preferably, in step 2), the solid content of the MXene two-dimensional nanomaterial aqueous dispersion is 8-12 wt%; the cellulose is sodium carboxymethyl cellulose, and the amount used is 0.1 parts by weight, and the amount of the MXene two-dimensional nanomaterial aqueous dispersion is 45-55 parts by weight.

[0019] Preferably, in step 3), the cellulose is sodium carboxymethyl cellulose, the amount of which is 0.1 parts by weight, the amount of ceramic fiber is 1-5 parts by weight, the amount of silicon source is 25-35 parts, the amount of aluminum source is 25-35 parts, and the amount of water is 80-120 parts by weight.

[0020] Preferably, in step 3), the ceramic fiber is one or more of aluminum silicate fiber, zirconium oxide fiber, basalt fiber and mullite fiber.

[0021] Preferably, in step 3), the ceramic fiber has a diameter of 50-300 nm and a length of 10-200 μm.

[0022] Preferably, in step 3), the silicon source is one or more of methyl orthosilicate, ethyl orthosilicate, polyethoxydisiloxane, methyltrimethoxysilane, methyltriethoxysilane, and sodium silicate (Na2SiO3).

[0023] Preferably, in step 3), the aluminum source is one or more of aluminum powder, aluminum chloride, aluminum sulfate, aluminum nitrate, aluminum silicate, aluminum sulfide, aluminum isopropoxide, and aluminum nitrate nonahydrate.

[0024] Preferably, in step 4), the amount of the mixed slurry B is 10 parts by weight, the amount of the mixed slurry A is 0.1-0.7 parts (more preferably 0.3-0.5 parts by weight), and the amount of citric acid is 0.005-0.03 parts by weight (more preferably 0.01-0.02 parts by weight).

[0025] The present invention found that the amount of MXene two-dimensional nanomaterials and the amount of citric acid used have a significant impact on the high-temperature thermal conductivity and rebound rate of the composite thermal insulation material.

[0026] As the amount of MXene two-dimensional nanomaterial increases, the high-temperature thermal conductivity of the composite insulation material first gradually decreases and then increases. This is because MXene two-dimensional nanomaterials have a good effect of inhibiting high-temperature radiation, so when used in appropriate amounts, they can effectively reduce the high-temperature thermal conductivity; however, excessive addition will increase the solid thermal conductivity of the material, which in turn increases the high-temperature thermal conductivity. Citric acid has a cross-linking effect. If its content is low and the degree of cross-linking is too low, the mechanical stability of the material will be poor during the freeze-drying process, and it will be more likely to shrink or the microporous structure will collapse. If its content is too high, the degree of cross-linking will be too high, the rigidity will increase, and it will also be detrimental to the freeze-drying molding of the material. Therefore, the high-temperature thermal conductivity and compression rebound rate of the composite insulation material are closely related to the amount of the above materials added. At the same time, the present invention also found that adding an appropriate amount of nano-ceramic fiber can improve the tensile strength of the composite insulation material.

[0027] Preferably, in step 4), the heating reaction temperature is 70-90° C. and the time is 25-35 min.

[0028] Preferably, in step 5), the directional freezing device comprises a mold with polytetrafluoroethylene as side walls and copper as a base, and a refrigeration mechanism located below the mold.

[0029] Copper has good thermal conductivity, and the copper base is placed on the refrigeration mechanism; the polytetrafluoroethylene on the upper part has good thermal insulation properties, which can reduce the ability of the mixed slurry's own heat to diffuse to the surroundings, thereby forming a vertical macro temperature gradient inside the mixed slurry. The direction of this temperature gradient is the direction of directional freezing. During the freezing process, the slurry's own heat is continuously conducted away from the bottom copper base, and the mixed slurry undergoes directionally solidification under this condition.

[0030] Preferably, in step 5), the temperature at the bottom of the directional freezing device is -100°C to -20°C (more preferably -80°C to -50°C), and the freezing time is 30-240 min (more preferably 60-120 min).

[0031] The lower the directional freezing temperature, the faster the freezing rate of the mixed slurry. Therefore, as the freezing temperature decreases, the freezing time is shorter; the faster the freezing rate, the smaller the holes formed, which will affect the high-temperature thermal conductivity and compression rebound rate of the composite thermal insulation material; at a suitable freezing rate, the high-temperature thermal conductivity of the composite thermal insulation material is low and the compression rebound rate is high.

[0032] Preferably, in step 5), the freeze-drying conditions are: the temperature of the freeze-drying chamber is 0-10°C, the temperature of the freeze-drying cold trap is -80°C to -50°C, the pressure is 1-30 Pa, and the time is 24-96h.

[0033] Preferably, in step 5), the calcination conditions are: calcination temperature is 500-1000° C., and the calcination time is 2-6 h.

[0034] In a second aspect, the present invention provides a ceramic aerogel / ceramic fiber / MXene composite thermal insulation material obtained by the above-mentioned preparation method, which has a thermal conductivity of ≤0.070W / (mK) at 1000°C, a compression rebound rate of ≥85%, and a tensile strength of ≥712KPa.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) The present invention utilizes cellulose / citric acid to combine MXene with ceramic aerogel and ceramic fiber through covalent bond interactions, and successively performs directional freezing, freeze drying and high-temperature calcination, thereby successfully obtaining a composite thermal insulation material with relatively regular hexagonal honeycomb pores.

[0037] (2) The ceramic aerogel / ceramic fiber / MXene composite thermal insulation material prepared by the method of the present invention not only has an extremely low thermal conductivity at room temperature, but also has a relatively low thermal conductivity under high temperature conditions (the thermal conductivity at 1000°C is ≤0.070W / (mK)), and has a good high-temperature thermal insulation effect.

[0038] (3) The ceramic aerogel / ceramic fiber / MXene composite thermal insulation material prepared by the method of the present invention has excellent compression resilience (compression rebound rate ≥85%) and tensile strength (≥5.6 kPa). BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is an electron microscope image of the composite thermal insulation material obtained in Test Example 2-1;

[0040] Figure 2 This is an electron microscope image of the composite thermal insulation material obtained in Test Example 2-2;

[0041] Figure 3 This is an electron microscope image of the composite thermal insulation material obtained in Test Example 2-3. DETAILED DESCRIPTION

[0042] The present invention will be further described below with reference to the embodiments.

[0043] Overall embodiment

[0044] A method for preparing a ceramic aerogel / ceramic fiber / MXene composite thermal insulation material comprises the following steps:

[0045] 1) TiAlC2 ceramic particles were etched with chemical etchant, and Ti3C2T was obtained after cleaning and peeling. xMXene two-dimensional nanomaterial aqueous dispersion; wherein the chemical etchant is a mixed solution of acid (hydrochloric acid or hydrofluoric acid) and lithium fluoride in a ratio of 10mL:1-5g.

[0046] 2) 0.1 parts by weight of sodium carboxymethyl cellulose and 45-55 parts by weight of an aqueous dispersion of a MXene two-dimensional nanomaterial having a solid content of 8-12 wt% were uniformly mixed to prepare a mixed slurry A.

[0047] 3) 0.1 parts by weight of sodium carboxymethyl cellulose, 1-5 parts by weight of ceramic fiber, 25-35 parts by weight of a silicon source, 25-35 parts by weight of an aluminum source, and 80-120 parts by weight of water are uniformly mixed to prepare a mixed slurry B. The ceramic fiber is one or more of aluminum silicate fiber, zirconia fiber, basalt fiber, and mullite fiber, and has a diameter of 50-300 nm and a length of 10-200 μm; the silicon source is one or more of methyl orthosilicate, ethyl orthosilicate, polyethoxydisiloxane, methyltrimethoxysilane, methyltriethoxysilane, and sodium silicate; and the aluminum source is one or more of aluminum powder, aluminum chloride, aluminum sulfate, aluminum nitrate, aluminum silicate, aluminum sulfide, aluminum isopropoxide, and aluminum nitrate nonahydrate.

[0048] 4) 10 parts by weight of mixed slurry B, 0.1-0.7 parts by weight (preferably 0.3-0.5 parts by weight) of mixed slurry A and 0.005-0.03 parts by weight (preferably 0.01-0.02 parts by weight) of citric acid were mixed uniformly, the pH was adjusted to 8.5-11.0, and the mixture was heated at 70-90° C. for 25-35 minutes. After cooling, mixed slurry C was obtained.

[0049] 5) The mixed slurry C is first transferred to a directional freezing device for directional freezing, and then freeze-dried, and the ceramic fiber / MXene composite thermal insulation material is obtained after roasting. The directional freezing device includes a mold with polytetrafluoroethylene as the side wall and copper as the base, and a refrigeration mechanism located below the mold. The temperature at the bottom of the directional freezing device is -100°C to -20°C (preferably -80°C to -50°C), and the freezing time is 30-240min (preferably 60-120min). The freeze-drying conditions are: the temperature of the freeze dryer chamber is 0-10°C, the temperature of the freeze dryer cold trap is -80°C to -50°C, the pressure is 1-30Pa, and the time is 24-96h. The roasting conditions are: the roasting temperature is 500-1000°C, and the time is 2-6h.

[0050] Specific Examples and Comparative Examples

[0051] (1) Effect of MXene dosage and citric acid dosage on the performance of composite thermal insulation materials

[0052] 1) TiAlC2 ceramic particles were etched with chemical etchant, and Ti3C2T was obtained after cleaning and peeling.x MXene two-dimensional nanomaterial aqueous dispersion; wherein the chemical etchant is a mixed solution of acid (hydrofluoric acid) and lithium fluoride in a ratio of 10mL:3g.

[0053] 2) 0.1 phr of sodium carboxymethyl cellulose and 50 phr of a MXene two-dimensional nanomaterial aqueous dispersion with a solid content of 10 wt% were mixed to obtain a mixed slurry A.

[0054] 3) 0.1 phr of sodium carboxymethyl cellulose, 3 phr of ceramic fiber (zirconia fiber, diameter 50-300 nm, length 10-200 μm), 30 phr of silicon source (sodium silicate), 30 phr of aluminum source (aluminum chloride) and 100 phr of water were mixed to prepare a mixed slurry B.

[0055] 4) 10 phr of mixed slurry B, 0-0.7 phr of mixed slurry A and 0-0.03 phr of citric acid were mixed evenly, the pH was adjusted to about 10.5, heated at 80° C. for reaction for 30 minutes, and cooled to obtain mixed slurry C.

[0056] 5) The mixed slurry C is first transferred to a directional freezing device for directional freezing, and then freeze-dried. After calcination, a ceramic fiber / MXene composite thermal insulation material is obtained. The directional freezing device includes a mold with polytetrafluoroethylene as the side wall and a copper base, and a refrigeration mechanism located below the mold. The temperature at the bottom of the directional freezing device is -50°C, and the freezing time is 120 minutes. The freeze-drying conditions are: the temperature of the freeze dryer chamber is set to 5°C, the temperature of the freeze dryer cold trap is set to -65°C, the pressure is set to 15Pa, and the time is 96 hours. It is then calcined at a high temperature of 600°C for 3 hours.

[0057] Performance Comparison

[0058] Table 1: Properties of thermal insulation materials at different MXene and citric acid dosages

[0059]

[0060]

[0061] From the data in the above table, we can see that:

[0062] In Test Examples 1-1 to 1-5, as the amount of MXene 2D nanomaterial increases, the high-temperature thermal conductivity of the insulation material gradually decreases and then increases, while the compression rebound and tensile strength first increase and then decrease. This is because MXene 2D nanomaterials have a strong ability to suppress high-temperature radiation. Therefore, when used in appropriate amounts, they can effectively reduce the high-temperature thermal conductivity. However, excessive addition increases the solid thermal conductivity of the material, which in turn increases the high-temperature thermal conductivity. The composite insulation material with the best overall performance was obtained when the final mixed slurry dosage was 0.3-0.5 phr.

[0063] In test examples 1-6, 1-7, 1-4, 1-8, and 1-9, the amount of citric acid is increased successively. Citric acid plays a cross-linking role. If its content is less (test examples 1-6 and 1-7), the cross-linking degree is too low, and the material structure is relatively loose during freeze drying, so high-temperature thermal conductivity, compression rebound rate, and tensile strength are all poor. If its content is too much (test examples 1-9), the cross-linking degree is too high again, and the product hardness increases, so compression rebound rate and tensile strength will appear to decline, while having a certain influence on thermal conductivity, but relatively less influence.

[0064] (2) Effects of cellulose modification and citric acid cross-linking on the micromorphology of composite insulation materials

[0065] 1) TiAlC2 ceramic particles were etched with chemical etchant, and Ti3C2T was obtained after cleaning and peeling. x MXene two-dimensional nanomaterial aqueous dispersion; wherein the chemical etchant is a mixed solution of acid (hydrofluoric acid) and lithium fluoride in a ratio of 10mL:3g.

[0066] 2) 0-0.1 phr of sodium carboxymethyl cellulose and 50 phr of a MXene two-dimensional nanomaterial aqueous dispersion with a solid content of 10 wt% were uniformly mixed to prepare a mixed slurry A.

[0067] 3) 0-0.1 phr of sodium carboxymethyl cellulose, 3 phr of ceramic fiber (zirconia fiber, diameter 50-200 nm, length 10-200 μm), 30 phr of silicon source (sodium silicate), 30 phr of aluminum source (aluminum chloride) and 100 phr of water were mixed to prepare a mixed slurry B.

[0068] 4) 10 phr of mixed slurry B, 0.3 phr of mixed slurry A and 0-0.01 phr of citric acid were mixed evenly, the pH was adjusted to about 10.5, heated at 80° C. for reaction for 30 minutes, and cooled to obtain mixed slurry C.

[0069] 5) The mixed slurry C is first transferred to a directional freezing device for directional freezing, and then freeze-dried. After calcination, a ceramic fiber / MXene composite thermal insulation material is obtained. The directional freezing device includes a mold with polytetrafluoroethylene as the side wall and a copper base, and a refrigeration mechanism located below the mold. The temperature at the bottom of the directional freezing device is -50°C, and the freezing time is 120 minutes. The freeze-drying conditions are: the temperature of the freeze dryer chamber is set to 5°C, the temperature of the freeze dryer cold trap is set to -65°C, the pressure is set to 15Pa, and the time is 96 hours. It is then calcined at a high temperature of 600°C for 3 hours.

[0070] Performance Comparison

[0071] Table 2: Effects of cellulose modification and citric acid cross-linking on the microstructure of composite insulation materials

[0072]

[0073] From the results in the above table we can see that:

[0074] In Test Example 2-1, cellulose was used to modify ceramic fiber and MXene, and then cross-linked with citric acid. Figure 1 As shown, it can be found that the cross-section of the obtained composite thermal insulation material presents a relatively regular hexagonal honeycomb pore structure. Combined with the test data of Test Examples 1-2, it has a lower high-temperature thermal conductivity and a higher resilience.

[0075] In Test Example 2-2, cellulose was not modified in advance and was directly cross-linked by citric acid. Figure 2 As shown, the hexagonal honeycomb pore structure in the cross section of the composite thermal insulation material is not regular enough. This is because the cellulose has not been modified, which will reduce the movable space around the MXene and is not conducive to orientation during the freeze-drying process.

[0076] In Test Example 2-3, no citric acid cross-linking treatment was performed. Figure 3 As shown, the cross-section of the composite thermal insulation material presents an irregular porous structure, and the MXene two-dimensional nanosheet structure is also disordered, which has poor effect in blocking high-temperature radiation and poor resilience.

[0077] (3) The influence of ceramic fiber dosage on the performance of thermal insulation materials

[0078] 1) TiAlC2 ceramic particles were etched with chemical etchant, and Ti3C2T was obtained after cleaning and peeling. x MXene two-dimensional nanomaterial aqueous dispersion; wherein the chemical etchant is a mixed solution of acid (hydrofluoric acid) and lithium fluoride in a ratio of 10mL:3g.

[0079] 2) 0.1 phr of sodium carboxymethyl cellulose and 50 phr of a MXene two-dimensional nanomaterial aqueous dispersion with a solid content of 10 wt% were mixed to obtain a mixed slurry A.

[0080] 3) 0.1 phr of sodium carboxymethyl cellulose, 0-5 phr of ceramic fiber (zirconia fiber, diameter 50-300 nm, length 10-200 μm), 30 phr of silicon source (sodium silicate), 30 phr of aluminum source (aluminum chloride) and 100 phr of water were mixed to prepare a mixed slurry B.

[0081] 4) 10 phr of mixed slurry B, 0.5 phr of mixed slurry A and 0.01 phr of citric acid were mixed evenly, the pH was adjusted to about 10.5, heated at 80° C. for reaction for 30 min, and cooled to obtain mixed slurry C.

[0082] 5) The mixed slurry C is first transferred to a directional freezing device for directional freezing, and then freeze-dried. After calcination, a ceramic fiber / MXene composite thermal insulation material is obtained. The directional freezing device includes a mold with polytetrafluoroethylene as the side wall and a copper base, and a refrigeration mechanism located below the mold. The temperature at the bottom of the directional freezing device is -50°C, and the freezing time is 120 minutes. The freeze-drying conditions are as follows: the temperature of the freeze dryer chamber is set to 5°C, the temperature of the freeze dryer cold trap is set to -65°C, the pressure is set to 15Pa, the time is 96 hours, and then calcined at 600°C for 3 hours.

[0083] Performance Comparison

[0084] Table 3: Performance of thermal insulation materials at different ceramic fiber dosages

[0085] Case Ceramic fiber (phr) Compression rebound rate (%) Tensile strength (kPa) Test Example 3-1 0 79 5.2 Test Example 3-2 1 85 5.8 Test Example 3-3 3 94 6.7 Test Example 3-4 5 90 6.4

[0086] From the data in the above table, we can see that:

[0087] In Test Examples 3-1 to 3-4, as the amount of ceramic fiber increased, the compression rebound rate and tensile strength first increased and then decreased. This is because the ceramic fiber has a reinforcing effect. Finally, the composite insulation material with a ceramic fiber dosage of 3 phr achieved the best overall performance.

[0088] (4) Effect of directional freezing temperature and time on the performance of composite insulation materials

[0089] 1) TiAlC2 ceramic particles were etched with chemical etchant, and Ti3C2T was obtained after cleaning and peeling. x MXene two-dimensional nanomaterial aqueous dispersion; wherein the chemical etchant is a mixed solution of acid (hydrofluoric acid) and lithium fluoride in a ratio of 10mL:3g.

[0090] 2) 0.1 phr of sodium carboxymethyl cellulose and 50 phr of a MXene two-dimensional nanomaterial aqueous dispersion with a solid content of 10 wt% were mixed to obtain a mixed slurry A.

[0091] 3) 0.1 phr of sodium carboxymethyl cellulose, 3 phr of ceramic fiber (zirconia fiber, diameter 50-200 nm, length 10-200 μm), 30 phr of silicon source (sodium silicate), 30 phr of aluminum source (aluminum chloride) and 100 phr of water were mixed to prepare a mixed slurry B.

[0092] 4) 10 phr of mixed slurry B, 0.5 phr of mixed slurry A and 0.01 phr of citric acid were mixed evenly, the pH was adjusted to about 10.5, heated at 80° C. for reaction for 30 min, and cooled to obtain mixed slurry C.

[0093] 5) The mixed slurry C is first transferred to a directional freezing device for directional freezing, and then freeze-dried. After calcination, a ceramic fiber / MXene composite thermal insulation material is obtained. The directional freezing device includes a mold with polytetrafluoroethylene as the side wall and copper as the base, and a refrigeration mechanism located under the mold. The temperature at the bottom of the directional freezing device is -20°C to -100°C, and the freezing time is 30-240min. The freeze-drying conditions are: the temperature of the freeze dryer chamber is set to 5°C, the temperature of the freeze dryer cold trap is set to -65°C, the pressure is set to 15Pa, and the time is 96h. It is then calcined at 600°C for 3h.

[0094] Performance Comparison

[0095] Table 4: Effects of directional freezing temperature and time on the properties of composite insulation materials

[0096] Case Directional freezing temperature (℃) Directional freezing time (min) Thermal conductivity (W / (m·K), 1000℃) Compression rebound rate (%) Test Example 4-1 -20 240 0.079 86 Test Example 4-2 -50 120 0.067 94 Test Example 4-3 -80 60 0.065 91 Test Example 4-4 -100 30 0.073 82

[0097] The data in the table above demonstrates that lower directional freezing temperatures lead to faster freezing rates, shortening freezing times. Faster freezing rates also result in smaller pores, which impacts high-temperature thermal conductivity and compression rebound. At appropriate freezing rates, composite insulation materials exhibit the lowest high-temperature thermal conductivity and the highest compression rebound. Experimental results show that directional freezing temperatures between -50°C and -80°C achieve optimal results.

[0098] Unless otherwise specified, the raw materials and equipment used in the present invention are commonly used in the art; the methods used in the present invention are conventional methods in the art unless otherwise specified.

[0099] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing a ceramic aerogel / ceramic fiber / MXene composite thermal insulation material, characterized in that include: 1) Preparation of MXene two-dimensional nanomaterial aqueous dispersion; 2) Mixing 0.1 parts by weight of sodium carboxymethyl cellulose and 45-55 parts by weight of MXene two-dimensional nanomaterial aqueous dispersion to prepare a mixed slurry A; 3) Mixing 0.1 parts by weight of sodium carboxymethyl cellulose, 1-5 parts by weight of ceramic fiber, 25-35 parts by weight of a silicon source, 25-35 parts by weight of an aluminum source, and water to prepare a mixed slurry B; 4) Mix 10 parts by weight of mixed slurry B, 0.3-0.5 parts by weight of mixed slurry A, and 0.01-0.02 parts by weight of citric acid, adjust the pH to 8.5-11.0, heat to react, and cool to obtain mixed slurry C; 5) The mixed slurry C is first transferred to a directional freezing device for directional freezing, then freeze-dried, and finally calcined to obtain a ceramic aerogel / ceramic fiber / MXene composite insulation material.

2. The preparation method according to claim 1, wherein: In step 1), the MXene two-dimensional nanomaterial is Ti3C2Tx MXene two-dimensional nanomaterial.

3. The preparation method according to claim 1, wherein: In step 2), the solid content of the MXene two-dimensional nanomaterial aqueous dispersion is 8-12 wt%.

4. The preparation method according to claim 1, wherein: In step 3), the amount of water used is 80-120 parts by weight.

5. The preparation method according to claim 1 or 3, wherein: In step 3), The ceramic fiber is one or more of aluminum silicate fiber, zirconium oxide fiber, basalt fiber and mullite fiber; the diameter is 50-300nm and the length is 10-200μm; The silicon source is one or more of methyl orthosilicate, ethyl orthosilicate, polyethoxydisiloxane, methyltrimethoxysilane, methyltriethoxysilane and sodium silicate; The aluminum source is one or more of aluminum powder, aluminum chloride, aluminum sulfate, aluminum nitrate, aluminum silicate, aluminum sulfide, aluminum isopropoxide and aluminum nitrate nonahydrate.

6. The preparation method according to claim 1, wherein: In step 4), the heating reaction temperature is 70-90° C. and the time is 25-35 minutes.

7. The preparation method according to claim 1, wherein: In step 5), the directional freezing device includes a mold with polytetrafluoroethylene as the side wall and copper as the base, and a refrigeration mechanism located below the mold.

8. The preparation method according to claim 1 or 7, wherein: In step 5), The temperature at the bottom of the directional freezing device is -80°C to -50°C, and the freezing time is 60-120 minutes; The freeze drying conditions are as follows: the temperature of the freeze drying chamber is 0-10°C, the temperature of the freeze drying cold trap is -80°C to -50°C, and the pressure is 1-30Pa.

9. The preparation method according to claim 1, wherein: In step 5), the calcination conditions are: calcination temperature is 500-1000° C., and time is 2-6 hours.

10. The ceramic aerogel / ceramic fiber / MXene composite thermal insulation material obtained by the preparation method according to any one of claims 1 to 9, characterized in that: Thermal conductivity at 1000℃≤0.070W / (m﹒K), compression rebound rate≥85%.

Images