Thermal insulation composite material based on 3D printed ceramic framework and preparation method thereof

Abstract

The application relates to a heat-insulating composite material based on a 3D-printed ceramic framework and a preparation method thereof, and relates to a heat-insulating material based on a 3D-printed ceramic framework and a preparation method thereof. The application aims to solve the technical problem that the existing aerogel heat-insulating material cannot have high strength and low thermal conductivity. Compared with the traditional ceramic particle aerogel, the 3D-printed ceramic framework can provide high strength and reduce weight, in-situ grown mullite whiskers and filled mullite fibers can fill the pores of the ceramic framework, on the basis of not damaging the original structure and performance of the ceramic framework, the nanoscale pore structure formed by the mullite whiskers crossing each other also endows the framework with excellent high-temperature heat-insulating characteristics, so that the framework has high strength and low thermal conductivity; the filled mullite fibers provide efficient fire prevention and heat insulation, and realize preparation of an emergency heat runaway protection and heat-insulating sheet with high strength and high heat insulation.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of heat insulation material based on 3D printing ceramic framework and its preparation method. BACKGROUND

[0002] With the rapid development of aerospace and energy field, there is an urgent need for efficient thermal insulation materials for high-temperature thermal insulation and extreme environment thermal protection. In this context, aerogel thermal insulation materials have been rapidly developed due to their excellent high-temperature stability, light weight, and high-temperature chemical stability. However, effective thermal insulation in extreme environments requires aerogel materials to have both high strength and low thermal conductivity. Existing ceramic particle aerogels composed of 0-dimensional ceramic particles and ceramic fiber aerogels composed of 1-dimensional fibers both have structural defects, such as the brittleness of ceramic particle aerogels and the low strength of ceramic fiber aerogels. Therefore, single-scale raw materials cannot meet the performance goals of high strength and low thermal conductivity, and there is an urgent need to develop new structural aerogel materials that provide both high strength and excellent thermal insulation performance for efficient thermal insulation in extreme environments. SUMMARY

[0003] The present application is to solve the technical problem that existing aerogel thermal insulation materials cannot have both high strength and low thermal conductivity, and to provide a kind of heat insulation composite material based on 3D printing ceramic framework and its preparation method.

[0004] The 3D printing ceramic framework-based thermal insulation composite material of the present application has two types, which are 3D printing ceramic framework in-situ grown mullite whisker composite material and 3D printing ceramic framework filled mullite fiber thermal insulation sheet composite material.

[0005] The preparation method of the 3D printing ceramic framework in-situ grown mullite whisker composite material is carried out according to the following steps:

[0006] I. Preparation of mixed sol: mix aluminum sol and silicon sol uniformly to obtain mixed sol; the molar ratio of aluminum element to silicon element in the mixed sol is 3:(1-1.2);

[0007] II. Immersion: place the 3D printing ceramic framework into a container, and pour the mixed sol prepared in step I into the container so that the 3D printing ceramic framework is completely immersed in the mixed sol;

[0008] III. Freezing and freeze-drying:

[0009] Place the container of step II into a freeze-drying machine, freeze to complete freezing at a temperature of -50℃ to -55℃, and then freeze-dry at a temperature of -50℃ to -55℃ and a vacuum degree of 50Pa to 55Pa for 72h to 75h to obtain a 3D ceramic framework / sol composite blank;

[0010] IV. Heat treatment:

[0011] Put the aluminum fluoride powder into the bottom of a crucible, and then put the 3D ceramic framework / sol composite blank of step three above the aluminum fluoride powder in the crucible, seal the crucible with a cover and put it into a muffle furnace, heat at 400-410 DEG C for 30-35 min in an air atmosphere, then heat to 1000-1100 DEG C and heat for 2-2.5 h, then cool to room temperature with the furnace, to obtain a 3D ceramic framework in-situ grown mullite whisker composite material;

[0012] The mass ratio of the 3D ceramic framework / sol composite blank to aluminum fluoride is 1:(1-1.1);

[0013] The preparation method of the 3D printed ceramic framework filled mullite fiber heat insulation sheet composite material is carried out according to the following steps:

[0014] I. Filling mullite fiber:

[0015] Disperse the chopped mullite fiber into a mixed solution of deionized water and silica sol, and stir uniformly to form a mixed slurry; wherein the addition amount of the chopped mullite fiber and the silica sol is 1-1.5% and 5-6% of the mass of the deionized water, respectively;

[0016] Put the 3D printed ceramic framework into the funnel of a vacuum filtration device, then pour the above-mentioned mixed slurry, connect the vacuum pump and start, adjust the vacuum degree to 0.06-0.065 MPa, after all the solution is filtered, the fiber is completely filled in the 3D printed ceramic framework, turn off the vacuum pump, to obtain the filled framework wet blank;

[0017] II. Freezing and freeze-drying:

[0018] Put the filled framework wet blank of step I into a freeze dryer, freeze to complete freezing at a temperature of -50 to -55 DEG C, then freeze-dry at a temperature of -45 to -50 DEG C and a vacuum degree of 30-100 Pa for 72-75 h, to obtain a 3D printed ceramic framework filled mullite fiber composite material.

[0019] The preparation method of the 3D printed ceramic framework is not limited in the present application, as long as the strength is high, preferably greater than 1 MPa.

[0020] Characteristics of the present application:

[0021] 3D printed ceramic framework in-situ grown with mullite whiskers composite: 3D printed ceramic framework can provide high strength while reducing weight compared to traditional ceramic particle aerogels. In-situ grown mullite whiskers fill the pores of the ceramic framework. Without damaging the original structure and performance of the ceramic framework, the nano-scale pore structure formed by the intercrossing of the whiskers also endows the framework with excellent high-temperature thermal insulation characteristics, thereby combining high strength and low thermal conductivity.

[0022] 3D printed ceramic framework filled with mullite fiber thermal insulation sheet composite: The thermal insulation sheet for preventing thermal runaway must have small thickness and high thermal insulation efficiency in high temperature and high pressure environment, which requires the thermal insulation sheet to have mechanical stability and thermal insulation. The 3D ceramic framework has higher strength than ceramic fiber materials, but the open large pore structure makes it not have thermal insulation performance. Therefore, the two are combined to take advantage of each other. The high-strength ceramic framework bears pressure and deformation, and the filled mullite fiber provides efficient fireproofing and thermal insulation, realizing the preparation of an emergency thermal runaway protection thermal insulation sheet with high strength and high thermal insulation.

[0023] Advantages of the present application:

[0024] 3D printed ceramic framework in-situ grown with mullite whiskers composite: The advantages of the process method are convenient and fast preparation of high-performance aerogel materials due to the advancement of 3D printed ceramic framework and the simple operation of in-situ grown mullite whiskers. The prepared 3D printed ceramic framework in-situ grown with mullite whiskers can have low density (can reach 0.3 g / cm 3 ), low high-temperature thermal conductivity (can reach 0.138 W / (m·K) at 1200℃, and high strength (can reach 1.9 MPa).

[0025] 3D printed ceramic framework filled with mullite fiber thermal insulation sheet composite: The process of the present application is simple and low in cost, and can prepare low density (0.2 g / cm 3 ), low high-temperature thermal conductivity (800℃ high-temperature thermal conductivity is 0.092 W / (m·K)), high strength (1.57 MPa), and efficient emergency thermal runaway protection (the cold-hot surface temperature difference is as high as 545℃ in the simulated 0.9 MPa high pressure and 685℃ high temperature test). The method of 3D printed ceramic framework filled with mullite fiber meets the standard for preventing thermal runaway. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is the real object diagram of the 3D printed ceramic framework in-situ grown with mullite whiskers sample prepared in Test One;

[0027] Figure 2 It is the SEM diagram of the 3D printed ceramic framework in-situ grown with mullite whiskers sample prepared in Test One;

[0028] Figure 3 The mechanical test diagram of the 3D printed ceramic frame in-situ grown with the mullite whisker sample prepared in Test One;

[0029] Figure 4 The thermal evaluation diagram of the 3D printed ceramic frame in-situ grown with the mullite whisker sample prepared in Test One;

[0030] Figure 5 The physical diagram of the 3D printed ceramic frame prepared in Step Two of Test One;

[0031] Figure 6 The physical diagram of the 3D printed ceramic frame filled with the mullite fiber composite material prepared in Test Two;

[0032] Figure 7 The SEM diagram of the 3D printed ceramic frame filled with the mullite fiber composite material prepared in Test Two;

[0033] Figure 8 The mechanical test diagram of the 3D printed ceramic frame filled with the mullite fiber composite material prepared in Test Two;

[0034] Figure 9 The thermal evaluation diagram of the 3D printed ceramic frame filled with the mullite fiber composite material prepared in Test Two. DETAILED DESCRIPTION

[0035] Specific implementation one: the specific implementation is a kind of heat insulation composite material based on 3D printed ceramic frame, specifically two, respectively, 3D printed ceramic frame in-situ growth mullite whisker composite material and 3D printed ceramic frame filling mullite fiber heat insulation sheet composite material.

[0036] Specific implementation two: the specific implementation is the preparation method of 3D printed ceramic frame in-situ growth mullite whisker composite material in specific implementation one, specifically is carried out according to the following steps:

[0037] I, the preparation of mixed sol: the aluminum sol is mixed with silica sol uniformly, and the mixed sol is obtained;The molar ratio of aluminum element and silicon element in the mixed sol is 3:(1-1.2);

[0038] II, impregnation: the 3D printed ceramic frame is placed in a container, and the mixed sol prepared in step one is poured into the container so that the 3D printed ceramic frame is completely immersed in the mixed sol;

[0039] III, freezing and freeze-drying:

[0040] The container of step two is placed into a freeze dryer, frozen to complete freezing at a temperature of minus 50℃ to minus 55℃, and then freeze-dried at a temperature of minus 50℃ to minus 55℃ and a vacuum degree of 50Pa to 55Pa for 72h to 75h to obtain a 3D ceramic framework / sol / gel composite green body;

[0041] Four, heat treatment:

[0042] The aluminum fluoride powder is placed at the bottom of a crucible, and the 3D ceramic framework / sol / gel composite green body of step three is placed in the crucible and above the aluminum fluoride powder. After the crucible is sealed with a cover and placed in a muffle furnace, it is kept at a temperature of 400℃ to 410℃ for 30min to 35min, then heated to 1000℃ to 1100℃ and kept for 2h to 2.5h, and then cooled to room temperature with the furnace to obtain 3D ceramic framework in-situ grown mullite whiskers.

[0043] The mass ratio of the 3D ceramic framework / sol / gel composite green body to aluminum fluoride is 1:(1-1.1).

[0044] Specific implementation method three: the difference between this embodiment and specific implementation method two is that the preparation method of the aluminum sol in step one is: aluminum sec-butoxide and water are mixed, the molar ratio of aluminum sec-butoxide to water is 1:60, reflux stirring is carried out under the condition of a water bath at 90℃ for 1h, then dilute nitric acid aqueous solution is added, and then reflux stirring is continued under the condition of a water bath at 90℃ for 9h to obtain aluminum sol; the concentration of the dilute nitric acid aqueous solution is 1mol / L; the mass ratio of the dilute nitric acid aqueous solution to aluminum sec-butoxide is 1:7.

[0045] The preparation method of the silicon sol in step one is: tetraethyl orthosilicate, anhydrous ethanol, deionized water and dilute hydrochloric acid are mixed into a beaker according to a molar ratio of 1:4:4:7.5x10 -4 The concentration of the hydrochloric acid aqueous solution is 0.2mol / L. The others are the same as specific implementation method two.

[0046] Specific implementation method four: the difference between this embodiment and specific implementation method two is that the molar ratio of aluminum element to silicon element in the mixed sol in step one is 3:1. The others are the same as specific implementation method two.

[0047] Specific implementation method five: the difference between this embodiment and specific implementation method two is that the container of step two is placed into a freeze dryer, frozen to complete freezing at a temperature of minus 50℃. The others are the same as specific implementation method two.

[0048] Specific embodiment six: the embodiment is the preparation method of the 3D printing ceramic framework filled with mullite fiber heat insulation sheet composite material in specific embodiment one, specifically as follows:

[0049] I. Fill mullite fiber:

[0050] The chopped mullite fiber is dispersed into the mixed solution of deionized water and silica sol, and stirred uniformly to form a mixed slurry; wherein the addition amount of the chopped mullite fiber and the silica sol is 1% to 1.5% and 5% to 6% of the mass of the deionized water respectively;

[0051] The 3D printing ceramic framework is placed into the funnel of the vacuum filtration device, and then the above-mentioned mixed slurry is poured into it, the vacuum pump is connected and started, the vacuum degree is adjusted to 0.06 MPa to 0.065 MPa, after all the solution is filtered, the fiber is filled in the 3D printing ceramic framework, the vacuum pump is turned off, and the filled framework wet blank is obtained;

[0052] II. Freeze and freeze-dry:

[0053] The framework wet blank filled in step one is placed into the freeze-drying machine, frozen to complete freezing under the condition of -50℃ to -55℃, and then freeze-dried under the condition of -45℃ to -50℃ and the vacuum degree of 30 Pa to 100 Pa for 72 h to 75 h, and the 3D printing ceramic framework filled with mullite fiber composite material is obtained.

[0054] Specific embodiment seven: the difference between this embodiment and specific embodiment six is that the length of the chopped mullite fiber in step one is 20 μm to 300 μm. The others are the same as specific embodiment six.

[0055] Specific embodiment eight: the difference between this embodiment and specific embodiment six is that the preparation method of the silica sol in step one is as follows: tetraethyl orthosilicate, anhydrous ethanol, deionized water and dilute hydrochloric acid are mixed into a beaker according to the molar ratio of 1:4:4:7.5×10 -4 , and then incubated in a water bath at 50℃ for 1 h to obtain silica sol; the concentration of the hydrochloric acid aqueous solution is 0.2 mol / L. The others are the same as specific embodiment six.

[0056] Specific embodiment nine: the difference between this embodiment and specific embodiment six is that the freezing is performed under the condition of -50℃ in step two. The others are the same as specific embodiment six.

[0057] Specific embodiment ten: the difference between this embodiment and specific embodiment six is that the freeze-drying is performed under the condition of -45℃ and the vacuum degree of 50 Pa in step two, and the 3D printing ceramic framework filled with mullite fiber composite material is obtained. The others are the same as specific embodiment six.

[0058] The present application is verified by the following tests:

[0059] Test one: the present application is a preparation method of 3D printing ceramic framework in-situ growth of mullite whisker composite material, which is carried out according to the following steps:

[0060] I. Preparation of mixed sol: mix the aluminum sol and the silica sol uniformly to obtain the mixed sol; the molar ratio of aluminum element to silicon element in the mixed sol is 3:1;

[0061] The preparation method of the aluminum sol is as follows: mix aluminum sec-butoxide and water, the molar ratio of aluminum sec-butoxide to water is 1:60, reflux and stir under the condition of water bath at 90℃ for 1h, then add dilute nitric acid aqueous solution, and then continue to reflux and stir under the condition of water bath at 90℃ for 9h to obtain the aluminum sol;

[0062] The concentration of the dilute nitric acid aqueous solution is 1mol / L;

[0063] The mass ratio of the dilute nitric acid aqueous solution to aluminum sec-butoxide is 1:7;

[0064] The preparation method of the silica sol is as follows: mix tetraethyl orthosilicate, anhydrous ethanol, deionized water and dilute hydrochloric acid in a beaker according to a molar ratio of 1:4:4:7.5x10 -4 The concentration of the hydrochloric acid aqueous solution is 0.2mol / L;

[0065] II. Immersion: put the 3D printing ceramic framework into a container, and pour the mixed sol prepared in step I into the container so that the 3D printing ceramic framework is completely immersed in the mixed sol;

[0066] The 3D printing ceramic framework is prepared according to the following method:

[0067] ①. Preparation of printing slurry:

[0068] Mix 50g of ceramic precursor PDMS, 3g of crosslinking agent hydrogen-containing silicone oil and 0.17g of inhibitor 1-ethynyl-1-cyclohexanol together and stir for 5min at a speed of 6500r / min; then add 50g of ceramic precursor PDMS and 0.1g of platinum catalyst, and stir for another 5min at a speed of 6500r / min; then add 20g of alumina fiber, stir for 10min, then add 3g of filler boron powder, stir for 5min, then add 25g of white carbon black, which is added in two equal portions, stir for 10min after the first addition, and stir for 30min after the second addition at a speed of 10000r / min to ensure uniform stirring of the slurry;

[0069] ii. Printing the ceramic framework body:

[0070] (1) The Cinema 4D software was used to draw a three-dimensional printing model and export the model to an STL format file. The exported STL format file was imported into the Cura slicing software for slicing, i.e. the three-dimensional model drawn was divided into multiple two-dimensional planes;

[0071] (2) According to the actual needs, the corresponding printing parameters were set on the Cura slicing software, the printing parameters were as follows: the needle diameter was 0.84 mm, the printing layer spacing was 0.6 mm, the printing speed was 20 mm / s, the framework filling rate was 43%, the printing pressure was 0.6 MPa, the filling pattern was sawtooth, and the layer angle was 90°; then printing was carried out, the needle extruded a single filament along the preset printing path, after printing a layer, the printing platform descended along the Z axis by a layer height distance, the single filament printed in the second layer was rotated by 90° on the basis of the single filament printed in the first layer, forming a lap joint unit between the single filaments, and thus the whole ceramic framework body was obtained by repeated printing;

[0072] iii. Printing framework solidification and heat treatment:

[0073] The printed ceramic framework was placed in an oven for solidification, the solidification temperature was 130℃, and the time was 1h; then the heat treatment was carried out in the following two steps:

[0074] (1) Pre-oxidation at low temperature: the solidified ceramic framework was placed in a muffle furnace, heated from room temperature to 320℃ and kept for 6h, the heating rate was 1℃ / min, and then cooled to room temperature with the furnace;

[0075] (2) The pre-oxidized ceramic framework was heated from room temperature to 1300℃ under argon protection and kept for 2h, the heating rate was 2℃ / min, and then cooled to room temperature with the furnace, i.e. the 3D printed polymer-derived porous ceramic framework was obtained, and the thickness of the framework was 10mm;

[0076] III. Freezing and freeze-drying:

[0077] The container of step two was placed in a freeze dryer, frozen to complete freezing at a temperature of minus 50℃, and then freeze-dried at a temperature of minus 50℃ and a vacuum degree of 50Pa for 72h to obtain a 3D ceramic framework / sol composite blank;

[0078] IV. Heat treatment:

[0079] Put the aluminum fluoride powder into the bottom of a crucible, and then put the 3D ceramic framework / sol composite blank of step three above the aluminum fluoride powder in the crucible, seal the crucible with a cover and put it into a muffle furnace, heat it from room temperature to 400℃ at a heating rate of 3℃ / min and keep it for 30min, then heat it to 1000℃ at a heating rate of 3℃ / min and keep it for 2h, and then cool it to room temperature with the furnace, to obtain a 3D ceramic framework in-situ grown with mullite whiskers composite material;

[0080] The mass ratio of the 3D ceramic framework / sol composite blank to aluminum fluoride is 1:1.

[0081] Figure 1 The 3D framework in-situ grown with mullite whiskers sample prepared in test one is shown in the figure, and it can be seen from the figure that the pores between the 3D framework are all filled with mullite whiskers, and the macroscopic morphology is good.

[0082] Figure 2 The SEM image of the 3D framework in-situ grown with mullite whiskers sample prepared in test one is shown in the figure, wherein figure a is the microstructure of the mullite whiskers grown on the surface of the framework, and figure b is the in-situ grown mullite whiskers in the pores of the framework, and it can be seen that the nanometer porous structure formed by the chaotic accumulation of the whiskers is beneficial to the improvement of the heat insulation performance of the material.

[0083] Figure 3 The mechanical test figure of the 3D framework in-situ grown with mullite whiskers sample prepared in test one is shown in the figure, and it can be seen from the figure that the compressive strength of the sample is as high as 1.9MPa, which is better than most aerogel thermal insulation materials.

[0084] Figure 4 The thermal evaluation figure of the 3D framework in-situ grown with mullite whiskers sample prepared in test one is shown in the figure, and one side of the sample is directly heated, that is, the hot side, and the other side is the cold side. It can be seen from the figure that after the sample is burned by a heat source of 1200℃ for 20min, the temperature of the cold side of the sample is only 200℃, and the huge temperature difference (1000℃) between the hot side and the cold side of the 10mm thick sample is realized, indicating that the sample has excellent high-temperature thermal insulation performance.

[0085] Figure 5 The 3D ceramic framework prepared in step two of test one is shown in the figure, and it can be seen from the figure that the 3D ceramic framework after inert gas heat treatment is gray-black, and the structure is complete, indicating that the ceramic framework has high temperature resistance.

[0086] Test two: this test is a preparation method of a 3D printed ceramic framework filled with mullite fiber thermal insulation sheet composite material, which is carried out according to the following steps:

[0087] I. Filling mullite fiber:

[0088] The short-cut mullite fibers are dispersed into a mixture of deionized water and silica sol to form a mixed slurry by stirring; wherein the short-cut mullite fibers and the silica sol are added in an amount of 1% and 5% of the mass of the deionized water, respectively;

[0089] The length of the short-cut mullite fibers is 20-300 μm;

[0090] The preparation method of the silica sol is: tetraethyl orthosilicate, anhydrous ethanol, deionized water and dilute hydrochloric acid are mixed in a beaker in a molar ratio of 1:4:4:7.5x10 -4 , and then incubated in a water bath at 50°C for 1 h to obtain silica sol; the concentration of the hydrochloric acid aqueous solution is 0.2 mol / L;

[0091] The 3D-printed ceramic framework is placed in the funnel of a vacuum filtration device, and the above-mentioned mixed slurry is poured into it, the vacuum pump is connected and started, the vacuum degree is adjusted to 0.06 MPa, and after all the solution is filtered, the fibers are completely filled in the 3D-printed ceramic framework, the vacuum pump is turned off, and the filled framework wet body is obtained;

[0092] The thickness of the 3D-printed ceramic framework is 3 mm, and the rest is exactly the same as in Test 1;

[0093] II. Freezing and freeze-drying:

[0094] The filled framework wet body of step I is placed in a freeze dryer, frozen to complete freezing at a temperature of minus 50°C, and then freeze-dried at minus 45°C and a vacuum degree of 30 Pa for 72 h to obtain a 3D-printed ceramic framework filled with mullite fiber composite material.

[0095] Figure 6 The physical map of the 3D-printed ceramic framework filled with mullite fiber composite material prepared in Test 2, as shown in the figure, the holes of the framework are completely filled with mullite fibers, the upper left corner of the picture is a macroscopic morphology of incomplete filtration, and the rest is a macroscopic morphology after complete filtration, indicating that the filtration method is an effective method for filling mullite fibers in 3D ceramic framework.

[0096] Figure 7 The SEM image of the 3D-printed ceramic framework filled with mullite fiber composite material prepared in Test 2, as shown in the figure, the porous structure composed of 3D ceramic framework and mullite fibers, this composite structure is conducive to the lightweight, high bearing and heat insulation of the sample.

[0097] Figure 8The mechanical test graph of the 3D-printed ceramic framework filled with mullite fiber composite material prepared for test two can be seen from the graph that the compression strength of the sample is about 1.57 MPa, which has high strength and bearing capacity, and can ensure that the structure is not damaged during emergency heat protection.

[0098] Figure 9 The thermal evaluation graph of the 3D-printed ceramic framework filled with mullite fiber composite material prepared for test two can be seen from the graph that the compression strength of the sample is about 1.57 MPa, which has high strength and bearing capacity, and can ensure that the structure is not damaged during emergency heat protection.

[0098] Figure 9 The thermal evaluation graph of the 3D-printed ceramic framework filled with mullite fiber composite material prepared for test two can be seen from the graph that the compression strength of the sample is about 1.57 MPa, which has high strength and bearing capacity, and can ensure that the structure is not damaged during emergency heat protection.

Claims

1.A thermal insulation composite material based on a 3D-printed ceramic framework, specifically two kinds, namely a 3D-printed ceramic framework in-situ grown mullite whisker composite material and a 3D-printed ceramic framework filled with mullite fiber thermal insulation sheet composite material; The preparation method of the 3D-printed ceramic framework in-situ grown mullite whisker composite material is carried out according to the following steps: I. Preparation of mixed sol: uniformly mix aluminum sol and silicon sol to obtain mixed sol;The molar ratio of aluminum element to silicon element in the mixed sol is 3:(1-1.2); The preparation method of the aluminum sol in step one is as follows: mix aluminum sec-butoxide and water, the molar ratio of aluminum sec-butoxide to water is 1:60, reflux and stir under the condition of water bath at 90℃ for 1h, then add dilute nitric acid aqueous solution, and then continue to reflux and stir under the condition of water bath at 90℃ for 9h to obtain aluminum sol;The concentration of the dilute nitric acid aqueous solution is 1mol / L;The mass ratio of the dilute nitric acid aqueous solution to aluminum sec-butoxide is 1:7; The preparation method of the silica sol in step one is as follows: tetraethyl orthosilicate, anhydrous ethanol, deionized water and dilute hydrochloric acid are mixed into a beaker according to a molar ratio of 1:4:4:7.5x10 -4 , and then kept in a water bath at 50°C for 1h to obtain a silica sol; the concentration of the hydrochloric acid aqueous solution is 0.2mol / L; The molar ratio of aluminum element to silicon element in the mixed sol in step one is 3:1; II. Impregnation: put the 3D-printed ceramic framework into a container, pour the mixed sol prepared in step one into the container so that the 3D-printed ceramic framework is completely immersed in the mixed sol; III. Freezing and freeze-drying: Put the container of step two into a freeze-drying machine, freeze to complete freezing under the condition of temperature of minus 50℃, then freeze-dry under the condition of temperature of minus 50℃ to minus 55℃ and vacuum degree of 50Pa to 55Pa for 72h to 75h to obtain a 3D ceramic framework / sol composite green body; IV. Heat treatment: Put aluminum fluoride powder into the bottom of a crucible, then put the 3D ceramic framework / sol composite green body of step three above the aluminum fluoride powder in the crucible, seal the crucible with a cover, and then put it into a muffle furnace, heat it in air atmosphere at 400℃ to 410℃ for 30min to 35min, then increase the temperature to 1000℃ to 1100℃ and heat it for 2h to 2.5h, then cool it to room temperature in the furnace, to obtain a 3D ceramic framework in-situ grown mullite whisker;The mass ratio of the 3D ceramic framework / sol composite green body to aluminum fluoride is 1:(1-1.1); The preparation method of the 3D-printed ceramic framework filled with mullite fiber thermal insulation sheet composite material is carried out according to the following steps: I. Filling mullite fiber: Disperse short-cut mullite fiber into a mixed solution of deionized water and silica sol, stir uniformly to form a mixed slurry;The addition amount of short-cut mullite fiber and silica sol is 1%-1.5% and 5%-6% of the mass of deionized water, respectively; Put the 3D-printed ceramic framework into the funnel of a vacuum filtration device, then pour the above-mentioned mixed slurry, connect the vacuum pump and start, adjust the vacuum degree to 0.06MPa-0.065MPa, after all the solution is filtered, the fiber is completely filled in the 3D-printed ceramic framework, turn off the vacuum pump, to obtain the filled framework wet green body; The length of the short-cut mullite fiber in step one is 20μm-300μm; The preparation method of the silica sol in step one is as follows: tetraethyl orthosilicate, anhydrous ethanol, deionized water and dilute hydrochloric acid are mixed into a beaker according to a molar ratio of 1:4:4:7.5x10 -4 , and then the mixture is kept in a water bath at 50°C for 1h to obtain the silica sol; the concentration of the hydrochloric acid aqueous solution is 0.2mol / L; II. Freezing and freeze-drying: The wet framework filled in step one is put into a freeze dryer, frozen to complete freezing at a temperature of minus 50 ℃, and then freeze-dried at a temperature of minus 45 ℃ and a vacuum degree of 50 Pa for 72 h to obtain a 3D printed ceramic framework filled with mullite fiber composite material.

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