A method for preparing a large-size, irregular rigid aerogel composite member

Abstract

The application provides a preparation method of a large-size special-shaped rigid aerogel composite component and relates to the field of special-shaped aerogels. The preparation method of the large-size special-shaped rigid aerogel composite component is characterized by comprising the following steps: preparing a silica sol, performing a gel dipping treatment, performing gelation and aging, and drying. The preparation method of the large-size special-shaped rigid aerogel composite component can effectively improve the forming stability of the large-size special-shaped rigid aerogel component, avoids the problems of uneven impregnation, uneven thickness, cracking and poor roughness of the large-size special-shaped rigid aerogel component prepared by the existing process, and improves the quality of the aerogel component. Meanwhile, the sol utilization rate is effectively improved, the forming operation difficulty is reduced, the production efficiency is improved, and the production cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of irregularly shaped aerogels, and in particular to a method for preparing large-sized, irregularly shaped rigid aerogel composite components. Background Technology

[0002] New spacecraft fly at high Mach numbers in the atmosphere for extended periods, and their fuselages are subjected to severe aerodynamic heating, noise and vibration, and maneuvering overload impacts. Therefore, the large-area heat-insulating materials of the fuselage should have characteristics such as high strength, excellent heat insulation performance, high temperature resistance, and lightweight.

[0003] Aerogel, as a novel and highly efficient thermal insulation material, possesses characteristics such as high temperature resistance, lightweight, good mechanical properties, and moldability, and has shown broad application prospects in the aerospace field. However, due to the complex structures of surfaces and cabins in new aircraft and the need for vibration resistance during use, flexible aerogel insulation materials (such as thermal insulation felt) suffer from severe powder shedding and poor vibration resistance, making it difficult to meet usage requirements. Therefore, there is an urgent need for large-size, irregularly shaped rigid aerogel insulation materials that can ensure good adhesion between the aerogel surface and the metal cabin surface while meeting stringent requirements for vibration resistance and impact resistance during use.

[0004] Existing methods for impregnating rigid aerogel components mostly involve first positioning and shaping the fiber body using an impregnation mold. The mold, containing the shaped fiber body, is then placed in a specialized vacuum impregnation device, through which sol is introduced to impregnate the shaped fiber body within the mold, thus obtaining the impregnated component. However, due to limitations in existing impregnation processes and molds, large-sized, irregularly shaped rigid aerogel components with dimensions greater than 1000mm in length or width and greater than 100mm in thickness often exhibit unstable impregnation processes. This results in uneven impregnation, inconsistent thickness, cracking, and poor roughness, leading to poor aerogel component quality. Furthermore, existing methods for impregnating large-sized, irregularly shaped rigid aerogel components also suffer from low sol utilization, high operational difficulty, and time-consuming processing, resulting in high overall production costs. Summary of the Invention

[0005] To address the technical problems existing in the prior art, this invention provides a method for preparing large-size, irregularly shaped rigid aerogel composite components. This method can effectively improve the molding stability of large-size, irregularly shaped rigid aerogel components, avoid problems such as uneven impregnation, uneven thickness, cracking, and poor roughness in large-size, irregularly shaped rigid aerogel components prepared by existing processes, and improve the quality of aerogel components. At the same time, it effectively improves the sol utilization rate, reduces the difficulty of molding operations, increases production efficiency, and reduces production costs.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a large-size, irregularly shaped rigid aerogel composite component includes the following steps: preparing silica sol, impregnation treatment, gelation and aging, and drying;

[0008] The method for preparing silica sol is as follows: under heating conditions, an alkaline catalyst solution is added to an organosilane precursor to obtain silica sol, which is then ready for use.

[0009] The impregnation process is as follows: the shaped fiber preform is placed into a vacuum bag of the impregnation mold, and then the entire vacuum bag is placed inside the cavity of the impregnation mold; a vacuum is drawn through the upper interface tube of the impregnation mold, and the inside of the vacuum bag is kept in a vacuum state for 10-15 minutes. Then, silica sol is drawn in through the lower interface tube of the impregnation mold until the silica sol enters the upper interface tube of the impregnation mold. The drawing in of silica sol is stopped, and the liquid level of silica sol in the upper interface tube is obtained and recorded as the first position. The vacuum is then drawn in for another 10-15 minutes. The liquid level of silica sol in the upper interface tube is obtained again and recorded as the second position. When the second position does not decrease compared to the first position, the vacuum is stopped. When the difference between the theoretical amount of impregnation required to obtain the shaped fiber preform and the total amount of silica sol entering the impregnation mold is less than or equal to ±3%, the impregnation process is completed.

[0010] The length or width of the irregular fiber preform is greater than 1000 mm, and the thickness is greater than 100 mm.

[0011] Preferably, the heating temperature in the preparation of silica sol is 45-75℃;

[0012] The organosilane precursor is a mixture of methyltrimethoxysilane and tetraethyl orthosilicate, or a mixture of methyltrimethoxysilane and methyl orthosilicate;

[0013] The alkaline catalyst solution is an aqueous solution of ammonia in ethanol.

[0014] Preferably, the mass fraction of ammonia in the alkaline catalyst solution is 0.25-0.5 wt%, and the volume ratio of ethanol to water is 1-1.2:1;

[0015] The molar ratio of the alkaline component to the organosilane precursor in the alkaline catalyst solution is 0.1-0.5:1.

[0016] Furthermore, during the impregnation process, when the second position decreases compared to the first position, the following operation is repeated: silica sol is drawn in through the lower interface tube of the impregnation mold until the silica sol enters the first position in the upper interface tube of the impregnation mold, at which point the drawing of silica sol is stopped; after continuing to evacuate for 10-15 minutes, the liquid level of the silica sol in the upper interface tube is re-acquired until the re-acquired liquid level is no lower than the first position.

[0017] Furthermore, in the impregnation process, when the difference between the theoretical amount of impregnation required for the shaped fiber preform and the total amount of silica sol entering the impregnation mold is greater than ±3%, 15-25% of the volume of silica sol in the impregnation mold is discharged under pressure. Then, vacuum is applied again and silica sol is drawn in through the lower interface tube of the impregnation mold until the silica sol enters the first position in the upper interface tube of the impregnation mold. Vacuum is then applied for 10-15 minutes. The liquid level of silica sol in the upper interface tube (2) is then obtained again and recorded as the second position. When the second position does not decrease compared to the first position, vacuuming is stopped. The impregnation process is completed when the difference between the theoretical amount of impregnation required for the shaped fiber preform and the total amount of silica sol entering the impregnation mold is less than or equal to ±3%.

[0018] Preferably, in the impregnation process, the irregular fiber preform is made by using ceramic fiber felt and / or ceramic fiber as the main raw materials and processing them to a predetermined shape and size;

[0019] The processing methods include, but are not limited to: cutting, weaving, needle punching, molding, lay-up, and 3D printing.

[0020] Furthermore, the impregnation mold used in the impregnation process includes a mold body, an upper interface tube, and a lower interface tube; the mold body has a split structure, including a left mold and a right mold; a cavity is formed inside the mold body; a vacuum bag for placing the irregular fiber preform is movably disposed in the cavity.

[0021] Furthermore, the upper interface tube is made of transparent material and is connected to the vacuum pump in order to maintain the vacuum bag inside the cavity in a vacuum state and to obtain the liquid level position inside the upper interface tube.

[0022] The lower interface pipe is equipped with a flow meter to measure the total amount of silica sol entering the impregnation mold.

[0023] Furthermore, the gelation and aging method is as follows: after the impregnation treatment is completed, the entire impregnated mold is placed in an oven and heated to 40-60℃. After heat preservation and gelation for 4-5 hours, it is allowed to stand and age for 22-24 hours, then demolded to obtain a gel composite.

[0024] Furthermore, the drying method involves supercritical drying of the gel composite, controlling the supercritical drying temperature at 270-280℃, the pressure at 8-10MPa, the pressure reduction rate at 2-3MPa / h, and the supercritical drying time at 2-4h, to obtain large-sized, irregularly shaped rigid aerogel composite components.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] (1) The preparation method of the large-size, irregularly shaped rigid aerogel composite component of the present invention can effectively overcome the problems of low sol utilization, high operation difficulty and time-consuming processing in the preparation of irregularly shaped rigid aerogel components with a length or width greater than 1000 mm and a thickness greater than 100 mm, as well as the problems of uneven impregnation, uneven thickness, cracking and poor roughness of the large-size, irregularly shaped rigid aerogel components. It can effectively improve the molding stability of large-size, irregularly shaped rigid aerogel components and improve the processing quality of components.

[0027] Specifically, through a specific impregnation process, silica sol uniformly fills the fiber preform, effectively and fully impregnating large-sized, irregularly shaped fiber preforms, thus improving the processing quality of large-sized, irregularly shaped rigid aerogel components. The vacuum impregnation process, using a vacuum bag inside the mold, minimizes sol loss during impregnation, significantly improving sol utilization and increasing the uniformity of sol impregnation. Simultaneously, by controlling the degree of impregnation (judged by liquid level) and the amount of impregnation (judged by comparing impregnation amounts), problems such as uneven impregnation, uneven thickness, cracking, and poor roughness that are prone to occur during the preparation process are effectively avoided, thus improving the quality of aerogel components and increasing the yield. Furthermore, it further improves sol utilization, reduces the difficulty of molding operations, increases production efficiency, and reduces overall production costs. Moreover, supercritical drying further enhances the processing quality of large-sized, irregularly shaped rigid aerogel components.

[0028] (2) The method for preparing large-size, irregularly shaped rigid aerogel composite components of the present invention allows for aerogel components with a thickness exceeding 100 mm and a length or width exceeding 1000 mm; moreover, one set of molds can be used for various irregularly shaped parts, reducing mold costs and increasing yield. Vacuum impregnation of irregularly shaped fiber preforms by vacuum bag encapsulation allows the sol to fully impregnate the irregularly shaped fiber preforms, eliminating the need for a special vacuum impregnation tank, resulting in stable product quality, high sol utilization, reduced production costs, and increased yield. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the impregnation mold used in an embodiment of the present invention. In the figure, 1-mold body, 2-upper interface tube, 3-lower interface tube. Detailed Implementation

[0030] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific embodiments are now described. It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0031] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, "first," "second," etc., are used to distinguish similar objects and are not used to describe a particular order or sequence. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0032] This invention provides a method for preparing large-size, irregularly shaped rigid aerogel composite components, comprising the following steps: preparing silica sol, impregnation treatment, gelation and aging, and drying.

[0033] The method for preparing silica sol involves using an organosilane precursor to prepare silica sol for later use. Specifically, an alkaline catalyst solution is added to the organosilane precursor under heating conditions of 45-75℃, and the mixture is kept at this temperature and stirred for 6-24 hours to obtain silica sol. The silica sol is then transferred to a sol-gel container for later use.

[0034] In the preparation of silica sol, the organosilane precursor is a mixture of methyltrimethoxysilane and tetraethyl orthosilicate, or a mixture of methyltrimethoxysilane and methyl orthosilicate; preferably, the weight ratio of methyltrimethoxysilane to tetraethyl orthosilicate (or methyl orthosilicate) is 1:0.3-0.4.

[0035] In the preparation of silica sol, the alkaline catalyst solution is an aqueous solution of ammonia in ethanol, with an ammonia mass fraction of 0.25-0.5 wt% and a volume ratio of ethanol to water of 1-1.2:1.

[0036] The molar ratio of the alkaline component to the organosilane precursor in the alkaline catalyst solution is 0.1-0.5:1.

[0037] The impregnation process is performed using an impregnation mold (e.g., ...). Figure 1As shown in the diagram, the mold includes a mold body 1, an upper interface pipe 2, and a lower interface pipe 3. The mold body 1 is a split structure, comprising a left mold and a right mold, which are bolted together. An internal cavity is formed within the mold body 1; a vacuum bag for holding the shaped fiber preform is movably disposed within the cavity. The upper interface pipe 2 is made of transparent material and is connected to a vacuum pump to maintain a vacuum inside the vacuum bag within the cavity and to monitor the liquid level within the pipe; the upper interface pipe 2 also has an upper valve. The lower interface pipe 3 is connected to a sol tank containing silica sol; the lower interface pipe 3 also has a lower valve and a flow meter, which measures the total amount of silica sol entering the cavity of the impregnation mold.

[0038] The specific method for impregnation is as follows: The shaped fiber preform is placed into a vacuum bag of the impregnation mold, and then the entire vacuum bag is placed inside the cavity of the impregnation mold, fixing the mold in place. The vacuum pump connected to the upper interface pipe 2 is turned on, and the upper valve is opened, maintaining a vacuum state (vacuum degree 0.08-0.099 MPa) inside the vacuum bag for 10-15 minutes. Then, the lower valve of the lower interface pipe 3 is opened, allowing the silica sol in the sol tank to be drawn into the vacuum bag inside the cavity of the impregnation mold. When the silica sol enters the transparent upper interface pipe 2 of the impregnation mold, the lower valve is closed, and the liquid level of the silica sol in the upper interface pipe 2 is obtained and recorded as the first position. Vacuuming continues for 10-15 minutes. Then, the liquid level of the silica sol in the upper interface pipe 2 is obtained again and recorded as the second position. It is determined whether the second position is lower than the first position, and the following processing is performed accordingly:

[0039] a. When the second position is lower than the first position, reopen the lower valve of the lower interface tube 3 to draw in silica sol until the liquid level of the silica sol in the upper interface tube 2 reaches the first position. Then close the lower valve of the lower interface tube 3 and continue to evacuate for 10-15 minutes. Repeat the above judgment operation.

[0040] b. When the second position does not decrease compared to the first position, close the upper valve of the upper interface pipe 2 to stop vacuuming; compare the theoretical amount of resin impregnation required for the shaped fiber preform with the total amount of silica sol entering the impregnation mold cavity obtained by the flow meter at the lower interface pipe 3 (i.e., the actual amount of resin impregnation), and perform the following processing respectively:

[0041] m. The impregnation process is completed when the difference between the actual impregnation amount and the theoretical impregnation amount is less than or equal to ±3%.

[0042] n. When the difference between the actual impregnation amount and the theoretical impregnation amount is greater than ±3%, open the upper valve of the upper interface pipe 2 and pressurize it to discharge 15-25% of the volume of silica sol in the impregnation mold. Then, turn on the vacuum pump again to draw in the silica sol to the first position and repeat the above operation.

[0043] In the impregnation process, the irregular fiber preform is made by using ceramic fiber felt and / or ceramic fiber as the main raw materials and processing it to a predetermined shape and size using existing processing methods; the existing processing methods include, but are not limited to: cutting, weaving, needle punching, molding, lay-up, and 3D printing.

[0044] The gelation and aging method is as follows: after the impregnation treatment is completed, the entire impregnated mold is placed in an oven and heated to 40-60℃. It is kept at this temperature for 4-8 hours to gel, and then allowed to stand for aging for 22-24 hours before demolding to obtain the gel composite.

[0045] The drying method involves supercritical drying of the gel composite, controlling the supercritical drying temperature at 270-280℃, the pressure at 8-10MPa, the pressure reduction rate at 2-3MPa / h, and the supercritical drying time at 2-4h, to obtain large-sized, irregularly shaped rigid aerogel composite components.

[0046] The present invention will be further described below with reference to some specific embodiments.

[0047] Example 1

[0048] This embodiment provides a method for preparing large-sized, irregularly shaped rigid aerogel composite components, including the following steps:

[0049] S1. Preparation of silica sol

[0050] Silica sol was prepared using an organosilane precursor and set aside for use. Specifically, an alkaline catalyst solution was added to the organosilane precursor under heating at 50°C, and the mixture was stirred for 24 hours to obtain silica sol. The silica sol was then transferred to a sol-gel container and set aside for use.

[0051] The organosilane precursor is a mixture of methyltrimethoxysilane and tetraethyl orthosilicate, with a ratio of 1:0.3.

[0052] The alkaline catalyst solution is an aqueous solution of ammonia in ethanol, with an ammonia mass fraction of 0.25 wt% and a volume ratio of ethanol to water of 1:1.

[0053] The molar ratio of the alkaline component to the organosilane precursor in the alkaline catalyst solution is 0.2:1.

[0054] S2, Impregnation treatment

[0055] The impregnation process is performed using an impregnation mold, which includes a mold body 1, an upper interface pipe 2, and a lower interface pipe 3. The mold body 1 is a split structure, consisting of a left mold and a right mold, which are bolted together. An internal cavity is formed within the mold body 1; a vacuum bag for holding the shaped fiber preform is movably disposed within this cavity. The upper interface pipe 2 is made of transparent material and is connected to a vacuum pump to maintain a vacuum inside the vacuum bag and to monitor the liquid level within the pipe; the upper interface pipe 2 also has an upper valve. The lower interface pipe 3 is connected to a sol tank containing silica sol; the lower interface pipe 3 also has a lower valve and a flow meter, which measures the total amount of silica sol entering the impregnation mold cavity.

[0056] The specific method for impregnation is as follows: The irregularly shaped fiber preform (1200mm in length and width, 135mm in thickness) is placed into the vacuum bag of the impregnation mold. The entire preform, including the vacuum bag, is then placed inside the cavity of the impregnation mold, and the mold is fixed. The vacuum pump connected to the upper interface pipe 2 is turned on, and the upper valve is opened to maintain a vacuum state (0.09MPa) inside the vacuum bag for 15 minutes. Then, the lower valve of the lower interface pipe 3 is opened to draw the silica sol from the sol tank into the vacuum bag inside the cavity of the impregnation mold. Once the silica sol enters the transparent upper interface pipe 2 of the impregnation mold, the lower valve is closed, and the liquid level of the silica sol in the upper interface pipe 2 is recorded as the first position. Vacuuming continues for 15 minutes. The liquid level of the silica sol in the upper interface pipe 2 is then recorded as the second position. It is determined whether the second position is lower than the first position, and the following treatments are performed accordingly:

[0057] a. When the second position decreases compared to the first position, reopen the lower valve of the lower interface pipe 3 until the liquid level of the silica sol in the upper interface pipe 2 reaches the first position, close the lower valve of the lower interface pipe 3, continue to evacuate for 15 minutes, and repeat the aforementioned judgment operation.

[0058] b. When the second position does not decrease compared to the first position, close the upper valve of the upper interface pipe 2 to stop vacuuming; compare the theoretical amount of resin impregnation required for the shaped fiber preform with the total amount of silica sol entering the impregnation mold cavity obtained by the flow meter at the lower interface pipe 3 (i.e., the actual amount of resin impregnation), and perform the following processing respectively:

[0059] m. The impregnation process is completed when the difference between the actual impregnation amount and the theoretical impregnation amount is less than or equal to ±3%.

[0060] n. When the difference between the actual impregnation amount and the theoretical impregnation amount is greater than ±3%, open the upper valve of the upper interface pipe 2 and pressurize it to discharge 15% of the volume of silica sol in the impregnation mold. Then, turn on the vacuum pump again to draw in the silica sol to the first position and repeat the above operation.

[0061] Among them, the irregular fiber preform is made by using ceramic fiber felt as the main raw material and cutting it to a predetermined shape and size.

[0062] S3, Gel and Aging

[0063] After the impregnation process is completed, the entire impregnated mold is placed in an oven and heated to 45°C. It is kept at this temperature for 8 hours to gel, and then allowed to stand for 22 hours to age before being demolded to obtain the gel composite.

[0064] S4, Drying

[0065] The gel composite was subjected to supercritical drying at a temperature of 270℃, a pressure of 10MPa, a pressure drop rate of 2MPa / h, and a supercritical drying time of 2.5h to obtain large-sized, irregularly shaped rigid aerogel composite components.

[0066] The large-sized, irregularly shaped rigid aerogel composite components prepared by the method of this embodiment do not exhibit uneven impregnation, uneven thickness, cracking, or poor roughness, resulting in high component quality. The preparation method provides good component molding stability, high sol utilization, ease of operation, and a stable and efficient preparation process.

[0067] Example 2

[0068] This embodiment provides a method for preparing large-sized, irregularly shaped rigid aerogel composite components, including the following steps:

[0069] S1. Preparation of silica sol

[0070] Silica sol was prepared using an organosilane precursor and set aside for use. Specifically, an alkaline catalyst solution was added to the organosilane precursor under heating at 60°C, and the mixture was stirred for 18 hours to obtain silica sol. The silica sol was then transferred to a sol-gel container and set aside for use.

[0071] The organosilane precursor is a mixture of methyltrimethoxysilane and methyl orthosilicate; the weight ratio of methyltrimethoxysilane to methyl orthosilicate is 1:0.3-0.4.

[0072] The alkaline catalyst solution is an aqueous solution of ammonia in ethanol, with an ammonia mass fraction of 0.35 wt% and a volume ratio of ethanol to water of 1.1:1.

[0073] The molar ratio of the alkaline component to the organosilane precursor in the alkaline catalyst solution is 0.25:1.

[0074] S2, Impregnation treatment

[0075] The impregnation mold used in the impregnation process is the same as in Example 1. The specific method of impregnation is as follows: the irregular fiber preform (length and width dimensions are both 1200mm, thickness dimension is 135mm) is placed into the vacuum bag of the impregnation mold, and then the entire vacuum bag is placed in the cavity of the impregnation mold, and the impregnation mold is fixed; the vacuum pump connected to the upper interface pipe 2 is turned on and the upper valve is opened to maintain a vacuum state (vacuum degree 0.098MPa) inside the vacuum bag for 10 minutes; then the lower valve of the lower interface pipe 3 is opened to draw the silica sol in the sol tank into the vacuum bag in the cavity of the impregnation mold; when the silica sol enters the transparent upper interface pipe 2 of the impregnation mold, the lower valve is closed, the liquid level position of the silica sol in the upper interface pipe 2 is obtained and recorded as the first position, and the vacuum is continued for 10 minutes; then the liquid level position of the silica sol in the upper interface pipe 2 is obtained again and recorded as the second position; it is determined whether the second position is lower than the first position, and the following processing is performed respectively:

[0076] a. When the second position is lower than the first position, reopen the lower valve of the lower interface pipe 3 until the liquid level of the silica sol in the upper interface pipe 2 reaches the first position, close the lower valve of the lower interface pipe 3, continue to evacuate for 10 minutes, and repeat the above judgment operation.

[0077] b. When the second position does not decrease compared to the first position, close the upper valve of the upper interface pipe 2 to stop vacuuming; compare the theoretical amount of resin impregnation required for the shaped fiber preform with the total amount of silica sol entering the impregnation mold cavity obtained by the flow meter at the lower interface pipe 3 (i.e., the actual amount of resin impregnation), and perform the following processing respectively:

[0078] m. The impregnation process is completed when the difference between the actual impregnation amount and the theoretical impregnation amount is less than or equal to ±3%.

[0079] n. When the difference between the actual impregnation amount and the theoretical impregnation amount is greater than ±3%, open the upper valve of the upper interface pipe 2 and pressurize it to discharge 20% of the volume of silica sol in the impregnation mold. Then, turn on the vacuum pump again to draw in the silica sol to the first position and repeat the above operation.

[0080] Among them, the irregular fiber preform is made by using ceramic fiber felt as the main raw material and cutting it to a predetermined shape and size.

[0081] S3, Gel and Aging

[0082] After the impregnation process is completed, the entire impregnated mold is placed in an oven, heated to 50°C, kept warm for 7 hours for gelation, and allowed to stand for 23 hours for aging before demolding to obtain the gel composite.

[0083] S4, Drying

[0084] The gel composite was subjected to supercritical drying at a temperature of 275℃, a pressure of 9MPa, a pressure drop rate of 2.4MPa / h, and a supercritical drying time of 3h to obtain large-sized, irregularly shaped rigid aerogel composite components.

[0085] The large-sized, irregularly shaped rigid aerogel composite components prepared by the method of this embodiment do not exhibit uneven impregnation, uneven thickness, cracking, or poor roughness, resulting in high component quality. The preparation method provides good component molding stability, high sol utilization, ease of operation, and a stable and efficient preparation process.

[0086] Example 3

[0087] This embodiment provides a method for preparing large-sized, irregularly shaped rigid aerogel composite components, including the following steps:

[0088] S1. Preparation of silica sol

[0089] Silica sol was prepared using an organosilane precursor and set aside for use. Specifically, an alkaline catalyst solution was added to the organosilane precursor under heating at 70°C, and the mixture was stirred for 14 hours to obtain silica sol. The silica sol was then transferred to a sol-gel container and set aside for use.

[0090] The organosilane precursor is a mixture of methyltrimethoxysilane and tetraethyl orthosilicate; the weight ratio of methyltrimethoxysilane to tetraethyl orthosilicate is 1:0.4.

[0091] The alkaline catalyst solution is an aqueous solution of ammonia in ethanol, with an ammonia mass fraction of 0.4 wt% and a volume ratio of ethanol to water of 1.2:1.

[0092] The molar ratio of the alkaline component to the organosilane precursor in the alkaline catalyst solution is 0.3:1.

[0093] S2, Impregnation treatment

[0094] The impregnation mold used in the impregnation process is the same as in Example 1. The specific method of impregnation is as follows: the irregular fiber preform (length and width dimensions are both 1200mm, thickness dimension is 135mm) is placed into the vacuum bag of the impregnation mold, and then the entire vacuum bag is placed in the cavity of the impregnation mold, and the impregnation mold is fixed; the vacuum pump connected to the upper interface pipe 2 is turned on and the upper valve is opened to keep the vacuum bag in a vacuum state (vacuum degree 0.09MPa) for 10min; then the lower valve of the lower interface pipe 3 is opened to draw the silica sol in the sol tank into the vacuum bag in the cavity of the impregnation mold; when the silica sol enters the transparent upper interface pipe 2 of the impregnation mold, the lower valve is closed, the liquid level position of the silica sol in the upper interface pipe 2 is obtained and recorded as the first position, and the vacuum is continued for 10min; then the liquid level position of the silica sol in the upper interface pipe 2 is obtained again and recorded as the second position; it is determined whether the second position is lower than the first position, and the following processing is performed respectively:

[0095] a. When the second position is lower than the first position, reopen the lower valve of the lower interface pipe 3 until the liquid level of the silica sol in the upper interface pipe 2 reaches the first position, close the lower valve of the lower interface pipe 3, continue to evacuate for 10 minutes, and repeat the above judgment operation.

[0096] b. When the second position does not decrease compared to the first position, close the upper valve of the upper interface pipe 2 to stop vacuuming; compare the theoretical amount of resin impregnation required for the shaped fiber preform with the total amount of silica sol entering the impregnation mold cavity obtained by the flow meter at the lower interface pipe 3 (i.e., the actual amount of resin impregnation), and perform the following processing respectively:

[0097] m. The impregnation process is completed when the difference between the actual impregnation amount and the theoretical impregnation amount is less than or equal to ±3%.

[0098] n. When the difference between the actual impregnation amount and the theoretical impregnation amount is greater than ±3%, open the upper valve of the upper interface pipe 2 and pressurize it to discharge 18% of the volume of silica sol in the impregnation mold. Then, turn on the vacuum pump again to draw in the silica sol to the first position and repeat the above operation.

[0099] Among them, the irregular fiber preform is made by using ceramic fiber felt and ceramic fiber as the main raw materials and then needle-punching it to a predetermined shape and size.

[0100] S3, Gel and Aging

[0101] After the impregnation process is completed, the entire impregnated mold is placed in an oven, heated to 60°C, kept warm for 5 hours to gel, and allowed to stand for 22 hours to age before demolding to obtain the gel composite.

[0102] S4, Drying

[0103] The gel composite was subjected to supercritical drying at a temperature of 280℃, a pressure of 8MPa, a pressure reduction rate of 3MPa / h, and a supercritical drying time of 3h to obtain large-sized, irregularly shaped rigid aerogel composite components.

[0104] The large-sized, irregularly shaped rigid aerogel composite components prepared by the method of this embodiment do not exhibit uneven impregnation, uneven thickness, cracking, or poor roughness, resulting in high component quality. The preparation method provides good component molding stability, high sol utilization, ease of operation, and a stable and efficient preparation process.

[0105] Unless otherwise stated, all percentages used in this invention are mass percentages.

[0106] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a large-size, irregularly shaped rigid aerogel composite component, characterized in that, Includes the following steps: Preparation of silica sol, impregnation treatment, gelation and aging, drying; The method for preparing silica sol is as follows: under heating conditions, an alkaline catalyst solution is added to an organosilane precursor to obtain silica sol, which is then ready for use. The impregnation process is as follows: the shaped fiber preform is placed into the vacuum bag of the impregnation mold, and then the entire vacuum bag is placed in the cavity of the impregnation mold; the upper interface tube (2) of the impregnation mold is used to draw a vacuum, and the vacuum bag is kept in a vacuum state for 10-15 minutes. Then, silica sol is drawn in through the lower interface tube (3) of the impregnation mold until the silica sol enters the upper interface tube (2) of the impregnation mold. The silica sol is then drawn in, and the liquid level of the silica sol in the upper interface tube (2) is obtained and recorded as the first position. The vacuum is then drawn in for another 10-15 minutes. The liquid level of the silica sol in the upper interface tube (2) is obtained again and recorded as the second position. The vacuum is stopped when the second position is not lower than the first position. The impregnation process is completed when the difference between the theoretical amount of impregnation required to obtain the shaped fiber preform and the total amount of silica sol entering the impregnation mold is less than or equal to ±3%. The length or width of the irregular fiber preform is greater than 1000 mm, and the thickness is greater than 100 mm.

2. The method for preparing large-size, irregularly shaped rigid aerogel composite components according to claim 1, characterized in that, In the preparation of the silica sol, the heating temperature is 45-75℃; The organosilane precursor is a mixture of methyltrimethoxysilane and tetraethyl orthosilicate, or a mixture of methyltrimethoxysilane and methyl orthosilicate; The alkaline catalyst solution is an aqueous solution of ammonia in ethanol.

3. The method for preparing large-size, irregularly shaped rigid aerogel composite components according to claim 2, characterized in that, The alkaline catalyst solution contains 0.25-0.5 wt% ammonia and has a volume ratio of ethanol to water of 1-1.2:

1. The molar ratio of the alkaline component to the organosilane precursor in the alkaline catalyst solution is 0.1-0.5:

1.

4. The method for preparing large-size, irregularly shaped rigid aerogel composite components according to claim 1, characterized in that, In the impregnation process, when the second position is lower than the first position, the following operation is repeated: silica sol is drawn in through the lower interface tube (3) of the impregnation mold until the silica sol enters the first position in the upper interface tube (2) of the impregnation mold. Then, the silica sol is drawn in, and vacuuming is continued for 10-15 minutes. The liquid level of the silica sol in the upper interface tube (2) is then obtained again until the liquid level obtained again is no lower than the first position.

5. The method for preparing large-size, irregularly shaped rigid aerogel composite components according to claim 1, characterized in that, In the impregnation process, when the difference between the theoretical amount of impregnation required for the shaped fiber preform and the total amount of silica sol entering the impregnation mold is greater than ±3%, 15-25% of the volume of silica sol in the impregnation mold is discharged under pressure. Then, vacuum is applied again and silica sol is drawn in through the lower interface tube (3) of the impregnation mold until the silica sol enters the first position in the upper interface tube (2) of the impregnation mold. Vacuum is then applied for 10-15 minutes. The liquid level of silica sol in the upper interface tube (2) is then obtained again and recorded as the second position. When the second position is not lower than the first position, vacuuming is stopped. The difference between the theoretical amount of impregnation required for the shaped fiber preform and the total amount of silica sol entering the impregnation mold is compared and determined until the difference is less than or equal to ±3%, at which point the impregnation process is completed.

6. The method for preparing large-size, irregularly shaped rigid aerogel composite components according to claim 1, characterized in that, In the impregnation process, the irregular fiber preform is made by using ceramic fiber felt and / or ceramic fiber as the main raw materials and processing them to a predetermined shape and size. The processing methods include, but are not limited to: cutting, weaving, needle punching, molding, lay-up, and 3D printing.

7. The method for preparing large-size, irregularly shaped rigid aerogel composite components according to claim 1, characterized in that, The impregnation mold used in the impregnation process includes a mold body (1), an upper interface tube (2), and a lower interface tube (3); the mold body (1) is a left-right split structure, including a left mold and a right mold; a cavity is formed inside the mold body (1); a vacuum bag for placing the irregular fiber preform is movably arranged in the cavity.

8. The method for preparing large-size, irregularly shaped rigid aerogel composite components according to claim 7, characterized in that, The upper interface tube (2) is made of transparent material and is connected to the vacuum pump in order to keep the vacuum bag inside the cavity in a vacuum state and to obtain the liquid level position inside the upper interface tube (2). The lower interface pipe (3) is equipped with a flow meter to measure the total amount of silica sol entering the impregnation mold.

9. The method for preparing large-size, irregularly shaped rigid aerogel composite components according to claim 1, characterized in that, The gelation and aging method is as follows: after the impregnation treatment is completed, the entire impregnated mold is placed in an oven and heated to 40-60℃. After gelation for 4-5 hours, it is allowed to stand for aging for 22-24 hours, then demolded to obtain a gel composite.

10. The method for preparing large-size, irregularly shaped rigid aerogel composite components according to claim 1, characterized in that, The drying method involves supercritical drying of the gel composite, controlling the supercritical drying temperature at 270-280℃, the pressure at 8-10MPa, the pressure reduction rate at 2-3MPa / h, and the supercritical drying time at 2-4h, to obtain large-sized, irregularly shaped rigid aerogel composite components.

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