Preparation method of large-size special-shaped rigid aerogel composite component

Abstract

The invention provides a preparation method of a large-size special-shaped rigid aerogel composite component, and relates to the field of special-shaped aerogel. The preparation method of the large-size special-shaped rigid aerogel composite component is characterized by comprising the following steps: preparing silicon oxide sol, carrying out gum dipping treatment, gelling and aging, and drying. According to the preparation method of the large-size and special-shaped rigid aerogel composite component, the forming stability of the large-size and special-shaped rigid aerogel component can be effectively improved, the problems of non-uniform impregnation, non-uniform thickness, cracking and poor roughness of the large-size and special-shaped rigid aerogel component prepared by an existing process are avoided, and the quality of the aerogel component is improved; 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] The present invention relates to the field of special-shaped aerogels, and in particular to a method for preparing a large-sized, special-shaped rigid aerogel composite component. Background Art

[0002] New spacecraft fly in the atmosphere at high Mach numbers for a long time, and the fuselage is in a harsh environment such as severe aerodynamic heating, noise and vibration, and maneuvering flight overload impact. The large area of ​​the fuselage's thermal insulation material should have the characteristics of high strength, excellent thermal insulation performance, high temperature resistance, and light weight.

[0003] As a new, highly efficient thermal insulation material, aerogel boasts high-temperature resistance, lightweight, excellent mechanical properties, and excellent formability, demonstrating promising applications in the aerospace sector. However, due to the complex structures of new aircraft surfaces and cabins, as well as the need for vibration resistance during use, flexible aerogel insulation materials (such as insulation felt) suffer from severe powder shedding and poor vibration resistance, making them difficult to meet operational requirements. Consequently, there is an urgent need for large-scale, custom-shaped rigid aerogel insulation materials that ensure a good fit between the aerogel surface and the metal cabin, while also meeting stringent requirements for vibration and impact resistance during use.

[0004] Most existing methods for forming rigid aerogel components by dipping them in a resin-based molding mold first position and shape the fiber body, then place the mold with the positioned fiber body in a dedicated vacuum impregnation device, and then pass a sol into the dedicated vacuum impregnation device. The sol is then used to impregnate the shaped fiber body in the mold to produce a dipping molded body. However, due to the limitations of existing dipping processes and molds, large-sized, irregularly shaped rigid aerogel components with a length or width greater than 1000mm and a thickness greater than 100mm can easily suffer from unstable dipping molding. The prepared rigid aerogel components suffer from uneven dipping, uneven thickness, cracking, and poor roughness, resulting in poor quality of the aerogel components. At the same time, existing dipping molding methods for large-sized, irregularly shaped rigid aerogel components also suffer from low sol utilization, difficult operation, and time-consuming processing, resulting in high overall production costs. Summary of the Invention

[0005] In order to solve the technical problems existing in the prior art, the present invention provides a method for preparing large-sized and special-shaped rigid aerogel composite components, which can effectively improve the molding stability of large-sized and special-shaped rigid aerogel components, avoid the problems of uneven impregnation, uneven thickness, cracking, and poor roughness of large-sized and special-shaped rigid aerogel components produced by existing processes, and improve the quality of aerogel components; at the same time, it effectively improves the utilization rate of sol, reduces the difficulty of molding operation, improves production efficiency, and reduces production costs.

[0006] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows: A method for preparing a large-sized, special-shaped rigid aerogel composite component comprises the following steps: preparing silica sol, impregnation, gelation and aging, and drying; The method for preparing silica sol is to add an alkaline catalyst solution to an organosilane precursor under heating conditions to prepare silica sol for standby use; The dipping method comprises the following steps: placing the shaped fiber preform into a vacuum bag of a dipping mold, and then placing the whole thereof together with the vacuum bag in a cavity of the dipping mold; evacuating the upper interface tube of the dipping mold, maintaining the vacuum state inside the vacuum bag for 10-15 minutes, and then sucking silica sol from the lower interface tube of the dipping mold until the silica sol enters the upper interface tube of the dipping mold, stopping sucking silica sol, obtaining the liquid level position of the silica sol in the upper interface tube, recording it as a first position, and continuing to evacuate the mold for 10-15 minutes; re-obtaining the liquid level position of the silica sol in the upper interface tube, recording it as a second position; stopping evacuating the mold when the second position does not decrease compared to the first position; and completing the dipping process when the difference between the theoretical dipping amount required to obtain the shaped fiber preform and the total amount of silica sol entering the dipping mold is determined by comparison to be less than or equal to ±3%. The length or width of the special-shaped fiber preform is greater than 1000 mm, and the thickness is greater than 100 mm.

[0007] Preferably, in the preparation of the silica sol, the heating temperature is 45-75°C; The organosilane precursor is a mixture of methyltrimethoxysilane and ethyl orthosilicate, or a mixture of methyltrimethoxysilane and methyl orthosilicate; The alkaline catalyst solution is an aqueous solution of ammonia in ethanol.

[0008] Preferably, the mass fraction of ammonia in the alkaline catalyst solution is 0.25-0.5wt%, and the volume ratio of ethanol to water is 1-1.2:1; The molar ratio of the alkaline component in the alkaline catalyst solution to the organosilane precursor is 0.1-0.5:1.

[0009] Furthermore, during the dipping process, when the second position is lower than the first position, the following operation is repeated: the silica sol is sucked from the lower interface tube of the dipping mold until the silica sol enters the first position in the upper interface tube of the dipping mold, and then the silica sol is stopped from being sucked; after continuing to vacuum for 10-15 minutes, the liquid level position of the silica sol in the upper interface tube is re-obtained until the re-obtained liquid level position is no lower than the first position.

[0010] Furthermore, during the dipping process, when the difference between the theoretical dipping amount required for the shaped fiber preform and the total amount of silica sol entering the dipping mold is greater than ±3%, 15-25% of the volume of the silica sol in the dipping mold is discharged by pressure, and then vacuum is drawn again and the silica sol is sucked into the lower interface tube of the dipping mold until the silica sol enters the first position in the upper interface tube of the dipping mold, and vacuum is continued for 10-15 minutes; the liquid level position of the silica sol in the upper interface tube (2) is obtained again and recorded as the second position; when the second position does not decrease compared to the first position, vacuum is stopped; and the dipping process is completed when the difference between the theoretical dipping amount required for obtaining the shaped fiber preform and the total amount of silica sol entering the dipping mold is less than or equal to ±3%.

[0011] Preferably, in the resin dipping process, the shaped fiber preform is made by using ceramic fiber felt and / or ceramic fiber as main raw materials and processing them into a predetermined shape and size; The processing methods include but are not limited to: cutting, weaving, acupuncture, molding, laying, and 3D printing.

[0012] Furthermore, the dipping mold used in the dipping process includes a mold body, an upper interface tube, and a lower interface tube; the mold body is a left-right split structure, including a left mold and a right mold; a cavity is formed inside the mold body; a vacuum bag for placing a special-shaped fiber preform is movably arranged in the cavity.

[0013] Furthermore, the upper interface tube is made of a transparent material and is connected to a vacuum pump to maintain a vacuum state inside the vacuum bag in the cavity and to obtain the liquid level position in the upper interface tube; The lower interface pipe is provided with a flow meter to measure the total amount of silica sol entering the dipping mold.

[0014] Furthermore, the gelation and aging method is as follows: after the dipping treatment is completed, the mold after dipping is placed in an oven, heated to 40-60°C, kept warm for gelation for 4-5 hours, aged for 22-24 hours, and demolded to obtain a gel composite.

[0015] Furthermore, the drying method is to perform supercritical drying on the gel composite, control the supercritical drying temperature to 270-280°C, the pressure to 8-10MPa, the pressure reduction rate to 2-3MPa / h, and the supercritical drying time to 2-4h, to obtain large-sized, special-shaped rigid aerogel composite components.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) The method for preparing large-sized and special-shaped rigid aerogel composite components of the present invention can effectively overcome the problems of low sol utilization, great operation difficulty and time-consuming processing in the preparation of special-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-sized and special-shaped rigid aerogel components prepared, thereby effectively improving the molding stability of large-sized and special-shaped rigid aerogel components and improving the processing quality of the components.

[0017] Specifically, through a specific impregnation process, the silica sol uniformly fills the fiber preform, effectively and fully impregnating large-sized and irregularly shaped fiber preforms, thereby improving the processing quality of large-sized and irregularly shaped rigid aerogel components. The vacuum impregnation process, using a vacuum bag built into the mold, results in virtually no sol loss during the impregnation process, significantly improving sol utilization and enhancing the uniformity of sol impregnation. Furthermore, by combining the degree of impregnation (determined by the liquid level) and the amount of impregnation (determined by comparing the amount of impregnation), problems that are common during the preparation process, such as uneven impregnation, uneven thickness, cracking, and poor roughness, are effectively avoided. This effectively improves the quality of aerogel components and increases the yield rate. It also further increases sol utilization, reduces the difficulty of the molding operation, improves production efficiency, and reduces overall production costs. Furthermore, supercritical drying helps further improve the processing quality of large-sized and irregularly shaped rigid aerogel components.

[0018] (2) The present invention provides a method for preparing large-sized, irregularly shaped rigid aerogel composite components. The aerogel components processed using this method can have a thickness exceeding 100 mm and a length or width exceeding 1000 mm. Furthermore, a set of molds can be used for a variety of irregularly shaped components, thereby reducing mold costs and improving yield rates. Vacuum impregnation is performed by vacuum-bag-wrapping irregularly shaped fiber preforms, allowing the sol to be fully impregnated with the irregularly shaped fiber preforms. This eliminates the need for a dedicated vacuum impregnation tank, resulting in stable product quality and high sol utilization, reducing production costs and improving yield rates. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of a dipping mold used in an embodiment of the present invention. In the figure, 1 is the mold body, 2 is the upper interface pipe, and 3 is the lower interface pipe. DETAILED DESCRIPTION

[0020] In order to provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention are now described. It should be noted that the following detailed description is illustrative and is intended to further illustrate the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0021] It should be noted that the terms used herein are intended only to describe specific embodiments and are not intended to limit the exemplary embodiments of the present invention. As used herein, "first," "second," and the like are used to distinguish similar objects and are not used to describe a specific order or precedence. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0022] The embodiment of the present invention provides a method for preparing a large-sized, special-shaped rigid aerogel composite component, comprising the following steps: preparing silica sol, impregnation treatment, gelation and aging, and drying.

[0023] The method for preparing silica sol comprises: using an organosilane precursor to prepare silica sol, and setting aside. Specifically, adding an alkaline catalyst solution to the organosilane precursor under heating conditions of 45-75° C., and stirring at this temperature for 6-24 hours to obtain silica sol; and introducing the silica sol into a sol tank and setting aside.

[0024] In the preparation of the silica sol, the organosilane precursor is a mixture of methyltrimethoxysilane and ethyl orthosilicate, or a mixture of methyltrimethoxysilane and methyl orthosilicate; preferably, the weight ratio of methyltrimethoxysilane to ethyl orthosilicate (or methyl orthosilicate) is 1:0.3-0.4.

[0025] In the preparation of the silica sol, the alkaline catalyst solution is an ethanol aqueous solution of ammonia, the mass fraction of ammonia is 0.25-0.5wt%, and the volume ratio of ethanol to water is 1-1.2:1; The molar ratio of the alkaline component in the alkaline catalyst solution to the organosilane precursor is 0.1-0.5:1.

[0026] The dipping process is carried out using a dipping mold (such as Figure 1 As shown in FIG. 1 , the mold 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, comprising a left mold and a right mold, which are fixedly connected by bolts. A cavity is formed inside the mold body 1; a vacuum bag for placing a shaped fiber preform is movably provided in the cavity. The upper interface tube 2 is made of a transparent material and is connected to a vacuum pump to maintain a vacuum state inside the vacuum bag in the cavity and to obtain the liquid level in the tube; the upper interface tube 2 is also provided with an upper valve. The lower interface tube 3 is connected to a sol tank containing silica sol; the lower interface tube 3 is also provided with a lower valve and a flowmeter, which is used to measure the total amount of silica sol entering the inner cavity of the dipping mold.

[0027] The specific method of the dipping treatment is as follows: the shaped fiber preform is placed in a vacuum bag of the dipping mold, and then the whole body is placed together with the vacuum bag in the cavity of the dipping mold, and the dipping mold is fixed; the vacuum pump connected to the upper interface tube 2 is turned on and the upper valve is opened to maintain the 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 tube 3 is opened to allow the silica sol in the sol tank to be sucked into the vacuum bag in the cavity of the dipping mold; until the silica sol enters the transparent upper interface tube 2 of the dipping mold, the lower valve is closed, the liquid level position of the silica sol in the upper interface tube 2 is obtained, recorded as the first position, and the vacuum is continued for 10-15 minutes; then the liquid level position of the silica sol in the upper interface tube 2 is again obtained, recorded as the second position; it is determined whether the second position is lower than the first position, and the following treatments are performed respectively: a. When the second position is lower than the first position, reopen the lower valve of the lower interface tube 3 to inhale the silica sol until the liquid level of the silica sol in the upper interface tube 2 reaches the first position, close the lower valve of the lower interface tube 3, continue to vacuum for 10-15 minutes, and repeat the above judgment operation; 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 impregnation required for the shaped fiber preform with the total amount of silica sol entering the inner cavity of the impregnation mold (i.e., the actual amount of impregnation) obtained by the flow meter at the lower interface pipe 3, and perform the following processing respectively: m. When the difference between the actual dipping amount and the theoretical dipping amount is less than or equal to ±3%, the dipping process is completed; n. When the difference between the actual dipping amount and the theoretical dipping 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 the silica sol in the dipping mold. Then, turn on the vacuum pump again to suck the silica sol to the first position and repeat the above operation.

[0028] In the resin dipping process, the shaped fiber preform is made of ceramic fiber felt and / or ceramic fiber as the main raw materials, and is processed into a predetermined shape and size using existing processing methods; the existing processing methods include but are not limited to: cutting, weaving, acupuncture, molding, laying, and 3D printing.

[0029] The gelation and aging method comprises the following steps: after the dipping treatment is completed, the mold after dipping is placed in an oven, heated to 40-60° C., kept warm for 4-8 hours for gelation, aged for 22-24 hours, and then demolded to obtain a gel composite.

[0030] The drying method comprises the following steps: performing supercritical drying on the gel composite, controlling the supercritical drying temperature to be 270-280° C., the pressure to be 8-10 MPa, the pressure reduction rate to be 2-3 MPa / h, and the supercritical drying time to be 2-4 hours, thereby obtaining a large-sized, special-shaped rigid aerogel composite component.

[0031] The present invention will be further described below with reference to some specific embodiments.

[0032] Example 1 This embodiment provides a method for preparing a large-sized, special-shaped rigid aerogel composite component, comprising the following steps: S1. Preparation of silica sol A silica sol is prepared using an organosilane precursor and set aside. Specifically, an alkaline catalyst solution is added to the organosilane precursor under heating conditions of 50° C., and the mixture is stirred for 24 hours to obtain a silica sol. The silica sol is then introduced into a sol tank and set aside.

[0033] The organosilane precursor is a mixture of methyltrimethoxysilane and ethyl orthosilicate, with a ratio of methyltrimethoxysilane to ethyl orthosilicate of 1:0.3.

[0034] The alkaline catalyst solution is an ethanol-water solution of ammonia, with a mass fraction of ammonia of 0.25 wt % and a volume ratio of ethanol to water of 1:1; The molar ratio of the alkaline component in the alkaline catalyst solution to the organosilane precursor is 0.2:1.

[0035] S2, dipping treatment The dipping process is performed using a dipping mold, which 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, comprising a left mold and a right mold, which are fixedly connected by bolts. A cavity is formed within the mold body 1; a vacuum bag for placing the shaped fiber preform is movably disposed within the cavity. The upper interface tube 2 is made of a transparent material and is connected to a vacuum pump to maintain a vacuum state within the vacuum bag within the cavity and to monitor the liquid level within the tube. The upper interface tube 2 is also provided with an upper valve. The lower interface tube 3 is connected to a sol tank containing silica sol. The lower interface tube 3 is also provided with a lower valve and a flowmeter for measuring the total amount of silica sol entering the inner cavity of the dipping mold.

[0036] The specific method of the dipping treatment is to put the shaped fiber preform (length and width dimensions are both 1200 mm, and thickness dimension is 135 mm) into the vacuum bag of the dipping mold, and then place the whole body together with the vacuum bag in the cavity of the dipping mold, and fix the dipping mold; start the vacuum pump connected to the upper interface tube 2 and open the upper valve to maintain the vacuum state (vacuum degree 0.09 MPa) inside the vacuum bag for 15 minutes; then open the lower valve of the lower interface tube 3 to allow the silica sol in the sol tank to be sucked into the vacuum bag in the cavity of the dipping mold; until the silica sol enters the transparent upper interface tube 2 of the dipping mold, close the lower valve, obtain the liquid level position of the silica sol in the upper interface tube 2, record it as the first position, and continue to evacuate for 15 minutes; then re-obtain the liquid level position of the silica sol in the upper interface tube 2, record it as the second position; determine whether the second position is lower than the first position, and perform the following treatments respectively: a. When the second position is lower than the first position, reopen the lower valve of the lower interface tube 3 until the liquid level of the silica sol in the upper interface tube 2 reaches the first position, close the lower valve of the lower interface tube 3, continue to vacuum for 15 minutes, and repeat the above judgment operation; 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 impregnation required for the shaped fiber preform with the total amount of silica sol entering the inner cavity of the impregnation mold (i.e., the actual amount of impregnation) obtained by the flow meter at the lower interface pipe 3, and perform the following processing respectively: m. When the difference between the actual dipping amount and the theoretical dipping amount is less than or equal to ±3%, the dipping process is completed; n. When the difference between the actual dipping amount and the theoretical dipping 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 the silica sol in the dipping mold. Then, turn on the vacuum pump again to suck the silica sol to the first position and repeat the above operation.

[0037] Among them, the special-shaped fiber preform is made by using ceramic fiber felt as the main raw material and cutting it into a predetermined shape and size.

[0038] S3. Gel and aging After the dipping treatment is completed, the entire mold after dipping is placed in an oven, heated to 45° C., kept warm for 8 hours for gelation, and then aged for 22 hours before demoulding to obtain a gel composite.

[0039] S4. Drying The gel composite was subjected to supercritical drying, and the supercritical drying temperature was controlled to be 270°C, the pressure to be 10 MPa, the pressure reduction rate to be 2 MPa / h, and the supercritical drying time to be 2.5 h to obtain large-sized, special-shaped rigid aerogel composite components.

[0040] The large-sized, special-shaped rigid aerogel composite components prepared by the method of this embodiment have no uneven impregnation, uneven thickness, cracking, or poor roughness, and the component quality is good; the component molding stability of the preparation method is good, the sol utilization rate is high, the operation is easy, and the preparation process is stable and efficient.

[0041] Example 2 This embodiment provides a method for preparing a large-sized, special-shaped rigid aerogel composite component, comprising the following steps: S1. Preparation of silica sol A silica sol is prepared using an organosilane precursor and set aside. Specifically, an alkaline catalyst solution is added to the organosilane precursor under heating conditions of 60° C., and the mixture is stirred for 18 hours to obtain a silica sol. The silica sol is then introduced into a sol tank and set aside.

[0042] 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.

[0043] The alkaline catalyst solution is an ethanol-water solution of ammonia, with a mass fraction of ammonia of 0.35 wt % and a volume ratio of ethanol to water of 1.1:1; The molar ratio of the alkaline component in the alkaline catalyst solution to the organosilane precursor is 0.25:1.

[0044] S2, dipping treatment The dipping mold used for the dipping treatment is the same as that in Example 1. The specific method of the dipping treatment is as follows: the shaped fiber preform (length and width dimensions are both 1200 mm, and thickness dimension is 135 mm) is placed in the vacuum bag of the dipping mold, and then placed together with the vacuum bag in the cavity of the dipping mold, and the dipping mold is fixed; the vacuum pump connected to the upper interface tube 2 is turned on and the upper valve is opened to maintain the vacuum state (vacuum degree 0.098 MPa) inside the vacuum bag for 10 minutes; then the lower valve of the lower interface tube 3 is opened to allow the silica sol in the sol tank to be sucked into the vacuum bag in the cavity of the dipping mold; until the silica sol enters the transparent upper interface tube 2 of the dipping mold, the lower valve is closed, the liquid level position of the silica sol in the upper interface tube 2 is obtained, 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 tube 2 is re-obtained, recorded as the second position; it is determined whether the second position is lower than the first position, and the following treatments are performed respectively: a. When the second position is lower than the first position, reopen the lower valve of the lower interface tube 3 until the liquid level of the silica sol in the upper interface tube 2 reaches the first position, close the lower valve of the lower interface tube 3, continue to vacuum for 10 minutes, and repeat the above judgment operation; 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 impregnation required for the shaped fiber preform with the total amount of silica sol entering the inner cavity of the impregnation mold (i.e., the actual amount of impregnation) obtained by the flow meter at the lower interface pipe 3, and perform the following processing respectively: m. When the difference between the actual dipping amount and the theoretical dipping amount is less than or equal to ±3%, the dipping process is completed; n. When the difference between the actual dipping amount and the theoretical dipping amount is greater than ±3%, open the upper valve of the upper interface pipe 2 and pressurize it. After discharging 20% ​​of the volume of the silica sol in the dipping mold, turn on the vacuum pump again to suck the silica sol to the first position and repeat the above operation.

[0045] Among them, the special-shaped fiber preform is made by using ceramic fiber felt as the main raw material and cutting it into a predetermined shape and size.

[0046] S3. Gel and aging After the dipping process is completed, the entire mold after dipping is placed in an oven, heated to 50° C., kept warm for 7 hours for gelation, and aged for 23 hours before demoulding to obtain a gel composite.

[0047] S4. Drying The gel composite was subjected to supercritical drying, and the supercritical drying temperature was controlled to be 275°C, the pressure to be 9 MPa, the pressure reduction rate to be 2.4 MPa / h, and the supercritical drying time to be 3 h to obtain large-sized, special-shaped rigid aerogel composite components.

[0048] The large-sized, special-shaped rigid aerogel composite components prepared by the method of this embodiment have no uneven impregnation, uneven thickness, cracking, or poor roughness, and the component quality is good; the component molding stability of the preparation method is good, the sol utilization rate is high, the operation is easy, and the preparation process is stable and efficient.

[0049] Example 3 This embodiment provides a method for preparing a large-sized, special-shaped rigid aerogel composite component, comprising the following steps: S1. Preparation of silica sol A silica sol is prepared using an organosilane precursor and set aside. Specifically, an alkaline catalyst solution is added to the organosilane precursor under heating conditions of 70° C., and the mixture is stirred for 14 hours to obtain a silica sol. The silica sol is then introduced into a sol tank and set aside.

[0050] The organosilane precursor is a mixture of methyltrimethoxysilane and ethyl orthosilicate; the weight ratio of methyltrimethoxysilane to ethyl orthosilicate is 1:0.4.

[0051] The alkaline catalyst solution is an ethanol-water solution of ammonia, with a mass fraction of ammonia of 0.4 wt % and a volume ratio of ethanol to water of 1.2:1; The molar ratio of the alkaline component in the alkaline catalyst solution to the organosilane precursor is 0.3:1.

[0052] S2, dipping treatment The dipping mold used for the dipping treatment is the same as that in Example 1. The specific method of the dipping treatment is as follows: the shaped fiber preform (length and width dimensions are both 1200 mm, and thickness dimension is 135 mm) is placed in the vacuum bag of the dipping mold, and then placed together with the vacuum bag in the cavity of the dipping mold, and the dipping mold is fixed; the vacuum pump connected to the upper interface tube 2 is turned on and the upper valve is opened to maintain the vacuum state (vacuum degree 0.09 MPa) inside the vacuum bag for 10 minutes; then the lower valve of the lower interface tube 3 is opened to allow the silica sol in the sol tank to be sucked into the vacuum bag in the cavity of the dipping mold; until the silica sol enters the transparent upper interface tube 2 of the dipping mold, the lower valve is closed, the liquid level position of the silica sol in the upper interface tube 2 is obtained, 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 tube 2 is re-obtained, recorded as the second position; it is determined whether the second position is lower than the first position, and the following processes are performed respectively: a. When the second position is lower than the first position, reopen the lower valve of the lower interface tube 3 until the liquid level of the silica sol in the upper interface tube 2 reaches the first position, close the lower valve of the lower interface tube 3, continue to vacuum for 10 minutes, and repeat the above judgment operation; 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 impregnation required for the shaped fiber preform with the total amount of silica sol entering the inner cavity of the impregnation mold (i.e., the actual amount of impregnation) obtained by the flow meter at the lower interface pipe 3, and perform the following processing respectively: m. When the difference between the actual dipping amount and the theoretical dipping amount is less than or equal to ±3%, the dipping process is completed; n. When the difference between the actual dipping amount and the theoretical dipping 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 the silica sol in the dipping mold. Then, turn on the vacuum pump again to suck the silica sol to the first position and repeat the above operation.

[0053] Among them, the special-shaped fiber preform is made of ceramic fiber felt and ceramic fiber as the main raw materials, and is produced after being needle-punched into a predetermined shape and size.

[0054] S3. Gel and aging After the dipping process is completed, the mold after dipping is placed in an oven, heated to 60°C, kept warm for 5 hours for gelation, and aged for 22 hours before demoulding to obtain a gel composite.

[0055] S4. Drying The gel composite was subjected to supercritical drying, and the supercritical drying temperature was controlled to be 280°C, the pressure to be 8 MPa, the pressure reduction rate to be 3 MPa / h, and the supercritical drying time to be 3 h, thereby obtaining a large-sized, special-shaped rigid aerogel composite component.

[0056] The large-sized, special-shaped rigid aerogel composite components prepared by the method of this embodiment have no uneven impregnation, uneven thickness, cracking, or poor roughness, and the component quality is good; the component molding stability of the preparation method is good, the sol utilization rate is high, the operation is easy, and the preparation process is stable and efficient.

[0057] Unless otherwise specified, all percentages used in the present invention are by mass.

[0058] 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 aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing large-sized, special-shaped rigid aerogel composite components, characterized in that: The following steps are involved: Preparation of silica sol, impregnation treatment, gelation and aging, and drying; The method for preparing silica sol is to add an alkaline catalyst solution to an organosilane precursor under heating conditions to prepare silica sol for standby use; The method for the dipping treatment is as follows: the shaped fiber preform is placed in a vacuum bag of the dipping mold, and then the whole is placed in the cavity of the dipping mold together with the vacuum bag; vacuum is drawn through the upper interface tube (2) of the dipping mold, and the interior of the vacuum bag is kept in a vacuum state for 10-15 minutes, and the silica sol is sucked through the lower interface tube (3) of the dipping mold until the silica sol enters the upper interface tube (2) of the dipping mold, and the silica sol is stopped from being sucked, and the liquid level position of the silica sol in the upper interface tube (2) is obtained and recorded as the first position, and the vacuum is continued for 10-15 minutes; the liquid level position of the silica sol in the upper interface tube (2) is obtained again and recorded as the second position; when the second position does not decrease compared with the first position, the vacuum is stopped; and when the difference between the theoretical dipping amount required to obtain the shaped fiber preform and the total amount of silica sol entering the dipping mold is judged to be less than or equal to ±3%, the dipping treatment is completed; The length or width of the special-shaped fiber preform is greater than 1000 mm, and the thickness is greater than 100 mm.

2. The method for preparing a large-sized, special-shaped rigid aerogel composite component according to claim 1, characterized in that: In the preparation of the silica sol, the heating temperature is 45-75°C; The organosilane precursor is a mixture of methyltrimethoxysilane and ethyl 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 a large-sized, special-shaped rigid aerogel composite component according to claim 2, characterized in that: The mass fraction of ammonia in the alkaline catalyst solution is 0.25-0.5wt%, and the volume ratio of ethanol to water is 1-1.2:1; The molar ratio of the alkaline component in the alkaline catalyst solution to the organosilane precursor is 0.1-0.5:

1.

4. The method for preparing a large-sized, special-shaped rigid aerogel composite component according to claim 1, characterized in that: During the dipping process, when the second position is lower than the first position, the following operation is repeated: the silicon oxide sol is sucked from the lower interface tube (3) of the dipping mold until the silicon oxide sol enters the first position in the upper interface tube (2) of the dipping mold, the silicon oxide sol is stopped from being sucked, and the vacuum is continued for 10-15 minutes, and the liquid level position of the silicon oxide sol in the upper interface tube (2) is re-obtained until the re-obtained liquid level position is no lower than the first position.

5. The method for preparing a large-sized, special-shaped rigid aerogel composite component according to claim 1, characterized in that: During the dipping process, when the difference between the theoretical dipping amount required for the shaped fiber preform and the total amount of silica sol entering the dipping mold is greater than ±3%, 15-25% of the volume of the silica sol in the dipping mold is discharged by pressure, and then vacuum is drawn again and the silica sol is sucked into the lower interface tube (3) of the dipping mold until the silica sol enters the first position in the upper interface tube (2) of the dipping mold, and vacuum is continued for 10-15 minutes; the liquid level position of the silica sol in the upper interface tube (2) is obtained again and recorded as the second position; when the second position does not decrease compared to the first position, vacuum is stopped; and the difference between the theoretical dipping amount required for obtaining the shaped fiber preform and the total amount of silica sol entering the dipping mold is compared and judged until the difference is less than or equal to ±3%, the dipping process is completed.

6. The method for preparing a large-sized, special-shaped rigid aerogel composite component according to claim 1, characterized in that: In the resin dipping process, the shaped fiber preform is made by using ceramic fiber felt and / or ceramic fiber as the main raw material and processing it into a predetermined shape and size; The processing methods include but are not limited to: cutting, weaving, acupuncture, molding, laying, and 3D printing.

7. The method for preparing a large-sized, special-shaped rigid aerogel composite component according to claim 1, characterized in that: The dipping mold used in the dipping process comprises 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, comprising a left mold and a right mold; a cavity is formed inside the mold body (1); a vacuum bag for placing a special-shaped fiber preform is movably arranged in the cavity.

8. The method for preparing a large-sized, special-shaped rigid aerogel composite component according to claim 7, characterized in that: The upper interface tube (2) is made of a transparent material and is connected to a vacuum pump so as to maintain a vacuum state inside the vacuum bag in the cavity and obtain the position of the liquid level in the upper interface tube (2); The lower interface pipe (3) is provided with a flow meter to measure the total amount of silica sol entering the dipping mold.

9. The method for preparing a large-sized, special-shaped rigid aerogel composite component according to claim 1, characterized in that: The gelation and aging method is as follows: after the dipping treatment is completed, the mold after dipping is placed in an oven, heated to 40-60° C., kept warm for 4-5 hours for gelation, then aged for 22-24 hours, and demolded to obtain a gel composite.

10. The method for preparing a large-sized, special-shaped rigid aerogel composite component according to claim 1, characterized in that: The drying method comprises the following steps: performing supercritical drying on the gel composite, controlling the supercritical drying temperature to be 270-280° C., the pressure to be 8-10 MPa, the pressure reduction rate to be 2-3 MPa / h, and the supercritical drying time to be 2-4 hours, thereby obtaining a large-sized, special-shaped rigid aerogel composite component.

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