CN118184301B - Aerogel composite material and preparation method and application thereof - Google Patents

Abstract

The invention relates to the technical field of aerogel composite materials, and discloses an aerogel composite material and a preparation method and application thereof, comprising the following steps: mixing silica sol with an acid catalyst, heating and stirring to fully hydrolyze to obtain sol A, and adding an alkali catalyst to the hydrolyzed sol A, stirring to obtain sol B; mixing sol B with a reinforced preform, gel aging to obtain a wet gel composite material, and then gel aging and high temperature and high pressure aging; drying at normal pressure; after drying, dipping for multiple times and gel aging after each dipping, and further high temperature and high pressure aging after each aging; sintering to obtain an aerogel composite material. A normal pressure drying process is adopted; the nanoparticle unit structure and nanopore structure of the skeleton are maintained, and the skeleton strength is greatly improved while the thermal conductivity does not increase significantly; it can meet the requirements of high load-bearing performance and high temperature resistant insulation materials in the fields of aerospace and the like.

Description

A kind of aerogel composite material and its preparation method and application

Technical Field

The present invention relates to the technical field of aerogel composite materials, and in particular, to a method for preparing a high-strength aerogel composite material. In addition, the present invention also relates to a high-strength aerogel composite material prepared by the method for preparing the high-strength aerogel composite material. In addition, the present invention also relates to an application of the high-strength aerogel composite material.

Background Art

Aerospace and other fields have put forward an urgent demand for high-load-bearing, high-temperature resistant thermal insulation materials. However, it is currently a big challenge to prepare high-strength, high-temperature resistant, and low-thermal conductivity silica aerogel composite materials. The key issues are as follows:

(1) Silica aerogel has a high porosity and significant brittleness. Although the mechanical properties of silica aerogel can be improved by fiber reinforcement, it still cannot meet the requirements of high load-bearing performance in the fields of aerospace and aerospace. The commonly used reinforcement method is to increase the density of silica aerogel. This method has a certain improvement effect, but when the density of aerogel increases, its solid-state thermal conductivity also increases accordingly, and the comprehensive thermal conductivity increases. Increasing the density will increase the mass of the material itself, and the aerospace field has extremely strict requirements on the quality of its own materials.

(2) Silica aerogel is composed of stacked micro-nano-scale particles and has high surface activity. It is prone to sintering and pore structure collapse at high temperatures. Therefore, the operating temperature of silica aerogel composite materials is usually limited to below 800°C and cannot meet the requirements of use at higher temperatures.

(3) Existing silica aerogel composite materials are usually prepared by hydrolysis-condensation reaction of organic silicon source to form gel, and then combined with supercritical drying method, which has high energy consumption and is accompanied by greater safety risks. Some technologies use silica aerogels obtained by atmospheric pressure drying, which need to undergo complex modification processes and have long cycles. In addition, the mechanical properties and temperature resistance are average, which makes it difficult to meet the requirements of high-load-bearing, high-temperature resistant thermal insulation materials in the aerospace field.

Summary of the invention

The present invention provides a high-strength, high-temperature-resistant, low-thermal-conductivity aerogel composite material and a preparation method and application thereof, in order to solve the technical problems of existing silica aerogel composite materials, that increasing the density in order to enhance the mechanical properties will lead to increased thermal conductivity and increased mass, the preparation process is cumbersome and the cycle is long, and the mechanical properties and temperature resistance of the prepared material are still difficult to meet the application requirements in the fields of aerospace and the like.

According to one aspect of the present invention, a method for preparing an aerogel composite material is provided, comprising the following steps: S100, mixing silica sol with an acid catalyst, heating and stirring to fully hydrolyze to obtain sol A, and adding an alkali catalyst to the hydrolyzed sol A, stirring to obtain sol B; S200, mixing sol B with a reinforced preform, gel aging to obtain a wet gel composite material, and then gel aging and high temperature and high pressure aging; wherein the conditions for high temperature and high pressure aging are: heating to 120°C-300°C, high temperature for 0.5-36h, and pressure range of 1.5-10MPa; S300, drying at normal pressure; after drying, multiple impregnations are performed and gel aging is performed after each impregnation, and high temperature and high pressure aging is further performed after each aging; S400, after sintering, an aerogel composite material is obtained. The silicon oxide particles are impregnated multiple times by liquid phase deposition and then repeatedly deposited on the silicon oxide aerogel skeleton, and gel aging is performed after each impregnation, and high temperature and high pressure aging is further performed after each aging.

Further, step S100 specifically includes: S101, using silica sol of an aqueous system as a raw material, mixing the silica sol with an acid catalyst to obtain a sol precursor A, and heating and stirring the sol precursor A to fully hydrolyze it; S102, adding an alkali catalyst to the hydrolyzed sol A, and stirring to obtain a sol B; step S200 specifically includes: S201, mixing the sol B with the reinforced preform, and aging the gel to obtain a wet gel composite material; S202, placing the wet gel composite material in a pressure vessel, heating it to 120°C-300°C, high temperature for 0.5-36h, and a pressure range of 1.5-10MPa; step S300 specifically includes: S301, placing the material obtained in step S202 in a 120-400°C oven, and drying it for 12-48h; S302, repeating steps S101 to S301 2-5 times. Step S400 specifically includes: S401, placing in a muffle furnace, sintering at 700° C.-1100° C. for 0.5-36 hours.

Furthermore, the number of multiple impregnations is 2-6 times. With each additional composite process, the density and compression strength of the aerogel gradually increase.

Further, in the silica sol in step S100, the particle size of the solid particles is uniform and the average particle size is greater than 10 nm. Optionally, the particle size of the solid particles is uniform and the average particle size is 10 nm-50 nm.

Furthermore, after the aqueous silica sol forms silica gel, a high temperature and high pressure treatment is performed, so that the particles of the silica gel further grow and undergo physical and chemical cross-linking. In step S202, by using a silica sol with uniform particle size and large average particle size, a high temperature and high pressure treatment is performed after the sol forms silica gel, so that the particles of the silica gel further grow and undergo physical and chemical cross-linking, so that the skeleton strength of the prepared silica aerogel is significantly improved, the sintering stress of the aerogel particles with uniform particle size is small, and the surface activity of the aerogel particles with larger particle size is significantly reduced, the ability to resist sintering and shrinkage at high temperature and the specific surface area (retention rate) are significantly improved, and the use temperature is greatly increased.

Furthermore, the sintering step S400 specifically includes: placing in a muffle furnace, and sintering at 700° C.-1100° C. for 0.5-36 hours.

Furthermore, the solid content of the silica sol is 10%-50%. Within this solid content range, as the solid content of the selected aqueous silica sol increases, the density, mechanical strength and thermal conductivity of the corresponding composite material will increase accordingly. If the solid content is too low, less than 10%, the density and strength of the material prepared under the same number of impregnation conditions are low; if the solid content is too high, higher than 50%, the sol viscosity is high and cannot be fully impregnated.

Furthermore, the acid catalyst is nitric acid, hydrochloric acid, sulfuric acid or acetic acid; the alkali catalyst is ammonia water; the reinforcement preform is a fiber preform. Optionally, the reinforcement preform is a ceramic fiber preform.

According to another aspect of the present invention, an aerogel composite material is further provided, which is prepared by using the preparation method of the aerogel composite material.

According to another aspect of the present invention, there is also provided an application of the above-mentioned aerogel composite material in the aerospace field.

The present invention has the following beneficial effects:

(1) The preparation method of the aerogel composite material of the present invention uses silica sol in an aqueous system as a raw material and adopts a normal pressure drying process to obtain high-strength, high-temperature resistant silica aerogel and its composite material. Silica sol raw materials are easy to obtain and have low costs, and the normal pressure drying method has a simple process and low safety risks.

(2) The preparation method of the aerogel composite material of the present invention uses liquid phase deposition to repeatedly impregnate silicon oxide particles and repeatedly deposit them on the silicon oxide aerogel skeleton, thereby maintaining the nanoparticle unit structure and nanopore structure of the skeleton. The typical value of the high-temperature thermal conductivity at 800°C is 0.13 W/(m·K), and the typical value of the 10% compression deformation strength is 15 MPa. The skeleton strength is greatly improved while the thermal conductivity does not increase significantly.

(3) The preparation method of the aerogel composite material of the present invention maintains the nano-particle unit structure and nano-pore structure of the skeleton, so the ambient temperature for use is higher. The material can withstand temperatures of 1100°C and above. After testing at 1100°C for 30 minutes, the thickness shrinkage is less than 0.3%.

(4) The method for preparing the aerogel composite material of the present invention can meet the requirements of the aerospace and other fields for high load-bearing performance and high temperature resistant thermal insulation materials.

In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

FIG1 is a flow chart of a method for preparing an aerogel composite material according to an embodiment of the present invention;

FIG2 is a SEM image of the pure aerogel of Example 1 of the present invention after the gel is further grown and strengthened through a high temperature and high pressure process;

FIG3 is a SEM image of pure aerogel particles of Comparative Example 1 of the present invention after gelation without high temperature and high pressure process;

FIG4 is a thickness comparison diagram of Comparative Example 1 of the present invention before and after the test at 1100° C.;

FIG5 is a thickness comparison diagram of Example 1 of the present invention before and after the test at 1100° C.;

FIG6 is a shear test sample obtained in Example 1 of the present invention;

FIG7 is a compression test sample obtained in Example 1 of the present invention;

FIG8 is a thermal conductivity test sample obtained in Example 1 of the present invention.

DETAILED DESCRIPTION

The following embodiments of the present invention are described in detail with reference to the accompanying drawings, but the present invention can be implemented in a variety of different ways as defined and covered below. Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

Fig. 1 is a flow chart of the method for preparing the aerogel composite material of the embodiment of the present invention; Fig. 2 is a SEM image of the pure aerogel of the embodiment of the present invention after the gelation and the particles are further grown and strengthened through the high temperature and high pressure process; Fig. 3 is a SEM image of the pure aerogel of the comparative example 1 of the present invention after the gelation and the particles are not subjected to the high temperature and high pressure process; Fig. 4 is a thickness comparison diagram of the comparative example 1 of the present invention before and after the test at 1100°C; Fig. 5 is a thickness comparison diagram of the embodiment of the present invention before and after the test at 1100°C; Fig. 6 is a shear test sample obtained in the embodiment of the present invention; Fig. 7 is a compression test sample obtained in the embodiment of the present invention; and Fig. 8 is a thermal conductivity test sample obtained in the embodiment of the present invention.

As shown in FIG1 , a method for preparing an aerogel composite material of this embodiment includes the following steps:

The silica sol is mixed with an acid catalyst to obtain a sol precursor A, and the sol precursor A is heated and stirred to be fully hydrolyzed.

A base catalyst is added to the hydrolyzed sol A, and the sol B is obtained by stirring.

After mixing sol B with the reinforced preform, the gel is aged at 60°C±5°C for 18-24h (if it is less than 18h, no wet gel is formed; if it is more than 24h, it has no effect on the material properties, but it will extend the production cycle) to obtain a wet gel composite material.

The wet gel composite material is placed in a pressure vessel, heated to 120℃-300℃, high temperature for 0.5-36h, and the pressure range is 1.5-10MPa; the temperature range is 120℃-300℃, and as the temperature in the pressure vessel increases, the Si-OH reaction activity on the surface of the silica gel particles is significantly enhanced, so that it reacts to generate more Si-O-Si bonds, so that the particles grow and strengthen further; below 120℃, the material strength is insufficient after high-temperature aging; above 300℃, the material strength after high-temperature aging does not increase significantly. The time interval is 0.5-36h, in this interval, the Si-OH reaction activity on the surface of the silica gel particles is significantly enhanced, so that it reacts to generate more Si-O-Si bonds, so that the particles grow and strengthen further; below 0.5h, the reaction time is insufficient, resulting in insufficient material strength after high-temperature aging; above 36h, the material strength after high-temperature aging does not increase significantly. The pressure range is 1.5-10MPa, and the pressure range changes with temperature.

Place the material in a 120-400℃ oven and dry for 12-48h; the temperature range and time range are set within the above range. Below 120℃ and below 12h will not dry thoroughly, and above 400℃ and above 48h will not increase the drying effect. Generally speaking, the slower the evaporation rate, the less damage to the pore structure, thereby ensuring the strength of the material.

Sol B was prepared again, mixed with the composite material obtained in the previous step, and the gel was aged for 1 day to obtain a wet gel composite material.

The wet gel composite material is placed in a pressure vessel, heated to 120°C-300°C, high temperature for 0.5-36 hours, and pressure range is 1.5-10MPa.

Place the material in a 120-400℃ oven and dry for 12-48h.

Take out the dried material, put it into the muffle furnace, and sinter it at 700℃-1100℃ for 0.5-36h; the temperature range and time range are set in the above range. The material strength does not increase significantly after sintering below 700℃ and less than 0.5h, and the material strength will decrease after sintering above 1100℃ and more than 36h. This may be because at this temperature and time (sintering at 700℃-1100℃ for 0.5-36h), the linear expansion coefficients of silica aerogel and fiber in the composite material are inconsistent, resulting in the contraction and expansion of the aerogel and fiber, which just makes the two have a good interface bonding force, and at the same time, new chemical bonds are generated between the aerogel and the fiber, thereby further enhancing the mechanical strength of the composite material.

It has the following technical effects:

(1) Using silica sol in water system as raw material, high-strength, high-temperature resistant silica aerogel and its composite materials are obtained by atmospheric pressure drying process. Silica sol raw materials are easy to obtain and have low cost, and atmospheric pressure drying method has simple process and low safety risk.

(2) By using silica sol with uniform particle size and large average particle size, high temperature and high pressure treatment is performed after the sol forms silica gel, so that the particles of silica gel can further grow and undergo physical and chemical cross-linking, the skeleton strength of the prepared silica aerogel is significantly improved, the sintering stress of aerogel particles with uniform particle size is small, and the surface activity of aerogel particles with larger particle size is significantly reduced. The ability to resist sintering and shrinkage at high temperature and the specific surface area (retention rate) are significantly improved, and the use temperature is greatly increased.

The mechanism of high temperature and high pressure is: silica gel (or gel/composite material) and a certain amount of water or alcohol are placed in a closed container, heated to a certain temperature and pressure for a certain period of time, and then cooled. During the heating process, water or alcohol gradually evaporates to form a high temperature and high pressure environment in the closed container, which significantly enhances the Si-OH reaction activity on the surface of silica gel particles, causing them to react to generate more Si-O-Si bonds, allowing the particles to further grow and strengthen.

(3) The silica particles are repeatedly deposited (immersed multiple times) on the silica aerogel skeleton by liquid phase deposition, maintaining the nanoparticle unit structure and nanopore structure of the skeleton. The strength of the skeleton is greatly improved while the thermal conductivity does not increase significantly.

Example 1

(1) 3000 g of aqueous silica sol having a solid content of 20% was mixed with 30 g of 0.3 mol/L nitric acid to obtain a sol precursor A, and the sol precursor A was heated to 40° C. and stirred to be fully hydrolyzed;

(2) Add 60 g of 0.8 mol/L ammonia water to the hydrolyzed Sol A and stir to obtain Sol B;

(3) After mixing sol B with the mullite fiber preform, the gel was aged for 1 day to obtain a wet gel composite material;

(4) placing the wet gel composite material into a pressure vessel, heating it to 150°C, and subjecting it to high temperature and high pressure for 5 hours, with the maximum pressure reaching 2 MPa;

(5) Place the material in a 150°C oven and dry for 12 hours;

(6) preparing sol B again, mixing it with the composite material obtained in step (5), and aging the gel for 1 day to obtain a wet gel composite material;

(7) placing the wet gel composite material obtained in (6) into a pressure vessel, heating it to 150°C, and subjecting it to high temperature and high pressure for 5 h, with the maximum pressure reaching 2 MPa;

(8) Place the material in a 150°C oven and dry for 12 hours;

(9) Take out the dried material, put it into a muffle furnace, and sinter it at 800℃ for 5h.

Going a step further, sample testing is performed:

(10) The prepared material blank is machined into corresponding compression, shear, thermal conductivity, and temperature resistance test size specimens, and then the corresponding performance tests are carried out. The performance test uses a mechanical testing machine (model: FL4204) for compression and shear tests of the specimens; a test equipment (model: HFM446M) for room temperature thermal conductivity tests of the specimens; and a test equipment (PBDR-HT13A) for 800°C thermal conductivity tests of the specimens.

In the field of materials science and engineering, "evaluation" refers to the process of testing and evaluating the performance of materials or components under specific conditions. Thickness shrinkage test at 1100℃ for 30 minutes: The sample is placed in a high temperature environment of 1100℃ for 30 minutes, and the reduction in thickness is measured to evaluate the thermal stability and heat resistance of the sample at 1100℃.

Example 2

(1) 3000 g of aqueous silica sol having a solid content of 30% was mixed with 30 g of 0.3 mol/L hydrochloric acid to obtain a sol precursor A, and the sol precursor A was heated to 40° C. and stirred to fully hydrolyze the sol precursor A;

(2) Add 60 g of 0.8 mol/L ammonia water to the hydrolyzed Sol A and stir to obtain Sol B;

(3) After mixing sol B with the mullite fiber preform, the gel was aged for 1 day to obtain a wet gel composite material;

(4) placing the wet gel composite material into a pressure vessel, heating it to 170°C, and subjecting it to high temperature and high pressure for 5 hours, with the maximum pressure reaching 4 MPa;

(5) Place the material in a 150°C oven and dry for 12 hours;

(6) preparing sol B again, mixing it with the composite material obtained in step (5), and aging the gel for 1 day to obtain a wet gel composite material;

(7) placing the wet gel composite material obtained in (6) into a pressure vessel, heating it to 170°C, and subjecting it to high temperature and high pressure for 5 h, with the maximum pressure reaching 4 MPa;

(8) Place the material in a 150°C oven and dry for 12 hours;

(9) Take out the dried material, put it into a muffle furnace, and sinter it at 800℃ for 5h.

Going a step further, sample testing is performed:

(10) The prepared material blank is machined into corresponding compression, shear, thermal conductivity, and temperature resistance test size specimens, and then the corresponding performance tests are carried out. The performance test uses a mechanical testing machine (model: FL4204) for compression and shear tests of the specimens; a test equipment (model: HFM446M) for room temperature thermal conductivity tests of the specimens; and a test equipment (PBDR-HT13A) for 800°C thermal conductivity tests of the specimens.

Thickness shrinkage test at 1100℃ for 30min: The sample is placed in a high temperature environment of 1100℃ for 30min, and the reduction in thickness is measured to evaluate the thermal stability and heat resistance of the sample at 1100℃.

Example 3

(1) 3000 g of aqueous silica sol having a solid content of 40% and 15 g of 0.3 mol/L sulfuric acid were mixed to obtain a sol precursor A, and the sol precursor A was heated to 40° C. and stirred to fully hydrolyze the sol precursor A;

(2) Add 60 g of 0.8 mol/L ammonia water to the hydrolyzed Sol A and stir to obtain Sol B;

(3) After mixing sol B with the mullite fiber preform, the gel was aged for 1 day to obtain a wet gel composite material;

(4) The wet gel composite material was placed in a pressure vessel, heated to 190°C, and kept under high temperature and high pressure for 5 hours, with the maximum pressure reaching 6 MPa;

(5) Place the material in a 150°C oven and dry for 12 hours;

(6) preparing sol B again, mixing it with the composite material obtained in step (5), and aging the gel for 1 day to obtain a wet gel composite material;

(7) placing the wet gel composite material obtained in (6) into a pressure vessel, heating it to 190°C, and subjecting it to high temperature and high pressure for 5 h, with the maximum pressure reaching 6 MPa;

(8) Place the material in a 150°C oven and dry for 12 hours;

(9) Take out the dried material, put it into a muffle furnace, and sinter it at 800℃ for 5h.

Going a step further, sample testing is performed:

(10) The prepared material blank is machined into corresponding compression, shear, thermal conductivity, and temperature resistance test size specimens, and then the corresponding performance tests are carried out. The performance test uses a mechanical testing machine (model: FL4204) for compression and shear tests of the specimens; a test equipment (model: HFM446M) for room temperature thermal conductivity tests of the specimens; and a test equipment (PBDR-HT13A) for 800°C thermal conductivity tests of the specimens.

Thickness shrinkage test at 1100℃ for 30min: The sample is placed in a high temperature environment of 1100℃ for 30min, and the reduction in thickness is measured to evaluate the thermal stability and heat resistance of the sample at 1100℃.

Comparative Example 1

Step (4) and step (7) in Example 1 are omitted, and the rest of the steps are the same as those in Example 1, that is, the high temperature and high pressure aging step is removed.

Comparative Example 2

Step (4) and step (7) in Example 2 are omitted, and the rest of the steps are the same as those in Example 2, that is, the high temperature and high pressure aging step is removed.

Comparative Example 3

Step (4) and step (7) in Example 3 are omitted, and the rest of the steps are the same as those in Example 3, that is, the high temperature and high pressure aging step is removed.

Comparative Example 4

(1) 3000 g of aqueous silica sol having a solid content of 40% and 15 g of 0.3 mol/L sulfuric acid were mixed to obtain a sol precursor A, and the sol precursor A was heated to 40° C. and stirred to fully hydrolyze the sol precursor A;

(2) Add 60 g of 0.8 mol/L ammonia water to the hydrolyzed Sol A and stir to obtain Sol B;

(3) After mixing sol B with the mullite fiber preform, the gel was aged for 1 day to obtain a wet gel composite material;

(4) The wet gel composite material was placed in a pressure vessel, heated to 100 °C, and kept under high temperature and high pressure for 10 min, with the maximum pressure reaching 1.2 MPa;

(5) Place the material in a 150°C oven and dry for 12 hours;

(6) preparing sol B again, mixing it with the composite material obtained in step (5), and aging the gel for 1 day to obtain a wet gel composite material;

(7) placing the wet gel composite material obtained in (6) into a pressure vessel, heating it to 100°C, and subjecting it to high temperature and high pressure for 10 min, with the maximum pressure reaching 1.2 MPa;

(8) Place the material in a 150°C oven and dry for 12 hours;

(9) Take out the dried material, put it into a muffle furnace, and sinter it at 800℃ for 5h.

Going a step further, sample testing is performed:

(10) The prepared material blank is machined into corresponding compression, shear, thermal conductivity, and temperature resistance test size specimens, and then the corresponding performance tests are carried out. The performance test uses a mechanical testing machine (model: FL4204) for compression and shear tests of the specimens; a test equipment (model: HFM446M) for room temperature thermal conductivity tests of the specimens; and a test equipment (PBDR-HT13A) for 800°C thermal conductivity tests of the specimens.

Thickness shrinkage test at 1100℃ for 30min: The sample is placed in a high temperature environment of 1100℃ for 30min, and the reduction in thickness is measured to evaluate the thermal stability and heat resistance of the sample at 1100℃.

In Comparative Example 4, the high temperature and high pressure aging conditions are set to a value range lower than the high temperature and high pressure aging conditions of the present invention.

Comparative Example 5

(1) 3000 g of aqueous silica sol having a solid content of 40% and 15 g of 0.3 mol/L sulfuric acid were mixed to obtain a sol precursor A, and the sol precursor A was heated to 40° C. and stirred to fully hydrolyze the sol precursor A;

(2) Add 60 g of 0.8 mol/L ammonia water to the hydrolyzed Sol A and stir to obtain Sol B;

(3) After mixing sol B with the mullite fiber preform, the gel was aged for 1 day to obtain a wet gel composite material;

(4) The wet gel composite material was placed in a pressure vessel, heated to 330°C, and kept under high temperature and high pressure for 48 hours, with the maximum pressure reaching 14 MPa;

(5) Place the material in a 150°C oven and dry for 12 hours;

(6) preparing sol B again, mixing it with the composite material obtained in step (5), and aging the gel for 1 day to obtain a wet gel composite material;

(7) placing the wet gel composite material obtained in (6) into a pressure vessel, heating it to 330°C, and subjecting it to high temperature and high pressure for 48 hours, with the maximum pressure reaching 14 MPa;

(8) Place the material in a 150°C oven and dry for 12 hours;

(9) Take out the dried material, put it into a muffle furnace, and sinter it at 800℃ for 5h.

Going a step further, sample testing is performed:

(10) The prepared material blank is machined into corresponding compression, shear, thermal conductivity, and temperature resistance test size specimens, and then the corresponding performance tests are carried out. The performance test uses a mechanical testing machine (model: FL4204) for compression and shear tests of the specimens; a test equipment (model: HFM446M) for room temperature thermal conductivity tests of the specimens; and a test equipment (PBDR-HT13A) for 800°C thermal conductivity tests of the specimens.

Thickness shrinkage test at 1100℃ for 30min: The sample is placed in a high temperature environment of 1100℃ for 30min, and the reduction in thickness is measured to evaluate the thermal stability and heat resistance of the sample at 1100℃.

In Comparative Example 5, the high temperature and high pressure aging conditions are set to a value range higher than the high temperature and high pressure aging conditions of the present invention.

The properties of the composite materials obtained by the above examples and comparative examples are shown in Table 1.

Table 1 Properties of composite materials

Conclusion 1: By comparing Example 1, Example 2, and Example 3 with each other or by comparing Comparative Example 1, Comparative Example 2, and Comparative Example 3 with each other, as the solid content of the aqueous silica sol increases, the density of the corresponding composite material will increase accordingly, and the mechanical strength of the composite material will increase (not significantly), but the thermal conductivity of the composite material will increase significantly with the increase in density. As shown in Figures 4 and 5, Figure 4 shows the thickness comparison of Comparative Example 1 before and after the test at 1100°C, and the thickness has changed significantly and decreased; Figure 5 shows the thickness comparison of Example 1 before and after the test at 1100°C, and the thickness has not changed significantly. As shown in Figure 6, the shear test sample of Example 1 is shown. As shown in Figure 7, the compression test sample of Example 1 is shown. As shown in Figure 8, the thermal conductivity test sample of Example 1 is shown.

Embodiment 1 is the most preferred embodiment. The obtained composite material has improved mechanical properties (compressive stress, shear strength, full strength, tensile strength) while having a lower density and thus a lower mass, making it more suitable for the requirements of lightweight materials in the aerospace field.

The aerogel composite material obtained by the method of Example 1 shown in Figure 2 is compared with the aerogel composite material obtained by the method of Comparative Example 1 shown in Figure 3. The particle size of the aerogel composite material in Figure 2 is larger. The larger the particle size of the aerogel composite material, the greater the strength and temperature resistance of the composite material, but the thermal conductivity is not significantly affected.

Conclusion 2: By comparing Example 1 with Comparative Example 1, the density of the composite material is basically unchanged before and after high-temperature aging, the room-temperature 10%ε compressive stress of the composite material increases from 4.23MPa before high-temperature and high-pressure aging to 13.12MPa after high-temperature and high-pressure aging, the room-temperature interlaminar shear strength increases from 0.3MPa before high-temperature and high-pressure aging to 1.2MPa after high-temperature and high-pressure aging, the room-temperature flexural strength increases from 6.32MPa before high-temperature and high-pressure aging to 10.01MPa after high-temperature and high-pressure aging, and the room-temperature tensile strength increases from 2.01MPa before high-temperature and high-pressure aging to 4.56MPa after high-temperature and high-pressure aging. The room temperature and high temperature thermal conductivity basically did not change before and after high temperature and high pressure aging, and the thickness shrinkage at 1100°C for 30 minutes was reduced from 1.568% before high temperature and high pressure aging to 0.242% after high temperature and high pressure aging; comparing Example 2 with Comparative Example 2, and comparing Example 3 with Comparative Example 3, the same rule can be drawn, that is, through high temperature and high pressure aging, the mechanical strength of the composite material is greatly improved without increasing the density, and its thermal conductivity does not change significantly, and its thickness shrinkage rate under the condition of 1100°C for 30 minutes is significantly reduced (the temperature resistance is significantly improved after high temperature and high pressure aging).

Conclusion 3: By comparing Example 3 with Comparative Examples 4 and 5, the material strength is insufficient after high temperature and high pressure aging at temperatures below 120°C, below 0.5h, and below 1.5MPa; the material strength does not increase significantly after high temperature and high pressure aging at temperatures above 300°C, above 36h, and above 10MPa. Moreover, the change in high temperature and high pressure conditions has little effect on the thermal conductivity and temperature resistance of the material.

Main principle: During the heating process, the solvent gradually evaporates to form a high-temperature, high-pressure environment in a closed container, which significantly enhances the Si-OH reaction activity on the surface of the silica gel particles, causing them to react to generate more Si-O-Si bonds, allowing the particles to further grow and strengthen, but at the same time maintaining the nanoparticle unit structure and nanopore structure of the skeleton. The skeleton strength is greatly improved while the thermal conductivity does not increase significantly.

It can be seen that after the gelation process of high temperature and high pressure, the particles further grow and strengthen, but at the same time maintain the nanoparticle unit structure and nanopore structure of the skeleton.

The aerogel composite material of this embodiment is prepared by using the above-mentioned preparation method of the aerogel composite material.

The aerogel composite material of this embodiment is applied in the aerospace field as described above.

Matters not covered by the present invention are known technologies.

The technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims (10)

1.A method of preparing an aerogel composite comprising the steps of:

s100, mixing silica sol with an acid catalyst, heating, stirring, fully hydrolyzing to obtain sol A, adding an alkali catalyst into the hydrolyzed sol A, and stirring to obtain sol B;

S200, mixing the sol B with the reinforced prefabricated member, performing gel aging to obtain a wet gel composite material, and performing high-temperature high-pressure aging; wherein the conditions of high temperature and high pressure aging are as follows: heating to 150 ℃, and heating to high temperature and high pressure for 5 hours, wherein the highest pressure reaches 2MPa;

S300, performing normal-pressure drying; drying, soaking for multiple times, aging in gel after each soaking, and further aging at high temperature and high pressure after each aging; wherein the conditions of high temperature and high pressure aging are as follows: heating to 150 ℃, and heating to high temperature and high pressure for 5 hours, wherein the highest pressure reaches 2MPa;

S400, sintering to obtain the aerogel composite material.

2. The method of preparing an aerogel composite as claimed in claim 1, wherein,

The step S100 specifically includes:

S101, mixing silica sol with an acid catalyst by taking the silica sol of a water system as a raw material to obtain a sol precursor A, and heating and stirring the sol precursor A to fully hydrolyze the sol precursor A;

s102, adding an alkali catalyst into the hydrolyzed sol A, and stirring to obtain sol B;

the step S200 specifically includes:

S201, mixing the sol B with the reinforced prefabricated member, and then aging the gel to obtain a wet gel composite material;

s202, placing the wet gel composite material into a pressure container, heating to 150 ℃, and raising the temperature and the pressure for 5 hours, wherein the highest pressure reaches 2MPa;

the step S300 specifically includes:

s301, placing the material obtained in the step S202 into a baking oven at 120-400 ℃ and drying for 12-48h;

s302, repeating the steps S101 to S301 for 2-5 times;

The step S400 specifically includes:

s401, putting the mixture into a muffle furnace, and sintering the mixture for 0.5 to 36 hours at the temperature of 700 to 1100 ℃.

3. The method of preparing an aerogel composite as claimed in claim 1, wherein,

The number of times of the multiple times of the dipping is 2-6 times.

4. The method of preparing an aerogel composite as claimed in claim 2, wherein,

The silica sol in step S100 has uniform particle size of the solid particles and an average particle size of more than 10nm.

5. The method of preparing an aerogel composite as claimed in claim 4, wherein,

And (3) performing high-temperature and high-pressure treatment after the aqueous silica sol forms silica gel, so that the particles of the silica gel further grow up and undergo physicochemical crosslinking.

6. The method of preparing an aerogel composite as claimed in claim 1, wherein,

The step S400 of sintering specifically comprises the following steps: placing the mixture into a muffle furnace, and sintering the mixture for 0.5 to 36 hours at the temperature of 700 to 1100 ℃.

7. The method for producing an aerogel composite as claimed in any of claim 1 to 6, wherein,

The solid content of the silica sol is 10% -50%.

8. The method for producing an aerogel composite as claimed in any of claim 2 to 6, wherein,

The acid catalyst adopts nitric acid, hydrochloric acid, sulfuric acid or acetic acid;

the alkali catalyst adopts ammonia water;

The reinforcement preform is a fibrous preform.

9. An aerogel composite produced by the method of any one of claims 1 to 8.

10. Use of the aerogel composite of claim 9 in the aerospace field.