A high-strength, low-thermal-conductivity silicon oxide-based thermal insulation material and its preparation method and application

Abstract

The present invention relates to the technical field of thermal insulation materials and provides a high-strength, low-thermal-conductivity silica-based thermal insulation material, its preparation method, and application. The material comprises a fiber cloth laminated preform and a silica ceramic matrix. The fiber cloth laminated preform comprises a laminated structure of five layers of quartz fiber cloth and one layer of carbon fiber cloth, and a quartz suture of a flat-stitched laminated structure. The silica ceramic matrix is a porous structure formed by nano-silicon oxide, with a particle size range of 120 to 180 nm. The fiber cloth laminated preform accounts for 65 to 80% of the total mass, and the silica ceramic matrix accounts for 20 to 35% of the total mass, resulting in a porosity of 30 to 45%. The preparation method comprises three steps: preparing the fiber cloth laminated preform, preparing the laminated preform / gel composite, and performing high-temperature heat treatment. The prepared material has both high strength and low thermal conductivity, and the material preparation process is simple, safe, and environmentally friendly, making it easy to mass-produce and apply.

Description

Technical Field

[0001] The present invention generally relates to the technical field of thermal insulation materials, and in particular to a high-strength, low-thermal-conductivity silicon oxide-based thermal insulation material, a preparation method thereof, and applications thereof. Background Art

[0002] When the satellite is in orbit, it is in a high vacuum (no higher than 10 -3 Satellites operate in harsh environments subject to high temperatures (-120°C to +120°C) and cyclic shocks from hot and cold temperatures (-120°C to +120°C). Satellites must rely on thermal control systems to maintain a certain temperature range to ensure the normal or high-precision operation of their instruments and equipment. Generally, the internal temperature of a satellite must be maintained within a range of 5°C to 45°C, with individual areas only permitted to fluctuate within a constant temperature range of 1°C to 2°C. To this end, fiberglass gaskets (CN 103448920B) or polyimide gaskets (CN 108528760A) are installed at the interconnections between instruments and equipment in satellite thermal control systems as thermal insulation gaskets (with a room-temperature thermal conductivity of approximately 0.50 W / (m·K)), providing effective thermal resistance. With the increasing demand for satellite miniaturization and functionalization, the thermal conductivity of existing thermal insulation gaskets is relatively high, necessitating the development of new, higher-strength gasket materials with lower thermal conductivity.

[0003] The most studied, low thermal conductivity and high strength materials at present are mainly silica-based thermal insulation materials. Silica aerogel has very low room temperature thermal conductivity, but pure aerogel has low strength and is easy to break. In order to improve its mechanical properties, fibers are usually added for mechanical reinforcement. CN 105565774B discloses a high-strength, high-insulation silica aerogel and a preparation method thereof. Hollow natural clay fiber halloysite is used as a reinforcing phase. The obtained silica aerogel thermal insulation composite material has high porosity, low density, and excellent mechanical properties. The compressive strength is 3.78MPa and the thermal conductivity at room temperature is 0.014W / (m·K). CN104609820B discloses a glass fiber directionally reinforced nano-silica thermal insulation material and a preparation method thereof. First, a low-temperature freeze-drying process is used to directionally arrange the glass fibers in the nano-silica. Then, through molding and sintering processes, the prepared insulation material has a compressive strength of 16.23MPa and a thermal conductivity of 0.059W / (m·K) at room temperature. The mechanical properties of silica aerogel have been improved to a certain extent through fiber reinforcement, but compared with thermal insulation gaskets used for satellite thermal control, its strength is far from meeting the use requirements.

[0004] Compared to silica aerogel, fiber-reinforced silica ceramic-based composite materials have higher compressive strength. CN 111703148B discloses a silica-based composite thermal insulation pad. The thermal insulation pad is prepared by applying a silica-based thermal insulation material to a fiber cloth substrate. The thermal insulation pad has a room temperature compressive strength of 21.1 MPa and a thermal conductivity of 0.132 W / (m·K) at 70°C. CN 111454701B discloses a rock wool fiber-reinforced silica-based high-strength thermal insulation composite material and its preparation method. The composite material is prepared by impregnating silica sol with a rock wool fiber preform to form a fiber preform / sol mixture, gelling, drying at normal pressure, and repeating the impregnation-drying process 2 to 6 times. Finally, high-temperature sintering is performed to obtain a composite material with a room temperature thermal conductivity of 0.185 W / (m·K) and a corresponding compressive strength of 122.9 MPa. Although the compressive strength of silica ceramic-based composite materials is significantly higher than that of silica aerogel composite materials, it is still difficult to meet the requirements of satellites for thermal insulation pads with both high strength and low thermal conductivity.

[0005] CN 115449219A discloses a silica aerogel, quartz fiber, and polyimide ternary composite material and its preparation method. The method proposes mixing the polyimide resin and silica aerogel by ball milling. The resulting suspension is coated on quartz fiber cloth, then layered in a mold. After drying and hot pressing, the resulting composite material exhibits high compressive strength (570-650 MPa) and relatively high thermal conductivity (0.5-0.6 W / (m·K)).

[0006] As can be seen, existing silica aerogel composites have very low thermal conductivity but insufficient compressive strength, while silica ceramic-based composites have very high strength but excessively high thermal conductivity. Using existing preparation methods, it is difficult to produce high-strength thermal insulation gasket materials that meet the requirements of future miniaturized and functionalized satellite thermal control systems. Summary of the Invention

[0007] In response to the defects of the existing technology, the present invention provides a high-strength, low-thermal conductivity silicon oxide-based thermal insulation material and its preparation method and application. The material has both high strength and low thermal conductivity. The material preparation process is simple, safe and environmentally friendly, and easy to mass produce and apply.

[0008] The present invention provides a high-strength, low-thermal-conductivity silica-based thermal insulation material, comprising a fiber cloth laminated preform and a silica ceramic matrix; the fiber cloth laminated preform comprises a laminated structure formed by sequentially stacking five layers of quartz fiber cloth and a layer of carbon fiber cloth, with the five layers of quartz fiber cloth serving as outer layers, and a quartz suture thread stitching the laminated structure with a flat needle; the silica ceramic matrix is a porous structure formed by nano-silicon oxide, with the nano-silicon oxide particle size ranging from 120 to 180 nm.

[0009] Furthermore, based on the total mass of the high-strength, low-thermal-conductivity silicon oxide-based thermal insulation material being 100%, the fiber cloth laminated preform accounts for 65-80% of the total mass, and the silicon oxide ceramic matrix accounts for 20-35% of the total mass; the porosity of the material is 30-45%.

[0010] Furthermore, the thickness of a single layer of the quartz fiber cloth is 0.1 to 0.2 mm, and the thickness of a single layer of the carbon fiber cloth is 0.1 mm; the linear density of the quartz fiber suture thread is 100 to 190 tex, and the suture stitch spacing is 5 to 15 mm.

[0011] Furthermore, the bulk density of the fiber cloth laminated preform is 0.8 to 1.1 g / cm 3 The thickness of the preform is 2 to 20 mm; the thermal conductivity of the high-strength, low-thermal-conductivity silicon oxide-based thermal insulation material is 0.033 to 0.052 W / (m·K) under a pressure of 4 Pa, and the pressure strength range is 125.6 to 135.7 MPa.

[0012] The present invention also provides a method for preparing the above-mentioned high-strength and low-thermal-conductivity silicon oxide-based thermal insulation material, comprising the following steps:

[0013] S1. preparing a fiber cloth laminated preform;

[0014] S2. Preparing a laminated preform / gel composite: The fiber cloth laminated preform is clamped between two steel plates, and the clamped fiber cloth laminated preform is placed in a sol pool of an impregnation tank containing silica sol. Vacuum is applied for negative pressure impregnation, and the pressure is maintained for a period of time to allow the sol in the preform to gel, thereby obtaining a laminated preform / gel composite clamped by the steel plates;

[0015] S3: High-temperature heat treatment: The stacked preform / gel composite clamped by the steel plates is placed in an open container filled with deionized water, and the open container is placed in a sealed container for hydrothermal treatment. The open container is then taken out for drying at normal pressure, the bolts are loosened, and the steel plates are removed to obtain the high-strength, low-thermal-conductivity silicon oxide-based thermal insulation material.

[0016] Furthermore, in the above step S2, the method of clamping the fiber cloth laminated preform between the two steel plates is: punching holes at the corresponding positions of the four corners of the two steel plates, clamping the laminated preform in the middle position between the two steel plates, and then fixing and tightening the four corners of the two steel plates with bolts; the thickness of the two steel plates is 5 to 10 mm.

[0017] Furthermore, in the above step S2: the solid content of the silica sol is 42-50%, the solvent is water, and the sol particle size is 110-160 nm; before the vacuuming and negative pressure impregnation, a 0.1 mol / L acid solution is added to the silica sol; the pressure of the negative pressure impregnation is -0.1 MPa, and the holding time is 0.5-1 h.

[0018] Furthermore, in the above step S2: the acid is nitric acid or acetic acid; the volume ratio of silica sol to acid solution is 100:(0.5-2);

[0019] Furthermore, in the above step S3: the temperature of the hydrothermal treatment is 260-340° C., and the time is 4-10 h; the temperature of the atmospheric pressure drying is 90-99° C., and the time is 24-48 h.

[0020] The present invention further provides the application of the above-mentioned high-strength and low-thermal-conductivity silicon oxide-based thermal insulation material, which can be applied to no more than 10 -3 Pa vacuum and -120 ~ +120 ℃ hot and cold cycle shock satellite.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. The thermal conductivity of the silicon oxide-based thermal insulation material provided by the present invention is low: the thermal insulation material of the present invention uses a laminated preform formed by sequentially laying and stacking quartz fiber cloth and carbon fiber cloth as a reinforcement phase or skeleton, and the nano-silica ceramic filled inside is used as a matrix phase: the nano-silica ceramic is dispersed in the gaps between the fibers and the fibers of the laminated preform with a certain particle size. By designing the particle size of the silicon oxide particles and the solid content of the silica sol raw material, the silicon oxide ceramic exists in the form of a ceramic matrix with a porous structure, and the obtained silicon oxide-based thermal insulation material The porosity is as high as 30-45%, resulting in a very low solid thermal conductivity coefficient of the material. In addition, the quartz fiber cloth and carbon fiber layers in the thermal insulation material of the present invention are stacked and laid out in a horizontal direction. The quartz fiber cloth has a very low thermal conductivity, and the carbon fiber cloth can strongly inhibit radiative heat transfer. This stacked layout structure and the introduction of carbon fiber cloth significantly reduce the thermal conductivity coefficient of the material in the thickness direction. Therefore, the thermal conductivity of the material of the present invention in the thickness direction and at low pressure is very low, with a room temperature thermal conductivity of 0.033-0.052 W / (m·K) at 4 Pa.

[0023] 2. The silica-based thermal insulation material provided by the present invention has high strength: on the one hand, the multi-layer fiber cloth in the material of the present invention is formed by stacking and laying, and the initial fiber preform can be given a higher compressive strength by controlling the higher fiber volume density; on the other hand, the size of the silica ceramic particles in the matrix of the material of the present invention is larger than that of the prior art. These relatively large silica ceramic particles are interconnected and fused to form a relatively continuous and robust nano-ceramic matrix skeleton, which further enhances the overall mechanical strength of the thermal insulation material.

[0024] 3. In the preparation method provided by the present invention, a sol with a certain particle size and solid content is used as a raw material to perform a vacuum impregnation on the fiber cloth laminated preform. After the spherical silica particles in the silica sol are gelled in the pores of the preform, the particles are connected end to end and their positions in space are "fixed"; further, in the hydrothermal treatment process in the high-temperature heat treatment step, by controlling the hydrothermal temperature and time, the contact points between the spherical particles are fused to a certain extent, forming a relatively continuous and thick nano-skeleton; in the normal pressure drying process, the water around the skeleton is converted into water vapor and removed, forming a nano-skeleton. The porous nano-silica ceramic matrix is formed, in which the particle size of the sol, the solid content and the parameters of the hydrothermal treatment are the key to controlling the ceramic particle size and material porosity in the product matrix, and thus also the key to the low thermal conductivity and high strength of the product. That is: the particles in the gel state can be regarded as an accumulation of spherical particles, and each sphere is in point contact; under hydrothermal conditions, the points between the spheres will "weld" and the point contact will become "surface contact", but the contact surface cannot be too large (by controlling the hydrothermal temperature and time, the appropriate welding "surface" can be achieved to achieve the purpose of both high strength and low thermal conductivity).

[0025] 4. In the step of preparing the laminated preform / gel composite, the present invention controls the amount of acid so that the silica sol (the sol is in a liquid flow state at this time, and the positions of the silica spherical particles therein are always "randomly moving") is completely impregnated into the pores of the fiber preform and then gelled in situ to form the laminated preform / gel composite. At this time, the position of each silica spherical particle in the gel is "fixed"; then, in the high-temperature heat treatment step, by controlling the process conditions (hydrothermal temperature and time), the gaps above and below the fiber cloth and around each fiber are formed in situ with strong A strong porous nano-silica ceramic matrix is formed (through the temperature and time control of the hydrothermal treatment, the contact points between the silica spherical particles in the gel undergo a certain fusion, forming a relatively continuous and thick nano-skeleton in situ), and in this step, the silica spherical particles in the gel will also undergo appropriate interface bonding with the quartz fiber, so that the fiber quartz fiber cloth, suture thread and matrix form a strong three-dimensional porous structure that is interconnected and supported by each other, so that the material has low density and low thermal conductivity while also having high compressive strength (125.6~135.7MPa).

[0026] 5. The preparation process of the silica-based thermal insulation material provided by the present invention is simple, safe and environmentally friendly: the material of the present invention is obtained through three steps, namely, preparing a fiber cloth laminated preform, preparing a laminated preform / gel composite, and high-temperature heat treatment (temperature 260-340°C). Compared with the sintering temperature of traditional silica ceramic-based composite materials (800-1000°C), the process is lower and the process is simple; the only solvent used in the preparation process is water, and no flammable and explosive organic solvents are used or by-products are produced, which is safe and environmentally friendly.

[0027] This invention uses commercially available silica sol using water as the solvent, a preform made of laminated quartz fiber cloth and carbon fibers as the main raw materials. Through three steps: preparing the fiber cloth laminated preform, preparing the laminated preform / gel composite, and then performing high-temperature heat treatment, a silica-based thermal insulation material with both high strength and ultra-low thermal conductivity is produced. The preparation process is simple, safe, and environmentally friendly, and can be easily scaled up for production. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] These and / or other aspects and advantages of the present invention will become more apparent and more readily understood from the following detailed description of embodiments of the present invention in conjunction with the accompanying drawings, in which:

[0029] Figure 1 Schematic diagram of the structure of the silicon oxide-based thermal insulation material of the present invention; wherein: 1-quartz fiber cloth; 2-fiber suture; 3-fiber cloth laminated preform; 4-carbon fiber cloth

[0030] Figure 2 The figure is a general flow chart of the method for preparing silicon oxide-based thermal insulation materials of the present invention. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] Example 1

[0033] The preparation method of high-strength and low-thermal-conductivity silicon oxide-based thermal insulation material comprises the following steps:

[0034] (1) Preparation of fiber cloth laminated preforms

[0035] Quartz fiber cloth and carbon fiber cloth with a thickness of 0.1 mm were used. First, 5 layers of quartz fiber cloth were laid out, followed by 1 layer of carbon fiber cloth, and then 5 layers of quartz fiber cloth and 1 layer of carbon fiber cloth were laid out. This stacking method was followed until the preform thickness reached 18.5 mm. Quartz fiber sewing thread with a linear density of 100 tex was used for sewing (stitch spacing of 15 mm) to obtain a fiber cloth stacked preform. The volume density of the preform was 1.0 g / cm 3 .

[0036] (2) Preparation of laminated preform / gel composite

[0037] The fiber cloth laminated preform was clamped between 10mm-thick steel plates and placed in an impregnation tank containing silica sol. Vacuum impregnation was performed at -0.1MPa and maintained at this pressure for 0.5h. The sol in the preform gelled, resulting in a laminated preform / gel composite. The silica sol had a solids content of 45%, the solvent was water, and the sol particle size was 160nm. Before the vacuum impregnation, a 0.1mol / L nitric acid solution was added, with a volume ratio of 100:1.5.

[0038] (3) High temperature heat treatment

[0039] The laminated preform / gel composite was placed in an iron box filled with deionized water. The iron box was then placed in a sealed container for hydrothermal treatment. The container was then removed and dried at atmospheric pressure to produce a high-strength, low-thermal-conductivity silica-based insulation material. The hydrothermal treatment was performed at 260°C for 4 hours, while the atmospheric drying was performed at 90°C for 48 hours.

[0040] The density of the silicon oxide-based thermal insulation material prepared in Example 1 is 1.30 g / cm 3 The porosity is 40.9%, the thermal conductivity in the thickness direction at room temperature is 0.040W / (m·K) at 4Pa, and the compressive strength is 130.2MPa.

[0041] Example 2:

[0042] (1) Preparation of fiber cloth laminated preforms

[0043] Quartz fiber cloth with a thickness of 0.2mm and carbon fiber cloth with a thickness of 0.1mm are stacked and laid out, and then sewn with quartz fiber sewing thread with a linear density of 190tex (sewing stitch spacing of 10mm) to obtain a fiber cloth stacked preform. When stacking and laying out the preform, first lay out 5 layers of quartz fiber cloth, then lay out 1 layer of carbon fiber cloth, then lay out 5 layers of quartz fiber cloth, and then lay out 1 layer of carbon fiber cloth. This stacking and laying method is used until the preform thickness reaches 12.5mm. The volume density of the preform is 0.88g / cm 3 .

[0044] (2) Preparation of laminated preform / gel composite

[0045] The fiber cloth laminated preform was clamped between 5mm-thick steel plates and placed in an impregnation tank containing silica sol. Vacuum impregnation was performed at -0.1MPa and maintained at this pressure for 1 hour. The sol in the preform gelled, resulting in a laminated preform / gel composite. The silica sol used had a solids content of 50%, water as the solvent, and a particle size of 110nm. Before the vacuum impregnation, 0.1mol / L acetic acid solution was added, with a volume ratio of 100:0.5.

[0046] (3) High temperature heat treatment

[0047] The laminated preform / gel composite was placed in an iron box filled with deionized water. The iron box was then placed in a sealed container for hydrothermal treatment. The container was then removed and dried at atmospheric pressure to produce a high-strength, low-thermal-conductivity silica-based insulation material. The hydrothermal treatment was performed at 300°C for 7 hours, and the atmospheric drying was performed at 99°C for 25 hours.

[0048] The density of the silicon oxide-based thermal insulation material prepared in Example 2 is 1.28 g / cm 3 The porosity is 41.8%, the thermal conductivity in the thickness direction at room temperature is only 0.033W / (m·K) at 4Pa, and the compressive strength is 125.6MPa.

[0049] Example 3

[0050] (1) Preparation of fiber cloth laminated preforms

[0051] A quartz fiber cloth with a thickness of 0.13 mm and a carbon fiber cloth with a thickness of 0.1 mm were stacked and laid out, and then sewn together using quartz fiber sewing thread with a linear density of 133 tex (sewing stitch spacing of 5 mm) to obtain a fiber cloth stacked preform. The stacking method is as follows: first lay out 5 layers of quartz fiber cloth, then lay out 1 layer of carbon fiber cloth, then lay out 5 layers of quartz fiber cloth, and then lay out 1 layer of carbon fiber cloth, and continue this stacking method until the preform thickness reaches 6.65 mm and the volume density of the preform is 1.1 g / cm 3 .

[0052] (2) Preparation of laminated preform / gel composite

[0053] The fiber cloth laminated preform was clamped between 10mm-thick steel plates and placed in an impregnation tank containing silica sol. Vacuum impregnation was performed at a negative pressure (-0.1MPa) and maintained at that pressure for 0.5 hours. The sol in the preform gelled, resulting in a laminated preform / gel composite. The silica sol had a solids content of 42%, was prepared using water as the solvent, and had an average particle size of 135nm. Before the negative pressure impregnation, a 0.1mol / L nitric acid solution was added, with a volume ratio of silica sol to nitric acid solution of 100:1.

[0054] (3) High temperature heat treatment

[0055] The laminated preform / gel composite was placed in an iron box filled with deionized water. The iron box was then placed in a sealed container for hydrothermal treatment. The container was then removed and dried at atmospheric pressure to produce a high-strength, low-thermal-conductivity silica-based insulation material. The hydrothermal treatment was performed at 340°C for 8 hours, and the atmospheric drying was performed at 95°C for 36 hours.

[0056] The density of the silicon oxide-based thermal insulation material prepared in Example 3 is 1.46 g / cm 3 The porosity is 33.6%, the thermal conductivity in the thickness direction at room temperature is 0.052W / (m·K) at 4Pa, and the compressive strength is 135.7MPa.

[0057] While various embodiments of the present invention have been described above, the foregoing description is intended to be illustrative, non-exhaustive, and not limiting of the disclosed embodiments. Numerous modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. Therefore, the scope of the present invention shall be determined by the scope of the claims.

Claims

1. A high-strength, low-thermal-conductivity silicon oxide-based thermal insulation material, characterized in that: It includes a fiber cloth laminated preform and a silicon oxide ceramic matrix; The fiber cloth laminated preform comprises five layers of quartz fiber cloth and one layer of carbon fiber cloth laminated in sequence, a laminated structure formed by using the five layers of quartz fiber cloth as an outer layer, and a quartz suture thread stitching the laminated structure with a flat needle; The silicon oxide ceramic matrix is a porous structure formed by nano-silicon oxide, and the particle size of the nano-silicon oxide ranges from 120 to 180 nm; Assuming the total mass of the high-strength, low-thermal-conductivity silica-based insulation material is 100%, the fiber cloth laminated preform accounts for 65-80% of the total mass, and the silica ceramic matrix accounts for 20-35% of the total mass; the porosity of the material is 30-45%; The bulk density of the fiber cloth laminated preform is 0.8-1.1 g / cm3, and the thickness of the preform is 2-20 mm. The thermal conductivity of the high-strength, low-thermal-conductivity silica-based thermal insulation material is 0.033-0.052 W / (m·K) at a pressure of 4 Pa, and the pressure strength range is 125.6-135.7 MPa. The fiber cloth laminated preform is clamped between two steel plates, and the clamped fiber cloth laminated preform is placed in a sol pool of an impregnation tank containing silica sol. Vacuum is applied for negative pressure impregnation, and the pressure is maintained for a period of time to allow the sol in the preform to gel, thereby obtaining a laminated preform / gel composite clamped by the steel plates. The silica sol has a solid content of 42-50%, a solvent of water, and a sol particle size of 110-160 nm. Before vacuuming and performing negative pressure impregnation, a 0.1 mol / L acid solution is added to the silica sol. The negative pressure impregnation pressure is -0.1 MPa, and the pressure is maintained for 0.5-1 hour. The stacked preform / gel composite clamped by steel plates is placed in an open container filled with deionized water, and the open container is placed in a sealed container for hydrothermal treatment. The open container is then taken out for normal pressure drying. The bolts are loosened and the steel plates are removed to obtain the high-strength and low-thermal-conductivity silicon oxide-based thermal insulation material. The hydrothermal treatment temperature is 260-340°C and the time is 4-10 hours. The normal pressure drying temperature is 90-99°C and the time is 24-48 hours.

2. The high-strength, low-thermal-conductivity silicon oxide-based thermal insulation material according to claim 1, characterized in that: The thickness of the single layer of the quartz fiber cloth is 0.1-0.2 mm, and the thickness of the single layer of the carbon fiber cloth is 0.1 mm; The linear density of the quartz fiber suture is 100-190 tex, and the suture stitch spacing is 5-15 mm.

3. A method for preparing the high-strength, low-thermal-conductivity silicon oxide-based thermal insulation material according to claim 1 or 2, characterized in that: The following steps are involved: S1. preparing a fiber cloth laminated preform; S2. Preparing a laminated preform / gel composite: The fiber cloth laminated preform is clamped between two steel plates, and the clamped fiber cloth laminated preform is placed in a sol pool of an impregnation tank containing silica sol. Vacuum is applied for negative pressure impregnation, and the pressure is maintained for a period of time to allow the sol in the preform to gel, thereby obtaining a laminated preform / gel composite clamped by the steel plates; S3: High-temperature heat treatment: The stacked preform / gel composite clamped by the steel plates is placed in an open container filled with deionized water, and the open container is placed in a sealed container for hydrothermal treatment. The open container is then taken out for drying at normal pressure, the bolts are loosened, and the steel plates are removed to obtain the high-strength, low-thermal-conductivity silicon oxide-based thermal insulation material.

4. The method for preparing a high-strength, low-thermal-conductivity silicon oxide-based thermal insulation material according to claim 3, wherein: In step S2, the fiber cloth laminate preform is clamped between the two steel plates by punching holes at corresponding positions at the four corners of the two steel plates, clamping the laminate preform in the middle position between the two steel plates, and then fixing and tightening the four corners of the two steel plates with bolts; the thickness of the two steel plates is 5-10 mm.

5. The method for preparing the high-strength and low-thermal-conductivity silicon oxide-based thermal insulation material according to claim 3, wherein: In the step S2: The solid content of the silica sol is 42-50%, the solvent is water, and the sol particle size is 110-160 nm; Before performing the vacuum impregnation, a 0.1 mol / L acid solution is added to the silica sol; the pressure of the negative pressure impregnation is -0.1 MPa, and the pressure holding time is 0.5 to 1 h.

6. The method for preparing the high-strength and low-thermal-conductivity silicon oxide-based thermal insulation material according to claim 3, characterized in that: In the step S2: The acid is nitric acid or acetic acid; the volume ratio of the silica sol to the acid solution is 100:(0.5~2).

7. The method for preparing a high-strength, low-thermal-conductivity silicon oxide-based thermal insulation material according to claim 3, wherein: In the step S3: The temperature of the hydrothermal treatment is 260~340℃ and the time is 4~10 h; The temperature of atmospheric pressure drying is 90~99 ℃ and the time is 24~48 hours.

8. An application of the high-strength, low-thermal-conductivity silicon oxide-based thermal insulation material according to claim 1 or 2, characterized in that: Applicable to no more than 10 -3 Pa vacuum and -120 ~ +120 ℃ hot and cold cycle shock in the satellite.

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