A whisker-reinforced silica aerogel thermal insulation material and its preparation method

Abstract

This invention discloses a whisker-reinforced silica aerogel thermal insulation material and its preparation method. The invention uses low-cost aqueous silica sol as the silicon source and ceramic whisker porous framework as the reinforcing phase to prepare a high-temperature resistant and low-thermal-conductivity whisker-reinforced silica aerogel thermal insulation material with a simple process. The invention uses inexpensive aqueous silica sol as the silicon source precursor, and the sol preparation only requires one step. The process is simple and does not require complicated concentration, solvent replacement and other processes. The raw materials and preparation process of the sol are low in cost.

Description

Technical Field

[0001] This invention belongs to the technical field of aerogel thermal insulation materials, specifically relating to a whisker-reinforced silica aerogel thermal insulation material and its preparation method. Background Technology

[0002] New high-speed aircraft are characterized by high Mach numbers and long flight times. When flying in the atmosphere, their surfaces must withstand extremely harsh aerodynamic environments, with temperatures exceeding 1000°C. This necessitates the use of lightweight, high-insulation, and mechanically sound thermal protection materials to prevent heat from entering the aircraft's interior and ensure the normal operation of internal components. Traditional insulation materials such as fiber cotton and heat-insulating tiles cannot meet these stringent requirements.

[0003] Silica aerogel, due to its high porosity and unique three-dimensional nanoporous structure, has extremely low room temperature thermal conductivity (as low as 0.013 W / (m·K)), making it a novel high-performance thermal insulation material.

[0004] Currently, silica aerogel composites reinforced with ceramic fibers have been used as thermal insulation materials for aircraft. However, silica aerogels prepared by existing methods are prone to sintering and densification at high temperatures (above 700°C), leading to increased density, pore collapse, dimensional shrinkage, and decreased thermal insulation performance. Therefore, the operating temperature of silica aerogel composites is limited to below 800°C, which cannot meet the thermal insulation requirements at higher temperatures.

[0005] There has been some research within the industry on silica aerogel composites with higher temperature resistance, such as: the design, preparation, and performance study of high-temperature resistant SiO2 aerogel thermal insulation composites (by Cai Huafei); and the preparation of high-temperature resistant silica aerogel composites based on monodisperse silica sol, with a typical density of 0.360 g / cm³. 3 The thermal conductivity at 1000 and 1100℃ is 0.054 and 0.062 W / (m·K), respectively. The density and high-temperature thermal conductivity are both relatively high. The operating temperature should not exceed 1100℃. Furthermore, the preparation of monodisperse silica sol requires concentration and displacement methods, making the process relatively complex. Summary of the Invention

[0006] To address the limitations of existing silica aerogel composite materials, which have an operating temperature not exceeding 1100℃ and require complex processes involving concentration and displacement to prepare monodisperse silica sol, this invention provides a whisker-reinforced silica aerogel thermal insulation material and its preparation method. The alumina aerogel material prepared using this invention exhibits characteristics such as temperature resistance up to 1200℃, low thermal conductivity over a wide temperature range, high compressive strength, and simple and low-cost processing, making it promising for applications in high-speed aircraft thermal protection and nuclear power plant insulation.

[0007] The technical solution of the present invention is as follows:

[0008] The preparation method of this invention includes five steps: preparation of silica sol; formation of porous framework of ceramic whiskers; impregnation and gel aging of silica sol; supercritical drying; and high-temperature sintering.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] A method for preparing a whisker-reinforced silica aerogel thermal insulation material includes the following steps:

[0011] 1) Preparation of silica sol: Add alcohol to aqueous silica sol and stir until it is diluted. Then add acid or alkali as a catalyst and stir until it is diluted to obtain silica sol.

[0012] The alcohols, catalysts, and aqueous silica sols are prepared in a mass ratio of (1.0-4.5):(0.001-0.05):1.

[0013] The aqueous silica sol has a solid content of 30-55%.

[0014] The average particle size of the aqueous silica sol particles is 25-100 nm;

[0015] When the aqueous silica sol is acidic, an alkaline catalyst is added; when the aqueous silica sol is alkaline, an acidic catalyst is added.

[0016] The alcohols mentioned are selected from one of ethanol, methanol, isopropanol, n-propanol, n-butanol, isobutanol, sec-butanol, and tert-butanol;

[0017] The acid catalyst is selected from one of hydrochloric acid, nitric acid, hydrofluoric acid, and acetic acid;

[0018] The alkaline catalyst is selected from ammonia or urea.

[0019] 2) Ceramic whisker porous framework molding: Add organic and inorganic binders to deionized water and stir evenly to form a viscous dispersion.

[0020] Ceramic whiskers are added to the dispersion and stirred until a slurry is formed.

[0021] The slurry is injected into a mold, then vacuum filtered, and then dried in an oven to obtain a ceramic whisker blank.

[0022] The ceramic whisker blank is heated to 750-1150℃ in a high-temperature furnace and held for 1-12 hours, then naturally cooled to obtain a porous ceramic whisker framework.

[0023] The organic adhesive, inorganic adhesive, ceramic whiskers, and deionized water are disposed in a mass ratio of (0.5-3.0):(1.0-5.0):(8-18):100.

[0024] The organic adhesive is selected from gelatin or starch;

[0025] The inorganic adhesive is selected from one of silicon dioxide, zirconium oxide, boric acid, and boron carbide;

[0026] The ceramic whiskers are selected from one of the following: lanthanum zirconate, zirconium oxide, aluminum oxide, mullite, silicon oxide, silicon carbide, potassium titanate, aluminum borate, magnesium oxide, and silicon nitride whiskers.

[0027] The ceramic whiskers have an average diameter of 100-800 nm and an aspect ratio of 3000-20000.

[0028] 3) Silica sol impregnation and gel aging: Silica sol is injected into the porous framework of ceramic whiskers at an injection pressure of -0.1-0 MPa. After full injection, the porous framework / sol composite is placed at a high temperature of 40-120℃ to gel and age for 4-24 hours to obtain the porous framework / gel composite.

[0029] 4) Supercritical drying: High-temperature supercritical drying or low-temperature supercritical drying is used to remove the liquid from the porous framework / gel composite to obtain a porous framework / aerogel preform.

[0030] 5) High-temperature sintering: The obtained porous skeleton / aerogel preform is placed in a high-temperature furnace and heated to 750-1100℃ for 1-24 hours, then naturally cooled to obtain a whisker-reinforced silica aerogel insulation material. The whisker-reinforced silica aerogel insulation material has the following properties:

[0031] 1) When the long-term operating temperature reaches 1200℃, after heat treatment in a muffle furnace at 1200℃ for 2 hours and 72 hours, the typical linear shrinkage rates of the material are 0-1.1% and 0.4-2.4%, respectively; when the short-term operating temperature reaches 1300℃, after heat treatment in a muffle furnace at 1300℃ for 2 hours, the typical linear shrinkage rate of the material is 1.5-4.7%.

[0032] 2) Typical values ​​for thermal conductivity at room temperature are 0.023-0.026 W / (m·K), at 1100℃ are 0.036-0.043 W / (m·K), and at 1200℃ are 0.040-0.048 W / (m·K);

[0033] 3) The typical density of thermal insulation materials is 0.28-0.30 g / cm³. 3The typical compressive strength at 3% deformation is 0.23-0.38 MPa, and the typical compressive strength at 10% deformation is 0.94-1.60 MPa.

[0034] In this invention:

[0035] The solid content of the aqueous silica sol mentioned in step 1) is 30-55%. When the solid content is less than 30%, the water content in the prepared silica sol is too high, which affects the supercritical drying effect and makes it impossible to obtain a silica aerogel with a good structure. When the solid content is higher than 55%, the aqueous silica sol is difficult to preserve stably.

[0036] The average particle size of the aqueous silica sol particles is 25-120 nm. When the average particle size is less than 25 nm, the prepared silica aerogel has low temperature resistance. When the average particle size is greater than 120 nm, the silica sol is difficult to gel, and the prepared silica aerogel has low strength and poor bulking.

[0037] The ceramic whiskers mentioned in step 2) are selected from lanthanum zirconate, zirconium oxide, or mullite.

[0038] The high-temperature supercritical drying described in step 4) uses alcohols as the drying medium; the low-temperature supercritical drying uses carbon dioxide as the drying medium.

[0039] This invention also relates to a whisker-reinforced silica aerogel thermal insulation material, obtained by the above-mentioned preparation method of a whisker-reinforced silica aerogel thermal insulation material, wherein the whisker-reinforced silica aerogel thermal insulation material has excellent comprehensive performance:

[0040] 1) When the long-term operating temperature reaches 1200℃, after heat treatment in a muffle furnace at 1200℃ for 2 hours and 72 hours, the typical linear shrinkage rates of the material are 0-1.1% and 0.4-2.4%, respectively; when the short-term operating temperature reaches 1300℃, after heat treatment in a muffle furnace at 1300℃ for 2 hours, the typical linear shrinkage rate of the material is 1.5-4.7%.

[0041] 2) Typical values ​​for thermal conductivity at room temperature are 0.023-0.026 W / (m·K), at 1100℃ are 0.036-0.043 W / (m·K), and at 1200℃ are 0.040-0.048 W / (m·K);

[0042] 3) The typical density of thermal insulation materials is 0.28-0.30 g / cm³. 3 The typical compressive strength at 3% deformation is 0.23-0.38 MPa, and the typical compressive strength at 10% deformation is 0.94-1.60 MPa.

[0043] Compared with the prior art, the present invention has the following advantages:

[0044] 1. The present invention discloses a method for preparing a whisker-reinforced silica aerogel thermal insulation material, which uses low-cost aqueous silica sol as the silicon source and ceramic whisker porous framework as the reinforcing phase to prepare a high-temperature resistant and low-thermal-conductivity whisker-reinforced silica aerogel thermal insulation material with a simple process; it uses inexpensive aqueous silica sol as the silicon source precursor, the sol preparation only requires one step, the process is simple and does not require complicated concentration, solvent replacement and other processes, and the raw materials and preparation process of the sol are low cost.

[0045] 2. The whisker-reinforced silica aerogel insulation material of this invention uses large-particle silica sol as the silicon source precursor. The resulting silica aerogel has lower activity, is less prone to sintering at high temperatures, and can withstand temperatures of 1100-1200℃, significantly improving its operating temperature compared to existing silica aerogels. The ceramic whiskers have a single-crystal structure with no obvious lattice defects or dislocations, resulting in low sintering activity. The formation of a porous framework further enhances its resistance to sintering, thus providing high temperature resistance. The whisker size is comparable to that of aerogel nanoparticles, allowing for uniform nanoscale composite bonding. Therefore, the high-temperature resistant whiskers provide excellent isolation between silica aerogel particles, inhibiting atomic diffusion and sintering, significantly improving the temperature resistance of the silica aerogel. The resulting whisker-reinforced aerogel insulation material exhibits excellent temperature resistance (above 1200℃). Conventional coarse-diameter (micrometer-scale) ceramic fibers cannot achieve the aforementioned significant effects.

[0046] 3. The whisker-reinforced silica aerogel thermal insulation material of this invention features high porosity and nanopore size, resulting in very low solid-state and gaseous thermal conductivity. Furthermore, the silica aerogel's skeletal particles have a larger particle size, providing a certain degree of infrared blocking compared to conventional high-transmittance silica aerogels. The ceramic whiskers are smaller in size (diameter and length) than conventional ceramic fibers, have even lower solid-state thermal conductivity, and provide excellent infrared blocking at high temperatures, significantly reducing the high-temperature thermal conductivity of the silica aerogel. Therefore, the whisker-reinforced silica aerogel thermal insulation material prepared by this invention exhibits low thermal conductivity across the entire temperature range.

[0047] 4. The whisker-reinforced silica aerogel insulation material of this invention uses a whisker framework as the reinforcing phase. Since whiskers are single crystals, they lack significant lattice defects or dislocations, resulting in mechanical strength close to theoretical values. The whiskers are bonded together with a binder, and the porous framework formed after high-temperature sintering already possesses a certain compressive strength. After the whisker porous framework is combined with silica aerogel, the specific surface area of ​​the whiskers is significantly higher than that of ordinary ceramic fibers, leading to a relatively higher interfacial bonding strength between the whiskers and silica aerogel. This interfacial bonding strength is further improved through subsequent high-temperature sintering. Therefore, compared to existing silica aerogel composite materials using ceramic fibers as the reinforcing phase, the whisker-reinforced silica aerogel insulation material prepared by this invention exhibits better compressive strength at the same density. Attached Figure Description

[0048] Figure 1 This is a scanning electron microscope image of silica aerogel in the thermal insulation material prepared in Experimental Example 1 of this invention;

[0049] Figure 2 This is a scanning electron microscope image of the silica aerogel in the thermal insulation material prepared in Experimental Example 1 of this invention after heat treatment at 1200℃ for 2 hours. Detailed Implementation

[0050] The present invention will be further described in detail below through embodiments, but these embodiments should not be considered as limiting the present invention.

[0051] Example 1:

[0052] A method for preparing a whisker-reinforced silica aerogel thermal insulation material includes the following steps:

[0053] 1) Preparation of silica sol: Isopropanol is added to acidic aqueous silica sol and stirred evenly to dilute it. Then ammonia is added as a catalyst and stirred evenly to obtain silica sol.

[0054] The isopropanol, ammonia, and aqueous silica sol are prepared in a mass ratio of 1.2:0.005:1.

[0055] The aqueous silica sol has a solid content of 40%.

[0056] The average particle size of the aqueous silica sol particles is 40 nm;

[0057] 2) Ceramic whisker porous framework molding: Add starch and zirconium oxide sol to deionized water and stir evenly to form a viscous dispersion.

[0058] Lanthanum zirconate whiskers were added to the dispersion and stirred until a slurry was formed.

[0059] The slurry is injected into a mold, then vacuum filtered, and then dried in an oven to obtain lanthanum zirconate whisker blanks.

[0060] Lanthanum zirconate whisker blanks were heated to 1000℃ in a high-temperature furnace and held for 6 hours before being naturally cooled to obtain a porous framework of lanthanum zirconate whiskers.

[0061] The starch, zirconium oxide, lanthanum zirconate whiskers, and deionized water are disposed in a mass ratio of 1.2:3.0:12.5:100.

[0062] The lanthanum zirconate whiskers have an average diameter of 500 nm and an aspect ratio of 10000.

[0063] 3) Silica sol impregnation and gel aging: Silica sol is injected into the porous framework of ceramic whiskers at an injection pressure of -0.1MPa. After full injection, the porous framework / sol composite is placed at a high temperature of 60℃ to gel and age for 12h to obtain the porous framework / gel composite.

[0064] 4) Supercritical drying: The liquid in the porous framework / gel composite is removed by high-temperature supercritical drying to obtain a porous framework / aerogel preform;

[0065] 5) High-temperature sintering: The obtained porous skeleton / aerogel preform is placed in a high-temperature furnace, heated to 1000℃ and held for 12 hours, and then naturally cooled to obtain whisker-reinforced silica aerogel thermal insulation material.

[0066] The obtained whisker-reinforced silica aerogel insulation material has the following properties:

[0067] 1) When the long-term operating temperature reaches 1200℃, after heat treatment in a muffle furnace at 1200℃ for 2 hours and 72 hours, the linear shrinkage rate of the material is 0.1% and 1.5%, respectively; when the short-term operating temperature reaches 1300℃, after heat treatment in a muffle furnace at 1300℃ for 2 hours, the linear shrinkage rate of the material is 2.8%.

[0068] 2) The thermal conductivity at room temperature is 0.024 W / (m·K), at 1100℃ it is 0.038 W / (m·K), and at 1200℃ it is 0.042 W / (m·K);

[0069] 3) The density of the insulation material is 0.30 g / cm³. 3 The compressive strength at 3% deformation is 0.35 MPa, and the compressive strength at 10% deformation is 1.4 MPa.

[0070] Example 2:

[0071] A method for preparing a whisker-reinforced silica aerogel thermal insulation material includes the following steps:

[0072] 1) Preparation of silica sol: Isopropanol is added to acidic aqueous silica sol and stirred evenly to dilute it. Then ammonia is added as a catalyst and stirred evenly to obtain silica sol.

[0073] The isopropanol, ammonia, and aqueous silica sol are prepared in a mass ratio of 4.5:0.001:1; the aqueous silica sol has a solid content of 55%.

[0074] The average particle size of the aqueous silica sol particles is 25 nm.

[0075] 2) Ceramic whisker porous framework molding: Add starch and zirconium oxide sol to deionized water and stir evenly to form a viscous dispersion.

[0076] Lanthanum zirconate whiskers were added to the dispersion and stirred until a slurry was formed.

[0077] The slurry is injected into a mold, then vacuum filtered, and then dried in an oven to obtain lanthanum zirconate whisker blanks.

[0078] Lanthanum zirconate whisker blanks were heated to 1150℃ in a high-temperature furnace and held for 1 hour before being naturally cooled to obtain a porous framework of lanthanum zirconate whiskers.

[0079] The starch, zirconium oxide, lanthanum zirconate whiskers, and deionized water are disposed in a mass ratio of 3.0:5.0:18.0:100.

[0080] The lanthanum zirconate whiskers have an average diameter of 800 nm and an aspect ratio of 3000.

[0081] 3) Silica sol impregnation and gel aging: Silica sol is injected into the porous framework of ceramic whiskers at an injection pressure of 0 MPa. After full injection, the porous framework / sol composite is placed at a high temperature of 40°C to gel and age for 24 hours to obtain the porous framework / gel composite.

[0082] 4) Supercritical drying: The liquid in the porous framework / gel composite is removed by high-temperature supercritical drying to obtain a porous framework / aerogel preform;

[0083] 5) High-temperature sintering: The obtained porous skeleton / aerogel preform is placed in a high-temperature furnace, heated to 750℃ and held for 24 hours, and then naturally cooled to obtain whisker-reinforced silica aerogel thermal insulation material.

[0084] The obtained whisker-reinforced silica aerogel insulation material has the following properties:

[0085] 1) When the long-term operating temperature reaches 1200℃, after heat treatment in a muffle furnace at 1200℃ for 2 hours and 72 hours, the typical linear shrinkage rates of the material are 0.8% and 2.4%, respectively; when the short-term operating temperature reaches 1300℃, after heat treatment in a muffle furnace at 1300℃ for 2 hours, the typical linear shrinkage rate of the material is 4.7%.

[0086] 2) The typical thermal conductivity at room temperature is 0.023 W / (m·K), the typical thermal conductivity at 1100℃ is 0.036 W / (m·K), and the typical thermal conductivity at 1200℃ is 0.040 W / (m·K);

[0087] 3) The typical density of thermal insulation material is 0.28 g / cm³. 3 The typical compressive strength at 3% deformation is 0.30 MPa, and the typical compressive strength at 10% deformation is 1.24 MPa.

[0088] Example 3:

[0089] A method for preparing a whisker-reinforced silica aerogel thermal insulation material includes the following steps:

[0090] 1) Preparation of silica sol: Ethanol is added to acidic aqueous silica sol and stirred evenly to dilute it. Then ammonia is added as a catalyst and stirred evenly to obtain silica sol.

[0091] The ethanol, ammonia, and aqueous silica sol are prepared in a mass ratio of 1.0:0.05:1.

[0092] The aqueous silica sol has a solid content of 30%.

[0093] The average particle size of the aqueous silica sol particles is 100 nm.

[0094] 2) Ceramic whisker porous framework molding: Add starch and zirconium oxide sol to deionized water and stir evenly to form a viscous dispersion.

[0095] Lanthanum zirconate whiskers were added to the dispersion and stirred until a slurry was formed.

[0096] The slurry is injected into a mold, then vacuum filtered, and then dried in an oven to obtain lanthanum zirconate whisker blanks.

[0097] Lanthanum zirconate whisker blanks were heated to 750°C in a high-temperature furnace and held for 12 hours before being naturally cooled to obtain a porous framework of lanthanum zirconate whiskers.

[0098] The starch, zirconium oxide, lanthanum zirconate whiskers, and deionized water are in a mass ratio of 0.5:1.0:8.0:100.

[0099] The lanthanum zirconate whiskers have an average diameter of 300 nm and an aspect ratio of 2000.

[0100] 3) Silica sol impregnation and gel aging: Silica sol is injected into the porous framework of ceramic whiskers at an injection pressure of 0 MPa. After full injection, the porous framework / sol composite is placed at a high temperature of 120℃ to gel and age for 1 hour to obtain the porous framework / gel composite.

[0101] 4) Supercritical drying: The liquid in the porous framework / gel composite is removed by high-temperature supercritical drying to obtain a porous framework / aerogel preform;

[0102] 5) High-temperature sintering: The obtained porous skeleton / aerogel preform is placed in a high-temperature furnace, heated to 1100℃ and held for 1 hour, and then naturally cooled to obtain whisker-reinforced silica aerogel thermal insulation material.

[0103] The obtained whisker-reinforced silica aerogel insulation material has the following properties:

[0104] 1) When the long-term operating temperature reaches 1200℃, after heat treatment in a muffle furnace at 1200℃ for 2 hours and 72 hours, the typical linear shrinkage rates of the material are 0.0% and 0.4%, respectively; when the short-term operating temperature reaches 1300℃, after heat treatment in a muffle furnace at 1300℃ for 2 hours, the typical linear shrinkage rate of the material is 1.5%.

[0105] 2) The typical thermal conductivity at room temperature is 0.026 W / (m·K), the typical thermal conductivity at 1100℃ is 0.041 W / (m·K), and the typical thermal conductivity at 1200℃ is 0.046 W / (m·K);

[0106] 3) The typical density of thermal insulation material is 0.29 g / cm³. 3 The typical compressive strength at 3% deformation is 0.23 MPa, and the typical compressive strength at 10% deformation is 0.94 MPa.

[0107] Example 4:

[0108] A method for preparing a whisker-reinforced silica aerogel thermal insulation material includes the following steps:

[0109] 1) Preparation of silica sol: Add sec-butanol to alkaline aqueous silica sol and stir until homogeneous to dilute it. Then add nitric acid as a catalyst and stir until homogeneous to obtain silica sol.

[0110] The sec-butanol, nitric acid, and aqueous silica sol are prepared in a mass ratio of 1.2:0.005:1.

[0111] The aqueous silica sol has a solid content of 40%.

[0112] The average particle size of the aqueous silica sol particles is 40 nm;

[0113] 2) Ceramic whisker porous framework molding: Gelatin and boron carbide are added to deionized water and stirred evenly to form a viscous dispersion;

[0114] Zirconia whiskers were added to the dispersion and stirred until a slurry was formed.

[0115] The slurry is injected into a mold, then vacuum filtered, and then dried in an oven to obtain a zirconia whisker blank.

[0116] The zirconia whisker blank was heated to 1000℃ in a high-temperature furnace and held for 6 hours, then naturally cooled to obtain a porous zirconia whisker framework.

[0117] The gelatin, boron carbide, zirconium oxide whiskers, and deionized water are prepared in a mass ratio of 1.2:3.0:12.5:100.

[0118] The zirconium oxide whiskers have an average diameter of 500 nm and an aspect ratio of 10000.

[0119] 3) Silica sol impregnation and gel aging: Silica sol is injected into the porous framework of ceramic whiskers at an injection pressure of -0.1MPa. After full injection, the porous framework / sol composite is placed at a high temperature of 60℃ to gel and age for 12h to obtain the porous framework / gel composite.

[0120] 4) Supercritical drying: The liquid in the porous framework / gel composite is removed by low-temperature supercritical drying to obtain a porous framework / aerogel preform;

[0121] 5) High-temperature sintering: The obtained porous skeleton / aerogel preform is placed in a high-temperature furnace, heated to 1000℃ and held for 12 hours, and then naturally cooled to obtain whisker-reinforced silica aerogel thermal insulation material.

[0122] The obtained whisker-reinforced silica aerogel insulation material has the following properties:

[0123] 1) When the long-term operating temperature reaches 1200℃, after heat treatment in a muffle furnace at 1200℃ for 2 hours and 72 hours, the linear shrinkage rate of the material is 0.2% and 1.6%, respectively; when the short-term operating temperature reaches 1300℃, after heat treatment in a muffle furnace at 1300℃ for 2 hours, the linear shrinkage rate of the material is 2.9%.

[0124] 2) The thermal conductivity at room temperature is 0.024 W / (m·K), at 1100℃ it is 0.040 W / (m·K), and at 1200℃ it is 0.044 W / (m·K);

[0125] 3) The density of the insulation material is 0.30 g / cm³. 3 The compressive strength at 3% deformation is 0.36 MPa, and the compressive strength at 10% deformation is 1.45 MPa.

[0126] Example 5:

[0127] A method for preparing a whisker-reinforced silica aerogel thermal insulation material includes the following steps:

[0128] 1) Preparation of silica sol: Isopropanol is added to acidic aqueous silica sol and stirred evenly to dilute it. Then ammonia is added as a catalyst and stirred evenly to obtain silica sol.

[0129] The isopropanol, ammonia, and aqueous silica sol are prepared in a mass ratio of 1.2:0.005:1.

[0130] The aqueous silica sol has a solid content of 40%.

[0131] The average particle size of the aqueous silica sol particles is 40 nm;

[0132] 2) Ceramic whisker porous framework molding: Add starch and zirconium oxide sol to deionized water and stir evenly to form a viscous dispersion.

[0133] Add mullite whiskers to the dispersion and stir until homogeneous to form a slurry;

[0134] The slurry is injected into a mold, then vacuum filtered, and then dried in an oven to obtain a mullite whisker blank.

[0135] The mullite whisker blank was heated to 1000℃ in a high-temperature furnace and held for 6 hours, then naturally cooled to obtain a porous mullite whisker framework.

[0136] The starch, zirconium oxide, mullite whiskers, and deionized water are prepared in a mass ratio of 1.2:3.0:12.5:100.

[0137] The mullite whiskers described above have an average diameter of 500 nm and an aspect ratio of 10000.

[0138] 3) Silica sol impregnation and gel aging: Silica sol is injected into the porous framework of ceramic whiskers at an injection pressure of -0.1MPa. After full injection, the porous framework / sol composite is placed at a high temperature of 60℃ to gel and age for 12h to obtain the porous framework / gel composite.

[0139] 4) Supercritical drying: The liquid in the porous framework / gel composite is removed by high-temperature supercritical drying to obtain a porous framework / aerogel preform;

[0140] 5) High-temperature sintering: The obtained porous skeleton / aerogel preform is placed in a high-temperature furnace, heated to 1000℃ and held for 12 hours, and then naturally cooled to obtain whisker-reinforced silica aerogel thermal insulation material.

[0141] The obtained whisker-reinforced silica aerogel insulation material has the following properties:

[0142] 1) When the long-term operating temperature reaches 1200℃, after heat treatment in a muffle furnace at 1200℃ for 2 hours and 72 hours, the linear shrinkage rate of the material is 0.1% and 1.1%, respectively; when the short-term operating temperature reaches 1300℃, after heat treatment in a muffle furnace at 1300℃ for 2 hours, the linear shrinkage rate of the material is 2.0%.

[0143] 2) The thermal conductivity at room temperature is 0.026 W / (m·K), at 1100℃ it is 0.043 W / (m·K), and at 1200℃ it is 0.048 W / (m·K);

[0144] 3) The density of the insulation material is 0.30 g / cm³. 3 The compressive strength at 3% deformation is 0.38 MPa, and the compressive strength at 10% deformation is 1.6 MPa.

[0145] Comparative Example 1:

[0146] The difference between Comparative Example 1 and Example 1 is that the average particle size of the aqueous silica sol in step 1) is 15 nm, while the rest is the same as in Example 1;

[0147] The obtained silica aerogel insulation material, after being heat-treated in a muffle furnace at 1200℃ for 2 hours and 72 hours, showed linear shrinkage rates of 1.4% and 3.1%, respectively; after being heat-treated in a muffle furnace at 1300℃ for 2 hours, the linear shrinkage rate was 5.6%.

[0148] This indicates that small sol particle size will significantly affect the temperature resistance of the insulation material.

[0149] Comparative Example 2:

[0150] The difference between Comparative Example 2 and Example 1 is that the solid content of the aqueous silica sol in step 1) is 20%, while the rest is the same as in Example 1;

[0151] The density of the obtained silica aerogel insulation material is 0.24 g / cm³. 3 The compressive strength at 3% deformation is 0.15 MPa, and the compressive strength at 10% deformation is 0.76 MPa.

[0152] This indicates that a low sol solids content will significantly reduce the density and strength of the material.

[0153] Comparative Example 3:

[0154] The difference between Comparative Example 3 and Example 1 is that in step 2), the mass ratio of zirconium oxide to deionized water is 0.5:100, while the rest is the same as in Example 1;

[0155] The obtained silica aerogel insulation material has a compressive strength of 0.20 MPa at 3% deformation and 0.91 MPa at 10% deformation.

[0156] This indicates that a low content of inorganic binder will significantly reduce the strength of the material.

[0157] Comparative Example 4:

[0158] The difference between Comparative Example 4 and Example 1 is that in step 2), the diameter of the lanthanum zirconate whiskers is 1000 nm, while the rest is the same as in Example 1;

[0159] The obtained silica aerogel insulation material has a thermal conductivity of 0.029 W / (m·K) at room temperature, 0.041 W / (m·K) at 1100℃, and 0.046 W / (m·K) at 1200℃.

[0160] This indicates that a larger whisker diameter significantly increases the thermal conductivity of the material.

[0161] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. Various process solutions that are not substantially different from the concept of the present invention are all within the scope of protection of the present invention.

Claims

1. A method for preparing a whisker-reinforced silica aerogel thermal insulation material, characterized in that: Includes the following steps: 1) Preparation of silica sol: Add alcohol to aqueous silica sol and stir until it is diluted. Then add acid or alkali as a catalyst and stir until it is diluted to obtain silica sol. The alcohols, catalysts, and aqueous silica sols are prepared in a mass ratio of (1.0-4.5):(0.001-0.05):

1. The aqueous silica sol has a solid content of 30-55%. The average particle size of the aqueous silica sol particles is 25-100 nm; When the aqueous silica sol is acidic, an alkaline catalyst is added; when the aqueous silica sol is alkaline, an acidic catalyst is added. The alcohols mentioned are selected from one of ethanol, methanol, isopropanol, n-propanol, n-butanol, isobutanol, sec-butanol, and tert-butanol; The acid catalyst is selected from one of hydrochloric acid, nitric acid, hydrofluoric acid, and acetic acid; The alkaline catalyst is selected from ammonia or urea. 2) Ceramic whisker porous framework molding: Add organic and inorganic binders to deionized water and stir evenly to form a viscous dispersion; Ceramic whiskers are added to the dispersion and stirred until a slurry is formed. The slurry is injected into a mold, then vacuum filtered, and then dried in an oven to obtain a ceramic whisker blank. The ceramic whisker blank is heated to 750-1150℃ in a high-temperature furnace and held for 1-12 hours, then naturally cooled to obtain a porous ceramic whisker framework. The organic adhesive, inorganic adhesive, ceramic whiskers, and deionized water are disposed in a mass ratio of (0.5-3.0):(1.0-5.0):(8-18):

100. The organic adhesive is selected from gelatin or starch; The inorganic adhesive is selected from one of silicon dioxide, zirconium oxide, boric acid, and boron carbide; The ceramic whiskers are selected from one of the following: lanthanum zirconate, zirconium oxide, aluminum oxide, mullite, silicon oxide, silicon carbide, potassium titanate, aluminum borate, magnesium oxide, and silicon nitride whiskers. The ceramic whiskers have an average diameter of 100-800 nm and an aspect ratio of 3000-20000. 3) Silica sol impregnation and gel aging: Silica sol is injected into the porous framework of ceramic whiskers at an injection pressure of -0.1-0 MPa. After full injection, the porous framework / sol composite is placed at a high temperature of 40-120℃ to gel and age for 4-24 hours to obtain the porous framework / gel composite. 4) Supercritical drying: High-temperature supercritical drying or low-temperature supercritical drying is used to remove the liquid from the porous framework / gel composite to obtain a porous framework / aerogel preform. 5) High-temperature sintering: The obtained porous skeleton / aerogel preform is placed in a high-temperature furnace and heated to 750-1100℃ for 1-24 hours, then naturally cooled to obtain a whisker-reinforced silica aerogel insulation material. The whisker-reinforced silica aerogel insulation material has the following properties: ① When the long-term operating temperature reaches 1200℃, after heat treatment in a muffle furnace at 1200℃ for 2 hours and 72 hours, the typical linear shrinkage rates of the material are 0-1.1% and 0.4-2.4%, respectively; when the short-term operating temperature reaches 1300℃, after heat treatment in a muffle furnace at 1300℃ for 2 hours, the typical linear shrinkage rate of the material is 1.5-4.7%. ② The typical thermal conductivity at room temperature is 0.023-0.026 W / (m·K), the typical thermal conductivity at 1100℃ is 0.036-0.043 W / (m·K), and the typical thermal conductivity at 1200℃ is 0.040-0.048 W / (m·K); ③ The typical density of thermal insulation material is 0.28-0.30 g / cm³. 3 The typical compressive strength at 3% deformation is 0.23-0.38 MPa, and the typical compressive strength at 10% deformation is 0.94-1.60 MPa.

2. The method for preparing a whisker-reinforced silica aerogel thermal insulation material according to claim 1, characterized in that: The ceramic whiskers mentioned in step 2) are selected from lanthanum zirconate, zirconium oxide, or mullite.

3. The method for preparing a whisker-reinforced silica aerogel thermal insulation material according to claim 1, characterized in that: In step 4), the high-temperature supercritical drying uses alcohols as the drying medium; the low-temperature supercritical drying uses carbon dioxide as the drying medium.

4. A whisker-reinforced silica aerogel thermal insulation material, characterized in that: The whisker-reinforced silica aerogel thermal insulation material, obtained by any one of claims 1-3, possesses the following properties: ① When the long-term operating temperature reaches 1200℃, after heat treatment in a muffle furnace at 1200℃ for 2 hours and 72 hours, the typical linear shrinkage rates of the material are 0-1.1% and 0.4-2.4%, respectively; when the short-term operating temperature reaches 1300℃, after heat treatment in a muffle furnace at 1300℃ for 2 hours, the typical linear shrinkage rate of the material is 1.5-4.7%. ② The typical thermal conductivity at room temperature is 0.023-0.026 W / (m·K), the typical thermal conductivity at 1100℃ is 0.036-0.043 W / (m·K), and the typical thermal conductivity at 1200℃ is 0.040-0.048 W / (m·K); ③ The typical density of thermal insulation material is 0.28-0.30 g / cm³. 3 The typical compressive strength at 3% deformation is 0.23-0.38 MPa, and the typical compressive strength at 10% deformation is 0.94-1.60 MPa.

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