A method for preparing an alumina aerogel insulation blanket

Abstract

The application discloses a preparation method of an alumina aerogel heat insulation felt, and comprises the following steps: adding an aluminum source precursor into a ketone substance to form a precursor solution through sufficient dissolution; adding an alcohol solvent containing a silicon source precursor, an amine substance and a catalyst into the precursor solution to form an alumina sol through uniform stirring; adding a surfactant into the alumina sol to form an alumina sol containing a light shielding agent through uniform stirring; adding light shielding agent particles into the alumina sol to form the alumina sol containing the light shielding agent; immersing a ceramic fiber felt into the alumina sol containing the light shielding agent to perform gel aging, so as to obtain a fiber felt / gel composite; and performing drying and heat treatment on the fiber felt / gel composite, so as to obtain the alumina aerogel heat insulation felt. The alumina aerogel heat insulation felt prepared by the method has the advantages of high temperature resistance, excellent heat insulation performance and good flexibility.

Description

Technical Field

[0001] This application relates to the field of aerogel composite materials technology, and in particular to a method for preparing an alumina aerogel thermal insulation felt. Background Technology

[0002] In the aerospace field, high-speed aircraft flying at high Mach numbers in the atmosphere generate intense aerodynamic heat on their surfaces, with temperatures reaching over 1500°C. This necessitates the use of lightweight, high-temperature resistant, low-thermal-conductivity insulation materials to prevent heat transfer to the aircraft's interior and ensure the normal operation of electronic components. Typical ceramic fiber insulation felts and tiles cannot meet these requirements. In the metallurgical and cement industries, the internal operating temperature of high-temperature furnaces reaches 1000–1500°C. Currently, refractory bricks and ceramic fibers are used for insulation, but their inadequate insulation effect leads to very high furnace surface temperatures and significant heat dissipation. These fields urgently require new types of insulation materials that are high-temperature resistant, low-thermal-conductivity, flexible, and easy to install.

[0003] Aerogel materials are currently the solid materials with the lowest thermal conductivity. Silica aerogel blankets are already used in fields such as petrochemical pipelines, exhibiting excellent thermal insulation and coverage properties, and are relatively easy to install; however, their operating temperature generally does not exceed 800℃. Compared to silica aerogels, alumina aerogels possess characteristics such as high temperature resistance, excellent thermal insulation performance, and low density, making them promising candidates for high-temperature insulation materials. Alumina aerogel blankets can replace silica aerogel blankets for use at higher temperatures. The conventional preparation method for alumina aerogels involves adding an aluminum precursor to a mixture of ethanol and water to form a hydrolysate of the aluminum precursor, followed by the addition of a chelating agent to chelate the highly reactive aluminum precursor, and then performing subsequent gel aging and other processes. However, the hydrolysate of the aluminum precursor is highly reactive and readily reacts with moisture in the air to form solids, resulting in uneven sol formation. While adding a chelating agent can reduce the hydrolysis rate, it also reduces the integrity of the alumina aerogel network structure, negatively impacting the aerogel's bulking and thermal insulation performance. Meanwhile, current alumina aerogel felts suffer from insufficient temperature resistance, high thermal conductivity, complex preparation processes, and long preparation cycles, which require further improvement. Summary of the Invention

[0004] This invention provides a method for preparing alumina aerogel insulation felt, which is used to quickly and stably prepare a high-temperature resistant alumina aerogel insulation felt.

[0005] To achieve the above objectives, this invention proposes a method for preparing alumina aerogel insulation felt, comprising the following steps:

[0006] S1. The aluminum source precursor is added to a ketone substance to fully dissolve and form a precursor solution. An alcohol solvent containing a silicon source precursor, an amine substance, and a catalyst is added to the precursor solution and stirred evenly to form an alumina sol.

[0007] S2. Add the surfactant to the alumina sol and stir until homogeneous. Then add the opaque agent particles to the alumina sol and stir until homogeneous to form an alumina sol containing the opaque agent.

[0008] S3. The ceramic fiber felt is immersed in alumina sol containing a light-blocking agent for gel aging to obtain a fiber felt / gel composite.

[0009] S4. The fiber felt / gel composite is dried and heat-treated to obtain alumina aerogel insulation felt.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0011] 1. The aluminum source precursor is directly dissolved in a solvent containing ketones, and then added to an alcohol solvent containing amines and a catalyst to form an alumina sol. The ketones and amines react to produce water under catalytic conditions, avoiding the problem of excessively rapid reaction rates caused by directly adding water to the sol. This effectively controls the hydrolysis and condensation reaction rates of the highly active aluminum source precursor, thereby precisely controlling the gelation time of the alumina sol. This facilitates thorough impregnation of the alumina sol with the fiber mat, resulting in alumina aerogel with a good network structure and strength, and a stable alumina aerogel insulation mat.

[0012] 2. Using highly flexible ceramic fiber felt as a reinforcing phase and as a high-temperature resistant fiber skeleton, the ability of alumina aerogel to resist sintering at high temperatures is further improved, so that the heat insulation felt has very small dimensional shrinkage at high temperatures, while giving the aerogel heat insulation felt good formability and flexibility.

[0013] 3. Introducing a high-temperature resistant light-blocking agent into alumina aerogel insulation felt significantly improves the insulation felt's ability to block infrared radiation and reduces its high-temperature thermal conductivity. The light-blocking agent is dispersed in the alumina sol through a simple sol-gel mixing and stirring process, and then the sol containing the light-blocking agent is impregnated into the pores of the fiber felt using an atmospheric pressure impregnation method, thus ensuring the light-blocking agent is evenly distributed throughout the insulation felt. This method effectively achieves uniform introduction of the light-blocking agent into the fiber felt.

[0014] 4. This method utilizes readily available raw materials, employs a simple process, and has a short cycle time. The prepared alumina aerogel insulation felt can withstand high temperatures of 1500℃, while also exhibiting very low high-temperature thermal conductivity and good flexibility. Its density is less than 0.2 g / cm³. 3The thickness shrinkage rate after treatment at 1500℃ for 2 hours can be as low as 0.3%. The thermal conductivity at room temperature and at 1400℃ is as low as 0.034 and 0.13 W / (m·K), respectively. The compressive strength at 25% deformation reaches over 0.5 MPa, the tensile strength reaches over 0.3 MPa, and the compression rebound rate is higher than 90%. The molding size can reach 40m in length, 1500mm in width, and 30mm in thickness, allowing for rapid cutting and quick wrapping and installation. A 20mm thick alumina aerogel insulation felt, after being heated to 1500℃ on one side for 1800s, has a cold surface temperature below 400℃. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0016] Figure 1 This is a photograph of the alumina aerogel insulation felt from Example 1.

[0017] Figure 2 The graph shows the thermal conductivity of the alumina aerogel insulation felt in Example 1.

[0018] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0021] Unless otherwise specified, all medicines / reagents used are commercially available.

[0022] This invention provides a method for preparing alumina aerogel insulation felt, comprising the following steps:

[0023] S1. The aluminum source precursor is added to a ketone substance to fully dissolve and form a precursor solution. An alcohol solvent containing a silicon source precursor, an amine substance, and a catalyst is added to the precursor solution and stirred evenly to form an alumina sol.

[0024] S2. Add the surfactant to the alumina sol and stir until homogeneous. Then add the opaque agent particles to the alumina sol and stir until homogeneous to form an alumina sol containing the opaque agent.

[0025] S3. The ceramic fiber felt is immersed in alumina sol containing a light-blocking agent for gel aging to obtain a fiber felt / gel composite.

[0026] S4. The fiber felt / gel composite is dried and heat-treated to obtain alumina aerogel insulation felt.

[0027] Preferably, in step S1, the aluminum source precursor is any one of aluminum sec-butoxide, aluminum isopropoxide, aluminum n-butoxide, and aluminum tert-butoxide.

[0028] Ketones are any one of acetone, propylene glycol, butanone, butanone, pentanone, isopentaneone, and pentanone.

[0029] The silicon source precursor is any one of tetraethyl orthosilicate, methyltriethoxysilane, ethyltriethoxysilane, dimethyldiethoxysilane, diethyldiethoxysilane, trimethylethoxysilane, triethylethoxysilane, methyl orthosilicate, methyltrimethoxysilane, ethyltrimethoxysilane, dimethyldimethoxysilane, diethyldimethoxysilane, trimethylmethoxysilane, and triethylmethoxysilane;

[0030] The amines are any one of aniline, p-phenylenediamine, m-phenylenediamine, and o-phenylenediamine;

[0031] The catalyst is any one of nitric acid, hydrochloric acid, acetic acid, sulfuric acid, hydrofluoric acid, and phosphoric acid;

[0032] The alcohol solvent is any one of ethanol, isopropanol, n-propanol, n-butanol, sec-butanol, and tert-butanol.

[0033] Preferably, in step S1, the molar ratio of ketones to aluminum source precursors is 1.2 to 3:1. When the ratio is less than 1.2:1, the hydrolysis-condensation reaction is incomplete, resulting in poor bulking and pore structure of the alumina aerogel, leading to a decrease in the mechanical properties and temperature resistance of the insulation felt. When the ratio is greater than 3:1, the density and structural strength of the alumina aerogel are low, resulting in high thermal conductivity and easy powder shedding of the aerogel insulation felt.

[0034] Preferably, in step S1, the molar ratio of silicon source precursor to aluminum source precursor is 0.1 to 0.5:1. When the ratio is lower than 0.1:1 or higher than 0.5:1, the resulting alumina aerogel is prone to sintering and shrinkage at high temperatures, resulting in a significant decrease in temperature resistance.

[0035] Preferably, in step S1, the molar ratio of amine to aluminum source precursor is 1–2.5:1. When the ratio is less than 1:1, the hydrolysis-condensation reaction is incomplete, resulting in poor bulking and pore structure of the alumina aerogel, leading to a decrease in the mechanical properties and temperature resistance of the insulation felt. When the ratio is greater than 2.5:1, the density and structural strength of the alumina aerogel are low, resulting in a high thermal conductivity and easy powder shedding of the aerogel insulation felt.

[0036] Preferably, in step S1, the molar ratio of the alcohol solvent to the aluminum source precursor is 8–30:1. When the ratio is less than 8:1, the alumina sol solid content and alumina aerogel density are high, resulting in insufficient flexibility of the obtained alumina aerogel insulation felt; when the ratio is greater than 30:1, the alumina aerogel density and strength are low, resulting in low alumina aerogel content in the obtained alumina aerogel insulation felt, high thermal conductivity, and easy powder shedding.

[0037] Preferably, in step S1, the molar ratio of the catalyst to the aluminum source precursor is 0.01 to 0.3:1. When the ratio is less than 0.01:1, the alumina sol is difficult to form a gel; when the ratio is greater than 0.3:1, the gelation time of the alumina sol is shortened, and the viscosity increases in a very short time, resulting in poor impregnation of the sol with the fiber.

[0038] Preferably, in step S1, the molar ratio of ketones to amines is 1.0 to 1.3:1 to ensure that the reaction is complete and the excess amount of reactants is well controlled.

[0039] Preferably, in step S2, the light-shielding agent particles are any one of silicon carbide, zirconium oxide, titanium oxide, boron carbide, and boron nitride.

[0040] The surfactant is any one of alkyl succinic anhydride sodium salt, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, sodium secondary alkyl sulfonate, dodecyl trimethyl ammonium chloride, dodecyl dimethyl benzyl ammonium chloride, didodecyl dimethyl ammonium chloride, dodecyl glucoside, fatty alcohol polyoxyethylene ether glucoside, dodecyl betaine, dodecyl dimethyl ammonium chloride, dodecyl dimethylamine oxide, fatty alcohol polyoxyethylene ether, and dodecylphenol polyoxyethylene ether.

[0041] The mass ratio of surfactant to alumina sol is 0.2 to 3:100, which ensures good dispersion of the opacifier in the sol, while the cost of surfactant raw materials is relatively low.

[0042] A mass ratio of light-blocking agent to sol of 0.5–6:100 ensures optimal infrared radiation blocking without significantly increasing solid-state heat conduction, resulting in the lowest overall thermal conductivity of aerogel insulation felt. The average diameter of the light-blocking agent particles ranges from 0.2 to 5 μm. Within this range, the light-blocking agent exhibits optimal blocking effect on infrared radiation waves corresponding to the temperature range of 500–1500℃, significantly reducing the overall thermal conductivity of the insulation felt within this temperature range.

[0043] Surfactant molecules, composed of hydrophilic and lipophilic ends, can significantly improve the compatibility and uniformity of mixtures of polar and non-polar substances, allowing the opacifier particles to be stably and uniformly suspended in the alumina sol. The surfactant lowers the surface area of ​​the sol, increasing its wettability with the fiber felt and enabling rapid impregnation. After adding an appropriate amount of surfactant to the alumina sol, the opacifier particles are added and stirred until homogeneous. The fiber felt is then immersed in the sol, allowing for full impregnation followed by rapid aging and gelation to obtain a fiber felt / gel composite doped with the opacifier. Through the aforementioned beneficial effect 1, the sol's viscosity increases and gels within a certain time, preventing the opacifier from settling and ensuring uniform distribution within the insulation felt.

[0044] Preferably, step S3 specifically involves: immersing the ceramic fiber felt in an alumina sol containing a light-blocking agent under normal pressure for 0.5–30 minutes until gelation occurs, followed by maintaining the solution at room temperature to 75°C for 0.5–4 hours to obtain the fiber felt / gel composite. The immersion period of 0.5–30 minutes ensures sufficient impregnation with a short impregnation cycle; maintaining the gel at room temperature to 75°C for 0.5–4 hours after gelation achieves complete gelation with a short aging cycle. The ceramic fiber felt can be either alumina fiber felt or mullite fiber felt.

[0045] It can be seen that the gel aging time of this solution is very short, which ensures the production efficiency of the heat insulation felt. The entire sol preparation process is much simpler and more controllable compared with conventional methods.

[0046] Preferably, in step S4, the drying process specifically involves placing the fiber felt / gel composite in a supercritical drying vessel and sealing it, using carbon dioxide fluid as the drying medium; the temperature inside the vessel is 40–80°C, the pressure is 12–25 MPa, and the holding time is 6–24 hours. Setting the above temperature, pressure, and holding time ensures that the carbon dioxide fluid fully replaces the liquid in the gel pores and achieves high drying efficiency.

[0047] The heat treatment process is as follows: the dried alumina aerogel insulation felt blank is placed in a high-temperature furnace and heat-treated at 500–1000℃ for 4–16 hours. After supercritical drying, the alumina aerogel insulation felt is heat-treated at 500–1000℃ to remove the hydroxyl groups from the alumina aerogel matrix, ensuring that the chemical composition of the insulation felt is entirely composed of high-temperature resistant inorganic components (mainly alumina and silicon dioxide), guaranteeing the stability and complete non-combustibility of the aerogel insulation felt at high temperatures. If the heat treatment temperature is below 500℃ and the time is less than 4 hours, impurities cannot be completely removed, leading to a decrease in the thermal stability and a higher thermal conductivity of the insulation felt. If the heat treatment temperature is too high or the time is too long, it will increase the design difficulty of the high-temperature furnace and prolong the heat treatment cycle.

[0048] In summary, this invention utilizes an organoaluminum source precursor to prepare alumina sol, and high-temperature resistant ceramic fiber felt as the reinforcing phase. Alumina aerogel insulation felt is prepared through a simple process of sol-fiber impregnation, rapid gel aging, supercritical carbon dioxide drying, and heat treatment. The alumina aerogel insulation felt prepared using this invention exhibits characteristics such as high-temperature resistance up to 1500℃, excellent thermal insulation performance, good flexibility, and easy installation, showing broad application prospects in fields such as thermal protection for high-speed aircraft and thermal insulation for civilian high-temperature furnaces.

[0049] Example 1:

[0050] The first step is the preparation of alumina sol.

[0051] Aluminum sec-butoxide was dissolved in methyl ethyl ketone (MEK) to form a precursor solution. Isopropanol containing methyltriethoxysilane, o-phenylenediamine, and nitric acid was then added to the precursor solution and stirred until homogeneous to form an alumina sol. The stirring time was 15 min. The molar ratio of aluminum sec-butoxide, MEK, methyltriethoxysilane, o-phenylenediamine, nitric acid, and isopropanol was 1:2:0.33:1.8:0.08:11.

[0052] The second step is to add a light-blocking agent.

[0053] Dodecylphenol polyoxyethylene ether was added to the alumina sol and stirred until homogeneous. Then, zirconium oxide particles with an average diameter of 1 μm were added to the sol and stirred until homogeneous to form a sol containing zirconium oxide particles. The mass ratio of dodecylphenol polyoxyethylene ether to sol was 1:100, and the mass ratio of zirconium oxide particles to sol was 2:100.

[0054] The third step is sol impregnation and gel aging.

[0055] Under normal pressure, a 20 mm thick alumina fiber felt was immersed in alumina sol with added zirconium oxide particles. After 20 min, gelation occurred, and then the fiber felt / gel composite was obtained by maintaining it at 60 °C for 2 h.

[0056] The fourth step is supercritical drying.

[0057] The fiber felt / gel composite was placed in a supercritical drying autoclave and sealed, using carbon dioxide fluid as the drying medium. The temperature inside the autoclave was 60℃ and the pressure was 16MPa. After maintaining this temperature for 10 hours, the carbon dioxide fluid was discharged at a rate of 6MPa / h to obtain an alumina aerogel insulation felt blank.

[0058] Step 5: Heat treatment.

[0059] The dried alumina aerogel insulation felt blank is placed in a high-temperature furnace and heat-treated at 800℃ for 10 hours to remove impurities from the insulation felt, thus obtaining the final alumina aerogel insulation felt.

[0060] The alumina aerogel insulation felt prepared in Example 1 has excellent temperature resistance, very low high-temperature thermal conductivity and good flexibility. Figure 1 The image shown is of the alumina aerogel insulation felt from Example 1. It has good formability and flexibility, and can be bent at 90° without damage.

[0061] The alumina aerogel insulation felt prepared in Example 1 has a density of 0.18 g / cm³. 3 The thickness shrinkage rate after treatment at 1500℃ for 2 hours was 0.3%, the compressive strength at 25% deformation reached 0.54MPa, the tensile strength reached 0.38MPa, and the compression rebound rate was 93%. The alumina aerogel insulation felt (20mm thick) of Example 1, after being heated on one side at 1500℃ for 1800s, had a cold surface temperature of 365℃.

[0062] Figure 2 The graph shows the thermal conductivity of the alumina aerogel insulation felt in Example 1 within the range of room temperature to 1400°C. Its thermal conductivity at room temperature is 0.034 W / (m·K). The thermal conductivity increases relatively slowly with increasing temperature, and the thermal conductivity at 1400°C is only 0.13 W / (m·K), which shows a very low thermal conductivity.

[0063] Example 2:

[0064] The first step is the preparation of alumina sol.

[0065] Aluminum sec-butoxide was dissolved in dimethyl ethyl ketone to form a precursor solution. Then, sec-butanol containing methyltrimethoxysilane, p-phenylenediamine, and hydrochloric acid was added to the precursor solution and stirred until homogeneous to form an alumina sol. The stirring time was 10 min. The molar ratio of aluminum sec-butoxide, dimethyl ethyl ketone, methyltrimethoxysilane, p-phenylenediamine, hydrochloric acid (HCl), and sec-butanol was 1:1.6:0.33:1.4:0.05:12.

[0066] The second step is to add a light-blocking agent.

[0067] Sodium dodecylbenzenesulfonate was added to the alumina sol and stirred until homogeneous. Then, titanium dioxide particles with an average diameter of 0.8 μm were added to the sol and stirred until homogeneous to form a sol containing titanium dioxide particles. The mass ratio of sodium dodecylbenzenesulfonate to sol was 1.5:100, and the mass ratio of titanium dioxide particles to sol was 3:100.

[0068] The third step is sol impregnation and gel aging.

[0069] Under normal pressure, a 15 mm thick mullite fiber felt was immersed in an alumina sol with added titanium dioxide particles. After 25 min, gelation occurred, and then the mixture was kept at 55 °C for 3 h to obtain a fiber felt / gel composite.

[0070] The fourth step is supercritical drying.

[0071] The fiber felt / gel composite was placed in a supercritical drying autoclave and sealed, using carbon dioxide fluid as the drying medium. The temperature inside the autoclave was 65℃ and the pressure was 14MPa. After maintaining this temperature for 12 hours, the carbon dioxide fluid was discharged at a rate of 5MPa / h to obtain an alumina aerogel insulation felt blank.

[0072] Step 5: Heat treatment.

[0073] The dried alumina aerogel insulation felt blank was placed in a high-temperature furnace and heat-treated at 700℃ for 12 hours to remove impurities, yielding the final alumina aerogel insulation felt. The alumina aerogel insulation felt prepared in Example 2 had a density of 0.17 g / cm³. 3 The thickness shrinkage rate after treatment at 1500℃ for 2 hours was 0.9%, the thermal conductivity at room temperature and at 1400℃ was 0.035 and 0.138 W / (m·K), respectively, the compressive strength at 25% deformation reached 0.49 MPa, the tensile strength reached 0.33 MPa, and the compression rebound rate was 95%. The alumina aerogel insulation felt (20 mm thick) in Example 1, after being heated to 1500℃ on one side for 1800 s, had a cold surface temperature of 395℃.

[0074] Example 3:

[0075] The first step is the preparation of alumina sol.

[0076] Aluminum isopropoxide was dissolved in acetone to form a precursor solution. Then, n-propanol containing tetraethyl orthosilicate, aniline, and nitric acid was added to the precursor solution and stirred until homogeneous to form an alumina sol. The stirring time was 30 min. The molar ratio of aluminum isopropoxide, acetone, tetraethyl orthosilicate, aniline, nitric acid, and n-propanol was 1:2.5:0.3:2.2:0.1:10.

[0077] The second step is to add a light-blocking agent.

[0078] Fatty alcohol polyoxyethylene ether was added to the alumina sol and stirred until homogeneous. Then, silicon carbide particles with an average diameter of 1 μm were added to the sol and stirred until homogeneous to form a sol containing silicon carbide particles. The mass ratio of fatty alcohol polyoxyethylene ether to sol was 1.2:100, and the mass ratio of silicon carbide particles to sol was 3:100.

[0079] The third step is sol impregnation and gel aging.

[0080] Under normal pressure, a 30 mm thick alumina fiber felt was immersed in alumina sol with added silicon carbide particles. After 10 min, gelation occurred, and then the mixture was kept at 70 °C for 1 h to obtain a fiber felt / gel composite.

[0081] The fourth step is supercritical drying.

[0082] The fiber felt / gel composite was placed in a supercritical drying autoclave and sealed, using carbon dioxide fluid as the drying medium. The temperature inside the autoclave was 70℃ and the pressure was 18MPa. After maintaining this temperature for 6 hours, the carbon dioxide fluid was discharged at a rate of 6MPa / h to obtain an alumina aerogel insulation felt blank.

[0083] Step 5: Heat treatment.

[0084] The dried alumina aerogel insulation felt blank was placed in a high-temperature furnace and heat-treated at 800℃ for 12 hours to remove impurities from the insulation felt, thus obtaining the final alumina aerogel insulation felt.

[0085] The alumina aerogel insulation felt prepared in Example 2 has a density of 0.17 g / cm³. 3 The thickness shrinkage rate after treatment at 1500℃ for 2 hours was 0.7%, the thermal conductivity at room temperature and at 1400℃ was 0.036 and 0.136 W / (m·K), respectively, the compressive strength at 25% deformation reached 0.58 MPa, the tensile strength reached 0.34 MPa, and the compression rebound rate was 92%. The alumina aerogel insulation felt (20 mm thick) in Example 3, after being heated to 1500℃ on one side for 1800 s, had a cold surface temperature of 386℃.

[0086] Comparative Example 1:

[0087] The difference between Comparative Example 1 and Example 1 is that the molar ratio of aluminum sec-butoxide to methyl ethyl ketone in the first step is 1:1. The density of the alumina aerogel insulation felt in Comparative Example 1 is 0.19 g / cm³. 3The thickness shrinkage rate after treatment at 1500℃ for 2 hours is 2.2%, the thermal conductivity at room temperature and at 1400℃ is 0.042 and 0.152 W / (m·K) respectively, the compressive strength at 25% deformation is 0.28 MPa, and the tensile strength is 0.15 MPa.

[0088] It can be seen that when the molar ratio of ketones to aluminum source precursors is less than 1.2:1, the mechanical properties and temperature resistance of the thermal insulation felt decrease.

[0089] Comparative Example 2:

[0090] The difference between Comparative Example 2 and Example 1 is that the molar ratio of aluminum sec-butoxide to o-phenylenediamine in the first step is 1:0.8. The density of the alumina aerogel insulation felt in Comparative Example 2 is 0.20 g / cm³. 3 The thickness shrinkage rate after treatment at 1500℃ for 2 hours is 2.4%, the thermal conductivity at room temperature and at 1400℃ is 0.041 and 0.150 W / (m·K) respectively, the compressive strength at 25% deformation is 0.29 MPa, and the tensile strength is 0.16 MPa.

[0091] It can be seen that when the molar ratio of amines to aluminum source precursors is less than 1:1, the mechanical properties and temperature resistance of the thermal insulation felt decrease.

[0092] Comparative Example 3:

[0093] The difference between Comparative Example 3 and Example 1 is that the molar ratio of aluminum sec-butoxide to nitric acid in the first step is 1:0.005. The alumina sol in Comparative Example 3 required 10 hours at 70°C to gel. The density of the alumina aerogel insulation felt was 0.18 g / cm³. 3 The thickness shrinkage rate after treatment at 1500℃ for 2 hours is 0.4%, the thermal conductivity at room temperature and at 1400℃ is 0.034 and 0.131 W / (m·K) respectively, the compressive strength at 25% deformation is 0.53 MPa, and the tensile strength is 0.33 MPa.

[0094] It can be seen that when the molar ratio of catalyst to aluminum source precursor is less than 0.01:1, alumina sol is difficult to form gel, the required gelation time is prolonged, the preparation cycle is prolonged, and the production efficiency is reduced.

[0095] Comparative Example 4:

[0096] The difference between Comparative Example 4 and Example 1 is that the mass ratio of zirconium oxide particles to sol in the second step is 10:100. The density of the alumina aerogel insulation felt in Comparative Example 4 is 0.22 g / cm³. 3The thickness shrinkage rate after treatment at 1500℃ for 2 hours is 0.9%, the thermal conductivity at room temperature and at 1400℃ is 0.042 and 0.160 W / (m·K) respectively, the compressive strength at 25% deformation is 0.75 MPa, and the tensile strength is 0.41 MPa.

[0097] It can be seen that when the mass ratio of the opaque agent to the sol exceeds the range of 0.5 to 6:100, the thermal conductivity of the alumina aerogel insulation felt is relatively high.

[0098] Table 1 shows the product performance test results for the examples and comparative examples.

[0099] Table 1. Product performance test results of the examples and comparative examples.

[0100]

[0101] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many 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 protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing an alumina aerogel insulation felt, characterized in that, Includes the following steps: S1. An aluminum precursor is dissolved in a ketone to form a precursor solution. An alcohol solvent containing a silicon precursor, an amine, and a catalyst is added to the precursor solution and stirred until homogeneous to form an alumina sol. The molar ratio of the ketone to the aluminum precursor is 1.2–3:1; the molar ratio of the silicon precursor to the aluminum precursor is 0.1–0.5:1; the molar ratio of the amine to the aluminum precursor is 1–2.5:1; the molar ratio of the catalyst to the aluminum precursor is 0.01–0.3:1; the molar ratio of the alcohol solvent to the aluminum precursor is 8–30:1; and the molar ratio of the ketone to the amine is 1.0–1.3:

1. The amine is any one of aniline, p-phenylenediamine, m-phenylenediamine, and o-phenylenediamine. S2. Add the surfactant to the alumina sol and stir until homogeneous. Then add the opaque agent particles to the alumina sol and stir until homogeneous to form an alumina sol containing the opaque agent. The opaque agent particles are any one of zirconium oxide, silicon carbide, titanium oxide, boron carbide, and boron nitride. The mass ratio of the opaque agent to the alumina sol is 0.5 to 6:

100. S3. Under normal pressure, ceramic fiber felt is immersed in alumina sol containing a light-blocking agent and kept for 0.5 to 30 minutes until gelation occurs. Then, it is kept at room temperature to 75°C for 0.5 to 4 hours to obtain fiber felt / gel composite. S4. The fiber felt / gel composite is dried and heat-treated to obtain alumina aerogel insulation felt. The drying process is as follows: the fiber felt / gel composite is placed in a supercritical drying vessel and sealed, and carbon dioxide fluid is used as the drying medium; the temperature inside the vessel is 40-80℃, the pressure is 12-25MPa, and the holding time is 6-24h. The heat treatment process is as follows: the dried alumina aerogel insulation felt blank is placed in a high-temperature furnace and heat-treated at 500-1000℃ for 4-16 hours.

2. The preparation method according to claim 1, characterized in that, In step S1, the aluminum source precursor is any one of aluminum sec-butoxide, aluminum isopropoxide, aluminum n-butoxide, and aluminum tert-butoxide. The ketones are any one of acetone, butanone, and dimethyl ethyl ketone. The silicon source precursor is any one of tetraethyl orthosilicate, methyltriethoxysilane, ethyltriethoxysilane, dimethyldiethoxysilane, diethyldiethoxysilane, trimethylethoxysilane, triethylethoxysilane, methyl orthosilicate, methyltrimethoxysilane, ethyltrimethoxysilane, dimethyldimethoxysilane, diethyldimethoxysilane, trimethylmethoxysilane, and triethylmethoxysilane. The catalyst is any one of nitric acid, hydrochloric acid, acetic acid, sulfuric acid, and phosphoric acid; The alcohol solvent is any one of ethanol, isopropanol, n-propanol, n-butanol, and sec-butanol.

3. The preparation method according to claim 1, characterized in that, In step S2, the surfactant is any one of alkyl succinic anhydride sodium salt, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, sodium secondary alkyl sulfonate, dodecyl glucoside, fatty alcohol polyoxyethylene ether glucoside, fatty alcohol polyoxyethylene ether, and dodecylphenol polyoxyethylene ether. The mass ratio of surfactant to alumina sol is 0.2–3:100.

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