Lightweight and high-efficiency thermal-insulation elastic aerogel material and preparation method thereof

Abstract

This invention relates to a lightweight, high-efficiency thermally insulating elastic aerogel material and its preparation method. The method comprises: mixing titanium dioxide nanoparticles and an alkaline solution uniformly with water to obtain a mixture; then placing the mixture in a reaction vessel lined with polytetrafluoroethylene (PTFE) and subjecting it to a hydrothermal reaction at 200–300°C to obtain a titanate wet gel; immersing the titanate wet gel in an acidic solution with a pH of 1–5 for 6–72 hours to obtain an acid-treated gel; immersing the acid-treated gel in water for 5–110 hours to obtain a water-washed gel; placing the water-washed gel in an ethanol solution of tetraethyl orthosilicate for solvent replacement for 6–72 hours, repeating this step at least once to obtain a gel block; and subjecting the gel block to supercritical drying and heat treatment sequentially to obtain a lightweight, high-efficiency thermally insulating elastic aerogel material. This invention yields a high-temperature resistant, low-density, highly efficient, and highly elastic titanium dioxide nanowire aerogel material.

Description

Technical Field

[0001] This invention relates to the field of aerogel preparation technology, and in particular to a lightweight, high-efficiency thermal insulation elastic aerogel material and its preparation method. Background Technology

[0002] Nanoporous aerogels (or simply aerogels) are gel materials with a gaseous dispersion medium. They are nanoporous solid materials with a network structure, composed of colloidal particles or polymer molecules, and the pore size is on the nanometer scale. Aerogel materials have broad application potential in thermal, acoustic, optical, microelectronic, and particle detection fields. Currently, the most widespread application of aerogels remains in thermal insulation, as their unique nanostructure can effectively reduce convection, solid-phase conduction, and thermal radiation.

[0003] Traditional aerogel materials are mostly pearl necklace-like structures formed by the stacking of nanoparticles. These aerogels are brittle and require fiber reinforcement for structural strengthening in practical applications. In practical applications, elastic aerogels possess high thermal insulation and elasticity, making them suitable for heat sealing. However, existing elastic aerogel materials are mainly nanofiber aerogels. These are produced by redispersing nanofiber membranes prepared through electrospinning and then freeze-drying. The redispersed fibers have a lower aspect ratio and weaker strength. Therefore, nanofiber aerogels exhibit low density and high elasticity; however, these nanofiber materials often have large pores, are not heat-resistant, and have relatively weak strength, making them prone to heat leakage and insulation failure in practical sealing applications. Therefore, developing elastic aerogel materials with sufficient strength, high temperature resistance, and high thermal insulation efficiency is crucial.

[0004] In summary, it is essential to provide a lightweight, high-efficiency thermal insulation elastic aerogel material and its preparation method. Summary of the Invention

[0005] To address one or more technical problems existing in the prior art, this invention provides a lightweight, high-efficiency thermal insulation elastic aerogel material and its preparation method.

[0006] In a first aspect, this invention provides a method for preparing a lightweight, high-efficiency, heat-insulating elastic aerogel material, the method comprising the following steps:

[0007] (1) Mix titanium dioxide nanopowder and alkaline solution evenly with water to obtain a mixture. Then place the mixture in a reaction vessel lined with polytetrafluoroethylene material and carry out a hydrothermal reaction at 200-300°C to obtain titanate wet gel.

[0008] (2) The titanate wet gel is immersed in an acidic solution with a pH of 1 to 5 for 6 to 72 hours to obtain an acid-immersed gel;

[0009] (3) Soak the acid-treated gel in water for 5 to 110 hours to obtain a water-washed gel;

[0010] (4) The water-washed gel is placed in an ethanol solution of tetraethyl orthosilicate for solvent replacement for 6 to 72 hours. This step is repeated at least once to obtain a gel block.

[0011] (5) The gel block is subjected to supercritical drying and heat treatment in sequence to obtain a lightweight, high-efficiency heat-insulating elastic aerogel material.

[0012] Preferably, the alkaline solution is a potassium hydroxide solution and / or a sodium hydroxide solution; the concentration of the alkaline solution is 8-10 mol / L, preferably 10 mol / L; and / or the hydrothermal reaction time is 24-48 h.

[0013] Preferably, the mass fraction of titanium dioxide nanoparticles contained in the mixture is 0.5-10%, more preferably 1-1.5%; and / or in step (1), the mass ratio of water to alkaline solution is (20-40):100.

[0014] Preferably, when the soaking is performed in step (2), the volume ratio of the titanate wet gel to the acidic solution is 1:(1-10), and the soaking time is 48-72h; and / or when the soaking is performed in step (3), the volume ratio of the acid soaking treatment gel to the water is 1:(5-20), and the soaking time is 48-110h.

[0015] Preferably, the pH of the acidic solution is 2 to 3; and / or the acidic solution is one or more of hydrochloric acid, sulfuric acid solution and nitric acid solution.

[0016] Preferably, the volume fraction of tetraethyl orthosilicate in the ethanol solution is 0.2-10%, more preferably 0.5-1.5%.

[0017] Preferably, the volume ratio of the water-washed gel to the ethanol solution of tetraethyl orthosilicate is 1:(1-10); the solvent replacement time is 48-72 h; and / or step (3) is repeated 1-5 times.

[0018] Preferably, the supercritical drying is supercritical carbon dioxide drying, and more preferably, the temperature of the supercritical drying is 20-60°C and the pressure is 10-16 MPa.

[0019] Preferably, the heat treatment temperature is 600–1000°C, more preferably 600–800°C, and the heat treatment time is 0.5–2 hours; and / or the heat treatment is carried out in an air atmosphere.

[0020] In a second aspect, the present invention provides a lightweight, high-efficiency thermal insulation elastic aerogel material prepared by the preparation method described in the first aspect; preferably, the density of the lightweight, high-efficiency thermal insulation elastic aerogel material is as low as 0.025 g / cm³. 3 The porosity is not less than 98%, the compressive strength is not less than 0.05 MPa, the thermal conductivity is as low as 0.026 W / (m·K), the compression resilience is not less than 99%, and the heat resistance temperature is above 800℃.

[0021] Compared with the prior art, the present invention has at least the following beneficial effects:

[0022] (1) After obtaining the titanate wet gel, the present invention soaks the titanate wet gel in an acidic solution with a pH of 1 to 5 for 6 to 72 hours. The present invention found that this step helps to achieve the elastic, lightweight and efficient heat-insulating elastic aerogel material described in the present invention. This is because the present invention found that soaking in an acidic solution with a pH of 1 to 5 can promote the rearrangement of pores in the gel or the formation of more pores. This helps to form more nanowire structures and optimize the pore structure, increase the specific surface area and porosity of the aerogel, thereby improving the heat insulation performance. Furthermore, the optimization of the pore structure and the soaking in the acidic solution can make the nanowires in the aerogel better connected together to form a more elastic network structure, which can improve the overall elasticity of the aerogel. In addition, soaking the titanate wet gel in the acidic solution with a pH of 1 to 5 can lead to the formation of finer nanostructures, enhance the heat insulation performance and elasticity of the aerogel, and reduce the density of the aerogel.

[0023] (2) In this invention, the water-washed gel is placed in an ethanol solution of tetraethyl orthosilicate for solvent replacement. Compared with solvent replacement directly in ethanol, the ethanol solution of tetraethyl orthosilicate is more compatible with the pore structure and surface properties of the water-washed gel, and therefore can more easily penetrate into the interior of the aerogel, effectively replacing the water and other substances in the wet gel. The ethanol solution of tetraethyl orthosilicate can better maintain the structural integrity of the aerogel and reduce shrinkage during the solvent replacement process. The addition of an appropriate amount of tetraethyl orthosilicate can effectively adjust the surface properties and chemical characteristics of the aerogel, which helps to maintain the thermal insulation performance and elasticity of the aerogel.

[0024] (3) Compared with traditional pearl necklace-shaped aerogel materials, the present invention has better mechanical strength, and its microstructure is composed of intertwined nanowires; the density of the aerogel material prepared by the present invention can be as low as 0.025 g / cm³. 3It has the characteristic of ultra-low density; the gelation process in the preparation method of the aerogel of the present invention is a hydrothermal process, which is different from the traditional RTM pressure injection process. It is not limited by the shape and size of the reinforcement and can prepare aerogel materials of arbitrary shape and thickness.

[0025] (4) The aerogel material obtained from gelation, soaking treatment, solvent replacement to supercritical drying in the preparation process of the present invention has no obvious dimensional shrinkage, and the net size of the product can be formed, avoiding the problem of increased cost and cycle caused by mechanical processing; the method of the present invention does not require a relatively high temperature heat treatment process or a complex step-by-step heat treatment process, and the lightweight and efficient heat-insulating elastic aerogel material can be obtained directly through a relatively low temperature heat treatment step; the lightweight and efficient heat-insulating aerogel material obtained in the present invention is a titanium dioxide aerogel material, which has catalytic and elastic properties and can be used as a functional aerogel material.

[0026] (5) The basic structure of the lightweight and efficient heat-insulating elastic aerogel material prepared by the present invention is a nanowire structure, which has a self-supporting effect and has a higher temperature resistance than the aerogel material prepared by the traditional solution-gel method. The lightweight and efficient heat-insulating elastic aerogel nanowires prepared by the present invention have a finer diameter than the nanofibers prepared by electrospinning or melt spinning, and have better heat insulation performance.

[0027] (6) The lightweight, high-efficiency thermal insulation elastic aerogel material prepared by the method of this invention maintains a low thermal conductivity of 0.026 (W / (m·K)) while also exhibiting excellent high-temperature resistance, enabling long-term thermal insulation applications at 800℃. The lightweight, high-efficiency thermal insulation elastic nanowire aerogel material prepared by the method of this invention has a porosity of over 98%, a pore size of 5–500 nm, a nanowire diameter of 10–50 nm, an aspect ratio of 100–500, and a specific surface area of ​​100–600 m². 2 / g, with a heat resistance temperature of over 800℃; the present invention yields a lightweight and efficient heat-insulating elastic aerogel material (titanium dioxide nanowire aerogel material) that is heat-resistant, low-density, moderately strong, and highly efficient in heat insulation. Attached Figure Description

[0028] Figure 1 This is a flowchart of the preparation process of the present invention.

[0029] Figure 2 This is a SEM image of the lightweight, high-efficiency thermal insulation elastic aerogel material prepared in Example 1 of this invention.

[0030] Figure 3 These are TEM images of the lightweight, high-efficiency thermal insulation elastic aerogel material prepared in Example 1 of this invention at different magnifications.

[0031] Figure 4These are macroscopic optical photographs of the lightweight, high-efficiency heat-insulating elastic aerogel material prepared in Example 1 of the present invention before and after heat treatment; in the figure: (a) is a macroscopic optical photograph before heat treatment in Example 1; (b) is a macroscopic optical photograph after heat treatment at 600℃ for 0.5h in Example 1; (c) is a macroscopic optical photograph of the lightweight, high-efficiency heat-insulating elastic aerogel material prepared in Example 1 after treatment at 800℃ for 2h. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0033] In its first aspect, this invention provides a method for preparing a lightweight, high-efficiency thermally insulating elastic aerogel material, the preparation process of which is shown in the flowchart below. Figure 1 As shown, the method includes the following steps:

[0034] (1) Titanium oxide nanopowder (titanium dioxide nanopowder) and an alkaline solution are mixed evenly with water to obtain a mixture. The mixture is then placed in a reactor with a liner (liner material) of polytetrafluoroethylene (PTFE) and subjected to a hydrothermal reaction at 200–300°C to obtain a titanate wet gel. In this invention, for example, titanium oxide nanopowder and an alkaline solution are mixed in deionized water and then stirred and / or ultrasonically treated to obtain a uniform mixture. This invention does not specifically limit the stirring and ultrasonic treatment, as these are conventional techniques in the field. In this invention, the titanium oxide nanopowder refers to… Titanium dioxide nanoparticles, wherein the particle size of the titanium dioxide nanoparticles is, for example, 10-100 nm, preferably 10-50 nm; in this invention, the hydrothermal reaction time is, for example, 1-72 h, preferably 24-48 h; in some specific embodiments, the mixture is poured into a reaction vessel lined with polytetrafluoroethylene and kept at 200-300°C in an oven for 24-48 h, and after the heat preservation is completed, titanate nanowire wet gel is obtained; the hydrothermal reaction needs to be carried out under completely sealed conditions, and the container material needs to be a polymer material that does not react with the system.

[0035] (2) The titanate wet gel is immersed in an acidic solution with a pH of 1 to 5 (e.g., 1, 2, 3, 4 or 5) for 6 to 72 hours (e.g., 6, 12, 18, 24, 30, 36, 42, 48, 54, 60, 66 or 72 hours) to obtain an acid-treated gel; in this invention, the immersion is carried out such that the surface of the acidic solution completely covers the titanate wet gel;

[0036] (3) Soak the acid-treated gel in water for 5 to 110 hours to obtain a water-washed gel;

[0037] (4) The water-washed gel is placed in an ethanol solution of tetraethyl orthosilicate for solvent replacement for 6 to 72 hours (e.g., 6, 12, 18, 24, 30, 36, 42, 48, 54, 60, 66 or 72 hours), and this step is repeated at least once to obtain a gel block; In this invention, the ethanol solution of tetraethyl orthosilicate is a mixture of tetraethyl orthosilicate and ethanol; In this invention, the soaking in step (2), the soaking in step (3) and the solvent replacement in step (4) can be carried out at room temperature, for example at room temperature of 20 to 35°C.

[0038] (5) The gel block is subjected to supercritical drying and heat treatment in sequence to obtain a lightweight, high-efficiency heat-insulating elastic aerogel material.

[0039] After obtaining the titanate wet gel, this invention involves immersing the titanate wet gel in an acidic solution with a pH of 1-5 for 6-72 hours. This invention has found that this step helps achieve the elastic, lightweight, and highly efficient thermally insulating properties of the lightweight, high-efficiency thermally insulating elastic aerogel material described in this invention. This is because the immersion treatment in an acidic solution with a pH of 1-5 promotes the rearrangement of pores in the gel or the formation of more pores. This helps to form more nanowire structures and optimize the pore structure, increasing the specific surface area and porosity of the aerogel, thereby improving its thermal insulation performance. Furthermore, the optimization of the pore structure and the immersion treatment in the acidic solution allow the nanowires in the aerogel to connect better, forming a more elastic network structure, which can improve the overall elasticity of the aerogel. In addition, immersing the titanate wet gel in this acidic solution with a pH of 1-5 can lead to the formation of finer nanostructures, enhancing the thermal insulation performance and elasticity of the aerogel and reducing its density. In this invention, the water-washed gel is placed in an ethanol solution of tetraethyl orthosilicate for solvent replacement. Compared with direct solvent replacement in ethanol, the ethanol solution of tetraethyl orthosilicate is more compatible with the pore structure and surface properties of the water-washed gel, thus allowing it to penetrate more easily into the interior of the aerogel and effectively replace water and other substances in the wet gel. The ethanol solution of tetraethyl orthosilicate can better maintain the structural integrity of the aerogel and reduce shrinkage during the solvent replacement process. The addition of an appropriate amount of tetraethyl orthosilicate can effectively adjust the surface properties and chemical characteristics of the aerogel, which helps to maintain the thermal insulation performance and elasticity of the aerogel.

[0040] The aerogel material prepared in this invention, from gelation, soaking treatment, solvent replacement to supercritical drying, exhibits no significant dimensional shrinkage, enabling net-size product molding and avoiding the increased costs and time associated with machining. This invention eliminates the need for high-temperature or complex step-by-step heat treatment processes; the lightweight, high-efficiency thermal insulation elastic aerogel material can be directly obtained through relatively low-temperature heat treatment steps. The lightweight, high-efficiency thermal insulation aerogel material prepared in this invention is a titanium dioxide aerogel material, possessing catalytic and elastic properties, and can be used as a functional aerogel material.

[0041] The lightweight, high-efficiency thermal insulation elastic aerogel material prepared by this invention has a basic nanowire structure with self-supporting properties, exhibiting a higher temperature resistance rating than aerogel materials prepared by traditional solution-gel methods. The lightweight, high-efficiency thermal insulation elastic aerogel nanowires prepared by this invention have a finer diameter than nanofibers prepared by electrospinning or melt spinning, resulting in superior thermal insulation performance. The lightweight, high-efficiency thermal insulation elastic aerogel material prepared by this invention maintains a low thermal conductivity of 0.026 (W / (m·K)) while also exhibiting excellent high-temperature resistance, enabling long-term thermal insulation applications at 800℃. The lightweight, high-efficiency thermal insulation elastic nanowire aerogel material prepared by this invention has a porosity of over 98%, a pore size of 5–500 nm, a nanowire diameter of 10–50 nm, an aspect ratio of 100–500, and a specific surface area of ​​100–600 m². 2 / g, with a heat resistance temperature of over 800℃; the present invention yields a lightweight and efficient heat-insulating elastic aerogel material that is heat-resistant, low-density, moderately strong, and highly efficient in heat insulation.

[0042] According to some preferred embodiments, the alkaline solution is a potassium hydroxide solution and / or a sodium hydroxide solution; in this invention, both potassium hydroxide solution and sodium hydroxide solution refer to aqueous solutions, namely, aqueous solutions of potassium hydroxide and sodium hydroxide, respectively; the concentration of the alkaline solution is 8 to 10 mol / L (e.g., 8, 9 or 10 mol / L), preferably 10 mol / L; and / or the hydrothermal reaction time is 24 to 48 h (e.g., 24, 30, 36 or 48 h).

[0043] According to some preferred embodiments, the mass fraction of titanium dioxide nanoparticles contained in the mixture is 0.5% to 10% (e.g., 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5% or 10%), preferably 1% to 1.5% (e.g., 1% or 1.5%); and / or in step (1), the mass ratio of water to the alkaline solution is (20 to 40): 100 (e.g., 20:100, 25:100, 30:100, 35:100 or 40:100).

[0044] In this invention, it is preferred that the mass fraction of titanium dioxide nanoparticles in the mixture is 1 to 1.5%. This is beneficial to ensuring the production of the lightweight, high-efficiency thermal insulation elastic aerogel material with ultra-low density, high thermal insulation and high elasticity. This invention has found that if the mass fraction of titanium dioxide nanoparticles in the mixture is too high, it will reduce the porosity and specific surface area of ​​the aerogel, and will also affect the elasticity and thermal insulation performance of the aerogel material.

[0045] According to some preferred embodiments, when the soaking is performed in step (2), the volume ratio of the titanate wet gel to the acidic solution is 1:(1 to 10) (e.g., 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10), and the soaking time is 48 to 72 hours (e.g., 48, 60 or 72 hours); and / or when the soaking is performed in step (3), the volume ratio of the acid-treated gel to the water is 1:(5 to 20) (e.g., 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19 or 1:20), and the soaking time is 48 to 110 hours (e.g., 48, 60, 72, 84, 96 or 110 hours).

[0046] According to some preferred embodiments, the pH of the acidic solution is 2 to 3 (e.g., 2, 2.5 or 3); and / or the acidic solution is one or more of hydrochloric acid, sulfuric acid solution and nitric acid solution; in this invention, hydrochloric acid, sulfuric acid solution and nitric acid solution all refer to aqueous solutions, that is, aqueous solutions of hydrochloric acid, sulfuric acid and nitric acid respectively.

[0047] Unlike washing or acid washing of titanate wet gels to pH 7, in this invention, it is preferable to use an acidic solution with pH 1 to 5, more preferably pH 2 to 3, for the soaking treatment. This is beneficial to ensure that the lightweight, high-efficiency thermal insulation, high elasticity, and moderate strength of the lightweight, high-efficiency thermal insulation elastic aerogel material is achieved simultaneously. This invention has found that using an excessively acidic solution for soaking treatment is not only detrimental to environmental protection and operation, but may also cause damage to the gel structure to a certain extent, leading to pore deformation, shrinkage, or collapse, thereby affecting the pore structure and performance of the aerogel. On the other hand, if an acidic solution with too weak an acidity is used for soaking treatment, the microstructure of the titanate wet gel cannot be effectively adjusted, resulting in the prepared aerogel lacking the required pore characteristics and surface properties, which will also affect the elasticity and thermal insulation performance of the aerogel material.

[0048] According to some preferred embodiments, the volume fraction of tetraethyl orthosilicate in the ethanol solution of the orthosilicate is 0.2% to 10% (e.g., 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, or 10%), preferably 0.5% to 1.5% (e.g., 0.5%, 1%, or 1.5%).

[0049] In this invention, it is preferred that the volume fraction of tetraethyl orthosilicate in the ethanol solution is 0.5% to 1.5%. This is beneficial for ensuring the preparation of a lightweight, high-efficiency, and highly elastic thermally insulating elastic aerogel material with ultra-low density. This invention has found that if the volume fraction of tetraethyl orthosilicate in the ethanol solution is too high, the pores of the aerogel material will be overfilled, reducing the porosity and specific surface area. Furthermore, using an ethanol solution containing excessive tetraethyl orthosilicate for solvent replacement will result in an irregular or discontinuous pore structure in the aerogel. These factors ultimately lead to a significant reduction in the thermal insulation performance and elasticity of the aerogel material.

[0050] According to some preferred embodiments, the volume ratio of the water-washed gel to the ethanol solution of the tetraethyl orthosilicate is 1:(1 to 10) (e.g., 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10); the solvent replacement time is 48 to 72 hours (e.g., 48, 60 or 72 hours); and / or step (3) is repeated 1 to 5 times (e.g., 1, 2, 3, 4 or 5 times).

[0051] According to some preferred embodiments, the supercritical drying is supercritical carbon dioxide drying. Preferably, the supercritical drying temperature is 20–60°C and the pressure is 10–16 MPa. This invention does not have special requirements for the supercritical drying time; conventional time parameters can be used, such as 18–36 hours.

[0052] According to some preferred embodiments, the heat treatment temperature is 600–1000°C (e.g., 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, or 1000°C), preferably 600–800°C (e.g., 600°C, 650°C, 700°C, 750°C, or 800°C), and the heat treatment time is 0.5–2 hours (e.g., 0.5, 1, 1.5, or 2 hours); and / or the heat treatment is carried out in an air atmosphere.

[0053] In this invention, it is preferred that the heat treatment temperature is 600-800°C. This is beneficial to ensure that the lightweight, high-efficiency thermal insulation elastic aerogel material with ultra-low density, high thermal insulation efficiency, and high elasticity is obtained. This invention has found that if the heat treatment temperature is too high, it will cause the pore structure to collapse, significantly reducing the porosity and specific surface area of ​​the aerogel material. At the same time, it will also significantly reduce the thermal insulation performance of the aerogel material and cause a significant decrease in the elasticity of the aerogel material.

[0054] According to some specific embodiments, the preparation of the lightweight, high-efficiency thermal insulation elastic aerogel material includes the following steps:

[0055] ① Titanium oxide nanoparticles and an alkaline solution are mixed in deionized water and stirred and / or sonicated to obtain a homogeneous mixture; the mass fraction of titanium oxide nanoparticles in the mixture is 0.5%-10%. The mixture is placed in a sealed container and subjected to a hydrothermal reaction at 200-300℃ for 1-72 hours to obtain a semi-solid gel block; specifically, the mixture is poured into a reaction vessel lined with polytetrafluoroethylene and placed in an oven at 200-300℃ for 48 hours. After the heat treatment, titanate nanowire wet gel (titanate wet gel) is obtained. This hydrothermal reaction needs to be carried out under completely sealed conditions, and the container material needs to be a polymer material that does not react with the system.

[0056] ② The above titanate wet gel is immersed in an acidic solution (pH 1-5) for 6-72 hours, and the volume ratio of the titanate wet gel to the acidic solution is 1:(1-10) to obtain an acid-immersed gel.

[0057] ③ Soak the acid-treated gel in water. During soaking, the volume ratio of the acid-treated gel to water is 1:(5-20), and the soaking time is 5-110h to obtain a water-washed gel.

[0058] ④ The water-washed gel is placed in an ethanol solution of tetraethyl orthosilicate for solvent replacement for 6-72 hours, and this step is repeated at least once to obtain a gel block; In this invention, the ethanol solution of tetraethyl orthosilicate is a mixture of tetraethyl orthosilicate and ethanol.

[0059] ⑤ The obtained gel block is subjected to supercritical drying and heat treatment in sequence to obtain a lightweight, high-efficiency heat-insulating elastic nanowire aerogel material (lightweight, high-efficiency heat-insulating elastic aerogel material); the supercritical drying is supercritical carbon dioxide drying, the supercritical drying temperature is 20-60℃, and the pressure is 10-16MPa; the heat treatment is carried out in an air atmosphere, the heat treatment temperature is 600-1000℃, and the heat treatment time is 0.5-2h.

[0060] In a second aspect, the present invention provides a lightweight, high-efficiency thermally insulating elastic aerogel material prepared by the preparation method described in the first aspect of the present invention.

[0061] According to some preferred embodiments, the density of the lightweight, high-efficiency thermal insulation elastic aerogel material is as low as 0.025 g / cm³. 3 The porosity is not less than 98%, the compressive strength is not less than 0.05 MPa, the thermal conductivity is as low as 0.026 W / (m·K), the compression resilience is not less than 99%, and the heat resistance temperature is above 800℃.

[0062] The present invention will be further described below by way of examples, but the scope of protection of the present invention is not limited to these embodiments.

[0063] Example 1

[0064] ① Titanium oxide nanoparticles (particle size 10-50 nm) are mixed in 30 g of water, and then 100 g of sodium hydroxide solution with a concentration of 10 mol / L is added. The mixture is stirred and ultrasonically treated to obtain a homogeneous solution. The mass fraction of titanium oxide nanoparticles in the solution is 1%. The solution is poured into a reaction vessel lined with polytetrafluoroethylene and placed in an oven at 220°C for 48 h. After the heat treatment, sodium titanate wet gel is obtained.

[0065] ② The above-mentioned sodium titanate wet gel was soaked in hydrochloric acid with a pH of 2 for 48 hours, and the volume ratio of the sodium titanate wet gel to the hydrochloric acid was 1:10, to obtain an acid-soaked gel.

[0066] ③ Soak the acid-treated gel in water. The volume ratio of the acid-treated gel to water is 1:20, and the soaking time is 96 hours to obtain a water-washed gel.

[0067] ④ The water-washed gel was placed in an ethanol solution of tetraethyl orthosilicate for solvent replacement for 72 hours. This step was repeated 3 times to obtain a gel block. The ethanol solution of tetraethyl orthosilicate was composed of a mixture of tetraethyl orthosilicate and ethanol, and the volume fraction of tetraethyl orthosilicate in the ethanol solution of tetraethyl orthosilicate was 0.5%. During each solvent replacement, the volume ratio of the water-washed gel to the ethanol solution of tetraethyl orthosilicate was 1:10.

[0068] ⑤ The obtained gel block is subjected to supercritical drying and heat treatment in sequence to obtain a lightweight, high-efficiency heat-insulating elastic nanowire aerogel material (lightweight, high-efficiency heat-insulating elastic aerogel material); the supercritical drying is supercritical carbon dioxide drying, the supercritical drying temperature is 50℃, the pressure is 14MPa, and the time is 24h; the heat treatment is carried out in an air atmosphere, the heat treatment temperature is 600℃, and the heat treatment time is 0.5h.

[0069] The lightweight and efficient thermal insulation elastic aerogel material prepared in this embodiment has good structural strength. When the thermal insulation performance was tested, it was found that the surface of the lightweight and efficient thermal insulation elastic aerogel material did not lose its gloss, change color, or peel off.

[0070] SEM image of the lightweight, high-efficiency thermal insulation elastic aerogel material prepared in this embodiment, as shown below. Figure 2 As shown; TEM images of the lightweight, high-efficiency thermal insulation elastic aerogel material prepared in this embodiment at different magnifications, as shown. Figure 3 As shown, from Figure 3 It can be seen that the nanowire diameter distribution range of the lightweight, high-efficiency thermal insulation elastic aerogel material is 18–50 nm, and the aspect ratio is 100–500; the density of the lightweight, high-efficiency thermal insulation elastic aerogel material prepared in this embodiment is only 0.025 g / cm³. 3 Its thermal conductivity is only 0.026 W / (m·K), and its specific surface area is 160 m². 2With a porosity of 98.5%, a compressive strength of 0.05 MPa at 10% compression, a resilience of 99% at 30% compression, and a heat resistance temperature of 800℃, this is a lightweight, high-efficiency, high-temperature resistant, low-density, highly efficient, and highly elastic thermal insulation elastic aerogel material. The heat resistance temperature is tested by heat-treating the aerogel material obtained in each embodiment at a certain high temperature (in air) for 2 hours. If the linear shrinkage rate of the aerogel material is no greater than 5%, it indicates that the aerogel material can withstand that high temperature. In this embodiment, the lightweight, high-efficiency, thermal insulation elastic aerogel material obtained in this embodiment, after heat-treating at 800℃ (in air) for 2 hours, exhibits a linear shrinkage rate of no more than 5% and a heat resistance temperature of 800℃, enabling long-term thermal insulation applications at 800℃.

[0071] Example 2

[0072] Example 2 is basically the same as Example 1, except that:

[0073] ① Titanium oxide nanoparticles (particle size 10-50 nm) are mixed in 30 g of water, and then 100 g of sodium hydroxide solution with a concentration of 5 mol / L is added. The mixture is stirred and ultrasonically treated to obtain a homogeneous solution. The mass fraction of titanium oxide nanoparticles in the solution is 1%. The solution is poured into a reaction vessel lined with polytetrafluoroethylene and placed in an oven at 220°C for 48 h. After the heat treatment, sodium titanate wet gel is obtained.

[0074] The aerogel material finally prepared by steps ① to ⑤ in this embodiment has relatively weak strength and does not form a complete block. The performance indicators are shown in Table 1.

[0075] Example 3

[0076] Example 3 is basically the same as Example 1, except that:

[0077] ① Titanium oxide nanoparticles (particle size 10-50 nm) were mixed in 30 g of water, and then 100 g of sodium hydroxide solution with a concentration of 12 mol / L was added. The mixture was stirred and ultrasonically treated to obtain a homogeneous solution. The mass fraction of titanium oxide nanoparticles in the solution was 1%. The solution was poured into a reaction vessel lined with polytetrafluoroethylene and placed in an oven at 220°C for 48 h. After the heat treatment, sodium titanate wet gel was obtained.

[0078] In this embodiment, the specific surface area and porosity of the aerogel material prepared by steps ① to ⑤ are reduced, and the resilience of the aerogel material is significantly reduced. The performance test results are shown in Table 1.

[0079] Example 4

[0080] Example 4 is basically the same as Example 1, except that:

[0081] ① Titanium oxide nanoparticles (particle size 10-50 nm) were mixed in 30 g of water, and then 100 g of sodium hydroxide solution with a concentration of 10 mol / L was added. The mixture was stirred and ultrasonically treated to obtain a homogeneous solution. The mass fraction of titanium oxide nanoparticles in the solution was 10%. The solution was poured into a reaction vessel lined with polytetrafluoroethylene and placed in an oven at 220°C for 48 h. After the heat treatment, sodium titanate wet gel was obtained.

[0082] In this embodiment, the mass fraction of titanium dioxide nanoparticles in the mixture is too high. The specific surface area and porosity of the aerogel material finally prepared after steps ① to ⑤ are significantly reduced, the thermal conductivity is significantly increased, the thermal insulation performance is significantly reduced, and it is basically not elastic. The performance test results are shown in Table 1.

[0083] Example 5

[0084] Example 5 is basically the same as Example 1, except that:

[0085] ① Titanium oxide nanoparticles (particle size 10-50 nm) are mixed in 30 g of water, and then 100 g of sodium hydroxide solution with a concentration of 10 mol / L is added. The mixture is stirred and ultrasonically treated to obtain a homogeneous solution. The mass fraction of titanium oxide nanoparticles in the solution is 1%. The solution is poured into a reaction vessel lined with polytetrafluoroethylene and placed in an oven at 180°C for 48 h.

[0086] In this embodiment, the product is in a liquid state during the preparation process and cannot be formed into a block.

[0087] Example 6

[0088] Example 6 is basically the same as Example 1, except that:

[0089] ① Titanium oxide nanoparticles (particle size 10-50 nm) are mixed in 30 g of water, and then 100 g of sodium hydroxide solution with a concentration of 10 mol / L is added. The mixture is stirred and ultrasonically treated to obtain a homogeneous solution. The mass fraction of titanium oxide nanoparticles in the solution is 1%. The solution is poured into a reaction vessel lined with polytetrafluoroethylene and placed in an oven at 220°C for 10 h. After the heat treatment, sodium titanate wet gel is obtained.

[0090] In this embodiment, it is impossible to form a block during the preparation process.

[0091] Example 7

[0092] ① Titanium oxide nanoparticles (particle size 10-50 nm) are mixed in 30 g of water, and then 100 g of sodium hydroxide solution with a concentration of 10 mol / L is added. The mixture is stirred and ultrasonically treated to obtain a homogeneous solution. The mass fraction of titanium oxide nanoparticles in the solution is 1%. The solution is poured into a reaction vessel lined with polytetrafluoroethylene and placed in an oven at 220°C for 48 h. After the heat treatment, sodium titanate wet gel is obtained.

[0093] ② The sodium titanate wet gel is soaked in water at a volume ratio of 1:20 to water for 96 hours to obtain a water-washed gel.

[0094] ③ The water-washed gel was placed in an ethanol solution of tetraethyl orthosilicate for solvent replacement for 72 hours. This step was repeated 3 times to obtain a gel block. The ethanol solution of tetraethyl orthosilicate was composed of a mixture of tetraethyl orthosilicate and ethanol, and the volume fraction of tetraethyl orthosilicate in the ethanol solution of tetraethyl orthosilicate was 0.5%. During each solvent replacement, the volume ratio of the water-washed gel to the ethanol solution of tetraethyl orthosilicate was 1:10.

[0095] ④ The obtained gel block is subjected to supercritical drying and heat treatment in sequence to obtain aerogel material; the supercritical drying is supercritical carbon dioxide drying, the supercritical drying temperature is 50℃, the pressure is 14MPa, and the time is 24h; the heat treatment is carried out in an air atmosphere, the heat treatment temperature is 600℃, and the heat treatment time is 0.5h.

[0096] In this embodiment, the sodium titanate wet gel was not soaked in an acidic solution with a pH of 2. Although the rebound rate of the final aerogel material decreased to only 83% under 30% compression, the elastic properties of the aerogel material were significantly reduced, and the heat resistance temperature dropped to only 500℃. The performance test results are shown in Table 1.

[0097] Example 8

[0098] ① Titanium oxide nanoparticles (particle size 10-50 nm) are mixed in 30 g of water, and then 100 g of sodium hydroxide solution with a concentration of 10 mol / L is added. The mixture is stirred and ultrasonically treated to obtain a homogeneous solution. The mass fraction of titanium oxide nanoparticles in the solution is 1%. The solution is poured into a reaction vessel lined with polytetrafluoroethylene and placed in an oven at 220°C for 48 h. After the heat treatment, sodium titanate wet gel is obtained.

[0099] ② The above-mentioned sodium titanate wet gel was soaked in hydrochloric acid with a pH of 2 for 48 hours, and the volume ratio of the sodium titanate wet gel to the hydrochloric acid was 1:10, to obtain an acid-soaked gel.

[0100] ③ Soak the acid-treated gel in water. The volume ratio of the acid-treated gel to water is 1:20, and the soaking time is 96 hours to obtain a water-washed gel.

[0101] ④ The obtained water-washed gel is subjected to supercritical drying and heat treatment in sequence to obtain an aerogel material; the supercritical drying is supercritical carbon dioxide drying, the supercritical drying temperature is 50℃, the pressure is 14MPa, and the time is 24h; the heat treatment is carried out in an air atmosphere, the heat treatment temperature is 600℃, and the heat treatment time is 0.5h.

[0102] In this embodiment, the aerogel material was prepared without solvent replacement using an ethanol solution of tetraethyl orthosilicate, resulting in a decrease in the specific surface area of ​​the aerogel material to only 23 m². 2 / g, the porosity decreased to only 50%, the thermal insulation performance of the aerogel material decreased significantly, the resilience decreased to only 48%, and it lost its high elasticity. The performance test results are shown in Table 1.

[0103] Example 9

[0104] Example 9 is basically the same as Example 1, except that:

[0105] ⑤ The obtained gel block is subjected to atmospheric pressure drying and heat treatment in sequence to obtain aerogel material; the atmospheric pressure drying temperature is 60℃ and the atmospheric pressure drying time is 24h; the heat treatment is carried out in an air atmosphere, the heat treatment temperature is 600℃ and the heat treatment time is 0.5h.

[0106] The aerogel material prepared in this embodiment has a large shrinkage and high density. Other performance indicators are shown in Table 1.

[0107] Example 10

[0108] Example 10 is basically the same as Example 1, except that:

[0109] ⑤ The obtained gel block is subjected to supercritical drying to obtain an aerogel material; the supercritical drying is supercritical carbon dioxide drying, the temperature of supercritical drying is 50℃, the pressure is 14MPa, and the time is 24h.

[0110] The aerogel material prepared in this embodiment was not subjected to heat treatment, and its performance indicators are shown in Table 1.

[0111] Example 11

[0112] Example 11 is basically the same as Example 1, except that:

[0113] ⑤ The obtained gel block is subjected to supercritical drying and heat treatment in sequence to obtain an aerogel material; the supercritical drying is supercritical carbon dioxide drying, the supercritical drying temperature is 50℃, the pressure is 14MPa, and the time is 24h; the heat treatment is carried out in an air atmosphere, the heat treatment temperature is 1000℃, and the heat treatment time is 0.5h.

[0114] The performance indicators of the aerogel material prepared in this embodiment are shown in Table 1.

[0115] Example 12

[0116] Example 12 is basically the same as Example 1, except that:

[0117] ④ The water-washed gel was placed in ethanol for solvent replacement for 72 hours. This step was repeated 3 times to obtain a gel block. During each solvent replacement, the volume ratio of the water-washed gel to the ethanol was 1:10.

[0118] The performance indicators of the aerogel material finally prepared by steps ① to ⑤ in this embodiment are shown in Table 1.

[0119] Example 13

[0120] Example 13 is basically the same as Example 1, except that:

[0121] ④ The water-washed gel was placed in an ethanol solution of tetraethyl orthosilicate for solvent replacement for 72 hours. This step was repeated 3 times to obtain a gel block. The ethanol solution of tetraethyl orthosilicate was composed of a mixture of tetraethyl orthosilicate and ethanol, and the volume fraction of tetraethyl orthosilicate in the ethanol solution of tetraethyl orthosilicate was 5%. During each solvent replacement, the volume ratio of the water-washed gel to the ethanol solution of tetraethyl orthosilicate was 1:10.

[0122] The performance indicators of the aerogel material finally prepared by steps ① to ⑤ in this embodiment are shown in Table 1.

[0123] Example 14

[0124] Example 14 is basically the same as Example 1, except that:

[0125] ② The above-mentioned sodium titanate wet gel was soaked in hydrochloric acid with a pH of 1 for 48 hours, and the volume ratio of the sodium titanate wet gel to the hydrochloric acid was 1:10, to obtain an acid-soaked gel.

[0126] The performance indicators of the aerogel material finally prepared by steps ① to ⑤ in this embodiment are shown in Table 1.

[0127] Example 15

[0128] Example 15 is basically the same as Example 1, except that:

[0129] ② The above-mentioned sodium titanate wet gel was soaked in hydrochloric acid with a pH of 5 for 48 hours, and the volume ratio of the sodium titanate wet gel to the hydrochloric acid was 1:10, to obtain an acid-soaked gel.

[0130] The performance indicators of the aerogel material finally prepared by steps ① to ⑤ in this embodiment are shown in Table 1.

[0131] Comparative Example 1

[0132] 1.3 g of titanium dioxide nanoparticles, 650 mL of water, and 234 g of sodium hydroxide were placed in a reaction vessel lined with polytetrafluoroethylene. After sonication for 30 min, the mixture was reacted for 6 days under hydrothermal conditions at 220 °C to obtain sodium titanate gel. The product was then repeatedly washed with deionized water until the pH of the solution reached 7. After drying, the product was placed in a tube furnace and calcined at 350 °C for 2 h in air to obtain TiO2 nanosheets.

[0133] The springback rate of the materials prepared in this comparative example is shown in Table 1.

[0134] Comparative Example 2

[0135] ① Take 1.3g of titanium dioxide nanopowder, 650mL of water and 234g of sodium hydroxide and place them in a closed reaction vessel with polytetrafluoroethylene lining. After sonication for 30min, react under hydrothermal conditions at 220℃ for 48h to obtain sodium titanate wet gel. Then wash the sodium titanate wet gel product repeatedly with deionized water until the solution pH value is equal to 7 to obtain water-washed gel.

[0136] ② The water-washed gel was placed in an ethanol solution of tetraethyl orthosilicate for solvent replacement for 72 hours. This step was repeated 3 times to obtain a gel block. The ethanol solution of tetraethyl orthosilicate was a mixture of tetraethyl orthosilicate and ethanol, and the volume fraction of tetraethyl orthosilicate in the ethanol solution of tetraethyl orthosilicate was 0.5%. During each solvent replacement, the volume ratio of the water-washed gel to the ethanol solution of tetraethyl orthosilicate was 1:10.

[0137] ③ The obtained gel block is subjected to supercritical drying and heat treatment in sequence to obtain aerogel material; the supercritical drying is supercritical carbon dioxide drying, the supercritical drying temperature is 50℃, the pressure is 14MPa, and the time is 24h; the heat treatment is carried out in an air atmosphere, the heat treatment temperature is 600℃, and the heat treatment time is 0.5h.

[0138] The resilience of the aerogel materials prepared in this comparative example is shown in Table 1.

[0139]

[0140]

[0141] In Table 1, the symbol “—” indicates that the performance indicator was not tested.

[0142] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0143] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a lightweight, high-efficiency thermal insulation elastic aerogel material, characterized in that, The method includes the following steps: (1) Titanium oxide nanoparticles and alkaline solution are mixed evenly with water to obtain a mixture. Then, the mixture is placed in a reaction vessel lined with polytetrafluoroethylene material and subjected to hydrothermal reaction at 200~300℃ for 24~48h to obtain titanate wet gel. The mass fraction of titanium oxide nanoparticles contained in the mixture is 1~1.5%; the concentration of the alkaline solution is 8~10mol / L. (2) The titanate wet gel is soaked in an acidic solution with a pH of 2 to 3 for 6 to 72 hours to obtain an acid-soaked gel; (3) Soak the acid-treated gel in water for 5-110 hours to obtain a water-washed gel; (4) The water-washed gel is placed in an ethanol solution of tetraethyl orthosilicate for solvent replacement for 6-72 hours, and this step is repeated at least once to obtain a gel block; the volume fraction of tetraethyl orthosilicate in the ethanol solution of tetraethyl orthosilicate is 0.5-1.5%; (5) The gel block is subjected to supercritical drying and heat treatment in sequence to obtain a lightweight, high-efficiency heat-insulating elastic aerogel material; the heat treatment temperature is 600~800℃ and the heat treatment time is 0.5~2h.

2. The preparation method according to claim 1, characterized in that: The alkaline solution is a potassium hydroxide solution and / or a sodium hydroxide solution; The concentration of the alkaline solution is 10 mol / L.

3. The preparation method according to claim 1, characterized in that: In step (1), the mass ratio of the water to the alkaline solution is (20~40):

100.

4. The preparation method according to claim 1, characterized in that: In step (2), the volume ratio of the titanate wet gel to the acidic solution is 1:(1~10), and the soaking time is 48~72h; and / or When the soaking is performed in step (3), the volume ratio of the acid soaking treatment gel to the water is 1:(5~20), and the soaking time is 48~110h.

5. The preparation method according to claim 1, characterized in that: The acidic solution is one or more of hydrochloric acid, sulfuric acid, and nitric acid.

6. The preparation method according to claim 1, characterized in that: The volume ratio of the water-washed gel to the ethanol solution of tetraethyl orthosilicate is 1:(1~10). The solvent replacement time is 48-72 hours; and / or Repeat step (3) 1 to 5 times.

7. The preparation method according to claim 1, characterized in that: The supercritical drying is supercritical carbon dioxide drying.

8. The preparation method according to claim 7, characterized in that: The temperature of the supercritical drying is 20~60℃ and the pressure is 10~16MPa.

9. The preparation method according to claim 1, characterized in that: The heat treatment is carried out in an air atmosphere.

10. A lightweight, high-efficiency thermally insulating elastic aerogel material prepared by any one of claims 1 to 9.

11. The lightweight, high-efficiency thermal insulation elastic aerogel material according to claim 10, characterized in that: The density of the light-weight high-efficiency thermal insulation elastic aerogel material is as low as 0.025 g / cm 3 The porosity is not less than 98%, the compressive strength is not less than 0.05 MPa, the thermal conductivity is as low as 0.026 W / (m*K), the compression resilience is not less than 99%, and the heat resistance temperature is above 800 DEG C.

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