Preparation method of mixed silicon source silicon dioxide aerogel

Abstract

The invention discloses a preparation method of mixed silicon source silicon dioxide aerogel, which comprises the following steps: uniformly mixing two silicon sources, ethanol and water according to a molar ratio of (0.1-0.9): (0.1-0.9): (5-10): (2-5), adding acid, magnetically stirring at room temperature for 3-60 minutes to obtain a mixed solution, and standing at room temperature for hydrolytic polycondensation; the solution and fiber base material composite sol are subjected to standing for 12-50 h, hydrolytic condensation polymerization is performed, gel is obtained, and a fiber wet gel product is formed; sealing and aging the wet gel product; adding ethanol and a hydrophobic modifier into the wet gel aging product, and carrying out liquid aging modification; and drying the aged and modified product to obtain a silicon oxide aerogel product. The prepared silicon-source-mixed silicon oxide aerogel is good in strength, low in compression ratio, low in heat conductivity and good in heat insulation performance, the product performance is guaranteed while the cost is saved, and cost reduction and efficiency improvement are achieved in the fields of construction and building materials, petrochemical engineering, new energy batteries, military industry, aerospace and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of aerogels, and in particular to a method for preparing mixed silicon source silica aerogels. Background Art

[0002] As a nanoporous material, silica aerogel, with its unique three-dimensional network nanostructure, demonstrates enormous application potential in numerous fields. This material possesses extremely low density, high porosity, and astonishingly low thermal conductivity, making it an excellent thermal insulation material. For example, silica aerogel can be made into highly efficient insulation panels and coatings, effectively reducing energy consumption and improving energy efficiency in buildings. It can also be used for thermal insulation of pipes and equipment, reducing heat loss and ensuring production safety.

[0003] However, the selection and utilization of silicon sources in the preparation of silica aerogels has been a key factor restricting their development. Currently, a wide variety of silicon sources can be used to prepare silica aerogels, encompassing both organic and inorganic silicon sources. These silicon sources vary significantly in chemical structure, reactivity, cost, and the resulting aerogel properties.

[0004] The use of a single silicon source in the preparation of silica aerogels presents numerous limitations. From a cost perspective, some high-performance single silicon sources are very expensive due to the complex synthesis process and high purity requirements of their raw materials. This makes the cost of preparing silica aerogels from a single silicon source high, severely limiting its application in large-scale industrial production.

[0005] From a performance perspective, a single silicon source can hardly meet diverse application requirements. Aerogels prepared from a single silicon source often excel in one aspect but fall short in others. For example, while aerogels prepared from some silicon sources have excellent thermal insulation properties, they have poor mechanical properties and are easily broken when subjected to external forces, limiting their application in applications requiring high material strength. Meanwhile, aerogels prepared from other silicon sources have good mechanical properties but suboptimal thermal insulation properties. Summary of the Invention

[0006] In view of the above-mentioned deficiencies in the prior art, the present invention provides a method for preparing a mixed silicon source silica aerogel, the purpose of which is to solve the problems of high price and single performance of a single silicon source.

[0007] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0008] A method for preparing a mixed silicon source silica aerogel comprises the following steps:

[0009] S1: Mix two silicon sources, ethanol, and water in a molar ratio of 0.1-0.9:0.1-0.9:5-10:2-5, add acid, and magnetically stir at room temperature for 3-60 minutes to obtain a mixed solution, which is then allowed to stand at room temperature for hydrolysis and polycondensation;

[0010] S2: The solution obtained in step S1 is mixed with the fiber substrate sol, and the mixture is allowed to stand for 12 hours to 50 hours for hydrolysis and polycondensation to form a fiber wet gel product;

[0011] S3: sealing and aging the wet gel product obtained in step S2;

[0012] S4: placing the wet gel aging product from step S3 into ethanol and a hydrophobic modifier for liquid aging modification;

[0013] S5: Drying the product aged and modified in step S4 to obtain a silica aerogel product.

[0014] Preferably, the silicon source in step S1 is tetraethyl orthosilicate 40 or tetraethyl orthosilicate 28, the acid is one of hydrochloric acid, nitric acid or oxalic acid, and the molar ratio of the acid to the silicon source is 1:0.01.

[0015] Furthermore, the fiber substrate described in step S2 is a pre-oxidized silk fiber substrate, a glass fiber substrate, a polyester fiber substrate or a ceramic fiber substrate.

[0016] Preferably, the wet gel aging temperature in step S3 is 40° C. to 60° C., and the aging time is 1 day to 3 days.

[0017] Preferably, the hydrophobic modifier in step S4 is a silane coupling agent, a siloxane compound or a silazane compound.

[0018] Preferably, the drying in step S5 is carbon dioxide supercritical drying, ethanol supercritical drying or atmospheric pressure drying.

[0019] The beneficial effects of the present invention are:

[0020] The present invention discloses a method for preparing a mixed silicon source silica aerogel, wherein the prepared silica aerogel has extremely low thermal conductivity, which is due to the unique combination of the mixed silicon source and the precise control of the hydrolysis and condensation reaction during the preparation process. The synergistic effect of different silicon sources enables the formation of a rich and complex three-dimensional network structure inside the aerogel, effectively limiting the thermal motion of gas molecules, thereby greatly reducing the efficiency of heat conduction. In the construction field, the use of the aerogel as a thermal insulation material can significantly reduce the energy consumption of buildings and reduce dependence on equipment such as air conditioners and heaters, which is in line with the national policy orientation of energy conservation and emission reduction and helps promote the development of green buildings. In industrial fields, such as petrochemicals, metallurgy and other industries, its application in thermal insulation of pipelines and equipment can effectively reduce heat loss, improve energy utilization efficiency and reduce production costs.

[0021] The silica aerogel produced by the present invention's method for preparing mixed silicon-source silica aerogel exhibits high strength and good toughness. The introduction of a fiber substrate further enhances the aerogel's mechanical properties. Different types of fiber substrates can be selected based on specific application scenarios to meet varying mechanical performance requirements. When subjected to external forces, the aerogel maintains its structural integrity and is less susceptible to rupture or collapse, ensuring its reliability and stability during long-term use.

[0022] The silica aerogel prepared by the present invention has a wide temperature resistance range and can maintain a stable structure and performance in a high-temperature environment. The difference in thermal stability of different silicon sources enables the aerogel to exert a good thermal insulation effect in different temperature ranges. In high-temperature industrial production, such as ceramic firing and glass melting, aerogel can be used as an efficient thermal insulation material to prevent heat from being transferred to the surrounding environment while protecting the safety of equipment and operators. In the low-temperature field, such as cold storage, liquid nitrogen storage and other scenarios, aerogel can also effectively prevent the introduction of external heat and maintain the stability of the low-temperature environment.

[0023] The present invention utilizes a mixed silicon source for preparation. Compared to a single silicon source, the use of a mixed silicon source allows for flexible adjustment of the ratio of the two silicon sources based on market price fluctuations, thereby reducing raw material procurement costs. Furthermore, the choice of acid also offers diversity, as the price and availability of different acids vary. The most cost-effective acid can be selected for the reaction based on actual conditions, further reducing production costs. Furthermore, the availability of a variety of fiber substrates allows for optimal matching of fiber substrates based on price and performance during production, achieving an optimal balance between cost and performance.

[0024] The present invention offers multiple drying methods, allowing companies to select the appropriate drying method based on their production equipment, cost budget, and product requirements. Supercritical carbon dioxide drying and ethanol supercritical drying can produce aerogel products with superior performance, but they require relatively high equipment costs and operating requirements. Atmospheric pressure drying offers the advantages of simple equipment, convenient operation, and low cost. This diverse drying method offers greater flexibility for companies of varying sizes and application scenarios, further improving production efficiency and economic benefits.

[0025] The method for preparing a mixed silicon source silica aerogel of the present invention has significant performance advantages, cost advantages and innovation advantages, and can prepare high-performance, low-cost silica aerogel products to meet market demands in multiple fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a sample photo of the silica aerogel thermal insulation sheet prepared in Example 4 of the present invention;

[0027] Figure 2 Schematic diagram of the stress-strain curve of the mechanical properties of the silica aerogel thermal insulation sheet prepared in Example 1 of the present invention;

[0028] Figure 3 Schematic diagram of the stress-strain curve of the mechanical properties of the silica aerogel thermal insulation sheet prepared in Example 3 of the present invention;

[0029] Figure 4 Schematic diagram of stress-strain curve of mechanical properties of silica aerogel thermal insulation sheet prepared in Example 5 of the present invention;

[0030] Figure 5 This is a schematic diagram of the thermal insulation temperature rise curve of the silica aerogel thermal insulation sheet prepared in Example 1 of the present invention at 650°C;

[0031] Figure 6 This is a schematic diagram of the 650°C thermal insulation temperature rise curve of the silica aerogel thermal insulation sheet prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present invention are described clearly and completely below with reference to the accompanying drawings.

[0033] Example 1

[0034] S1: Ethyl silicate 40, ethyl silicate 28, ethanol, and water were uniformly mixed in a molar ratio of 0.5:0.5:6:2, and hydrochloric acid was added. The molar ratio of silicon source to hydrochloric acid was 1:0.01. The mixture was uniformly magnetically stirred at room temperature for 5 minutes. After standing for hydrolysis, it was poured into a container and the solution was soaked with the glass fiber substrate.

[0035] S2: The solution obtained in step S1 was mixed with the glass fiber substrate to form a composite sol, and then allowed to stand for 30 hours for hydrolysis and polycondensation to obtain a glass fiber wet gel. The glass fiber substrate had a thickness of 3.0 mm and a density of 120 kg / m 3 .

[0036] S3: The glass fiber wet gel obtained in step S2 is sealed and aged for 24 hours.

[0037] S4: The glass fiber wet gel aged in step S3 is placed in ethanol and a silane coupling agent for modification.

[0038] S5: placing the glass fiber wet gel modified by aging in step S4 into supercritical carbon dioxide for drying to obtain glass fiber aerogel.

[0039] The glass fiber aerogel prepared in this embodiment has a thermal conductivity (25°C) of 0.015 W / (m·K), a temperature resistance of 620°C-720°C, and a compression rate of 52±5% at 2 MPa. The glass fiber aerogel has high strength, a high thickness retention rate, high thermal insulation performance, and a cost reduction of 7%.

[0040] like Figure 2 As shown in FIG, a schematic diagram of stress-strain curves of the mechanical properties of 5 groups of silica aerogel insulation sheets prepared in this embodiment.

[0041] like Figure 5 As shown in FIG. 1 , a schematic diagram of a 650° C. thermal insulation temperature rise curve of the silica aerogel thermal insulation sheet prepared in this embodiment is shown.

[0042] Example 2

[0043] S1: Ethyl silicate 40, ethyl silicate 28, ethanol, and water were uniformly mixed in a molar ratio of 0.6:0.4:6.5:2, and hydrochloric acid was added. The molar ratio of silicon source to hydrochloric acid was 1:0.01. The mixture was uniformly magnetically stirred at room temperature for 15 minutes. After standing for hydrolysis, the mixture was poured into a container and the solution was soaked with the glass fiber substrate.

[0044] S2: The solution obtained in step S1 was mixed with the glass fiber substrate to form a composite sol, and then allowed to stand for 35 hours for hydrolysis and polycondensation to obtain a glass fiber wet gel. The glass fiber substrate had a thickness of 3.0 mm and a density of 120 kg / m 3 .

[0045] S3: Aging the glass fiber wet gel obtained in step S2 for 20 hours.

[0046] S4: The glass fiber wet gel aged in step S3 is placed in ethanol and a silane coupling agent for modification.

[0047] S5: placing the glass fiber wet gel modified by aging in step S4 into supercritical carbon dioxide for drying to obtain glass fiber aerogel.

[0048] The glass fiber aerogel prepared in this embodiment has a thermal conductivity (25°C) of 0.014 W / (m·K), a temperature resistance of 630°C-730°C, and a compression rate of 45±5% at 2 MPa. The glass fiber aerogel has high strength, high thickness retention, good compressive resistance, high thermal insulation performance, and a cost reduction of 5%.

[0049] Example 3

[0050] S1: Ethyl silicate 40, ethyl silicate 28, ethanol, and water were uniformly mixed in a molar ratio of 0.7:0.3:7:2, and hydrochloric acid was added. The molar ratio of silicon source to hydrochloric acid was 1:0.01. The mixture was uniformly magnetically stirred at room temperature for 20 minutes. After standing for hydrolysis, it was poured into a container and the solution was soaked with the glass fiber substrate.

[0051] S2: The solution obtained in step S1 was mixed with the glass fiber substrate to form a composite sol, and then allowed to stand for 40 hours for hydrolysis and polycondensation to obtain a glass fiber wet gel. The glass fiber substrate had a thickness of 3.0 mm and a density of 120 kg / m 3 .

[0052] S3: Aging the glass fiber wet gel obtained in step S2 for 12 hours.

[0053] S4: The glass fiber wet gel aged in step S3 is placed in ethanol and a silane coupling agent for modification.

[0054] S5: placing the glass fiber wet gel modified by aging in step S4 into supercritical carbon dioxide for drying to obtain glass fiber aerogel.

[0055] The glass fiber aerogel prepared in this embodiment has a thermal conductivity (25°C) of 0.013 W / (m·K), a temperature resistance of 670°C-770°C, and a compression ratio of 38±5% at 2 MPa. The glass fiber aerogel has high strength, good thickness retention, better compressive resistance, high thermal insulation performance, and a 3% cost reduction.

[0056] like Figure 3 As shown in FIG, a schematic diagram of stress-strain curves of the mechanical properties of 5 groups of silica aerogel insulation sheets prepared in this embodiment.

[0057] like Figure 6 As shown in FIG. 1 , a schematic diagram of a 650° C. thermal insulation temperature rise curve of the silica aerogel thermal insulation sheet prepared in this embodiment is shown.

[0058] Example 4

[0059] S1: Ethyl silicate 40, ethyl silicate 28, ethanol, and water were uniformly mixed in a molar ratio of 0.2:0.8:7.5:2, and hydrochloric acid was added. The molar ratio of silicon source to hydrochloric acid was 1:0.01. The mixture was uniformly magnetically stirred at room temperature for 25 minutes. After standing for hydrolysis, the mixture was poured into a container and the solution was soaked with the glass fiber substrate.

[0060] S2: The solution obtained in step S1 was mixed with the glass fiber substrate to form a composite sol, and then allowed to stand for 45 hours for hydrolysis and polycondensation to obtain a glass fiber wet gel. The glass fiber substrate had a thickness of 3.0 mm and a density of 120 kg / m 3 .

[0061] S3: Aging the glass fiber wet gel obtained in step S2 for 30 hours.

[0062] S4: The glass fiber wet gel aged in step S3 is placed in ethanol and a silane coupling agent for modification.

[0063] S5: placing the glass fiber wet gel modified by aging in step S4 into supercritical carbon dioxide for drying to obtain glass fiber aerogel.

[0064] The glass fiber aerogel prepared in this embodiment has a thermal conductivity (25°C) of 0.012 W / (m·K), a temperature resistance of 610°C-710°C, and a compression rate of 58±5% at 2 MPa. The glass fiber aerogel has high strength, good thickness retention, good compressive resistance, high thermal insulation performance, and a 10% cost reduction.

[0065] like Figure 1 As shown, this is a sample photo of a 30cm×3030cm silica aerogel insulation sheet prepared in this embodiment.

[0066] Example 5

[0067] S1: Ethyl silicate 40, ethyl silicate 28, ethanol, and water were uniformly mixed in a molar ratio of 0.1:0.9:8:2, and hydrochloric acid was added. The molar ratio of silicon source to hydrochloric acid was 1:0.01. The mixture was uniformly magnetically stirred at room temperature for 30 minutes. After standing for hydrolysis, it was poured into a container and the solution was soaked with the glass fiber substrate.

[0068] S2: The solution obtained in step S1 was mixed with the glass fiber substrate to form a composite sol, and then allowed to stand for 60 hours for hydrolysis and polycondensation to obtain a glass fiber wet gel. The glass fiber substrate had a thickness of 3.0 mm and a density of 120 kg / m 3 .

[0069] S3: Aging the glass fiber wet gel obtained in step S2 for 48 hours.

[0070] S4: The glass fiber wet gel aged in step S3 is placed in ethanol and a silane coupling agent for modification.

[0071] S5: placing the glass fiber wet gel modified by aging in step S4 into supercritical carbon dioxide for drying to obtain glass fiber aerogel.

[0072] The glass fiber aerogel (25°C) prepared in this embodiment has a thermal conductivity of 0.011 W / (m·K), a temperature resistance of 600°C-700°C, and a compression rate of 60±5% at 2 MPa. The glass fiber aerogel has good strength, good thickness retention, good compressive resistance, good thermal insulation performance, and a cost reduction of 13%.

[0073] like Figure 4 As shown in FIG, a schematic diagram of stress-strain curves of the mechanical properties of 5 groups of silica aerogel insulation sheets prepared in this embodiment.

[0074] The present invention provides a method for preparing a mixed silicon-source silica aerogel. The prepared mixed silicon-source silica aerogel exhibits excellent strength, low compressibility, low thermal conductivity, and excellent thermal insulation properties, saving costs while ensuring product performance. This method also achieves cost reduction and efficiency improvement in the fields of construction and building materials, petrochemicals, new energy batteries, military and aerospace, and so on.

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A method for preparing a mixed silicon source silica aerogel, characterized in that: The following steps are involved: S1: Mix two silicon sources, ethanol, and water in a molar ratio of 0.1-0.9:0.1-0.9:5-10:2-5, add acid, and magnetically stir at room temperature for 3-60 minutes to obtain a mixed solution, which is then allowed to stand at room temperature for hydrolysis and polycondensation; S2: The solution obtained in step S1 is mixed with the fiber substrate sol, and the mixture is allowed to stand for 12 hours to 50 hours for hydrolysis and polycondensation to form a fiber wet gel product; S3: sealing and aging the wet gel product obtained in step S2; S4: placing the wet gel aging product from step S3 into ethanol and a hydrophobic modifier for liquid aging modification; S5: Drying the product modified by aging in step S4 to obtain a silica aerogel product.

2. The method for preparing a mixed silicon source silica aerogel according to claim 1, wherein: The silicon source in step S1 is 40% ethyl orthosilicate or 28% ethyl orthosilicate, the acid is one of hydrochloric acid, nitric acid or oxalic acid, and the molar ratio of the acid to the silicon source is 1:0.

01.

3. The method for preparing a mixed silicon source silica aerogel according to claim 1, wherein: The fiber substrate described in step S2 is a pre-oxidized silk fiber substrate, a glass fiber substrate, a polyester fiber substrate or a ceramic fiber substrate.

4. The method for preparing a mixed silicon source silica aerogel according to claim 1, wherein: The wet gel aging temperature in step S3 is 40° C. to 60° C., and the aging time is 1 day to 3 days.

5. The method for preparing a mixed silicon source silica aerogel according to claim 1, wherein: The hydrophobic modifier in step S4 is a silane coupling agent, a siloxane compound or a silazane compound.

6. The method for preparing a mixed silicon source silica aerogel according to claim 1, wherein: The drying in step S5 is carbon dioxide supercritical drying, ethanol supercritical drying or atmospheric pressure drying.

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