Silica aerogel composite felt material, preparation method and application thereof

Abstract

The application provides a silica aerogel composite felt material, a preparation method and application thereof. The composite felt material is a silica aerogel reinforced composite fiber felt. The silica aerogel is fully impregnated in the fiber felt by using a negative pressure adsorption vacuum impregnation method. Then, the resin in the composite fiber felt is melted, and the silica aerogel and the fiber interface are better combined and better pore structures are presented by using the adhesion of the melted resin in the composite fiber felt. The silica aerogel composite felt material is simple and convenient to prepare. The heat insulation performance and the interface bonding capacity are enhanced by impregnating the silica gel while the high strength and the compactness characteristics of the fiber felt are maintained. The hydrophobicity, the strength and other performances of the composite felt material are improved. The prepared composite material has low density and good pore structures by impregnating the fiber felt with appropriate pores. The problem that the aerogel felt is easy to drop slag and powder is solved.

Description

Technical Field

[0001] This invention belongs to the field of thermal insulation and heat preservation aerogels, specifically relating to a silica aerogel composite felt material, its preparation method, and its application. Technical Background

[0002] Aerogels are a novel type of low-density amorphous material with ultra-high porosity and a three-dimensional network structure. For example, in SiO2 aerogel, approximately 95% of the volume is composed of air, while the remaining 5% consists of cross-linked three-dimensional network silica nanoparticles. The unique properties and nanostructure of aerogels make them the lowest density solid material in the world. The density of silica aerogels typically ranges from 3 to 500 mg / cm³. 3 The porosity can reach 80%–99.8%, the pore size is between 1 and 100 nm, and the specific surface area can be as high as 1000 m². 2 / g, and due to its porous structure, it has an extremely low thermal conductivity and good thermal insulation performance; at the same time, its unique structure also gives it properties such as low refractive index, low elastic modulus, low dielectric constant, and low acoustic impedance. These physical properties make aerogels a promising material for development in many fields such as aerospace, automobile manufacturing, thermal and sound insulation materials, supercapacitors, electrode batteries, catalysis, and military industry.

[0003] Although silica aerogel possesses excellent thermal insulation properties, its high porosity results in extremely low mechanical properties, brittleness, and a tendency to shed dust, with mechanical strength typically ranging from 0.1 to 1.0 MPa. Existing reported silica aerogel composite materials mainly include: Patent CN110770168A, which uses a roller to bond aerogel and fiber felt, a commonly used industrial bonding method. While this improves the mechanical strength and provides some toughness to the aerogel, it still cannot solve the problem of dust and shed dust after the fiber and silica aerogel are bonded. Therefore, how to ensure that silica aerogel composite materials do not shed dust and dust, while simultaneously achieving optimal mechanical properties, low thermal conductivity, and high hydrophobicity, is a pressing technical challenge that needs to be addressed. Summary of the Invention

[0004] To address the aforementioned technical challenges, this invention provides a silica aerogel composite felt material, the preparation method of which includes the following steps:

[0005] S1: Mix the silicon source, solvent, and water, then add an acid solution to adjust the pH to 3-6. Stir with a magnetic stirrer for 30-120 minutes, and hydrolyze at 10℃-50℃ for 6-8 hours to obtain a silicon mixed solution. The silicon source is one or any combination of tetraethyl orthosilicate, methyl orthosilicate, butyl orthosilicate, isopropyl orthosilicate, or water glass; the solvent is one or any combination of ethanol, methanol, and acetone; and the acid solution is one or any combination of hydrochloric acid and oxalic acid.

[0006] S2: The fiber felt is laid in the mold, and the silicon mixed solution obtained in S1 is added. It is adsorbed under a negative pressure of -0.1MPa for 1-10 minutes to fully fill the fiber felt with the solution. Then an alkaline solution is added, which is any combination of ammonia or sodium hydroxide solution. After standing at room temperature, the fiber felt composite silica wet gel is obtained.

[0007] S3: The fiber felt composite silica wet gel prepared in S2 is immersed in the precursor solution for room temperature aging treatment, and then a mixed solution of n-hexane and trimethylchlorosilane (TMCS) is added for hydrophobic modification and solution exchange for 12-48 hours; then freeze-drying and heat treatment are performed to obtain silica aerogel composite felt material, wherein the volume ratio of n-hexane to TMCS is 1-9:1.

[0008] The molar ratio of silicon source, solvent, and water in step S1 is 1:6-10:4, and the concentration of acid solution is 0.1-1 mol / L.

[0009] The fiber felt mentioned in step S2 is one or any combination of carbon fiber felt, basalt fiber felt, hemp fiber felt, cellulose fiber felt, glass fiber felt, aluminosilicate fiber felt, quartz fiber felt, pre-oxidized fiber felt, mullite fiber felt, alumina fiber felt or boron nitride fiber felt, with an ammonia concentration of 0.1-2 mol / L and a sodium hydroxide concentration of 0.1-1 mol / L.

[0010] The precursor solution in step S3 is a solution in which silicon source, solvent and water are mixed in a molar ratio of 1:6-10:4. The silicon source is one or any combination of tetraethyl orthosilicate, methyl orthosilicate, butyl orthosilicate, isopropyl orthosilicate or water glass; the solvent is one or any combination of ethanol, methanol and acetone.

[0011] Furthermore, the aging treatment described in step S3 lasts for 8-24 hours, the freeze-drying is performed at -70 to -150°C for 24-36 hours, and the heat treatment is performed at 150-180°C for 2-15 minutes.

[0012] This invention also provides an application of silica aerogel composite felt material in the fields of heat insulation and thermal insulation.

[0013] Compared with the prior art, the advantages of the present invention are:

[0014] Existing silica aerogels or their composites exhibit powder and flaking under various forms of damage, including vibration, bending, and friction. This is primarily due to poor compatibility and adhesion between aerogels and other materials, leading to phase separation or delamination and ultimately powder and flaking. Furthermore, achieving high mechanical properties, toughness, thermal insulation, lightweighting, and high hydrophobicity simultaneously is challenging. This invention, however, utilizes the synergistic control of raw materials, raw material ratios, vacuum adsorption, and melting processes and parameters. Using fiber felt as the matrix and silica aerogel as the reinforcement, negative pressure adsorption is employed to achieve a good bond between the fiber felt and the silica aerogel, resulting in a fully charged aerogel. The silica aerogel is incorporated into the fiber felt, and then the resin fibers in the composite fiber felt are melted. The adhesive properties of the molten resin fibers in the composite fiber felt allow for better bonding between the silica aerogel and the fiber interface. This enhances both the strength of the aerogel and the bonding ability between the fiber and the aerogel, providing a robust spatial structure for the aerogel. This achieves optimal synergistic control over the pore structure of the aerogel composite material and the bonding between the aerogel and fiber interface. Specifically, the silica aerogel provides a favorable pore structure for the fiber aerogel felt, effectively reducing slagging and powdering. Furthermore, the better bonding between the silica aerogel and the fiber interface allows for better application in various fields. Therefore, this invention avoids the slagging and powdering of traditional aerogel and aerogel felt materials while simultaneously enhancing the thermal insulation, heat insulation, and flame retardant properties of the fibers. It also simultaneously achieves excellent comprehensive properties of the aerogel composite material, including lightweight, high strength, high hydrophobicity, and low thermal conductivity. Attached Figure Description

[0015] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0016] Figure 1 This is a flowchart illustrating the preparation of silica aerogel composite felt material according to the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention.

[0018] Example 1

[0019] (1) Tetraethyl orthosilicate, anhydrous ethanol and deionized water were mixed in a molar ratio of 1:8:4, and then 0.5 mol / L hydrochloric acid solution was added to adjust the pH of the solution to 3. The solution was stirred with a magnetic stirrer for 60 min and then hydrolyzed for 8 h in a water bath at room temperature to obtain a silicon mixed solution.

[0020] (2) Carbon fiber felt (composed of carbon fiber and polypropylene (PP) resin in a mass ratio of 8:2) is laid in a mold, and then the silicon mixed solution obtained in step (1) is added. Under the adsorption condition of -0.1MPa, the solution is adsorbed for 2 minutes to fully fill the carbon fiber felt. Then, ammonia water with a concentration of 1mol / L is added to obtain a mixed solution. The pH of the mixed solution is adjusted to 8. After standing, carbon fiber felt composite silica wet gel is obtained.

[0021] (3) The carbon fiber felt composite silica wet gel prepared in step (2) is immersed in a precursor solution, wherein the precursor solution is a solution of tetraethyl orthosilicate, anhydrous ethanol and deionized water in a molar ratio of 1:8:4. After aging at room temperature for 12 hours, a mixed solution of hexane and trimethylchlorosilane (TMCS) is added for hydrophobic modification for 24 hours, wherein the volume ratio of hexane to trimethylchlorosilane is 9:1. After drying in a freeze-drying environment at -70°C for 36 hours, it is heated at 175°C for 10 minutes to obtain silica aerogel composite carbon fiber felt material.

[0022] The thermal conductivity of the prepared silica aerogel composite carbon fiber felt material is 0.020 W / m·K.

[0023] Example 2

[0024] (1) Mix tetraethyl orthosilicate, anhydrous ethanol and deionized water in a molar ratio of 1:10:4, then add oxalic acid solution with a concentration of 1 mol / L, adjust the pH of the solution to 5, stir with a magnetic stirrer for 80 min, and hydrolyze for 12 h in a 50℃ water bath to obtain a silicon mixed solution.

[0025] (2) The hemp fiber felt (composed of hemp fiber and polypropylene (PP) resin in a mass ratio of 6:4) is laid in the mold, and the silicon mixed solution obtained in step (1) is added. The solution is adsorbed for 5 minutes under an adsorption condition of -0.1MPa to fully fill the hemp fiber felt. Then, ammonia water with a concentration of 1.5mol / L is added to obtain a mixed solution. The solution is added until the pH is 7, and the solution is allowed to stand to gel, thus obtaining hemp fiber felt composite silica wet gel.

[0026] (3) The hemp fiber felt composite silica wet gel prepared in step (2) was immersed in an ethanol solution and aged at 50°C for 8 hours. Then, a mixed solution of hexane and trimethylchlorosilane (TMCS) was added for hydrophobic modification for 24 hours, wherein the volume ratio of hexane to trimethylchlorosilane was 5:1. After drying in a freeze-drying environment at -85°C for 48 hours, it was heated at 170°C for 8 minutes to obtain silica aerogel composite hemp fiber felt material.

[0027] The thermal conductivity of the prepared silica aerogel composite hemp fiber felt material is 0.025 W / m·K.

[0028] Example 3

[0029] (1) Tetraethyl orthosilicate, anhydrous ethanol and deionized water were mixed in a molar ratio of 2:9:4, and then 0.2 mol / L hydrochloric acid solution was added to adjust the pH of the solution to 4. The solution was stirred with a magnetic stirrer for 120 min and hydrolyzed for 8 h in a 30℃ water bath to obtain a silicon mixed solution.

[0030] (2) Basalt fiber felt (composed of basalt fiber and polypropylene (PP) resin in a mass ratio of 7:3) is laid in a mold, and then the silicon mixed solution obtained in step (1) is added. The solution is adsorbed for 5 minutes under an adsorption condition of -0.1MPa to fully fill the basalt fiber felt. Then, ammonia water with a concentration of 0.8mol / L is added to obtain a mixed solution. The pH of the solution is adjusted to 8, and the gel is allowed to stand to obtain basalt fiber felt composite silica wet gel.

[0031] (3) The basalt fiber felt composite silica wet gel prepared in step (2) is immersed in a precursor solution. The precursor solution is a solution in which tetraethyl orthosilicate, anhydrous ethanol and deionized water are mixed in a molar ratio of 2:9:4. After aging at 30°C for 24 hours, hexane solution is added for hydrophobic modification for 24 hours. After freeze-drying at -90°C for 40 hours, it is heated at 180°C for 5 minutes to obtain silica aerogel composite basalt fiber felt material.

[0032] The thermal conductivity of the prepared silica aerogel composite basalt fiber felt material is 0.023 W / m·K.

[0033] Comparative Example 1: Carbon Fiber Aerogel Felt

[0034] In their paper "Preparation and Performance Study of Glass Fiber and Carbon Fiber Reinforced Silica Aerogel Composites", Luo Dan et al. combined silica aerogel and carbon fiber by impregnation. The carbon fiber reinforced aerogel felt they obtained had a thermal conductivity of 0.034 W / m·K, a contact angle of 139°, and a compressive strength of 1.225 MPa.

[0035] The thermal conductivity, contact angle and compressive strength of the composite materials obtained in Examples 1-3 and Comparative Example 1 were compared and tested. The data are shown in Table 1.

[0036] Table 1 Comparison of Implementation Case Data

[0037] thermal conductivity Contact angle compressive strength Example 1 0.020 W / m·K 150° 2.086MPa Example 2 0.025W / m·K 145° 1.683MPa Example 3 0.023 W / m·K 150° 1.819MPa Comparative Example 1 0.034 W / m·K 139° 1.225MPa

[0038] Through comparative testing, this invention enables a good bond between the composite fiber felt and silica aerogel. It was found that the aerogel composite material prepared by melting exhibits good toughness, low thermal conductivity, high hydrophobicity, and high compressive strength. Furthermore, it does not shed powder or slag under various forms of damage, including vibration, bending, and friction. In summary, compared with existing technologies, this invention overcomes the technical bottleneck of simultaneously improving the mechanical properties, thermal conductivity, and hydrophobicity of silica aerogel composites, as well as suppressing powder and slag shedding. Through the synergistic control of raw materials, raw material ratios, processes, and parameters, the final composite material does not shed powder or slag even under various forms of damage such as vibration, bending, and friction, simultaneously achieving low thermal conductivity, high hydrophobicity, toughness, and mechanical properties.

Claims

1. A silica aerogel composite felt material, the preparation method of which includes the following steps: S1: Mix the silicon source, solvent, and water, then add an acid solution to adjust the pH to 3-6. Stir with a magnetic stirrer for 30-120 minutes, and hydrolyze at 10℃-50℃ for 6-8 hours to obtain a silicon mixed solution. The silicon source is one or any combination of tetraethyl orthosilicate, methyl orthosilicate, butyl orthosilicate, isopropyl orthosilicate, or water glass; the solvent is one or any combination of ethanol, methanol, and acetone; and the acid solution is one or any combination of hydrochloric acid and oxalic acid. S2: The fiber felt is laid in the mold, and the silicon mixed solution obtained in S1 is added. It is adsorbed under a negative pressure of -0.1MPa for 1-10 minutes to fully fill the fiber felt with the solution. Then an alkaline solution is added, which is any combination of ammonia or sodium hydroxide solution. After standing at room temperature, the fiber felt composite silica wet gel is obtained. S3: The fiber felt composite silica wet gel prepared in S2 is immersed in the precursor solution for room temperature aging treatment, and then a mixed solution of n-hexane and trimethylchlorosilane (TMCS) is added for hydrophobic modification and solution exchange for 12-48 hours; then freeze-drying and heat treatment are performed to obtain silica aerogel composite felt material, wherein the volume ratio of n-hexane to TMCS is 1-9:

1. The molar ratio of silicon source, solvent, and water in step S1 is 1:6-10:4, and the concentration of acid solution is 0.1-1 mol / L; The fiber felt mentioned in step S2 is one or any combination of carbon fiber felt, basalt fiber felt, and hemp fiber felt, with an ammonia concentration of 0.1-2 mol / L and a sodium hydroxide concentration of 0.1-1 mol / L. The carbon fiber felt is composed of carbon fiber and polypropylene resin in a mass ratio of 8:2; the basalt fiber felt is composed of basalt fiber and polypropylene resin in a mass ratio of 7:3; and the hemp fiber felt is composed of hemp fiber and polypropylene resin in a mass ratio of 6:

4. The precursor solution in step S3 is a solution in which silicon source, solvent and water are mixed in a molar ratio of 1:6-10:

4. The silicon source is one or any combination of tetraethyl orthosilicate, methyl orthosilicate, butyl orthosilicate, isopropyl orthosilicate or water glass. The solvent is one or any combination of ethanol, methanol, acetone. The heating treatment is to keep the temperature at 150-180℃ for 2-15 minutes.

2. The silica aerogel composite felt material according to claim 1, wherein the aging treatment in step S3 lasts for 8-24 hours, and the freeze-drying is performed at -70 to -150°C for 24-36 hours.

3. The application of the silica aerogel composite felt material as described in claim 1 in the fields of heat insulation and thermal insulation.

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