A method for preparing anisotropic glass fiber aerogel

Abstract

The application discloses a preparation method of anisotropic glass fiber aerogel, which comprises the following steps: preparing a glass fiber dispersion solution; preparing an aluminum dihydrogen phosphate solution; preparing a polyvinyl alcohol solution; uniformly mixing the three solutions, pouring into a customized mold, freezing until complete solidification, and then performing freeze drying to obtain the glass fiber aerogel. Due to the influence of multiple temperature gradients on the aerogel, ice crystals grow vertically along the temperature gradient to form lamellas, and different cold surfaces interact to cause them to grow along the radial plane to the center of the square mold, finally forming an array radiation structure composed of four cones. The glass fiber aerogel prepared through the synergistic cooperation of the freeze casting technology and the aluminum dihydrogen phosphate has anisotropy and highly ordered lamellas, and therefore exhibits good low thermal conductivity.

Description

Technical Field

[0001] This invention relates to the field of materials technology, and specifically to a method for preparing anisotropic glass fiber aerogel. Background Technology

[0002] Aerogels are lightweight, three-dimensional network materials with advantages such as high specific surface area, high porosity, low thermal conductivity, and low density, making them promising for applications in thermal engineering, optoelectronics, aerospace, and construction. Aerogels can be prepared from materials such as cellulose, graphene, polymers, and SiO2. Glass fibers, with their low thermal conductivity and excellent insulation properties, are frequently used in thermal insulation applications. Glass fiber-bonded aerogels can reduce heat transfer between fibers, effectively improving the material's insulation performance. The introduction of glass fibers enhances the mechanical properties of aerogels, increasing compressive strength while reducing their volumetric size. It also helps maintain the long-term integrity and stability of the aerogel network structure.

[0003] Aerogels formed through the sol-gel method and supercritical drying technology possess high thermal insulation properties, but still face the challenge of poor mechanical properties. Aerogels prepared by cryogenic casting, through the introduction of low-dimensional materials and the presence of highly ordered channels, endow the resulting porous materials with flexibility, allowing for recoverable deformation and minimizing material limitations. By using cryogenic casting technology, high levels of mechanical and thermodynamic performance can be achieved, thus overcoming the traditional limitations of aerogel brittleness. Due to the high gas interstitial density, cryogenically cast materials exhibit significantly better thermal insulation performance in the direction perpendicular to the pore orientation. Currently, purely oriented aerogels, due to their single-channel nature in the vertical direction and rapid heat flow, still have room for improvement in thermal insulation performance. Therefore, this application is proposed. Summary of the Invention

[0004] This invention proposes a method for preparing anisotropic glass fiber aerogels, addressing the technical challenge that while purely oriented aerogels exhibit superior thermal insulation due to their single-channel nature in the vertical direction and faster heat flow, random aerogels cannot achieve anisotropic thermal insulation.

[0005] The above-mentioned technical objective of the present invention is achieved through the following technical solution:

[0006] A method for preparing anisotropic glass fiber aerogel includes the following steps:

[0007] Preparation of glass fiber dispersion;

[0008] Preparation of aluminum dihydrogen phosphate solution;

[0009] Prepare a polyvinyl alcohol solution;

[0010] The three solutions are mixed evenly, poured into a custom mold and frozen until completely solidified, and then freeze-dried to obtain glass fiber aerogel.

[0011] In some embodiments, the preparation of the glass fiber dispersion includes:

[0012] Add glass fiber to pure water, then place it on a magnetic stirrer and stir at a speed of 400-600 rpm / min for 1-3 hours. The mass fraction of glass fiber is 5wt%-10wt%.

[0013] In some embodiments, the preparation of the aluminum dihydrogen phosphate solution includes:

[0014] Add aluminum dihydrogen phosphate powder to pure water, then place it on a magnetic stirrer and stir at a speed of 700-900 rpm / min for 1-2 hours to obtain a uniform aluminum dihydrogen phosphate solution with a mass fraction of 0wt%-3wt%.

[0015] In some embodiments, the preparation of the polyvinyl alcohol solution includes:

[0016] Polyvinyl alcohol granules were added to pure water and then placed on a magnetic stirrer for heating and stirring. The stirring speed was set to 500-700 rpm / min, the heating temperature was set to 80℃-90℃, and the heating time was 1-3h to obtain a uniform polyvinyl alcohol solution with a polyvinyl alcohol mass fraction of 0wt%-3wt%.

[0017] In some embodiments, mixing the three solutions uniformly includes:

[0018] Mix the three solutions in a mass ratio of 1:1:1, place them on a magnetic stirrer and stir continuously for 1-2 hours at a speed of 500-700 rpm / min to obtain a homogeneous solution.

[0019] In some embodiments, the customized mold is a square copper mold, the mold pre-freezing time is 3-6 h, and the freezing temperature is -60 ℃.

[0020] In some embodiments, the freeze-drying to obtain glass fiber aerogel includes:

[0021] The well-mixed solution was poured into a pre-frozen mold and frozen at -60 ℃ for 6-8 h. Then, it was freeze-dried to obtain glass fiber aerogel, with a freeze-drying time of 48-72 h.

[0022] The above-described technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0023] This invention utilizes cryogenic casting technology to prepare an array radiation structure consisting of four cones from aluminum dihydrogen phosphate solution, polyvinyl alcohol solution, and glass fiber dispersion. Through a specific mold design, a temperature gradient is generated along multiple cold surfaces perpendicular to the mold. Due to the anisotropy of ice crystals, they typically grow along the temperature gradient, causing them to grow along the plane from the temperature gradient to the center of the mold. The ice crystals within the square copper mold are arranged in a cone-shaped array structure. During freezing, polyvinyl alcohol, aluminum dihydrogen phosphate, and glass fibers are extruded from the ice crystals, discharged into the gaps between the ice crystals, and accumulate into an ordered layered structure. The layered structure, composed of internal vertical cavity channels, layered radiation, and porous thin walls, results in low thermal conductivity in the glass fiber aerogel. The multi-scale porous glass fiber aerogel prepared by cryogenic casting technology exhibits a higher level of low thermal conductivity compared to single-scale materials with similar porosity.

[0024] The combination of four conical array structures exhibits radial symmetry in the horizontal direction, with the channel ending at the center. Vertically, the highly ordered, transversely layered structure effectively extends the heat conduction path. The presence of pores aligned perpendicular to the thermal gradient results in a high density at the solid-air interface, and because air is confined within each micropore, thermal convection within the glass fiber aerogel is largely restricted. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a digital photograph of the cross-section of the glass fiber aerogel in Embodiment 1 of the present invention;

[0027] Figure 2 This is a scanning electron microscope image of the glass fiber aerogel in Example 1 of the present invention;

[0028] Figure 3 Digital photograph of the cross-section of glass fiber aerogel in Embodiment 2 of this invention;

[0029] Figure 4 This is a scanning electron microscope image of the glass fiber aerogel in Example 2 of the present invention;

[0030] Figure 5 Digital photograph of the longitudinal section of the glass fiber aerogel in Embodiment 3 of the present invention. Detailed Implementation

[0031] The following will provide a clear and complete description of the concept and technical effects of the present invention in conjunction with embodiments, so as to fully understand the purpose, solution and effects of the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. It should be understood that the following embodiments and the experimental data therein are intended to illustrate the technical concept of the present invention, and not to describe the technical concept of the present invention, nor to limit the present invention. Those skilled in the art can perform conventional optimization of process parameters while following the core ideas of the present invention.

[0032] Example 1

[0033] (1) Preparation of glass fiber dispersion

[0034] Weigh 0.5 g of glass fiber and add it to pure water. Then place it on a magnetic stirrer and stir at 500 rpm / min for 2 hours. The mass fraction of glass fiber is 5 wt%.

[0035] (2) Preparation of aluminum dihydrogen phosphate solution

[0036] Weigh 3 g of aluminum dihydrogen phosphate powder and add it to 97 mL of pure water. Then place it on a magnetic stirrer and stir at 800 rpm / min for 2 h to obtain a homogeneous aluminum dihydrogen phosphate solution with a mass fraction of 3 wt%.

[0037] (3) Preparation of polyvinyl alcohol solution

[0038] Weigh 3 g of polyvinyl alcohol granules and add them to 97 mL of pure water. Then place the mixture on a magnetic stirrer and heat and stir at a speed of 600 rpm / min and a heating temperature of 90 ℃ for 1 h to obtain a homogeneous polyvinyl alcohol solution with a polyvinyl alcohol mass fraction of 3 wt%.

[0039] (4) Preparation of low thermal conductivity glass fiber aerogel

[0040] Glass fiber dispersion, aluminum dihydrogen phosphate solution, and polyvinyl alcohol solution were mixed at a mass ratio of 1:1:1 and stirred on a magnetic stirrer for 2 hours at a speed of 600 rpm / min to obtain a homogeneous solution. The homogeneous solution was then poured into a custom-made copper mold and frozen at -60 °C for 6 hours, followed by freeze-drying for 72 hours to obtain a glass fiber aerogel with a cone-shaped array structure.

[0041] Figure 1 This is a digital photograph of the cross-section of the glass fiber aerogel in Embodiment 1 of the present invention. Figure 1As can be seen from the present invention, the glass fiber aerogel prepared by the present invention has a special array structure, which is an array structure composed of four cones.

[0042] Figure 2 This is a scanning electron microscope image of the glass fiber aerogel in Example 1 of the present invention. Figure 2 As can be seen in diagram a, the morphology produced by the four copper surfaces exhibits a multi-domain pattern, resulting in a long-range ordered layered structure. From... Figure 2 b shows that the glass sheets are parallel to each other, and the glass fibers are intertwined between the sheets. The anisotropy of this aerogel is beneficial to improving the thermal insulation performance of the material.

[0043] Example 2

[0044] (1) Preparation of glass fiber dispersion

[0045] Weigh 1 g of glass fiber and add it to pure water. Then place it on a magnetic stirrer and stir at 500 rpm / min for 2 hours. The mass fraction of glass fiber is 10 wt%.

[0046] (2) Preparation of aluminum dihydrogen phosphate solution

[0047] Weigh 3 g of aluminum dihydrogen phosphate powder and add it to 97 mL of pure water. Then place it on a magnetic stirrer and stir at 800 rpm / min for 2 h to obtain a homogeneous aluminum dihydrogen phosphate solution with a mass fraction of 3 wt%.

[0048] (3) Preparation of polyvinyl alcohol solution

[0049] Weigh 3 g of polyvinyl alcohol granules and add them to 97 mL of pure water. Then place the mixture on a magnetic stirrer and heat and stir at a speed of 600 rpm / min and a heating temperature of 90 ℃ for 1 h to obtain a homogeneous polyvinyl alcohol solution with a polyvinyl alcohol mass fraction of 3 wt%.

[0050] (4) Preparation of low thermal conductivity glass fiber aerogel

[0051] Glass fiber dispersion, aluminum dihydrogen phosphate solution, and polyvinyl alcohol solution were mixed at a mass ratio of 1:1:1 and stirred on a magnetic stirrer for 2 hours at a speed of 600 rpm / min to obtain a homogeneous solution. The homogeneous solution was then poured into a custom-made copper mold and frozen at -60 °C for 6 hours, followed by freeze-drying for 72 hours to obtain a glass fiber aerogel with a cone-shaped array structure.

[0052] Figure 3Digital photograph of the cross-section of glass fiber aerogel in Embodiment 2 of the present invention, from Figure 3 It can be seen that there is a clear array structure inside. The temperature gradient generated by the four cold surfaces causes the ice crystal growth interface to interact, resulting in an array structure that resembles four independent units.

[0053] Figure 4 This is a scanning electron microscope image of the glass fiber aerogel in Example 2 of the present invention. Figure 4 As can be seen, the entanglement of glass fibers between the layers becomes more pronounced with increasing glass fiber content. Because glass fibers have a lower thermal conductivity, this contributes to the material's overall excellent low thermal conductivity.

[0054] Example 3

[0055] (1) Preparation of glass fiber dispersion

[0056] Weigh 1 g of glass fiber and add it to pure water. Then place it on a magnetic stirrer and stir at 500 rpm / min for 2 hours. The mass fraction of glass fiber is 10 wt%.

[0057] (2) Preparation of polyvinyl alcohol solution

[0058] Weigh 3 g of polyvinyl alcohol granules and add them to 97 mL of pure water. Then place the mixture on a magnetic stirrer and heat and stir at a speed of 600 rpm / min and a heating temperature of 90 ℃ for 1 h to obtain a homogeneous polyvinyl alcohol solution with a polyvinyl alcohol mass fraction of 3 wt%.

[0059] (3) Preparation of low thermal conductivity glass fiber aerogel

[0060] Glass fiber dispersion and polyvinyl alcohol solution were mixed at a mass ratio of 1:1:1 and stirred on a magnetic stirrer for 2 hours at a speed of 600 rpm / min to obtain a homogeneous solution. The homogeneous solution was then poured into a custom-made copper mold and frozen at -60 °C for 6 hours, followed by freeze-drying for 72 hours to obtain a glass fiber aerogel with a cone-shaped array structure.

[0061] Figure 5 Digital photographs of the longitudinal section of the glass fiber aerogel in Embodiment 3 of this invention, from... Figure 5Within a single domain (contacting one copper surface), orderly parallel stratification is clearly visible. Interestingly, a narrow cavity is visible in the vertical direction. This is because as ice crystals grow inward along the temperature gradient generated by the four cold surfaces, they are compressed and stacked at the center, forming a vertical ice column. Subsequent freeze-drying then creates... Figure 5 The shape shown.

[0062] The results of the thermal conductivity measurement of glass fiber aerogel are shown in Table 1:

[0063]

[0064] Table 1

[0065] As shown in Table 1, the final products of Examples 1 and 2, which added aluminum dihydrogen phosphate solution, had lower thermal conductivity than the final product of Example 3, which did not add aluminum dihydrogen phosphate solution. This indicates that aluminum dihydrogen phosphate solution not only maintains good fiber dispersion and bonding during directional freezing and the stability of the orientation structure after drying, but also has good chemical compatibility with glass fibers. The synergistic effect of combining aluminum dihydrogen phosphate with the directional freezing process is beneficial to improving the thermal insulation performance of the material. A comparison of Examples 1 and 2 shows that with the increase of glass fiber content, the entanglement of glass fibers between the layers is more pronounced. Because glass fibers have a lower thermal conductivity, this contributes to the overall excellent low thermal conductivity of the material.

[0066] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing anisotropic glass fiber aerogel, characterized in that, Includes the following steps: Preparation of glass fiber dispersion; Preparation of aluminum dihydrogen phosphate solution; Prepare a polyvinyl alcohol solution; The three solutions are mixed evenly, poured into a custom mold and frozen until completely solidified, and then freeze-dried to obtain glass fiber aerogel. The prepared glass fiber dispersion comprises: Add glass fiber to pure water, then place it on a magnetic stirrer and stir at a speed of 400-600 rpm / min for 1-3 hours. The mass fraction of glass fiber is 5wt%-10wt%. The preparation of the aluminum dihydrogen phosphate solution includes: Add aluminum dihydrogen phosphate powder to pure water, then place it on a magnetic stirrer and stir at 700-900 rpm / min for 1-2 hours to obtain a homogeneous aluminum dihydrogen phosphate solution with a mass fraction of 0 wt%-3 wt% and no aluminum dihydrogen phosphate. The preparation of the polyvinyl alcohol solution includes: Polyvinyl alcohol granules were added to pure water and then heated and stirred on a magnetic stirrer at a speed of 500-700 rpm / min and a heating temperature of 80℃-90℃ for 1-3 hours to obtain a homogeneous polyvinyl alcohol solution with a polyvinyl alcohol mass fraction of 0wt%-3wt% and containing no 0%; The process of mixing the three solutions evenly includes: Mix the three solutions in a mass ratio of 1:1:1, place them on a magnetic stirrer and stir continuously for 1-2 hours at a speed of 500-700 rpm / min to obtain a homogeneous solution. The customized mold is a square copper mold, and the pre-freezing time of the mold is 3-6 hours, and the freezing temperature is -60 ℃.

2. The method for preparing anisotropic glass fiber aerogel according to claim 1, characterized in that, The process of freeze-drying to obtain glass fiber aerogel includes: The well-mixed solution was poured into a pre-frozen mold and frozen at -60 ℃ for 6-8 h. Then, it was freeze-dried to obtain glass fiber aerogel, with a freeze-drying time of 48-72 h.

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