Ceramic nanofiber aerogel material and preparation method and application thereof

Abstract

The application provides a ceramic nanofiber aerogel material and a preparation method and application thereof, and belongs to the technical field of high-temperature-resistant thermal insulation materials.The nanofiber film with a three-dimensional fluffy structure is prepared by an electrostatic spinning method, the fiber film is used as a basic building unit, and a three-dimensional network aerogel with a layered structure and a fiber bridging structure and being more compact is constructed by layer-by-layer stacking, sol immersion, freeze drying and heat crosslinking treatment.The volume density of the ceramic nanofiber aerogel prepared by the application is 5~40mg / cm 3 , the thermal conductivity is 0.025~0.050W / (m*K), the high-temperature-resistant thermal insulation performance is excellent, the aerogel has a rebound rate of up to >99% after 100 times of compression, and is expected to be widely applied in the fields of high-temperature insulation, adsorption and separation, catalyst carrier and the like.

Description

Technical Field

[0001] This invention relates to the field of high-temperature resistant thermal insulation materials, and in particular to a ceramic nanofiber aerogel material, its preparation method, and its application. Background Technology

[0002] Aerogels, as solid materials with a nanoporous network structure, are among the lightest solids in the world. Aerogels possess an open, cross-linked network structure with a porosity of 80%–99.8% and pore sizes typically less than 50 nm. They have attracted considerable attention due to their ultra-low density, low thermal conductivity, and high specific surface area.

[0003] Currently, the types, chemical compositions, and microstructural units of aerogel materials are becoming increasingly diverse. Ceramic aerogels are widely studied due to their advantages such as good temperature resistance, oxidation resistance, and environmental friendliness. However, despite these advantages, traditional ceramic aerogels still suffer from inherent defects such as high brittleness and easy sintering at high temperatures, which severely limits their application in extreme environments. Chinese patent CN110078425A discloses a method for dispersing mullite fiber membranes into single fibers, mixing them with a silica sol and acrylamide gel molding premix to form a gel, and then obtaining mullite nanofiber aerogels through freeze-drying and high-temperature calcination. The drawbacks of this method are that the aerogel has low mechanical strength, poor resilience, and high brittleness, and the preparation process is complex and costly, making it difficult to achieve large-scale production. Chinese patent CN121021173A discloses a ceramic nanofiber aerogel with high compressive strength and low thermal conductivity and its preparation method. The method involves stacking zirconium-based ceramic nanofiber membranes layer by layer and then freeze-drying them to obtain a ceramic nanofiber aerogel with high compressive strength and low thermal conductivity. The drawback is that the high-temperature insulation effect of the aerogel is affected by the porosity and internal pores, and the high-temperature heat convection is obvious.

[0004] Therefore, the problem of achieving synergistic optimization between the high mechanical properties and low thermal conductivity of existing aerogels urgently needs to be solved so that they can be widely applied to different application scenarios. Summary of the Invention

[0005] The purpose of this invention is to provide a ceramic nanofiber aerogel material, its preparation method and application, which can achieve synergistic optimization between high mechanical properties and low thermal conductivity of aerogel, and the method is simple, can be operated continuously and has good processability.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing ceramic nanofiber aerogel materials, comprising the following steps: Inorganic source, polymer, pH adjuster and solvent are mixed to obtain spinning precursor solution; The spinning precursor solution was electrospinned to obtain a ceramic fiber membrane precursor. The ceramic fiber membrane precursor is calcined to obtain a three-dimensional ceramic fiber membrane; Multiple three-dimensional ceramic fiber membranes are stacked layer by layer, and the resulting layered stack is impregnated in an adhesive sol to obtain a multilayer composite fiber membrane. The multilayer composite fiber membrane was pre-frozen and then freeze-dried under vacuum to obtain cross-linked ceramic nanofiber aerogel. The cross-linked ceramic nanofiber aerogel was subjected to thermal cross-linking treatment to obtain a ceramic nanofiber aerogel material.

[0007] Preferably, the inorganic source includes one or more of silicon, aluminum, zirconium, titanium, hafnium, yttrium, and lanthanum sources; The polymer includes one or more of polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), and polyethylene oxide (PEO); the mass ratio of the inorganic source to the solvent is (7~32):(30~36), and the mass ratio of the polymer to the total mass of the inorganic source, pH adjuster, and solvent is 0.5~4:50.

[0008] Preferably, the silicon source includes tetraethyl orthosilicate or polymethylhydrosiloxane; the aluminum source includes aluminum nitrate, aluminum chloride, aluminum isopropoxide, or aluminum acetylacetonate; the zirconium source includes zirconium acetate, zirconium chloride, zirconium propoxide, or zirconium butoxide; the titanium source includes tetrabutyl titanate, isopropyl titanate, tetraethyl titanate, or titanium oxysulfate; the hafnium source includes hafnium acetylacetonate, hafnium butoxide, hafnium tetrachloride, or hafnium oxychloride; the yttrium source includes yttrium nitrate hexahydrate, yttrium acetate tetrahydrate, or yttrium acetylacetonate; and the lanthanum source includes lanthanum acetylacetonate, lanthanum oxide, lanthanum chloride, lanthanum nitrate, or lanthanum acetate.

[0009] Preferably, the pH adjuster includes oxalic acid and / or acetic acid; the solvent includes one or more of water, methanol, ethanol and isopropanol; and the pH value of the spinning precursor solution is 2.6 to 2.8. The parameters for electrospinning include: spinning temperature of 20~30℃, spinning solution feed rate of 0.5~1.5mL / h, spinning voltage of 12~30kV, distance from spinning needle to receiving plate of 10~30cm, and humidity of 30%~45%.

[0010] Preferably, the calcination and thermal crosslinking treatments are performed at temperatures of 600~1100℃ and for times of 1~10h.

[0011] Preferably, the number of layers of the three-dimensional ceramic fiber membrane stacked layer by layer is 1 to 5.

[0012] Preferably, the binder sol comprises one or more of silica sol, aluminum sol, and aluminum borosilicate sol, and the concentration of the binder sol is 1~10 wt%. The impregnation treatment employs a vacuum-assisted impregnation method, and the conditions for the impregnation treatment include: a vacuum degree of -0.05 to -0.09 MPa and an impregnation time of 0.5 to 3 hours.

[0013] Preferably, the pre-freezing temperature is -50 to -196°C and the time is 5 min to 2 h; the vacuum freeze-drying temperature is -50 to -80°C and the time is 30 to 50 h.

[0014] This invention provides a ceramic nanofiber aerogel material prepared by the preparation method described in the above technical solution.

[0015] This invention provides the application of the ceramic nanofiber aerogel material described above in the fields of high-temperature insulation, adsorption and separation, or catalyst support.

[0016] This invention provides a method for preparing ceramic nanofiber aerogel materials. First, a nanofiber membrane with a three-dimensional, fluffy structure is prepared by direct electrospinning. Then, using the three-dimensional fiber membrane as the basic building block, a denser three-dimensional network aerogel with a layered structure and fiber bridging is constructed through layer-by-layer stacking, sol impregnation, freeze-drying, and thermal cross-linking. This structure combines the continuity of the fiber membrane with the anisotropy of the layered structure, effectively solving the problems of high brittleness and easy cracking in traditional particulate aerogels. This invention utilizes the multi-level porous structure constructed by stacking fluffy nanofibers to achieve separation of mechanical support and thermal resistance. This is because the wavy fiber network provides excellent elasticity through bending and recovery, while the abundant interlayer pores and limited contact points effectively extend the heat conduction path and reduce the thermal conductivity of the solid, thereby solving the constraint between mechanical and thermal conductivity in traditional ceramic aerogels and achieving synergistic optimization of both.

[0017] This invention uses fluffy nanofibers obtained by electrospinning as basic building blocks, stacked layer by layer. This allows for the introduction of more air gaps between layers, reducing the fiber contact area and extending the heat conduction path, thereby effectively suppressing solid heat conduction and heat radiation transfer. The prepared layered multi-level porous network can reduce the interlayer thermal bridging effect, extend the heat conduction path, and improve high-temperature stability, thus enhancing the high-temperature thermal insulation performance of aerogels.

[0018] The ceramic nanofiber aerogel prepared by this invention has a bulk density of 5~40 mg / cm³. 3With a thermal conductivity of 0.025~0.050 W / (m·K), it exhibits excellent high-temperature insulation performance. After 100 compressions, the aerogel has a rebound rate of up to >99%. Furthermore, the aerogel possesses a continuous and uniform porous framework network with an intact framework structure, effectively resisting structural collapse. It is expected to find wide application in fields such as high-temperature insulation, adsorption and separation, and catalyst support. Attached Figure Description

[0019] Figure 1 This is a SEM image of the ceramic nanofiber aerogel in Example 1; Figure 2 Here is a SEM image of the ceramic nanofiber aerogel in Example 2; Figure 3 Here is a SEM image of the ceramic nanofiber aerogel in Example 3; Figure 4 The compressive stress-strain curve of the aerogel formed by stacking ceramic nanofiber membranes in Comparative Example 1 is shown. Figure 5 The compressive stress-strain curve of the ceramic nanofiber aerogel in Example 1 is shown. Figure 6 An optical photograph of the silicon-aluminum ceramic fiber membrane precursor obtained by electrospinning in Example 1; Figure 7 An optical photograph of the silicon-aluminum ceramic fiber membrane precursor obtained by electrospinning in Comparative Example 1; Figure 8 The image shows the TG curve of the ceramic nanofiber aerogel in Example 1. Figure 9 This is a frontal infrared photograph of the ceramic nanofiber aerogel in Example 1 heated by a butane spray gun; Figure 10 The image shows the back of the ceramic nanofiber aerogel from Example 1 after it has been heated with a butane spray gun for 600 seconds. Detailed Implementation

[0020] In this invention, unless otherwise specified, the raw materials or reagents required for preparation are all commercially available products well known to those skilled in the art.

[0021] This invention provides a method for preparing ceramic nanofiber aerogel materials, comprising the following steps: Inorganic source, polymer, pH adjuster and solvent are mixed to obtain spinning precursor solution; The spinning precursor solution was electrospinned to obtain a ceramic fiber membrane precursor. The ceramic fiber membrane precursor is calcined to obtain a three-dimensional ceramic fiber membrane; Multiple three-dimensional ceramic fiber membranes are stacked layer by layer, and the resulting layered stack is impregnated in an adhesive sol to obtain a multilayer composite fiber membrane. The multilayer composite fiber membrane was pre-frozen and then freeze-dried under vacuum to obtain cross-linked ceramic nanofiber aerogel. The cross-linked ceramic nanofiber aerogel was subjected to thermal cross-linking treatment to obtain a ceramic nanofiber aerogel material.

[0022] In this invention, the inorganic source preferably includes one or more of silicon, aluminum, zirconium, titanium, hafnium, yttrium and lanthanum.

[0023] In this invention, the silicon source preferably includes tetraethyl orthosilicate or polymethylhydrosiloxane; the aluminum source preferably includes aluminum nitrate, aluminum chloride, aluminum isopropoxide, or aluminum acetylacetonate; the zirconium source preferably includes zirconium acetate, zirconium chloride, zirconium propoxide, or zirconium butoxide; the titanium source preferably includes tetrabutyl titanate, isopropyl titanate, tetraethyl titanate, or titanium oxysulfate; the hafnium source preferably includes hafnium acetylacetonate, hafnium butoxide, hafnium tetrachloride, or hafnium oxychloride; the yttrium source preferably includes yttrium nitrate hexahydrate, yttrium acetate tetrahydrate, or yttrium acetylacetonate; and the lanthanum source preferably includes lanthanum acetylacetonate, lanthanum oxide, lanthanum chloride, lanthanum nitrate, or lanthanum acetate. When the inorganic source is two or more of the above, this invention does not have a special limitation on the ratio of different types of inorganic sources, and any ratio is acceptable.

[0024] In this invention, the polymer preferably includes one or more of polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), and polyethylene oxide (PEO); when the polymer is two or more of the above, this invention does not have a special limitation on the ratio of different types of polymers, and any ratio is acceptable. This invention utilizes polymers as spinning aids.

[0025] In this invention, the mass ratio of the inorganic source to the solvent is (7~32):(30~36), more preferably (10~20):(32~35), and the mass ratio of the polymer to the total mass of the inorganic source, pH adjuster and solvent is 0.5~4:50, more preferably 0.75~3:50, and even more preferably 1~2:50.

[0026] In this invention, the pH adjuster preferably includes oxalic acid and / or acetic acid; the amount of the pH adjuster preferably makes the pH of the spinning precursor solution reach 2.6 to 2.8, more preferably 2.7.

[0027] In this invention, the solvent preferably includes one or more of water, methanol, ethanol, and isopropanol; when the solvent is two or more of the above, this invention does not have a special limitation on the ratio of different types of solvents, and any ratio is acceptable. This invention does not have a special limitation on the amount of solvent used; it can be adjusted according to requirements to ensure uniform mixing of the materials.

[0028] In this invention, the inorganic source is preferably mixed with a pH adjuster and a solvent, stirred at room temperature for 5-10 hours, and then a polymer is added to the resulting inorganic solution. The mixture is stirred at room temperature for at least 6 hours (more preferably 12 hours) to obtain a spinning precursor solution.

[0029] In this invention, the spinning precursor solution is preferably injected into the syringe of the electrospinning equipment, and a three-dimensional fluffy ceramic fiber membrane precursor is produced by electrospinning.

[0030] In this invention, the preferred parameters for electrospinning include: a spinning temperature of 20-30°C, more preferably 22-25°C; a spinning solution feed rate of 0.5-1.5 mL / h, more preferably 1 mL / h; a spinning voltage of 12-30 kV, more preferably 18-25 kV, and even more preferably 22-23 kV; a distance from the spinning needle to the receiving plate of 10-30 cm, more preferably 13-20 cm, and even more preferably 15-18 cm; and a humidity of 30%-45%, more preferably 35-40%.

[0031] After electrospinning, the present invention preferably exposes the ceramic fiber membrane precursor to air for 24 hours to allow the solvent to evaporate before calcination.

[0032] In this invention, the calcination temperature is preferably 600~1100℃, more preferably 800~1000℃, the calcination time is preferably 1~10h, more preferably 2~6h, and the heating rate is preferably 2~5℃ / min, more preferably 3~5℃ / min. This invention removes polymers through calcination to obtain inorganic ceramic nanofiber membranes.

[0033] In this invention, the three-dimensional ceramic fiber membrane is preferably cut into the desired shape, and then multiple three-dimensional ceramic fiber membranes are stacked layer by layer in a mold to form a layered stack; the layered stack is then immersed in an adhesive sol to allow the sol to fully wet the gaps between the fiber layers.

[0034] In this invention, the number of layers of the three-dimensional ceramic fiber membrane stacked sequentially is preferably 1 to 5, more preferably 3 to 4. This invention does not impose any special limitations on the shape and size of the three-dimensional ceramic fiber membrane; adjustments can be made according to requirements.

[0035] In this invention, the binder sol preferably includes one or more of silica sol, aluminum sol and aluminum borosilicate sol, and the concentration of the binder sol is preferably 1~10wt%, more preferably 1~2.5wt%, and even more preferably 1.5~2wt%.

[0036] In this invention, the preferred method for preparing the aluminum borosilicate sol is as follows: tetraethyl orthosilicate, boric acid, aluminum chloride and deionized water are mixed in a mass ratio of 1.52:0.02:0.39:20 and stirred at room temperature for 4 hours to obtain a mother liquor. Water and the mother liquor are then mixed in different proportions to obtain an aluminum borosilicate sol of the desired concentration.

[0037] In this invention, the impregnation treatment preferably employs a vacuum-assisted impregnation method. The conditions for the impregnation treatment preferably include: a vacuum degree of -0.05 to -0.09 MPa, more preferably -0.06 to -0.08 MPa, and an impregnation time of 0.5 to 3 hours, more preferably 1 to 2 hours. This invention allows the adhesive to penetrate the fiber interior through the impregnation treatment, forming connection nodes at the fiber intersections.

[0038] In this invention, the pre-freezing temperature is preferably -50 to -196°C, more preferably -80 to -150°C, and the time is preferably 5 min to 2 h, more preferably 30 to 90 min; the vacuum freeze-drying temperature is preferably -50 to -80°C, more preferably -60 to -80°C, and the time is preferably 30 to 50 h, more preferably 38 to 40 h. This invention uses pre-freezing to transform the solvent in the binder into solid ice crystals, fixing the nanofiber skeleton in situ. Then, vacuum freeze-drying removes the solidified solvent while maintaining the original spatial structure of the fibers, resulting in a ceramic nanofiber aerogel with bonded and fixed fiber intersections.

[0039] In this invention, the temperature of the thermal crosslinking treatment is preferably 600~1100℃, more preferably 800~1000℃; the time is preferably 1~10h, more preferably 1~5h; and the heating rate is 5℃ / min. This invention promotes the inorganicization and network curing of the binder through thermal crosslinking treatment, enabling the binder to form stable connection nodes between adjacent ceramic nanofibers, thereby improving the structural integrity, mechanical strength, and high-temperature stability of the aerogel.

[0040] This invention provides a ceramic nanofiber aerogel material prepared by the preparation method described in the above technical solution.

[0041] This invention provides the application of the ceramic nanofiber aerogel material described above in the fields of high-temperature insulation, adsorption and separation, or catalyst support. This invention does not impose any particular limitation on the methods used in these applications; methods well-known in the art can be followed.

[0042] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0043] Unless otherwise specified, the experimental methods described in the various embodiments of this invention are conventional methods; unless otherwise specified, the raw materials used are all commercially available products, and the proportions are all by mass percentage.

[0044] In the following examples, the preparation method of aluminum borosilicate sol is as follows: tetraethyl orthosilicate, boric acid, aluminum chloride and deionized water are mixed in a mass ratio of 1.52:0.02:0.39:20 and stirred at room temperature for 4 hours to obtain a mother liquor. Water and the mother liquor are mixed in different proportions to obtain aluminum borosilicate sols of different concentrations (1wt%, 1.5wt%, 2wt%, 2.5wt%).

[0045] Example 1

[0046] (1) Tetraethyl orthosilicate, aluminum nitrate, aluminum isopropoxide, oxalic acid (solid), anhydrous ethanol and deionized water were mixed in a mass ratio of 7:5:20:0.1:6:30 and stirred for 10 h. Polyoxyethylene was added as a spinning aid in a mass ratio of 0.5:50 to the obtained mixture. The mixture was stirred at room temperature for 12 h to obtain a spinning precursor solution with pH=2.6. The spinning precursor solution was injected into the syringe of the electrospinning equipment for electrospinning: the spinning temperature was 25℃, the propulsion rate of the spinning solution was 1 mL / h, the spinning voltage was 18 kV, the distance from the spinning needle to the receiving plate was 15 cm, and the humidity was 30% to obtain a silicon-aluminum ceramic fiber membrane precursor. (2) The obtained silicon-aluminum ceramic fiber membrane precursor was exposed to air for 24 hours to allow the solvent to evaporate, and then calcined. The calcination atmosphere was air, the temperature was 1100℃, the heating rate was 5℃ / min, and the calcination time was 2 hours to obtain a three-dimensional ceramic fiber membrane. (3) Cut the three-dimensional ceramic fiber membrane obtained in step (2) into square blocks of 20mm×20mm, take 3 fiber membranes and stack them layer by layer in a square mold to form a layered stack. Prepare an aluminum borosilicate sol with a concentration of 1wt%, immerse the layered stack in the aluminum borosilicate sol, and impregnate it for 1h under a vacuum of -0.05MPa to obtain a multilayer composite fiber membrane. (4) The obtained multilayer composite fiber membrane was pre-frozen at -80℃ for 30 min, and then vacuum freeze-dried at -80℃ for 40 h to obtain cross-linked ceramic nanofiber aerogel; (5) The obtained cross-linked ceramic nanofiber aerogel was subjected to high-temperature heat treatment in an air atmosphere at a temperature of 800℃, a heating rate of 5℃ / min, and a calcination time of 1h to obtain aluminum-based ceramic nanofiber aerogel.

[0047] Example 2

[0048] (1) Tetraethyl orthosilicate, zirconium acetate, oxalic acid, anhydrous ethanol and deionized water were mixed in a mass ratio of 7:3:0.1:6:30 and stirred for 10 h. Polyvinyl alcohol with a mass ratio of 1:50 to the obtained mixture was added as a spinning aid and stirred at room temperature for 12 h to obtain a spinning precursor solution with pH=2.6. The spinning precursor solution was injected into the syringe of the electrospinning equipment for electrospinning: the spinning temperature was 25℃, the propulsion rate of the spinning solution was 1 mL / h, the spinning voltage was 22 kV, the distance from the spinning needle to the receiving plate was 15 cm, and the humidity was 35% to obtain a ceramic fiber membrane precursor. (2) The obtained ceramic fiber membrane precursor was exposed to air for 24 hours to allow the solvent to evaporate fully, and then calcined at high temperature. The high-temperature calcination atmosphere was air, the temperature was 800℃, the heating rate was 5℃ / min, and the calcination time was 2 hours to obtain a three-dimensional ceramic fiber membrane. (3) Cut the three-dimensional ceramic fiber membrane obtained in (2) into square blocks of 20mm×20mm, take 3 fiber membranes and stack them layer by layer in a square mold to form a layered stack; prepare an aluminum borosilicate sol with a concentration of 1.5wt%, immerse the layered stack in the aluminum borosilicate sol, and impregnate for 1h under a vacuum of -0.05MPa to obtain a multilayer composite fiber membrane; (4) The obtained multilayer composite fiber membrane was pre-frozen at -80℃ for 30 min, and then vacuum freeze-dried at -80℃ for 38 h to obtain cross-linked ceramic nanofiber aerogel; (5) The obtained cross-linked ceramic nanofiber aerogel was subjected to high-temperature heat treatment. The high-temperature heat treatment atmosphere was air, the temperature was 800℃, the heating rate was 5℃ / min, and the calcination time was 1h to obtain zirconium-based ceramic nanofiber aerogel.

[0049] Example 3

[0050] (1) Tetraethyl orthosilicate, yttrium nitrate, hafnium acetylacetonate, acetic acid and methanol were mixed in a mass ratio of 3.5:2:5.5:0.1:30 and stirred for 10 h. Polyoxyethylene was added as a spinning aid in a mass ratio of 0.75:50 to the obtained mixture. The mixture was stirred at room temperature for 6 h to obtain a spinning precursor solution with pH=2.7. The spinning precursor solution was injected into the syringe of the electrospinning equipment for electrospinning: the spinning temperature was 22℃, the propulsion rate of the spinning solution was 1 mL / h, the spinning voltage was 25 kV, the distance from the spinning needle to the receiving plate was 18 cm, and the humidity was 45% to obtain a ceramic fiber membrane precursor. (2) The obtained ceramic fiber membrane precursor was exposed to air for 24 hours to allow the solvent to evaporate fully, and then calcined at high temperature. The high-temperature calcination atmosphere was air, the temperature was 1100℃, the heating rate was 3℃ / min, and the calcination time was 2 hours to obtain a three-dimensional ceramic fiber membrane. (3) Cut the three-dimensional ceramic fiber membrane obtained in (2) into square blocks of 20mm×20mm, take 3 fiber membranes and stack them layer by layer in a square mold to form a layered stack; prepare an aluminum borosilicate sol with a concentration of 2wt%, immerse the layered stack in the aluminum borosilicate sol, and impregnate for 1h under a vacuum of -0.05MPa to obtain a multilayer composite fiber membrane; (4) The obtained multilayer composite fiber membrane was pre-frozen at -80℃ for 30 min, and then vacuum freeze-dried at -80℃ for 30 h to obtain cross-linked ceramic nanofiber aerogel; (5) The obtained cross-linked ceramic nanofiber aerogel was subjected to high-temperature heat treatment. The high-temperature heat treatment atmosphere was air, the temperature was 800℃, the heating rate was 5℃ / min, and the calcination time was 1h to obtain hafnium-based ceramic nanofiber aerogel product.

[0051] Example 4

[0052] (1) Tetrabutyl tetrasilicate, tetrabutyl titanate, glacial acetic acid and anhydrous ethanol were mixed in a mass ratio of 4:3:2:30 and stirred for 5 h. Polyvinylpyrrolidone in a mass ratio of 4:50 to the obtained mixture was added as a spinning aid and stirred at room temperature for 6 h to obtain a spinning precursor solution with pH=2.8. The spinning precursor solution was injected into the syringe of the electrospinning equipment for electrospinning: the spinning temperature was 22℃, the propulsion rate of the spinning solution was 1 mL / h, the spinning voltage was 23 kV, the distance from the spinning needle to the receiving plate was 13 cm, and the humidity was 40% to obtain a ceramic fiber membrane precursor. (2) The obtained ceramic fiber membrane precursor was exposed to air for 24 hours to allow the solvent to evaporate completely, and then calcined at high temperature. The high-temperature calcination atmosphere was air, the temperature was 600℃, the heating rate was 2℃ / min, and the calcination time was 2 hours to obtain a three-dimensional ceramic fiber membrane. (3) Cut the three-dimensional ceramic fiber membrane obtained in (2) into square blocks of 20mm×20mm, take 5 fiber membranes and stack them layer by layer in a square mold to form a layered stack; prepare an aluminum borosilicate sol with a concentration of 2.5wt%, immerse the layered stack in the aluminum borosilicate sol, and impregnate for 1h under a vacuum of -0.05MPa to obtain a multilayer composite fiber membrane; (4) The obtained multilayer composite fiber membrane was pre-frozen at -80℃ for 30 min, and then vacuum freeze-dried at -80℃ for 30 h to obtain cross-linked ceramic nanofiber aerogel; (5) The obtained cross-linked ceramic nanofiber aerogel was subjected to high-temperature heat treatment. The high-temperature heat treatment atmosphere was air, the temperature was 600℃, the heating rate was 5℃ / min, and the calcination time was 1h to obtain titanium-based ceramic nanofiber aerogel.

[0053] Comparative Example 1 (Change in spinning solution ratio)

[0054] (1) Tetraethyl orthosilicate, aluminum nitrate, aluminum isopropoxide, oxalic acid (solid), anhydrous ethanol and deionized water were mixed in a mass ratio of 7:3.5:22.5:0.1:3:25 and stirred for 10 h. Polyoxyethylene was added as a spinning aid in a mass ratio of 0.5:50 to the obtained mixture and stirred at room temperature for 12 h to obtain a spinning precursor solution. The spinning precursor solution was injected into the syringe of the electrospinning equipment for electrospinning: the spinning temperature was 25℃, the propulsion rate of the spinning solution was 1 mL / h, the spinning voltage was 18 kV, the distance from the spinning needle to the receiving plate was 18 cm, and the humidity was 30% to obtain a silicon-aluminum ceramic fiber membrane precursor. Steps (2) to (5) are the same as in Example 1, and aluminum-based ceramic nanofiber aerogel is obtained.

[0055] Structural characterization and performance testing

[0056] Figure 1 This is a SEM image of the ceramic nanofiber aerogel from Example 1; by Figure 1 It can be seen that there is obvious cross-linking between fibers, while the material still retains a rich porous structure.

[0057] Figure 2 This is a SEM image of the ceramic nanofiber aerogel from Example 2; by Figure 2 It can be seen that there is obvious cross-linking between fibers, while the material still retains a rich porous structure.

[0058] Figure 3 This is a SEM image of the ceramic nanofiber aerogel from Example 3; by Figure 3 It can be seen that there is obvious cross-linking between fibers, while the material still retains a rich porous structure.

[0059] Figure 4 The figure shows the compressive stress-strain curves of the aerogel formed by the stacking of ceramic nanofiber membranes in Comparative Example 1; from Figure 4 It can be seen that aerogel has poor resilience, and its deformation exceeds 15% after 50 compression cycles.

[0060] Figure 5 The compressive stress-strain curve of the ceramic nanofiber aerogel in Example 1 is shown below; Figure 5 It can be seen that aerogel has good resilience properties, and the deformation is still less than 1% after 100 compression cycles.

[0061] Figure 6 An optical photograph of the silicon-aluminum ceramic fiber membrane precursor obtained by electrospinning in Example 1; by Figure 6 It can be seen that the fiber membrane has a fluffy three-dimensional structure.

[0062] Figure 7An optical photograph of the silicon-aluminum ceramic fiber membrane precursor obtained by electrospinning in Comparative Example 1; by Figure 7 It can be seen that the fiber membrane does not have a fluffy structure.

[0063] Figure 8 The image shows the TG curve of the ceramic nanofiber aerogel in Example 1; from Figure 8 It can be seen that the aerogel does not show significant mass change in the range of room temperature to 800℃, and has good high temperature resistance.

[0064] Figure 9 This is a frontal infrared photograph of the ceramic nanofiber aerogel in Example 1 heated by a butane spray gun; (The image is from...) Figure 9 It can be seen that the highest temperature on the front side of the aerogel is 692.1℃.

[0065] Figure 10 This is a back infrared photograph of the ceramic nanofiber aerogel in Example 1 after being heated with a butane spray gun for 600 seconds; (The image is from...) Figure 10 It can be seen that the center temperature on the back of the aerogel is only 175.2℃, indicating that it has excellent high-temperature insulation performance.

[0066] Compression cycle tests were conducted using a universal testing machine. The results showed that after 100 cycles of compression testing, the aerogel sample prepared in Example 1 exhibited a compression rebound rate >99% and a bulk density of 10 mg / cm³. 3 The sample has a thermal conductivity of 0.026 W / (m·K). Combined with the material's inherent high-temperature resistance, it has broad applications in catalysis, heat insulation, and other fields.

[0067] The aerogel sample prepared in Example 2, after 100 cycles of compression testing, showed a compression rebound rate >90% and a bulk density of 15 mg / cm³. 3 The sample has a thermal conductivity of 0.0265 W / (m·K). Combined with the material's inherent high-temperature resistance, it has broad applications in catalysis, heat insulation, and other fields.

[0068] The aerogel sample prepared in Example 3, after 100 cycles of compression testing, showed a compression rebound rate >92% and a bulk density of 20 mg / cm³. 3 The sample has a thermal conductivity of 0.038 W / (m·K). Combined with the material's inherent high-temperature resistance, it has broad applications in catalysis, heat insulation, and other fields.

[0069] The aerogel sample prepared in Example 4, after 100 cycles of compression testing, showed a compression rebound rate >85% and a sample bulk density of 25 mg / cm³. 3 The sample has a thermal conductivity of 0.026 W / (m·K). Combined with the material's inherent high-temperature resistance, it has broad applications in catalysis, heat insulation, and other fields.

[0070] The aerogel sample prepared in Comparative Example 1 showed a compression rebound rate of <85% after 100 cycles of compression testing, and the sample bulk density was 10 mg / cm³. 3 The thermal conductivity of the sample was 0.029 W / (m·K), indicating that Comparative Example 1 could not achieve a synergistic improvement in mechanical and thermal properties. This is because the electrospinning in Comparative Example 1 prepared a dense nanofiber membrane (without a fluffy structure). The aerogel formed by stacking this fiber membrane has a discontinuous load transfer path due to the tight fiber arrangement, low interlayer interlocking degree, and insufficient three-dimensional connection. During the compression process, interlayer slippage and local stress concentration are prone to occur, making it difficult for the material to achieve effective energy dissipation and stress release, thus exhibiting poor elastic recovery performance.

[0071] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a ceramic nanofiber aerogel material, characterized in that, Includes the following steps: Inorganic source, polymer, pH adjuster and solvent are mixed to obtain spinning precursor solution; The spinning precursor solution was electrospinned to obtain a ceramic fiber membrane precursor. The ceramic fiber membrane precursor is calcined to obtain a three-dimensional ceramic fiber membrane; Multiple three-dimensional ceramic fiber membranes are stacked layer by layer, and the resulting layered stack is impregnated in an adhesive sol to obtain a multilayer composite fiber membrane. The multilayer composite fiber membrane was pre-frozen and then freeze-dried under vacuum to obtain cross-linked ceramic nanofiber aerogel. The cross-linked ceramic nanofiber aerogel was subjected to thermal cross-linking treatment to obtain a ceramic nanofiber aerogel material.

2. The preparation method according to claim 1, characterized in that, The inorganic source includes one or more of the following: silicon source, aluminum source, zirconium source, titanium source, hafnium source, yttrium source, and lanthanum source; The polymer includes one or more of polyvinylpyrrolidone, polyvinyl alcohol, and polyethylene oxide; the mass ratio of the inorganic source to the solvent is (7~32):(30~36), and the mass ratio of the polymer to the total mass of the inorganic source, pH adjuster, and solvent is 0.5~4:

50.

3. The preparation method according to claim 2, characterized in that, The silicon source includes tetraethyl orthosilicate or polymethylhydrosiloxane; the aluminum source includes aluminum nitrate, aluminum chloride, aluminum isopropoxide, or aluminum acetylacetonate; the zirconium source includes zirconium acetate, zirconium chloride, zirconium propoxide, or zirconium butoxide; the titanium source includes tetrabutyl titanate, isopropyl titanate, tetraethyl titanate, or titanium oxysulfate; the hafnium source includes hafnium acetylacetonate, hafnium butoxide, hafnium tetrachloride, or hafnium oxychloride; the yttrium source includes yttrium nitrate hexahydrate, yttrium acetate tetrahydrate, or yttrium acetylacetonate; and the lanthanum source includes lanthanum acetylacetonate, lanthanum oxide, lanthanum chloride, lanthanum nitrate, or lanthanum acetate.

4. The preparation method according to claim 1, characterized in that, The pH adjuster includes oxalic acid and / or acetic acid; the solvent includes one or more of water, methanol, ethanol and isopropanol; the pH value of the spinning precursor solution is 2.6~2.8; The parameters for electrospinning include: spinning temperature of 20~30℃, spinning solution feed rate of 0.5~1.5mL / h, spinning voltage of 12~30kV, distance from spinning needle to receiving plate of 10~30cm, and humidity of 30%~45%.

5. The preparation method according to claim 1, characterized in that, The calcination and thermal crosslinking treatments are performed at temperatures ranging from 600 to 1100°C and for periods ranging from 1 to 10 hours.

6. The preparation method according to claim 1, characterized in that, The three-dimensional ceramic fiber membrane is stacked in layers of 1 to 5.

7. The preparation method according to claim 1, characterized in that, The binder sol includes one or more of silica sol, aluminum sol, and aluminum borosilicate sol, and the concentration of the binder sol is 1~10 wt%. The impregnation treatment employs a vacuum-assisted impregnation method, and the conditions for the impregnation treatment include: a vacuum degree of -0.05 to -0.09 MPa and an impregnation time of 0.5 to 3 hours.

8. The preparation method according to claim 1, characterized in that, The pre-freezing temperature is -50 to -196℃, and the time is 5 min to 2 h; the vacuum freeze-drying temperature is -50 to -80℃, and the time is 30 to 50 h.

9. The ceramic nanofiber aerogel material prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the ceramic nanofiber aerogel material of claim 9 in the fields of high-temperature insulation, adsorption and separation or catalyst support.

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