Zirconia-based fiber membrane and method for preparing the same, hydrophobically modified zirconia-based fiber membrane and method for preparing and using the same

Abstract

The application belongs to the field of flexible fiber preparation, and provides a zirconia-based fiber membrane and a preparation method thereof, a hydrophobically modified zirconia-based fiber membrane and a preparation method and application thereof. The preparation method of the zirconia-based fiber membrane comprises the following steps: (1) mixing an A sol containing a zirconia precursor-lanthanum salt, a B sol containing an aluminum oxide precursor and a template agent to obtain a spinning solution; (2) performing airflow-assisted electrospinning on the spinning solution to obtain a zirconia-based precursor nanofiber membrane; and (3) drying and calcining the zirconia-based precursor nanofiber membrane to obtain a zirconia-based fiber membrane. The method is simple to operate, and the obtained zirconia-based fiber membrane has the characteristics of high thermal stability.

Description

Technical Field

[0001] This invention relates to the field of flexible fiber preparation, specifically to a zirconia-based fiber membrane and its preparation method, a hydrophobically modified zirconia-based fiber membrane and its preparation method and application. Background Technology

[0002] Nanotechnology, as an emerging technology, can improve the properties of conventional materials when introduced into the field of materials science. Electrospinning is widely used due to its ease of operation, wide applicability, and high productivity. In recent years, research on the flexibility of electrospun inorganic nanofibers has been particularly active. Zirconia, as a polycrystalline refractory fiber material, possesses advantages such as high-temperature chemical stability, corrosion resistance, oxidation resistance, thermal shock resistance, non-volatile nature, and non-polluting properties, and is used in fields such as temperature resistance and flame retardancy.

[0003] However, current zirconia fibers are composed of zirconia microparticles with fiber diameters in the micrometer range. They come in various forms, including short fibers, fiber mats, fiber fabrics, fiber boards, fiber tubes, and shaped products. However, these zirconia fibers suffer from problems such as poor flexibility, low strength, poor mechanical processability, and poor hydrophobicity.

[0004] Therefore, current zirconia-based fiber membranes still need improvement. Summary of the Invention

[0005] The present invention aims to at least partially solve one of the technical problems in the related art.

[0006] In a first aspect, the present invention provides a method for preparing a zirconia-based fiber membrane, comprising the following steps:

[0007] (1) A sol containing zirconium oxide precursor-lanthanum salt, B sol containing alumina precursor and template agent are first mixed to obtain spinning solution;

[0008] (2) Electrospinning the spinning solution to obtain a zirconia-based precursor nanofiber membrane.

[0009] (3) The zirconia-based precursor nanofiber membrane is dried and calcined to obtain a zirconia-based fiber membrane.

[0010] The method of the present invention is simple to operate, and the obtained zirconia-based fiber membrane has good surface flatness, uniform and continuous distribution, no surface pore defects, and uniform zirconia grain distribution, thereby giving the fiber membrane good temperature resistance, thermal insulation and comprehensive mechanical properties.

[0011] According to an embodiment of the present invention, the first mixing is carried out at room temperature under stirring conditions for 5-12 hours.

[0012] According to an embodiment of the present invention, the amounts of sol A and sol B are such that the alumina content in the zirconia-based fiber membrane is 2.5-20 mol%.

[0013] According to an embodiment of the present invention, the content of the template agent in the spinning solution is 0.4-1 wt%.

[0014] According to an embodiment of the present invention, step (1) further includes:

[0015] Lanthanum salt and zirconium salt are mixed a second time to form the A sol containing zirconium oxide precursor-lanthanum salt;

[0016] Inorganic aluminum salt, aluminum isopropoxide, and water are mixed in a third step to form the B sol containing the alumina precursor.

[0017] According to an embodiment of the present invention, in the A sol, the molar ratio of lanthanum salt to zirconium salt is (0.04-0.2):1.

[0018] According to an embodiment of the present invention, in the B sol, the molar ratio of inorganic aluminum salt, aluminum isopropoxide and water is 1:(2-5):(25-100).

[0019] According to an embodiment of the present invention, the third mixing includes a first stage and a second stage performed sequentially. The first stage involves stirring the inorganic aluminum salt, aluminum isopropoxide, and water at room temperature for 3-8 hours. The second stage involves heating and refluxing for 1-3 hours.

[0020] According to embodiments of the present invention, the lanthanum salt includes at least one of lanthanum nitrate, lanthanum chloride, and lanthanum carbonate.

[0021] According to embodiments of the present invention, the zirconium salt includes at least one of zirconium acetate, zirconium oxychloride, and basic zirconium carbonate.

[0022] According to an embodiment of the present invention, the inorganic aluminum salt includes at least one of aluminum nitrate, aluminum chloride, aluminum silicate, and aluminum sulfate.

[0023] According to embodiments of the present invention, the template agent includes at least one of PEO, PVA, PVB and PAN.

[0024] According to an embodiment of the present invention, the airflow-assisted electrospinning includes: inputting the spinning solution into the spinneret of the electrospinning device at a flow rate of 1-12 mL / h, controlling the distance between the receiving device and the spinneret at 15-20 cm, and connecting the spinneret to a high-voltage power supply and controlling the voltage at 10-30 kV to perform electrospinning.

[0025] According to an embodiment of the present invention, the drying is vacuum drying, and the drying temperature is 70-100°C.

[0026] According to an embodiment of the present invention, the calcination includes: gradually increasing the temperature from room temperature to 800-1000°C at a heating rate of 3-8°C / min, and holding at that temperature for 1-3 hours.

[0027] In a second aspect, the present invention provides a zirconia-based fiber membrane prepared according to the first aspect. The zirconia-based fiber membrane exhibits good surface smoothness, uniform and continuous distribution, and no surface pores or defects. The zirconia grains are uniformly distributed, resulting in good overall mechanical properties and thermal insulation performance. This fiber membrane can be used as a reinforcing material, a high-temperature catalyst carrier, a high-temperature insulation material, and a filter material, and is particularly suitable for use in fire-fighting fabrics.

[0028] In a third aspect, the present invention provides a method for preparing a hydrophobically modified zirconia-based fiber membrane, comprising depositing a hydrophobic layer on the surface of a zirconia-based fiber membrane prepared in the second aspect to obtain a hydrophobically modified zirconia-based fiber membrane, wherein the hydrophobic layer comprises polydimethylsiloxane. This method is simple to operate, and the hydrophobic layer uniformly covers the surface of the zirconia-based fiber membrane, isolating the zirconia-based fiber membrane from water to form an insulating interface, thereby improving the hydrophobic properties of the zirconia-based fiber membrane.

[0029] According to an embodiment of the present invention, the deposition includes: immersing the zirconia-based fiber membrane in an alcoholic solution of polydimethylsiloxane and drying it to form a hydrophobic layer on the surface of the zirconia-based fiber membrane.

[0030] According to an embodiment of the present invention, the thickness of the hydrophobic layer is 2-10 nm.

[0031] According to an embodiment of the present invention, the impregnation is ultrasonic impregnation, and the ultrasonic impregnation time is 5-15 minutes;

[0032] According to an embodiment of the present invention, the drying temperature is 70-90°C and the time is 0.5-3 hours.

[0033] In a fourth aspect, the present invention provides a hydrophobically modified zirconia-based fiber membrane prepared by the method described in the third aspect. This hydrophobically modified zirconia-based fiber membrane exhibits good hydrophobicity and high-temperature resistance, and can be used in fields such as high-temperature protection and chemical protection.

[0034] In a fifth aspect, the present invention proposes the application of the hydrophobically modified zirconia-based fiber membrane of the fourth aspect in fire-fighting protective clothing. This fire-fighting protective clothing exhibits good thermal protection performance. Attached Figure Description

[0035] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0036] Figure 1 Spinning equipment for electrospinning, as described in some embodiments;

[0037] Figure 2 Photographs of sol A, sol B, and spinning solution from Example 1;

[0038] Figure 3 A photograph of the zirconia-based precursor nanofiber membrane of Example 1;

[0039] Figure 4 A photograph of the zirconia-based fiber membrane of Example 1;

[0040] Figure 5 This is a schematic diagram illustrating the process of preparing hydrophobically modified zirconia-based fiber membranes using impregnation in some embodiments;

[0041] Figure 6 SEM image of the zirconium oxide precursor nanofiber membrane of Comparative Example 1.

[0042] Figure 7 SEM image and EDS elemental analysis diagram of the zirconia fiber membrane in Comparative Example 1;

[0043] Figure 8 Photograph of the zirconia fiber membrane in Comparative Example 1;

[0044] Figure 9 The image shows the XRD pattern of the zirconia fiber membrane in Comparative Example 1.

[0045] Figure 10 Here is a SEM image of the zirconia-based fiber membrane from Example 1;

[0046] Figure 11 Here is the EDS elemental analysis diagram of the zirconia-based fiber membrane of Example 1;

[0047] Figure 12 This is a diagram illustrating the flexibility of the zirconia-based fiber membrane in Example 1;

[0048] Figure 13 XRD patterns of the zirconia-based fiber membranes of Examples 1 and 7-11;

[0049] Figure 14 Here is an HR-TEM image of the zirconia-based fiber membrane from Example 1;

[0050] Figure 15 The tensile stress curve of the zirconia-based fiber membrane in Example 1 is shown.

[0051] Figure 16 This is a diagram illustrating the combustion experiment of an aramid fiber (the heat insulation layer used in commercial fire suits);

[0052] Figure 17This is a diagram illustrating the combustion experiment process of the zirconia-based fiber membrane in Example 1;

[0053] Figure 18 This is a diagram illustrating the hydrophobicity of the hydrophobic modified zirconia-based fiber membrane of Example 1;

[0054] Figure 19 The hydrophobic angle diagram is shown for the hydrophobic modified zirconia-based fiber membrane of Example 1;

[0055] Figure 20 This is a SEM image of the hydrophobically modified zirconia-based fiber membrane from Example 1.

[0056] Figure 21 EDS elemental analysis diagram of the hydrophobically modified zirconia-based fiber membrane of Example 1;

[0057] Figure 22 The graph shows the hydrophobicity analysis of the hydrophobic modified zirconia-based fiber membrane of Example 1 at different temperatures.

[0058] Figure 23 The graph shows the relationship between the thermal conductivity and alumina content of the zirconia-based fiber membranes in Examples 1-6.

[0059] Figure 24 This is a diagram showing the material composition of fire-fighting protective clothing.

[0060] Figure 25 The heat flow curve and Stoll curve of fire-fighting protective clothing over time under convective and radiative heat sources;

[0061] Figure 26 A macroscopic view of the fire protective suit after the TPP test;

[0062] Figure 27 This diagram illustrates the thermal protection performance of fire-fighting protective clothing after being burned with a butane torch for different durations. Detailed Implementation

[0063] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0064] In a first aspect, the present invention provides a method for preparing a zirconia-based fiber membrane, comprising the following steps:

[0065] (1) A sol containing zirconium oxide precursor-lanthanum salt, B sol containing alumina precursor and template agent are first mixed to obtain spinning solution;

[0066] (2) The spinning solution is subjected to airflow-assisted electrospinning to obtain a zirconia-based precursor nanofiber membrane.

[0067] (3) The zirconia-based precursor nanofiber membrane is dried and calcined to obtain a zirconia-based fiber membrane.

[0068] The method of this invention is simple to operate, and the resulting zirconia-based fiber membrane has good surface flatness, uniform and continuous distribution, and no surface pore defects. The zirconia grains are also uniformly distributed, resulting in good high-temperature insulation properties and excellent mechanical properties, including flexibility. This fiber membrane can be used as a reinforcing material, a high-temperature catalyst carrier, a high-temperature insulation material, and a filtration material.

[0069] The method of this invention involves doping a lanthanum salt (such as lanthanum nitrate) into a zirconia precursor sol, followed by high-temperature calcination to form lanthanum oxide-doped zirconia fibers. Doping the zirconia fibers with a small amount of lanthanum oxide can stabilize the phase transformation of zirconia by forming oxygen vacancies, thereby inhibiting malignant grain growth. The introduction of amorphous alumina creates a unique crystalline-amorphous coexistence structure, resulting in a stable amorphous phase surrounding the uniformly distributed nanocrystals on the zirconia-based fiber film. This forms numerous grain boundaries and phase boundaries. The mutual inhibition between the amorphous and crystalline phases during zirconia grain growth, along with the synergistic effect between the grains and the surrounding stable amorphous phase, contributes to the excellent mechanical flexibility and superior temperature resistance of the zirconia-based fiber film. Simultaneously, Al₂O₃ promotes the formation of La₂Zr₂O₇. A small amount of La₂Zr₂O₇ can inhibit malignant grain growth, improve the concentration of grain distribution and the smoothness of the fiber surface, and, under high-temperature conditions, reduce surface thermal erosion grooves, thus improving the mechanical properties of the fiber.

[0070] In step (1), a spinning solution is obtained by first mixing a sol containing zirconium oxide precursor-lanthanum salt, a sol containing alumina precursor, and a template agent.

[0071] In some embodiments, the first mixing is carried out at room temperature (15-45°C) under stirring conditions for 5-12 hours, such as 5 hours, 8 hours, 10 hours, 12 hours, etc.

[0072] In some embodiments, the amounts of sol A and sol B are such that the alumina content in the zirconia-based fiber membrane is 2.5-20 mol%, for example, 2.5 mol%, 5 mol%, 7.5 mol%, 15 mol%, 20 mol%, etc. That is, based on the molar content of alumina in the zirconia-based fiber membrane formed after calcination (in terms of Al2O3, La2O3, etc.), the content is determined. 3、 Based on the total amount of ZrO2 used, calculate the amount of A sol and B sol to be added.

[0073] In step (1), adding a template agent to the spinning solution helps to increase the viscosity and spinnability of the spinning solution. Optionally, the content of the template agent in the spinning solution is 0.4-1 wt%, such as 0.4 wt%, 0.6 wt%, 0.8 wt%, 1 wt%, etc.

[0074] In some embodiments, the template agent comprises a polymeric template agent. Optionally, the template agent comprises at least one of PEO, PVA, PVB, and PAN.

[0075] According to the present invention, the preparation of spinning solution using sol A containing zirconium oxide precursor-lanthanum salt is beneficial for the mixing of zirconium and lanthanum at the atomic level to form a single-phase sol.

[0076] In some embodiments, step (1) further includes the step of preparing the A sol: monoclinic

[0077] Lanthanum salt and zirconium salt are mixed a second time to dissolve lanthanum salt in zirconium salt, thereby obtaining sol A containing zirconium oxide precursor - lanthanum salt.

[0078] Optionally, the molar ratio of the lanthanum salt to the zirconium salt is (0.04-0.2):1, such as 0.04:1, 0.06:1, 0.1:1, 0.2:1, etc.

[0079] Alternatively, the lanthanum salt includes at least one of lanthanum nitrate, lanthanum chloride, and lanthanum carbonate.

[0080] Optionally, the zirconium salt provides a zirconium source and can also serve as a solvent to dissolve the lanthanum salt. Further, the zirconium salt includes at least one of zirconium acetate, zirconium oxychloride, and basic zirconium carbonate.

[0081] According to the present invention, the preparation of spinning solution using sol B containing alumina precursor is beneficial for the mixing of zirconium and lanthanum provided by sol A with aluminum in sol B at the atomic level to form a single-phase sol.

[0082] In some embodiments, step (1) further includes the step of preparing the B sol:

[0083] The inorganic aluminum salt, aluminum isopropoxide, and water are mixed in a third step to hydrolyze the inorganic aluminum salt and aluminum isopropoxide, forming the B sol containing the alumina precursor.

[0084] Optionally, the molar ratio of inorganic aluminum salt, aluminum isopropoxide, and water is 1:(2-5):(25-100), such as 1:2:25, 1:3:60, 1:5:80, 1:5:100, etc.

[0085] Optionally, the inorganic aluminum salt includes at least one of aluminum nitrate, aluminum chloride, aluminum silicate, and aluminum sulfate. It is understood that the inorganic aluminum salt may also be in hydrate form. For example, aluminum nitrate may be anhydrous aluminum nitrate (Al(NO)3) or aluminum nitrate nonahydrate (Al(NO3)3·9H2O).

[0086] In some embodiments, to further promote sol formation, the third mixing includes a first stage and a second stage performed sequentially.

[0087] First stage: Stir the inorganic aluminum salt, aluminum isopropoxide and water at room temperature for 3-8 hours, such as 3 hours, 5 hours, 8 hours, etc.

[0088] The second stage involves heating the product to reflux the water for 1-3 hours. High-temperature condensation during reflux promotes the complete hydrolysis of aluminum isopropoxide and aluminum salts. The reflux temperature is 70-100℃, such as 70℃, 80℃, 90℃, or 100℃.

[0089] As an example, the process for preparing the B sol includes:

[0090] At room temperature, the inorganic aluminum salt is stirred in water for 1-3 hours to allow it to hydrolyze first. Then, aluminum isopropoxide is added, and stirring is continued for 2-5 hours to allow the aluminum isopropoxide to hydrolyze. This sequential addition of inorganic aluminum salts to water allows the first hydrolyzed inorganic aluminum salt to release hydrogen ions, which promotes the hydrolysis of aluminum isopropoxide. The water is then heated to a high temperature of reflux for 1-3 hours to further promote the hydrolysis of aluminum isopropoxide and the aluminum salt.

[0091] According to the present invention, in step (2), the spinning solution is subjected to airflow-assisted electrospinning to obtain a zirconia-based precursor nanofiber membrane. Thus, during the electrospinning process, the solvent rapidly evaporates and solidifies, leaving a very small amount of solvent inside the sol. This facilitates the formation of a nanoscale zirconia-based precursor nanofiber membrane with a dense structure, thereby improving the mechanical properties and high-temperature resistance of the ceramic fiber.

[0092] In some embodiments, the airflow-assisted electrospinning specifically includes: inputting the spinning solution into the spinneret of the electrospinning equipment at a flow rate of 1-12 mL / h, controlling the distance between the receiving device and the spinneret at 15-20 cm, connecting the spinneret to a high-voltage power supply, and controlling the voltage of the high-voltage power supply at 10-30 kV to perform electrospinning.

[0093] Generally, electrospinning can be carried out at room temperature.

[0094] As an example, see reference Figure 1Spinning was performed using the Yongkang Leyue ET-2535X spinning equipment. During the spinning process, an airflow-assisted electrospinning platform was constructed. A 20mL syringe was filled with spinning solution, and a metal needle was placed at the outlet. The syringe (plastic syringe) was then fixed to the infusion and propulsion device of the electrospinning equipment. A high-voltage power supply was activated to create an electric field, generating electrostatic polarization. This caused charges to form on the surface of the droplet at the syringe needle. The increasing voltage and the eddy current effect generated by the airflow gradually overcame the electrostatic repulsion force on the droplet surface at the syringe tip, allowing it to overcome its surface tension. Under the interaction of these two forces, the droplet surface gradually transformed from a rounded outline into a Taylor cone, eventually breaking through the surface tension and generating a jet. Upon reaching the receiving device (collector), the jet was continuously stretched into fibers, forming a ZrO2-based precursor nanofiber membrane. The process allows for control of the slide speed at 50-100 cm / min, the drum speed at 30-100 rpm, the spinning solution flow rate at 1-12 mL / h, the high-voltage power supply voltage at 10-30 kV, and the receiving distance at 15-20 cm.

[0095] According to the present invention, in step (3), the zirconia-based precursor nanofiber membrane is dried and calcined to obtain a zirconia-based fiber membrane.

[0096] Optionally, the drying is vacuum drying, and the drying temperature is 70-100℃, such as 70℃, 80℃, 90℃, 100℃, etc. Furthermore, the present invention does not particularly limit the drying time, as long as the drying purpose is achieved.

[0097] In step (3), by calcining the zirconia-based precursor nanofiber membrane, on the one hand, the crystalline phase of zirconia is stabilized in the tetragonal phase, thus exhibiting better flexibility and stronger mechanical properties; on the other hand, under high temperature, the nanoscale zirconia in the zirconia-based precursor nanofiber membrane is transformed into a crystalline phase, thereby uniformly fixed in the amorphous phase of alumina, thus constructing a crystalline-amorphous multiphase composite network structure to form ceramic fibers with fewer pores and relatively dense structure.

[0098] In some embodiments, the calcination temperature is 800-1000℃, such as 800℃, 900℃, 1000℃, etc. This is conducive to the formation of tetragonal zirconia crystal phase. If the temperature is too low, the tetragonal phase may not be able to be formed; if the temperature is too high, it may lead to the malicious growth of zirconia grains, causing the zirconia-based fiber film to pulverize.

[0099] Optionally, the heating rate during the calcination process is 3-8℃ / min, such as 3℃ / min, 5℃ / min, 8℃ / min, etc.

[0100] Optionally, the holding time at the calcination temperature is 1-3 hours, such as 1 hour, 2 hours, or 3 hours. This is beneficial for the formation of the tetragonal zirconia crystal phase.

[0101] In a second aspect, the present invention provides a zirconia-based fiber membrane prepared according to the first aspect. The zirconia-based fiber membrane exhibits good surface smoothness, uniform and continuous distribution, and no surface pores or defects. The zirconia grains are uniformly distributed, resulting in good overall mechanical properties and high-temperature insulation. This fiber membrane can be used as a reinforcing material, a high-temperature catalyst carrier, a high-temperature insulation material, and a filter material, and is particularly suitable for use in fire-fighting fabrics.

[0102] In some embodiments, the ultimate stress of the zirconia-based fiber membrane is at least 1.5-3 MPa.

[0103] In a third aspect, the present invention provides a method for preparing a hydrophobically modified zirconia-based fiber membrane, comprising depositing a hydrophobic layer on the surface of the zirconia-based fiber membrane prepared in the second aspect to obtain a hydrophobically modified zirconia-based fiber membrane, wherein the hydrophobic layer comprises polydimethylsiloxane. This method further hydrophobically modifies the zirconia-based fiber membrane. The operation is simple, and the hydrophobic layer uniformly covers the surface of the zirconia-based fiber membrane, isolating the zirconia-based fiber membrane from water to form an insulating interface. This improves the hydrophobic properties of the zirconia-based fiber membrane, enabling it to maintain structural integrity and thermal protection performance under severe hydrothermal shocks. Specifically, the polydimethylsiloxane contains nonpolar -CH3 groups, which can reduce the surface energy of the zirconia-based fiber membrane, thereby improving its hydrophobicity.

[0104] In some embodiments, polydimethylsiloxane is an ethanol solution with a concentration of 0.05-1 wt%, such as 0.05 wt%, 0.1 wt%, 0.3 wt%, 0.6 wt%, 1 wt%, etc.

[0105] In some embodiments, deposition includes: immersing the zirconia-based fiber membrane in an alcoholic solution of polydimethylsiloxane and drying it to form a hydrophobic layer on the surface of the zirconia-based fiber membrane.

[0106] In some embodiments, the thickness of the hydrophobic layer is 2-10 nm.

[0107] In some embodiments, the impregnation is ultrasonic impregnation, and the ultrasonic impregnation time is 5-15 minutes.

[0108] In some embodiments, the drying temperature is 70-90°C and the time is 0.5-3 hours.

[0109] In a fourth aspect, the present invention provides a hydrophobically modified zirconia-based fiber membrane prepared by the method described in the third aspect. This hydrophobically modified zirconia-based fiber membrane exhibits good hydrophobicity and high-temperature resistance. As shown in the examples below, the hydrophobically modified fiber membrane maintains good hydrophobic properties even after being exposed to a high-temperature environment of 450°C for 30 minutes. After exposure to a butane spray gun (1100°C) for 5 minutes, the fiber surface shows no change, and its flexibility remains excellent.

[0110] In a fifth aspect, the present invention proposes the application of the hydrophobically modified zirconia-based fiber membrane described in the fourth aspect in fire-fighting protective clothing. This fire-fighting protective clothing exhibits good thermal protection performance.

[0111] The present invention will be described below through specific embodiments. It should be noted that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention.

[0112] Example 1

[0113] (1) Preparation of spinning solution

[0114] Sol A: Lanthanum nitrate was dissolved in zirconium acetate. After complete dissolution, a transparent zirconium oxide precursor, lanthanum nitrate sol, was formed. The molar amount of lanthanum nitrate was 0.06 times the molar amount of zirconium acetate. A photograph of sol A is shown below. Figure 2 As shown.

[0115] B sol: At room temperature, deionized water was placed in an Erlenmeyer flask, and aluminum nitrate nonahydrate was added and stirred for 2 hours. Aluminum isopropoxide was then added and stirred for another 3 hours. The mixture was then heated to 80°C and refluxed for 1 hour to form a transparent alumina precursor sol. The molar ratio of aluminum nitrate nonahydrate to aluminum isopropoxide to water was 1:3:60. A photograph of this B sol is shown below. Figure 2 As shown.

[0116] Spinning solution: Sol A, sol B, and PEO were stirred at room temperature for 8 hours to form a transparent spinning solution. A photograph of this spinning solution is shown below. Figure 2 As shown. The PEO content in the spinning solution is 0.6 wt%, and the amounts of sol A and sol B are adjusted to ensure that the Al2O3 content in the zirconia-based fiber membrane is 7.5 mol%.

[0117] (2) Preparation of zirconia-based precursor nanofiber membranes

[0118] A 20mL syringe was filled with spinning solution, and a metal needle was attached to the outlet. The syringe was then fixed to the infusion propulsion device of the electrospinning equipment. A high-voltage power supply was activated to create an electric field, generating electrostatic polarization. This caused charges to form on the surface of the droplet at the syringe needle. The increasing voltage and the eddy current effect generated by the airflow gradually overcame the electrostatic repulsion of the droplet surface at the syringe tip, allowing it to overcome its surface tension. Under the interaction of these two forces, the droplet surface gradually transformed from a rounded outline to a Taylor cone, eventually breaking through the surface tension and generating a jet. As it reached the receiving device (drum), it was continuously stretched into fibers, forming a ZrO2-based precursor nanofiber membrane. The process was controlled with a slide speed of 70cm / min, a drum speed of 60rpm, a spinning solution flow rate of 5mL / h, a power supply voltage of 20kV, and a receiving distance of 18cm. The resulting zirconium oxide-based precursor nanofiber membrane is shown in the image below. Figure 3 As shown.

[0119] (3) Preparation of zirconia-based fiber membranes

[0120] The prepared ZrO2-based precursor nanofiber membrane was dried in a vacuum drying oven at 80°C. It was then placed in a muffle furnace and calcined at 1000°C for 2 hours in air at a heating rate of 5°C / min. After cooling to room temperature in the furnace, a zirconia-based fiber membrane was obtained. A photograph of the obtained zirconia-based fiber membrane is shown below. Figure 4 As shown.

[0121] (4) Preparation of hydrophobically modified zirconia-based fiber membranes

[0122] like Figure 5 As shown, a hydrophobic modified layer was deposited on a zirconia-based fiber membrane. The specific operation was as follows: the zirconia-based fiber membrane was immersed in a 0.1 wt% ethanol solution prepared by polydimethylsiloxane, and the zirconia-based fiber membrane was ultrasonically impregnated for 10 min. The membrane was then dried at 80 °C for 1 h to obtain a hydrophobic modified zirconia-based fiber membrane with a hydrophobic layer thickness of 5 nm.

[0123] Examples 2-6

[0124] Hydrophobic modified zirconia-based fiber membranes were prepared according to the method in Example 1, except that the amount of B sol was adjusted according to the content of alumina in the zirconia-based fibers as 2.5 mol%, 5 mol%, 10 mol%, 15 mol%, and 20 mol%, respectively, and the content of PEO in the spinning solution was maintained at 0.6 wt%.

[0125] Examples 7-11

[0126] Hydrophobic modified zirconia-based fiber membranes were prepared according to the method in Example 1, except that the calcination temperatures for preparing the zirconia-based fiber membranes were 700℃, 800℃, 900℃, 1100℃, and 1200℃, respectively.

[0127] Comparative Example 1

[0128] (1) Preparation of spinning solution

[0129] Take 50g of zirconium acetate and add it to the polymer template agent PEO to form a spinning solution with a PEO concentration of 0.6wt%.

[0130] (2) Preparation of zirconia precursor nanofiber membrane

[0131] A 20mL syringe is filled with spinning solution, and a metal needle is attached to the outlet. The syringe is then fixed to the infusion and propulsion device of the electrospinning equipment. A high-voltage power supply is activated to create an electric field, generating electrostatic polarization. This causes a charge to form on the surface of the droplet at the syringe needle. The increasing voltage and the eddy current effect generated by the airflow gradually overcome the electrostatic repulsion of the droplet surface at the syringe tip, allowing it to overcome its surface tension. Under the interaction of these two forces, the droplet surface gradually transforms from a rounded outline into a Taylor cone, eventually breaking through the surface tension and generating a jet. As it reaches the receiving device (drum), it is continuously stretched into fibers, forming a ZrO2-based precursor nanofiber membrane. The process is controlled with a slide speed of 70cm / min, a drum rotation speed of 60rpm, a spinning solution flow rate of 5mL / h, a power supply voltage of 20kV, and a receiving distance of 18cm.

[0132] (3) Preparation of zirconia fiber membrane

[0133] The prepared ZrO2-based precursor nanofiber membrane was dried in a vacuum drying oven at 80°C. It was then placed in a muffle furnace and calcined at 800°C for 2 hours in air at a heating rate of 5°C / min. After cooling to room temperature in the furnace, the zirconia fiber membrane was obtained. A photograph of the zirconia fiber membrane is shown below. Figure 8 As shown.

[0134] (4) Preparation of hydrophobically modified zirconia fiber membrane

[0135] Polydimethylsiloxane was prepared into a 0.1 wt% ethanol solution and then used to vapor deposit a zirconia-based fiber membrane. The vapor deposition process was controlled at a vacuum of -0.1 MPa and a temperature of 80 °C to obtain a hydrophobic modified zirconia fiber membrane with a hydrophobic layer of 20 mm.

[0136] Figure 6 This is a SEM image of the zirconium oxide precursor nanofiber membrane of Comparative Example 1.

[0137] Figure 7These are the SEM images and EDS elemental analysis results of the zirconia fiber membrane in Comparative Example 1. Combined with... Figure 6 and Figure 7 It can be seen that the uncalcined zirconia fiber membrane has good fiber continuity and uniform diameter distribution, exhibiting a porous fiber structure with irregular deposition. The calcined pure zirconia fiber membrane contains more short fibers, indicating that the pure zirconia fibers break down at high temperatures during calcination, forming more short fibers. Comparing the average diameter before and after calcination shows that the fiber diameter decreased by 400 nm, mainly due to the complete decomposition and removal of the polymer template and organic functional groups during high-temperature calcination. EDS elemental analysis shows that the elemental distribution in the zirconia fibers is also characterized by a uniform distribution of only Zr and O elements.

[0138] Figure 9 This is the XRD pattern of the zirconia fiber membrane in Comparative Example 1. The zirconia in the pure zirconia fiber membrane is monoclinic and contains a small amount of tetragonal ZrO2. The monoclinic crystal form causes cracking within the single fiber, making the ZrO2 nanofiber membrane exhibit significant brittleness.

[0139] Figure 10 The image shows an SEM image of the zirconia-based fiber membrane from Example 1. As can be seen from the SEM morphology image, the zirconia grains are small, the fiber membrane has good continuity, and the macroscopic manifestation is flexible reinforcement.

[0140] Figure 11 This is the EDS elemental analysis diagram of the zirconia-based fiber membrane from Example 1. The EDS elemental analysis shows that the zirconia fibers also contain Zr, Al, La, and O elements, and these elements are evenly distributed. This indicates that the zirconia-based fiber membrane ultimately formed oxides of zirconium, aluminum, and lanthanum during the high-temperature calcination process in air.

[0141] Figure 12 This is a diagram demonstrating the flexibility of the zirconia-based fiber membrane in Example 1. As can be seen, it can return to its original shape after being squeezed and bent by hand.

[0142] Figure 13The figures show the XRD patterns of the zirconia-based fiber membranes from Examples 1 and 7-11. The figures illustrate the phase composition of the zirconia-based fiber membranes at different calcination temperatures. Zirconia exists in a tetragonal ZrO2 crystal form. It can be seen that doping the zirconia fibers with a small amount of lanthanum oxide can stabilize the phase transformation of zirconia by forming oxygen vacancies, thereby inhibiting the malignant growth of grains. The introduction of amorphous alumina creates a unique structure where crystalline and amorphous phases coexist. This results in a stable amorphous phase surrounding the uniformly distributed nanocrystals on the zirconia-based fiber membrane, forming numerous grain boundaries and phase boundaries. The mutual inhibition between the amorphous and crystalline phases during zirconia grain growth, as well as the synergistic effect between the grains and the surrounding stable amorphous phase, contributes to the excellent mechanical flexibility and superior temperature resistance of the zirconia-based fiber membrane. Meanwhile, Al2O3 promotes the formation of La2Zr2O7. A small amount of La2Zr2O7 can inhibit the malignant growth of grains, improve the concentration of grain distribution and the smoothness of fiber surface. Under high temperature environment, it is conducive to the reduction of surface thermal erosion grooves and improves the mechanical properties of fiber.

[0143] Figure 14 The image shows an HR-TEM image of the zirconia-based fiber membrane from Example 1. In the image, amorphous Al₂O₃ is distributed around the zirconia grains, forming amorphous grain boundaries that hinder the slippage of the zirconia grains and improve the mechanical properties of the zirconia-based ceramic fiber membrane. Simultaneously, the introduction of amorphous alumina slows down the growth rate of the zirconia grains, inhibiting abnormal growth and fusion of the zirconia grains.

[0144] Figure 15 The figure shows the tensile stress curve of the zirconia-based fiber membrane in Example 1. The tensile stress-strain curve was tested using a universal testing machine. As can be seen from the figure, the ultimate stress of the zirconia-based fiber membrane in Example 1 is 1.9 MPa, indicating that the zirconia-based fiber membrane has good tensile strength.

[0145] Figure 16 This is a diagram illustrating the combustion process of an aramid fiber (the insulation layer used in commercial fire suits). Figure 17 This is a diagram illustrating the combustion experiment of the zirconia-based fiber membrane in Example 1. Both the aramid fiber (the insulation layer used in commercially available fire-fighting suits) and the zirconia-based fiber membrane were burned using a butane torch at 1100°C for 5 minutes. It can be seen that the aramid fiber was directly burned and charred, while the zirconia-based fiber membrane showed no significant change before and after combustion. Furthermore, the zirconia-based fiber membrane did not shrink, emit black smoke or odor during combustion, and its flexibility performance was minimally affected. (Comparison) Figure 16 and 17 It can be seen that the zirconia-based fiber membrane of the present invention has good high-temperature resistance.

[0146] Figure 18This is a diagram illustrating the hydrophobicity of the hydrophobic modified zirconia-based fiber membrane of Example 1. Orange in the diagram represents colored water. As can be seen from the diagram, water droplets sprayed onto the fiber surface quickly slide off, indicating that the modified zirconia-based fiber membrane has good hydrophobicity.

[0147] Figure 19 This is a hydrophobic angle test diagram of the hydrophobic modified zirconia-based fiber membrane of Example 1. L is the hydrophobic angle on the left, R is the hydrophobic angle on the right, and CA is the average hydrophobic angle. As can be seen from the figure, the hydrophobic angle is 146.32°.

[0148] Figure 20 This is a SEM image of the hydrophobically modified zirconia-based fiber membrane of Example 1. It can be seen that the microstructure of the zirconia-based fiber membrane before and after hydrophobic modification is basically the same. The difference is that the modified zirconia-based fiber has a thin layer of polydimethylsiloxane hydrophobic layer on its surface.

[0149] Figure 21 This is the EDS elemental analysis diagram of the hydrophobically modified zirconia-based fiber membrane of Example 1. As can be seen from the figure, silicon is uniformly distributed, indicating that polydimethylsiloxane was vapor-deposited onto the zirconia-based fiber membrane.

[0150] Figure 22 The graph shows the hydrophobicity analysis of the hydrophobic modified zirconia-based fiber membrane in Example 1 at different temperatures. It can be seen that the hydrophobic modified zirconia-based fiber membrane becomes hydrophilic after heat treatment at 500℃. However, the hydrophobicity and thermal stability of the hydrophobic modified zirconia-based fiber membrane still exceed 400℃.

[0151] Figure 23 The graph shows the relationship between the thermal conductivity of the zirconia-based fiber membranes in Examples 1-6 and the alumina content. The thermal conductivity was tested using the plate instantaneous heat source method. As can be seen from the graph, the thermal conductivity of the zirconia-based fiber membranes in Examples 1-6 ranges from 0.024 to 0.031 W / m·K. It can also be seen that the thermal conductivity of the zirconia-based fiber membrane increases with the increase of Al2O3 doping content. This is mainly because Al2O3 has a relatively high intrinsic thermal conductivity, which to some extent improves the thermal conductivity of the Al2O3 / La2O3 / ZrO2 nanofiber membrane.

[0152] Figure 24 This is a material composition diagram of fire protective clothing. Fire protective clothing B consists of an outer layer 4, a hydrophobic modified zirconia-based fiber membrane 2 as described in Example 1, and a comfort layer 1. Existing fire protective clothing A on the market consists of a comfort layer 1, a heat insulation layer 2, a waterproof and breathable layer 3, and an outer layer 4. It can be seen that using the hydrophobic modified zirconia-based fiber membrane of the present invention to make fire protective clothing can reduce the number of layers in the fire protective clothing.

[0153] Figure 25The figures show the heat flux and Stoll curves of fire-fighting protective suits under convective and radiative heat sources over time. Figure a represents the Stoll curve; figure b represents the thermal protection performance (TPP) test curve of a commercial fire-fighting protective suit with an outer layer, hydrophobic layer, aramid fiber, and comfort layer; figure c represents the thermal protection performance test curve of a fire-fighting protective suit with an outer layer, a single layer of hydrophobic modified zirconia-based fiber membrane, and a comfort layer; and figure d represents the thermal protection performance test curve of a fire-fighting protective suit with an outer layer, two layers of hydrophobic modified zirconia-based fiber membrane, and a comfort layer. The vertical axis represents the accumulated heat flux during the test, while the TPP value is calculated as TPP = F * T, where F is the total heat flux (84.3 kW / m²). 2 T represents the intersection of the curve and the Stoll curve. It can be seen that the time to achieve second-degree burns on the skin from commercial fire suits is 16.2 seconds, corresponding to a TPP value of 1360.8 kW·s / m². 2 Replacing the hydrophobic and heat-insulating layers in commercial fire suits with a single-layer hydrophobically modified zirconia-based fiber membrane to form a three-layer composite structure resulted in a second-degree skin burn time of 19.1 seconds, corresponding to a TPP value of 1610.1 kW·s / m. 2 Replacing the hydrophobic and heat-insulating layers in commercial fire suits with a double-layer hydrophobic modified zirconia-based fiber membrane to form a three-layer composite structure resulted in a second-degree skin burn time of 28.5 seconds, corresponding to a TPP value of 2402.6 kW·s / m. 2 Compared to commercial fire suits, the hydrophobic modified zirconia-based fiber membrane replaces the hydrophobic and heat-insulating layers in commercial fire suits to form a three-layer composite structure, achieving a longer time to second-degree burns and a higher TPP value.

[0154] Figure 26 The images show macroscopic views of fire-fighting protective clothing after the TPP test. It can be seen that after the TPP test, the outer layer of the commercial fire-fighting suit (a) exhibited shrinkage, deformation, carbonization, and brittleness, while the comfort layer showed severe shrinkage and carbonization, resulting in compromised thermal protection performance. Replacing the hydrophobic and heat-insulating layers of the commercial fire-fighting suit with a hydrophobically modified zirconia-based fiber membrane to form a three-layer composite structure (b) consisting of an outer layer + a single layer of hydrophobically modified zirconia-based fiber membrane + a comfort layer, and c consisting of an outer layer + two layers of hydrophobically modified zirconia-based fiber membrane + a comfort layer, also resulted in shrinkage, deformation, carbonization, and brittleness of the outer layer. However, the comfort layer did not shrink or carbonize; only some areas showed carbon buildup and ash due to combustion. This demonstrates that the hydrophobically modified zirconia-based fiber membrane significantly outperforms the commercial aramid fiber membrane in terms of heat insulation, flame retardancy, and high-temperature resistance. This is of great significance for protecting the safe operation of high-temperature equipment and the lives of emergency rescue personnel in extreme environments.

[0155] Figure 27 The image shows the thermal protection performance of the fire-fighting protective clothing prepared using the hydrophobically modified zirconia-based fiber of Example 1 after being burned with a butane torch for different times.

[0156] Unless otherwise stated, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. All patents and publications related to this invention are incorporated herein by reference in their entirety. The terms "comprising" or "including" are open-ended expressions, meaning they include the contents specified in this invention but do not exclude other aspects.

[0157] In the description of this specification, references to terms such as "one embodiment," "another embodiment," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples, without contradiction. Additionally, it should be noted that in this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0158] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method of making a zirconia-based fibrous membrane, characterized by, Includes the following steps: (1) A sol containing zirconium oxide precursor-lanthanum salt, B sol containing alumina precursor and template agent are first mixed to obtain spinning solution; In this process, lanthanum salt and zirconium salt are mixed in a second step to form the A sol containing zirconium oxide precursor-lanthanum salt; Inorganic aluminum salt, aluminum isopropoxide and water are mixed in a third step to form the B sol containing the alumina precursor; In the A sol, the molar ratio of lanthanum salt to zirconium salt is (0.04-0.2):1; In the B sol, the molar ratio of inorganic aluminum salt, aluminum isopropoxide and water is 1:(2-5):(25-100); The third mixing specifically includes a first stage and a second stage performed sequentially; First stage: At room temperature, stir the inorganic aluminum salt in water for 1-3 hours to allow the inorganic aluminum salt to hydrolyze first, then add aluminum isopropoxide and continue stirring for 2-5 hours to allow the aluminum isopropoxide to hydrolyze. This sequential addition of inorganic aluminum salt to water allows the first inorganic aluminum salt to hydrolyze to release hydrogen ions, which is beneficial to the hydrolysis of aluminum isopropoxide. Second stage: Heating and refluxing for 1-3 hours to further promote the hydrolysis of aluminum isopropoxide and aluminum salt; The template agent includes at least one of PEO, PVA, PVB and PAN; (2) The spinning solution is subjected to airflow-assisted electrospinning to obtain a zirconia-based precursor nanofiber membrane; (3) The zirconia-based precursor nanofiber membrane is dried and calcined to obtain a zirconia-based fiber membrane; The drying process is vacuum drying at a temperature of 70-100℃; the calcination process includes gradually increasing the temperature from room temperature to 800-1000℃ at a heating rate of 3-8℃ / min and holding the temperature for 1-3 hours.

2. The method of claim 1, wherein, Step (1) must satisfy at least one of the following conditions: The first mixing was carried out at room temperature under stirring conditions for 5-12 hours. The template agent has a content of 0.4-1 wt% in the spinning solution; The amounts of sol A and sol B used result in an aluminum oxide content of 2.5-20 mol in the zirconia-based fiber membrane.

3. The method of claim 1, wherein, The lanthanum salt includes at least one of lanthanum nitrate, lanthanum chloride, and lanthanum carbonate; The zirconium salt includes at least one of zirconium acetate, zirconium oxychloride, and basic zirconium carbonate; The inorganic aluminum salt includes at least one of aluminum nitrate, aluminum chloride, aluminum silicate, and aluminum sulfate.

4. The method according to claim 1 or 2, characterized in that, The airflow-assisted electrospinning includes: inputting the spinning solution into the spinneret of the electrospinning equipment at a flow rate of 1-12 mL / h, controlling the distance between the receiving device and the spinneret at 15-20 cm, connecting the spinneret to a high-voltage power supply, and controlling the voltage at 10-30 kV to perform electrospinning.

5. A zirconia-based fiber membrane prepared by the method according to any one of claims 1-4.

6. A method of making a hydrophobically modified zirconia-based fibrous membrane, characterized in that, include: A hydrophobic layer is deposited on the surface of the zirconia-based fiber membrane according to claim 5 to obtain a hydrophobically modified zirconia-based fiber membrane, wherein the hydrophobic layer comprises polydimethylsiloxane.

7. The method of claim 6, wherein, The deposition includes: immersing the zirconia-based fiber membrane in an alcoholic solution of polydimethylsiloxane and drying it to form a hydrophobic layer on the surface of the zirconia-based fiber membrane; The thickness of the hydrophobic layer is 2-10 nm; The impregnation is ultrasonic impregnation, and the time of the ultrasonic impregnation is 5-15 min; The temperature of the drying is 70-90℃, and the time is 0.5-3 h.

8. The hydrophobically modified zirconia-based fiber membrane prepared by the method of claim 6 or 7.

9. The use of the hydrophobically modified zirconia-based fiber membrane of claim 8 in fire protection clothing.

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