Alumina synthetic fiber felt and airflow melting preparation method thereof

Abstract

The invention relates to the technical field of refractory materials, in particular to an aluminum oxide synthetic fiber felt and an airflow melting preparation method thereof. The invention relates to an airflow melting preparation method of an aluminum oxide synthetic fiber felt. The method comprises the following steps: preparing composite sol from aluminum oxide powder, rare earth element powder, tetrabutyl titanate and / or tetrabutyl zirconate and a nano reinforcing material; and adding an organic template agent, carrying out dry spinning, presintering and high-temperature sintering, and blowing the sintered fibers into a collector through high-speed airflow to obtain the aluminum oxide synthetic fiber felt. The rare earth element powder and the nano reinforcing material are introduced, a micro-nano-scale reinforcing phase is formed in the aluminum oxide synthetic fiber, stress can be effectively dispersed, crack propagation is prevented, the mechanical strength and fracture toughness of the fiber are improved, and the structural integrity and performance stability of the fiber felt at high temperature are kept; the metal oxide can enhance the hardness and wear resistance of the fibrofelt, and also endows the fibrofelt with excellent chemical stability and multiple functions.

Description

Technical Field

[0001] The present invention relates to the technical field of refractory materials, and in particular to an alumina synthetic fiber felt and an airflow melting preparation method thereof. Background Art

[0002] Alumina fiber is a high-performance ceramic material with excellent mechanical strength, high-temperature resistance, chemical stability, and thermal conductivity. It has a wide range of applications in aerospace, high-temperature filters, thermal insulation materials, the automotive industry, and medical implants. The melt process was initially used primarily to produce polymer fibers and glass fibers, but has since been adapted to produce fibers with lower alumina content (<70%). This method can be used to produce both continuous and short fibers. Inorganic oxides are melted by electrical heating to form a melt, which is then spinnable by controlling its composition and temperature. The target product is then formed through various fiber-forming methods. However, as the alumina content increases, the melt viscosity increases, resulting in poor spinnability and difficulty in control. Therefore, the melt process is currently limited to producing fibers with low alumina contents. These fibers can generally only be used at temperatures below 1200°C, resulting in relatively low fiber quality and insufficient high-temperature resistance, limiting the application of alumina fibers.

[0003] Traditional alumina synthetic fiber felts have limited mechanical strength and toughness under high-temperature conditions, making them prone to crack propagation and fracture, making them difficult to meet practical application requirements. Furthermore, the uneven distribution of internal stress easily leads to stress concentration points, which can trigger cracks and rapidly propagate, leading to material failure. Fibers with high alumina content must not only possess higher temperature resistance but also maintain good mechanical strength, thermal shock resistance, and chemical stability to adapt to more demanding working conditions. To meet the stringent requirements for material properties in high-temperature environments, it is particularly urgent to develop a gas-flow melting method for preparing alumina synthetic fiber felts with high alumina content and excellent high-temperature resistance. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide an alumina synthetic fiber felt and a method for preparing the same by airflow melting.

[0005] The present invention provides a method for preparing an alumina synthetic fiber felt by air flow melting, comprising the following steps: (1) Mixing and sol preparation: Alumina powder and rare earth element powder are mixed, the mixed powder is added to the dispersion medium, stirred at room temperature for 1-2 hours, and then stirred at 60°C for 2-3 hours to obtain aluminum sol; Tetrabutyl titanate and / or tetrabutyl zirconate are added to an anhydrous ethanol solution containing a nano-reinforced material, stirred and dissolved to form a mixed solution, and the mixed solution is slowly dripped into the aluminum sol to prepare a composite sol; (2) Preparation of fiber precursor: adding an organic template to the composite sol, stirring it thoroughly to dissolve it completely, and using dry spinning technology to form the composite sol into a fiber precursor; (3) Heat treatment process: The collected fiber precursor is placed in a muffle furnace for pre-sintering, and then transferred to a high-temperature tube furnace for high-temperature sintering to form sintered fibers; (4) Preparation of fiber felt by air flow melting: Using an air flow melting device with a nozzle and a collector, the amount of fiber added is adjusted according to the required felt density. The sintered fibers are blown into the collector by a high-speed air flow, naturally stacked into a randomly distributed fiber network, and naturally cooled to room temperature to obtain alumina synthetic fiber felt. The alumina synthetic fiber felt comprises, by weight percentage, 94%-96% alumina, 0.5%-3% rare earth element powder, 0.1%-1% nano-reinforcement material, and 1%-4% metal oxide, wherein the metal oxide is silicon dioxide and / or zirconium dioxide. The rare earth element powder is lanthanum oxide and / or yttrium oxide, the nano-reinforcement material is silicon carbide nanowires and / or boron nitride nanosheets, and tetrabutyl titanate and / or tetrabutyl zirconate are added according to the content of the metal oxide.

[0006] Furthermore, in the (1) mixing and sol preparation, the alumina powder and the rare earth element powder are mixed and then stirred in a high-speed stirrer at a speed of 800-1200 rpm for 20-40 minutes.

[0007] Furthermore, in the mixing and sol preparation (1), anhydrous ethanol is used as a dispersion medium, and dilute nitric acid is added to adjust the pH value to 2.5-3.5.

[0008] Furthermore, in the (1) mixing and sol preparation, the mixed solution is slowly dripped into the aluminum sol, and then the mixture is stirred and reacted at 60-80° C. for 2-6 hours.

[0009] Furthermore, in the preparation of the fiber precursor in (2), the organic template is polyvinyl alcohol or polyethylene glycol, and its amount is 2%-5% of the weight of the composite sol.

[0010] Furthermore, in the preparation of the fiber precursor in (2), during the dry spinning process, the inner diameter of the needle is set to 0.6-0.8 mm, the voltage is 12-18 kV, the collection distance is 15-25 cm, the feeding rate is 10-30 μL / min, and aluminum foil is used as the collection carrier.

[0011] Furthermore, during the heat treatment process (3), the pre-sintering process is carried out in an air atmosphere, with the temperature rising to 500°C at a heating rate of 4-6°C / min and kept at that temperature for 1-2 hours.

[0012] Furthermore, during the heat treatment (3), high-temperature sintering is carried out in a high-temperature tube furnace under the protection of high-purity argon, with the temperature rising to 1300°C at a heating rate of 8-10°C / min and kept at that temperature for 2-3h.

[0013] Furthermore, in the (4) air flow melting to prepare the fiber felt, the nozzle diameter of the air flow melting device is 0.4-0.6 mm, the air flow velocity is set to 15-25 m / s, and the spraying temperature is maintained at 1400-1600°C.

[0014] Description of some raw materials in the above scheme: 1. Alumina is the main component of fiber felt, providing the basic structure and basic properties of the fiber. It has excellent mechanical strength, high temperature resistance and chemical stability. During the high-temperature sintering process, alumina forms a stable α-Al2O3 crystal phase, which gives the fiber an extremely high melting point and good creep resistance, enabling it to remain stable in extremely high temperature environments.

[0015] 2. Rare earth element powder (lanthanum oxide or yttrium oxide) acts as a grain refiner to promote the formation of fine grains during high-temperature sintering, prevent excessive grain growth, and help improve the density and uniformity of the fiber. Rare earth elements can improve the thermal expansion coefficient of alumina, reduce thermal stress concentration, thereby improving the thermal shock resistance and thermal stability of the fiber. They can also enhance the interfacial bonding between the components within the fiber, reduce interface defects, and improve the overall mechanical properties.

[0016] 3. Nano-reinforcement materials (silicon carbide nanowires or boron nitride nanosheets) form a micro-nanoscale reinforcement phase within the fiber, effectively dispersing stress and preventing crack propagation, thereby significantly improving the fiber's fracture toughness. Leveraging the material's high thermal conductivity, strength, electrical insulation, and high-temperature resistance, the fiber mat is endowed with multiple functionalities. A complex three-dimensional network is formed between the nano-reinforcement material and the matrix material, enhancing the overall structural stability and mechanical properties of the fiber mat.

[0017] 4. Metal oxides (titanium dioxide or zirconium dioxide) can increase the hardness and wear resistance of the fiber and enhance the overall performance of the fiber felt; organic templates (polyvinyl alcohol or polyethylene glycol) can provide temporary structural support and improve fluidity, thereby increasing the success rate and efficiency of dry spinning and airflow melting processes. They will eventually be completely decomposed by high temperature without affecting the physical and chemical properties of the fiber felt.

[0018] The present invention also provides an alumina synthetic fiber felt prepared by the above preparation method.

[0019] The beneficial effects achieved by the present application are: 1. The present application introduces rare earth elements, metal oxides and nano-enhanced materials into alumina, which can improve the mechanical strength, thermal stability and oxidation resistance of the fiber felt; Specifically, alumina is used as the main material, rare earth element powder and nano-enhanced material are introduced to form α-Al2O3 crystal phase and micro-nano scale reinforced phase inside the alumina synthetic fiber, which can effectively disperse stress, prevent crack propagation, improve the mechanical strength and fracture toughness of the fiber, and maintain the structural integrity and performance stability of the fiber felt at high temperature; At the same time, the synergistic effect of rare earth elements and nano-enhanced materials greatly improves the thermal shock resistance of the fiber felt, which is suitable for working environment with frequent temperature changes, and metal oxides can enhance the hardness and wear resistance of the fiber felt, and also endow it with excellent chemical stability and multiple functions.

[0020] 2. The present application mixes and disperses alumina powder, rare earth element powder, tetrabutyl titanate and / or tetrabutyl zirconate, nano-enhanced material and other components in anhydrous ethanol to ensure good dispersibility of each component, forms a uniform and stable composite sol, and adjusts the pH value to promote the dissolution of each component and prevent precipitation. Adding an organic template to the composite sol can form a temporary network structure in the melt, help maintain an appropriate viscosity range, and provide temporary structural support, which helps control the fiber morphology and size.

[0021] 3. The present application adopts a combination of pre-sintering and high-temperature sintering. The fiber precursor is first pre-sintered in an air atmosphere to remove the organic template and preliminarily solidify the fiber structure, and then high-temperature sintering is carried out under high-purity argon protection, so that the inorganic components in the fiber undergo solid-phase reaction to form a stable crystal structure, while the mechanical strength and high-temperature resistance of the fiber are enhanced, ensuring the integrity of the fiber structure and the stability of the performance, and improving the quality of the final product.

[0022] 4. The present application blows the sintered fiber into a collector by high-speed airflow, and the fibers naturally accumulate into a random fiber network. The high-speed airflow rapidly cools the fibers, fixing their morphology and avoiding the problems of crystal growth or phase change caused by slow cooling. As more and more fibers are deposited, they will naturally interweave with each other to form a fiber felt with certain thickness and density. The three-dimensional porous network structure provides excellent thermal insulation effect and endows the fiber felt with good flexibility and compression resistance. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The flow chart of the gas melt preparation method of the alumina synthetic fiber felt adopted by the present application. DETAILED DESCRIPTION

[0024] The technical solutions of the present application will be further described in detail below in combination with specific embodiments.

[0025] It should be understood that the following examples are merely illustrative and explanatory in nature and are not to be construed as limiting the scope of the present application. Any technical based on the above description of the present application is covered within the scope intended to be protected by the present application. In the present application, unless specified, all equipment and raw materials can be purchased from the market or commonly used in the industry, and the methods in the following examples are conventional methods in the art, unless otherwise specified.

[0026] Example 1: A gas flow melt preparation method of an alumina synthetic fiber felt, as shown in Figure 1 includes the following steps: (1) mixing and sol preparation: mix alumina powder and lanthanum oxide powder, stir in a high-speed stirrer at a speed of 1000 rpm for 30 min, add the mixed powder to anhydrous ethanol, and add dilute nitric acid to adjust the pH value to 3, stir at room temperature for 1.5 h, and then stir at 60°C for 2 h to obtain an aluminum sol; Add tetrabutyl titanate to an anhydrous ethanol solution containing silicon carbide nanowires, stir to dissolve to form a mixed solution, slowly drop the mixed solution into the aluminum sol, and continue to stir at 70°C for 4 h to prepare a composite sol; (2) Fiber precursor preparation: Add 3% by weight of polyvinyl alcohol to the composite sol, stir thoroughly to dissolve completely, use dry spinning technology, set the needle inner diameter to 0.7 mm, the voltage to 15 kV, the fiber collection distance to 20 cm, and the feeding rate to 20 μL / min, use aluminum foil as the fiber collection carrier to form the fiber precursor; (3) Heat treatment process: Place the collected fiber precursor in a muffle furnace, raise the temperature to 500°C at a rate of 5°C / min in an air atmosphere, and heat for 1.5 h for pre-sintering, then transfer to a high-temperature tube furnace, raise the temperature to 1300°C at a rate of 10°C / min under high-purity argon protection, and heat for 2.5 h for high-temperature sintering to form sintered fibers; (4) Gas flow melt preparation of fiber felt: Use a gas flow melt device with a nozzle diameter of 0.5 mm, set the gas flow speed to 20 m / s, and maintain the jet temperature at 1500°C, according to the felt density 20 g / m 3 Adjust the fiber addition amount, blow the sintered fibers into the collector by high-speed airflow, naturally accumulate into a randomly distributed fiber network, and naturally cool to room temperature to obtain an alumina synthetic fiber felt.

[0027] The composition of the alumina synthetic fiber felt is: alumina 96%, lanthanum oxide 1%, silicon carbide nanowires 0.5%, and titanium dioxide 2.5% by weight percentage.

[0028] Example 2: A gas flow melt preparation method of an alumina synthetic fiber felt, as shown in Figure 1As shown, the process comprises the following steps: (1) mixing and sol preparation: mixing aluminum oxide powder and yttrium oxide powder, stirring at 1000 rpm in a high-speed stirrer for 30 min, adding the mixed powder into anhydrous ethanol, and adding dilute nitric acid to adjust the pH value to 3, stirring at room temperature for 1.5 h, and then stirring at 60°C for 2.5 h to obtain aluminum sol; Tetrabutyl zirconate was added to an anhydrous ethanol solution containing boron nitride nanosheets, stirred and dissolved to form a mixed solution, and the mixed solution was slowly dripped into the aluminum sol, and the mixture was stirred and reacted at 70°C for 5 hours to obtain a composite sol; (2) Preparation of fiber precursor: 4% of polyethylene glycol by weight was added to the composite sol, stirred thoroughly to dissolve it completely, and dry spinning technology was used with the needle inner diameter set to 0.7 mm, the voltage set to 15 kV, the spinning distance set to 20 cm, the feed rate set to 20 μL / min, and aluminum foil used as the spinning carrier to form a fiber precursor; (3) Heat treatment process: The collected fiber precursor was placed in a muffle furnace, heated to 500 °C at a heating rate of 5 °C / min in an air atmosphere, and kept warm for 1.5 h for pre-sintering. It was then transferred to a high-temperature tube furnace, heated to 1300 °C at a heating rate of 10 °C / min under high-purity argon protection, and kept warm for 2.5 h for high-temperature sintering to form sintered fibers; (4) Preparation of fiber felt by air flow melting: An air flow melting device with a nozzle diameter of 0.5 mm was used, the air flow velocity was set to 20 m / s, the spray temperature was maintained at 1500 °C, and the density of the felt was 20 g / m 3 The fiber addition amount is adjusted, and the sintered fibers are blown into a collector through a high-speed airflow, naturally stacked into a randomly distributed fiber network, and naturally cooled to room temperature to obtain alumina synthetic fiber felt.

[0029] Calculated by weight percentage, the composition of the alumina synthetic fiber felt is: 95% alumina, 2% yttrium oxide, 0.8% boron nitride nanosheets, and 2.2% zirconium dioxide.

[0030] Example 3: A method for preparing alumina synthetic fiber felt by air flow melting, such as Figure 1 As shown, the process comprises the following steps: (1) mixing and sol preparation: mixing aluminum oxide powder, lanthanum oxide powder and yttrium oxide powder, stirring at 1000 rpm in a high-speed stirrer for 30 min, adding the mixed powder into anhydrous ethanol, and adding dilute nitric acid to adjust the pH value to 3, stirring at room temperature for 1.5 h, and then stirring at 60 ° C for 2.5 h to obtain aluminum sol; Tetrabutyl titanate and tetrabutyl zirconate were added to an anhydrous ethanol solution containing silicon carbide nanowires and boron nitride nanosheets, stirred and dissolved to form a mixed solution, and the mixed solution was slowly dripped into the aluminum sol. The mixture was stirred and reacted at 80°C for 6 hours to obtain a composite sol. (2) Preparation of fiber precursor: Add 5% of polyvinyl alcohol by weight to the composite sol, stir thoroughly to dissolve completely, use dry spinning technology, set the needle inner diameter to 0.7 mm, voltage to 15 kV, collection distance to 20 cm, feed rate to 20 μL / min, and use aluminum foil as a collection carrier to form a fiber precursor; (3) Heat treatment process: The collected fiber precursor was placed in a muffle furnace, heated to 500 °C at a heating rate of 5 °C / min in an air atmosphere, and kept warm for 1.5 h for pre-sintering. It was then transferred to a high-temperature tube furnace, heated to 1300 °C at a heating rate of 10 °C / min under high-purity argon protection, and kept warm for 2.5 h for high-temperature sintering to form sintered fibers; (4) Preparation of fiber felt by air flow melting: An air flow melting device with a nozzle diameter of 0.5 mm was used, the air flow velocity was set to 20 m / s, the spray temperature was maintained at 1500 °C, and the density of the felt was 20 g / m 3 The fiber addition amount is adjusted, and the sintered fibers are blown into a collector through a high-speed airflow, naturally stacked into a randomly distributed fiber network, and naturally cooled to room temperature to obtain alumina synthetic fiber felt.

[0031] Calculated by weight percentage, the composition of alumina synthetic fiber felt is: 94% alumina, 0.75% lanthanum oxide, 0.75% yttrium oxide, 0.3% silicon carbide nanowires, 0.3% boron nitride nanosheets, 1.5% titanium dioxide, and 2.4% zirconium dioxide.

[0032] Comparative Example 1: No rare earth element powder (lanthanum oxide powder of Example 1) was used, specifically: (1) Mixing and sol preparation: Alumina powder was added to anhydrous ethanol, and dilute nitric acid was added to adjust the pH to 3. The mixture was stirred at room temperature for 1.5 h, and then stirred at 60 °C for 2 h to obtain aluminum sol. The remaining steps of (1) mixing and sol preparation, (2) preparation of fiber precursor, (3) heat treatment process, (4) preparation of fiber felt by air flow melting, and the composition of the alumina synthetic fiber felt are consistent with those in Example 1.

[0033] Comparative Example 2: Tetrabutyl titanate and silicon carbide nanowires are not used, specifically: (1) Mixing and sol preparation: Alumina powder and lanthanum oxide powder were mixed and stirred in a high-speed stirrer at 1000 rpm for 30 min. The mixed powder was added to anhydrous ethanol and the pH value was adjusted to 3 by adding dilute nitric acid. The mixture was stirred at room temperature for 1.5 h and then at 60 °C for 2 h to obtain aluminum sol, which is the composite sol. The remaining steps (2) preparation of fiber precursor, (3) heat treatment process, (4) preparation of fiber felt by air flow melting and the composition of alumina synthetic fiber felt are consistent with those in Example 1.

[0034] Performance test: relevant performance tests were performed on the alumina synthetic fiber felts of Examples 1-3 and Comparative Examples 1-2; 1. High temperature resistance: According to ASTM C1114-15 (Test of Dimensional Change of Ceramic Materials at High Temperature), prepare a specimen with a size of 25 mm × 25 mm × 100 mm. Use a vernier caliper with an accuracy of ±0.01 mm to measure the length of the specimen. Place the specimen in a high-temperature furnace and raise the temperature to 1600°C at a rate of 10°C / min. Hold for 1 hour and naturally cool to room temperature. Use a vernier caliper to measure the length of the specimen again and calculate the shrinkage rate.

[0035] 2. Mechanical properties: According to ASTM C1275-18 (Tensile Strength Test of Ceramic Fiber and Fiber Felt), prepare a specimen with a width of 25 mm and a length of 150 mm. Fix the specimen in the fixture of a universal testing machine, ensuring that the clamping is firm and uniform. Apply a tensile force at 1 mm / min until the specimen breaks. Record the maximum load and displacement at break, and calculate the tensile strength. As with the tensile strength test, a small cyclic load was applied on a universal testing machine at a loading speed of 0.1 mm / min and 5 cycles. The stress-strain curve was recorded and the elastic modulus was calculated.

[0036] 3. Thermal shock resistance: According to ASTM C773-19 (Determination of thermal shock resistance of ceramic materials), prepare specimens with dimensions of 50 mm × 50 mm × 10 mm and pre-sinter them in air at 1000°C for 1 hour. Rapidly heat the specimen to 1000°C and hold for 1 minute. Immediately remove the specimen and immerse it in room temperature water and hold for 1 minute. Repeat the above heating-cooling cycle 10 times. Inspect the specimen surface for cracks and spalling, and record the extent of damage.

[0037] 4. Thermal conductivity: According to ASTM E1461-13 (Determination of Thermal Diffusivity, Specific Heat, and Kinetic Viscosity of Solid Materials by the Laser Flash Method), prepare a round or square thin sheet sample with a thickness of 1-2 mm, place the sample on the sample stage of the laser flash instrument, ensure good contact, use a short pulse laser to irradiate the back of the sample, make the sample temperature rise instantaneously, use an infrared detector to measure the temperature change on the front of the sample, calculate the thermal diffusivity according to the measured temperature response curve, and calculate the thermal conductivity in combination with the density and specific heat capacity.

[0038] The results of the performance tests are shown in Table 1.

[0039] Table 1. Results of performance tests of aluminum oxide synthetic fiber felt

[0040] The above examples are only illustrative of the principles and effects of the present application, and are not intended to limit the present application. Any person skilled in the art can modify or change the above examples without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical ideas disclosed by the present application shall be covered by the claims of the present application.

Claims

1. A method for preparing alumina synthetic fiber felt by air flow melting, characterized in that: The method comprises the following steps: (1) mixing and sol preparation: mixing aluminum oxide powder and rare earth element powder, adding the mixed powder into a dispersion medium, stirring at room temperature for 1-2 hours, and then stirring at 60°C for 2-3 hours to obtain aluminum sol; Tetrabutyl titanate and / or tetrabutyl zirconate are added to an anhydrous ethanol solution containing a nano-reinforced material, stirred and dissolved to form a mixed solution, and the mixed solution is slowly dripped into the aluminum sol to prepare a composite sol; (2) Preparation of fiber precursor: adding an organic template to the composite sol, stirring it thoroughly to dissolve it completely, and using dry spinning technology to form the composite sol into a fiber precursor; (3) Heat treatment process: The collected fiber precursor is placed in a muffle furnace for pre-sintering, and then transferred to a high-temperature tube furnace for high-temperature sintering to form sintered fibers; (4) Preparation of fiber felt by air flow melting: Using an air flow melting device with a nozzle and a collector, the amount of fiber added is adjusted according to the required felt density. The sintered fibers are blown into the collector by a high-speed air flow, naturally stacked into a randomly distributed fiber network, and naturally cooled to room temperature to obtain alumina synthetic fiber felt. The alumina synthetic fiber felt comprises, by weight percentage, 94%-96% alumina, 0.5%-3% rare earth element powder, 0.1%-1% nano-reinforcement material, and 1%-4% metal oxide, wherein the metal oxide is silicon dioxide and / or zirconium dioxide. The rare earth element powder is lanthanum oxide and / or yttrium oxide, the nano-reinforcement material is silicon carbide nanowires and / or boron nitride nanosheets, and tetrabutyl titanate and / or tetrabutyl zirconate are added according to the content of the metal oxide.

2. The method for preparing alumina synthetic fiber felt by air flow melting according to claim 1, characterized in that: In the (1) mixing and sol preparation, the aluminum oxide powder and the rare earth element powder are mixed and stirred in a high-speed stirrer at a speed of 800-1200 rpm for 20-40 minutes.

3. The method for preparing alumina synthetic fiber felt by air flow melting according to claim 1, characterized in that: In the mixing and sol preparation (1), anhydrous ethanol is used as the dispersion medium, and dilute nitric acid is added to adjust the pH value to 2.5-3.

5.

4. The method for preparing alumina synthetic fiber felt by air flow melting according to claim 1, characterized in that: In the mixing and sol preparation (1), the mixed solution is slowly dripped into the aluminum sol, and then the mixture is stirred and reacted at 60-80° C. for 2-6 hours.

5. The method for preparing alumina synthetic fiber felt by air flow melting according to claim 1, characterized in that: In the preparation of the fiber precursor (2), the organic template is polyvinyl alcohol or polyethylene glycol, and its amount is 2%-5% of the weight of the composite sol.

6. The method for preparing alumina synthetic fiber felt by air flow melting according to claim 1, characterized in that: In the preparation of the fiber precursor (2), during the dry spinning process, the inner diameter of the needle is set to 0.6-0.8 mm, the voltage is 12-18 kV, the collection distance is 15-25 cm, the feeding rate is 10-30 μL / min, and aluminum foil is used as the collection carrier.

7. The method for preparing alumina synthetic fiber felt by air flow melting according to claim 1, characterized in that: During the heat treatment (3), the pre-sintering process is carried out in an air atmosphere, with the temperature rising to 500°C at a heating rate of 4-6°C / min and kept at that temperature for 1-2 hours.

8. The method for preparing alumina synthetic fiber felt by air flow melting according to claim 1, characterized in that: During the heat treatment (3), high-temperature sintering is carried out in a high-temperature tube furnace under the protection of high-purity argon gas, with the temperature rising to 1300°C at a heating rate of 8-10°C / min and kept at this temperature for 2-3 hours.

9. The method for preparing alumina synthetic fiber felt by air flow melting according to claim 1, characterized in that: In the (4) air flow melting to prepare the fiber felt, the nozzle diameter of the air flow melting device is 0.4-0.6 mm, the air flow velocity is set to 15-25 m / s, and the spraying temperature is maintained at 1400-1600°C.

10. Alumina synthetic fiber felt prepared by the preparation method according to any one of claims 1 to 9.

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