A method for preparing alumina synthetic fiber based on electrospinning

Abstract

The application relates to the technical field of alumina fiber preparation, in particular to a method for preparing alumina synthetic fiber based on electrostatic spinning, which comprises the following steps: adding ZIF-8 into a mixed solvent to form a metal organic framework dispersion liquid, adding aluminum sec-butyl alcohol to form a uniform precursor solution, adding yttrium stabilized zirconium dispersion liquid into the precursor solution, and finally adding polyvinylpyrrolidone to obtain a composite spinning liquid; then electrostatic spinning, heat treatment and high-temperature sintering are carried out to obtain alumina synthetic fiber. In the application, aluminum sec-butyl alcohol is used as a precursor, and ZIF-8 is used as a structure directing agent; the ordered arrangement of alumina nanoparticles is guided through the porous structure of the material; a more compact and ordered alumina crystal structure is formed; the internal structure of the fiber is more compact; meanwhile, the uniform dispersion of the alumina nanoparticles in the fiber is ensured; the crystallinity and mechanical properties of the alumina synthetic fiber are improved; and the overall uniformity and consistency are improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of alumina fiber preparation, in particular to a method for preparing alumina synthetic fiber based on electrostatic spinning. BACKGROUND

[0002] The electrostatic spinning technology is also called the electric spinning technology, is used for gradually stretching polymer or sol under the action of an electric field to obtain nanometer-sized fibers, and can continuously prepare nanofibers, is a simple and universal nanofiber preparation method, and the electrospun nanofibers have the characteristics of fiber ultra-length, various chemical compositions, uniform fiber diameter, polycrystalline or amorphous structure and the like, including electrostatic spinning ceramic fibers. The alumina synthetic fiber is a kind of high-temperature ceramic fiber, and the fiber not only has excellent fire resistance, but also has good mechanical strength and chemical stability, and is widely used in the fields of aerospace, high-temperature heat insulation materials, high-temperature filters and catalyst carriers.

[0003] However, in the preparation of high-temperature ceramic fibers such as alumina synthetic fibers, the existing precursor solution has poor uniformity and stability, which can cause the size and speed of the droplets sprayed in the spinning process to be inconsistent, thereby causing the fiber diameter to fluctuate, and can cause the formation of a beaded structure. Stable solution properties are the key to ensuring accurate control of spinning process parameters, reducing fiber quality problems caused by solution changes; and once the spinning process is affected, the compactness of the internal structure of the fiber will be reduced, increasing the possibility of phase change and grain growth at high temperatures, making it difficult to form a stable phase structure, thereby reducing the high-temperature stability of the alumina synthetic fiber and weakening the overall mechanical properties thereof. SUMMARY

[0004] In view of the deficiencies in the prior art, the purpose of the present application is to provide a method for preparing alumina synthetic fiber based on electrostatic spinning.

[0005] A method for preparing alumina synthetic fiber based on electrostatic spinning, comprising the following steps:

[0006] (1) preparing a composite spinning solution: adding ZIF-8 powder into a mixed solvent of ethanol and N,N-dimethylformamide, stirring and uniformly dispersing to form a metal organic framework dispersion liquid;

[0007] Slowly adding aluminum sec-butoxide into the metal organic framework dispersion liquid, slowly stirring to completely dissolve, and forming a uniform precursor solution;

[0008] Dispersing yttrium-stabilized zirconia powder into N,N-dimethylformamide, uniformly dispersing by ultrasonic treatment, and forming a yttrium-stabilized zirconia dispersion liquid;

[0009] slowly adding yttrium stabilized zirconium oxide dispersion into the precursor solution while keeping continuous stirring to ensure the two solutions are mixed uniformly, forming a mixed solution;

[0010] slowly adding polyvinylpyrrolidone into the mixed solution, continuously stirring for a period of time until a stable composite spinning solution is obtained;

[0011] (2) Electrospinning: using a syringe pump to spray the composite spinning solution through a nozzle to form a Taylor cone, which is sprayed onto a receiving device to obtain a primary spun fiber; the primary spun fiber is placed in an oven and dried at 80℃ for 3 hours, and then the temperature is adjusted to 170℃ for further drying for 2 hours to crosslink and solidify the primary spun fiber;

[0012] (3) Heat treatment and high-temperature sintering: placing the solidified primary spun fiber in a high-temperature furnace and gradually increasing the temperature to 1100-1400℃ at a rate of 2℃ / min for calcination, and then taking it out after cooling to obtain an aluminum oxide synthetic fiber.

[0013] Preferably, in the preparation of the composite spinning solution in (1), the mass ratio of ZIF-8 powder, aluminum sec-butoxide, yttrium stabilized zirconium oxide powder, and polyvinylpyrrolidone is 0.5-1:2-4:3-6:1-2.

[0014] Preferably, in the preparation of the composite spinning solution in (1), the volume ratio of ethanol to N,N-dimethylformamide in the mixed solvent of ethanol and N,N-dimethylformamide is 7-8:2-3.

[0015] Preferably, in the preparation of the composite spinning solution in (1), 3-6 parts by mass of yttrium stabilized zirconium oxide powder is dispersed in 30 parts by volume of N,N-dimethylformamide.

[0016] Preferably, in the preparation of the composite spinning solution in (1), after slowly adding polyvinylpyrrolidone to the mixed solution, the continuous stirring includes stirring at 700 rpm for 20-30 minutes, and then adjusting the stirring speed to 500 rpm and continuously stirring for 3-5 hours.

[0017] Preferably, in the preparation of the composite spinning solution in (1), the ultrasonic treatment time is 5-10 minutes.

[0018] Preferably, in the preparation of the composite spinning solution in (1), the stirring speed is not more than 700 rpm.

[0019] Preferably, in the electrospinning in (2), the electrospinning conditions include: voltage 10-15 kV, receiving distance 10-15 cm, spinning rate 0.3-0.7 ml / h, ambient temperature 20-25℃, and humidity 30%-50%.

[0020] Preferably, the (3) heat treatment and high-temperature sintering are divided into three stages, the first stage is from room temperature to 500-550 DEG C, the holding time is 60 minutes, the second stage is from the first stage temperature to 1200-1300 DEG C, the holding time is 60 minutes, the third stage is from the second stage temperature to 1400 DEG C, the holding time is 90 minutes, and the heating rate of the three stages is 2 DEG C / min.

[0021] Preferably, the (3) heat treatment and high-temperature sintering are divided into three stages, the first stage is from room temperature to 500-550 DEG C, the holding time is 60 minutes, the second stage is from the first stage temperature to 1200-1300 DEG C, the holding time is 60 minutes, the third stage is from the second stage temperature to 1400 DEG C, the holding time is 90 minutes, and the heating rate of the three stages is 2 DEG C / min.

[0022] Regarding the specific description of part of the raw materials in the above scheme:

[0023] 1、ZIF-8 is a kind of metal organic framework material, which is composed of zinc ions (Zn²⁺) and organic ligand (such as 2-methyl imidazole), has regular pore structure and large specific surface area, provides abundant nucleation site, helps other components (such as alumina) to be uniformly deposited and crystallized on its surface, forms zirconia wrapping layer, the existence of ZIF-8 makes alumina and other components more uniformly dispersed in the spinning solution, avoids local aggregation, thereby improves the uniformity of the final fiber, in addition, ZIF-8 leaves nanoscale voids or defects after decomposition at high temperature, which can be used as templates for subsequent alumina crystal growth, promote the formation of smaller and more uniform grains, improve the mechanical strength and thermal stability of the fiber.

[0024] 2、Aluminium sec-butoxide is an aluminum source precursor, which is decomposed into alumina and isopropyl alcohol at high temperature, ensuring the content and uniform distribution of alumina in the fiber, by adjusting its amount and decomposition conditions, the size and morphology of alumina grains can be controlled, thereby affecting the microstructure and performance of the fiber, alumina has high melting point and hardness, which can improve the mechanical strength and heat resistance of the fiber.

[0025] 3、Yttrium stabilized zirconia is mainly composed of zirconia (ZrO2), and a small amount of yttrium (Y2O3) is doped to stabilize cubic or tetragonal zirconia, yttrium stabilized zirconia remains stable at high temperature and does not change phase or decompose, and has good mechanical strength, thermal stability and thermal shock resistance.

[0026] The beneficial effects achieved by the present application are: 1、The present application uses aluminium sec-butoxide as a precursor and ZIF-8 (metal organic framework MOFs) as a structure directing agent, which guides the ordered arrangement of alumina nanoparticles through the porous structure of the material, helps to form a more compact and ordered alumina crystal structure, and the ordered arrangement of alumina nanoparticles makes the internal structure of the fiber more compact, which can improve the crystallinity and mechanical properties of the fiber, and the template effect of MOFs can ensure the uniform dispersion of alumina nanoparticles in the fiber, thereby improving the overall uniformity and consistency of the alumina synthetic fiber.

[0027] 2、The application can effectively inhibit phase transition and grain growth at high temperatures by introducing yttrium-stabilized zirconia to wrap alumina, ensuring the structural integrity and stability of the fiber in a high-temperature environment, improving the durability of the alumina synthetic fiber in a high-temperature environment, and prolonging its service life.

[0028] 3、The application combines electrospinning, segmented temperature rising sintering, etc., to improve the quality consistency and reliability of the fiber, and uses a step-by-step heating method for high-temperature sintering to promote the complete crystallization and densification of alumina, reduce stress concentration and structural defects, and help improve the thermal stability of the alumina synthetic fiber. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The application employs a schematic flowchart of a method for preparing an alumina synthetic fiber based on electrospinning. DETAILED DESCRIPTION

[0030] The application will be further described in detail below in conjunction with specific examples.

[0031] Example 1: A method for preparing an alumina synthetic fiber based on electrospinning, as shown in FIG. 1, includes the following steps: Figure 1

[0032] (1) Prepare a composite spinning solution: Add 0.75g ZIF-8 powder to 75ml ethanol and 25ml N,N-dimethylformamide mixed solvent, stir and disperse uniformly to form a metal organic framework dispersion liquid;

[0033] Slowly add 3g aluminum sec-butoxide to the metal organic framework dispersion liquid, slowly stir at 300rpm to make it completely dissolved, and form a uniform precursor solution;

[0034] Disperse 4.5g yttrium-stabilized zirconia powder into 30ml N,N-dimethylformamide, ultrasonic treatment for 7 minutes, and form a yttrium-stabilized zirconia dispersion liquid;

[0035] Slowly add the yttrium-stabilized zirconia dispersion liquid to the precursor solution, and continuously stir at 500rpm to form a mixed solution;

[0036] Slowly add 1.5g polyvinylpyrrolidone to the mixed solution, first stir at 700rpm for 25 minutes, then adjust the speed to 500rpm and continuously stir for 4 hours to obtain a stable composite spinning solution;

[0037] ​(2) Electrospun fiber: The composite spinning solution is sprayed out through the nozzle using an injection pump to form a Taylor cone and sprayed onto the receiving device to obtain the initial spun fiber. The conditions include a voltage of 12kV, a receiving distance of 12cm, a spinning rate of 0.5ml / h, an ambient temperature of 22℃, and a humidity of 40%. The initial spun fiber is placed in an oven and dried at 80℃ for 3 hours. The temperature is then adjusted to 170℃ and dried for another 2 hours to allow the initial spun fiber to crosslink and solidify.

[0038] (3) Heat treatment and high-temperature sintering: The solidified spun fibers are placed in a high-temperature furnace, heated from room temperature to 525°C and held for 60 minutes, then heated from 525°C to 1250°C and held for 60 minutes; finally heated from 1250°C to 1400°C and held for 90 minutes; the heating rate is 2°C / min, and the cooling rate is controlled not to exceed 2°C / min. After cooling, the fibers are taken out to obtain alumina synthetic fibers.

[0039] Example 2: A method for preparing alumina synthetic fibers based on electrospinning, such as... Figure 1 As shown, it includes the following steps:

[0040] (1) Preparation of composite spinning solution: Add 1g ZIF-8 powder to a mixed solvent of 80ml ethanol and 20ml N,N-dimethylformamide, stir and disperse evenly to form a metal-organic framework dispersion;

[0041] 4g of aluminum sec-butoxide was slowly added to the metal-organic framework dispersion and stirred slowly at 300rpm until it was completely dissolved to form a homogeneous precursor solution.

[0042] 6g of yttrium-stabilized zirconium oxide powder was dispersed in 30ml of N,N-dimethylformamide and sonicated for 10 minutes to form a yttrium-stabilized zirconium oxide dispersion.

[0043] The yttrium-stabilized zirconium oxide dispersion was slowly added to the precursor solution while continuously stirring at 500 rpm to form a mixed solution.

[0044] 2g of polyvinylpyrrolidone was slowly added to the mixed solution. The mixture was stirred at 700rpm for 30 minutes, and then the speed was adjusted to 500rpm and stirred continuously for 5 hours to obtain a stable composite spinning solution.

[0045] (2) Electrospun fiber: The composite spinning solution is sprayed out through the nozzle using an injection pump to form a Taylor cone and sprayed onto the receiving device to obtain the initial spun fiber. The conditions include a voltage of 15kV, a receiving distance of 15cm, a spinning rate of 0.7ml / h, an ambient temperature of 25℃, and a humidity of 50%. The initial spun fiber is placed in an oven and dried at 80℃ for 3 hours. The temperature is then adjusted to 170℃ and dried for another 2 hours to allow the initial spun fiber to crosslink and solidify.

[0046] (3) Heat treatment and high-temperature sintering: place the solidified as-spun fiber in a high-temperature furnace, from room temperature to 550°C, keep for 60 minutes, then from 550°C to 1300°C, keep for 60 minutes; finally from 1300°C to 1400°C, keep for 90 minutes; the heating rate is 2°C / min, the cooling rate is controlled to be not more than 2°C / min, then take out after cooling, to obtain the alumina synthetic fiber.

[0047] Example 3: A method for preparing an alumina synthetic fiber based on electrospinning, as shown in Figure 1 , comprising the following steps:

[0048] (1) Preparation of composite spinning solution: add 0.5g ZIF-8 powder into 70ml ethanol and 30ml N,N-dimethylformamide mixed solvent, stir and disperse uniformly to form a metal organic framework dispersion liquid;

[0049] Slowly add 2g aluminum sec-butoxide into the metal organic framework dispersion liquid, slowly stir at 300rpm to make it completely dissolved, to form a uniform precursor solution;

[0050] Disperse 3g yttrium-stabilized zirconia powder into 30ml N,N-dimethylformamide, ultrasonic treatment for 5 minutes, to form a yttrium-stabilized zirconia dispersion liquid;

[0051] Slowly add the yttrium-stabilized zirconia dispersion liquid into the precursor solution, and continuously stir at 500rpm to form a mixed solution;

[0052] Slowly add 1g polyvinylpyrrolidone into the mixed solution, first stir at 700rpm for 20 minutes, then adjust the speed to 500rpm and continuously stir for 3 hours, to obtain a stable composite spinning solution;

[0053] (2) Electrospinning fiber: use a syringe pump to spray the composite spinning solution through a nozzle to form a Taylor cone, spray onto a receiving device to obtain an as-spun fiber, the conditions include voltage 10kV, receiving distance 10cm, spinning rate 0.3ml / h, ambient temperature 20°C, humidity 30%; place the as-spun fiber in an oven, dry at 80°C for 3 hours, adjust the temperature to 170°C and continue to dry for 2 hours to make the as-spun fiber crosslink and solidify;

[0054] (3) Heat treatment and high-temperature sintering: place the solidified as-spun fiber in a high-temperature furnace, from room temperature to 500°C, keep for 60 minutes, then from 500°C to 1200°C, keep for 60 minutes; finally from 1200°C to 1400°C, keep for 90 minutes; the heating rate is 2°C / min, the cooling rate is controlled to be not more than 2°C / min, then take out after cooling, to obtain the alumina synthetic fiber.

[0055] Comparative Example 1: Compared with Example 1, the comparative example does not use ZIF-8 powder and yttrium stabilized zirconium powder in the preparation of the composite spinning solution, specifically: (1) preparation of the composite spinning solution: aluminum sec-butoxide is added to the mixed solvent of ethanol and N,N-dimethylformamide, and stirred to completely dissolve, forming a uniform precursor solution; polyvinylpyrrolidone is slowly added to the precursor solution, and continuous stage stirring is performed until a stable composite spinning solution is obtained.

[0056] The yttrium stabilized zirconium dispersion solution is slowly added to the precursor solution, and continuous stirring is maintained to ensure uniform mixing of the two solutions, forming a mixed solution; polyvinylpyrrolidone is slowly added to the mixed solution, and continuous stage stirring is performed until a stable composite spinning solution is obtained.

[0057] Other steps and process parameter conditions are consistent with Example 1, and an aluminum oxide synthetic fiber is obtained.

[0058] Comparative Example 2: Compared with Example 1, the comparative example does not use ZIF-8 powder and yttrium stabilized zirconium powder in the preparation of the composite spinning solution, specifically: (1) preparation of the composite spinning solution: aluminum sec-butoxide is added to the mixed solvent of ethanol and N,N-dimethylformamide, and stirred to completely dissolve, forming a uniform precursor solution; polyvinylpyrrolidone is slowly added to the precursor solution, and continuous stage stirring is performed until a stable composite spinning solution is obtained.

[0059] Other steps and process parameter conditions are consistent with Example 1, and an aluminum oxide synthetic fiber is obtained.

[0060] Performance test: the aluminum oxide synthetic fibers obtained in Examples 1-3 and Comparative Examples 1-2 are tested for relevant performance, including thermal stability, mechanical properties and electrical properties;

[0061] 1. Thermal stability: the fiber sample is placed in a high temperature furnace, gradually increased from room temperature to 1600℃ at a rate of 5℃ / min, and held for 2 hours, then naturally cooled and observed for the appearance of the aluminum oxide synthetic fiber.

[0062] 2. Mechanical properties: the fiber sample is fixed on the tensile clamps of a universal testing machine, the tensile rate is set to 5mm / min, the test environment is room temperature and humidity is 40%, the universal testing machine is started, the force-displacement data during the tensile process is recorded, and the maximum tensile force and elongation at break are recorded, the tensile strength and elastic modulus of the fiber are calculated according to the tensile stress-strain curve.

[0063] 3. Electrical properties: the fiber sample is fixed on a four-probe test platform, the current is set to 1mA, the test environment is room temperature and humidity is 40%, the four-probe tester is started, the voltage drop and current value are recorded, and the resistivity is calculated according to the measured voltage drop and current value.

[0064] The test results are shown in the following table.

[0065] Table 1. Results of various performance tests of aluminum oxide synthetic fibers

[0066]

[0067] The above examples are merely illustrative of the principles of the application and its best mode and are not intended to limit the application as construed in accordance with the appended claims and their equivalents. All changes, modifications, and equivalents that fall within the spirit and scope of the application are therefore intended to be embraced by the claims that follow.

Claims

1. A method for preparing alumina synthetic fibers based on electrospinning, characterized in that, Includes the following steps: (1) Preparation of composite spinning solution: ZIF-8 powder is added to a mixed solvent of ethanol and N,N-dimethylformamide, stirred and dispersed evenly to form a metal-organic framework dispersion; Aluminum sec-butoxide was slowly added to the metal-organic framework dispersion and stirred slowly to dissolve it completely, forming a homogeneous precursor solution. Yttrium-stabilized zirconium oxide powder was dispersed in N,N-dimethylformamide and then ultrasonically treated to ensure uniform dispersion, thus forming a yttrium-stabilized zirconium oxide dispersion. The yttrium-stabilized zirconium oxide dispersion was slowly added to the precursor solution while continuously stirring to ensure that the two solutions were uniformly mixed to form a mixed solution. Polyvinylpyrrolidone was slowly added to the mixed solution, and the mixture was continuously stirred until a stable composite spinning solution was obtained. (2) Electrospun fiber: The composite spinning solution is sprayed out through the nozzle using an injection pump to form a Taylor cone and sprayed onto the receiving device to obtain the initial spun fiber; the initial spun fiber is placed in an oven and dried at 80°C for 3 hours, and the temperature is adjusted to 170°C and dried for another 2 hours to allow the initial spun fiber to crosslink and solidify. (3) Heat treatment and high-temperature sintering: The solidified spun fibers are placed in a high-temperature furnace and calcined at a rate of 2℃ / min to 1100℃-1400℃. After cooling, they are taken out to obtain alumina synthetic fibers.

2. The method for preparing alumina synthetic fibers based on electrospinning according to claim 1, characterized in that, In the preparation of the composite spinning solution in (1), the mass ratio of ZIF-8 powder, aluminum sec-butoxide, yttrium-stabilized zirconium oxide powder, and polyvinylpyrrolidone is 0.5-1:2-4:3-6:1-2.

3. The method for preparing alumina synthetic fibers based on electrospinning according to claim 1, characterized in that, In the preparation of the composite spinning solution in (1), the volume ratio of ethanol to N,N-dimethylformamide in the mixed solvent of ethanol and N,N-dimethylformamide is 7-8:2-3.

4. The method for preparing alumina synthetic fibers based on electrospinning according to claim 1, characterized in that, In the preparation of the composite spinning solution in (1), 3-6 parts by weight of yttrium-stabilized zirconium oxide powder are dispersed in 30 parts by volume of N,N-dimethylformamide.

5. The method for preparing alumina synthetic fibers based on electrospinning according to claim 1, characterized in that, In the preparation of the composite spinning solution (1), polyvinylpyrrolidone is slowly added to the mixed solution and then continuously stirred at 700 rpm for 20-30 minutes, and then the speed is adjusted to 500 rpm and stirred continuously for 3-5 hours.

6. The method for preparing alumina synthetic fibers based on electrospinning according to claim 1, characterized in that, In the preparation of the composite spinning solution in (1), the ultrasonic treatment time is 5-10 minutes.

7. The method for preparing alumina synthetic fibers based on electrospinning according to claim 1, characterized in that, In the preparation of the composite spinning solution in (1), the stirring speed does not exceed 700 rpm.

8. The method for preparing alumina synthetic fibers based on electrospinning according to claim 1, characterized in that, In the electrospun fiber described in (2), the electrospun conditions include: voltage 10-15kV, receiving distance 10-15cm, spinning rate 0.3-0.7ml / h, ambient temperature 20-25℃, and humidity 30%-50%.

9. The method for preparing alumina synthetic fibers based on electrospinning according to claim 1, characterized in that, In the heat treatment and high-temperature sintering described in (3), there are three stages. The first stage is from room temperature to 500-550℃, and the holding time is 60 minutes. The second stage is from the temperature of the first stage to 1200-1300℃, and the holding time is 60 minutes. The third stage is from the temperature of the second stage to 1400℃, and the holding time is 90 minutes. The heating rate of the three stages is 2℃ / min.

10. The method for preparing alumina synthetic fibers based on electrospinning according to claim 1, characterized in that, In the heat treatment and high-temperature sintering described in (3), a slow cooling method is adopted, including natural cooling or controlling the cooling rate to not exceed 2℃ / min.

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