An ultra-fine alkaline earth hexaaluminate inorganic fiber and a method of making the same

Abstract

The present application relates to a kind of superfine alkali earth hexaaluminate inorganic fiber and its preparation method, the diameter of the alkali earth hexaaluminate inorganic fiber described is 0.1 μm-3.0 μm, and it is continuously adjustable in this range, the prepared alkali earth hexaaluminate fiber keeps fiber flexibility in the temperature range of room temperature to high temperature 1300 DEG C, and keeps fiber crystal phase stability and fiber form integrity at high temperature 1400 DEG C.The preparation method is to mix aluminum sol, alkali earth salt, high molecular polymer and dissolve in water to obtain sol, then electrospinning precursor fiber is obtained, and the precursor fiber is obtained by high-temperature heat treatment to obtain alkali earth hexaaluminate inorganic fiber.The present application has low cost, and fiber structure stability is good, has wide application prospect in the fields such as catalyst, catalyst carrier, fiber structure reinforcement, heat insulation and the like.

Description

Technical Field

[0001] The invention relates to an ultrafine alkaline earth hexaaluminate inorganic fiber and a preparation method thereof, belonging to the field of inorganic non-metallic materials. Background Art

[0002] Alkaline earth hexaaluminates have a hexagonal layered structure, with crystal structures primarily consisting of magneto-plumbite and β-Al2O3. Calcium hexaaluminate and strontium hexaaluminate exhibit a magneto-plumbite structure, while barium hexaaluminate exhibits a β-Al2O3 structure. This type of structure not only offers high melting points, high-temperature structural stability, and excellent sintering resistance, but also boasts high thermal resistance, high specific surface area, good structural adjustability, and strong thermal shock resistance. It has been extensively studied in areas such as structural reinforcement, high-temperature thermal insulation, catalysts, and catalyst supports. Among various material forms, one-dimensional fiber structures and their fiber products offer advantages such as light weight, large specific surface area, low thermal conductivity, high porosity, and high air permeability. Combined with the alkaline earth hexaaluminate phase structure, the preparation of alkaline earth hexaaluminate fibers can further enhance the application advantages of alkaline earth hexaaluminates in high-temperature thermal insulation, structural reinforcement, catalysts, and catalyst supports.

[0003] Currently, research on alkaline earth hexaaluminates primarily focuses on the preparation of high-surface-area powders and their applications in catalysts and catalyst supports. For example, patent CN202110105190.3 discloses a hexaaluminate catalyst and a method for selectively oxidizing hydrogen sulfide to produce sulfur at medium and high temperatures. This catalyst exhibits high catalytic activity under these conditions. Furthermore, alkaline earth hexaaluminates can be used as thermal barrier coatings in high-temperature applications. For example, patent CN109023203A discloses a method for preparing a stable crystalline hexaaluminate thermal barrier coating. This hexaaluminate thermal barrier coating exhibits excellent phase stability and resistance to thermal shock cycles at high temperatures. However, reports on alkaline earth hexaaluminate fibers are relatively scarce. To address this gap in research on alkaline earth hexaaluminate fibers and to provide a new method and product for their application in catalysis and high-temperature thermal insulation, the present invention is proposed. Summary of the Invention

[0004] In response to the lack of research on existing alkaline earth hexaaluminate inorganic fibers, the present invention provides an ultrafine alkaline earth hexaaluminate inorganic fiber and a preparation method thereof, which provides a new form for the application of alkaline earth hexaaluminate materials, and provides a new idea and new product for the development of alkaline earth hexaaluminate fibers and fiber products, and their application in high-temperature thermal insulation, high-temperature catalysis and catalyst carrier fields.

[0005] The ultrafine alkaline earth hexaaluminate inorganic fiber prepared by the present invention has a main crystal phase molecular formula of AAl 12 O 19(A=Ca, Sr, Ba), the ultrafine fiber diameter is 0.1μm~3.0μm, and it is continuously adjustable within this range. The alkaline earth hexaaluminate fiber maintains fiber flexibility in the temperature range from room temperature to high temperature 1300℃, and maintains fiber crystal phase stability and fiber morphology integrity at high temperature 1400℃. Detailed Description of the Invention

[0007] The technical solutions of the present invention are as follows:

[0008] According to the present invention, a method for preparing ultrafine alkaline earth hexaaluminate inorganic fiber comprises the following steps:

[0009] (a) Preparation of alkaline earth hexaaluminate precursor sol

[0010] adding an aluminum source and an alkaline earth source as raw materials to a solvent water at a metal ion molar ratio of aluminum:alkaline earth metal =(11-12):(0.25-3):(0.25-3), stirring and dissolving to obtain an alkaline earth hexaaluminate solution having a mass fraction of 8-30%; adding a high molecular weight polymer having a mass fraction of 0.2-10% to the alkaline earth hexaaluminate solution under heating and stirring at 20-90° C., and fully dissolving to obtain an alkaline earth hexaaluminate precursor sol;

[0011] (b) Preparation of alkaline earth hexaaluminate inorganic fibers

[0012] The alkaline earth hexaaluminate precursor sol obtained in step (a) is electrospinned to produce alkaline earth hexaaluminate precursor fibers, and then the alkaline earth hexaaluminate precursor fibers are heat-treated to 450-600° C. at a heating rate of 0.5-10° C. / min under atmospheric conditions and kept warm for 0-4 hours; and then heat-treated to 1000-1300° C. at a heating rate of 2-10° C. / min and kept warm for 1-4 hours to produce alkaline earth hexaaluminate inorganic fibers.

[0013] According to a preferred embodiment of the present invention, the molar ratio of the aluminum source and the alkaline earth source in step (a) is aluminum:alkaline earth metal=(11-12):(0.5-1.5);

[0014] According to the present invention, the spinning aid in step (a) is preferably one of polyvinyl pyrrolidone, polyethylene oxide, polyvinyl alcohol or a combination thereof;

[0015] According to the preferred embodiment of the present invention, the mass fraction of the spinning aid in step (a) is: 0.5% to 8%;

[0016] According to the preferred embodiment of the present invention, the process conditions of the electrospinning method described in step (b) are: sol injection rate of 0.8 to 2.2 mL / h, spinning voltage of 14 to 35 kV, fiber receiving distance of 12 to 35 cm, spinning environment temperature of 20 to 45 ° C, and spinning environment humidity of 20 to 55%.

[0017] According to the preferred embodiment of the present invention, the atmosphere in step (b) is an air atmosphere.

[0018] According to the preferred embodiment of the present invention, the heat treatment system described in step (b) is: heat treatment to 400-600°C at a heating rate of 2-5°C / min, and then heat treatment to 1050-1200°C at a heating rate of 4-10°C / min, and keeping warm for 1-2 hours to obtain ultrafine alkaline earth hexaaluminate inorganic fibers.

[0019] The excellent effects of the present invention are as follows:

[0020] 1. The raw materials used in the present invention are widely available, low in cost, have low spinning environment requirements, and are easy to achieve spinning conditions.

[0021] 2. The alkaline earth hexaaluminate inorganic fiber prepared by the present invention has a diameter of 0.1 μm to 3.0 μm, maintains fiber flexibility in the temperature range from room temperature to high temperature of 1300°C, and maintains fiber crystal phase stability and fiber morphology integrity at a high temperature of 1400°C.

[0022] 3. The alkaline earth hexaaluminate inorganic fiber prepared by the present invention is composed of hexagonal AAl 12 O 19 (A=Ca, Sr, Ba), and the microstructure of the fiber is lamellar crystal or equiaxed crystal, which has excellent high-temperature crystal phase stability and microstructural stability.

[0023] 4. The alkaline earth hexaaluminate inorganic fiber prepared by the present invention has excellent high-temperature stability and microstructural stability, which makes it have broad application prospects in the fields of catalysts, catalyst carriers, fiber structure reinforcement, thermal insulation and heat preservation. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is an optical photograph of the calcium hexaaluminate inorganic fiber membrane obtained in Example 1 after heat treatment to 1200°C.

[0025] Figure 2 This is a SEM image of the calcium hexaaluminate inorganic fiber membrane obtained in Example 1 after heat treatment to 1200°C.

[0026] Figure 3 The XRD pattern of the barium hexaaluminate inorganic fiber obtained in Example 3 after heat treatment at 1200°C is shown in FIG.

[0027] Figure 4 This is the SEM image of the barium hexaaluminate inorganic fiber obtained in Example 3 after heat treatment at 1200°C. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to embodiments and accompanying drawings, but is not limited thereto.

[0029] The raw materials used in the examples are all commercially available.

[0030] Example 1:

[0031] A method for preparing ultrafine calcium hexaaluminate inorganic fiber comprises the following steps:

[0032] (a) To 10.00 g of 24 wt% aluminum hydroxychloride sol was added 3.00 g of water to dissolve the sol to obtain an aluminum sol. Calcium acetate was added to the aluminum sol at a molar ratio of Al:Ca = 11:1, and then 0.12 g of polyethylene oxide was added and stirred to dissolve the sol to obtain a calcium hexaaluminate precursor sol.

[0033] (b) Calcium hexaaluminate precursor fibers were prepared by electrospinning. The electrospinning process conditions were as follows: ambient humidity of 30% to 40%, ambient temperature of 25°C, injection rate of 0.8 mL / h, voltage of 16 kV, and spinning distance of 18 cm. The obtained calcium hexaaluminate precursor fibers were heat-treated in air at a heating rate of 1°C / min to 600°C and then at a heating rate of 2°C / min to 1200°C. The heat treatment was carried out for 2 hours to obtain calcium hexaaluminate inorganic fibers. The prepared calcium hexaaluminate inorganic fiber membrane is shown in FIG. Figure 1 As shown in the SEM image of the fiber membrane Figure 2 shown.

[0034] Example 2:

[0035] A method for preparing ultrafine strontium hexaaluminate inorganic fiber

[0036] As described in Example 1, except that the calcium acetate in step (a) is replaced by strontium acetate.

[0037] Example 3:

[0038] A method for preparing ultrafine barium hexaaluminate inorganic fiber

[0039] As described in Example 1, the difference is that the calcium acetate in step (a) is replaced by barium acetate, and the molar ratio of Al:Ca=11:1 is changed to Al:Ba=12:0.5. The XRD pattern of the prepared barium hexaaluminate inorganic fiber is shown in FIG. Figure 3 As shown in the SEM images Figure 4 shown.

[0040] Example 4:

[0041] An ultrafine multi-component calcium strontium barium hexaaluminate (Ca 0.33 Sr 0.33 Ba 0.33 Al 12 O 19) The method for preparing inorganic fibers is as described in Example 1, except that the calcium acetate in step (a) is replaced with calcium acetate, strontium acetate, and barium acetate, and the molar ratio Al:Ca = 11:1 is replaced with Al:Ca:Sr:Ba = 12:0.33:0.33:0.33.

[0042] Example 5:

[0043] A method for preparing ultrafine calcium hexaaluminate inorganic fiber

[0044] As described in Example 1, except that the calcium acetate in step (a) is replaced by calcium nitrate, and the spinning aid polyethylene oxide is replaced by polyvinyl pyrrolidone.

Claims

1. An ultrafine alkaline earth hexaaluminate inorganic fiber, characterized in that: The alkaline earth hexaaluminate comprises a multi-component hexaaluminate consisting of one or more of calcium hexaaluminate, strontium hexaaluminate, and barium hexaaluminate. The alkaline earth hexaaluminate inorganic fiber has a diameter of 0.1 μm to 3.0 μm, maintains fiber flexibility within a temperature range from room temperature to a high temperature of 1300°C, and maintains fiber crystal phase stability and fiber morphology integrity at a high temperature of 1400°C. The alkaline earth hexaaluminate inorganic fiber is prepared by the following steps: (a) Preparation of alkaline earth hexaaluminate precursor sol The raw materials of aluminum source and alkaline earth source are added to solvent water at a metal ion molar ratio of aluminum:alkaline earth metal = (11-12) : (0.5-1.5), and stirred to dissolve to obtain an alkaline earth hexaaluminate solution with a mass fraction of 8-30%. Under heating and stirring conditions at 20-90°C, a high molecular weight polymer with a mass fraction of 0.2-10% is added to the alkaline earth hexaaluminate solution to fully dissolve it to obtain an alkaline earth hexaaluminate precursor sol. (b) Preparation of alkaline earth hexaaluminate inorganic fibers The alkaline earth hexaaluminate precursor sol obtained in step (a) is electrospinned to produce alkaline earth hexaaluminate precursor fibers, which are then heat-treated to 450-600°C at a heating rate of 0.5-10°C / min under atmospheric conditions and kept warm for 0-4 hours; and then heat-treated to 1000-1300°C at a heating rate of 2-10°C / min and kept warm for 1-4 hours to produce alkaline earth hexaaluminate inorganic fibers.

2. The alkaline earth hexaaluminate inorganic fiber according to claim 1, characterized in that The aluminum source in step (a) is one of aluminum chloride, aluminum hydroxychloride, and aluminum carboxylate, or a combination thereof.

3. The alkaline earth hexaaluminate inorganic fiber according to claim 1, wherein When the alkaline earth hexaaluminate is calcium hexaaluminate, the alkaline earth source in step (a) is one of calcium formate, calcium acetate, calcium nitrate, and calcium chloride, or a combination thereof; when the alkaline earth hexaaluminate is strontium hexaaluminate, the alkaline earth source in step (a) is one of strontium acetate, strontium nitrate, and strontium chloride, or a combination thereof; when the alkaline earth hexaaluminate is barium hexaaluminate, the alkaline earth source in step (a) is barium acetate.

4. The alkaline earth hexaaluminate inorganic fiber according to claim 1, wherein The high molecular polymer in step (a) is one of polyvinyl pyrrolidone, polyvinyl butyral, polymethyl methacrylate, polyethylene oxide, and polyvinyl alcohol, or a combination thereof.

5. The alkaline earth hexaaluminate inorganic fiber according to claim 1, wherein The electrospinning process conditions in step (b) are as follows: spinning distance 6 to 50 cm, spinning voltage 6 to 50 kV, sol propulsion rate 0.2 to 5.0 mL / h, ambient temperature 20 to 95°C, and ambient humidity 10 to 65%.

6. The alkaline earth hexaaluminate inorganic fiber according to claim 1, wherein The atmosphere in step (b) is air or water vapor.

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