A rare earth aluminate inorganic fiber and its preparation method

Abstract

This invention relates to a rare earth aluminate inorganic fiber and its preparation method, wherein the main crystalline phase of the rare earth aluminate is composed of ReAl. 11 O 18 Composed of ReAlO3 (Re = La, Ce, Pr, Nd), the relative content of the two phases is continuously adjustable within the range of 0–100 wt%. The fiber diameter ranges from 0.2 μm to 6.0 μm. The fiber maintains flexibility under high-temperature conditions from room temperature to 1450℃ and maintains microstructure and crystalline phase stability from room temperature to 1650℃. The preparation method uses aluminum sol as the aluminum source, rare earth salts as the rare earth source, and a polymer as a spinning aid. Precursor fibers are obtained by electrospinning or centrifugation, and the precursor fibers are then heat-treated to obtain rare earth aluminate inorganic fibers. This invention features sol stability, good spinnability, simple preparation process, and low cost. The prepared inorganic fibers have a stable and controllable structure, intact morphology, and good flexibility, showing promising applications in thermal insulation, flexible electronics, flue gas dust removal, and battery separators.

Description

Technical Field

[0001] This invention relates to a rare earth aluminate inorganic fiber and its preparation method, belonging to the field of inorganic non-metallic materials. Background Technology

[0002] Rare earth aluminates not only possess excellent physicochemical properties such as high thermal decomposition temperature, low thermal conductivity, good chemical stability, superior oxidation resistance, and good resistance to water vapor erosion, but their excellent lamellar microstructure also endows them with good high-temperature stability, interfacial stability, and structural reinforcement. Furthermore, compared to powders, bulk materials, and thin films, structural components formed by one-dimensional fibers can inherit the excellent physicochemical properties of rare earth aluminates while also leveraging the lightweight, low-density, and good thermal shock resistance of one-dimensional fiber structures. This makes them highly promising for applications in high-temperature thermal insulation and protection, material structural reinforcement, high-temperature gas and dust filtration, and liquid separation and purification.

[0003] Rare earth aluminate inorganic fibers, due to their high melting point and low viscosity at high temperatures, suffer from high costs in high-temperature melt preparation and poor spinning performance. Therefore, obtaining these fibers through chemical precursor methods is currently the most economical and effective approach. In 2008, an article titled "Sintering-resistant hollow fibers of LaMgAl" was published. 11 O 19 In this study, LaMgAl was prepared by electrospinning using metal nitrates as precursors, polyvinylpyrrolidone (PVP) as template agent, and water and anhydrous ethanol as solvents. 11 O 19 Precursor fibers were heat-treated at 1100℃ to obtain LaMgAl with a hollow crystalline structure. 11 O 19 LaMgAl 11 O 19 The ceramic yield was approximately 10 wt%, and it maintained a good fibrous structure at 1200℃. Subsequently, there were few reports on the preparation of rare-earth aluminate inorganic fibers. From the literature on LaMgAl... 11 O 19 The current methods for fiber preparation and processing have problems such as poor spinnability of precursor sol, low solid content of precursor fibers, and non-dense structure at high temperatures. Further optimization of fiber structure is needed to obtain rare earth aluminate fibers with stable microstructure at high temperatures, so as to provide a technical basis for the application of rare earth aluminate fibers in specific industries and mining environments.

[0004] Therefore, in order to further optimize the rare earth aluminate inorganic fiber precursor sol, improve sol spinning properties and ceramic yield, obtain rare earth aluminate fibers with stable high-temperature structure, and promote the application of rare earth aluminate fibers in high-temperature thermal insulation and protection, material structure reinforcement, battery separators, high-temperature gas and dust filtration, liquid separation and purification, etc., this invention is proposed. Summary of the Invention

[0005] To address the shortcomings of existing technologies, such as low spinnability of sol, low solid content, and non-dense microstructure at high temperatures, this invention provides a method for preparing high-temperature stable rare earth aluminate inorganic fibers, offering a new approach for the engineering application of rare earth aluminate inorganic fibers. Invention Overview

[0007] The rare earth aluminate main crystalline phase is composed of the molecular formula ReAl 11 O 18 It is composed of ReAlO3 (Re = La, Ce, Pr, Nd), where ReAl 11 O 18 The relative content of the two phases is 0-100%, and the mass fraction of the main crystalline phase in the inorganic fiber is not less than 90%. The rare earth aluminate fiber crystalline phase prepared by this invention can achieve ReAl 11 O 18 The content of ReAlO3 and the two phases can be continuously adjusted. At the same time, the two phases exist in the microstructure as a lamellar structure and a granular structure, respectively. From the microscopic mechanism, the granular structure is restricted by the lamellar structure, which is conducive to improving the mechanical strength of the fiber, while the lamellar structure can promote crack deflection, thereby improving the fracture toughness of the fiber.

[0008] The invention utilizes aluminum chloride and aluminum hydroxychloride (molecular formula Al(OH)). x Cl y (x = 0.5~2, y = 0~2), aluminum carboxylate (molecular formula Al(RCOO)) x Using precursors with certain spinnability, such as aluminum isopropoxide (x = 0.5–2, R = H, -CH3, -CH2CH3, -CH2CH2CH3), aluminum isopropoxide, and aluminum acetylacetonate, as aluminum sources can significantly improve the spinnability of the sol. Using commercially available rare earth metal salts as rare earth sources can significantly reduce the preparation cost of the sol. Precursor fibers are prepared by electrospinning or centrifugal spinning, and then subjected to high-temperature heat treatment to obtain ReAl 11 O 18 Rare earth aluminate fibers, which consist of ReAlO3 (Re=La,Ce,Pr,Nd) as the main crystalline phase and have a main crystalline phase content of not less than 90%, have both of these crystalline phases that have high melting points, complex crystal structures and low thermal conductivity, providing a physicochemical basis for the high-temperature application of the fibers.

[0009] Compared with existing methods for preparing rare earth aluminate inorganic fibers, this method is characterized by a main crystalline phase with the molecular formula ReAl. 11 O 18 (Re=La,Ce,Pr,Nd) The raw materials are economical, cheap and readily available. The sol solids content is high and the fiber structure is dense. It can maintain the flexibility and morphological integrity of the fiber under high temperature conditions from room temperature to 1450℃, and maintain the stability of the fiber microstructure and crystal phase from room temperature to 1650℃. It has broad application prospects under extreme environmental conditions.

[0010] In addition, the electrospinning technology provided by this invention can not only obtain rare earth aluminate inorganic fiber cotton, but also obtain rare earth aluminate inorganic fiber membrane with high temperature structural stability and good flexibility through roller collection or flat plate collection device. Invention Details

[0012] The technical solution of the present invention is as follows:

[0013] According to the present invention, a method for preparing rare earth aluminate inorganic fibers includes the following steps:

[0014] (a) Preparation of rare earth aluminate precursor sol

[0015] Aluminum source and rare earth source are added to a solvent with a mass ratio of solid to solvent of 1:(1 to 10) at a molar ratio of Al:Re = 11:(0.5 to 5.0) to obtain a rare earth aluminate solution. Under the condition of heating and stirring at 20 to 90°C, a polymer with a mass fraction of 0.5 to 10% is added to the rare earth aluminate solution and dissolved completely to obtain a rare earth aluminate precursor sol.

[0016] (b) Preparation of rare earth aluminate precursor fibers

[0017] Rare earth aluminate precursor fibers are obtained by electrospinning of the rare earth aluminate precursor sol in step (a); or the rare earth aluminate precursor sol in step (a) is concentrated under reduced pressure at a temperature of 45 to 90°C to obtain a precursor sol with a viscosity of 3 to 30 Pa·s, and then aluminate precursor fibers are obtained by centrifugal spinning.

[0018] (c) Preparation of rare earth aluminate inorganic fibers

[0019] The rare earth aluminate precursor fibers obtained in step (b) are heat-treated under atmospheric conditions to obtain rare earth aluminate inorganic fibers.

[0020] According to a preferred embodiment of the present invention, the molar ratio of aluminum source to rare earth source in step (a) is Al:Re = 11:(0.5~1.5);

[0021] According to a preferred embodiment of the present invention, the mass ratio of the solid to the solvent in step (a) is solid:solvent = 1:(1-6);

[0022] According to a preferred embodiment of the present invention, the spinning aid described in step (a) is one or a combination of polyvinylpyrrolidone, polyethylene oxide, and polyvinyl alcohol;

[0023] According to a preferred embodiment of the present invention, the mass fraction of the spinning aid in step (a) is 1% to 7.5%.

[0024] According to a preferred embodiment of the present invention, the process conditions for the electrospinning method in step (b) are as follows: sol injection rate of 0.6-2.0 mL / h, spinning voltage of 12-30 kV, fiber receiving distance of 15-30 cm, spinning ambient temperature of 20-45 °C, and spinning ambient humidity of 20-55%.

[0025] According to a preferred embodiment of the present invention, the process conditions for the centrifugal spinning method in step (b) are as follows: the spinning environment temperature is 35-80℃, the spinning environment humidity is 25-40%, the centrifuge speed is 17000-26000 r / min, the spinning hole linear velocity is 28-46 m / s, and the spinning hole diameter is 0.20-0.50 mm.

[0026] According to a preferred embodiment of the present invention, the atmosphere described in step (c) is an air atmosphere.

[0027] According to a preferred embodiment of the present invention, the heat treatment process in step (c) is as follows: heating to 400-600°C at a heating rate of 2-5°C / min, and then heating to 1000-1250°C at a heating rate of 4-10°C / min / min.

[0028] The superior effects of this invention are as follows:

[0029] 1. The spinnable aluminum source used in this invention is widely available, aluminum sol is inexpensive and readily available, and rare earth source can be commercially available rare earth salts, which is low in cost. The solid content of rare earth aluminates in the sol is high, and the electrospinning and centrifugal spinning technologies are simple and have low requirements for the spinning environment. Therefore, the preparation of rare earth aluminate precursor fibers can be achieved efficiently and economically.

[0030] 2. The rare earth aluminate fiber phase prepared in this invention is composed of ReAl 11 O 18 It consists of two phases, ReAlO3 and Rare Earth Aluminate Fiber, and the relative content of the two phases can be continuously adjusted in the range of 0 to 100%, which provides a phase basis for Rare Earth Aluminate Fiber to be suitable for different environmental conditions. In addition, the two phases are mainly composed of sheet-like and granular structures, respectively, which provides a structural basis for Rare Earth Aluminate Fiber to be suitable for different environmental conditions and has good environmental adaptability.

[0031] 3. The rare earth aluminate fibers prepared by this invention maintain fiber flexibility and morphological integrity under high temperature conditions from room temperature to 1450℃, and maintain fiber microstructure and crystal phase stability from room temperature to 1650℃, providing a good foundation for the application of fibers under extreme environmental conditions such as high temperature.

[0032] 4. The electrospinning process of the present invention can also obtain a flexible inorganic fiber membrane with adjustable size and high temperature stability by using collection devices such as rollers and flat plates.

[0033] 5. The rare earth aluminate fiber or inorganic fiber membrane prepared by this invention has a wide range of tunable crystal phases, good high-temperature crystal phase stability and structural stability, making it widely applicable in fields such as heat insulation, thermal insulation, flexible electronics, flue gas dust removal, gas purification, and battery separators. Attached Figure Description

[0034] Figure 1 This is an optical photograph of the lanthanum aluminate precursor fiber membrane obtained in Example 1.

[0035] Figure 2 This is an optical photograph of the lanthanum aluminate fiber membrane obtained in Example 2 after heat treatment to 1200°C.

[0036] Figure 3 This is the XRD pattern of the lanthanum aluminate fiber obtained in Example 3 after heat treatment to 1200°C.

[0037] Figure 4 This is a SEM image of the lanthanum aluminate fiber from Example 3 after heat treatment to 1200°C. Detailed Implementation

[0038] The present invention will be further described below with reference to the embodiments and accompanying drawings, but is not limited thereto.

[0039] All raw materials used in the examples were commercially available.

[0040] Example 1:

[0041] A method for preparing rare earth lanthanum aluminate inorganic fibers includes the following steps:

[0042] (a) 10.00 g of water was added to 100.00 g of 24 wt% aluminum hydroxychloride sol to dissolve and obtain aluminum sol. Lanthanum acetate was added to the aluminum sol at a molar ratio of Al:La = 11:1, and then 2.00 g of polyethylene oxide was added. The mixture was stirred and dissolved to obtain lanthanum aluminate precursor sol.

[0043] (b) Lanthanum aluminate precursor fibers were prepared by electrospinning. The electrospinning process conditions were: voltage 18 kV, spinning distance 16 cm, injection rate 0.8 mL / h, ambient temperature 25-35℃, ambient humidity 35%-55%, and a drum as the collection device with a rotation speed of 300 r / min. The lanthanum aluminate precursor fiber membrane prepared under these process conditions is as follows: Figure 1 As shown.

[0044] (c) The lanthanum aluminate precursor fiber obtained in step (b) is heated to 600°C in air at a heating rate of 1°C / min and then to 1200°C at a heating rate of 2°C / min, and held for 2 hours to obtain lanthanum aluminate fiber.

[0045] Example 2:

[0046] As described in Example 1, except that the molar ratio Al:La = 11:1 in step (a) is replaced with Al:La = 11:2, the resulting lanthanum aluminate fiber membrane after heat treatment to 1200°C is shown in the figure. Figure 2 As shown.

[0047] Example 3:

[0048] As described in Example 1, except that in step (a) the molar ratio Al:La = 11:1 is replaced with Al:La = 11:3, and the XRD pattern of the obtained lanthanum aluminate fiber after heat treatment to 1200°C is shown below. Figure 3 As shown, the SEM image of the obtained fiber is as follows. Figure 4 As shown.

[0049] Example 4:

[0050] As described in Example 1, the difference is in step (a).

[0051] 100.00g of solid aluminum acetate coordination carboxylate was dissolved in 300g of water and stirred to obtain aluminum sol. Lanthanum acetate was then added to the aluminum sol at a molar ratio of Al:La = 11:1, followed by 2.00g of polyethylene oxide. The mixture was stirred to obtain lanthanum aluminate precursor sol.

[0052] Example 5:

[0053] As described in Example 1, except that lanthanum acetate in step (a) is replaced with lanthanum nitrate.

[0054] Example 6:

[0055] As described in Example 1, except that in step (a) the polyethylene oxide is replaced with polyvinyl alcohol.

[0056] Example 7:

[0057] A method for preparing rare earth lanthanum aluminate inorganic fibers includes the following steps:

[0058] (a) Add 50.00 g of water to 100.00 g of 24 wt% aluminum hydroxychloride sol to obtain aluminum sol. Add lanthanum acetate to the aluminum sol according to the molar ratio Al:La = 11:1, and then add 1.50 g of polyethylene oxide. Stir to dissolve, and then concentrate under reduced pressure to obtain lanthanum aluminate precursor sol with a viscosity of 5-10 Pa·s.

[0059] (b) Lanthanum aluminate precursor fibers were prepared by centrifugal spinning. The centrifugal spinning process conditions were: spinning ambient temperature of 25–45℃, spinning ambient humidity of 10–45%, centrifuge speed of 20000–24000 r / min, and spinning aperture of 0.35 mm. (c) The lanthanum aluminate precursor fibers obtained in step (b) were heated to 600℃ in air at a heating rate of 2℃ / min, and then heated to 1200℃ at a heating rate of 4℃ / min, and held at this temperature for 2 h to obtain lanthanum aluminate fibers.

[0060] Example 8:

[0061] A method for preparing rare earth cerium aluminate inorganic fibers.

[0062] As described in Example 1, except that lanthanum acetate in step (a) is replaced with cerium acetate.

[0063] Example 9:

[0064] A method for preparing rare earth cerium aluminate inorganic fibers.

[0065] As described in Example 7, except that lanthanum acetate in step (a) is replaced with cerium acetate.

Claims

1. A rare earth aluminate inorganic fiber, characterized in that, The rare earth aluminate inorganic fiber's main crystalline phase is composed of ReAl. 11 O 18 Composed of ReAlO3, where Re = one or a combination of La, Ce, Pr, and Nd, ReAl 11 O 18 The relative content of the two phases is 0-100%, the mass fraction of the main crystalline phase in the inorganic fiber is not less than 90%, the fiber diameter is 0.2-6.0μm, and the fiber maintains flexibility and morphological integrity under high temperature conditions from room temperature to 1450℃, and maintains fiber microstructure stability and crystalline phase stability from room temperature to 1650℃. The rare earth aluminate inorganic fibers are obtained through the following steps: (a) Preparation of rare earth aluminate precursor sol Aluminum source and rare earth source are added to a solvent with a mass ratio of solid to solvent of 1:(1 to 10) at a molar ratio of Al:Re = 11:(0.5 to 5.0) to obtain a rare earth aluminate solution. Under the condition of heating and stirring at 20 to 90°C, a polymer with a mass fraction of 0.5 to 10% is added to the rare earth aluminate solution and dissolved completely to obtain a rare earth aluminate precursor sol. (b) Preparation of rare earth aluminate precursor fibers Rare earth aluminate precursor fibers are obtained by electrospinning of the rare earth aluminate precursor sol in step (a); or the rare earth aluminate precursor sol in step (a) is concentrated under reduced pressure at a temperature of 45 to 90°C to obtain a precursor sol with a viscosity of 3 to 30 Pa·s, and then rare earth aluminate precursor fibers are obtained by centrifugal spinning. (c) Preparation of rare earth aluminate inorganic fibers The rare earth aluminate precursor fibers obtained in step (b) are heated to 450–600°C at a heating rate of 0.5–10°C / min under atmospheric conditions and held for 0–4 h; then heated to 1000–1250°C at a heating rate of 2–10°C / min and held for 1–4 h to obtain rare earth aluminate inorganic fibers.

2. The rare earth aluminate inorganic fiber as described in claim 1, characterized in that, The rare earth aluminates include one or more rare earth aluminates such as lanthanum aluminate, cerium aluminate, praseodymium aluminate, and neodymium aluminate.

3. The rare earth aluminate inorganic fiber as described in claim 1, characterized in that, The aluminum source mentioned in step (a) is one or a combination of aluminum chloride, aluminum hydroxychloride, aluminum carboxylate, aluminum isopropoxide, and aluminum acetylacetonate, wherein the molecular formula of aluminum hydroxychloride is Al(OH). x Cl y For x = 0.5–2 and y = 0–2, the molecular formula of aluminum carboxylate is Al(RCOO). x x = 0.5 ~ 2, R = one or a combination of H, -CH3, -CH2CH3, and -CH2CH2CH3.

4. The rare earth aluminate inorganic fiber as described in claim 1, characterized in that, The rare earth source in step (a) is one or a combination of rare earth acetate, rare earth nitrate, and rare earth chloride.

5. The rare earth aluminate inorganic fiber as described in claim 1, characterized in that, When the aluminum source is aluminum chloride, aluminum hydroxychloride, or aluminum carboxylate, the solvent in step (a) is water; when the aluminum source is aluminum isopropoxide or aluminum acetylacetonate, the solvent in step (a) is ethanol or an aqueous solution of ethanol with a volume fraction of 90-99%.

6. The rare earth aluminate inorganic fiber as described in claim 1, characterized in that, The polymer mentioned in step (a) is one or a combination of polyvinylpyrrolidone, polyethylene oxide, polyethylene glycol, and polyvinyl alcohol.

7. The rare earth aluminate inorganic fiber as described in claim 1, characterized in that, The electrospinning process conditions described in step (b) are: spinning distance of 5–40 cm, spinning voltage of 4–50 kV, sol propulsion rate of 0.4–4.0 mL / h, ambient temperature of 20–85 °C, and ambient humidity of 10–65%.

8. The rare earth aluminate inorganic fiber as described in claim 1, characterized in that, The process conditions for the centrifugal spinning method described in step (b) are as follows: the spinning environment temperature is 15-85℃, the spinning environment humidity is 10-65%, the centrifuge speed is 10000-28000r / min, the spinning hole linear velocity is 25-65m / s, and the spinning hole diameter is 0.10-0.80mm.

9. The rare earth aluminate inorganic fiber as described in claim 1, characterized in that, The atmosphere described in step (c) is one or a combination of air, water vapor, nitrogen, argon.

Images