High-entropy rare earth molybdate ceramic fiber, and preparation method and application thereof

Abstract

The application discloses a high-entropy rare earth molybdate ceramic fiber, a preparation method and application thereof, and the chemical formula of the ceramic fiber is RE6MoO 12 wherein RE is selected from at least five of La, Y, Sm, Eu, Gd, Er, Ho and Tm, and each rare earth element is in an equal stoichiometric ratio or a near equal stoichiometric ratio.The preparation method of the high-entropy rare earth molybdate ceramic fiber comprises the following steps: electrostatic spinning a solution containing a rare earth metal source, a Mo source and a spinning aid, and high-temperature heat treatment to obtain the high-entropy rare earth molybdate ceramic fiber.The high-entropy rare earth molybdate ceramic fiber prepared by the application has a diameter of 200-1000 nm, and has high near-infrared reflectivity, so that the application has a wide application prospect in the fields of heat insulation and heat preservation.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-entropy ceramic fiber material preparation, and in particular relates to a high-entropy rare earth molybdate ceramic fiber and a preparation method and application thereof. Background Art

[0002] High-entropy ceramics are single-phase solid solutions formed by dissolving multiple rare earth elements in equimolar or near-equimolar ratios. High-entropy ceramics possess numerous exceptional properties due to their thermodynamic high-entropy effect, structural lattice distortion, dynamic hysteresis diffusion, and a "cocktail" effect. These four core effects of high-entropy solid solution can be exploited to optimize the mechanical, electrical, and thermal properties of ceramic materials for applications in thermal protection, catalysis, energy storage, thermocompression, and thermoelectrics.

[0003] Rare earth molybdate ceramics, due to their excellent properties such as high-temperature phase stability, low thermal conductivity, and good thermal shock resistance, have broad application prospects in thermal barrier coatings and high-temperature thermal insulation. Research has shown that introducing rare earth molybdate ceramics into high-entropy solid solutions to prepare high-entropy molybdate ceramics can modulate the thermal expansion coefficient, further improve phase stability, and reduce thermal conductivity. Currently, research on high-entropy molybdate ceramics has primarily focused on ceramic powders and blocks, and these are often prepared through high-temperature solid-phase methods. However, there are no reports on high-entropy molybdate ceramic fibers. In light of this, the present invention was developed. Summary of the Invention

[0004] In order to improve the above technical problems, the present invention provides a high-entropy rare earth molybdate ceramic fiber and its preparation method and application. The present invention obtains a high-entropy rare earth molybdate ceramic fiber material with good thermal insulation performance through the high entropy effect of the material.

[0005] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is as follows:

[0006] A method for preparing high-entropy rare earth molybdate ceramic fibers comprises electrostatically spinning a precursor solution containing a rare earth-based material, a Mo source and a spinning aid, and performing high-temperature heat treatment to prepare the high-entropy rare earth molybdate ceramic fibers.

[0007] According to an embodiment of the present invention, the precursor of the rare earth-based material contains at least five rare earth elements RE in desired stoichiometric amounts, and RE is selected from La, Y, Sm, Eu, Gd, Er, Ho or Tm.

[0008] According to an embodiment of the present invention, the precursor of the rare earth-based material is provided by a rare earth salt, preferably a soluble rare earth salt.

[0009] Preferably, the soluble rare earth salt is selected from at least one of rare earth nitrates, rare earth chlorides, rare earth acetates, rare earth bromides, and rare earth iodides, and is preferably a rare earth nitrate.

[0010] According to an embodiment of the present invention, the Mo source is preferably a soluble compound of molybdenum. Preferably, the soluble compound of Mo is selected from molybdenum pentachloride or molybdenum trichloride.

[0011] According to an embodiment of the present invention, the spinning aid is selected from at least one of polyvinyl pyrrolidone (PVP), polyethylene oxide (PEO), polyvinyl alcohol (PVA), polyacrylonitrile (PAN) and polyvinyl acetate (PVAc).

[0012] Here, the term "soluble" refers to a property of being soluble in the solvent used.

[0013] According to an embodiment of the present invention, the molar ratio of the total rare earth elements in the soluble rare earth salt to the molybdenum element in the soluble molybdenum compound is 6:(1-1.01), exemplified by 6:1.

[0014] According to an embodiment of the present invention, the molar amounts of the rare earth elements in the precursor of the rare earth-based material may be the same or different, and are preferably the same. For example, the rare earth elements in the precursor of the rare earth-based material are selected from La, Y, Er, Ho, and Tm, and the molar ratio of La, Y, Er, Ho, and Tm is 1:1:1:1:1.

[0015] According to an embodiment of the present invention, the solvent used in the precursor solution is selected from at least one of water, methanol, ethanol, n-propanol, isopropanol, N,N-dimethylformamide, and acetone. Preferably, the solvent is a mixed solvent of two or three of water, ethanol, and DMF. Preferably, when the solvent is a composite of two solvents, the mass ratio of the two is 1:(0.5-2), exemplified by 1:1.2, 1:1.4, and 1:1.5. Preferably, when the solvent is a composite of three solvents, the mass ratio of the three is 1:(0.5-2):(2-4), exemplified by 1:1:3.

[0016] In the present invention, those skilled in the art can adjust the amount of solvent added according to the requirements of the spinning process, as long as the desired spinning solution can be obtained. Exemplarily, the mass ratio of the solvent to the spinning aid is (8-12): (0.8-1), and exemplarily 10:0.8.

[0017] According to an embodiment of the present invention, the temperature of the high-temperature heat treatment is 600-1000° C.; and the time of the high-temperature heat treatment is 1-4 hours (eg, 2 hours).

[0018] According to an embodiment of the present invention, the heating method before the high-temperature heat treatment includes: heating to 600-1000°C in stages. For example, first heating to 600-800°C, and then heating to 800-1000°C.

[0019] According to an exemplary embodiment of the present invention, the heating method before high-temperature heat treatment specifically includes: first heating to 600-800°C at a heating rate of 1-2°C / min, and then heating to 800-1000°C at a heating rate of 1-5°C / min.

[0020] According to an embodiment of the present invention, the method for preparing the high entropy rare earth molybdate ceramic fiber comprises the following steps:

[0021] (1) dissolving a rare earth-based material precursor and a Mo source in a solvent to obtain a rare earth molybdate-based precursor solution;

[0022] (2) adding a spinning aid to the rare earth molybdate precursor solution obtained in step (1) to obtain a rare earth molybdate precursor spinning solution;

[0023] (3) electrospinning the rare earth molybdate precursor spinning solution obtained in step (2) to obtain rare earth molybdate precursor fibers;

[0024] (4) subjecting the rare earth molybdate-based precursor fiber obtained in step (3) to high-temperature heat treatment to obtain high-entropy rare earth molybdate ceramic fiber.

[0025] According to an embodiment of the present invention, in step (2), the spinning aid is dissolved at room temperature, wherein the room temperature refers to 10-40°C.

[0026] According to an embodiment of the present invention, the usage ratio of the spinning aid to the rare earth molybdate-based precursor is (0.3-0.6) g: 0.0005 mol.

[0027] According to an embodiment of the present invention, the dissolution in step (1) or (2) can also be carried out under stirring. The present invention does not specifically limit the stirring method and stirring time, as long as the soluble rare earth salt or the soluble molybdenum compound is fully dissolved. For example, the stirring can be carried out under magnetic stirring conditions or mechanical stirring conditions. For example, in steps (1) and (2), the stirring time can be 1 to 6 hours or 1 to 12 hours, respectively.

[0028] According to the embodiment of the present invention, the present invention does not specifically limit the electrospinning process of step (3), and the spinning operation can be carried out using the electrospinning conditions commonly used by those skilled in the art. By adjusting the distance between the nozzle and the collecting plate, the spinning voltage, and the injection rate, molybdate rare earth salt precursor fibers with different morphologies can be obtained.

[0029] According to an exemplary embodiment of the present invention, in step (3), the electrospinning voltage is 15-25 kV, the spinning speed is 0.4-1.0 ml / h, the receiving distance is 10-60 cm, the spinning humidity is 20%-40%, and the spinning temperature is 20-27° C. The term “receiving distance” refers to the distance between the nozzle and the collecting plate.

[0030] According to an embodiment of the present invention, the mass ratio of the metal salt (soluble rare earth salt and soluble molybdenum compound) to the spinning solution and the spinning aid is (0.5-1.5): (5-15): (0.6-1.2).

[0031] The present invention also provides high-entropy rare earth molybdate ceramic fibers prepared by the above preparation method.

[0032] According to an embodiment of the present invention, the chemical formula of the ceramic fiber is as follows: RE6MoO 12 , wherein RE is selected from at least five rare earth elements such as La, Y, Sm, Eu, Gd, Er, Ho and Tm.

[0033] According to the present invention, the average diameter of the high-entropy rare earth molybdate ceramic fiber is 200-1000 nm.

[0034] According to an embodiment of the present invention, the high-entropy rare earth molybdate ceramic fiber has a defective fluorite structure.

[0035] According to an embodiment of the present invention, the rare earth elements are uniformly distributed in the high-entropy rare earth molybdate ceramic fiber.

[0036] According to an embodiment of the present invention, the molar number of each rare earth element in the high-entropy rare earth molybdate ceramic fiber is the same.

[0037] According to an embodiment of the present invention, the reflectivity of the high-entropy rare earth molybdate ceramic fiber in the near-infrared band is 90-100%.

[0038] According to an embodiment of the present invention, the thermal conductivity of the high entropy rare earth molybdate ceramic fiber can be as low as 0.21 W·m -1 ·K -1 , and has potential application prospects in the fields of thermal insulation and heat preservation.

[0039] According to an embodiment of the present invention, the high entropy rare earth molybdate ceramic fiber is (La 0.2 Y 0.2 Er 0.2 Ho 0.2 Tm 0.2 )6MoO 12 .

[0040] The present invention also provides applications of the high-entropy rare earth molybdate ceramic fiber in the fields of thermal insulation, ceramic toughening, etc.

[0041] Beneficial effects of the present invention:

[0042] (1) The present invention prepares for the first time a high-entropy rare earth molybdate ceramic fiber containing five rare earth elements of La, Y, Sm, Eu, Gd, Er, Ho, and Tm. The rare earth elements in the ceramic fiber of the present invention are in an equal stoichiometric ratio or a nearly equal stoichiometric ratio, thereby enriching the existing ceramic fiber system.

[0043] (2) The solid solution formation temperature of the high-entropy rare earth molybdate ceramic fiber prepared by the present invention is low, and a single-phase high-entropy solid solution can be obtained at 800°C, and the elements in the ceramic fiber are evenly distributed.

[0044] (3) The high-entropy rare earth molybdate ceramic fibers prepared by the present invention have uniform diameters; they do not require complex heat treatment or atmosphere protection, and the preparation process is simple.

[0045] (5) The reflectivity of the high-entropy rare earth molybdate ceramic fiber prepared by the present invention in the near-infrared band is 90-100%.

[0046] (6) The thermal conductivity of the high entropy rare earth molybdate ceramic fiber prepared by the present invention can be as low as 0.21 W·m -1 ·K -1 , so it has broad application prospects in the fields of thermal insulation and heat insulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 The high entropy rare earth molybdate ceramic fiber (La 0.2 Y 0.2 Er 0.2 Ho 0.2 Tm 0.2 )6MoO 12 XRD pattern of .

[0048] Figure 2 The high entropy rare earth molybdate ceramic fiber (La 0.2 Y 0.2 Er 0.2 Ho 0.2 Tm 0.2 )6MoO 12 Near-infrared spectrum.

[0049] Figure 3 The high entropy rare earth molybdate ceramic fiber (La 0.2 Y 0.2 Er 0.2 Ho0.2 Tm 0.2 )6MoO 12 SEM image of .

[0050] Figure 4 The high entropy rare earth molybdate ceramic fiber (La 0.2 Y 0.2 Er 0.2 Ho 0.2 Tm 0.2 )6MoO 12 SEM image of .

[0051] Figure 5 The high entropy rare earth molybdate ceramic fiber (La 0.2 Y 0.2 Er 0.2 Ho 0.2 Tm 0.2 )6MoO 12 SEM image of . DETAILED DESCRIPTION

[0052] The technical solutions of the present invention will be described in further detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are encompassed within the scope of protection that the present invention is intended to protect.

[0053] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0054] Example 1

[0055] A method for preparing high-entropy rare earth molybdate ceramic fiber comprises the following steps:

[0056] (1) Weigh 0.0012 mol of La(NO3)3·6H2O, 0.0012 mol of Y(NO3)3·6H2O, 0.0012 mol of Ho(NO3)3·6H2O, 0.0012 mol of Er(NO3)3·6H2O, 0.0012 mol of Tm(NO3)3·6H2O and 0.001 mol of MoCl5 respectively, dissolve them in a mixed solution of 4 g of anhydrous ethanol and 6 g of N,N-dimethylformamide, add a magnetic bar for stirring, and after the solution is clarified, add 0.8 g of polyvinylpyrrolidone (PVP) and stir magnetically. After complete dissolution, the solution is clarified to obtain the required high entropy ceramic precursor spinning solution.

[0057] (2) The prepared spinning solution was subjected to electrospinning at a spinning voltage of 20 kV, a syringe pump propulsion speed of 0.6 ml / h, an ambient humidity of 30%, and a spinning temperature of 25±3°C.

[0058] (3) The precursor fiber obtained in (2) is heat-treated at 800°C, wherein the heating rate before 600°C is 1°C / min, the heating rate from 600°C to 800°C is 5°C / min, the holding time is 2h, and then cooled in the furnace to obtain high entropy rare earth molybdate ceramic fiber.

[0059] Figure 1 The high entropy rare earth molybdate ceramic fiber (La 0.2 Y 0.2 Er 0.2 Ho 0.2 Tm 0.2 )6MoO 12 From the XRD diagram, it can be seen that the high entropy rare earth molybdate ceramic fiber obtained in this embodiment has a fluorite structure, a good peak shape and crystallinity, and no impurity peaks.

[0060] Figure 2 The high entropy rare earth molybdate ceramic fiber (La 0.2 Y 0.2 Er 0.2 Ho 0.2 Tm 0.2 )6MoO 12 As can be seen from the figure, the high-entropy rare earth molybdate ceramic fiber obtained in this embodiment has a high reflectivity in the near-infrared region, and its near-infrared reflectivity is 99.06%.

[0061] Figure 3 The high entropy rare earth molybdate ceramic fiber (La 0.2 Y 0.2 Er 0.2 Ho 0.2 Tm 0.2 )6MoO 12 As can be seen from the figure: the high entropy rare earth molybdate ceramic fiber obtained in this embodiment has a thin diameter, a uniform and smooth surface, and no defects such as pores.

[0062] The thermal conductivity of the high entropy rare earth molybdate ceramic fiber obtained in this example is 0.21 W·m -1 ·K -1 .

[0063] Example 2

[0064] A method for preparing high-entropy rare earth molybdate ceramic fiber comprises the following steps:

[0065] (1) Weigh 0.0012 mol of La(NO3)3·6H2O, 0.0012 mol of Y(NO3)3·6H2O, 0.0012 mol of Ho(NO3)3·6H2O, 0.0012 mol of Er(NO3)3·6H2O, 0.0012 mol of Tm(NO3)3·6H2O and 0.001 mol of MoCl5 respectively, dissolve them in a mixed solution of 2 g of anhydrous ethanol, 2 g of deionized water and 6 g of N,N-dimethylformamide, add a magnetic bar for stirring, and after the solution is clarified, add 0.8 g of polyvinylpyrrolidone (PVP) and stir magnetically. After complete dissolution, the solution is clarified to obtain the required high entropy ceramic precursor spinning solution.

[0066] (2) The prepared spinning solution was subjected to electrospinning at a spinning voltage of 20 kV, a syringe pump propulsion speed of 0.6 ml / h, an ambient humidity of 30%, and a spinning temperature of 25±3°C.

[0067] (3) The precursor fiber obtained in (2) is heat-treated at 800°C, wherein the heating rate before 600°C is 1°C / min, the heating rate from 600°C to 800°C is 5°C / min, the holding time is 2h, and then cooled in the furnace to obtain high entropy rare earth molybdate ceramic fiber.

[0068] Figure 4 The high entropy rare earth molybdate ceramic fiber (La 0.2 Y 0.2 Er 0.2 Ho 0.2 Tm 0.2 )6MoO 12 As can be seen from the figure, the surface of the high-entropy rare earth molybdate ceramic fiber obtained in this embodiment has holes and particles, and the surface has become rough. This is because the addition of water to the precursor spinning solution reduces its spinnability.

[0069] Example 3

[0070] A method for preparing high-entropy rare earth molybdate ceramic fiber comprises the following steps:

[0071] (1) Weigh 0.0012 mol of La(NO3)3·6H2O, 0.0012 mol of Y(NO3)3·6H2O, 0.0012 mol of Ho(NO3)3·6H2O, 0.0012 mol of Er(NO3)3·6H2O, 0.0012 mol of Tm(NO3)3·6H2O and 0.001 mol of MoCl5 respectively, dissolve them in a mixed solution of 4 g of anhydrous ethanol and 6 g of N,N-dimethylformamide, add a magnetic stirrer, and after the solution is clarified, add 0.8 g of polyvinylpyrrolidone (PVP) and stir magnetically. After complete dissolution, the solution is clarified to obtain the desired high entropy ceramic precursor spinning solution.

[0072] (2) The prepared spinning solution was subjected to electrospinning at a spinning voltage of 20 kV, a syringe pump propulsion speed of 0.6 ml / h, an ambient humidity of 30%, and a spinning temperature of 25±3°C.

[0073] (3) The precursor fiber obtained in (2) is heat-treated at 1000°C, wherein the heating rate before 600°C is 1°C / min, the heating rate from 600°C to 1000°C is 5°C / min, the holding time is 2h, and then cooled in the furnace to obtain high entropy rare earth molybdate ceramic fiber.

[0074] Figure 5 The high entropy rare earth molybdate ceramic fiber (La 0.2 Y 0.2 Er 0.2 Ho 0.2 Tm 0.2 )6MoO 12 As can be seen from the figure: the high entropy rare earth molybdate ceramic fiber obtained in this embodiment has a thicker diameter, excessive grain growth on the fiber surface, and a rough surface with particles and holes.

[0075] The above describes the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A method for preparing high-entropy rare earth molybdate ceramic fiber, characterized in that: The method comprises electrospinning a precursor solution containing a rare earth-based material, a Mo source and a spinning aid, and performing high-temperature heat treatment to prepare the high-entropy rare earth molybdate ceramic fiber; The rare earth elements in the precursor of the rare earth-based material are selected from the group consisting of La, Y, Er, Ho, and Tm, and the molar ratio of La, Y, Er, Ho, and Tm is 1:1:1:1:1; The Mo source is a soluble compound of molybdenum; The precursor of the rare earth-based material is provided by a soluble rare earth salt; The molar ratio of the total rare earth elements in the soluble rare earth salt to the molybdenum element in the soluble molybdenum compound is 6:(1~1.01).

2. The preparation method according to claim 1, wherein The soluble rare earth salt is selected from at least one of rare earth nitrates, rare earth chlorides, rare earth acetates, rare earth bromides, and rare earth iodides; And / or, the Mo source is selected from molybdenum pentachloride or molybdenum trichloride.

3. The preparation method according to claim 1, wherein The spinning aid is selected from at least one of polyvinyl pyrrolidone (PVP), polyethylene oxide (PEO), polyvinyl alcohol (PVA), polyacrylonitrile (PAN) and polyvinyl acetate (PVAc).

4. The preparation method according to any one of claims 1 to 3, wherein The solvent used in the precursor solution is at least one selected from water, methanol, ethanol, n-propanol, isopropanol, N,N-dimethylformamide, and acetone.

5. The preparation method according to claim 4, wherein The solvent is a mixed solvent of two or three of water, ethanol and DMF; When the solvent is a composite of two solvents, the mass ratio of the two solvents is 1:(0.5-2); When the solvent is a composite of three solvents, the mass ratio of the three solvents is 1:(0.5-2):(2-4).

6. The preparation method according to any one of claims 1 to 3, wherein The temperature of the high-temperature heat treatment is 600-1000° C.; the time of the high-temperature heat treatment is 1-4 hours.

7. The preparation method according to claim 6, wherein The heating method before the high-temperature heat treatment includes: first heating to 600-800°C, and then heating to 800-1000°C.

8. The preparation method according to claim 7, wherein The heating method before the high temperature heat treatment specifically includes: first heating the temperature to 600-800° C. at a heating rate of 1-2° C. / min, and then heating the temperature to 800-1000° C. at a heating rate of 1-5° C. / min.

9. The preparation method according to any one of claims 1 to 3, wherein The preparation method of the high-entropy rare earth molybdate ceramic fiber comprises the following steps: (1) dissolving a rare earth-based material precursor and a Mo source in a solvent to obtain a rare earth molybdate-based precursor solution; (2) adding a spinning aid to the rare earth molybdate precursor solution obtained in step (1) to obtain a rare earth molybdate precursor spinning solution; (3) electrospinning the rare earth molybdate precursor spinning solution obtained in step (2) to obtain rare earth molybdate precursor fibers; (4) subjecting the rare earth molybdate-based precursor fiber obtained in step (3) to high-temperature heat treatment to obtain high-entropy rare earth molybdate ceramic fiber.

10. The preparation method according to claim 9, characterized in that In step (3), the electrospinning voltage is 15-25 kV, the spinning speed is 0.4-1.0 ml / h, the receiving distance is 10-60 cm, the spinning humidity is 20%-40%, and the spinning temperature is 20-27°C.

11. The preparation method according to claim 9, wherein The mass ratio of the metal salt composed of the soluble rare earth salt and the soluble molybdenum compound to the spinning solution and the spinning auxiliary agent is (0.5-1.5): (5-15): (0.6-1.2).

12. High entropy rare earth molybdate ceramic fiber prepared by the preparation method according to any one of claims 1 to 11.

13. The high entropy rare earth molybdate ceramic fiber according to claim 12, characterized in that: The chemical formula of the ceramic fiber is as follows: RE6MoO 12 , wherein RE is selected from at least five rare earth elements of La, Y, Er, Ho and Tm.

14. The high entropy rare earth molybdate ceramic fiber according to claim 12, wherein: The average diameter of the high entropy rare earth molybdate ceramic fiber is 200-1000 nm; And / or, the high entropy rare earth molybdate ceramic fiber has a defective fluorite structure; And / or, in the high entropy rare earth molybdate ceramic fiber, each rare earth element is evenly distributed; And / or, the molar number of each rare earth element in the high entropy rare earth molybdate ceramic fiber is the same; And / or, the reflectivity of the high entropy rare earth molybdate ceramic fiber in the near infrared band is 90-100%.

15. Use of the high-entropy rare earth molybdate ceramic fiber according to any one of claims 12 to 14 in the fields of thermal insulation and ceramic toughening.

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