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

Abstract

The invention discloses a high-entropy rare earth molybdate ceramic fiber and a preparation method and application thereof, the chemical formula of the ceramic fiber is RE6MoO12, RE is selected from at least five of La, Y, Sm, Eu, Gd, Er, Ho and Tm, and the rare earth elements are in equal stoichiometric ratio or nearly equal stoichiometric ratio. The preparation method of the high-entropy rare earth molybdate ceramic fiber comprises the following steps: carrying out electrostatic spinning on a solution containing a rare earth metal source, a Mo source and a spinning auxiliary agent, and carrying out high-temperature heat treatment to prepare the high-entropy rare earth molybdate ceramic fiber. The diameter of the prepared high-entropy rare earth molybdate ceramic fiber is 200-1000 nm, the near-infrared reflectivity is high, and the high-entropy rare earth molybdate ceramic fiber has wide application prospects in the fields of heat insulation, heat preservation and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of high entropy ceramic fiber material preparation, and specifically 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 equal or approximately equal molar ratios. High entropy ceramics have many excellent properties due to their thermodynamic high entropy effect, structural lattice distortion effect, dynamic hysteresis diffusion effect, and "cocktail" effect. The above four core effects of high entropy solid solution can be used to optimize the mechanical, electrical, thermal and other properties of ceramic materials for application in thermal protection, catalysis, energy storage, hot pressing and thermoelectricity.

[0003] Rare earth molybdate ceramics have excellent properties such as good high-temperature phase stability, low thermal conductivity, and good thermal shock resistance, and have broad application prospects in the fields of thermal barrier coatings and high-temperature thermal insulation. Studies have shown that the introduction of rare earth molybdate ceramics into high-entropy solid solutions to prepare high-entropy molybdate ceramics can regulate the thermal expansion coefficient, further improve phase stability and reduce thermal conductivity. At present, high-entropy molybdate ceramics are basically mainly focused on the research of ceramic powders and blocks, and they are all prepared by high-temperature solid phase methods, and there is no report on high-entropy molybdate ceramic fibers. In view of this, the present invention is specially proposed. 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 a preparation method and application thereof. The present invention obtains a high-entropy rare earth molybdate ceramic fiber material with good thermal insulation properties 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 fiber comprises electrostatic spinning and high-temperature heat treatment of a precursor solution containing a rare earth-based material, a Mo source and a spinning aid to obtain the high-entropy rare earth molybdate ceramic fiber.

[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 required stoichiometric amounts, and RE is selected from La, Y, Sm, Eu, Gd, Er, Ho or Tm, etc.

[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" means having the 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), exemplarily 6:1.

[0014] According to an embodiment of the present invention, the molar amount of each rare earth element in the precursor of the rare earth-based material may be the same or different, preferably the same. Exemplarily, the rare earth element in the precursor of the rare earth-based material is selected from five kinds of 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), 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.; 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 molybdate rare earth-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, so as to achieve sufficient dissolution of the soluble rare earth salt or the soluble compound of molybdenum. 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 electrospinning conditions commonly used by technicians in this field can be used for spinning operations. 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. Wherein, 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 metal salt (soluble rare earth salt and soluble compound of molybdenum) to spinning solution and 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 fiber 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 200-1000nm.

[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, in the high entropy rare earth molybdate ceramic fiber, each rare earth element is evenly distributed.

[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 application 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, 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 fiber prepared by the present invention has a uniform diameter; no complicated heat treatment is required, and no atmosphere protection is required, 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 Therefore, 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 scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions 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 included in the scope 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 polyvinyl pyrrolidone (PVP) for magnetic stirring. After complete dissolution, the solution is clarified to obtain the desired 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 XRD diagram. It can be seen from the figure that the high entropy rare earth molybdate ceramic fiber obtained in this embodiment has a fluorite structure, has a good peak shape and crystallinity, and has 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 It can be seen from the figure that 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 polyvinyl pyrrolidone (PVP) for magnetic stirring. After complete dissolution, the solution is clarified to obtain the desired 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, holes and particles appear on the surface of the high entropy rare earth molybdate ceramic fiber obtained in this embodiment, and the surface becomes rough. This is because water is added to the precursor spinning solution, which 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 bar for stirring, and after the solution is clarified, add 0.8 g of polyvinyl pyrrolidone (PVP) for magnetic stirring. 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 diameter of the high entropy rare earth molybdate ceramic fiber obtained in this embodiment becomes coarser, the grains on the fiber surface grow excessively, and the surface is not smooth with particles and holes.

[0075] The above is an explanation of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing high entropy rare earth molybdate ceramic fiber, characterized in that: The method comprises subjecting a precursor containing a rare earth-based material, a Mo source and a precursor solution of a spinning aid to electrostatic spinning and high-temperature heat treatment to prepare the high-entropy rare earth molybdate ceramic fiber.

2. The preparation method according to claim 1, characterized in that The precursor of the rare earth-based material contains at least five rare earth elements RE in required stoichiometric amounts, and RE is selected from La, Y, Sm, Eu, Gd, Er, Ho or Tm, etc. Preferably, the precursor of the rare earth-based material is provided by a rare earth salt, preferably a soluble rare earth salt. 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. Preferably, the Mo source is selected from molybdenum pentachloride or molybdenum trichloride. Preferably, 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).

3. The preparation method according to claim 2, characterized in that: 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). Preferably, the molar amounts of the rare earth elements in the precursor of the rare earth-based material may be the same or different, preferably the same. Preferably, 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.

4. The preparation method according to any one of claims 1 to 3, characterized in that: 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 solvents is 1:(0.5-2). Preferably, when the solvent is a composite of three solvents, the mass ratio of the three solvents is 1:(0.5-2):(2-4).

5. The preparation method according to any one of claims 1 to 4, characterized in that: The temperature of the high temperature heat treatment is 600-1000° C.; the time of the high temperature heat treatment is 1-4 hours. Preferably, the heating method before the high temperature heat treatment includes: heating to 600-1000°C in stages. For example, heating to 600-800°C first, and then heating to 800-1000°C. Preferably, the heating method before the 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.

6. The preparation method according to any one of claims 1 to 5, characterized in that: 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 molybdate rare earth-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.

7. The preparation method according to claim 6, characterized in that: In step (3), the spinning voltage of the electrospinning 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. Preferably, the mass ratio of metal salt (soluble rare earth salt and soluble compound of molybdenum) to spinning solution and spinning aid is (0.5-1.5):(5-15):(0.6-1.2).

8. High entropy rare earth molybdate ceramic fiber prepared by the preparation method according to any one of claims 1 to 7.

9. The high entropy rare earth molybdate ceramic fiber according to claim 8, 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 such as La, Y, Sm, Eu, Gd, Er, Ho and Tm. Preferably, the average diameter of the high entropy rare earth molybdate ceramic fiber is 200-1000 nm. Preferably, the high entropy rare earth molybdate ceramic fiber has a defective fluorite structure. Preferably, in the high-entropy rare earth molybdate ceramic fiber, each rare earth element is evenly distributed. Preferably, the molar number of each rare earth element in the high entropy rare earth molybdate ceramic fiber is the same. Preferably, the reflectivity of the high entropy rare earth molybdate ceramic fiber in the near infrared band is 90-100%.

10. Use of the high entropy rare earth molybdate ceramic fiber according to claim 8 or 9 in the fields of thermal insulation, ceramic toughening, etc.

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