A rare earth tantalate ceramic based on hydrothermal method and preparation method thereof

Abstract

The present invention relates to the field of rare earth materials, and discloses a rare earth tantalate ceramic based on a hydrothermal method and a preparation method thereof. The chemical formula of the tantalate material is (MO2) x ‑(Y3TaO7) 1‑x Where 0 < X ​​< 0.2, and M represents an equimolar mixture of three metal cations: Ti, Hf, and Zr. The ceramic material is formed by hydrothermally sintering TaCl₅ powder, YCl₃ powder, TiCl₄ powder, ZrCl₄ powder, and HfCl₄ powder. This invention comprehensively optimizes the composition and preparation process of rare earth tantalate ceramics, achieving both low thermal conductivity and high fracture toughness, which is of great significance in the industry.

Description

Technical Field

[0001] The present invention relates to the field of rare earth materials, and in particular to a rare earth tantalate ceramic based on a hydrothermal method and a preparation method thereof. Background Art

[0002] Thermal barrier coatings (TBCs) are advanced materials used to protect high-temperature alloy substrates and are widely used in high-temperature equipment such as aerospace engines and gas turbines. The primary function of TBCs is thermal insulation, extending the service life of the substrate and improving its operating efficiency. As novel thermal barrier coating materials, rare earth tantalates (Y3TaO7, YTaO4, and YTa3O9) show promising application prospects due to their excellent high-temperature stability, low thermal conductivity, and good thermal shock resistance. In the Y2O3-Ta2O5 binary phase diagram, at high temperatures, the ratio of Y2O3 to Ta2O5 varies, resulting in the formation of different rare earth tantalates. As the Y2O3 content decreases, the resulting rare earth tantalates are shown as follows: Y3TaO7-YTaO4-YTa3O9.

[0003] Y3TaO7 has a melting point above 2000°C and exhibits excellent phase stability in high-temperature environments, resisting phase transitions and maintaining structural stability under extreme high-temperature conditions. Its low thermal conductivity also provides excellent thermal insulation properties in high-temperature environments. Its high coefficient of thermal expansion reduces thermal stress and enhances the material's resistance to thermal shock. However, Y3TaO7 lacks the ferroelastic domain toughening mechanism found in YSZ and YTaO4, resulting in lower fracture toughness. Summary of the Invention

[0004] The present invention aims to provide a rare earth tantalate ceramic based on a hydrothermal method and a preparation method thereof, so as to solve the problem of unsatisfactory fracture toughness of rare earth tantalate ceramic materials in the prior art.

[0005] To achieve the above object, the present invention adopts the following technical solution: a rare earth tantalate ceramic based on a hydrothermal method, the chemical formula of the tantalate material is (MO2) x -(Y3TaO7) 1-x ; Wherein 0<X<0.2, M is a mixture of three metal cations of Ti, Hf and Zr in equimolar content; the ceramic material is formed by sintering TaCl5 powder, YCl3 powder, TiCl4 powder, ZrCl4 powder and HfCl4 powder through a hydrothermal method.

[0006] Preferably, as an improvement, the purity of TaCl5 powder, YCl3 powder, TiCl4 powder, ZrCl4 powder and HfCl4 powder are all ≥99.9%.

[0007] Preferably, as an improvement, a method for preparing rare earth tantalate ceramics based on a hydrothermal method comprises the following steps:

[0008] Step (1): TaCl5 powder, YCl3 powder, TiCl4 powder, ZrCl4 powder and HfCl4 powder are weighed in proportion, and solvent is added to each of them for the first stirring to obtain a uniform solution A;

[0009] Step (2): mixing the solution A obtained in step (1) and stirring for a second time, while adding ammonia water (NH3·H2O) to adjust the pH value to obtain solution B;

[0010] Step (3): placing the solution B obtained in step (2) in a reactor for hydrothermal reaction to obtain solution C;

[0011] Step (4): washing and drying the solution C in step (3) to obtain powder D;

[0012] Step (5): molding the powder D in step (4) to form a block E;

[0013] Step (6): Sintering the block E in step (5) to obtain rare earth tantalate ceramics.

[0014] Preferably, as an improvement, in step (1), the solvent is ethanol or deionized water, and the mass ratio of the powder to the solvent is (1:10) to (1:20).

[0015] Preferably, as an improvement, in step (1), the rotation speed of the first stirring is 300-600 r / min, and the stirring time is 1-2 h.

[0016] Preferably, as an improvement, in step (2), the pH value is adjusted to 8-10.

[0017] Preferably, as an improvement, in step (2), the rotation speed of the second stirring is 600-1000 r / min, and the stirring time is 1-2 h.

[0018] Preferably, as an improvement, in step (3), the temperature of the hydrothermal reaction is 150-250° C., and the reaction time is 24-60 h.

[0019] Preferably, as an improvement, in step (4), the washing liquid is ethanol or deionized water; the drying temperature is 80-100° C., and the drying time is 10-24 h.

[0020] Preferably, as an improvement, in step (5), the holding pressure is 200-300 MPa, and the holding time is 2-4 min; in step (6), the sintering temperature is 1500-1700° C., and the sintering time is 3-5 h.

[0021] The principles and advantages of this solution are as follows: In practical application, this technical solution addresses the unsatisfactory fracture toughness of existing rare earth tantalate ceramic materials by comprehensively upgrading the composition and preparation process of rare earth tantalate ceramics. The thermodynamic properties of Y3TaO7 are optimized by co-doping the rare earth tantalate ceramic with three metal cations: Ti, Hf, and Zr, and optimizing the metal ion ratio. During the technical research and development phase, determining the range of values ​​for X was one of the challenges of this technical solution, as it is highly correlated with the mechanical properties of the material. Studies have shown that when X is outside the restricted range, a large amount of secondary phases appear in the grains, resulting in reduced material performance. Furthermore, in the preparation process, the rare earth tantalate ceramic is hydrothermally sintered from TaCl5 powder, YCl3 powder, TiCl4 powder, ZrCl4 powder, and HfCl4 powder. This hydrothermal method controls the grain size, thereby improving fracture toughness. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 XRD patterns of the rare earth tantalate materials prepared in Examples 1 to 4 of the present invention;

[0023] Figure 2 This is an SEM image of the rare earth tantalate material prepared in Example 4 of the present invention;

[0024] Figure 3 Graphs showing the thermal conductivity of rare earth tantalate materials prepared in Examples 1 to 3 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0025] The following is further described in detail through specific embodiments, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the technical means used in the following embodiments are conventional means well known to those skilled in the art; the experimental methods used are all conventional methods; and the materials, reagents, etc. used are all commercially available.

[0026] Program Overview:

[0027] A rare earth tantalate ceramic based on a hydrothermal method, the chemical formula of the tantalate material is (MO2) x -(Y3TaO7) 1-x Wherein 0 < X ​​< 0.2, M represents an equimolar mixture of three metal cations: Ti, Hf, and Zr. The ceramic material is formed by hydrothermally sintering TaCl₅ powder, YCl₅ powder, TiCl₄ powder, ZrCl₄ powder, and HfCl₄ powder. The purity of the TaCl₅ powder, YCl₃ powder, TiCl₄ powder, ZrCl₄ powder, and HfCl₄ powder is ≥ 99.9%.

[0028] A method for preparing rare earth tantalate ceramics based on a hydrothermal method comprises the following steps:

[0029] Step (1): TaCl5 powder, YCl3 powder, TiCl4 powder, ZrCl4 powder and HfCl4 powder are weighed in proportion, and ethanol or deionized water are added respectively at a mass ratio of powder to solvent of (1:10) to (1:20) for the first stirring to obtain a uniform solution A.

[0030] The first stirring speed is 300-600 r / min, the stirring time is 1-2 h, and the purity of TaCl5 powder, YCl3 powder, TiCl4 powder, ZrCl4 powder and HfCl4 powder is not less than 99.9%.

[0031] Step (2): Solution A obtained in step (1) is mixed and stirred for a second time, and aqueous ammonia (NH3·H2O) is added to adjust the pH value to 8-10 to obtain solution B.

[0032] The second stirring speed is 600-1000 r / min, and the stirring time is 1-2 h.

[0033] Step (3): placing the solution B obtained in step (2) in a reaction kettle, and performing a hydrothermal reaction in an electric blast drying oven to obtain a solution C, wherein the hydrothermal reaction temperature is 150 to 250° C., and the reaction time is 24 to 60 hours.

[0034] Step (4): washing the solution C in step (3) with ethanol or deionized water, and drying at 80-100° C. for 10-24 h to obtain powder D.

[0035] Step (5): Powder D in step (4) is placed in a mold and compacted to form a block E, wherein the holding pressure is 200 to 300 MPa and the holding time is 2 to 4 minutes.

[0036] Step (6): Sintering the block E in step (5) to obtain rare earth tantalate ceramics, wherein the sintering temperature is 1500-1700° C. and the sintering time is 3-5 hours.

[0037] The method of this technical solution can be used to prepare (MO2) with low thermal conductivity and high fracture toughness x -(Y3TaO7) 1-x Rare earth tantalate ceramics.

[0038] In order to fully illustrate the low thermal conductivity and high fracture toughness of (MO2) prepared by the above method x -(Y3TaO7) 1-xThe following six groups of examples are used to illustrate rare earth tantalate ceramics. The difference between each example lies in the value of x and the specific parameter settings of the preparation process, as shown in Table 1:

[0039] Table 1 List of specific parameters of Examples 1 to 6 of the present invention

[0040]

[0041]

[0042] Comparative Example 1

[0043] The difference between this comparative example and Example 1 is that in this comparative example, only YCl3 powder and TaCl5 powder are added to the raw material powder, that is, the content of TiCl4 powder, ZrCl4 powder and HfCl4 powder is 0% mol.

[0044] Comparative Example 2

[0045] The difference between this comparative example and Example 1 is that in this comparative example, only YCl3 powder, TaCl5 powder and TiCl4 powder are added to the raw material powder, that is, the content of ZrCl4 powder and HfCl4 powder is 0% mol.

[0046] Comparative Example 3

[0047] The difference between this comparative example and Example 1 is that in this comparative example, only YCl3 powder, TaCl5 powder and ZrCl4 powder are added to the raw material powder, that is, the content of TiCl4 powder and HfCl4 powder is 0% mol.

[0048] Comparative Example 4

[0049] The difference between this comparative example and Example 1 is that in this comparative example, only YCl3 powder, TaCl5 powder and HfCl4 powder are added to the raw material powder, that is, the content of TiCl4 powder and ZrCl4 powder is 0% mol.

[0050] Comparative Example 5

[0051] The difference between this comparative example and Example 1 is that in this comparative example, X=0.2.

[0052] Comparative Example 6

[0053] The difference between this comparative example and Example 1 is that in this comparative example, 0.005 mol HfCl4 powder, 0.01 mol TiCl4 powder and 0.015 mol ZrCl4 powder were added.

[0054] Comparative Example 7

[0055] The difference between this comparative example and Example 1 is that in this comparative example, 0.01 mol HfCl4 powder, 0.01 mol AlCl3 powder and 0.01 mol ZrCl4 powder were added.

[0056] Experimental Example 1 XRD Characterization

[0057] The ceramic blocks obtained in Examples 1 to 6 and Comparative Examples 1 to 7 were tested using an X-ray diffractometer. Taking the rare earth tantalate material obtained in Examples 1 to 4 as an example, the XRD patterns thereof are as follows: Figure 1 As shown, the diffraction peaks of the XRD test results of Examples 1-4 correspond exactly to the standard peaks of their standard PDF card #38-1413, with no secondary diffraction peaks present, indicating that the prepared samples are single-phase rare earth tantalate materials. Furthermore, it can be seen that the main peak at 2θ≈30° shifts to the right with increasing doping. This shift is due to lattice expansion caused by the incorporation of Ti, Zr, and Hf ions into the Y3TaO7 lattice.

[0058] Experimental Example 2 SEM Characterization

[0059] The ceramic blocks obtained in Examples 1 to 6 and Comparative Examples 1 to 7 were examined using a scanning electron microscope. Taking the rare earth tantalate material obtained in Example 1 as an example, its SEM spectrum is as follows: Figure 2 As shown, according to Figure 2 Observations of the rare earth tantalate material reveal a crystal structure free of pores, uniformly distributed grains with distinct grain boundaries, and well-bonded grains. The grain size ranges from 1 to 3 microns, smaller than that obtained using the solid-state method. Hydrothermal preparation of rare earth tantalate materials can reduce grain size, thereby improving fracture toughness.

[0060] Experimental Example 3 Thermal Conductivity Detection

[0061] The ceramic blocks obtained in Examples 1 to 6 and Comparative Examples 1 to 7 were ground into The thermal conductivity of the circular thin piece is measured by a laser thermal conductivity meter. Taking the ceramic blocks prepared in Examples 1 to 3 and Comparative Example 1 as an example, the curve of the thermal conductivity versus temperature is shown as follows: Figure 3 As shown in the figure, it can be seen that as the temperature continues to rise, the thermal conductivity of the ceramic blocks prepared in Examples 1 to 3 and Comparative Example 1 decreases sharply, indicating that the thermal conductivity is excellent at high temperatures. However, the thermal conductivity of Examples 1 to 3 at high temperatures is lower than that of Comparative Example 1, reaching a minimum of 1.1 W·m -1 ·K -1 ,900℃. This shows that due to the incorporation of Ti, Zr, and Hf ions, lattice distortion occurs, resulting in strong phonon scattering, which reduces the phonon mean free path and significantly reduces the thermal conductivity.

[0062] Experimental Example 4 Fracture Toughness Test

[0063] The ceramic blocks obtained in Examples 1 to 6 and Comparative Examples 1 to 7 were polished, and the fracture toughness of the tantalate ceramics was calculated using the indentation method. The specific method is as follows: the polished ceramic blocks were indented with a Vickers hardness tester at a certain load (F) to obtain the hardness (H), and each sample was subjected to 10 indentations; then, the diagonal length of the indentation (a) and the length of the crack extending along the diagonal (c) were obtained from the scanning electron microscope image; using the formula E is the Young's modulus, which is used to calculate the fracture toughness (the average value of 10 times is taken for each sample). The calculation results are shown in Table 2. It can be seen that the average fracture toughness of Examples 1 to 6 is at least 56% higher than that of Comparative Examples 1 to 4. This is because the grains are small, and at the same time, the three metal cations of Ti, Hf, and Zr have a solid solution strengthening effect, which improves the fracture toughness. Comparative Example 5 exceeds the range of X, resulting in the generation of a second phase at the grain boundary, which reduces the fracture toughness. The results of Comparative Examples 6-7 show that the ratio and type of metal cations have a great influence on the fracture toughness, especially when the type of metal cations is replaced, the fracture toughness of Comparative Example 7 is significantly reduced to only 2.13.

[0064] Table 2 Fracture toughness (n=3)

[0065] <![CDATA[Average fracture toughness (MPam 0.5 )]]> Example 1 3.95 Example 2 4.02 Example 3 4.14 Example 4 4.21 Example 5 4.19 Example 6 4.17 Comparative Example 1 2.47 Comparative Example 2 2.52 Comparative Example 3 2.23 Comparative Example 4 2.41 Comparative Example 5 3.12 Comparative Example 6 2.76 Comparative Example 7 2.13

[0066] The above is only an embodiment of the present invention, and the common knowledge such as the specific technical solutions and / or characteristics in the solution are not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the description can be used to interpret the content of the claims.

Claims

1. A rare earth tantalate ceramic produced by a hydrothermal method, characterized in that: The chemical formula of tantalate material is (MO2) x -(Y3TaO7) 1-x ; Wherein 0<X<0.2, M is a mixture of three metal cations of Ti, Hf and Zr in equimolar content; the ceramic material is formed by sintering TaCl5 powder, YCl3 powder, TiCl4 powder, ZrCl4 powder and HfCl4 powder through a hydrothermal method.

2. The rare earth tantalate ceramic produced by hydrothermal method according to claim 1, characterized in that: The purity of the TaCl5 powder, YCl3 powder, TiCl4 powder, ZrCl4 powder and HfCl4 powder is ≥99.9%.

3. The method for preparing rare earth tantalate ceramics based on a hydrothermal method according to claim 1 or 2, characterized in that: The steps include: Step (1): TaCl5 powder, YCl3 powder, TiCl4 powder, ZrCl4 powder and HfCl4 powder are weighed in proportion, and solvent is added to each of them for the first stirring to obtain a uniform solution A; Step (2): mixing the solution A obtained in step (1) and stirring for a second time, while adding ammonia water (NH3·H2O) to adjust the pH value to obtain solution B; Step (3): placing the solution B obtained in step (2) in a reactor for hydrothermal reaction to obtain solution C; Step (4): washing and drying the solution C in step (3) to obtain powder D; Step (5): molding the powder D in step (4) to form a block E; Step (6): Sintering the block E in step (5) to obtain rare earth tantalate ceramics.

4. The method for preparing rare earth tantalate ceramics based on a hydrothermal method according to claim 3, characterized in that: In step (1), the solvent is ethanol or deionized water, and the mass ratio of the powder to the solvent is (1:10) to (1:20).

5. The method for preparing rare earth tantalate ceramics based on a hydrothermal method according to claim 4, characterized in that: In step (1), the rotation speed of the first stirring is 300-600 r / min, and the stirring time is 1-2 h.

6. The method for preparing rare earth tantalate ceramics based on a hydrothermal method according to claim 5, characterized in that: In step (2), the pH value is adjusted to 8-10.

7. The method for preparing rare earth tantalate ceramics based on a hydrothermal method according to claim 6, characterized in that: In step (2), the second stirring speed is 600-1000 r / min, and the stirring time is 1-2 h.

8. The method for preparing rare earth tantalate ceramics based on a hydrothermal method according to claim 7, characterized in that: In step (3), the temperature of the hydrothermal reaction is 150 to 250° C., and the reaction time is 24 to 60 hours.

9. The method for preparing rare earth tantalate ceramics based on a hydrothermal method according to claim 8, characterized in that: In step (4), the washing liquid is ethanol or deionized water; the drying temperature is 80-100° C., and the drying time is 10-24 hours.

10. The method for preparing rare earth tantalate ceramics based on a hydrothermal method according to claim 9, characterized in that: In step (5), the holding pressure is 200-300 MPa, and the holding time is 2-4 min; in step (6), the sintering temperature is 1500-1700° C., and the sintering time is 3-5 h.

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