Preparation method and application of rare earth cerate high-entropy ceramic material

Abstract

The application relates to the technical field of ceramic materials, in particular to a preparation method and application of a rare earth cerate high-entropy ceramic material; and a preparation method of a rare earth cerate ceramic material, which comprises the following steps: S1, adding mixed rare earth oxides into deionized water to obtain a mixed solution; S2, adding zirconium sulfate into deionized water to obtain a zirconium sulfate solution; S3, adding the zirconium sulfate solution into the mixed solution, and then adding tetrabutyl titanate to obtain a reaction solution; S4, adding citric acid and ethylene glycol into the reaction solution to obtain a sol solution, and evaporating to obtain a wet gel; and S5, drying and crushing the wet gel, and sintering to obtain a ceramic material. The ceramic material utilizes the synergistic effect of multiple elements, produces obvious lattice distortion effect, and realizes the balance between thermal expansion and stability through the combination of multiple rare earth elements, so that the ceramic material has low thermal conductivity and good high-temperature stability.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials technology, specifically to a method for preparing rare earth cerate high-entropy ceramic materials and their applications. Background Technology

[0002] Thermal barrier coatings are typically heat-resistant ceramic coatings deposited on the surface of high-temperature alloys. They protect the high-temperature alloy substrate from high-temperature oxidation and corrosion, thus providing thermal insulation and reducing the surface temperature of high-temperature alloy parts, thereby increasing their operating temperature.

[0003] Currently, the most studied thermal barrier coating materials include yttrium-stabilized zirconium oxide and its modified materials, rare earth zirconates, rare earth tantalates, rare earth hexaaluminates, rare earth cerates, and rare earth silicates. However, the thermal expansion properties of these thermal barrier coating materials differ somewhat from those of high-temperature alloy substrates. After prolonged use, significant thermal stress will be generated within the coating, leading to cracking and peeling during thermal cycling, thus affecting the service life of the thermal barrier coating. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for preparing rare-earth cerate high-entropy ceramic materials and their applications.

[0005] The technical solution of this invention is: a method for preparing rare earth cerate high-entropy ceramic materials, comprising the following steps: S1. Add the mixed rare earth oxides to deionized water, adjust the pH of the deionized water to 3-4 using dilute nitric acid, and then stir at 50-60℃ for 20-30 minutes to obtain a mixed solution; wherein, the mass ratio of the mixed rare earth oxides to deionized water is 1:10-15. S2. Add zirconium sulfate to deionized water and stir until completely dissolved to obtain a zirconium sulfate solution; wherein the mass ratio of zirconium sulfate to deionized water is 1:5~6. S3. Add zirconium sulfate solution to the mixture and stir for 15-20 min, then add tetrabutyl titanate and continue stirring for 20-25 min to obtain the reaction solution; wherein, the mass ratio of zirconium sulfate solution to the mixture is 1:8-10, and the amount of tetrabutyl titanate added accounts for 1.2-1.6% of the mass of the mixture; S4. Add citric acid and ethylene glycol to the reaction solution and stir for 1-2 hours to obtain a sol solution. Evaporate the sol solution to remove the liquid and obtain a wet gel. S5. Dry the wet gel to obtain dry gel, then crush and sieve the dry gel to obtain gel particles. Place the gel particles into a high-temperature sintering furnace for sintering to obtain ceramic material.

[0006] Note: The above-mentioned ceramic materials utilize the synergistic effect of multiple elements to promote the construction of a stable fluorite solid solution phase and produce a significant lattice distortion effect. Furthermore, the combination of multiple rare earth elements can achieve a balance between thermal expansion and stability, ensuring that the ceramic materials have low thermal conductivity and good high-temperature stability.

[0007] Further, in step S1, the mixed rare earth oxide is a mixture of lanthanum oxide, cerium oxide, ytterbium oxide, yttrium oxide and lutetium oxide in a mass ratio of 1:0.7~0.9:0.1~0.3:0.1~0.2:0.1~0.2.

[0008] Note: The mixed rare earth oxides of the above components can increase configurational entropy and enhance the high-entropy effect, thereby inducing local lattice distortion in ceramic materials and ensuring the thermal insulation performance of ceramic materials.

[0009] Furthermore, in step S2, the mass concentration of the dilute nitric acid is 10-15%.

[0010] Note: The dilute nitric acid of the above-mentioned mass concentration is safe to use and can quickly adjust the pH value to effectively promote the formation of sol.

[0011] Further, in step S4, the evaporation method is as follows: the sol solution is placed in a water bath at 95~100℃ and stirred at a stirring rate of 300~500r / min.

[0012] Note: The above evaporation method can effectively remove liquid from the sol solution with minimal interference, thus ensuring the structural integrity of the wet gel.

[0013] Furthermore, in step S5, the drying temperature is 120~140℃ and the drying time is 1~2h.

[0014] Note: Limiting the drying parameters ensures that the moisture in the wet gel is fully removed, reducing impurities in the ceramic material after sintering and improving the purity of the ceramic material.

[0015] Further, in step S5, the sintering process is as follows: the temperature is increased to 1550-1650°C at a heating rate of 6-8°C / min, then held for 6-8 hours, and then cooled to room temperature in the furnace.

[0016] Note: Limiting sintering parameters can ensure the grain size of ceramic materials, reduce internal defects, and guarantee the structural stability of ceramic materials.

[0017] Further, in step S5, the process for adding citric acid and ethylene glycol is as follows: First, heat the reaction solution to 50-55°C at a heating rate of 6-8°C / min. Then, add citric acid to the reaction solution once while stirring, and then stop heating. The amount of citric acid added is 4-6% of the initial mass of the reaction solution. When the temperature of the reaction solution drops to 35-40℃, heat the reaction solution to 70-75℃ at a heating rate of 4-5℃ / min. Then, while stirring, add citric acid and ethylene glycol to the reaction solution once, and then stop heating. The amount of citric acid added is 1-2% of the initial mass of the reaction solution, and the amount of ethylene glycol added is 2-3% of the initial mass of the reaction solution. When the temperature of the reaction solution drops to 60-65℃, heat the reaction solution to 80-90℃ at a heating rate of 2-3℃ / min. Then, add ethylene glycol to the reaction solution once while stirring, and then stop heating. The addition of citric acid and ethylene glycol is complete. The amount of ethylene glycol added accounts for 5-6% of the initial mass of the reaction solution.

[0018] Explanation: The above method, by adding citric acid and ethylene glycol in stages, can ensure that citric acid and metal ions are fully chelated. Then, through the esterification reaction of ethylene glycol and citric acid, a stable three-dimensional network structure is formed, which ensures that the metal ions are firmly locked within the three-dimensional network structure, so as to form a uniform and stable gel structure and ensure the structural stability of the ceramic material.

[0019] Furthermore, in step S5, the aperture of the sieve during sieving is 300-400 mesh.

[0020] Note: Limiting the pore size of the sieve ensures the particle size of the gel particles, resulting in a dense and uniform structure of the sintered ceramic material.

[0021] On the other hand, the present invention also provides the application of the above-mentioned rare earth cerate high-entropy ceramic materials in the field of thermal barrier coatings.

[0022] Note: The above-mentioned ceramic materials have good thermal insulation properties and a high coefficient of thermal expansion. As a thermal barrier coating, they can protect the high-temperature alloy substrate from high-temperature oxidation and corrosion, improve the service life of the high-temperature alloy substrate, and the ceramic materials can bond well with the high-temperature alloy substrate to reduce the thermal stress generated during thermal cycling and improve the anti-stripping performance of the thermal barrier coating.

[0023] The beneficial effects of this invention are: (1) The ceramic material of the present invention utilizes the synergistic effect of multiple elements to promote the construction of a stable fluorite solid solution phase and produce a significant lattice distortion effect. Furthermore, the combination of multiple rare earth elements can achieve a balance between thermal expansion and stability, ensuring that the ceramic material has low thermal conductivity and good high-temperature stability.

[0024] (2) The ceramic material of the present invention has good thermal insulation performance and a high coefficient of thermal expansion. As a thermal barrier coating, it can protect the high-temperature alloy substrate from high-temperature oxidation and corrosion, improve the service life of the high-temperature alloy substrate, and the ceramic material can be well bonded to the high-temperature alloy substrate to reduce the thermal stress generated during thermal cycling and improve the anti-stripping performance of the thermal barrier coating. Detailed Implementation

[0025] To further illustrate the methods and effects of this invention, the technical solution of this invention will be clearly and completely described below in conjunction with experiments.

[0026] Example 1: A method for preparing a rare earth cerate high-entropy ceramic material, comprising the following steps: S1. Add the mixed rare earth oxides to deionized water, adjust the pH of the deionized water to 3.5 using 12% dilute nitric acid, and then stir at 55°C for 25 minutes to obtain a mixed solution; wherein, the mass ratio of the mixed rare earth oxides to deionized water is 1:12. The mixed rare earth oxide is composed of lanthanum oxide, cerium oxide, ytterbium oxide, yttrium oxide, and lutetium oxide mixed in a mass ratio of 1:0.8:0.2:0.15:0.15; S2. Add zirconium sulfate to deionized water and stir until completely dissolved to obtain a zirconium sulfate solution; wherein the mass ratio of zirconium sulfate to deionized water is 1:5.5. S3. Add zirconium sulfate solution to the mixture and stir for 18 min, then add tetrabutyl titanate and continue stirring for 22 min to obtain the reaction solution; wherein, the mass ratio of zirconium sulfate solution to the mixture is 1:9, and the amount of tetrabutyl titanate added accounts for 1.4% of the mass of the mixture; S4. Add citric acid and ethylene glycol to the reaction solution and stir for 1.5 hours to obtain a sol solution. Evaporate the sol solution to remove the liquid and obtain a wet gel. The evaporation method is as follows: the sol solution is placed in a water bath at 98°C and stirred at a stirring rate of 400 r / min. S5. Dry the wet gel to obtain a dry gel. Then, crush the dry gel and sieve it through a 350-mesh sieve to obtain gel particles. Place the gel particles into a high-temperature sintering furnace for sintering to obtain ceramic materials. The drying temperature is 130℃ and the drying time is 1.5h. The sintering process is as follows: heat up to 1600℃ at a heating rate of 7℃ / min, then hold for 7h, and then cool to room temperature with the furnace. The process for adding citric acid and ethylene glycol is as follows: The reaction solution was first heated to 52°C at a heating rate of 7°C / min. Then, citric acid was added to the reaction solution once while stirring, and then heating was stopped. The amount of citric acid added was 5% of the initial mass of the reaction solution. When the reaction solution temperature drops to 37°C, the reaction solution is heated to 72°C at a heating rate of 4.5°C / min. Then, citric acid and ethylene glycol are added to the reaction solution once while stirring, and then heating is stopped. The amount of citric acid added is 1.5% of the initial mass of the reaction solution, and the amount of ethylene glycol added is 2.5% of the initial mass of the reaction solution. When the temperature of the reaction solution drops to 62°C, the reaction solution is heated to 85°C at a heating rate of 2.5°C / min. Then, ethylene glycol is added to the reaction solution once while stirring, and then heating is stopped. The addition of citric acid and ethylene glycol is complete. The amount of ethylene glycol added accounts for 5.5% of the initial mass of the reaction solution.

[0027] Example 2: This example is basically the same as Example 1, except that the mixed rare earth oxide is lanthanum oxide, cerium oxide, ytterbium oxide, yttrium oxide and lutetium oxide mixed in a mass ratio of 1:0.7:0.1:0.1:0.1.

[0028] Example 3: This example is basically the same as Example 1, except that the mixed rare earth oxides are lanthanum oxide, cerium oxide, ytterbium oxide, yttrium oxide and lutetium oxide mixed in a mass ratio of 1:0.9:0.3:0.2:0.2.

[0029] Example 4: This example is basically the same as Example 1, except that the pH value of the deionized water is adjusted to 3 using dilute nitric acid with a mass concentration of 10~15%.

[0030] Example 5: This example is basically the same as Example 1, except that the pH value of the deionized water is adjusted to 4 using dilute nitric acid with a mass concentration of 10~15%.

[0031] Example 6: This example is basically the same as Example 1, except that the mass ratio of the mixed rare earth oxides to deionized water is 1:10.

[0032] Example 7: This example is basically the same as Example 1, except that the mass ratio of the mixed rare earth oxides to deionized water is 1:15.

[0033] Example 8: This example is basically the same as Example 1, except that the mass ratio of zirconium sulfate to deionized water is 1:5.

[0034] Example 9: This example is basically the same as Example 1, except that the mass ratio of zirconium sulfate to deionized water is 1:6.

[0035] Example 10: This example is basically the same as Example 1, except that the mass ratio of zirconium sulfate solution to mixture is 1:8, and the amount of tetrabutyl titanate added accounts for 1.2% of the mass of mixture.

[0036] Example 11: This example is basically the same as Example 1, except that the mass ratio of zirconium sulfate solution to mixture is 1:10, and the amount of tetrabutyl titanate added accounts for 1.6% of the mass of mixture.

[0037] Example 12: This example is basically the same as Example 1, except that the sintering process is as follows: the temperature is raised to 1550°C at a heating rate of 6°C / min, then held for 7 hours, and then cooled to room temperature in the furnace.

[0038] Example 13: This example is basically the same as Example 1, except that the sintering process is as follows: the temperature is raised to 1650°C at a heating rate of 8°C / min, then held for 7 hours, and then cooled to room temperature in the furnace.

[0039] Example 14: This example is basically the same as Example 1, except that the reaction solution is first heated to 52°C at a heating rate of 6°C / min, and then citric acid is added to the reaction solution once while stirring, and then heating is stopped; When the temperature of the reaction solution drops to 37°C, the reaction solution is heated to 72°C at a heating rate of 4°C / min. Then, citric acid and ethylene glycol are added to the reaction solution once while stirring, and then heating is stopped. When the temperature of the reaction solution drops to 62°C, the reaction solution is heated to 85°C at a heating rate of 2°C / min. Then, ethylene glycol is added to the reaction solution once while stirring, and then heating is stopped. The addition of citric acid and ethylene glycol is complete. Example 15: This example is basically the same as Example 1, except that the reaction solution is first heated to 52°C at a heating rate of 8°C / min, and then citric acid is added to the reaction solution once while stirring, and then heating is stopped. When the temperature of the reaction solution drops to 37°C, the reaction solution is heated to 72°C at a heating rate of 5°C / min. Then, citric acid and ethylene glycol are added to the reaction solution once while stirring, and then heating is stopped. When the temperature of the reaction solution drops to 62°C, the reaction solution is heated to 85°C at a heating rate of 3°C / min. Then, ethylene glycol is added to the reaction solution once while stirring, and then heating is stopped. The addition of citric acid and ethylene glycol is complete.

[0040] Example 16: This example is basically the same as Example 1, except that the reaction solution is first heated to 50°C at a heating rate of 7°C / min, and then citric acid is added to the reaction solution once while stirring, and then heating is stopped. When the temperature of the reaction solution drops to 35°C, the reaction solution is heated to 70°C at a heating rate of 4.5°C / min. Then, citric acid and ethylene glycol are added to the reaction solution once while stirring, and then heating is stopped. When the temperature of the reaction solution drops to 60°C, the reaction solution is heated to 80°C at a heating rate of 2.5°C / min. Then, ethylene glycol is added to the reaction solution once while stirring, and then heating is stopped. The addition of citric acid and ethylene glycol is complete.

[0041] Example 17: This example is basically the same as Example 1, except that the reaction solution is first heated to 55°C at a heating rate of 7°C / min, and then citric acid is added to the reaction solution once while stirring, and then heating is stopped. When the temperature of the reaction solution drops to 40°C, the reaction solution is heated to 75°C at a heating rate of 4.5°C / min. Then, citric acid and ethylene glycol are added to the reaction solution once while stirring, and then heating is stopped. When the temperature of the reaction solution drops to 65°C, the reaction solution is heated to 90°C at a heating rate of 2.5°C / min. Then, ethylene glycol is added to the reaction solution once while stirring, and then heating is stopped. The addition of citric acid and ethylene glycol is complete.

[0042] Example 18: This example is basically the same as Example 1, except that the reaction solution is first heated to 52°C at a heating rate of 7°C / min, and then citric acid is added to the reaction solution once while stirring, after which heating is stopped; wherein, the amount of citric acid added accounts for 4% of the initial mass of the reaction solution; When the reaction solution temperature drops to 37°C, the reaction solution is heated to 72°C at a heating rate of 4.5°C / min. Then, citric acid and ethylene glycol are added to the reaction solution once while stirring, and then heating is stopped. The amount of citric acid added is 1% of the initial mass of the reaction solution, and the amount of ethylene glycol added is 2% of the initial mass of the reaction solution. When the temperature of the reaction solution drops to 62°C, the reaction solution is heated to 85°C at a heating rate of 2.5°C / min. Then, ethylene glycol is added to the reaction solution once while stirring, and then heating is stopped. The addition of citric acid and ethylene glycol is complete. The amount of ethylene glycol added accounts for 5% of the initial mass of the reaction solution.

[0043] Example 19: This example is basically the same as Example 1, except that the reaction solution is first heated to 52°C at a heating rate of 7°C / min, and then citric acid is added to the reaction solution once while stirring, after which heating is stopped; wherein, the amount of citric acid added accounts for 6% of the initial mass of the reaction solution; When the reaction solution temperature drops to 37°C, the reaction solution is heated to 72°C at a heating rate of 4.5°C / min. Then, citric acid and ethylene glycol are added to the reaction solution once while stirring, and then heating is stopped. The amount of citric acid added is 2% of the initial mass of the reaction solution, and the amount of ethylene glycol added is 3% of the initial mass of the reaction solution. When the temperature of the reaction solution drops to 62°C, the reaction solution is heated to 85°C at a heating rate of 2.5°C / min. Then, ethylene glycol is added to the reaction solution once while stirring, and then heating is stopped. The addition of citric acid and ethylene glycol is complete. The amount of ethylene glycol added accounts for 6% of the initial mass of the reaction solution.

[0044] Comparative Example 1: Referring to Example 1, citric acid and ethylene glycol were added to the reaction solution all at once.

[0045] Comparative Example 2: Referring to Example 1, after each addition of citric acid or ethylene glycol, heating was continued directly without waiting for the temperature of the reaction solution to drop.

[0046] Comparative Example 3: Referring to Example 1, in the process of adding citric acid and ethylene glycol, the heating rate of the reaction solution was kept constant at 4.5℃ / min.

[0047] Experimental Example: To investigate the influence of preparation parameters of each embodiment and comparative example on the properties of ceramic materials, rectangular specimens of 5mm × 2.5mm × 17.5mm were prepared using the hot isostatic pressing method. The thermal conductivity at 1000℃ and the coefficient of thermal expansion at 1180℃ of the specimens prepared in each embodiment and comparative example were then tested. The specific investigation is as follows: Experiment Example 1: Investigating the Influence of Mixed Rare Earth Oxide Composition on the Properties of Ceramic Materials Using Examples 1, 2, and 3 as experimental comparisons, the thermal conductivity and thermal expansion properties of ceramic materials with different mixed rare earth oxide compositions are shown in Table 1 below: Table 1. Thermal conductivity and thermal expansion properties of ceramic materials with different mixed rare earth oxide compositions.

[0048] As shown in Table 1, compared with Examples 1, 2, and 3, the ceramic material of Example 1 has the lowest thermal conductivity and the highest coefficient of thermal expansion, indicating that the ceramic material of Example 1 has the best thermal insulation performance and the best compatibility with the high-temperature alloy substrate. This may be because the ceramic material of Example 1 has a more uniform composition and the most stable structure under the mixed rare earth oxide composition. Therefore, the mixed rare earth oxide composition selected in Example 1 is the optimal one.

[0049] Experiment Example 2: Investigating the effect of pH value of the mixed solution on the properties of ceramic materials. Using Examples 1, 4, and 5 as experimental comparisons, the thermal conductivity and thermal expansion properties of the ceramic materials at different pH values ​​of the mixed solutions are shown in Table 2 below: Table 2. Thermal conductivity and thermal expansion properties of ceramic materials at different pH values ​​of the mixed solution.

[0050] As shown in Table 2, compared with Examples 1, 4, and 5, the ceramic material of Example 1 has the lowest thermal conductivity and the highest coefficient of thermal expansion, indicating that the ceramic material of Example 1 has the best thermal insulation performance and the best compatibility with the high-temperature alloy substrate. This may be because the metal ions can be uniformly mixed at the pH value of the mixture in Example 1, so the pH value of the mixture selected in Example 1 is optimal.

[0051] Experiment Example 3: Investigating the effect of the composition of the mixture on the properties of ceramic materials. Using Examples 1, 6, and 7 as experimental comparisons, the thermal conductivity and thermal expansion properties of ceramic materials with different mixture compositions are shown in Table 3 below: Table 3. Thermal conductivity and thermal expansion properties of ceramic materials with different mixture compositions

[0052] As shown in Table 3, compared with Examples 1, 6, and 7, the ceramic material of Example 1 has the lowest thermal conductivity and the highest coefficient of thermal expansion, indicating that the ceramic material of Example 1 has the best thermal insulation performance and the best compatibility with the high-temperature alloy substrate. This may be because the rare earth oxides mixed in the mixture of Example 1 can be uniformly dispersed in the mixture. Therefore, the composition of the mixture selected in Example 1 is optimal.

[0053] Experiment Example 4: Investigating the Influence of Zirconium Sulfate Solution Composition on the Properties of Ceramic Materials Using Examples 1, 8, and 9 as experimental comparisons, the thermal conductivity and thermal expansion properties of ceramic materials with different zirconium sulfate solution compositions are shown in Table 4 below: Table 4 Thermal conductivity and thermal expansion properties of ceramic materials with different zirconium sulfate solution compositions

[0054] As shown in Table 4, compared with Examples 1, 8, and 9, the ceramic material of Example 1 has the lowest thermal conductivity and the highest coefficient of thermal expansion, indicating that the ceramic material of Example 1 has the best thermal insulation performance and the best compatibility with the high-temperature alloy substrate. This may be because the microstructure of the ceramic material is the most stable under the zirconium sulfate solution composition of Example 1. Therefore, the zirconium sulfate solution composition selected in Example 1 is the optimal one.

[0055] Experiment Example 5: Investigating the Influence of Reaction Solution Composition on the Properties of Ceramic Materials Using Examples 1, 10, and 11 as experimental comparisons, the thermal conductivity and thermal expansion properties of ceramic materials with different reaction solution compositions are shown in Table 5 below: Table 5 Thermal conductivity and thermal expansion properties of ceramic materials with different reaction solution compositions

[0056] As shown in Table 5, compared with Examples 1, 10, and 11, the ceramic material of Example 1 has the lowest thermal conductivity and the highest coefficient of thermal expansion, indicating that the ceramic material of Example 1 has the best thermal insulation performance and the best compatibility with the high-temperature alloy substrate. This may be because the reaction liquid composition of Example 1 can fully gel, so the reaction liquid composition selected in Example 1 is optimal.

[0057] Experiment Example 6: Investigating the Influence of Sintering Parameters on the Properties of Ceramic Materials Using Examples 1, 12, and 13 as experimental comparisons, the thermal conductivity and thermal expansion properties of ceramic materials under different sintering parameters are shown in Table 6 below: Table 6 Thermal conductivity and thermal expansion properties of ceramic materials under different sintering parameters

[0058] As shown in Table 6, compared with Examples 1, 12, and 13, the ceramic material of Example 1 has the lowest thermal conductivity and the highest coefficient of thermal expansion, indicating that the ceramic material of Example 1 has the best thermal insulation performance and the best matching with the high-temperature alloy substrate. This may be because the ceramic material has the most uniform grain size under the sintering parameters of Example 1. Therefore, the sintering parameters selected in Example 1 are optimal.

[0059] Experiment Example 7: Investigating the effect of the heating rate of the reaction solution on the properties of ceramic materials. Using Examples 1, 14, 15 and Comparative Examples 1, 2, 3 as experimental comparisons, the thermal conductivity and thermal expansion properties of ceramic materials under different reaction liquid heating rates are shown in Table 7 below: Table 7 Thermal conductivity and thermal expansion properties of ceramic materials at different heating rates of the reaction solution

[0060] As shown in Table 7, compared with Examples 1, 14, and 15, the ceramic material of Example 1 has the lowest thermal conductivity and the highest coefficient of thermal expansion, indicating that the ceramic material of Example 1 has the best thermal insulation performance and the best compatibility with the high-temperature alloy substrate. This may be because the metal ions can be uniformly dispersed in the gel at the heating rate of the reaction solution in Example 1. Therefore, the heating rate of the reaction solution selected in Example 1 is the optimal one.

[0061] Compared with Comparative Examples 1, 2, and 3, in Example 1, the ceramic material exhibited an increase in thermal conductivity and a decrease in the coefficient of thermal expansion when citric acid and ethylene glycol were added to the reaction solution all at once, or when the temperature of the reaction solution was not waited for to drop, or when the heating rate of the reaction solution was kept constant. This may be because the esterification reaction of citric acid and ethylene glycol was affected, resulting in the metal ions not being able to fully chelate with the gel. Therefore, the method of adding citric acid and ethylene glycol selected in Example 1 was the optimal one.

[0062] Experiment Example 8: Investigating the effect of reaction solution temperature on the properties of ceramic materials Using Examples 1, 16, 17 and Comparative Example 3 as experimental comparisons, the thermal conductivity and thermal expansion properties of the ceramic materials at different reaction liquid temperatures are shown in Table 8 below: Table 8 Thermal conductivity and thermal expansion properties of ceramic materials at different reaction liquid temperatures

[0063] As shown in Table 8, compared with Examples 1, 16, and 17, the ceramic material of Example 1 has the lowest thermal conductivity and the highest coefficient of thermal expansion, indicating that the ceramic material of Example 1 has the best thermal insulation performance and the best compatibility with the high-temperature alloy substrate. This may be because the gel structure of Example 1 is the most stable at the reaction liquid temperature, so the reaction liquid temperature selected in Example 1 is optimal.

[0064] Experiment Example 9: Investigating the effects of citric acid and ethylene glycol addition on the properties of ceramic materials. Using Examples 1, 18, and 19 as comparative experiments, the thermal conductivity and thermal expansion properties of ceramic materials with different amounts of citric acid and ethylene glycol added are shown in Table 9 below: Table 9. Thermal conductivity and thermal expansion properties of ceramic materials with different amounts of citric acid and ethylene glycol.

[0065] As shown in Table 9, compared with Examples 1, 18, and 19, the ceramic material of Example 1 has the lowest thermal conductivity and the highest coefficient of thermal expansion, indicating that the ceramic material of Example 1 has the best thermal insulation performance and the best compatibility with the high-temperature alloy substrate. This may be because the metal ions can be fully chelated by the gel under the addition amount of citric acid and ethylene glycol in Example 1. Therefore, the addition amount of citric acid and ethylene glycol selected in Example 1 is the optimal.

Claims

1. A method for preparing a rare-earth cerate high-entropy ceramic material, characterized in that, Includes the following steps: S1. Add the mixed rare earth oxides to deionized water, adjust the pH of the deionized water to 3-4 using dilute nitric acid, and then stir at 50-60℃ for 20-30 minutes to obtain a mixed solution; wherein, the mass ratio of the mixed rare earth oxides to deionized water is 1:10-15. S2. Add zirconium sulfate to deionized water and stir until completely dissolved to obtain a zirconium sulfate solution; wherein the mass ratio of zirconium sulfate to deionized water is 1:5~6. S3. Add zirconium sulfate solution to the mixture and stir for 15-20 min, then add tetrabutyl titanate and continue stirring for 20-25 min to obtain the reaction solution; wherein, the mass ratio of zirconium sulfate solution to the mixture is 1:8-10, and the amount of tetrabutyl titanate added accounts for 1.2-1.6% of the mass of the mixture; S4. Add citric acid and ethylene glycol to the reaction solution and stir for 1-2 hours to obtain a sol solution. Evaporate the sol solution to remove the liquid and obtain a wet gel. S5. Dry the wet gel to obtain dry gel, then crush and sieve the dry gel to obtain gel particles. Place the gel particles into a high-temperature sintering furnace for sintering to obtain ceramic material.

2. The method for preparing a rare earth cerate high-entropy ceramic material according to claim 1, characterized in that, In step S1, the mixed rare earth oxide is a mixture of lanthanum oxide, cerium oxide, ytterbium oxide, yttrium oxide and lutetium oxide in a mass ratio of 1:0.7~0.9:0.1~0.3:0.1~0.2:0.1~0.

2.

3. The method for preparing a rare earth cerate high-entropy ceramic material according to claim 1, characterized in that, In step S2, the mass concentration of the dilute nitric acid is 10-15%.

4. The method for preparing a rare earth cerate high-entropy ceramic material according to claim 1, characterized in that, In step S4, the evaporation method is as follows: the sol solution is placed in a water bath at 95~100℃ and stirred at a stirring rate of 300~500r / min.

5. The method for preparing a rare earth cerate high-entropy ceramic material according to claim 1, characterized in that, In step S5, the drying temperature is 120~140℃ and the drying time is 1~2h.

6. The method for preparing a rare earth cerate high-entropy ceramic material according to claim 1, characterized in that, In step S5, the sintering process is as follows: the temperature is increased to 1550-1650°C at a heating rate of 6-8°C / min, then held for 6-8 hours, and then cooled to room temperature in the furnace.

7. The method for preparing a rare earth cerate high-entropy ceramic material according to claim 1, characterized in that, In step S5, the process for adding citric acid and ethylene glycol is as follows: First, heat the reaction solution to 50-55°C at a heating rate of 6-8°C / min. Then, add citric acid to the reaction solution once while stirring, and then stop heating. The amount of citric acid added is 4-6% of the initial mass of the reaction solution. When the temperature of the reaction solution drops to 35-40℃, heat the reaction solution to 70-75℃ at a heating rate of 4-5℃ / min. Then, while stirring, add citric acid and ethylene glycol to the reaction solution once, and then stop heating. The amount of citric acid added is 1-2% of the initial mass of the reaction solution, and the amount of ethylene glycol added is 2-3% of the initial mass of the reaction solution. When the temperature of the reaction solution drops to 60-65℃, heat the reaction solution to 80-90℃ at a heating rate of 2-3℃ / min. Then, add ethylene glycol to the reaction solution once while stirring, and then stop heating. The addition of citric acid and ethylene glycol is complete. The amount of ethylene glycol added accounts for 5-6% of the initial mass of the reaction solution.

8. The method for preparing a rare earth cerate high-entropy ceramic material according to claim 1, characterized in that, In step S5, the aperture of the sieve during sieving is 300-400 mesh.

9. The application of the rare earth cerate ceramic material as described in any one of claims 1 to 8 in the field of thermal barrier coatings.

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