Anti-sintering low-thermal-diffusivity rare-earth tantalate environmental barrier coating ceramic material, and preparation method and application thereof

Abstract

The application discloses an anti-sintering low-thermal-diffusion-coefficient rare earth tantalate environmental barrier coating ceramic material and a preparation method and application thereof. x Al 1‑x TaO4; the density of the ceramic material is 94.9-98.4%, the pore shrinkage rate is less than 0.5% after long-time heat preservation at 1500 DEG C high temperature; the RE element is Sc, Y or Yb, and the value range of x is 0.02-0.16. The preparation method is that Sc2O3 powder, Y2O3 powder or Yb2O3 powder, aluminum nitrate solution and tantalum chloride solution are used as raw materials, a reaction precipitation colloid is prepared by adopting a chemical co-precipitation method, mixed powder is obtained after washing, drying, grinding and sieving, and ceramic bulk material is obtained after high-temperature hot pressing calcination. The ceramic material prepared by the application has excellent high-temperature thermodynamic performance, a lower thermal diffusion coefficient and a hardness value far exceeding that of common environmental barrier coating materials, and a thermal expansion coefficient matched with carbon fiber reinforced ceramic matrix composite materials, and is an environmental barrier coating material with great potential.

Description

Technical Field

[0001] This invention belongs to the field of ceramic coating technology, specifically relating to a rare earth tantalate environmental barrier coating ceramic material with low thermal diffusivity and sintering resistance, and its preparation method. Background Technology

[0002] Environmental barrier coatings (EBCs) are an advanced technology for protecting ceramic matrix composites (CMCs) in the complex service environment formed by the coupling of high-temperature corrosive media and high-speed combustion gases. The preparation of these materials requires stringent material selection conditions, demanding advantages such as low coefficient of thermal expansion, low thermal conductivity, excellent high-temperature mechanical properties, and high-temperature phase structure stability. Following YSZ, mullite, and BSAS, rare earth silicates have become widely used in the field of environmental barrier coatings due to their stable performance and extensive research. However, most rare earth silicate materials exhibit polymorphism, which poses challenges under high-temperature and wide-temperature range conditions. Its poor stability, high SiO2 reactivity, and relatively poor thermal compatibility with the matrix greatly limit its application range. Furthermore, other promising high-temperature ceramics such as cerates, phosphates, and zircons have high coefficients of thermal expansion, which cause large internal stresses to be generated rapidly at the interface of the coating system in thermal shock environments, making it difficult to effectively protect ceramic matrix composites in thermal shock environments. As the temperature at the turbine inlet of engines continues to increase, the demand for ceramic matrix composites in hot-end components of engines is becoming increasingly urgent. Therefore, finding a high-performance environmental barrier coating material is an urgent problem to be solved. Summary of the Invention

[0003] The first objective of this invention is to provide a rare earth tantalate environmental barrier coating ceramic material with low thermal diffusivity and sintering resistance. The second objective of this invention is to provide a method for preparing and applying the aforementioned rare earth tantalate environmental barrier coating ceramic material with low thermal diffusivity and sintering resistance.

[0004] The first objective of this invention is achieved by providing a rare-earth tantalate environmental barrier coating ceramic material with low thermal diffusivity and sintering resistance, having the chemical formula RE. x Al 1-x TaO4 has a density of 94.9-98.4%, and its porosity shrinkage is less than 0.5% after prolonged holding at 1500℃; its fracture toughness reaches 3.45 MPa·m. 1 / 2 The coefficient of thermal expansion is 5.40 × 10⁻⁶. -6 K -1 -5.73×10 -6 K -1 ;

[0005] In this context, the RE element is Sc, Y, or Yb, and the value of x ranges from 0.02 to 0.16.

[0006] The second objective of this invention is achieved as follows: the preparation method of the sintering-resistant, low thermal diffusivity rare earth tantalate environmental barrier coating ceramic material is specifically implemented according to the following steps:

[0007] 1) Calculate the amount of RE oxide according to the molar ratio of each element in the required tantalate ceramic material. Add the RE oxide to a mixed solution of aluminum nitrate and tantalum chloride in anhydrous ethanol as solvent. After mixing, slowly add a low-concentration basic salt solution while stirring to stabilize the pH value of the solution to between 8 and 9. Continue stirring to allow the system to react fully to obtain a homogeneous colloidal solution.

[0008] 2) The colloidal solution obtained in step 1) is filtered by suction, and the precipitated mixed colloid is washed repeatedly with deionized water and anhydrous ethanol. The precipitate is dried, ground and sieved to obtain composite oxide powder.

[0009] 3) The composite oxide powder obtained in step 2) is placed in a graphite mold for high-temperature hot pressing and sintering, then cooled, and then heat-treated to obtain the target anti-sintering low thermal diffusivity rare earth tantalate environmental barrier coating material.

[0010] In this context, the RE element is Sc, Y, or Yb.

[0011] The application of the sintering-resistant, low thermal diffusivity rare earth tantalate environmental barrier coating ceramic material is in the preparation of a high-temperature protective coating on the surface of silicon carbide fiber reinforced composite materials.

[0012] The preparation method of this invention uses specific raw materials and proportions. Based on the original properties of tantalates, it further optimizes the anti-sintering properties of the material by optimizing the large atomic mass difference and ion radius difference between trace rare earth elements and host elements. The host lattice shrinks, the lattice constant decreases, the interatomic force increases, the thermal expansion of the material decreases, and the thermal compatibility with ceramic matrix composites is improved. As the content of rare earth elements increases, the mean free path of phonons decreases, the phonon scattering coefficient increases, and the thermal diffusivity of the ceramic material decreases.

[0013] The preparation method of this invention addresses the differences in properties between powders and bulk materials by combining co-precipitation and solid-state sintering. It has advantages such as simple preparation process, low cost, easy control of preparation conditions, and short synthesis cycle. It allows for more accurate calculation of the content of each component in the powder, and the particle size of the mixed rare earth oxide powder reaches the nanoscale. This has a significant effect on refining the grain size and mechanical properties of ceramic materials. Applying appropriate pressure during the sintering process, while ensuring phase consistency, can further achieve structural homogenization and densification of the bulk material.

[0014] The preferred doping element content range and preparation parameters of the preparation method of this invention play a decisive role in the final microstructure, phase composition and high-temperature thermodynamic properties of the ceramic material, and dominate the directional optimization principles such as single phase, grain refinement, interatomic forces and phonon scattering mechanism.

[0015] In the method for preparing rare earth tantalate environmental barrier coating material with anti-sintering thermal diffusivity described in this invention, a high-temperature heat treatment process with a small temperature window is used to thoroughly remove carbon permeation on the material surface and eliminate residual internal stress formed in the material due to temperature difference as much as possible. This fully utilizes the advantages of the liquid phase method in terms of powder and grain size, making the material structure more stable and its anti-sintering ability more outstanding.

[0016] The ceramic material prepared by this invention has excellent high-temperature thermodynamic properties, a low thermal diffusivity, a hardness value far exceeding that of common environmental barrier coating materials, and a thermal expansion coefficient that matches that of carbon fiber reinforced ceramic matrix composites, making it a highly promising environmental barrier coating material. Attached Figure Description

[0017] Figure 1 These are the XRD phase diagrams of the ceramic materials prepared in Example 1 and Comparative Examples 1-2 of this invention;

[0018] Figure 2 This is a SEM microstructure characterization image of the ceramic material surface prepared in Example 1 of this invention;

[0019] Figure 3 This is an EDS composition distribution diagram of the ceramic material prepared in Example 1 of this invention;

[0020] Figure 4 These are the fracture toughness test results of the ceramic materials prepared in Examples 1-6 and Comparative Examples 1-5 of this invention. Detailed Implementation

[0021] The present invention will be further described below, but this is not intended to limit the invention in any way. Any modifications made based on the present invention are within the scope of protection of the present invention.

[0022] This invention discloses a rare-earth tantalate environmental barrier coating ceramic material with low thermal diffusivity and sintering resistance, the chemical formula of which is RE. x Al 1-x TaO4 has a density of 94.9-98.4%, and its porosity shrinkage is less than 0.5% after prolonged holding at 1500℃; its fracture toughness reaches 3.45 MPa·m. 1 / 2 The coefficient of thermal expansion is 5.40 × 10⁻⁶. -6 K -1 -5.73×10 -6 K -1;

[0023] In this context, the RE element is Sc, Y, or Yb, and the value of x ranges from 0.02 to 0.16.

[0024] The RE oxide powder has a purity of ≥99.99% and a particle size of 150-1000 nm.

[0025] This invention also provides a method for preparing the aforementioned sintering-resistant, low thermal diffusivity rare earth tantalate environmental barrier coating ceramic material, specifically implemented according to the following steps:

[0026] 1) Calculate the amount of RE oxide according to the molar ratio of each element in the required tantalate ceramic material. Add the RE oxide to a mixed solution of aluminum nitrate and tantalum chloride in anhydrous ethanol as solvent. After mixing, slowly add a low-concentration basic salt solution while stirring to stabilize the pH value of the solution to between 8 and 9. Continue stirring to allow the system to react fully to obtain a homogeneous colloidal solution.

[0027] 2) The colloidal solution obtained in step 1) is filtered by suction, and the precipitated mixed colloid is washed repeatedly with deionized water and anhydrous ethanol. The precipitate is dried, ground and sieved to obtain composite oxide powder.

[0028] 3) The composite oxide powder obtained in step 2) is placed in a graphite mold for high-temperature hot pressing and sintering, then cooled, and then heat-treated to obtain the target anti-sintering low thermal diffusivity rare earth tantalate environmental barrier coating material.

[0029] In this context, the RE element is Sc, Y, or Yb.

[0030] The aluminum nitrate solution has a mass concentration of 0.3-0.6 g / ml, and the tantalum chloride solution has a mass concentration of 0.3-0.6 g / ml.

[0031] In step 1), the basic salt solution is an ammonium ion salt solution, and the stirring speed is 250-400 r / min.

[0032] In step 2), the drying temperature is 70-90℃ and the drying time is more than 24 hours; the upper limit of the specified mesh size is used for sieving to ensure that the particle size distribution range of the powder is 23-38μm.

[0033] In step 3), the sintering temperature is 1650-1750℃, the sintering time is 2-6h, and the sintering pressure is 50-70MPa; the heat treatment temperature is 900-1100℃, and the heat treatment time is 1-3h.

[0034] The present invention also provides the application of the sintering-resistant, low thermal diffusivity rare earth tantalate environmental barrier coating ceramic material, specifically its application in the preparation of high-temperature protective coatings on the surface of silicon carbide fiber reinforced composite materials.

[0035] Example 1

[0036] A sintering-resistant low thermal diffusivity Sc 0.04 Al 0.96 The preparation method of TaO4 environmental barrier coated ceramic material includes the following steps:

[0037] (1) Prepare Sc according to requirements 0.04 Al 0.96 To calculate the amount of rare earth oxides used in TaO4 ceramic materials based on elemental molar ratios, 20g of scandium oxide (Sc2O3) powder (with a weighing accuracy of less than 0.001g) was weighed and added to a mixed solution of aluminum nitrate and tantalum chloride (TaCl5) in 1600ml of anhydrous ethanol. The scandium oxide (Sc2O3) dopant was then added to the solution. 3+ The ratio of aluminum nitrate content to Al ion content in the mixed solution is 1:24; the mass concentration of aluminum nitrate solution is 0.3 g / ml; and the mass concentration of tantalum chloride solution is 0.3 g / ml.

[0038] (2) Stir the above mixed solution evenly and slowly add 10% ammonia water to stabilize the pH value of the solution to between 8 and 9. At the same time, stir continuously to allow the system to react fully in order to obtain a uniform colloidal solution. The stirring speed is 250 r / min.

[0039] (3) The obtained colloidal solution was filtered by suction, and the precipitated mixed colloid was washed repeatedly with deionized water and anhydrous ethanol.

[0040] (4) The precipitate was placed in an oven and dried at 70°C for 24 hours. The dried powder was then ground in a mortar. The ground powder was sieved through 400 mesh and 600 mesh to ensure that the particle size distribution range was within 23.38 μm, thereby obtaining a uniform and fine composite oxide powder.

[0041] (5) Weigh a small amount of composite oxide powder and put it into The powder was placed in a 12mm graphite mold with a gasket between the mold and the powder. The mold was covered with high-temperature cotton. The whole mold was then placed in a hot press furnace for high-pressure sintering at a temperature of 1650℃ for 2 hours and a pressure of 50MPa. The mold was then cooled with the furnace.

[0042] (6) Cool the Sc 0.04 Al 0.96 TaO4 ceramic blocks were placed in a high-temperature tube furnace and heat-treated at 900℃ for 1 hour to obtain sintering-resistant ceramics with a low thermal diffusivity (Sc). x Al 1-x TaO4 environmental barrier coated ceramic material.

[0043] Example 2

[0044] A sintering-resistant low thermal diffusivity Sc 0.12 Al 0.88 The preparation method of TaO4 environmental barrier coated ceramic material includes the following steps:

[0045] (1) Prepare Sc according to requirements 0.12 Al 0.88 To calculate the amount of oxide used in TaO4 ceramic materials based on the elemental molar ratio, 24g of dopant scandium oxide (Sc2O3) powder was weighed with a weighing accuracy of less than 0.001g and added to a mixed solution of 293ml aluminum nitrate solution and 333ml tantalum chloride (TaCl5) using anhydrous ethanol as the solvent. The dopant Sc... 3+ The ratio of aluminum nitrate content to Al ion content in the mixed solution is 3:22, the mass concentration of aluminum nitrate solution is 0.6 g / ml, and the mass concentration of tantalum chloride solution is 0.6 g / ml.

[0046] (2) Stir the above mixed solution evenly and slowly add 10 mol / L (NH4)2CO3 solution to stabilize the pH value of the solution to between 8 and 9. At the same time, stir continuously to allow the system to react fully and obtain a uniform colloidal solution. The stirring speed is 400 r / min.

[0047] (3) The obtained colloidal solution was filtered by suction, and the precipitated mixed colloid was washed repeatedly with deionized water and anhydrous ethanol.

[0048] (4) The precipitate was placed in an oven and dried at 90°C for 30 hours. The dried powder was then ground in an agate mortar. The ground powder was then sieved through 400 mesh and 600 mesh to ensure that the particle size distribution range was 23-38 μm, thereby obtaining a uniform and fine composite oxide powder.

[0049] (5) Weigh a small amount of composite oxide powder and put it into The powder was placed in a 12mm graphite mold with a gasket between the mold and the powder. The mold was covered with high-temperature cotton. The mold was then placed in a hot press furnace for high-pressure sintering at a temperature of 1750℃ for 6 hours and a pressure of 70MPa. The mold was then cooled with the furnace.

[0050] (6) Cool the Sc 0.12 Al 0.88 TaO4 ceramic blocks were placed in a high-temperature tube furnace and heat-treated at 1100℃ for 3 hours to obtain sintering-resistant ceramics with a low thermal diffusivity (Sc). 0.12 Al 0.88 TaO4 environmental barrier coated ceramic material.

[0051] Example 3

[0052] This embodiment provides a sintering-resistant, low thermal diffusivity Y... 0.04 Al 0.96 The preparation method of TaO4 environmental barrier coated ceramic material includes the following steps:

[0053] (1) Prepare Y according to the required amount 0.04 Al 0.96 To calculate the amount of oxide used in TaO4 ceramic material based on the elemental molar ratio, 20g of scandium oxide (Sc2O3) powder (with a weighing accuracy of less than 0.001g) was weighed and added to a mixed solution of aluminum nitrate and tantalum chloride (TaCl5) in 1600ml of anhydrous ethanol. The dopant Y... 3+ The ratio of aluminum nitrate content to Al ion content in the mixed solution is 1:24; the mass concentration of aluminum nitrate solution is 0.3 g / ml; and the mass concentration of tantalum chloride solution is 0.3 g / ml.

[0054] (2) Stir the above mixed solution evenly and slowly add 10% ammonia water to stabilize the pH value of the solution to between 8 and 9. At the same time, stir continuously to allow the system to react fully in order to obtain a uniform colloidal solution. The stirring speed is 250 r / min.

[0055] (3) The obtained colloidal solution was filtered by suction, and the precipitated mixed colloid was washed repeatedly with deionized water and anhydrous ethanol.

[0056] (4) The precipitate was placed in an oven and dried at 70°C for 24 hours. The dried powder was then ground in an agate mortar. The ground powder was then sieved through 400 mesh and 600 mesh to ensure that the particle size distribution range was within 23.38 μm, thereby obtaining a uniform and fine composite oxide powder.

[0057] (5) Weigh a small amount of composite oxide powder and put it into The powder was placed in a 12mm graphite mold with a gasket between the mold and the powder. The mold was covered with high-temperature cotton. The whole mold was then placed in a hot press furnace for high-pressure sintering at a temperature of 1650℃ for 2 hours and a pressure of 50MPa. The mold was then cooled with the furnace.

[0058] (6) Cool the Y 0.04 Al 0.96 TaO4 ceramic blocks were placed in a high-temperature tube furnace and heat-treated at 900℃ for 1 hour to obtain sintering-resistant, low thermal diffusivity Y. 0.04 Al 0.96 TaO4 environmental barrier coated ceramic material.

[0059] Example 4

[0060] This embodiment provides a sintering-resistant, low thermal diffusivity Y... 0.12 Al0.88 The preparation method of TaO4 environmental barrier coated ceramic material includes the following steps:

[0061] (1) Prepare Y according to the required amount 0.12 Al 0.88 The amount of oxide used in the TaO4 ceramic material was calculated based on the elemental molar ratio. Then, 24g of dopant scandium oxide (Sc2O3) powder was weighed with a weighing accuracy of less than 0.001g and added to a mixed solution of 293ml aluminum nitrate solution and 333ml tantalum chloride (TaCl5) in anhydrous ethanol. The dopant Y... 3+ The ratio of aluminum nitrate content to Al ion content in the mixed solution is 3:22, the mass concentration of aluminum nitrate solution is 0.6 g / ml, and the mass concentration of tantalum chloride solution is 0.6 g / ml.

[0062] (2) Stir the above mixed solution evenly and slowly add 10 mol / L (NH4)2CO3 solution to stabilize the pH value of the solution to between 8 and 9. At the same time, stir continuously to allow the system to react fully and obtain a uniform colloidal solution. The stirring speed is 400 r / min.

[0063] (3) The obtained colloidal solution was filtered by suction, and the precipitated mixed colloid was washed repeatedly with deionized water and anhydrous ethanol.

[0064] (4) The precipitate was placed in an oven and dried at 90°C for 30 hours. The dried powder was then ground in an agate mortar. The ground powder was then sieved through 400 mesh and 600 mesh to ensure that the particle size distribution range was 23-38 μm, thereby obtaining a uniform and fine composite oxide powder.

[0065] (5) Weigh a small amount of composite oxide powder and put it into The powder was placed in a 12mm graphite mold with a gasket between the mold and the powder. The mold was covered with high-temperature cotton. The whole mold was then placed in a hot press furnace for high-pressure sintering at a temperature of 1720℃ for 4 hours and a pressure of 65MPa. The mold was then cooled with the furnace.

[0066] (6) Cool the Y 0.12 Al 0.88 TaO4 ceramic blocks were placed in a high-temperature tube furnace and heat-treated at 1000℃ for 2 hours to obtain sintering-resistant, low thermal diffusivity Y. 0.12 Al 0.88 TaO4 environmental barrier coated ceramic material.

[0067] Example 5

[0068] A sintering-resistant low thermal diffusivity Yb 0.04 Al 0.96The preparation method of TaO4 environmental barrier coated ceramic material includes the following steps:

[0069] (1) Prepare Yb according to the required amount 0.04 Al 0.96 To calculate the amount of oxide used in TaO4 ceramic material based on the elemental molar ratio, 20g of scandium oxide (Sc2O3) powder (with a weighing accuracy of less than 0.001g) was weighed and added to a mixed solution of aluminum nitrate and tantalum chloride (TaCl5) in 1600ml of anhydrous ethanol. The dopant Yb... 3+ The ratio of aluminum nitrate content to Al ion content in the mixed solution is 1:24; the mass concentration of aluminum nitrate solution is 0.3 g / ml; and the mass concentration of tantalum chloride solution is 0.3 g / ml.

[0070] (2) Stir the above mixed solution evenly and slowly add 10% ammonia water to stabilize the pH value of the solution to between 8 and 9. At the same time, stir continuously to allow the system to react fully in order to obtain a uniform colloidal solution. The stirring speed is 350 r / min.

[0071] (3) The obtained colloidal solution was filtered by suction, and the precipitated mixed colloid was washed repeatedly with deionized water and anhydrous ethanol.

[0072] (4) The precipitate was placed in an oven and dried at 70°C for 24 hours. The dried powder was then ground in an agate mortar. The ground powder was then sieved through 400 mesh and 600 mesh to ensure that the particle size distribution range was 23-38 μm, thereby obtaining a uniform and fine composite oxide powder.

[0073] (5) Weigh a small amount of composite oxide powder and put it into The powder was placed in a 12mm graphite mold with a gasket between the mold and the powder. The mold was covered with high-temperature cotton. The whole mold was then placed in a hot press furnace for high-pressure sintering at a temperature of 1650℃ for 2 hours and a pressure of 50MPa. The mold was then cooled with the furnace.

[0074] (6) Cool Yb 0.04 Al 0.96 TaO4 ceramic blocks were placed in a high-temperature tube furnace and heat-treated at 900℃ for 1 hour to obtain sintering-resistant, low thermal diffusivity Yb. 0.04 Al 0.96 TaO4 environmental barrier coated ceramic material.

[0075] Example 6

[0076] This embodiment provides a sintering-resistant, low thermal diffusivity Yb 0.12 Al 0.88 The preparation method of TaO4 environmental barrier coated ceramic material includes the following steps:

[0077] (1) Prepare Yb according to the required amount 0.12 Al 0.88 The amount of oxide used in the TaO4 ceramic material was calculated based on the elemental molar ratio. Then, 24g of scandium oxide (Sc2O3) powder, with a weighing accuracy of less than 0.001g, was weighed and added to a mixed solution of 293ml aluminum nitrate solution and 333ml tantalum chloride (TaCl5) in anhydrous ethanol. The dopant Yb... 3+ The ratio of aluminum nitrate content to Al ion content in the mixed solution is 3:22, the mass concentration of aluminum nitrate solution is 0.6 g / ml, and the mass concentration of tantalum chloride solution is 0.6 g / ml.

[0078] (2) Stir the above mixed solution evenly and slowly add 10 mol / L (NH4)2CO3 solution to stabilize the pH value of the solution to between 8 and 9. At the same time, stir continuously to allow the system to react fully and obtain a uniform colloidal solution. The stirring speed is 400 r / min.

[0079] (3) The obtained colloidal solution was filtered by suction, and the precipitated mixed colloid was washed repeatedly with deionized water and anhydrous ethanol.

[0080] (4) The precipitate was placed in an oven and dried at 90°C for 30 hours. The dried powder was then ground in an agate mortar. The ground powder was then sieved through 400 mesh and 600 mesh to ensure that the particle size distribution range was 23-38 μm, thereby obtaining a uniform and fine composite oxide powder.

[0081] (5) Weigh 1.5g of composite oxide powder and put it into The powder was placed in a 12mm graphite mold with a gasket between the mold and the powder. The mold was covered with high-temperature cotton. The whole mold was then placed in a hot press furnace for high-pressure sintering at a temperature of 1720℃ for 4 hours and a pressure of 65MPa. The mold was then cooled with the furnace.

[0082] (6) Cool Yb 0.12 Al 0.88 TaO4 ceramic blocks were heat-treated at 1000℃ for 2 hours in a high-temperature tube furnace to obtain sintering-resistant, low thermal diffusivity Yb. 0.12 Al 0.88 TaO4 environmental barrier coated ceramic material.

[0083] Comparative Example 1

[0084] The difference from Example 1 is that the molar ratio of Sc to Al is 0.2:0.8, while the other preparation conditions remain the same.

[0085] Comparative Example 2

[0086] The difference from Example 1 is that the heat treatment temperature is 700°C, while the other preparation conditions remain the same.

[0087] Comparative Example 3

[0088] The difference from Example 1 is that the sintering temperature is 1400℃ and the sintering pressure is 30MPa during the preparation of the ceramic material, while the other preparation conditions remain the same.

[0089] Comparative Example 4

[0090] This comparative example is for the preparation of Ho. 0.04 Al 0.96 The TaO4 environmental barrier coated ceramic material differs from Example 1 in that the dopant is the rare earth element Ho, while the other preparation conditions remain the same.

[0091] Comparative Example 5

[0092] The ceramic material used in this comparative example is a common environmental barrier coating rare earth silicate material.

[0093] Detection example

[0094] The composition, microstructure, fracture toughness, and thermal diffusivity of the ceramic materials prepared in Examples 1-6 and Comparative Examples 1-5 were detected by XRD, SEM, Vickers hardness tester, and laser thermal conductivity meter. The changes in porosity of the ceramic blocks were observed after being held at 1500℃ for 100 hours. The porosity after high-temperature testing was compared with the initial porosity of the samples, and the resistance to sintering was also tested.

[0095] 1. XRD characterization of the ceramic bulk materials prepared in Example 1 and Comparative Examples 1-2

[0096] The results are as follows Figure 1 As shown, by comparing with the standard PDF card, it can be seen that the ceramic blocks prepared in Examples 1-6 are all single phases, with no second phase generated. The rare earth elements are completely dissolved into the host lattice to form a solid solution, which belongs to the monoclinic crystal system with space group C2 / m (12). Moreover, within the range of doping elements and doping content required by this invention, the phases all satisfy this rule. However, Comparative Examples 1 and 2, while generating a single solid solution, also have impurities such as tantalum oxide and other rare earth oxides. This shows that the preparation parameters in this invention play a decisive role in ensuring that the sintering-resistant, low thermal diffusivity carbonate environment barrier coating material has the correct single phase.

[0097] 2. Microstructure of the anti-sintering, low thermal diffusivity tantalate environmental barrier coating material prepared in Example 1

[0098] The results are as follows Figure 2 As shown, it has an extremely dense microstructure with a grain size of only 1-2 μm. This specific structural feature...

[0099] The increased grain boundary scattering and strengthening mechanism also directly affect the thermodynamic properties of ceramic materials. The compositional distribution of the microscopic observation area is studied using SEM, such as... Figure 3 As shown, the sintering-resistant, low thermal diffusivity tantalate environmental barrier coating material prepared in Example 1 has low porosity, dense structure, uniform composition distribution, and no obvious segregation.

[0100] 3. Calculate the corresponding fracture toughness of the ceramic materials prepared in Examples 1-6 and Comparative Examples 1-5 based on the diagonal length of the indentation and the crack length measured by Vickers hardness.

[0101] The calculation formulas involved are as follows:

[0102]

[0103] Where Z = 0.018, load P is 2.942 N, HV is Vickers hardness, and c is the average crack length.

[0104] Test results as follows Figure 4 As shown, the blue area on the right is only in the range of 1.4-2.4 MPa·m. 1 / 2 Within the range, the fracture toughness of the red area on the left in Examples 1-6 can reach up to 3.45 MPa·m. 1 / 2 This is significantly higher than the values ​​in comparative examples 1-5, which provides a favorable material basis for the coating's resistance to high-speed particle impact and crack propagation.

[0105] 4. The coefficient of thermal expansion, thermal conductivity, and anti-sintering properties of the ceramic materials prepared in Examples 1-6 and Comparative Examples 1-5

[0106] As shown in Table 1, the density of the ceramic materials prepared by this invention is 94.9-98.4%. The coefficients of thermal expansion of the layered ceramic materials provided in Comparative Examples 1-5 are all much greater than the CMC coefficient of thermal expansion, while the coefficients of thermal expansion of the ceramic materials prepared using the parameters required by this invention are all maintained at (5.40-5.73) × 10⁻⁶. -6 K -1 Within the specified range, the CMC thermal expansion coefficient of the coating material is highly compatible with that of the ceramic matrix composite material, reducing the thermal stress between the coating and the substrate in a wide temperature range service environment, enhancing the system's thermal stress tolerance, and significantly extending the service life of the environmental barrier coating. Compared to the extremely high thermal conductivity of Comparative Examples 1-4, the ceramic material prepared in this invention has a lower thermal diffusivity, which can effectively isolate external heat and provide a larger thermal insulation gradient for hot-end components, enabling them to operate in a more temperate temperature environment. Furthermore, comparing the porosity of the material before and after 100 hours of thermal testing, the pore shrinkage rate shows that the anti-sintering performance of the environmental barrier coating material prepared in this invention is far superior to that of ceramic materials with parameters other than those specified, and it also has significant advantages compared to common environmental barrier coating materials.

[0107] Table 1. Thermal expansion coefficient, thermal conductivity, and anti-sintering properties of the ceramic materials prepared in Examples 1-6 and Comparative Examples 1-5.

[0108]

[0109] In summary, the sintering-resistant, low thermal diffusivity tantalate ceramic material prepared by this invention has excellent high-temperature thermodynamic properties and is a highly promising environmental barrier coating material.

Claims

1. A rare-earth tantalate environmental barrier coating ceramic material with low thermal diffusivity and sintering resistance, characterized in that, The chemical formula of the environmental barrier coating ceramic material is RE x Al 1-x TaO4 has a density of 94.9-98.4%, and its porosity shrinkage is less than 0.5% after prolonged holding at 1500℃; its fracture toughness reaches 3.45 MPa·m. 1 / 2 The coefficient of thermal expansion is 5.40 × 10⁻⁶. -6 K -1 ~5.73×10 -6 K -1 Wherein, RE element is Sc, Y or Yb, and x ranges from 0.02 to 0.16; the preparation method of the environmental barrier coating ceramic material is specifically implemented according to the following steps: 1) Calculate the amount of RE oxide according to the molar ratio of each element in the required tantalate ceramic material. Add the RE oxide to a mixed solution of aluminum nitrate and tantalum chloride in anhydrous ethanol as solvent. After mixing, slowly add a low-concentration basic salt solution while stirring to stabilize the pH value of the solution between 8 and 9. Continue stirring to allow the system to react fully to obtain a homogeneous colloidal solution. 2) The colloidal solution obtained in step 1) is filtered by suction, and the precipitated mixed colloid is washed repeatedly with deionized water and anhydrous ethanol. The precipitate is dried, ground and sieved to obtain composite oxide powder. 3) The composite oxide powder obtained in step 2) is placed in a graphite mold for high-temperature hot pressing sintering, then cooled, and then heat-treated to obtain the target anti-sintering low thermal diffusivity rare earth tantalate environmental barrier coating material; the high-temperature hot pressing sintering temperature is 1650~1750℃, the sintering time is 2~6h, and the sintering pressure is 50~70MPa; the heat treatment temperature is 900~1100℃, and the heat treatment time is 1~3h.

2. The sintering-resistant, low thermal diffusivity rare earth tantalate environmental barrier coating ceramic material according to claim 1, characterized in that, The RE oxide has a purity of ≥99.99% and a particle size of 150~1000nm.

3. The sintering-resistant, low thermal diffusivity rare earth tantalate environmental barrier coating ceramic material according to claim 1, characterized in that, The aluminum nitrate solution has a mass concentration of 0.3~0.6 g / mL, and the tantalum chloride solution has a mass concentration of 0.3~0.6 g / mL.

4. The sintering-resistant, low thermal diffusivity rare earth tantalate environmental barrier coating ceramic material according to claim 1, characterized in that, In step 1), the basic salt solution is an ammonium ion salt solution, and the stirring speed is 250~400 r / min.

5. The sintering-resistant, low thermal diffusivity rare earth tantalate environmental barrier coating ceramic material according to claim 1, characterized in that, In step 2), the drying temperature is 70~90℃ and the drying time is more than 24 hours; sieving ensures that the powder particle size is 23~38μm.

6. The application of the sintering-resistant, low thermal diffusivity rare earth tantalate environmental barrier coating ceramic material as described in any one of claims 1 to 5 in the preparation of a high-temperature protective coating on the surface of silicon carbide fiber reinforced composite materials.

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