A coating material, its preparation method and application

Abstract

The present invention relates to a coating material, a preparation method thereof and an application. The preparation method of the coating material includes: S1. preparing rare earth phosphate powder by a sol-gel method; S2. preparing aluminum tantalate powder by a solid-phase sintering method; S3. mixing the rare earth phosphate powder and the aluminum tantalate powder, and performing spark plasma sintering to obtain the coating material. In the present invention, a rare earth phosphate second phase is introduced into the main phase of the aluminum tantalate ceramic, and thus grain boundary phonon scattering and second-phase toughening mechanisms are introduced. By refining the grains, the proportion of grain boundaries is increased, the overall phonon scattering is enhanced, the thermal conductivity of the system is further reduced, and a higher heat insulation gradient is provided. Before the crack propagates, it is necessary to first overcome the internal residual strain energy of the dual-phase ceramic itself. At the same time, due to the relatively high thermal expansion coefficient of the rare earth phosphate, a compressive stress is generated on the lattice of the main phase in a high-temperature working environment, which can inhibit the generation and propagation of cracks, thereby achieving the purpose of toughening and effectively improving the performance stability of the coating material.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and particularly relates to a coating material, a preparation method thereof, and an application thereof. Background Art

[0002] The increase in the thrust-to-weight ratio of aeroengines has a direct impact on the complexity of the service environment of their hot-end components. On the one hand, as the thrust-to-weight ratio of aeroengines increases, the working environment temperature of high-temperature components continues to rise, which will cause the temperature distribution of the components to be affected by many factors such as radiation, convection, and heat conduction. On the other hand, as the thrust-to-weight ratio of aeroengines increases, the stress level borne by high-temperature components increases accordingly, which will make the components more sensitive to design errors, internal defects of materials, changes in engine operating conditions, and manufacturing tolerances. Moreover, the high thrust-to-weight ratio promotes the refinement of the structural design of aeroengines, and advanced technologies such as integral bladed disks and bladed rings need to be adopted to reduce the weight of corresponding components, improve the performance of components such as fans, compressors, and turbines, so as to extend the service life and improve the reliability.

[0003] The above factors cause the surface passivation layer of ceramic matrix composites to decay rapidly due to the coupling effect of various environmental corrosion media, resulting in the decline and failure of the internal material properties, which greatly limits the application prospects of ceramic matrix composites. In the prior art, preparing a dense high-temperature isolation layer on its surface to block the erosion of environmental corrosion media is the most effective method to extend its service life, that is, environmental / thermal barrier coatings.

[0004] Among them, YSZ (i.e., ZrO2 / Y2O3) is a kind of high-temperature coating material with the most mature and extensive application. YSZ has relatively stable high-temperature properties, but in the service environment with a large temperature range, there is a large thermal expansion difference between YSZ and ceramic matrix composites, making it difficult for YSZ to meet the application requirements of environmental barrier coatings. Rare earth silicates have achieved good results in experiments due to their relatively low thermal expansion coefficient and corrosion resistance, but their high SiO2 activity and high-temperature polymorphic state also greatly limit their application. Moreover, the fracture toughness of YSZ and rare earth silicate materials is low, making it difficult to support the long-term stable performance of the coatings. Summary of the Invention

[0005] One of the objectives of the present invention is to provide a preparation method of a coating material to solve the following technical problems: YSZ has relatively stable high-temperature performance, but in a service environment with a large temperature range, there is a large thermal expansion difference between YSZ and the ceramic matrix composite material, making it difficult for YSZ to meet the application requirements of environmental barrier coatings. Rare earth silicate has achieved good results in experiments due to its relatively low thermal expansion coefficient and corrosion resistance, but its high SiO2 activity and high-temperature polymorphic state also greatly limit its application. Moreover, the fracture toughness of YSZ and rare earth silicate materials is low, making it difficult to support the long-term stable performance of the coating. The second objective is to provide a coating material prepared according to the above-mentioned preparation method. The third objective is to provide the application of the coating material prepared according to the above-mentioned preparation method or the above-mentioned coating material in a methanol fuel cell.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] In the first aspect, the present application provides a preparation method of a coating material, and the preparation method includes:

[0008] S1. Prepare rare earth phosphate powder by the sol-gel method;

[0009] S2. Prepare aluminum tantalate powder by the solid-phase sintering method;

[0010] S3. Mix the rare earth phosphate powder and the aluminum tantalate powder, and perform spark plasma sintering to obtain the coating material.

[0011] Optionally, in step S1, preparing the rare earth phosphate powder includes: mixing a rare earth nitrate ceramic powder and a dihydrogen phosphate ceramic powder in deionized water to obtain a mixed solution, heating, sequentially adding ethylene glycol, nitric acid, and ethyl acetate to the mixed solution, adjusting the pH to 1.2 - 2.5, stirring to form a gel, drying, and sintering to obtain the rare earth phosphate powder

[0012] Optionally, in step S1, the rare earth nitrate includes nitrates formed by at least one rare earth element among yttrium, gadolinium, terbium, thulium, erbium, ytterbium, and lutetium.

[0013] Optionally, in step S1, the molar ratio of the rare earth nitrate ceramic powder to the dihydrogen phosphate ceramic powder is 1:1.

[0014] Optionally, the mass ratio of the total amount of the rare earth nitrate ceramic powder and the dihydrogen phosphate ceramic powder to deionized water is 1:6 - 10, preferably 1:7 - 10.

[0015] Optionally, in step S1, the volume ratio of the ethylene glycol to the deionized water is 1:2 - 3.5, preferably 1:2 - 3.

[0016] Optionally, in step S1, the volume ratio of ethyl acetate to deionized water is 1:4-6, preferably 1:5-6.

[0017] Optionally, in step S1, heat to 60-80 °C at a heating rate of 5-15 °C / min, preferably heat to 65-80 °C at a heating rate of 10-15 °C / min.

[0018] Optionally, in step S1, the rotation speed during the stirring process is 150-250 r / min, preferably 200-250 r / min.

[0019] Optionally, in step S1, the drying temperature is 150-180 °C, preferably 160-180 °C; the drying duration is 12-24 h, preferably 18-24 h.

[0020] Optionally, in step S1, the sintering temperature is 1100-1300 °C, preferably 1150-1250 °C; the sintering duration is 6-12 h, preferably 6-10 h.

[0021] Optionally, in step S2, preparing aluminum tantalate powder includes: mixing tantalum oxide, aluminum oxide and silicon dioxide powder in a solvent, wet ball milling, drying, grinding, sieving, and sintering to obtain aluminum tantalate powder.

[0022] Optionally, in step S2, the molar ratio of tantalum oxide, aluminum oxide and silicon dioxide is 1-x:1-x:4x, where 0.02 ≤ x ≤ 0.06.

[0023] Optionally, in step S2, the solvent includes water, ethanol or a mixture of the two.

[0024] Optionally, in step S2, during the wet ball milling process, the material ratio is 10-20:1, preferably 12-20:1.

[0025] Optionally, in step S2, the drying temperature is 70-90 °C, preferably 75-85 °C; the drying duration is 24-48 h, preferably 35-48 h.

[0026] Optionally, in step S2, the sintering temperature is 1500-1650 °C, preferably 1550-1650 °C; the sintering duration is 3-6 h, preferably 4.5-6 h.

[0027] Optionally, in step S3, the molar ratio of rare earth phosphate powder to aluminum tantalate powder is y:1-y, where 0.2 ≤ y ≤ 0.3.

[0028] Optionally, in step S3, the temperature of the spark plasma sintering is 1200-1450 °C, preferably 1250-1400 °C; the pressure of the spark plasma sintering is 45-70 MPa, preferably 50-65 MPa; the duration of the spark plasma sintering is 15-45 min, preferably 20-45 min.

[0029] In a second aspect, the present application also provides a coating material prepared by the preparation method as described above.

[0030] In a third aspect, the present application also provides an application of a coating material prepared by the preparation method as described above or the coating material as described above in an aeroengine or a gas turbine.

[0031] Advantages of the present invention:

[0032] In the present invention, aluminum tantalate ceramic is used as the main phase, and Si element is used as an optimizing agent. By double substitution, Si occupies both Al ions and Ta ions simultaneously, resulting in the shrinkage of the host lattice, the reduction of atomic spacing, the enhancement of ionic force, the reduction of the thermal expansion coefficient, a higher degree of thermal adaptation with the ceramic matrix composite material, and a weaker volume difference of the system with temperature, greatly enhancing the thermal shock resistance of the coating material.

[0033] In the present invention, the Si element causes lattice distortion of the host lattice, increases the phonon scattering coefficient, shortens the phonon mean free path, enhances phonon scattering, thereby reducing the thermal diffusion coefficient and providing a relatively mild working environment for the internal matrix.

[0034] In the present invention, a rare earth phosphate second phase is introduced into the aluminum tantalate ceramic main phase, and then the grain boundary phonon scattering and the second phase toughening mechanism are introduced. By refining the grains, the proportion of grain boundaries is increased, the overall phonon scattering is enhanced, the thermal conductivity of the system is further reduced, and a higher heat insulation gradient is provided. Before the crack propagates, it is necessary to overcome the internal residual strain energy of the duplex ceramic itself. At the same time, due to the relatively high thermal expansion coefficient of rare earth phosphate, a compressive stress is generated on the main phase lattice in a high-temperature working environment, which can inhibit the generation and propagation of cracks, thereby achieving the purpose of toughening and effectively improving the performance stability of the coating material.

[0035] In the present invention, sol-gel method and solid-phase sintering method are respectively adopted for rare-earth phosphates and tantalates with different intrinsic properties of materials. While ensuring the accurate material phase and structure of the materials, the operation difficulty and consumable cost are reduced. Among them, ethylene glycol as a stabilizer replaces hydrogen bonds to participate in the polymerization reaction of complex molecules, greatly improving the gel stability, forming a gel with excellent transparency and uniformity, which does not ionize in aqueous solution and is not affected by strong electrolytes. At the same time, ethyl acetate as a latent acid reagent induces rapid solute polymerization to generate sol-gel through its hydrolysis reaction in the solution, which can effectively avoid the ionization of nitrates in aqueous solution and effectively improve the purity of reactants, thereby preparing rare-earth phosphate powder.

[0036] The raw materials used in the present invention have low cost and high stability, and there are no safety hazards in the preparation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is an X-ray diffraction pattern (i.e., XRD diffraction pattern);

[0038] Figure 2 is a diagram of the detection result of density;

[0039] Figure 3 is an optical micrograph of a rhombic indentation during the Vickers hardness test of the bi-phase ceramic prepared in Example 1;

[0040] Figure 4 is a diagram of the detection result of fracture toughness. DETAILED DESCRIPTION OF THE INVENTION

[0041] The present invention will be further described below through specific specific examples. It should be noted that the specific material ratios, process conditions, results, etc. described in the examples of the present invention are only used to illustrate the present invention, and the protection scope of the present invention cannot be limited thereby. Any equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

[0042] The present application provides a method for preparing a coating material, including:

[0043] S1. Prepare rare earth phosphate powder by sol-gel method: Mix rare earth nitrate ceramic powder and dihydrogen phosphate in deionized water to obtain a mixed solution. The rare earth nitrate includes nitrate formed by at least one rare earth element among yttrium, gadolinium, terbium, thulium, erbium, ytterbium, and lutetium. The molar ratio of rare earth nitrate ceramic powder to dihydrogen phosphate ceramic powder is 1:1. Heat it to 60 - 80 °C at a heating rate of 5 - 15 °C / min. Add ethylene glycol, nitric acid, and ethyl acetate to the mixed solution in sequence to make the pH 1.2 - 2.5. Then stir at a speed of 150 - 250 r / min to form a gel. Then dry it at a temperature of 150 - 180 °C for 12 - 24 h, and sinter it at a temperature of 1100 - 1300 °C for 6 - 12 h to obtain rare earth phosphate powder. The mass ratio of the total amount of rare earth nitrate ceramic powder and dihydrogen phosphate ceramic powder to deionized water is 1:6 - 10. The volume ratio of ethylene glycol to deionized water is 1:2 - 3.5. The volume ratio of ethyl acetate to deionized water is 1:4 - 6;

[0044] S2. Prepare aluminum tantalate powder by solid-phase sintering method: Mix tantalum oxide, aluminum oxide, and silicon dioxide powder in a solvent. The solvent includes water, ethanol, or a mixture of the two. The molar ratio of tantalum oxide, aluminum oxide, and silicon dioxide is 1 - x:1 - x:4x, where 0.02 ≤ x ≤ 0.06. Then carry out wet ball milling. During the wet ball milling process, the material ratio is 10 - 20:1. Then dry it at a temperature of 70 - 90 °C for 24 - 48 h. Then grind and sieve it. Then sinter it at a temperature of 1500 - 1650 °C for 3 - 6 h to obtain aluminum tantalate powder;

[0045] S3. Mix rare earth phosphate powder and aluminum tantalate powder. The molar ratio of rare earth phosphate powder to aluminum tantalate powder is y:1 - y, where 0.2 ≤ y ≤ 0.3. Then carry out spark plasma sintering at a temperature of 1200 - 1450 °C and a pressure of 45 - 70 MPa for 15 - 45 min to obtain a coating material.

[0046] In the second aspect, the present application provides a composite catalyst prepared by the preparation method as described above.

[0047] In the third aspect, the present application provides an application of the composite catalyst prepared by the preparation method as described above or the composite catalyst as described above in a methanol fuel cell.

[0048] The present invention will be described in detail below by means of specific exemplary embodiments. It should also be understood that the following embodiments are only used to specifically illustrate the present invention and should not be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention all fall within the protection scope of the present invention. The specific process parameters and the like in the following examples are also only an example within a suitable range, that is, those skilled in the art can make selections within a suitable range through the description herein, rather than being limited to the specific values in the following examples.

[0049] Example 1

[0050] A biphasic ceramic material is specifically prepared according to the following steps:

[0051] S1. Mix yttrium nitrate ceramic powder and ammonium dihydrogen phosphate ceramic powder in a molar ratio of 1:1, add 120 ml of deionized water to obtain a mixed solution, heat it to 60°C at a heating rate of 5°C / min, add 55 ml of ethylene glycol and 30 ml of ethyl acetate to the mixed solution in sequence, and slowly add nitric acid to make the pH 1.4. Then, magnetically stir at a rotation speed of 150 r / min to form a gel, and then place it in an oven and dry at 150°C for 12 h to obtain a precursor. Subsequently, place the precursor in a high-temperature furnace and sinter at 1100°C for 6 h to obtain yttrium phosphate powder;

[0052] The mass ratio of the total amount of yttrium nitrate ceramic powder and ammonium dihydrogen phosphate ceramic powder to deionized water is 1:6.5;

[0053] S2. Mix tantalum oxide, alumina, and silica powder in a molar ratio of 0.98:0.98:0.08, add deionized water to the obtained mixture to obtain a mixed solution, and then perform wet ball milling. During the wet ball milling process, the material ratio is 15:1. Then, dry at 70°C for 24 h, and then grind, sieve, and then sinter at 1550°C for 3 h to obtain aluminum tantalate powder;

[0054] S3. Mix yttrium phosphate powder and aluminum tantalate powder in a molar ratio of 0.2:0.8, and then perform spark plasma sintering at a temperature of 1200°C and a pressure of 45 MPa for 15 min, and then perform demolding treatment to obtain the biphasic ceramic material.

[0055] Example 2

[0056] A biphasic ceramic material is specifically prepared according to the following steps:

[0057] S1. Mix gadolinium nitrate ceramic powder and ammonium dihydrogen phosphate ceramic powder in a molar ratio of 1:1, add 100 ml of deionized water to obtain a mixed solution, heat it to 65 °C at a heating rate of 7 °C / min, sequentially add 50 ml of ethylene glycol and 20 ml of ethyl acetate to the mixed solution, and slowly add nitric acid to make the pH 1.4. Then, magnetically stir at a speed of 150 r / min to form a gel. Next, place it in an oven and dry it at 170 °C for 16 h to obtain a precursor. Subsequently, place the precursor in a high-temperature furnace and sinter it at 1100 °C for 7 h to obtain gadolinium phosphate powder;

[0058] The total mass ratio of gadolinium nitrate ceramic powder and ammonium dihydrogen phosphate ceramic powder to deionized water is 1:8;

[0059] S2. Mix tantalum oxide, alumina and silica powder in a molar ratio of 0.96:0.96:0.16, add absolute ethanol to the obtained mixture to obtain a mixed solution, and then perform wet ball milling. During the wet ball milling process, the material ratio is 15:1. Then, dry it at 75 °C for 26 h, and then grind and screen it. Then, sinter it at 1570 °C for 3.5 h to obtain aluminum tantalate powder;

[0060] S3. Mix gadolinium phosphate powder and aluminum tantalate powder in a molar ratio of 0.25:0.75, and then perform spark plasma sintering at a temperature of 1240 °C and a pressure of 50 MPa for 20 min. Then, perform demolding treatment to obtain a biphasic ceramic material.

[0061] Example 3

[0062] A biphasic ceramic material is prepared specifically according to the following steps:

[0063] S1. Mix terbium nitrate 3 ceramic powder and ammonium dihydrogen phosphate ceramic powder in a molar ratio of 1:1, add 120 ml of deionized water to obtain a mixed solution, heat it to 70 °C at a heating rate of 8 °C / min, sequentially add 60 ml of ethylene glycol and 30 ml of ethyl acetate to the mixed solution, and slowly add nitric acid to make the pH 1.6. Then, magnetically stir at a speed of 200 r / min to form a gel. Next, place it in an oven and dry it at 170 °C for 18 h to obtain a precursor. Subsequently, place the precursor in a high-temperature furnace and sinter it at 1150 °C for 8 h to obtain terbium phosphate powder;

[0064] The total mass ratio of terbium nitrate ceramic powder and ammonium dihydrogen phosphate ceramic powder to deionized water is 1:6;

[0065] S2. Mix tantalum oxide, aluminum oxide and silica powders in a molar ratio of 0.94:0.94:0.24. Add deionized water to the obtained mixture to get a mixed solution, and then carry out wet ball milling. During the wet ball milling process, the material ratio is 15:1. Then dry at 80 °C for 30 h, followed by grinding and sieving. Then sinter at 1600 °C for 4.5 h to obtain aluminum tantalate powder;

[0066] S3. Mix terbium phosphate powder and aluminum tantalate powder in a molar ratio of 0.25:0.75. Then carry out spark plasma sintering at a temperature of 1300 °C and a pressure of 53 MPa for 23 min, and then carry out demolding treatment to obtain a biphasic ceramic material.

[0067] Example 4

[0068] A biphasic ceramic material is prepared specifically according to the following steps:

[0069] S1. Mix thulium nitrate Y(NO3)3 ceramic powder and ammonium dihydrogen phosphate ceramic powder in a molar ratio of 1:1. Add 110 ml of deionized water to get a mixed solution, heat it to 75 °C at a heating rate of 9 °C / min, add 55 ml of ethylene glycol and 30 ml of ethyl acetate to the mixed solution in sequence, and slowly add nitric acid to make the pH 1.7. Then carry out magnetic stirring at a rotation speed of 210 r / min to form a gel. Then place it in an oven and dry at 180 °C for 20 h to obtain a precursor. Then place the precursor in a high-temperature furnace and sinter at 1200 °C for 9 h to obtain thulium phosphate powder;

[0070] The total amount of thulium nitrate ceramic powder and ammonium dihydrogen phosphate ceramic powder is in a mass ratio of 1:7 to deionized water;

[0071] S2. Mix tantalum oxide, aluminum oxide and silica powders in a molar ratio of 0.96:0.96:0.16. Add absolute ethanol to the obtained mixture to get a mixed solution, and then carry out wet ball milling. During the wet ball milling process, the material ratio is 15:1. Then dry at 85 °C for 24 h, followed by grinding and sieving. Then sinter at 1610 °C for 4.8 h to obtain aluminum tantalate powder;

[0072] S3. Mix thulium phosphate powder and aluminum tantalate powder in a molar ratio of 0.3:0.7. Then carry out spark plasma sintering at a temperature of 1310 °C and a pressure of 55 MPa for 24 min, and then carry out demolding treatment to obtain a biphasic ceramic material.

[0073] Example 5

[0074] A biphasic ceramic material is prepared specifically according to the following steps:

[0075] S1. Mix erbium nitrate ceramic powder and ammonium dihydrogen phosphate ceramic powder in a molar ratio of 1:1, add 130 ml of deionized water to obtain a mixed solution, heat it to 75 °C at a heating rate of 12 °C / min, sequentially add 50 ml of ethylene glycol and 35 ml of ethyl acetate to the mixed solution, and slowly add nitric acid to make the pH 2.0. Then, magnetically stir at a rotation speed of 230 r / min to form a gel. Next, place it in an oven and dry it at 180 °C for 23 h to obtain a precursor. Subsequently, place the precursor in a high-temperature furnace and sinter it at 1250 °C for 10 h to obtain erbium phosphate powder;

[0076] The total amount of erbium nitrate ceramic powder and ammonium dihydrogen phosphate ceramic powder and the mass ratio of deionized water is 1:9.5;

[0077] S2. Mix tantalum oxide, alumina, and silica powder in a molar ratio of 0.98:0.98:0.08. Add deionized water to the obtained mixture to obtain a mixed solution, and then perform wet ball milling. During the wet ball milling process, the material ratio is 15:1. Then, dry it at 87 °C for 33 h, followed by grinding, sieving, and then sintering at 1640 °C for 5 h to obtain aluminum tantalate powder;

[0078] S3. Mix erbium phosphate powder and aluminum tantalate powder in a molar ratio of 0.2:0.8. Then, perform spark plasma sintering at a temperature of 1330 °C and a pressure of 60 MPa for 35 min, and then carry out demolding treatment to obtain a biphasic ceramic material.

[0079] Example 6

[0080] A biphasic ceramic material is prepared specifically according to the following steps:

[0081] S1. Mix lutetium nitrate ceramic powder and ammonium dihydrogen phosphate ceramic powder in a molar ratio of 1:1, add 120 ml of deionized water to obtain a mixed solution, heat it to 80 °C at a heating rate of 15 °C / min, sequentially add 50 ml of ethylene glycol and 20 ml of ethyl acetate to the mixed solution, and slowly add nitric acid to make the pH 1.2. Then, magnetically stir at a rotation speed of 250 r / min to form a gel. Next, place it in an oven and dry it at 180 °C for 24 h to obtain a precursor. Subsequently, place the precursor in a high-temperature furnace and sinter it at 1300 °C for 12 h to obtain lutetium phosphate powder;

[0082] The total amount of lutetium nitrate ceramic powder and ammonium dihydrogen phosphate ceramic powder and the mass ratio of deionized water is 1:7;

[0083] S2. Mix tantalum oxide, aluminum oxide and silicon dioxide powders in a molar ratio of 0.94:0.94:0.24. Add deionized water to the obtained mixture to get a mixed solution, and then perform wet ball milling. During the wet ball milling process, the material ratio is 15:1. Then dry at 90 °C for 48 h, followed by grinding, sieving, and then sinter at 1650 °C for 6 h to obtain aluminum tantalate powder;

[0084] S3. Mix lutetium phosphate powder and aluminum tantalate powder in a molar ratio of 0.2:0.8. Then perform spark plasma sintering at a temperature of 1450 °C and a pressure of 70 MPa for 45 min, and then carry out demolding treatment to obtain a biphasic ceramic material.

[0085] Comparative Example 1

[0086] S1. Mix yttrium nitrate ceramic powder and ammonium dihydrogen phosphate ceramic powder in a molar ratio of 1:1. Add 120 ml of deionized water to obtain a mixed solution. Add 55 ml of ethylene glycol and 30 ml of ethyl acetate to the mixed solution in sequence, and slowly add nitric acid to make the pH 1.4. Then stir magnetically at a speed of 150 r / min to form a gel. Then place it in an oven and dry at 150 °C for 12 h to obtain a precursor. Then place the precursor in a high-temperature furnace and sinter at 1100 °C for 6 h to obtain yttrium phosphate powder;

[0087] The total amount of yttrium nitrate ceramic powder and ammonium dihydrogen phosphate ceramic powder is in a mass ratio of 1:6.5 to the deionized water;

[0088] S2. Mix tantalum oxide, aluminum oxide and silicon dioxide powders in a molar ratio of 0.98:0.98:0.08. Add deionized water to the obtained mixture to get a mixed solution, and then perform wet ball milling. During the wet ball milling process, the material ratio is 15:1. Then dry at 70 °C for 24 h, followed by grinding, sieving, and then sinter at 1550 °C for 3 h to obtain aluminum tantalate powder;

[0089] S3. Mix yttrium phosphate powder and aluminum tantalate powder in a molar ratio of 0.2:0.8. Then perform spark plasma sintering at a temperature of 1200 °C and a pressure of 45 MPa for 15 min, and then carry out demolding treatment to obtain a biphasic ceramic material.

[0090] That is, the difference between this comparative example and Example 1 is that heating is not carried out during the preparation process of yttrium phosphate powder.

[0091] Comparative Example 2

[0092] A coating material is specifically prepared according to the following steps:

[0093] S1. Mix yttrium nitrate ceramic powder and ammonium dihydrogen phosphate ceramic powder in a molar ratio of 1:1, add 120 ml of deionized water to obtain a mixed solution, heat it to 60 °C at a heating rate of 5 °C / min, sequentially add 55 ml of ethylene glycol and 30 ml of ethyl acetate to the mixed solution, and slowly add nitric acid to make the pH 5.0. Then, magnetically stir at a rotation speed of 150 r / min to form a gel. Next, place it in an oven and dry it at 150 °C for 12 h to obtain a precursor. Subsequently, place the precursor in a high-temperature furnace and sinter it at 1100 °C for 6 h to obtain yttrium phosphate powder;

[0094] The total mass ratio of yttrium nitrate ceramic powder and ammonium dihydrogen phosphate ceramic powder to deionized water is 1:6.5;

[0095] S2. Mix tantalum oxide, alumina, and silica powder in a molar ratio of 0.98:0.98:0.08, add deionized water to the obtained mixture to obtain a mixed solution, and then perform wet ball milling. During the wet ball milling process, the material ratio is 15:1. Then, dry it at 70 °C for 24 h, followed by grinding, sieving, and then sintering at 1550 °C for 3 h to obtain aluminum tantalate powder;

[0096] S3. Mix yttrium phosphate powder and aluminum tantalate powder in a molar ratio of 0.2:0.8, and then perform spark plasma sintering at a temperature of 1200 °C and a pressure of 45 MPa for 15 min. Then, perform demolding treatment to obtain a biphasic ceramic material.

[0097] That is, the difference between this comparative example and Example 1 is that in step S1, the pH is adjusted to 5.0.

[0098] Comparative Example 3

[0099] The difference between this comparative example and Example 1 is that in step S2, the sintering temperature is 1200 °C and the sintering duration is 3 h.

[0100] Comparative Example 4

[0101] The difference between this comparative example and Example 3 is that in step S3, the pressure of spark plasma sintering is 20 MPa.

[0102] Comparative Example 5

[0103] The difference between this comparative example and Example 2 is that the aluminum tantalate powder prepared in step S2 is used as the ceramic material (i.e., the coating material).

[0104] Comparative Example 6

[0105] Use a certain rare earth silicate as the coating material.

[0106] Performance test

[0107] The biphasic ceramic material prepared in Example 1 and the coating material prepared in Comparative Example 5 were subjected to X-ray diffraction (i.e., XRD) to detect the phase. The XRD parameters were set as follows: the working voltage was 40 kV, the working current was 20 mA, the scanning range was 10°-60°, the step size was set to 0.02°, and the scanning speed was 2° / min. The results are as Figure 1 shown. Among them, the standard PDF cards in the figure are the spectra of the monoclinic system of orthophosphate and the monazite structure from top to bottom, and the space groups are P21 / n and the monoclinic system of aluminum tantalate, C2 / m space group.

[0108] It can be Figure 1 seen that the biphasic ceramic material prepared in Example 1 contains and only contains the characteristic phases of yttrium phosphate and aluminum carbonate, while in Comparative Example 5, there is only the single phase of aluminum tantalate of PDF#97-003-3885.

[0109] The porosity, density, coefficient of thermal expansion, thermal conductivity and hardness of the biphasic ceramic materials prepared in Examples 1-6 and the coating materials prepared in Comparative Examples 1-6 were detected, and the results are as Figure 2 、 Figure 3 and Table 1 show;

[0110] Among them, the porosity was measured by the Archimedes drainage method. The specific steps were as follows: Place the cleaned coating material on the balance and weigh the dry weight m1, wet weight m2, and suspended weight m3 respectively. Query and calculate the theoretical density ρ’, and calculate its porosity through the following formula:

[0111]

[0112] The density was calculated according to the formula density = 1 - porosity;

[0113] The coefficient of thermal expansion was measured by the optical method. The specific steps were as follows: Cut the test sample into 2 mm * 3 mm * 14 mm, place it horizontally in the sample chamber of the thermomechanical analyzer, move the thermocouple to the middle of the sample, and record the relationship between the sample deformation and the temperature-time function under the action of the programmed temperature and non-vibrating load. Calculate the coefficient of thermal expansion according to the formula coefficient of thermal expansion = ((L - L0) / L0) / (T - T0). In the formula, L is the high-temperature length of the test sample, in mm; L0 is the initial length of the test sample, in mm; T is the test temperature corresponding to the high-temperature length of the test sample, in °C; T0 is the initial temperature, in °C;

[0114] The thermal conductivity was measured by the flash method. The specific steps were as follows: Completely cover the symmetric measurement surface of the test sample with nano-graphite powder to increase the absorption rate of the sample. Place the pretreated sample on the sample stage of the laser thermal conductivity meter and select the corresponding correction model to obtain the thermal conductivity of the material;

[0115] Hardness was measured by the indentation method. The specific steps were as follows: polish the upper and lower surfaces of the sample to be measured until they are parallel, move the Vickers hardness tester along the magnetic track of the sample stage, set the pressure and holding time, and record the hardness value of the material;

[0116] And according to the test results of the indentation method, calculate the fracture toughness according to the following formula, and the results are as Figure 4 shown in Table 2:

[0117]

[0118] where K IC is the fracture toughness, with the unit of MPa·m 1 / 2 ; Z is an empirical constant, which is taken as 0.018 in the present invention; Ε is the modulus, with the unit of GPa; HV is the Vickers hardness, with the unit of GPa; P is the load, with the unit of N; C is the average crack length, with the unit of m.

[0119] Table 1 Test results of porosity, coefficient of thermal expansion, thermal conductivity and hardness

[0120]

[0121] As can be seen from Table 1, compared with Comparative Examples 1-3, the porosity of Example 1 decreased significantly, the coefficient of thermal expansion decreased significantly, the thermal conductivity decreased significantly, and the hardness increased significantly. Compared with Comparative Example 4, the porosity of Example 3 decreased significantly, the coefficient of thermal expansion decreased significantly, the thermal conductivity decreased significantly, and the hardness increased significantly. This result indicates that by controlling the pH within a specific range (1.2 - 2.5), the heating temperature, the sintering temperature in Step S2 and the spark plasma sintering pressure in the present invention, it is beneficial to reduce the porosity of the coating material and reduce the coefficient of thermal expansion of the coating material.

[0122] As can be seen from Table 1, compared with Comparative Example 5, the porosity of Example 2 decreased significantly, the coefficient of thermal expansion decreased significantly, the thermal conductivity decreased significantly, and the hardness increased significantly. This result indicates that compared with single-phase aluminum carbonate ceramic materials, under the action of phonon scattering and solid solution strengthening mechanisms, the rare earth phosphate / aluminum tantalate biphasic ceramic of the present invention is beneficial to reduce the porosity of the coating material, reduce the coefficient of thermal expansion and thermal conductivity of the coating material, and is beneficial to improve the hardness of the coating material.

[0123] Table 2 Test results of fracture toughness

[0124] Group <![CDATA[Fracture toughness (MPa·m 1 / 2 )]]> Example 1 3.52 Example 2 3.68 Example 3 3.52 Example 4 3.48 Example 5 3.29 Example 6 3.75 Comparative Example 1 1.89 Comparative Example 2 2.60 Comparative Example 3 2.35 Comparative Example 4 2.81 Comparative Example 5 2.92 Comparative Example 6 1.96

[0125] As can be seen from Table 2, compared with Comparative Examples 1-6, the fracture toughness of Examples 1-6 was significantly improved. This result indicates that the coating material of the present invention (i.e., rare earth phosphate / aluminum tantalate biphasic ceramics) has significantly better fracture toughness. Specifically, in the present invention, before crack propagation, it is first necessary to overcome the second-phase toughening mechanism introduced by the internal residual strain energy of the biphasic ceramics itself, and the fracture toughness of the traditional material (about 2.5 MPa·m 1 / 2 ) is increased to 3.75 MPa·m 1 / 2 , greatly improving the service life of the environmental barrier coating material.

[0126] The above embodiments are only preferred embodiments given to fully illustrate the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or transformations made by those skilled in the art on the basis of the present invention are within the protection scope of the present invention.

Claims

1. A method for preparing a coating material, characterized in that, The preparation method includes the following steps: S1. Prepare rare earth phosphate powder by sol-gel method: Mix rare earth nitrate ceramic powder and dihydrogen phosphate ceramic powder in deionized water to obtain a mixed solution. Heat the solution, and sequentially add ethylene glycol, nitric acid, and ethyl acetate to the mixed solution to make the pH 1.2 - 2.

5. Stir to form a gel, dry, and sinter to obtain rare earth phosphate powder. S2. Prepare aluminum tantalate powder by solid-phase sintering method. Mix tantalum oxide, aluminum oxide, and silicon dioxide powder in a solvent, then perform wet ball milling, drying, grinding, sieving, and sintering to obtain aluminum tantalate powder. The molar ratio of tantalum oxide, aluminum oxide, and silicon dioxide is 1 - x : 1 - x : 4x, where 0.02 ≤ x ≤ 0.

06. S3. Mix the rare earth phosphate powder and aluminum tantalate powder, and perform spark plasma sintering to obtain the coating material. The molar ratio of the rare earth phosphate powder to the aluminum tantalate powder is y : 1 - y, where 0.2 ≤ y ≤ 0.

3.

2. The preparation method according to claim 1, characterized in that, The rare earth nitrate includes nitrate formed by at least one rare earth element among yttrium, gadolinium, terbium, thulium, erbium, ytterbium, and lutetium. And / or, in step S1, the molar ratio of the rare earth nitrate to the dihydrogen phosphate ceramic powder is 1 :

1. And / or, the mass ratio of the total amount of the rare earth nitrate ceramic powder and the dihydrogen phosphate ceramic powder to deionized water is 1 : 6 - 10. And / or, in step S1, the volume ratio of the ethylene glycol to the deionized water is 1 : 2 - 3.

5. And / or, in step S1, the volume ratio of the ethyl acetate to the deionized water is 1 : 4 - 6. And / or, in step S1, heat to 60 - 80°C at a heating rate of 5 - 15°C / min. And / or, in step S1, the rotation speed during the stirring process is 150 - 250 r / min.

3. The preparation method according to claim 1, characterized in that, In step S1, the drying temperature is 150 - 180°C, and the drying duration is 12 - 24 h. And / or, in step S1, the sintering temperature is 1100 - 1300°C, and the sintering duration is 6 - 12 h.

4. The preparation method according to claim 1, characterized in that, In step S2, the solvent includes water, ethanol, or a mixture of the two. During the wet ball milling process, the material ratio is 10 - 20 :

1. And / or, in step S2, the drying temperature is 70 - 90°C, and the drying duration is 24 - 48 h.

5. The preparation method according to claim 1, characterized in that, In step S2, the sintering temperature is 1500 - 1650°C, and the sintering duration is 3 - 6 h.

6. The preparation method according to claim 1, characterized in that, In step S3, the temperature of the spark plasma sintering is 1200 - 1450°C, the pressure of the spark plasma sintering is 45 - 70 MPa, and the duration of the spark plasma sintering is 15 - 45 min.

7. A coating material prepared by the preparation method according to any one of claims 1 - 6.

8. Application of the coating material prepared by the preparation method according to any one of claims 1 - 6 or the coating material according to claim 7 in an aeroengine or a gas turbine.

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