Lutetium silicate ceramic material and method for improving high temperature water vapor corrosion resistance of lutetium silicate ceramic

Abstract

The application belongs to the field of inorganic materials, and particularly relates to a lutetium silicate ceramic material and a method for improving high-temperature water-vapor corrosion resistance of the lutetium silicate material, and is suitable for performance optimization and development and application of rare earth silicate materials for environmental barrier coating. The method comprises the following steps: (1) controlling the content of solvent atoms Ho in Lu2SiO5 according to the stoichiometric ratio; (2) increasing the wetting angle of the Lu2SiO5 ceramic material from 80.1+ / -0.5 degrees to 87.5+ / -0.6 degrees; and (3) reducing the weight loss of the material after corrosion in a water-vapor environment of 1000-1400 DEG C, 30% H2O-70% O2 for 30 hours from 0.221 mg / cm 2 2 to 0.0911 mg / cm 2 2. The application can significantly improve the corrosion resistance of the Lu2SiO5 material in a high-temperature water-vapor environment by designing the composition of Lu2SiO5 through specific rare earth element doping and optimizing the proportion of the doped rare earth elements in Lu2SiO5. Meanwhile, the wetting angle of the Lu2SiO5 material is increased and the hydrophobic property is improved after the rare earth atom solid solution doping, which provides important support for optimizing the high-temperature water-vapor corrosion resistance.

Description

Technical Field

[0001] This invention belongs to the field of inorganic materials, specifically including a lutetium silicate ceramic material and a method for improving the water vapor corrosion resistance of the lutetium silicate material. It is applicable to the performance optimization and development of rare earth silicate materials for environmental barrier coatings. Background Technology

[0002] High-performance ceramic matrix composites (CMCs), such as SiC / SiC(f) composites, offer the high-temperature mechanical properties required for engine applications due to their excellent high-temperature strength and durability, and are expected to replace nickel-based superalloys as materials for aero-engine hot components. However, in high-temperature steam, the SiO2 protective layer generated by SiC oxidation reacts with water vapor to form easily volatile Si(OH)4. This volatilization process causes the substrate oxide layer to become loose, cracked, or even peeled off, leading to further corrosion of the matrix by the water-oxygen medium and causing performance degradation of the ceramic components. In addition, the Na2SO4 generated by the reaction of sodium salts in the atmosphere with sulfur impurities in the fuel can deposit on turbine blades, accelerating material corrosion and reducing their service life. Recognizing that water vapor and corrosive compounds (such as alkali salts or debris) seriously jeopardize the efficient use of CMCs, researchers have developed environmental barrier protective coatings (EBCs) to prevent or reduce the damage of the external environment to SiC ceramic materials. A successful EBC must meet the following basic conditions: (1) the coefficients of thermal expansion of each layer are matched to reduce thermal stress; (2) each layer material has a stable crystalline phase at high temperature to avoid cracks caused by volume changes during phase transformation; (3) each layer material has good chemical compatibility; (4) the surface material is able to resist various debris and impurities in the external environment, such as molten salt (generally CMAS, CaO-MgO-Al2O3-SiO2) deposition; and (5) it has excellent resistance to water vapor corrosion under high-temperature steam environment. To this day, rare earth silicate ceramics have attracted widespread attention as a third-generation environmental barrier coating.

[0003] To address the aforementioned issues, this application proposes a method to improve resistance to water vapor corrosion. This method employs a solid solution doping strategy, using a sol-gel method to synthesize powder, followed by dry pressing isostatic pressing combined with pressureless sintering to prepare rare earth-doped lutetium silicate ceramic materials with excellent resistance to water vapor corrosion. Summary of the Invention

[0004] The purpose of this invention is to provide a method for optimizing the water vapor corrosion resistance of rare earth lutetium silicate materials. The aim is to reduce the distortion of the [SiO4] coordination polyhedra within the rare earth silicate cell by solid solution doping with rare earth elements, thereby improving the stability of the [SiO4] coordination polyhedra within the lutetium silicate cell and alleviating the mismatch between the thermal expansion coefficient of lutetium silicate ceramics and SiC ceramics. While exhibiting good mechanical and thermal properties, the method addresses the problem of poor water vapor corrosion resistance. This invention proposes a compositional design approach for rare earth element-doped lutetium silicate ceramics, and through pressureless sintering, significantly improves the water vapor corrosion resistance of lutetium silicate ceramics at high temperatures.

[0005] The technical solution adopted in this application is as follows:

[0006] A method for improving the water vapor corrosion resistance of lutetium silicate (Lu2SiO5) ceramic materials includes the following steps:

[0007] (1) Control the content of solvent atoms Ho in Lu2SiO5 according to the stoichiometry;

[0008] (2) The wetting angle of Lu2SiO5 ceramic material increased from 80.1±0.5° to 87.5±0.6°;

[0009] (3) After corrosion for 30 hours under a water vapor environment of 1000-1400℃ and 30% H2O-70% O2, the weight loss of Lu2SiO5 ceramic material decreased from 0.221 mg / cm³. 2 Reduced to 0.0911 mg / cm 2 .

[0010] Optionally, the Ho element content in lutetium silicate materials is controlled at 50% to 75% according to stoichiometry.

[0011] Optionally, the phase of the synthesized Ho-doped Lu2SiO5 powder is X2-RE2SiO5.

[0012] Optionally, the average Si-O bond length of the synthesized Ho-doped Lu₂SiO₅ powder is in the range of...

[0013] Optionally, the distortion degree of [SiO4] in the synthesized Ho-doped Lu2SiO5 powder is between 0.44913% and 0.46516%.

[0014] Optionally, the Ho-doped Lu2SiO5 powder used has a particle size of 200–400 nm.

[0015] Optionally, the phase of the Ho-doped Lu2SiO5 ceramic obtained by sintering is X2-RE2SiO5.

[0016] Optionally, the grain size of Lu2SiO5 ceramics after solid solution doping is 2 to 5 μm.

[0017] The design concept and principle of the method for optimizing the water vapor corrosion resistance of rare earth lutetium silicate materials proposed in this invention are as follows:

[0018] After conducting preliminary research on rare-earth silicate materials for environmental barrier coatings both domestically and internationally, the applicant of this invention discovered that when silicate materials are subjected to water vapor corrosion in high-temperature environments, the Si-O bonds break, reacting with water vapor to generate easily volatile Si(OH)4. This volatilization process causes the oxide layer on the coating surface to become loose, cracked, or even peeled off, leading to further corrosion of the substrate by the water-oxygen medium and causing performance degradation of the component. Having identified the main causes of silicate material failure, the research aimed to improve the stability of the Si-O bond coordination environment through rational component design, thereby further optimizing the corrosion resistance of the material. Therefore, the following design ideas and principles are proposed:

[0019] (1) After X2-RE2SiO5 (RE=Tb,Dy,Ho,Er,Tm,Yb,Lu,Y) was corroded for 4 hours in an environment of 1400℃, 9.2%H2O-90.8%O2, it was found that the weight loss of Ho2SiO5 showed a linear decrease with the smallest slope, while the weight loss of Lu2SiO5 showed the largest slope.

[0020] (2) In X2-RE2SiO5(RE=Tb,Dy,Ho,Er,Tm,Yb,Lu,Y), the wetting angle of Ho2SiO5 bulk ceramic is 95.9±0.8°. The increase in wetting angle improves the hydrophobicity and can slow down water vapor corrosion.

[0021] The advantages and beneficial effects of this invention are as follows:

[0022] (1) The traditional solution to improve the corrosion resistance of rare earth silicate materials is to prepare multi-component gradient ceramics, such as Lu2Si2O7 / Lu2SiO5 composites or Lu2SiO5 / Er2SiO5 composites. This usually requires multiple preparations of different raw materials, increasing the production cycle. At the same time, the multi-gradient composite process is prone to thermal stress caused by the mismatch of thermal expansion coefficients, which accelerates the material failure.

[0023] (2) This invention provides the solid solution elements and content ranges for the composition design of lutetium silicate materials, ensuring that the material has a single phase structure, and that the weight loss of Lu2SiO5 ceramics is reduced in an environment of 1400℃, 30%H2O-70%O2 after solid solution doping. Attached Figure Description

[0024] Figure 1 Different concentrations (Lu) 1-x Ho x Wettability test of 2SiO5 ceramics.

[0025] Figure 2 Different concentrations (Lu) 1-x Ho x Surface morphology of 2SiO5 ceramic after corrosion at 1400℃ in an environment of 30% H2O-70% O2.

[0026] Figure 3 Different concentrations (Lu) 1-x Ho x Weight loss curve of 2SiO5 ceramic in an environment of 1400℃, 30%H2O-70%O2. Detailed Implementation

[0027] In specific implementation, this invention improves the resistance of Lu2SiO5 to water vapor corrosion by adjusting the content of solvent atoms Ho in Lu2SiO5 between 5% and 80% to increase the wetting angle and improve its hydrophobicity.

[0028] To demonstrate the improved water vapor corrosion resistance of Lu2SiO5 through component design in this invention, specific embodiments are provided below. These embodiments illustrate the improvements in wettability and water vapor resistance of Lu2SiO5 resulting from component design, illustrating the superiority of this invention. Given the principles of this invention, it can be predicted that other rare-earth silicate materials used in environmental barrier coatings will also exhibit the same application effects, and therefore are also within the scope of protection of this invention.

[0029] The above solution will be further explained below with reference to specific implementation examples:

[0030] Comparative Example 1

[0031] The preparation process of the lutetium silicate ceramic in Comparative Example 1 is the same as that in Example 1, except that the ratio of the chemical raw materials Lu2O3, Ho2O3, HCl and TEOs is changed to prepare Lu2SiO5 powder.

[0032] Figure 1 (a) shows the wetting angle test results of Lu2SiO5 ceramic, with the measured wetting angle being [value missing].

[0033] Figure 2 (a) shows the surface morphology of Lu2SiO5 lutetium silicate ceramic after corrosion at 1400℃ in an environment of 30% H2O-70% O2. Observation revealed obvious corrosion traces at the grain boundaries.

[0034] exist Figure 3 The middle part indicates (Lu) 15 / 16 Ho 1 / 16The weight loss curves of 2SiO5 ceramics in an environment of 1400℃ and 30% H2O-70% O2 show that the weight loss after 10h, 20h, and 30h in this environment is 0.0707 mg / cm³. 2 0.1416 mg / cm 2 0.2158 mg / cm 2 .

[0035] Example 1

[0036] a. Weigh Lu₂O₃, Ho₂O₃, HCl, and TEOs according to stoichiometric ratios, and synthesize (Lu₂O₃) via the sol-gel method. 15 / 16 Ho 1 / 16 )2SiO5 powder precursor powder and calcined.

[0037] b. Using XRD to obtain (Lu 15 / 16 Ho 1 / 16 Phase characterization of 2SiO5 powder

[0038] c. Place the obtained powder in The ceramic blank is formed by pressing in a mold.

[0039] d. Set the sintering temperature to 1650℃ and perform pressureless sintering on the ceramic green body to obtain the ceramic block.

[0040] Figure 1 (b) is (Lu) 15 / 16 Ho 1 / 16 The wetting angle of the 2SiO5 ceramic was measured to be 81.5 ± 0.2°.

[0041] Figure 2 (b) is (Lu) 15 / 16 Ho 1 / 16 The surface morphology of lutetium silicate ceramic (2SiO5) after corrosion at 1400℃ in an environment of 30% H2O-70% O2. Observation revealed obvious protrusions at the grain boundaries, indicating signs of corrosion.

[0042] exist Figure 3 The middle part indicates (Lu) 15 / 16 Ho 1 / 16 The weight loss curves of 2SiO5 ceramics in an environment of 1400℃ and 30% H2O-70% O2 were obtained. The results showed that the weight loss after 10h, 20h, and 30h in the environment of 1400℃ and 30% H2O-70% O2 was 0.0636 mg / cm³. 2 0.1237 mg / cm 2 0.1873 mg / cm2 Compared with the control group, the difference in mass loss was 0.0071 mg / cm³. 2 0.0179 mg / cm 2 0.285 mg / cm 2 .

[0043] Example 2

[0044] The preparation process of lutetium silicate ceramics in Example 2 is the same as in Example 1, except that the ratio of the chemical raw materials Lu2O3, Ho2O3, HCl, and TEOs is changed. 3 / 4 Ho 1 / 4 )2SiO5 powder.

[0045] Figure 1 (c) is (Lu) 3 / 4 Ho 1 / 4 The wetting angle of the 2SiO5 ceramic was measured to be 86.6 ± 0.8°.

[0046] Figure 2 (c) is (Lu) 3 / 4 Ho 1 / 4 The surface morphology of lutetium silicate ceramic (SiO5) after corrosion at 1400℃ in an environment of 30% H2O-70% O2 was observed. Grain growth was observed during the corrosion process, and the grain surfaces remained intact.

[0047] exist Figure 3 The middle part indicates (Lu) 15 / 16 Ho 1 / 16 The weight loss curves of 2SiO5 ceramics in an environment of 1400℃ and 30% H2O-70% O2 were obtained. The results showed that the weight loss after 10h, 20h, and 30h in the environment of 1400℃ and 30% H2O-70% O2 was 0.0424 mg / cm³. 2 0.0816 mg / cm 2 0.1265 mg / cm 2 Compared with the comparative example, the difference in mass loss was 0.0283 mg / cm³. 2 0.06 mg / cm 2 0.0893 mg / cm 2 .

[0048] Example 3

[0049] The preparation process of lutetium silicate ceramics in Example 3 is the same as in Example 1, except that the ratio of the chemical raw materials Lu2O3, Ho2O3, HCl, and TEOs is changed. 1 / 4 Ho 3 / 4 )2SiO5 powder.

[0050] Figure 1 (d) is (Lu) 1 / 4 Ho 3 / 4 The wetting angle of the 2SiO5 ceramic was measured to be 86.6 ± 0.8°.

[0051] Figure 2 (d) is (Lu) 1 / 4 Ho 3 / 4 The surface morphology of lutetium silicate ceramic (SiO5) after corrosion at 1400℃ in an environment of 30% H2O-70% O2 was observed. The grain surface remained smooth with no significant changes.

[0052] exist Figure 3 The middle part indicates (Lu) 1 / 4 Ho 3 / 4 The weight loss curves of 2SiO5 ceramics in an environment of 1400℃ and 30% H2O-70% O2 were obtained. The results showed that the weight loss after 10h, 20h, and 30h in the environment of 1400℃ and 30% H2O-70% O2 was 0.0323 mg / cm³. 2 0.0613 mg / cm 2 0.09132 mg / cm 2 Compared with the comparative example, the weight loss difference was 0.0384 mg / cm³. 2 0.0803 mg / cm 2 0.12448 mg / cm 2 .

[0053] The results show that the present invention can improve the hydrophobicity of Lu2SiO5 lutetium silicate ceramics through solid solution doping, thereby extending the service life of the material in resisting water vapor corrosion, thus obtaining an optimized method for the water vapor corrosion resistance of rare earth lutetium silicate materials.

Claims

1. A method for improving the high-temperature resistance to water vapor corrosion of lutetium silicate ceramics, characterized in that, Includes the following steps: The content of Ho atoms in Lu2SiO5 is controlled according to the stoichiometry. According to the stoichiometry, the Ho element content in lutetium silicate materials should be controlled between 50% and 75%. By controlling the Ho element content, the distortion degree of [SiO4] in the synthesized Ho-doped Lu2SiO5 powder is between 0.44913% and 0.46516%. The wetting angle of Lu2SiO5 ceramic material is from Increase to ; After corrosion for 30 hours in a water vapor environment of 1000-1400℃ and 30%H2O-70%O2, the weight loss of Lu2SiO5 ceramic material decreased from 0.221 mg / cm³. 2 Reduced to 0.0911 mg / cm 2 .

2. The method for improving the high-temperature water vapor corrosion resistance of lutetium silicate ceramics according to claim 1, characterized in that, The phase of the synthesized Ho-doped Lu2SiO5 powder is X2-RE2SiO5.

3. The method for improving the high-temperature water vapor corrosion resistance of lutetium silicate ceramics according to claim 1, characterized in that, The average Si-O bond length of the synthesized Ho-doped Lu2SiO5 powder is between 1.6258 Å and 1.6466 Å.

4. The method for improving the high-temperature water vapor corrosion resistance of lutetium silicate ceramics according to claim 1, characterized in that, The Ho-doped Lu2SiO5 powder used has a particle size of 200~400nm.

5. The method for improving the high-temperature water vapor corrosion resistance of lutetium silicate ceramics according to claim 1, characterized in that, The relative density of the Ho-doped Lu2SiO5 ceramic obtained by sintering is >98%.

6. The method for improving the high-temperature water vapor corrosion resistance of lutetium silicate ceramics according to claim 1, characterized in that, After solid solution doping, the grain size of Lu2SiO5 ceramics is 2~5μm.

7. A lutetium silicate ceramic material, characterized in that, The ceramic material is prepared using the method described in any one of claims 1 to 6.

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