Erosion-resistant silicon carbide ceramic-based composite material in high-temperature water-oxygen environment and preparation method thereof

Abstract

The invention belongs to the technical field of aerospace thermal structure ceramic-based composite materials, and particularly relates to an erosion-resistant silicon carbide ceramic-based composite material in a high-temperature water-oxygen environment and a preparation method of the erosion-resistant silicon carbide ceramic-based composite material. The preparation method of the erosion-resistant silicon carbide ceramic-based composite material in the high-temperature water-oxygen environment is provided for solving the problems that rare earth elements are not uniformly distributed in the composite material, aggregation distribution is easily caused and the like, and comprises the following steps: paving a layer of rare earth diffusions on the surface of the silicon carbide ceramic-based composite material, and then placing in an inert atmosphere and carrying out thermal diffusion treatment at 1000-1600 DEG C for 1-3 hours to obtain the erosion-resistant silicon carbide ceramic-based composite material in the high-temperature water-oxygen environment. The volume fraction of free Si in the silicon carbide ceramic-based composite material is 5-30%. The corrosion rate of water and oxygen to an internal interface phase and fibers of the composite material is slowed down, and the service stability of the composite material in a high-temperature water and oxygen environment is greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of aerospace thermal structural ceramic matrix composite technology, specifically relating to a silicon carbide ceramic matrix composite material resistant to corrosion in high-temperature water and oxygen environments and its preparation method, particularly relating to a silicon carbide ceramic matrix composite material with rare earth elements gradient distribution in the inner surface of the ceramic matrix and its preparation method. Background Technology

[0002] With the increasing thrust-to-weight ratio of aero engines, the turbine inlet operating temperature is also continuously increasing, gradually exceeding the temperature resistance limit of high-temperature alloys. Therefore, there is an urgent need to develop new high-temperature structural materials. Continuous silicon carbide fiber-reinforced silicon carbide ceramic matrix composites (SiC) are a suitable candidate. f SiC possesses excellent properties such as high temperature resistance, corrosion resistance, low density, high strength, creep resistance, and non-brittle fracture resistance, and is considered to be the preferred material to replace some high temperature alloys in the hot-end components of next-generation high-performance aero engines.

[0003] Despite SiC f SiC composite materials possess excellent resistance to dry oxygen, but their application in aero-engines faces the severe challenge of water-oxygen erosion from the combustion gases. Under water-oxygen erosion, the SiO2 generated from the oxidation of SiC reacts with water vapor to form volatile substances such as Si-O. x -H y This damages the SiO2 protective layer, allowing water and oxygen to further erode the internal structure of the material, accelerating the material failure process. Currently, improving SiC... f The main way to extend the service life of SiC in a gas-fired environment is through surface-prepared environmental barrier coatings. These coatings leverage the low oxygen diffusion and volatilization rates of rare-earth silicate phases in high-temperature gas-fired environments to isolate water and oxygen media and reduce material erosion rates. Reference 1 describes a plasma spraying method for applying these coatings to SiC. f The surface of the SiC composite material was coated with a Yb₂Si₂O₇ coating, which greatly improved the stability of the composite material in a water-oxygen environment. In Reference 2, magnetron sputtering was used to coat SiC... f A multiphase layer of Y₂SiO₅ and Y₂Si₂O₇ was constructed on the surface of the SiC composite material, reducing the corrosion rate of the composite material in a water-oxygen environment. Although the rare earth silicate coating effectively blocks the penetration of water-oxygen media into the composite material, significantly improving the corrosion rate of SiC... f The service life of SiC composites is inevitably affected by cracking and spalling during service. Reference 3 introduced yttrium silicates into the composite matrix via slurry impregnation, improving the composite's stability in high-temperature, water-oxygen environments. However, rare-earth silicates tend to aggregate in the composite matrix, thus reducing the composite's high-temperature mechanical properties. Therefore, designing and controlling the distribution morphology of rare-earth silicate phases to eliminate their negative impact on SiC is crucial.f The adverse effects of SiC's mechanical properties hinder the acquisition of highly reliable SiC in gas-fired environments. f The key to / SiC.

[0004] References: [1]DU J, LIU R, WAN F, et al. Failure mechanism of ytterbium silicate / silicon bi-layer environmental barrier coatings on SiCf / SiC composites upon long-time water vapor and oxygen corrosion test [J]. SurfaceandCoatingsTechnology, 2022,447. [2]DONG L, LIU MJ, ZHANG [3]HE F, LIU Y, LI J, et al. Effect of heat treatment on the microstructure and strength of yttrium silicate matrix-modified SiCf / SiCcomposites[J]. Journal of the European Ceramic Society, 2021, 41(16):93-100. Summary of the Invention

[0005] To address the issues of uneven distribution of rare earth elements in composite materials and their tendency to aggregate, the present invention aims to provide a silicon carbide ceramic matrix composite material resistant to corrosion in high-temperature water and oxygen environments and its preparation method.

[0006] On one hand, the present invention provides a method for preparing a silicon carbide ceramic matrix composite material resistant to corrosion in a high-temperature water and oxygen environment, comprising: spreading a layer of rare earth diffuser on the surface of the silicon carbide ceramic matrix composite material, and then subjecting it to a thermal diffusion treatment at 1000-1600°C under an inert atmosphere for 1-3 hours to obtain a silicon carbide ceramic matrix composite material resistant to corrosion in a high-temperature water and oxygen environment; wherein the volume fraction of free Si in the silicon carbide ceramic matrix composite material is 5-30%, preferably 10-25%; preferably, the rare earth diffuser layer comprises at least one of rare earth elemental powder, rare earth alloy powder, and rare earth halide salt powder.

[0007] In this invention, a rare earth diffusing agent of a specific composition is uniformly spread on the surface of a silicon carbide ceramic matrix composite material containing a certain amount of free silicon (the volume fraction of free Si is 5-30%, preferably 10-25%). Then, it is kept at a high temperature and inert atmosphere (1000-1600℃) for a certain time (1-3 hours) to construct a rare earth element gradient distribution structure on the inner surface of the composite matrix. (If the amount of rare earth diffusing agent added is too large, the residual rare earth diffusing agent on the surface can be removed at the end), thereby obtaining a silicon carbide ceramic matrix composite material resistant to corrosion in a high-temperature water and oxygen environment. Specifically, the silicon carbide ceramic matrix composite material in this invention must have a "free silicon phase" because the diffusing agent needs the free silicon in the material to achieve rapid diffusion, thereby shortening the diffusion time. Moreover, this diffusion process does not involve a chemical reaction.

[0008] Preferably, the rare earth diffuser is at least one selected from elemental yttrium powder, elemental ytterbium powder, yttrium aluminum alloy powder, ytterbium aluminum alloy powder, yttrium chloride powder, and ytterbium chloride powder, with yttrium aluminum alloy powder being the most preferred. More preferably, the rare earth element mass percentage in the rare earth diffuser is 10-100%. For example, the rare earth element mass percentage in yttrium aluminum alloy powder is 10-100%, and the rare earth element mass percentage in ytterbium aluminum alloy powder is 10-100%. The inventors realized that SiC... f The maximum temperature that SiC fibers or carbon fibers in SiC can withstand is around 1600℃. To ensure that the diffusing material can be evenly spread on the material surface and to shorten the diffusion time to reduce damage to the fibers, this invention specifically selects the aforementioned rare earth diffusing materials with the lowest possible melting point. Rare earth oxide powders or rare earth silicate ceramic powders have higher melting points (>2000℃), so these two types are not considered as diffusing materials.

[0009] Preferably, the particle size of the rare earth diffuser is 0.01–20 μm, and more preferably 0.5–10 μm.

[0010] Preferably, the rare earth diffuser has a layer thickness of 200–2500 μm, more preferably 500–2000 μm.

[0011] Preferably, the inert atmosphere is argon; more preferably, the flow rate of the inert atmosphere is 3-8 L / min.

[0012] Preferably, the volume fraction of fiber in the silicon carbide ceramic matrix composite material is 10-50%, the volume fraction of SiC matrix is ​​25-40%, and the volume fraction of free Si is 10-25%; more preferably, the fiber is silicon carbide fiber or carbon fiber.

[0013] Preferably, the preparation method of the silicon carbide ceramic matrix composite material includes: first impregnating the fiber preform in an organic carbon source precursor, and then subjecting it to pyrolysis and reactive silicon infiltration treatment to obtain the silicon carbide ceramic matrix composite material; preferably, the open porosity of the preform is 10-35%.

[0014] Preferably, the fiber preform comprises at least one of silicon carbide fiber or carbon fiber; the fiber surface of the fiber preform comprises an interface phase layer; the interface phase layer comprises at least one or any combination of two of BN layer, SiC layer and PyC layer; the thickness is 200nm to 2500nm, preferably 500nm to 2000nm.

[0015] Furthermore, preferably, the organic carbon source precursor comprises at least one of phenolic resin, epoxy resin, or sugar alcohol resin; the pyrolysis parameters include: a temperature of 500–1200°C and a time of 1–10 h; the open porosity of the preform is 5–35%. The parameters for the reactive silicon infiltration treatment include: temperature of 1400–1600℃, time of 0.5–2h, and vacuum degree ≤10Pa.

[0016] Furthermore, preferably, the fiber preform comprises at least one of silicon carbide fiber or carbon fiber and SiC powder; preferably, the volume fraction of silicon carbide fiber or carbon fiber in the fiber preform is 30-60%, the volume fraction of SiC powder is 10-50 vol%, and the volume fraction of pyrolyzed carbon is 0-35 vol%. The method for preparing the fiber preform includes: introducing SiC powder into the fiber preform using one of the following methods: chemical vapor infiltration, slurry impregnation, or a combination of chemical vapor infiltration and slurry impregnation. Preferably, the method for preparing the fiber preform includes: (1) Mix silicon carbide powder, binder and solvent to obtain a mixed slurry; (2) Impregnate silicon carbide fiber cloth or carbon fiber cloth in a mixed slurry to obtain fiber prepreg; (3) The obtained fiber prepreg is dried, laminated, cured and heat-treated to obtain fiber preform.

[0017] Furthermore, preferably, the binder is selected from at least one of polyvinyl alcohol, polyvinyl butyral, and polymethyl methacrylate; the solvent is at least one of ethanol, isopropanol, and xylene; preferably, the mass ratio of SiC powder, binder, and solvent is (40-60):(5-15):(35-65). The thickness of the silicon carbide fiber cloth or carbon fiber cloth is 0.1-1 mm; the thickness of the fiber prepreg is 0.2-2 mm; the curing temperature is 100-400℃, the curing pressure is 1-30 MPa, and the curing time is 1-10 h. The heat treatment temperature is 700–1200℃, and the time is 1–10 hours.

[0018] In another aspect, the present invention provides a high-temperature water and oxygen environment corrosion-resistant silicon carbide ceramic matrix composite material prepared according to the above preparation method. In the high-temperature water and oxygen environment corrosion-resistant silicon carbide ceramic matrix composite material, the rare earth diffusers are gradient distributed in the inner surface layer of the silicon carbide ceramic matrix composite material matrix to form a diffusion layer. Preferably, the depth of the diffusion layer is 20 to 2000 μm, more preferably 100 to 300 μm.

[0019] In this invention, by constructing a rare earth element gradient distribution structure on the inner surface of the composite matrix, the problem of rare earth element aggregation within the material can be avoided. Simultaneously, this allows the material to form a rare earth silicate glass phase on the surface in a water-oxygen coupled corrosion environment, significantly limiting the diffusion and propagation of oxidants within the composite material, thereby improving the material's resistance to water-oxygen corrosion. In specific applications, the corrosion-resistant silicon carbide ceramic matrix composite material in a high-temperature water-oxygen environment undergoes an oxidation process. During this oxidation, rare earth elements oxidize to rare earth oxides, while silicon carbide and silicon oxidize to silicon dioxide. The rare earth oxides and silicon dioxide can ultimately react to form a rare earth silicate phase.

[0020] The beneficial effects of this invention are: In this disclosure, a rare earth element gradient distribution structure is formed on the inner surface of the matrix of silicon carbide ceramic matrix composite material by rare earth thermal diffusion infiltration method. This alloy component can be transformed in situ into water and oxygen resistant rare earth silicates in a high-temperature water and oxygen environment, thereby blocking further water and oxygen erosion and effectively improving the water and oxygen resistance of silicon carbide ceramic matrix composite material. Attached Figure Description

[0021] Figure 1 Roadmap for the preparation of rare earth thermally diffusing modified silicon carbide ceramic matrix composites; Figure 2 The figures show cross-sectional views of the SiC matrix before and after rare earth thermal diffusion modification in Example 16. As can be seen from the figures, after thermal diffusion modification, rare earth elements have been distributed in a gradient in the SiC matrix. Figure 3 The figure shows the surface and cross-section of the oxide layer of the rare earth thermally diffused SiC matrix in Example 16. It can be seen from the figure that the thermally diffused SiC matrix can form a corrosion-resistant rare earth silicate layer on the material surface after oxidation. Detailed Implementation

[0022] The present invention will be further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0023] In this disclosure, by controlling the alloy composition and thermal diffusion parameters, a silicon carbide ceramic matrix composite material with rare earth gradient distribution can be prepared. After oxidation in a high-temperature water-oxygen environment, a rare earth silicate stable phase is formed in situ on the surface oxide layer, which slows down the erosion rate of water and oxygen on the internal interface phase and fiber of the composite material, and greatly improves the service stability of the composite material in a high-temperature water-oxygen environment.

[0024] like Figure 1 As shown, the following exemplary method illustrates the preparation method of a silicon carbide ceramic matrix composite material resistant to corrosion in a high-temperature water and oxygen environment.

[0025] Silicon carbide (SiC) powder, binder, and solvent are mixed and ball-milled to obtain a uniform slurry. The SiC powder has a particle size of 0.01–20 μm, preferably 0.5–10 μm. The binder is one or more combinations of polyvinyl alcohol, polyvinyl butyral, or polymethyl methacrylate; the solvent is one or more combinations of ethanol, isopropanol, or xylene. In an alternative embodiment, the mass ratio of SiC powder, binder, and solvent can be (40-60):(5-15):(35-65).

[0026] A fiber prepreg is obtained by completely impregnating silicon carbide fiber cloth or carbon fiber cloth in a uniformly mixed slurry. Furthermore, an interface phase is deposited on the surface of the silicon carbide fiber cloth or carbon fiber cloth. The interface phase can be BN, SiC, or a combination of both, and the total thickness of the interface phase can be 0.1-10 μm. To ensure uniform impregnation of the slurry into the fiber bundle, the thickness of the fiber cloth should be controlled within a suitable range. In alternative embodiments, the thickness of the silicon carbide fiber cloth or carbon fiber cloth can be 0.1-1 mm, and the thickness of the fiber prepreg can be 0.2-2 mm.

[0027] Fiber prepregs are obtained by drying, cutting, laminating, curing, and pyrolyzing fiber prepregs. The curing temperature of the laminated fiber prepregs can be 100-400℃, the curing pressure can be 1-30MPa, and the curing time can be 1-10h. Preferably, curing is performed directly after impregnation, as the surface slurry between the layers of the fiber prepreg results in a tighter bond. The pyrolyzing temperature after curing can be 700-1200℃, and the time can be 1-10h. After one pyrolyzing step, the resulting fiber prepregs contain 30-60% fiber cloth by volume, 10-50% SiC powder by volume, and 0-35 vol% pyrolyzed carbon by volume.

[0028] A silicon carbide ceramic matrix composite material is obtained by impregnating a fiber preform with resin, followed by secondary pyrolysis and reactive infiltration treatment. The resin can be one or more combinations of phenolic resin, epoxy resin, or sugar alcohol resin. The secondary pyrolysis temperature can be 500-1200℃, and the time can be 1-10h. After secondary pyrolysis, the open porosity of the fiber preform is 5-35%.

[0029] The fiber preform after secondary pyrolysis is embedded in silicon powder, where the mass of the silicon powder can be 1.5-4 times that of the fiber preform. The reaction melting temperature can be 1400-1600℃, the time can be 0.5-2 hours, and the vacuum degree ≤10Pa. After silicon infiltration, a silicon carbide ceramic matrix composite material is obtained.

[0030] In silicon carbide ceramic matrix composites, the volume fraction of fibers is 10-50%, the volume fraction of SiC matrix is ​​25-40%, and the volume fraction of free Si is 10-25%.

[0031] A rare earth diffuser is uniformly spread on the surface of a silicon carbide ceramic matrix composite material, and then kept at 1000-1600℃ for 1-3 hours in an inert atmosphere to obtain a high-temperature water and oxygen environment resistant silicon carbide ceramic matrix composite material.

[0032] The rare earth diffuser contains 10-100% rare earth elements by mass, and the rare earth powder has a particle size of 0.01-20 μm, preferably 0.5-10 μm. The inert atmosphere is argon; preferably, the flow rate of the inert atmosphere is 3-8 L / min. After thermal diffusion infiltration, the rare earth elements will be gradient-distributed in the inner surface layer of the silicon carbide ceramic matrix composite material matrix to a depth of 20-2000 μm; preferably, the depth is 100-300 μm.

[0033] In high-temperature, water-oxygen-resistant silicon carbide ceramic matrix composites, rare earth elements are gradient-distributed in the inner and outer layers of the SiC matrix. When placed in a high-temperature, water-oxygen environment, the rare earth components in the inner and outer layers of the SiC matrix can react with water and oxygen and transform in situ into rare earth silicate corrosion-resistant structures, effectively preventing further corrosion by water and oxygen and improving the stability of the composite material in a high-temperature, water-oxygen-resistant environment. Preferably, the porosity of the high-temperature, water-oxygen-resistant silicon carbide ceramic matrix composite material is less than 20%, and the flexural strength can be 200–300 MPa.

[0034] In this invention, the test parameters for high-temperature water-oxygen environments include: heating and cooling rates controlled at 1–10 °C / min, and gas flow rates controlled at 100–1000 ml / min (oxygen:water vapor = 0.3–15). The oxidation rate constant of the obtained high-temperature water-oxygen environment corrosion-resistant silicon carbide ceramic matrix composite material does not exceed 2.6 × 10⁻⁶. -5 mg 2 ·cm -4 ·s -1 .

[0035] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0036] Example 1 (1) SiC powder (particle size 5μm), polyvinyl alcohol (binder) and ethanol (solvent) were ball-milled and mixed to obtain a stable slurry. The mass ratio of SiC powder, polyvinyl alcohol (binder) and ethanol (solvent) was 50:15:35; (2) Silicon carbide fiber cloth (0.6 mm thick, with BN / SiC interface phase deposited on the surface) was completely impregnated in a uniformly mixed slurry to obtain a fiber prepreg. The fiber prepreg was dried, cut, laminated, cured, and pyrolyzed to obtain a fiber preform. The thickness of the BN interface layer was 0.6 μm, the thickness of the SiC interface layer was 1 μm, the thickness of the fiber prepreg was 0.7 mm, the curing temperature after prepreg lamination was 250℃, the curing pressure was 2 MPa, and the pyrolysis temperature was 700℃. (3) The fiber preform is impregnated with phenolic resin, and after drying and curing, it undergoes secondary pyrolysis and reactive infiltration treatment to obtain silicon carbide ceramic matrix composite material. The curing temperature is 140℃, the pyrolysis temperature is 700℃, the reactive infiltration temperature is 1450℃, the holding time is 1h, and the vacuum degree during infiltration is ≤10Pa. (4) A layer of yttrium aluminum alloy (yttrium mass fraction of 20%) powder (average thickness 1500 μm) was uniformly spread on the surface of the silicon carbide ceramic matrix composite material, and kept at 1400℃ for 1 h in an argon atmosphere to obtain yttrium aluminum alloy thermally diffused silicon carbide ceramic matrix composite material. The particle size of the yttrium aluminum alloy powder was 5 μm, and the argon flow rate was 5 L / min.

[0037] Example 2 Similar to the steps in Example 1, except that the SiC powder particle size in step (1) is 10 μm. The mass ratio of SiC powder, polyvinyl alcohol (binder), and ethanol (solvent) is 55:10:35.

[0038] Example 3 Similar to the steps in Example 1, except that the SiC powder particle size in step (1) is 0.1 μm. The mass ratio of SiC powder, polyvinyl alcohol (binder), and ethanol (solvent) is 45:15:40.

[0039] Example 4 Similar to the steps in Example 1, except that the mass fraction of yttrium in the yttrium aluminum alloy used in step (4) is 40%.

[0040] Example 5 Similar to the steps in Example 1, except that the mass fraction of yttrium in the yttrium aluminum alloy used in step (4) is 60%.

[0041] Example 6 Similar to the steps in Example 1, except that the yttrium aluminum alloy powder used in step (4) has a particle size of 10 μm.

[0042] Example 7 Similar to the steps in Example 1, except that the yttrium aluminum alloy powder used in step (4) has a particle size of 0.1 μm.

[0043] Example 8 Similar to the steps in Example 1, except that the alloy used in step (4) is a ytterbium-aluminum alloy (ytterbium mass fraction is 20%).

[0044] Example 9 Similar to the steps in Example 1, except that the alloy used in step (4) is a ytterbium-aluminum alloy (ytterbium mass fraction is 40%).

[0045] Example 10 Similar to the steps in Example 1, except that the SiC powder particle size in step (1) is 10 μm. The mass ratio of SiC powder, polyvinyl alcohol (binder), and ethanol (solvent) is 35:30:35.

[0046] Example 11 Similar to the steps in Example 1, except that yttrium powder is used in step (4).

[0047] Example 12 Similar to the steps in Example 1, except that yttrium chloride powder is used in step (4).

[0048] Example 13 Similar to the steps in Example 1, except that in step (1), the thickness of the silicon carbide fiber cloth is 1.2 mm.

[0049] Example 14 Similar to the steps in Example 11, except that in step (4), the temperature is maintained at 1000°C for 1 hour in an argon atmosphere.

[0050] Example 15 Similar to the steps in Example 11, except that in step (4), the temperature is maintained at 1200°C for 1 hour in an argon atmosphere.

[0051] Example 16 Similar to the steps in Example 11, except that in step (4), the temperature is maintained at 1600°C for 1 hour in an argon atmosphere.

[0052] Example 17 Similar to the steps in Example 11, except that in step (1), the mass ratio of SiC powder, polyvinyl alcohol (binder), and ethanol (solvent) is 25:40:35. The resulting untreated silicon carbide ceramic matrix composite material contains only 5 wt% free silicon.

[0053] Example 18 Similar to the steps in Example 11, except that in step (1), the mass ratio of SiC powder, polyvinyl alcohol (binder), and ethanol (solvent) is 60:5:35. The resulting untreated silicon carbide ceramic matrix composite material has a free silicon content as high as 30 wt%.

[0054] Comparative Example 1 Similar to the steps in Example 11, except that in step (4), the temperature is maintained at 800°C for 1 hour in an argon atmosphere.

[0055] Comparative Example 2 Similar to the steps in Example 11, except that in step (4), the temperature is maintained at 1800°C for 1 hour in an argon atmosphere.

[0056] Table 1: The term "fiber" here refers to "silicon carbide fiber or carbon fiber".

[0057] Table 2:

Claims

1. A method for preparing a silicon carbide ceramic matrix composite material resistant to corrosion in a high-temperature water and oxygen environment, characterized in that, include: A rare earth diffuser is spread on the surface of a silicon carbide ceramic matrix composite material, and then subjected to thermal diffusion treatment at 1000-1600°C for 1-3 hours in an inert atmosphere to obtain a high-temperature water and oxygen environment resistant silicon carbide ceramic matrix composite material; the volume fraction of free Si in the silicon carbide ceramic matrix composite material is 5-30%, preferably 10-25%; preferably, the rare earth diffuser layer comprises at least one of rare earth elemental powder, rare earth alloy powder, and rare earth halide salt powder.

2. The preparation method according to claim 1, characterized in that, The rare earth diffuser is at least one of elemental yttrium powder, elemental ytterbium powder, yttrium aluminum alloy powder, ytterbium aluminum alloy powder, yttrium chloride powder, and ytterbium chloride powder, preferably yttrium aluminum alloy powder; preferably, the mass percentage of rare earth elements in the rare earth diffuser is 10-100%.

3. The preparation method according to claim 1 or 2, characterized in that, The particle size of the rare earth diffuser is 0.01–20 μm, preferably 0.5–10 μm.

4. The preparation method according to any one of claims 1-3, characterized in that, The thickness of the rare earth diffuser is 200–2500 μm, preferably 500–2000 μm.

5. The preparation method according to any one of claims 1-4, characterized in that, The inert atmosphere is argon; preferably, the flow rate of the inert atmosphere is 3-8 L / min.

6. The preparation method according to any one of claims 1-5, characterized in that, The volume fraction of fiber in the silicon carbide ceramic matrix composite material is 10-50%, the volume fraction of SiC matrix is ​​25-40%, and the volume fraction of free Si is 10-25%; preferably, the fiber is silicon carbide fiber or carbon fiber.

7. The preparation method according to any one of claims 1-6, characterized in that, The preparation method of the silicon carbide ceramic matrix composite material includes: first impregnating the fiber preform in an organic carbon source precursor, and then subjecting it to pyrolysis and reactive silicon infiltration treatment to obtain the silicon carbide ceramic matrix composite material; preferably, the open porosity of the preform is 10-35%.

8. The preparation method according to claim 7, characterized in that, The fiber preform comprises at least one of silicon carbide fiber or carbon fiber; the fiber surface in the fiber preform comprises an interface phase layer; the interface phase layer comprises at least one or any combination of two of BN layer, SiC layer and PyC layer; the thickness is 200nm to 2500nm, preferably 500 to 2000nm.

9. The preparation method according to claim 7, characterized in that, The organic carbon source precursor comprises at least one of phenolic resin, epoxy resin, or sugar alcohol resin; the pyrolysis parameters include: a temperature of 500–1200°C and a time of 1–10 h; the open porosity of the preform is 5–35%. The parameters for the reactive silicon infiltration treatment include: temperature of 1400–1600℃, time of 0.5–2h, and vacuum degree ≤10Pa.

10. The preparation method according to claim 8, characterized in that, The fiber preform comprises at least one of silicon carbide fiber or carbon fiber and SiC powder; preferably, the volume fraction of silicon carbide fiber or carbon fiber in the fiber preform is 30-60%, the volume fraction of SiC powder is 10-50%, and the volume fraction of pyrolyzed carbon is 0-35%. The method for preparing the fiber preform includes: introducing SiC powder into the fiber preform using one of the following methods: chemical vapor infiltration, slurry impregnation, or a combination of chemical vapor infiltration and slurry impregnation. Preferably, the method for preparing the fiber preform includes: (1) Mix silicon carbide powder, binder and solvent to obtain a mixed slurry; (2) Impregnate silicon carbide fiber cloth or carbon fiber cloth in a mixed slurry to obtain fiber prepreg; (3) The obtained fiber prepreg is dried, laminated, cured and heat-treated to obtain fiber preform.

11. The preparation method according to claim 10, characterized in that, The binder is selected from at least one of polyvinyl alcohol, polyvinyl butyral, and polymethyl methacrylate; the solvent is at least one of ethanol, isopropanol, and xylene; preferably, the mass ratio of SiC powder, binder, and solvent is (40-60):(5-15):(35-65); The thickness of the silicon carbide fiber cloth or carbon fiber cloth is 0.1-1 mm; the thickness of the fiber prepreg is 0.2-2 mm; the curing temperature is 100-400℃, the curing pressure is 1-30 MPa, and the curing time is 1-10 h. The heat treatment temperature is 700–1200℃, and the time is 1–10 hours.

12. A high-temperature water-oxygen environment-resistant silicon carbide ceramic matrix composite material prepared by the preparation method according to any one of claims 1-11, characterized in that, In the high-temperature water and oxygen environment resistant silicon carbide ceramic matrix composite material, the rare earth diffusers are gradient-distributed in the inner surface layer of the silicon carbide ceramic matrix composite material matrix to form a diffusion layer; preferably, the depth of the diffusion layer is 20-2000 μm, more preferably 100-300 μm.

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