A Glass-B2O3@SiO2 / SiB6@Al2O3-SiC antioxidant gradient coating on the surface of a C / C composite material and its preparation method.

Abstract

This invention discloses a method for preparing a Glass-B2O3@SiO2 / SiB6@Al2O3-SiC antioxidant gradient coating on the surface of a C / C composite material. The method includes adding B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder to a first mixture to obtain suspension A; adding I2 to suspension A to obtain suspension B; depositing a C / C-SiC sample in suspension B to obtain a C / C-SiC-B2O3@SiO2 / SiB6@Al2O3 sample; preparing suspensions C, D, and E; and sequentially immersing the C / C-SiC-B2O3@SiO2 / SiB6@Al2O3 sample in suspensions C, D, and E to obtain a Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample. This method is simple to operate and improves preparation efficiency.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, specifically to a Glass-B2O3@SiO2 / SiB6@Al2O3-SiC antioxidant gradient coating on the surface of a C / C composite material and its preparation method. Background Technology

[0002] Carbon-carbon composites, which use carbon fiber as reinforcement and carbon as the matrix, possess a variety of excellent properties. They have low density, high specific strength and modulus, high thermal conductivity, low coefficient of thermal expansion, good fracture toughness, wear resistance, and ablation resistance. In particular, their strength does not decrease with increasing temperature but may even increase, making them one of the best high-temperature resistant materials known. Due to their excellent properties, their applications are widespread. The literature [Huang Jianfeng, Zhang Yutao, Li Hejun, Zeng Xierong, Cao Liyun. New progress in the research of high-temperature anti-oxidation coatings for carbon / carbon composites in China [J]. Journal of Aeronautical Materials, 2007(02):74-78.] mentions that this material has excellent performance stability and durability under high-temperature environments, making it suitable for high-temperature structural applications in aerospace, automotive manufacturing, and other fields. However, because carbon materials have high oxidation reactivity and chemical affinity, they easily react with oxygen to generate carbon dioxide, leading to material ablation and loss. Therefore, carbon-carbon composites are prone to oxidation and ablation under high-temperature and oxidizing environments, thus requiring anti-oxidation protection.

[0003] Currently, during the use of carbon-carbon composite materials, a coating is applied to the C / C composite matrix for protection. The commonly used coating is SiC coating, which is a layer of SiC coating applied to the C / C composite matrix. However, the SiC coating material will gradually decrease over time during use, thus limiting the protection time of the C / C composite matrix. Therefore, in the market, other coatings are often added outside the SiC coating to increase the protection of the C / C composite matrix.

[0004] The coating added to SiC coatings on the market is boron oxide (B2O3), which has excellent anti-oxidation properties. Due to the melting point of B2O3 being greater than 450℃ and its excellent thermal stability, it can maintain a stable structure and performance at high temperatures. However, this material will still be oxidized in high-temperature and oxidizing environments during long-term use.

[0005] Meanwhile, silicon boride (SiB6) is also used in the market. Due to its high melting point (2503K) and excellent oxidation resistance, SiB6 forms a borosilicate glass phase at temperatures exceeding 823K. This glass phase exhibits excellent oxidation resistance and can heal and seal defects such as cracks in the coating at high temperatures. However, SiB6 has a low initial oxidation temperature. Therefore, when the temperature on the C / C composite matrix exceeds this low initial oxidation temperature, it cannot produce enough glass phase to seal the cracks in the coating, making the C / C composite matrix easily damaged during use.

[0006] Meanwhile, SiB6@Al2O3 coatings and B2O3@SiO2 coatings with core-shell structures have been proposed in the market. These coatings utilize the high strength, lightweight, and high fatigue resistance of the core-shell structure, as well as the mechanical properties and excellent thermal and chemical stability of SiO2 nanomaterials. In the preparation process, the shell material is Al2O3, which reacts with the oxidation product B2O3 of SiB6 at 900-1300℃. These two coatings can generate abundant glass phase healed cracks, achieving the purpose of toughening the coating. Although both coatings can protect the C / C composite matrix, their thermal shock resistance is poor under high temperature conditions, which reduces the protective effect of the coating on the C / C composite matrix, making the C / C composite matrix easily damaged. Summary of the Invention

[0007] To address the problem that existing protective coatings for C / C composite matrices have poor thermal shock resistance under high-temperature conditions, thus failing to effectively protect the C / C composite matrix, this invention provides a Glass-B2O3@SiO2 / SiB6@Al2O3-SiC antioxidant gradient coating for the surface of C / C composite materials and its preparation method.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] This invention discloses a method for preparing a Glass-B2O3@SiO2 / SiB6@Al2O3-SiC antioxidant gradient coating on the surface of a C / C composite material, comprising the following steps:

[0010] Step 1: Add B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder to the first mixture obtained by mixing isopropanol solution and ethanol to obtain suspension A;

[0011] Step 2: Add I2 to suspension A from step 1 to obtain suspension B;

[0012] Step 3: Place the C / C-SiC sample into the suspension B in step 2 for deposition to obtain the C / C-SiC-B2O3@SiO2 / SiB6@Al2O3 sample;

[0013] Step 4: Prepare suspensions C, D, and E;

[0014] SiB6@Al2O3 core-shell powder and B2O3@SiO2 core-shell powder were mixed in different proportions to obtain mixed powder C1 and mixed powder D1; silica sol and water were mixed to obtain a second mixture.

[0015] The mixed powder C1 is added to the second mixture and stirred to obtain suspension C;

[0016] The mixed powder D1 is added to the second mixture and stirred to obtain suspension D;

[0017] Glass powder is added to the second mixture and stirred to obtain suspension E;

[0018] Step 5: The C / C-SiC-B2O3@SiO2 / SiB6@Al2O3 sample from Step 3 is sequentially immersed in the suspensions C, D, and E prepared in Step 4 to obtain the Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample.

[0019] Preferably, in step 1, the mass ratio of B2O3@SiO2 and SiB6@Al2O3 core-shell powders is 1:2 to 10; and the volume ratio of isopropanol solution to ethanol is 6 to 10:1.

[0020] Preferably, the concentration of suspension A in step 1 is 20 g / L to 40 g / L.

[0021] Preferably, in the suspension B of step 2, the mass of I2 is 0.2 to 0.3 g.

[0022] Preferably, step 3, which involves placing the C / C-SiC sample into suspension B from step 2 for deposition, includes:

[0023] The C / C-SiC sample was placed in suspension B, and then suspension B was placed in a reactor with a deposition temperature of 80℃~120℃ and a deposition voltage of 340~450V. The filling ratio of the reactor was controlled to be 50%~80%. After deposition for 15min~30min, the sample was dried at 50℃~70℃ for 2~8h to obtain the C / C-SiC-B2O3@SiO2 / SiB6@Al2O3 sample.

[0024] Preferably, the glass powder in step 4 is a mixture of SiO2, Al2O3 and B2O3 in a mass percentage ratio of 55-78%: 2-5%: 20-40%, and the sum of the mass percentages of SiO2, Al2O3 and B2O3 is 100%.

[0025] Preferably, in step 4, the mass percentage of SiB6@Al2O3 core-shell powder in mixed powder C1 is 20% to 60%, the mass percentage of SiB6@Al2O3 core-shell powder in mixed powder D1 is 40% to 80%, and the total mass percentage of SiB6@Al2O3 core-shell powder and B2O3@SiO2 core-shell powder in mixed powder C1 and mixed powder D1 is 100%.

[0026] Preferably, in step 5, the preparation of the Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample includes:

[0027] The C / C-SiC-B2O3@SiO2 / SiB6@Al2O3 sample obtained in step 3 is preheated to 200-300℃ to obtain a preheated specimen.

[0028] The preheated specimen is first immersed in suspension C for 10-20 seconds and then taken out. After ultrasonic cleaning for 10-20 seconds, it is placed in an oven and dried at 60-70℃ for 1-2 minutes to obtain the intermediate first coating specimen.

[0029] The intermediate first coating sample is immersed in suspension D for 10-20 seconds and then taken out. After ultrasonic cleaning for 10-20 seconds, it is placed in an oven and dried at 60-70℃ for 1-2 minutes to obtain the intermediate second coating sample.

[0030] The intermediate second coating sample is immersed in suspension E for 10-20 seconds and then taken out. After ultrasonic cleaning for 10-20 seconds, it is placed in an oven and dried at 60-70℃ for 1-2 minutes to obtain the intermediate third coating sample.

[0031] The intermediate third coating sample was heat-treated to obtain the Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample.

[0032] Preferably, the process of heat-treating the intermediate third coating sample to obtain the Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample includes: placing the intermediate third coating sample in a heat treatment reactor, then setting the temperature to 1300℃~1500℃ and treating it under argon gas conditions for 2~6 minutes to obtain the Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample.

[0033] The present invention also discloses a Glass-B2O3@SiO2 / SiB6@Al2O3-SiC antioxidant gradient coating on the surface of a C / C composite material prepared by the above method.

[0034] Compared with the prior art, the present invention has the following beneficial technical effects:

[0035] This invention discloses a method for preparing a Glass-B2O3@SiO2 / SiB6@Al2O3-SiC antioxidant gradient coating on the surface of a C / C composite material. In this method, a C / C-SiC sample is placed in a suspension A obtained by mixing B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder with isopropanol solution and ethanol. A coating is then deposited on the surface of the C / C-SiC sample using pulsed arc discharge, resulting in a Glass-B2O3@SiO2 / SiB6@Al2O3-SiC antioxidant gradient coating. In the SiO2 / SiB6@Al2O3 sample, the electric arc generated by the pulsed voltage instantly raises the temperature of the particles deposited on the sample surface, causing them to sinter together, which can effectively improve the density and crystallinity of the coating. Then, the resulting C / C-SiC-B2O3@SiO2 / SiB6@Al2O3 sample is sequentially immersed in suspensions C, D, and E for hot impregnation, thus obtaining a Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample. In the sample, a coating structure is formed according to an objective temperature distribution. The outermost layer has a higher temperature and contains more SiB6@Al2O3 core-shell microcapsules, while the innermost layer has a relatively lower temperature and contains more B2O3@SiO2 core-shell microcapsules. This results in a gradient in the coating within the prepared Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample, increasing the... The Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample exhibits good toughness, and at high temperatures, it can form flowing SiO2·B2O3, which can provide high-temperature protection for the C / C composite matrix and self-repair cracks appearing on the Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample, thereby improving the protective effect of the Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating on the C / C composite matrix.

[0036] Furthermore, in the preparation method proposed in this invention, C / C-SiC sample is deposited by pulsed arc discharge to generate C / C-SiC-B2O3@SiO2 / SiB6@Al2O3 sample. The reaction conditions are mild, the operation is simple and easy to implement, which effectively improves the preparation efficiency and reduces the production cost. Moreover, no waste is generated in the preparation process, which is environmentally friendly.

[0037] Furthermore, in this invention, the mass percentage of SiB6@Al2O3 core-shell powder in mixed powder C1 is 20%–60%, and the mass percentage of SiB6@Al2O3 core-shell powder in mixed powder D1 is 40%–80%. Consequently, the SiB6@Al2O3 core-shell powder in suspensions C and D prepared from mixed powders C1 and D1 differs. Therefore, by sequentially treating C / C-SiC-B2O3@SiO2 / SiB6@Al2O3 samples through suspensions C and D, coatings containing different masses of SiB6@Al2O3 are obtained, thus forming an antioxidant gradient coating. This allows the antioxidant properties in the coating to be layered, improving the coating's performance.

[0038] This invention also discloses a Glass-B2O3@SiO2 / SiB6@Al2O3-SiC antioxidant gradient coating on the surface of a C / C composite material. This antioxidant gradient coating can form flowing SiO2·B2O3 at high temperatures, thereby providing high-temperature protection for the C / C composite material matrix and automatically repairing cracks generated on the Glass-B2O3@SiO2 / SiB6@Al2O3-SiC antioxidant gradient coating. Attached Figure Description

[0039] Figure 1 SEM image of the surface of a Glass-B2O3@SiO2 / SiB6@Al2O3-SiC antioxidant gradient coating on a C / C composite material provided by the present invention;

[0040] Figure 2 XRD pattern of an anti-oxidation gradient coating surface of a C / C composite material, Glass-B2O3@SiO2 / SiB6@Al2O3-SiC, provided for this invention;

[0041] Figure 3 Thermal shock resistance curve of a C / C composite material sample with Glass-B2O3@SiO2 / SiB6@Al2O3-SiC anti-oxidation gradient coating at 1473K in air provided by the present invention. Detailed Implementation

[0042] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0043] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0044] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0045] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0046] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0047] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0048] This invention discloses a method for preparing a Glass-B2O3@SiO2 / SiB6@Al2O3-SiC antioxidant gradient coating on the surface of a C / C composite material, specifically including the following steps:

[0049] Step 1: Add B2O3@SiO2 and SiB6@Al2O3 core-shell powders to a mixture of isopropanol solution and ethanol to obtain a first mixture, thus obtaining suspension A;

[0050] Specifically, B2O3@SiO2 core-shell powder was prepared:

[0051] The third solution is prepared by mixing deionized water and anhydrous ethanol in a volume ratio of 1:2 to 4, and the fourth mixture is prepared by mixing tetraethyl orthosilicate and anhydrous ethanol in a volume ratio of 1:5 to 7.

[0052] Boron oxide was added to the third solution and magnetically stirred to prepare a second solution with a concentration of 5-10 g / L. Then, a fourth mixture was slowly added to the second solution, and ammonia was added to the second solution to adjust the pH value to 7-8. The solution was stirred for 16-24 h to obtain a B2O3@Si(OH)4 suspension. After centrifugation and washing with water, B2O3@Si(OH)4 powder was obtained. The B2O3@Si(OH)4 powder was calcined at 300℃ for 3-8 h to obtain B2O3@SiO2 powder.

[0053] Preparation of SiB6@Al2O3 core-shell powder:

[0054] Silicon boride was added to deionized water to prepare a first solution of 2-5 g / L. The solution was magnetically stirred for 12-16 h to ensure that the silicon oxide was fully dissolved in the deionized water. An aqueous solution of aluminum nitrate nonahydrate was added to the first solution, along with ammonia or sodium carbonate. The pH of the first solution was adjusted to 7-9. The solution was magnetically stirred for 16-24 h to obtain a SiB6@Al(OH)3 suspension. The suspension was then filtered, dried, and calcined at 300 °C to obtain SiB6@Al2O3 powder.

[0055] Measure out an isopropanol solution and ethanol at a volume ratio of 7 to 10:1, mix the measured isopropanol solution and ethanol to prepare a first mixture, weigh out B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder at a mass ratio of 1:2 to 10, then add the weighed B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder to the first mixture, and stir magnetically for 16 to 24 hours to obtain a suspension A with a concentration of 20 g / L to 40 g / L;

[0056] Step 2: Add I2 to suspension A from step 1 to obtain suspension B;

[0057] Specifically, 0.2–0.3 g of I2 is added to the reaction vessel containing suspension A in step 1. After ultrasonic dispersion for 10–50 min using an ultrasonic disperser, magnetic stirring is performed for 16–24 h to ensure that I2 is fully and uniformly dispersed in suspension A, thus obtaining suspension B.

[0058] Step 3: Place the C / C-SiC sample into the suspension B from step 2 for deposition to obtain the C / C-SiC-B2O3@SiO2 / SiB6@Al2O3 sample;

[0059] Specifically, the C / C sample is embedded in a first powder obtained by mixing silicon powder, carbon powder and yttrium oxide powder in a mass percentage ratio of 70%:20%:10%, and the sum of the mass percentages of silicon powder, carbon powder and yttrium oxide powder is 100%. The mixture is kept at a temperature of 2000-2400℃ under the protection of argon for 2-8 hours to obtain a first-embedded C / C sample.

[0060] The first-embedded C / C sample is then embedded in a second powder obtained by mixing silicon powder, carbon powder and zirconium oxide powder in a mass percentage ratio of 70%:35%:5%, and the sum of the mass percentages of silicon powder, carbon powder and yttrium oxide powder is 100%. The mixture is kept at a temperature of 2000-2400℃ under a protective gas for 2-8 hours to obtain the C / C-SiC sample.

[0061] The C / C-SiC sample was placed in the suspension B from step 2, and then the suspension B was placed in the reactor of a pulsed arc discharge deposition equipment with a deposition temperature of 80℃~120℃ and a deposition voltage of 340~450V. The filling ratio of the reactor was controlled to be 50%~80%. After deposition for 15min~30min, the sample was dried at a temperature of 50℃~70℃ for 2~8h to obtain the C / C-SiC-B2O3@SiO2 / SiB6@Al2O3 sample.

[0062] In the pulsed arc discharge deposition equipment, the anode in the reactor is a 20mm*10mm*3mm graphite substrate, and the cathode is a C / C-SiC sample.

[0063] Step 4: Prepare suspensions C, D, and E;

[0064] SiB6@Al2O3 core-shell powder and B2O3@SiO2 core-shell powder were mixed in different proportions to obtain mixed powder C1 and mixed powder D1; silica sol and water were mixed to obtain a second mixture.

[0065] The mixed powder C1 is added to the second mixture and stirred to obtain suspension C;

[0066] The mixed powder D1 is added to the second mixture and stirred to obtain suspension D;

[0067] Glass powder is added to the second mixture and stirred to obtain suspension E;

[0068] Specifically, a second mixture is prepared by mixing silica sol and water in a volume ratio of 1:2 to 4.

[0069] The B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder prepared in step 1 are mixed to obtain mixed powder C1, wherein the B2O3@SiO2 core-shell powder accounts for 20% to 60% of the total mass of mixed powder C1, and the total mass percentage of B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder is 100%; then mixed powder C1 is added to the second mixture and magnetically stirred for 15 to 20 hours to obtain suspension C;

[0070] The B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder prepared in step 1 are mixed to obtain mixed powder D1, wherein the B2O3@SiO2 core-shell powder accounts for 40% to 80% of the total mass of mixed powder D1, and the total mass percentage of B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder is 100%; then mixed powder D1 is added to the second mixture and magnetically stirred for 15 to 20 hours to obtain suspension D;

[0071] SiO2, Al2O3 and B2O3 are mixed in a mass ratio of 55-75%: 2-10%: 20-40%, and the sum of the mass percentages of SiO2, Al2O3 and B2O3 is 100% to obtain glass powder.

[0072] Glass powder is added to the third mixture and magnetically stirred for 12–18 hours to obtain suspension E;

[0073] Step 5: The C / C-SiC-B2O3@SiO2 / SiB6@Al2O3 sample from Step 3 is sequentially immersed in the suspensions C, D, and E prepared in Step 4 to obtain the Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample.

[0074] Specifically, the C / C-SiC-B2O3@SiO2 / SiB6@Al2O3 sample obtained in step 3 is preheated to 200-300℃ to obtain a preheated specimen;

[0075] The preheated specimen is first immersed in suspension C for 10-20 seconds and then taken out. After ultrasonic cleaning for 10-20 seconds, it is placed in an oven and dried at 60-70℃ for 1-2 minutes. Then it is preheated again and immersed in suspension C again. Then it is ultrasonically cleaned and dried. The above operation is repeated until a first intermediate coating specimen with a thickness of 40-50μm is obtained.

[0076] The intermediate first coating sample is preheated to 200-300℃, immersed in suspension D for 10-20 seconds, then removed, ultrasonically cleaned for 10-20 seconds, and placed in an oven to dry at 60-70℃ for 1-2 minutes. It is then preheated again, immersed in suspension D again, ultrasonically cleaned, and dried. This process is repeated until an intermediate second coating sample with a thickness of 40-50 μm is obtained.

[0077] The intermediate second coating sample is preheated to 200-300℃, immersed in suspension E for 10-20s, then removed, ultrasonically cleaned for 10-20s, and placed in an oven to dry at 60-70℃ for 1-2min. It is then preheated again, immersed in suspension E again, ultrasonically cleaned, and dried. This process is repeated until an intermediate third coating sample with a thickness of 20-40μm is obtained.

[0078] The intermediate third coating sample was placed in a heat treatment reactor, and the temperature was set to 1300℃~1500℃. It was then treated for 2~6 minutes under argon gas to obtain Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample.

[0079] The above preparation method will be further illustrated and explained below with reference to the embodiments;

[0080] Example 1

[0081] Step 1, Preparation of B2O3@SiO2 core-shell powder:

[0082] The third solution was prepared by mixing deionized water and anhydrous ethanol in a volume ratio of 1:2, and the fourth mixture was prepared by mixing tetraethyl orthosilicate and anhydrous ethanol in a volume ratio of 1:7.

[0083] A certain amount of boron oxide was added to the third solution and magnetically stirred for 6 hours to prepare a second solution with a concentration of 5 g / L. Then, 0.03 L of the fourth mixture was slowly added to 0.2 L of the second solution. At the same time, ammonia water was added to the second solution to adjust the pH value of the second solution to 7. The mixture was stirred for 16 hours to obtain a B2O3@Si(OH)4 suspension. After centrifugation and washing with water, B2O3@Si(OH)4 powder was obtained. The B2O3@Si(OH)4 powder was calcined at 300℃ for 3 hours to obtain B2O3@SiO2 powder.

[0084] Preparation of SiB6@Al2O3 core-shell powder:

[0085] 3.2 g of silicon boride was added to deionized water to prepare a first solution with a concentration of 2 g / L. The solution was magnetically stirred for 12 h. Aluminum nitrate nonahydrate and sodium carbonate were added to 0.8 L of the first solution to adjust the pH value to 7. The solution was magnetically stirred for 16 h to obtain a SiB6@Al(OH)3 suspension. The suspension was then filtered, dried, and calcined at 300 °C to obtain SiB6@Al2O3 powder.

[0086] Isopropanol solution and ethanol were measured in a volume ratio of 6:1, with 0.090 L of isopropanol solution and 0.015 L of ethanol. The 0.090 L of isopropanol solution and 0.015 L of ethanol were mixed to prepare a first mixture. B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder were weighed in a mass ratio of 1:10, with 0.3 g of B2O3@SiO2 core-shell powder and 3 g of SiB6@Al2O3 core-shell powder. The weighed 0.3 g of B2O3@SiO2 core-shell powder and 3 g of SiB6@Al2O3 core-shell powder were added to 0.15 L of the first mixture and magnetically stirred for 16 h to obtain a suspension A with a concentration of 22 g / L.

[0087] Step 2: Add 0.2g of I2 to the reaction vessel containing suspension A from step 1, disperse it using an ultrasonic disperser for 10 minutes, and then perform magnetic stirring. After magnetic stirring for 16 hours, suspension B is obtained.

[0088] Step 3: The C / C sample is embedded in a first powder mixture of 70% silicon powder, 20% carbon powder and 10% yttrium oxide powder, and kept at 2000℃ for 2 hours under argon protection to obtain a first-embedded C / C sample.

[0089] The first-embedded C / C sample was then embedded in a second powder mixture of 60% silicon powder, 35% carbon powder and 5% zirconium oxide, and kept at 2000℃ under a protective gas for 2 hours to obtain the C / C-SiC sample.

[0090] The C / C-SiC sample was placed in the suspension B in step 2, and then the suspension B was placed in the reactor of a pulsed arc discharge deposition equipment with a deposition temperature of 80℃ and a deposition voltage of 340V. The filling ratio of the reactor was controlled to be 50%. After deposition for 15 minutes, it was dried at 50℃ for 2 hours to obtain the C / C-SiC-B2O3@SiO2 / SiB6@Al2O3 sample.

[0091] In the pulsed arc discharge deposition equipment, the anode in the reactor is a 20mm*10mm*3mm graphite substrate, and the cathode is a C / C-SiC sample.

[0092] Step 4: Prepare the second mixture by combining silica sol and water;

[0093] The B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder prepared in step 1 were mixed to obtain 4g of mixed powder C1, wherein the B2O3@SiO2 core-shell powder accounted for 20% of the total mass of mixed powder C1, and the total mass percentage of B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder was 100%; then 4g of mixed powder C1 was added to 0.04L of a second mixture, wherein the volume ratio of silica sol to water was 1:2, and the mixture was magnetically stirred for 15h to obtain suspension C;

[0094] The B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder prepared in step 1 were mixed to obtain 4g of mixed powder D1, wherein the B2O3@SiO2 core-shell powder accounted for 40% of the total mass of mixed powder D1, and the total mass percentage of B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder was 100%; then 4g of mixed powder D1 was added to 0.04L of a second mixture, wherein the volume ratio of silica sol to water was 1:2, and the mixture was magnetically stirred for 15h to obtain suspension D;

[0095] SiO2, Al2O3 and B2O3 were mixed in a ratio of 55%:5%:40% to obtain glass powder;

[0096] 4g of glass powder was added to 0.04L of a second mixture, wherein the volume ratio of silica sol to water was 1:2, and the mixture was magnetically stirred for 12h to obtain suspension E.

[0097] Step 5: Preheat the C / C-SiC-B2O3@SiO2 / SiB6@Al2O3 sample obtained in Step 3 to 200℃ to obtain a preheated specimen;

[0098] The preheated specimen was first immersed in suspension C for 20 seconds and then removed. After ultrasonic cleaning for 20 seconds, it was placed in an oven and dried at 60°C for 2 minutes. Then it was preheated again and immersed in suspension C again. Then it was ultrasonically cleaned and dried. The above operation was repeated until a first intermediate coating specimen with a thickness of 50 μm was obtained.

[0099] The intermediate first coating sample was preheated to 200°C, immersed in suspension D for 20 seconds, then removed, ultrasonically cleaned for 20 seconds, and placed in an oven to dry at 60°C for 2 minutes. It was then preheated again, immersed in suspension C again, ultrasonically cleaned, and dried. This process was repeated until the intermediate second coating sample with a thickness of 50 μm was obtained.

[0100] The intermediate second coating sample was preheated to 200°C, immersed in suspension E for 20 seconds, then removed, ultrasonically cleaned for 20 seconds, and placed in an oven to dry at 60°C for 2 minutes. It was then preheated again, immersed in suspension C again, ultrasonically cleaned, and dried. This process was repeated until an intermediate third coating sample with a thickness of 40 μm was obtained.

[0101] The intermediate third coating sample was placed in a heat treatment reactor, and then treated for 6 minutes at a temperature of 1300℃ with argon gas to obtain the Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample.

[0102] Example 2

[0103] Step 1, Preparation of B2O3@SiO2 core-shell powder:

[0104] The third solution was prepared by mixing deionized water and anhydrous ethanol at a volume ratio of 1:2.4, and the fourth mixture was prepared by mixing tetraethyl orthosilicate and anhydrous ethanol at a volume ratio of 1:6.4.

[0105] A certain amount of boron oxide was added to the third solution and magnetically stirred for 6 hours to prepare a second solution with a concentration of 6 g / L. Then, 0.03 L of the fourth mixture was slowly added to 0.2 L of the second solution. At the same time, ammonia water was added to the second solution to adjust the pH value of the second solution to 8. The mixture was stirred for 17 hours to obtain a B2O3@Si(OH)4 suspension. After centrifugation and washing with water, B2O3@Si(OH)4 powder was obtained. The B2O3@Si(OH)4 powder was calcined at 300℃ for 5 hours to obtain B2O3@SiO2 powder.

[0106] Preparation of SiB6@Al2O3 core-shell powder:

[0107] 3.2 g of silicon boride was added to deionized water to prepare a first solution with a concentration of 3 g / L. The solution was magnetically stirred for 14 h. Aluminum nitrate nonahydrate and sodium carbonate were added to 0.8 L of the first solution to adjust the pH value to 8. The solution was magnetically stirred for 19 h to obtain a SiB6@Al(OH)3 suspension. The suspension was then filtered, dried, and calcined at 300 °C to obtain SiB6@Al2O3 powder.

[0108] Isopropanol solution and ethanol were measured in a volume ratio of 7:1, with 0.105 L of isopropanol solution and 0.015 L of ethanol. The 0.105 L of isopropanol solution and 0.015 L of ethanol were mixed to prepare the first mixture. B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder were weighed in a mass ratio of 1:8, with 0.4 g of B2O3@SiO2 core-shell powder. The SiB6@Al2O3 core-shell powder has a composition of 3.2%. g, then the weighed 0.4g B2O3@SiO2 core-shell powder and 3.2g SiB6@Al2O3 core-shell powder were added to 0.15L of the first mixture and magnetically stirred for 20h to obtain a suspension A with a concentration of 24g / L;

[0109] Step 2: Add 0.22g of I2 to the reaction vessel containing suspension A from step 1, disperse using an ultrasonic disperser for 35min, then perform magnetic stirring for 22h to obtain suspension B.

[0110] Step 3: The C / C sample is embedded in a first powder mixture of 70% silicon powder, 20% carbon powder and 10% yttrium oxide powder, and kept at 2200℃ for 6 hours under argon protection to obtain a first-embedded C / C sample.

[0111] The first-embedded C / C sample was then embedded in a second powder mixture of 60% silicon powder, 35% carbon powder and 5% zirconium oxide, and kept at 2200℃ under a protective gas for 6 hours to obtain the C / C-SiC sample.

[0112] The C / C-SiC sample was placed in the suspension B in step 2, and then the suspension B was placed in the reactor of a pulsed arc discharge deposition equipment with a deposition temperature of 90℃ and a deposition voltage of 400V. The filling ratio of the reactor was controlled to be 65%. After deposition for 18 minutes, it was dried at 54℃ for 5 hours to obtain the C / C-SiC-B2O3@SiO2 / SiB6@Al2O3 sample.

[0113] In the pulsed arc discharge deposition equipment, the anode in the reactor is a 20mm*10mm*3mm graphite substrate, and the cathode is a C / C-SiC sample.

[0114] Step 4: Prepare the second mixture by combining silica sol and water;

[0115] The B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder prepared in step 1 were mixed to obtain 4g of mixed powder C1, wherein the B2O3@SiO2 core-shell powder accounted for 30% of the total mass of mixed powder C1, and the total mass percentage of B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder was 100%; then 4g of mixed powder C1 was added to 0.04L of a second mixture, wherein the volume ratio of silica sol to water was 1:2.6, and the mixture was magnetically stirred for 17h to obtain suspension C;

[0116] The B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder prepared in step 1 were mixed to obtain 4g of mixed powder D1, wherein the B2O3@SiO2 core-shell powder accounted for 50% of the total mass of mixed powder D1, and the total mass percentage of B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder was 100%; then 4g of mixed powder D1 was added to 0.04L of a second mixture, wherein the volume ratio of silica sol to water was 1:2.6, and the mixture was magnetically stirred for 17h to obtain suspension D;

[0117] SiO2, Al2O3 and B2O3 were mixed in a ratio of 60%:2%:38% to obtain glass powder;

[0118] 4g of glass powder was added to 0.04L of a second mixture, wherein the volume ratio of silica sol to water was 1:2.6, and the mixture was magnetically stirred for 15h to obtain suspension E.

[0119] Step 5: Preheat the C / C-SiC-B2O3@SiO2 / SiB6@Al2O3 sample obtained in Step 3 to 230℃ to obtain a preheated specimen;

[0120] The preheated specimen was first immersed in suspension C for 19 seconds and then removed. After ultrasonic cleaning for 19 seconds, it was placed in an oven and dried at 62°C for 2 minutes. Then it was preheated again and immersed in suspension C again. Then it was ultrasonically cleaned and dried. The above operation was repeated until a first intermediate coating specimen with a thickness of 48 μm was obtained.

[0121] The intermediate first coating sample was preheated to 230°C, immersed in suspension D for 19 seconds, then removed, ultrasonically cleaned for 19 seconds, and placed in an oven to dry at 62°C for 2 minutes. It was then preheated again, immersed in suspension D again, ultrasonically cleaned, and dried. This process was repeated until the intermediate second coating sample with a thickness of 48 μm was obtained.

[0122] The intermediate second coating sample was preheated to 230°C, immersed in suspension E for 19 seconds, then removed, ultrasonically cleaned for 19 seconds, and placed in an oven to dry at 62°C for 2 minutes. It was then preheated again, immersed in suspension E again, ultrasonically cleaned, and dried. This process was repeated until the intermediate third coating sample with a thickness of 35 μm was obtained.

[0123] The intermediate third coating sample was placed in a heat treatment reactor, and then treated for 2 minutes at a temperature of 1400℃ with argon gas to obtain the Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample.

[0124] Example 3

[0125] Step 1, Preparation of B2O3@SiO2 core-shell powder:

[0126] The third solution was prepared by mixing deionized water and anhydrous ethanol in a volume ratio of 1:3, and the fourth mixture was prepared by mixing tetraethyl orthosilicate and anhydrous ethanol in a volume ratio of 1:5.

[0127] A certain amount of boron oxide was added to the third solution and magnetically stirred for 6 hours to prepare a second solution with a concentration of 6 g / L. Then, 0.03 L of the fourth mixture was slowly added to 0.2 L of the second solution. At the same time, ammonia water was added to the second solution to adjust the pH value of the second solution to 8. The mixture was stirred for 20 hours to obtain a B2O3@Si(OH)4 suspension. After centrifugation and washing with water, B2O3@Si(OH)4 powder was obtained. The B2O3@Si(OH)4 powder was calcined at 300℃ for 5 hours to obtain B2O3@SiO2 powder.

[0128] Preparation of SiB6@Al2O3 core-shell powder:

[0129] 3.2 g of silicon boride was added to deionized water to prepare a first solution with a concentration of 4 g / L. The solution was magnetically stirred for 15 h. Aluminum nitrate nonahydrate and sodium carbonate were added to 0.8 L of the first solution to adjust the pH value to 7.5. The solution was magnetically stirred for 20 h to obtain a SiB6@Al(OH)3 suspension. The suspension was then filtered, dried, and calcined at 300 °C to obtain SiB6@Al2O3 powder.

[0130] Isopropanol solution and ethanol were measured in a volume ratio of 6.5:1, with 0.13 L of isopropanol solution and 0.02 L of ethanol. The 0.13 L of isopropanol solution and 0.02 L of ethanol were mixed to prepare a first mixture. B2O3@SiO2 and SiB6@Al2O3 core-shell powders were weighed in a mass ratio of 1:4, with 0.9 g of B2O3@SiO2 core-shell powder and 3.6 g of SiB6@Al2O3 core-shell powder. The weighed 0.9 g of B2O3@SiO2 core-shell powder and 3.6 g of SiB6@Al2O3 core-shell powder were added to 0.15 L of the first mixture and magnetically stirred for 20 h to obtain a suspension A with a concentration of 30 g / L.

[0131] Step 2: Add 0.25g of I2 to the reaction vessel containing suspension A from step 1, then use an ultrasonic disperser to disperse the suspension for 30 minutes, followed by magnetic stirring for 24 hours to obtain suspension B.

[0132] Step 3: The C / C sample is embedded in a first powder mixture of 70% silicon powder, 20% carbon powder and 10% yttrium oxide powder, and kept at 2100℃ for 8 hours under argon protection to obtain a first-embedded C / C sample.

[0133] The first-embedded C / C sample was then embedded in a second powder mixture of 60% silicon powder, 35% carbon powder and 5% zirconium oxide, and kept at 2100℃ under protective gas for 8 hours to obtain the C / C-SiC sample.

[0134] The C / C-SiC sample was placed in the suspension B in step 2, and then the suspension B was placed in the reactor of a pulsed arc discharge deposition equipment with a deposition temperature of 100℃ and a deposition voltage of 380V. The filling ratio of the reactor was controlled to be 70%. After deposition for 30 minutes, it was dried at 60℃ for 4 hours to obtain the C / C-SiC-B2O3@SiO2 / SiB6@Al2O3 sample.

[0135] In the pulsed arc discharge deposition equipment, the anode in the reactor is a 20mm*10mm*3mm graphite substrate, and the cathode is a C / C-SiC sample.

[0136] Step 4: Prepare the second mixture by combining silica sol and water;

[0137] The B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder prepared in step 1 were mixed to obtain 4g of mixed powder C1, wherein the B2O3@SiO2 core-shell powder accounted for 40% of the total mass of mixed powder C1, and the total mass percentage of B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder was 100%; then 4g of mixed powder C1 was added to 0.04L of a second mixture, wherein the volume ratio of silica sol to water was 1:3, and the mixture was magnetically stirred for 15h to obtain suspension C;

[0138] The B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder prepared in step 1 were mixed to obtain 4g of mixed powder D1, wherein the B2O3@SiO2 core-shell powder accounted for 60% of the total mass of mixed powder D1, and the total mass percentage of B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder was 100%; then 4g of mixed powder D1 was added to 0.04L of a second mixture, wherein the volume ratio of silica sol to water was 1:3, and the mixture was magnetically stirred for 16h to obtain suspension D;

[0139] SiO2, Al2O3 and B2O3 were mixed in a mass ratio of 65%:3%:32% to obtain glass powder;

[0140] 4g of glass powder was added to 0.04L of a second mixture, wherein the volume ratio of silica sol to water was 1:3, and the mixture was magnetically stirred for 16h to obtain suspension E.

[0141] Step 5: Preheat the C / C-SiC-B2O3@SiO2 / SiB6@Al2O3 sample obtained in Step 3 to 260℃ to obtain a preheated specimen;

[0142] The preheated specimen was first immersed in suspension C for 15 seconds and then removed. After ultrasonic cleaning for 15 seconds, it was placed in an oven and dried at 70°C for 1 minute. Then it was preheated again and immersed in suspension C again. Then it was ultrasonically cleaned and dried. The above operation was repeated until a first intermediate coating specimen with a thickness of 45 μm was obtained.

[0143] The intermediate first coating sample was preheated to 260°C, immersed in suspension D for 15 seconds, then removed, ultrasonically cleaned for 15 seconds, and placed in an oven to dry at 70°C for 1 minute. It was then preheated again, immersed in suspension D again, ultrasonically cleaned, and dried. This process was repeated until the intermediate second coating sample with a thickness of 45 μm was obtained.

[0144] The intermediate second coating sample was preheated to 260°C, immersed in suspension E for 15 seconds, then removed, ultrasonically cleaned for 15 seconds, and placed in an oven to dry at 60°C for 2 minutes. It was then preheated again, immersed in suspension E again, ultrasonically cleaned, and dried. This process was repeated until the intermediate third coating sample with a thickness of 30 μm was obtained.

[0145] The intermediate third coating sample was placed in a heat treatment reactor, and then treated at a temperature of 1500℃ for 6 minutes under argon gas to obtain the Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample.

[0146] Example 4

[0147] Step 1, Preparation of B2O3@SiO2 core-shell powder:

[0148] The third solution was prepared by mixing deionized water and anhydrous ethanol at a volume ratio of 1:3.4, and the fourth mixture was prepared by mixing tetraethyl orthosilicate and anhydrous ethanol at a volume ratio of 1:5.5.

[0149] A certain amount of boron oxide was added to the third solution and magnetically stirred for 6 hours to prepare a second solution with a concentration of 8 g / L. Then, 0.03 L of the fourth mixture was slowly added to 0.2 L of the second solution. At the same time, ammonia water was added to the second solution to adjust the pH value of the second solution to 7. The mixture was stirred for 24 hours to obtain a B2O3@Si(OH)4 suspension. After centrifugation and washing with water, B2O3@Si(OH)4 powder was obtained. The B2O3@Si(OH)4 powder was calcined at 300℃ for 6 hours to obtain B2O3@SiO2 powder.

[0150] Preparation of SiB6@Al2O3 core-shell powder:

[0151] 3.2 g of silicon boride was added to deionized water to prepare a first solution with a concentration of 4 g / L. The solution was magnetically stirred for 16 h. Aluminum nitrate nonahydrate and sodium carbonate were added to 0.8 L of the first solution to adjust the pH value to 8.5. The solution was magnetically stirred for 24 h to obtain a SiB6@Al(OH)3 suspension. The suspension was then filtered, dried, and calcined at 300 °C to obtain SiB6@Al2O3 powder.

[0152] Isopropanol solution and ethanol were measured in a volume ratio of 8.5:1, with 0.129 L of isopropanol solution and 0.016 L of ethanol. The measured 0.129 L of isopropanol solution and 0.016 L of ethanol were mixed to prepare a first mixture. B2O3@SiO2 and SiB6@Al2O3 core-shell powders were weighed in a mass ratio of 1:10, with 0.3 g of B2O3@SiO2 core-shell powder and 3 g of SiB6@Al2O3 core-shell powder. The weighed 0.3 g of B2O3@SiO2 core-shell powder and 3 g of SiB6@Al2O3 core-shell powder were added to the first mixture and magnetically stirred for 24 h to obtain a suspension A with a concentration of 22 g / L.

[0153] Step 2: Add 0.25g of I2 to the reaction vessel containing suspension A from step 1. After stopping the addition of I2, use an ultrasonic disperser to disperse the suspension for 45 minutes, then perform magnetic stirring for 20 hours to obtain suspension B.

[0154] Step 3: The C / C sample is embedded in a first powder mixture of 70% silicon powder, 20% carbon powder and 10% yttrium oxide powder, and kept at 2300℃ for 7 hours under argon protection to obtain a first-embedded C / C sample.

[0155] The first-embedded C / C sample was then embedded in a second powder mixture of 60% silicon powder, 35% carbon powder and 5% zirconium oxide, and kept at 2300℃ under protective gas for 7 hours to obtain the C / C-SiC sample.

[0156] The C / C-SiC sample was placed in the suspension B in step 2, and then the suspension B was placed in the reactor of a pulsed arc discharge deposition equipment with a deposition temperature of 110℃ and a deposition voltage of 430V. The filling ratio of the reactor was controlled to be 75%. After deposition for 28 minutes, it was dried at 65℃ for 7 hours to obtain the C / C-SiC-B2O3@SiO2 / SiB6@Al2O3 sample.

[0157] In the pulsed arc discharge deposition equipment, the anode in the reactor is a 20mm*10mm*3mm graphite substrate, and the cathode is a C / C-SiC sample.

[0158] Step 4: Prepare the second mixture by combining silica sol and water;

[0159] The B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder prepared in step 1 were mixed to obtain 4g of mixed powder C1, wherein the B2O3@SiO2 core-shell powder accounted for 55% of the total mass of mixed powder C1, and the total mass percentage of B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder was 100%; then 4g of mixed powder C1 was added to 0.04L of a second mixture, wherein the volume ratio of silica sol to water was 1:3.4, and the mixture was magnetically stirred for 15h to obtain suspension C;

[0160] The B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder prepared in step 1 were mixed to obtain 4g of mixed powder D1, wherein the B2O3@SiO2 core-shell powder accounted for 75% of the total mass of mixed powder D1, and the total mass percentage of B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder was 100%; then 4g of mixed powder D1 was added to 0.04L of a second mixture, wherein the volume ratio of silica sol to water was 1:3.4, and the mixture was magnetically stirred for 18h to obtain suspension D;

[0161] SiO2, Al2O3 and B2O3 were mixed in a mass ratio of 70%:10%:20% to obtain glass powder;

[0162] 4g of glass powder was added to 0.04L of a second mixture, wherein the volume ratio of silica sol to water was 1:3.4, and the mixture was magnetically stirred for 16h to obtain suspension E.

[0163] Step 5: Preheat the C / C-SiC-B2O3@SiO2 / SiB6@Al2O3 sample obtained in Step 3 to 280℃ to obtain a preheated specimen;

[0164] The preheated specimen was first immersed in suspension C for 14 seconds and then removed. After ultrasonic cleaning for 14 seconds, it was placed in an oven and dried at 64°C for 1 minute. Then it was preheated again and immersed in suspension C again. Then it was ultrasonically cleaned and dried. The above operation was repeated until a first intermediate coating specimen with a thickness of 43 μm was obtained.

[0165] The intermediate first coating sample was preheated to 280°C, immersed in suspension D for 14 seconds, then removed, ultrasonically cleaned for 14 seconds, and placed in an oven to dry at 64°C for 2 minutes. It was then preheated again, immersed in suspension D again, ultrasonically cleaned, and dried. This process was repeated until the intermediate second coating sample with a thickness of 43 μm was obtained.

[0166] The intermediate second coating sample was preheated to 280°C, immersed in suspension E for 15 seconds, then removed, ultrasonically cleaned for 15 seconds, and placed in an oven to dry at 60°C for 2 minutes. It was then preheated again, immersed in suspension E again, ultrasonically cleaned, and dried. This process was repeated until the intermediate third coating sample with a thickness of 25 μm was obtained.

[0167] The intermediate third coating sample was placed in a heat treatment reactor, and then treated for 6 minutes at a temperature of 1300℃ with argon gas to obtain the Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample.

[0168] Example 5

[0169] Step 1, Preparation of B2O3@SiO2 core-shell powder:

[0170] The third solution was prepared by mixing deionized water and anhydrous ethanol in a volume ratio of 1:4, and the fourth mixture was prepared by mixing tetraethyl orthosilicate and anhydrous ethanol in a volume ratio of 1:6.

[0171] A certain amount of boron oxide was added to the third solution and magnetically stirred for 6 hours to prepare a second solution with a concentration of 10 g / L. Then, 0.03 L of the fourth mixture was slowly added to 0.2 L of the second solution. At the same time, ammonia water was added to the second solution to adjust the pH value of the second solution to 7. The mixture was stirred for 24 hours to obtain a B2O3@Si(OH)4 suspension. After centrifugation and washing with water, B2O3@Si(OH)4 powder was obtained. The B2O3@Si(OH)4 powder was calcined at 300℃ for 8 hours to obtain B2O3@SiO2 powder.

[0172] Preparation of SiB6@Al2O3 core-shell powder:

[0173] 3.2 g of silicon boride was added to deionized water to prepare a first solution of 5 g / L. The solution was magnetically stirred for 15 h. Aluminum nitrate nonahydrate and sodium carbonate were added to 0.8 L of the first solution to adjust the pH value of the first solution to 7.5. The solution was magnetically stirred for 24 h to obtain a SiB6@Al(OH)3 suspension. The suspension was then filtered, dried, and calcined at 300 °C to obtain SiB6@Al2O3 powder.

[0174] Isopropanol solution and ethanol were measured in a volume ratio of 10:1, with 0.170 L of isopropanol solution and 0.017 L of ethanol. The measured 0.170 L of isopropanol solution and 0.017 L of ethanol were mixed to prepare a first mixture. B2O3@SiO2 and SiB6@Al2O3 core-shell powders were weighed in a mass ratio of 3:7, with 0.9 g of B2O3@SiO2 core-shell powder and 2.1 g of SiB6@Al2O3 core-shell powder. The weighed 0.9 g of B2O3@SiO2 core-shell powder and 2.1 g of SiB6@Al2O3 core-shell powder were added to the first mixture and magnetically stirred for 24 h to obtain a suspension A with a concentration of 40 g / L.

[0175] Step 2: Add 0.3g of I2 to the reaction vessel containing suspension A from step 1. After stopping the addition of I2, use an ultrasonic disperser to disperse the suspension for 50 minutes, then perform magnetic stirring for 16 hours to obtain suspension B.

[0176] Step 3: The C / C sample is embedded in a first powder mixture of 70% silicon powder, 20% carbon powder and 10% yttrium oxide powder, and kept at 2400℃ for 8 hours under argon protection to obtain a first-embedded C / C sample.

[0177] The first-embedded C / C sample was then embedded in a second powder mixture of 60% silicon powder, 35% carbon powder and 5% zirconium oxide, and kept at 2400℃ under a protective gas for 8 hours to obtain the C / C-SiC sample.

[0178] The C / C-SiC sample was placed in the suspension B in step 2, and then the suspension B was placed in the reactor of a pulsed arc discharge deposition equipment with a deposition temperature of 120℃ and a deposition voltage of 450V. The filling ratio of the reactor was controlled to be 80%. After deposition for 30 minutes, it was dried at 70℃ for 8 hours to obtain the C / C-SiC-B2O3@SiO2 / SiB6@Al2O3 sample.

[0179] In the pulsed arc discharge deposition equipment, the anode in the reactor is a 20mm*10mm*3mm graphite substrate, and the cathode is a C / C-SiC sample.

[0180] Step 4: Prepare the second mixture by combining silica sol and water;

[0181] The B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder prepared in step 1 were mixed to obtain 4g of mixed powder C1, wherein the B2O3@SiO2 core-shell powder accounted for 60% of the total mass of mixed powder C1, and the total mass percentage of B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder was 100%; then 4g of mixed powder C1 was added to 0.04L of a second mixture, wherein the volume ratio of silica sol to water was 1:4, and the mixture was magnetically stirred for 20h to obtain suspension C;

[0182] The B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder prepared in step 1 were mixed to obtain 4g of mixed powder D1, wherein the B2O3@SiO2 core-shell powder accounted for 80% of the total mass of mixed powder D1, and the total mass percentage of B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder was 100%; then 4g of mixed powder D1 was added to 0.04L of a second mixture, wherein the volume ratio of silica sol to water was 1:4, and the mixture was magnetically stirred for 20h to obtain suspension D;

[0183] SiO2, Al2O3 and B2O3 were mixed in a mass ratio of 75%:2%:23% to obtain glass powder;

[0184] 4g of glass powder was added to 0.04L of a second mixture, wherein the volume ratio of silica sol to water was 1:4, and the mixture was magnetically stirred for 18h to obtain suspension E.

[0185] Step 5: Preheat the C / C-SiC-B2O3@SiO2 / SiB6@Al2O3 sample obtained in Step 3 to 300℃ to obtain a preheated specimen;

[0186] The preheated specimen was first immersed in suspension C for 10 seconds and then removed. After ultrasonic cleaning for 10 seconds, it was placed in an oven and dried at 70°C for 1 minute. Then it was preheated again and immersed in suspension C again. Then it was ultrasonically cleaned and dried. The above operation was repeated until a first intermediate coating specimen with a thickness of 50 μm was obtained.

[0187] The intermediate first coating sample was preheated to 300°C, immersed in suspension D for 10 seconds, then removed, ultrasonically cleaned for 10 seconds, and placed in an oven to dry at 70°C for 1 minute. It was then preheated again, immersed in suspension D again, ultrasonically cleaned, and dried. This process was repeated until the intermediate second coating sample with a thickness of 40 μm was obtained.

[0188] The intermediate second coating sample was preheated to 300°C, immersed in suspension E for 10 seconds, then removed, ultrasonically cleaned for 10 seconds, and placed in an oven to dry at 70°C for 2 minutes. It was then preheated again, immersed in suspension E again, ultrasonically cleaned, and dried. This process was repeated until an intermediate third coating sample with a thickness of 40 μm was obtained.

[0189] The intermediate third coating sample was placed in a heat treatment reactor, and then treated at a temperature of 1500℃ for 6 minutes under argon gas to obtain the Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample.

[0190] See Figure 1 By testing the Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample prepared in Example 3 above, SEM images of the surface morphology of the Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample were obtained. It can be seen from the images that the particles on the coating surface are densely packed, with a particle size of 10 μm. The particles are sintered together and are very uniform, resulting in good overall density of the coating. This reduces the diffusion channels of oxygen during the thermal shock resistance process, enabling the prepared coating to have better thermal shock resistance performance.

[0191] See Figure 2 The Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample prepared in Example 3 was tested, and the surface XRD pattern of the Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample was obtained. It can be seen from the pattern that the peaks of each substance in the Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample prepared by this method are very narrow. The peak heights of SiO2, B2O3 and Al2O3 generally tend to be consistent and the difference in peak height is small. Therefore, the prepared coating material has high crystallinity, the crystal arrangement is relatively complete, the crystal quality is good, and the prepared coating has better thermal shock resistance.

[0192] Thermal shock resistance tests were conducted on the Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating samples prepared in Example 3. The Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating samples were placed in a silicon carbide rod high-temperature furnace, and the furnace temperature was adjusted to 1200℃. The resulting spectral data are shown below. Figure 3As shown in the figure, the curves represent the isothermal oxidation resistance curves of the coating material in air at 1473K. The figure reveals that the mass loss rate of the Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample gradually decreases from 0 to 130 cycles, reaching its maximum value of 0.45% at 150 cycles. Between 150 and 250 cycles, the mass loss rate is negative, indicating that the Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample is self-repairing. After self-repair, the mass of the coating material is lower than that at 0 cycles. Therefore, after 250 cycles, the mass loss of the Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample is only -0.40%, demonstrating strong wear resistance, self-repair capabilities, and high toughness.

[0193] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the scope of the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0194] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing a C / C composite surface Glass-B2O3@SiO2 / SiB6@Al2O3-SiC oxidation-resistant gradient coating, characterized in that, The method comprises the following steps: Step 1, B2O3@SiO2 core-shell powder and SiB6@Al2O3 core-shell powder are added into a first mixed solution obtained by mixing an isopropanol solution and ethanol to obtain a suspension A; wherein the mass ratio of B2O3@SiO2 and SiB6@Al2O3 core-shell powder is 1:2-10; Step 2, I2 is added into the suspension A in step 1 to obtain a suspension B; Step 3, the C / C-SiC sample is placed into the suspension B in step 2 for pulse arc discharge deposition to obtain a C / C-SiC-B2O3@SiO2 / SiB6@Al2O3 sample; Step 4, a suspension C, a suspension D and a suspension E are prepared; The SiB6@Al2O3 core-shell powder and the B2O3@SiO2 core-shell powder are mixed in different proportions to obtain mixed powder C1 and mixed powder D1; a second mixed solution is prepared by configuring a silica sol and water; wherein the mass percentage of SiB6@Al2O3 core-shell powder in the mixed powder C1 is 60%, the mass percentage of SiB6@Al2O3 core-shell powder in the mixed powder D1 is 40%, and the mass percentage sum of SiB6@Al2O3 core-shell powder and B2O3@SiO2 core-shell powder in the mixed powder C1 and the mixed powder D1 is 100%; The mixed powder C1 is added into the second mixed solution to obtain the suspension C by stirring; The mixed powder D1 is added into the second mixed solution to obtain the suspension D by stirring; Glass powder is added into the second mixed solution to obtain the suspension E by stirring; wherein the glass powder is obtained by mixing SiO2, Al2O3 and B2O3 in a mass percentage ratio of 55-78%:2-5%:20-40%, and the mass percentage sum of SiO2, Al2O3 and B2O3 is 100%; Step 5, the C / C-SiC-B2O3@SiO2 / SiB6@Al2O3 sample in step 3 is sequentially immersed in the suspensions C, D and E prepared in step 4 to obtain a Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample.

2. The preparation method of the C / C composite surface Glass-B2O3@SiO2 / SiB6@Al2O3-SiC oxidation-resistant gradient coating according to claim 1, characterized in that, The volume ratio of the isopropanol solution to ethanol is 6-10:

1.

3. The method for preparing a C / C composite surface Glass-B2O3@SiO2 / SiB6@Al2O3-SiC oxidation-resistant gradient coating according to claim 1, characterized in that, The concentration of the suspension A in step 1 is 20-40 g / L.

4. The method for preparing a C / C composite surface Glass-B2O3@SiO2 / SiB6@Al2O3-SiC oxidation-resistant gradient coating according to claim 1, characterized in that, In the suspension B of step 2, the mass of I2 is 0.2-0.3 g.

5. The method for preparing a C / C composite surface Glass-B2O3@SiO2 / SiB6@Al2O3-SiC oxidation-resistant gradient coating according to claim 1, characterized in that, In step 3, the C / C-SiC sample is placed into the suspension B in step 2 for deposition, which comprises: The C / C-SiC sample is placed into the suspension B, and then the suspension B is placed into a reaction kettle with a deposition temperature of 80-120 ℃ and a deposition voltage of 340-450 V, the filling ratio of the reaction kettle is controlled to be 50-80%, and the C / C-SiC-B2O3@SiO2 / SiB6@Al2O3 sample is obtained after deposition for 15-30 min and drying at a temperature of 50-70 ℃ for 2-8 h.

6. The method for preparing a C / C composite surface Glass-B2O3@SiO2 / SiB6@Al2O3-SiC oxidation-resistant gradient coating according to claim 1, characterized in that, The Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample prepared in step 5 comprises: The C / C-SiC-B2O3@SiO2 / SiB6@Al2O3 sample obtained in step 3 is preheated to 200-300 DEG C to obtain a preheated sample; The preheated sample is first immersed in the suspension C for 10-20 s, then taken out, ultrasonically cleaned for 10-20 s, and then placed in an oven and dried at a temperature of 60-70 DEG C for 1-2 min to obtain an intermediate first coating sample; The intermediate first coating sample is immersed in the suspension D for 10-20 s, then taken out, ultrasonically cleaned for 10-20 s, and then placed in an oven and dried at a temperature of 60-70 DEG C for 1-2 min to obtain an intermediate second coating sample; The intermediate second coating sample is immersed in the suspension E for 10-20 s, then taken out, ultrasonically cleaned for 10-20 s, and then placed in an oven and dried at a temperature of 60-70 DEG C for 1-2 min to obtain an intermediate third coating sample; The intermediate third coating sample is heat treated to obtain the Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample.

7. The method for preparing a C / C composite surface Glass-B2O3@SiO2 / SiB6@Al2O3-SiC oxidation-resistant gradient coating according to claim 6, characterized in that, The intermediate third coating sample is heat treated to obtain the Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample, which comprises: placing the intermediate third coating sample in a heat treatment reactor, setting the temperature to 1300 DEG C-1500 DEG C, and introducing argon gas to treat for 2-6 min to obtain the Glass-B2O3@SiO2 / SiB6@Al2O3-SiC coating sample.

8. A C / C composite material surface Glass-B2O3@SiO2 / SiB6@Al2O3-SiC oxidation-resistant gradient coating prepared by the method of any one of claims 1-7.

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