Silicon carbide ceramic and preparation method and application thereof

Abstract

The present application relates to a kind of silicon carbide ceramics and its preparation method and application, the preparation method of the silicon carbide ceramics includes the following steps: (1) uniformly mix silicon carbide particles, sintering aid and binder, the obtained mud is formed, to obtain silicon carbide green body;(2) using silicon carbide slurry the silicon carbide green body obtained in step (1) is coated, then sintering, to obtain the silicon carbide ceramics;Step (2) the silicon carbide slurry is two different average particle size silicon carbide particles and solvent after mixing to obtain.This application can effectively inhibit the volatilization of sintering aid in the sintering process by coating silicon carbide coating on the surface of silicon carbide green body, significantly improve the density, strength and surface purity of silicon carbide ceramics, can meet the requirements as high-precision industry material.

Description

Technical Field

[0001] This invention relates to the field of ceramic material preparation technology, specifically to a silicon carbide ceramic and its preparation method and application. Background Technology

[0002] Silicon carbide ceramics are a typical covalently bonded compound with many excellent properties, such as high temperature strength, corrosion resistance, high hardness, excellent thermal conductivity, and low coefficient of thermal expansion. Therefore, silicon carbide ceramics are widely used in aerospace, defense, nuclear industry, semiconductor, petroleum, metallurgy, chemical industry, machinery and other fields, including high temperature long life kiln furniture, heat exchangers, microchannel reactors, semiconductor hardware, high power devices and ceramic membranes.

[0003] Currently, the main methods for preparing silicon carbide ceramics include hot isostatic pressing (HIP) and pressureless sintering. For example, CN108314455A discloses a silicon carbide ceramic, its preparation method, and its applications. The preparation method includes the following steps: mixing silicon carbide powder with a sintering aid to obtain a mixed powder, wherein the median particle size of the silicon carbide powder is 0.5-2.0 micrometers, and the mass ratio of silicon carbide powder to the sintering aid is 100:0.5-100:5. The sintering aid, by mass percentage, includes: 10-20% alumina, 10-20% carbon powder, 10-20% boron carbide, 10-20% mullite, 20-40% silicon nitride, and 20-40% zirconium oxide; and then, under a pressure of 30-200 MPa, subjecting the mixed powder to hot isostatic pressing sintering to obtain silicon carbide ceramic. However, due to the addition of additives, the purity of this silicon carbide ceramic still needs to be further improved.

[0004] Traditional pressureless sintering methods for manufacturing silicon carbide ceramic devices typically involve mixing silicon carbide powder, sintering aids, and dispersants in a specific ratio and forming a green body. Then, at a sufficiently high sintering temperature, the sintering aids melt to form a liquid phase. As the liquid phase flows, driven by capillary forces, the sliding particles rearrange themselves, significantly increasing density and resulting in high-strength silicon carbide ceramic products. However, in existing pressureless sintering processes, sintering aids are prone to volatilization at high temperatures, leading to increased porosity and decreased density in the product. This also reduces strength and increases the likelihood of crack formation. Furthermore, the addition of sintering aids lowers product purity, making it difficult to meet the requirements for high-precision applications.

[0005] CN 107188595A discloses a high-density silicon carbide ceramic and its pressureless sintering method. The pressureless sintering method includes: mixing silicon carbide, epoxy resin, bentonite, diatomaceous earth, boron carbide, glass fiber, carbon black, petroleum coke, and anhydrous ethanol, followed by ball milling to obtain a slurry M; drying, granulating, and aging the slurry M to obtain powder N; mixing powder N with sintering aids, followed by pressure molding and sintering to obtain the high-density silicon carbide ceramic. However, the silicon carbide ceramic prepared by this pressureless sintering method still suffers from problems such as the volatilization of sintering aids, which reduces density, and the purity failing to meet requirements.

[0006] Therefore, in order to address the shortcomings of existing technologies, there is a need to provide a method for preparing silicon carbide ceramics with high density, high purity and excellent mechanical properties. Summary of the Invention

[0007] The purpose of this invention is to provide a silicon carbide ceramic, its preparation method and application. By coating the silicon carbide blank with a silicon carbide coating, the problems of low density and low purity of pressureless sintered silicon carbide ceramic products are solved.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a method for preparing silicon carbide ceramics, the method comprising the following steps:

[0010] (1) The silicon carbide particles, sintering aid and binder are uniformly mixed and the resulting mud is shaped to obtain silicon carbide blanks.

[0011] (2) The silicon carbide blank obtained in step (1) is coated with silicon carbide slurry and then sintered to obtain the silicon carbide ceramic.

[0012] The silicon carbide slurry in step (2) is obtained by mixing two types of silicon carbide particles with different average particle sizes with a solvent.

[0013] The method for preparing silicon carbide ceramics provided by this invention involves coating the surface of the prepared silicon carbide blank with a silicon carbide coating. This coating effectively suppresses the volatilization of internal sintering aids during subsequent sintering, significantly improving the density and strength of the silicon carbide ceramics, while also increasing the purity of the silicon carbide ceramic surface. The service temperature and corrosion resistance of the finished silicon carbide ceramics prepared by this method are also greatly improved.

[0014] Preferably, the average particle size of silicon carbide in step (1) is 1-200 μm, for example, it can be 1 μm, 50 μm, 100 μm, 150 μm or 200 μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0015] Preferably, based on a total weight of 100 parts, the mud material in step (1) contains 60-77 parts of silicon carbide, 3-10 parts of sintering aid, and 20-30 parts of binder.

[0016] The weight percentage of silicon carbide in the mud is 60-77 parts, for example, 60 parts, 65 parts, 70 parts, 73 parts or 77 parts, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0017] The sintering aid in the clay material is 3-10 parts by weight, for example, 3 parts, 5 parts, 7 parts, 8 parts or 10 parts, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] The binder in the mud is 20-30 parts by weight, for example, 20 parts, 22 parts, 25 parts, 28 parts or 30 parts, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] Preferably, the sintering aid comprises alumina powder and yttrium oxide powder in a mass ratio of 3:(1.5-2.5), for example, 3:1.5, 3:1.8, 3:2, 3:2.2 or 3:2.5, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] Preferably, the adhesive comprises any one or a combination of at least two of ethylene glycol, polyvinyl alcohol, ammonium polyacrylate, cellulose, polyvinylpyrrolidone, glucose, or glycerol. Typical but non-limiting combinations include combinations of ethylene glycol and polyvinyl alcohol, combinations of ammonium polyacrylate, cellulose, polyvinylpyrrolidone, and glucose, or combinations of ethylene glycol, polyvinyl alcohol, ammonium polyacrylate, cellulose, polyvinylpyrrolidone, glucose, and glycerol.

[0021] Preferably, the molding process in step (1) includes extrusion molding or injection molding.

[0022] Preferably, step (1) further includes a drying step after molding.

[0023] Preferably, the drying temperature is ≤60℃, for example, it can be 60℃, 55℃, 50℃, 45℃ or 40℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0024] Before drying, the silicon carbide blank is placed in a slowly heated oven and then dried at the target temperature.

[0025] Preferably, the two types of silicon carbide particles with different average particle sizes include silicon carbide particles with an average particle size of 0.01-1 μm and silicon carbide particles with an average particle size of 10-100 μm.

[0026] In this invention, two types of silicon carbide particles with different average particle sizes are selected to make a slurry for coating silicon carbide blanks. The silicon carbide particles with different average particle sizes can form a dense silicon carbide film on the surface of the silicon carbide blanks, which inhibits the volatilization of the sintering aids inside during the sintering process.

[0027] The average particle size of the silicon carbide particles is 0.01-1 μm, for example, it can be 0.01 μm, 0.05 μm, 0.1 μm, 0.5 μm or 1 μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] The average particle size of the silicon carbide particles is 10-100 μm, for example, it can be 10 μm, 30 μm, 50 μm, 80 μm or 100 μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] Preferably, based on a total weight of 100 parts, the silicon carbide particles with an average particle size of 0.01-1 μm account for 45-55 parts, and the silicon carbide particles with an average particle size of 10-100 μm account for 45-55 parts.

[0030] The silicon carbide particles with an average particle size of 0.01-1μm are 45-55 parts, for example, 45 parts, 48 ​​parts, 50 parts, 52 parts or 55 parts, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] The silicon carbide particles with an average particle size of 10-100 μm are 45-55 parts, for example, 45 parts, 48 ​​parts, 50 parts, 52 parts or 55 parts, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] Preferably, based on a total weight of 100 parts, the silicon carbide slurry in step (2) contains 75-85 parts silicon carbide particles and 15-25 parts solvent.

[0033] In the silicon carbide slurry, the weight of silicon carbide particles is 75-85 parts, for example, 75 parts, 78 parts, 80 parts, 82 parts or 85 parts, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0034] In the silicon carbide slurry, the solvent is in the range of 15-25 parts by weight, for example, 15 parts, 18 parts, 20 parts, 22 parts or 25 parts, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] Preferably, the solvent includes water.

[0036] Preferably, step (2) further includes a step of vacuum degassing the silicon carbide slurry before the coating process.

[0037] The vacuum degassing process can remove air bubbles from the silicon carbide slurry, preventing the subsequent silicon carbide coating from containing pores, which would affect the density of the silicon carbide ceramic.

[0038] Preferably, the vacuum degree of the vacuum exhaust process is 0.001-0.01 Pa, for example, it can be 0.001 Pa, 0.003 Pa, 0.005 Pa, 0.008 Pa or 0.01 Pa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] Preferably, the coating method in step (2) includes soaking or spraying.

[0040] Preferably, the thickness of the silicon carbide coating obtained after coating in step (2) is 100-2000μm, for example, it can be 100μm, 300μm, 800μm, 1000μm, 1500μm or 2000μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] Preferably, step (2) includes a drying step after coating and before sintering.

[0042] Preferably, the drying temperature is ≤50℃, for example, it can be 50℃, 45℃, 40℃, 35℃ or 30℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0043] Preferably, the sintering temperature in step (2) is 2100-2300℃, for example, it can be 2100℃, 2150℃, 2200℃, 2250℃ or 2300℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0044] Preferably, the sintering in step (2) is carried out in a vacuum graphite furnace.

[0045] After sintering, the silicon carbide coating on the surface of the silicon carbide ceramic can effectively suppress the volatilization of the internal sintering aids, and the resulting silicon carbide ceramic has high surface purity.

[0046] As a preferred embodiment of the preparation method described in this invention, the preparation method includes the following steps:

[0047] (1) Silicon carbide particles with an average particle size of 1-200 μm, sintering aids and binders are uniformly mixed, and the resulting mud is extruded or injection molded and then dried at ≤60℃ to obtain a silicon carbide green body; based on a total weight of 100 parts, the mud contains 60-77 parts of silicon carbide, 3-10 parts of sintering aids and 20-30 parts of binders; the sintering aids include alumina powder and yttrium oxide powder in a mass ratio of 3:(1.5-2.5);

[0048] (2) The silicon carbide blank obtained in step (1) is coated with silicon carbide slurry to obtain a silicon carbide coating with a thickness of 100-2000μm. Then, it is dried at ≤50℃ and sintered in a vacuum graphite furnace at 2100-2300℃ to obtain the silicon carbide ceramic.

[0049] The silicon carbide slurry is obtained by mixing two types of silicon carbide particles with different average particle sizes and a solvent. Based on a total weight of 100 parts, the silicon carbide slurry contains 75-85 parts silicon carbide particles and 15-25 parts solvent. The two types of silicon carbide particles with different average particle sizes include silicon carbide particles with an average particle size of 0.01-1 μm and silicon carbide particles with an average particle size of 10-100 μm. Based on a total weight of 100 parts, the silicon carbide particles with an average particle size of 0.01-1 μm contain 45-55 parts, and the silicon carbide particles with an average particle size of 10-100 μm contain 45-55 parts. Before coating, the process further includes a step of vacuum degassing the silicon carbide slurry under a vacuum of 0.001-0.01 Pa.

[0050] In a second aspect, the present invention provides a silicon carbide ceramic, which is prepared by the preparation method described in the first aspect.

[0051] The silicon carbide ceramic provided by this invention has a density of up to 98.9%, a surface purity of 98.5-99.8%, excellent mechanical properties, and a bending strength of 395 MPa, which can meet the requirements of high-precision industry materials.

[0052] Thirdly, the present invention provides an application of silicon carbide ceramic as described in the second aspect, wherein the silicon carbide ceramic is used in the fabrication of semiconductor or photovoltaic devices.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] The method for preparing silicon carbide ceramics provided by this invention involves coating the surface of the prepared silicon carbide blank with a silicon carbide coating. This coating effectively suppresses the volatilization of internal sintering aids during subsequent sintering, significantly improving the density and strength of the silicon carbide ceramic. The density can reach 98.9%, and the flexural strength can reach 395 MPa. At the same time, it can also improve the purity of the silicon carbide ceramic surface, with a surface purity of 98.5-99.8%. The silicon carbide ceramic product prepared by this method also has significantly improved service temperature and corrosion resistance, meeting the requirements for high-precision industrial materials. Detailed Implementation

[0055] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0056] Example 1

[0057] This embodiment provides a silicon carbide ceramic, the preparation method of which includes the following steps:

[0058] (1) Silicon carbide particles with an average particle size of 100 μm, sintering aid and ethylene glycol are uniformly mixed, and the resulting mud is extruded and then dried at 50°C to obtain a silicon carbide blank; based on a total weight of 100 parts, the mud contains 70 parts of silicon carbide, 5 parts of sintering aid and 25 parts of ethylene glycol; the sintering aid includes alumina powder and yttrium oxide powder in a mass ratio of 3:2;

[0059] (2) The silicon carbide blank obtained in step (1) is soaked in silicon carbide slurry to obtain a silicon carbide coating with a thickness of 1000 μm. Then, it is dried at 40°C and sintered in a vacuum graphite furnace at 2200°C to obtain the silicon carbide ceramic.

[0060] The silicon carbide slurry is obtained by mixing two types of silicon carbide particles with water of different average particle sizes. Based on a total weight of 100 parts, the silicon carbide slurry contains 80 parts silicon carbide particles and 20 parts water. Based on a total weight of 100 parts, the silicon carbide particles of different average particle sizes consist of 50 parts silicon carbide particles with an average particle size of 0.1 μm and 50 parts silicon carbide particles with an average particle size of 30 μm. Prior to soaking, the process includes a step of vacuum degassing the silicon carbide slurry under a vacuum of 0.005 Pa.

[0061] Example 2

[0062] This embodiment provides a silicon carbide ceramic, the preparation method of which includes the following steps:

[0063] (1) Silicon carbide particles with an average particle size of 1 μm, sintering aid and polyvinyl alcohol are uniformly mixed, and the resulting mud is extruded and then dried at 40°C to obtain a silicon carbide blank; based on a total weight of 100 parts, the mud contains 60 parts of silicon carbide, 10 parts of sintering aid and 30 parts of polyvinyl alcohol; the sintering aid includes alumina powder and yttrium oxide powder in a mass ratio of 3:1.5;

[0064] (2) Spray the silicon carbide blank obtained in step (1) with silicon carbide slurry to obtain a silicon carbide coating with a thickness of 100 μm, and then dry it at 30°C and sinter it in a vacuum graphite furnace at 2100°C to obtain the silicon carbide ceramic.

[0065] The silicon carbide slurry is obtained by mixing two types of silicon carbide particles with water of different average particle sizes. Based on a total weight of 100 parts, the silicon carbide slurry contains 75 parts silicon carbide particles and 25 parts water. Based on a total weight of 100 parts, the silicon carbide particles of the two different average particle sizes consist of 55 parts silicon carbide particles with an average particle size of 0.01 μm and 45 parts silicon carbide particles with an average particle size of 10 μm. Before spraying, the process further includes a step of vacuum degassing the silicon carbide slurry under a vacuum of 0.001 Pa.

[0066] Example 3

[0067] This embodiment provides a silicon carbide ceramic, the preparation method of which includes the following steps:

[0068] (1) Silicon carbide particles with an average particle size of 200 μm, sintering aid and glycerol are uniformly mixed, and the resulting mud is molded and then dried at 60°C to obtain a silicon carbide blank; based on a total weight of 100 parts, the mud contains 77 parts of silicon carbide, 3 parts of sintering aid and 20 parts of glycerol; the sintering aid includes alumina powder and yttrium oxide powder in a mass ratio of 3:2.5;

[0069] (2) The silicon carbide blank obtained in step (1) is soaked in silicon carbide slurry to obtain a silicon carbide coating with a thickness of 2000 μm. Then, it is dried at 50°C and sintered in a vacuum graphite furnace at 2300°C to obtain the silicon carbide ceramic.

[0070] The silicon carbide slurry is obtained by mixing two types of silicon carbide particles with water of different average particle sizes. Based on a total weight of 100 parts, the silicon carbide slurry contains 85 parts silicon carbide particles and 15 parts water. Based on a total weight of 100 parts, the silicon carbide particles of different average particle sizes consist of 45 parts silicon carbide particles with an average particle size of 1 μm and 55 parts silicon carbide particles with an average particle size of 100 μm. Prior to soaking, the process includes a step of vacuum degassing the silicon carbide slurry under a vacuum of 0.01 Pa.

[0071] Example 4

[0072] This embodiment provides a silicon carbide ceramic. The difference between the preparation method of the silicon carbide ceramic and that of Embodiment 1 is that, except that the average particle size of the silicon carbide particles in the silicon carbide slurry in step (2) is adjusted to 0.005 μm and 5 μm respectively, the rest is the same as that of Embodiment 1.

[0073] Example 5

[0074] This embodiment provides a silicon carbide ceramic. The preparation method of the silicon carbide ceramic is different from that of Embodiment 1. Except for adjusting the average particle size of the silicon carbide particles in the silicon carbide slurry in step (2) to 5 μm and 120 μm respectively, the rest is the same as that of Embodiment 1.

[0075] Example 6

[0076] This embodiment provides a silicon carbide ceramic. The preparation method of the silicon carbide ceramic is different from that of Embodiment 1. Except that the weight of silicon carbide particles with an average particle size of 0.1 μm in step (2) is adjusted to 30 parts and the weight of silicon carbide particles with an average particle size of 30 μm is adjusted to 70 parts, the rest is the same as that of Embodiment 1.

[0077] Example 7

[0078] This embodiment provides a silicon carbide ceramic. The preparation method of the silicon carbide ceramic is different from that of Embodiment 1. Except that the weight of silicon carbide particles with an average particle size of 0.1 μm in step (2) is adjusted to 70 parts and the weight of silicon carbide particles with an average particle size of 30 μm is adjusted to 30 parts, the rest is the same as that of Embodiment 1.

[0079] Example 8

[0080] This embodiment provides a silicon carbide ceramic. The difference between the preparation method of the silicon carbide ceramic and that of Embodiment 1 is that the step of vacuum degassing the silicon carbide slurry before soaking in step (2) is not performed. All other steps are the same as those in Embodiment 1.

[0081] Example 9

[0082] This embodiment provides a silicon carbide ceramic. The preparation method of the silicon carbide ceramic is different from that of Embodiment 1. Except for adjusting the sintering temperature in step (2) to 2050°C, the rest is the same as that of Embodiment 1.

[0083] Example 10

[0084] This embodiment provides a silicon carbide ceramic. The difference between the preparation method of the silicon carbide ceramic and that of Embodiment 1 is that, except for adjusting the sintering temperature in step (2) to 2350°C, the rest is the same as that of Embodiment 1.

[0085] Comparative Example 1

[0086] This comparative example provides a silicon carbide ceramic. The difference between the preparation method of the silicon carbide ceramic and that of Example 1 is that the silicon carbide slurry in step (2) is obtained by mixing a single silicon carbide particle with an average particle size of 0.01 μm with water. The rest are the same as in Example 1.

[0087] Comparative Example 2

[0088] This comparative example provides a silicon carbide ceramic. The difference between the preparation method of the silicon carbide ceramic and that of Example 1 is that the silicon carbide slurry in step (2) is replaced with silicon carbide particles with an average particle size of 0.01 μm. All other aspects are the same as in Example 1.

[0089] Comparative Example 3

[0090] This comparative example provides a silicon carbide ceramic. The difference between the preparation method of the silicon carbide ceramic and that of Example 1 is that step (2) does not involve coating the silicon carbide blank with silicon carbide slurry. All other steps are the same as those in Example 1.

[0091] The silicon carbide ceramics provided in Examples 1-10 and Comparative Examples 1-3 were subjected to density tests using a density analyzer, surface purity tests using ICP, and flexural strength tests using a universal testing machine. The results are shown in Table 1.

[0092] Table 1

[0093] Example 1 98.9 99.8 395 Example 2 97.8 98.9 345 Example 3 98.7 99.5 387 Example 4 98.5 99.3 375 Example 5 98.3 99.2 362 Example 6 98.2 99.1 359 Example 7 98.1 98.9 356 Example 8 98.0 98.5 352 Example 9 97.3 98.6 342 Example 10 98.6 99.2 372 Comparative Example 1 98.3 98.4 365 Comparative Example 2 97.0 97.6 324 Comparative Example 3 96.0 92.0 317

[0094] As can be seen from Table 1, the preparation method provided by the present invention produces silicon carbide ceramics with high density and purity and excellent mechanical properties. This indicates that by coating the surface of the silicon carbide blank with silicon carbide slurry, the volatilization of internal sintering aids can be effectively suppressed, thereby ensuring the density and strength of silicon carbide ceramics and obtaining silicon carbide ceramics with high surface purity.

[0095] A comparison of Examples 1 and 4-7 shows that the particle size range and proportion of two different average particle sizes of silicon carbide particles in the silicon carbide slurry need to be strictly controlled in order to obtain good product density, strength and purity. A comparison of Examples 1 and 8 shows that without the vacuum degassing step of the silicon carbide slurry, the coated silicon carbide coating will contain pores, affecting the density and strength of the silicon carbide ceramic. A comparison of Examples 1 and Examples 9 and 10 shows that if the sintering temperature is too low, the sintering density of the coated silicon carbide film layer will be low and the volatilization inhibition effect of the sintering aid will be low. If the sintering temperature is too high, the volatilization effect of the internal sintering aid will be strong, which will lead to a decrease in surface purity and density.

[0096] A comparison of Example 1 and Comparative Example 1 shows that when silicon carbide slurry is prepared using silicon carbide particles with a single average particle size, the film layer coated with particles of a single size is prone to voids, resulting in poor inhibition of the volatilization of internal sintering aids. The volatilization of sintering aids leads to a decrease in density and surface purity. A comparison of Example 1 and Comparative Example 2 shows that directly coating the silicon carbide blank with silicon carbide particles cannot obtain a uniform silicon carbide coating layer, and the sintering aids still volatilize, resulting in a significant decrease in the density and strength of the obtained silicon carbide ceramic. A comparison of Example 1 and Comparative Example 3 shows that without coating the surface of the silicon carbide blank, the volatilization of sintering aids inside the silicon carbide ceramic leads to a significant decrease in density, strength, and product purity.

[0097] In summary, the method for preparing silicon carbide ceramics provided by this invention, by coating the surface of the prepared silicon carbide blank with a silicon carbide coating, can effectively suppress the volatilization of internal sintering aids during subsequent sintering, significantly improving the density and strength of the silicon carbide ceramic, with a density reaching 98.9% and a flexural strength reaching 395 MPa. It also improves the surface purity of the silicon carbide ceramic, achieving a surface purity of 98.5-99.8%. Furthermore, the silicon carbide ceramic product prepared by this method exhibits significantly improved service temperature and corrosion resistance, meeting the requirements for high-precision industrial materials.

[0098] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing silicon carbide ceramics, characterized in that, The preparation method includes the following steps: (1) The silicon carbide particles, sintering aid and binder are uniformly mixed and the resulting mud is shaped to obtain silicon carbide blank; (2) The silicon carbide blank obtained in step (1) is coated with silicon carbide slurry and then sintered to obtain the silicon carbide ceramic; The average particle size of the silicon carbide in step (1) is 1-200 μm; The sintering aid comprises alumina powder and yttrium oxide powder in a mass ratio of 3:(1.5-2.5); The silicon carbide slurry in step (2) is obtained by mixing two types of silicon carbide particles with different average particle sizes with a solvent; The two types of silicon carbide particles with different average particle sizes include silicon carbide particles with an average particle size of 0.01-1 μm and silicon carbide particles with an average particle size of 10-100 μm. Of the two types of silicon carbide particles with different average particle sizes, 45-55 parts are silicon carbide particles with an average particle size of 0.01-1 μm and 45-55 parts are silicon carbide particles with an average particle size of 10-100 μm. Step (2) before coating includes a step of vacuum degassing the silicon carbide slurry; The sintering temperature in step (2) is 2150-2300℃.

2. The preparation method according to claim 1, characterized in that, Based on a total weight of 100 parts, the mud material described in step (1) contains 60-77 parts silicon carbide, 3-10 parts sintering aid, and 20-30 parts binder.

3. The preparation method according to claim 1, characterized in that, The adhesive comprises any one or a combination of at least two of ethylene glycol, polyvinyl alcohol, ammonium polyacrylate, cellulose, polyvinylpyrrolidone, glucose, or glycerol.

4. The preparation method according to claim 1, characterized in that, The molding process described in step (1) includes extrusion molding or injection molding.

5. The preparation method according to claim 1, characterized in that, Step (1) after molding also includes a drying step.

6. The preparation method according to claim 5, characterized in that, The drying temperature is ≤60℃.

7. The preparation method according to claim 1, characterized in that, Based on a total weight of 100 parts, the silicon carbide slurry in step (2) contains 75-85 parts silicon carbide particles and 15-25 parts solvent.

8. The preparation method according to claim 7, characterized in that, The solvent includes water.

9. The preparation method according to claim 1, characterized in that, The vacuum degree of the vacuum exhaust process is 0.001-0.01 Pa.

10. The preparation method according to claim 1, characterized in that, The coating method described in step (2) includes soaking or spraying.

11. The preparation method according to claim 1, characterized in that, The thickness of the silicon carbide coating obtained after coating in step (2) is 100-2000 μm.

12. The preparation method according to claim 1, characterized in that, Step (2) includes a drying step after coating and before sintering.

13. The preparation method according to claim 12, characterized in that, The drying temperature is ≤50℃.

14. The preparation method according to claim 1, characterized in that, The preparation method includes the following steps: (1) Silicon carbide particles with an average particle size of 1-200 μm, sintering aids and binders are uniformly mixed, and the resulting mud is extruded or injection molded and then dried at ≤60℃ to obtain a silicon carbide blank; based on a total weight of 100 parts, the mud contains 60-77 parts of silicon carbide, 3-10 parts of sintering aids and 20-30 parts of binders; the sintering aids include alumina powder and yttrium oxide powder in a mass ratio of 3:(1.5-2.5); (2) The silicon carbide blank obtained in step (1) is coated with silicon carbide slurry to obtain a silicon carbide coating with a thickness of 100-2000μm. Then, it is dried at ≤50℃ and sintered at 2150-2300℃ to obtain the silicon carbide ceramic. The silicon carbide slurry is obtained by mixing two types of silicon carbide particles with different average particle sizes and a solvent. Based on a total weight of 100 parts, the silicon carbide slurry contains 75-85 parts silicon carbide particles and 15-25 parts solvent. The two types of silicon carbide particles with different average particle sizes include silicon carbide particles with an average particle size of 0.01-1 μm and silicon carbide particles with an average particle size of 10-100 μm. Based on a total weight of 100 parts, the silicon carbide particles with an average particle size of 0.01-1 μm contain 45-55 parts, and the silicon carbide particles with an average particle size of 10-100 μm contain 45-55 parts. Before coating, the process further includes a step of vacuum degassing the silicon carbide slurry under a vacuum of 0.001-0.01 Pa.

15. A silicon carbide ceramic, characterized in that, The silicon carbide ceramic is prepared by the preparation method according to any one of claims 1-14.

16. An application of the silicon carbide ceramic as described in claim 15, characterized in that, The silicon carbide ceramic is used in the fabrication of semiconductors or photovoltaic devices.