A silicon carbide-based ceramic material, its preparation method, and a large-sized silicon carbide ceramic furnace tube

Abstract

The present invention relates to the field of ceramic technology, and particularly to a silicon carbide-based ceramic material, a preparation method thereof, and a large-size silicon carbide ceramic furnace tube. The method includes: S1, mixing silica and toluene, and then dropwise adding dichloromethylsilane for a primary reaction to obtain silanized silica; S2, mixing silanized silica and toluene, and then dropwise adding a zero-valent platinum Karstedt catalyst for a secondary reaction, and then adding allyldimethylsilane for a tertiary reaction to obtain polycarbosilane-grafted silica; S3, mixing polycarbosilane-grafted silica, silicon carbide, and a sintering aid and performing a primary ball milling, and then adding a binder for a secondary ball milling to obtain a ceramic slurry; S4, injecting the ceramic slurry into a mold and drying to obtain a green body, and sintering the green body to obtain the silicon carbide-based ceramic material. The ceramic material provided by the present invention has excellent density, toughness, and thermal shock resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of ceramics, and particularly relates to a silicon carbide-based ceramic material, a preparation method thereof, and a large-size silicon carbide ceramic furnace tube. Background Art

[0002] Silicon carbide (SiC)-based ceramic materials are a class of high-performance ceramic materials with silicon carbide as the main component or matrix. They play an important role in modern industrial and technological fields. With their excellent high-temperature mechanical strength, high hardness, high elastic modulus, high wear resistance, high thermal conductivity, corrosion resistance and other properties, they are not only used in traditional industrial fields such as high-temperature kiln furniture, combustion nozzles, heat exchangers, sealing rings, sliding bearings, etc., but also can be used as bulletproof armor materials, space reflectors, fixture materials in semiconductor wafer preparation and nuclear fuel cladding materials. The advantages of silicon carbide-based ceramic materials are prominently manifested in their extreme environmental adaptability: extremely high heat resistance, capable of working stably at 1600-1700 °C for a long time, and the short-term tolerance temperature is as high as 2700 °C, significantly superior to traditional metals and alumina ceramics; high hardness and wear resistance, close to diamond, suitable for mechanical seals and cutting tools; chemical corrosion resistance, with excellent resistance to strong acids, strong alkalis and molten metals, and is an ideal material for chemical reactors and heat exchangers; high thermal conductivity, suitable for heat dissipation substrates of high-power electronic devices. However, it has high brittleness, weak impact resistance, and is prone to fracture due to stress concentration. Therefore, to make silicon carbide exert its excellent mechanical properties, its brittleness should be overcome first, that is, the toughness of silicon carbide ceramics should be improved.

[0003] For example, the invention with the publication number CN104030686A discloses a high-toughness silicon carbide ceramic and a preparation method thereof. The high-toughness silicon carbide ceramic is composed of 3-5% of toughening agent titanium carbide, 1-4% of sintering aid, the balance of silicon carbide and inevitable impurities. Among them, the sintering aid is composed of carbon and boron carbide with a mass percentage of 1:(0.6-8). The preparation method is to first mix silicon carbide, toughening agent titanium carbide, sintering aids carbon and boron carbide evenly, put them into a ball mill, add water-soluble resin and distilled water for ball milling, then dry and add them into a steel mold for molding. After molding, put them into a vacuum furnace for sintering, and finally perform surface grinding to obtain the final product of high-toughness silicon carbide ceramic. This application adds toughening agent titanium carbide to the silicon carbide matrix, making the fracture mode of the silicon carbide ceramic material change from mainly intergranular fracture to mainly transgranular fracture, increasing the energy required for transgranular and intergranular fractures, thereby enhancing the flexural strength. However, the introduction of titanium carbide requires the sintering temperature to be raised to 2100-2200 °C (300-500 °C higher than the sintering temperature of pure silicon carbide), resulting in an increase in energy consumption cost. And in a high-temperature environment, the interface between TiC and SiC is prone to in-situ reaction to generate Ti3SiC2 phase, which may cause abnormal coarsening of grain boundaries and reduce the material density.

[0004] The invention with the publication number CN117383940A provides a high-strength and high-toughness silicon carbide ceramic material and a preparation method thereof. This application includes the following steps: mixing SiC powder, graphite powder, dispersant, binder, and solvent, and performing ball milling to obtain a mixed slurry; performing spray granulation on the mixed slurry to obtain a composite powder; forming the composite powder to obtain a ceramic green body; degreasing the ceramic green body to obtain a degreased green body; and performing silicon infiltration on the degreased green body to obtain a high-strength and high-toughness silicon carbide ceramic material. In this application, by calculating the amount of silicon infiltration, it reacts with part of the graphite to completely generate silicon carbide, and the excess graphite is retained as a second phase in the SiC ceramic to improve the self-lubricating performance of the material, and finally a high-strength and high-toughness silicon carbide ceramic material is obtained. Although adding graphite as a toughening phase can improve the toughness of silicon carbide ceramics, the linear expansion coefficient of graphite is significantly lower than that of SiC, which causes interfacial microcracks during high-temperature sintering or thermal cycling, and the graphite sheets are prone to agglomeration to form local enrichment areas, becoming stress concentration sources and reducing the flexural strength of the material.

[0005] In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] The purpose of the present invention is to provide a silicon carbide-based ceramic material, a preparation method thereof, and a large-size silicon carbide ceramic furnace tube. The ceramic material provided by the present invention overcomes the core defects of traditional silicon carbide ceramics, such as high energy consumption for sintering, high brittleness, and insufficient high-temperature stability.

[0007] To achieve the above purpose, the present invention provides the following technical solutions:

[0008] In the first aspect, an embodiment of the present invention provides a preparation method of a silicon carbide-based ceramic material, including the following steps:

[0009] S1, mixing silicon dioxide and toluene, and then dropwise adding dichloromethylsilane for a primary reaction, followed by distillation, washing, and filtration to obtain silanized silicon dioxide;

[0010] S2, mixing silanized silicon dioxide and toluene, then dropwise adding a zero-valent platinum Karstedt catalyst for a secondary reaction, and then adding allyldimethylsilane for a tertiary reaction, and evaporating to remove toluene to obtain polycarbosilane-grafted silicon dioxide;

[0011] S3, mixing polycarbosilane-grafted silicon dioxide, silicon carbide, and a sintering aid and performing a primary ball milling, and then adding a binder for a secondary ball milling to obtain a ceramic slurry;

[0012] S4, injecting the ceramic slurry into a mold and drying to obtain a green body, and sintering the green body to obtain a silicon carbide-based ceramic material.

[0013] Through the synergistic optimization of sintering process, interfacial chemical bonding and microstructure of polycarbosilane grafted silica and silicon carbide, the present invention significantly improves the density, toughness and thermal shock resistance of silicon carbide ceramics, overcoming the core defects of traditional silicon carbide ceramics such as high sintering energy consumption, high brittleness and insufficient high-temperature stability.

[0014] Specifically, polycarbosilane is used as a precursor, which can in-situ generate nanoscale silicon carbide phase during pyrolysis. Compared with the traditional process with a high temperature above 2000 °C, the energy consumption is reduced, and at the same time, the increase in porosity caused by grain coarsening is avoided. The grafted silica forms a chemical bridge with SiC through silicon-oxygen bonds (Si-O-Si). This interfacial bonding not only enhances the binding force between particles, but also fills the grain boundary pores with nano-SiO2 and absorbs the energy of crack propagation, resulting in a significant improvement in fracture toughness. In addition, the difference in thermal expansion coefficients between SiO2 and SiC forms a gradient transition layer, relieving thermal stress and enhancing thermal shock resistance. At high temperatures, the dense protective layer formed by the oxidation of SiO2 and the oxide layer on the surface of SiC act synergistically to inhibit further oxidation of the material, and the acid and alkali resistance of SiO2 and the chemical inertness of SiC are complementary, expanding the application in extreme environments. Finally, while maintaining high hardness and corrosion resistance, this composite system achieves a reduction in process energy consumption, an improvement in toughness and a breakthrough in high-temperature stability.

[0015] In a preferred embodiment, in step S1, the average particle size of the silica is 100 - 200 nm.

[0016] In a preferred embodiment, in step S1, the mass ratio of the silica, toluene and dichloromethylsilane is 1:(10 - 50):(0.1 - 0.5).

[0017] In a preferred embodiment, in step S1, the conditions for the first reaction are: reacting at 50 - 80 °C for 2 - 5 h under a nitrogen atmosphere.

[0018] In a preferred embodiment, in step S2, the mass ratio of the silylated silica, toluene, zero-valent platinum Karstedt catalyst and allyldimethylsilane is 1:(10 - 50):(0.5 - 1):(2 - 5).

[0019] In a preferred embodiment, in step S2, the conditions for the second reaction are: reacting at 50 - 80 °C for 5 - 10 min under a nitrogen atmosphere.

[0020] In a preferred embodiment, in step S2, the conditions for the third reaction are: reacting at 50 - 80 °C for 24 - 72 h under a nitrogen atmosphere.

[0021] In a preferred embodiment, in step S3, the average particle size of the silicon carbide is 0.5 - 2 μm.

[0022] In a preferred embodiment, in step S3, the sintering aid is one or more of yttrium oxide, neodymium oxide, and magnesium oxide.

[0023] In a preferred embodiment, in step S3, the sintering aid is a mixture formed by yttrium oxide, neodymium oxide, and magnesium oxide in a mass ratio of 1:1:1.

[0024] The sintering aid mixture of yttrium oxide (Y2O3), neodymium oxide (Nd2O3), and magnesium oxide (MgO) in the present invention further overcomes the defects of high residual porosity, high-temperature grain boundary weakening, and insufficient thermal shock resistance of the polycarbosilane-grafted silica / silicon carbide composite ceramic through multi-scale interface regulation and liquid-phase synergistic effect.

[0025] Specifically, the rare-earth ion radii of Y2O3 and Nd2O3 are quite different from Si in the SiC lattice 4+ and it is difficult to directly form a substitutional solid solution, but an interstitial solid solution can be formed with the Si-O network in SiO2. Y 3+ is preferentially adsorbed at the SiC grain boundary, reducing the grain boundary energy through electrostatic interaction and inhibiting abnormal grain growth. At the same time, the high polarizability of Nd 3+ enables it to combine with the dangling bonds on the SiC surface to form Nd-O-Si covalent bonds, enhancing the grain boundary bonding strength. In addition, MgO can react with SiO2 to form low-melting-point magnesium silicate, but the coexisting Y2O3 and Nd2O3 in the system can further lower the liquid-phase formation temperature. This liquid phase promotes particle rearrangement through capillary force, fills the pores, reduces the porosity, and accelerates mass migration through the dissolution-reprecipitation mechanism, improving the sintering density; at the same time, the thermal expansion coefficients of Y2O3 and Nd2O3 are between those of SiC and Mg2SiO4, forming a gradient expansion layer from the grain interior to the grain boundary. This gradient structure buffers thermal shock through layer-by-layer stress release during thermal cycling, enabling the material to maintain a very high strength retention rate after rapid cooling and heating cycles. Moreover, Y2O3 preferentially oxidizes to form a Y2SiO5 protective layer at high temperatures, which synergistically inhibits the diffusion of oxygen into the material interior with the Si-O-C network formed by PCS pyrolysis, improving the oxidation resistance of the material. At the same time, the introduction of Nd2O3 inhibits the grain boundary migration of the Mg2SiO3 liquid phase at high temperatures, avoiding the increase in creep rate caused by grain boundary weakening.

[0026] In a preferred embodiment, in step S3, the binder is polyethylene glycol.

[0027] In a preferred embodiment, in step S3, the mass ratio of the polycarbosilane-grafted silica, silicon carbide, sintering aid, and binder is (30 - 50):(40 - 90):(5 - 10):(1 - 5).

[0028] In a preferred embodiment, in step S4, the sintering conditions are: sintering at 1500 - 1700 °C for 1 - 3 h, and then sintering at 1750 - 1850 °C for 1 - 3 h.

[0029] Secondly, the embodiment of the present invention provides a silicon carbide - based ceramic material obtained by using the preparation method of the silicon carbide - based ceramic material as described above.

[0030] Thirdly, the embodiment of the present invention provides a large - size silicon carbide ceramic furnace tube, which is sintered from the silicon carbide - based ceramic material as described above.

[0031] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0032] 1. By means of the sintering process, interfacial chemical bonding and microscopic structure co - optimization of polycarbosilane grafted with silica and silicon carbide, the present invention significantly improves the density, toughness and thermal shock resistance of silicon carbide ceramics, and overcomes the core defects of traditional silicon carbide ceramics, such as high sintering energy consumption, high brittleness and insufficient high - temperature stability.

[0033] 2. The sintering aid mixture of yttrium oxide (Y2O3), neodymium oxide (Nd2O3) and magnesium oxide (MgO) of the present invention further overcomes the defects of high residual porosity, high - temperature grain boundary weakening and insufficient thermal shock resistance of polycarbosilane grafted with silica / silicon carbide composite ceramics through multi - scale interface regulation and liquid - phase synergistic effect. Specific Embodiments

[0034] Next, the technical solutions in the embodiments of the present invention will be described clearly and completely. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0035] Unless otherwise specified, the reagents provided by the present invention are all obtained commercially.

[0036] Silica, with an average particle size of 100 nm, was purchased from Wuhan Jiyesheng Chemical Co., Ltd.;

[0037] Dichloromethylsilane was purchased from Guangdong Wengjiang Chemical Reagent Co., Ltd.;

[0038] Zero - valent platinum Karstedt catalyst was purchased from Shanghai Jingxi Chemicals Co., Ltd.;

[0039] Allyldimethylsilane was purchased from Hepeng (Shanghai) Biotechnology Co., Ltd.;

[0040] Silicon carbide (β-SiC, cubic crystal system), with an average particle size of 1 μm, was purchased from Zhejiang Hangling New Materials Co., Ltd.

[0041] Example 1

[0042] This example provides a method for preparing a silicon carbide-based ceramic material, including the following steps:

[0043] S1, Mix 10 g of silica with an average particle size of 100 nm and 100 ml of toluene, then gradually add dichloromethylsilane with an addition amount of 2.5 g. Then, under a nitrogen atmosphere, react at 60 °C for 3 h, and carry out vacuum distillation at 50 °C for 1 hour to remove any unreacted small molecule silanes. Wash and filter to obtain silanized silica.

[0044] S2, Mix 10 g of silanized silica and 100 ml of toluene, then gradually add zero-valent platinum Karstedt catalyst with an addition amount of 4.5 g. Under a nitrogen atmosphere, react at 60 °C for 8 min to anchor the zero-valent platinum catalyst on the silyl groups on the surface of silica. Then add 32 g of allyldimethylsilane and react at 70 °C for 48 h under a nitrogen atmosphere to complete the polymerization reaction. Evaporate to remove toluene to obtain polycarbosilane-grafted silica.

[0045] S3, Mix 10 g of polycarbosilane-grafted silica, 14 g of silicon carbide with an average particle size of 1 μm, 6 g of yttrium oxide, neodymium oxide, and magnesium oxide in a sintering aid formed in a mass ratio of 1:1:1, and ball mill at 300 r / min for 15 min. Then add 3 g of polyethylene glycol and ball mill at 300 r / min for 30 min to obtain a ceramic slurry.

[0046] S4, Inject the ceramic slurry into a mold and dry at 200 °C for 24 h to obtain a green body. Sinter the green body at 1600 °C for 2 h, and then sinter at 1800 °C for 2 h to obtain the silicon carbide-based ceramic material.

[0047] Example 2

[0048] This example provides a method for preparing a silicon carbide-based ceramic material, including the following steps:

[0049] S1, Mix 10 g of silica with an average particle size of 100 nm and 100 ml of toluene, then gradually add dichloromethylsilane with an addition amount of 3.5 g. Then, under a nitrogen atmosphere, react at 60 °C for 3 h, and carry out vacuum distillation at 50 °C for 1 hour to remove any unreacted small molecule silanes. Wash and filter to obtain silanized silica.

[0050] S2. Mix 10 g of silanized silica and 100 ml of toluene, then add the zerovalent platinum Karstedt catalyst dropwise. The addition amount of the zerovalent platinum Karstedt catalyst is 6.5 g. Under a nitrogen atmosphere, react at 60 °C for 8 min to anchor the zerovalent platinum catalyst on the silyl groups on the silica surface. Then add 44 g of allyldimethylsilane and react at 70 °C for 48 h under a nitrogen atmosphere to complete the polymerization reaction. Evaporate to remove toluene to obtain polycarbosilane grafted silica;

[0051] S3. Mix 10 g of polycarbosilane grafted silica, 18 g of silicon carbide with an average particle size of 1 μm, 8 g of yttrium oxide, neodymium oxide, and magnesium oxide as a sintering aid formed in a mass ratio of 1:1:1, and ball mill at 300 r / min for 15 min. Then add 5 g of polyethylene glycol and ball mill at 300 r / min for 30 min to obtain a ceramic slurry;

[0052] S4. Inject the ceramic slurry into a mold and dry at 200 °C for 24 h to obtain a green body. Sinter the green body at 1600 °C for 2 h, and then sinter at 1800 °C for 2 h to obtain a silicon carbide-based ceramic material.

[0053] Comparative Example 1

[0054] This comparative example provides a method for preparing a silicon carbide-based ceramic material, including the following steps:

[0055] S1. In 100 ml of toluene, add the zerovalent platinum Karstedt catalyst dropwise. The addition amount of the zerovalent platinum Karstedt catalyst is 4.5 g. Under a nitrogen atmosphere, react at 60 °C for 8 min. Then add 32 g of allyldimethylsilane and react at 70 °C for 48 h under a nitrogen atmosphere to complete the polymerization reaction. Evaporate to remove toluene to obtain polycarbosilane;

[0056] S2. Mix the polycarbosilane obtained in S1, 10 g of silica with an average particle size of 100 nm, 14 g of silicon carbide with an average particle size of 1 μm, 6 g of yttrium oxide, neodymium oxide, and magnesium oxide as a sintering aid formed in a mass ratio of 1:1:1, and ball mill at 300 r / min for 15 min. Then add 3 g of polyethylene glycol and ball mill at 300 r / min for 30 min to obtain a ceramic slurry;

[0057] S3. Inject the ceramic slurry into a mold and dry at 200 °C for 24 h to obtain a green body. Sinter the green body at 1600 °C for 2 h, and then sinter at 1800 °C for 2 h to obtain a silicon carbide-based ceramic material.

[0058] Comparative Example 2

[0059] This comparative example provides a method for preparing a silicon carbide-based ceramic material, including the following steps:

[0060] S1. Mix 10 g of silica with an average particle size of 100 nm, 14 g of silicon carbide with an average particle size of 1 μm, 6 g of yttrium oxide, neodymium oxide, and magnesium oxide to form a sintering aid in a mass ratio of 1:1:1, and ball-mill the mixture at 300 r / min for 15 min. Then add 3 g of polyethylene glycol and ball-mill at 300 r / min for 30 min to obtain a ceramic slurry.

[0061] S2. Inject the ceramic slurry into a mold and dry it at 200 °C for 24 h to obtain a green body. Sinter the green body at 1600 °C for 2 h, and then sinter it at 1800 °C for 2 h to obtain a silicon carbide-based ceramic material.

[0062] Comparative Example 3

[0063] This comparative example provides a method for preparing a silicon carbide-based ceramic material, including the following steps:

[0064] S1. Mix 10 g of silica with an average particle size of 100 nm and 100 ml of toluene, then gradually add dichloromethylsilane in an amount of 2.5 g. Then, under a nitrogen atmosphere, react at 60 °C for 3 h, and carry out vacuum distillation at 50 °C for 1 h to remove any unreacted small molecule silanes. Wash and filter to obtain silanized silica.

[0065] S2. Mix 10 g of silanized silica and 100 ml of toluene, then gradually add zero-valent platinum Karstedt catalyst in an amount of 4.5 g. Under a nitrogen atmosphere, react at 60 °C for 8 min to anchor the zero-valent platinum catalyst on the silyl groups on the silica surface. Then add 32 g of allyldimethylsilane and react at 70 °C for 48 h under a nitrogen atmosphere to complete the polymerization reaction. Evaporate to remove toluene to obtain polycarbosilane-grafted silica.

[0066] S3. Mix 10 g of polycarbosilane-grafted silica, 14 g of silicon carbide with an average particle size of 1 μm, 6 g of yttrium oxide, and neodymium oxide to form a sintering aid in a mass ratio of 1:1, and ball-mill the mixture at 300 r / min for 15 min. Then add 3 g of polyethylene glycol and ball-mill at 300 r / min for 30 min to obtain a ceramic slurry.

[0067] S4. Inject the ceramic slurry into a mold and dry it at 200 °C for 24 h to obtain a green body. Sinter the green body at 1600 °C for 2 h, and then sinter it at 1800 °C for 2 h to obtain a silicon carbide-based ceramic material.

[0068] Comparative Example 4

[0069] This comparative example provides a method for preparing a silicon carbide-based ceramic material, including the following steps:

[0070] S1. Mix 10 g of silica with an average particle size of 100 nm and 100 ml of toluene, then gradually add dichloromethylsilane in an amount of 2.5 g. Then, under a nitrogen atmosphere, react at 60 °C for 3 h, and carry out vacuum distillation at 50 °C for 1 h to remove any unreacted small molecule silanes. Wash and filter to obtain silanized silica;

[0071] S2. Mix 10 g of silanized silica and 100 ml of toluene, then gradually add zero-valent platinum Karstedt catalyst in an amount of 4.5 g. Under a nitrogen atmosphere, react at 60 °C for 8 min to anchor the zero-valent platinum catalyst on the silyl groups on the silica surface. Then add 32 g of allyldimethylsilane and react at 70 °C for 48 h under a nitrogen atmosphere to complete the polymerization reaction. Evaporate to remove toluene to obtain polycarbosilane-grafted silica;

[0072] S3. Mix 10 g of polycarbosilane-grafted silica, 14 g of silicon carbide with an average particle size of 1 μm, 6 g of yttrium oxide, and a sintering aid formed by magnesium oxide in a mass ratio of 1:1, and ball mill at 300 r / min for 15 min. Then add 3 g of polyethylene glycol and ball mill at 300 r / min for 30 min to obtain a ceramic slurry;

[0073] S4. Inject the ceramic slurry into a mold and dry at 200 °C for 24 h to obtain a green body. Sinter the green body at 1600 °C for 2 h, and then sinter at 1800 °C for 2 h to obtain a silicon carbide-based ceramic material.

[0074] Comparative Example 5

[0075] This comparative example provides a method for preparing a silicon carbide-based ceramic material, including the following steps:

[0076] S1. Mix 10 g of silica with an average particle size of 100 nm and 100 ml of toluene, then gradually add dichloromethylsilane in an amount of 2.5 g. Then, under a nitrogen atmosphere, react at 60 °C for 3 h, and carry out vacuum distillation at 50 °C for 1 h to remove any unreacted small molecule silanes. Wash and filter to obtain silanized silica;

[0077] S2. Mix 10 g of silanized silica and 100 ml of toluene, then gradually add zero-valent platinum Karstedt catalyst in an amount of 4.5 g. Under a nitrogen atmosphere, react at 60 °C for 8 min to anchor the zero-valent platinum catalyst on the silyl groups on the silica surface. Then add 32 g of allyldimethylsilane and react at 70 °C for 48 h under a nitrogen atmosphere to complete the polymerization reaction. Evaporate to remove toluene to obtain polycarbosilane-grafted silica;

[0078] S3. Mix 10 g of polycarbosilane-grafted silica, 14 g of silicon carbide with an average particle size of 1 μm, 6 g of neodymium oxide, and a sintering aid formed by mixing magnesium oxide in a mass ratio of 1:1:1, and ball-mill for 15 min at 300 r / min. Then add 3 g of polyethylene glycol and ball-mill for 30 min at 300 r / min to obtain a ceramic slurry;

[0079] S4. Inject the ceramic slurry into a mold and dry it at 200 °C for 24 h to obtain a green body. Sinter the green body at 1600 °C for 2 h, and then sinter it at 1800 °C for 2 h to obtain a silicon carbide-based ceramic material.

[0080] Performance Test

[0081] Test the toughness, density, flexural strength, Vickers hardness, and flexural strength at 1500 °C of the ceramic materials obtained in the examples and comparative examples. The test results are shown in Table 1:

[0082] Table 1 Performance Test Results

[0083]

[0084] From the above performance test results, it can be seen that the density, toughness, and thermal shock resistance of the ceramic materials obtained in Examples 1-2 have been significantly improved. In particular, the comprehensive performance of Example 2 is the most prominent, which is mainly due to the synergistic effect of the sintering aid, polycarbosilane-grafted silica, and silicon carbide provided by the present invention.

[0085] In the comparative example, because the necessary technical solutions were not adopted, its performance in the corresponding performance tests was significantly worse than that of the examples, which better proves the irreplaceability of the specific technical solutions of this application for achieving the technical effects and solving the technical problems.

[0086] The above is the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle described in the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a silicon carbide-based ceramic material, characterized in that, It includes the following steps: S1, Mix silica and toluene, then dropwise add dichloromethylsilane for a first reaction, and distill, wash, and filter to obtain silanized silica; S2, Mix silanized silica and toluene, then dropwise add zero-valent platinum Karstedt catalyst for a second reaction, and then add allyldimethylsilane for a third reaction, and evaporate to remove toluene to obtain polycarbosilane-grafted silica; S3, Mix polycarbosilane-grafted silica, silicon carbide, and sintering aid and perform a first ball milling, and then add a binder for a second ball milling to obtain a ceramic slurry; S4, Inject the ceramic slurry into a mold and dry to obtain a green body, and sinter the green body to obtain a silicon carbide-based ceramic material; In step S3, the sintering aid is a mixture formed by yttrium oxide, neodymium oxide, and magnesium oxide in a mass ratio of 1:1:1; In step S1, the average particle size of the silica is 100 - 200 nm; In step S1, the mass ratio of the silica, toluene, and dichloromethylsilane is 1:(10 - 50):(0.1 - 0.5); In step S1, the conditions for the first reaction are: reacting at 50 - 80 °C for 2 - 5 h under a nitrogen atmosphere; In step S3, the mass ratio of the polycarbosilane-grafted silica, silicon carbide, sintering aid, and binder is (30 - 50):(40 - 90):(5 - 10):(1 - 5); In step S4, the conditions for sintering are: sintering at 1500 - 1700 °C for 1 - 3 h, and then sintering at 1750 - 1850 °C for 1 - 3 h.

2. The preparation method of the silicon carbide-based ceramic material according to claim 1, characterized in that, In step S2, the mass ratio of the silanized silica, toluene, zero-valent platinum Karstedt catalyst, and allyldimethylsilane is 1:(10 - 50):(0.5 - 1):(2 - 5).

3. The preparation method of the silicon carbide-based ceramic material according to claim 1, characterized in that, In step S2, the conditions for the second reaction are: reacting at 50 - 80 °C for 5 - 10 min under a nitrogen atmosphere; And / or, in step S2, the conditions for the third reaction are: reacting at 50 - 80 °C for 24 - 72 h under a nitrogen atmosphere.

4. The preparation method of the silicon carbide-based ceramic material according to claim 1, wherein, In step S3, the average particle size of the silicon carbide is 0.5 - 2 μm; And / or, in step S3, the binder is polyethylene glycol.

5. A silicon carbide-based ceramic material obtained by using the preparation method of the silicon carbide-based ceramic material according to any one of claims 1 - 4.

6. A large-sized silicon carbide ceramic furnace tube, characterized in that, The large-size silicon carbide ceramic furnace tube is sintered and made of the silicon carbide-based ceramic material according to claim 5.

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