Silicon carbide-based ceramic material, preparation method thereof and large-size silicon carbide ceramic furnace tube

Abstract

The invention relates to the technical field of ceramics, in particular to a silicon carbide-based ceramic material, a preparation method thereof and a large-size silicon carbide ceramic furnace tube. The method comprises the following steps: S1, mixing silicon dioxide and methylbenzene, and then dropwise adding dichloromethylsilane for primary reaction to obtain silanized silicon dioxide; s2, mixing the silanized silicon dioxide and methylbenzene, then dropwise adding a zero-valent platinum-casts catalyst to carry out a secondary reaction, and then adding allyldimethylsilane to carry out a third reaction, so as to obtain polycarbosilane grafted silicon dioxide; s3, polycarbosilane grafted silicon dioxide, silicon carbide and a sintering aid are mixed and subjected to primary ball milling, then a binder is added for secondary ball milling, and ceramic slurry is obtained; and S4, injecting the ceramic slurry into a mold, drying to obtain a biscuit, and sintering the biscuit to obtain the silicon carbide-based ceramic material. The ceramic material provided by the 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, and 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 applied to 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 tolerated 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 and 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 of CN104030686A discloses a high-toughness silicon carbide ceramic and a preparation method thereof. The high-toughness silicon carbide ceramic is composed of 3-5% toughening agent titanium carbide, 1-4% sintering aid, the balance of silicon carbide and inevitable impurities, wherein 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 and 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, and 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, changing the fracture mode of the silicon carbide ceramic material 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 3 SiC 2 phase, which may cause abnormal grain boundary coarsening 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. The application includes the following steps: mixing SiC powder, graphite powder, a dispersant, a binder and a 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; performing silicon infiltration on the degreased green body to obtain a high-strength and high-toughness silicon carbide ceramic material. In this application, the amount of silicon infiltration is calculated so that it reacts with part of the graphite to completely form silicon carbide, and the excess graphite is retained in the SiC ceramic as the second phase 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 lamellae 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 object 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] In order to achieve the above object, the present invention provides the following technical solutions: 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: S1, mixing silicon dioxide and toluene, and then dropwise adding dichloromethylsilane for a first reaction, and performing distillation, washing and filtration to obtain silylated silicon dioxide; S2, mixing silylated silicon dioxide and toluene, and then dropwise adding a zero-valent platinum Karstedt catalyst for a second reaction, and then adding allyldimethylsilane for a third reaction, and evaporating to remove toluene to obtain polycarbosilane-grafted silicon dioxide; S3, mixing polycarbosilane-grafted silicon dioxide, silicon carbide and a sintering aid and performing a first ball milling, and then adding a binder for a second 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 a silicon carbide-based ceramic material.

[0008] The present invention significantly improves the density, toughness, and thermal shock resistance of silicon carbide ceramics through the synergistic optimization of sintering process, interfacial chemical bonding, and microstructure of polycarbosilane grafted silica and silicon carbide, overcoming the core defects of traditional silicon carbide ceramics such as high sintering energy consumption, high brittleness, and insufficient high-temperature stability.

[0009] Specifically, polycarbosilane is used as a precursor, which can in-situ generate nanoscale silicon carbide phases 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 2 fills the grain boundary pores and absorbs the energy of crack propagation, resulting in a significant improvement in fracture toughness. In addition, the difference in thermal expansion coefficients between SiO 2 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 SiO 2 acts synergistically with the oxide layer on the SiC surface to inhibit further oxidation of the material, while the acid and alkali resistance of SiO 2 complements the chemical inertness of SiC, expanding the application in extreme environments. Finally, this composite system achieves a reduction in process energy consumption, an improvement in toughness, and a breakthrough in high-temperature stability while maintaining high hardness and corrosion resistance.

[0010] In a preferred embodiment, in step S1, the average particle size of the silica is 100 - 200 nm.

[0011] In a preferred embodiment, in step S1, the mass ratio of the silica, toluene, and dichloromethylsilane is 1:(10 - 50):(0.1 - 0.5).

[0012] 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.

[0013] 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).

[0014] 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.

[0015] 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.

[0016] In a preferred embodiment, in step S3, the average particle size of the silicon carbide is 0.5 - 2 μm.

[0017] In a preferred embodiment, in step S3, the sintering aid is one or more of yttrium oxide, neodymium oxide, and magnesium oxide.

[0018] In a preferred embodiment, in step S3, the sintering aid is a mixture of yttrium oxide, neodymium oxide, and magnesium oxide formed in a mass ratio of 1:1:1.

[0019] Yttrium oxide (Y 2 O 3 ), neodymium oxide (Nd 2 O 3 ), and the sintering aid mixture of 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 the polycarbosilane-grafted silica / silicon carbide composite ceramic through multi-scale interface regulation and liquid-phase synergistic effect.

[0020] Specifically, the rare earth ion radii of Y 2 O 3 and Nd 2 O 3 differ greatly from that of Si in the SiC lattice and it is difficult to directly form a substitutional solid solution, but they can form an interstitial solid solution with the Si - O network in SiO 4+ 2 . 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 SiO 2 to generate low-melting-point magnesium silicate, but the simultaneous presence of Y 2 O 3 and Nd 2 O 3 in the system can further lower the liquid-phase formation temperature. This liquid phase promotes particle rearrangement through capillary force, fills the pores, reducing the porosity, and accelerates mass migration through the dissolution-reprecipitation mechanism, improving the sintering density; at the same time, the thermal expansion coefficients of Y 2 O 3 and Nd 2 O 3 are between those of SiC and Mg 2 SiO 4 ​Between them, a gradient expansion layer from the intragranular to the grain boundary is formed. 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, and Y 2 O 3 is preferentially oxidized at high temperatures to form Y 2 SiO 5 protective layer, which synergistically inhibits the diffusion of oxygen into the interior of the material with the Si-O-C network generated by the pyrolysis of PCS, improving the oxidation resistance of the material. At the same time, the introduction of Nd 2 O 3 inhibits the grain boundary migration of the Mg 2 SiO 3 liquid phase at high temperatures, avoiding the increase in creep rate caused by grain boundary weakening.

[0021] In a preferred embodiment, in step S3, the binder is polyethylene glycol.

[0022] In a preferred embodiment, in step S3, the mass ratio of polycarbosilane grafted silica, silicon carbide, sintering aid, and binder is (30 - 50):(40 - 90):(5 - 10):(1 - 5).

[0023] 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.

[0024] In a second aspect, an 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.

[0025] In a third aspect, an embodiment of the present invention provides a large-sized silicon carbide ceramic furnace tube, which is sintered from the silicon carbide-based ceramic material as described above.

[0026] Compared with the prior art, the advantages and beneficial effects of the present invention are: 1. The present invention significantly improves the density, toughness, and thermal shock resistance of silicon carbide ceramics through the synergistic optimization of polycarbosilane grafted silica and silicon carbide by sintering process, interfacial chemical bonding, and microstructure, overcoming the core defects of traditional silicon carbide ceramics such as high sintering energy consumption, high brittleness, and insufficient high-temperature stability.

[0027] 2. The present invention's yttrium oxide (Y 2 O 3 ), neodymium oxide (Nd 2 O 3)(The sintering aid mixture with magnesium oxide (MgO) 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 synergy effect.) Detailed implementation mode

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all 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.)

[0029] Unless otherwise specified, the reagents provided by the present invention are all obtained commercially.)

[0030] Silica, with an average particle size of 100 nm, was purchased from Wuhan Jiyesheng Chemical Co., Ltd.) Dichloromethylsilane was purchased from Guangdong Wengjiang Chemical Reagent Co., Ltd.) Zero-valent platinum Karstedt catalyst was purchased from Shanghai Jingxi Chemicals Co., Ltd.) Allyldimethylsilane was purchased from Hepeng (Shanghai) Biotechnology Co., Ltd.) Silicon carbide (β-SiC, cubic crystal system), with an average particle size of 1 μm, was purchased from Zhejiang Hangling New Materials Co., Ltd.)

[0031] Example 1

[0032] This example provides a preparation method of a silicon carbide-based ceramic material, including the following steps.) S1. Mix 10 g of silica with an average particle size of 100 nm and 100 ml of toluene, then gradually add dichloromethylsilane, and the addition amount of dichloromethylsilane is 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, and wash and filter to obtain silanized silica.) S2. Mix 10 g of silanized silica and 100 ml of toluene, then gradually add zero-valent platinum Karstedt catalyst, and the addition amount of zero-valent platinum Karstedt catalyst is 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, and evaporate to remove toluene to obtain polycarbosilane-grafted silica.) 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 mass ratio of 1:1:1 to form a sintering aid, 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. 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.

[0033] Example 2

[0034] This example provides a method for preparing a silicon carbide-based ceramic material, which includes the following steps: S1. Mix 10 g of silica with an average particle size of 100 nm and 100 ml of toluene, and then add dichloromethylsilane dropwise. The addition amount of dichloromethylsilane is 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 h to remove any unreacted small molecule silanes. Wash and filter to obtain silanized silica. S2. Mix 10 g of silanized silica and 100 ml of toluene, and then add zero-valent platinum Karstedt catalyst dropwise. The addition amount of zero-valent platinum Karstedt catalyst is 6.5 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 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. 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 in a mass ratio of 1:1:1 to form a sintering aid, and ball-mill the mixture 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. 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.

[0035] Comparative Example 1 This comparative example provides a method for preparing a silicon carbide-based ceramic material, which includes the following steps: S1. In 100 ml of toluene, add zero-valent platinum Karstedt catalyst dropwise. The addition amount of zero-valent 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. S2. Mix the polycarbosilane obtained in S1, 10 g of silicon dioxide 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 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. 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.

[0036] Comparative Example 2 This comparative example provides a method for preparing a silicon carbide-based ceramic material, including the following steps: S1. Mix 10 g of silicon dioxide 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 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. S2. 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.

[0037] Comparative Example 3 This comparative example provides a method for preparing a silicon carbide-based ceramic material, including the following steps: S1. Mix 10 g of silicon dioxide with an average particle size of 100 nm and 100 ml of toluene, then add dichloromethylsilane dropwise. The addition amount of dichloromethylsilane is 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 silicon dioxide. S2. Mix 10 g of silanized silicon dioxide and 100 ml of toluene, then add zero-valent platinum Karstedt catalyst dropwise. The addition amount of zero-valent platinum Karstedt catalyst is 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 silicon dioxide. 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 silicon dioxide. 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 neodymium oxide in a mass ratio of 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. 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.

[0038] Comparative Example 4 This comparative example provides a method for preparing a silicon carbide-based ceramic material, which includes the following steps: S1. Mix 10 g of silica with an average particle size of 100 nm and 100 ml of toluene. Then add dichloromethylsilane drop by drop, and the addition amount of dichloromethylsilane is 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. S2. Mix 10 g of silanized silica and 100 ml of toluene. Then add zero-valent platinum Karstedt catalyst drop by drop, and the addition amount of zero-valent platinum Karstedt catalyst is 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. 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 magnesium oxide in a mass ratio of 1:1 to form a sintering aid, 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. 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.

[0039] Comparative Example 5 This comparative example provides a method for preparing a silicon carbide-based ceramic material, which includes the following steps: S1. Mix 10 g of silica with an average particle size of 100 nm and 100 ml of toluene. Then add dichloromethylsilane drop by drop, and the addition amount of dichloromethylsilane is 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. S2. Mix 10 g of silylated silica and 100 ml of toluene, and then dropwise add 4.5 g of zero-valent platinum Karstedt catalyst. React at 60 °C for 8 min under a nitrogen atmosphere 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; 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 magnesium oxide 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; 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.

[0040] Performance Test 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: Table 1 Performance Test Results

[0041] 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.

[0042] 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.

[0043] 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 of 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: The following steps are involved: S1, mixing silica and toluene, then adding dichloromethylsilane dropwise for a reaction, distilling, washing and filtering to obtain silanized silica; S2, mixing silanized silica and toluene, then adding zero-valent platinum cast catalyst dropwise for secondary reaction, then adding allyl dimethyl silane for tertiary reaction, and evaporating toluene to obtain polycarbosilane grafted silica; S3, mixing polycarbosilane grafted silicon dioxide, silicon carbide, and a sintering aid and performing a first ball milling, and then adding a binder and performing a second ball milling to obtain a ceramic slurry; S4, injecting the ceramic slurry into a mold and drying it to obtain a green body, and sintering the green body to obtain a silicon carbide-based ceramic material.

2. The method for preparing a silicon carbide-based ceramic material according to claim 1, characterized in that: In step S1, the average particle size of the silicon dioxide is 100-200 nm; and / or, in step S1, the mass ratio of silicon dioxide, toluene and dichloromethylsilane is 1:(10-50):(0.1-0.5); In step S1, the conditions of the primary reaction are: reacting at 50-80° C. for 2-5 hours under a nitrogen atmosphere.

3. The method for preparing a 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-cast catalyst, and allyl dimethyl silane is 1: (10-50): (0.5-1): (2-5).

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

5. The method for preparing a silicon carbide-based ceramic material according to claim 1, characterized in that: 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; And / or, 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).

6. The method for preparing a silicon carbide-based ceramic material according to claim 1, characterized in that: In step S3, the sintering aid is one or more of yttrium oxide, neodymium oxide, and magnesium oxide.

7. The method for preparing a silicon carbide-based ceramic material according to claim 6, characterized in that: In step S3, the sintering aid is a mixture of yttrium oxide, neodymium oxide, and magnesium oxide in a mass ratio of 1:1:

1.

8. The method for preparing a silicon carbide-based ceramic material according to claim 1, characterized in that: 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.

9. A silicon carbide-based ceramic material obtained by using the method for preparing a silicon carbide-based ceramic material according to any one of claims 1 to 8.

10. A large-size silicon carbide ceramic furnace tube, characterized in that: The large-sized silicon carbide ceramic furnace tube is made by sintering the silicon carbide-based ceramic material as claimed in claim 9.

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