Method for preparing reaction sintered multi-faceted silicon carbide slab

Abstract

The present application belongs to the technical field of preparation of multi-curved surface silicon carbide, and discloses a preparation method of reaction sintering multi-curved surface silicon carbide whole plate, comprising: mixing 100 parts of alpha-SiC powder, 15-20 parts of composite carbon source, 1-2 parts of silicon carbide fiber, 2.3-3.8 parts of dispersing agent, 8-12 parts of water-soluble phenolic resin, 2-4 parts of additive and 42-46 parts of water according to weight parts, pre-dispersing, ball-milling, spray granulating, pressing into multi-curved surface green body; the green body is stacked with graphite support parts and filled with graded silicon particles, and is subjected to step-by-step degreasing and step-by-step reaction sintering under vacuum argon, and then is cooled after temperature control to obtain the product. Through the synergistic effect of formula control of composite carbon source, specific ternary additive and fine sintering process, the technical problem of sintering cracking and cracking of multi-curved surface whole plate is eliminated, and the product density, bending strength and fracture toughness are effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of multi-curved silicon carbide preparation technology, and particularly relates to a method for preparing a reaction-sintered multi-curved silicon carbide plate. Background Technology

[0002] The manufacturing process of reaction-sintered silicon carbide products involves mixing a carbon source and α-SiC, followed by slip casting, dry pressing, or cold isostatic pressing to prepare a green body. The green body and silicon particles are then heated to above 1500°C under vacuum or an inert atmosphere, allowing molten silicon to penetrate the green body and react with the carbon to form β-SiC. The newly formed silicon carbide integrates in situ with the existing silicon carbide particles in the green body, ultimately achieving densification. Controlling the C / Si ratio is crucial when using reaction sintering. Excessive carbon leads to incomplete reaction, large shrinkage of the green body during sintering, porous structure, and low strength. Conversely, excessive free silicon disrupts the microstructure density of the silicon carbide product, reduces the effective bonding between silicon carbide particles, resulting in brittleness, poor thermal shock resistance, easy cracking, and reduced compressive and flexural strength.

[0003] In the existing technology, when using reaction sintering process to prepare multi-curved silicon carbide products, the point support and the suspended curved surface during furnace sintering cause stress concentration. In addition, different curvature parts have different shrinkage rates during sintering, so cracks or hidden cracks are very easy to occur, resulting in unsatisfactory performance of the finished product.

[0004] Therefore, there is an urgent need to develop a method for preparing reaction-sintered multi-curved silicon carbide plates to solve the technical problems of existing reaction-sintered multi-curved silicon carbide products, such as easy cracking, high brittleness, and insufficient compressive and bending resistance. Summary of the Invention

[0005] The technical problem to be solved by this invention is to overcome the shortcomings and defects mentioned in the background art above, and to provide a method for preparing a reaction-sintered multi-curved silicon carbide plate. This method can effectively avoid cracking of the multi-curved silicon carbide plate during the reaction sintering process, improve the yield, and enhance the bending strength and fracture toughness of the product.

[0006] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows: A method for preparing a reaction-sintered multi-curved silicon carbide plate includes the following steps: (1) Weigh out 100 parts by weight of α-SiC powder, 15-20 parts by weight of composite carbon source, 1-2 parts by weight of silicon carbide fiber, 2.3-3.8 parts by weight of dispersant, 8-12 parts by weight of water-soluble phenolic resin, 2-4 parts by weight of additives and 42-46 parts by weight of water. The dispersant is KV5088 and polyvinylpyrrolidone. The additives are a mixture of silicon molybdenum alloy, molybdenum carbide and silicon nitride. The composite carbon source is composed of carbon black and graphite in a mass ratio of 3:2. (2) Dissolve polyvinylpyrrolidone in water, add silicon carbide fiber and stir, adjust the pH of the slurry to weak alkalinity, then add KV5088 and mix, add the composite carbon source in batches and stir to obtain a pre-dispersed slurry; (3) Add the α-SiC powder to the pre-dispersed slurry and ball mill at a set rate, then add the additive and continue ball milling, and finally add water-soluble phenolic resin and ball mill to obtain a mixed slurry; (4) The mixed slurry is spray-granulated to obtain spherical granulated powder; (5) Press the spherical granulated powder to obtain a multi-curved green body; (6) The multi-curved green blank is placed on a graphite boat and subjected to reaction sintering to obtain a multi-curved silicon carbide plate.

[0007] In the above preparation method, preferably, in step (1), the α-SiC powder is composed of three particle sizes, D50≈30μm, D50≈10μm and D50≈2μm, in a mass ratio of 65∶25∶10; the purity of the α-SiC powder is ≥98%.

[0008] Preferably, in step (1), KV5088 is 0.3-0.8 parts and polyvinylpyrrolidone is 2-3 parts.

[0009] Preferably, in step (1), the carbon black has a particle size of 300-600 nm and the graphite has a particle size of 10-20 μm.

[0010] Preferably, in step (1), the mass ratio of the silicon-molybdenum alloy, molybdenum carbide and silicon nitride is 1:1.5 to 2:1.

[0011] Preferably, in step (2), after adding silicon carbide fiber, stir at 300-500 rpm for 2-3 minutes, then increase to 600-900 rpm and stir for 5-10 minutes; adjust the pH of the slurry to 8.0-9.5; when adding composite carbon source in batches, add carbon black in batches first, then add graphite. After each addition of material, stir at 800-1000 rpm for 2-3 minutes, then increase to 1200-1500 rpm and stir for 3-5 minutes.

[0012] Preferably, in step (3), after adding α-SiC powder, the mixture is ball-milled at 300-500 rpm for 0.5-1 h; after adding silicon molybdenum alloy, molybdenum carbide, and silicon nitride, the mixture is ball-milled for 1-2 h; after adding water-soluble phenolic resin, the mixture is ball-milled at 300-500 rpm for 1-2 h, and the ball-milling medium is silicon carbide grinding balls with a diameter of 8 mm-20 mm.

[0013] Preferably, in step (4), the viscosity of the slurry is adjusted to 800-1200 mPa·s and then spray granulation is performed, and the moisture content of the resulting granulated powder is <2%.

[0014] Preferably, in step (5), the pressing pressure is 40-50 MPa and the pressing time is 5-15 s.

[0015] Preferably, in step (6), the silicon particles are made by mixing two specifications with diameters of 1-2 mm and 300-500 μm at a mass ratio of 1:2, and the total weight of the silicon particles is 25-30% of the weight of the green blank.

[0016] Preferably, in step (6), under a vacuum of <30 Pa and an argon atmosphere, the temperature is first increased to 600-700℃ at 1-3℃ / min and held for 1-1.5h, then increased to 800-900℃ at 1-3℃ / min and held for 1-1.5h; then increased to 1200-1400℃ at 5℃ / min and held for 1-1.5h, then increased to 1450-1650℃ and held for 10h; then decreased to 1200℃ at 1-3℃ / min, and then decreased to below 100℃ at 10℃ / min to cool and remove from the furnace.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention achieves high densification of the product through the gradation of multi-level silicon carbide powder, the design of composite carbon sources, and the in-situ reaction sintering mechanism. Specifically, three types of silicon carbide powder with different particle sizes are used to form a skeleton structure with high packing density. Carbon black and graphite are used as the main carbon sources, and the residual carbon from high-temperature resin pyrolysis is used as the secondary carbon source. The carbon reacts fully with molten silicon at high temperature, and the β-SiC generated in situ uniformly fills the pores of the green body, forming a strong bond with the original α-SiC particles, which significantly improves the density. Among them, the compound ratio of carbon black and graphite plays a key role in the bulk density and flexural strength. Appropriately increasing the carbon black content can improve the density and strength of the product, but excessive carbon black can easily cause the product to crack during sintering, which will reduce the performance. This invention achieves a balance between performance and process stability by optimizing the ratio of the two.

[0018] 2. This invention utilizes silicon carbide fibers to achieve multiple functions, including reinforcement and toughening, thermophysical property regulation, and auxiliary molding. On the one hand, silicon carbide fibers act as a skeletal support during mixing and molding, which helps in the formation of green bodies and effectively inhibits deformation and macroscopic crack generation during sintering. On the other hand, when the finished product is subjected to stress, silicon carbide fibers consume a large amount of crack propagation energy mainly through microscopic mechanisms such as crack bridging, fiber pull-out, and fiber breakage, effectively hindering further crack extension, thereby significantly improving the fracture toughness and flexural strength of the product.

[0019] 3. This invention employs a two-component dispersant system of KV5088 and polyvinylpyrrolidone (PVP), which synergistically enhances the uniformity and stability of the mixed slurry. KV5088 adsorbs onto the surface of particles such as carbon black and silicon carbide, generating electrostatic repulsion to separate the particles and reduce slurry viscosity. Furthermore, adjusting the slurry pH to a slightly alkaline level of 8.0-9.5 during the pre-dispersion stage increases the negative charge density on the carbon black surface, further strengthening the electrostatic repulsion and making the dispersion more stable. PVP improves the dispersibility of silicon carbide fibers by reducing their interfacial tension, while also providing excellent coating for the carbon black, promoting its wetting by water, effectively preventing particle agglomeration, and further improving slurry fluidity. Moreover, the pyrolysis products of PVP during subsequent sintering and degumming are mainly carbon dioxide and water, with minimal residual carbon and minimal impact on matrix properties. Based on this, phenolic resin acts as a binder, connecting the powder particles into a network structure, ensuring good formability of the green body.

[0020] 4. This invention, through a composite additive system, synergistically improves material properties from three dimensions: sintering aid, reinforcement and toughening, and mitigation of thermal mismatch, solving the technical problems of easy cracking and high brittleness in sintering of multi-curved solid plates. First, the silicon-molybdenum alloy is a Mo-Si binary alloy system with a Si content of approximately 15-30 at.%. The silicon-molybdenum alloy can react with silicon at relatively low temperatures to form molybdenum disilicide, promoting green shrinkage and early densification. Meanwhile, molybdenum carbide reacts with silicon in situ at higher temperatures to form MoSi2 and SiC. Utilizing the in-situ reinforcement effect of silicon carbide and the reaction-driven densification effect, the mechanical properties and sintering density of the material are simultaneously improved. During sintering at 1450℃-1650℃, molybdenum carbide reacts with silicon to generate MoSi2 and SiC (Mo2C+3Si→MoSi2+SiC). The newly generated MoSi2, as an in-situ reinforcing phase, maintains high strength at high temperatures, reducing material creep deformation. It also absorbs fracture energy through mechanisms such as crack deflection, bridging, and particle pull-out, improving brittleness. Simultaneously, MoSi2 can form a Si-Mo-Si system low eutectic liquid phase with excess free silicon, acting as a sintering aid, efficiently wetting SiC particles and carbon fibers, filling pores, and significantly improving density. Firstly, during cooling and subsequent use, MoSi2, as a hard second phase with extremely high high-temperature strength and creep resistance, is dispersed in the silicon carbide matrix, generating load transfer and second-phase strengthening effects, further improving the bending strength, hardness, and creep resistance of the material. Secondly, the thermal expansion coefficient of silicon nitride (Si3N4) is between that of silicon carbide and carbon fiber. When combined with MoSi2, it can effectively adjust the overall thermal expansion coefficient of the finished product, reduce thermal cracks caused by thermal mismatch during heating and cooling, and ultimately obtain defect-free, high-performance multi-curved silicon carbide whole plate products. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a picture of the product obtained after sintering in Embodiment 1 of the present invention.

[0023] Figure 2 This is a picture of the product obtained after sintering in Comparative Example 1 of this invention.

[0024] Figure 3 This is a picture of the product obtained after sintering in Comparative Example 2 of this invention.

[0025] Figure 4 This is a picture of the product obtained after sintering in Comparative Example 3 of this invention.

[0026] Figure 5 This is a picture of the product obtained after sintering in Comparative Example 4 of this invention.

[0027] Figure 6 This is a picture of the product obtained after sintering in Comparative Example 5 of this invention.

[0028] Figure 7 This is a picture of the product obtained after sintering in Comparative Example 6 of this invention.

[0029] Figure 8 This is a picture of the product obtained after sintering in Comparative Example 7 of this invention.

[0030] Figure 9 This is a picture of the product obtained after sintering in Comparative Example 8 of this invention. Detailed Implementation

[0031] This invention provides a method for preparing a reaction-sintered multi-curved silicon carbide plate, the steps of which include: 1. Weigh the raw materials and mix them in parts by weight. 100 parts of α-SiC powder (Zhejiang Carbonbang Technology Co., Ltd., model R5), with a purity ≥98%, and three particle size combinations, D50≈30μm∶D50≈10μm∶D50≈2μm=65∶25∶10; Composite carbon source: carbon black 300-600nm ∶ graphite 10-20μm = 3 ∶ 2, totaling 15-20 parts; Toughening phase: 1-2 parts silicon carbide fiber, Two types of dispersants: 0.3-0.8 parts of KV5088 dispersant (product of Zschimmer & Schwarz, Germany), and 2-3 parts of polyvinylpyrrolidone (PVP, model K30, BASF); Adhesive: 8-12 parts of water-soluble phenolic resin (Shandong Shengquan New Material Co., Ltd., resin model PF5151); Three additives are used: 0.5-1 part of silicon-molybdenum alloy, 1-2 parts of molybdenum carbide (Mo2C), and 0.5-1 part of silicon nitride. The technical effect is optimal when the mass ratio of the three is 1:1.5 to 2:1. Solvent: 42-46 parts of deionized water.

[0032] 2. Preparation of granulated powder S1. Pre-dispersion: Add polyvinylpyrrolidone (PVP) to deionized water, add silicon carbide fiber, stir at 300-500 rpm for 2-3 minutes, then increase to 600-900 rpm and stir for 5-10 minutes. Adjust the pH of the slurry to 8.0-9.5, then add KV5088 and mix for 2-3 minutes. When adding the composite carbon source in batches, first add carbon black in batches, then add graphite. After each addition, stir at 800-1000 rpm for 2-3 minutes, then increase to 1200-1500 rpm and stir for 3-5 minutes. S2. Slurry preparation: After adding SiC micro powder, ball mill at 300-500 rpm for 0.5-1 h, then add silicon molybdenum alloy, molybdenum carbide, and silicon nitride, and continue ball milling for 1-2 h. Finally, add water-soluble phenolic resin and ball mill at 300-500 rpm for 1-2 h. The ball milling media is silicon carbide grinding balls, to obtain a uniformly mixed slurry.

[0033] S3. Spray granulation: Adjust the viscosity of the mixed slurry to 800-1200 mPa·s, pump it into the spray granulation tower to prepare spherical granulated powder with a moisture content of <2%.

[0034] S4. Molding: Place the granulated powder into a hydraulic mold and press it under hydraulic pressure of 40-50MPa for 5-15s to obtain a multi-curved green body.

[0035] S5. Reaction sintering: Boron nitride coating is sprayed onto a graphite boat and dried. Supports (graphite rings or rods coated with boron nitride) are placed on the bottom and surface of the green blanks. Multiple green blanks are horizontally stacked, with adjacent layers separated by supports. Silicon particles (1-2 mm in diameter : 300-500 μm = 1 : 2) are filled between the green blanks and between the supports, with the total weight of the silicon particles being 25-30% of the weight of the green blanks. Under a vacuum of <30 Pa and an Ar atmosphere, the temperature is increased to 600-700℃ at a rate of 1-3℃ / min and held for 1-1.5 hours. Then, the temperature is increased to 800-900℃ at a rate of 1-3℃ / min and held for 1-1.5 hours. During this stage, the dispersant and phenolic resin decompose at high temperature. The heating rate is controlled to ensure that the decomposition products escape slowly, to ensure complete degreasing, and to avoid cracking caused by uneven residual carbon leading to local shrinkage differences. Then, the temperature is increased to 1200-1400℃ at a rate of 5℃ / min and held for 1-1.5h, then increased to 1450-1650℃ and held for 10h. During this stage, the holding time allows silicon to penetrate evenly and the reaction to be gradual. Sufficient holding time helps to eliminate defects and improve performance, ensuring that different parts can fully react and densify. Next, the temperature is lowered to 1200℃ at a rate of 1-3℃ / min. During this stage, the cooling rate needs to be controlled to reduce phase transformation stress and avoid large temperature differences between the inside and outside causing cracks. Then, the temperature is lowered to below 100℃ at a rate of 10℃ / min, the furnace door is opened for cooling, and the product is removed. Finally, sandblasting is performed to increase the surface smoothness of the product.

[0036] Final qualified sample performance test results: Density: 3.02-3.08 g / cm³ 3 Flexural strength: 250-380 MPa; Fracture toughness: 3.0-4.0 MPa·m 1 / 2 Vickers hardness HV1: 21-26 GPa.

[0037] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0038] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0039] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0040] The α-SiC powder used in this invention is α-phase silicon carbide, CAS number 409-21-2, which belongs to the hexagonal crystal system. It has a relatively stable structure and is usually formed under high temperature conditions above 1700℃, exhibiting high thermal stability and mechanical strength.

[0041] Example 1 This invention provides a method for preparing a reaction-sintered multi-curved silicon carbide plate, the steps of which are as follows: 1. Weigh the raw materials and mix them in parts by weight. 100 parts of α-SiC powder, with a purity of ≥98%, with three particle size combinations: D50≈30μm: D50≈10μm: D50≈2μm = 65∶25∶10; Composite carbon source: 9 parts 300-600nm carbon black, 6 parts 10-20μm graphite; Toughening phase: 1 part silicon carbide fiber; Two types of dispersants: 0.3 parts of KV5088 dispersant and 3 parts of polyvinylpyrrolidone (PVP) (model K30); Adhesive: 8 parts water-soluble phenolic resin; Additives: 0.5 parts silicon-molybdenum alloy, 1 part molybdenum carbide (Mo2C), 0.5 parts silicon nitride; Solvent: 42 parts deionized water; The total weight of silicon grains is 25% of the weight of the green blank.

[0042] 2. Preparation of granulated powder S1. Pre-dispersion: Add 3 parts polyvinylpyrrolidone to 42 parts deionized water, add 1 part silicon carbide fiber, stir at 300 rpm for 3 min, then increase to 900 rpm and stir for 5 min. Adjust the pH of the slurry to 8.0-8.5, then add KV5088 and continue mixing for 3 min. Add 9 parts carbon black in 3 batches, then add 6 parts graphite. After each addition, stir at 1000 rpm for 2 min, then increase to 1200 rpm and stir for 3 min.

[0043] S2. Slurry preparation: After adding 100 parts of α-SiC micro powder, ball mill at 300 rpm for 1 hour, then add 0.5 parts of silicon molybdenum alloy, molybdenum carbide, and silicon nitride, and continue ball milling for 2 hours. Finally, add 8 parts of water-soluble phenolic resin, and ball mill at 300 rpm for 2 hours. The ball milling media is silicon carbide grinding balls, to obtain a mixed slurry.

[0044] S3. Spray granulation: Adjust the viscosity of the mixed slurry to 800-1200 mPa·s, pump it into the spray granulation tower to prepare spherical granulated powder with a moisture content of <2%.

[0045] S4. Molding: Place the granulated powder into a hydraulic mold and press it under 40MPa hydraulic pressure for 15s to obtain a multi-curved green body.

[0046] S5. Reaction sintering: Boron nitride coating is sprayed onto a graphite boat and dried. Supports (graphite rings or rods coated with boron nitride) are placed on the bottom and surface of the green blanks. Multiple green blanks are horizontally stacked, with adjacent layers separated by supports. Silicon particles (1-2 mm in diameter: 300-500 μm = 1:2) are filled between the green blanks and between the supports, with the total weight of the silicon particles being 25% of the weight of the green blanks. With a vacuum degree <30Pa, heat to 600-650℃ at a rate of 2℃ / min and hold for 1.5h, then heat to 800-850℃ and hold for 1.5h. In an Ar atmosphere, heat to 1300-1350℃ at a rate of 5℃ / min and hold for 1h, then hold at 1450-1550℃ for 10h. Cool down to 1200℃ at a rate of 2℃ / min, then cool down to below 100℃ at a rate of 10℃ / min. Open the furnace door to cool, remove the product, and sandblast it to increase the surface smoothness.

[0047] Depend on Figure 1 It can be seen that the surface transition of the reaction-sintered multi-curved silicon carbide whole plate product is natural, and the surface is intact without cracks.

[0048] The density of the reaction-sintered multi-curved silicon carbide plate product obtained in this embodiment is 3.031 g / cm³, according to testing. 3 The flexural strength is 342 MPa, and the fracture toughness is 3.6 MPa·m. 1 / 2 Its Vickers hardness is 24.3 GPa.

[0049] Example 2 This invention provides a method for preparing a reaction-sintered multi-curved silicon carbide plate, the steps of which are as follows: 1. Weigh the raw materials and mix them in parts by weight. 100 parts of α-SiC powder, with a purity of ≥98%, with three particle size combinations: D50≈30μm: D50≈10μm: D50≈2μm = 65∶25∶10; Composite carbon source: 12 parts 300-600nm carbon black, 8 parts 10-20μm graphite; Toughening phase: 1.5 parts silicon carbide fiber; Two types of dispersants: 0.5 parts of KV5088 dispersant and 2 parts of polyvinylpyrrolidone (PVP) (model K30); Adhesive: 10 parts water-soluble phenolic resin; Three additives: 0.8 parts silicon-molybdenum alloy, 1.2 parts molybdenum carbide (Mo2C), and 0.8 parts silicon nitride; Solvent: 45 parts deionized water; The total weight of silicon grains is 28% of the weight of the green blank.

[0050] 2. Preparation of granulated powder S1. Pre-dispersion: Add 2 parts of polyvinylpyrrolidone (PVP) to 45 parts of deionized water, add 1.5 parts of silicon carbide fiber, stir at 500 rpm for 2 minutes, then increase to 900 rpm and stir for 5 minutes. Adjust the pH of the slurry to 8.5-9.0, then add 0.5 parts of KV5088, mix at 800 rpm for 2 minutes, add 12 parts of carbon black in 3 batches, then add 8 parts of graphite, stirring at 1000 rpm for 2 minutes after each addition, then increase to 1400 rpm and stir for 5 minutes.

[0051] S2. Slurry preparation: After adding 100 parts of α-SiC micro powder, ball mill at 500 rpm for 0.5 h, then add silicon molybdenum alloy, molybdenum carbide, and silicon nitride, and continue ball milling for 1.5 h. Finally, add 10 parts of water-soluble phenolic resin, and ball mill at 500 rpm for 1.5 h. The ball milling media is silicon carbide grinding balls, to obtain a mixed slurry.

[0052] S3. Spray granulation: Adjust the viscosity of the mixed slurry to 800-1200 mPa·s, pump it into the spray granulation tower to prepare spherical granulated powder with a moisture content of <2%.

[0053] S4. Molding: Place the granulated powder into a hydraulic mold and press it under 45MPa hydraulic pressure for 10s to obtain a multi-curved green body.

[0054] S5. Reaction sintering: Boron nitride coating is sprayed onto a graphite boat and dried. Graphite rods coated with boron nitride are placed on the bottom and surface of the green blanks. Multiple green blanks are horizontally stacked, with adjacent layers separated by supports. Silicon particles (1-2 mm diameter: 300-500 μm = 1:2) are filled between the green blanks and the supports, with the total weight of the silicon particles being 28% of the green blank weight. With a vacuum degree <30Pa, the temperature is increased to 650-700℃ at a rate of 3℃ / min and held for 1 hour, then increased to 850-900℃ and held for 1 hour. Under an Ar atmosphere, the temperature is increased to 1200-1300℃ at a rate of 5℃ / min and held for 1.5 hours, then increased to 1550-1650℃ and held for 10 hours. The temperature is then decreased to 1200℃ at a rate of 3℃ / min, and then decreased to below 100℃ at a rate of 10℃ / min. The furnace door is then opened for cooling, and the product is removed. Finally, sandblasting is performed to increase the surface smoothness of the product.

[0055] The density of the reaction-sintered multi-curved silicon carbide plate product obtained in this embodiment is 3.036 g / cm³, according to testing. 3 The flexural strength is 365 MPa, and the fracture toughness is 3.7 MPa·m. 1 / 2 Its Vickers hardness is 24.6 GPa.

[0056] Example 3 This invention provides a method for preparing a reaction-sintered multi-curved silicon carbide plate, the steps of which are as follows: 1. Weigh the raw materials and mix them in parts by weight. 100 parts of α-SiC powder, with a purity of ≥98%, with three particle size combinations: D50≈30μm: D50≈10μm: D50≈2μm = 65∶25∶10; Composite carbon source: 12 parts 300-600nm carbon black, 8 parts 10-20μm graphite; Toughening phase: 2 parts silicon carbide fiber; Two types of dispersants: 0.8 parts of KV5088 dispersant and 1.6 parts of polyvinylpyrrolidone (PVP) (model K30); Adhesive: 12 parts water-soluble phenolic resin; Three additives: 1 part silicon-molybdenum alloy, 2 parts molybdenum carbide (Mo2C), and 1 part silicon nitride; Solvent: 46 parts deionized water; The total weight of silicon grains is 30% of the weight of the green blank.

[0057] 2. Preparation of granulated powder S1. Pre-dispersion: Add 1.6 parts of polyvinylpyrrolidone (PVP) to 46 parts of deionized water, add 2 parts of silicon carbide fiber, stir at 400 rpm for 3 minutes, then increase to 800 rpm and stir for 8 minutes. Adjust the pH of the slurry to 9.0-9.5, then add 0.8 parts of KV5088, mix at 700 rpm for 3 minutes, add 20 parts of carbon black in 3 batches, then add 8 parts of graphite, stirring at 900 rpm for 3 minutes after each addition, then increase to 1500 rpm and stir for 3 minutes.

[0058] S2. Slurry preparation: After adding 100 parts of α-SiC micro powder, ball mill at 400 rpm for 1 hour, then add silicon molybdenum alloy, molybdenum carbide, and silicon nitride, and continue ball milling for 2 hours. Finally, add water-soluble phenolic resin and ball mill at 400 rpm for 2 hours to obtain a mixed slurry.

[0059] S3. Spray granulation: Adjust the viscosity of the mixed slurry to 800-1200 mPa·s, pump it into the spray granulation tower to prepare spherical granulated powder with a moisture content of <2%.

[0060] S4. Molding: Place the granulated powder into a hydraulic mold and press it under 50MPa hydraulic pressure for 5s to obtain a multi-curved green body.

[0061] S5. Reaction sintering: Boron nitride coating is sprayed onto a graphite boat and dried. Graphite rods coated with boron nitride are placed on the bottom and surface of the green blanks. Multiple green blanks are horizontally stacked, with adjacent layers separated by supports. Silicon particles (1-2 mm diameter: 300-500 μm = 1:2) are filled between the green blanks and the supports, with the total weight of the silicon particles being 30% of the green blank weight. With a vacuum degree <30Pa, the temperature is increased to 600-650℃ at a rate of 1℃ / min and held for 1.5h, then increased to 800-850℃ and held for 1.5h. Under an Ar atmosphere, the temperature is increased to 1250-1300℃ at a rate of 5℃ / min and held for 1h, then increased to 1500-1600℃ and held for 10h. The temperature is then decreased to 1200℃ at a rate of 1℃ / min, and then decreased to below 100℃ at a rate of 10℃ / min. The furnace door is then opened for cooling, and the product is removed. Finally, sandblasting is performed to increase the surface smoothness of the product.

[0062] The density of the reaction-sintered multi-curved silicon carbide plate product obtained in this embodiment is 3.049 g / cm³. 3 The flexural strength is 369 MPa, and the fracture toughness is 3.8 MPa·m. 1 / 2 Its Vickers hardness is 25.1 GPa.

[0063] Comparative Example 1 A method for preparing a silicon carbide plate, comprising the following steps: 1. Weigh the raw materials and mix them in parts by weight. 100 parts of α-SiC powder, with a purity of ≥98%, with three particle size combinations: D50≈30μm: D50≈10μm: D50≈2μm = 65∶25∶10; Carbon source: 20 parts of 300-600nm carbon black; Toughening phase: 1 part silicon carbide fiber; Two types of dispersants: 0.3 parts of KV5088 dispersant and 3 parts of polyvinylpyrrolidone (PVP) (model K30); Adhesive: 8 parts water-soluble phenolic resin; Two types of additives: 0.9 parts Al2O3 and 0.6 parts Y2O3; Solvent: 42 parts deionized water; The total weight of silicon grains is 25% of the weight of the green blank.

[0064] 2. Preparation of granulated powder S1. Pre-dispersion: Add 20 parts of carbon black in 3 portions, and the rest is the same as in Example 1.

[0065] S2. Pulping: After adding 100 parts of α-SiC micro powder, ball mill at 300 rpm for 1 hour, then add 0.9 parts of Al2O3 and 0.6 parts of Y2O3, and the rest is the same as in Example 1.

[0066] S3. Spray granulation: Same as in Example 1.

[0067] S4. Molding: Same as in Example 1.

[0068] S5. Reaction sintering: With a vacuum degree <30Pa, heat to 600-650℃ at a rate of 10℃ / min and hold for 1.5h, then heat to 800-850℃ and hold for 1.5h. In an Ar atmosphere, heat to 1300-1350℃ at a rate of 10℃ / min and hold for 1h, then heat to 1450-1600℃ and hold for 10h. Cool down to below 100℃ at a rate of 10℃ / min and remove the product. The preparation work and silicon particle dosage are the same as in Example 1.

[0069] Figure 2 The image shows a reaction-sintered multi-curved silicon carbide plate product after sintering in Comparative Example 1. Graphite rods are placed on the product surface to isolate different green blanks, and the surface is covered with residual silicon. It can be seen that the upper half of the product exhibits a transverse fracture, and the transverse crack in the middle extends to the lower left to form a longitudinal crack.

[0070] The density of the reaction-sintered multi-curved silicon carbide plate obtained in this comparative example is 3.013 g / cm³. 3 Due to severe product defects, no other performance tests were conducted.

[0071] Comparative Example 2 A method for preparing a silicon carbide plate, comprising the following steps: 1. Weigh the raw materials and mix them in parts by weight. 100 parts of α-SiC powder, with a purity of ≥98%, with three particle size combinations: D50≈30μm: D50≈10μm: D50≈2μm = 65∶25∶10; Composite carbon source: 9 parts 300-600nm carbon black, 6 parts 10-20μm graphite; Toughening phase: 1 part silicon carbide fiber; Two types of dispersants: 0.3 parts of KV5088 dispersant and 3 parts of polyvinylpyrrolidone (PVP) (model K30); Adhesive: 8 parts water-soluble phenolic resin; Two types of additives: 0.9 parts Al2O3 and 0.6 parts Y2O3; Solvent: 42 parts deionized water; The total weight of silicon grains is 25% of the weight of the green blank.

[0072] 2. Preparation of granulated powder S1. Pre-dispersion: Same as in Example 1.

[0073] S2. Pulping: After adding 100 parts of α-SiC micro powder, ball mill at 300 rpm for 1 hour, then add 0.9 parts of Al2O3 and 0.6 parts of Y2O3, and the rest is the same as in Example 1.

[0074] S3. Spray granulation: Same as in Example 1.

[0075] S4. Molding: Same as in Example 1.

[0076] S5. Reaction sintering: Same as comparative example 1.

[0077] Figure 3 The image shows a reaction-sintered multi-curved silicon carbide plate after preliminary cleaning following sintering in Comparative Example 2 (the surface deposits are residual silicon). S-shaped cracks are present in the upper part of the product, with deeper cracks at the side edges and shallower cracks near the top. This indicates that compared to Comparative Example 1, which uses only carbon black as the carbon source, Comparative Example 2 uses a combination of carbon black and graphite as the carbon source, which can reduce the degree of transverse fracture in the product.

[0078] The density of the reaction-sintered multi-curved silicon carbide plate obtained in this comparative example is 3.017 g / cm³. 3 The Vickers hardness HV1 is 22.4 GPa. Due to severe product defects, no other performance tests were conducted.

[0079] Comparative Example 3 A method for preparing a silicon carbide plate, comprising the following steps: 1. Weigh the raw materials and mix them in parts by weight. 100 parts of α-SiC powder, with a purity of ≥98%, with three particle size combinations: D50≈30μm: D50≈10μm: D50≈2μm = 65∶25∶10; Carbon source: 20 parts of 300-600nm carbon black; Toughening phase: 1 part silicon carbide fiber; Two types of dispersants: 0.3 parts of KV5088 dispersant and 3 parts of polyvinylpyrrolidone (PVP) (model K30); Adhesive: 8 parts water-soluble phenolic resin; One type of additive: 1.5 parts of molybdenum carbide (Mo2C); Solvent: 42 parts deionized water; The total weight of silicon grains is 25% of the weight of the green blank.

[0080] 2. Preparation of granulated powder S1. Pre-dispersion: Add 20 parts of carbon black in 3 portions, and the rest is the same as in Example 1.

[0081] S2. Pulping: Add 100 parts of α-SiC micro powder and ball mill at 300 rpm for 1 hour, then add 1.5 parts of molybdenum carbide (Mo2C), and the rest is the same as in Example 1.

[0082] S3. Spray granulation: Same as in Example 1.

[0083] S4. Molding: Same as in Example 1.

[0084] S5. Reaction sintering: Same as comparative example 1.

[0085] Figure 4 The image shown in Comparative Example 3 is of the product after it has been removed from the furnace (the surface deposits are residual silicon). A transverse crack can be seen extending from the lower left corner of the product to the middle and right edge. The crack depth at the lower left corner exceeds half the thickness of the product, and the crack gradually becomes shallower from left to right.

[0086] In Comparative Example 1, 0.9 parts of Al2O3 and 0.6 parts of Y2O3 were added as additives. In this comparative example, the additive was 1.5 parts of molybdenum carbide (Mo2C). The crack defects in Comparative Example 3 were shallower than those in Comparative Example 1, indicating that the additive in Comparative Example 3 was more effective than that in Comparative Example 1.

[0087] The density of the reaction-sintered multi-curved silicon carbide plate obtained in this comparative example is 3.024 g / cm³. 3 The Vickers hardness HV1 is 23.5 GPa. Due to obvious product defects, no other performance tests were conducted.

[0088] Comparative Example 4 A method for preparing a silicon carbide plate, comprising the following steps: 1. Weigh the raw materials and mix them in parts by weight. 100 parts of α-SiC powder, with a purity of ≥98%, with three particle size combinations: D50≈30μm: D50≈10μm: D50≈2μm = 65∶25∶10; Composite carbon source: 9 parts 300-600nm carbon black, 6 parts 10-20μm graphite; Toughening phase: 1 part silicon carbide fiber; Two types of dispersants: 0.3 parts of KV5088 dispersant and 3 parts of polyvinylpyrrolidone (PVP) (model K30); Adhesive: 8 parts water-soluble phenolic resin; One type of additive: 1.5 parts of molybdenum carbide (Mo2C); Solvent: 42 parts deionized water; The total weight of silicon grains is 25% of the weight of the green blank.

[0089] 2. Preparation of granulated powder S1. Pre-dispersion: Same as in Example 1.

[0090] S2. Pulping: Add 100 parts of α-SiC micro powder and ball mill at 300 rpm for 1 hour, then add 1.5 parts of molybdenum carbide (Mo2C), and the rest is the same as in Example 1.

[0091] S3. Spray granulation: Same as in Example 1.

[0092] S4. Molding: Same as in Example 1.

[0093] S5. Reaction sintering: Same as comparative example 1.

[0094] Figure 5 The image shows the reaction-sintered multi-curved silicon carbide plate product after exiting the furnace in Comparative Example 4 (the surface deposits are residual silicon). A distinct transverse S-shaped crack is visible in the lower center of the front of the product. The crack depth is shallower than that in Comparative Example 3. Compared to Comparative Example 3, which uses carbon black as the sole carbon source, this comparative example demonstrates that using a composite carbon source of carbon black and graphite can mitigate crack defects. Comparative Example 4 differs from Comparative Example 2 in its additives. Comparative Example 4 uses the same weight proportion of molybdenum carbide as an additive, yet its crack depth is less than that of Comparative Example 2. This indicates that the technical effect of using molybdenum carbide in Comparative Example 4 is superior to that of using alumina and yttrium oxide in Comparative Example 2.

[0095] The density of the reaction-sintered multi-curved silicon carbide plate obtained in this comparative example is 3.037 g / cm³. 3 The Vickers hardness HV1 is 23.6 GPa. Due to obvious product defects, no other performance tests were conducted.

[0096] Comparative Example 5 A method for preparing a silicon carbide plate, comprising the following steps: 1. Weigh the raw materials and mix them in parts by weight. 100 parts of α-SiC powder, with a purity of ≥98%, with three particle size combinations: D50≈30μm: D50≈10μm: D50≈2μm = 65∶25∶10; Composite carbon source: 9 parts 300-600nm carbon black, 6 parts 10-20μm graphite; Toughening phase: 1 part silicon carbide fiber; Two types of dispersants: 0.3 parts of KV5088 dispersant and 3 parts of polyvinylpyrrolidone (PVP) (model K30); Adhesive: 8 parts water-soluble phenolic resin; One type of additive: 1.5 parts of molybdenum carbide (Mo2C); Solvent: 42 parts deionized water; The total weight of silicon grains is 25% of the weight of the green blank.

[0097] 2. Preparation of granulated powder S1. Pre-dispersion: Same as in Example 1.

[0098] S2. Pulping: Add 100 parts of α-SiC micro powder and ball mill at 300 rpm for 1 hour, then add 1.5 parts of molybdenum carbide (Mo2C), and the rest is the same as in Example 1.

[0099] S3. Spray granulation: Same as in Example 1.

[0100] S4. Molding: Same as in Example 1.

[0101] S5. Reaction sintering: Same as in Example 1.

[0102] Down Figure 6 The image shows the reaction-sintered multi-curved silicon carbide plate product of Comparative Example 5 (the surface dots represent residual silicon). Cracks of 5-8 cm are visible on both the right and bottom edges. The crack defects are less severe than in Comparative Example 4, indicating that reducing the heating and cooling rates helps mitigate crack defects. Comparing the results of Comparative Example 5 with those of Example 1, it is clear that molybdenum carbide as an additive in Comparative Example 5 cannot completely solve the technical problem of surface cracks in the product.

[0103] The density of the reaction-sintered multi-curved silicon carbide plate obtained in this comparative example is 3.039 g / cm³. 3 The Vickers hardness HV1 is 23.6 GPa.

[0104] Comparative Example 6 A method for preparing a silicon carbide plate, comprising the following steps: 1. Weigh the raw materials and mix them in parts by weight. 100 parts of α-SiC powder, with a purity of ≥98%, with three particle size combinations: D50≈30μm: D50≈10μm: D50≈2μm = 65∶25∶10; Composite carbon source: 9 parts 300-600nm carbon black, 6 parts 10-20μm graphite; Toughening phase: 1 part silicon carbide fiber; Two types of dispersants: 0.3 parts of KV5088 dispersant and 3 parts of polyvinylpyrrolidone (PVP) (model K30); Adhesive: 8 parts water-soluble phenolic resin; Additives: 1.5 parts silicon nitride; Solvent: 42 parts deionized water; The total weight of silicon grains is 25% of the weight of the green blank.

[0105] 2. Preparation of granulated powder S1. Pre-dispersion: Same as in Example 1.

[0106] S2. Slurry preparation: After adding 100 parts of α-SiC micro powder, ball mill at 300 rpm for 1 hour, then add 1.5 parts of silicon nitride, and the rest is the same as in Example 1.

[0107] S3. Spray granulation: Same as in Example 1.

[0108] S4. Molding: Same as in Example 1.

[0109] S5. Reaction sintering: Same as in Example 1.

[0110] Figure 7 The image shows the reaction-sintered multi-curved silicon carbide plate product of Comparative Example 6 after it exits the furnace (the surface deposits are residual silicon). Y-shaped cracks are visible in the lower middle section, and the length and depth of these cracks are greater than those in Comparative Example 5. This indicates that the use of silicon nitride as an additive in Comparative Example 6 is less effective than the use of molybdenum carbide in Comparative Example 5. Compared to Example 1, Comparative Example 6 demonstrates that the combination of silicon-molybdenum alloy, molybdenum carbide (Mo2C), and silicon nitride in Example 1 effectively solves the crack defects in the multi-curved silicon carbide plate.

[0111] The density of the reaction-sintered multi-curved silicon carbide plate obtained in this comparative example is 3.02 g / cm³. 3 The Vickers hardness HV1 is 22.5 GPa. Due to obvious product defects, no other performance tests were conducted.

[0112] Comparative Example 7 A method for preparing a silicon carbide plate, comprising the following steps: 1. Weigh the raw materials and mix them in parts by weight. 100 parts of α-SiC powder, with a purity of ≥98%, with three particle size combinations: D50≈30μm: D50≈10μm: D50≈2μm = 65∶25∶10; Composite carbon source: 9 parts 300-600nm carbon black, 6 parts 10-20μm graphite; Toughening phase: 1 part silicon carbide fiber; Two types of dispersants: 0.3 parts of KV5088 dispersant and 3 parts of polyvinylpyrrolidone (PVP) (model K30); Adhesive: 8 parts water-soluble phenolic resin; Two types of additives: 1 part molybdenum carbide (Mo2C) and 0.5 parts silicon nitride; Solvent: 42 parts deionized water; The total weight of silicon grains is 25% of the weight of the green blank.

[0113] 2. Preparation of granulated powder S1. Pre-dispersion: Same as in Example 1.

[0114] S2. Pulping: After adding 100 parts of α-SiC micro powder, ball mill at 300 rpm for 1 hour, then add 1 part of molybdenum carbide (Mo2C) and 0.5 parts of silicon nitride, and the rest is the same as in Example 1.

[0115] S3. Spray granulation: Same as in Example 1.

[0116] S4. Molding: Same as in Example 1.

[0117] S5. Reaction sintering: Same as in Example 1.

[0118] Figure 8 The image shows the reaction-sintered multi-curved silicon carbide plate product of Comparative Example 7 after it exits the furnace (the surface dots are residual silicon). Shallow cracks are visible on the right edge, shallower and fewer in number than those in Comparative Example 5. This indicates that the 2:1 mixture of molybdenum carbide and silicon nitride used as an additive in Comparative Example 7 is more effective than using molybdenum carbide alone as an additive in Comparative Example 5. Compared to the results of Example 1, it is clear that using a 2:1 mixture of molybdenum carbide and silicon nitride as an additive in Comparative Example 7 still failed to solve the technical problem of product cracks.

[0119] The density of the reaction-sintered multi-curved silicon carbide plate obtained in this comparative example is 3.024 g / cm³. 3 The Vickers hardness HV1 is 22.9 GPa. Due to obvious product defects, no other performance tests were conducted.

[0120] Comparative Example 8 A method for preparing a silicon carbide plate, comprising the following steps: 1. Weigh the raw materials and mix them in parts by weight. 100 parts of α-SiC powder, with a purity of ≥98%, with three particle size combinations: D50≈30μm: D50≈10μm: D50≈2μm = 65∶25∶10; Composite carbon source: 12 parts 300-600nm carbon black, 8 parts 10-20μm graphite; Toughening phase: 1.5 parts silicon carbide fiber; Two types of dispersants: 0.5 parts of KV5088 dispersant and 2 parts of polyvinylpyrrolidone (PVP) (model K30); Adhesive: 10 parts water-soluble phenolic resin; Three additives: 0.5 parts silicon-molybdenum alloy, 0.5 parts molybdenum carbide (Mo2C), and 0.5 parts silicon nitride; Solvent: 45 parts deionized water; The total weight of silicon grains is 28% of the weight of the green blank.

[0121] 2. Preparation of granulated powder S1. Pre-dispersion: Same as in Example 1.

[0122] S2. Slurry preparation: After adding 100 parts of α-SiC micro powder, ball mill at 300 rpm for 1 hour, then add 0.5 parts of silicon-molybdenum alloy, 0.5 parts of molybdenum carbide (Mo2C), and 0.5 parts of silicon nitride, and the rest is the same as in Example 1.

[0123] S3. Spray granulation: Same as in Example 1.

[0124] S4. Molding: Same as in Example 1.

[0125] S5. Reaction sintering: Same as in Example 1.

[0126] Figure 9 The image shows a reaction-sintered multi-curved silicon carbide plate product after sandblasting in Comparative Example 8. Shallow cracks are visible on the bottom edge. These shallow cracks were not visible to the naked eye before sandblasting but are visible after sandblasting.

[0127] This indicates that the 1:1:1 mixture of silicon-molybdenum alloy, molybdenum carbide, and silicon nitride used in Comparative Example 8 is more effective than the 2:1 mixture of molybdenum carbide and silicon nitride used in Comparative Example 7. Comparing Comparative Example 8 with Example 1 shows that the 1:2:1 mixture of silicon-molybdenum alloy, molybdenum carbide, and silicon nitride used in Example 1 can eliminate latent cracks on the product surface and improve the product's density, flexural strength, and fracture toughness.

[0128] The density of the reaction-sintered multi-curved silicon carbide plate obtained in this comparative example is 3.023 g / cm³. 3 The flexural strength is 323 MPa, and the fracture toughness is 3.4 MPa·m. 1 / 2 Its Vickers hardness is 23.2 GPa.

Claims

1. A method for preparing a reaction-sintered multi-curved silicon carbide plate, characterized in that, Includes the following steps: (1) Weigh out 100 parts by weight of α-SiC powder, 15-20 parts by weight of composite carbon source, 1-2 parts by weight of silicon carbide fiber, 2.3-3.8 parts by weight of dispersant, 8-12 parts by weight of water-soluble phenolic resin, 2-4 parts by weight of additives and 42-46 parts by weight of water. The dispersant is KV5088 and polyvinylpyrrolidone. The additives are a mixture of silicon molybdenum alloy, molybdenum carbide and silicon nitride. The composite carbon source is composed of carbon black and graphite in a mass ratio of 3:

2. (2) Dissolve polyvinylpyrrolidone in water, add silicon carbide fiber and stir, adjust the pH of the slurry to weak alkalinity, then add KV5088 and mix, add the composite carbon source in batches and stir to obtain a pre-dispersed slurry; (3) Add the α-SiC powder to the pre-dispersed slurry and ball mill at a set rate, then add the additive and continue ball milling, and finally add water-soluble phenolic resin and ball mill to obtain a mixed slurry; (4) The mixed slurry is spray-granulated to obtain spherical granulated powder; (5) Press the spherical granulated powder to obtain a multi-curved green body; (6) The multi-curved green blank is placed on a graphite boat and subjected to reaction sintering to obtain a multi-curved silicon carbide plate.

2. The preparation method according to claim 1, characterized in that, In step (1), the α-SiC powder is composed of three particle sizes, D50≈30μm, D50≈10μm and D50≈2μm, in a mass ratio of 65:25:10; the purity of the α-SiC powder is ≥98%.

3. The preparation method according to claim 1, characterized in that, In step (1), the carbon black has a particle size of 300-600 nm and the graphite has a particle size of 10-20 μm.

4. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of the silicon-molybdenum alloy, molybdenum carbide and silicon nitride is 1:1.5 to 2:

1.

5. The preparation method according to claim 1, characterized in that, In step (2), after adding silicon carbide fiber, stir at 300-500 rpm for 2-3 minutes, then increase to 600-900 rpm and stir for 5-10 minutes; adjust the pH of the slurry to 8.0-9.5; when adding composite carbon source in batches, add carbon black in batches first, then add graphite. After each addition of material, stir at 800-1000 rpm for 2-3 minutes, then increase to 1200-1500 rpm and stir for 3-5 minutes.

6. The preparation method according to claim 1, characterized in that, In step (3), after adding α-SiC powder, ball milling is performed at 300-500 rpm for 0.5-1 h; after adding silicon molybdenum alloy, molybdenum carbide, and silicon nitride, ball milling continues for 1-2 h; after adding water-soluble phenolic resin, ball milling is performed at 300-500 rpm for 1-2 h, and the ball milling medium is silicon carbide grinding balls.

7. The preparation method according to claim 1, characterized in that, In step (4), the viscosity of the slurry is adjusted to 800-1200 mPa·s and then spray granulation is performed, and the moisture content of the resulting granulated powder is <2%.

8. The preparation method according to claim 1, characterized in that, In step (5), the pressing pressure is 40-50 MPa and the pressing time is 5-15 s.

9. The preparation method according to claim 1, characterized in that, In step (6), the silicon particles are made of two specifications with diameters of 1-2 mm and 300-500 μm, mixed at a mass ratio of 1:2, and the total weight of the silicon particles is 25-30% of the weight of the green blank.

10. The preparation method according to any one of claims 1-9, characterized in that, In step (6), under a vacuum of <30 Pa and an argon atmosphere, the temperature is first increased to 600-700℃ at 1-3℃ / min and held for 1-1.5h, then increased to 800-900℃ at 1-3℃ / min and held for 1-1.5h; then increased to 1200-1400℃ at 5℃ / min and held for 1-1.5h, then increased to 1450-1650℃ and held for 10h; then decreased to 1200℃ at 1-3℃ / min, and then decreased to below 100℃ to cool and remove from the furnace.

Images