Method for producing silicon carbide parts based on gelcasting

Abstract

The application discloses a silicon carbide part preparation method based on gel injection molding, and steps include: mixing and ball-milling silicon carbide powder, carbon black, phenolic resin, solvent, dispersing agent and acrylic crosslinking agent to obtain first slurry; adding curing agent to the first slurry, continuing ball-milling, and removing bubbles to obtain second slurry; pouring the second slurry into a polypropylene mold, curing, and demolding to obtain a wet blank; drying and sintering the wet blank to obtain a silicon carbide part. The method has high uniformity, low defect control and complex shape manufacturing capacity, can be used for preparing large-size silicon carbide devices, and is suitable for industrial large-scale production. Phenolic resin and acrylic crosslinking agent are used as binders, gradient curing can be performed to prevent particle sedimentation, uniform blanks can be generated, and nano-carbon can be generated by pyrolysis of phenolic resin, which can fill pores, inhibit the formation of silicon points, and in-situ generate nano-silicon carbide, so that the density and mechanical properties of the sintered body are significantly improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of silicon carbide ceramic material preparation, and particularly relates to a silicon carbide part preparation method based on gel injection molding. BACKGROUND

[0002] With the rapid development of the semiconductor industry, silicon carbide has become a key advanced material for manufacturing many high-temperature and corrosive environment core components such as oxidation furnaces, diffusion furnaces, epitaxial reactors, etching equipment cavities and boat racks, due to its excellent high-temperature mechanical properties, outstanding chemical stability, low thermal expansion coefficient and excellent thermal shock resistance. Compared with traditional quartz or silicon-based materials, silicon carbide parts can operate stably for a long time under extreme conditions above 1300℃, fundamentally overcoming the problems of high-temperature softening, creep and particle contamination, and significantly improving the reliability, service life and process cleanliness of semiconductor equipment.

[0003] However, the preparation of high-performance and complex-shaped silicon carbide parts suitable for the semiconductor field still has obvious technical bottlenecks. The acrylamide system used in traditional gel injection molding not only has biological toxicity, but also easily causes component segregation between organic monomers and ceramic powders due to its oxygen inhibition effect, and the carbon powder is difficult to disperse uniformly, resulting in low green body strength, many defects and low sintering yield. Although the grouting forming process is simple, the serious powder sedimentation and component gradient will form local silicon pools and abnormal grain growth in the subsequent reaction sintering, which becomes the crack initiation source of the part in thermal cycling, seriously restricting its service life. The 3D printing technology based on photocuring provides a possibility for complex structure forming, but it faces high printing cost, insufficient efficiency and the problem of slurry stability and sedimentation which is difficult to solve completely. Although the gel injection molding system using phenolic / epoxy resin partially improves the dispersion stability and oxygen inhibition contradiction, the solid content is limited (usually below 35%), resulting in unsatisfactory green body density and uniformity, and there are still silicon phase aggregation and pore residues in the sintering densification process, affecting the mechanical and thermal properties of the final part. SUMMARY

[0004] The technical problem solved by the present application is to provide a silicon carbide part preparation method based on gel injection molding, which takes into account high uniformity, low defect control and complex shape manufacturing capability, in view of the shortcomings of the prior art.

[0005] To solve the above technical problems, the technical scheme adopted by the present application is as follows:

[0006] A silicon carbide part preparation method based on gel injection molding, comprising the following steps:

[0007] (1) mixing and ball-milling silicon carbide powder, carbon black, phenolic resin, solvent, dispersant and acrylic crosslinking agent to obtain a first slurry;

[0008] (2) adding a curing agent to the first slurry, continuing ball milling, and removing bubbles to obtain a second slurry;

[0009] (3) pouring the second slurry into a polypropylene mold, curing, and demolding to obtain a wet blank;

[0010] (4) drying and sintering the wet blank to obtain a silicon carbide part;

[0011] The curing agent reacts with the phenolic resin to produce water molecules, and the water molecules solidify the acrylic crosslinking agent.

[0012] In the above-mentioned method for preparing a silicon carbide part based on gel injection molding, preferably, in step (1), the silicon carbide powder is 60% to 80% by mass, the carbon black is 5% to 10% by mass, the phenolic resin is 1% to 5% by mass, the solvent is 5% to 20% by mass, the acrylic crosslinking agent is 5% to 10% by mass, and the dispersant is 0 to 1.5% by mass.

[0013] In the above-mentioned method for preparing a silicon carbide part based on gel injection molding, preferably, in step (1), the phenolic resin is at least one selected from Resole type phenolic resin and Novolac type phenolic resin, the acrylic crosslinking agent is at least one of EBECRYL acrylic crosslinking agents, the solvent is ethyl acetate or butyl acetate, and the dispersant is at least one of PEG200, PEG400, and PEG600; in step (2), the curing agent is a room temperature curing agent that can crosslink and solidify the phenolic resin at room temperature, and the room temperature is 20°C to 30°C.

[0014] In the above-mentioned method for preparing a silicon carbide part based on gel injection molding, preferably, in step (2), the curing agent is urotropine curing agent or NL curing agent.

[0015] In the above-mentioned method for preparing a silicon carbide part based on gel injection molding, preferably, in step (2), the amount of the curing agent is 5% to 15% of the mass of the phenolic resin.

[0016] In the above-mentioned method for preparing a silicon carbide part based on gel injection molding, preferably, in step (1), the ball milling medium is any one of zirconium oxide, aluminum oxide, silicon carbide, and silicon nitride balls, the mass ratio of the ball milling medium to the silicon carbide powder is 1 to 3:1, and the ball milling time is 6 h to 24 h.

[0017] In the above-mentioned method for preparing a silicon carbide part based on gel injection molding, preferably, in step (2), the time for continuing ball milling is 5 min to 10 min.

[0018] Preferably, in the step (2), the defoaming time is 20 min to 60 min, and the defoaming vacuum degree is 100 Pa to 1000 Pa.

[0019] Preferably, in the step (4), the drying temperature is 20℃ to 45℃, and the drying time is 12 h to 24 h.

[0020] Preferably, in the step (4), the sintering is to cover the dried green body obtained after drying with silicon particles, and the sintering temperature is 1500℃ to 1700℃, the holding time is 2 h to 6 h, and the heating rate is 1℃ / min to 5℃ / min.

[0021] Compared with the prior art, the present application has the following advantages:

[0022] (1) The present application is based on the gel injection molding of the silicon carbide part preparation method, which realizes high solid content slurry preparation by using low viscosity solvent / binder system, and cooperates with the gradient curing of phenolic resin and acrylic crosslinking agent to prevent the sedimentation of silicon carbide particles. The curing system itself does not have the problem of oxygen inhibition, and can realize rapid curing to prevent sedimentation. Specifically, phenolic resin and acrylic crosslinking agent are used as binders and solvents to form a low viscosity liquid phase system, which is much lower than the liquid phase viscosity of phenolic / epoxy resin gel injection molding system, so that more silicon carbide powder can be added to obtain a slurry with high solid content (more than 45%). High solid content slurry can form high density green body, effectively inhibit the generation of silicon point in the reaction sintering process, and significantly improve the service life of the product. The high solid content system greatly reduces the drying shrinkage rate of the cured slurry, not only improves the forming size precision, but also effectively reduces the defects. The water molecules released during the curing of the curing agent and the phenolic resin can promote the curing reaction of the acrylic crosslinking agent, and the two cooperate in sequence to form a high-strength blank, which provides reliable support for the subsequent drying, transfer and sintering process. In the sintering process, the pyrolysis of phenolic resin generates nano-carbon, which can not only fill the pores and inhibit the formation of silicon points, but also generate nano-silicon carbide in situ, significantly improving the density and mechanical properties of the sintered body. The method has high uniformity, low defect control and complex shape manufacturing capacity, and can be used to prepare large-size silicon carbide devices, and is suitable for industrial large-scale production. Moreover, the phenolic resin and acrylic crosslinking agent used as binders are non-toxic and harmless, and meet the green environmental protection requirements.

[0023] (2) The silicon carbide part preparation method based on gel casting molding of the present application can precisely control the curing behavior of the slurry by adjusting the addition amount of the curing agent, realizes process controllability; at the same time, the viscosity of the system after curing is improved, effectively inhibits particle sedimentation, ensures the stability of the slurry, and further ensures the uniformity of the green body.

[0024] (3) The silicon carbide part preparation method based on gel casting molding of the present application selects a solvent with small surface tension such as ethyl acetate or butyl acetate, which can reduce the drying capillary force to further avoid drying defects, and at the same time, the low boiling point characteristics of such solvents can be used to realize rapid drying, greatly improving the preparation efficiency of the green body. DETAILED DESCRIPTION

[0025] The present application will be further described below in combination with specific preferred embodiments, but the protection scope of the present application is not limited thereby. The materials and instruments used in the following examples are all commercially available, wherein the silicon carbide powder is purchased from Weifang Kaixia Silicon Carbide Micro Powder Co., Ltd., product model F240 and F1200, D50 of F240 = 48 μm, D50 of F1200 = 3.8 μm. The carbon black is purchased from Tianjin Tianyi Century Chemical Product Science and Technology Development Co., Ltd., D50 = 60 nm; the PEG400 dispersant is purchased from the National Pharmaceutical Group Chemical Reagent Co., Ltd.; the acrylic crosslinking agent is EBECRYL acrylic crosslinking agent, purchased from Allnex Company, product model EBECRYL-4765; the phenolic resin is 2140 phenolic resin, purchased from Zhejiang Jiemin New Material Co., Ltd.; the curing agent is NL-curing agent, purchased from Zhejiang Jiemin New Material Co., Ltd. In the following examples, the room temperature usually refers to 20℃-30℃.

[0026] Example 1

[0027] A silicon carbide part preparation method based on gel casting molding of the present application takes the preparation of silicon carbide furnace tube as an example, which includes the following steps:

[0028] (1) 3000g of F240 silicon carbide powder, 1000g of F1200 silicon carbide powder, 400g of carbon black, 240g of phenolic resin, 900g of butyl acetate, 80g of PEG400 dispersant and 500g of acrylic crosslinking agent are weighed and placed in a ball mill tank for mixing and ball milling, the ball milling medium is silicon carbide ball, the mass ratio of the ball milling medium to the silicon carbide powder is 2:1, and the ball milling time is 12h;

[0029] (2) 24g of NL-curing agent is added to the first slurry, and the ball milling is continued for 5min, then the slurry is poured into a stirring vacuum degassing machine for degassing, the degassing time is 30min, and the vacuum degree of degassing is 500Pa;

[0030] (3) Pour the second slurry into a polypropylene mold, and solidify, the mold height is 1000 mm, the inner diameter is 240 mm, and the outer diameter is 252 mm, and a wet blank is obtained after demolding;

[0031] (4) Naturally dry the wet blank at a temperature of 20 ℃ for 18 h to obtain a dry blank, and the dry blank is buried with silicon particles and placed in a vacuum sintering furnace for sintering, the sintering temperature is 1600 ℃, the heating rate before 1200 ℃ is 1 ℃ / min, the heating rate from 1200 ℃ to 1600 ℃ is 5 ℃ / min, the holding time is 3 h, and the vacuum degree is controlled to be less than 10 Pa during the sintering process; the sintered blank body is taken out, and the surface silicon particles are removed to obtain a silicon carbide furnace tube.

[0032] The NL-curing agent can react with the phenolic resin at room temperature to release water molecules in situ, which can be used to cure the acrylic crosslinking agent, and of course, curing agents with the same effect such as urushiol curing agent can also be used in other embodiments.

[0033] Of course, in other embodiments, the silicon carbide powder can also be used in only one particle size specification, but the effect is not as good as that of the grading of different coarse and fine specifications, and other particle sizes of coarse particles and fine particles can also be preferably used for grading in the application, the average particle size of the coarse particles is 30 μm-100 μm, the average particle size of the fine particles is 2 μm-10 μm, and the mass ratio of the coarse particles to the fine particles is preferably 2-4:1.

[0034] Example 2

[0035] A silicon carbide part preparation method based on gel injection molding, taking the preparation of a silicon carbide furnace tube as an example, comprises the following steps:

[0036] (1) Put 3200 g of F240 silicon carbide powder, 800 g of F1200 silicon carbide powder, 500 g of carbon black, 240 g of phenolic resin, 950 g of butyl acetate, 80 g of PEG400 dispersant and 550 g of acrylic crosslinking agent into a ball mill tank for mixing and ball milling, the ball milling medium is silicon carbide balls, the mass ratio of the ball milling medium to the silicon carbide powder is 2:1, and the ball milling time is 24 h;

[0037] (2) Add 30 g of NL-curing agent to the first slurry, continue to ball mill for 5 min, pour the slurry into a stirring vacuum degassing machine for degassing, obtain the second slurry, the degassing time is 30 min, and the vacuum degree of degassing is 500 Pa;

[0038] (3) Pour the second slurry into a polypropylene mold, and solidify, the mold height is 1000 mm, the inner diameter is 240 mm, and the outer diameter is 252 mm, and a wet blank is obtained after demolding;

[0039] (4) the wet body is naturally dried at 20℃ for 24 h to obtain a dry body, the dry body is buried with silicon particles, and is placed into a vacuum sintering furnace to be sintered, the sintering temperature is 1600℃, the temperature rising rate before 1200℃ is 1℃ / min, the temperature rising rate from 1200℃ to 1600℃ is 5℃ / min, the holding time is 3h, and the vacuum degree is controlled to be less than 10 Pa during the sintering process; the sintered body is taken out, and the surface silicon particles are removed to obtain a silicon carbide furnace tube.

[0040] Example 3

[0041] A silicon carbide part preparation method based on gel casting, taking preparation of a silicon carbide furnace tube as an example, comprises the following steps:

[0042] (1) 3000g of F240 silicon carbide powder, 1000g of F1200 silicon carbide powder, 350g of carbon black, 300g of phenolic resin, 850g of butyl acetate, 70g of PEG400 dispersant and 500g of acrylic crosslinking agent are placed in a ball mill tank to mix and ball mill, the ball mill medium is silicon carbide ball, the mass ratio of the ball mill medium to the silicon carbide powder is 2:1, and the ball mill time is 18h;

[0043] (2) 30g of NL-curing agent is added to the first slurry, and the ball milling is continued for 5min, the slurry is poured into a stirring vacuum degassing machine to be degassed, the second slurry is obtained, the degassing time is 30min, and the vacuum degree of degassing is 500Pa;

[0044] (3) the second slurry is poured into a polypropylene mold to be cured, the mold height is 1000mm, the inner diameter is 240mm, and the outer diameter is 252mm, and the wet body is obtained after demolding;

[0045] (4) the wet body is naturally dried at 20℃ for 24 h to obtain a dry body, the dry body is buried with silicon particles, and is placed into a vacuum sintering furnace to be sintered, the sintering temperature is 1600℃, the temperature rising rate before 1200℃ is 1℃ / min, the temperature rising rate from 1200℃ to 1600℃ is 5℃ / min, the holding time is 3h, and the vacuum degree is controlled to be less than 10 Pa during the sintering process; the sintered body is taken out, and the surface silicon particles are removed to obtain a silicon carbide furnace tube.

[0046] Comparative Example 1

[0047] A silicon carbide part preparation method, taking preparation of a silicon carbide furnace tube as an example, comprises the following steps:

[0048] (1) Put 3000g of F240 silicon carbide powder, 1000g of F1200 silicon carbide powder, 400g of carbon black, 900g of butyl acetate, 80g of PEG400 dispersant and 740g of acrylic crosslinking agent into a ball mill tank for mixing and ball milling, to obtain a first slurry, the ball milling medium is silicon carbide ball, the mass ratio of the ball milling medium to the silicon carbide powder is 2:1, and the ball milling time is 12h;

[0049] (2) Pour the first slurry into a stirring vacuum degassing machine for degassing to obtain a second slurry, the degassing time is 30min, and the degassing vacuum degree is 500Pa;

[0050] (3) Pour the second slurry into a polypropylene mold for curing, the mold height is 1000mm, the inner diameter is 240mm, and the outer diameter is 252mm, and a wet blank is obtained after demolding;

[0051] (4) Naturally dry the wet blank at a temperature of 20℃ for 18h to obtain a dry blank, bury the dry blank with silicon particles, and place it into a vacuum sintering furnace for sintering, the sintering temperature is 1600℃, the heating rate before 1200℃ is 1℃ / min, the heating rate from 1200℃ to 1600℃ is 5℃ / min, the holding time is 3h, and the vacuum degree is controlled to be less than 10Pa during the sintering process; take out the sintered blank body, remove the surface silicon particles, and obtain a silicon carbide furnace tube.

[0052] Comparative Example 2

[0053] A silicon carbide part preparation method, taking the preparation of a silicon carbide furnace tube as an example, includes the following steps:

[0054] (1) Put 3000g of F240 silicon carbide powder, 1000g of F1200 silicon carbide powder, 400g of carbon black, 740g of phenolic resin, 900g of butyl acetate and 80g of PEG400 dispersant into a ball mill tank for mixing and ball milling, to obtain a first slurry, the ball milling medium is silicon carbide ball, the mass ratio of the ball milling medium to the silicon carbide powder is 2:1, and the ball milling time is 12h;

[0055] (2) Add 74g of NL-curing agent to the first slurry and continue ball milling for 5min; pour the slurry into a stirring vacuum degassing machine for degassing to obtain a second slurry, the degassing time is 30min, and the degassing vacuum degree is 500Pa;

[0056] (3) Pour the second slurry into a polypropylene mold for curing, the mold height is 1000mm, the inner diameter is 240mm, and the outer diameter is 252mm, and a wet blank is obtained after demolding;

[0057] (4) The wet body is naturally dried at a temperature of 20°C for 18 h to obtain a dry body, the dry body is buried with silicon particles, and is placed into a vacuum sintering furnace to be sintered, the sintering temperature is 1600°C, the temperature rising rate before 1200°C is 1°C / min, the temperature rising rate from 1200°C to 1600°C is 5°C / min, the holding time is 3h, and the vacuum degree is controlled to be less than 10 Pa during the sintering process; the sintered body is taken out, and the surface silicon particles are removed to obtain a silicon carbide furnace tube.

[0058] Comparative Example 3

[0059] A silicon carbide part preparation method, taking the preparation of a silicon carbide furnace tube as an example, includes the following steps:

[0060] (1) 3000g of F240 silicon carbide powder, 1000g of F1200 silicon carbide powder, 400g of carbon black, 240g of phenolic resin, 900g of butyl acetate, 80g of PEG400 dispersant, and 500g of acrylic crosslinking agent are weighed into a ball mill tank and mixed and ball milled, the ball milling medium is silicon carbide balls, the mass ratio of the ball milling medium to the silicon carbide powder is 2:1, and the ball milling time is 12 h;

[0061] (2) 24g of NL-curing agent is added to the first slurry, and the ball milling is continued for 5 min; the slurry is poured into a stirring vacuum debubbling machine for debubbling, and the second slurry is obtained, the debubbling time is 30 min, and the vacuum degree during debubbling is 500 Pa;

[0062] (3) The second slurry is poured into an ethylene-vinyl acetate copolymer mold for curing, the mold height is 1000mm, the inner diameter is 240mm, and the outer diameter is 252mm, and the wet body is obtained after demolding;

[0063] (4) The wet body is naturally dried at a temperature of 20°C for 18 h to obtain a dry body, the dry body is buried with silicon particles, and is placed into a vacuum sintering furnace to be sintered, the sintering temperature is 1600°C, the temperature rising rate before 1200°C is 1°C / min, the temperature rising rate from 1200°C to 1600°C is 5°C / min, the holding time is 3h, and the vacuum degree is controlled to be less than 10 Pa during the sintering process; the sintered body is taken out, and the surface silicon particles are removed to obtain a silicon carbide furnace tube.

[0064] Product performance test:

[0065] The densities of the body and the sintered body are measured by the Archimedes drainage method, the strengths of the body and the sintered body are tested by the three-point bending method, the prepared silicon carbide furnace tube is placed in a polycrystalline silicon reduction furnace to test its cyclic use performance, and the results are shown in Table 1.

[0066] Table 1 Performance of examples and comparative examples

[0067]

[0068] As can be seen from the data in Table 1, the gel casting method for preparing silicon carbide furnace tubes provided by the present application has significant advantages. The green bodies prepared in Examples 1-3 exhibit excellent performance: the green body densities are all over 2 g / cm 3 , and the green body bending strengths are all higher than 15 MPa, indicating that the method can be used to prepare high-density, high-strength silicon carbide furnace tube green bodies. More importantly, the performance of the sintered products is even more outstanding: the densities are all over 3 g / cm 3 , the sintered body bending strengths are all over 300 MPa, and the cycle life is over 5 months.

[0069] In contrast, the experimental results of Comparative Examples 1-2 demonstrate that the synergistic effect of the phenolic resin and the acrylic crosslinking agent is crucial. The use of either component alone will result in a significant decrease in performance: the green body density is less than 2 g / cm 3 , the green body bending strength is less than 10 MPa; the sintered body density is less than 3 g / cm 3 , the sintered body bending strength is only about 250 MPa, and the service life is less than 1 month. These data indirectly demonstrate the effect of silicon spots on performance, and the method of the present application can effectively avoid sedimentation, component segregation, and silicon spot formation.

[0070] It is particularly noteworthy that Comparative Example 3 used an ethylene-vinyl acetate copolymer mold, which resulted in difficult demolding, leading to defects such as microcracks and holes on the surface of the green body, and ultimately the performance of the sintered product deteriorated and could not be used.

[0071] The experimental data collectively demonstrate that the scheme provided by the present application can be used to prepare silicon carbide furnace tubes with excellent performance, which exhibit significant advantages in key indicators such as density, strength, and cycle life.

[0072] Although the present application is disclosed with reference to the preferred embodiments above, it is not intended to limit the present application. Any person skilled in the art, without departing from the spirit and technical solutions of the present application, can make many possible changes and modifications to the technical solutions disclosed above, or modify equivalent embodiments. Therefore, any simple modification, equivalent replacement, equivalent change, and modification made to the above embodiments according to the technical essence of the present application, without departing from the technical solutions of the present application, all still belong to the scope of protection of the technical solutions of the present application.

Claims

1. A method for preparing silicon carbide parts based on gel casting, characterized in that, Includes the following steps: (1) Mix silicon carbide powder, carbon black, phenolic resin, solvent, dispersant and acrylic crosslinking agent and ball mill to obtain the first slurry; (2) Add a curing agent to the first slurry, continue ball milling, remove bubbles, and obtain a second slurry; (3) Pour the second slurry into a polypropylene mold, cure it, and obtain a wet blank after demolding; (4) The wet blank is dried and sintered to obtain silicon carbide parts; The curing agent reacts with the phenolic resin to produce water molecules, which then cure the acrylic crosslinking agent. The phenolic resin is selected from at least one of Resole-type phenolic resin and Novolac-type phenolic resin, and the acrylic crosslinking agent is at least one of EBECRYL acrylic crosslinking agents.

2. The method for preparing silicon carbide parts based on gel casting according to claim 1, characterized in that, In step (1), by mass percentage, silicon carbide powder is 60% to 80%, carbon black is 5% to 10%, phenolic resin is 1% to 5%, solvent is 5% to 20%, acrylic crosslinking agent is 5% to 10%, and dispersant is 0% to 1.5%.

3. The method for preparing silicon carbide parts based on gel casting according to claim 1, characterized in that, In step (1), the solvent is ethyl acetate or butyl acetate, and the dispersant is at least one of PEG200, PEG400 and PEG600; in step (2), the curing agent is a room temperature curing agent that enables the phenolic resin to crosslink and cure at room temperature.

4. The method for preparing silicon carbide parts based on gel casting according to claim 1, characterized in that, In step (2), the curing agent is hexamethylenetetramine curing agent or NL curing agent.

5. The method for preparing silicon carbide parts based on gel casting according to claim 1, characterized in that, In step (2), the amount of curing agent used is 5% to 15% of the mass of phenolic resin.

6. The method for preparing silicon carbide parts based on gel casting according to claim 1, characterized in that, In step (1), the ball milling media is any one of zirconium oxide, alumina, silicon carbide, and silicon nitride balls, the mass ratio of the ball milling media to silicon carbide powder is 1 to 3:1, and the ball milling time is 6 h to 24 h.

7. The method for preparing silicon carbide parts based on gel casting according to claim 1, characterized in that, In step (2), the ball milling time is 5 min to 10 min.

8. The method for preparing silicon carbide parts based on gel casting according to claim 1, characterized in that, In step (2), the defoaming time is 20 min to 60 min, and the vacuum degree of defoaming is 100 Pa to 1000 Pa.

9. The method for preparing silicon carbide parts based on gel casting according to claim 1, characterized in that, In step (4), the drying temperature is 20℃~45℃ and the drying time is 12h~24h.

10. The method for preparing silicon carbide parts based on gel casting according to any one of claims 1 to 9, characterized in that, In step (4), the sintering is to cover the dried blank with silicon particles and perform vacuum sintering. The sintering temperature is 1500℃~1700℃, the holding time is 2h~6h, and the heating rate is 1℃ / min~5℃ / min.

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