A method for preparing a carbon-based large-scale crucible support

Abstract

The application relates to the technical field of single crystal silicon growth in the photovoltaic industry, and particularly discloses a preparation method of a carbon-based large-scale crucible support, which comprises the following steps: S1, carbon fiber cloth is weighed and arranged in an impregnation liquid for impregnation, then the carbon fiber cloth is taken out, baked, laminated and isostatic pressed to solidify, and a semi-finished product is prepared; S2, the semi-finished product is subjected to high-temperature treatment and finishing to prepare a finished product; the method has the advantages of short production cycle, high strength and uniform material, and can be used for preparing a large-scale and continuous drawing single crystal furnace.

Description

Technical Field

[0001] This application relates to the field of monocrystalline silicon growth technology in the photovoltaic industry, and more specifically, it relates to a method for preparing a carbon-based large crucible holder. Background Technology

[0002] The photovoltaic power generation industry is developing rapidly, leading to a significant increase in demand for C / C hot zone structural components, which is projected to reach 8,000 tons in 2023. The crucible support is a crucial hot zone structural component in single-crystal furnaces. It bears the weight of the entire silicon material, crucible, and crucible sides, requiring high thermal conductivity and proper crucible rotation during crystal pulling. The safety and reliability of the crucible support play a key role in the stability of the entire hot zone. Furthermore, as single-crystal silicon pulling furnaces develop towards larger sizes (36-40 inches) and continuous crystal pulling (pulling time > 300 hours), the increased furnace load and high-temperature corrosion time place even higher demands on the crucible support.

[0003] Graphite materials are brittle, have low strength, and poor safety, making them prone to systemic risks. Graphite crucible holders are ill-suited to the demands of large-scale and continuous single-crystal furnaces. In contrast, C / C materials possess superior high-temperature mechanical properties, thermophysical properties, and resistance to siliconization compared to graphite. Therefore, using C / C crucible holders instead of graphite crucible holders will significantly improve the safety performance and service life of the crucible holders.

[0004] However, using existing methods (preform-CVD method) to produce large crucible holders (thickness 30-60mm) has problems such as long production cycle, high manufacturing cost, uneven material, low thermal conductivity, affecting the stability of the thermal field and reducing the efficiency of the thermal field.

[0005] Therefore, how to prepare a new type of crucible holder with advantages such as short production cycle, high strength, and uniform material, and which can be used to prepare large-scale, continuous single crystal pulling furnaces, is a problem that needs to be solved. Summary of the Invention

[0006] In order to prepare a new type of crucible holder with advantages such as short production cycle, high strength and uniform material, which can be used to prepare large-scale, continuous single crystal pulling furnaces, this application provides a method for preparing a carbon-based large crucible holder.

[0007] In a first aspect, this application provides a method for preparing a carbon-based large crucible holder, employing the following technical solution:

[0008] A method for preparing a carbon-based large crucible holder includes the following steps:

[0009] S1. Weigh out carbon fiber cloth and immerse it in the impregnation solution. Then take out the carbon fiber cloth, bake it, stack it, and cure it by isostatic pressing to obtain a semi-finished product.

[0010] S2. The semi-finished product is processed by high temperature treatment and fine processing to obtain the finished product.

[0011] By adopting the above technical solution, the high strength and resistance to siliconization of carbon fiber cloth are utilized to create a finished crucible holder with high strength and resistance to siliconization. Combined with impregnation in the impregnation solution, the carbon fiber cloth layers, bundles, and adjacent fibers are filled with the impregnation solution. Under isostatic pressing curing conditions, the impregnation solution diffuses evenly, and each component is uniformly coated, resulting in a material with uniform properties. Under high temperature conditions, the resin in the impregnation solution carbonizes, and complex chemical reactions occur between the components, producing a uniformly filled ceramic product with high mechanical properties and corrosion resistance. Furthermore, the overall process is simple and has a short production cycle.

[0012] Preferably, the impregnation solution comprises the following raw materials in parts by weight:

[0013] 35-40 parts phenolic resin, 10-15 parts carbon black, 3-5 parts chopped carbon fiber, 5-10 parts silicon powder, 5-10 parts silicon carbide powder, 15-20 parts graphite powder, and 25-30 parts alcohol.

[0014] By adopting the above technical solution, phenolic resin and alcohol in liquid state are used as liquid, and powder materials are fully and uniformly dispersed in the liquid to prepare impregnation liquid. By utilizing the liquid flow effect of the impregnation liquid, each component is uniformly penetrated into the pores between adjacent carbon fiber filaments, so as to achieve the effect of relatively uniform loading of impregnation liquid on the internal pores and surface of carbon fiber cloth, thereby improving the uniformity of the crucible support material.

[0015] During high-temperature processing, phenolic resin can decompose to produce carbon. The resin carbon, carbon black, graphite powder and silicon powder react chemically at high temperature to form a chemical bond. This not only fills the pores but also ensures high bonding strength and resistance to silicon corrosion, thus guaranteeing the high strength and service life of the crucible support.

[0016] The components undergo complex chemical reactions at high temperatures to produce a high-performance ceramic phase, which has high strength, high density, and strong corrosion resistance, thus ensuring the quality of the crucible support.

[0017] Preferably, the carbon black particle size is 40-100 nm and the chopped carbon fiber length is 2-5 mm.

[0018] By adopting the above technical solution, the particle size of carbon black and the particle size of chopped carbon fibers are limited, making it easier for nano-sized carbon black to penetrate into the pores of adjacent fibers in the carbon fiber cloth. Liquid phenolic resin can also impregnate and bond to the surface of carbon fiber filaments. With high-temperature treatment, phenolic resin decomposes into carbon, and resin carbon, carbon black, graphite powder and silicon powder react to produce a ceramic phase. The carbon originally bonded to the surface of carbon fiber filaments forms a dense ceramic phase, which further protects the carbon fiber filaments and maintains the high strength of the carbon fiber, thereby improving the strength and uniformity of the finished crucible holder.

[0019] Preferably, the silicon powder is composed of silicon powder passing through a 300-325 mesh sieve and silicon powder passing through a 6000-10000 mesh sieve in a mass ratio of 1:0.2-0.5, and the silicon carbide powder passes through a 300-325 mesh sieve.

[0020] Preferably, the graphite powder passes through an 8000-12500 mesh sieve.

[0021] By adopting the above technical solution, the particle size of silicon powder and silicon carbide is limited, making it easier for small-particle-size silicon powder, graphite powder, and carbon black to fill the pores of the connected carbon fiber filaments inside the carbon fiber cloth. Silicon powder has a larger particle size, followed by graphite powder, which is easier to fill between the larger pores of adjacent fiber filaments. Carbon black has the smallest particle size and can fill even smaller pores. Through the hierarchical filling effect of the network structure, large-particle-size silicon powder and silicon carbide can adhere to the surface of the carbon fiber cloth, producing a continuous and dense ceramic layer at high temperature, further protecting the carbon fiber and improving the overall strength of the crucible support.

[0022] The impregnation solution penetrates into the interlayers of the carbon fiber cloth, the fiber bundles, and the spaces between adjacent fibers, thus adhering to the carbon fiber filaments. At high temperatures, the phenolic resin, carbon black, and graphite powder inside the carbon fiber cloth react and connect with small-particle-size silicon powder to generate silicon carbide, which fills the pores in the internal structure of the carbon fiber cloth. Furthermore, the phenolic resin on the carbon fiber filaments on the surface of the carbon fiber cloth, as well as the carbon black and graphite powder remaining on the surface, readily react with large-particle-size silicon powder to generate a ceramic phase, which fills the pore structure on the surface of the carbon fiber cloth. Combined with the greater mechanical strength of the ceramic phase, the finished crucible holder can have higher strength and better surface uniformity.

[0023] Preferably, the baking temperature is 100-110℃, and baking is stopped when the adhesive content is 40-50%.

[0024] By adopting the above technical solution, the impregnation liquid on the surface of the carbon fiber cloth can be stably adhered to the inside and surface of the carbon fiber cloth, thereby facilitating the deposition of silicon carbide while improving the strength and material uniformity of the finished crucible holder.

[0025] Preferably, the isostatic pressing curing process is as follows: Under a vacuum of -0.09 to -0.1 MPa, the pressure is maintained for 2.5-3.5 hours at a pressure rise rate of 20-45 Pa / h. Pressure is then applied at a rate of 0.07-0.09 MPa / min, reaching 1.8-2.2 MPa, and maintained at this pressure. Simultaneously, the temperature is increased to 180-200℃ at a rate of 4-6℃ / h, and maintained at this temperature for 1.5-2.5 hours.

[0026] By adopting the above technical solution, the mold is heated and cooled by cold air outside the mold. The temperature inside the mold is high and the temperature on the outer surface is low. The temperature gradually decreases from the inner surface to the outer surface, forming a temperature gradient. With the increase of pressure, the inner surface melts and solidifies first, and then melts and solidifies sequentially from the inner surface to the outer surface, ensuring that the inner and outer surfaces are uniform, thereby obtaining a high-density crucible blank.

[0027] Preferably, the high-temperature treatment is carried out at a temperature of 1600-1800℃ for 3-5 hours, and then cooled to 150-250℃ before being removed from the furnace.

[0028] By adopting the above technical solution, phenolic resin is thermally decomposed into resin carbon, and resin carbon, carbon black, graphite powder and silicon powder react together; and it can react with silicon powder and other substances to generate silicon carbide that coats the surface of carbon fiber cloth, thereby improving the strength of the finished crucible holder while also improving its density and uniformity.

[0029] Preferably, the carbon fiber cloth is made by impregnating a carbon fiber base cloth with polyethylene glycol solution and then adding nano boron carbide whiskers.

[0030] By adopting the above technical solution, carbon fiber base fabric, polyethylene glycol liquid, and boron carbide nano whiskers are combined. The good penetration and fluidity of polyethylene glycol liquid facilitate its penetration into the carbon fiber base fabric. Combined with the small particle whisker structure of boron carbide nano whiskers, it is easy for them to interweave between adjacent carbon fiber filaments inside the carbon fiber base fabric. In addition, the viscosity of the polyethylene glycol liquid increases as the solvent gradually disappears, so that the boron carbide nano whiskers loaded with polyethylene glycol adhere relatively stably to the internal structure of the carbon fiber base fabric.

[0031] By utilizing the polyethylene glycol hydroxyl groups on the surface of boron carbide whiskers within the carbon fiber substrate, combined with phenolic resin and alcohol in the impregnation solution, the phenolic resin and alcohol can promote the penetration of powder particles into the internal structure of the carbon fiber substrate. Due to the piercing and building effect of the boron carbide whiskers, adjacent carbon fiber filaments can be stably bonded in the early stage of curing, making it less likely for adjacent carbon fiber filaments to shrink during processing, ensuring the contact effect between adjacent carbon fiber filaments. Furthermore, due to its spiky whisker structure, the boron carbide whiskers do not easily affect the deposition effect of silicon carbide between adjacent carbon fiber filaments, thereby further improving the strength and density of the crucible support.

[0032] Preferably, the carbon fiber cloth is made by impregnating a carbon fiber base cloth with polyethylene glycol solution and then adding nano boron carbide whiskers.

[0033] By employing the above technical solution, carbon fiber filaments, carboxymethyl chitosan solution, and amino-modified silicon nitride whiskers are combined. The viscosity of the carboxymethyl chitosan solution facilitates the adhesion of the amino-modified silicon nitride whiskers to the surface of the carbon fiber filaments. The carboxyl, amino, and hydroxyl groups on the surface of the short carbon fibers in the impregnation solution further stabilize the adhesion to the carbon fiber cloth surface. Combined with the spiky structure of the amino-modified silicon nitride whiskers and the hydroxyl groups of polyethylene glycol within the carbon fiber cloth, this further promotes the insertion of the short carbon fibers into the larger pores of adjacent carbon fiber filaments, filling the pores and increasing the structural density of the carbon fiber cloth, thereby improving the strength and density of the finished crucible holder. Furthermore, the high-temperature carbonization of carboxymethyl chitosan and the silicon powder on the surface of the carbon fiber cloth further promote the formation of silicon carbide. Simultaneously, the short carbon fibers and the amino-modified silicon nitride whiskers on their surface act as a matrix support, further promoting the stable adhesion of silicon carbide to the carbon fiber cloth surface, thus improving the strength and density of the finished crucible holder and giving it a uniform material composition.

[0034] In summary, this application has the following beneficial effects:

[0035] 1. Utilizing the high strength and resistance to siliconization of carbon fiber, the finished crucible holder possesses both high strength and resistance to siliconization. Combined with impregnation in the impregnation solution, the carbon fiber cloth layers, bundles, and adjacent fibers are filled with the solution. Under temperature and isostatic pressure, the impregnation solution diffuses evenly, uniformly coating each component and resulting in a homogeneous material. Under high-temperature conditions, the resin in the impregnation solution carbonizes, and complex chemical reactions occur between the components, with the products uniformly filling the material, improving the product's uniformity and density. Furthermore, the overall process is simple, resulting in a short production cycle.

[0036] 2. Using phenolic resin and alcohol in liquid state as the liquid, and the powder material is uniformly dispersed in the liquid to prepare the impregnation solution; taking advantage of the liquid flow effect of the impregnation solution, it is easy to penetrate into the pores between adjacent carbon fiber filaments, so as to achieve the effect of relatively uniform loading of impregnation solution on the internal pores and surface of carbon fiber cloth, thereby improving the uniformity of the crucible support material.

[0037] 3. By limiting the particle size of silicon powder and silicon carbide, small-particle-size silicon powder, graphite powder, and carbon black can easily fill the pores of the interconnected carbon fiber filaments inside the carbon fiber cloth. Silicon powder has a larger particle size, followed by graphite powder, which is easy to fill between the larger pores of adjacent fibers. Carbon black has the smallest particle size and can fill even smaller pores. Through the hierarchical filling effect of the network structure, the internal structural density of the carbon fiber cloth is improved. On the other hand, large-particle-size silicon powder and silicon carbide can adhere to the surface of the carbon fiber cloth and are not easy to enter the gaps between the fibers inside the carbon fiber cloth, further improving the strength and material uniformity of the carbon fiber cloth. Detailed Implementation

[0038] The present application will be further described in detail below with reference to the embodiments.

[0039] Example of carbon fiber cloth preparation

[0040] The carbon fiber base fabric in the following raw materials was purchased from Zhongfu Shenying Carbon Fiber Co., Ltd., model SYT49S; the other raw materials and equipment were all commercially available.

[0041] Preparation Example 1: Carbon fiber cloth was prepared by the following method:

[0042] Carbon fiber substrate was weighed and immersed in polyethylene glycol solution. The polyethylene glycol solution was prepared by dissolving 10 kg of polyethylene glycol 10000 in 90 kg of water and stirring until completely dissolved. The immersion temperature was 50℃ and the immersion time was 10 min. Then, boron carbide nano whiskers with a length of 100 nm were added and ultrasonically dispersed at 20 kHz for 10 min. The polyethylene glycol solution was then separated, and the carbon fiber substrate was dried to obtain the finished carbon fiber fabric.

[0043] Preparation example of amino-modified silicon nitride whiskers

[0044] Preparation Example 2: Amine-modified silicon nitride whiskers were prepared by the following method:

[0045] Weigh out silicon nitride whiskers and immerse them in a dopamine solution to disperse them. The length of the silicon nitride whiskers is 80 nm. The dopamine solution is a 2% (w / w) aqueous solution of dopamine. Then separate the silicon nitride whiskers, dry and disperse them to obtain the finished product.

[0046] Example of chopped carbon fiber preparation

[0047] Preparation Example 3: Short-cut carbon fibers were prepared using the following method:

[0048] 0.1 kg of a 0.2% carboxymethyl chitosan solution was uniformly sprayed onto the surface of 1 kg of carbon fiber short filaments. The length of the carbon fiber short filaments was 2-3 mm, and the solvent of the carboxymethyl chitosan solution was water. Then, 0.05 kg of amino-modified silicon nitride whiskers prepared in Preparation Example 2 were added at a rate of 30 g / min. During the addition process, the carbon fiber short filaments were continuously stirred at a speed of 200 r / min. After drying and dispersion, the finished short carbon fiber was obtained.

[0049] Example of impregnation solution preparation

[0050] Preparation Example 4: The impregnation solution was prepared by the following method:

[0051] Weigh out 38 kg of phenolic resin, 12 kg of carbon black, 4 kg of chopped carbon fiber, 8 kg of silicon powder, 8 kg of silicon carbide powder, 18 kg of graphite powder, and 28 kg of alcohol. Mix and stir evenly to prepare the finished impregnation solution. The phenolic resin is of type KJ-04 and is in liquid state. The average particle size of the carbon black is 80 nm, the length of the chopped carbon fiber is 2-5 mm, the silicon powder passes through a 300-mesh sieve, the silicon carbide powder passes through a 300-mesh sieve, the graphite powder passes through a 10,000-mesh sieve, and the mass fraction of the alcohol is 75%.

[0052] Preparation Example 5: The difference between this preparation example and Preparation Example 4 is that:

[0053] Weigh out 35 kg of phenolic resin, 10 kg of carbon black, 3 kg of chopped carbon fiber, 5 kg of silicon powder, 5 kg of silicon carbide powder, 15 kg of graphite powder, and 25 kg of alcohol. Mix and stir evenly to prepare the finished impregnation solution. The phenolic resin is of type KJ-04 and is in liquid state. The average particle size of the carbon black is 100 nm, the length of the chopped carbon fiber is 2-5 mm, the silicon powder passes through a 300-mesh sieve, the silicon carbide powder passes through a 300-mesh sieve, and the graphite powder passes through an 8000-mesh sieve.

[0054] Preparation Example 6: The difference between this preparation example and Preparation Example 4 is that:

[0055] Weigh out 40 kg of phenolic resin, 15 kg of carbon black, 5 kg of chopped carbon fiber, 10 kg of silicon powder, 10 kg of silicon carbide powder, 20 kg of graphite powder, and 30 kg of alcohol. Mix and stir evenly to prepare the finished impregnation solution. The phenolic resin is of type KJ-04 and is in liquid state. The average particle size of the carbon black is 40 nm, the length of the chopped carbon fiber is 2-5 mm, the silicon powder passes through a 325-mesh sieve, the silicon carbide powder passes through a 325-mesh sieve, and the graphite powder passes through a 12500-mesh sieve.

[0056] Preparation Example 7: The difference between this preparation example and Preparation Example 6 is that:

[0057] The silicon powder consists of silicon powder passing through a 325-mesh sieve and silicon powder passing through a 10,000-mesh sieve in a mass ratio of 1:0.5.

[0058] Preparation Example 8: The difference between this preparation example and Preparation Example 7 is that:

[0059] The chopped carbon fiber used was the chopped carbon fiber prepared in Preparation Example 3.

[0060] Example

[0061] The carbon fiber cloth in the following raw materials was purchased from Zhongfu Shenying Carbon Fiber Co., Ltd., model SYT49S; the other raw materials and equipment are all commercially available.

[0062] Example 1: A method for preparing a carbon-based large crucible holder:

[0063] S1. Place the impregnation solution in the glue tank of the impregnation machine, arrange the carbon fiber in the impregnation solution prepared in Preparation Example 4, impregnate and coat it with glue, impregnate for 20 minutes, then take out the carbon fiber cloth, bake it at 110°C until the glue content is 45-50%, stop drying, roll it up, and obtain the prepreg cloth; then stack the prepreg cloth, place it in the curing oven, lock the oven cover, evacuate to -0.098MPa, hold the pressure for 3 hours, pressure rise rate is 35Pa / h, start pressurizing with an air compressor, the pressurizing medium is compressed air, the pressurization rate is 0.08MPa / min, pressurize to 2MPa and hold the pressure, at the same time power on the heating, the heating rate is 5°C / h, heat to 200°C, hold the temperature for 2 hours, complete the isostatic pressing curing, and obtain the semi-finished product;

[0064] S2. The semi-finished product is heated to 1700℃ under nitrogen protection for high-temperature treatment and held at that temperature for 4 hours. Then it is cooled in the furnace to 200℃ and removed from the furnace. Finally, it is refined to obtain the finished product.

[0065] Example 2: The difference between this example and Example 1 is that:

[0066] S1. Place the impregnation solution in the glue tank of the impregnation machine, arrange the carbon fibers in the impregnation solution prepared in Preparation Example 5, impregnate and coat them with glue, impregnate for 20 minutes, then take out the carbon fiber cloth, bake it at 100°C until the glue content is 40-45%, stop drying, roll it up, and obtain the prepreg cloth; then stack the prepreg cloth, place it in the curing oven, lock the oven cover, evacuate to -0.09MPa, hold the pressure for 3.5h, pressure rise rate 45Pa / h, start pressurizing with an air compressor, the pressurizing medium is compressed air, the pressurization rate is 0.07MPa / min, pressurize to 2.2MPa and hold the pressure, at the same time power on the heating, the heating rate is 4°C / h, heat to 180°C, hold the temperature for 2.5h, complete the isostatic pressing curing, and obtain the semi-finished product;

[0067] S2. The semi-finished product is heated to 1600℃ under nitrogen protection for high-temperature treatment and held at that temperature for 5 hours. Then it is cooled in the furnace to 150℃ and removed from the furnace. Finally, it is finely processed to obtain the finished product.

[0068] Example 3: The difference between this example and Example 1 is that:

[0069] S1. Place the impregnation solution in the glue tank of the impregnation machine, arrange the carbon fibers in the impregnation solution prepared in Preparation Example 6 for 20 min, then take out the carbon fiber cloth and bake it at 110°C until the glue content is 45-50%. Stop drying, roll it up, and obtain the prepreg cloth. Then stack the prepreg cloth and place it in the curing oven. Lock the oven cover, evacuate to -0.1 MPa, hold the pressure for 2.5 h, and the pressure rise rate is 20 Pa / h. Start pressurizing with an air compressor. The pressurizing medium is compressed air, and the pressurization rate is 0.09 MPa / min. After pressurizing to 1.8 MPa, hold the pressure and simultaneously turn on the power to heat up at a rate of 6°C / h. Heat up to 200°C and hold for 1.5 h to complete isostatic pressing curing and obtain the semi-finished product.

[0070] S2. The semi-finished product is heated to 1800℃ under nitrogen protection for high-temperature treatment, held at that temperature for 3 hours, then cooled in the furnace to 250℃ before being removed from the furnace. Finally, it undergoes fine processing to obtain the finished product.

[0071] Example 4: The difference between this example and Example 1 is that:

[0072] The carbon fiber cloth used was prepared in Preparation Example 1.

[0073] Example 5: The difference between this example and Example 4 is that:

[0074] The impregnation solution used was the impregnation solution prepared in Preparation Example 7.

[0075] Example 6: The difference between this example and Example 5 is that:

[0076] The impregnation solution used was the impregnation solution prepared in Preparation Example 8.

[0077] Example 7: The difference between this example and Example 1 is that:

[0078] The average particle size of carbon black in the impregnation solution is 100 μm, the average particle size of silicon powder is 150 μm, the average particle size of silicon carbide is 200 μm, and the average particle size of graphite powder is 80 μm.

[0079] Example 8: The difference between this example and Example 1 is that:

[0080] No silicon powder was added to the impregnation solution.

[0081] Example 9: The difference between this example and Example 6 is that:

[0082] In the preparation of short-cut carbon fibers in the impregnation solution, the amino-modified silicon nitride whiskers were replaced with the same mass of silicon nitride whiskers, and the carboxymethyl chitosan solution was replaced with the same mass of ethyl cellulose ethanol solution. The mass fraction of the ethyl cellulose ethanol solution was 0.2%, and the mass fraction of ethanol was 99%.

[0083] Example 10: The difference between this example and Example 4 is that:

[0084] No nano-boron carbide whiskers were added during the preparation of the carbon fiber cloth.

[0085] Comparative Example

[0086] Comparative Example 1: The difference between this comparative example and Example 1 is that:

[0087] The carbon fiber cloth was not impregnated with impregnation solution.

[0088] Comparative Example 2: This comparative example differs from Example 1 in that:

[0089] S1 was not subjected to isostatic pressing curing; it was directly cured at 200℃.

[0090] Performance testing

[0091] 1. Density detection

[0092] Finished crucible holders were prepared using the methods described in Examples 1-10 and Comparative Examples 1-2, respectively. Density was tested and data were recorded in accordance with GB / T1033.1-2008.

[0093] 2. Mechanical performance testing

[0094] Finished crucible holders were prepared using the preparation methods of Examples 1-10 and Comparative Examples 1-2, respectively. The bending strength and bending modulus were tested according to GB / T1499-2005, and the data were recorded.

[0095] 3. Ash content detection

[0096] Finished crucible holders were prepared using the methods described in Examples 1-3, and the ash content was tested and recorded in accordance with GB / T9345.1-2008.

[0097] 4. Uniformity detection

[0098] Finished crucible holders were prepared using the preparation methods of Examples 1-7 and Comparative Examples 1-2, respectively. The uniformity of their materials was scored out of 10 points, and the data were recorded.

[0099] In the following data, " / " indicates that the corresponding embodiment did not detect the item, so there is no data.

[0100] Table 1 Performance Test Table

[0101]

[0102] As can be seen from Examples 1-3 and Table 1, the crucible holder prepared in this application has high density, high bending strength and bending modulus, and good uniformity.

[0103] As can be seen from Examples 1 and 4 and Table 1, carbon fibers prepared by treatment with polyethylene glycol liquid and nano boron carbide whiskers can improve the density and structural compactness of carbon fiber cloth, thereby giving the finished crucible holder higher strength and better material uniformity.

[0104] As can be seen from Examples 4 and 5 and Table 1, mixing silicon powders of different particle sizes can penetrate into the interior and surface of the carbon fiber cloth structure, respectively, thereby facilitating the formation of silicon carbide in the internal structure of the carbon fiber cloth and improving the density and strength of the finished crucible holder.

[0105] As can be seen from Example 5 and Comparative Example 6, and Table 1, after being treated with carboxymethyl chitosan and amino-modified silicon nitride whiskers, the chopped carbon fibers can improve the bonding strength between the chopped carbon fibers and the carbon fiber cloth, and facilitate the insertion of the chopped carbon fibers into the carbon fiber filaments with larger pores adjacent to each other in the carbon fiber cloth, thereby improving the density and mechanical strength of the finished crucible holder.

[0106] Combining Examples 1 and 7-8 with Table 1, it can be seen that the average particle size of carbon black in the impregnation solution is 100 μm, the average particle size of silicon powder is 150 μm, the average particle size of silicon carbide is 200 μm, and the average particle size of graphite powder is 80 μm. Compared with Example 1, the crucible prepared in Example 7 has a lower density, flexural strength, and flexural modulus than that of Example 1. This indicates that larger particle sizes of carbon black, silicon powder, silicon carbide, and graphite powder are not easy to fill and connect between adjacent carbon fiber filaments in the carbon fiber cloth, thus affecting the density and strength of the finished crucible.

[0107] In Example 8, no silicon powder was added to the impregnation solution. Compared with Example 1, the crucible prepared in Example 8 had a lower density, flexural strength, and flexural modulus than that of Example 1. This indicates that silicon powder can react with carbon produced by the high-temperature decomposition of phenolic resin, graphite powder, and carbon black, thereby facilitating the formation of silicon carbide which fills the pores of adjacent carbon fiber filaments in the carbon fiber cloth, thus improving the density and mechanical strength of the finished crucible.

[0108] Combining Examples 6 and 9 with Table 1, it can be seen that in the preparation of short-cut carbon fibers in the impregnation solution of Example 9, when the same mass of silicon nitride whiskers were used to replace the amino-modified silicon nitride whiskers, and the same mass of ethyl cellulose ethanol solution was used to replace the carboxymethyl chitosan solution, the crucible density, bending strength, and bending modulus of the crucible prepared in Example 9 were lower than those in Example 6 compared to Example 6. This indicates that the amino-treated silicon nitride whiskers are easier to insert into the internal structure of the carbon fiber cloth, and the amino and carboxyl groups in the carboxymethyl chitosan are easier to attract and connect with the hydroxyl groups in the carbon fiber cloth, thereby improving the strength and density of the finished product.

[0109] Combining Examples 4 and 10 with Table 1, it can be seen that in the preparation process of carbon fiber cloth in Example 10, no nano boron carbide whiskers were added. Compared with Example 4, the density of the crucible prepared in Example 10 was lower than that in Example 4, and the bending strength and bending modulus were also lower than those in Example 4. This indicates that the addition of nano boron carbide whiskers can further improve the strength of the finished crucible.

[0110] Based on Example 1 and Comparative Examples 1-2, and in conjunction with Table 1, it can be seen that the carbon fiber cloth in Comparative Example 1 was not impregnated with the impregnation solution. Compared with Example 1, the density, bending strength, and bending modulus of the crucible holder prepared in Comparative Example 1 were all lower than those in Example 1, and the uniformity score was also lower than that in Example 1. This indicates that the impregnation treatment with the impregnation solution can improve the strength and material uniformity of the finished crucible holder.

[0111] In Comparative Example 2, the crucible holder was not subjected to isostatic pressing during preparation and was directly cured at 200°C. Compared with Example 1, the crucible holder prepared in Comparative Example 2 had a lower density, flexural strength, and flexural modulus, and a lower uniformity score. This indicates that the isostatic pressing operation can melt and solidify sequentially from the inner surface to the outer surface, ensuring uniformity of the inner and outer surfaces, thereby obtaining a high-density finished crucible holder.

[0112] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing a carbon-based large crucible holder, characterized in that, Includes the following steps: S1. Weigh out carbon fiber and impregnate it in the impregnation solution. Then take out the carbon fiber cloth, bake it, stack it, and cure it by isostatic pressing to obtain a semi-finished product. The carbon fiber cloth is made by impregnating carbon fiber base cloth with polyethylene glycol solution and then adding nano boron carbide whiskers. S2. The semi-finished product is processed by high temperature treatment and fine processing to obtain the finished product; The impregnation solution comprises the following raw materials in parts by weight: The mixture comprises 35-40 parts phenolic resin, 10-15 parts carbon black, 3-5 parts chopped carbon fiber, 5-10 parts silicon powder, 5-10 parts silicon carbide powder, 15-20 parts graphite powder, and 25-30 parts alcohol. The chopped carbon fiber is prepared by bonding amino-modified silicon nitride whiskers to carbon fiber filaments after treatment with carboxymethyl chitosan solution.

2. The method for preparing a carbon-based large crucible holder according to claim 1, characterized in that, The carbon black has a particle size of 40-100 nm and the chopped carbon fiber has a length of 2-5 mm.

3. The method for preparing a carbon-based large crucible holder according to claim 1, characterized in that, The silicon powder consists of silicon powder passing through a 300-325 mesh sieve and silicon powder passing through a 6000-10000 mesh sieve in a mass ratio of 1:0.2-0.5, and the silicon carbide powder passes through a 300-325 mesh sieve.

4. The method for preparing a carbon-based large crucible holder according to claim 1, characterized in that, The graphite powder is passed through an 8000-12500 mesh sieve.

5. The method for preparing a carbon-based large crucible holder according to claim 1, characterized in that, The baking temperature is 100-110℃, and baking is stopped when the adhesive content is 40-50%.

6. The method for preparing a carbon-based large crucible holder according to claim 1, characterized in that, The specific steps of the isostatic pressing curing are as follows: Under a vacuum of -0.09 to -0.1 MPa, maintain pressure for 2.5-3.5 hours with a pressure rise rate of 20-45 Pa / h, start pressurizing at a rate of 0.07-0.09 MPa / min, pressurize to 1.8-2.2 MPa and maintain pressure, while simultaneously raising the temperature to 180-200℃ at a rate of 4-6℃ / h and maintaining the temperature for 1.5-2.5 hours.

7. The method for preparing a carbon-based large crucible holder according to claim 1, characterized in that, The high-temperature treatment is carried out at 1600-1800℃ for 3-5 hours, and then cooled to 150-250℃ before being removed from the furnace.

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