Carbon-ceramic crucible, preparation method thereof and liquid-phase-method melt siliconizing reaction tool
By preparing a carbon-ceramic crucible substrate and coating it with boric acid, the problem of easy corrosion of graphite crucibles was solved, and the anti-oxidation and anti-silicon corrosion properties were improved, thus extending the service life of the equipment.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-05
- Publication Date
- 2026-03-13
AI Technical Summary
Existing graphite crucibles are prone to corrosion and have a short service life during the liquid phase melt infiltration process. Traditional coatings are not dense enough to effectively prevent molten silicon from penetrating, leading to the rapid scrapping of the crucibles.
The crucible substrate is prepared using materials such as carbon fiber powder, graphite powder, and silicon carbide, and a boric acid-containing coating slurry is coated on the substrate surface. A dense coating is formed by high-temperature sintering, which improves the antioxidant and silicon corrosion resistance.
This extends the service life of carbon ceramic crucibles, reduces the frequency of downtime for tooling replacement, and ensures production continuity and equipment durability.
Smart Images
Figure CN121651968A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of molten silicon infiltration technology, and in particular to carbon ceramic crucibles and their preparation methods, as well as liquid-phase molten silicon infiltration reaction equipment. Background Technology
[0002] Fused silicon infiltration technology uses carbon-based materials as a substrate and employs liquid-phase or gas-phase silicon infiltration processes to induce a reaction between silicon and carbon. The silicon fills the pores within the material, forming a dense and high-performance Si / SiC product. Liquid-phase fused silicon infiltration involves heating the material to its melting point to generate liquid silicon. Through capillary action, this liquid silicon infiltrates the preform and reacts with carbon, achieving material densification.
[0003] In the liquid-phase melt infiltration process, crucibles are required as tooling containers for the liquid-phase reaction. The industry conventionally uses isostatic graphite crucibles, but these crucibles not only have high manufacturing and processing costs, but are also susceptible to silicon corrosion, resulting in a short service life. Therefore, there is an urgent need to find suitable products to replace traditional graphite crucibles to meet the production requirements of the liquid-phase melt infiltration reaction. Summary of the Invention
[0004] Therefore, it is necessary to provide a method for preparing a carbon ceramic crucible, which aims to improve the crucible's resistance to silicon corrosion and extend its service life.
[0005] One aspect of the present invention provides a method for preparing a carbon ceramic crucible, comprising the following steps:
[0006] S1. Mix carbon fiber powder, graphite powder, resin adhesive and silicon carbide to obtain a mixed slurry;
[0007] S2. Pour the mixed slurry obtained in step S1 into a mold and press it to form a crucible substrate green body.
[0008] S3. The crucible substrate green body obtained in step S2 is subjected to a first high-temperature sintering to obtain a crucible substrate with a porous structure.
[0009] S4. Mix silica sol, flake graphite, resin, silicon carbide, boric acid and solvent to obtain coating slurry;
[0010] S5. Apply the coating slurry described in step S4 to the surface of the crucible substrate;
[0011] S6. The crucible substrate coated with the coating slurry in step S5 is subjected to a second high-temperature sintering to obtain a carbon ceramic crucible.
[0012] The aforementioned method for preparing carbon-ceramic crucibles utilizes a specific crucible matrix composition to provide a support structure with certain mechanical strength and oxidation resistance. Carbon fiber powder serves as a reinforcing phase, enhancing the mechanical properties of the carbon-ceramic crucible and enabling it to withstand certain mechanical impacts and thermal stresses, thus ensuring structural integrity and preventing cracking during repeated use. Silicon carbide acts as an antioxidant, improving the crucible matrix's resistance to oxygen corrosion in high-temperature environments and reducing the likelihood of cracking under thermal shock. Meanwhile, the surface of the crucible substrate is coated and sintered with a coating of a specific composition, which can protect the carbon ceramic crucible in the harsh molten silicon environment. By adding boric acid as a sintering accelerator to the coating slurry, and the fact that boric acid can be transformed into boron oxide during the sintering process, the boron oxide has a certain binding effect under high temperature sintering conditions, which can promote the bonding strength between the coating and the crucible substrate. In addition, boric acid will be transformed into a liquid phase during the heating and holding process of sintering, thereby driving the powder particles in the coating slurry to flow, filling the porous structure of the crucible substrate, and obtaining a continuous, dense and smooth coating, thereby improving the carbon ceramic crucible's resistance to silicon corrosion.
[0013] In one embodiment, the mixed slurry, by weight, comprises the following components: 5-20 parts carbon fiber powder, 40-80 parts graphite powder, 10-20 parts resin adhesive, and 10-30 parts silicon carbide.
[0014] In one embodiment, the graphite powder includes at least one of the following: waste generated during the production of carbon-based composite materials, waste generated during the production of graphite anode materials, and graphite anode materials recycled from retired lithium batteries.
[0015] In one embodiment, the graphite powder has a particle morphology including at least one of flake, spherical and near-spherical shapes, the particle size of the graphite powder is 100μm-1000μm, and the ash content of the graphite powder is <800ppm.
[0016] In one embodiment, in step S2, the molding pressure of the compression molding is 10MPa-300MPa, the molding time of the compression molding is 5min-40min, and the molding temperature of the compression molding is 100℃-300℃.
[0017] In one embodiment, in step S3, the temperature of the first high-temperature sintering is 800℃-1000℃, and the time of the first high-temperature sintering is 4h-6h.
[0018] In one embodiment, the coating slurry, by weight, comprises the following components: 50-70 parts silica sol, 5-20 parts flake graphite, 10-20 parts resin, 10-30 parts silicon carbide, 5-15 parts boric acid, and solvent.
[0019] In one embodiment, in step S5, the coating thickness of the coating slurry is 0.1 mm to 0.6 mm; and / or,
[0020] In step S5, the temperature of the second high-temperature sintering is 1000℃-2000℃, and the time of the second high-temperature sintering is 1h-11h.
[0021] In another aspect, the present invention provides a carbon-ceramic crucible, which is prepared by the above-described method for preparing carbon-ceramic crucibles; or,
[0022] The carbon ceramic crucible includes a crucible substrate and a functional coating disposed inside and on the surface of the porous structure of the crucible substrate. The components of the functional coating include silicon oxide, flake graphite, silicon carbide, and boron oxide. The components of the crucible substrate include carbon fiber, graphite powder, and silicon carbide.
[0023] The aforementioned carbon-ceramic crucibles possess high density, superior flexural strength, and compressive strength, exhibiting advantages in both strength and toughness. The high density ensures minimal internal porosity and a dense structure, reducing the likelihood of cracking. The superior flexural and compressive strength enhance the crucible's thermal shock resistance, preventing cracking due to thermal stress and extending its service life. Furthermore, the boron oxide functional coating ensures a relatively continuous and dense coating, improving the crucible's resistance to silica penetration and oxidation, thus enhancing its durability and extending its service life.
[0024] In another aspect, the present invention provides a liquid-phase melt infiltration reaction apparatus, comprising the aforementioned carbon ceramic crucible.
[0025] The aforementioned liquid-phase melt infiltration reaction fixture has a long service life when applied to the liquid-phase melt infiltration reaction, which can reduce the frequency of downtime for fixture replacement, thereby reducing downtime and maintenance time and ensuring production continuity. Attached Figure Description
[0026] Figure 1 A schematic flowchart illustrating a method for preparing a carbon ceramic crucible according to one embodiment;
[0027] Figure 2 A schematic diagram of a carbon ceramic crucible substrate according to one embodiment;
[0028] Figure 3 for Figure 2 The cross-sectional view of the carbon ceramic crucible substrate shown;
[0029] Figure 4 This is a photograph of the carbon ceramic crucible prepared in Example 1.
[0030] Explanation of reference numerals in the attached figures:
[0031] 1. Inner surface; 2. Outer surface. Detailed Implementation
[0032] To facilitate understanding of the present invention, a more complete description will be given below with reference to relevant embodiments. Preferred embodiments of the invention are shown below. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that a thorough and complete understanding of the disclosure of the invention will be achieved.
[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.
[0034] Traditionally, crucibles used in molten silicon environments are typically ordinary graphite crucibles or uncoated carbon / carbon composite crucibles. However, carbon reacts with molten silicon at high temperatures to form silicon carbide. This silicon carbide is not a protective agent but rather a destructive corrosive reaction. Molten silicon rapidly penetrates the porous structure of the graphite or carbon / carbon composite crucible. The resulting silicon carbide, due to volume changes, causes localized stress concentration, leading to cracking and breakage. Simultaneously, the molten silicon continuously corrodes the crucible, thinning the crucible walls, reducing its strength, and ultimately rendering the crucible unusable.
[0035] Even with a coating formed on the crucible surface to resist molten silicon penetration, traditional coatings are often not dense enough to effectively block the infiltration of molten silicon. During the cycles of thermal shock and cooling, the adhesion between traditional coatings and the crucible substrate is weak, and there is a significant difference in the coefficients of thermal expansion between the two. This difference in expansion can cause cracking, peeling, and detachment, making it difficult to ensure the long-term effective use of the crucible.
[0036] Please see Figure 1 This application provides a method for preparing a carbon ceramic crucible, comprising the following steps:
[0037] S1. Mix carbon fiber powder, graphite powder, resin adhesive and silicon carbide to obtain a mixed slurry;
[0038] S2. Pour the mixed slurry obtained in step S1 into a mold and press it to form a crucible substrate green body.
[0039] S3. The crucible substrate green body obtained in step S2 is subjected to a first high-temperature sintering to obtain a crucible substrate with a porous structure.
[0040] S4. Mix silica sol, flake graphite, resin, silicon carbide, boric acid and solvent to obtain coating slurry;
[0041] S5. Apply the coating slurry from step S4 to the surface of the crucible substrate;
[0042] S6. The crucible substrate coated with the coating slurry in step S5 is subjected to a second high-temperature sintering to obtain the crucible.
[0043] The aforementioned method for preparing carbon-ceramic crucibles utilizes a specific crucible matrix composition to provide a support structure with certain mechanical strength and oxidation resistance. Carbon fiber powder serves as a reinforcing phase, enhancing the mechanical properties of the carbon-ceramic crucible and enabling it to withstand certain mechanical impacts and thermal stresses, thus ensuring structural integrity and preventing cracking during repeated use. Silicon carbide acts as an antioxidant, improving the crucible matrix's resistance to oxygen corrosion in high-temperature environments and reducing the likelihood of cracking under thermal shock. Meanwhile, the surface of the crucible substrate is coated and sintered with a coating of a specific composition, which can protect the carbon ceramic crucible in the harsh molten silicon environment. By adding boric acid as a sintering accelerator to the coating slurry, the sintering temperature of the coating is reduced. At the same time, boric acid can be transformed into boron oxide during sintering. Under high-temperature sintering conditions, boron oxide has a certain binding effect, which can promote the bonding strength between the coating and the crucible substrate. In addition, boric acid will be transformed into a liquid phase during the heating and holding process of sintering, thereby driving the powder particles in the coating slurry to flow, filling the porous structure of the crucible substrate, and obtaining a continuous, dense and smooth coating, thereby improving the carbon ceramic crucible's resistance to silicon corrosion.
[0044] Please see Figures 2 to 3 The crucible base has a receiving cavity with one end open. The surface inside the receiving cavity is the inner surface 1 of the crucible base, and the surface of the other part of the crucible base excluding the inner surface is the outer surface 2 of the crucible base.
[0045] Understandably, in the liquid-phase melt infiltration reaction, liquid silicon is placed inside the crucible substrate and in contact with the inner surface 1 of the crucible substrate, so the coating slurry is coated at least on the inner surface 1 of the crucible substrate. Furthermore, the coating slurry is coated not only on the inner surface 1 of the crucible substrate, but also on the outer surface 2.
[0046] In one embodiment, the mixed slurry, by weight, comprises the following components: 5-20 parts carbon fiber powder, 40-80 parts graphite powder, 10-20 parts resin adhesive, and 10-30 parts silicon carbide.
[0047] As an example, the mass fraction of carbon fiber powder can be 5 parts, 10 parts, 15 parts, 20 parts, or any two of the above values within the range, such as 5 parts to 15 parts.
[0048] As an example, the mass fraction of graphite powder can be 40 parts, 50 parts, 60 parts, 70 parts, 80 parts, or any two of the above values within the range, such as 50 parts to 60 parts.
[0049] As an example, the mass fraction of the resin adhesive can be 10 parts, 15 parts, 20 parts, or any two of the above values within the range, such as 15 parts to 20 parts.
[0050] As an example, the mass fraction of silicon carbide can be 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, or any two of the above values within a range, such as 15 parts to 25 parts.
[0051] In one embodiment, the mixed slurry, by weight, comprises the following components: 5-15 parts carbon fiber powder, 50-60 parts graphite powder, 15-20 parts resin adhesive, and 15-25 parts silicon carbide.
[0052] In one embodiment, the carbon fiber powder has a mesh size of 100-300 mesh.
[0053] Optionally, the carbon fiber powder has a mesh size of 150.
[0054] In one embodiment, the diameter of the carbon fiber powder is 5μm-10μm.
[0055] Optionally, the diameter of the carbon fiber powder is 7 μm.
[0056] In one embodiment, the aspect ratio of the carbon fiber powder is 1:15-1:25.
[0057] Optionally, the aspect ratio of the carbon fiber powder is 1:20.
[0058] The above-mentioned method for preparing carbon ceramic crucibles introduces carbon fiber powder into the crucible matrix, which plays a role in strengthening and toughening, and effectively prevents crack propagation.
[0059] In one embodiment, the graphite powder includes at least one of the following: waste generated during the production of carbon-based composite materials, waste generated during the production of graphite anode materials, and graphite anode materials recycled from retired lithium batteries.
[0060] In one embodiment, the graphite powder has a particle morphology including at least one of flake-like, spherical, and near-spherical shapes, a particle size of 100 μm-1000 μm, and an ash content of <800 ppm.
[0061] The above-mentioned method for preparing carbon-ceramic crucibles utilizes a high proportion of recycled carbon-based composite materials, carbon waste from the production of graphite-based anode materials, and graphite-based anode materials recycled from retired lithium batteries as the base phase of the crucible matrix. This transforms waste into treasure, significantly reduces the raw material cost of carbon-ceramic crucibles, and achieves high-value reuse of solid waste. Simultaneously, the recycled carbon-based composite materials, carbon waste from the production of graphite-based anode materials, and graphite-based anode materials recycled from retired lithium batteries are all purified and graphitized, resulting in relatively uniform particle shape and size distribution. As the base phase of the crucible matrix, they can be more tightly packed, thereby increasing the density and strength of the crucible matrix green body. Furthermore, after purification and graphitization, the ash content is low, and the chemical properties remain relatively stable during the sintering process of the crucible matrix green body.
[0062] In one embodiment, the resin adhesive is a thermosetting resin, including at least one of phenolic resin, epoxy resin, amino resin, unsaturated polyester resin, and silicone ether resin.
[0063] In one embodiment, the silicon carbide has a particle size of 80 μm-120 μm and a purity of 99.5%-99.9%.
[0064] Optionally, the silicon carbide has a particle size of 100 μm and a purity of 99.8%.
[0065] In one embodiment, in step S2, the molding pressure is 10MPa-300MPa, the molding time is 5min-40min, and the molding temperature is 100℃-300℃.
[0066] As an example, the molding pressure for compression molding can be 10MPa, 20MPa, 30MPa, 40MPa, 50MPa, 60MPa, 70MPa, 80MPa, 90MPa, 100MPa, 150MPa, 200MPa, 250MPa, 300MPa or any two of the above values, for example, 10MPa-30MPa.
[0067] As an example, the molding time for compression molding can be 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, or any two of the above values, such as 5 min to 30 min.
[0068] As an example, the molding temperature can be 100℃, 150℃, 200℃, 250℃, 300℃ or any two of the above values, such as 100℃-200℃.
[0069] In one embodiment, the temperature of the first high-temperature sintering is 800℃-1000℃, and the time of the first high-temperature sintering is 4h-6h.
[0070] As an example, the temperature of the first high-temperature sintering can be 800℃, 850℃, 900℃, 950℃, 1000℃ or any two of the above values, such as 850℃-1000℃.
[0071] As an example, the first high-temperature sintering time can be 4h, 5h, 6h or any two of the above values within the range, such as 5h-6h.
[0072] In one embodiment, the mixed slurry, by weight, comprises the following components: 10 parts carbon fiber powder, 50 parts graphite powder, 15 parts resin adhesive, and 25 parts silicon carbide.
[0073] In one embodiment, the coating slurry, by weight, comprises the following components: 50-70 parts silica sol, 5-20 parts flake graphite, 10-20 parts resin, 10-30 parts silicon carbide, 5-15 parts boric acid, and solvent.
[0074] As an example, the mass fraction of the silica sol can be 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, or any two of the above values within the range, such as 55 parts to 65 parts.
[0075] As an example, the mass fraction of flake graphite can be 5 parts, 10 parts, 15 parts, 20 parts, or any two of the above values within the range, such as 5 parts to 15 parts.
[0076] As an example, the mass fraction of the resin can be 10 parts, 13 parts, 15 parts, 17 parts, 20 parts, or any two of the above values within the range, such as 15 parts to 17 parts.
[0077] As an example, the mass fraction of silicon carbide can be 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, or any two of the above values within a range, such as 10 parts to 20 parts.
[0078] As an example, the mass fractions of boric acid can be 5 parts, 10 parts, 15 parts, or any two of the above values within the range, such as 10 to 15 parts.
[0079] In one embodiment, the solid content in the coating slurry is 15wt%-40wt%.
[0080] In one embodiment, the coating slurry, by weight, comprises the following components: 55-65 parts silica sol, 5-15 parts flake graphite, 15-17 parts resin, 10-20 parts silicon carbide, 10-15 parts boric acid, and solvent.
[0081] In one embodiment, the silica sol comprises nano-silica particles and a solvent, wherein the nano-silica particles have a particle size of 40nm-60nm, the mass fraction of the nano-silica in the silica sol is 15%-25%, and the solvent comprises water.
[0082] Optionally, the particle size of the nano-silica is 50 nm, and the mass fraction of the nano-silica in the silica sol is 20%.
[0083] In one embodiment, the flake graphite has a particle size of 80μm-120μm and a carbon content of 99.9%-99.99%.
[0084] Optionally, the flake graphite has a particle size of 100 μm and a carbon content of 99.9%.
[0085] In one embodiment, the resin includes at least one of epoxy resin, polyurethane resin, and acrylic resin.
[0086] In one embodiment, the silicon carbide has a particle size of 80 μm-120 μm and a purity of 99.5%-99.9%.
[0087] Optionally, the silicon carbide has a particle size of 100 μm and a purity of 99.8%.
[0088] In one embodiment, the purity of boric acid is 99%-99.9%.
[0089] Optionally, the purity of boric acid is 99%.
[0090] In one embodiment, the solvent is water and / or ethanol.
[0091] In one embodiment, in step S5, the coating is applied 2 to 6 times, and the coating thickness of the coating slurry is 0.1 mm to 0.6 mm.
[0092] As an example, the number of coatings can be 2, 3, 4, 5, 6, or any two of the above values, such as 3 to 5 times.
[0093] As an example, the coating thickness of the coating slurry can be 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm or within the range of any two of the above values, such as 0.1 mm to 0.3 mm.
[0094] In one embodiment, in step S6, the temperature of the second high-temperature sintering is 1000℃-2000℃, and the time of the second high-temperature sintering is 1h-11h.
[0095] As an example, the temperature for the second high-temperature sintering can be 1000℃, 1250℃, 1500℃, 1750℃, 2000℃ or any two of the above values, such as 1250℃-1750℃.
[0096] As an example, the second high-temperature sintering time can be 1h, 3h, 5h, 7h, 9h, 11h or any two of the above values, such as 3h-7h.
[0097] In the above-mentioned method for preparing carbon ceramic crucibles, boric acid generates low-melting-point boron oxide during sintering, which then transforms into a glassy phase. This introduces the glassy boron oxide phase into the sintering system of the coating, thereby reducing the sintering temperature.
[0098] Some embodiments of this application provide a carbon ceramic crucible, which is prepared using the above-described method for preparing carbon ceramic crucibles.
[0099] In one embodiment, the carbon ceramic crucible includes a crucible substrate and a functional coating disposed inside and on the surface of the porous structure of the crucible substrate. The components of the functional coating include silicon oxide, flake graphite, silicon carbide, and boron oxide. The components of the crucible substrate include carbon fiber, graphite powder, and silicon carbide.
[0100] The aforementioned carbon-ceramic crucibles possess high density, superior flexural strength, and compressive strength, exhibiting advantages in both strength and toughness. The high density ensures minimal internal porosity and a dense structure, reducing the likelihood of cracking. The superior flexural and compressive strength enhance the crucible's thermal shock resistance, preventing cracking due to thermal stress and extending its service life. Furthermore, the boron oxide functional coating ensures a relatively continuous and dense coating, improving the crucible's resistance to silica penetration and oxidation, thus enhancing its durability and extending its service life.
[0101] In some embodiments, the components of the functional coating, by weight, include 10-40 parts of silicon oxide, 5-10 parts of flake graphite, 5-10 parts of calcined resin, 10-30 parts of silicon carbide, and 5-10 parts of boron oxide.
[0102] In some embodiments, silica is derived from silica sol, resin calcined material is derived from resin, and boron oxide is derived from boric acid.
[0103] In some embodiments, the crucible matrix comprises, by weight, 10-20 parts carbon fiber, 20-40 parts graphite powder, 5-10 parts calcined resin, and 15-35 parts silicon carbide.
[0104] In some of these embodiments, the resin calcined product is derived from resin.
[0105] Some embodiments of this application provide a liquid-phase melt infiltration reaction apparatus, including the carbon ceramic crucible described above.
[0106] The aforementioned liquid-phase melt infiltration reaction fixture has a long service life when applied to the liquid-phase melt infiltration reaction, which can reduce the frequency of downtime for fixture replacement, thereby reducing downtime and maintenance time and ensuring production continuity.
[0107] The following are specific examples.
[0108] Example 1
[0109] Please see Figure 4 This embodiment provides a method for preparing a carbon ceramic crucible, including the following steps:
[0110] S1. By weight, mix 10 parts carbon fiber powder, 60 parts flake graphite powder with a particle size of 100 μm and an ash content of 99.9%, 15 parts phenolic resin adhesive, and 15 parts silicon carbide with a particle size of 100 μm and a purity of 99.8% to obtain a mixed slurry. The carbon fiber powder has a mesh size of 150 mesh, a diameter of 7 μm, and an aspect ratio of 1:20.
[0111] S2. Pour the mixed slurry obtained in step S1 into a mold and mold it to obtain a crucible substrate green body. The molding pressure is 20 MPa, the molding time is 30 min, and the molding temperature is 150℃.
[0112] S3. The crucible substrate green body obtained in step S2 is subjected to a first high-temperature sintering to obtain a crucible substrate with a porous structure. The temperature of the first high-temperature sintering is 900℃ and the time of the first high-temperature sintering is 5h.
[0113] S4. According to the mass fraction, mix 60 parts of silica sol with a particle size of 50nm and a mass fraction of 20%, 10 parts of flake graphite with a particle size of 100μm and a carbon content of 99.9%, 10 parts of phenolic resin, 15 parts of silicon carbide with a particle size of 100μm and a purity of 99.9%, 10 parts of boric acid with a purity of 99%, and 200 parts of water to obtain the coating slurry.
[0114] S5. Apply the coating slurry from step S4 to the inner surface 1 and outer surface 2 of the crucible substrate, wherein the coating is applied 3 times and the total coating thickness is 0.2 mm.
[0115] S6. The crucible substrate coated with the coating slurry in step S5 is subjected to a second high-temperature sintering to obtain a carbon ceramic crucible. The temperature of the second high-temperature sintering is 1500℃ and the time of the second high-temperature sintering is 5h.
[0116] Example 2
[0117] The preparation method of Example 2 is basically the same as that of Example 1, except that the mass parts of each component in the mixed slurry are: 10 parts carbon fiber powder, 50 parts graphite powder, 15 parts phenolic resin adhesive and 25 parts silicon carbide.
[0118] Example 3
[0119] The preparation method of Example 3 is basically the same as that of Example 1, except for the mass fraction of boric acid in the coating slurry and the second high-temperature sintering temperature and time; that is, 5 parts of boric acid and the second high-temperature sintering temperature is 180°C and the time is 6h.
[0120] Example 4
[0121] The preparation method of Example 4 is basically the same as that of Example 1, except that the coating thickness of the coating slurry is 0.1 mm.
[0122] Comparative Example 1
[0123] The preparation method of Comparative Example 1 is basically the same as that of Example 1, except that steps S4-S6 are omitted; that is, the crucible substrate with porous structure obtained in step S3 is not coated and subjected to a second high-temperature sintering treatment.
[0124] Comparative Example 2
[0125] The preparation method of Comparative Example 2 is basically the same as that of Example 1, except that steps S1-S3 are omitted; that is, the coating slurry is directly coated on the graphite crucible and subjected to a second high-temperature sintering treatment.
[0126] Comparative Example 3
[0127] The preparation method of Comparative Example 3 is basically the same as that of Example 1, except that boric acid in the coating slurry is omitted.
[0128] Comparative Example 4
[0129] Comparative Example 4 is a graphite crucible with the same dimensions and shape as Example 1.
[0130] The carbon ceramic crucibles prepared in each embodiment and comparative example were subjected to density testing, flexural strength testing, compressive strength testing, and durability testing according to the following standards:
[0131] Density test: The test standard is GB / T 4472-2011;
[0132] Bending strength: The test standard is GB / T 13465.2-2014;
[0133] Compressive strength: The test standard is GB / T 13465.3-2014;
[0134] Durability testing: the lifespan of the product during normal production;
[0135] Silicon infiltration corrosion test: After one use of silicon infiltration, the thickness of the silicon infiltrated layer in the carbon ceramic crucible is observed by scanning electron microscopy and metallographic microscopy.
[0136] The composition and formulation of the mixed slurry and coating slurry used for the substrate in each embodiment and comparative example are shown in Table 1. The process parameters such as molding, first high-temperature sintering, second high-temperature sintering, and number of coatings in each embodiment and comparative example are shown in Table 2. The test results are shown in Table 3.
[0137] Table 1
[0138]
[0139] Table 2
[0140]
[0141] Table 3
[0142]
[0143] As shown in Table 3 above, through Examples 1-2 and Comparative Examples 1-2 and Comparative Examples 4, the service life of Comparative Example 1 decreased significantly, proving that coating and sintering is a key factor in extending the service life of the carbon-ceramic crucible and preventing molten silicon corrosion. Although the service life of Comparative Example 2 was comparable to that of Examples 1 and 2, its bending strength and compressive strength were lower than those of Examples 1 and 2, proving that the crucible substrate prepared in this application has certain mechanical strength and mechanical properties, and can withstand the mechanical and thermal stresses during the molten silicon infiltration reaction, reducing cracking. The bending strength, compressive strength, and service life of Comparative Example 4 decreased significantly, proving that the high-strength crucible substrate and dense coating prepared in this application have a synergistic effect in improving the mechanical strength and service life of the carbon-ceramic crucible.
[0144] Meanwhile, the silicon infiltration corrosion test results of each embodiment and comparative example demonstrate that boric acid is key to achieving efficient coating densification and that coating thickness is an important factor affecting the protective effect. The primary silicon infiltration layer thickness in Example 1 was 532 μm, and in Comparative Example 3 it was 1531 μm, proving that boric acid is crucial for forming a dense, glass-transformed functional coating. The primary silicon infiltration layer thickness in Example 3 was 1475 μm, demonstrating, compared to Example 1, that a more preferred boric acid content better blocks molten silicon corrosion. The primary silicon infiltration layer thickness in Example 4 was 660 μm, demonstrating, compared to Example 1, that under the premise of coating density, a thicker coating can provide a better physical barrier, extend the molten silicon penetration path, and thus further improve the protective effect.
[0145] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0146] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.
Claims
1. A method for preparing a carbon ceramic crucible, characterized in that, Includes the following steps S1-S6: S1. Mix carbon fiber powder, graphite powder, resin adhesive and silicon carbide to obtain a mixed slurry; S2. Place the mixed slurry obtained in step S1 into a mold and press it to form a crucible substrate green body. S3. The crucible substrate green body obtained in step S2 is subjected to a first high-temperature sintering to obtain a crucible substrate with a porous structure. S4. Mix silica sol, flake graphite, resin, silicon carbide, boric acid and solvent to obtain coating slurry; S5. The coating slurry described in step S4 is applied to the surface of the crucible substrate, and a second high-temperature sintering is performed to obtain a carbon ceramic crucible.
2. The method for preparing the carbon ceramic crucible as described in claim 1, characterized in that, The mixed slurry comprises, by weight, the following components: 5-20 parts carbon fiber powder, 40-80 parts graphite powder, 10-20 parts resin adhesive, and 10-30 parts silicon carbide.
3. The method for preparing the carbon ceramic crucible as described in claim 1, characterized in that, The graphite powder includes at least one of the following: waste generated during the production of carbon-based composite materials, waste generated during the production of graphite anode materials, and graphite anode materials recycled from retired lithium batteries.
4. The method for preparing the carbon ceramic crucible as described in claim 1, characterized in that, The graphite powder has a particle morphology including at least one of flake, spherical and near-spherical shapes, the particle size of the graphite powder is 100μm-1000μm, and the ash content of the graphite powder is <800ppm.
5. The method for preparing the carbon ceramic crucible as described in claim 1, characterized in that, In step S2, the molding pressure is 10MPa-300MPa, the molding time is 5min-40min, and the molding temperature is 100℃-300℃.
6. The method for preparing the carbon ceramic crucible as described in claim 1, characterized in that, In step S3, the temperature of the first high-temperature sintering is 800℃-1000℃, and the time of the first high-temperature sintering is 4h-6h.
7. The method for preparing the carbon ceramic crucible according to any one of claims 1 to 6, characterized in that, The coating slurry comprises, by weight, the following components: 50-70 parts silica sol, 5-20 parts flake graphite, 10-20 parts resin, 10-30 parts silicon carbide, 5-15 parts boric acid, and solvent.
8. The method for preparing the carbon ceramic crucible according to any one of claims 1 to 6, characterized in that, In step S5, the coating thickness of the coating slurry is 0.1 mm to 0.6 mm; and / or, In step S5, the temperature of the second high-temperature sintering is 1000℃-2000℃, and the time of the second high-temperature sintering is 1h-11h.
9. A carbon ceramic crucible, characterized in that, It is prepared by the method for preparing the carbon ceramic crucible according to any one of claims 1 to 8; or, The carbon ceramic crucible includes a crucible substrate and a functional coating disposed inside and on the surface of the porous structure of the crucible substrate. The components of the functional coating include silicon oxide, flake graphite, silicon carbide, and boron oxide. The components of the crucible substrate include carbon fiber, graphite powder, and silicon carbide.
10. A liquid-phase melt infiltration reaction apparatus, characterized in that, Includes the carbon ceramic crucible as described in claim 9.