A graphite crucible, its preparation method and application

Abstract

The present invention provides a graphite crucible, a preparation method thereof and an application. The graphite crucible comprises the following raw materials for preparation in parts by weight: 55 - 60 parts of classified graphite powder, 20 - 25 parts of modified carbon fiber, 1 - 2 parts of polycarbosilane, 1 - 1.5 parts of silicon carbide whiskers, 12 - 15 parts of binder, and 4.5 - 6 parts of compound antioxidant. The raw materials for preparation of the graphite crucible of the present invention include classified graphite powder, modified carbon fiber, polycarbosilane, and silicon carbide whiskers. The combined use of classified graphite powder and modified carbon fiber can significantly improve the flexural strength and toughness of the graphite crucible and extend its service life; the addition of polycarbosilane and silicon carbide whiskers can further improve the high-temperature resistance and antioxidant performance of the graphite crucible, enabling it to maintain good stability at high temperatures.

Description

Technical Field

[0001] This application belongs to the field of new energy material processing, and particularly relates to a graphite crucible, a preparation method thereof, and an application thereof. Background Art

[0002] Graphite crucibles are used as graphitization sintering containers for the negative electrode materials of lithium batteries due to their high carbon content, high temperature resistance, and oxidation resistance. Generally, there are two types of graphite crucibles on the market. One is the dug-out crucible, which uses isostatic pressing high-purity graphite blocks as raw materials and adopts the dug-out process to take out the core material and then prepares the crucible by machining. The raw material utilization rate of this graphite crucible production process is extremely low (less than 20%), generating a large amount of waste, and the production capacity is severely restricted by high-purity graphite raw materials, unable to meet the demands brought by the explosive growth of the new energy industry in recent years. The other is the crucible prepared by applying high pressure in a mold with graphite powder and petroleum coke as the main raw materials and then carbonizing at high temperature. The production equipment for this type of crucible has a large investment, low production efficiency, and low yield. Moreover, due to the large thermal stress of the materials formed by this method at high temperature, indicators such as flexural strength and fracture strength are reduced. Therefore, in actual use, its service life is low.

[0003] Therefore, it is necessary to provide a graphite crucible with better bending strength to extend the service life of the product. Summary of the Invention

[0004] This application provides a graphite crucible, a preparation method thereof, and an application thereof to solve the technical problem of the short service life of existing graphite crucibles.

[0005] In the first aspect of the present invention, a graphite crucible is provided, which comprises the following raw materials in parts by weight:

[0006] 55 - 60 parts of classified graphite powder, 20 - 25 parts of modified carbon fiber, 1 - 2 parts of polycarbosilane, 1 - 1.5 parts of silicon carbide whiskers, 12 - 15 parts of binder, and 4.5 - 6 parts of composite antioxidant;

[0007] The classified graphite powder comprises fine powder with a particle size of 4 - 6 μm and coarse powder with a particle size of 18 - 25 μm, and the mass ratio of the fine powder to the coarse powder is 1:1.2 - 1.8;

[0008] The modified carbon fiber is obtained by mixing and modifying short carbon fibers and carbon nanotubes under the action of a coupling agent, and the mass ratio of the short carbon fibers to the carbon nanotubes is 7 - 9:1.

[0009] Further, the binder is one of epoxy-modified phenolic resin, polyimide resin, polyphenylene sulfide resin, phosphate-based binder, or isocyanate adhesive.

[0010] Further, the composite antioxidant is a mixture of B4C / Y2O3 composite powder and La-Ce oxide.

[0011] The second aspect of the present invention provides a method for preparing a graphite crucible, comprising the following steps:

[0012] S1. Dry-mix classified graphite powder, modified carbon fiber, and silicon carbide whiskers to obtain a dry mixture.

[0013] S2. Mix a binder, polycarbosilane, and a composite antioxidant in ethanol, add the dry mixture and mix again to obtain a mixed slurry.

[0014] S3. Dry, cure, and hot-press the mixed slurry to obtain a graphite crucible.

[0015] Further, in step S1, the rotation speed of the dry mixing is 50-100 rpm, and the time is 30-60 min.

[0016] Further, in step S2, the binder, polycarbosilane, and composite antioxidant are stirred in ethanol for 1-3 h, and the blade linear velocity is 4-6 m / s;

[0017] The viscosity of the mixed slurry is 1200-1500 Pa·s.

[0018] Further, the hot pressing in step S3 is divided into the following three stages:

[0019] Keep the temperature at 170-185 °C for 1-2 h under a pressure of 8-12 MPa;

[0020] Increase the pressure to 14-16 MPa and increase the temperature to 210-230 °C, then keep the temperature for 2-3 h;

[0021] Reduce the pressure to 7-8 MPa and increase the temperature to 250-265 °C, then keep the temperature for 1-2 h.

[0022] The third aspect of the present invention provides an application of the graphite crucible in the preparation of electrode materials.

[0023] Compared with the prior art, the beneficial effects of the present application are as follows:

[0024] (1) The raw materials for preparing the graphite crucible of the present invention include classified graphite powder, modified carbon fiber, polycarbosilane, and silicon carbide whiskers. The combined use of classified graphite powder and modified carbon fiber can significantly improve the flexural strength and toughness of the graphite crucible and extend its service life; the addition of polycarbosilane and silicon carbide whiskers can further improve the high-temperature resistance and oxidation resistance of the graphite crucible, enabling it to maintain good stability at high temperatures.

[0025] (2) The preparation method of the graphite crucible of the present invention has a simple process, convenient operation, high production efficiency, and a high yield of the prepared graphite crucible with stable quality, which can meet the requirements of large-scale industrial production.

[0026] (3) The graphite crucible of the present invention has a broad application prospect in the preparation of electrode materials, which can improve the performance and quality of electrode materials, reduce production costs, and promote the development of the new energy industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0028] Figure 1 It is a schematic diagram of the graphite crucible provided in Embodiment 10. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] In order to make the technical problems to be solved, technical solutions and beneficial effects of the present application more clear, the following further details the present application in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0030] An embodiment of the first aspect of the present invention provides a graphite crucible, which includes the following raw materials in parts by weight for preparation:

[0031] 55 - 60 parts of classified graphite powder, 20 - 25 parts of modified carbon fiber, 1 - 2 parts of polycarbosilane, 1 - 1.5 parts of silicon carbide whiskers, 12 - 15 parts of binder, 4.5 - 6 parts of compound antioxidant.

[0032] The weight parts of the classified graphite powder are any value or any value range among 55 parts, 56 parts, 57 parts, 58 parts, 59 parts, and 60 parts. If the amount of the classified graphite powder is greater than the above range, it may cause the density of the graphite crucible to be too large, affecting its heat conduction performance; if it is less than the above range, it may reduce its flexural strength and affect its service life.

[0033] The weight parts of the modified carbon fiber are any value or any value range among 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, and 25 parts. If the amount of the modified carbon fiber is too much, it may cause the brittleness of the graphite crucible to increase, affecting its toughness; if the amount is too little, it may reduce its thermal shock resistance and shorten its service life.

[0034] The weight fraction of the polycarbosilane is 1 part or 2 parts. If the dosage of the polycarbosilane is greater than the above range, the high-temperature resistance of the graphite crucible may decrease, affecting its stability in a high-temperature environment; if the dosage is too small, it is difficult to form an effective antioxidant protective layer, reducing its antioxidant performance.

[0035] The weight fraction of the silicon carbide whiskers is any value or any value range among 1 part, 1.2 parts, 1.3 parts, 1.4 parts, or 1.5 parts. If the dosage is too much, it may increase the brittleness of the graphite crucible, affecting its toughness; if the dosage is too small, it is difficult to improve its flexural strength, reducing its service life.

[0036] The weight fraction of the binder is any value or any value range among 12 parts, 13 parts, 14 parts, or 15 parts. If the dosage is too much, it may cause the density of the graphite crucible to be too large, affecting its heat conduction performance; if the dosage is too small, it is difficult to ensure its structural stability.

[0037] The weight fraction of the composite antioxidant is any value or any value range among 4.5 parts, 5 parts, 5.5 parts, or 6 parts. If the dosage is too much, it may affect the heat conduction performance of the graphite crucible; if the dosage is too small, it is difficult to effectively prevent oxidation, reducing its service life. By precisely controlling the ratio of each raw material, it is ensured that the graphite crucible has excellent heat conduction, flexural strength, and antioxidant properties, is suitable for high-temperature environments, and extends its service life.

[0038] Preferably, the graphite crucible comprises the following raw materials in weight fractions: 58 parts of classified graphite powder, 22 parts of modified carbon fiber, 1.5 parts of polycarbosilane, 1.2 parts of silicon carbide whiskers, 13 parts of binder, and 5 parts of composite antioxidant.

[0039] The raw materials for preparing the graphite crucible of the present invention include classified graphite powder, modified carbon fiber, polycarbosilane, and silicon carbide whiskers. Among them, the combined use of classified graphite powder and modified carbon fiber can significantly improve the flexural strength and toughness of the graphite crucible and extend its service life; the addition of polycarbosilane and silicon carbide whiskers can further improve the high-temperature resistance and antioxidant properties of the graphite crucible, enabling it to maintain good stability at high temperatures.

[0040] In the embodiment of the present invention, the classified graphite powder comprises fine powder with a particle size of 4 - 6 μm and coarse powder with a particle size of 18 - 25 μm, and the mass ratio of the fine powder to the coarse powder is 1:1.2 - 1.8. The preparation method of the classified graphite powder is to ultrasonically disperse the fine powder and the coarse powder in ethanol for 30 min with an ultrasonic power of 500 W, then perform centrifugal classification and dry at 80°C for 4 h to obtain it. The reasonable ratio of the fine powder to the coarse powder ensures the uniformity and compactness of the internal structure of the graphite crucible, effectively improving its heat conduction performance and mechanical strength.

[0041] In an embodiment of the present invention, the modified carbon fiber is formed by mixing and modifying short-cut carbon fiber and carbon nanotubes under the action of a coupling agent. The mass ratio of the short-cut carbon fiber to the carbon nanotubes is 7-9:1. The preparation method of the modified carbon fiber is to subject the short-cut carbon fiber (3 mm) to steam treatment with KH560 coupling agent (concentration 3 wt%) at 120 °C for 2 h, and then dry-mix it with carbon nanotubes according to a mass ratio of 8:1 and ball-mill and mix for 30 min at a rotation speed of 200 rpm to form a composite reinforcement for improving the overall mechanical properties and thermal stability of the graphite crucible.

[0042] In an embodiment of the present invention, the binder is one of epoxy-modified phenolic resin, polyimide resin, polyphenylene sulfide resin, phosphate-based binder or isocyanate adhesive. Epoxy-modified phenolic resin has good bonding strength and high-temperature resistance and is suitable for the preparation of graphite crucibles in high-temperature environments.

[0043] In an embodiment of the present invention, the composite antioxidant is a mixture of B4C / Y2O3 composite powder and La-Ce oxide. Among them, the mass ratio of B4C to Y2O3 in the B4C / Y2O3 composite powder is 3:1, and the addition of La-Ce oxide further enhances the antioxidant effect. The composite antioxidant forms a protective film at high temperatures, effectively inhibiting the oxidation reaction of the graphite crucible and extending its service life. The B4C / Y2O3 composite powder and La-Ce oxide are mixed in a ratio of 4-5:0.5-1, effectively inhibiting graphite oxidation and improving the durability of the crucible.

[0044] An embodiment of the second aspect of the present invention provides a method for preparing a graphite crucible, including the following steps:

[0045] S1. Dry-mix the classified graphite powder, modified carbon fiber, and silicon carbide whiskers to obtain a dry mixture;

[0046] S2. Mix the binder, polycarbosilane, and composite antioxidant in ethanol, and add the dry mixture and mix again to obtain a mixed slurry;

[0047] S3. Dry, cure, and hot-press the mixed slurry to obtain a graphite crucible.

[0048] In an embodiment of the present invention, the rotation speed of the dry-mixing in step S1 is 50-100 rpm, and the time is 30-60 min. Preferably, the rotation speed of the dry-mixing is 60 rpm, and the time is 45 min to ensure uniform dispersion of each component and improve the uniformity and stability of the mixture.

[0049] In an embodiment of the present invention, in step S2, the binder, polycarbosilane, and compound antioxidant are stirred in ethanol for 1 - 3 h, and the blade linear velocity is 4 - 6 m / s; specifically, in step S2, the binder, polycarbosilane, and compound antioxidant are mixed in ethanol with a solid-liquid ratio of 1:1.2 and stirred for 2 h to obtain a wet mixture, so as to optimize the fluidity and viscosity of the slurry. Dry mixture is added to the wet mixture, and planetary ball milling is carried out at 400 rpm and stirring is continued for 30 min to ensure that all components are fully fused to form a uniform and consistent mixed slurry. The viscosity of the mixed slurry is adjusted to 1200 - 1500 Pa·s.

[0050] In an embodiment of the present invention, the drying in step S3 is vacuum drying. After injecting the slurry into the mold, it is quickly frozen to -40 °C and held for 12 h, then transferred to a vacuum drying oven and dried at 60 °C for 8 h with a vacuum degree of -0.09 MPa to form a porous preform, avoiding density stratification.

[0051] Subsequently, curing treatment is carried out. In the initial stage, it is kept at a constant temperature of 150 °C for 10 min to preferentially cure the surface resin, then the temperature value is adjusted to 180 °C and kept at a constant temperature for 30 min, and the pressure in the mold is maintained at 0.5 MPa to ensure that the binder is fully cured and the structural strength is enhanced.

[0052] The hot pressing in step S3 is divided into the following three stages:

[0053] Insulate at 170 - 185 °C under a pressure of 8 - 12 MPa for 1 - 2 h, and the resin completes the polycondensation reaction;

[0054] Increase the pressure to 14 - 16 MPa and increase the temperature to 210 - 230 °C and insulate for 2 - 3 h, and the whiskers are oriented and arranged along the pressure direction;

[0055] Reduce the pressure to 7 - 8 MPa and increase the temperature to 250 - 265 °C and insulate for 1 - 2 h to eliminate thermal stress.

[0056] Finally, it is cooled to room temperature, the graphite crucible is taken out, with a smooth surface, a dense structure, no obvious defects, and significantly improved antioxidant performance, suitable for high-temperature environments. The graphite crucible prepared by this method not only has excellent high-temperature resistance, but also has greatly enhanced antioxidant ability, extended service life, effectively reduces production costs, and provides a reliable guarantee for high-temperature industrial applications.

[0057] The third aspect of the present invention provides an application of a graphite crucible in the preparation of electrode materials.

[0058] In the process of preparing electrode materials, as a carrier container, the high-temperature resistance and antioxidant properties of the graphite crucible ensure that the electrode materials are not contaminated during the high-temperature sintering process, with a stable structure and improved electrode performance.

[0059] To enable those skilled in the art to clearly understand the above implementation details and operations of this application, and to significantly demonstrate the progressive performance of the embodiments of this application, the above technical solutions will be illustrated by multiple embodiments below.

[0060] Embodiment 1

[0061] A graphite crucible comprises the following preparation raw materials in parts by weight: 58 parts of classified graphite powder, 22 parts of modified carbon fiber, 1.5 parts of polycarbosilane, 1.2 parts of silicon carbide whiskers, 13 parts of binder, and 5 parts of compound antioxidant.

[0062] Embodiment 2

[0063] The preparation raw materials of the graphite crucible in this embodiment are basically the same as those in Embodiment 1, except that the weight part of the classified graphite powder is 55 parts.

[0064] Embodiment 3

[0065] The preparation raw materials of the graphite crucible in this embodiment are basically the same as those in Embodiment 1, except that the weight part of the classified graphite powder is 60 parts.

[0066] Embodiment 4

[0067] The preparation raw materials of the graphite crucible in this embodiment are basically the same as those in Embodiment 1, except that the weight part of the modified carbon fiber is 20 parts.

[0068] Embodiment 5

[0069] The preparation raw materials of the graphite crucible in this embodiment are basically the same as those in Embodiment 1, except that the weight part of the modified carbon fiber is 25 parts.

[0070] Embodiment 6

[0071] The preparation raw materials of the graphite crucible in this embodiment are basically the same as those in Embodiment 1, except that the weight part of the polycarbosilane is 2 parts.

[0072] Embodiment 7

[0073] The preparation raw materials of the graphite crucible in this embodiment are basically the same as those in Embodiment 1, except that the weight part of the polycarbosilane is 1 part.

[0074] Embodiment 8

[0075] The preparation raw materials of the graphite crucible in this embodiment are basically the same as those in Embodiment 1, except that the weight part of the silicon carbide whiskers is 1.5 parts.

[0076] Embodiment 9

[0077] The raw materials for preparing the graphite crucible in this example are basically the same as those in Example 1, except that the weight fraction of silicon carbide whiskers is 1 part.

[0078] Example 10

[0079] A method for preparing a graphite crucible, using the raw materials of Example 1, includes the following steps:

[0080] S1. Dry-mix the classified graphite powder, modified carbon fiber, and silicon carbide whiskers at a rotation speed of 60 rpm for 60 minutes to obtain a dry-mixed material.

[0081] S2. Mix the binder, polycarbosilane, and compound antioxidant in ethanol, stir for 1 hour with a blade linear velocity of 6 m / s, add the dry-mixed material, and then use planetary ball milling at 400 rpm and continue stirring for 30 minutes to obtain a mixed slurry.

[0082] S3. Inject the slurry into a mold and quickly freeze it to -40°C and hold for 12 hours, then transfer it to a vacuum drying oven and dry it at 60°C for 8 hours with a vacuum degree of -0.09 MPa to form a porous preform. Subsequently, perform a curing treatment. Initially, keep it at a constant temperature of 150°C for 10 minutes to preferentially cure the surface resin, then adjust the temperature to 180°C and keep it at a constant temperature for 30 minutes with the pressure in the mold maintained at 0.5 MPa. Then, perform hot pressing for final curing, specifically, keep it at 170°C for 2 hours under a pressure of 8 MPa; increase the pressure to 14 MPa and raise the temperature to 210°C and keep it for 3 hours; reduce the pressure to 7 MPa and raise the temperature to 250°C and keep it for 2 hours to obtain the graphite crucible.

[0083] Example 11

[0084] A method for preparing a graphite crucible, using the raw materials of Example 3, includes the following steps:

[0085] S1. Dry-mix the classified graphite powder, modified carbon fiber, and silicon carbide whiskers at a rotation speed of 80 rpm for 50 minutes to obtain a dry-mixed material.

[0086] S2. Mix the binder, polycarbosilane, and compound antioxidant in ethanol, stir for 2 hours with a blade linear velocity of 5 m / s, add the dry-mixed material, and then use planetary ball milling at 400 rpm and continue stirring for 30 minutes to obtain a mixed slurry.

[0087] S3. After injecting the slurry into the mold, it is quickly frozen to -40°C and kept for 12 hours, then transferred to a vacuum drying oven and dried at 60°C for 8 hours with a vacuum degree of -0.09 MPa to form a porous preform. Subsequently, curing treatment is carried out. In the initial stage, it is kept at a constant temperature of 150°C for 10 minutes to preferentially cure the surface resin, then the temperature value is adjusted to 180°C and kept at a constant temperature for 30 minutes with the pressure in the mold maintained at 0.5 MPa. Then, hot pressing final curing is carried out, specifically, it is kept at 180°C for 1.5 hours under a pressure of 10 MPa; the pressure is increased to 15 MPa and the temperature is raised to 220°C and kept for 2.5 hours; the pressure is decreased to 7 MPa and the temperature is raised to 260°C and kept for 1.5 hours to obtain a graphite crucible.

[0088] Example 12

[0089] A preparation method of a graphite crucible, using the raw materials of Example 5, includes the following steps:

[0090] S1. The classified graphite powder, modified carbon fiber, and silicon carbide whiskers are dry-mixed at a rotation speed of 100 rpm for 30 minutes to obtain a dry-mixed material.

[0091] S2. The binder, polycarbosilane, and compound antioxidant are mixed in ethanol and stirred for 3 hours with the blade linear velocity of 4 m / s. After adding the dry-mixed material, planetary ball milling is carried out at 400 rpm and stirring continues for 30 minutes to obtain a mixed slurry.

[0092] S3. After injecting the slurry into the mold, it is quickly frozen to -40°C and kept for 12 hours, then transferred to a vacuum drying oven and dried at 60°C for 8 hours with a vacuum degree of -0.09 MPa to form a porous preform. Subsequently, curing treatment is carried out. In the initial stage, it is kept at a constant temperature of 150°C for 10 minutes to preferentially cure the surface resin, then the temperature value is adjusted to 180°C and kept at a constant temperature for 30 minutes with the pressure in the mold maintained at 0.5 MPa. Then, hot pressing final curing is carried out, specifically, it is kept at 185°C for 1 hour under a pressure of 12 MPa; the pressure is increased to 16 MPa and the temperature is raised to 230°C and kept for 2 hours; the pressure is decreased to 8 MPa and the temperature is raised to 265°C and kept for 1 hour to obtain a graphite crucible.

[0093] Comparative Example 1

[0094] The preparation method of this comparative example is basically the same as that of Example 10, the difference is that the raw materials do not contain silicon carbide whiskers.

[0095] Comparative Example 2

[0096] The preparation method of this comparative example is basically the same as that of Example 10, the difference is that the carbon nanotubes in the modified carbon fiber are removed in the raw materials and replaced with ordinary carbon fiber.

[0097] Comparative Example 3

[0098] The preparation method of this comparative example is basically the same as that of Example 10, except that the raw materials do not contain polycarbosilane.

[0099] Comparative Example 4

[0100] The preparation method of this comparative example is basically the same as that of Example 10, except that the composite oxidant is a single B4C.

[0101] Comparative Example 5

[0102] The preparation method of this comparative example is basically the same as that of Example 10, except that the composite oxidant does not contain La-Ce oxide.

[0103] Comparative Example 6

[0104] The preparation method of this comparative example is basically the same as that of Example 10, except that the classified graphite powder is replaced with ordinary graphite powder.

[0105] The performance of the graphite crucibles of Examples 10-12 and Comparative Examples 1-6 was tested, and the results are shown in Table 1.

[0106]

[0107] It can be seen from Example 10 and Comparative Examples 1-2 that when the raw materials do not contain silicon carbide whiskers and carbon nanotubes, the bulk density and flexural strength of the graphite crucible decrease sharply. This is because carbon nanotubes can fill microcracks, improving the overall strength and toughness of the material, while silicon carbide whiskers produce a pull-out effect, increasing the fracture work by 3 times, playing a dual role of strengthening and toughening. The synergistic effect of the two significantly improves the mechanical properties of the graphite crucible. At the same time, from the data of the lithium battery sintering life and the oxidation weight loss at 1000 °C, the graphite crucible containing silicon carbide whiskers and carbon nanotubes shows better high-temperature resistance and oxidation resistance, ensuring the stability of the electrode material during high-temperature sintering and the improvement of electrode performance.

[0108] It can be seen from Example 10 and Comparative Example 3 that when the raw materials do not contain polycarbosilane, the flexural strength and lithium battery sintering life of the graphite crucible decrease significantly. This is because polycarbosilane can effectively improve the interfacial bonding force of the material and enhance the overall structural stability. The absence of it leads to an increase in internal defects of the material, resulting in a significant decrease in mechanical properties and high-temperature stability.

[0109] As can be seen from Example 10 and Comparative Examples 4-5, when the composite oxidant is a single B4C, the oxidation weight loss of the graphite crucible increases significantly, indicating that the single B4C oxidant cannot effectively inhibit high-temperature oxidation, and the synergistic effect of the composite oxidant is crucial for improving the antioxidant performance. The deficiency of single B4C leads to poor stability of the material in a high-temperature environment and affects its service life. When the La-Ce oxide is missing in the composite oxidant, the oxidation weight loss of the graphite crucible increases significantly. However, the material in Example 10 has excellent antioxidant ability, which may be because B4C oxidizes to form a B2O3 liquid phase above 600 °C, and Y2O3 forms a YBO3 crystal phase with it. The La-Ce oxide promotes the densification of the oxide film, effectively preventing oxygen diffusion, thus significantly improving the antioxidant performance and further extending the high-temperature service life of the material.

[0110] In addition, from the data comparison of Examples 10-12 and Comparative Example 6, it can be seen that the use of graded graphite powder also has a significant impact on the performance of the graphite crucible. Compared with ordinary graphite powder, graded graphite powder can ensure the uniformity and densification of the internal structure of the graphite crucible through a reasonable ratio of fine powder and coarse powder and the preparation process, effectively improving its thermal conductivity and mechanical strength. Therefore, the graphite crucible prepared with graded graphite powder shows more excellent performance in terms of bulk density, flexural strength, high-temperature resistance, and antioxidant performance. The application of graded graphite powder not only optimizes the microstructure but also reduces internal defects, enhances the thermal stability and mechanical properties of the material, thus providing more reliable guarantee during the high-temperature sintering process and ensuring the efficient and stable operation of the electrode material.

[0111] In the above embodiments, the descriptions of each embodiment have their own emphases. For the parts not detailed or recorded in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0112] The above-described embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit them. Although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments or perform equivalent replacements for some of the technical features. These modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application and should all be included in the protection scope of the present application.

Claims

1. A graphite crucible, characterized in that, It comprises the following raw materials for preparation in parts by weight: 55 - 60 parts of classified graphite powder, 20 - 25 parts of modified carbon fiber, 1 - 2 parts of polycarbosilane, 1 - 1.5 parts of silicon carbide whiskers, 12 - 15 parts of binder, and 4.5 - 6 parts of compound antioxidant; The classified graphite powder comprises fine powder with a particle size of 4 - 6 μm and coarse powder with a particle size of 18 - 25 μm, and the mass ratio of the fine powder to the coarse powder is 1:1.2 - 1.8; The modified carbon fiber is obtained by mixing and modifying short - cut carbon fiber and carbon nanotubes under the action of a coupling agent, and the mass ratio of the short - cut carbon fiber to the carbon nanotubes is 7 - 9:1; The compound antioxidant is a mixture of B4C / Y2O3 composite powder and La - Ce oxide.

2. The graphite crucible according to claim 1, characterized in that, The binder is one of epoxy - modified phenolic resin, polyimide resin, polyphenylene sulfide resin, phosphate - based binder or isocyanate adhesive.

3. A preparation method of the graphite crucible according to any one of claims 1-2, characterized in that, It comprises the following steps: S1. Dry - mix the classified graphite powder, modified carbon fiber and silicon carbide whiskers to obtain a dry - mixed material; S2. Mix the binder, polycarbosilane and compound antioxidant in ethanol, and add the dry - mixed material and mix again to obtain a mixed slurry; S3. Dry, cure and hot - press the mixed slurry to obtain a graphite crucible.

4. The preparation method of the graphite crucible according to claim 3, characterized in that, In step S1, the rotation speed of dry - mixing is 50 - 100 rpm and the time is 30 - 60 min.

5. The preparation method of the graphite crucible according to claim 3, characterized in that, In step S2, the binder, polycarbosilane and compound antioxidant are stirred in ethanol for 1 - 3 h, and the blade linear velocity is 4 - 6 m / s; The viscosity of the mixed slurry is 1200 - 1500 Pa·s.

6. The preparation method of the graphite crucible according to claim 3, characterized in that, In step S3, the hot - pressing is divided into the following three stages: Keep the temperature at 170 - 185 °C for 1 - 2 h under a pressure of 8 - 12 MPa; Increase the pressure to 14 - 16 MPa and increase the temperature to 210 - 230 °C and keep the temperature for 2 - 3 h; Reduce the pressure to 7 - 8 MPa and increase the temperature to 250 - 265 °C and keep the temperature for 1 - 2 h.

7. Use of a graphite crucible according to any one of claims 1 - 2 in the preparation of an electrode material.

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