Durable graphite crucible and preparation method thereof

Abstract

The invention relates to the technical field of graphite materials, and provides a durable graphite crucible and a preparation method thereof. The durable graphite crucible comprises the following raw material components in parts by weight: 60-75 parts of graphitized coke, 6-8 parts of phenolic resin and 30-36 parts of asphalt. The phenolic resin comprises phenolic resin TY03 and phenolic resin 2402. According to the technical scheme, the problem of poor compression strength of the graphite crucible in the prior art is solved.

Description

Technical Field

[0001] The invention relates to the technical field of graphite materials, and in particular to a durable graphite crucible and a preparation method thereof. Background Art

[0002] In the field of high-temperature industrial equipment, graphite crucibles are the core carriers for molten metals, semiconductor melts and new energy materials. Their compressive strength directly determines the safety and stability of equipment operation. However, the unique layered crystal structure of graphite materials (the layers are bonded by van der Waals forces) leads to a natural shortcoming in its compressive performance. The weak interlayer bonding makes the material prone to slippage or grain boundary cracking when bearing loads. Impurities in natural raw materials and pores formed during the preparation process will aggravate stress concentration, resulting in a significant increase in the failure risk of traditional graphite crucibles under complex loads.

[0003] From the perspective of the intrinsic properties of graphite, the anisotropy of graphite crystals causes its compressive strength to show significant directional differences, and the bearing capacity along the interlayer direction is much lower than that in the intralayer direction. This structural characteristic is particularly unfavorable in a three-dimensional load environment. In the traditional process of preparing graphite crucibles, whether it is the uneven distribution of the binder during the kneading process, or the density defects caused by insufficient pressure during molding (such as internal pores and particle agglomeration), the intrinsic defects of the material will be further amplified. For example, in metallurgical smelting, the crucible needs to withstand the static pressure of the molten metal and the shear stress caused by the vibration of the furnace body. Traditional graphite crucibles often cause crack propagation due to local compressive failure, resulting in leakage of molten metal; in the growth of semiconductor silicon single crystals, the stable bearing of the crucible on the melt directly affects the quality of crystal growth, and the attenuation of compressive strength at high temperature will cause the melt to shake, thereby introducing crystal defects.

[0004] Under this background, it is of vital importance to develop a durable graphite crucible to improve the compressive strength of the graphite crucible. Summary of the invention

[0005] The invention provides a durable graphite crucible and a preparation method thereof, which solves the problem of poor compressive strength of the graphite crucible in the related art.

[0006] The technical solution of the present invention is as follows: The present invention provides a durable graphite crucible, wherein the raw materials include the following components in parts by weight: 60-75 parts of graphitized coke, 6-8 parts of phenolic resin, and 30-36 parts of asphalt; The phenolic resin includes phenolic resin TY03 and phenolic resin 2402.

[0007] In the present invention, graphitized coke serves as the main framework material of the durable graphite crucible. After high-temperature graphitization treatment, it has a good graphite crystal structure. Asphalt mainly functions as a binder in the raw material formula of the graphite crucible. During the kneading process, when the temperature reaches a certain range, the asphalt changes from a solid state to a liquid state with good fluidity, fully infiltrates the graphitized coke and phenolic resin 2402 particles, and forms a uniform coating film on the surface of the particles. Through physical bonding, the particles are tightly combined together, enabling the graphite crucible to be initially formed and have a certain shape retention ability. During the subsequent roasting process, the asphalt further undergoes a carbonization reaction, intertwining with the graphite structure of the graphitized coke and the cross-linked structure formed by the phenolic resin, enhancing the bonding force between the particles and maintaining the density and mechanical properties of the graphite crucible.

[0008] As a further technical solution, the mass ratio of phenolic resin TY03 to phenolic resin 2402 is 5:3 to 4.

[0009] In the present invention, the mass ratio of phenolic resin TY03 to phenolic resin 2402 can be 5:3, 5:3.1, 5:3.2, 5:3.3, 5:3.4, 5:3.5, 5:3.6, 5:3.7, 5:3.8, 5:3.9, 5:4, and is preferably 5:3.5.

[0010] In the present invention, by adjusting the mass ratio of phenolic resin TY03 to phenolic resin 2402 to 5:3 to 4, the compressive strength of the graphite crucible is further improved. When the mass ratio is greater than 5:3 to 4 or less than 5:3 to 4, the compressive strength of the graphite crucible decreases. This is because when the mass ratio of phenolic resin TY03 to phenolic resin 2402 is greater than 5:3 to 4, too much phenolic resin TY03 may increase the viscosity of the material, resulting in increased difficulty in the kneading process and a decline in the performance of the graphite crucible. When the mass ratio of phenolic resin TY03 to phenolic resin 2402 is less than 5:3 to 4, too much phenolic resin 2402 will increase the brittleness of the graphite crucible. When subjected to the thermal stress generated by temperature changes, due to the lack of sufficient flexibility to buffer the thermal stress, the graphite crucible is more likely to crack and the compressive strength decreases.

[0011] As a further technical solution, the graphitized coke is composite graphitized coke; The raw materials of the composite graphitized coke include graphitized coke and 3-allyl-4-hydroxyacetophenone.

[0012] Thermal cycle durability is a core indicator for measuring the structural integrity and performance stability of graphite crucibles in an environment of repeated high and low temperature alternations. Graphite crucibles are commonly used in scenarios such as metallurgical smelting, photovoltaic crystalline silicon sintering, and semiconductor material purification. In these processes, the crucibles need to frequently experience drastic temperature changes from room temperature to over a thousand degrees Celsius. If the thermal cycle durability of the crucible is insufficient, frequent cracking, bottom penetration, or spalling will cause leakage of the molten material, leading to unplanned shutdowns, not only causing material waste but also potentially polluting the furnace and even triggering safety accidents. Therefore, in the present invention, in order to improve the thermal cycle durability of graphite crucibles, 3-allyl-4-hydroxyacetophenone is used to modify graphitized coke. The molecular structure of 3-allyl-4-hydroxyacetophenone contains reactive groups such as allyl and hydroxyl groups. During the preparation process of the composite graphitized coke, these reactive groups can interact with the carbon atoms or functional groups on the surface of the graphitized coke. These interactions modify the surface of the graphitized coke, changing its surface properties. When using the 3-allyl-4-hydroxyacetophenone composite graphitized coke to prepare a graphite crucible, the modified surface of the graphitized coke can form a stronger binding force with phenolic resin and has better compatibility, thus stabilizing the internal structure of the graphite crucible and improving the thermal cycle durability of the graphite crucible.

[0013] As a further technical solution, the preparation method of the composite graphitized coke includes the following steps: Add graphitized coke and 3-allyl-4-hydroxyacetophenone to ethanol, mix until uniform, concentrate, and dry to obtain the composite graphitized coke.

[0014] As a further technical solution, in the raw materials of the composite graphitized coke, the mass ratio of the graphitized coke to 3-allyl-4-hydroxyacetophenone is 50:1 to 2.

[0015] In the present invention, when the mass ratio of graphitized coke to 3-allyl-4-hydroxyacetophenone is in the range of 50:1 to 2, the content of 3-allyl-4-hydroxyacetophenone can not only ensure sufficient modification of the surface of the graphitized coke but also will not change the excellent properties of the graphitized coke itself due to excessive content. An appropriate amount of 3-allyl-4-hydroxyacetophenone molecules can fully contact and react or adsorb with the surface of the graphitized coke. The allyl and hydroxyl and other reactive groups in its molecules interact with the carbon atoms or functional groups on the surface of the graphitized coke, forming a uniform and appropriate modification layer on the surface of the graphitized coke. This modification layer enhances the binding force and compatibility between the graphitized coke and other components such as phenolic resin and pitch, while retaining the good thermal conductivity, high strength and other inherent properties of the graphitized coke, thereby further improving the thermal cycle durability of the graphite crucible. If the content of 3-allyl-4-hydroxyacetophenone is too low, it may not be able to fully modify the surface of the graphitized coke, resulting in weak binding with other components; if the content is too high, it may overly change the structure of the graphitized coke and affect its original performance.

[0016] As a further technical method, the mass-to-volume ratio of graphitized coke to ethanol is 1 g: 5-10 mL.

[0017] In the present invention, ethanol, as a common organic solvent, has good solubility and dispersibility. When graphitized coke and ethanol are mixed in a ratio of 1 g: 5-10 mL, ethanol can effectively disperse graphitized coke particles. For such solid particles as graphitized coke, it reduces the agglomeration phenomenon between particles and enables them to be evenly distributed in the system. 3-Allyl-4-hydroxyacetophenone can be evenly dissolved in the ethanol solution and then evenly contact with graphitized coke particles.

[0018] As a further technical solution, the graphitized coke includes graphitized coke I and graphitized coke II, and the particle size of the graphitized coke I is: 0 mm < particle size ≤ 2 mm; The particle size of the graphitized coke II is: 2 mm < particle size ≤ 8 mm.

[0019] As a further technical solution, the mass ratio of the graphitized coke I to the graphitized coke II is 8.5-9.5:1.

[0020] In the present invention, the mass ratio of the graphitized coke I to the graphitized coke II can be 8.5:1, 8.6:1, 8.7:1, 8.8:1, 8.9:1, 9:1, 9.1:1, 9.2:1, 9.3:1, 9.4:1, 9.5:1.

[0021] In the present invention, using graphitized coke with different particle sizes in combination can achieve a close-packed structure. The particle size of graphitized coke II is relatively large, forming the framework structure of a durable graphite crucible and providing basic support force. While the particle size of graphitized coke I is small and can fill the pores between the particles of graphitized coke II. The combination of large and small particles can make the graphitized coke reach a higher packing density during mixing. When the graphitized coke I and graphitized coke II are mixed in a ratio of 8.5-9.5:1, the small-particle graphitized coke I can fill the voids between the large-particle graphitized coke II to the maximum extent, reducing the internal porosity and making the whole system more dense. When under pressure, stress can be more effectively transmitted between particles, avoiding stress concentration in local areas.

[0022] The present invention also provides a preparation method of a durable graphite crucible for preparing the durable graphite crucible described above, including the following steps: Mix the graphitized coke with phenolic resin TY03, then mix it evenly with phenolic resin 2402, and then knead it with pitch, shape it, and bake it to obtain the durable graphite crucible.

[0023] In the present invention, first, graphite is mixed with phenolic resin TY03. The phenolic resin TY03 can initially infiltrate and fill the voids on the surface of graphite particles, enabling the two to be initially combined. Then, it is mixed with phenolic resin 2402. The phenolic resin 2402 can further fill the gaps between the graphite particles that have been initially coated with the phenolic resin TY03. The two phenolic resins cooperate with each other to more comprehensively cover the graphite particles, forming a tighter bonding structure. At this time, the crosslinking network of the phenolic resin TY03 and the phenolic resin 2402 begins to be initially constructed, laying a foundation for subsequent kneading with pitch and ultimately forming a stable structure. Finally, it is kneaded with pitch. As a binder, the pitch evenly coats the graphite particles that have been coated with the phenolic resin during the kneading process. As the temperature rises, the pitch softens and flows, further filling the voids between the particles and enhancing the bonding force between the particles. In this step-by-step mixing process, each component can be more evenly dispersed, and the formed structure is more stable, which is beneficial to improving the overall performance of the graphite crucible.

[0024] As a further technical solution, during the kneading, the temperature is 140 - 155 °C and the time is 65 - 75 min. During the molding, the pressure is 12 - 14 MPa.

[0025] In the present invention, the kneading temperature is controlled at 140 - 155 °C. Within this temperature range, the molecular activity of the phenolic resin is increased, and the interaction between its active groups (such as phenolic hydroxyl groups) and the carbon atoms or active sites on the surface of graphitized coke is enhanced, thereby strengthening the bonding effect of the phenolic resin on graphitized coke. At the same time, the pitch reaches a suitable softening state at this temperature, its viscosity decreases, and its fluidity increases, enabling it to better coat the graphitized coke particles and fill the tiny voids between the particles. The kneading time is set to 65 - 75 min to ensure that the phenolic resin, pitch, and graphitized coke can be fully mixed and interact with each other. When molding, a pressure of 12 - 14 MPa is applied. This pressure can make the kneaded material tightly packed in the mold. Within this pressure range, the distance between the graphitized coke particles is further reduced, and the phenolic resin better fills the remaining voids between the particles under the action of pressure, enhancing the bonding force between the particles. At the same time, it enables the graphite crucible to initially form a structure with a certain strength and stability after molding.

[0026] As a further technical solution, during the roasting, the temperature is 1000 - 1200 °C and the time is 30 - 35 d.

[0027] In the present invention, during roasting, the temperature is 1000 - 1200 °C and the time is 30 - 35 days. Under these conditions, the carbonization process of phenolic resin and pitch, as well as the perfection of the graphitized coke crystal structure, can gradually reach an ideal level. At the same time, the longer roasting time makes the reaction closer to the equilibrium state, the interaction between components is more sufficient, the pitch can be completely carbonized and achieve good fusion with other components, and the degree of order of the graphitized coke crystal structure is continuously improved.

[0028] The working principle and beneficial effects of the present invention are as follows: In the present invention, the compounding of phenolic resin TY03 and phenolic resin 2402 improves the pressure resistance of the graphite crucible. In the prior art, during the production of graphite materials, the mechanism of adding phenolic resin is that after phenolic resin is cured and carbonized, the generated glassy carbon serves as the reinforcing phase of the graphite material to improve the tensile and flexural strength of the graphite material. In the present invention, after phenolic resin is carbonized, it not only serves as the reinforcing phase of the graphite material, but also pays attention to the mixing process of phenolic resin and graphitized coke and other components before carbonization. The compounding of phenolic resin TY03 and phenolic resin 2402 synergistically optimizes the mixing effect of graphitized coke and other components. Phenolic resin TY03 is a boron-modified phenolic resin solution. With its excellent rigid molecular structure, during the preparation of the graphite crucible, it fills the voids of graphitized coke and connects raw material particles such as graphitized coke together, increasing the internal stability. Phenolic resin 2402 is a phenolic resin particle that gradually softens during the preparation of the graphite crucible and interacts with the surface of graphitized coke, strengthening the bonding force between graphitized coke particles and pitch. Therefore, first use phenolic resin TY03 to fill graphitized coke, and then use phenolic resin 2402 to further improve the bonding force between graphitized coke particles and pitch after softening. The synergistic effect of the two phenolic resins enables the raw materials of the graphite crucible to be fully combined, improving the compactness of the graphite crucible, and thus improving the pressure resistance of the graphite crucible. Specific embodiments

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention.

[0030] In the following embodiments and comparative examples: The pitch is medium-temperature coal tar pitch, meeting the requirements of No. 1 medium-temperature pitch in GB / T 2290 - 2012; The particle size of graphitized coke I: 0 mm < particle size ≤ 2 mm; The particle size of graphitized coke II: 2 mm < particle size ≤ 8 mm; The phenolic resin TY03 was purchased from Green Link (Jining) Chemical Technology Co., Ltd., and the solid content was 45% (105 °C, 2 h). The phenolic resin 2402 was purchased from Jinan Shanhaichem Chemical Technology Co., Ltd.

[0031] Example 1 A durable graphite crucible, the raw materials of which include the following components in parts by weight: 75 parts of graphitized coke, 8 parts of phenolic resin, and 36 parts of pitch; The phenolic resin includes phenolic resin TY03 and phenolic resin 2402 with a mass ratio of 5:6; The graphitized coke includes graphitized coke I and graphitized coke II with a mass ratio of 9.5:1; The preparation method of the durable graphite crucible includes the following steps: Mix the graphitized coke with phenolic resin TY03, then mix it evenly with phenolic resin 2402, and then knead it with pitch at 155 °C for 65 min, mold it under a pressure of 14 MPa, and then bake it at 1200 °C for 30 d to obtain the durable graphite crucible.

[0032] Example 2 A durable graphite crucible, the raw materials of which include the following components in parts by weight: 60 parts of graphitized coke, 6 parts of phenolic resin, and 30 parts of pitch; The phenolic resin includes phenolic resin TY03 and phenolic resin 2402 with a mass ratio of 5:1; The graphitized coke includes graphitized coke I and graphitized coke II with a mass ratio of 8.5:1; The preparation method of the durable graphite crucible includes the following steps: Mix the graphitized coke with phenolic resin TY03, then mix it evenly with phenolic resin 2402, and then knead it with pitch at 140 °C for 75 min, mold it under a pressure of 12 MPa, and then bake it at 1000 °C for 35 d to obtain the durable graphite crucible.

[0033] Example 3 A durable graphite crucible, the raw materials of which include the following components in parts by weight: 70 parts of graphitized coke, 7 parts of phenolic resin, and 34 parts of pitch; The phenolic resin includes phenolic resin TY03 and phenolic resin 2402 with a mass ratio of 1:1; The graphitized coke includes graphitized coke I and graphitized coke II with a mass ratio of 9:1; The preparation method of the durable graphite crucible includes the following steps: Mix the graphitized coke with phenolic resin TY03, then mix it evenly with phenolic resin 2402, and then knead it with pitch at 145 °C for 70 min, mold it under a pressure of 13 MPa, and then bake it at 1100 °C for 33 d to obtain the durable graphite crucible.

[0034] Example 4 The difference between this example and Example 3 is only that the phenolic resin in this example includes phenolic resin TY03 and phenolic resin 2402 with a mass ratio of 5:2.

[0035] Example 5 The difference between this example and Example 3 is only that the phenolic resin in this example includes phenolic resin TY03 and phenolic resin 2402 with a mass ratio of 5:3.

[0036] Example 6 The difference between this example and Example 3 is only that the phenolic resin in this example includes phenolic resin TY03 and phenolic resin 2402 with a mass ratio of 5:4.

[0037] Example 7 The difference between this example and Example 6 is only that the graphitized coke in this example is replaced with an equal mass of composite graphitized coke; The preparation method of the composite graphitized coke includes the following steps: Add graphitized coke and 3-allyl-4-hydroxyacetophenone into ethanol (the mass ratio of graphitized coke to 3-allyl-4-hydroxyacetophenone is 50:1, and the mass-volume ratio of graphitized coke to ethanol is 1 g:10 mL), mix until uniform, concentrate, and dry to obtain the composite graphitized coke.

[0038] Example 8 The difference between this example and Example 6 is only that the graphitized coke in this example is replaced with an equal mass of composite graphitized coke; The preparation method of the composite graphitized coke includes the following steps: Add graphitized coke and 3-allyl-4-hydroxyacetophenone into ethanol (the mass ratio of graphitized coke to 3-allyl-4-hydroxyacetophenone is 25:1, and the mass-volume ratio of graphitized coke to ethanol is 1 g:5 mL), mix until uniform, concentrate, and dry to obtain the composite graphitized coke.

[0039] Comparative Example 1 The difference between this comparative example and Example 3 is only that the phenolic resin 2402 in this comparative example is replaced with an equal mass of phenolic resin TY03.

[0040] Comparative Example 2 The difference between this comparative example and Example 3 is only that the phenolic resin TY03 in this comparative example is replaced with an equal mass of phenolic resin 2402.

[0041] Comparative Example 3 The difference between this comparative example and Example 3 is only that no phenolic resin is added in this comparative example.

[0042] Experimental Example 1 The normal temperature compressive strength of the durable graphite crucibles prepared in Examples 1-6 and Comparative Examples 1-3 was tested according to Method 2 specified in GB / T 5072-2023 "Test Method for Normal Temperature Compressive Strength of Refractory Materials". The specimen size was a cube of 20mm×20mm×20mm. The test results are shown in Table 1.

[0043] Table 1 Test Results of Compressive Strength

[0044] As can be seen from Table 1, the normal temperature compressive strength of the durable graphite crucibles prepared in Examples 1-6 of the present invention reached more than 101.7 MPa. Therefore, in the present invention, the synergistic effect of two phenolic resins was used to improve the compressive strength of the graphite crucible.

[0045] Experimental Example 2 The durable graphite crucibles prepared in Examples 6-8 were tested for the number of high and low temperature resistance cycles in the temperature range of 0-1500°C. The test results are shown in Table 2.

[0046] Table 2 Test Results of the Number of High and Low Temperature Resistance Cycles

[0047] As can be seen from Table 2, the number of high and low temperature resistance cycles of the durable graphite crucibles prepared in Examples 7-8 of the present invention reached more than 69 times. Therefore, in the present invention, 3-allyl-4-hydroxyacetophenone was used to treat graphitized coke, improving the thermal cycle durability of the durable graphite crucible.

[0048] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A durable graphite crucible, characterized in that, The raw materials include the following components in parts by weight: 60 - 75 parts of graphitized coke, 6 - 8 parts of phenolic resin, and 30 - 36 parts of pitch; The phenolic resin includes phenolic resin TY03 and phenolic resin 2402.

2. A durable graphite crucible according to claim 1, characterized in that, The mass ratio of phenolic resin TY03 to phenolic resin 2402 is 5:3 - 4.

3. A durable graphite crucible according to any one of claims 1 to 2, characterized in that, The graphitized coke is composite graphitized coke; The raw materials of the composite graphitized coke include graphitized coke and 3 - allyl - 4 - hydroxyacetophenone.

4. The durable graphite crucible according to claim 3, wherein, The preparation method of the composite graphitized coke includes the following steps: Adding graphitized coke and 3 - allyl - 4 - hydroxyacetophenone into ethanol, mixing until uniform, concentrating, and drying to obtain the composite graphitized coke.

5. A durable graphite crucible according to claim 3, characterized in that, In the raw materials of the composite graphitized coke, the mass ratio of graphitized coke to 3 - allyl - 4 - hydroxyacetophenone is 50:1 - 2.

6. A durable graphite crucible according to claim 1, characterized in that, The graphitized coke includes graphitized coke Ⅰ and graphitized coke Ⅱ. The particle size of graphitized coke Ⅰ: 0mm < particle size ≤ 2mm; The particle size of graphitized coke Ⅱ: 2mm < particle size ≤ 8mm.

7. A durable graphite crucible according to claim 6, characterized in that, The mass ratio of graphitized coke Ⅰ to graphitized coke Ⅱ is 8.5 - 9.5:

1.

8. A method for preparing a durable graphite crucible, which is used to prepare a durable graphite crucible as described in claim 1, and is characterized in that, Including the following steps: Mixing graphitized coke with phenolic resin TY03, then mixing evenly with phenolic resin 2402, and then kneading with pitch, forming, and roasting to obtain the durable graphite crucible.

9. The preparation method of a durable graphite crucible according to claim 8, characterized in that, When kneading, the temperature is 140 - 155°C and the time is 65 - 75 min; When forming, the pressure is 12 - 14 MPa.

10. The preparation method of a durable graphite crucible according to claim 8, characterized in that, When roasting, the temperature is 1000 - 1200°C and the time is 30 - 35 d.

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