Graphite crucible and preparation method thereof

Abstract

The invention relates to the technical field of graphite materials, and provides a graphite crucible and a preparation method thereof. Raw materials of the graphite crucible comprise the following components in parts by weight: 72-80 parts of graphitized coke, 30-35 parts of asphalt and 5-8 parts of metal nitride. The metal nitride includes zirconium nitride and titanium nitride. According to the technical scheme, the problem of poor thermal cycle durability of the graphite crucible in the prior art is solved.

Description

Technical Field

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

[0002] In the field of high-temperature material applications, graphite crucibles have become key equipment in industries such as metallurgy, semiconductors, and new energy due to their excellent thermal conductivity and chemical stability. However, in actual working conditions, they often face the severe test of extreme temperature cycles, with frequent rapid changes from room temperature to over a thousand degrees Celsius, resulting in the repeated accumulation of thermal stress inside the material, leading to problems such as crack initiation, coating peeling, and structural failure, which seriously restrict the efficiency and stability of industrial production.

[0003] The layered crystal structure of graphite determines the anisotropy of its thermophysical properties. The weak interlayer bonding force leads to easy slip at high temperatures, and the thermal stress generated by rapid cooling and heating will concentrate at grain boundaries and defects, triggering the initiation and propagation of microcracks. Moreover, silicates in graphite further exacerbate this problem. These impurities not only change the thermal expansion coefficient and thermal conductivity uniformity of the material but also react with molten metal or furnace gas at high temperatures, resulting in a thinner crucible wall and a loose structure.

[0004] Currently, existing graphite crucibles still have the problem of poor thermal cycle durability. Therefore, it is of crucial significance to develop a graphite crucible that can improve thermal cycle durability. Summary of the Invention

[0005] The present invention provides a graphite crucible and a preparation method thereof, which solve the problem of poor thermal cycle durability of graphite crucibles in related technologies.

[0006] The technical solution of the present invention is as follows: The present invention provides a graphite crucible, and the raw materials include the following components in parts by weight: 72 - 80 parts of graphitized coke, 30 - 35 parts of pitch, and 5 - 8 parts of metal nitride; The metal nitride includes zirconium nitride and titanium nitride.

[0007] As a further technical solution, the mass ratio of zirconium nitride to titanium nitride is 7 - 9:3.

[0008] As a further technical solution, the mass ratio of zirconium nitride to titanium nitride is 8:3.

[0009] In the present invention, the mass ratio of zirconium nitride to titanium nitride can be 7:3, 7.1:3, 7.2:3, 7.3:3, 7.4:3, 7.5:3, 7.6:3, 7.7:3, 7.8:3, 7.9:3, 8:3, 8.1:3, 8.2:3, 8.3:3, 8.4:3, 8.5:3, 8.6:3, 8.7:3, 8.8:3, 8.9:3, 3:1, and preferably 8:3.

[0010] In the present invention, by adjusting the mass ratio of zirconium nitride to titanium nitride to 7 - 9:3, the thermal cycle durability of the graphite crucible is further improved. Within this mass ratio range, when zirconium nitride and titanium nitride are kneaded with other raw materials such as graphitized coke and pitch, they can be more evenly dispersed in the graphite matrix. Due to the rationality of the ratio of the two, under the bonding action of pitch, their combination with each other and with graphitized coke is closer and more stable.

[0011] As a further technical solution, the metal nitride further includes rare earth nitride; The rare earth nitride includes one or more of cerium nitride, yttrium nitride, and scandium nitride.

[0012] In the present invention, when the metal nitride further includes rare earth nitride, the compressive strength of the graphite crucible is improved. The rare earth nitride is uniformly dispersed in the graphite matrix in the form of fine particles. When the graphite crucible is subjected to external force at room temperature, dislocation movement is the main cause of material deformation and failure, while the rare earth nitride particles can effectively hinder the slip of dislocations, causing phenomena such as pile-up and bypassing of dislocations when they encounter particles during movement. Moreover, the rare earth nitride can improve the interfacial bonding strength between graphitized coke, pitch, and other metal nitrides, thereby improving the compressive strength of the graphite crucible.

[0013] As a further technical solution, when the rare earth nitride is cerium nitride, the mass ratio of zirconium nitride, titanium nitride, and cerium nitride is 8:3:1 - 2.

[0014] In the present invention, the mass ratio of zirconium nitride, titanium nitride, and cerium nitride can be 8:3:1, 8:3:1.1, 8:3:1.2, 8:3:1.3, 8:3:1.4, 8:3:1.5, 8:3:1.6, 8:3:1.7, 8:3:1.8, 8:3:1.9, 8:3:2.

[0015] In the present invention, by adjusting the mass ratio of zirconium nitride, titanium nitride and cerium nitride to 8:3:1 to 2, the uniform distribution of cerium nitride in the graphite matrix and the mixed system with zirconium nitride and titanium nitride is ensured. The appropriate proportion of cerium nitride can precisely control the growth of graphite grains, making the graphite grain size small and evenly distributed. The zirconium nitride and titanium nitride particles are also evenly dispersed among the refined grains. When under pressure, each component cooperates to efficiently disperse and transfer stress, further improving the pressure resistance of the graphite crucible.

[0016] As a further technical solution, the graphitized coke includes graphitized coke I and graphitized coke II. The particle size of the graphitized coke I: 0 mm < particle size ≤ 2 mm; The particle size of the graphitized coke II: 2 mm < particle size ≤ 8 mm.

[0017] As a further technical solution, the mass ratio of the graphitized coke I and the graphitized coke II is 8.5 to 9.5:1.

[0018] In the present invention, the mass ratio of the graphitized coke I and 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.

[0019] In the present invention, using graphitized coke with different particle sizes can achieve a closely packed structure. The particle size of the graphitized coke II is relatively large, forming the framework structure of the graphite crucible and providing basic support. While the particle size of the graphitized coke I is small and can fill the pores between the particles of the graphitized coke II. This reasonable combination of large and small particles can make the graphitized coke reach a high packing density during mixing. When the graphitized coke I and the graphitized coke II are mixed in a ratio of 8.5 to 9.5:1, the small-particle graphitized coke I can maximize the filling of the voids between the large-particle graphitized coke II, reducing the internal porosity and making the whole system more dense. When under pressure, the stress can be more effectively transferred between the particles, avoiding stress concentration in local areas.

[0020] The present invention also provides a method for preparing a graphite crucible for preparing the above-mentioned graphite crucible, which includes the following steps: uniformly mixing the graphitized coke with the metal nitride, then kneading with pitch, forming, and roasting to obtain the graphite crucible.

[0021] In the present invention, the graphitized coke and the metal nitride are firstly mixed evenly to ensure that the metal nitride is evenly dispersed in the graphitized coke matrix, and then kneaded with asphalt, and the asphalt can wrap the evenly mixed graphitized coke and metal nitride particles, and in the kneading process, the asphalt forms a good interface bonding with them. When the graphite crucible is subjected to pressure, the good interface bonding can ensure that the stress is effectively transferred between different materials, avoiding structural damage caused by interface debonding.

[0022] As a further technical solution, during the kneading, the temperature is 145-155°C and the time is 60-70 minutes; During the molding, the pressure is 10-15 MPa.

[0023] In the present invention, the kneading temperature is within the range of 145-155°C, and the asphalt gradually softens within this temperature range, changing from a solid state to a viscous flow state with good fluidity. The asphalt can fully infiltrate the graphitized coke and metal nitride particles to form a uniform coating on the surface of the particles. If the temperature is too low, the asphalt cannot be fully softened and it is difficult to evenly wrap the particles, resulting in poor bonding effect and easy relative sliding between particles when subjected to force; if the temperature is too high, the asphalt may be over-oxidized or decomposed, affecting its bonding performance.

[0024] In the present invention, a pressure of 10-15 MPa is applied during molding. Within this pressure range, the kneaded material can be further tightly arranged, the graphitized coke with larger particle size forms a skeleton structure, and the graphitized coke with smaller particle size fills it, and the metal nitride is evenly distributed in the gap. Under the action of pressure, the contact between the particles is closer, and the porosity is further reduced. When the tightly arranged structure is under pressure, the stress can be more effectively transmitted between the particles to avoid stress concentration in local areas. At the same time, appropriate pressure can also make the asphalt further flow and fill between the particles, enhance the bonding force between the particles, thereby improving the compressive strength of the graphite crucible. When the pressure is less than this range, the material cannot reach a sufficient degree of tightness, the internal pores are more, and the compressive strength is lower; when the pressure is greater than this range, it may cause the particles to break and destroy the original structure, which is also not conducive to the improvement of the compressive strength.

[0025] As a further technical solution, during the calcination, the temperature is 950-1200° C. and the time is 30-35 days.

[0026] The working principle and beneficial effects of the present invention are: In the present invention, graphitized coke is used as the main component, ensuring that the crucible has the necessary thermal stability and mechanical strength foundation. The pitch can fully infiltrate the graphitized coke and metal nitride particles, forming a uniform coating film on the particle surface, and tightly binding each particle together through physical bonding, enabling the graphite crucible to be initially formed and have a certain shape retention ability. The thermal expansion coefficients of zirconium nitride and titanium nitride are relatively close to that of graphite. During the thermal cycling process, when the graphite crucible undergoes temperature changes, the thermal expansion and contraction degrees of each component are similar, which can effectively reduce the thermal stress generated inside the material due to thermal expansion differences. Moreover, zirconium nitride and titanium nitride act synergistically to improve the thermal cycling durability of the graphite crucible. Detailed implementation manners

[0027] 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.

[0028] In the following examples 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.

[0029] Example 1 A preparation method of a graphite crucible includes the following steps: By weight, 80 parts of graphitized coke are mixed evenly with 8 parts of metal nitride, and then mixed with 35 parts of pitch at 155 °C for kneading for 60 min, formed under a pressure of 15 MPa, and then calcined at 1200 °C for 30 d to obtain the graphite crucible; The metal nitride includes zirconium nitride and titanium nitride with a mass ratio of 11:3; The graphitized coke includes graphitized coke Ⅰ and graphitized coke Ⅱ with a mass ratio of 9.5:1.

[0030] Example 2 A preparation method of a graphite crucible includes the following steps: By weight, 72 parts of graphitized coke are mixed evenly with 5 parts of metal nitride, and then mixed with 30 parts of pitch at 145 °C for kneading for 70 min, formed under a pressure of 10 MPa, and then calcined at 950 °C for 35 d to obtain the graphite crucible; The metal nitride includes zirconium nitride and titanium nitride with a mass ratio of 5:3; The graphitized coke includes graphitized coke Ⅰ and graphitized coke Ⅱ with a mass ratio of 8.5:1.

[0031] Example 3 A preparation method of a graphite crucible includes the following steps: By weight, 76 parts of graphitized coke are mixed evenly with 7 parts of metal nitride, and then mixed with 32 parts of pitch at 150 °C for 65 min, molded under a pressure of 13 MPa, and then calcined at 1100 °C for 33 d to obtain the graphite crucible; The metal nitride includes zirconium nitride and titanium nitride with a mass ratio of 10:3; The graphitized coke includes graphitized coke I and graphitized coke II with a mass ratio of 9:1.

[0032] Example 4 The difference between this example and Example 3 is only that the mass ratio of zirconium nitride and titanium nitride in this example is 2:1.

[0033] Example 5 The difference between this example and Example 3 is only that the mass ratio of zirconium nitride and titanium nitride in this example is 7:3.

[0034] Example 6 The difference between this example and Example 3 is only that the mass ratio of zirconium nitride and titanium nitride in this example is 8:3.

[0035] Example 7 The difference between this example and Example 3 is only that the mass ratio of zirconium nitride and titanium nitride in this example is 3:1.

[0036] Example 8 The difference between this example and Example 6 is only that the metal nitride in this example includes zirconium nitride, titanium nitride and cerium nitride with a mass ratio of 8:3:2.

[0037] Example 9 The difference between this example and Example 6 is only that the metal nitride in this example includes zirconium nitride, titanium nitride and yttrium nitride with a mass ratio of 8:3:2.

[0038] Example 10 The difference between this example and Example 6 is only that the metal nitride in this example includes zirconium nitride, titanium nitride and scandium nitride with a mass ratio of 8:3:2.

[0039] Example 11 The difference between this example and Example 6 is only that the metal nitride in this example includes zirconium nitride, titanium nitride and cerium nitride with a mass ratio of 8:3:1.

[0040] Comparative Example 1 The difference between this comparative example and Example 3 is only that the metal nitride in this comparative example is zirconium nitride.

[0041] Comparative Example 2 The difference between this comparative example and Example 3 is only that the metal nitride in this comparative example is titanium nitride.

[0042] Comparative Example 3 The difference between this comparative example and Example 3 is only that there is no metal nitride in this comparative example.

[0043] Comparative Example 4 The difference between this comparative example and Example 6 is only that the metal nitride in this comparative example includes zirconium nitride and cerium nitride with a mass ratio of 8:1.

[0044] Comparative Example 5 The difference between this comparative example and Example 6 is only that the metal nitride in this comparative example includes zirconium nitride and cerium nitride with a mass ratio of 3:1.

[0045] Experimental Example 1 The graphite crucibles prepared in Examples 1 to 7 and Comparative Examples 1 to 3 were subjected to high and low temperature resistance cycle tests in the temperature range of 0 to 1500°C. The test results are shown in Table 1.

[0046] Table 1 Test results of high and low temperature resistance cycle

[0047] As can be seen from Table 1, in the present invention, the number of high and low temperature resistance cycles of the graphite crucibles prepared in Examples 1 to 7 reached 42 or more. Therefore, in the present invention, the co-addition of zirconium nitride and titanium nitride synergistically improves the thermal cycle durability of the graphite crucible.

[0048] Experimental Example 2 The graphite crucibles prepared in Example 6, Examples 8 to 11 and Comparative Examples 4 to 5 were tested for normal temperature compressive strength according to Method 2 specified in GB / T 5072-2023 "Refractory materials - Test method for normal temperature compressive strength". The specimen size was a cube of 20 mm × 20 mm × 20 mm. The test results are shown in Table 2.

[0049] Table 2 Test results of compressive strength

[0050] As can be seen from Table 2, in the present invention, the normal temperature compressive strength of the graphite crucibles prepared in Examples 8 to 11 reached 108.6 MPa or more. Therefore, in the present invention, the addition of rare earth nitride in combination with zirconium nitride and titanium nitride improves the compressive strength of the graphite crucible.

[0051] 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 principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A graphite crucible, characterized in that, The raw materials include the following components in parts by weight: 72-80 parts of graphitized coke, 30-35 parts of pitch, and 5-8 parts of metal nitride; The metal nitride includes zirconium nitride and titanium nitride.

2. A graphite crucible according to claim 1, wherein, The mass ratio of the zirconium nitride to the titanium nitride is 7-9:

3.

3. A graphite crucible according to claim 2, characterized in that, The mass ratio of the zirconium nitride to the titanium nitride is 8:

3.

4. A graphite crucible according to claim 3, characterized in that, The metal nitride further includes rare earth nitride; The rare earth nitride includes one or more of cerium nitride, yttrium nitride, and scandium nitride.

5. A graphite crucible according to claim 4, characterized in that, When the rare earth nitride is cerium nitride, the mass ratio of zirconium nitride, titanium nitride, and cerium nitride is 8:3:1-2.

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

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

1.

8. A method for preparing a graphite crucible, which is used to prepare the graphite crucible according to any one of claims 1 to 7, characterized in that, It includes the following steps: After uniformly mixing the graphitized coke and the metal nitride, knead it with pitch, form it, and bake it to obtain a graphite crucible.

9. The preparation method of a graphite crucible according to claim 8, characterized in that, During the kneading, the temperature is 145-155 °C and the time is 60-70 min; During the forming, the pressure is 10-15 MPa.

10. The preparation method of a graphite crucible according to claim 8, characterized in that, During the baking, the temperature is 950-1200 °C and the time is 30-35 d.

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