Preparation method of high-purity and high-density silicon carbide ceramic without additives
Patent Information
- Application Number
- CN202610877434.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-17
- Publication Date
- 2026-08-18
AI Technical Summary
[0003]本发明要解决现有高致密SiC制备技术添加助剂会引入第二相，从而降低材料纯度与热导率，难以同时实现纯度≥99.9%、相对密度≥99.0%的问题，进而提供一种无助剂高纯高致密碳化硅陶瓷的制备方法
[0013] This invention obtains high-density ceramic parts using only silicon carbide without the use of other sintering aids.
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Figure CN122586570A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of advanced structural ceramics preparation technology. Background Technology
[0002] Silicon carbide (SiC) ceramics possess high hardness, high thermal conductivity, low coefficient of thermal expansion, excellent corrosion resistance, and high-temperature stability, making them important for applications in semiconductor equipment and structural materials for extreme environments. However, silicon carbide has a low self-diffusion coefficient; at 2100℃, the self-diffusion coefficients of Si and C in SiC are only 2.5 × 10⁻⁶. -13 cm 2 / s and 1.5×10 -10 cm 2 Therefore, when actually sintering SiC-based ceramics, it is often necessary to take certain measures to promote the rearrangement and densification of particles. Commonly used measures include adding sintering aids. For example, the journal "Low temperature pressureless sintering of α-SiC with Al2O3 and CeO2 as additives" (Journal of the European Ceramic Society, 34(3):831-835) reported that Al2O3 and Y2O3 were used as sintering aids to lower the sintering temperature. The journal "Liquid phasesintering of SiC with additions of Y2O3, Al2O3 and SiO2" (Journal of the European Ceramic Society, 24(9):2895-2903) reported a method using Al2O3, Y2O3 and SiO2 as sintering aids. The addition of sintering aids helps to lower the sintering temperature, but it introduces second-phase impurities, reducing the purity and thermal conductivity of the material. Therefore, the above technology is difficult to achieve high density (relative density ≥99.0%) while achieving high purity (≥99.9%). Summary of the Invention
[0003] This invention aims to address the problem that existing high-density SiC preparation techniques introduce a second phase when additives are added, thereby reducing material purity and thermal conductivity, making it difficult to simultaneously achieve a purity ≥99.9% and a relative density ≥99.0%. The invention provides a method for preparing high-purity, high-density silicon carbide ceramics without additives.
[0004] A method for preparing additive-free, high-purity, high-density silicon carbide ceramics, comprising the following steps:
[0005] 1. Mix silicon carbide powder with a solvent to obtain silicon carbide slurry;
[0006] The silicon carbide powder is composed of micron-sized silicon carbide powder and ultrafine silicon carbide powder; the percentage content of ultrafine silicon carbide powder in the silicon carbide powder is 1wt%~40wt%, and the balance is micron-sized silicon carbide powder;
[0007] The ultrafine silicon carbide powder is one or a combination of submicron-sized silicon carbide powder and nano-sized silicon carbide powder.
[0008] The D50 particle size of the micron-sized silicon carbide powder is 1.0 μm to 3 μm; the D50 particle size of the submicron-sized silicon carbide powder is 0.3 μm to 0.9 μm; and the D50 particle size of the nano-sized silicon carbide powder is 30 nm to 100 nm.
[0009] 2. Mix silicon carbide slurry, dispersant, binder and lubricant, then spray granulate, and finally dry to obtain spherical silicon carbide powder with good flowability;
[0010] 3. The spherical silicon carbide powder with good flowability is pressure molded to obtain a green blank;
[0011] 4. Place the green blank in a hot press furnace and first evacuate it until the vacuum degree is less than 5×10. -4 Pa, then nitrogen or argon is introduced, and the green blank is hot-pressed and sintered for 60 min to 540 min at a temperature of 2300℃ to 2350℃ and a pressure of 30 MPa to 70 MPa. Finally, it is cooled with the furnace to obtain high-purity and high-density silicon carbide ceramic.
[0012] The beneficial effects of this invention are:
[0013] This invention obtains high-density ceramic parts using only silicon carbide without the use of other sintering aids.
[0014] 1. This invention does not introduce impurity phases as metals or oxides as sintering aids;
[0015] 2. The silicon carbide preform prepared by this invention has a high density, with a density greater than 1.90 g / cm³. 3 The highest concentration can reach 2.03 g / cm³. 3 ;
[0016] 3. The high-purity, high-density silicon carbide ceramics prepared by this invention have a relative density ≥99.9% and a SiC mass purity ≥99.9%.
[0017] 4. The high-purity, high-density silicon carbide ceramics prepared by this invention have significantly improved thermal conductivity, reaching 229.84 W / m·K at 25℃. Attached Figure Description
[0018] Figure 1SEM image of the free-flowing spherical silicon carbide powder prepared in step two of Example 1;
[0019] Figure 2 This is a particle size distribution diagram of the free-flowing spherical silicon carbide powder prepared in step two of Example 1;
[0020] Figure 3 This is a density comparison diagram of the green bodies prepared in step three of Examples 1 to 7;
[0021] Figure 4 The XRD patterns are of the high-purity, high-density silicon carbide ceramics prepared in step four of Examples 1, 4, and 5.
[0022] Figure 5 This is a SEM image of the high-purity, high-density silicon carbide ceramic prepared in step four of Example 1;
[0023] Figure 6 The diagram shows the flexural strength of the high-purity, high-density silicon carbide ceramics prepared in step four of Examples 1 to 5. Detailed Implementation
[0024] Specific Implementation Method 1: This implementation method is a method for preparing high-purity, high-density silicon carbide ceramics without additives, which is carried out according to the following steps:
[0025] 1. Mix silicon carbide powder with a solvent to obtain silicon carbide slurry;
[0026] The silicon carbide powder is composed of micron-sized silicon carbide powder and ultrafine silicon carbide powder; the percentage content of ultrafine silicon carbide powder in the silicon carbide powder is 1wt%~40wt%, and the balance is micron-sized silicon carbide powder;
[0027] The ultrafine silicon carbide powder is one or a combination of submicron-sized silicon carbide powder and nano-sized silicon carbide powder.
[0028] The D50 particle size of the micron-sized silicon carbide powder is 1.0 μm to 3 μm; the D50 particle size of the submicron-sized silicon carbide powder is 0.3 μm to 0.9 μm; and the D50 particle size of the nano-sized silicon carbide powder is 30 nm to 100 nm.
[0029] 2. Mix silicon carbide slurry, dispersant, binder and lubricant, then spray granulate, and finally dry to obtain spherical silicon carbide powder with good flowability;
[0030] 3. The spherical silicon carbide powder with good flowability is pressure molded to obtain a green blank;
[0031] 4. Place the green blank in a hot press furnace and first evacuate it until the vacuum degree is less than 5×10. -4Pa, then nitrogen or argon is introduced, and the green blank is hot-pressed and sintered for 60 min to 540 min at a temperature of 2300℃ to 2350℃ and a pressure of 30 MPa to 70 MPa. Finally, it is cooled with the furnace to obtain high-purity and high-density silicon carbide ceramic.
[0032] This embodiment grades ultrafine silicon carbide powder with micron-sized silicon carbide powder. Its core function is to improve the packing density of the green body by grading micron-sized powder, submicron-sized powder, and nano-sized powder. At the same time, during the sintering process, the high specific surface area and high surface energy of the nano-sized powder promote surface diffusion and grain boundary diffusion, thereby improving the density of the ceramic parts.
[0033] (1) Micron-sized silicon carbide powder with a D50 particle size of 1.0μm~3μm was selected as the main skeleton particles;
[0034] (2) Submicron-sized silicon carbide powder with a D50 particle size of 0.3μm~0.9μm and micron-sized powder were selected together as the main skeleton particles;
[0035] (3) Select nanoscale silicon carbide powder with a D50 particle size of 30nm~100nm as filler particles.
[0036] The beneficial effects of this embodiment are:
[0037] This embodiment obtains high-density ceramic parts using only silicon carbide without using other sintering aids.
[0038] 1. This embodiment does not introduce impurity phases as metals or oxides as sintering aids;
[0039] 2. The silicon carbide preform prepared in this embodiment has a high density, with a density greater than 1.90 g / cm³. 3 The highest concentration can reach 2.03 g / cm³. 3 ;
[0040] 3. The high-purity, high-density silicon carbide ceramics prepared in this embodiment have a relative density ≥99.9% and a SiC mass purity ≥99.9%.
[0041] 4. The high-purity, high-density silicon carbide ceramic prepared in this embodiment has significantly improved thermal conductivity, reaching 229.84 W / m·K at 25℃.
[0042] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that: in step one, silicon carbide powder is mixed with solvent for 0.1h to 3h at a stirring speed of 50rpm to 500rpm to obtain silicon carbide powder; the solvent mentioned in step one is deionized water; and the mass ratio of the solvent to silicon carbide powder in step one is (1.5~2):1. Everything else is the same as in Specific Implementation Method One.
[0043] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that: the dispersant mentioned in step two is WE8 dispersant; the binder mentioned in step two is ET85 binder; and the lubricant mentioned in step two is AC95 lubricant. Everything else is the same as in Specific Implementation Method One or Two.
[0044] The WE8 dispersant, ET85 binder, and AC95 lubricant described in this specific embodiment were all purchased from SMA Chemical Company, Germany; and the ET85 binder is also used as a wetting aid, and the AC95 lubricant is also used as a pressing aid.
[0045] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: the mass of the dispersant mentioned in step two is 1.5% to 3.2% of the mass of the silicon carbide powder in step one; the mass of the binder mentioned in step two is 1.6% to 7.2% of the mass of the silicon carbide powder in step one; and the mass of the lubricant mentioned in step two is 2% to 4% of the mass of the silicon carbide powder in step one. Everything else is the same as in Specific Implementation Methods One to Three.
[0046] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that, in step two, the silicon carbide slurry, dispersant, binder, and lubricant are mixed for 1 to 3 hours at a stirring speed of 200 rpm to 400 rpm. Everything else is the same as in Specific Implementation Methods One to Four.
[0047] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the spray granulation described in step two is specifically carried out according to the following steps: spray granulation is performed under the following conditions: an atomizer frequency of 100Hz~300Hz, a peristaltic pump feed speed of 20rpm~50rpm, an inlet air temperature of 150℃~210℃, and an outlet air temperature of 120℃~150℃. Everything else is the same as in Specific Implementation Methods One to Five.
[0048] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the drying process in step two is specifically carried out at a temperature of 100℃ to 300℃ for 12 to 36 hours. Everything else is the same as in Specific Implementation Methods One to Six.
[0049] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that the pressure forming in step three is unidirectional molding or cold isostatic pressing, and the pressure for pressure forming is 150MPa~300MPa. Everything else is the same as Specific Implementation Methods One to Seven.
[0050] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that: in step four, the temperature is first raised from room temperature to 800℃ to 1200℃ at a heating rate of 8.2℃ / min to 10.8℃ / min. Then, a pressure of 30MPa to 50MPa is applied, and under the conditions of a pressure of 30MPa to 50MPa and a heating rate of 5.2℃ / min to 6.4℃ / min, the temperature is raised to 1750℃ to 2000℃. Finally, under the conditions of a pressure of 30MPa to 50MPa and a heating rate of 4.1℃ / min to 5.3℃ / min, the temperature is raised to 2300℃ to 2350℃. Everything else is the same as in Specific Implementation Methods One to Eight.
[0051] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that the relative density of the high-purity, high-density silicon carbide ceramic described in step four is ≥99.0%, and the SiC mass purity is ≥99.9%. Everything else is the same as in Specific Implementation Methods One to Nine.
[0052] The beneficial effects of the present invention are verified using the following embodiments:
[0053] Example 1:
[0054] A method for preparing additive-free, high-purity, high-density silicon carbide ceramics, comprising the following steps:
[0055] 1. Under the condition of stirring speed of 300 rpm, silicon carbide powder and solvent are mixed for 1 hour to obtain silicon carbide slurry;
[0056] The silicon carbide powder is composed of micron-sized silicon carbide powder, submicron-sized silicon carbide powder, and nano-sized silicon carbide powder, wherein the percentage content of micron-sized silicon carbide powder is 70 wt%, the percentage content of submicron-sized silicon carbide powder is 25 wt%, and the percentage content of nano-sized silicon carbide powder is 5 wt%.
[0057] The D50 particle size of the micron-sized silicon carbide powder is 2 μm; the D50 particle size of the submicron-sized silicon carbide powder is 0.5 μm; and the D50 particle size of the nano-sized silicon carbide powder is 60 nm.
[0058] The solvent is deionized water; the mass ratio of the solvent to silicon carbide powder is 1.5:1.
[0059] 2. Under the condition of stirring speed of 300 rpm, silicon carbide slurry, dispersant, binder and lubricant are mixed for 1 hour to obtain a mixed system. Under the conditions of atomizer frequency of 300 Hz, peristaltic pump feed speed of 40 rpm, inlet air temperature of 190 ℃ and outlet air temperature of 150 ℃, the mixed system is spray granulated. Finally, it is dried at a temperature of 100 ℃ for 12 hours to obtain spherical silicon carbide powder with good flowability.
[0060] The dispersant is WE8 dispersant; the binder is ET85 binder; the lubricant is AC95 lubricant; the mass of the dispersant is 1.5% of the mass of the silicon carbide powder in step one; the mass of the binder is 1.6% of the mass of the silicon carbide powder in step one; the mass of the lubricant is 2% of the mass of the silicon carbide powder in step one.
[0061] The WE8 dispersant, ET85 binder, and AC95 lubricant mentioned above were all purchased from SMA Chemical Company in Germany.
[0062] 3. Under a pressure of 300 MPa, spherical silicon carbide powder with good flowability is unidirectionally molded to obtain a green blank;
[0063] 4. Place the green blank in a hot press furnace and first evacuate it until the vacuum degree is less than 5×10. -4 The process involves applying pressure of 50 MPa, then introducing nitrogen gas, and heating from room temperature to 800°C at a rate of 10°C / min. The temperature is then increased to 1800°C under a pressure of 50 MPa and a heating rate of 6°C / min. Finally, the green blank is hot-pressed and sintered at 2300°C and a pressure of 50 MPa for 180 min, and then cooled in the furnace to obtain high-purity, high-density silicon carbide ceramic.
[0064] Example 2: This example differs from Example 1 in that the percentage content of micron-sized silicon carbide powder in step one is 75 wt%, the percentage content of submicron-sized silicon carbide powder is 20 wt%, and the percentage content of nano-sized silicon carbide powder is 5 wt%. Everything else is the same as in Example 1.
[0065] Example 3: This example differs from Example 1 in that the percentage content of micron-sized silicon carbide powder in step one is 85 wt%, the percentage content of submicron-sized silicon carbide powder is 10 wt%, and the percentage content of nano-sized silicon carbide powder is 5 wt%. Everything else is the same as in Example 1.
[0066] Example 4: This example differs from Example 1 in that the silicon carbide powder mentioned in step one is composed of micron-sized silicon carbide powder and submicron-sized silicon carbide powder, wherein the percentage content of micron-sized silicon carbide powder is 75 wt% and the percentage content of submicron-sized silicon carbide powder is 25 wt%. Everything else is the same as in Example 1.
[0067] Example 5: This example differs from Example 1 in that the silicon carbide powder mentioned in step one is composed of micron-sized silicon carbide powder and submicron-sized silicon carbide powder, wherein the percentage content of micron-sized silicon carbide powder is 80 wt% and the percentage content of submicron-sized silicon carbide powder is 20 wt%. Everything else is the same as in Example 1.
[0068] Example 6: This example differs from Example 1 in that the silicon carbide powder mentioned in step one is composed of micron-sized silicon carbide powder and submicron-sized silicon carbide powder, wherein the percentage content of micron-sized silicon carbide powder is 85 wt% and the percentage content of submicron-sized silicon carbide powder is 15 wt%. Everything else is the same as in Example 1.
[0069] Example 7: This example differs from Example 1 in that the silicon carbide powder is composed of micron-sized silicon carbide powder and nano-sized silicon carbide powder, wherein the percentage content of micron-sized silicon carbide powder is 90 wt% and the percentage content of nano-sized silicon carbide powder is 10 wt%. Everything else is the same as in Example 1.
[0070] Figure 1 The image shows a SEM image of the free-flowing spherical silicon carbide powder prepared in step two of Example 1. As can be seen from the image, the powder has a good spherical shape and good flowability.
[0071] Figure 2 The figure shows the particle size distribution of the free-flowing spherical silicon carbide powder prepared in step two of Example 1. As can be seen from the figure, the D50 particle size of the powder after spray granulation is 26.43±8.55μm.
[0072] Figure 3 The figures show a comparison of the densities of the green bodies prepared in step three of Examples 1 to 7; as can be seen from the figures, the densities of the green bodies prepared in step three of Examples 1 to 7 are all greater than 1.90 g·cm³. -3 It has a high green body density; the green body prepared in step three of Example 7 has the highest density, reaching 2.03 g·cm³. -3 .
[0073] Figure 4 The images show the XRD patterns of the high-purity, high-density silicon carbide ceramics prepared in step four of Examples 1, 4, and 5. As can be seen from the images, the ceramics are mostly β-SiC phase after sintering, with a small portion being α-SiC phase.
[0074] Figure 5 This is a SEM image of the high-purity, high-density silicon carbide ceramic prepared in step four of Example 1. As shown in the image, the ceramic is dense with no visible pores, indicating that the sintered silicon carbide ceramic is dense. The relative density, measured by Archimedes' displacement method, is 99.7%, and the density is 3.20 g / cm³. 3 .
[0075] Figure 6The graph shows the flexural strength of the high-purity, high-density silicon carbide ceramics prepared in step four of Examples 1 to 5. As can be seen from the graph, the highest flexural strength in Example 1 is 527.46 MPa, and the lowest in Example 4 is 314.68 MPa, indicating that the prepared silicon carbide ceramics have high flexural strength.
[0076] The high-purity, high-density silicon carbide ceramic prepared in step four of Example 1 was tested and found to have a thermal conductivity of 229.84 W / m·K at 25℃.
[0077] According to glow discharge mass spectrometry (GDMS) testing, the SiC mass purity in the high-purity, high-density silicon carbide ceramic prepared in step four of Example 1 is 99.93%.
Claims
1. A method for preparing additive-free, high-purity, high-density silicon carbide ceramic, characterized in that... It is done in the following steps:
1. Mix silicon carbide powder with a solvent to obtain silicon carbide slurry; The silicon carbide powder is composed of micron-sized silicon carbide powder and ultrafine silicon carbide powder; the percentage content of ultrafine silicon carbide powder in the silicon carbide powder is 1wt%~40wt%, and the balance is micron-sized silicon carbide powder; The ultrafine silicon carbide powder is one or a combination of submicron-sized silicon carbide powder and nano-sized silicon carbide powder. The D50 particle size of the micron-sized silicon carbide powder is 1.0 μm to 3 μm; the D50 particle size of the submicron-sized silicon carbide powder is 0.3 μm to 0.9 μm; and the D50 particle size of the nano-sized silicon carbide powder is 30 nm to 100 nm.
2. Mix silicon carbide slurry, dispersant, binder and lubricant, then spray granulate, and finally dry to obtain spherical silicon carbide powder with good flowability; 3. The spherical silicon carbide powder with good flowability is pressure molded to obtain a green blank; 4. Place the green blank in a hot press furnace and first evacuate it until the vacuum degree is less than 5×10. -4 Pa, then nitrogen or argon is introduced, and the green blank is hot-pressed and sintered for 60 min to 540 min at a temperature of 2300℃ to 2350℃ and a pressure of 30 MPa to 70 MPa. Finally, it is cooled with the furnace to obtain high-purity and high-density silicon carbide ceramic.
2. The method for preparing additive-free, high-purity, high-density silicon carbide ceramic according to claim 1, characterized in that... In step one, silicon carbide powder is mixed with solvent for 0.1h to 3h at a stirring speed of 50rpm to 500rpm to obtain silicon carbide powder; the solvent mentioned in step one is deionized water; the mass ratio of the solvent to silicon carbide powder mentioned in step one is (1.5~2):
1.
3. The method for preparing additive-free, high-purity, high-density silicon carbide ceramic according to claim 1, characterized in that... The dispersant mentioned in step two is WE8 dispersant; the binder mentioned in step two is ET85 binder; and the lubricant mentioned in step two is AC95 lubricant.
4. The method for preparing additive-free, high-purity, high-density silicon carbide ceramic according to claim 1, characterized in that... The mass of the dispersant mentioned in step two is 1.5% to 3.2% of the mass of the silicon carbide powder in step one; the mass of the binder mentioned in step two is 1.6% to 7.2% of the mass of the silicon carbide powder in step one; and the mass of the lubricant mentioned in step two is 2% to 4% of the mass of the silicon carbide powder in step one.
5. The method for preparing additive-free, high-purity, high-density silicon carbide ceramic according to claim 1, characterized in that... In step two, the silicon carbide slurry, dispersant, binder and lubricant are mixed for 1h to 3h at a stirring speed of 200rpm to 400rpm.
6. The method for preparing additive-free, high-purity, high-density silicon carbide ceramic according to claim 1, characterized in that... The spray granulation described in step two is carried out in the following steps: spray granulation is performed under the following conditions: atomizer frequency of 100Hz~300Hz, peristaltic pump feed speed of 20rpm~50rpm, inlet air temperature of 150℃~210℃ and outlet air temperature of 120℃~150℃.
7. The method for preparing additive-free, high-purity, high-density silicon carbide ceramic according to claim 1, characterized in that... The drying process described in step two specifically involves drying at a temperature of 100℃ to 300℃ for 12 to 36 hours.
8. The method for preparing additive-free, high-purity, high-density silicon carbide ceramic according to claim 1, characterized in that... The pressure forming described in step three is unidirectional molding or cold isostatic pressing, and the pressure of pressure forming is 150MPa~300MPa.
9. The method for preparing additive-free, high-purity, high-density silicon carbide ceramic according to claim 1, characterized in that... In step four, the temperature is first raised from room temperature to 800℃ to 1200℃ at a heating rate of 8.2℃ / min to 10.8℃ / min. Then, a pressure of 30MPa to 50MPa is applied, and the temperature is raised to 1750℃ to 2000℃ at a pressure of 30MPa to 50MPa and a heating rate of 5.2℃ / min to 6.4℃ / min. Finally, the temperature is raised to 2300℃ to 2350℃ at a pressure of 30MPa to 50MPa and a heating rate of 4.1℃ / min to 5.3℃ / min.
10. The method for preparing additive-free, high-purity, high-density silicon carbide ceramic according to claim 1, characterized in that... The high-purity, high-density silicon carbide ceramic mentioned in step four has a relative density ≥99.0% and a SiC mass purity ≥99.9%.