A silicon carbide ceramic product and its preparation method and a silicon carbide ceramic crucible

Abstract

The present invention belongs to the technical field of ceramic materials, and provides a silicon carbide ceramic product, a preparation method thereof, and a silicon carbide ceramic crucible side. In the present invention, a mixture is injected into a mold, pressed, and demolded to obtain a green body; the green body is sequentially subjected to low-temperature drying and high-temperature drying to obtain a dried green body; the dried green body is carbonized under vacuum conditions to obtain a carburized green body; silicon powder is sprinkled on the hollow position of the obtained carburized green body, and then sintered under vacuum conditions to obtain a silicon carbide ceramic product. The silicon carbide ceramic product can be a silicon carbide ceramic crucible side. The silicon carbide ceramic crucible side prepared by the present invention does not react with silicon vapor during use, and has good oxidation resistance, which can greatly increase the service life of the silicon side.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic materials, in particular to a silicon carbide ceramic product and a preparation method thereof, and a silicon carbide ceramic crucible rim. Background Art

[0002] Silicon carbide ceramics are the next generation of high-performance thermal field materials, following carbon-carbon composites. They not only possess the high specific strength and modulus, good toughness, excellent strength retention at high temperatures, creep resistance, and thermal shock resistance inherent in carbon-carbon composites, but also possess superior oxidation and corrosion resistance. Compared to carbon-carbon composites, silicon carbide ceramics have a shorter preparation cycle, lower costs, and can be directly formed without extensive machining, making them environmentally friendly and the optimal choice for thermal field materials in next-generation single crystal furnaces.

[0003] The main failure modes of the crucible ribs in traditional carbon-carbon hot fields include corrosion, cracking, and slagging. This is primarily due to prolonged exposure to high-temperature silicon vapor, which reacts with carbon, corroding the hot field. With increasing service life, the corrosion of the substrate by silicon vapor accelerates rapidly, degrading the mechanical properties of the crucible ribs and leading to cracking, which in turn increases crystal pulling costs.

[0004] When the corrosion temperature remains constant, the saturated vapor pressure and diffusion rate of silicon remain relatively stable, and a gradually densified silicon carbide layer forms on the surface of the thermal field component, hindering further penetration of silicon. In later stages, the silicon carbide produced by the reaction itself is not evenly distributed on the surface and may flake off, causing the silicon vapor to react more rapidly with the interior of the thermal field component, increasing the corrosion rate. However, the silicon carbide ceramic crucible rim is made of silicon carbide and does not react with silicon vapor, resulting in stronger corrosion resistance and a longer lifespan.

[0005] At the same time, the main component of the carbon-carbon crucible is carbon, and it also contains some metal impurities. The N-type silicon wafer has higher requirements for the purity of the thermal field, resulting in the carbon-carbon thermal field gradually failing to meet the needs of the N-type silicon wafer. Summary of the Invention

[0006] The object of the present invention is to provide a silicon carbide ceramic product and a preparation method thereof and a silicon carbide ceramic crucible rim, so as to make up for the deficiencies of the prior art.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a method for preparing a silicon carbide ceramic product, comprising the following steps:

[0009] (1) injecting the mixed material into a mold, pressing it, and demoulding it to obtain a green body;

[0010] The mixture comprises chopped carbon fibers, α-type silicon carbide powder, graphite powder and thermoplastic boron phenolic resin in a mass ratio of (30-40): (40-70): (5-10): (5-10),

[0011] (2) subjecting the obtained green body to low-temperature drying and high-temperature drying in sequence to obtain a dried green body;

[0012] The temperature of the low-temperature drying is 35-45°C, and the temperature of the high-temperature drying is 60-70°C;

[0013] (3) carbonizing the obtained dried green body under vacuum conditions to obtain a carbonized green body;

[0014] (4) After sprinkling silicon powder into the hollow position of the obtained carbonized body, sintering is performed under vacuum conditions to obtain a silicon carbide ceramic product.

[0015] Preferably, in step (1), a reinforcing material is applied to the inner wall of the mold, and a release agent is coated on the reinforcing material.

[0016] Preferably, the reinforcement material in step (1) comprises carbon fiber cloth, and the application thickness of the reinforcement material is 0.4 to 2 mm;

[0017] The release agent contains graphite powder.

[0018] Preferably, the length of the chopped carbon fibers in step (1) is 3 to 5 mm;

[0019] The α-type silicon carbide powder comprises two particle sizes: 0.4-0.6 μm and 170-190 μm, and the mass ratio of 0.4-0.6 μm α-type silicon carbide powder to 170-190 μm α-type silicon carbide powder is 1:1.8-2.4;

[0020] The pressing pressure is 20 to 25 tons and the pressing time is 10 to 15 minutes.

[0021] Preferably, the low-temperature drying time in step (2) is 24 to 36 hours, and the high-temperature drying time is 18 to 24 hours.

[0022] Preferably, in step (3), the vacuum degree is 40-60 Pa, the carbonization temperature is 1000-1200° C., and the carbonization time is 20-40 h.

[0023] Preferably, in step (4), the mass ratio of silicon powder to carbonized body is 0.3 to 0.45:1.

[0024] Preferably, the sintering in step (4) is specifically as follows: introducing nitrogen to atmospheric pressure, heating from room temperature to 800-900°C, heating for 3-6 hours, keeping warm for 0.4-0.6 hours, and heating from 800-900°C to 1600-1900°C after vacuuming, heating for 8-10 hours, and keeping warm for 1-3 hours.

[0025] The present invention also provides a silicon carbide ceramic product obtained by the preparation method.

[0026] Preferably, the product is a silicon carbide ceramic crucible rib.

[0027] The beneficial effects of the present invention are as follows:

[0028] 1. The traditional carbon-carbon crucible side requires sufficient processing allowance, and 40% of the material is processed away, resulting in a large amount of cost waste. At the same time, due to the high hardness of carbon-carbon materials, it is very difficult to machine. The present invention uses a new molding process, not only the processing allowance is very small, but also machining can be performed at the embryo stage, ultimately meeting the product's external dimension requirements.

[0029] 2. The silicon carbide ceramic crucible rib prepared by the present invention does not react with silicon vapor during use and has good oxidation resistance, which can greatly increase the service life of the silicon rib. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the mold used in Example 1 of the present invention;

[0031] Figure 2 This is a schematic cross-sectional view of the crucible rim embryo obtained in Example 1 of the present invention;

[0032] Figure 3 This is a schematic cross-sectional view of the crucible rim blank after machining in accordance with Example 1 of the present invention;

[0033] Figure 4 This is a schematic diagram of the finished crucible side of Example 1 of the present invention. DETAILED DESCRIPTION

[0034] The present invention provides a method for preparing a silicon carbide ceramic product, comprising the following steps:

[0035] (1) injecting the mixed material into a mold, pressing it, and demoulding it to obtain a green body;

[0036] The mixture comprises chopped carbon fibers, α-type silicon carbide powder, graphite powder and thermoplastic boron phenolic resin in a mass ratio of (30-40): (40-70): (5-10): (5-10),

[0037] (2) subjecting the obtained green body to low-temperature drying and high-temperature drying in sequence to obtain a dried green body;

[0038] The temperature of the low-temperature drying is 35-45°C, and the temperature of the high-temperature drying is 60-70°C;

[0039] (3) carbonizing the obtained dried green body under vacuum conditions to obtain a carbonized green body;

[0040] (4) After sprinkling silicon powder into the hollow position of the obtained carbonized body, sintering is performed under vacuum conditions to obtain a silicon carbide ceramic product.

[0041] In the present invention, the mass ratio of the chopped carbon fiber, α-type silicon carbide powder, graphite powder and thermoplastic boron phenolic resin is (30-40): (40-70): (5-10): (5-10), preferably (35-38): (50-60): (6-8): (6-8).

[0042] In the present invention, in step (1), a reinforcing material is applied to the inner wall of the mold, the reinforcing material comprises carbon fiber cloth, and the application thickness of the reinforcing material is 0.4 to 2 mm, preferably 1 to 1.5 mm; the reinforcing material is coated with a release agent, and the release agent comprises graphite powder.

[0043] In the present invention, the length of the chopped carbon fiber in step (1) is 3 to 5 mm, preferably 4 to 4.5 mm; the chopped carbon fiber is broken up by a carding machine before use, and the chopped carbon fiber can be T700 grade 12K carbon fiber; the α-type silicon carbide powder comprises two particle sizes of 0.4 to 0.6 μm and 170 to 190 μm, and the mass ratio of 0.4 to 0.6 μm α-type silicon carbide powder to 170 to 190 μm α-type silicon carbide powder is 1:1.8 to 2.4, preferably 1:2 to 2.2. The combination of these two particle size ranges can increase the roughness of the entire system, increase the number of surface active points, improve the overall mass uniformity of the ceramic powder, and make the ceramic powders more tightly bonded; the pressing pressure is 20 to 25 tons, preferably 22 to 24 tons, and the pressing time is 10 to 15 minutes, preferably 12 to 13 minutes.

[0044] In the present invention, an isostatic press cast iron mold is prepared according to the actual size of the required product, and a margin of 1 to 2 mm is retained between the mold size and the finished product size as a finishing allowance. The mold consists of a mold core and a mold sleeve.

[0045] In the present invention, the pressing is performed by an isostatic press or a dry press.

[0046] In the present invention, the low-temperature drying temperature in step (2) is 35-45°C, preferably 38-42°C, and the low-temperature drying time is 24-36 hours, preferably 28-32 hours; the high-temperature drying temperature is 60-70°C, preferably 63-67°C, and the high-temperature drying time is 18-24 hours, preferably 20-22 hours. The present invention adopts a two-step drying method, which can achieve very thorough drying.

[0047] After drying in step (2) of the present invention, the green body has a certain strength, generally with a flexural strength of 2 to 3 MPa, and can be machined. The present invention can use CNC to fine-tune the green body to achieve product dimensional accuracy, and then carbonize it.

[0048] In the present invention, in step (3), the vacuum degree is 40-60 Pa, preferably 50-53 Pa, the carbonization temperature is 1000-1200° C., preferably 1050-1150° C., and more preferably 1000-1120° C.; the carbonization time is 20-40 h, preferably 25-35 h.

[0049] In the present invention, in step (4), the carbonized body is placed in a vacuum sintering furnace, placed on a tool, and silicon powder is evenly sprinkled into the hollow position of the product, and the silicon powder cannot directly contact the product; the mass ratio of silicon powder to carbonized body is 0.3 to 0.45:1, preferably 0.35 to 0.4:1.

[0050] In the present invention, in the step (4), the temperature is heated from room temperature to 800-900°C, preferably 830-870°C, more preferably 850-860°C, for 3-6 hours, preferably 4-5 hours, and kept warm for 0.4-0.6 hours, preferably 0.5-0.55 hours; then heated from 800-900°C to 1600-1900°C, preferably 1700-1800°C, for 8-10 hours, preferably 9 hours, and kept warm for 1-3 hours, preferably 2 hours; the vacuum degree of the vacuum is 50-2000 Pa, preferably 500-1500 Pa.

[0051] In the present invention, the furnace is cooled after the sintering in step (4) is completed.

[0052] The present invention also provides a silicon carbide ceramic product obtained by the preparation method.

[0053] In the present invention, the product is a silicon carbide ceramic crucible rib.

[0054] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0055] Example 1

[0056] 1) Mixed chopped carbon fiber slurry:

[0057] The T700 grade 12K carbon fiber is cut into segments by a cutting machine to prepare short-cut carbon fibers with a length of 3 to 5 mm; the short-cut fibers are then dispersed by a carding machine;

[0058] The silicon carbide powder is granulated by a spray granulator;

[0059] The chopped carbon fibers, α-silicon carbide powder, graphite powder, and thermoplastic boron phenolic resin are fully mixed in the proportions of 32%, 52%, 8.5%, and 7.5% by mass to obtain a powder;

[0060] In the embodiment, α-SiC powder 1 is selected with a particle size of 0.5 μm and a purity of 99.5%, and α-SiC powder 2 is selected with a particle size of 180 μm and a purity of 99.8%. The two are mixed at a mass ratio of 1:1.9 and then granulated using a spray granulator.

[0061] 2) Preparation of mold

[0062] Prepare an isostatic press cast iron mold based on the desired crucible rim dimensions. Allow a 2mm margin between the mold and the finished product. The mold consists of a core and a sleeve. Carbon fiber cloth is applied to the mold's inner wall as reinforcement, creating a mold with a polymer mesh. The reinforcement is applied to a thickness of 0.9mm.

[0063] 3) Isostatic extrusion molding: Graphite powder is brushed on the mold surface to facilitate demoulding, the aforementioned powder is injected into the mold, and the mold is pressed by an isostatic press at a pressure of 25 tons for 10 minutes;

[0064] 4) Drying: Demolding the pressed embryo body, placing the embryo body in an oven, and sequentially performing low-temperature drying and high-temperature drying, wherein the low-temperature drying temperature is 45° C. and the high-temperature drying temperature is 70° C. The low-temperature drying time is 24 hours, and the high-temperature drying time is 18 hours;

[0065] 5) Machining: After step 4), the embryo body has a certain strength, with a flexural strength of 2.3MPa. The internal and external surfaces of the embryo body are finely processed by the CNC machining center to achieve product dimensional accuracy;

[0066] 6) Carbonization: Place the embryo body after finishing in step 5) in a high-temperature furnace, evacuate to 50 Pa and perform carbonization at a temperature of 1100° C. for 38 hours.

[0067] 7) Vacuum Sintering: Place the blank from step 6) into a vacuum sintering furnace on a dedicated fixture. Evenly sprinkle silicon powder into the hollow area of ​​the product, ensuring that the silicon powder does not come into direct contact with the product. The silicon powder weight to blank weight ratio is 0.35:1. After nitrogen is introduced into the sintering furnace to atmospheric pressure, heating is performed. The heating temperature and time relationship is as follows: heating from room temperature to 800°C for 6 hours, holding for 0.6 hours, evacuating to 100 Pa, heating from 800°C to 1750°C for 10 hours, holding for 3 hours, and finally cooling to room temperature and removing from the furnace to obtain the finished product.

[0068] The outer dimensions of the silicon carbide ceramic crucible are: Φ956 outer diameter * Φ916 inner diameter * 485mm, the roundness range is ±2mm, and the density is 3.04g / cm 3 , three-point bending strength is 350MPa, and service life is more than 12 months.

[0069] Example 2

[0070] 1) Mixed chopped carbon fiber slurry:

[0071] The T700 grade 12K carbon fiber is cut into segments by a cutting machine to prepare short-cut carbon fibers with a length of 3 to 5 mm; the short-cut fibers are then dispersed by a carding machine;

[0072] The silicon carbide powder is granulated by a spray granulator;

[0073] The chopped carbon fibers, α-silicon carbide powder, graphite powder, and thermoplastic boron phenolic resin are fully mixed in proportions of 30%, 54%, 9%, and 7% by mass to obtain a powder;

[0074] In the embodiment, α-SiC powder 1 is selected with a particle size of 0.5 μm and a purity of 99.5%, and α-SiC powder 2 is selected with a particle size of 180 μm and a purity of 99.8%. The two are mixed in a mass ratio of 1:2.3 and then granulated using a spray granulator.

[0075] 2) Preparation of mold

[0076] Prepare an isostatic press cast iron mold based on the desired crucible rim dimensions. Allow a 2mm margin between the mold and the finished product. The mold consists of a core and a sleeve. Carbon fiber cloth is applied to the mold's inner wall as reinforcement, creating a mold with a polymer mesh. The reinforcement is applied to a thickness of 0.9mm.

[0077] 3) Isostatic extrusion molding: Graphite powder is brushed on the mold surface to facilitate demoulding, the aforementioned powder is injected into the mold, and the mold is pressed by an isostatic press at a pressure of 22 tons for 15 minutes;

[0078] 4) Drying: Demolding the pressed embryo body, placing the embryo body in an oven, and sequentially performing low-temperature drying and high-temperature drying, wherein the low-temperature drying temperature is 35° C.; the high-temperature drying temperature is 65° C.; the low-temperature drying time is 30 hours, and the high-temperature drying time is 20 hours;

[0079] 5) Machining: After step 4), the embryo body has a certain strength, with a flexural strength of 2.4MPa. The internal and external surfaces of the embryo body are refined by CNC machining to achieve product dimensional accuracy.

[0080] 6) Carbonization: Place the embryo body after finishing in step 5) in a high-temperature furnace and evacuate to 50 Pa for carbonization at a temperature of 1150° C. for 38 hours.

[0081] 7) Vacuum Sintering: Place the blank from step 6) into a vacuum sintering furnace on a dedicated fixture. Evenly sprinkle silicon powder into the hollow area of ​​the product, ensuring that the silicon powder does not come into direct contact with the product. The silicon powder weight to blank weight ratio is 0.45:1. After nitrogen is introduced into the sintering furnace to atmospheric pressure, heating is performed. The heating temperature and time relationship is as follows: heating from room temperature to 850°C for 6 hours, holding for 0.6 hours, evacuating to 1000 Pa, heating from 850°C to 1750°C for 10 hours, holding for 3 hours, and finally cooling to room temperature before removing from the furnace to obtain the finished product.

[0082] The outer dimensions of the silicon carbide ceramic crucible are: Φ956 outer diameter * Φ916 inner diameter * 485mm, the roundness range is ±2mm, and the density is 3.06g / cm 3 , three-point bending strength is 355MPa, and service life is more than 12 months.

[0083] Example 3

[0084] 1) Mixed chopped carbon fiber slurry:

[0085] The T700 grade 12K carbon fiber is cut into segments by a cutting machine to prepare short-cut carbon fibers with a length of 3 to 5 mm; the short-cut fibers are then dispersed by a carding machine;

[0086] The silicon carbide powder is granulated by a spray granulator;

[0087] The chopped carbon fibers, α-silicon carbide powder, graphite powder, and thermoplastic boron phenolic resin are fully mixed in a ratio of 40%, 44%, 8.5%, and 7.5% by mass to obtain a powder;

[0088] In the embodiment, α-SiC powder 1 is selected with a particle size of 0.5 μm and a purity of 99.5%, and α-SiC powder 2 is selected with a particle size of 180 μm and a purity of 99.8%. The two are mixed at a mass ratio of 1:1.9 and then granulated using a spray granulator.

[0089] 2) Preparation of mold

[0090] Prepare an isostatic press cast iron mold based on the desired crucible rim dimensions. Allow a 2mm margin between the mold and the finished product. The mold consists of a core and a sleeve. Carbon fiber cloth is applied to the mold's inner wall as reinforcement, creating a mold with a polymer mesh. The reinforcement is applied to a thickness of 0.9mm.

[0091] 3) Isostatic extrusion molding: Graphite powder is brushed on the mold surface to facilitate demoulding, the aforementioned powder is injected into the mold, and the mold is pressed by an isostatic press at a pressure of 25 tons for 15 minutes;

[0092] 4) Drying: Demolding the pressed embryo body, placing the embryo body in an oven, and sequentially performing low-temperature drying and high-temperature drying, wherein the low-temperature drying temperature is 40° C.; the high-temperature drying temperature is 60° C.; the low-temperature drying time is 24 hours, and the high-temperature drying time is 18 hours;

[0093] 5) Machining: After step 4), the embryo body has a certain strength, with a flexural strength of 2.3MPa. The internal and external surfaces of the embryo body are finely processed by the CNC machining center to achieve product dimensional accuracy;

[0094] 6) Carbonization: Place the embryo body after finishing in step 5) into a high-temperature furnace, evacuate to 50 Pa and perform carbonization at a temperature of 1200° C. for 30 hours.

[0095] 7) Vacuum Sintering: Place the blank from step 6) into a vacuum sintering furnace on a dedicated fixture. Evenly sprinkle silicon powder into the hollow area of ​​the product, ensuring that the silicon powder does not come into direct contact with the product. The silicon powder weight to blank weight ratio is 0.40:1. After nitrogen is introduced into the sintering furnace to atmospheric pressure, heating is performed. The heating temperature and time relationship is as follows: heating from room temperature to 800°C for 6 hours, holding for 0.6 hours, evacuating to 1500 Pa, heating from 800°C to 1850°C for 10 hours, holding for 3 hours, and finally cooling to room temperature and removing from the furnace to obtain the finished product.

[0096] The outer dimensions of the silicon carbide ceramic crucible are: Φ956 outer diameter * Φ916 inner diameter * 485mm, the roundness range is ±2mm, and the density is 3.01g / cm 3 , three-point bending strength is 357MPa, and service life is more than 12 months.

[0097] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a silicon carbide ceramic crucible rim, characterized in that: The following steps are included: (1) injecting the mixed material into a mold, pressing it, and demoulding it to obtain a green body; The mixture comprises chopped carbon fibers, α-type silicon carbide powder, graphite powder and thermoplastic boron phenolic resin in a mass ratio of (30-40): (40-70): (5-10): (5-10), (2) subjecting the obtained green body to low-temperature drying and high-temperature drying in sequence to obtain a dried green body; The temperature of the low-temperature drying is 35-45°C, and the temperature of the high-temperature drying is 60-70°C; (3) carbonizing the obtained dried green body under vacuum conditions to obtain a carbonized green body; (4) Sprinkling silicon powder into the hollow position of the obtained carbonized body and sintering it under vacuum conditions to obtain a silicon carbide ceramic product; In the step (3), the vacuum degree is 40-60 Pa, the carbonization temperature is 1000-1200° C., and the carbonization time is 20-40 h; The sintering in step (4) is specifically as follows: introducing nitrogen to atmospheric pressure, heating from room temperature to 800-900°C, heating for 3-6 hours, keeping warm for 0.4-0.6 hours, and heating from 800-900°C to 1600-1900°C after vacuuming, heating for 8-10 hours, and keeping warm for 1-3 hours.

2. The preparation method according to claim 1, characterized in that In the step (1), a reinforcing material is applied to the inner wall of the mold, and a release agent is coated on the reinforcing material.

3. The preparation method according to claim 2, characterized in that In step (1), the reinforcement material comprises carbon fiber cloth, and the thickness of the reinforcement material is 0.4 to 2 mm; The release agent contains graphite powder.

4. The preparation method according to any one of claims 1 to 3, characterized in that The length of the chopped carbon fibers in step (1) is 3 to 5 mm; The α-type silicon carbide powder comprises two particle sizes: 0.4-0.6 μm and 170-190 μm, and the mass ratio of 0.4-0.6 μm α-type silicon carbide powder to 170-190 μm α-type silicon carbide powder is 1:1.8-2.4; The pressing pressure is 20-25 tons and the pressing time is 10-15 minutes.

5. The preparation method according to claim 4, characterized in that In step (2), the low-temperature drying time is 24 to 36 hours, and the high-temperature drying time is 18 to 24 hours.

6. The preparation method according to claim 5, characterized in that In the step (4), the mass ratio of silicon powder to carbonized body is 0.3-0.45:

1.

7. The silicon carbide ceramic crucible rib obtained by the preparation method according to any one of claims 1 to 6.

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