Normal-pressure sintered silicon carbide ceramic and preparation method thereof

Abstract

The invention provides normal-pressure sintered silicon carbide ceramic and a preparation method thereof. The normal-pressure sintered silicon carbide ceramic is prepared from the following raw materials in percentage by weight: 40 to 90 percent of silicon carbide micro powder, 5 to 60 percent of quartz powder, 2 to 10 percent of graphite powder, 2 to 20 percent of phenolic resin solution, 40 to 60 percent of absolute ethyl alcohol solution and 0.5 to 2 percent of oleic acid. The preparation method comprises the following steps: stirring, grinding, dispersing, granulating and carrying out dry pressing to obtain a product, putting the pressed and molded product into a vacuum furnace, pre-sintering at 1200 DEG C, putting the pre-sintered product into a vacuum furnace into which argon is introduced, and carrying out high-temperature sintering to obtain the high-purity silicon carbide sintered body. The normal-pressure sintered silicon carbide ceramic produced by the method is stable and reliable in product quality, the shrinkage distortion is less than 18%, the porosity is less than 1%, the qualified rate of the product can reach more than 95%, a siliconizing process is canceled, waste products are greatly reduced, the production operation environment is improved, pollution is completely eradicated, and the occupational health of production operation personnel is ensured.

Description

Technical Field

[0001] The present invention relates to the field of silicon carbide ceramics, and in particular to a pressure-sintered silicon carbide ceramic and a preparation method thereof. Background Art

[0002] As a new type of high-temperature structural ceramic, silicon carbide ceramics possess numerous exceptional properties, including wear resistance, high thermal conductivity, high temperature resistance, excellent thermal stability, resistance to various acids and bases, non-magnetic conductivity, radiation protection, and excellent mechanical and thermal properties. Silicon carbide ceramics are widely used in industries such as petroleum, chemical engineering, electronics, semiconductors, aviation, aerospace, metallurgy, machinery, nuclear power, and defense. In particular, silicon carbide ceramic materials used in semiconductors, polysilicon, high vacuum, and space technology must not contain oxide additives such as boron, aluminum, yttrium, and lanthanum.

[0003] With the rapid development of the semiconductor industry, the demand for boat and wafer trays is increasing and becoming more urgent. At present, the domestic and mainstream developed countries in Europe and the United States are mainly based on reaction-sintered silicon carbide ceramic materials. This is because reaction-sintered silicon carbide ceramic materials have the advantages of acid and alkali corrosion resistance, high temperature resistance, high temperature oxidation resistance, high thermal conductivity, wear resistance, high hardness, and good thermal shock resistance.

[0004] Most domestic manufacturers of reaction-sintered silicon carbide boat and crystal trays use reaction-sintered silicon carbide production methods. The production process for reaction-sintered silicon carbide ceramics generally involves embedding granular silicon into a slip-cast or extruded silicon carbide blank and then sintering it at high temperature to produce silicon carbide ceramic products. However, the production method using embedded granular silicon has many problems:

[0005] 1) After high-temperature siliconization at 1700°C, 2-3mm silicon particles are not uniformly infiltrated with silicon, resulting in poor consistency. Residual silicon adheres to the surface of the ceramic part, requiring surface polishing and oxidation before use.

[0006] 2) Surface grinding generates a large amount of dust, which seriously pollutes the environment, causing health problems or silicosis to operators, and the production site environment is poor.

[0007] 3) Reaction-sintered silicon carbide products have some residual silicon slag on the surface during siliconization, resulting in uneven siliconization and a density gradient difference, which leads to a high scrap rate.

[0008] In order to better solve the common problems in the reaction-sintered silicon carbide ceramic industry, the present invention provides a pressure-sintered silicon carbide ceramic and a preparation method thereof. Summary of the Invention

[0009] To address the problems in the prior art of 2-3 mm silicon particles undergoing high-temperature siliconization at 1700°C, such as uneven silicon infiltration requiring grinding, the generation of large amounts of dust during surface grinding that seriously pollutes the environment, and residual silicon slag on the surface during siliconization, resulting in uneven siliconization and a poor density gradient, which increases the scrap rate, the present invention provides a pressureless sintered silicon carbide ceramic and a preparation method thereof.

[0010] The present invention provides a pressureless sintered silicon carbide ceramic and a preparation method thereof using the following technical solutions:

[0011] A pressure-sintered silicon carbide ceramic comprises the following raw materials in weight percentage: 40%-90% silicon carbide micropowder, 5%-60% quartz powder, 2%-10% graphite powder, 2%-20% phenolic resin solution, 40%-60% anhydrous ethanol solution, and 0.5%-2% oleic acid.

[0012] Furthermore, the purity of the silicon carbide powder is greater than 99.7%.

[0013] Furthermore, the purity of the quartz powder is greater than 99.999%, the purity of the graphite powder is greater than 99.999%, and the solid content of the phenolic resin solution is greater than 65%.

[0014] Furthermore, the particle size of the silicon carbide micropowder is D50=0.5 micron, the particle size of the quartz powder is D50=0.5-1 micron, and the particle size of the graphite powder is D50=1 micron.

[0015] A method for preparing pressureless sintered silicon carbide ceramics comprises the following steps:

[0016] S1, ingredients: according to the weight percentage, take 40%-90% of silicon carbide powder, 10%-60% of quartz powder, 2%-10% of toner, 2%-20% of phenolic resin solution, 40%-60% of anhydrous ethanol solution, and 0.5%-2% of oleic acid, respectively, add them to a stirring tank lined with silicon carbide and stir for 1.5 hours to obtain a uniformly dispersed silicon carbide slurry;

[0017] S2. Control the pH of the slurry: adjust the pH value of the slurry to between 6.5 and 7.5;

[0018] S3. Granulation: Granulation is performed using a pressure spray granulation tower, with the inlet temperature of the granulation tower set within the range of 100-150°C and the outlet temperature within the range of 70-100°C to obtain granulated powder;

[0019] S4. Drying: Place the granulated powder in a drying room at 20-40°C for 24 hours and then dry press or wait for static pressing;

[0020] S5. Molding: Density test is performed on the green compact after pressing. If the measured density is more than 55% of the theoretical density, it is considered a qualified compact.

[0021] S6. Pretreatment: Pre-process the qualified pressed products into the required size and shape;

[0022] S7, pre-sintering debinding: pre-sintering debinding treatment is performed, the debinding treatment temperature is increased to 1200 ° C at a heating rate of 3-5 ° C per minute, kept at this temperature for 1.5 hours, and then cooled to room temperature and taken out of the furnace to obtain a pre-sintered blank;

[0023] S8, high temperature sintering: the pre-sintered blanks are placed on the sintering plates and placed in a high temperature sintering furnace with flowing argon gas for high temperature sintering at a temperature of 1700-2300°C for 1-5 hours, and then cooled to room temperature with the furnace;

[0024] S9. Finished product inspection and processing: Density inspection of the product after it leaves the oven should be conducted to reach 3.1-3.16 g / cm 3 Qualified products will be processed.

[0025] In summary, the beneficial effects of the present invention are:

[0026] The pressureless sintered silicon carbide ceramic and its preparation method of the present invention are characterized by stirring, grinding, dispersing, granulating, and dry-pressing the formed product into a product. The pressed product is then pre-fired in a vacuum furnace at 1200°C. The pre-fired product is then placed in a vacuum furnace with argon gas for high-temperature sintering to produce a high-purity silicon carbide sintered body. This process eliminates the siliconization process and solves the problems of sintering cracking, sintering inclusions, and non-density in the prior art. This significantly reduces waste while improving the production environment, eliminating pollution, and ensuring the occupational health of production workers. The pressureless sintered silicon carbide ceramic produced using the present invention has a shrinkage deformation of less than 18%, a porosity of less than 1%, and a product qualification rate of over 95%. DETAILED DESCRIPTION

[0027] The present invention is described in further detail below;

[0028] The present invention discloses a pressure-sintered silicon carbide ceramic:

[0029] A pressureless sintered silicon carbide ceramic comprises the following raw materials in weight percentage: 40%-90% silicon carbide micropowder, 5%-60% quartz powder, 2%-10% graphite powder, 2%-20% phenolic resin solution, 40%-60% anhydrous ethanol solution, and 0.5%-2% oleic acid. Preferably, the purity of the silicon carbide micropowder is greater than 99.7%. Preferably, the purity of the quartz powder is greater than 99.999%, the purity of the graphite powder is greater than 99.999%, and the solid content of the phenolic resin solution is greater than 65%. Preferably, the particle size D50 of the silicon carbide micropowder is 0.5 microns, the particle size D50 of the quartz powder is 0.5-1 microns, and the particle size D50 of the graphite powder is 1 micron.

[0030] The present invention discloses a method for preparing pressure-sintered silicon carbide ceramics:

[0031] (1) Ingredients: 40%-90% of silicon carbide powder with a particle size of D50 = 0.5 μm, 5%-60% of quartz powder with a particle size of D50 = 0.5-1 μm, 2%-10% of graphite powder with a particle size of D50 = 1 μm, 2%-20% of phenolic resin solution, 40%-60% of anhydrous ethanol solution, and 0.5%-2% of oleic acid were added to a stirring tank lined with silicon carbide and stirred for 1.5 hours to prepare a silicon carbide mixed slurry with a content of 50%. The stirrer speed was controlled at 35 rpm to obtain a uniformly dispersed silicon carbide slurry.

[0032] (2) Control the acid-base concentration of the slurry: adjust the pH value of the slurry between 6.5 and 7.5, and pass the slurry through a 300-mesh vibrating screen and send it into a storage tank for standby use.

[0033] (3) Granulation: Use a pressure spray granulation tower for granulation, set the inlet temperature of the granulation tower in the range of 100-150℃, and the outlet temperature in the range of 70-100℃, transport the slurry for granulation to obtain granulated powder; pass the granulated powder through a 120-mesh vibrating sieve, weigh each 15kg bag for standby use.

[0034] (4) Drying: Place the granulated powder in a drying room at 20-40°C and let it stand for 24 hours before dry pressing or static pressing.

[0035] (5) Molding: Density test is performed on the green body after pressing and molding. If the measured density is greater than 55% of the theoretical density, it is considered a qualified pressed product.

[0036] (6) Pretreatment: The qualified pressed products are pre-processed into the required size and shape.

[0037] (7) Pre-sintering degumming: Pre-sintering degumming treatment is carried out, and the degumming treatment temperature is heated to 1200℃ at a heating rate of 3-5℃ per minute, kept at this temperature for 1.5 hours, and then cooled to room temperature and taken out of the furnace to obtain a pre-sintered blank.

[0038] (8) High temperature sintering: Place the pre-sintered blanks on the sintering plates and put them into a high temperature sintering furnace with flowing argon gas for high temperature sintering. The sintering temperature is 1700-2300℃, keep warm for 1-5 hours, and then cool to room temperature with the furnace.

[0039] (9) Finished product inspection and processing: The density of the product after being baked is tested to reach 3.1-3.16g / cm 3 Qualified products will be processed.

[0040] The pressure-sintered silicon carbide ceramics produced by the method of the present invention have stable and reliable product quality, shrinkage deformation less than 18%, porosity less than 1%, and a product qualification rate of more than 95%.

[0041] The following is a first embodiment of the present invention:

[0042] Select 80% by weight, 99.95% pure silicon carbide powder with a D50 of 0.5 micron; 15% by weight, 99.999% pure quartz powder with a D50 of 0.5 micron; 5% by weight, 99.999% pure graphite powder with a D50 of 1 micron; 8% by weight, greater than 65% solids content of an alcohol-soluble phenolic resin solution; and 50% by weight, 99.999% pure anhydrous ethanol. Add these powders to a grinding barrel and grind and disperse for 10 hours. Then, add 1% by weight of oleic acid and grind together. The grinding barrel must have a silicon carbide ceramic inner wall. The ground slurry is sieved through a 400-mesh sieve and placed in a mixing tank for later use.

[0043] The pH value of the slurry is detected to be between 6.5 and 7.5. It is sent to the pressure spray granulation tower for granulation through a micro pump. The granulated powder is passed through a 120-mesh vibrating screen and bagged for later use. The granulated powder is placed in a mold and pressed into a silicon carbide blank. Degreasing and sintering to 1200°C are carried out under vacuum conditions. After keeping warm for 1.5 hours, it is cooled to room temperature and then taken out of the furnace; then it is loaded into a high-temperature sintering furnace, first evacuated to -0.1 Pa, and then filled with flowing argon for heating and sintering. It is sintered to 2200°C at a heating rate of 5°C per minute, kept warm for 1.5 hours, and then turned off and cooled to room temperature and taken out of the furnace. The products are tested after being taken out of the furnace, and only qualified products that meet the following standards can be further processed: Volume density 3.05g / cm 3, flexural strength 340MPa, hardness 2300kg / mm, elastic modulus 320GPa, thermal conductivity 122W / m·K, fracture toughness 4.2MPa√m.

[0044] The following is a second embodiment of the present invention:

[0045] Select 70% by weight, 99.95% pure silicon carbide powder with a D50 of 0.5 micron; 20% by weight, 99.999% pure quartz powder with a D50 of 0.5 micron; 10% by weight, 99.999% pure graphite powder with a D50 of 1 micron; 8.5% by weight alcohol-soluble phenolic resin solution with a solids content greater than 65%; and 50% by weight, 99.999% pure anhydrous ethanol. Add these powders to a grinding barrel and grind and disperse for 12 hours. Then, add 1% by weight oleic acid and grind together. The grinding barrel must have a silicon carbide ceramic inner wall. The ground slurry is passed through a 400-mesh sieve and placed in a mixing tank for later use.

[0046] The pH value of the slurry is detected to be between 6.5 and 7.5. It is sent to the pressure spray granulation tower for granulation through a micro pump. The granulated powder is passed through a 120-mesh vibrating screen and bagged for later use. The granulated powder is placed in a mold and pressed into a silicon carbide blank. Degreasing and sintering to 1200°C are carried out under vacuum conditions. After keeping warm for 1.5 hours, it is cooled to room temperature and then taken out of the furnace; then it is loaded into a high-temperature sintering furnace, first evacuated to -0.1 Pa, and then filled with flowing argon for heating and sintering. It is sintered to 2250°C at a heating rate of 5°C per minute, kept warm for 1.5 hours, and then turned off and cooled to room temperature and taken out of the furnace. The products are tested after being taken out of the furnace, and only qualified products that meet the following standards can be further processed: Volume density 3.14g / cm 3 , flexural strength 350MPa, hardness 2430kg / mm, elastic modulus 340GPa, thermal conductivity 125W / m·K, fracture toughness 4.5MPa√m.

[0047] The following is a third embodiment of the present invention:

[0048] Select silicon carbide micropowder (85% by weight, 99.95% purity, and a D50 particle size of 0.5 microns); quartz powder (8% by weight, 99.999% purity, and a D50 particle size of 0.5 microns); graphite powder (7% by weight, 99.999% purity, and a D50 particle size of 1 micron); an alcohol-soluble phenolic resin solution (8.5% by weight, with a solids content greater than 65%); and anhydrous ethanol (50% by weight, 99.999% purity). These powders are added to a grinding barrel and ground and dispersed for 12 hours. Then, 1% by weight of oleic acid is added and ground together. The grinding barrel must have a silicon carbide ceramic inner wall. The ground slurry is passed through a 400-mesh sieve and placed in a mixing tank for later use.

[0049] The pH value of the slurry is detected to be between 6.5 and 7.5. It is sent to the pressure spray granulation tower for granulation through a micro pump. The granulated powder is passed through a 120-mesh vibrating screen and bagged for later use. The granulated powder is placed in a mold and pressed into a silicon carbide blank. Degreasing and sintering to 1200°C are carried out under vacuum conditions. After keeping warm for 1.5 hours, it is cooled to room temperature and then taken out of the furnace; then it is loaded into a high-temperature sintering furnace, first evacuated to -0.1 Pa, and then filled with flowing argon for heating and sintering. It is sintered to 2180°C at a heating rate of 5°C per minute, kept warm for 1 hour, and then turned off and cooled to room temperature and taken out of the furnace. The products are tested after being taken out of the furnace, and only qualified products that meet the following standards can be further processed: Volume density 3.02g / cm 3 , flexural strength 330MPa, hardness 2300kg / mm, elastic modulus 330GPa, thermal conductivity 122W / m·K, fracture toughness 4.3MPa√m.

[0050] The above shows and describes the basic principles, main features, and advantages of the present invention. The various components mentioned in the present invention are conventional technologies in the prior art. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and improvements may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and improvements are intended to fall within the scope of the invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A pressureless sintered silicon carbide ceramic, characterized in that: The invention comprises the following raw materials in weight percentage: 40%-90% of silicon carbide micropowder, 5%-60% of quartz powder, 2%-10% of graphite powder, 2%-20% of phenolic resin solution, 40%-60% of anhydrous ethanol solution and 0.5%-2% of oleic acid.

2. The pressureless sintered silicon carbide ceramic according to claim 1, characterized in that: The purity of the silicon carbide micropowder is greater than 99.7%.

3. The pressureless sintered silicon carbide ceramic according to claim 1, characterized in that: The purity of the quartz powder is greater than 99.999%, the purity of the graphite powder is greater than 99.999%, and the solid content of the phenolic resin solution is greater than 65%.

4. The pressureless sintered silicon carbide ceramic according to claim 1, characterized in that: The particle size of the silicon carbide micropowder is D50=0.5 micron, the particle size of the quartz powder is D50=0.5-1 micron, and the particle size of the graphite powder is D50=1 micron.

5. A method for preparing pressureless sintered silicon carbide ceramics according to any one of claims 1 to 4, characterized in that: The steps include: S1, ingredients: according to the weight percentage, take 40%-90% of silicon carbide powder, 5%-60% of quartz powder, 2%-10% of toner, 2%-20% of phenolic resin solution, 40%-60% of anhydrous ethanol solution, and 0.5%-2% of oleic acid, respectively, add them to a stirring tank lined with silicon carbide and stir for 1.5 hours to obtain a uniformly dispersed silicon carbide slurry; S2. Control the pH of the slurry: adjust the pH value of the slurry to between 6.5 and 7.5; S3. Granulation: Granulate using a pressure spray granulation tower, set the inlet temperature of the granulation tower in the range of 100-150°C, and the outlet temperature in the range of 70-100°C to obtain granulated powder; S4. Drying: Place the granulated powder in a drying room at 20-40°C for 24 hours and then dry press or wait for static pressing; S5. Molding: Density test is performed on the green compact after pressing. If the measured density is more than 55% of the theoretical density, it is considered a qualified compact. S6. Pretreatment: Pre-process the qualified pressed products into the required size and shape; S7, pre-sintering debinding: pre-sintering debinding treatment is performed, the debinding treatment temperature is increased to 1200 ° C at a heating rate of 3-5 ° C per minute, kept at this temperature for 1.5 hours, and then cooled to room temperature and taken out of the furnace to obtain a pre-sintered blank; S8, high temperature sintering: the pre-sintered blanks are placed on the sintering plates and placed in a high temperature sintering furnace with flowing argon gas for high temperature sintering at a temperature of 1700-2300°C for 1-5 hours, and then cooled to room temperature with the furnace; S9. Finished product inspection and processing: Density inspection of the product after it leaves the oven should be conducted to reach 3.1-3.16 g / cm 3 Qualified products will be processed.