Efficient production process of silicon carbide

Abstract

The invention relates to the technical field of concealed project acceptance, and discloses an efficient silicon carbide production process which comprises the following steps: pickling quartz sand, and screening and drying petroleum coke; then mixing and molding, adding a binder and a dispersant, and carrying out dry pressing or isostatic pressing molding; then high-temperature sintering is carried out under argon protection according to a specific heating and cooling program; the silicon carbide product obtained by the process has the advantages of high purity, excellent physical properties, Mohs hardness of 9.2 or more, bending strength of not less than 400MPa, heat conductivity of 120-160W / (m.K), good electrical properties and uniform particle size, the raw materials are strictly pretreated, the process is simple, the production cost is low, the production efficiency is high, and the production cost is low. Impurities in the raw materials are effectively removed through acid pickling of quartz sand and fine screening of petroleum coke, and introduction of the impurities is further reduced through accurate temperature control and argon protective atmosphere in the subsequent high-temperature sintering process.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor device processing, and in particular to a high-efficiency production process for silicon carbide. Background Art

[0002] As a wide-bandgap semiconductor material, silicon carbide (SiC) boasts excellent physical and electrical properties, including high hardness, high thermal conductivity, high electron saturation drift velocity, and high breakdown voltage. It holds broad application prospects in power electronics, automotive electronics, aerospace, and new energy. With the continuous advancement of science and technology, the demand for SiC materials is increasing, and so are the requirements for its quality and performance.

[0003] Traditional methods for preparing silicon carbide mainly include solid-phase, liquid-phase, and vapor-phase methods. However, these traditional methods often have several shortcomings. For example, the solid-phase method typically requires high temperature and pressure, resulting in high energy consumption and uneven product particle size distribution. While the liquid-phase method can be performed at lower temperatures, the reaction process is complex and product quality control is difficult. While the vapor-phase method can produce high-purity silicon carbide, its production cost is high and its yield is low, making it unsuitable for large-scale industrial production. Therefore, developing an efficient, stable, low-cost silicon carbide preparation process that can be implemented on a large scale is of great practical significance. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the present invention provides an efficient silicon carbide production process to solve the problems of low production efficiency, unstable product quality, high energy consumption, etc. in the existing technology, while improving the purity and performance of silicon carbide products to meet the diverse needs of different fields for silicon carbide materials.

[0005] The above technical objectives of the present invention are achieved through the following technical solutions:

[0006] An efficient production process for silicon carbide, the specific steps are as follows:

[0007] S1.1: Select high-purity natural quartz sand as the silicon source and grind it in a ball mill;

[0008] S1.2: The crushed quartz sand is placed in a pickling tank and pickled with hydrochloric acid solution;

[0009] S1.3: Stirring is performed during the pickling process to fully dissolve the impurity ions;

[0010] S1.4: After the acid wash is completed, the quartz sand is rinsed with deionized water several times until the pH value of the washing solution is close to 7. The quartz sand is then placed in a drying oven and dried to a constant weight to obtain high-purity quartz sand.

[0011] S1.5: Select high-quality petroleum coke as the carbon source, place the petroleum coke in a crusher for preliminary crushing, and then place it in a jet mill for further crushing;

[0012] S1.6: The crushed petroleum coke is placed in a screening device for screening to remove particles that are too large or too small to ensure uniform particle size of the petroleum coke;

[0013] S1.7: Dry the sieved petroleum coke in a drying oven to a constant weight to obtain pretreated petroleum coke;

[0014] S2.1: Weigh pre-treated high-purity quartz sand and petroleum coke according to the stoichiometric ratio and actual production requirements;

[0015] S2.2: Add appropriate amount of binder and dispersant to improve the molding performance and dispersibility of the raw materials;

[0016] S2.3: Weigh the quartz sand, petroleum coke, binder, and dispersant into a high-speed blender. Add an appropriate amount of deionized water and mix thoroughly.

[0017] S2.4: Pour the mixed slurry into a specific mold and press the slurry into a green body by dry pressing or isostatic pressing;

[0018] Preferably, the steps further include: S3.1: carefully placing the formed green body into a high-temperature sintering furnace, and evenly laying a layer of carbon powder around the green body to prevent the green body from sticking to other components in the furnace during the sintering process;

[0019] S3.2: High-purity argon gas is introduced into the sintering furnace as a protective atmosphere;

[0020] S3.3: Start the heating device of the sintering furnace and increase the temperature according to the predetermined temperature increase program;

[0021] S3.4: After sintering is completed, turn off the heating device and allow the green body to cool naturally to room temperature in the sintering furnace;

[0022] S3.5: Continue to introduce argon gas during the cooling process to prevent the silicon carbide product from being oxidized. After cooling to room temperature, open the furnace door and take out the silicon carbide product.

[0023] S4.1: Place the sintered silicon carbide product into a crusher for preliminary crushing; then use a jet mill or ball mill to further crush it to the required particle size range;

[0024] S4.2: The crushed product is placed in a grading device for grading. The product is classified into different grades according to the particle size to meet the needs of different application fields.

[0025] S4.3: Place the graded product in a cleaning device and rinse it multiple times with deionized water to remove impurities and residual binders, dispersants, and other substances on the product surface;

[0026] S4.4: Appropriate surfactants are added during the cleaning process to improve the cleaning effect. After cleaning, the product is dehydrated in a centrifuge and then dried in a drying oven to a constant weight. The dried silicon carbide product is strictly quality tested, and qualified products are packaged in vacuum packaging or other appropriate packaging methods.

[0027] Preferably, the SiO2 content of the natural quartz sand is not less than 99.5%; the ball milling time is 3-5 hours, so that the particle size of the quartz sand is refined to 5-10 μm; the concentration of the hydrochloric acid solution is 10-20%, the pickling temperature is 60-80°C, and the pickling time is 2-4 hours; the fixed carbon content of the carbon source is not less than 98%; the particle size of the carbon source after initial crushing is 5-10 mm, and it is placed in a jet mill and further crushed to a particle size of 3-8 μm.

[0028] Preferably, the molar ratio of the quartz sand to the petroleum coke is controlled between 1:1.1-1.3; the binder is 5-10% of the total mass of the raw materials; the dispersant is 3-5% of the total mass of the raw materials; the stirring time is 2-3 hours, and the stirring speed is 800-1200 rpm.

[0029] Preferably, the pressure of the dry pressing is 20-30 MPa, and the holding time is 10-20 seconds; the pressure of the isostatic pressing is 100-200 MPa, and the holding time is 5-10 minutes.

[0030] Preferably, the purity of the argon is not less than 99.999%, and the flow rate is controlled at 1-2m 3 / h.

[0031] Preferably, the heating process is divided into three stages. In the first stage, the temperature is slowly increased from room temperature to 800°C at a heating rate of 5-10°C / min and kept warm for 30 minutes to allow the binder and dispersant in the green body to fully volatilize and decompose; in the second stage, the temperature is quickly increased from 800°C to 2300°C at a heating rate of 10-15°C / min and kept warm for 2-3 hours to allow quartz sand and petroleum coke to undergo a carbon thermal reduction reaction at high temperature to generate silicon carbide; in the third stage, the temperature is slowly decreased from 2300°C to room temperature at a cooling rate of 5-10°C / min; the temperature control accuracy of the entire sintering process does not exceed ±10°C.

[0032] Preferably, the silicon carbide product is placed in a crusher for preliminary crushing to a particle size of 1-5 mm; the air flow mill or ball mill further crushes it to a desired particle size range of 1-10 μm; and the drying temperature is controlled at 80-120°C.

[0033] A silicon carbide product prepared by an efficient silicon carbide production process has high purity (purity of 99.9% or more), excellent physical properties, a hardness of Mohs hardness of 9.2 or more, a flexural strength of not less than 400 MPa, a thermal conductivity of 120-160 W / (m·K), good electrical properties, good electrical conductivity and insulation properties, and uniform particle size (distributed between 1 and 10 μm).

[0034] According to the silicon carbide product prepared as described above, when the product is used in the field of power electronic devices, it can reduce energy loss and improve the efficiency and reliability of the device; when used in the mechanical field, it has excellent wear resistance and corrosion resistance.

[0035] In summary, the present invention mainly has the following beneficial effects:

[0036] First, through rigorous raw material pretreatment, such as acid washing of quartz sand and fine screening of petroleum coke, impurities are effectively removed. During the subsequent high-temperature sintering process, precise temperature control and an argon protective atmosphere further reduce the introduction of impurities. These measures ensure a final product purity exceeding 99.9%, meeting the stringent purity requirements of silicon carbide materials for high-end applications. This prevents the adverse effects of impurities on product performance, such as reducing defects in the crystal structure, thereby improving product quality and reliability.

[0037] Second, the optimized raw material ratio and mixing process allow quartz sand and petroleum coke to fully react during the high-temperature sintering process, forming silicon carbide with a complete crystal structure and high density. Its hardness can reach Mohs hardness of 9.2 or above, and its flexural strength is no less than 400 MPa. This makes silicon carbide products resistant to deformation and cracking when subjected to high pressure and friction, making them suitable for manufacturing high-performance mechanical components such as sealing rings and grinding discs, significantly improving their service life and operating efficiency. Due to its high hardness and strength, the product exhibits excellent wear resistance. When in contact with other materials and in relative motion, silicon carbide exhibits minimal surface wear, maintaining excellent dimensional stability and surface accuracy. This characteristic makes it widely used as a wear-resistant material in mechanical processing, chemical production, and other fields, reducing equipment maintenance costs and downtime. Silicon carbide inherently has a high melting point and thermal conductivity. Products produced using the present process can achieve thermal conductivity of 120-160 W / (m·K). In high-temperature environments, the product can quickly conduct heat, avoiding performance degradation or damage caused by localized overheating. Therefore, it can be used to manufacture high-temperature structural parts, heat exchangers and other components that work under high-temperature conditions, ensuring the stable operation of equipment under high-temperature conditions and extending the service life of the equipment.

[0038] 3. The high purity and complete crystal structure of the product give it good electrical conductivity and insulation properties in electrical applications. In power electronic devices, such as as a substrate material for power devices, it can effectively conduct current, reduce the energy loss of electrons during transmission, and improve the energy efficiency of the device. At the same time, good insulation performance can prevent current leakage, ensure the safety and stability of the device, reduce power consumption, and meet the requirements of modern energy conservation and environmental protection. Excellent electrical properties help to improve the reliability of power electronic devices. In harsh working environments such as high temperature, high pressure, and high frequency, silicon carbide materials can maintain stable electrical properties and are not prone to breakdown, leakage and other fault phenomena. This makes the silicon carbide product of the present invention have obvious advantages in the manufacture of high-performance and high-reliability power electronic devices, such as applications in the fields of electronic control systems of new energy vehicles, photovoltaic power generation inverters, etc., which can improve the operating efficiency and stability of the entire system and reduce the occurrence rate of failures. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a process flow chart of silicon carbide production according to the present invention. DETAILED DESCRIPTION

[0040] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0041] Example 1

[0042] refer to Figure 1 , a high-efficiency silicon carbide production process, comprising:

[0043] Raw material pretreatment: Quartz sand pretreatment: Select 10 kg of high-purity natural quartz sand (SiO2 content 99.7%), put it into a ball mill and crush it for 3.5 hours to refine the particle size to about 8 μm; then transfer it to a pickling tank and pickle it with 15% hydrochloric acid solution at 70°C for 3 hours to remove impurities; after pickling, wash it with deionized water to a pH value of 6.8, and then put it into a drying oven at 110°C to dry to constant weight to obtain pretreated quartz sand.

[0044] Petroleum coke pretreatment: Take 5 kg of high-quality petroleum coke (fixed carbon content 98.5%), first use a crusher to initially crush it to 7 mm, and then use a jet mill to further crush it to 5 μm; the crushed petroleum coke is sieved through a multi-layer vibrating screen to remove particles of unqualified particle size, and finally dried at 110°C to constant weight to obtain pretreated petroleum coke.

[0045] Mixing and molding: Weigh 15 kg of pretreated quartz sand and petroleum coke in a molar ratio of 1:1 and place them in a three-dimensional mixer. At the same time, add 7% of polyvinyl alcohol and 4% of polyethylene glycol as a binder and dispersant equivalent to the total weight of the raw materials. Mix at a speed of 25 rpm for 2.5 hours to ensure that the raw materials are fully mixed.

[0046] The mixed blank is placed in a mold and dry pressed at a pressure of 15 MPa for 12 minutes to form a blank with a certain shape and strength, with a density of 60% of the theoretical density.

[0047] High-temperature sintering: The formed green body is placed in a vacuum sintering furnace and high-purity argon (flow rate 1.5 cubic meters / hour) is introduced as a protective atmosphere; the temperature is raised from room temperature to 800°C at a heating rate of 8°C / min and kept warm for 30 minutes; then the temperature is raised from 800°C to 2300°C at a heating rate of 12°C / min and kept warm for 2.5 hours; finally, the temperature is slowly lowered to room temperature at a cooling rate of 8°C / min. The whole process takes 30 hours to obtain the sintered product.

[0048] Post-processing: The sintered product is removed and initially crushed using a coarse crusher, then finely ground using a jet mill to a particle size of approximately 8μm. Finally, it is graded using a multi-layer vibrating screen, and products that meet the particle size requirements are collected to obtain a high-purity silicon carbide product with excellent physical and electrical properties. Testing has shown that the product has a purity of 99.9%, a Mohs hardness of 9.2, a flexural strength of 450MPa, a thermal conductivity of 120W / (m·K), and a resistivity of 0.01Ω·cm.

[0049] Example 2

[0050] refer to Figure 1 , a high-efficiency silicon carbide production process, comprising:

[0051] Raw material pretreatment: Quartz sand pretreatment: Select 12 kg of high-purity natural quartz sand (SiO2 content 99.6%), put it into a ball mill and crush it for 4 hours to refine the particle size to about 7 μm; then transfer it to a pickling tank and pickle it with 18% hydrochloric acid solution at 75°C for 3.5 hours to remove impurities; after pickling, wash it with deionized water to a pH value of 6.9, and then put it into a drying oven at 115°C to dry to constant weight to obtain pretreated quartz sand.

[0052] Petroleum coke pretreatment: 6 kg of high-quality petroleum coke (fixed carbon content 98.8%) was initially crushed to 6 mm using a crusher, and then further crushed to 4 μm using a jet mill; the crushed petroleum coke was sieved through a multi-layer vibrating screen to remove particles of unqualified particle size, and finally dried at 115°C to constant weight to obtain pretreated petroleum coke.

[0053] Mixing and molding: Weigh 18 kg of pretreated quartz sand and petroleum coke in a molar ratio of 1:1.1 and place them in a three-dimensional mixer. At the same time, add 8% of the total weight of polyvinyl alcohol and 5% of polyethylene glycol as a binder and dispersant. Mix at 28 rpm for 2.8 hours to ensure that the raw materials are fully mixed.

[0054] The mixed blank is placed in a mold and isostatically pressed at a pressure of 180 MPa for 14 minutes to form a blank with a certain shape and strength. The density of the blank reaches 62% of the theoretical density.

[0055] High-temperature sintering: The formed green body is placed in an atmosphere-protected sintering furnace, and high-purity argon (flow rate 1.8 cubic meters / hour) is introduced as a protective atmosphere; the temperature is raised from room temperature to 800°C at a heating rate of 9°C / min and kept warm for 35 minutes; then the temperature is raised from 800°C to 2300°C at a heating rate of 13°C / min and kept warm for 2.8 hours; finally, the temperature is slowly lowered to room temperature at a cooling rate of 9°C / min. The whole process takes 32 hours to obtain the sintered product.

[0056] Post-processing: The sintered product is removed and initially crushed using a coarse crusher, then finely ground using a sand mill to a particle size of approximately 6 μm. Finally, it is graded using a multi-layer vibrating screen to collect products that meet the particle size requirements. This results in a high-purity silicon carbide product with excellent physical and electrical properties. Testing has shown that the product has a purity of 99.95%, a Mohs hardness of 9.3, a flexural strength of 480 MPa, a thermal conductivity of 130 W / (m·K), and a resistivity of 0.008 Ω·cm.

[0057] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A high-efficiency production process for silicon carbide, characterized in that: The specific steps are as follows: S1.1: Select high-purity natural quartz sand as the silicon source and grind it in a ball mill; S1.2: The crushed quartz sand is placed in a pickling tank and pickled with hydrochloric acid solution; S1.3: Stirring is performed during the pickling process to fully dissolve the impurity ions; S1.4: After the acid wash is completed, the quartz sand is rinsed with deionized water several times until the pH value of the washing solution is close to 7. The quartz sand is then placed in a drying oven and dried to a constant weight to obtain high-purity quartz sand. S1.5: Select high-quality petroleum coke as the carbon source, place the petroleum coke in a crusher for preliminary crushing, and then place it in a jet mill for further crushing; S1.6: The crushed petroleum coke is placed in a screening device for screening to remove particles that are too large or too small to ensure uniform particle size of the petroleum coke; S1.7: Dry the sieved petroleum coke in a drying oven to a constant weight to obtain pretreated petroleum coke; S2.1: Weigh pre-treated high-purity quartz sand and petroleum coke according to the stoichiometric ratio and actual production requirements; S2.2: Add appropriate amount of binder and dispersant to improve the molding performance and dispersibility of the raw materials; S2.3: Weigh the quartz sand, petroleum coke, binder, and dispersant into a high-speed blender. Add an appropriate amount of deionized water and mix thoroughly. S2.4: Pour the mixed slurry into a specific mold and press the slurry into a green body by dry pressing or isostatic pressing.

2. The efficient production process of silicon carbide according to claim 1, characterized in that: The steps also include: S3.1: Carefully place the formed green body into the high-temperature sintering furnace and evenly spread a layer of carbon powder around the green body to prevent it from sticking to other parts in the furnace during the sintering process; S3.2: High-purity argon gas is introduced into the sintering furnace as a protective atmosphere; S3.3: Start the heating device of the sintering furnace and increase the temperature according to the predetermined temperature increase program; S3.4: After sintering is completed, turn off the heating device and allow the green body to cool naturally to room temperature in the sintering furnace; S3.5: Continue to introduce argon gas during the cooling process to prevent the silicon carbide product from being oxidized. After cooling to room temperature, open the furnace door and take out the silicon carbide product. S4.1: Place the sintered silicon carbide product into a crusher for preliminary crushing; then use a jet mill or ball mill to further crush it to the required particle size range; S4.2: The crushed product is placed in a grading device for grading. The product is classified into different grades according to the particle size to meet the needs of different application fields. S4.3: Place the graded product in a cleaning device and rinse it multiple times with deionized water to remove impurities and residual binders, dispersants, and other substances on the product surface; S4.4: Appropriate surfactants are added during the cleaning process to improve the cleaning effect. After cleaning, the product is dehydrated in a centrifuge and then dried in a drying oven to a constant weight. The dried silicon carbide product is strictly quality tested, and qualified products are packaged in vacuum packaging or other appropriate packaging methods.

3. The efficient production process for silicon carbide according to claim 2, characterized in that: The SiO2 content of the natural quartz sand is not less than 99.5%; The ball milling time is 3-5 hours, so that the particle size of the quartz sand is refined to 5-10 μm; The concentration of the hydrochloric acid solution is 10-20%, the pickling temperature is 60-80°C, and the pickling time is 2-4 hours; The fixed carbon content of the carbon source is not less than 98%; The carbon source is initially crushed to a particle size of 5-10 mm, and is then placed in a jet mill and further crushed to a particle size of 3-8 μm.

4. A high-efficiency silicon carbide production process according to claim 3, characterized in that: The molar ratio of the quartz sand to the petroleum coke is controlled between 1:1.1-1.3; The binder is 5-10% of the total mass of the raw materials; 3-5% of the total mass of the dispersant raw materials; The stirring time is 2-3 hours, and the stirring speed is 800-1200 rpm.

5. A high-efficiency silicon carbide production process according to claim 4, characterized in that: The dry pressing pressure is 20-30 MPa, and the holding time is 10-20 seconds; The isostatic pressing pressure is 100-200 MPa, and the holding time is 5-10 minutes.

6. The efficient production process for silicon carbide according to claim 5, characterized in that: The purity of the argon gas is not less than 99.999%, and the flow rate is controlled at 1-2m 3 / h.

7. The efficient production process of silicon carbide according to claim 6, characterized in that: The heating process is divided into three stages. In the first stage, the temperature is slowly increased from room temperature to 800°C at a heating rate of 5-10°C / min and kept at this temperature for 30 minutes to fully volatilize and decompose the binder and dispersant in the green body; in the second stage, the temperature is quickly increased from 800°C to 2300°C at a heating rate of 10-15°C / min and kept at this temperature for 2-3 hours to cause the quartz sand and petroleum coke to undergo a carbon thermal reduction reaction at high temperature to generate silicon carbide; in the third stage, the temperature is slowly decreased from 2300°C to room temperature at a cooling rate of 5-10°C / min; the temperature control accuracy of the entire sintering process does not exceed ±10°C.

8. The efficient silicon carbide production process according to claim 7, characterized in that: The silicon carbide product is placed in a crusher for preliminary crushing to a particle size of 1-5 mm; the air flow mill or ball mill further crushes it to a desired particle size range of 1-10 μm; and the drying temperature is controlled at 80-120° C.

9. The silicon carbide product prepared by the silicon carbide efficient production process according to claim 1, characterized in that: The silicon carbide product has high purity, with a purity of more than 99.9%, excellent physical properties, a hardness of more than 9.2 on the Mohs scale, a bending strength of not less than 400 MPa, a thermal conductivity of 120-160 W / (m·K), good electrical properties, good electrical conductivity and insulation properties, and uniform particle size, with a particle size distribution of 1-10 μm.

10. The silicon carbide product according to claim 9, characterized in that When the product is used in the field of power electronic devices, it can reduce energy loss and improve the efficiency and reliability of the devices; when used in the mechanical field, it has excellent wear resistance and corrosion resistance.

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