Preparation method of silicon carbide

Abstract

The invention discloses a preparation method of silicon carbide, which comprises the following steps: drying silicon powder with the purity of 99-99.9999%; mixed gas is preheated to 300-500 DEG C, the mixed gas comprises hydrocarbon gas and carrier gas, and argon or hydrogen is adopted as the carrier gas; the dried silicon powder and the preheated mixed gas are fed into a rotary kiln for a reaction, the molar ratio of Si to C is controlled to be 1: 1, beta-SiC powder is generated, the reaction temperature ranges from 1100 DEG C to 1400 DEG C, the absolute pressure in the rotary kiln ranges from 60 kPa to 85 kPa, and the rotation speed of a rotary kiln body ranges from 1 r / min to 5 r / min; the beta-SiC powder is fed into a vacuum reaction furnace, argon is introduced, the temperature is increased to 1900-2100 DEG C, a reaction is conducted for 3-10 h, the beta-SiC powder grows and is recrystallized and converted into the alpha-SiC powder, and the purity of the obtained alpha-SiC powder is 99-99.999%.

Description

Technical Field

[0001] This application relates to the field of semiconductor material preparation technology, and in particular to a method for preparing silicon carbide. Background Technology

[0002] Silicon carbide (SiC) is an important semiconductor material with excellent thermal, electrical and mechanical properties, and is widely used in electronic devices, refractory materials, wear-resistant materials and other fields.

[0003] Currently, the commonly used methods for preparing silicon carbide powder mainly include the Acheson method, vapor deposition method, and solid-phase synthesis method.

[0004] While the Acheson method is low-cost, it's difficult to achieve high product purity. Vapor deposition produces high-purity products, but the equipment is complex and expensive. Solid-state synthesis involves mixing silicon powder and carbon powder and reacting them at high temperatures to produce silicon carbide. However, this process primarily uses a closed reactor, is slightly exothermic, and localized runaway temperatures can easily cause silicon melting, reducing silicon carbide quality. Furthermore, it requires precise control of the reactor temperature and reaction rate, resulting in long reaction times and low production efficiency. Summary of the Invention

[0005] The purpose of this application is to provide a method for preparing silicon carbide.

[0006] To achieve one of the above-mentioned objectives, one embodiment of this application provides a method for preparing silicon carbide, the method comprising the following steps: The silicon powder is dried, and the purity of the silicon powder is 99~99.9999%. The mixed gas is preheated to 300~500°C. The mixed gas includes hydrocarbon gas and carrier gas, and the carrier gas is argon or hydrogen. The dried silicon powder and the preheated mixed gas are fed into a rotary kiln for reaction. The molar ratio of Si to C is controlled to be 1:1 to generate β-SiC powder. The reaction temperature is 1100~1400℃, the pressure inside the rotary kiln is absolute 60~85kPa, and the rotation speed of the rotary kiln body is 1~5 rpm. β-SiC powder is fed into a vacuum reactor, argon gas is introduced, and the temperature is raised to 1900~2100℃. The reaction is carried out for 3~10 hours. β-SiC powder grows and recrystallizes into α-SiC powder. The purity of the obtained α-SiC powder is 99~99.999%.

[0007] As a further improvement to one embodiment of this application, the mass flow rate of the silicon powder introduced into the rotary kiln is 5~800 kg / h, and the volumetric flow rate of the mixed gas is 10~8000 Nm³. 3 / h, the volumetric flow rate ratio of the hydrocarbon gas to the carrier gas in the mixed gas is 1:5 to 1:30.

[0008] As a further improvement of one embodiment of this application, the hydrocarbon gas is a C1-C10 alkane, olefin, or alkyne.

[0009] As a further improvement of one embodiment of this application, the hydrocarbon gas is at least one of methane, ethane, propane, ethylene, and acetylene.

[0010] As a further improvement of one embodiment of this application, the particle size of the silicon powder is 0.1~50μm, the crystal particle size of the generated β-SiC powder is 1~100μm, and the crystal particle size of the obtained α-SiC powder is 300~2000μm.

[0011] As a further improvement to one embodiment of this application, the "drying of silicon powder" specifically includes: The silicon powder is dried by introducing hot inert gas or hydrogen, and the drying process is controlled to be water-free, oxygen-free, and nitrogen-free.

[0012] As a further improvement to one embodiment of this application, the preparation method further includes the step of: Before preheating the mixed gas, multiple adsorption columns connected in series are used to remove water and oxygen from the mixed gas.

[0013] As a further improvement to one embodiment of this application, the preparation method further includes the step of: Before the reaction, the rotary kiln is heated to 80~200°C, and argon gas is circulated into the rotary kiln for purging until the oxygen concentration in the rotary kiln drops below 0.1%.

[0014] As a further improvement to one embodiment of this application, the preparation method further includes the step of: After the β-SiC powder is fed into the vacuum reactor, it is first heated to 1000~1200℃ and CO2 or O2 is introduced to remove the free carbon on the surface of the β-SiC powder. Then the introduction of CO2 or O2 is stopped, and argon gas is introduced and the temperature is raised to recrystallize.

[0015] As a further improvement to one embodiment of this application, the carrier gas is argon; the preparation method further includes the following steps: The gas discharged from the rotary kiln is sequentially passed through a cyclone dust collector and a bag filter for gas-solid separation. The separated solid is sent into the vacuum reactor for growth and recrystallization. The separated gas is collected in a buffer tank and then sent to a two-stage vacuum pressure swing adsorption system to remove hydrogen and unreacted hydrocarbon gases, resulting in purified argon.

[0016] Compared with the prior art, the beneficial effects of the present application are as follows: In the preparation method of silicon carbide of the present application, high-purity silicon powder and preheated hydrocarbon gas are used as raw materials, and a rotary kiln is used as the reaction device, which can optimize the fluidity of the gas phase and the solid phase, improve the reaction contact efficiency, ensure the full mixing and efficient reaction of the silicon powder and the hydrocarbon gas, and improve the preparation efficiency and stability of silicon carbide; through the thermal decomposition of the hydrocarbon gas at 1100-1400 °C, a carbon-containing intermediate gas phase with high reactivity is generated during the high-temperature thermal decomposition process, and then reacts with the silicon powder to generate β-SiC, and the molar ratio of Si to C is controlled to be 1:1, high-purity silicon carbide powder can be synthesized at a lower temperature and in a shorter time, and the particle size of the silicon carbide powder is uniform, with lower energy consumption. It is not only suitable for large-scale production, but also the production cost is greatly reduced, the reaction time is short, and the production efficiency is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a flowchart of the preparation method of silicon carbide according to an embodiment of the present application; Figure 2 is a schematic structural diagram of a rotary kiln according to an embodiment of the present application.

[0018] 10. Rotary kiln; 1. Feed bin; 2. Feeder; 3. Kiln body; 31. Rotary furnace tube; 32. Heating furnace; 4. Discharge bin; 5. Intake pipe; 6. Exhaust pipe; 7. Kiln body angle adjustment accessory. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] The present application will be described in detail below with reference to the specific embodiments shown in the drawings.

[0020] In the various drawings of the present application, for the convenience of illustration, the dimensions of some structures or parts are enlarged relative to other structures or parts. Therefore, it is only used to illustrate the basic structure of the subject matter of the present application.

[0021] It should be understood that although the terms "first", "second", "third", etc. may be used herein to describe various elements, structures or parameters, the described objects should not be limited by these terms. These terms are only used to distinguish these described objects from each other.

[0022] Refer Figures 1 to 2 As shown, an embodiment of the present application provides a preparation method of silicon carbide.

[0023] The preparation method includes the following steps: S1. Pretreatment The pretreatment step specifically includes: Drying the silicon powder, and the purity of the silicon powder is 99-99.9999%; and, The mixed gas is preheated to 300~500°C. The mixed gas includes hydrocarbon gas and carrier gas, and the carrier gas is argon or hydrogen.

[0024] Drying the silicon powder before the reaction removes moisture, preventing interference and ensuring reaction purity. The increased fluidity of the dried silicon powder also prevents localized agglomeration. By controlling the purity of the silicon powder, a foundation can be laid for the final preparation of high-purity silicon carbide.

[0025] By preheating the mixed gas to 300-500℃ before the reaction, reaction time can be saved, and the preheating temperature can be controlled to avoid the decomposition of hydrocarbon gases due to excessive preheating temperature, thereby avoiding affecting the subsequent formation of SiC.

[0026] Preferably, the silicon powder has a particle size of 0.1~50μm. By controlling the particle size of the silicon powder, the crystal particle size of the intermediate product β-SiC powder can be controlled, thereby laying the foundation for controlling the crystal particle size of the final α-SiC powder.

[0027] Preferably, the "drying of silicon powder" specifically includes: passing hot inert gas or hydrogen gas through the silicon powder to dry it, and controlling the drying process to be water-free, oxygen-free, and nitrogen-free. This avoids introducing impurities and moisture during the drying process.

[0028] Preferably, the hydrocarbon gas is a C1-C10 alkanes, alkenes, or alkynes. Thus, the hydrocarbon gas can be obtained from industrial gas sources such as natural gas and petroleum cracking gas, ensuring sufficient supply and controllable costs. Using the hydrocarbon gas as a carbon source, thermal decomposition occurs at a certain temperature, generating gaseous carbon-containing intermediates with high reactivity, such as various free radicals and small-molecule hydrocarbons, which then react with silicon powder to form silicon carbide.

[0029] More preferably, the hydrocarbon gas is at least one selected from methane, ethane, propane, ethylene, and acetylene. This not only makes it readily available industrially, reducing costs, and suitable for large-scale production, but also allows for simpler decomposition pathways, fewer byproducts, higher reactivity, and better gas-phase fluidity, thus improving the contact between the gas and solid phases.

[0030] When argon is used as the carrier gas, the purity of the argon gas is ≥99.99%.

[0031] S2. Reaction produces β-SiC powder. The dried silicon powder and the preheated mixed gas are fed into the rotary kiln 10 for reaction. The molar ratio of silicon to carbon is controlled at 1:1 to generate β-SiC powder. The reaction temperature is 1100~1400℃, the pressure inside the rotary kiln 10 is absolute pressure of 60~85kPa, and the rotation speed of the kiln body 3 of the rotary kiln 10 is 1~5 rpm.

[0032] By using the rotary kiln 10 as the reaction device and controlling the temperature, pressure and rotation speed of the rotary kiln 10, the fluidity of the gas phase and the solid phase can be optimized, the reaction contact efficiency can be improved, the full mixing and efficient reaction of silicon powder and hydrocarbon gas can be ensured, and the preparation efficiency and stability of silicon carbide can be improved. First, the hydrocarbon gas undergoes thermal decomposition at 1100-1400 °C. During the high-temperature thermal decomposition process, carbon-containing intermediates (such as various free radicals and small hydrocarbon compounds) with high reactivity in the gas phase are generated, and then react with silicon powder to form β-SiC. By controlling the molar ratio of Si to C to be 1:1, β-SiC powder can be synthesized at a lower temperature and in a shorter time.

[0033] After detection, the crystal particle size of the generated β-SiC powder is 1-100 μm, which lays a foundation for controlling the crystal particle size of the finally obtained α-SiC powder.

[0034] Preferably, the mass flow rate of the silicon powder fed into the rotary kiln 10 is 5-800 kg / h, and the volume flow rate of the mixed gas is 10-8000 Nm 3 / h. In this way, the ratio of the gas phase to the solid phase can be ensured to be in the efficient range, which can not only ensure the full contact between the gas phase and the solid phase and a high reaction conversion rate, but also avoid increasing the heating energy consumption due to excessive gas flow rate. The volume flow rate ratio of the hydrocarbon gas to the carrier gas in the mixed gas is 1:5-1:30, so as to ensure that the concentration of the hydrocarbon gas is lower than the explosion limit of 1:3, avoid the risk of combustion and explosion, and prevent the surface of the silicon powder from being heavily carbon-deposited due to too high concentration of the hydrocarbon gas, which affects the purity of the finally obtained α-SiC powder.

[0035] As shown in Figure 2 Specifically, the rotary kiln 10 includes a feed bin 1, a feeder 2, a kiln body 3, a discharge bin 4, an intake pipe 5, an exhaust pipe 6 and a kiln body angle adjustment accessory 7.

[0036] Among them, the feed bin 1, the feeder 2, the kiln body 3 and the discharge bin 4 are connected in sequence. The kiln body 3 includes a rotary furnace tube 31 and a heating furnace 32. The feeder 2 is connected to the feed bin 1 and the rotary furnace tube 31. The rotary furnace tube 31 has a feed inlet connected to the feeder 2 and a discharge outlet connected to the discharge bin 4. An intake port is opened on the side wall of the horizontal conveying section of the feeder 2, and the intake port is connected to the intake pipe 5 to introduce the hydrocarbon gas and the carrier gas.

[0037] The silicon powder falls from the feed bin 1 into the feeder 2. During the transportation by the feeder 2, the hydrocarbon gas and the carrier gas enter the feeder 2 from the intake pipe 5 through the intake port. The hydrocarbon gas, the carrier gas and the silicon powder are preliminarily mixed in the feeder 2 and then enter the rotary furnace tube 31.

[0038] The heating furnace 32 heats the rotary furnace tube 31. The discharge hopper 4 is a sealed hopper with a water-cooled jacket. The discharge hopper 4 is connected to the discharge port of the rotary furnace tube 31. A discharge valve is installed at the bottom of the discharge hopper 4 to control the discharge.

[0039] The exhaust pipe 6 is used for exhaust gas discharge inside the kiln body 3. The exhaust pipe 6 is equipped with a vacuum pump and a pressure sensor to control the vacuum environment inside the rotary kiln 10 and control the pressure inside the rotary kiln 10.

[0040] The kiln body angle adjustment accessory 7 adjusts the height difference between the feed inlet and discharge outlet of the rotary kiln tube 31, thereby causing the material to move towards the discharge outlet under the action of gravity.

[0041] The inner wall material of the rotary kiln 10 is made of a high-temperature resistant and corrosion-resistant material. Specifically, the inner wall material of the rotary kiln 10 can be high-performance ceramic materials such as pressureless sintered silicon carbide or hot-pressed sintered silicon carbide. Alternatively, the inner wall of the rotary kiln 10 can be made of a graphite matrix with a silicon carbide coating deposited on its surface. These materials possess excellent high-temperature stability (withstanding operating conditions above 1400℃) and chemical inertness. Thus, the rotary kiln 10 can resist the decomposition products of hydrocarbon gases and the erosion caused by the silicon powder reaction, while also preventing reactions with the materials that could contaminate the final silicon carbide powder, thereby ensuring the smooth progress of the reaction and preventing contamination of the final silicon carbide.

[0042] The rotary furnace tube 31 can be made of pressureless sintered silicon carbide material. The connection between the rotary furnace tube 31 and the feeder 2, and the connection between the rotary furnace tube 31 and the discharge hopper 4, are all sealed to ensure that the rotary kiln 10 has good sealing performance, so as to control the reaction atmosphere and prevent air from flowing back into the rotary kiln 10.

[0043] S3. Recrystallization to form α-SiC powder β-SiC powder is fed into a vacuum reactor, argon gas is introduced, and the temperature is raised to 1900~2100℃. The reaction is carried out for 3~10 hours. β-SiC powder grows and recrystallizes into α-SiC powder. The purity of the obtained α-SiC powder is 99~99.999%.

[0044] Testing revealed that the obtained α-SiC powder had a crystal particle size of 300~2000μm, uniform particle size, and good crystallinity.

[0045] Specifically, β-SiC powder is fed into a purified graphite crucible inside a vacuum reactor.

[0046] Thus, the silicon carbide preparation method of this application, using high-purity silicon powder and preheated hydrocarbon gas as raw materials and a rotary kiln 10 as the reaction device, can optimize the flowability of the gas and solid phases, improve the reaction contact efficiency, ensure that the silicon powder and hydrocarbon gas are fully mixed and react efficiently, and improve the preparation efficiency and stability of silicon carbide. By thermally decomposing the hydrocarbon gas at 1100~1400℃, a gaseous carbon-containing intermediate with high reactivity is generated during the high-temperature thermal decomposition process. This intermediate then reacts with the silicon powder to generate β-SiC. By controlling the molar ratio of Si to C to be 1:1, high-purity silicon carbide powder can be synthesized at a lower temperature and in a shorter time. The silicon carbide powder has uniform particle size and low energy consumption. It is not only suitable for large-scale production, but also significantly reduces production costs, with short reaction time and high production efficiency.

[0047] Furthermore, the preparation method further includes the following steps: Before preheating the mixed gas, multiple adsorption columns connected in series are used to remove water and oxygen from the mixed gas.

[0048] In this way, trace amounts of water and oxygen in the mixed gas can be removed, preventing silicon powder oxidation and thus ensuring the purity of the final SiC powder.

[0049] Furthermore, the preparation method further includes: Before the reaction, the rotary kiln 10 is heated to 80~200℃, and argon gas is circulated into the rotary kiln 10 for purging until the oxygen concentration in the rotary kiln 10 drops to below 0.1%.

[0050] In this way, water and oxygen can be removed from the rotary kiln 10 before the reaction, avoiding silicon powder oxidation and thus ensuring the purity of the final SiC powder.

[0051] Furthermore, the preparation method further includes the following steps: After the β-SiC powder is fed into the vacuum reactor, it is first heated to 1000~1200℃ and CO2 or O2 is introduced to remove the free carbon on the surface of the β-SiC powder. Then the introduction of CO2 or O2 is stopped, and argon gas is introduced and the temperature is raised to recrystallize.

[0052] During production, it was found that after the reaction produces β-SiC powder, some free carbon exists on the surface of the β-SiC powder. By introducing CO2 or O2, the free carbon on the surface of the β-SiC powder can be removed, thereby achieving the effect of impurity removal and purification, and thus improving the purity of the β-SiC powder, laying the foundation for obtaining high-purity α-SiC in the future.

[0053] Specifically, by monitoring the concentration of CO or CO2 in the exhaust gas emitted from the vacuum reactor in real time, it can be determined whether the free carbon on the surface of the β-SiC powder has been removed. Specifically, if the concentration of CO or CO2 in the exhaust gas drops to below 10 ppm and remains below 10 ppm for 1 to 2 hours, it is determined that the free carbon on the surface of the β-SiC powder has been removed.

[0054] Furthermore, when argon is used as the carrier gas, the preparation method further includes the following steps: The gas discharged from the rotary kiln 10 is sequentially passed through a cyclone dust collector and a bag filter for gas-solid separation. The separated solid is sent into a vacuum reactor for growth and recrystallization. The separated gas is collected in a buffer tank and then sent to a secondary vacuum pressure swing adsorption system to remove hydrogen and unreacted hydrocarbon gases, obtaining purified argon for recycling.

[0055] Since the gas discharged from the rotary kiln 10 carries some β-SiC dust, gas-solid separation can be achieved through cyclone dust removal and bag dust removal. The separated solid, namely β-SiC powder, is then sent to the discharge hopper 4 of the rotary kiln 10 and then into the vacuum reactor for growth and recrystallization into α-SiC powder, thereby improving the yield of SiC.

[0056] The gas discharged from the rotary kiln 10 includes argon, hydrogen, and a small amount of unreacted hydrocarbon gas. After gas-solid separation, this gas is collected in a buffer tank and then sent to a secondary vacuum pressure swing adsorption system (PSA system). The PSA system captures hydrogen and hydrocarbon gas, thereby purifying and recovering argon. The hydrogen and hydrocarbon gas captured by the PSA system can be used for post-combustion heating, which is clean, environmentally friendly, and improves energy efficiency.

[0057] The PSA system comprises two stages of adsorption. The first stage uses activated carbon or carbon molecular sieves to adsorb hydrocarbon gases under high pressure, with argon and hydrogen as exhaust gases. By selecting suitable adsorbents and optimizing process parameters (such as adjusting pressure and cycle time), effective adsorption and separation of most common hydrocarbon gases (such as C1-C4 alkanes and alkenes) can be achieved. The second stage uses a specially designed molecular sieve (such as 5A molecular sieve) to selectively adsorb argon, with hydrogen permeating as a byproduct. Finally, argon is desorbed under reduced pressure, achieving an argon purity of over 99.9%.

[0058] The purified argon gas can be further pressurized by a blower and recycled as a carrier gas, achieving efficient recovery and recycling of argon gas, reducing raw material waste, and improving economic efficiency. Of course, there is an argon gas loss of about 5-10% during the preparation of silicon carbide, so additional argon gas needs to be added to ensure sufficient carrier gas flow.

[0059] In summary, this application has the following beneficial effects: The silicon carbide preparation method of this application uses high-purity silicon powder and preheated hydrocarbon gas as raw materials, and a rotary kiln 10 as the reaction device. This method can optimize the flowability of the gas phase and solid phase, improve the reaction contact efficiency, ensure that the silicon powder and hydrocarbon gas are fully mixed and react efficiently, and improve the preparation efficiency and stability of silicon carbide. By thermally decomposing the hydrocarbon gas at 1100~1400℃, a gaseous carbon-containing intermediate with high reactivity is generated during the high-temperature thermal decomposition process. This intermediate then reacts with the silicon powder to generate β-SiC. By controlling the molar ratio of Si to C to be 1:1, high-purity silicon carbide powder can be synthesized at a lower temperature and in a shorter time. The silicon carbide powder has uniform particle size and low energy consumption. This method is not only suitable for large-scale production, but also significantly reduces production costs, and has a short reaction time and high production efficiency.

[0060] The above description, based on the embodiments shown in the drawings, details the structure, features, and effects of this application. The above description is only a preferred embodiment of this application, but this application does not limit the scope of implementation to what is shown in the drawings. Any changes made in accordance with the concept of this application, or modifications to equivalent embodiments, that do not exceed the spirit covered by the specification and drawings, should be within the protection scope of this application.

Claims

1. A method for producing silicon carbide, characterized by, The preparation method comprises the following steps: The silicon powder is dried, and the purity of the silicon powder is 99-99.9999%; The mixed gas is preheated to 300-500 DEG C, and the mixed gas comprises a hydrocarbon gas and a carrier gas, and the carrier gas is argon or hydrogen; The dried silicon powder and the preheated mixed gas are sent into a rotary kiln to react, the molar ratio of Si to C is controlled to be 1:1, the reaction temperature is 1100-1400 DEG C, the pressure in the rotary kiln is 60-85 kPa, and the rotary speed of the rotary kiln is 1-5 rounds / min; The β-SiC powder is sent into a vacuum reaction furnace, argon is introduced, and the temperature is raised to 1900-2100 DEG C, and the β-SiC powder is grown and recrystallized into α-SiC powder, and the purity of the obtained α-SiC powder is 99-99.999%.

2. The method of claim 1, wherein the silicon carbide is prepared by the steps of: The mass flow of the silicon powder into the rotary kiln is 5-800 kg / h, the volume flow of the mixed gas is 10-8000 Nm 3 / h, and the volume flow ratio of the hydrocarbon gas to the carrier gas in the mixed gas is 1:5-1:

30.

3. The method of claim 1, wherein the silicon carbide is prepared by the steps of: The hydrocarbon gas is C1-C10 alkane, alkene or alkyne.

4. The method of claim 3, wherein the silicon carbide is prepared by the steps of: The hydrocarbon gas is at least one of methane, ethane, propane, ethylene and acetylene.

5. The method of claim 1, wherein the silicon carbide is prepared by the steps of: The particle size of the silicon powder is 0.1-50 microns, the crystal particle size of the generated β-SiC powder is 1-100 microns, and the crystal particle size of the obtained α-SiC powder is 300-2000 microns.

6. The method of claim 1, wherein the silicon carbide is prepared by the steps of: The drying of the silicon powder specifically comprises: The silicon powder is dried by introducing hot inert gas or hydrogen, and the drying process is controlled to be free of water, oxygen and nitrogen.

7. The method of claim 1, wherein the silicon carbide is prepared by the steps of: The preparation method further comprises the following steps: ​ Before the mixed gas is preheated, a plurality of adsorption columns are connected in series to remove water and oxygen in the mixed gas.

8. The method of claim 1, wherein the silicon carbide is prepared by the steps of: The preparation method further comprises the following steps: Before the reaction, the rotary kiln is heated to 80-200 DEG C, and argon is introduced into the rotary kiln to circulate and purge until the oxygen concentration in the rotary kiln is reduced to below 0.1%.

9. The method of claim 1, wherein the silicon carbide is prepared by the steps of: The preparation method further comprises the following steps: ​ After the β-SiC powder is sent into the vacuum reaction furnace, the temperature is first raised to 1000-1200 DEG C, and CO2 or O2 is introduced to remove free carbon on the surface of the β-SiC powder, then the introduction of CO2 or O2 is stopped, argon is introduced again, and recrystallization is carried out by heating.

10. The method of claim 1, wherein the silicon carbide is prepared by the steps of: The carrier gas is argon; and the preparation method further comprises the following steps: ​ The gas discharged from the rotary kiln is subjected to gas-solid separation by cyclone dust removal and bag dust removal in sequence, the separated solid is sent into the vacuum reaction furnace for growth and recrystallization, the separated gas is collected into a buffer tank, and then sent into a two-stage vacuum pressure swing adsorption system to remove hydrogen and unreacted hydrocarbon gas, so as to obtain purified argon.

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