A method for preparing 6N grade high-purity silicon carbide powder

Abstract

The present invention belongs to the field of advanced ceramic materials technology and specifically discloses a method for preparing 6N-grade high-purity silicon carbide powder. The method comprises the following steps: step S1, batching; step S2, acoustic resonance mixing; step S3, high-temperature pyrolysis and calcination; step S4, acid washing, purification and washing; and step S5, vacuum shaking and drying. The present invention adopts the above-mentioned method for preparing 6N-grade high-purity silicon carbide powder, which solves the problems of poor uniformity, low efficiency, and high energy consumption of traditional processes. This method can produce silicon carbide powder with a purity of ≥99.9999%. The prepared silicon carbide powder has high purity and good dispersibility, and is suitable for high-end fields such as semiconductors and new energy.

Description

Technical Field

[0001] The present invention belongs to the technical field of advanced ceramic materials, and in particular relates to a method for preparing 6N-grade high-purity silicon carbide powder. Background Art

[0002] Silicon carbide (SiC) powder is a core raw material for semiconductor devices, high-temperature structural materials, and optical coatings. Its purity and uniformity directly determine the performance of downstream products. Grade 6N (99.9999%) high-purity SiC powder is a key base material for the preparation of high-thermal-conductivity substrates, semi-insulating single crystals, and high-end ceramics. Synthesis methods for high-purity SiC powder primarily include vapor-phase methods (represented by CVD), liquid-phase methods (represented by sol-gel), and solid-phase methods (represented by self-propagating high-temperature synthesis). The vapor-phase method generates SiC powder through a high-temperature reaction with a high-purity source gas (such as SiH₄ and CH₄), resulting in ultrafine powders with purities of less than 10 ppb. However, the synthesis rate is low, fluctuations in the source gas purity directly affect the impurity content of the powder, and the equipment and raw material costs are high. The liquid-phase method has a long process cycle, is highly dependent on raw materials, and the reaction system is sensitive to temperature and pH. This leads to poor batch stability during scale-up, making industrial continuous production difficult. The solid-phase method synthesizes silicon carbide through a high-temperature solid-phase reaction of silicon powder and carbon powder. It has the advantages of low cost and high output and is currently the most widely used method in industrial applications.

[0003] Chinese invention patent CN 117383941 A wet-mixes high-purity carbon powder and high-purity silicon powder, then dries, presses them into billets, stacks them, and calcines them in three stages to produce 5N-grade silicon carbide powder with a purity exceeding 99.999%. Chinese invention patent CN 111704139 A uses crystalline silicon as a silicon source to prepare silicon micropowder and glucose as a carbon source to prepare a glucose solution. The silicon micropowder and glucose solution are then mixed uniformly, dried, carbonized, vacuum sintered, calcined, and pickled to remove impurities, resulting in 5N-grade silicon carbide powder with a purity of 99.999%. Chinese invention patent CN 111717918 A uniformly mixes high-purity carbon powder and silicon powder, adds polycarbosilane (PCS) powder, and calcines them in an atmosphere to produce 4N-grade silicon carbide powder with a purity of 99.99%. However, these methods suffer from insufficient raw material mixing uniformity and limited impurity control capabilities. For example, mechanical ball milling or stirring makes it difficult to achieve uniform nanoscale dispersion of silicon and carbon powders. Localized agglomeration leads to incomplete reactions and the introduction of impurities. Silicon and carbon powders also easily absorb nitrogen from the air, forming silicon nitride impurities during high-temperature reactions. PCS, as a molecular-level precursor, has been used in the preparation of high-purity silicon carbide powders. However, its high viscosity makes it difficult to achieve uniform mixing and effective wetting with solid powders using traditional mixing methods, resulting in inadequate interfacial reactions.

[0004] Therefore, a method for preparing 6N grade high-purity silicon carbide powder needs to be developed in the art to effectively solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing 6N-grade high-purity silicon carbide powder, which solves the problems of poor uniformity, low efficiency and high energy consumption of traditional processes; this method can obtain silicon carbide powder with a purity of ≥99.9999%, and the prepared silicon carbide powder has high purity and good dispersibility, and is suitable for high-end fields such as semiconductors and new energy.

[0006] To achieve the above object, the present invention provides a method for preparing 6N grade high-purity silicon carbide powder, comprising the following steps:

[0007] Step S1, ingredients; weigh high-purity silicon powder and high-purity carbon powder according to a molar ratio of 1:1.02 to 1:1.05; weigh high-purity liquid polycarbosilane according to 45 to 60% of the total mass of the high-purity silicon powder and high-purity carbon powder;

[0008] Step S2, acoustic resonance mixing: adding the weighed high-purity silicon powder, high-purity carbon powder and high-purity liquid polycarbosilane into a quartz container, introducing high-purity argon gas, and starting the acoustic resonance device at room temperature to perform acoustic resonance mixing to obtain a uniform slurry;

[0009] Step S3, high-temperature pyrolysis and calcination; pouring the uniform slurry into a graphite crucible, introducing high-purity argon gas into the furnace reaction chamber, performing a first heating, and keeping the temperature for 2 hours to complete the pyrolysis of the high-purity liquid polycarbosilane; continuing the second heating to obtain silicon carbide powder;

[0010] Step S4, acid washing, purification and washing: preparing a mixed solution of hydrofluoric acid and nitric acid in a volume ratio of 1:1, ultrasonically washing the silicon carbide powder with the mixed solution to remove alkali metals adsorbed on the surface; ultrasonically washing the acid-washed silicon carbide powder with deionized water to remove residual acid, and obtaining a filter material by suction filtration;

[0011] Step S5, vacuum shaking drying: add the filter material to the vacuum shaking dryer, evacuate to -0.095~-0.1MPa, and preheat to 50~60℃ at an oscillation frequency of 10~20Hz for 1h, then heat to 80~100℃ and keep warm for 2~3h. After natural cooling, 6N grade high-purity silicon carbide powder is obtained.

[0012] Preferably, in step S1, the average particle size of the high-purity silicon powder and the high-purity carbon powder are both ≤1 μm, and the purity is both ≥99.9999%; the metal impurities of the high-purity liquid polycarbosilane are ≤0.8 ppm, the hydrogen content is 4.5-5.5%, and the viscosity at 25°C is 800-1500 cP.

[0013] Preferably, in step S2, the acoustic resonance mixing is specifically as follows: firstly, the powder agglomerates are dispersed by low-frequency vibration of 8-10 kHz for 5-10 minutes, and then switched to high-frequency vibration of 15-20 kHz for 10-15 minutes to quickly coat the powder particles to obtain a uniform slurry.

[0014] Preferably, in step S2 and step S3, the purity of the high-purity argon gas is ≥99.9999%.

[0015] Preferably, in step S3, the first heating is performed at a heating rate of 5-10°C / min to 1000-1200°C; the second heating is performed at a heating rate of 3-8°C / min to 1400-1700°C and calcined for 4-6 hours.

[0016] Preferably, in step S4, the mixed solution is ultrasonically washed for 2 to 5 times on the silicon carbide powder; and the acid-washed silicon carbide powder is ultrasonically washed for 1 to 3 times on the deionized water.

[0017] Preferably, in step S5, the purity of the obtained 6N grade high-purity silicon carbide powder is ≥99.9999%.

[0018] The present invention adopts the above-mentioned method for preparing 6N grade high-purity silicon carbide powder, and the beneficial effects are as follows:

[0019] (1) The present invention adopts acoustic resonance mixing technology to mix high-purity liquid polycarbosilane (LPCS), silicon powder and carbon powder. Through non-contact energy transfer and high-frequency vibration dispersion, a molecular-level mixed precursor is quickly formed, avoiding mechanical mixing and effectively solving the problems of uneven raw material mixing and impurity contamination in traditional methods.

[0020] (2) In the present invention, the micro-jet impact generated by LPCS through acoustic resonance can quickly penetrate into the pores of carbon powder and silicon powder, shortening the mixing time from hours in traditional mechanical mixing to minutes.

[0021] (3) The LPCS in the present invention has simple molecular segments and many active sites. The activation energy required for high-temperature cracking is lower than that of PDS. It can be completely cracked at relatively low temperatures (900-1100°C) to generate amorphous carbon and active silicon species, which react with carbon powder and silicon powder to form silicon carbide.

[0022] (4) The vacuum shaking drying process in the preparation method of the present invention has the advantages of high vacuum degree and low drying temperature, which effectively avoids the oxidation of high-purity silicon carbide powder during the drying process; at the same time, the synchronous shaking process effectively avoids the agglomeration of powder, and highly dispersed powder can be obtained without secondary mechanical treatment (grinding, ball milling, etc., which are easy to introduce impurities).

[0023] (5) The process of the present invention is suitable for the controllable synthesis of β-SiC and α-SiC, and can meet the needs of multiple scenarios such as semiconductor substrates and high-temperature ceramics.

[0024] (6) Compared with the traditional process, the preparation process of the present invention improves production efficiency by more than 50% and reduces energy consumption by more than 40%.

[0025] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a process flow chart for preparing 6N grade high-purity silicon carbide powder according to the present invention;

[0027] Figure 2 This is a microscopic morphology of the 6N grade high-purity β-SiC powder prepared in Example 1 of the method for preparing 6N grade high-purity silicon carbide powder of the present invention;

[0028] Figure 3 This is a microscopic morphology of the 6N grade high-purity α-SiC powder prepared in Example 2 of the method for preparing 6N grade high-purity silicon carbide powder of the present invention;

[0029] Figure 4 This is a microscopic morphology of the 6N grade high-purity β-SiC powder prepared in Example 3 of the method for preparing 6N grade high-purity silicon carbide powder of the present invention;

[0030] Figure 5 This is a microscopic morphology of the silicon carbide powder prepared in Comparative Example 2 of the preparation method of 6N grade high-purity silicon carbide powder of the present invention. DETAILED DESCRIPTION

[0031] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0032] Unless otherwise defined, technical or scientific terms used in the present invention shall have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0033] Example 1

[0034] like Figure 1 As shown, a method for preparing 6N grade high-purity β-SiC powder includes the following steps:

[0035] Step S1: Mixing Ingredients. Weigh high-purity silicon powder and high-purity carbon powder at a molar ratio of 1:1.02. Weigh high-purity liquid polycarbosilane (LPCS) at 55% of the total mass of the high-purity silicon powder and high-purity carbon powder. Testing indicates that the viscosity of LPCS at 25°C is 1150 cP.

[0036] Step S2, acoustic resonance mixing. Weighed high-purity silicon powder, high-purity carbon powder, and high-purity liquid polycarbosilane were added to a quartz container, and high-purity argon gas was introduced. The acoustic resonance device was activated at room temperature for acoustic resonance mixing. The powder agglomerates were dispersed by low-frequency vibration at 10 kHz for 12 minutes, and then the high-frequency vibration at 18 kHz was switched to rapidly coat the powder particles for 12 minutes to obtain a uniform slurry.

[0037] Step S3: High-temperature pyrolysis and calcination. Pour the homogenized slurry into a graphite crucible. A stream of high-purity argon is introduced into the furnace reaction chamber. The temperature is raised to 1000°C at a rate of 8°C / min and held for 2 hours to complete the pyrolysis of the LPCS. The temperature is then raised to 1400°C at a rate of 5°C / min and calcined for 5 hours to produce silicon carbide powder.

[0038] Step S4: Acid washing, purification, and cleaning. Prepare a mixture of hydrofluoric acid and nitric acid at a volume ratio of 1:1. Ultrasonicate the silicon carbide powder three times with the mixture to remove alkali metals adsorbed on the surface. Ultrasonicate the acid-washed silicon carbide powder twice with deionized water to remove residual acid, and filter to obtain a filter material.

[0039] Step S5, vacuum shaking drying: Add the filter material to a vacuum shaking dryer, evacuate to -0.095~-0.1MPa, and oscillate at a frequency of 15Hz. First, heat to 55℃ for 1 hour, then heat to 90℃ for 2 hours, and cool naturally to obtain 6N grade high-purity β-SiC powder.

[0040] The performance of the 6N grade high-purity β-SiC powder prepared in this example was tested:

[0041] The main crystal phase of the prepared 6N grade high purity β-SiC powder is β-SiC, with a purity of ≥99.9999%. The micromorphology of the 6N grade high purity β-SiC powder is as follows Figure 2 As shown, the particle size distribution is concentrated (D 10 =0.64μm, D 50 =0.87μm, D 90 =1.13μm).

[0042] Example 2

[0043] A method for preparing 6N grade high-purity α-SiC powder comprises the following steps:

[0044] Step S1: Mixing Ingredients. Weigh high-purity silicon powder and high-purity carbon powder at a molar ratio of 1:1.02. Weigh high-purity liquid polycarbosilane (LPCS) at 55% of the total mass of the high-purity silicon powder and high-purity carbon powder. Testing indicates that the viscosity of LPCS at 25°C is 1150 cP.

[0045] Step S2, acoustic resonance mixing. Weighed high-purity silicon powder, high-purity carbon powder, and high-purity liquid polycarbosilane were added to a quartz container, and high-purity argon gas was introduced. The acoustic resonance device was activated at room temperature for acoustic resonance mixing. The powder agglomerates were dispersed by low-frequency vibration at 10 kHz for 12 minutes, and then the high-frequency vibration at 18 kHz was switched to rapidly coat the powder particles for 12 minutes to obtain a uniform slurry.

[0046] Step S3: High-temperature pyrolysis and calcination. Pour the homogenized slurry into a graphite crucible. Pass high-purity argon gas through the furnace reaction chamber and heat the mixture to 1200°C at a rate of 8°C / min. Hold the temperature for 2 hours to complete LPCS pyrolysis. Continue heating the mixture to 1650°C at a rate of 5°C / min and calcine for 5 hours to promote the transformation of the β phase to the α phase, yielding silicon carbide powder.

[0047] Step S4: Acid washing, purification, and cleaning. Prepare a mixture of hydrofluoric acid and nitric acid at a volume ratio of 1:1. Ultrasonicate the silicon carbide powder three times with the mixture to remove alkali metals adsorbed on the surface. Ultrasonicate the acid-washed silicon carbide powder twice with deionized water to remove residual acid, and filter to obtain a filter material.

[0048] Step S5, vacuum shaking drying: Add the filter material to a vacuum shaking dryer, evacuate to -0.095~-0.1MPa, and oscillate at a frequency of 15Hz. First, heat to 55°C for 1 hour, then heat to 90°C for 2 hours, and cool naturally to obtain 6N grade high-purity α-SiC powder.

[0049] The performance of the 6N grade high-purity α-SiC powder prepared in this example was tested:

[0050] The main crystal phase of the prepared 6N grade high purity α-SiC powder is α-SiC, with a purity of ≥99.9999%. The micromorphology of the 6N grade high purity β-SiC powder is as follows Figure 3 As shown, the particle size distribution is concentrated (D 10 =0.69μm, D 50 =0.95μm, D 90 =1.28μm).

[0051] Example 3

[0052] A method for preparing 6N grade high-purity β-SiC powder comprises the following steps:

[0053] Step S1: Mixing Ingredients. Weigh high-purity silicon powder and high-purity carbon powder at a molar ratio of 1:1.05. Weigh high-purity liquid polycarbosilane (LPCS) at 55% of the total mass of the high-purity silicon powder and high-purity carbon powder. Testing indicates that the viscosity of LPCS at 25°C is 1150 cP.

[0054] Step S2, acoustic resonance mixing. Weighed high-purity silicon powder, high-purity carbon powder, and high-purity liquid polycarbosilane were added to a quartz container, and high-purity argon gas was introduced. The acoustic resonance device was activated at room temperature for acoustic resonance mixing. The powder agglomerates were dispersed by low-frequency vibration at 10 kHz for 12 minutes, and then the high-frequency vibration at 18 kHz was switched to rapidly coat the powder particles for 12 minutes to obtain a uniform slurry.

[0055] Step S3: High-temperature pyrolysis and calcination. Pour the homogenized slurry into a graphite crucible. A stream of high-purity argon is introduced into the furnace reaction chamber. The temperature is raised to 1000°C at a rate of 8°C / min and held for 2 hours to complete the pyrolysis of the LPCS. The temperature is then raised to 1400°C at a rate of 5°C / min and calcined for 5 hours to produce silicon carbide powder.

[0056] Step S4: Acid washing, purification, and cleaning. Prepare a mixture of hydrofluoric acid and nitric acid at a volume ratio of 1:1. Ultrasonicate the silicon carbide powder three times with the mixture to remove alkali metals adsorbed on the surface. Ultrasonicate the acid-washed silicon carbide powder twice with deionized water to remove residual acid, and filter to obtain a filter material.

[0057] Step S5, vacuum shaking drying: Add the filter material to a vacuum shaking dryer, evacuate to -0.095~-0.1MPa, and oscillate at a frequency of 15Hz. First, heat to 55℃ for 1 hour, then heat to 90℃ for 2 hours, and cool naturally to obtain 6N grade high-purity β-SiC powder.

[0058] The performance of the 6N grade high-purity β-SiC powder prepared in this example was tested:

[0059] The main crystal phase of the prepared 6N grade high purity β-SiC powder is β-SiC, with a purity of ≥99.9999%. The micromorphology of the 6N grade high purity β-SiC powder is as follows Figure 4 As shown, the particle size distribution is concentrated (D 10 =0.61μm, D 50 =0.821μm, D 90 =1.23μm).

[0060] Comparative Example 1

[0061] A method for preparing silicon carbide powder comprises the following steps:

[0062] Step S1: Mixing Ingredients. Weigh high-purity silicon powder and high-purity carbon powder at a molar ratio of 1:1.02. Weigh high-purity liquid polycarbosilane (LPCS) at 55% of the total mass of the high-purity silicon powder and high-purity carbon powder. Testing indicates that the viscosity of LPCS at 25°C is 1150 cP.

[0063] Step S2: Mechanical stirring: The weighed high-purity silicon powder, high-purity carbon powder, and high-purity liquid polycarbosilane were mechanically stirred at a speed of 100 rpm for 6 hours to obtain a slurry.

[0064] Step S3: High-temperature pyrolysis and calcination. Pour the slurry into a graphite crucible, introduce high-purity argon gas into the furnace reaction chamber, and heat the furnace to 1000°C at a rate of 8°C / min. Hold the temperature for 2 hours. Continue heating the temperature to 1400°C and calcine for 5 hours to obtain silicon carbide powder.

[0065] Step S4: Acid washing, purification, and cleaning. Prepare a mixture of hydrofluoric acid and nitric acid at a volume ratio of 1:1. Ultrasonicate the silicon carbide powder three times with the mixture to remove alkali metals adsorbed on the surface. Ultrasonicate the acid-washed silicon carbide powder twice with deionized water to remove residual acid, and filter to obtain a filter material.

[0066] Step S5, vacuum shaking drying: Add the filter material to a vacuum shaking dryer, evacuate to -0.095~-0.1MPa, and oscillate at a frequency of 15Hz. First, heat to 55℃ for 1 hour, then heat to 90℃ for 2 hours, and cool naturally to obtain silicon carbide powder.

[0067] After testing, the purity of the silicon carbide powder prepared in Comparative Example 1 was only 99.85%, which proves that the acoustic resonance process has significant advantages in the uniformity and purity of silicon carbide powder.

[0068] Comparative Example 2

[0069] A method for preparing silicon carbide powder comprises the following steps:

[0070] Step S1: Mixing Ingredients. Weigh high-purity silicon powder and high-purity carbon powder at a molar ratio of 1:1.02. Weigh high-purity liquid polycarbosilane (LPCS) at 55% of the total mass of the high-purity silicon powder and high-purity carbon powder. Testing indicates that the viscosity of LPCS at 25°C is 1150 cP.

[0071] Step S2, acoustic resonance mixing. Weighed high-purity silicon powder, high-purity carbon powder, and high-purity liquid polycarbosilane were added to a quartz container, and high-purity argon gas was introduced. The acoustic resonance device was activated at room temperature for acoustic resonance mixing. The powder agglomerates were dispersed by low-frequency vibration at 10 kHz for 12 minutes, and then the high-frequency vibration at 18 kHz was switched to rapidly coat the powder particles for 12 minutes to obtain a uniform slurry.

[0072] Step S3: High-temperature pyrolysis and calcination. Pour the homogenized slurry into a graphite crucible. A furnace reaction chamber is filled with high-purity argon gas. The temperature is raised to 1000°C at a rate of 8°C / min and held for 2 hours to complete the pyrolysis of the LPCS. The temperature is then raised to 1400°C and calcined for 5 hours to obtain silicon carbide powder.

[0073] Step S4: Acid washing, purification, and cleaning. Prepare a mixture of hydrofluoric acid and nitric acid at a volume ratio of 1:1. Ultrasonicate the silicon carbide powder three times with the mixture to remove alkali metals adsorbed on the surface. Ultrasonicate the acid-washed silicon carbide powder twice with deionized water to remove residual acid, and filter to obtain a filter material.

[0074] Step S5: Electric heating drying: Add the filter material into an electric heating dryer at a drying temperature of 120° C. for 6 hours, and obtain silicon carbide powder after natural cooling.

[0075] After testing, the purity of the silicon carbide powder prepared in Comparative Example 2 is only 99.94%. The microscopic morphology of the silicon carbide powder is as follows Figure 5 As shown, the particle size distribution is not concentrated (D 10 =0.59μm, D 50 =1.86μm, D 90 =3.54μm), which proves that the vacuum shaking drying process has significant advantages in avoiding silicon carbide oxidation and improving powder dispersibility.

[0076] Therefore, the present invention adopts the above-mentioned method for preparing 6N grade high-purity silicon carbide powder, which solves the problems of poor uniformity, low efficiency and high energy consumption of traditional processes; this method can obtain silicon carbide powder with a purity of ≥99.9999%, and the prepared silicon carbide powder has high purity and good dispersibility, and is suitable for high-end fields such as semiconductors and new energy.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing 6N grade high-purity silicon carbide powder, characterized in that: The following steps are involved: Step S1, ingredients; weigh high-purity silicon powder and high-purity carbon powder according to a molar ratio of 1:1.02 to 1:1.05; weigh high-purity liquid polycarbosilane according to 45 to 60% of the total mass of the high-purity silicon powder and high-purity carbon powder; Step S2, acoustic resonance mixing: adding the weighed high-purity silicon powder, high-purity carbon powder and high-purity liquid polycarbosilane into a quartz container, introducing high-purity argon gas, and starting the acoustic resonance device at room temperature to perform acoustic resonance mixing to obtain a uniform slurry; Step S3, high-temperature pyrolysis and calcination; pour the uniform slurry into a graphite crucible, introduce high-purity argon gas into the furnace reaction chamber, perform the first heating, and keep the temperature for 2 hours; Continue heating for the second time to obtain silicon carbide powder; Step S4, acid washing, purification and washing: preparing a mixed solution of hydrofluoric acid and nitric acid in a volume ratio of 1:1, and ultrasonically washing the silicon carbide powder with the mixed solution; The acid-washed silicon carbide powder is ultrasonically washed with deionized water, and filter material is obtained by suction filtration; Step S5, vacuum shaking drying: add the filter material to the vacuum shaking dryer, evacuate to -0.095~-0.1MPa, and preheat to 50~60℃ at an oscillation frequency of 10~20Hz for 1h, then heat to 80~100℃ and keep warm for 2~3h. After natural cooling, 6N grade high-purity silicon carbide powder is obtained.

2. The method for preparing 6N grade high-purity silicon carbide powder according to claim 1, characterized in that: In step S1, the average particle size of the high-purity silicon powder and the high-purity carbon powder are both ≤1 μm, and the purity is both ≥99.9999%; The metal impurities of high-purity liquid polycarbosilane are ≤0.8ppm, the hydrogen content is 4.5~5.5%, and the viscosity at 25℃ is 800~1500cP.

3. The method for preparing 6N grade high-purity silicon carbide powder according to claim 1, characterized in that: In step S2, the acoustic resonance mixing is specifically as follows: first, the powder agglomerates are dispersed by low-frequency vibration of 8-10 kHz for 5-10 minutes, and then switched to high-frequency vibration of 15-20 kHz for 10-15 minutes to quickly coat the powder particles to obtain a uniform slurry.

4. The method for preparing 6N grade high-purity silicon carbide powder according to claim 1, characterized in that: In step S2 and step S3, the purity of the high-purity argon gas is ≥99.9999%.

5. The method for preparing 6N grade high-purity silicon carbide powder according to claim 1, characterized in that: In step S3, the first heating is performed at a heating rate of 5-10°C / min to 1000-1200°C; the second heating is performed at a heating rate of 3-8°C / min to 1400-1700°C and calcined for 4-6 hours.

6. The method for preparing 6N grade high-purity silicon carbide powder according to claim 1, characterized in that: In step S4, the mixed solution is ultrasonically washed with the silicon carbide powder for 2 to 5 times; and the acid-washed silicon carbide powder is ultrasonically washed with deionized water for 1 to 3 times.

7. The method for preparing 6N grade high-purity silicon carbide powder according to claim 1, characterized in that: In step S5, the purity of the obtained 6N grade high-purity silicon carbide powder is ≥99.9999%.

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