A method for preparing high-purity silicon carbide powder

Abstract

The application provides a preparation method of high-purity silicon carbide powder. Compared with the prior art, the high-purity silicon carbide powder can be obtained by high-temperature solid-phase reaction of carbon-silicon mixed raw materials in a perforated graphite cylinder, meanwhile, the carbon-silicon raw materials have directionality in the synthesis process by adjusting the holes of the perforated graphite cylinder, so that the high-purity silicon carbide powder with controllable particle size and uniform distribution is obtained; and the silicon carbide powder with the required particle size can be obtained without crushing and screening steps, impurity elements are avoided to be introduced in the crushing process, the purity of the silicon carbide powder is improved, the complexity of the process is reduced, the reaction process is stable, the preparation effect is improved, and the production cost is reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor materials, and particularly relates to a preparation method of high-purity silicon carbide powder. BACKGROUND

[0002] As the third generation semiconductor material, silicon carbide (SiC) has excellent properties such as wide band gap, high breakdown electric field, high thermal conductivity, high electron mobility, high temperature resistance, high frequency, and radiation resistance, and has several times more outstanding advantages than silicon-based semiconductor materials, and is widely used in the fields of power semiconductor devices and microwave radio frequency devices. At present, silicon carbide single crystals are synthesized by using the PVT (physical vapor transport) method, and the key lies in the growth environment and the purity of the powder, especially the purity of the SiC raw material directly affects the crystalline quality and electrical properties of the grown single crystal.

[0003] At present, the high-temperature solid-phase method is mainly used to prepare silicon carbide powder, and solid carbon powder and silicon powder are used as raw materials, which are in contact with each other and continuously react under high-temperature conditions to obtain silicon carbide powder. However, the high-temperature solid-phase method for preparing silicon carbide powder still has the following problems: first, the synthesized silicon carbide raw material needs to be crushed, washed and sieved to obtain silicon carbide powder with different particle sizes, which is a complicated process and is easy to introduce metal impurities in the crushing process, thereby reducing the purity of the silicon carbide powder; second, due to the temperature difference of different positions of the crucible used for synthesizing silicon carbide powder, the powder grains are large at high-temperature positions and small at low-temperature positions, so that the particle size of the synthesized silicon carbide powder is uneven. The prior art also points out that the impurities in the raw material can be removed by using high-temperature conditions for secondary synthesis to improve the purity of the raw material, but this method is complex and has high cost.

[0004] Therefore, a new method is needed to solve the above problems in the prior art and improve the preparation efficiency and quality of silicon carbide powder. SUMMARY

[0005] Therefore, the technical problem to be solved by the application is to provide a preparation method of high-purity silicon carbide powder with controllable and uniform particle size.

[0006] The application provides a preparation method of high-purity silicon carbide powder, which comprises the following steps:

[0007] S1) mixing carbon powder and silicon powder to obtain carbon-silicon mixed raw material;

[0008] S2) placing a plurality of perforated graphite cylinders and the carbon-silicon mixed raw material in the crucible in the crucible diameter direction alternately, performing high-vacuum heat treatment and inert gas cleaning, then introducing inert gas, and performing reaction under high-temperature and high-pressure conditions to obtain high-purity silicon carbide powder; the side wall of the perforated graphite cylinder is provided with a plurality of through holes.

[0009] Preferably, the molar ratio of the carbon powder to the silicon powder is 1:1 to 1:1.5.

[0010] Preferably, the pore size of the holes is 2 to 5 mm; and the distance between adjacent holes is 1 to 3 mm.

[0011] Preferably, the distribution density of the holes is 30% to 60%.

[0012] Preferably, the thickness ratio of the perforated graphite cylinder to the carbon-silicon mixed raw material is (1 to 10):1.

[0013] Preferably, in the step S2), the perforated graphite cylinder is in contact with the side wall of the crucible.

[0014] Preferably, in the step S2), the vacuum degree of the high-vacuum heat treatment is 4x10 -6 to 6x10 -4 mbar; the temperature of the high-vacuum heat treatment is 1100°C to 1300°C; the heating rate of the high-vacuum heat treatment is 10 to 50°C / min; and the time of the high-vacuum heat treatment is 3 to 6 h.

[0015] Preferably, in the step S2), the inert gas cleaning is specifically as follows: inert gas is introduced to a pressure of 200 to 300 mbar, and maintained for 0.5 to 1 h; then vacuum is drawn to a vacuum degree of not higher than 6x10 -4 mbar, and maintained for at least 3 h; and the above-mentioned steps of introducing inert gas and vacuum drawing are repeated at least twice.

[0016] Preferably, the temperature of the reaction is 1800°C to 2300°C; the pressure of the reaction is 300 to 800 mbar; and the time of the reaction is 10 to 30 h.

[0017] Preferably, after the step S2), the reaction product is cooled to room temperature to obtain high-purity silicon carbide powder; and the particle size of the high-purity silicon carbide powder is 40 to 60 mesh.

[0018] This invention provides a method for preparing high-purity silicon carbide powder, comprising the following steps: S1) mixing carbon powder and silicon powder to obtain a carbon-silicon mixed raw material; S2) alternately placing multiple perforated graphite cylinders and the carbon-silicon mixed raw material in a crucible along the diameter direction, performing high-vacuum heat treatment and inert gas cleaning, then introducing inert gas and reacting under high temperature and high pressure conditions to obtain high-purity silicon carbide powder; the sidewalls of the perforated graphite cylinders are provided with multiple through holes. Compared with the prior art, this invention can obtain high-purity silicon carbide powder by subjecting the carbon-silicon mixed raw material to a high-temperature solid-state reaction in a perforated graphite cylinder. Simultaneously, the directionality of the carbon-silicon raw material during synthesis can be controlled by adjusting the holes in the perforated graphite cylinders, thereby obtaining high-purity silicon carbide powder with controllable particle size and uniform distribution. Furthermore, this method eliminates the need for crushing and sieving steps to obtain silicon carbide powder of the desired particle size, avoids the introduction of impurity elements during crushing, improves the purity of the silicon carbide powder, reduces process complexity, stabilizes the reaction process, improves preparation efficiency, and reduces production costs. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the longitudinal section of the crucible loading structure provided by the present invention;

[0020] Figure 2 This is a top view of the crucible loading structure provided by the present invention;

[0021] Figure 3 This is a graph showing the EDS test data of silicon carbide powder obtained in Example 1 of the present invention;

[0022] Figure 4 The particle size distribution diagrams are of the silicon carbide powders obtained in Examples 1-3 and Comparative Example 1 of the present invention. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] This invention provides a method for preparing high-purity silicon carbide powder, comprising the following steps: S1) mixing carbon powder and silicon powder to obtain a carbon-silicon mixed raw material; S2) alternately placing multiple perforated graphite cylinders and the carbon-silicon mixed raw material in a crucible along the diameter direction, performing high-vacuum heat treatment and inert gas cleaning, then introducing inert gas and reacting under high temperature and high pressure conditions to obtain high-purity silicon carbide powder; the sidewall of the perforated graphite cylinder is provided with multiple through holes.

[0025] The preparation method has the advantages of simplicity, high efficiency, accurate control of particle size and size distribution, and accurate control of porous graphite cylinder distribution and size.

[0026] In the present application, all raw materials are commercially available.

[0027] The carbon powder and the silicon powder are mixed to obtain a carbon-silicon mixed raw material; the particle size of the carbon powder and the silicon powder is preferably less than 30 mesh; the purity of the carbon powder and the silicon powder is preferably greater than 99.99%; the molar ratio of the carbon powder to the silicon powder is preferably 1:1-1:1.5, more preferably 1:1.1-1:1.4, and even more preferably 1:1.2-1:1.3.

[0028] A plurality of perforated graphite cylinders and the carbon-silicon mixed raw material are alternately placed in the crucible along the diameter direction of the crucible; see Figure 1 and Figure 2 , Figure 1 A longitudinal sectional view of the crucible loading structure provided by the present application is shown in Figure 2A top view of the crucible loading structure provided by the present application, wherein 1 is a crucible, 2 is a perforated graphite cylinder, and 3 is a carbon-silicon mixed raw material; the height of the perforated graphite cylinder is preferably lower than the height of the crucible; in a specific embodiment provided by the present application, the height difference between the perforated graphite cylinder and the crucible is preferably 10-50 mm, more preferably 10-40 mm, and even more preferably 20-30 mm; the side wall of the perforated graphite cylinder is provided with a plurality of through holes; the diameter of the holes is preferably 2-5 mm; the diameters of the holes on the side wall of each perforated graphite cylinder in the plurality of perforated graphite cylinders can be the same or different, and there is no special limitation; in a specific embodiment provided by the present application, the diameters of the holes on the side wall of each perforated graphite cylinder in the plurality of perforated graphite cylinders are the same; in some embodiments provided by the present application, the diameter of the holes is specifically 2 mm, 4 mm or 5 mm; the distribution density of the holes on the side wall of the perforated graphite cylinder is preferably 30%-60%, more preferably 35%-58%, and even more preferably 39%-56%; the distribution densities of the holes of the plurality of perforated graphite cylinders can be the same or different; in a specific embodiment provided by the present application, the distribution densities of the holes of the plurality of perforated graphite cylinders are the same; the plurality of through holes are preferably uniformly distributed on the side wall of the perforated graphite cylinder; the distance between adjacent holes of the plurality of through holes is preferably 1-3 mm, and more preferably 2-3 mm; the thicknesses of the plurality of perforated graphite cylinders can be the same or different, and there is no special limitation; the thickness of the perforated graphite cylinder is preferably 10-50 mm, more preferably 20-40 mm, and even more preferably 20-30 mm; in the present application, the plurality of perforated graphite cylinders and the carbon-silicon mixed raw material are alternately placed along the diameter direction of the crucible, so that the carbon-silicon mixed raw material at the central position is arranged in a circular ring shape; the thickness ratio of the perforated graphite cylinder to the carbon-silicon mixed raw material is preferably (1-10):1, more preferably (1-8):1, even more preferably (1-5):1, again more preferably (2-4):1, and most preferably (2-3):1; the carbon-silicon mixed raw material at the central position is arranged in a cylindrical shape, and at this time, the thickness ratio of the perforated graphite cylinder to the radius of the carbon-silicon mixed raw material is preferably (1-10):1, more preferably (1-8):1, even more preferably (1-5):1, again more preferably (2-4):1, and most preferably (2-3):1; the plurality of perforated graphite cylinders and the carbon-silicon mixed raw material are alternately placed along the diameter direction of the crucible, and preferably the perforated graphite cylinder is in contact with the side wall of the crucible, i.e., the two sides of the carbon-silicon mixed raw material except the central position are both perforated graphite cylinders; the number of perforated graphite cylinders is determined by the diameter of the crucible; in the present application, specifically, the following steps are performed: A1) placing a first layer of perforated graphite cylinders near the side wall of the crucible, and then placing a second layer of perforated graphite cylinders at a distance from the first layer of perforated graphite cylinders;A2) placing the carbon-silicon mixed raw material between the first layer of perforated graphite cylinders and the second layer of perforated graphite cylinders, and repeating the steps of placing the perforated graphite cylinders and the carbon-silicon mixed raw material, so that the perforated graphite cylinders and the carbon-silicon mixed raw material are alternately placed in the crucible along the diameter direction of the crucible; or, specifically, placing the first layer of perforated graphite cylinders near the side wall of the crucible, and then placing the other perforated graphite cylinders at intervals, and after the perforated graphite cylinders are placed, filling the carbon-silicon mixed raw material between the two layers of perforated graphite cylinders and at the center, so that the perforated graphite cylinders and the carbon-silicon mixed raw material are alternately placed in the crucible along the diameter direction of the crucible.

[0029] The assembled crucible is subjected to high vacuum heat treatment and inert gas cleaning; in the present application, the assembled crucible is preferably placed in a heating furnace, more preferably in a medium-frequency induction heating furnace, for high vacuum heat treatment and inert gas cleaning; the vacuum degree of the high vacuum heat treatment is preferably 4x10 -6 ~ 6x10 -4 mbar, more preferably 4x10 -6 ~ 5x10 - 4 mbar; the temperature of the high vacuum heat treatment is preferably 1100°C ~ 1300°C, more preferably 1100°C ~ 1200°C; the heating rate of the high vacuum heat treatment is preferably 10 ~ 50°C / min, more preferably 20 ~ 40°C / min, and more preferably 30°C / min; the time of the high vacuum heat treatment is preferably 3 ~ 6h, more preferably 4 ~ 5h; in the present application, the time of the high vacuum heat treatment refers to the time of maintaining the temperature at the treatment temperature, unless otherwise specified; after the high vacuum heat treatment, inert gas cleaning is performed; the method of the inert gas cleaning is well known to those skilled in the art and is not particularly limited, and in the present application, it is preferably as follows: inert gas is introduced to a pressure of 200 ~ 300mbar, maintained for 0.5 ~ 1h, then vacuumed to a vacuum degree of not higher than 6x10 -4 mbar, maintained for at least 3h, and the above steps of introducing inert gas and vacuuming are repeated at least 2 times; the inert gas is preferably high-purity argon and / or high-purity helium; in the present application, the inert gas is preferably introduced to a pressure of 200 ~ 300mbar, more preferably 240 ~ 300mbar, more preferably 260 ~ 300mbar, and most preferably 285mbar; after the inert gas is introduced to a pressure of 200 ~ 300mbar, it is preferably maintained for 0.6 ~ 0.9h, more preferably 0.8h; in the present application, the above steps of introducing inert gas and vacuuming are preferably repeated at least 3 times, more preferably at least 4 times.

[0030] After the inert gas cleaning, the inert gas is introduced, and the reaction is carried out under high temperature and high pressure; the inert gas is the same as described above, which is not repeated here; the temperature of the reaction is preferably 1800-2300 DEG C, more preferably 1900-2300 DEG C; the pressure of the reaction is preferably 300-800 mbar, more preferably 400-800 mbar, more preferably 500-700 mbar, and most preferably 600 mbar; the time of the reaction is preferably 10-30 h, more preferably 15-25 h, and more preferably 20 h.

[0031] After the reaction is completed, the temperature is reduced to room temperature, and the high-purity silicon carbide powder is obtained; the particle size of the high-purity silicon carbide powder is preferably 40-60 mesh.

[0032] The present application can obtain high-purity silicon carbide powder by high-temperature solid-phase reaction of carbon-silicon mixed raw materials in a perforated graphite cylinder, and can control the particle size and distribution of the high-purity silicon carbide powder by adjusting the holes of the perforated graphite cylinder, thereby obtaining high-purity silicon carbide powder with controllable particle size and uniform distribution; and the method does not need to be crushed and sieved, so that the desired particle size of the silicon carbide powder can be obtained, avoiding the introduction of impurity elements in the crushing process, improving the purity of the silicon carbide powder, reducing the complexity of the process, stabilizing the reaction process, improving the preparation effect, and reducing the production cost.

[0033] The high-purity silicon carbide powder prepared by the present application has a small and uniform size distribution, and can be used to prepare high-temperature materials such as ceramics, furnaces and refractory materials; and can be applied to silicon carbide crystal growth, preparation of silicon carbide transistors, diodes and power modules and other electronic devices, to improve the performance and reliability of the devices.

[0034] In order to further illustrate the present application, the following examples provide a detailed description of the preparation method of the present application.

[0035] The reagents used in the following examples are commercially available; the particle size of the carbon powder and the silicon powder in the examples is less than 30 mesh.

[0036] The perforated graphite cylinder parameters used in the examples are as follows:

[0037] The perforated graphite cylinder has a hole size range of 2-5 mm, different holes are 2 mm apart, and the holes are uniformly distributed on the graphite cylinder; the perforated graphite cylinder is sequentially from the outside to the inside: the first perforated graphite cylinder, the second perforated graphite cylinder, the third perforated graphite cylinder, and the fourth perforated graphite cylinder, and the inner diameter and the outer diameter size are different, as shown in Table 1.

[0038] Table 1 Size of perforated graphite cylinder

[0039] Name Inner diameter Outer diameter Height First perforated graphite cylinder 120 mm 150 mm 180 mm Second perforated graphite cylinder 80 mm 110 mm 180 mm Third perforated graphite cylinder 40 mm 70 mm 180 mm Fourth perforated graphite cylinder 10 mm 30 mm 180 mm

[0040] The outer diameter and height of the first perforated graphite cylinder are determined according to the inner diameter of the used crucible, and the height of the perforated graphite cylinder is determined according to the height of the used crucible. In the embodiment, the inner diameter of the crucible is 151 mm, and the height is 200 mm. The size of the hole diameter determines the particle size of the synthesized silicon carbide powder. The detailed parameters are shown in the embodiment.

[0041] The impurity content detection method of the embodiment: the impurity content is detected and analyzed by using a NexION 300D type inductively coupled plasma mass spectrometer detection instrument. The detection is based on GB / T 24582-2009, and the detected elements are copper, nickel, chromium, sodium, potassium, zinc, calcium, aluminum, iron, magnesium, titanium, vanadium, cobalt, manganese, and tungsten.

[0042] Example 1

[0043] Step 1: The high-purity carbon powder and the high-purity silicon powder are fully mixed and uniformly mixed according to a carbon-silicon molar ratio of 1:1.2;

[0044] Step 2: A first perforated graphite cylinder is placed near the graphite crucible wall, with a hole diameter of 2 mm. A second perforated graphite cylinder is placed 5 mm away from the first layer of perforated graphite cylinder, with a hole diameter of 2 mm. The uniformly mixed carbon-silicon raw material is placed between the first layer and the second layer of perforated graphite cylinder;

[0045] Step 3: A third perforated graphite cylinder is placed 5 mm away from the second perforated graphite cylinder, with a hole diameter of 2 mm. The uniformly mixed carbon-silicon raw material is placed between the second and third perforated graphite cylinders;

[0046] Step 4: A fourth perforated graphite cylinder is placed 5 mm away from the third perforated graphite cylinder. The uniformly mixed carbon-silicon raw material is placed between the third and fourth perforated graphite cylinders, with a hole diameter of 2 mm. That is, the perforated graphite cylinders and the carbon-silicon raw material are placed in turn;

[0047] Step 5: The assembled graphite crucible is placed in a medium-frequency induction heating furnace;

[0048] Step 6: The vacuum degree of the reaction chamber is controlled below 5x10 -4 mbar, and the temperature is raised to 1100℃ at a rate of 30℃ / min. After keeping for 4h, Ar is introduced into the heating furnace, and the atmosphere pressure is 285mbar, keeping for 0.8h. The vacuum degree is again reduced below 6x10 -4 mbar, keeping for 3h. The above inert gas cleaning is repeated 4 times;

[0049] Step 7: The temperature of the reaction chamber is raised to 2100℃, the inert gas atmosphere pressure is 600mbar, and the reaction time is 20h;

[0050] Step 8: After the furnace cavity temperature is reduced to room temperature, the graphite crucible is opened, and the porous graphite cylinder is taken out, thereby obtaining the high-purity silicon carbide powder with a specific particle size.

[0051] Example 2

[0052] Step 1: The high-purity carbon powder and the high-purity silicon powder are mixed uniformly according to a carbon-silicon molar ratio of 1:1.2;

[0053] Step 2: A first perforated graphite cylinder is placed near the wall of the graphite crucible, with a hole diameter of 4 mm; a second perforated graphite cylinder is placed 5 mm away from the first perforated graphite cylinder, with a hole diameter of 4 mm; and the mixed carbon-silicon raw material is placed between the first and second perforated graphite cylinders;

[0054] Step 3: A third perforated graphite cylinder is placed 5 mm away from the second perforated graphite cylinder, with a hole diameter of 4 mm; and the mixed carbon-silicon raw material is placed between the second and third perforated graphite cylinders;

[0055] Step 4: A fourth perforated graphite cylinder is placed 5 mm away from the third perforated graphite cylinder, with a hole diameter of 4 mm; and the mixed carbon-silicon raw material is placed between the third and fourth perforated graphite cylinders, i.e., the perforated graphite cylinders and the carbon-silicon raw material are placed in turn and overlapped;

[0056] Step 5: The assembled graphite crucible is placed in a medium-frequency induction heating furnace;

[0057] Step 6: The vacuum degree of the reaction chamber is controlled below 5×10 -4 mbar, the temperature is raised to 1100℃ at a rate of 30℃ / min, and maintained for 4h; then Ar is introduced into the heating furnace, with an atmosphere pressure of 285mbar, and maintained for 0.8h; the vacuum degree is again reduced below 6×10 -4 mbar, and maintained for 3h; the above inert gas cleaning is repeated 4 times;

[0058] Step 7: The temperature of the reaction chamber is raised to 2100℃, the inert gas atmosphere pressure is 600mbar, and the reaction time is 20h;

[0059] Step 8: After the furnace cavity temperature is reduced to room temperature, the graphite crucible is opened, and the porous graphite cylinder is taken out, thereby obtaining the high-purity silicon carbide powder with a specific particle size.

[0060] Example 3

[0061] According to the method of Example 1, the difference is that in steps 2, 3, and 4, the hole diameter of the perforated graphite cylinder is 5mm, and the remaining conditions are unchanged, thereby obtaining the high-purity silicon carbide powder with a specific particle size.

[0062] Comparative Example 1

[0063] Step 1: high-purity carbon powder and high-purity silicon powder are mixed uniformly according to a carbon-silicon molar ratio of 1:1.2;

[0064] Step 2: the mixed raw materials are added into a crucible, the material surface is level, and the assembled graphite crucible is placed in a medium-frequency induction heating furnace;

[0065] Step 3: the vacuum degree of the reaction chamber is controlled below 5x10 -4 mbar, the temperature is raised to 1100℃ at a speed of 30℃ / min, and then maintained for 4h; Ar is introduced into the heating furnace, and the atmosphere pressure is 285mbar, and then maintained for 0.8h; the vacuum degree is again controlled below 6x10 -4 mbar, and then maintained for 3h; the above inert gas cleaning is repeated for 4 times;

[0066] Step 4: the temperature of the reaction chamber is raised to 2100℃, the inert gas atmosphere pressure is 600mbar, and the reaction time is 20h;

[0067] Step 5: the temperature of the furnace cavity is reduced to room temperature, the graphite crucible is opened after the furnace is opened, and then the silicon carbide powder is obtained.

[0068] The silicon carbide powder obtained in Example 1 is detected by an energy spectrometer, and EDS test data are obtained as shown in Figure 3 The energy spectrum of the middle peak can be determined as silicon carbide, and the carbon-silicon ratio is close to 1:1. Figure 3

[0069] The pore diameter parameters of the perforated graphite cylinder used in Examples 1, 2, 3 and Comparative Example 1 and the particle size detection of the obtained silicon carbide powder are shown in Table 2, and the particle size distribution graph of the silicon carbide powder is shown in Figure 4 From the content shown in Table 2, it can be concluded that, compared with the prior art Comparative Example 1, the grain size of the synthesized silicon carbide powder is more uniform by using the method provided by the present application, and different particle sizes of the silicon carbide powder can be obtained by adjusting the pore diameter of the perforated graphite cylinder, thereby reducing the process complexity and cost.

[0070] Table 2: Pore diameter parameters of perforated graphite cylinder and silicon carbide particle size detection results

[0071] Sample number Porous graphite cylinder pore size Pore size distribution density High purity silicon carbide powder particle size Appearance Example 1 2 mm 39.2％ 60 mesh Uniform particle size distribution Example 2 4 mm 52.3％ 50 mesh Uniform particle size distribution Example 3 5 mm 55.9％ 40 mesh Uniform particle size distribution Comparative Example 1 None None 5-50 mesh Non-uniform particle size distribution Comparative Example 2 None None 5-50 mesh Non-uniform particle size distribution

[0072] ​The impurity content of the synthesized silicon carbide powder of Example 1, 2, 3 and Comparative Example 1 is detected (ICP test) by inductively coupled plasma, and the bulk metal impurity content is shown in Table 3. The purity can be judged according to the total impurity content: the lower the total impurity content, the higher the purity; the higher the total impurity content, the lower the purity. From the content shown in Table 3, it can be concluded that, compared with the prior art Comparative Example 1, the silicon carbide powder synthesized by the method provided in the application has lower impurity content, and does not need to be crushed, thereby avoiding the introduction of impurity elements in the crushing process, improving the preparation efficiency and reducing the production cost.

[0073] Table 3: Impurity detection results of the silicon carbide powder obtained in Example 1-3 and Comparative Example 1

[0074]

[0075]

Claims

1. A method of producing a high purity silicon carbide powder, characterized by, The method comprises the following steps: S1) mixing carbon powder and silicon powder to obtain carbon-silicon mixed raw materials; S2) placing a plurality of perforated graphite cylinders and the carbon-silicon mixed raw materials alternately in a crucible along the diameter direction of the crucible, performing high-vacuum heat treatment and inert gas cleaning, then introducing inert gas, and performing reaction under high temperature and high pressure to obtain high-purity silicon carbide powder; the side wall of the perforated graphite cylinder is provided with a plurality of through holes; The pore diameter of the holes is 2-5 mm; the distance between adjacent holes is 1-3 mm; The distribution density of the holes is 30%-60%.

2. The production method according to claim 1, characterized by, The molar ratio of the carbon powder to the silicon powder is 1:1-1:1.

5.

3. The preparation method according to claim 1, characterized in that, The thickness ratio of the perforated graphite cylinder to the carbon-silicon mixed raw materials is (1-10):

1.

4. The production method according to claim 1, characterized by, In the step S2), the perforated graphite cylinder is in contact with the side wall of the crucible.

5. The method of claim 1, wherein, The vacuum degree of the high vacuum heat treatment in the step S2) is 4 x 10 -6 ~ 6 x 10 -4 mbar; the temperature of the high vacuum heat treatment is 1100°C ~ 1300°C; the heating rate of the high vacuum heat treatment is 10 ~ 50°C / min; and the time of the high vacuum heat treatment is 3 ~ 6h.

6. The method of claim 1, wherein, The inert gas cleaning in step S2) is specifically as follows: the inert gas is introduced to a pressure of 200-300 mbar, and maintained for 0.5-1 h, then vacuumized to a vacuum degree of not higher than 6x10 - 4 mbar, and maintained for at least 3 h, and the above-mentioned steps of introducing the inert gas and vacuumizing are repeated for at least 2 times.

7. The preparation method according to claim 1, characterized in that, The reaction temperature is 1800-2300°C; the reaction pressure is 300-800 mbar; and the reaction time is 10-30 h.

8. The method of claim 1, wherein, After the reaction in the step S2), the temperature is lowered to room temperature to obtain high-purity silicon carbide powder; and the particle size of the high-purity silicon carbide powder is 40-60 mesh.

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