Method and device for synthesizing silicon carbide powder

Abstract

The embodiment of the invention provides a silicon carbide powder synthesis method and device, and relates to the technical field of silicon carbide powder synthesis. The silicon carbide powder synthesis method can be applied to the silicon carbide powder synthesis device. In the process of synthesizing the silicon carbide powder, the raw material powder and the silicon crystal raw material are contained in the crucible, the silicon crystal raw material comprises a plurality of silicon rods, the silicon rods are arranged at intervals, and the silicon rods are contained in the raw material powder. In the synthesis process of the silicon carbide powder, when the temperature in the crucible is increased to a certain temperature, silicon rods start to melt and diffuse into carbon powder, the carbon powder and silicon melt can be mutually permeated to form a large silicon-carbon mixture, then the silicon carbide powder can be generated through reaction at high temperature, each silicon rod can form a nucleation point of the silicon-carbon mixture, and the silicon carbide powder can be formed through the nucleation point of the silicon-carbon mixture. And thus, the yield of the large-size silicon carbide powder can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of silicon carbide powder synthesis, and in particular to a method and device for synthesizing silicon carbide powder. Background Art

[0002] With the advancement of silicon carbide crystal growth technology, downstream epitaxial manufacturers have increasingly stringent requirements for substrate quality. Currently, most companies are still using commercially available 8-20 mesh silicon carbide powder for crystal growth. Most of the existing silicon carbide powder synthesis adopts chemical vapor deposition. The powder is decomposed into Si, Si2C, SiC2, SiC and other gases at high temperature. The gas is transported under the drive of temperature gradient, and then recrystallized on SiC seed crystals to achieve crystal growth. The particles of this synthetic silicon carbide powder are fine, and a large number of carbon particles are produced when it is decomposed at high temperature. Among them, the finer particles are mixed in the high-temperature atmosphere, which is easy to form defects such as carbon inclusions and microtubes in the crystal, seriously affecting the quality of the substrate.

[0003] In order to reduce defects such as carbon inclusions, some companies have begun to use large-size silicon carbide powder for crystal growth in recent years, which has greatly reduced inclusion defects.

[0004] In the related art, the particle size of silicon carbide powder produced by chemical vapor deposition is mostly less than 6 mm. By synthesizing silicon carbide powder by solid phase method, some particle sizes of silicon carbide powder produced can reach 15 mm, but the yield is lower than that of vapor deposition method. Summary of the invention

[0005] The purpose of the present invention includes providing a method and device for synthesizing silicon carbide powder, which can improve the yield of producing silicon carbide powder with large size, such as 15mm particle size.

[0006] The embodiments of the present invention can be implemented as follows: In a first aspect, the present invention provides a method for synthesizing silicon carbide powder, the method comprising: Filling the crucible with raw material powder, wherein the raw material powder includes carbon powder; The silicon crystal raw material is filled into the crucible, wherein the silicon crystal raw material includes a plurality of silicon rods, the plurality of silicon rods are arranged at intervals, and the silicon rods are accommodated in the raw material powder; The silicon crystal raw material is melted in the carbon powder, and the silicon crystal raw material and the carbon powder are reacted together at a first preset temperature to generate silicon carbide powder.

[0007] In an optional embodiment, the raw material powder further includes a crystal stabilizer, and the crystal stabilizer is used to reduce the interfacial energy of the silicon carbide particles.

[0008] In an optional embodiment, the crystal stabilizer accounts for 0.5-1.2% of the raw material powder charge.

[0009] In an alternative embodiment, the crystal form stabilizer is any one of magnesium borate, cerium oxide or cerium silicide.

[0010] In an alternative embodiment, the first preset temperature is 2000 - 2400 °C.

[0011] In an alternative embodiment, before the silicon crystal raw material and the carbon powder react together to form silicon carbide powder at the first preset temperature, it further includes: Vacuumizing the crucible to make the pressure inside the crucible be at the first preset pressure; Filling the crucible with an inert gas and making the pressure inside the crucible be at the second preset pressure, and the inert gas includes argon.

[0012] In an alternative embodiment, the crucible is further provided with a silicon carbide wafer, and the silicon carbide wafer separates the first chamber and the second chamber arranged in the crucible. The first chamber is located on the side of the silicon carbide wafer away from the raw material powder, and the silicon carbide wafer is used for depositing silicon carbide powder at the first preset temperature.

[0013] In an alternative embodiment, the inner wall of the first chamber is coated with a heat-insulating coating.

[0014] In an alternative embodiment, the silicon crystal raw material further includes a silicon plate, and a plurality of silicon rods are arranged at intervals on the silicon plate; The method for filling the raw material powder into the crucible includes: Laying a raw material powder with a preset thickness at the bottom of the crucible; Placing the silicon crystal raw material into the crucible and making the silicon plate be placed on the surface of the raw material powder with the preset thickness; Continuing to pour the raw material powder into the crucible and submerging the silicon crystal raw material with the raw material powder.

[0015] In a second aspect, the present invention provides a silicon carbide powder synthesis device for preparing silicon carbide powder by the silicon carbide powder synthesis method according to any one of the foregoing embodiments, including: A crucible; Raw material powder, the raw material powder includes carbon powder and is contained in the crucible; Silicon crystal raw material, the silicon crystal raw material includes a plurality of silicon rods, the plurality of silicon rods are arranged at intervals, and the silicon rods are contained in the raw material powder.

[0016] An embodiment of the present invention provides a method and device for synthesizing silicon carbide powder. The method for synthesizing silicon carbide powder is applied to a silicon carbide powder synthesis device. During the synthesis of silicon carbide powder, since the silicon rod is embedded in the raw material powder, at a certain temperature, the silicon rod begins to melt and diffuse into the carbon powder. Due to the high porosity and good adsorption of the carbon powder, the carbon powder can penetrate into the silicon melt to form large silicon-carbon mixtures, and then react at high temperature to generate silicon carbide powder. Moreover, each silicon rod can form a nucleation point for the silicon-carbon mixture, so that under the action of multiple silicon rods, large silicon-carbon mixtures can be formed, which is convenient for reacting at high temperature to form silicon carbide powder, thereby improving the yield of large-size silicon carbide powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0018] Figure 1 It is a schematic structural diagram of the silicon carbide powder synthesis device provided in this embodiment; Figure 2 It is a schematic structural diagram of the crucible body provided in this embodiment.

[0019] Reference numerals: 1 - silicon carbide powder synthesis device; 100 - crucible; 110 - crucible body; 1110 - installation groove; 1111 - connecting inner wall; 1112 - connecting end wall; 120 - crucible cover; 101 - first chamber; 102 - second chamber; 130 - silicon carbide wafer; 140 - thermal insulation coating; 200 - raw material powder; 300 - silicon crystal raw material; 310 - silicon plate; 320 - silicon rod. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and illustrated herein can be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0022] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0023] In the description of the present invention, it should be noted that if the terms "upper", "lower", "inside", "outside", etc. appear to indicate an orientation or position relationship, they are based on the orientation or position relationship shown in the accompanying drawings, or are the orientation or position relationship in which the product of the invention is usually placed when used. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0024] In addition, the terms “first”, “second”, etc., if used, are merely used to distinguish between the descriptions and should not be understood as indicating or implying relative importance.

[0025] It should be noted that, in the absence of conflict, the features in the embodiments of the present invention may be combined with each other.

[0026] At present, most companies are still using commercially available 8~20 mesh silicon carbide powder for crystal growth. Most of the existing silicon carbide powder synthesized by chemical vapor deposition, the powder is decomposed into Si, Si2C, SiC2, SiC and other gases at high temperature, the gas is transported under the drive of temperature gradient, and then recrystallized on SiC seed crystal to achieve crystal growth, the obtained silicon carbide powder particle size is less than 6mm, the synthetic silicon carbide powder particles are fine, and a large amount of carbon particles are produced when decomposed at high temperature, among which the finer particles are mixed in the high temperature atmosphere, which easily forms defects such as carbon inclusions and microtubes in the crystal, seriously affecting the quality of the substrate.

[0027] In order to reduce defects such as carbon inclusions, some companies have begun to use large-size silicon carbide powder for crystal growth in recent years. The particle size of the obtained silicon carbide powder can be 15mm, but its yield is low, only about 50%.

[0028] An embodiment of the present invention provides a method for synthesizing silicon carbide powder, and the method for synthesizing silicon carbide powder includes: First, the raw material powder 200 is filled into the crucible 100 . It should be noted that the raw material powder 200 includes carbon powder.

[0029] The silicon crystal raw material 300 is filled in the crucible 100 . The silicon crystal raw material 300 includes a plurality of silicon rods 320 . The plurality of silicon rods 320 are arranged at intervals and the silicon rods 320 are accommodated in the raw material powder 200 .

[0030] Melt the silicon crystal raw material 300 in carbon powder, and react the silicon crystal raw material with the carbon powder at a first preset temperature to generate silicon carbide powder.

[0031] It can be understood that since the silicon rod 320 is embedded in the raw material powder 200, at a certain temperature, generally around 1414 °C, the silicon rod 320 starts to melt and diffuses into the carbon powder. Due to the high porosity and good adsorption of the carbon powder, the carbon powder can penetrate with the silicon melt to form a large silicon-carbon mixture, and then can react at high temperature to generate silicon carbide powder.

[0032] In this embodiment, multiple silicon rods 320 are arranged at intervals. After each silicon rod 320 melts, it diffuses into the carbon powder, and each silicon rod 320 can form a nucleation point of the silicon-carbon mixture. Under the action of multiple silicon rods 320, a large silicon-carbon mixture can be formed, so as to react at high temperature to form silicon carbide powder. After cooling, the silicon carbide powder can be taken out, broken with a hammer, and filtered through a sieve. The silicon carbide powder on the sieve can be the powder with the target particle size obtained.

[0033] Since each silicon rod 320 can form a nucleation point of the silicon-carbon mixture, and each silicon rod 320 can form a large silicon-carbon mixture with the carbon powder after melting, therefore, it is convenient to react at high temperature to form silicon carbide powder. The yield of the synthesized silicon carbide powder larger than 15 mm can reach 85%, so the yield of large-size silicon carbide powder can be increased.

[0034] Optionally, the first preset temperature is 2000 - 2400 °C. For example, the first preset temperature can be 2000 °C, 2050 °C, 2100 °C, 2200 °C, 2300 °C or 2400 °C, so that the silicon crystal raw material 300 can fully react with the carbon powder to form silicon carbide powder.

[0035] Optionally, in some embodiments, in order to facilitate the stable placement of the silicon rod 320 in the raw material powder 200, the silicon crystal raw material 300 further includes a silicon plate 310, and multiple silicon rods 320 are arranged at intervals on the silicon plate 310.

[0036] Therefore, when filling the raw material powder 200 and the silicon crystal raw material 300, first lay a preset thickness of the raw material powder 200 at the bottom of the crucible 100. The preset thickness can be 10 - 15 mm. Among them, the raw material powder 200 can be a mixed powder including carbon powder and crystal stabilizer. It can be understood that the mixed powder formed by the raw material powder 200 and the crystal stabilizer can support the silicon plate 310.

[0037] It can be understood that during the synthesis of silicon carbide powder, when the crucible 100 is heated to a certain temperature, about 1414 °C, the silicon rod 320 and the silicon plate 310 begin to melt and diffuse into the carbon powder. Due to the high porosity and good adsorption of the carbon powder, a nucleation point of silicon-carbon mixture can be formed on each of the silicon plate 310 and the silicon rod 320. The carbon powder and the silicon melt can penetrate each other to form a large piece of silicon-carbon mixture, which can then react at high temperature to generate silicon carbide powder.

[0038] It should be noted that before laying the raw material powder 200 with a preset thickness at the bottom of the crucible 100, the raw material powder 200 can be prepared in advance. The steps for preparing the raw material powder 200 include weighing a certain mass of carbon powder according to a certain molar ratio, adding a crystal form stabilizer, and mixing for a certain time on a roller mixer to obtain the raw material powder 200, so as to ensure that the crystal form stabilizer is evenly mixed with the carbon powder in the raw material powder 200.

[0039] Then, the silicon crystal raw material 300 is placed in the crucible 100, and the silicon plate 310 is placed on the surface of the raw material powder 200 with a preset thickness.

[0040] Then, the raw material powder 200 can be continuously poured into the crucible 100, and the raw material powder 200 is used to submerge the silicon crystal raw material 300.

[0041] It should be noted that the above-mentioned mixed raw material powder can be obtained by weighing a certain mass of C powder according to a certain molar ratio, adding a crystal form stabilizer, and the crystal form stabilizer accounts for 0.5-1.2% of the loading amount of the raw material powder 200, so as to ensure the proportion of carbon powder in the raw material powder 200 and provide sufficient carbon source for the synthesis of silicon carbide powder. The loading amount can be understood as the sum of the crystal form stabilizer and the raw material powder 200. Mix on a roller mixer for 2 h to obtain the mixed raw material powder.

[0042] The crystal form stabilizer can be magnesium borate, cerium oxide or cerium silicide. In this embodiment, the crystal form stabilizer is magnesium borate to promote the formation of α-SiC crystal form. The powder synthesis temperature can be reduced from 2300 °C to about 2100 °C, which can effectively reduce energy consumption.

[0043] Optionally, in some embodiments, a silicon carbide wafer 130 is further provided in the crucible 100. The silicon carbide wafer 130 divides the crucible 100 into a first chamber 101 and a second chamber 102. The silicon crystal raw material 300 and the raw material powder 200 are placed in the second chamber 102. The first chamber 101 is located on the side of the silicon carbide wafer 130 away from the raw material powder 200. The silicon carbide wafer 130 is used to deposit silicon carbide powder at a first preset temperature.

[0044] That is to say, the gaseous state of the silicon crystal raw material 300 and the raw material powder 200 after sublimation is used to crystallize on the silicon carbide wafer 130, and silicon carbide powder is formed on the silicon carbide wafer 130.

[0045] It can be understood that the waste silicon carbide wafers 130 in the upper part of the crucible 100 can act as seeds, inducing the gas containing Si components volatilized at high temperature to recrystallize and grow silicon carbide powder on their surfaces, fully recovering part of the gasified raw materials, improving the utilization rate of the raw materials, and thus being able to increase the output of the synthesized silicon carbide powder.

[0046] Before the silicon crystal raw material and the carbon powder react together to form silicon carbide powder at the first preset temperature, it further includes: Furthermore, the crucible 100 is evacuated so that the pressure inside the crucible 100 is at the first preset pressure.

[0047] It can be understood that when evacuating, the gas inside the crucible 100 can be pumped out to provide a relatively clean environment for the subsequent synthesis of silicon carbide powder. Optionally, the first preset pressure can be 3 - 10 Pa. For example, the first preset pressure is 3 Pa, 4 Pa, 5 Pa, 6 Pa, 8 Pa or 10 Pa.

[0048] Furthermore, an inert gas can be filled into the crucible 100 and the pressure inside the crucible 100 is at the second preset pressure.

[0049] It should be noted that the inert gas can be argon. It can be understood that when synthesizing the powder, the Ar gas diffuses through the wall of the crucible 100 into the first chamber 101 to form an Ar gas layer. It can be understood that the Ar gas has poor thermal conductivity and can form a heat insulation layer inside the first chamber 101 to improve the thermal utilization rate during powder synthesis.

[0050] Optionally, in order to further improve the thermal utilization rate, a heat insulation coating 140 can also be coated on the inner wall of the first chamber 101. The heat insulation coating 140 can be a tantalum carbide coating or a niobium carbide coating. Of course, the heat insulation coating 140 can also be a coating formed by other materials that can achieve heat insulation.

[0051] Optionally, the second preset pressure can be 5500 - 6500 Pa. In this embodiment, the second preset pressure is 6000 Pa. Of course, in some other embodiments, the second preset pressure can be 5500 Pa, 5800 Pa, 6200 Pa or 6500 Pa.

[0052] Heat the crucible 100 to a first preset temperature within a first preset time, and keep the crucible 100 at the first preset temperature within a second preset time. Optionally, in this embodiment, the crucible 100 assembled and containing the raw material powder 200 and the silicon crystal raw material 300 can be placed into a resistance furnace and heated to within the range of 2050 - 2100°C within two hours. And keep it at a temperature within the range of 2050 - 2100°C for 20 - 25 hours to enable the silicon crystal raw material and the carbon powder to react together to form silicon carbide powder.

[0053] Then cool the crucible 100 to a second preset temperature within the second preset time. Optionally, in this embodiment, the temperature can be reduced to room temperature within 1 h, and the room temperature is generally 20 - 25°C.

[0054] Finally, the synthesized cylindrical large piece of SiC can be poured out of the crucible 100, broken with a hammer and then passed through a sieve. The silicon carbide powder on the sieve can be the powder with the target particle size.

[0055] The following will introduce in detail the specific structure of a silicon carbide powder synthesis device provided by an embodiment of the present invention in combination with the patent drawings and the corresponding technical effects brought thereby.

[0056] Please refer to Figure 1 - Figure 2 , an embodiment of the present invention further provides a silicon carbide powder synthesis device 1, which is mainly used to prepare silicon carbide powder by the above synthesis method. The silicon carbide powder synthesis device 1 includes a crucible 100, a raw material powder 200 and a silicon crystal raw material 300. The raw material powder 200 includes carbon powder and is contained in the crucible 100. The silicon crystal raw material 300 includes a plurality of silicon rods 320, and the plurality of silicon rods 320 are arranged at intervals and contained in the raw material powder 200.

[0057] It can be understood that in order to facilitate the stable accommodation of the silicon rods 320 in the raw material powder 200, the silicon crystal raw material 300 further includes silicon plates 310. The plurality of silicon plates 310 are arranged at intervals on the silicon plates 310, and the silicon plates 310 and the silicon rods 320 are contained in the raw material powder 200.

[0058] It should be noted that the fact that the silicon rods 320 and the silicon plates 310 are contained in the raw material powder 200 can be understood as that the raw material powder 200 in the crucible 100 completely covers the silicon rods 320 and the silicon plates 310, and the axial dimension of the material surface of the raw material powder 200 is higher than the upper side dimension of the silicon rods 320.

[0059] Therefore, in this embodiment, the crucible 100 filled with raw material powder 200 and silicon crystal raw material 300 is heated up to synthesize silicon carbide powder. Since the silicon rod 320 and the silicon plate 310 are embedded in the raw material powder 200, at a certain temperature, generally around 1414 °C, the silicon rod 320 and the silicon plate 310 start to melt and diffuse into the carbon powder. Due to the high porosity and good adsorption of the carbon powder, the carbon powder can penetrate into the silicon melt to form large silicon-carbon mixtures, which can then react at high temperature to generate silicon carbide powder.

[0060] In this embodiment, a plurality of silicon rods 320 are arranged at intervals on the silicon plate 310. After each silicon rod 320 melts, it diffuses into the carbon powder, and each silicon rod 320 can form a nucleation point of a silicon-carbon mixture. Thus, under the action of the silicon plate 310 and the plurality of silicon rods 320, large silicon-carbon mixtures can be formed, which is convenient for reacting at high temperature to form silicon carbide powder, thereby increasing the yield of large-size silicon carbide powder.

[0061] In this embodiment, the silicon plate 310 is arranged at an interval from the bottom surface of the crucible 100, and there is raw material powder 200 on both the upper and lower sides of the silicon plate 310, so as to form a silicon-carbon mixture between the lower side of the silicon plate 310 and the raw material powder 200 below the silicon plate 310, and then react at a high temperature state to form silicon carbide powder.

[0062] In this embodiment, the silicon rod 320 is arranged on the upper side of the silicon plate 310. It can be understood that the silicon plate 310 can support the silicon rod 320. Under the support of the silicon plate 310, the silicon rod 320 is ensured to be stably in the raw material powder 200, so as to ensure that each silicon rod 320 can diffuse relatively stably into the surrounding carbon powder when melting, and ensure the smooth formation of large silicon-carbon mixtures.

[0063] It should be noted that the silicon plate 310 in this embodiment can be in the shape of a circular plate, and the silicon plate 310 is coaxial with the crucible 100, and the radial dimension of the silicon plate 310 is smaller than the radial dimension of the inner wall of the crucible 100.

[0064] For example, in some embodiments, the difference between the radial dimension of the inner wall of the crucible 100 and the radial dimension of the silicon plate 310 can be in the range of 10 - 15 mm, the thickness dimension of the silicon plate 310 can be 10 mm, the radial dimension of the silicon rod 320 can also be 10 mm, the spacing dimension between any two adjacent silicon rods 320 can be 20 - 25 mm, and the axial dimension of the silicon rod 320 can be 10 - 12 mm.

[0065] Of course, in some other embodiments, the difference in the radial dimensions of the two can also be within other ranges, or the difference between the radial dimension of the inner wall of the crucible 100 and the radial dimension of the silicon plate 310 can be greater than 15 mm, and the difference between the radial dimension of the inner wall of the crucible and the radial dimension of the silicon plate 310 can be less than 10 mm. Of course, the thickness dimension of the silicon plate 310 can also be less than or greater than 10 mm, and the diameter of the silicon rod 320 is not limited to 10 mm. Similarly, the dimension of the silicon rod 320 in the axial direction is not limited to 10 - 12 mm, and the spacing dimension between any two adjacent silicon rods 320 can also be less than 20 mm or greater than 25 mm. Here, the dimensions of the silicon plate 310 and the silicon rod 320 of the silicon crystal raw material 300 are not restricted.

[0066] It should be noted that in this embodiment, there is a spacing between the upper surface of the raw material powder 200 and the upper side of the silicon rod 320 to ensure that there is sufficient raw material powder 200 on the upper side of the silicon rod 320 to form a silicon-carbon mixture with the molten silicon rod 320, so as to create a basis for the subsequent reaction to form silicon carbide powder.

[0067] Optionally, in this embodiment, the silicon plate 310 is provided with a plurality of mounting holes, and the plurality of silicon rods 320 are inserted into the plurality of mounting holes in a one-to-one correspondence. It can be understood that the silicon rod 320 and the silicon plate 310 can be detachably arranged for easy assembly. During the transportation of the silicon crystal raw material 300, the silicon rod 320 and the silicon plate 310 can be separated to facilitate the transfer of the silicon crystal raw material 300. Of course, in some other embodiments, the silicon plate 310 and the silicon rod 320 can also be integrally arranged.

[0068] Optionally, in order to better form silicon carbide powder, the raw material powder 200 further includes a crystal form stabilizer, which is used to reduce the interfacial energy of silicon carbide particles. Among them, the crystal form stabilizer can be magnesium borate, cerium oxide or cerium silicide. In this embodiment, the crystal form stabilizer is magnesium borate to promote the formation of the α-SiC crystal form, and the powder synthesis temperature can be reduced from 2300 °C to about 2100 °C, which can effectively reduce energy consumption.

[0069] In this embodiment, the crystal form stabilizer accounts for 0.5 - 1.2% of the overall charge amount. It should be noted that the overall charge amount can be understood as the sum of the carbon powder and the crystal form stabilizer.

[0070] Optionally, in this embodiment, in the raw material powder 200 and the silicon crystal raw material 300, the molar ratio of silicon element to carbon element is 1 - 1.05 to ensure the utilization rate of the raw material powder 200 and the silicon crystal raw material 300 when synthesizing silicon carbide powder.

[0071] Optionally, in order to further improve the utilization rate of raw materials in the synthesis of silicon carbide powder, the silicon carbide powder synthesis device 1 further includes a silicon carbide wafer 130. Among them, the silicon carbide wafer 130 can be a discarded silicon carbide wafer 130, which can save the cost of silicon carbide powder synthesis. The silicon carbide wafer 130 is installed in the crucible 100 and is spaced apart from the raw material powder 200. That is to say, there is a spacing between the silicon carbide wafer 130 and the surface of the raw material powder 200 on the upper side. The gaseous phase sublimated from the silicon crystal raw material 300 and the raw material powder 200 is used to crystallize on the silicon carbide wafer 130, and silicon carbide powder is formed on the silicon carbide wafer 130.

[0072] That is to say, the waste silicon carbide wafer 130 in the upper part of the crucible 100 can act as a seed crystal, inducing the Si component gas volatilized at high temperature to recrystallize and grow silicon carbide powder on its surface, fully recovering the gasified part of the raw materials, improving the raw material utilization rate, and thus effectively improving the yield of synthesized silicon carbide powder.

[0073] Specifically, in this embodiment, the silicon carbide wafer 130 divides the crucible 100 into a first chamber 101 and a second chamber 102 which are separately arranged. The first chamber 101 is located on the side of the silicon carbide wafer 130 away from the raw material powder 200, and a heat insulation coating 140 is coated on the inner side of the first chamber 101.

[0074] Since the first chamber 101 and the second chamber 102 in this embodiment are separately arranged, the gaseous phase sublimated from the raw material powder 200 and the gaseous phase sublimated from the silicon crystal raw material 300 can be reduced from flowing into the first chamber 101, thus ensuring the utilization rate of the raw material powder 200 and the silicon crystal raw material 300 during the synthesis of silicon carbide powder.

[0075] It can be understood that by coating the heat insulation coating 140 on the inner side of the first chamber 101, the heat dissipation in the crucible 100 can be reduced. The first chamber 101 can play a certain heat insulation role and improve the heat utilization rate of the crucible 100 during the synthesis of powder.

[0076] Optionally, the above heat insulation coating 140 can be a tantalum carbide coating or a niobium carbide coating. Of course, the heat insulation coating 140 can also be a coating formed by other materials that can achieve heat insulation.

[0077] Specifically, in this embodiment, the crucible 100 includes a crucible body 110 and a crucible cover 120. The crucible body 110 is provided with an annular installation groove 1110. The installation groove 1110 includes a connecting inner wall 1111 and a connecting end wall 1112 that form an angle. The connecting inner wall 1111 is provided with internal threads, and the crucible cover 120 is provided with external threads that are threadedly connected to the crucible body 110, thereby ensuring the connection strength between the crucible cover 120 and the crucible body 110.

[0078] In this embodiment, the silicon carbide wafer 130 is lapped on the connecting end wall 1112, and the crucible cover 120 is pressed on the side of the silicon carbide wafer 130 away from the connecting end wall 1112, so as to effectively ensure the installation strength of the silicon carbide wafer 130 in the crucible 100. That is to say, in this embodiment, the heat insulation coating 140 is applied to the inner wall of the crucible cover 120.

[0079] The silicon carbide powder synthesis device 1 further includes a heating component. Optionally, the heating component includes a resistance furnace. The crucible 100 is used to be placed in the resistance furnace, and the resistance furnace is used to heat the crucible 100. It can be understood that when using a resistance furnace for heating, the temperature gradients in the radial and axial directions of the resistance furnace are both small, which is beneficial for the raw materials to undergo in-situ reactions to form silicon carbide powder.

[0080] Of course, in some other embodiments, the crucible 100 can also be heated by other means.

[0081] In summary, the embodiments of the present invention provide a method and a device for synthesizing silicon carbide powder. The method for synthesizing silicon carbide powder is applied to the silicon carbide powder synthesis device 1. During the synthesis of silicon carbide powder, at a certain temperature, the silicon rod 320 begins to melt and diffuse into the carbon powder. Since the carbon powder has a high porosity and good adsorption properties, the carbon powder can penetrate into the silicon melt to form large silicon-carbon mixtures. Then, the silicon-carbon mixtures can react at high temperature to form silicon carbide powder. Moreover, each silicon rod 320 can form a nucleation point for the silicon-carbon mixture. Under the action of multiple silicon rods 320, large silicon-carbon mixtures can be formed, which is convenient for reacting at high temperature to form silicon carbide powder, thereby improving the yield of large-size silicon carbide powder.

[0082] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for synthesizing silicon carbide powder, characterized in that, The method includes: filling raw material powder (200) into a crucible (100), and the raw material powder (200) includes carbon powder; filling silicon crystal raw material (300) into the crucible (100), the silicon crystal raw material (300) includes a plurality of silicon rods (320), the plurality of silicon rods (320) are arranged at intervals, and the silicon rods (320) are placed in the raw material powder (200); melting the silicon crystal raw material (300) in the carbon powder, and reacting the silicon crystal raw material with the carbon powder at a first preset temperature to generate silicon carbide powder.

2. The method for synthesizing silicon carbide powder according to claim 1, wherein: The raw material powder (200) further contains a crystal form stabilizer, and the crystal form stabilizer is used to reduce the interfacial energy of silicon carbide particles.

3. The method for synthesizing silicon carbide powder according to claim 2, wherein: The crystal form stabilizer accounts for 0.5-1.2% of the charging amount of the raw material powder (200).

4. The method for synthesizing silicon carbide powder according to claim 2, wherein: The crystal form stabilizer is any one of magnesium borate, cerium oxide or cerium silicide.

5. The method for synthesizing silicon carbide powder according to claim 1, wherein: The first preset temperature is 2000-2400 °C.

6. The method for synthesizing silicon carbide powder according to claim 1, wherein Before reacting the silicon crystal raw material with the carbon powder at the first preset temperature to generate silicon carbide powder, it further includes: performing vacuum pumping on the crucible (100) so that the pressure in the crucible (100) is at a first preset pressure; filling an inert gas into the crucible (100) and making the pressure in the crucible (100) at a second preset pressure, and the inert gas includes argon.

7. The method for synthesizing silicon carbide powder according to claim 1, characterized in that : The crucible (100) is further provided with a silicon carbide wafer (130), and the silicon carbide wafer (130) separates the first chamber (101) and the second chamber (102) provided in the crucible (100), and the first chamber (101) is located on the side of the silicon carbide wafer (130) away from the raw material powder (200), and the silicon carbide wafer (130) is used for depositing silicon carbide powder at the first preset temperature.

8. The method for synthesizing silicon carbide powder according to claim 7, wherein: The inner wall of the first chamber (101) is coated with a heat-insulating coating (140).

9. The method for synthesizing silicon carbide powder according to claim 1, wherein: The silicon crystal raw material (300) further includes a silicon plate (310), and the plurality of silicon rods (320) are arranged at intervals on the silicon plate (310); The method of filling the raw material powder (200) into the crucible (100) includes: laying a preset thickness of raw material powder (200) at the bottom of the crucible (100); placing the silicon crystal raw material (300) into the crucible (100), and placing the silicon plate (310) on the surface of the raw material powder (200) with the preset thickness; Continue to pour the raw material powder (200) into the crucible (100), and submerge the silicon crystal raw material (300) with the raw material powder (200).

10. A silicon carbide powder synthesis device for preparing silicon carbide powder by the silicon carbide powder synthesis method according to any one of claims 1-9, characterized in that, Comprising: A crucible (100); Raw material powder (200), the raw material powder (200) includes carbon powder and is contained in the crucible (100); Silicon crystal raw material (300), the silicon crystal raw material (300) includes a plurality of silicon rods (320), the plurality of silicon rods (320) are arranged at intervals, and the silicon rods (320) are contained in the raw material powder (200).

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