Method for synthesizing large-capacity silicon carbide powder

Abstract

The present invention provides a method for synthesizing large amounts of silicon carbide powder, which relates to the technical field of silicon carbide powder production. The method involves heating the furnace chamber to a first impurity removal temperature T1 and using the primary decomposition gas from the PVC particle layer to remove a large amount of impurity gases, thereby achieving primary impurity removal. The furnace chamber is then heated to a second impurity removal temperature T2 and the secondary decomposition gas generated by the continuous decomposition is used to continuously remove the impurity gases, thereby achieving secondary impurity removal. Finally, the furnace chamber is heated to a third impurity removal temperature and the tertiary decomposition gas is used to achieve tertiary impurity removal. Compared to the prior art, one aspect of the present invention is to reduce the accumulation of raw materials through distributed loading, thereby reducing carbonization and volatilization, achieving large-volume powder production and improving yield. According to another aspect, the reaction crucible can achieve multiple gas exchanges and impurity removal at different temperature ranges, significantly improving the impurity removal effect and effectively improving powder purity.

Description

[Technical Field]

[0001] The present invention relates to the technical field of silicon carbide powder production, and in particular to a method for synthesizing large-volume silicon carbide powder. [Background technology]

[0002] In conventional silicon carbide powder manufacturing methods, carbon and silicon raw materials are typically added directly to a large crucible, and then heated to achieve a synthesis reaction to synthesize silicon carbide powder. In one aspect, this manufacturing method cannot produce large quantities of powder. If the carbon and silicon raw materials are added in large quantities, carbonization and crystallization occur during the synthesis process, affecting subsequent synthesis. In another aspect, the carbon and silicon raw materials are both placed in a large crucible, resulting in relatively high wastage, significant accumulation, and a relatively low yield. Furthermore, conventional silicon carbide powder manufacturing methods have a relatively low impurity removal effect and a relatively low purity. Furthermore, conventional impurity removal methods typically involve a single high-temperature section for impurity removal, resulting in a low impurity removal effect. Summary of the Invention

[0003] The object of the present invention is to provide a method for synthesizing large-capacity silicon carbide powder and silicon carbide powder, which can reduce the amount of carbonization and effectively improve the yield, and can also provide effective gas exchange and impurity removal for the raw materials, effectively improving the purity of the powder, and by dispersing the loading of the raw materials, reduce the accumulation of the raw materials, delay the carbonization and crystallization phenomena, thereby achieving the production of large-capacity powder, and at the same time, provide excellent impurity removal effect.

[0004] An embodiment of the present invention can be implemented in this way.

[0005] According to a first aspect, an embodiment of the present invention comprises:

[0006] A plurality of reaction crucibles are filled with carbon and silicon raw materials at a predetermined ratio, and an impurity removal hole is opened at the top of each of the reaction crucibles;

[0007] Stacking a plurality of the reaction crucibles in a container crucible and placing the container crucible in a furnace chamber;

[0008] Laying a PVC particle layer on the bottom of the containing crucible;

[0009] performing a purging and evacuation operation on the furnace chamber;

[0010] the furnace chamber is heated to a first impurity removal temperature T1, maintained for a first predetermined time t1, a rare gas is injected into the furnace chamber, and then the furnace chamber is evacuated to decompose the primary decomposition products and primary decomposition gases generated by the PVC particle layer, and the primary impurity removal is achieved by using the primary decomposition gases;

[0011] the furnace chamber is heated to a second impurity removal temperature T2, maintained for a second predetermined time t2, a rare gas is injected into the furnace chamber, and then the furnace chamber is evacuated to decompose secondary decomposition products and secondary decomposition gases generated by the primary decomposition products, and secondary impurity removal is achieved using the secondary decomposition gases;

[0012] the furnace chamber is heated to a third impurity removal temperature T3, maintained for a third predetermined time t3, a rare gas is injected into the furnace chamber, and then the furnace chamber is evacuated to decompose the tertiary decomposition products and tertiary decomposition gases generated by the secondary decomposition products, and the tertiary decomposition gases are used to remove the tertiary impurities;

[0013] The temperature of the furnace chamber is raised to a preliminary reaction temperature T4 and maintained for a fourth predetermined time t4, thereby causing a preliminary synthesis reaction between the carbon and silicon raw materials;

[0014] The temperature of the furnace chamber is raised to a conversion reaction temperature T5 and maintained for a fifth predetermined time t5, thereby causing a conversion synthesis reaction between the carbon and silicon raw materials;

[0015] and cooling the furnace chamber.

[0016] A method for synthesizing large-volume silicon carbide powder is provided.

[0017] In an alternative embodiment, prior to the step of charging the carbon and silicon raw materials in a predetermined ratio into a plurality of reaction crucibles, the synthesis method further comprises:

[0018] The method further comprises laying a layer of PVC particles on the bottom of the plurality of reaction crucibles.

[0019] In an alternative embodiment, the steps of heating the furnace chamber to a first impurity removal temperature T1, maintaining the temperature for a first predetermined time t1, injecting a rare gas into the furnace chamber, and then evacuating the furnace chamber include:

[0020] the temperature of the furnace chamber is raised to 100 to 500°C and maintained at that temperature for 1 to 5 hours, thereby decomposing and generating primary decomposition products and primary decomposition gases in the PVC particle layer;

[0021] Injecting argon gas into the furnace chamber to a pressure of 500 to 700 torr and maintaining the pressure therein for 10 to 30 minutes;

[0022] The furnace chamber is evacuated to at least e-4pa, and impurity gases are attached and discharged using the primary decomposition gas.

[0023] In an alternative embodiment, the steps of heating the furnace chamber to a second impurity removal temperature T2, maintaining the temperature for a second predetermined time t2, injecting a rare gas into the furnace chamber, and then evacuating the furnace chamber include:

[0024] The temperature of the furnace chamber is raised to 500 to 900°C and maintained at this temperature for 10 to 15 hours, thereby decomposing the primary decomposition products into secondary decomposition products and secondary decomposition gases.

[0025] Injecting argon gas into the furnace chamber to a pressure of 100 to 500 torr and maintaining the pressure therein for 10 to 30 minutes;

[0026] The furnace chamber is evacuated to at least e-4pa, and impurity gases are attached and discharged using the secondary decomposition gas.

[0027] In an alternative embodiment, the steps of heating the furnace chamber to a third impurity removal temperature T3, maintaining the temperature for a third predetermined time t3, injecting a rare gas into the furnace chamber, and then evacuating the furnace chamber include:

[0028] The temperature of the furnace chamber is increased to 1200 to 1400°C and maintained at this temperature for 5 to 10 hours, thereby decomposing the secondary decomposition products to generate tertiary decomposition products and tertiary decomposition gases.

[0029] Injecting argon gas into the furnace chamber to a pressure of 20 to 100 torr and maintaining the pressure therein for 10 to 30 minutes;

[0030] The furnace chamber is evacuated to at least e-4pa, and impurity gases are attached and discharged using the tertiary decomposition gas;

[0031] Here, the tertiary decomposition product is carbon, and the tertiary decomposition gas is hydrogen gas and chlorine gas.

[0032] In an alternative embodiment, prior to the step of stacking and placing a plurality of reaction crucibles in a containing crucible, the synthesis method further comprises:

[0033] The method further includes uniformly and flatly attaching a multi-layer graphite sheet to the bottoms of the plurality of reaction crucibles.

[0034] In an alternative embodiment, before the steps of raising the temperature of the furnace chamber to a first impurity removal temperature T1, maintaining the temperature for a first predetermined time t1, injecting a rare gas into the furnace chamber, and then evacuating the furnace chamber, the synthesis method includes:

[0035] adjusting the temperature field so that the axial gradient of the upper temperature section of the temperature field is 100 to 200°C and the axial gradient of the lower temperature section of the temperature field is 30 to 80°C;

[0036] and adjusting the relative position of the receiving crucible in the temperature field so that the receiving crucible is in the upper temperature zone.

[0037] In an alternative embodiment, the step of raising the furnace chamber temperature to a conversion reaction temperature T5 and maintaining the temperature for a fifth predetermined time t5 comprises:

[0038] adjusting the relative position of the receiving crucible in the temperature field so that the receiving crucible is in the lower temperature zone;

[0039] The temperature of the furnace chamber is raised to 2100 to 2200°C to carry out the conversion synthesis reaction, and the conversion synthesis time lasts for 15 to 30 hours.

[0040] In an alternative embodiment, the step of raising the temperature of the furnace chamber to a pre-reaction temperature T4 and maintaining the temperature for a fourth predetermined time t4 includes:

[0041] The furnace chamber is heated to 1800 to 1900°C to carry out a pre-synthesis reaction, and the pre-synthesis time lasts for 4 to 6 hours.

[0042] According to a second aspect, the present invention provides silicon carbide powder produced using the method for synthesizing large volume silicon carbide powder according to any one of the preceding embodiments.

[0043] Beneficial effects of embodiments of the present invention include, for example:

[0044] In the actual production of the large-volume silicon carbide powder synthesis method and silicon carbide powder provided by the embodiments of the present invention, first, carbon and silicon raw materials are filled into a plurality of reaction crucibles in a predetermined ratio, and then the plurality of reaction crucibles are stacked in a containing crucible, and the containing crucible is placed in a furnace chamber, and then a layer of PVC particles is laid on the bottom of the containing crucible, and then the furnace chamber is purged and evacuated to remove the air inside the furnace chamber. In the heating stage, first, the furnace chamber is heated to a first impurity removal temperature T1, rare gas is injected into the furnace chamber, and a vacuum is drawn. The primary decomposition gas of the PVC particle layer is used to remove the pure gas in the furnace chamber and the material to achieve primary impurity removal. Next, the furnace chamber is heated to a second impurity removal temperature T2, and the secondary decomposition gas generated by the continuous decomposition is used to continuously remove the impurity gas to achieve secondary impurity removal. Finally, the furnace chamber is heated to a third impurity removal temperature T4, and the tertiary decomposition gas is used to achieve tertiary impurity removal. After the impurity removal is completed, the furnace chamber is heated sequentially to a pre-reaction temperature T4, whereby the carbon and silicon raw materials are pre-synthesized and reacted. Next, the furnace chamber is heated to a conversion reaction temperature T5, whereby the carbon and silicon raw materials are converted and reacted to produce silicon carbide powder. Finally, the furnace chamber is cooled, and the silicon carbide powder is removed. Compared with the prior art, one aspect of the present invention is to use stacked reaction crucibles to achieve dispersed placement of raw materials, which reduces raw material accumulation and delays carbonization and crystallization, enabling the production of large-volume powder and improving yield. Another aspect is to use gaseous substances generated by PVC particles in different temperature ranges to achieve multiple impurity removal at different temperature intervals, greatly improving the impurity removal effect and effectively improving powder purity. [Brief explanation of the drawings]

[0045] In order to more clearly explain the technical solutions of the embodiments of the present invention, the drawings that need to be used in the embodiments will be briefly described below. However, the following drawings only illustrate some embodiments of the present invention, and therefore should not be considered as limiting the scope. It should be understood that those skilled in the art can obtain other related drawings according to these drawings without requiring creative efforts. [Figure 1]1 is a block diagram of the steps of the method for synthesizing high-capacity silicon carbide powder provided by the present invention. [Figure 2] 1 is a schematic diagram of the equipment for the method for synthesizing large-volume silicon carbide powder provided by the present invention. [Figure 3] FIG. 1 is a test verification diagram of the synthesis method for large-capacity silicon carbide powder provided by the present invention. [Figure 4] FIG. 3 is a locally enlarged view of IV in FIG. 2. [Figure 5] 1 is a morphology diagram of a silicon carbide powder provided by the present invention from a first perspective. FIG. [Figure 6] FIG. 2 is a morphology diagram of the silicon carbide powder provided by the present invention from a second perspective. [Figure 7] 1 is a microscopic morphology diagram of the silicon carbide powder provided by the present invention.

[0046] Symbols on the drawing: 100 - receiving crucible, 200 - reaction crucible, 300 - carbon and silicon raw materials, 400 - PVC particle layer, 500 - volatile solution layer, 510 - adhesive layer. DETAILED DESCRIPTION OF THE INVENTION

[0047] In order to make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions of the embodiments of the present invention in conjunction with the drawings of the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, and not all embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings in this specification can be arranged and designed in a variety of different configurations.

[0048] Therefore, the following detailed description of the embodiments of the present invention, provided by the drawings, is not intended to limit the scope of the claimed invention, but represents only selected embodiments of the present invention. All other embodiments that can be obtained by those skilled in the art based on the embodiments of the present invention without requiring creative effort are included in the scope of the claims of the present invention.

[0049] It should be noted that like symbols and letters indicate like items in the following drawings, so that once an item is defined in one drawing, it need not be further defined or explained in subsequent drawings.

[0050] In describing the present invention, it should be explained that terms such as "upper," "lower," "inner," "outer," etc., when the indicated orientation or positional relationship is the orientation or positional relationship shown in the drawings or the orientation or positional relationship in which the product of the invention is customarily disposed when used, are intended to facilitate and simplify the description of the present invention, and are not intended to indicate or imply that the referred device or element must have a particular orientation, be configured, or operate in a particular orientation, and therefore should not be understood as a limitation of the present invention.

[0051] Additionally, when terms such as "first," "second," etc. appear, they are used for descriptive purposes only and are not to be understood as indicating or implying relative importance.

[0052] As disclosed in the background art, the synthesis methods of silicon carbide powder in the prior art usually have the following drawbacks:

[0053] 1. The raw materials are usually mixed directly and added to a large crucible. If the amount of carbon and silicon raw materials is too large, high temperatures are required to fully synthesize the internal raw materials, which will cause carbonization and volatilization at the outer edge of the powder. In addition, the traditional synthesis of large-volume powder will cause accumulation, resulting in incomplete synthesis inside the powder, making it difficult to synthesize large-volume silicon carbide powder using this method.

[0054] 2. Since the carbon and silicon raw materials are both in a large crucible, the loss is relatively large, the accumulation effect is obvious, and the yield is relatively low.

[0055] 3. In the conventional method for producing silicon carbide powder, impurities are removed at high temperatures during the impurity removal process, which results in a relatively low impurity removal effect, resulting in low purity of the synthesized powder, and high-temperature impurity removal costs.

[0056] 4. Conventional impurity removal methods usually require direct introduction of process gases such as hydrogen gas and chlorine gas. Hydrogen gas and chlorine gas have high risk factors, making them inconvenient to store. In addition, introducing them into the furnace body increases equipment and maintenance costs.

[0057] In order to solve the above problems, the present invention provides a novel method for synthesizing large-capacity silicon carbide powder and silicon carbide powder. It should be noted that, unless contradictory, the features in the embodiments of the present invention can be combined with each other.

[0058] Specific Examples

[0059] 1 and 2, this embodiment provides a novel method for synthesizing large-volume silicon carbide powder to produce high-purity silicon carbide powder. This method can reduce the amount of carbonization during the synthesis process, effectively improving the yield, and can also effectively exchange gases and remove impurities from the raw materials, effectively improving the purity of the powder. Furthermore, the dispersion equipment can be easily used.

[0060] By filling, no accumulation occurs due to stacking of crucibles, synthesis is complete, and carbonization and volatilization are relatively small, which improves both the capacity and yield, reduces the accumulation of raw materials, delays the carbonization and crystallization phenomena, and realizes the production of large-volume powder.In addition, there is no need to add process gases such as hydrogen gas or chlorine gas, which ensures the safety and reliability of the synthesis process, and the equipment structure is simple and the cost is low.

[0061] The synthesis method for large-capacity silicon carbide powder provided by this example includes the following steps:

[0062] S1: Carbon and silicon raw materials 300 are filled into a plurality of reaction crucibles 200 in a predetermined ratio.

[0063] Specifically, the carbon and silicon raw materials 300 can be filled into the reaction crucible 200 in a molar ratio of 1:1 to 1.1. During the filling process, the raw materials can fill 2 / 5 to 4 / 5 of the reaction crucible 200, preferably 2 / 3 of the reaction crucible 200, to ensure the effectiveness of the synthesis reaction and leave enough space for the impurity removal airflow in the subsequent impurity removal process.

[0064] It should be noted that the reaction crucible 200 in this embodiment has a secondary sealing structure, and the secondary sealing part is located at the top of the reaction crucible 200, that is, the crucible lid of the reaction crucible 200 is sealed to the body, and an impurity removal hole is opened on the crucible lid, which makes it convenient to remove impurities later.

[0065] In this embodiment, before the raw materials are filled, a PVC particle layer 400 can be laid on the bottom of the reaction crucibles 200. The PVC particle layer 400 is made of high-purity fine powder, has a thickness of 10-50 mm, preferably 20 mm, and has a high-purity PVC impurity content of <5 ppm.

[0066] 2 and 4, specifically, before the reaction crucible 200 is placed in the receiving crucible 100, a volatile solution can be applied to the bottom wall of the receiving crucible 100. The volatile solution can include an alcohol-based solution or an ether-based solution, and the concentration of the volatile solution can be relatively high. Preferably, the volatile solution can be relatively concentrated. That is, the volatile solution is preferably applied in a semi-fluid state to form a volatile solution layer 500, which can achieve a better fixing effect when applied to the bottom wall of the receiving crucible 100.

[0067] It should be noted that the volatile solution herein refers to a solution that is thermally volatile, i.e., that volatilizes the corresponding gas under heating, and the amount of evaporation during the coating process and in the non-heated state is relatively negligible. Furthermore, in this embodiment, the volatile solution is applied to the bottom of the containing crucible 100, so that the volatile gas can quickly carry away the impurity gases in the containing crucible 100, accelerating the discharge of the impurity gases in the reaction crucible 200. Unlike the conventional method of adding a volatile material to the raw material mixture, the volatile solution in this embodiment does not occupy the internal volume of the reaction crucible 200 and does not directly come into contact with and react with the raw material mixture, further ensuring the production efficiency and purity.

[0068] Of course, it is also possible to remove impurities at low temperatures only by changing the temperature and air pressure, without applying a volatile solution to the bottom wall of the containing crucible 100 .

[0069] Furthermore, to prevent the volatile solution from flowing or displacing along the wall surface during the application process, an adhesive layer 510 with a relatively low melting point, such as an epoxy resin adhesive layer, can be applied again to the surface of the volatile solution after the application of the volatile solution layer. In one aspect, this can protect and fix the volatile solution, and in another aspect, it can prevent the volatile solution from volatilizing in large quantities before reaching the low-temperature impurity removal temperature. Furthermore, the adhesive layer 510 may be decomposed during the subsequent low-temperature impurity removal process by heating, reducing the impact.

[0070] S2: A plurality of reaction crucibles 200 are stacked and placed in the containing crucible 100, and the containing crucible 100 is placed in the furnace chamber.

[0071] Specifically, multiple reaction crucibles 200 can be placed in the containing crucible 100 so as to be stacked vertically. Specifically, the bottommost reaction crucible 200 is placed first, and then another layer of reaction crucibles 200 is placed on top of the bottommost reaction crucible 200, and so on until the entire containing crucible 100 is filled. The horizontal distribution of each layer of reaction crucibles 200 is not specifically limited here.

[0072] It should be noted that the reaction crucibles 200 may be placed inside the containing crucible 100 at intervals, and multiple layers of graphite sheets may be attached evenly and flatly to the bottoms of the reaction crucibles 200. Specifically, by attaching 5 to 8 layers of graphite sheets evenly and flatly to the bottoms of the outer layers of each reaction crucible 200, the volatile materials below may volatilize directly and be adsorbed on the bottom walls of the reaction crucibles 200, preventing the adjacent two layers of reaction crucibles 200 from adhering to each other. This makes it easier to remove the reaction crucibles 200 and prevents damage to the body of the reaction crucible 200 when removing the reaction crucibles 200. Here, the volatile materials below each reaction crucible 200 may come from the inside of the next layer of reaction crucible 200 or from the bottom wall of the containing crucible 100.

[0073] S3: A layer of PVC particles 400 is laid on the bottom of the containing crucible.

[0074] Specifically, after the reaction crucible 200 is placed in the receiving crucible 100, a PVC particle layer 400 can be laid on the bottom of the receiving crucible 100. The PVC particle layer 400 is laid around the reaction crucible 200 located at the bottom, and the PVC particle layer 400 is made of high-purity fine powder, has a thickness of 10-50 mm, preferably 20 mm, and has a high-purity PVC impurity content of <5 ppm.

[0075] S4: The furnace chamber is evacuated and evacuated.

[0076] Specifically, the furnace chamber is evacuated to at least 800 Pa, then argon gas is injected into the furnace chamber to a pressure of 500 to 700 torr, and this is held for 10 to 30 minutes. The furnace chamber is then evacuated to at least 800 Pa, and this process is repeated two to three times. This allows the gas inside the furnace chamber to be removed by replacement and evacuation.

[0077] S5: The furnace chamber is heated to a first impurity removal temperature T1, maintained for a first predetermined time t1, and a rare gas is injected into the furnace chamber, followed by evacuation.

[0078] Specifically, the first impurity removal temperature T1 may be 100-500°C, preferably 300°C. In actual Step S5, the furnace chamber is first heated to 100-500°C and maintained at this temperature for 1-5 hours. At this temperature, the PVC particle layer 400 undergoes pre-decomposition, producing primary decomposition products and primary decomposition gases. The primary decomposition products are primarily residual PVC, ethylene chloride, and some carbon tetrachloride and ethylene dichloride. The primary decomposition gases are primarily hydrogen chloride and other gases. Next, argon gas is further injected into the furnace chamber to a pressure of 500-700 torr and maintained for 10-30 minutes. This step ensures that the primary decomposition gases sufficiently contact and adhere to impurity gases such as HO, N2, O2, CO2, and CO present in the raw material or the furnace chamber. Finally, the furnace chamber is evacuated to at least 1-4 Pa, allowing the primary decomposition gases to adhere and be expelled, completing the primary impurity removal process.

[0079] At the same time, the volatile solution at the bottom of the receiving crucible 100 is in a completely volatilized state, and a large amount of volatile gas can be generated, which can adsorb the impurities in the reaction crucible 200 through the impurity removal holes, and at the same time, the volatile gas adsorbs the impurities in the receiving crucible and is extracted together with the vacuum operation, which can further realize the auxiliary removal of impurities.

[0080] It should be noted that before performing step S5, the temperature field can also be adjusted. Specifically, the temperature field is first adjusted so that the axial gradient of the upper temperature zone of the temperature field is 100-200°C and the axial gradient of the lower temperature zone is 30-80°C. Next, the relative position of the receiving crucible 100 in the temperature field is adjusted so that the receiving crucible 100 is in the upper temperature zone when the temperature is below 1800°C and then moves to the lower temperature zone after the temperature is raised to above 1800°C. By first placing the receiving crucible 100 in the upper temperature zone, carbonization of a large amount of raw material can be prevented during the subsequent high-temperature heating process, thereby improving the yield of powder synthesis.

[0081] S6: The furnace chamber is heated to a second impurity removal temperature T2, maintained for a second predetermined time t2, and a rare gas is injected into the furnace chamber, followed by evacuation.

[0082] Specifically, the second impurity removal temperature T2 may be 500-900°C, preferably 600°C. When actually performing step S6, the furnace chamber is first heated to 500-900°C and maintained at this temperature for 10-15 hours. At this temperature, the primary decomposition products, such as PVC, remaining in step S5 continue to decompose, producing secondary decomposition products and secondary decomposition gases. The secondary decomposition products are primarily the remaining PVC and some ethylene dichloride, carbon tetrachloride, and benzene-based substances, while the secondary decomposition gases are primarily hydrogen chloride, monochloromethane, dichloromethane, and other gases. Next, argon gas is further injected into the furnace chamber to a pressure of 100-500 torr and maintained for 10-30 minutes. This step ensures that the secondary decomposition gases fully contact and adhere to impurity gases, such as HO, N, O, CO, CO, and other gases in the raw material or the furnace chamber, and impurities, such as Pb, P, and Na, in the raw material. Finally, the furnace chamber is evacuated to at least e-4pa, and the secondary decomposition gas is used to attach and discharge impurities and other gases, completing the secondary impurity removal.

[0083] S7: The furnace chamber is heated to a third impurity removal temperature T3, maintained for a third predetermined time t3, and a rare gas is injected into the furnace chamber, followed by evacuation.

[0084] Specifically, the third impurity removal temperature T3 may be 1200-1400°C, preferably 1300°C. When actually performing step S7, the furnace chamber is first heated to 1200-1400°C and maintained for 5-10 hours. At this temperature, the secondary decomposition products remaining in step S6 are thoroughly decomposed, producing tertiary decomposition products and tertiary decomposition gases, of which the tertiary decomposition products are carbon and the tertiary decomposition gases are hydrogen and chlorine gases. Next, argon gas is further injected into the furnace chamber to a pressure of 20-100 torr and maintained for 10-30 minutes. This step ensures that the tertiary decomposition gases sufficiently contact and adhere to impurity gases such as HO, N2, O2, CO2, and CO in the raw material or the furnace chamber, as well as impurities such as Pb, P, and Na in the raw material. Finally, the furnace chamber is evacuated to at least e-4 Pa, and the tertiary decomposition gases are used to adhere and remove the impurity gases and impurities, completing the tertiary impurity removal process.

[0085] It should be noted that hydrogen gas can remove large amounts of residual nitrogen gas, while chlorine gas has strong oxidizing properties and can react with most metal impurities under heating conditions. For example, Au and Pt burn in high-temperature chlorine gas, while reacting with other valence metals such as Fe and Cu to produce high-valence metal chlorides. The chlorides are volatilized and discharged at high temperatures, thereby achieving impurity removal and purification of metal impurities and further ensuring the purity of the raw materials. Meanwhile, the tertiary decomposition product C accumulates at the bottom of the containing crucible 100 or reaction crucible 200, preventing corrosion of the crucible bottom by silicon and reacting to produce silicon carbide, thereby improving yield.

[0086] It should be noted that in the prior art, the removal of impurities usually requires the introduction of hydrogen gas as the process gas, which is a gas with a relatively high hazard coefficient under normal conditions, posing certain risks in storage and transportation, and the installation of additional input piping increases equipment and maintenance costs. Unlike the prior art, the PVC granular material in this embodiment is easy to store and is non-hazardous under normal conditions, and the impurity removal process in this embodiment does not require the introduction of additional hydrogen gas and chlorine gas, and does not require related process gas storage and transportation equipment, saving costs and achieving a higher safety coefficient.

[0087] The relationship between the pressure and temperature in the furnace chamber during an actual raw material synthesis heating process is shown in Figure 3. Tests have shown that the impurity removal effect is best at temperatures below 1000°C, while in conventional technologies, impurity removal is typically only performed at high temperatures (i.e., impurity removal and gas exchange are typically only performed at temperatures above 1200°C). In contrast, in this application, by utilizing impurity removal and gas exchange primarily consisting of low-temperature primary impurity removal (100-500°C), low-temperature secondary impurity removal (500-900°C), and high-temperature tertiary impurity removal and gas exchange (1200-1400°C), an impurity removal effect not achievable in conventional technologies can be achieved.

[0088] S8: The furnace chamber is heated to a preliminary reaction temperature T4 and maintained for a fourth predetermined time t4, thereby causing a preliminary synthesis reaction between the carbon and silicon raw materials.

[0089] Specifically, step S8 is performed to perform a pre-synthesis reaction between carbon and silicon raw materials 300. Specifically, the furnace chamber is heated to 1800 to 1900°C to perform the pre-synthesis reaction, and the pre-synthesis time lasts 4 to 6 hours. Specifically, step S8 can be performed immediately after step S7, and the synthesis reaction can be performed after the impurity removal is completed. Here, to achieve the pre-synthesis reaction, the furnace chamber is first heated to a relatively low pre-reaction temperature T4, and the synthesis time lasts 4 to 6 hours.

[0090] S9: The temperature of the furnace chamber is raised to the conversion reaction temperature T5 and maintained for a fifth predetermined time t5.

[0091] Specifically, by performing step S9, the carbon and silicon raw materials 300 can be subjected to a conversion synthesis reaction. First, the relative position of the crucible 100 in the temperature field can be adjusted so that the crucible 100 is in the lower temperature zone. Next, the furnace chamber is heated to 2100-2200°C to perform the conversion synthesis reaction, which lasts for 15-30 hours. By adjusting the crucible 100 to the lower temperature zone, the temperature gradient is made smaller, and the temperature of the conversion synthesis reaction can more easily reach the reaction temperature.

[0092] S10: Cool the furnace chamber.

[0093] Specifically, the heating power of the furnace chamber is gradually reduced to zero within 1 to 2 hours, and then the furnace chamber is naturally cooled to the furnace disassembly temperature. Through natural cooling, the structural stress between the reaction crucibles 200 can be eliminated, thereby facilitating the disassembly of the reaction crucibles 200 of different layers.

[0094] Referring also to Figures 5-7, this example further provides silicon carbide powder having relatively high purity and excellent powder quality, produced using the aforementioned synthesis method for large-volume silicon carbide powder. Specifically, Figures 5 and 6 are photographs showing the morphology of high-purity silicon carbide produced using the aforementioned synthesis method. As shown in the figures, its purity is very high and its N content is very low, allowing the synthesized silicon carbide to achieve excellent semi-insulating properties. In particular, measurements have shown that the silicon carbide powder provided in this example has a purity of ≥99.99977%, which is excellent. Figure 7 shows a microscope image of high-purity silicon carbide produced using the aforementioned synthesis method, showing that its crystalline form is 4H.

[0095] As can be seen from the above, in the actual production of the large-volume silicon carbide powder synthesis method and silicon carbide powder provided by this embodiment, first, a PVC particle layer 400 is laid on the bottom of the reaction crucible 200, carbon and silicon raw materials 300 are filled into a plurality of reaction crucibles 200 in a predetermined ratio, and then a plurality of reaction crucibles 200 are stacked inside the containing crucible 100, and the containing crucible 100 is placed in a furnace chamber, and then another PVC particle layer 400 is laid on the bottom of the containing crucible 100, and then the furnace chamber is purged and evacuated to remove the air inside the furnace chamber. In the heating stage, first, the furnace chamber is heated to a first impurity removal temperature T1, a rare gas is injected into the furnace chamber, a vacuum is drawn, and the primary decomposition gas of the PVC particle layer 400 is used to remove a large amount of impurity gas in the furnace chamber and the material, thereby achieving primary impurity removal at a low temperature. Next, the furnace chamber is heated to a second impurity removal temperature T2, and the secondary decomposition gas generated by the continuous decomposition is used to continuously remove the impurity gas, thereby achieving secondary impurity removal at a low temperature and continuously removing the impurities. Finally, the furnace chamber is heated to a third impurity removal temperature, and the tertiary decomposition gas is used to achieve tertiary impurity removal at a high temperature. After the impurity removal is completed, the furnace chamber is heated to a pre-reaction temperature T4 to cause a pre-synthesis reaction between the carbon and silicon raw materials. Next, the furnace chamber is heated to a conversion reaction temperature T5 to cause a conversion synthesis reaction between the carbon and silicon raw materials to produce silicon carbide powder. Finally, the furnace chamber is cooled, and the silicon carbide powder is removed. Compared with the prior art, one aspect of the present invention is that the stacked reaction crucibles allow the raw materials to be dispersed, and dispersed loading reduces the accumulation of raw materials, delays carbonization and crystallization, realizes the production of large quantities of powder, and improves yield. Another aspect is that the gaseous substances generated by the decomposition of the PVC particle layer 400 at different temperature ranges achieve primary impurity removal at low temperature, secondary impurity removal at low temperature, and tertiary impurity removal at high temperature, which greatly improves the impurity removal effect and effectively improves the purity of the powder.

[0096] The above are merely specific embodiments of the present invention, but the scope of the claims of the present invention is not limited thereto, and any modifications or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present invention are included in the scope of the claims of the present invention. Therefore, the scope of the claims of the present invention shall be subject to the protection scope of the claims described.

Claims

1. 1. A method for synthesizing high-capacity silicon carbide powder, comprising: A plurality of reaction crucibles are filled with carbon and silicon raw materials at a predetermined ratio, and an impurity removal hole is opened at the top of each of the reaction crucibles; Stacking a plurality of the reaction crucibles in a container crucible and placing the container crucible in a furnace chamber; Laying a PVC particle layer on the bottom of the containing crucible; performing a purging and evacuation operation on the furnace chamber; the furnace chamber is heated to a first impurity removal temperature T1, maintained for a first predetermined time t1, a rare gas is injected into the furnace chamber, and then the furnace chamber is evacuated to decompose the primary decomposition products and primary decomposition gases generated by the PVC particle layer, and the primary impurity removal is achieved by using the primary decomposition gases; the furnace chamber is heated to a second impurity removal temperature T2, maintained for a second predetermined time t2, a rare gas is injected into the furnace chamber, and then the furnace chamber is evacuated to decompose secondary decomposition products and secondary decomposition gases generated by the primary decomposition products, and secondary impurity removal is achieved using the secondary decomposition gases; the furnace chamber is heated to a third impurity removal temperature T3, maintained for a third predetermined time t3, a rare gas is injected into the furnace chamber, and then the furnace chamber is evacuated to decompose the tertiary decomposition products and tertiary decomposition gases generated by the secondary decomposition products, and the tertiary impurity removal is achieved by using the tertiary decomposition gases; raising the temperature of the furnace chamber to a preliminary reaction temperature T4 and maintaining the temperature for a fourth predetermined time t4 to cause a preliminary synthesis reaction between the carbon and silicon raw materials; The temperature of the furnace chamber is raised to a conversion reaction temperature T5, and maintained for a fifth predetermined time t5, thereby causing a conversion synthesis reaction between the carbon and silicon raw materials; and cooling the furnace chamber; wherein the first impurity removal temperature T1 is 100 to 500°C, the first predetermined time t1 is 1 to 5 hours, the second impurity removal temperature T2 is 500 to 900°C, the second predetermined time t2 is 10 to 15 hours, the third impurity removal temperature T3 is 1200 to 1400°C, the third predetermined time t3 is 5 to 10 hours, the preliminary reaction temperature T4 is 1800 to 1900°C, the fourth predetermined time t4 is 4 to 6 hours, the conversion reaction temperature T5 is 2100 to 2200°C, and the fifth predetermined time t5 is 15 to 30 hours. A method characterized by:

2. Before the step of charging the carbon and silicon raw materials into a plurality of reaction crucibles in a predetermined ratio, the synthesis method includes: Further comprising laying a PVC particle layer on the bottom of the plurality of reaction crucibles. The method for synthesizing large-capacity silicon carbide powder according to claim 1 .

3. the step of raising the temperature of the furnace chamber to a first impurity removal temperature T1, maintaining the temperature for a first predetermined time t1, injecting a rare gas into the furnace chamber, and then evacuating the furnace chamber, the temperature of the furnace chamber is raised to 100 to 500°C and maintained at that temperature for 1 to 5 hours, thereby decomposing and generating primary decomposition products and primary decomposition gases in the PVC particle layer; Injecting argon gas into the furnace chamber to a pressure of 500 to 700 torr and maintaining the pressure for 10 to 30 minutes; The furnace chamber is evacuated to at least 1E-4 Pa, and impurity gases are attached and discharged using the primary decomposition gas. The method for synthesizing large-capacity silicon carbide powder according to claim 1 .

4. the step of raising the temperature of the furnace chamber to a second impurity removal temperature T2, maintaining the temperature for a second predetermined time t2, injecting a rare gas into the furnace chamber, and then evacuating the furnace chamber, The temperature of the furnace chamber is raised to 500 to 900°C and maintained at this temperature for 10 to 15 hours, thereby decomposing the primary decomposition products into secondary decomposition products and secondary decomposition gases. Injecting argon gas into the furnace chamber to a pressure of 100 to 500 torr and maintaining the pressure therein for 10 to 30 minutes; The furnace chamber is evacuated to at least 1E-4 Pa, and impurity gases are attached and discharged using the secondary decomposition gas. The method for synthesizing large-capacity silicon carbide powder according to claim 1 .

5. the step of raising the temperature of the furnace chamber to a third impurity removal temperature T3, maintaining the temperature for a third predetermined time t3, injecting a rare gas into the furnace chamber, and then evacuating the furnace chamber, The furnace chamber is heated to 1200 to 1400 ° C. and maintained at this temperature for 5 to 10 hours to decompose the secondary decomposition products to generate tertiary decomposition products and tertiary decomposition gases; Injecting argon gas into the furnace chamber to a pressure of 20 to 100 torr and maintaining the pressure for 10 to 30 minutes; The furnace chamber is evacuated to a vacuum of at least 1E-4 Pa, and impurity gases are attached and discharged using the tertiary decomposition gas; wherein the tertiary decomposition product is carbon, and the tertiary decomposition gas is hydrogen gas and chlorine gas; The method for synthesizing large-capacity silicon carbide powder according to claim 1 .

6. Before the step of stacking and placing the plurality of reaction crucibles in the containing crucible, the synthesis method includes: The method further comprises uniformly and flatly attaching a multi-layer graphite sheet to the bottoms of the plurality of reaction crucibles. The method for synthesizing large-capacity silicon carbide powder according to claim 1 .

7. The synthesis method includes the steps of: heating the furnace chamber to a first impurity removal temperature T1, maintaining the temperature for a first predetermined time t1, injecting a rare gas into the furnace chamber, and then evacuating the furnace chamber. adjusting the temperature field such that the axial gradient of the upper temperature zone of the temperature field is 100-200°C and the axial gradient of the lower temperature zone of the temperature field is 30-80°C; adjusting the relative position of the containing crucible in the temperature field so that the containing crucible is in the upper temperature zone; The method for synthesizing large-capacity silicon carbide powder according to claim 1 .

8. The step of heating the furnace chamber to a conversion reaction temperature T5 and maintaining the temperature for a fifth predetermined time t5 includes: adjusting the relative position of the receiving crucible in the temperature field so that the receiving crucible is in the lower temperature zone; The furnace chamber is heated to 2100 to 2200 ° C. to carry out a conversion synthesis reaction, and the conversion synthesis time lasts for 15 to 30 hours. The method for synthesizing large-capacity silicon carbide powder according to claim 7,

Images