Silicon carbide powder, preparation method thereof and silicon carbide product

Abstract

The invention provides silicon carbide powder, a preparation method thereof and a silicon carbide product. The preparation method comprises the following steps that a silicon source and a carbon source are put into a reaction container, the silicon source and the carbon source are separated, and the carbon source is located above the silicon source; carrying out degassing purification treatment on the reaction container; the method comprises the following steps: heating a silicon source to 1500-1800 DEG C in a sealed and protective atmosphere to form silicon steam; contacting the silicon steam with a carbon source, and reacting at 2000-2200 DEG C for 10-50 hours; and cooling to prepare the silicon carbide powder. The preparation method of the silicon carbide powder has the advantages of high product purity, high powder yield and the like.

Description

Technical Field

[0001] This application relates to the field of silicon carbide synthesis technology, and in particular to silicon carbide powder and its preparation method, and silicon carbide products. Background Technology

[0002] Silicon carbide (SiC), as a core material for third-generation semiconductors, possesses excellent properties such as a wide bandgap, high thermal conductivity, and high breakdown field strength, making it widely used in high-temperature, high-frequency, and high-power electronic devices. High-purity semi-insulating silicon carbide single-crystal substrates are the cornerstone for fabricating these devices. The high resistivity of these devices primarily depends on the high purity of silicon carbide (extremely low content of impurities such as N, B, Al, and V) and effective intrinsic defect compensation. The growth of high-quality silicon carbide single crystals is directly limited by the performance of the high-purity semi-insulating silicon carbide powder, thus typically requiring it to meet the following conditions: ultra-high chemical purity (key impurities at the ppb / ppt level), excellent intrinsic semi-insulating properties (high resistivity), and good physical properties (high α-phase content, low oxygen content).

[0003] Traditional methods for synthesizing silicon carbide powder include self-propagation high-temperature synthesis (SHS), the Acheson method, chemical vapor deposition (CVD), the sol-gel method, and the polymer precursor method. While SHS and the Acheson method offer high yields and low costs, they are prone to introducing impurities such as nitrogen (N) into the raw materials and reaction process, resulting in insufficient product purity, the presence of β-phase, and high oxygen content, making it difficult to meet the resistivity requirements of high-end semi-insulating substrates. Although CVD can produce high-purity silicon carbide powder, its complex equipment, slow deposition rate, and extremely high energy consumption and cost severely limit its industrial application. The sol-gel method and the polymer precursor method also face challenges such as impurity residues and phase composition control.

[0004] Therefore, the traditional methods for synthesizing silicon carbide powder still need further improvement. Summary of the Invention

[0005] Based on this, one or more embodiments of this application provide a silicon carbide powder with high purity and high yield, a method for preparing the same, and silicon carbide products.

[0006] According to a first aspect of the embodiments of this application, a method for preparing silicon carbide powder is provided, comprising the following steps:

[0007] A silicon source and a carbon source are placed in a reaction vessel, and the silicon source is separated from the carbon source, with the carbon source positioned above the silicon source.

[0008] The reaction vessel was degassed and purified.

[0009] Under sealed and protective atmosphere conditions, the silicon source is heated to 1500℃~1800℃ to form silicon vapor; the silicon vapor is then brought into contact with the carbon source and reacted at 2000℃~2200℃ for 10h~50h; after cooling, silicon carbide powder is prepared.

[0010] In some embodiments, the degassing and purification process includes a first purification process and a second purification process performed sequentially;

[0011] The first purification process includes the following steps: evacuating the reaction vessel to a vacuum of 1×10⁻⁶. -4 Pa ~ 1×10 - 6 Pa, maintain for 1-2 hours;

[0012] The second purification process includes the following steps: charging the reaction vessel with a protective gas until the furnace pressure is 1×10⁻⁶. 3 Pa~5×10 3 Pa, maintain for 1-2 hours; evacuate the reaction vessel to 1×10⁻⁶ Pa. -4 Pa ~ 1×10 -6 Pa.

[0013] In some embodiments, the second purification process is performed 2 to 5 times; and / or,

[0014] The protective gas includes argon and hydrogen, and the volume ratio of argon to hydrogen is (8~12):1.

[0015] In some embodiments, the degassing and purification process is carried out at a temperature of 500°C to 900°C; and / or,

[0016] The purity of the silicon source is 99999%~99999999%; and / or,

[0017] The purity of the carbon source is ≥9999%; and / or,

[0018] The carbon source is selected from one or more of coarse graphite rods and porous graphite rods.

[0019] In some embodiments, the surface roughness Ra of the rough graphite rod is 150 μm to 500 μm; and / or,

[0020] The porosity of the porous graphite rod is 25%~45%.

[0021] In some embodiments, the reaction vessel includes a first crucible and a second crucible, the reaction chambers of the first crucible and the second crucible are interconnected, and the first crucible and the second crucible are sealed together.

[0022] The silicon source is placed in the first crucible, and the carbon source is placed in the second crucible.

[0023] In some embodiments, the second crucible includes a fixing component for fixing the carbon source.

[0024] In some embodiments, the carbon source is rod-shaped, and the carbon source is fixed in the second crucible with its axis parallel to the direction of gravity, and the pore size of the carbon source gradually increases from bottom to top.

[0025] According to a second aspect of the present application, a silicon carbide powder is provided, which is prepared by the above-described method for preparing silicon carbide powder.

[0026] According to a third aspect of the embodiments of this application, a silicon carbide article is provided, comprising the silicon carbide powder described above.

[0027] Compared with traditional technologies, this application has the following advantages:

[0028] In the preparation method of this application, the silicon source is fully vaporized under specific temperature conditions to form silicon vapor, which reacts with the carbon source under specific temperature conditions, enabling rapid and efficient synthesis of silicon carbide powder with low impurity content. By controlling the temperatures of silicon source vaporization and the reaction between silicon vapor and carbon source within appropriate ranges, the molar ratio of Si to C in the obtained silicon carbide powder can be made closer to 1:1, reducing the formation of silicon-rich and carbon-rich phases and thus improving the powder yield. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the specific embodiments of this application, the drawings used in the description of the specific embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings.

[0030] Figure 1 This is a cross-sectional view of the internal structure of the reaction vessel in Embodiment 1 of this application;

[0031] Figure 2 This is an appearance diagram of the silicon carbide powder prepared in Example 1.

[0032] Explanation of reference numerals in the attached drawings: 1. First crucible; 2. Second crucible; 3. Silicon source; 4. Carbon source; 5. Silicon carbide powder; 6. Thread; 7. Silicon vapor. Detailed Implementation

[0033] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, a detailed description of specific embodiments of this application is provided. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. Unless otherwise specifically stated, all raw materials, reagents, instruments, and equipment used in this application are commercially available or can be prepared by existing methods.

[0035] The terms "and / or," "or / and," and "and / or" as used herein include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected using at least two conjunctions selected from "and / or," "or / and," and "and / or," it should be understood that in this application, the technical solution undoubtedly includes technical solutions connected by "logical AND," and also undoubtedly includes technical solutions connected by "logical OR." For example, "A and / or B" includes three parallel solutions: A, B, and A+B. For example, the technical solution of "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, and D (that is, a technical solution that is connected by "logical OR"), as well as any and all combinations of A, B, C, and D, that is, combinations of any two or three of A, B, C, and D, and also combinations of all four of A, B, C, and D (that is, a technical solution that is connected by "logical AND").

[0036] In this application, the terms "multiple", "various", "multiple times", "multi-dimensional", etc., unless otherwise specified, refer to a quantity greater than or equal to 2. For example, "one or more" means one or more than or equal to two.

[0037] The terms “combinations of,” “any combination of,” and “any combination of” used in this article include all suitable combinations of any two or more of the listed items.

[0038] In this document, the term "suitable" as used in phrases such as "suitable combination," "suitable method," and "any suitable method" refers to the ability to implement the technical solution of this application, solve the technical problem of this application, and achieve the expected technical effect of this application.

[0039] In this document, terms such as “preferred,” “better,” “more suitable,” and “ideal” are merely used to describe implementation methods or examples that achieve better results, and should be understood not to limit the scope of protection of this application.

[0040] In this application, terms such as "further," "even further," and "particularly" are used to describe purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0041] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0042] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0043] In this application, numerical intervals (i.e., numerical ranges) are involved. Unless otherwise specified, the selected numerical distributions within the aforementioned numerical intervals are considered continuous and include the two endpoints (i.e., the minimum and maximum values) of the numerical range, as well as every value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints. In this document, this is equivalent to directly listing every integer. For example, if t is an integer selected from 1 to 10, it means that t is any integer selected from the group of integers consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Furthermore, when multiple ranges are provided to describe features or characteristics, these ranges can be merged. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0044] Unless otherwise specified, the temperature parameters in this application are permitted to be either constant-temperature treatment or variations within a certain temperature range. It should be understood that the constant-temperature treatment allows temperature fluctuations within the precision range of the instrument control, such as ±5℃, ±4℃, ±3℃, ±2℃, or ±1℃.

[0045] In this application, %(w / w) and wt% both represent weight percentage, %(v / v) refers to volume percentage, and %(w / v) refers to mass-volume percentage.

[0046] Some embodiments of this application provide a method for preparing silicon carbide powder, comprising the following steps:

[0047] S10. Place the silicon source and carbon source into the reaction vessel, and separate the silicon source from the carbon source, with the carbon source positioned above the silicon source.

[0048] S20. Degas and purify the reaction vessel;

[0049] S30. Under a sealed and protective atmosphere, the silicon source is heated to 1500℃~1800℃ to form silicon vapor; the silicon vapor is brought into contact with the carbon source and reacted at 2000℃~2200℃ for 10h~50h; after cooling, silicon carbide powder is obtained.

[0050] In the preparation method of this application, the silicon source is fully vaporized under specific temperature conditions to form silicon vapor, which reacts with the carbon source under specific temperature conditions, enabling rapid and efficient synthesis of silicon carbide powder with low impurity content. By controlling the temperatures of silicon source vaporization and the reaction between silicon vapor and carbon source within appropriate ranges, the molar ratio of Si to C in the obtained silicon carbide powder can be made closer to 1:1, reducing the formation of silicon-rich and carbon-rich phases and thus improving the powder yield.

[0051] It is understandable that in the above preparation method, the carbon source and silicon source can be placed in different areas of the reaction vessel, and the temperature of the different areas of the reaction vessel can be controlled separately, so that the vaporization temperature of the silicon source and the reaction temperature are different.

[0052] As an example, the temperature of the silicon source heating in S30 can be 1500℃, 1550℃, 1600℃, 1650℃, 1700℃, 1750℃, 1800℃, or any value within the range formed by any two of the above points.

[0053] As an example, the temperature at which silicon vapor reacts with the carbon source in S30 can be 2000℃, 2050℃, 2100℃, 2150℃, or 2200℃, or any value within the range formed by any two of the above points. The reaction time between silicon vapor and the carbon source can be 10h, 15h, 20h, 25h, 30h, 35h, 40h, 45h, or 50h, or any value within the range formed by any two of the above points.

[0054] In some embodiments, the purity of the silicon source in S10 is 99.9999%~99.9999999%.

[0055] In some specific examples, the silicon source is semiconductor-grade silicon.

[0056] In some of these embodiments, the purity of the carbon source in S10 is ≥99.999%.

[0057] Understandably, this application uses silicon sources with a purity of 99.9999%~99.9999999% and high-purity carbon sources to prepare silicon carbide powder, which enables the generated silicon carbide powder to have a high initial purity (above 6N), laying a good foundation for the subsequent growth of high-quality silicon carbide. In traditional silicon carbide synthesis methods, silicon and carbon sources are usually pulverized and directly mixed for reaction, which inevitably introduces many impurities, thus affecting the purity of the product; moreover, the reaction rate is slow and the product yield is low. In contrast, this application uses high-purity raw materials and vaporizes the silicon source by heating before contacting it with the carbon source, thus reducing the introduction of impurities.

[0058] In some embodiments, the carbon source is selected from one or more of coarse graphite rods and porous graphite rods.

[0059] In some specific embodiments, the diameter of the graphite rod is 20nm~40nm.

[0060] In some specific embodiments, the length of the graphite rod is 150nm~200nm.

[0061] In some embodiments, the surface roughness Ra of the rough graphite rod is 150 μm to 500 μm.

[0062] As an example, the surface roughness Ra of the rough graphite rod can be 150μm, 200μm, 250μm, 300μm, 350μm, 400μm, 450μm, 500μm, or any value within the range formed by any two of the above point values.

[0063] Understandably, during the synthesis process, the surface of the rough graphite rod is easily etched to form micro- and nano-structures, which can increase the density of nucleation sites and promote the formation of polycrystalline α-phase.

[0064] In some embodiments, the porosity of the porous graphite rod is 25% to 45%.

[0065] As an example, the porosity of the porous graphite rod can be 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, or any value within the range formed by any two of the above point values.

[0066] In some embodiments, the degassing and purification process in S20 includes a first purification process and a second purification process performed sequentially.

[0067] The first purification process includes the following steps: evacuating the reaction vessel to a vacuum of 1×10⁻⁶. -4 Pa ~ 1×10 -6 Pa, maintain for 1-2 hours;

[0068] The second purification process includes the following steps: charging the reaction vessel with protective gas until the furnace pressure reaches 1×10⁻⁶. 3 Pa~5×10 3 Maintain the pressure at 1 Pa for 1-2 hours; evacuate the reaction vessel to a vacuum of 1 × 10⁻⁶. -4 Pa ~ 1×10 -6 Pa.

[0069] In some embodiments, the second purification process in S20 is performed 2 to 5 times.

[0070] As an example, the second purification process in S20 can be performed 2, 3, 4 or 5 times.

[0071] Understandably, by repeatedly pressurizing, depressurizing, and circulating air, the residual impurities in the system can be gradually reduced until the target purity is achieved.

[0072] In some embodiments, the protective gas in S20 includes argon and hydrogen, with a volume ratio of argon to hydrogen of (8~12):1.

[0073] As an example, the volume ratio of argon to hydrogen can be 8:1, 9:1, 10:1, 11:1, 12:1, or any value within the range of any two of the above ratios.

[0074] In some embodiments, the temperature of the degassing and purification process in S20 is 500°C to 900°C.

[0075] As an example, the temperature for degassing and purification can be 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, or any value within the range formed by any two of the above points.

[0076] It is understandable that degassing and purifying the reaction vessel can effectively remove various impurities adsorbed inside and outside the furnace crucible. Furthermore, controlling the temperature within the aforementioned range during degassing and purification further facilitates impurity removal.

[0077] In some embodiments, the furnace pressure of the reaction vessel in S30 is 1×10⁻⁶. 3 Pa~5×10 3 Pa.

[0078] In some embodiments, the protective gas in S30 includes argon and hydrogen, with a volume ratio of argon to hydrogen of (8~12):1.

[0079] As an example, the volume ratio of argon to hydrogen can be 8:1, 9:1, 10:1, 11:1, 12:1, or any value within the range of any two of the above ratios.

[0080] In some embodiments, cooling in S30 includes the following steps: cooling from furnace temperature to room temperature at a rate of 5°C / min to 25°C / min.

[0081] As an example, the cooling rate in S30 can be 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, 11℃ / min, 12℃ / min, 13℃ / min, 14℃ / min, 15℃ / min, 16℃ / min, 17℃ / min, 18℃ / min, 19℃ / min, 20℃ / min, 21℃ / min, 22℃ / min, 23℃ / min, 24℃ / min, 25℃ / min, or any value within the range formed by any two of the above points.

[0082] In some embodiments, after the reaction is complete, the following step is also included: crushing the silicon carbide powder.

[0083] It is understandable that by crushing, the silicon carbide formed and attached to the surface of the carbon source can be removed and silicon carbide powder with a suitable particle size can be obtained.

[0084] In some specific examples, after the crushing process, the following step is also included: oxidizing the silicon carbide powder. It is understood that after removing the silicon carbide adhering to the carbon source surface, the residual carbon powder on the surface of the silicon carbide powder can be removed through oxidation, thereby further improving the purity of the silicon carbide powder.

[0085] In some of these embodiments, such as Figure 1 As shown, the reaction vessel includes a first crucible 1 and a second crucible 2. The reaction chambers of the first crucible and the second crucible are interconnected, and the first crucible and the second crucible are sealed together.

[0086] Silicon source 3 is placed in the first crucible 1, and carbon source 4 is placed in the second crucible 2.

[0087] In some specific examples, the first crucible and the second crucible are sealed together by thread 6.

[0088] In some embodiments, the inner wall of the reaction vessel has one or more of a tantalum carbide coating and a silicon carbide coating.

[0089] In some embodiments, the second crucible includes a fixing component for fixing the carbon source.

[0090] In some specific examples, the fixing component is a threaded socket. It is understood that one end of the carbon source can be rotated and screwed into the threaded socket to achieve fixation.

[0091] In some other specific examples, the fixing component is a stud-shaped fastener with external threads.

[0092] Understandably, the carbon source can also be directly bonded to the second crucible.

[0093] In some embodiments, the distance between the bottom of the carbon source and the top of the silicon source in the reaction vessel is 20 mm to 50 mm.

[0094] In some embodiments, the carbon source is rod-shaped, with its axis parallel to the direction of gravity and fixed in a second crucible, and the pore size of the carbon source gradually increases from bottom to top.

[0095] Understandably, as the pore size of the carbon source gradually increases, the contact area between the vaporized silicon source at the bottom of the reaction vessel and the carbon source also gradually increases, which can further improve the reaction efficiency.

[0096] In some embodiments, the carbon source may also be strip-shaped, branch-shaped, or other shapes. It is understood that a branch-shaped carbon source includes a trunk and multiple branches, which increases the contact area with silicon vapor and improves reaction efficiency.

[0097] Some embodiments of this application also provide a silicon carbide powder, which is prepared using the above-described method for preparing silicon carbide powder.

[0098] The silicon carbide powder of this application has extremely high purity, which can meet the requirements of third-generation semiconductor electronic devices for high-purity semi-insulating SiC single crystal substrates, and is conducive to promoting the development of high-performance SiC semiconductor devices.

[0099] Some embodiments of this application also provide a silicon carbide article comprising the aforementioned silicon carbide powder.

[0100] In some embodiments, the silicon carbide products described above are prepared using the silicon carbide powder described above as a raw material.

[0101] The present application will be further described below with reference to specific embodiments and comparative examples, but these should not be construed as limiting the scope of protection of the present application. Unless otherwise specified, the raw materials involved in the following specific embodiments are all commercially available, the instruments used are all commercially available, and the processes involved are conventionally selected by those skilled in the art unless otherwise specified.

[0102] Example 1

[0103] (1) such as Figure 1 As shown, the silicon source is placed at the bottom of the first crucible of the reaction vessel, and the porous graphite rod is screwed into the threaded hole at the top of the second crucible for fixation, so that the axis of the graphite rod is parallel to the direction of gravity; the reaction vessel is sealed and placed in the synthesis furnace.

[0104] The purity of the silicon source is 99.99999% (7N); the purity of the porous graphite rod is 99.999% (5N), and the porosity of the porous graphite rod is 40%.

[0105] (2) Evacuate the reaction vessel to a vacuum of 5×10⁻⁶. -6 The temperature was set below Pa, and then the reaction vessel was heated to 600°C and maintained for 2 hours.

[0106] (3) High-purity argon and hydrogen are introduced into the reaction vessel at a volume ratio of 9:1, maintaining the furnace pressure at 3×10⁻⁶. 3 Pa, keep for 2 hours.

[0107] (4) Evacuate the reaction vessel to a vacuum of 5 × 10⁻⁶. -5 Below Pa.

[0108] (5) Repeat steps (3) to (4) 5 times to fully remove all kinds of impurities adsorbed inside and outside the reaction vessel.

[0109] (6) Continue to introduce argon and hydrogen gas in a volume ratio of 9:1 into the reaction vessel to maintain a furnace pressure of 3 × 10⁻⁶. 3 Pa. Continue to raise the temperature in the first crucible to 1650℃, so that the silicon source vaporizes to form silicon vapor, which rises and contacts the graphite rod; control the temperature in the second crucible to 2100℃, so that the silicon vapor reacts with the graphite rod for 30 hours.

[0110] (7) After the reaction is complete, the temperature is reduced to room temperature at a rate of 25℃ / min. Then the graphite rod is removed, the silicon carbide on the graphite rod is scraped off and crushed, ball-milled and oxidized to obtain silicon carbide powder with a particle size between 5 and 40 mesh.

[0111] Figure 2 The image shows the appearance of the silicon carbide powder prepared in Example 1.

[0112] The black and white powders in the prepared silicon carbide were detected by secondary ion mass spectrometry (SIMS). The results showed that there was no significant difference in the content of N, B, Al, Ti, V and W in the black and white powders, and the contents of N, Al, Ti, V and W were all below the detection limit.

[0113] Example 2

[0114] It is basically the same as Example 1, except that steps (3) to (4) are not included.

[0115] Example 3

[0116] It is basically the same as Example 1, except that step (6) is different; specifically, in step (6) of Example 3, the temperature in the first crucible is 1500°C and the temperature in the second crucible is 2200°C, and the yield of raw materials with the target mesh size is low.

[0117] Example 4

[0118] It is basically the same as Example 1, except that step (1) is different; specifically, in Example 4, the graphite rod is replaced with a rough graphite rod with a roughness of 500 μm.

[0119] Example 5

[0120] It is basically the same as Example 1, except that step (1) is different; specifically, in Example 5, the graphite rod is a branch-shaped graphite.

[0121] Comparative Example 1

[0122] It is basically the same as Example 1, except that step (6) is different; specifically, in Comparative Example 1, the temperature in the first crucible and the second crucible in step (6) is 2000℃.

[0123] Comparative Example 2

[0124] Solid silicon powder (99.9995% purity) and solid carbon source (99.9997% purity) with a molar ratio of 7:3 were thoroughly mixed and then fed into the furnace. The furnace top temperature was set at 2150℃, the bottom temperature at 2300℃, and the furnace pressure at 2000Pa. Silicon carbide was synthesized after 23 hours.

[0125] Performance testing:

[0126] The purity of the silicon carbide powders prepared in the above examples and comparative examples was detected by GDMS (Glow Discharge Mass Spectrometry). The powder yield was calculated as follows: target mesh size powder yield = target mesh size powder weight / total weight of all mesh size powders × 100%. The results are shown in Table 1.

[0127] Table 1

[0128]

[0129] As shown in the table above, in Examples 1-4, placing the carbon source and silicon source in different chambers and controlling the vaporization and reaction synthesis temperatures of the silicon source within specific ranges not only improves the purity of the prepared 5-40 mesh silicon carbide powder but also increases the powder yield. In Comparative Example 1, the temperature of the first crucible is too high, and the silicon source sublimates too quickly, leaving insufficient time for the silicon vapor to react with the carbon source, resulting in a low silicon carbide powder yield. In Comparative Example 2, following a traditional method, solid carbon source and solid silicon source are directly mixed and reacted. The driving force of the solid-phase reaction originates from the self-diffusion of silicon-rich gases (Si, Si2C) from the sublimation and decomposition of the raw materials at the bottom. Due to the strong interaction between solid particles, the reaction is driven by diffusion, resulting in a slow reaction and a significantly lower silicon carbide powder yield than in this application.

[0130] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0131] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for preparing silicon carbide powder, characterized in that, Includes the following steps: A silicon source and a carbon source are placed in a reaction vessel, and the silicon source is separated from the carbon source, with the carbon source positioned above the silicon source. The reaction vessel was degassed and purified. Under sealed and protective atmosphere conditions, the silicon source is heated to 1500℃~1800℃ to form silicon vapor; the silicon vapor is then brought into contact with the carbon source and reacted at 2000℃~2200℃ for 10h~50h; after cooling, silicon carbide powder is prepared.

2. The method for preparing silicon carbide powder according to claim 1, characterized in that, The degassing and purification process includes a first purification process and a second purification process performed sequentially. The first purification process includes the following steps: evacuating the reaction vessel to a vacuum of 1×10⁻⁶. -4 Pa ~ 1×10 -6 Pa, maintain for 1-2 hours; The second purification process includes the following steps: charging the reaction vessel with a protective gas until the furnace pressure is 1×10⁻⁶. 3 Pa~5×10 3 Pa, maintain for 1-2 hours; evacuate the reaction vessel to 1×10⁻⁶ Pa. -4 Pa ~ 1×10 -6 Pa.

3. The method for preparing silicon carbide powder according to claim 2, characterized in that, The second purification process is performed 2 to 5 times; and / or, The protective gas includes argon and hydrogen, and the volume ratio of argon to hydrogen is (8~12):

1.

4. The method for preparing silicon carbide powder according to any one of claims 1 to 3, characterized in that, The degassing and purification treatment is performed at a temperature of 500℃~900℃; and / or, The purity of the silicon source is 99.9999%~99.9999999%; and / or, The purity of the carbon source is ≥99.999%; and / or, The carbon source is selected from one or more of coarse graphite rods and porous graphite rods.

5. The method for preparing silicon carbide powder according to claim 4, characterized in that, The surface roughness Ra of the rough graphite rod is 150 μm to 500 μm; and / or, The porosity of the porous graphite rod is 25%~45%.

6. The method for preparing silicon carbide powder according to any one of claims 1 to 3 and 5, characterized in that, The reaction vessel includes a first crucible and a second crucible, the reaction chambers of the first crucible and the second crucible are interconnected, and the first crucible and the second crucible are sealed together. The silicon source is placed in the first crucible, and the carbon source is placed in the second crucible.

7. The method for preparing silicon carbide powder according to claim 6, characterized in that, The second crucible includes a fixing component for fixing the carbon source.

8. The method for preparing silicon carbide powder according to claim 7, characterized in that, The carbon source is rod-shaped, and its axis is fixed in the second crucible parallel to the direction of gravity. The pore size of the carbon source gradually increases from bottom to top.

9. A silicon carbide powder, characterized in that, The silicon carbide powder is prepared by any one of the preparation methods of claims 1 to 8.

10. A silicon carbide product, characterized in that, It includes the silicon carbide powder as described in claim 9.

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