A method for preparing silicon carbide from gaseous elemental carbon
By using high-purity fullerene as a gaseous carbon source to react with silicon, high-purity, large-particle silicon carbide powder was prepared, solving the problems of low purity and high impurity content in existing technologies and achieving efficient production at low temperatures.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XIAMEN FUNANO NEW MATERIAL TECH COMPANY
- Filing Date
- 2024-03-18
- Publication Date
- 2026-06-23
AI Technical Summary
Existing methods for synthesizing silicon carbide powder suffer from problems such as low purity, high impurity content, high production costs, and difficulty in mass production. In particular, impurities are easily introduced when mixing carbon and silicon sources at high temperatures, making it difficult to improve the purity of the synthesized silicon carbide.
High-purity fullerene is used as a gaseous elemental carbon source to react with a high-purity solid or molten silicon source. Silicon carbide is synthesized at low temperature by controlling the reaction conditions. Large-particle silicon carbide powder is prepared by reacting gaseous elemental carbon with the surface of the silicon source.
The preparation of high-purity silicon carbide powder with a particle size of over 500 micrometers and a purity of over 99 wt% was achieved. Furthermore, the process was carried out at low temperatures, which reduced production costs and made the powder suitable for mass production.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of silicon carbide preparation technology, and in particular to a method for preparing silicon carbide by synthesizing gaseous carbon. Background Technology
[0002] Silicon carbide single crystals possess unique properties such as a large bandgap, high breakdown electric field, high thermal conductivity, high electron saturation drift velocity, low dielectric constant, strong radiation resistance, and good chemical stability. They have broad application prospects in white light illumination, optical storage, screen displays, aerospace, high-temperature radiation environments, oil exploration, automation, radar and communications, automotive electronics, and power electronics. Rapid development is seen in single-crystal substrates, homoepitaxial semiconductor thin films, and device fabrication, making them one of the most ideal third-generation semiconductors. Semi-insulating silicon carbide exhibits low dielectric loss at high frequencies, giving it a significant advantage as a single-crystal substrate for high-temperature, high-power, high-frequency electronic devices and sensors based on wide-bandgap semiconductors (such as SiC and GaN). The purity of SiC powder plays a crucial role in the sublimation growth of semiconductor SiC single crystals, directly affecting the crystal quality and electrical properties of the grown single crystal.
[0003] The main methods for synthesizing SiC powder include chemical vapor deposition (CVD), organic synthesis, self-propagating polymerization, and the Acheson method. Among these, CVD utilizes organosilicon sources (silanes, silicon tetrachloride, etc.) and organic carbon sources (carbon tetrachloride, methane, ethylene, acetylene, and propane, etc.) to synthesize high-purity silicon carbide powder under high-temperature conditions. However, the synthesized powder is a nano-scale ultrafine powder; although it has high purity, it is difficult to collect and is not suitable for large-scale synthesis of high-purity silicon carbide powder, which is detrimental to its later industrialization.
[0004] Organic synthesis involves dissolving inorganic salts or alkoxides in a solvent (water or alcohol) to form a homogeneous solution, resulting in a uniform sol. This sol is then dried or dehydrated to form a gel, followed by heat treatment to obtain the desired ultrafine powder. Organic synthesis is primarily used to prepare nanoscale SiC powder. However, the raw materials contain various impurity elements. Although high-purity SiC powder with impurity content below 1 ppm can be obtained through subsequent processing, the process is complex, and the collection of micro-powder is difficult, making it unsuitable for large-scale production.
[0005] The high-temperature self-propagating method is a method of synthesizing materials by igniting the reactant preform with an external heat source and then using the heat of chemical reaction of the substances themselves to spontaneously and continuously carry out the subsequent chemical reaction process. High-temperature self-propagating methods mostly use silicon powder and carbon black as raw materials. Since the reaction between silicon and carbon sources is a weakly exothermic reaction, other activators need to be added to ensure the heat required for the reaction to continue. This undoubtedly introduces other impurities, thus affecting the purity and quality of the synthesized product.
[0006] The Acheson method involves reducing a solid silicon source with a solid carbon source under high temperature and a strong electric field. The carbon source reacts with the reduced silicon source at high temperature to synthesize silicon carbide. This method produces SiC powder with an oxide content exceeding 1 wt%, resulting in hard solid agglomerates that require crushing and acid washing processes. This leads to a high impurity content, and the purity cannot reach the level required for growing semiconductor single crystals.
[0007] In summary, all the methods described above require mixing carbon and silicon sources and then heat-treating the mixture to obtain silicon carbide, each with its own drawbacks. For example, patent application CN102596802A discloses a system and method for preparing silicon carbide powder, including the step of preparing a mixture of silicon and carbon sources in a mixer; and synthesizing silicon carbide (SiC) powder by heating the mixture at a vacuum of greater than 0.03 Torr and equal to and less than 0.5 Torr and at a temperature of equal to or greater than 1300°C and equal to and less than 1900°C. This method addresses the conventional technique of preparing silicon carbide by mixing solid silicon sources (e.g., SiO2 and Si) and solid carbon sources (e.g., carbon and graphite) and then heat-treating at 1350℃–2000℃. This method suffers from issues related to SiC powder recovery, purity limitations, and relatively high composite temperatures. The proposed solution allows for preparation at low pressure and low temperature, saving processing costs and easily obtaining high-purity silicon carbide powder. It also reduces the temperature and time in the heat treatment process during silicon carbide powder synthesis and improves the recovery rate compared to general silicon compounds. However, this method requires mixing the solid carbon and silicon sources, necessitating repeated mixing, recovery, and collection of the carbon and silicon sources before powder preparation. Furthermore, it requires ball milling the silicon carbide raw material powder and filtering the mill balls to recover the silicon carbide mixture. In addition, this method requires the use of a carbonizer to carbonize the carbon source contained in the mixture at a temperature of 1600℃~1900℃, which is relatively high. Summary of the Invention
[0008] The purpose of this invention is to overcome the problems existing in the synthesis of silicon carbide powder and to provide a method for preparing silicon carbide by synthesizing gaseous elemental carbon. High-purity fullerene is used as a carbon source, which is sublimated into gaseous elemental carbon upon heating. This gaseous carbon then reacts with a high-purity solid / molten silicon source. By controlling the reaction conditions, large-particle silicon carbide powder materials with a certain size range can be obtained. For example, at 1300-1500℃, silicon carbide powder with a particle size of more than 500 micrometers can be obtained.
[0009] This invention creatively employs a two-phase separation process involving inorganic gaseous elemental carbon (fullerene) and a solid silicon source. The carbon and silicon sources are heated separately, sublimating the fullerene into gaseous elemental carbon, while the silicon source is heated to accelerate its molecular motion. The gaseous elemental carbon is then introduced into another reaction chamber, where it reacts with the surface of the silicon source to synthesize silicon carbide. This invention allows for the control of the particle size of the silicon carbide product by adjusting the reaction conditions.
[0010] Fullerenes are a class of hollow molecules composed entirely of carbon, possessing unique structures and superior properties, ushering in a new era for the carbon atom. To date, research on fullerenes has encompassed numerous disciplines, including organic chemistry, inorganic chemistry, life sciences, materials science, polymer science, catalysis chemistry, superconductors, and ferromagnets. The properties of fullerenes can almost all be applied practically in modern technology and industry. One of the unique properties of fullerene materials is their sublimation at relatively low temperatures; for example, C60, according to its TG-DSC chart, has a sublimation point of approximately 726°C, thus enabling low-temperature vaporization.
[0011] This invention proposes heating 5N fullerene powder to 700-800°C to sublimate it into gaseous elemental carbon, and then using the gaseous elemental carbon to react with a silicon source to synthesize silicon carbide powder.
[0012] The specific plan is as follows:
[0013] A method for preparing silicon carbide from gaseous elemental carbon involves placing a carbon source in reaction chamber 1 and a silicon source in reaction chamber 2. The carbon source is a fullerene. The carbon source is heated to obtain gaseous elemental carbon. The gaseous elemental carbon is introduced into reaction chamber 2 and reacted with the preheated silicon source, preferably at 1300-1500°C. After the reaction is completed, the mixture is cooled to obtain silicon carbide.
[0014] Furthermore, an embedded reaction chamber is adopted, wherein reaction chamber 1 is partially or completely embedded in reaction chamber 2, and the reaction space of reaction chamber 1 is connected to reaction chamber 2; the preparation method of gaseous elemental carbon to synthesize silicon carbide includes the following steps:
[0015] S1, place a carbon source in reaction chamber 1;
[0016] S2, place the silicon source in reaction chamber 2;
[0017] S3, the embedded reaction chamber is evacuated by a vacuum system, and then an inert gas is introduced to heat the embedded reaction chamber to 1100-1900°C. The carbon source in the reaction chamber 1 is sublimated into gaseous carbon, which enters the reaction chamber 2 and reacts with the silicon source. After the reaction is completed, the chamber is cooled to obtain silicon carbide.
[0018] Furthermore, in S3, the temperature at which the embedded reaction chamber is heated is 1200-1600℃, preferably 1300-1500℃, and the holding time is 5-8 hours.
[0019] Furthermore, an external reaction chamber is adopted, wherein reaction chamber 2 is independent of reaction chamber 1, and a ventilation pipe is provided between them, which allows the reactants in reaction chamber 1 to enter reaction chamber 2; the preparation method of synthesizing silicon carbide from gaseous elemental carbon includes the following steps:
[0020] M1, place a carbon source in reaction chamber 1, and heat the carbon source under an inert gas atmosphere to obtain gaseous elemental carbon;
[0021] M2, place the silicon source in reaction chamber 2, and heat it to 1100-1900℃ under the protection of an inert gas atmosphere;
[0022] In step M3, the gaseous elemental carbon is introduced into reaction chamber 2, heated and kept at a certain temperature, and the gaseous elemental carbon reacts with the silicon source. After the reaction is completed, the mixture is cooled to obtain silicon carbide. The order of steps M1 and M2 is arbitrary.
[0023] Furthermore, the heating temperature described in M1 is 400-800°C, preferably 720-780°C, and more preferably 740-760°C.
[0024] Furthermore, the temperature of the reaction chamber 2 in M3 is 1200-1600℃, preferably 1300-1500℃, and the holding time is 5-8h.
[0025] Furthermore, the fullerene has 20-560 carbon atoms, preferably one or more of C60, C70, C76, C78, C80 and C84;
[0026] Preferably, the silicon source is one or more of silicon-containing substances or minerals with a purity higher than 99 wt%, such as silicon powder, polycrystalline silicon, silicon dioxide, and silicon crystals.
[0027] Preferably, the molar ratio of silicon in the silicon source to carbon in the carbon source in S1 is 10:1 to 100:1, more preferably 30:1 to 80:1, and even more preferably 40 to 60:1.
[0028] Furthermore, the cooling temperature is 200-500℃, preferably 250-350℃, and more preferably 280-330℃.
[0029] Furthermore, it also includes exporting the gas in the reaction chamber 2 to a space equipped with a silicon carbide growth platform, preferably with a silicon carbide substrate as the substrate, and continuously introducing the gas so that silicon carbide can grow continuously on the substrate.
[0030] The present invention also protects the silicon carbide prepared by the method of synthesizing silicon carbide from gaseous elemental carbon, wherein the silicon carbide has a diameter of 500-900 micrometers and a purity of ≥99 wt%.
[0031] Beneficial effects: The silicon carbide preparation method provided by this invention uses gaseous elemental carbon as a carbon source to react with a silicon source, thereby achieving the synthesis of silicon carbide at low temperature and producing a product with high purity. At the same time, this method can continuously replenish the carbon and silicon sources, and after cooling, it can achieve continuous crystal growth, thereby obtaining large-particle silicon carbide powder with uniform size.
[0032] Furthermore, existing silicon carbide synthesis methods require mixing and heating the carbon and silicon sources. Due to the different vaporization temperatures of the two sources, the carbon source partially graphitizes during silicon vaporization, resulting in impurities in the produced silicon carbide and difficulty in improving purity. The method of this invention, however, uses fullerene as the carbon source, which is then vaporized and mixed with the silicon source. This avoids the problem of partial graphitization of the silicon source, resulting in silicon carbide with high purity. Attached Figure Description
[0033] To more clearly illustrate the technical solution of the present invention, the accompanying drawings will be briefly described below. Obviously, the drawings described below only relate to some embodiments of the present invention and are not intended to limit the present invention.
[0034] Figure 1 This is a schematic diagram of an embedded reaction chamber structure provided in Embodiment 1 of the present invention;
[0035] Figure 2 This is a silicon carbide powder structure detection diagram provided in Embodiment 1 of the present invention;
[0036] Figure 3 This is a particle size distribution detection diagram of silicon carbide powder provided in Embodiment 1 of the present invention;
[0037] Figure 4 This is a silicon carbide powder structure detection diagram provided in Embodiment 2 of the present invention;
[0038] Figure 5 This is a particle size distribution detection diagram of silicon carbide powder provided in Embodiment 2 of the present invention;
[0039] Figure 6 This is a silicon carbide powder structure detection diagram provided in Embodiment 3 of the present invention;
[0040] Figure 7 This is a particle size distribution detection diagram of silicon carbide powder provided in Embodiment 3 of the present invention;
[0041] Figure 8This is a schematic diagram of an external reaction chamber structure provided in Embodiment 4 of the present invention;
[0042] Figure 9 This is a silicon carbide powder structure detection diagram provided in Embodiment 4 of the present invention;
[0043] Figure 10 This is a particle size distribution detection diagram of silicon carbide powder provided in Embodiment 4 of the present invention;
[0044] Figure 11 This is a silicon carbide powder structure detection diagram provided in Embodiment 5 of the present invention;
[0045] Figure 12 This is a particle size distribution detection diagram of silicon carbide powder provided in Embodiment 5 of the present invention. Detailed Implementation
[0046] Preferred embodiments of the present invention will now be described in more detail. While preferred embodiments of the present invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products. In the following embodiments, unless otherwise specified, "%" refers to weight percentage.
[0047] The example used fullerene with a purity of 6N, which was determined to be 99.994585% by GDMS.
[0048] Example 1
[0049] A method for preparing silicon carbide employs an embedded reaction chamber, such as... Figure 1 As shown, the embedded reaction chamber includes a reaction chamber 1 and a reaction chamber 2. The reaction chamber 1 is partially or completely embedded in the reaction chamber 2, and the reaction space of the reaction chamber 1 is connected to the reaction chamber 2. For example, the gas in the reaction chamber 1 can enter the reaction chamber 2 through the opening in the inner wall of the reaction chamber 2.
[0050] In use, a carbon source is prepared in reaction chamber 1 and a silicon source is prepared in reaction chamber 2. A vacuum system is used to evacuate the system, and then inert gas is introduced through the inlet. The entire embedded reaction chamber is heated to 1100–1900°C, causing the carbon source in reaction chamber 1 to sublimate into gaseous carbon. The gaseous carbon flows through the pores to reaction chamber 2. In reaction chamber 2, the gaseous carbon reacts with the molten / solid silicon source to generate silicon carbide, thereby producing 3C-SiC.
[0051] Specifically, the following steps are included:
[0052] S1, Fullerene C is prepared in reaction chamber 1. 60 In reaction chamber 2, high-purity silicon powder (purity greater than 99.9%) is prepared.
[0053] S2, a vacuum is drawn through the vacuum system, and then inert gas is introduced through the air inlet;
[0054] S3, under the protection of argon in an inert gas atmosphere, the embedded reaction chamber is heated to 1100℃, gaseous elemental carbon flows into reaction chamber 2, gaseous elemental carbon reacts with the preheated silicon source, and the temperature is maintained for 5 hours. After the reaction is completed, it is cooled to obtain silicon carbide powder material.
[0055] The prepared silicon carbide powder material was tested, and the test results are shown in the figure. Figure 2 and Figure 3 As can be seen, the synthesized silicon carbide powders are all 3C-SiC with a particle size of approximately 6 μm. The product purity is greater than or equal to 99 wt%.
[0056] Example 2
[0057] A method for preparing silicon carbide, using the embedded reaction chamber of Example 1, includes the following steps:
[0058] S1, Fullerene C is prepared in reaction chamber 1. 60 In reaction chamber 2, high-purity silicon powder (purity greater than 99.9%) is prepared.
[0059] S2, a vacuum is drawn through the vacuum system, and then inert gas is introduced through the air inlet;
[0060] S3, under the protection of argon in an inert gas atmosphere, the embedded reaction chamber is heated to 1200℃, gaseous elemental carbon flows into reaction chamber 2, gaseous elemental carbon reacts with the preheated silicon source, and the temperature is maintained for 5 hours. After the reaction is completed, it is cooled to obtain silicon carbide powder material.
[0061] The prepared silicon carbide powder material was tested, and the test results are shown in the figure. Figure 4 and Figure 5 As can be seen, the synthesized silicon carbide powders are all 3C-SiC with a particle size of approximately 60 μm. The product purity is greater than or equal to 99 wt%.
[0062] Example 3
[0063] A method for preparing silicon carbide, using the embedded reaction chamber of Example 1, includes the following steps:
[0064] S1, Fullerene C is prepared in reaction chamber 1. 60 In reaction chamber 2, high-purity silicon powder (purity greater than 99.9%) is prepared.
[0065] S2, a vacuum is drawn through the vacuum system, and then inert gas is introduced through the air inlet;
[0066] S3, under the protection of argon in an inert gas atmosphere, the embedded reaction chamber is heated to 1300℃, gaseous elemental carbon flows into reaction chamber 2, gaseous elemental carbon reacts with the preheated silicon source, and the temperature is maintained for 5 hours. After the reaction is completed, it is cooled to obtain silicon carbide powder material.
[0067] The prepared silicon carbide powder material was tested, and the test results are shown in the figure. Figure 6 and Figure 7 As can be seen, the synthesized silicon carbide powders are all 3C-SiC with a particle size of approximately 587 μm. The product purity is greater than or equal to 99 wt%.
[0068] Example 4
[0069] A method for preparing silicon carbide, employing an external reaction chamber, such as... Figure 8 As shown, the external reaction chamber includes two independent reaction chambers, 1 and 2, with a ventilation pipe between them, which allows the reactants in reaction chamber 1 to enter reaction chamber 2.
[0070] When using this external reaction chamber, a carbon source is prepared in reaction chamber 1 and a silicon source is prepared in reaction chamber 2. A vacuum system is used to evacuate the chamber, and then inert gas is introduced through the inlet. Reaction chamber 2 is first heated to 1100–1900°C. After reaching the set temperature, reaction chamber 1 is then heated to 700–800°C, causing the carbon source to sublimate into gaseous carbon. The generated gaseous carbon is then guided to reaction chamber 2 through a ventilation pipe. Inside reaction chamber 2, the gaseous carbon reacts with the molten / solid silicon source to generate silicon carbide, thus producing 3C-SiC.
[0071] Specifically, the following steps are included:
[0072] M1 is evacuated by a vacuum system, and then inert gas is introduced through the inlet. Fullerene C60 is prepared in reaction chamber 1, and reaction chamber 1 is heated to 750°C to obtain gaseous elemental carbon.
[0073] M2, prepare high-purity silicon powder (purity greater than 99.9%) in reaction chamber 2, and heat reaction chamber 2 to 1400℃;
[0074] M3. After the reaction chamber 2 reaches the specified temperature, gaseous elemental carbon is introduced into the reaction chamber 2. The reaction chamber 2 is kept at the temperature for 5 hours. The gaseous elemental carbon reacts with the preheated silicon source. After the reaction is completed, the mixture is cooled to obtain silicon carbide powder material.
[0075] The prepared silicon carbide powder material was tested, and the test results are shown in the figure. Figure 9 and Figure 10As can be seen, the synthesized silicon carbide powders are all 3C-SiC with a particle size of approximately 760 μm. The product purity is greater than or equal to 99 wt%.
[0076] Example 5
[0077] A method for preparing silicon carbide, using the external reaction chamber described in Example 4, includes the following steps:
[0078] M1 is evacuated by a vacuum system, and then inert gas is introduced through the air inlet. High-purity silicon powder (purity greater than 99.9%) is prepared in reaction chamber 2, and reaction chamber 2 is heated to 1500℃.
[0079] M2, then fullerene C60 is prepared in reaction chamber 1, and reaction chamber 1 is heated to 750°C to obtain gaseous elemental carbon;
[0080] In step M3, gaseous elemental carbon is introduced into reaction chamber 2. Reaction chamber 2 is kept at 1500℃ for 5 hours. The gaseous elemental carbon reacts with the preheated silicon source. After the reaction is completed, the mixture is cooled to obtain silicon carbide powder material.
[0081] The prepared silicon carbide powder material was tested, and the test results are shown in the figure. Figure 11 and Figure 12 As can be seen, the synthesized silicon carbide powders are all 3C-SiC with a particle size of approximately 880 μm. The product purity is greater than or equal to 99 wt%.
[0082] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.
[0083] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.
[0084] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.
Claims
1. A method for preparing silicon carbide from gaseous elemental carbon, characterized in that: A carbon source is placed in reaction chamber 1, and a silicon source is placed in reaction chamber 2. The carbon source is a fullerene. The carbon source is heated to obtain gaseous elemental carbon. The gaseous elemental carbon is introduced into reaction chamber 2 and reacts with the preheated silicon source. After the reaction is completed, the mixture is cooled to obtain silicon carbide. An embedded reaction chamber is used, wherein reaction chamber 1 is partially or completely embedded in reaction chamber 2, and the reaction space of reaction chamber 1 is connected to reaction chamber 2; the preparation method of synthesizing silicon carbide from gaseous elemental carbon includes the following steps: S1, place a carbon source in reaction chamber 1; S2, a silicon source is placed in reaction chamber 2; the silicon source is one or more of silicon powder, polycrystalline silicon, and silicon dioxide with a purity higher than 99wt%. S3, the embedded reaction chamber is evacuated by a vacuum system, and then an inert gas is introduced to heat the embedded reaction chamber to 1300~1900℃. The carbon source in the reaction chamber 1 is sublimated into gaseous carbon, which enters the reaction chamber 2 and reacts with the silicon source. After the reaction is completed, the mixture is cooled to obtain silicon carbide powder. The diameter of the silicon carbide powder is 500-900 micrometers.
2. The method for preparing silicon carbide from gaseous elemental carbon according to claim 1, characterized in that: In S3, the embedded reaction chamber is heated to a temperature of 1300-1600℃ and held at that temperature for 5-8 hours.
3. The method for preparing silicon carbide from gaseous elemental carbon according to claim 1, characterized in that: The fullerene has 20-560 carbon atoms.
4. The method for preparing silicon carbide from gaseous elemental carbon according to claim 3, characterized in that: The fullerene is one or more of C60, C70, C76, C78, C80 and C84.
5. The method for preparing silicon carbide from gaseous elemental carbon according to claim 3, characterized in that: The molar ratio of silicon in the silicon source to carbon in the carbon source in S1 is 10:1 to 100:
1.
6. The method for preparing silicon carbide from gaseous elemental carbon according to claim 1, characterized in that: The molar ratio of silicon in the silicon source to carbon in the carbon source in S1 is 30:1 to 80:
1.
7. The method for preparing silicon carbide from gaseous elemental carbon according to claim 6, characterized in that: The molar ratio of silicon in the silicon source to carbon in the carbon source in S1 is 40~60:
1.
8. The method for preparing silicon carbide according to claim 1, characterized in that: The cooling temperature is 200-500℃.
9. The method for preparing silicon carbide from gaseous elemental carbon according to claim 8, characterized in that: The cooling temperature is 250-350℃.
10. The method for preparing silicon carbide from gaseous elemental carbon according to claim 9, characterized in that: The cooling temperature is 280-330℃.