Preparation method of flaky silicon carbide
By arranging the carbon source and silicon source in layers through microwave sintering technology, the problems of complex equipment and impurities in the preparation of flaky silicon carbide are solved, and efficient and high-purity flaky silicon carbide preparation is achieved, which is used in integrated circuits, composite materials and refractory materials.
Patent Information
- Application Number
- CN202510940302.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-08
- Publication Date
- 2025-09-16
AI Technical Summary
The existing method for preparing flaky silicon carbide has complex equipment, low production efficiency, and the product contains impurities, making it difficult to achieve large-scale production.
Using microwave sintering technology, the carbon source and silicon source are arranged in layers in the mold, and microwave energy is used to evenly heat the materials. Flake silicon carbide is formed through layered pressing to optimize heating efficiency and purity.
The efficient preparation of flaky silicon carbide with uniform thickness, high purity, good toughness and wave-absorbing properties has been achieved, making it suitable for integrated circuits, composite materials and refractory materials.
Smart Images
Figure CN120647387A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of silicon carbide preparation, and in particular to a method for preparing flaky silicon carbide. Background Art
[0002] Flaky silicon carbide (SiC) is a material with unique structure and properties. SiC inherently possesses excellent properties such as high hardness, high thermal conductivity, and high electron saturation mobility, making it an ideal material for high-temperature, high-frequency, and high-power semiconductor devices. In addition to these fundamental properties, flaky SiC exhibits unique properties and applications due to its unique flaky structure. In materials science, the flaky structure of SiC can influence its physical and chemical properties. For example, it can potentially impart a higher specific surface area, which is important for applications requiring large contact areas, such as adsorption and catalysis. In the electronics industry, flaky SiC can be used to fabricate high-performance electronic components, leveraging its high thermal conductivity and high electron saturation mobility to enhance heat dissipation and operating efficiency. In the ceramics industry, flaky SiC can be added as a reinforcement phase to ceramic materials, improving their strength, toughness, and wear resistance, and is used in the manufacture of refractory ceramics.
[0003] With the continuous development of science and technology, the demand for materials with special structures and properties is increasing. The research and development of flake silicon carbide is also deepening, aiming to explore its potential application value and optimize its performance to meet the needs of different fields. At present, the preparation methods of flake silicon carbide include chemical vapor deposition, physical vapor deposition, sol-gel method, hot pressing sintering method, reaction sintering method, etc. However, the above methods have the disadvantages of complex equipment, low production efficiency, and impurities in the prepared products, which make it impossible to carry out large-scale production of flake silicon carbide. Summary of the Invention
[0004] The present invention aims to provide a method for preparing flaky silicon carbide to address the shortcomings of the aforementioned flaky silicon carbide preparation methods, such as complex equipment, low production efficiency, and impurities in the prepared product. The present invention arranges a carbon source and a silicon source in layers in a mold and employs microwave sintering technology to prepare the silicon carbide. During the heating process, the material absorbs microwave energy, causing polar molecules to interact with the microwave electromagnetic field to generate microwave electromagnetic heat. This allows the material to be heated uniformly, with uniform heating inside and outside, resulting in high heating efficiency, rapid heating rate, short preparation time, and minimal environmental pollution. The resulting flaky silicon carbide has advantages such as uniform thickness and high purity.
[0005] To achieve the above object, the present invention provides a method for preparing flaky silicon carbide, comprising the following steps: (1) Mixing the carbon source and the binder and ball milling to obtain a mixed powder; (2) Alternately pouring the mixed powder and silicon source into a mold to form a carbon layer and a silicon layer, respectively, and finally pressing and molding to obtain a green body; (3) The green body is subjected to microwave sintering to obtain flaky silicon carbide.
[0006] Preferably, in step (1), the carbon source is activated carbon, the binder is PVA, and the mass ratio of the carbon source to the binder is (15-25):1.
[0007] Preferably, in step (1), during the ball milling of the carbon source and the binder, a grinding medium is added, the amount of the grinding medium added is 50-150% of the total mass of the carbon source and the binder, the grinding medium is anhydrous ethanol or deionized water, the ball-to-material ratio is 2-7:1, the rotation speed is 180-220 r / min, and the ball milling time is 2-4 h.
[0008] Preferably, in step (2), after ball milling, the mixed powder is dried, ground and sieved and then poured into a mold.
[0009] Preferably, in step (2), the drying temperature is 60-100° C., and the product is ground and passed through a 200-mesh sieve.
[0010] Preferably, the carbon-to-silicon molar ratio of the carbon source to the silicon source is 2-4:1.
[0011] Preferably, in step (2), the silicon source is quartz sand, and the particle size of the quartz sand is 200-250 mesh.
[0012] Preferably, in step (2), the mass of each layer of mixed powder in the mold and the mass of each layer of silicon source are 0.16-0.32 g:0.4 g.
[0013] Preferably, in step (2), quartz sand and activated carbon are alternately poured into the mold, with a total of 6 to 10 carbon layers and silicon layers.
[0014] In the prior art, in the process of preparing silicon carbide, the carbon source and the silicon source are directly mixed and sintered. This direct mixing and sintering method is not only prone to problems such as insufficient reaction, limited reaction kinetics, excessive sintering temperature and time, and a large number of residual impurities in the product, but also has poor microstructure control, making it difficult to control the contact mode and arrangement state between particles, which is not conducive to the formation of specific morphologies, such as flakes, nanowires, etc. In response to the above problems, the present invention alternately pours a mixed powder containing a carbon source and a silicon source into a mold in layers. This step can effectively improve the temperature field distribution of the blank in the microwave oven cavity. The carbon layer can effectively absorb microwaves to increase the temperature, and the silicon layer does not absorb microwaves at low temperatures. The temperature of the carbon layer inside the blank is higher than that of the silicon layer, forming an interval heat field, which prompts the reaction to concentrate in the carbon layer to generate silicon carbide. During the heating process, the formation of flaky silicon carbide relies on the template of the carbon layer. The carbon layer is used as a template to react to generate silicon carbide and eventually connect together to form flaky silicon carbide, which is very important for morphology control. In addition, the mass ratio of the mixed powder and the silicon source is also very important. When the proportion of activated carbon in the mixed powder is too low, the sintered product contains a large amount of silicon source (silicon oxide) that does not participate in the reaction. Part of the generated silicon carbide melts together with the silicon oxide, and the structure of the flaky silicon carbide disappears.
[0015] Preferably, in step (2), the pressing pressure is 4-6 MPa and the pressing time is 1-10 min.
[0016] Preferably, in step (2), the mold is a powder tableting mold with a diameter of 30 mm.
[0017] Preferably, in step (3), the microwave sintering conditions are: input power of 810~6800W, heating to 800~1200℃ at a heating rate of 10~60℃ / min, and then keeping warm for 10min~60min.
[0018] Preferably, in step (3), the heating frequency of microwave sintering is 915-2450 MHz, more preferably, the heating frequency of microwave sintering is 915 MHz or 2450 MHz.
[0019] Therefore, the present invention adopts the above-mentioned method for preparing flaky silicon carbide, which has the following beneficial effects: (1) The present invention utilizes microwave sintering to prepare flaky silicon carbide. The excellent microwave absorption properties of the carbon source and silicon source are fully utilized through the layered pressing process. The silicon source material and the carbon source material are heated alternately in the microwave field, and a large number of nuclei are formed and grown at the interface between the layers, and finally flaky silicon carbide is obtained.
[0020] (2) The flaky silicon carbide prepared by the present invention has uniform thickness, high purity, high hardness, good toughness and wave absorbing properties, and can be used in the fields of integrated circuits, composite materials and refractory materials.
[0021] (3) Compared with the traditional sintering method, the microwave sintering method of the present invention can directly interact with the material itself, thereby converting microwave energy into thermal energy, with short heating time, high efficiency, environmental protection and energy saving.
[0022] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1 This is the microwave sintering heating curve of the flaky silicon carbide prepared in Example 1; Figure 2 is the XRD pattern of the flaky silicon carbide prepared in Example 1; Figure 3 is an SEM image of the flaky silicon carbide prepared in Example 1; Figure 4 is an SEM image of silicon carbide prepared in Comparative Example 2; Figure 5 This is a digital photo of the flaky silicon carbide prepared in Example 1. DETAILED DESCRIPTION
[0024] The present invention will be further described below. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and specific operation process, but the present invention is not limited to this embodiment.
[0025] Example 1 A method for preparing flaky silicon carbide comprises the following steps: Step 1: Select activated carbon as the carbon source. The activated carbon is purchased from Tianjin Huasheng Chemical Reagent Co., Ltd., and quartz sand is used as the silicon source.
[0026] First, activated carbon and PVA were mixed in a mass ratio of 20:1 and placed in a nylon ball mill. Then, anhydrous ethanol was added, and the amount of anhydrous ethanol added was 100% of the total mass of activated carbon and PVA. Ball milling was carried out in a planetary ball mill. The ball mill speed was 200 r / min, forward rotation for 10 minutes, interval for 5 minutes, and reverse rotation for 10 minutes. The total ball milling time was 4 hours to ensure sufficient mixing. Subsequently, the mixture was dried at 80°C for 12 hours. After drying, it was ground through a 200-mesh sieve to obtain a mixed powder.
[0027] Step 2: After taking out the mixed powder and weighing it, alternately pour 0.32g of the mixed powder and 0.4g of quartz sand (particle size of 250 mesh) into a mold with a diameter of 30mm. The mixed powder forms a carbon layer and the quartz sand forms a silicon layer. The mixed powder and quartz sand are poured into the mold in layers and flattened. There are 10 layers of carbon and silicon layers in total. Use a powder tablet press to maintain a pressure of 4MPa for 3min to obtain a green body.
[0028] Step 3: Place the pressed green body into an alumina crucible, cover it with quartz sand, then place the crucible into a heat-insulating structure, and place the whole into a microwave sintering furnace. Heat it to 1100°C for microwave sintering, and keep it warm for 20 minutes. After the heating is completed, the flake silicon carbide is obtained. The specific process of microwave heating is shown in Figure 1 .
[0029] Example 2 The difference between this embodiment and embodiment 1 is that the holding time of microwave sintering is different. The holding time of this embodiment is 40 minutes.
[0030] Example 3 The difference between this embodiment and embodiment 1 is that the holding time of microwave sintering is different. The holding time of this embodiment is 60 minutes.
[0031] Example 4 The difference between this embodiment and embodiment 1 is that the microwave sintering temperature is different. The microwave sintering temperature of this embodiment is 800°C.
[0032] Example 5 The difference between this embodiment and embodiment 1 is that the microwave sintering temperature is different. The microwave sintering temperature of this embodiment is 900°C.
[0033] Example 6 The difference between this embodiment and embodiment 1 is that the microwave sintering temperature is different. The microwave sintering temperature of this embodiment is 1000°C.
[0034] Example 7 The difference between this embodiment and embodiment 1 is that the microwave sintering temperature is different. The microwave sintering temperature of this embodiment is 1200°C.
[0035] Comparative Example 1 A method for preparing silicon carbide comprises the following steps: Step 1: Select activated carbon as the carbon source and quartz sand as the silicon source.
[0036] First, activated carbon and PVA were mixed in a mass ratio of 20:1 and placed in a nylon ball mill. Then, anhydrous ethanol was added, and the amount of anhydrous ethanol added was 100% of the total mass of activated carbon and PVA. Ball milling was carried out in a planetary ball mill. The ball mill speed was 200 r / min, forward rotation for 10 minutes, interval for 5 minutes, and reverse rotation for 10 minutes. The total ball milling time was 4 hours to ensure sufficient mixing. Subsequently, the mixture was dried at 80°C for 12 hours. After drying, it was ground through a 200-mesh sieve to obtain a mixed powder.
[0037] Step 2: After taking out the mixed powder and weighing it, mix 3.2 g of the mixed powder and 4 g of quartz sand (particle size 250 mesh) and pour them into a mold with a diameter of 30 mm. Use a powder tablet press to maintain a pressure of 4 MPa for 3 minutes to obtain a green body.
[0038] Step 3: Place the pressed green body into an alumina crucible, cover it with quartz sand, then place the crucible into an insulation structure, and place the whole into a microwave sintering furnace. Heat it to 1100°C for microwave sintering, and keep it warm for 20 minutes. After heating, silicon carbide is obtained.
[0039] In this comparative example, activated carbon and quartz sand are directly mixed and then subjected to microwave heating. A layered pressing sampling method is not adopted, and thus a flaky silicon carbide product cannot be obtained. The sample obtained in this comparative example is silicon carbide particles.
[0040] Comparative Example 2 A method for preparing silicon carbide comprises the following steps: Step 1: Select activated carbon as the carbon source and quartz sand as the silicon source.
[0041] First, activated carbon and PVA were mixed in a mass ratio of 20:1 and placed in a nylon ball mill. Then, anhydrous ethanol was added, and the amount of anhydrous ethanol added was 100% of the total mass of activated carbon and PVA. Ball milling was carried out in a planetary ball mill. The ball mill speed was 200 r / min, forward rotation for 10 minutes, interval for 5 minutes, and reverse rotation for 10 minutes. The total ball milling time was 4 hours to ensure sufficient mixing. Subsequently, the mixture was dried at 80°C for 12 hours. After drying, it was ground through a 200-mesh sieve to obtain a mixed powder.
[0042] Step 2: After taking out the mixed powder and weighing it, alternately pour 0.08g of the mixed powder and 0.4g of quartz sand (particle size of 250 mesh) into a mold with a diameter of 30mm. The mixed powder forms a carbon layer and the quartz sand forms a silicon layer. The mixed powder and quartz sand are poured into the mold in layers and flattened. There are 10 layers of carbon and silicon layers in total. Use a powder tablet press to maintain a pressure of 4MPa for 3min to obtain a green body.
[0043] Step 3: Place the pressed green body into an alumina crucible, cover it with quartz sand, then place the crucible into an insulation structure, and place the whole into a microwave sintering furnace. Heat it to 1100°C for microwave sintering, and keep it warm for 20 minutes. After heating, silicon carbide is obtained.
[0044] The amount of mixed powder added in this comparative example is greatly reduced compared to the embodiment, which results in insufficient addition of the carbon source. Some quartz sand raw materials still remain in the product. The silicon carbide generated by the heating reaction melts with the remaining quartz sand raw materials, and the flaky structure of the silicon carbide disappears.
[0045] Test example The silicon carbide prepared in Example 1 was characterized. Figure 1 The heating curve of microwave sintering in Example 1 is shown in FIG. Figure 1 It can be seen that microwave sintering technology achieves rapid heating and precise control of materials by directly converting microwave energy into thermal energy. Figure 2 The XRD pattern of silicon carbide prepared in Example 1 is as follows. Figure 2 It can be seen that the product prepared in Example 1 has characteristic peaks of silicon carbide, indicating that flaky silicon carbide has been successfully synthesized and the purity of the silicon carbide product can be maintained at a high level. Figure 3 This is the SEM image of silicon carbide prepared in Example 1. Figure 3 It can be seen that silicon carbide has a flaky structure with a thickness of approximately 1 mm. The SEM image shows that the generated flaky silicon carbide has good crystallinity and the surface and boundary are closely connected. Figure 4 The SEM image of the sample prepared in Comparative Example 2 is as follows: Figure 4 It can be seen that when the quartz sand content is high, a molten silicon oxide layer will be formed on the surface, and silicon carbide will only be generated in small amounts on the surface. When the quartz sand content is high, the formation of silicon carbide will be hindered. Figure 5 This is the appearance of silicon carbide prepared in Example 1, Figure 5 It can be seen that the appearance of the silicon carbide product is also flaky.
[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.
Claims
1. A method for preparing flaky silicon carbide, characterized in that: The following steps are involved: (1) Mixing the carbon source and the binder and ball milling to obtain a mixed powder; (2) Alternately pouring the mixed powder and silicon source into a mold to form a carbon layer and a silicon layer, respectively, and finally pressing and molding to obtain a green body; (3) The green body is subjected to microwave sintering to obtain flaky silicon carbide.
2. The method for preparing flaky silicon carbide according to claim 1, wherein: In step (1), the carbon source is activated carbon, the binder is PVA, and the mass ratio of the carbon source to the binder is (15-25):
1.
3. The method for preparing flaky silicon carbide according to claim 1, wherein: In step (1), during the ball milling of the carbon source and the binder, a grinding medium is added, the amount of the grinding medium added is 50-150% of the total mass of the carbon source and the binder, the grinding medium is anhydrous ethanol or deionized water, the ball-to-material ratio is 2-7:1, the rotation speed is 180-220 r / min, and the ball milling time is 2-4 h.
4. The method for preparing flaky silicon carbide according to claim 1, wherein: In step (2), after ball milling, the mixed powder is dried, ground and sieved and then poured into a mold.
5. The method for preparing flaky silicon carbide according to claim 4, wherein: In step (2), the drying temperature is 60-100°C, and the product is ground and passed through a 200-mesh sieve.
6. The method for preparing flaky silicon carbide according to claim 1, wherein: The carbon-silicon molar ratio of the carbon source to the silicon source is 2-4:
1.
7. The method for preparing flaky silicon carbide according to claim 1, wherein: In step (2), the silicon source is quartz sand, and the particle size of the quartz sand is 200-250 mesh.
8. The method for preparing flaky silicon carbide according to claim 1, wherein: In step (2), the mass of each layer of mixed powder and the mass of each layer of silicon source in the mold are 0.16~0.32g:0.4g.
9. The method for preparing flaky silicon carbide according to claim 1, wherein: In step (2), the mold is a powder tableting mold with a diameter of 30 mm.
10. The method for preparing flaky silicon carbide according to claim 1, wherein: In step (3), the microwave sintering conditions are as follows: input power is 810~6800W, heating to 800~1200℃ at a heating rate of 10~60℃ / min, and then keeping warm for 10min~60min.