Preparation method of directionally arranged silicon carbide particles
By preparing silica-coated carbon particles using microwave sintering under a biomass carbon template, the problems of complex preparation process and low purity of oriented silicon carbide particles were solved, and efficient and simple large-scale production was achieved.
Patent Information
- Application Number
- CN202510940584.9
- 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 preparation methods of oriented silicon carbide particles are complex, the sintering environment is harsh, the product purity is low, and the production efficiency is low, making it difficult to achieve large-scale production.
The microwave sintering method is used to prepare a gel of silica-coated carbon particles under a biomass carbon template, which is converted into directional silicon carbide particles through microwave heating, simplifying the preparation process and improving purity and efficiency.
It achieves efficient and simple large-scale production of pure, directional silicon carbide particles, improves energy efficiency and shortens preparation time.
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Figure CN120647388A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of inorganic non-metallic materials, and in particular to a method for preparing directionally arranged silicon carbide particles. Background Art
[0002] Silicon carbide particles exhibit advantages in many aspects. For example, they have high strength and hardness, which can withstand wear and pressure under extreme conditions. Silicon carbide particles can remain stable at high temperatures and are not easily deformed or failed, which makes them perform well in high-temperature environments. Silicon carbide particles have strong chemical stability and can resist corrosion from a variety of chemicals, ensuring that they can maintain their performance in corrosive environments. Silicon carbide particles also have good thermal conductivity and electrical conductivity, which makes them have broad application prospects in electronic devices and heat dissipation. Silicon carbide particles have a relatively low density, which helps reduce the overall weight of components, which is particularly important in fields such as aerospace and automobiles that require lightweight design. Silicon carbide particles also exhibit excellent wear resistance and oxidation resistance, which can extend the service life of the material and reduce maintenance costs. These advantages make silicon carbide particles irreplaceable in many fields.
[0003] Silicon carbide itself has advantages such as good thermal conductivity, low density, and oxidation resistance. While possessing these advantages, oriented silicon carbide can also form a continuous thermal conductivity network with low thermal resistance, significantly improving the thermal conductivity of the composite material (especially along the arrangement direction). It can also effectively bear external forces, forming a continuous stress transfer path along a specific direction, reducing stress concentration, and thus improving the composite material's flexural strength, hardness, and fracture toughness. Therefore, research on the preparation method of oriented silicon carbide is very important.
[0004] Currently, researchers are exploring new processes for preparing aligned silicon carbide particles using a variety of raw materials and methods. However, these methods all rely on traditional heating methods, requiring a closed environment, high temperatures, a certain pressure, and inert gas filling. These complex techniques and demanding sintering conditions are also associated with expensive, environmentally polluting, low-purity raw materials, excessively high sintering temperatures, low production efficiency, and difficulties in large-scale production.
[0005] Therefore, there is an urgent need for a preparation method for sintering oriented silicon carbide particles with high sintering efficiency, fast rate, and easy large-scale production. Summary of the Invention
[0006] The purpose of the present invention is to provide a method for preparing oriented silicon carbide particles to address the problems of the above-mentioned methods for preparing oriented silicon carbide particles, such as the complex synthesis process, harsh sintering environment, and low product purity. The present invention uses microwave sintering to produce oriented silicon carbide particles under a biomass carbon template. The present invention uses microwave sintering to achieve overall heating of the material, uniform heating inside and outside, high sintering efficiency, fast sintering rate, shortened preparation time, improved energy efficiency, and produces high-purity oriented silicon carbide particles.
[0007] To achieve the above object, the present invention provides a method for preparing oriented silicon carbide particles, comprising the following steps:
[0008] (1) preparing a gel of silica-encapsulated carbon particles by a sol-gel method, and then drying the gel to obtain a precursor of silica-encapsulated carbon particles;
[0009] (2) The precursor is pressed into a green body, which is placed in a crucible and covered with quartz sand. The green body is then heated by microwaves. After the reaction is completed, oriented silicon carbide particles are obtained.
[0010] Preferably, in step (1), the specific preparation process of the gel of silicon dioxide-coated carbon particles is:
[0011] First, ethyl orthosilicate, anhydrous ethanol and deionized water are mixed to obtain a mixed solution. Then, citric acid is added to the mixed solution and heated and stirred. Then, charcoal particles are added and stirring is continued. Finally, an ammonia solution is added to form a gel in which the carbon particles are wrapped with silica.
[0012] Preferably, in step (1), the volume ratio of ethyl orthosilicate, anhydrous ethanol and deionized water is 23:50:(50-80), the mass volume ratio of citric acid and the mixed solution is 1 g:(20-25) mL, and the mass volume ratio of charcoal particles and the mixed solution is 1 g:(20-25) mL.
[0013] The present invention has specific restrictions on the amount of charcoal particles added. Microwave heating synthesis is mainly based on the chemical reaction between silicon dioxide and carbon to obtain silicon carbide and carbon monoxide. If the amount of charcoal particles added is too small, more silicon dioxide will remain in the product, which will reduce the purity of the silicon carbide. If the amount of charcoal particles added is too large, a large amount of carbon will remain in the product, which will also reduce the purity of the silicon carbide. The excess carbon may need to be removed by high-temperature calcination, increasing energy consumption and cost. In addition, if the amount of charcoal particles added is too large, it may also affect the growth and deposition of silicon carbide on the charcoal particles (biomass template) to a certain extent, resulting in the failure to obtain a directional silicon carbide product. Moreover, if too much silicon dioxide is wrapped around the charcoal particles, it may hinder gas-phase mass transfer, resulting in uneven local reaction and affecting the morphology.
[0014] Preferably, in step (1), the heating is water bath heating, the heating temperature is 35-45° C., the stirring time is 1-3 hours, the stirring time is continued for 1-3 hours, and the ammonia solution includes deionized water and ammonia water in a volume ratio of 2:1.
[0015] Preferably, in step (1), the particle size of the charcoal particles is 160-200 mesh.
[0016] Preferably, in step (1), the drying temperature is 60-100° C. and the drying time is 10-12 h.
[0017] Preferably, in step (2), the dried precursor is ground and sieved and then poured into a mold, and is pressed using a micro isostatic press to obtain a cylindrical green body.
[0018] Preferably, in step (2), the pressing pressure is 2-3 MPa and the pressing time is 0.5-3 min.
[0019] Preferably, in step (2), the sieve used for grinding and sieving is 150-250 mesh.
[0020] Preferably, in step (2), 25 g of the dried precursor is ground, sieved, poured into a mold with a diameter of 60 mm, and pressed to obtain a cylindrical green body.
[0021] Preferably, in step (2), the microwave heating temperature is 700-1200° C., the heating time is 0.5-2 h, the heating frequency is 915-2450 MHz, the holding time is 10-30 min, and the input power is 0.48-4 kW.
[0022] Therefore, the present invention adopts the above-mentioned method for preparing oriented silicon carbide particles, which has the following beneficial effects:
[0023] The present invention first prepares silicon dioxide-coated carbon particles as a precursor, and then converts them into silicon carbide by microwave heating. During the heating process, the growth of the silicon carbide particles uses biochar as a template, and finally forms silicon carbide particles with a directional arrangement. The preparation method is simple and easy, and is suitable for large-scale production of pure silicon carbide particles.
[0024] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 XRD patterns of SiC particles in Examples 1 to 6;
[0026] Figure 2 XRD patterns of SiC particles in Examples 7 to 12;
[0027] Figure 3 is a SEM image of the SiC particles of Example 1;
[0028] Figure 4 This is the SEM image of the SiC particles in Example 8. DETAILED DESCRIPTION
[0029] 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.
[0030] Example 1
[0031] A method for preparing oriented silicon carbide particles comprises the following steps:
[0032] Step 1: Selecting tetraethyl orthosilicate as the silicon source and litchi wood charcoal particles as the carbon source;
[0033] Tethyl orthosilicate, anhydrous ethanol and deionized water were mixed in a volume ratio of 23:35:50 to obtain 448 mL of a mixed solution. 20 g of citric acid was then added to the mixture, and the mixture was stirred in a water bath at 40 ° C for 2 h. Then, 20 g of litchi charcoal particles (200 mesh) were added, and the mixture was stirred in a water bath for 2 h. Ammonia solution (ammonia: deionized water = 1:2 v / v) was titrated until a gel was formed. After stirring for 1 h, the mixture was dried at 80 ° C for 12 h to obtain a precursor. Litchi charcoal particles were purchased from Taobao Yifang Charcoal Factory Enterprise Store and then ground through a 200 mesh sieve to obtain litchi charcoal particles (200 mesh).
[0034] Step 2: Grind the dried precursor through a 200-mesh sieve to obtain a precursor powder, pour 25 g of the precursor powder into a mold with a diameter of 60 mm, and use an isostatic press to maintain the pressure at 2.5 MPa for 1 minute to obtain a cylindrical green body. Place the pressed green body in an alumina crucible and cover it with quartz sand. The entire green body is covered with quartz sand, specifically 3 cm of quartz sand below the green body and 1 cm of quartz sand above the green body. Then place the crucible in a microwave sintering furnace with an input power of 720 kW and a heating frequency of 2450 MHz. Microwave sintering is performed at a temperature of 700°C for 10 minutes to obtain oriented silicon carbide fibers.
[0035] Example 2
[0036] The difference between this embodiment and embodiment 1 is that the microwave heating temperature is different. In this embodiment, the microwave heating temperature is increased to 800°C.
[0037] Example 3
[0038] The difference between this embodiment and embodiment 1 is that the microwave heating temperature is different. In this embodiment, the microwave heating temperature is increased to 900°C.
[0039] Example 4
[0040] The difference between this embodiment and embodiment 1 is that the microwave heating temperature is different. In this embodiment, the microwave heating temperature is increased to 1000°C.
[0041] Example 5
[0042] The difference between this embodiment and embodiment 1 is that the microwave heating temperature is different. In this embodiment, the microwave heating temperature is increased to 1100°C.
[0043] Example 6
[0044] The difference between this embodiment and embodiment 1 is that the microwave heating temperature is different. In this embodiment, the microwave heating temperature is increased to 1200°C.
[0045] Example 7
[0046] The difference between this embodiment and embodiment 1 is that the holding time of microwave heating is different. The holding time of microwave heating in this embodiment is 20 minutes.
[0047] Example 8
[0048] The difference between this embodiment and embodiment 1 is that the microwave heating temperature and the holding time are different. In this embodiment, the microwave heating temperature is raised to 800° C. and the holding time is 20 minutes.
[0049] Example 9
[0050] The difference between this embodiment and embodiment 1 is that the microwave heating temperature and the holding time are different. In this embodiment, the microwave heating temperature is raised to 900° C. and the holding time is 20 minutes.
[0051] Example 10
[0052] The difference between this embodiment and embodiment 1 is that the microwave heating temperature and the holding time are different. In this embodiment, the microwave heating temperature is raised to 1000° C. and the holding time is 20 minutes.
[0053] Example 11
[0054] The difference between this embodiment and embodiment 1 is that the microwave heating temperature and the holding time are different. In this embodiment, the microwave heating temperature is raised to 1100° C. and the holding time is 20 minutes.
[0055] Example 12
[0056] The difference between this embodiment and embodiment 1 is that the microwave heating temperature and the holding time are different. In this embodiment, the microwave heating temperature is raised to 1200° C. and the holding time is 20 minutes.
[0057] The microwave heating conditions of Examples 1 to 12 are shown in Table 1.
[0058] Table 1 Microwave heating conditions of the embodiment
[0059]
[0060]
[0061] Comparative Example 1
[0062] A method for preparing silicon carbide particles comprises the following steps:
[0063] Step 1: Selecting ethyl orthosilicate as a silicon source to prepare silicon dioxide;
[0064] TEOS, anhydrous ethanol, and deionized water were mixed in a volume ratio of 23:35:50 to obtain 448 mL of a mixed solution. 20 g of citric acid was then added to the mixed solution, and the mixture was stirred in a 40°C water bath for 2 h. An ammonia solution (ammonia: deionized water = 1:2 v / v) was titrated until a gel was formed. The mixture was stirred for 1 h, and then dried at 80°C for 12 h to obtain silica.
[0065] Step 2: Mix the silicon dioxide prepared in step 1 with 20 g of litchi charcoal particles (200 mesh) and mix them evenly to obtain a precursor;
[0066] Step 3: Grind the precursor through a 200-mesh sieve to obtain a precursor powder, pour 25 g of the precursor powder into a mold with a diameter of 60 mm, and use an isostatic press to maintain the pressure at 2.5 MPa for 1 min to obtain a cylindrical green body. Place the pressed green body in an alumina crucible and cover it with quartz sand. Then place the crucible in a microwave sintering furnace with an input power of 720 kW and a heating frequency of 2450 MHz. Microwave sintering is performed at a temperature of 700°C for 10 min to obtain silicon carbide.
[0067] In this comparative example, silica and charcoal particles are directly mixed. First, this physical mixing can easily cause uneven mixing, which makes the contact between silica and charcoal particles uneven, and the purity of the synthesized silicon carbide is low. Secondly, due to the physical mixing of silica and charcoal particles, the two substances are randomly distributed in the precursor. It is difficult to achieve directional arrangement of silicon carbide on the surface of the charcoal particles during microwave heating. The charcoal particles are only used as a carbon source and do not play their role as a biomass template. The obtained silicon carbide does not have the directional arrangement morphology described in the embodiment.
[0068] Test example
[0069] The silicon carbide particles prepared in Examples 1 to 12 were characterized. The phase analysis of the products prepared in Examples 1 to 12 was performed using an X-ray diffraction analyzer (XRD). The results are as follows: Figures 1-2 The micromorphology of the products obtained in Examples 1 and 8 was analyzed by scanning electron microscopy (SEM). Figures 3-4 shown.
[0070] from Figure 1 and Figure 2 It can be seen that the products prepared in Examples 1 to 12 have obvious characteristic peaks of silicon carbide, which indicates that the silicon dioxide-encapsulated carbon particles prepared in the present invention are subjected to microwave sintering to synthesize relatively pure silicon carbide particles.
[0071] from Figure 3 and Figure 4 It can be seen from the figure that the silicon carbide prepared by the present invention is granular and is oriented along the direction of the biochar template.
[0072] 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 oriented silicon carbide particles, characterized by: The following steps are involved: (1) preparing a silica-coated carbon particle gel by a sol-gel method, and then drying the gel to obtain a silica-coated carbon particle precursor; (2) The precursor is pressed into shape to obtain a green body, which is placed in a crucible and covered with quartz sand. The green body is then heated by microwaves. After the reaction is completed, oriented silicon carbide particles are obtained.
2. The method for preparing aligned silicon carbide particles according to claim 1, wherein: In step (1), the specific preparation process of the gel of silicon dioxide-coated carbon particles is as follows: First, ethyl orthosilicate, anhydrous ethanol and deionized water are mixed to obtain a mixed solution. Then, citric acid is added to the mixed solution and heated and stirred. Then, charcoal particles are added and stirring is continued. Finally, an ammonia solution is added to form a gel in which the carbon particles are wrapped with silica.
3. The method for preparing aligned silicon carbide particles according to claim 2, wherein: In step (1), the volume ratio of ethyl orthosilicate, anhydrous ethanol and deionized water is 23:50:(50-80), the mass volume ratio of citric acid to the mixed solution is 1 g:(20-25) mL, and the mass volume ratio of charcoal particles to the mixed solution is 1 g:(20-25) mL.
4. The method for preparing aligned silicon carbide particles according to claim 2, wherein: In step (1), the particle size of the charcoal particles is 160-200 mesh.
5. The method for preparing aligned silicon carbide particles according to claim 1, wherein: In step (1), the drying temperature is 60-100°C and the drying time is 10-12 hours.
6. The method for preparing aligned silicon carbide particles according to claim 5, wherein: In step (2), the dried precursor is ground and sieved and then poured into a mold, and a micro isostatic press is used to press and shape the precursor into a cylindrical green body.
7. The method for preparing aligned silicon carbide particles according to claim 6, wherein: In step (2), the pressing pressure is 2-3 MPa and the pressing time is 0.5-3 min.
8. The method for preparing aligned silicon carbide particles according to claim 6, wherein: In step (2), the sieve used for grinding and sieving is 150-250 mesh.
9. The method for preparing aligned silicon carbide particles according to claim 6, wherein: In step (2), 25 g of the dried precursor was ground, sieved, poured into a mold with a diameter of 60 mm, and pressed to obtain a cylindrical green body.
10. The method for preparing aligned silicon carbide particles according to claim 1, wherein: In step (2), the microwave heating temperature is 700~1200℃, the heating time is 0.5~2h, the heating frequency is 915~2450MHz, the holding time is 10~30min, and the input power is 0.48~4kW.