Process method for preparing SiC coating on C / C composite material by using molten salt method
The SiC coating was prepared on C/C composite material by molten salt method, which solved the problems of slow coating deposition rate, weak adhesion and high temperature reaction in the existing technology. It achieved efficient and low-cost SiC coating preparation, which is suitable for high temperature and oxygen environment.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHAOXING RES INST OF SHANGHAI UNIV
- Filing Date
- 2026-01-20
- Publication Date
- 2026-05-01
AI Technical Summary
Existing technologies for preparing coatings on C/C composite surfaces suffer from slow deposition rates, long preparation cycles, weak adhesion between the coating and the substrate, and the need for high-temperature reactions, all of which affect material properties.
A SiC coating was prepared on C/C composite material using the molten salt method. By reacting K2SiF6 and Si powder in a vacuum tube furnace under micro-positive pressure, and controlling the temperature and time, a uniform and continuous SiC coating was prepared, reducing damage to the carbon fiber.
The prepared SiC coating has good adhesion to the substrate, the process is simple and low-cost, and it reduces the impact of high-temperature reactions on material properties, making it suitable for high-temperature oxygen-containing environments.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of C / C composite material technology, and more particularly to a process for preparing a SiC coating on C / C composite materials using a molten salt method. Background Technology
[0002] Carbon / carbon (C / C) composites possess a range of excellent properties, such as low density, corrosion resistance, high specific strength, stable coefficient of friction, and good thermal and electrical conductivity. Their strength increases with temperature, enabling them to be successfully used as high-temperature structural composites in environments above 2000 °C.
[0003] However, C / C composites have a significant drawback in application: these excellent high-temperature properties can only be maintained under an inert atmosphere or at temperatures below 450 °C. In an aerobic environment, when the temperature exceeds 450 °C, C / C composites oxidize, leading to a sharp decline in their mechanical properties. This susceptibility to oxidation in high-temperature, aerobic environments severely restricts the practical application of C / C composites as thermal structural materials.
[0004] Solving the oxidation problem of C / C composites in high-temperature, aerobic environments has become crucial for their applications. Common methods for protecting C / C composites include preparing multilayer and gradient antioxidant ceramic coatings on their surfaces.
[0005] Currently, methods for preparing coatings include chemical vapor deposition (CVD), slurry brushing, plasma spraying, embedding, and the molten salt method mentioned in this paper. CVD utilizes precursor pyrolysis to deposit coatings on a substrate, producing uniform and continuous coatings. However, CVD has a slow deposition rate, a long coating preparation cycle, and the coating's microstructure and adhesion strength to the substrate are easily affected by deposition parameters. Slurry brushing is relatively simple, using a mixture of raw material powder and organic solvents to obtain a slurry, which is then brushed onto the surface of the C / C composite material and cured by heating to obtain the coating. Although slurry brushing is simple, the adhesion between the resulting coating and the substrate is weaker compared to other methods. Plasma spraying uses a plasma arc to melt powder and spray it at high speed onto the substrate surface. Plasma spraying has a basis for industrial applications, but the setup of plasma spraying equipment is relatively complex and has high equipment costs. The embedding method is similar to the molten salt method mentioned in this article, but the embedding method requires a higher temperature (above 1900 ℃) to carry out a full reaction, which will cause some damage to the carbon fiber and lead to a decrease in its mechanical properties. Summary of the Invention
[0006] In view of the aforementioned shortcomings of the prior art, the technical problem to be solved by the present invention is that existing methods for preparing coatings on the surface of C / C composite materials suffer from slow deposition rates, long coating preparation cycles, weak adhesion between the prepared coating and the substrate, and higher required temperatures. The present invention provides a process for preparing SiC coatings on C / C composite materials using the molten salt method. This method effectively reduces the impact of high-temperature reactions on the carbon fibers in the C / C composite material, has a simple process flow, low reaction temperature, inexpensive raw materials, and produces a uniform and continuous coating surface with good adhesion to the substrate.
[0007] To achieve the above objectives, this invention provides a process for preparing SiC coatings on C / C composite materials using the molten salt method, comprising the following steps:
[0008] The C / C composite material is pretreated and then used for later use.
[0009] Weigh 440 grams of K2SiF6 powder and 56 grams of Si powder in a 1:1 molar ratio, grind them thoroughly, and then dry them.
[0010] The dried mixed powder was spread evenly on the bottom of the graphite crucible, and then the pretreated C / C composite material was placed in the graphite crucible. The C / C composite material was then evenly covered with the mixed powder.
[0011] The graphite crucible was placed in a vacuum tube furnace for heating treatment, and then cooled to room temperature.
[0012] Remove the graphite crucible from the heating furnace, and take out the C / C composite material. After ultrasonic cleaning and drying with deionized water and anhydrous ethanol, the C / C-SiC composite material is obtained.
[0013] Furthermore, the C / C composite material is pretreated by sanding and polishing it with sandpaper, then cleaning and drying it, followed by ultrasonic cleaning and drying with deionized water and ethanol solution.
[0014] Furthermore, the C / C composite material was polished sequentially with 180, 320 and 400 grit sandpaper, then ultrasonically cleaned with deionized water and a mixture of deionized water and anhydrous ethanol for 30-40 min, and dried in a 60 ℃ drying oven for 12-30 h for later use.
[0015] Further, weigh 440 grams of K2SiF6 powder and 56 grams of Si powder in a 1:1 molar ratio, add the weighed K2SiF6 powder and Si powder to an agate mortar, grind them thoroughly with a grinding rod, place the ground and mixed powder in a storage container, and dry it in a 60 ℃ drying oven for 12~24 h for later use.
[0016] Furthermore, the dried mixed powder is spread evenly on the bottom of the graphite crucible, with the powder thickness being approximately 1 / 3 of the height of the graphite crucible.
[0017] Furthermore, the C / C composite material is uniformly covered with a mixed powder, the thickness of which is approximately 1 / 3 of the height of the graphite crucible.
[0018] Furthermore, the graphite crucible is placed in a vacuum tube furnace for heating treatment. Specifically, the graphite crucible is placed in a vacuum tube furnace, argon gas is introduced as a protective atmosphere, and the temperature is increased at a rate of 5~10 ℃ / min to raise the furnace temperature from room temperature to 1100~1500 ℃, and held at that temperature for 1~3 h.
[0019] Furthermore, after heat preservation, the temperature is reduced to 400℃ at a cooling rate of 5℃ / min to end the process and then cooled to room temperature with the furnace.
[0020] Further, the graphite crucible is removed from the heating furnace, and the C / C composite material is taken out and ultrasonically cleaned and dried with deionized water and anhydrous ethanol to obtain the C / C-SiC composite material. Specifically, the graphite crucible is removed from the heating furnace, the C / C composite material is taken out and ultrasonically cleaned with deionized water and a mixed solution of deionized water and anhydrous ethanol for 10~30 min, and then dried in a drying oven at 60 ℃ for 12~30 h to obtain the C / C-SiC composite material.
[0021] Furthermore, the purity of K2SiF6 powder is ≥99%, and the powder particle size is 1-3 μm.
[0022] Technical effect
[0023] This invention provides a process for preparing SiC coatings on C / C composite materials using the molten salt method. This method involves growing a SiC coating on C / C composite materials under slightly positive pressure using the molten salt method. The SiC coating effectively fills the pores in the C / C composite material and effectively encapsulates the carbon fibers. The raw material K2SiF6 used in the molten salt method for preparing SiC coatings is cheaper than trichloromethylsilane (MTS) and H2 used in chemical vapor deposition, and the process is simpler. Furthermore, during the heating process, the tubular furnace cavity does not require vacuuming and maintaining negative pressure; after heating, argon gas is introduced to maintain a slightly positive pressure, greatly reducing the requirements for equipment.
[0024] The following will further explain the concept, specific structure, and technical effects of the present invention in conjunction with the accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Attached Figure Description
[0025] Figure 1These are SEM images of the SiC coating on the surface of the C / C-SiC composite material prepared in Example 1;
[0026] Figure 2 These are surface energy dispersive spectroscopy (EDS) images of the C / C-SiC composite material prepared in Example 1;
[0027] Figure 3 These are SEM images of the SiC coating on the surface of the C / C-SiC composite material prepared in Example 2;
[0028] Figure 4 These are surface energy dispersive spectroscopy (EDS) images of the C / C-SiC composite material prepared in Example 2;
[0029] Figure 5 These are schematic diagrams of coating preparation in Examples 1 and 2. Detailed Implementation
[0030] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.
[0031] In the following description, specific details, such as particular internal procedures and techniques, are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will appreciate that the invention may be practiced in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of the invention with unnecessary detail.
[0032] like Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 As shown in Tables 1 and 2, the following examples illustrate the invention in detail by using the molten salt method to prepare a SiC coating on a C / C composite material under micro-positive pressure conditions. By controlling the reaction temperature and reaction time, the microstructure of the SiC coating on the surface of the C / C-SiC composite material is controlled, resulting in a uniform SiC coating morphology and improved adhesion between the coating and the substrate.
[0033] Example 1:
[0034] Step 1: Pretreatment of C / C composite material
[0035] With a density of 1.2 g / cm³ 3The C / C composite material was polished with 180, 320 and 400 grit sandpaper in sequence, then ultrasonically cleaned with deionized water and deionized water-anhydrous ethanol mixed solution for 30 min in sequence, and dried in a 60 ℃ drying oven for 12 h for later use.
[0036] Step 2: Prepare a SiC coating on the surface of the C / C composite material
[0037] 1) Weigh 440g of K2SiF6 powder and 56g of Si powder in a 1:1 ratio. Place the two powders in an agate mortar and grind them thoroughly in a clockwise direction. Collect the mixed powder after grinding and dry it in a 60 ℃ drying oven for 12 h for later use.
[0038] 2) Spread the mixed powder prepared in 1) evenly in a graphite crucible, with the powder thickness being approximately 1 / 3 of the height of the graphite crucible. Then place the pretreated C / C composite material into the graphite crucible, and subsequently cover the C / C composite material with the mixed powder, with the powder thickness being approximately 1 / 3 of the height of the graphite crucible.
[0039] 3) Place the graphite crucible in a vacuum furnace, introduce argon gas as a protective atmosphere, and raise the temperature from room temperature to 1300 ℃ at a rate of 5 ℃ / min, holding for 2 h; then lower the temperature to room temperature at a rate of 5 ℃ / min. Remove the crucible from the furnace, take out the C / C composite material, and ultrasonically clean it with deionized water and a mixture of deionized water and anhydrous ethanol for 20 min. Dry it in a 60 ℃ drying oven for 12 h to obtain the C / C-SiC composite material.
[0040] The purity of K2SiF6 powder is ≥99%, and the powder particle size is 1-3 μm.
[0041] The purity of the Si powder is 99.9%, and the particle size is 1-3 μm.
[0042] Example 2
[0043] Step 1: Pretreatment of C / C composite material
[0044] With a density of 1.2 g / cm³ 3 The C / C composite material was polished with 180, 320 and 400 grit sandpaper in sequence, then ultrasonically cleaned with deionized water and a mixture of deionized water and anhydrous ethanol for 35 min in sequence, and dried in a 60 ℃ drying oven for 24 h for later use.
[0045] Step 2: Prepare a SiC coating on the surface of the C / C composite material
[0046] 1) Weigh 440g of K2SiF6 powder and 56g of Si powder in a 1:1 ratio. Place the two powders in an agate mortar and grind them thoroughly in a clockwise direction. Collect the mixed powder after grinding and dry it in a 60 ℃ drying oven for 12 h for later use.
[0047] 2) Spread the mixed powder prepared in 1) evenly in a graphite crucible, with the powder thickness being approximately 1 / 3 of the height of the graphite crucible. Then place the pretreated C / C composite material into the graphite crucible, and subsequently cover the C / C composite material with the mixed powder, with the powder thickness being approximately 1 / 3 of the height of the graphite crucible.
[0048] 3) Place the graphite crucible in a vacuum furnace, introduce argon gas as a protective atmosphere, and raise the temperature from room temperature to 1350 ℃ at a rate of 5 ℃ / min, holding for 3 h; then lower the temperature to room temperature at a rate of 5 ℃ / min. Remove the crucible from the furnace, take out the C / C composite material, and ultrasonically clean it with deionized water and a mixture of deionized water and anhydrous ethanol for 20 min. Dry it in a 60 ℃ drying oven for 12 h to obtain the C / C-SiC composite material.
[0049] The purity of K2SiF6 powder is ≥99%, and the powder particle size is 1-3 μm.
[0050] The purity of the Si powder is 99.9%, and the particle size is 1-3 μm.
[0051] Figure 1 This is a SEM image of the SiC coating prepared on the surface of the carbon / carbon composite material as described in Example 1. It can be seen that a SiC coating was successfully prepared on the surface of the C / C composite material. The SiC coating begins to grow on the carbon fibers of the C / C composite material and gradually encapsulates the carbon fibers, providing protection.
[0052] Figure 2 These are energy dispersive spectroscopy (EDS) diffraction images of the C / C-SiC composite surface prepared in Example 1. It can be seen that the molten salt method can prepare SiC products on the C / C composite material, and these products adhere well to the C / C composite surface. Table 1 shows... Figure 2 The EDS energy spectrum data of the selected diffraction region shows that the atomic percentages of Si and C elements in the diffraction data are 30.37% and 54.90%, respectively. This is different from the 1:1 atomic percentage. This may be because the reaction temperature in Example 1 is low, resulting in an incomplete reaction process and a low SiC yield.
[0053] Table 1
[0054]
[0055] Figure 3The image shows a SEM image of the C / C-SiC composite material prepared in Example 2. It can be seen that when the temperature is increased to 1350 °C, the SiC coating on the surface is more uniformly and densely distributed.
[0056] Figure 4 Table 2 shows the energy dispersive spectroscopy (EDS) diffraction images of the C / C-SiC composite surface prepared in Example 2. Figure 4 The EDS energy dispersive spectroscopy data of the selected diffraction region shows that when the temperature rises to 1350 ℃, the atomic percentage of Si is 42.40% and the atomic percentage of C is 41.07%. The atomic percentages of Si and C are closer to 1:1, indicating that the reaction process is more complete at 1350 ℃, resulting in the formation of more SiC.
[0057] Table 2
[0058]
[0059] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.
Claims
1. A process for preparing a SiC coating on a C / C composite material using the molten salt method, characterized in that, Includes the following steps: The C / C composite material is pretreated and then used for later use. Weigh 440 grams of K2SiF6 powder and 56 grams of Si powder in a 1:1 molar ratio, grind them thoroughly, and then dry them. The dried mixed powder was spread evenly on the bottom of the graphite crucible, and then the pretreated C / C composite material was placed in the graphite crucible. The C / C composite material was then evenly covered with the mixed powder. The graphite crucible was placed in a vacuum tube furnace for heating treatment, and then cooled to room temperature. Remove the graphite crucible from the heating furnace, and then take out the C / C composite material. After ultrasonic cleaning and drying with deionized water and anhydrous ethanol, the C / C-SiC composite material is obtained.
2. The process for preparing a SiC coating on a C / C composite material using the molten salt method as described in claim 1, characterized in that, The pretreatment of C / C composite material involves sanding and polishing the C / C composite material with sandpaper, cleaning and drying it, and then ultrasonically cleaning and drying it with deionized water and ethanol solution.
3. The process for preparing a SiC coating on a C / C composite material using the molten salt method as described in claim 2, characterized in that, The C / C composite material was polished sequentially with 180, 320 and 400 grit sandpaper, then ultrasonically cleaned with deionized water and a mixture of deionized water and anhydrous ethanol for 30-40 min, and dried in a 60 ℃ drying oven for 12-30 h for later use.
4. The process for preparing a SiC coating on a C / C composite material using the molten salt method as described in claim 1, characterized in that, Weigh 440g of K2SiF6 powder and 56g of Si powder in a 1:1 molar ratio. Add the weighed K2SiF6 powder and Si powder to an agate mortar and grind them thoroughly with a grinding rod. Place the ground and mixed powder in a storage container and dry it in a 60 ℃ drying oven for 12~24 h before use.
5. The process for preparing a SiC coating on a C / C composite material using the molten salt method as described in claim 1, characterized in that, Spread the dried mixed powder evenly on the bottom of the graphite crucible, with the powder thickness being about 1 / 3 of the height of the graphite crucible.
6. The process for preparing a SiC coating on a C / C composite material using the molten salt method as described in claim 5, characterized in that, The C / C composite material is uniformly covered with a mixed powder, the thickness of which is about 1 / 3 of the height of the graphite crucible.
7. The process for preparing a SiC coating on a C / C composite material using the molten salt method as described in claim 1, characterized in that, The graphite crucible is placed in a vacuum tube furnace for heating treatment. Specifically, the graphite crucible is placed in a vacuum tube furnace, argon gas is introduced as a protective atmosphere, and the temperature is increased at a rate of 5~10 ℃ / min to raise the furnace temperature from room temperature to 1100~1500 ℃, and held at that temperature for 1~3 h.
8. The process for preparing a SiC coating on a C / C composite material using the molten salt method as described in claim 7, characterized in that, After heat preservation, the temperature is reduced to 400℃ at a cooling rate of 5℃ / min to end the process and then cooled to room temperature with the furnace.
9. The process for preparing a SiC coating on a C / C composite material using the molten salt method as described in claim 8, characterized in that, Remove the graphite crucible from the heating furnace, take out the C / C composite material, and ultrasonically clean and dry it with deionized water and anhydrous ethanol to obtain the C / C-SiC composite material. Specifically, remove the graphite crucible from the heating furnace, take out the C / C composite material, ultrasonically clean it with deionized water and a mixed solution of deionized water and anhydrous ethanol for 10~30 min, and dry it in a drying oven at 60 ℃ for 12~30 h to obtain the C / C-SiC composite material.
10. The process for preparing a SiC coating on a C / C composite material using the molten salt method as described in claim 1, characterized in that, The purity of K2SiF6 powder is ≥99%, and the powder particle size is 1-3 μm.