Method for efficiently preparing siC fiber by airflow assisted electrospinning

Abstract

This invention discloses a method for efficiently preparing SiC fibers using airflow-assisted electrospinning. The method includes the following steps: first, dissolving polycarbosilane in a mixed solvent, adding polyvinylpyrrolidone and sodium dodecyl sulfate, and mixing to obtain a spinning solution; wherein the mixed solvent includes ethanol and tetrahydrofuran; then, using an airflow-assisted electrospinning process, electrospinning the spinning solution to obtain a spun product; finally, drying the spun product and then sequentially subjecting it to heating pre-oxidation and calcination to obtain SiC fibers. This invention uses a spinning solution with specific components to prepare SiC fibers, utilizing sodium dodecyl sulfate to improve the conductivity of the spinning solution and increase spinning efficiency; simultaneously, introducing high-speed airflow to assist spinning, operating at a higher liquid supply rate, greatly improves spinning efficiency. Furthermore, using a grid-like irregular receiver, a fiber membrane containing a "skeleton structure" is prepared, which significantly improves spinning efficiency while maintaining high thermal insulation performance.

Description

Technical Field

[0001] This invention belongs to the field of ceramic materials technology, and specifically relates to a method for efficiently preparing SiC fibers by airflow-assisted electrospinning. Background Technology

[0002] Silicon carbide (SiC) fiber is a high-performance ceramic material with advantages such as high-temperature oxidation resistance, high hardness, high strength, high thermal stability, corrosion resistance, and low density. Under extreme conditions, SiC fiber can maintain good performance compared to traditional fiber materials such as carbon fiber. Traditional methods for synthesizing SiC fibers include vapor phase growth methods (such as chemical vapor deposition) and liquid phase growth methods (such as solvothermal methods), but these methods are relatively cumbersome and have relatively low preparation efficiency, making them unsuitable for large-scale preparation of SiC fibers.

[0003] Electrospinning is a technology that utilizes a polymer solution to form a jet stream between electrodes under the influence of an electric field for rapid spinning. It boasts advantages such as simple principle and relatively high production efficiency. In recent years, traditional electrospinning technology has been used to prepare SiC fibers, improving the preparation efficiency to some extent. However, the supply rate of the spinning solution during preparation is only 2 mL, which is still insufficient. Furthermore, due to the use of a single roller receiver, the spun fiber morphology is relatively uniform, consisting only of a film-like structure, a problem present in most current electrospinning technologies. Simultaneously, when spinning with traditional formulations, the spinning process is greatly affected by humidity, and the poor conductivity of the spinning solution often leads to the formation of droplets at the spinning needles, blocking the spinning process. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a method for efficiently preparing SiC fibers by airflow-assisted electrospinning. This method adopts an airflow-assisted electrospinning process, improves the composition of the spinning solution, and uses a receiver with a specific structure. At the same time, the spinning efficiency is greatly improved while the fibers still maintain high thermal insulation performance.

[0005] To address the aforementioned technical problems, a first aspect of the present invention provides a method for preparing SiC fibers, comprising the following steps:

[0006] (1) Dissolve polycarbosilane in a mixed solvent, add polyvinylpyrrolidone and sodium dodecyl sulfate, mix, and obtain a spinning solution; the mixed solvent includes ethanol and tetrahydrofuran;

[0007] (2) The spinning solution is electrospun using an airflow-assisted electrospinning process to obtain the spinning product;

[0008] (3) After drying the spinning product, it is subjected to heating pre-oxidation and calcination in sequence to obtain the SiC fiber.

[0009] Specifically, the SiC fibers of this invention are prepared by electrospinning with a spinning solution of specific components and by utilizing an airflow-assisted process, which greatly improves the preparation efficiency of SiC fibers. This invention uses polycarbosilane as the precursor for SiC fibers, ethanol and tetrahydrofuran as a mixed solvent, and adds a certain amount of sodium dodecyl sulfate and polyvinylpyrrolidone as the spinning solution. Sodium dodecyl sulfate is directly added to the spinning solution; ethanol and tetrahydrofuran help dissolve the sodium dodecyl sulfate, and the portion exceeding the solubility forms a suspension, directly promoting the increase in the conductivity of the spinning solution, thereby improving spinning efficiency. Simultaneously, the addition of sodium dodecyl sulfate can effectively reduce droplet aggregation at the needle tip during electrospinning, preventing spinning interruptions, improving the smoothness of the spinning process, and further improving spinning efficiency.

[0010] In some embodiments of the present invention, in step (1), the volume ratio of ethanol to tetrahydrofuran is 1:(3-6). Preferably, the volume ratio of ethanol to tetrahydrofuran is (1.5-2):(7.5-8).

[0011] In some embodiments of the present invention, in step (1), the mass-to-volume ratio of the polycarbosilane to ethanol is (0.5-1.5) g: 1 mL. Preferably, the mass-to-volume ratio of the polycarbosilane to ethanol is (1.6-1.9) g: (1.5-2) mL.

[0012] In some embodiments of the present invention, in step (1), the mass ratio of the polycarbosilane, polyvinylpyrrolidone, and sodium dodecyl sulfate is (3-7):1:(0.1-0.4). Preferably, the mass ratio of the polycarbosilane, polyvinylpyrrolidone, and sodium dodecyl sulfate is (1.6-1.9):(0.3-0.5):(0.07-0.12).

[0013] In some embodiments of the present invention, in step (1), the mixing is performed by stirring at a speed of 300-400 r / min for 3-7 days.

[0014] In some embodiments of the present invention, in step (2), the parameters of the airflow-assisted electrospinning process are: spinning voltage 20-30kV, distance between receiver and needle 10-17cm, gas flow rate 2-8L / min, liquid supply rate 12-20mL / h, and humidity 30-50%.

[0015] Specifically, the present invention uses a spinning solution with specific components and performs electrospinning with the assistance of a high-speed airflow, so that the solution supply rate can reach up to 20 mL / h, which greatly improves the spinning efficiency.

[0016] In some embodiments of the present invention, in step (2), the needle for airflow-assisted electrospinning is a 21-23G flat-mouth needle.

[0017] In some embodiments of the present invention, in step (2), the receiver has a curved grid structure. Preferably, the receiver is in the shape of a curved arc and is composed of a metal grid with a curvature of 140-170°.

[0018] Specifically, a grid-like irregular receiver is used. During the spinning process, the fibers tend to align along the conductive grid, while they are randomly arranged in the gaps of the grid. This creates a fiber membrane with an uneven "skeleton structure," resulting in different density regions within the fiber membrane. While significantly improving spinning efficiency, the fibers still maintain high thermal insulation properties.

[0019] In some embodiments of the present invention, in step (3), the temperature regime for the pre-oxidation heating is as follows: first, the temperature is increased to 100-120°C at a rate of 1-3°C / min and held for 3-5 hours; then, the temperature is increased to 130-150°C at a rate of 0.6-0.8°C / min and held for 1-3 hours; then, the temperature is increased to 180-190°C at a rate of 0.3-0.5°C / min and held for 1-3 hours; finally, the temperature is naturally cooled to room temperature. This segmented pre-oxidation heating of the spun product ensures that the long chains of polycarbosilane react fully at different temperatures, thereby completely softening the polycarbosilane.

[0020] In some embodiments of the present invention, in step (3), the calcination temperature regime is as follows: first, the temperature is raised to 280-320°C under vacuum at a rate of 4-6°C / min, and nitrogen gas is introduced at a flow rate of 5-10 L / min; then, the temperature is raised to 440-460°C at a rate of 4-6°C / min and held for 2-4 hours; then, the temperature is raised to 580-620°C at a rate of 2-4°C / min and held for 2-3 hours; then, the temperature is raised to 780-820°C at a rate of 2-4°C / min and held for 2-3 hours; finally, the temperature is raised to 1100-1300°C at a rate of 2-4°C / min and held for 1-2 hours. The present invention adopts a segmented heating regime and a certain period of holding time. Its main purpose is to: at low temperatures, completely decompose the organic components (such as polyvinylpyrrolidone) in the fiber; at high temperatures, completely thermally decompose the fiber, thereby further improving the overall performance of the fiber.

[0021] A second aspect of the present invention provides a SiC fiber, which is prepared by the above method, and the high-temperature diffusion coefficient of the SiC fiber is less than 0.6 mm. 2 / s.

[0022] A third aspect of the present invention provides the application of the above-mentioned SiC fibers in aerospace, nuclear energy, high-temperature gas turbines, metal-based or ceramic-based composite materials.

[0023] Compared with the prior art, the above-described technical solution of the present invention has at least the following technical effects or advantages:

[0024] Compared to traditional electrospinning processes, the method for preparing SiC fibers in this invention employs a specific spinning solution. Polycarbosilane is used as the precursor for SiC fibers, with ethanol and tetrahydrofuran as a mixed solvent. A certain amount of sodium dodecyl sulfate and polyvinylpyrrolidone are added. Sodium dodecyl sulfate enhances the conductivity of the spinning solution and reduces droplet aggregation at the needles during electrospinning, thereby improving the smoothness and efficiency of the spinning process. Furthermore, a high-speed airflow is introduced to assist spinning, operating at a higher liquid supply rate, significantly improving spinning efficiency. Simultaneously, this invention utilizes a grid-like irregular receiver. During spinning, the fibers tend to align along the conductive grid, while they are randomly arranged in the gaps of the grid, thus preparing a fiber membrane containing an internal "skeleton structure." While significantly improving spinning efficiency, the fibers still maintain high thermal insulation properties. Attached Figure Description

[0025] Figure 1 This is a physical image of the spinning receiver used in this invention;

[0026] Figure 2 A photograph of the SiC fibers prepared in Example 1;

[0027] Figure 3 A diagram showing the phenomenon of droplet aggregation at the needle tip during the preparation of SiC fibers for Comparative Example 1;

[0028] Figure 4 A photograph of the SiC fibers prepared in Comparative Example 3;

[0029] Figure 5 The XRD patterns of the SiC fibers prepared in Examples 1-3 are shown below.

[0030] Figure 6 SEM image of the SiC fiber "skeleton" prepared in Example 1;

[0031] Figure 7 The graph shows the thermal diffusivity curves of the SiC fibers prepared in Examples 1-3. Detailed Implementation

[0032] The present invention will now be described in detail with reference to embodiments to facilitate understanding of the invention by those skilled in the art. It is particularly important to note that the embodiments are merely illustrative of the invention and should not be construed as limiting the scope of protection of the invention. Non-essential improvements and adjustments made to the invention by those skilled in the art based on the above description should still fall within the scope of protection of the invention. Furthermore, all raw materials mentioned below, unless otherwise specified, are commercially available products; all process steps or preparation methods not mentioned in detail are process steps or preparation methods known to those skilled in the art.

[0033] Example 1

[0034] A method for efficiently preparing SiC fibers by airflow-assisted electrospinning includes the following steps:

[0035] (1) Preparation of spinning solution: Dissolve 1.6g of pure polycarbosilane in a mixed solvent of 2mL ethanol and 7.8mL tetrahydrofuran, add 0.35g polyvinylpyrrolidone (mW=1300000) and 0.07g sodium dodecyl sulfate; then stir at 350r / min for 4 days to obtain spinning solution.

[0036] (2) Electrospinning: The spinning solution prepared in step (1) is loaded into a 10mL syringe and a 21G flat-mouth needle with an airflow assist device is loaded. Then the syringe and the spinning receiver with a curved grid structure are placed into the spinning equipment to perform airflow-assisted electrospinning to obtain the spinning product.

[0037] The parameters for the airflow-assisted electrospinning process are as follows: spinning voltage 22kV, distance between receiver and needle 15cm, gas flow rate 2L / min, liquid supply rate 12mL / h, and humidity 30%.

[0038] The actual product of the spinning receiver is as follows Figure 1 As shown, the spinning receiver is in the shape of a curved arc and is composed of a metal grid with a curvature of 140°.

[0039] (3) Pre-oxidation: The spinning product obtained in step (2) is removed from the receiver and placed in a ceramic tray to be dried in an oven at 60°C for 30 minutes; then the dried raw yarn is transferred to an oven with a controllable heating program for pre-oxidation.

[0040] The temperature regime for pre-oxidation is as follows: first, the temperature is increased to 110℃ at a rate of 1.8℃ / min and held for 3 hours; then, the temperature is increased to 140℃ at a rate of 0.8℃ / min and held for 2 hours; then, the temperature is increased to 185℃ at a rate of 0.4℃ / min and held for 2 hours; finally, the temperature is allowed to cool naturally to room temperature.

[0041] (4) Calcination: The raw filaments pre-oxidized in step (3) are placed in a graphite vacuum furnace and calcined to obtain the SiC fiber of this embodiment.

[0042] The calcination temperature regime is as follows: first, the temperature is raised to 300℃ under vacuum at a rate of 5℃ / min, and nitrogen gas is introduced at a flow rate of 7L / min; then the temperature is raised to 450℃ at a rate of 3℃ / min and held for 3 hours; then the temperature is raised to 600℃ at a rate of 3℃ / min and held for 2 hours; then the temperature is raised to 800℃ at a rate of 3℃ / min and held for 2 hours; then the temperature is raised to 1100℃ at a rate of 3℃ / min and held for 1 hour.

[0043] Figure 2 Here is a physical image of the SiC fibers prepared in this embodiment, wherein: Figure 2 -B is Figure 2 -A local magnification. (From) Figure 2 It can be seen that the surface of the SiC fiber is grid-like, similar to the grid structure of the spinning receiver.

[0044] Example 2

[0045] A method for efficiently preparing SiC fibers by airflow-assisted electrospinning includes the following steps:

[0046] (1) Preparation of spinning solution: Dissolve 1.7g of pure polycarbosilane in a mixed solvent of 2mL ethanol and 8mL tetrahydrofuran, add 0.36g of polyvinylpyrrolidone (mW=1300000) and 0.1g of sodium dodecyl sulfate; then stir at 400r / min for 4 days to obtain spinning solution.

[0047] (2) Electrospinning: The spinning solution prepared in step (1) is loaded into a 10mL syringe and a 21G flat-mouth needle with an airflow assist device is loaded. Then the syringe and the spinning receiver with a curved grid structure are placed into the spinning equipment to perform airflow-assisted electrospinning to obtain the spinning product.

[0048] The parameters for the airflow-assisted electrospinning process are as follows: spinning voltage 24kV, distance between receiver and needle 15cm, gas flow rate 4L / min, liquid supply rate 15mL / h, and humidity 30%.

[0049] (3) Pre-oxidation: The spinning product obtained in step (2) is removed from the receiver and placed in a ceramic tray to be dried in an oven at 60°C for 30 minutes; then the dried raw yarn is transferred to an oven with a controllable heating program for pre-oxidation.

[0050] The temperature regime for pre-oxidation is as follows: first, the temperature is increased to 110℃ at a rate of 1.8℃ / min and held for 3 hours; then, the temperature is increased to 140℃ at a rate of 0.8℃ / min and held for 2 hours; then, the temperature is increased to 185℃ at a rate of 0.4℃ / min and held for 2 hours; finally, the temperature is allowed to cool naturally to room temperature.

[0051] (4) Calcination: The raw filaments pre-oxidized in step (3) are placed in a graphite vacuum furnace and calcined to obtain the SiC fiber of this embodiment.

[0052] The calcination temperature regime is as follows: first, the temperature is raised to 300℃ under vacuum at a rate of 5℃ / min, and nitrogen gas is introduced at a flow rate of 8L / min; then the temperature is raised to 450℃ at a rate of 3℃ / min and held for 3 hours; then the temperature is raised to 600℃ at a rate of 3℃ / min and held for 2 hours; then the temperature is raised to 800℃ at a rate of 3℃ / min and held for 2 hours; then the temperature is raised to 1300℃ at a rate of 3℃ / min and held for 1 hour.

[0053] Example 3

[0054] A method for efficiently preparing SiC fibers by airflow-assisted electrospinning includes the following steps:

[0055] (1) Preparation of spinning solution: Dissolve 1.7g of pure polycarbosilane in a mixed solvent of 2mL ethanol and 8mL tetrahydrofuran, add 0.36g of polyvinylpyrrolidone (mW=1300000) and 0.1g of sodium dodecyl sulfate; then stir at 400r / min for 4 days to obtain spinning solution.

[0056] (2) Electrospinning: The spinning solution prepared in step (1) is loaded into a 10mL syringe and a 21G flat-mouth needle with an airflow assist device is loaded. Then the syringe and the spinning receiver with a curved grid structure are placed into the spinning equipment to perform airflow-assisted electrospinning to obtain the spinning product.

[0057] The parameters for the airflow-assisted electrospinning process are as follows: spinning voltage 24kV, distance between receiver and needle 15cm, gas flow rate 4L / min, liquid supply rate 20mL / h, and humidity 50%.

[0058] (3) Pre-oxidation: The spinning product obtained in step (2) is removed from the receiver and placed in a ceramic tray to be dried in an oven at 60°C for 30 minutes; then the dried raw yarn is transferred to an oven with a controllable heating program for pre-oxidation.

[0059] The temperature regime for pre-oxidation is as follows: first, the temperature is increased to 110℃ at a rate of 1.8℃ / min and held for 3 hours; then, the temperature is increased to 140℃ at a rate of 0.8℃ / min and held for 2 hours; then, the temperature is increased to 185℃ at a rate of 0.4℃ / min and held for 2 hours; finally, the temperature is allowed to cool naturally to room temperature.

[0060] (4) Calcination: The raw filaments pre-oxidized in step (3) are placed in a graphite vacuum furnace and calcined to obtain the SiC fiber of this embodiment.

[0061] The calcination temperature regime is as follows: first, the temperature is raised to 300℃ under vacuum at a rate of 5℃ / min, and nitrogen gas is introduced at a flow rate of 8L / min; then, the temperature is raised to 450℃ at a rate of 3℃ / min and held for 3 hours; then, the temperature is raised to 600℃ at a rate of 3℃ / min and held for 2 hours; then, the temperature is raised to 800℃ at a rate of 3℃ / min and held for 2 hours; finally, the temperature is raised to 1200℃ at a rate of 3℃ / min and held for 1 hour.

[0062] Comparative Example 1

[0063] The only difference between Comparative Example 1 and Example 1 is the composition of the spinning solution. The spinning solution of Comparative Example 1 did not contain sodium dodecyl sulfate. Its preparation process was as follows: 1.6 g of pure polycarbosilane was dissolved in a mixed solvent of 2 mL of ethanol and 7.8 mL of tetrahydrofuran, and 0.35 g of polyvinylpyrrolidone (mW=1300000) was added; then the mixture was stirred at 350 r / min for 4 days to obtain the spinning solution.

[0064] In Comparative Example 1, during the electrospinning process, the phenomenon of droplet aggregation at the needle tip frequently occurs, such as... Figure 3 As shown, this causes the entire spinning process to be disrupted, often requiring interruptions to manually remove droplets, which greatly reduces spinning efficiency.

[0065] Comparative Example 2

[0066] The only difference between Comparative Example 2 and Example 1 is the composition of the spinning solution. In Comparative Example 2, xylene was used as the solvent. The preparation process was as follows: 1.6 g of pure polycarbosilane was dissolved in 9.8 mL of xylene, and 0.35 g of polyvinylpyrrolidone (mW = 1300000) and 0.07 g of sodium dodecyl sulfate were added; then the mixture was stirred at 350 r / min for 4 days. The experiment revealed that the xylene-based spinning solution was not completely dissolved, and precipitation occurred quickly after being loaded into the syringe. During the spinning process, xylene could not evaporate quickly in the air, resulting in the fiber still being liquid when it reached the receiver, thus preventing successful spinning.

[0067] Comparative Example 3

[0068] The only difference between Comparative Example 3 and Example 1 is the spinning receiver. Comparative Example 3 uses a traditional flat receiver without a grid structure. The actual SiC fibers prepared in Comparative Example 3 are shown below. Figure 4 As shown, the fiber only has a membrane structure and does not have the skeletal structure of the fibers prepared in Examples 1-3, which is detrimental to the thermal insulation performance of the fiber.

[0069] Performance testing

[0070] 1. XRD Analysis

[0071] The fibers prepared in Examples 1-3 were ground into powder and subjected to XRD tests using a Bruker D8 Advance X-ray diffractometer. The test results are as follows: Figure 5 As shown, where the horizontal axis 2θ represents the 2θ diffraction angle, and the vertical axis Intensity represents the intensity of the diffraction peak. Figure 5 It can be seen that the degree of fiber crystallization is not high when sintering at a lower temperature (1100℃), while the degree of fiber crystallization is greatly enhanced when sintering at a higher temperature (1300℃), and typical SiC crystal diffraction peaks appear.

[0072] 2. SEM Analysis

[0073] Figure 6 This is a SEM image of the SiC fiber "skeleton" prepared in Example 1. Figure 6 A and Figure 6 B represents the microstructure images at different magnifications, obtained using a Hitachi SU5000 thermal field emission scanning electron microscope. Figure 6 As can be seen, the fibers in the "skeleton" of the fiber membrane are arranged in the same direction, and the fiber density is significantly higher than in other areas.

[0074] 3. Thermal diffusivity

[0075] The thermal diffusivity of the SiC fibers prepared in Examples 1-3 was tested using a NETZSCH LFA 467 HT HyperFlash laser thermal conductivity meter, and the results are as follows: Figure 7 As shown, the horizontal axis represents temperature, and the vertical axis represents the thermal diffusivity. Figure 7 It can be seen that even samples sintered at a relatively low temperature (1100℃) still have a considerably low high-temperature thermal diffusivity (<0.6mm) at 1000℃. 2 / s); samples sintered at higher temperatures (1300℃) exhibit a high-temperature thermal diffusivity as low as 0.15 mm at 1000℃. 2 / s or less.

[0076] For those skilled in the art, several simple deductions or substitutions can be made without departing from the inventive concept, without requiring creative effort. Therefore, any simple improvements made to this invention by those skilled in the art based on the disclosure of this invention should be within the scope of protection of this invention. The above embodiments are preferred embodiments of this invention, and all processes similar to this invention and equivalent changes should fall within the scope of protection of this invention.

Claims

1. A method for preparing SiC fibers, characterized in that, Includes the following steps: (1) Dissolve polycarbosilane in a mixed solvent, add polyvinylpyrrolidone and sodium dodecyl sulfate, mix, and obtain a spinning solution; the mixed solvent includes ethanol and tetrahydrofuran; (2) The spinning solution is electrospun using an airflow-assisted electrospinning process to obtain the spinning product; The parameters of the airflow-assisted electrospinning process are as follows: spinning voltage 20-30kV, distance between receiver and needle 10-17cm, gas flow rate 2-8L / min, liquid supply rate 12-20mL / h, and humidity 30-50%. The receiver has a curved grid structure and is in the shape of a curved arc, composed of a metal grid with a curvature of 140-170°. (3) After drying the spinning product, it is subjected to heating pre-oxidation and calcination in sequence to obtain the SiC fiber.

2. The method for preparing SiC fibers according to claim 1, characterized in that, In step (1), the volume ratio of ethanol to tetrahydrofuran is 1:(3-6); and / or, the mass-volume ratio of polycarbosilane to ethanol is (0.5-1.5) g:1 mL.

3. The method for preparing SiC fibers according to claim 1 or 2, characterized in that, In step (1), the mass ratio of polycarbosilane, polyvinylpyrrolidone and sodium dodecyl sulfate is (3-7):1:(0.1-0.4).

4. The method for preparing SiC fibers according to claim 1, characterized in that, In step (1), the mixing is carried out by stirring at a speed of 300-400 r / min for 3-7 days.

5. The method for preparing SiC fibers according to claim 1, characterized in that, In step (3), the temperature regime for heating and pre-oxidation is as follows: first, the temperature is increased to 100-120℃ at a rate of 1-3℃ / min and held for 3-5 hours; then, the temperature is increased to 130-150℃ at a rate of 0.6-0.8℃ / min and held for 1-3 hours; then, the temperature is increased to 180-190℃ at a rate of 0.3-0.5℃ / min and held for 1-3 hours; finally, the temperature is naturally cooled to room temperature.

6. The method for preparing SiC fibers according to claim 1, characterized in that, In step (3), the calcination temperature regime is as follows: first, the temperature is raised to 280-320℃ under vacuum at a rate of 4-6℃ / min, and nitrogen gas is introduced at a flow rate of 5-10L / min; then, the temperature is raised to 440-460℃ at a rate of 4-6℃ / min and held for 2-4 hours; then, the temperature is raised to 580-620℃ at a rate of 2-4℃ / min and held for 2-3 hours; then, the temperature is raised to 780-820℃ at a rate of 2-4℃ / min and held for 2-3 hours; finally, the temperature is raised to 1100-1300℃ at a rate of 2-4℃ / min and held for 1-2 hours.

7. A SiC fiber, characterized in that, The SiC fiber is prepared by the method according to any one of claims 1-6, and the thermal diffusivity of the SiC fiber is less than 0.6 mm. 2 / s.

8. The application of the SiC fiber according to claim 7 in high-temperature gas turbines, metal-based or ceramic-based composite materials.

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