Two-dimensional boron nitride all-ceramic fiber, method for preparing same, and use thereof
By employing wet spinning and Joule heating sintering, the problem of complete nitriding of boron nitride fibers was solved, resulting in the preparation of high-strength, high-thermal-conductivity two-dimensional boron nitride all-ceramic fibers suitable for reinforcing materials and composite materials.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- TSINGHUA SHENZHEN INTERNATIONAL GRADUATE SCHOOL
- Filing Date
- 2023-12-27
- Publication Date
- 2026-07-24
AI Technical Summary
In the existing technology, boron nitride fibers are difficult to completely nitride, and tend to form a core-shell structure, making it difficult to prepare single boron nitride fibers.
Two-dimensional boron nitride all-ceramic fibers were prepared by adding an organic adhesive to a two-dimensional boron nitride dispersion and then performing wet spinning, hot pressing, and Joule thermal sintering. The process included pre-sintering and Joule thermal sintering steps to ensure close contact and fusion between the boron nitride nanosheets.
Two-dimensional boron nitride all-ceramic fibers with high strength and high thermal conductivity were prepared. The nanosheets are in close contact to form a high-strength and high-thermal-conductivity fiber structure, which is suitable for reinforcing materials and composite materials.
Smart Images
Figure CN117779240B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the technical field of ceramic fibers, and more particularly to a two-dimensional boron nitride all-ceramic fiber, its preparation method and application. Background Technology
[0002] Two-dimensional boron nitride (BNNS) is a two-dimensional material composed of nitrogen and boron, also known as "white graphite," with the chemical formula BN. Like graphite, BNNS consists of stacked monolayers bound together by van der Waals forces. Within each layer, nitrogen and boron atoms are sp2 hybridized, forming a hexagonal honeycomb structure. BNNS possesses high thermal conductivity, high insulation, and low dielectric constant, while also exhibiting flexibility, chemical stability, thermal stability, and biocompatibility. Therefore, it shows great application potential in many fields, such as electronic devices, optical equipment, thermal management, composite materials, and biomedicine.
[0003] In recent years, boron nitride fibers have mainly been produced by high-temperature nitriding of inorganic boron-containing raw materials such as boron oxide or boric acid. However, during the preparation process, the inorganic boron-containing raw materials are difficult to be fully nitrided, easily forming a core-sheath structure, making it difficult to form single boron nitride fibers. Summary of the Invention
[0004] In view of this, this application provides a two-dimensional boron nitride all-ceramic fiber, its preparation method and application.
[0005] To achieve the above objectives, this application provides a method for preparing two-dimensional boron nitride all-ceramic fibers. The method includes: providing a two-dimensional boron nitride dispersion, the two-dimensional boron nitride dispersion comprising two-dimensional boron nitride nanosheets and an organic solvent; adding an organic adhesive to the two-dimensional boron nitride dispersion to obtain a mixture; spinning the mixture using wet spinning to obtain a gel-like first fiber; hot-pressing the first fiber to obtain a second fiber; pre-sintering the second fiber in an oxygen-containing atmosphere to remove organic matter to obtain a precursor; and sintering the precursor in an inert gas using Joule heating to obtain the two-dimensional boron nitride all-ceramic fibers.
[0006] In some possible implementations, the organic adhesive includes at least one of graphene oxide, aramid fiber, polyvinylpyrrolidone, or polyvinyl butyral.
[0007] In some possible implementations, the wet spinning process includes ejecting the spun yarn formed from the mixture through a nozzle and allowing it to flow into a coagulation bath to obtain the first fiber body. The coagulation bath includes at least one of an aqueous solution of calcium chloride, water, dimethyl sulfoxide, dimethylacetamide, ethanol, isopropanol, ethyl acetate, or isoamyl acetate.
[0008] In some possible implementations, the mass of the organic adhesive is 0.1% to 1% of the mass of the two-dimensional boron nitride nanosheets.
[0009] In some possible implementations, the pressure of the hot press is greater than or equal to 5 MPa.
[0010] In some possible implementations, the pre-sintering temperature is 400–700°C.
[0011] In some possible implementations, the Joule heating sintering temperature is 1500–2500°C, the Joule heating sintering time is 10–1000 s, and the Joule heating sintering heating rate is 100–10000°C / min.
[0012] This application also provides a two-dimensional boron nitride all-ceramic fiber, the two-dimensional boron nitride all-ceramic fiber comprising a plurality of fibers, each fiber being composed of a plurality of boron nitride sheets, the plurality of boron nitride sheets being bonded to each other, and each boron nitride sheet comprising a plurality of mutually bonded two-dimensional boron nitride nanosheets.
[0013] In some possible implementations, the density of the two-dimensional boron nitride all-ceramic fiber is 1.8–2.25 g / cm³. 3 .
[0014] This application also provides the application of two-dimensional boron nitride all-ceramic fibers in ceramic composite materials.
[0015] This application provides a method for preparing two-dimensional boron nitride all-ceramic fibers. The method involves adding an organic adhesive to a two-dimensional boron nitride dispersion, wet spinning to obtain a first fiber body, and hot pressing to obtain a second fiber body. In the hot-pressed second fiber body, the two-dimensional boron nitride nanosheets achieve good contact between each other. After pre-sintering, the organic matter is removed from the second fiber body, and finally, it undergoes Joule heating sintering to obtain a single-component two-dimensional boron nitride fiber. In the two-dimensional boron nitride all-ceramic fibers provided by this application, the two-dimensional boron nitride nanosheets form flat fibers arranged in a highly parallel orientation, forming a high-strength whole. Furthermore, the two-dimensional boron nitride nanosheets fuse together, bonding to form high-strength, high-thermal-conductivity two-dimensional boron nitride all-ceramic fibers. Attached Figure Description
[0016] Figure 1 A scanning electron microscope image of the second fiber prepared in Example 1 of this application.
[0017] Figure 2 for Figure 1 Scanning electron microscope images of the second fibrous tissue at different magnifications.
[0018] Figure 3The image shows a cross-sectional scanning electron microscope image of the two-dimensional boron nitride all-ceramic fiber prepared in Example 1.
[0019] Figure 4 Scanning electron microscope image of the two-dimensional boron nitride all-ceramic fiber prepared in Example 1.
[0020] Figure 5 Scanning electron microscope image of the two-dimensional boron nitride all-ceramic fiber prepared for Comparative Example 1.
[0021] Figure 6 Scanning electron microscope image of the two-dimensional boron nitride all-ceramic fiber prepared in Example 6. Detailed Implementation
[0022] Embodiments of the present invention are described in detail below. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.
[0023] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
[0024] This application provides a method for preparing two-dimensional boron nitride all-ceramic fibers, the method comprising:
[0025] S1. Provides a two-dimensional boron nitride dispersion, which includes two-dimensional boron nitride nanosheets and an organic solvent.
[0026] At least one of ball milling, ultrasonication, and high-speed shearing methods can be used to exfoliate boron nitride powder to obtain two-dimensional boron nitride nanosheets. In this embodiment, boron nitride and an organic solvent are mixed and ball-milled using a wet ball milling method, which exfoliates the boron nitride to form two-dimensional boron nitride nanosheets, resulting in a two-dimensional boron nitride dispersion. Wet ball milling can efficiently obtain two-dimensional boron nitride nanosheets. The average particle size of the boron nitride powder before exfoliation is 1–50 μm, preferably 30–50 μm.
[0027] In some embodiments, the mass percentage of two-dimensional boron nitride nanosheets in the two-dimensional boron nitride dispersion is 1% to 50%, and in some embodiments, it is 20% to 40%, in order to obtain the two-dimensional boron nitride dispersion with high efficiency.
[0028] In some embodiments, the organic solvent includes at least one of ethanol, isopropanol, ethyl acetate, isoamyl acetate, toluene, xylene, dimethyl sulfoxide, dimethylacetamide, N,N-dimethylformamide, or N-methylpyrrolidone.
[0029] S2. Add an organic adhesive to the two-dimensional boron nitride dispersion to obtain a mixture.
[0030] Organic adhesives can be added to a two-dimensional boron nitride dispersion by ball milling, mechanical stirring, or ultrasonic dispersion.
[0031] In some embodiments, the organic adhesive comprises 0.1% to 1% of the mass of the two-dimensional boron nitride nanosheets to ensure that it sufficiently improves the rheological properties of the two-dimensional boron nitride dispersion and provides supporting strength to the two-dimensional boron nitride nanosheets during subsequent spinning, thereby promoting the formation of subsequent fibers. The organic adhesive comprises 0.1%, 0.2%, 0.3%, 0.5%, 0.7%, or 1% of the mass of the two-dimensional boron nitride nanosheets.
[0032] In some embodiments, the organic adhesive includes at least one of graphene oxide, aramid fiber, polyvinylpyrrolidone, or polyvinyl butyral.
[0033] S3. The mixture is spun using a wet spinning process to obtain a gel-like first fiber.
[0034] In some embodiments, the wet spinning process includes ejecting the spun fibers formed from the mixture through a nozzle and allowing them to flow into a coagulation bath to obtain the first fiber body. The coagulation bath includes at least one of an aqueous calcium chloride solution, water, dimethyl sulfoxide, dimethylacetamide, ethanol, isopropanol, ethyl acetate, or isoamyl acetate. In some embodiments, the coagulation bath is a 10% wt aqueous calcium chloride solution. During the flow of the spun fibers into the coagulation bath, the organic adhesive does not dissolve to avoid localized defects in the resulting first fiber body.
[0035] In the wet spinning process, a mixture is output as a spinning form using a nozzle or spinning plate, and then passed through a coagulation bath to obtain a gel-like first fiber body. The diameter of the fibers in the first fiber body is 30–100 μm.
[0036] In some embodiments, the diameter of the nozzle used for wet spinning is 5-500 μm, preferably 200-400 μm.
[0037] S4. The first fiber body is hot-pressed to obtain the second fiber body.
[0038] The first fiber body is hot-pressed to ensure good contact between the layers of the two-dimensional boron nitride nanosheets within it (see...). Figure 1 and Figure 2This process facilitates the fusion of two-dimensional boron nitride nanosheets during subsequent Joule hot sintering, thereby improving the structural strength of the sintered product. During this hot pressing process, the first fiber is subjected to upward and downward compression, forming flat fibers. Furthermore, the first fiber is dried during the hot pressing process, allowing some of the organic solvent or coagulation bath within the first fiber to evaporate, resulting in the second fiber.
[0039] In some embodiments, the hot-pressing pressure is greater than or equal to 5 MPa to ensure that the two-dimensional boron nitride nanosheets within the first fiber are sufficiently compressed, and that the two-dimensional boron nitride nanosheets in each layer are arranged parallel to the plane of the flat fiber (e.g., the horizontal direction) to form a highly oriented second fiber. In some embodiments, the hot-pressing pressure is greater than or equal to 15 MPa to improve the efficiency of the hot-pressing.
[0040] S5. The second fibrous body is pre-sintered in an oxygen-containing atmosphere to remove organic matter and obtain a precursor.
[0041] In some embodiments, the pre-sintering temperature is 400–700°C to ensure the removal of organic matter from the precursor. For example, the pre-sintering temperature may be 400°C, 500°C, 600°C, or 700°C. 700°C is preferred. The pre-sintering time is 0.5–2 hours.
[0042] In some embodiments, the pre-sintering heating rate is 1 to 10 °C / min. For example, 1 °C / min, 2 °C / min, 5 °C / min, or 10 °C / min.
[0043] In some embodiments, the oxygen-containing atmosphere includes air or oxygen.
[0044] S6. The precursor is sintered in an inert gas using Joule heating to obtain two-dimensional boron nitride all-ceramic fibers.
[0045] Joule heating sintering was employed to create a high-temperature environment, under which the two-dimensional boron nitride nanosheets in the precursor fused together to form high-strength, high-thermal-conductivity two-dimensional boron nitride all-ceramic fibers. Furthermore, the two-dimensional boron nitride all-ceramic fibers consist of individual two-dimensional boron nitride nanosheets, which, after sintering, form flattened fibers (see...). Figure 3 They are arranged in a highly parallel orientation, in close contact with each other, and have good contact properties.
[0046] Meanwhile, two-dimensional boron nitride nanosheets possess high thermal conductivity. Sintered bonding of these nanosheets reduces phonon loss between layers, increases the thermal conductivity between layers, and improves the overall thermal conductivity of the two-dimensional boron nitride all-ceramic fiber. Based on the fiber structure of the two-dimensional boron nitride all-ceramic fiber, it can also be used as a reinforcing material and incorporated into composite materials in fiber form. Utilizing the fiber toughening mechanism, various fiber-reinforced materials can be prepared, and the mechanical properties of composite materials can be controlled.
[0047] In some embodiments, the inert atmosphere includes at least one of argon, nitrogen, helium, or neon.
[0048] In some embodiments, the Joule sintering temperature is 1500–2500°C, and the Joule sintering holding time is 10–1000 s, so that the precursor can be fully sintered, and the layers in the two-dimensional boron nitride nanosheets, as well as the layers within the same layer, fuse and bond by sintering to form high-strength and high-thermal-conductivity two-dimensional boron nitride all-ceramic fibers. The Joule sintering holding time can be 180–800 s, such as 180 s, 200 s, 300 s, 400 s, 500 s, 600 s, 700 s, or 800 s, preferably 500 s.
[0049] Joule heating sintering refers to placing powder in a graphite heater, energizing the heater, and using the inherent resistance of graphite to generate Joule heat, thereby rapidly sintering the powder in the graphite heater at ultra-high temperatures. In some embodiments, the graphite heater includes a trough shape, a plate shape, or a funnel shape.
[0050] In some embodiments, the resistance of the graphite heater is 0.1-10Ω, preferably 0.5-5Ω. The specific heat capacity of the graphite heater is 500-2000J / (kg·K), preferably 700-1000J / (kg·K).
[0051] In some embodiments, the heating rate of Joule heating sintering is 100-10000℃ / min, which helps prevent low-temperature curing of the material during sintering. At this heating rate, the density and strength of the structure can be guaranteed. The cooling rate of Joule heating sintering is also 100-10000℃ / min. The heating and cooling rates of Joule heating sintering are related to the degree and duration of low-temperature curing during sintering, and also affect the likelihood of damage to the sintered material under thermal shock.
[0052] In some embodiments, during Joule heating sintering, the heating and cooling rates are all between 100 and 3000 °C / min, such as 100 °C / min, 200 °C / min, 500 °C / min, 700 °C / min, 1000 °C / min, 1500 °C / min, 2000 °C / min, or 3000 °C / min. The heating and cooling rates can be the same or different.
[0053] See Figure 3 The cross-section of the two-dimensional boron nitride all-ceramic fiber is an elliptical structure with a major axis of 10-100 μm and a minor axis of 0.05-10 μm.
[0054] This application also provides a two-dimensional boron nitride all-ceramic fiber. The fiber in the two-dimensional boron nitride all-ceramic fiber is flat, and each fiber is composed of multiple boron nitride sheets, which are bonded to each other, and each of the boron nitride sheets includes multiple bonded two-dimensional boron nitride nanosheets.
[0055] In some embodiments, the density of the two-dimensional boron nitride all-ceramic fiber is 1.8–2.25 g / cm³. 3 The preferred value is 2.15–2.25 g / cm³. 3 .
[0056] This application also provides an application of two-dimensional boron nitride all-ceramic fibers in ceramic composite materials. Two-dimensional boron nitride all-ceramic fibers can be used as reinforcing materials in high-Mach missile radomes, high-temperature resistant, low-ablation wave-transparent materials, or high thermal conductivity materials.
[0057] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following examples are for illustrative purposes only and should not be construed as limiting the invention. Unless otherwise stated, reagents, software, and instruments involved in the following embodiments that are not specifically described are all conventional commercially available products or open-source materials.
[0058] Example 1
[0059] Isopropanol was used as the organic solvent. 5g of 50-micron boron nitride powder and 10g of isopropanol were placed in a 250ml zirconia ball mill jar. 100g of 99% zirconia balls with a diameter of 10mm and 25g of 99% zirconia balls with a diameter of 1mm were added. The mixture was placed on a planetary ball mill and milled at 600rpm for 12 hours to obtain a two-dimensional boron nitride dispersion. Its solid content was determined, and the solid content of the two-dimensional boron nitride nanosheets was adjusted to 5%wt.
[0060] Graphene oxide was added to a two-dimensional boron nitride dispersion, accounting for 0.5% of the mass of the two-dimensional boron nitride nanosheets.
[0061] The coagulation bath used a 10% wt calcium chloride aqueous solution, and the spinning nozzle had a diameter of 200 μm. Wet spinning was performed to obtain the first fiber body.
[0062] The first fibrous body was hot-pressed using a hot press at a pressure of 15 MPa to obtain the second fibrous body, which had a density of 1.86 g / cm³. 3 Its cross-section is elliptical, with a major axis of 50 μm and a minor axis of 5 μm.
[0063] The second fiber was pre-sintered in air at a heating rate of 1℃ / min and a sintering temperature of 700℃ to obtain the precursor.
[0064] Two-dimensional boron nitride all-ceramic fibers were obtained by using a Joule heating precursor in an argon atmosphere with a trough-type graphite heater at a heating rate of 10000℃ / min, a heat holding temperature of 2000℃, and a heat holding time of 500s. Figure 4 .
[0065] Example 2
[0066] The difference between Example 2 and Example 1 is that the heating rate and cooling rate are both 1°C / min. All other conditions are the same as in Example 1.
[0067] Example 3
[0068] The difference between Example 3 and Example 1 is that the sintering temperature is 1800℃. All other conditions are the same as in Example 1.
[0069] Example 4
[0070] The difference between Example 4 and Example 1 is that the sintering temperature is 2200℃. All other conditions are the same as in Example 1.
[0071] Example 5
[0072] The difference between Example 5 and Example 1 is that the sintering heat holding time is 180s. All other conditions are the same as in Example 1.
[0073] Example 6
[0074] The difference between Example 6 and Example 1 is that the sintering heat holding time is 800s. All other conditions are the same as in Example 1.
[0075] Comparative Example 1
[0076] The difference between Comparative Example 1 and Example 1 is that the hot-pressing pressure was 0.1 MPa, resulting in a second fibrous body with a density of 1.12 g / cm³. 3The cross-section is rectangular, 50 μm long and 5 μm wide. The remaining steps are the same as in Example 1.
[0077] Comparative Example 2
[0078] The difference between Comparative Example 2 and Example 1 is that the 50-micron boron nitride particles were replaced with 1-micron boron nitride particles, and the ball milling time was changed to 0.5 hours. Under these conditions, the boron nitride in the dispersion did not peel off, meaning that the boron nitride did not form nanosheets. The change in boron nitride particle size was to match the particle size in the dispersion of Example 1. All other conditions were the same as in Example 1.
[0079] See Figure 1 and Figure 2 This application uses scanning electron microscopy to test the second fiber obtained by hot pressing in Example 1. Figure 1 and Figure 2 The images show electron microscope (EM) images of the second fiber at different magnifications. The images reveal close contact between the two-dimensional boron nitride nanosheets in the second fiber after hot pressing. This application also includes scanning electron microscopy (SEM) analysis of the sintered two-dimensional boron nitride all-ceramic fibers. Figure 3 ,from Figure 3 As can be seen, the cross-section of the two-dimensional boron nitride all-ceramic fiber exhibits a near-flat shape, and the sintered two-dimensional boron nitride nanosheets within it are in contact layer by layer, displaying a highly parallel orientation. From... Figure 4 As can be seen, the surface of the two-dimensional boron nitride all-ceramic fiber is smooth and dense. After sintering, the two-dimensional boron nitride nanosheets are fused together, with almost no gaps between the nanosheets, and the nanosheets are connected to form a whole.
[0080] This application also includes scanning electron microscopy testing of the two-dimensional boron nitride all-ceramic fiber prepared in Example 1. For example... Figure 5 The two-dimensional boron nitride all-ceramic fiber obtained in Comparative Example 1 had an uneven surface, weak sintering signs, large gaps between layers, and low fusion between layers.
[0081] Table 1. Test results under different heating / cooling rates and hot-pressing pressures.
[0082]
[0083]
[0084] Referring to Table 1, the densities of the second fiber and the two-dimensional boron nitride all-ceramic fiber in the above examples and comparative examples were determined using the Archimedes displacement method. The density of the two-dimensional boron nitride all-ceramic fiber prepared in Example 1 was 1.82 g / cm³. 3The tensile strength of the two-dimensional boron nitride all-ceramic fiber prepared in Example 1 was measured to be 84 MPa using a tensile testing instrument. The tensile strength of the second fiber obtained after spinning and hot pressing was 29 MPa, and the tensile strength of the first fiber was 2 MPa. This indicates that the tensile strength is significantly improved after sintering.
[0085] The two-dimensional boron nitride all-ceramic fiber prepared in Comparative Example 1 has a tensile strength of 3 MPa, which is essentially the same as that of the unsintered fiber (second fiber). Comparing the tensile strengths of the two-dimensional boron nitride all-ceramic fibers prepared in Example 1 and Comparative Example 1 demonstrates that the hot-pressing step is crucial in fiber preparation, promoting dense fiber contact; otherwise, effective sintering cannot be achieved in the subsequent sintering process.
[0086] As can be seen from Table 1, compared with Example 1, Comparative Example 2 used unpeeled boron nitride to prepare fibers, and the density of the prepared second fiber body was lower. The density and strength of the sintered all-ceramic fiber were also lower, indicating that two-dimensional boron nitride nanosheets can effectively improve fiber density and fiber sintering effect.
[0087] Compared to Example 1, Example 2 used a heating rate of 1℃ / min, resulting in a decrease in both the density and thermal conductivity of the obtained two-dimensional boron nitride all-ceramic fibers. This is because the sintering of the second fiber body is weaker at a lower heating rate.
[0088] Table 2. Test results at different hot sintering temperatures and heat holding times.
[0089]
[0090]
[0091] As shown in Table 2, compared to Example 1, the lower sintering temperature in Example 3 resulted in a decrease in both the tensile strength and thermal conductivity of the obtained two-dimensional boron nitride all-ceramic fibers. This is because sintering was incomplete at the lower sintering temperature. Example 4, with a higher sintering temperature than Example 1, yielded two-dimensional boron nitride all-ceramic fibers with tensile strength and thermal conductivity similar to those of Example 1. This indicates that a relatively higher temperature has little effect on the tensile strength and thermal conductivity of the two-dimensional boron nitride all-ceramic fibers.
[0092] Compared to Example 1, the sintering heat holding time in Example 5 was shorter, and the tensile strength and thermal conductivity of the obtained two-dimensional boron nitride all-ceramic fibers were slightly reduced. This indicates that the heat holding time affects the tensile strength and thermal conductivity of the two-dimensional boron nitride all-ceramic fibers to a certain extent.
[0093] Compared to Example 1, Example 6 had a longer sintering heat holding time. The thermal conductivity of the resulting two-dimensional boron nitride all-ceramic fibers did not change significantly, but the tensile strength decreased. This is because the excessively long sintering time led to excessive grain growth and the generation of some oxidation defects. Figure 6 , Figure 6 The presence of obvious pores between the layers indicates that excessively long heat retention time will reduce the performance of two-dimensional boron nitride all-ceramic fibers.
[0094] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention should not depart from the spirit and scope of the technical solutions of the present invention.
Claims
1. A method for preparing two-dimensional boron nitride all-ceramic fibers, characterized in that, The preparation method includes: A two-dimensional boron nitride dispersion is provided, the two-dimensional boron nitride dispersion comprising two-dimensional boron nitride nanosheets and an organic solvent, wherein the mass percentage of the two-dimensional boron nitride nanosheets in the two-dimensional boron nitride dispersion is 5%; An organic adhesive is added to the two-dimensional boron nitride dispersion to obtain a mixture, wherein the mass of the organic adhesive is 0.1-1% of the mass of the two-dimensional boron nitride nanosheets, and the organic adhesive includes graphene oxide. The mixture was spun using a wet spinning process to obtain a gel-like first fiber. The first fiber body is hot-pressed to obtain the second fiber body, and the hot-pressing pressure is 15 MPa. The second fiber body is pre-sintered in an oxygen-containing atmosphere at a temperature of 400-700°C to remove organic matter and obtain a precursor. The precursor is sintered in an inert gas using Joule heating at a heating rate of 10000℃ / min, at a temperature of 1800~2200℃, and for a time of 180~800s to obtain the two-dimensional boron nitride all-ceramic fiber.
2. The method for preparing two-dimensional boron nitride all-ceramic fibers as described in claim 1, characterized in that, The wet spinning process involves ejecting the filaments formed from the mixture using a nozzle and allowing them to flow into a coagulation bath to obtain the first fiber body, wherein the coagulation bath comprises an aqueous solution of calcium chloride.
3. A two-dimensional boron nitride all-ceramic fiber prepared by the preparation method described in claim 1 or 2.
4. The two-dimensional boron nitride all-ceramic fiber as described in claim 3, characterized in that, The density of the two-dimensional boron nitride all-ceramic fiber is 1.8~2.25 g / cm³. 3 .
5. The application of two-dimensional boron nitride all-ceramic fiber as described in claim 3 or 4 in ceramic composite materials.