Flexible pyrolytic boron nitride film, method of making and use thereof

Abstract

The application provides a flexible pyrolytic boron nitride film and a preparation method and application thereof, and belongs to the technical field of film material preparation, and the preparation method of the flexible pyrolytic boron nitride film comprises the following steps: placing a substrate in a reaction furnace, preheating the substrate to 1200-1300 DEG C; after preheating, nitrogen source is introduced into the reaction furnace; after the nitrogen source is introduced, gaseous boron halide is introduced, and the molar ratio of the nitrogen source and the gaseous boron halide is controlled to be 2:1-8:1; after the gaseous boron halide is introduced, calcination is carried out at a temperature of 1500-1700 DEG C, so that the flexible pyrolytic boron nitride film deposited on the substrate is obtained; wherein the substrate is selected from a graphite substrate or a monocrystalline silicon substrate, and the gas flow of the nitrogen source and the gaseous boron halide is 300-600 scc / min.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials, and particularly relates to a flexible pyrolytic boron nitride thin film, its preparation method, and its application. Background Technology

[0002] With the rapid development of nanotechnology and electronic devices, the demand for flexible, thin-film novel functional materials is increasing. Pyrolytic boron nitride has attracted much attention due to its high thermal conductivity, excellent high-temperature resistance, and chemical stability. However, traditional pyrolytic boron nitride crucibles or sheets often have high rigidity, limiting their application in flexible electronics. Therefore, the preparation of uniform and flexible boron nitride thin films has become a major research direction, especially obtaining large-area, highly flexible pyrolytic boron nitride thin films. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a flexible pyrolytic boron nitride thin film, its preparation method, and its applications, aiming to at least partially solve the above-mentioned technical problems. The specific technical solution provided by this invention is as follows.

[0004] As a first aspect of the present invention, a method for preparing a flexible pyrolytic boron nitride thin film is provided, comprising: placing a substrate in a reactor and preheating the substrate to 1200~1300°C; after preheating, introducing a nitrogen source into the reactor; after introducing the nitrogen source, introducing gaseous boron halide, controlling the molar ratio of nitrogen source to gaseous boron halide to be 2:1~8:1; after introducing gaseous boron halide, calcining at a temperature of 1500~1700°C to obtain a flexible pyrolytic boron nitride thin film deposited on the substrate; wherein the substrate is selected from a graphite substrate or a single-crystal silicon substrate, and the gas flow rates of nitrogen source and gaseous boron halide are 300~600 scc / min.

[0005] As a second aspect of the present invention, a flexible pyrolytic boron nitride thin film is provided, wherein the flexible pyrolytic boron nitride thin film is a multilayer stacked pyrolytic boron nitride.

[0006] As a third aspect of the present invention, an application of a flexible pyrolytic boron nitride thin film in the fabrication of electronic devices or energy storage is provided.

[0007] Based on the above technical solution, the flexible pyrolytic boron nitride thin film, its preparation method, and its application provided by the present invention have at least one of the following beneficial effects:

[0008] (1) In the embodiments of the present invention, graphite or single-crystal silicon is used as the substrate and preheated. After preheating, a nitrogen source is introduced into the reactor containing the substrate for activation, and then gaseous boron halide is introduced in proportion to mix with it. After uniform mixing, the nitrogen source and gaseous boron halide are calcined to obtain a flexible boron nitride film deposited on the substrate. By introducing the nitrogen source first and then the gaseous boron halide, on the one hand, the air in the reactor can be discharged and the heat in the reactor can be used to pre-activate the nitrogen source for bonding, thereby reducing the reaction temperature and reaction intensity of the subsequent calcination of nitrogen source and gaseous boron halide to form boron nitride, and avoiding the need to introduce additional dilution gas to reduce the reaction degree of nitrogen source and gaseous boron halide; on the other hand, it is convenient for the nitrogen source and gaseous boron halide to mix uniformly and form a pyrolytic boron nitride film with uniform thickness.

[0009] (2) In the embodiments of the present invention, multilayer stacked pyrolytic boron nitride is prepared by vapor deposition by controlling the molar ratio of nitrogen source and gaseous boron halide introduced into the reactor, the gas flow rate, and the calcination reaction temperature. Subsequently, a pyrolytic boron nitride film with a high area, moderate film thickness, and stable physicochemical properties can be obtained by simple manual peeling. Compared with the pyrolytic boron nitride crucible, the pyrolytic boron nitride film of the present invention has higher flexibility, thinner film thickness, and excellent mechanical properties.

[0010] (3) In the embodiments of the present invention, the flexible pyrolytic boron nitride thin film of the present invention can be used in the manufacture of electronic devices such as flexible displays and flexible sensors, and can also be used in energy storage such as batteries and supercapacitors. Attached Figure Description

[0011] Figure 1 This is a physical image of the flexible pyrolytic boron nitride thin film in Embodiment 1 of the present invention;

[0012] Figure 2 This is a cross-sectional scanning electron microscope image of the flexible pyrolytic boron nitride thin film in Embodiment 1 of the present invention;

[0013] Figure 3 This is a high-resolution transmission electron microscope (TEM) image of the flexible pyrolytic boron nitride thin film in Embodiment 1 of the present invention;

[0014] Figure 4 This is an X-ray diffraction (XRD) pattern of the flexible pyrolytic boron nitride thin film in Example 1 of the present invention;

[0015] Figure 5 This is the Raman spectrum of the flexible pyrolytic boron nitride thin film in Example 1 of the present invention;

[0016] Figure 6 This is a cross-sectional scanning electron microscope image of the flexible pyrolytic boron nitride thin film in Example 3 of the present invention;

[0017] Figure 7This is a scanning electron microscope image of the flexible pyrolytic boron nitride thin film in Comparative Example 1 of the present invention;

[0018] Figure 8 This is a cross-sectional scanning electron microscope image of the flexible pyrolytic boron nitride thin film in Example 7 of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0020] To address the problems of high rigidity, low flexibility, and small area of ​​currently prepared pyrolytic boron nitride films, this invention proposes a flexible pyrolytic boron nitride film, its preparation method, and its application. By selecting a suitable substrate, controlling the types and ratios of nitrogen source and gaseous boron halide, and controlling the reaction parameters for forming the boron nitride film, a pyrolytic boron nitride film with a large area, excellent flexibility, and good mechanical properties can be prepared.

[0021] Specifically, this invention provides a method for preparing a flexible pyrolytic boron nitride thin film, comprising the following steps: placing a substrate in a reactor and preheating the substrate to 1200~1300℃; after preheating, introducing a nitrogen source into the reactor; after introducing the nitrogen source, introducing gaseous boron halide, controlling the molar ratio of nitrogen source to gaseous boron halide to be 2:1~8:1; after introducing gaseous boron halide, calcining at a temperature of 1500~1700℃ to obtain a flexible pyrolytic boron nitride thin film deposited on the substrate; wherein, the substrate is selected from a graphite substrate or a single-crystal silicon substrate; the gas flow rates of the nitrogen source and gaseous boron halide are 300~600 scc / min.

[0022] In embodiments of the present invention, a method of first introducing a nitrogen source followed by gaseous boron halide is adopted. This approach serves two purposes: firstly, it allows for the removal of air from the reactor, and the preheating within the reactor pre-activates the nitrogen source for bonding, reducing the reaction temperature and intensity of the subsequent calcination of the nitrogen source with gaseous boron halide to form boron nitride; secondly, it facilitates uniform mixing of the nitrogen source and gaseous boron halide to form boron nitride with a uniform morphology. By controlling the molar ratio of nitrogen source and gaseous boron halide introduced into the reactor, the gas flow rate, and the calcination reaction temperature, the pyrolytic boron nitride film prepared by the vapor deposition method can achieve a large area. Compared to a pyrolytic boron nitride crucible, the pyrolytic boron nitride film of the present invention exhibits higher flexibility, thinner film thickness, and excellent mechanical properties.

[0023] According to an embodiment of the present invention, the substrate is placed in a reaction furnace and preheated in an air atmosphere. The reaction furnace is then preheated to the reaction temperature to allow for subsequent reaction of nitrogen and gaseous boron halide. The reaction furnace can be a high-temperature chemical vapor deposition furnace, with a furnace chamber outer diameter of 80-100 mm, designed to accommodate substrates of different sizes. When the nitrogen source is introduced, the vacuum level of the reaction furnace is maintained at 1*10⁻⁶. -2 ~9*10 -2 torr, preferably 5*10 -2 The torr vacuum level helps to obtain continuous, sheet-like pyrolytic boron nitride films. Inside the reactor, the temperature is increased to the preheating temperature at a rate of 1~5℃ / min to preactivate the subsequently introduced nitrogen source, wherein the preheating temperature is 1200~1300℃.

[0024] According to embodiments of the present invention, the substrate has a size of 2 to 3 inches and a thickness of 5 μm to 5 mm. Preferably, a graphite substrate is used, and the thickness of the graphite substrate is 5 to 20 μm.

[0025] According to embodiments of the present invention, the nitrogen source is ammonia, and the gaseous boron halide is selected from at least one of boron chloride (BCl3) and boron bromide (BBr3). Preferably, the molar ratio of nitrogen source to gaseous boron halide is 3:1 to 6:1. Within this ratio range, pyrolytic boron nitride films with larger area, thinner film, and higher flexibility can be obtained. A flexible pyrolytic boron nitride film can also be obtained by mixing and calcining ammonia, boron chloride, and boron bromide. Pyrolytic boron nitride films obtained in this manner have the characteristics of smaller size and thinner film.

[0026] According to an embodiment of the present invention, after introducing a nitrogen source and gaseous boron halide into the reactor, the preheating temperature is increased to the calcination temperature at a heating rate of 1~5℃ / min, and the calcination reaction temperature is 1500~1700℃. Further, a preferred calcination temperature is 1600~1700℃. In this embodiment of the invention, preheating pre-activates the nitrogen source for bonding, reducing the reaction temperature at which the nitrogen source and gaseous boron halide calcine to form boron nitride, thus achieving the formation of a pyrolytic boron nitride film below 2000℃ and avoiding the use of dilution gas. During the calcination process, the nitrogen source and boron halide react to generate boron nitride, which is deposited on the substrate.

[0027] Furthermore, the gas flow rate of the nitrogen source is 400~500 scc / min, the gas flow rate of boron chloride is 350~400 scc / min, and the gas flow rate of boron bromide is 300~350 scc / min. Within this range, the obtained pyrolytic boron nitride film is uniformly formed, with uniform film thickness, high flexibility, and no brittleness.

[0028] According to an embodiment of the present invention, a flexible pyrolytic boron nitride thin film prepared by the method described in the above embodiments is provided, wherein the flexible pyrolytic boron nitride thin film is a multilayer stacked pyrolytic boron nitride.

[0029] In embodiments of the present invention, a large-area (2-3 inches) and highly flexible pyrolytic boron nitride film can be obtained by simple peeling of multilayer stacked pyrolytic boron nitride films without the need for additional substrate processing.

[0030] According to an embodiment of the present invention, in the flexible pyrolytic boron nitride thin film, the thickness of each layer of flexible pyrolytic boron nitride is 20 μm to 60 μm, and the thickness of the flexible pyrolytic boron nitride thin film is 80 μm to 240 μm.

[0031] Furthermore, using graphite as a substrate, the thickness of the prepared flexible pyrolytic boron nitride film is 80μm~150μm, the size of the flexible pyrolytic boron nitride film is 2~3 inches, and the thickness of each layer of flexible pyrolytic boron nitride is 20μm~50μm.

[0032] In the embodiments of the present invention, the preparation method of pyrolytic boron nitride in the above embodiments is adopted. By controlling the molar ratio of nitrogen source and gaseous boron nitride, gas flow rate, calcination reaction temperature and other related parameters, a flexible pyrolytic boron nitride film with a thin film thickness is obtained. The pyrolytic boron nitride film has high purity, and each layer of boron nitride has a uniform thickness and clear boundaries.

[0033] According to embodiments of the present invention, the present invention also provides applications of flexible pyrolytic boron nitride thin films in electronic device fabrication or energy storage. For example, flexible pyrolytic boron nitride thin films can be used in the manufacture of electronic devices such as flexible displays and flexible sensors, and can also be used in energy storage applications such as batteries and supercapacitors.

[0034] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention. Unless otherwise specified, the experimental methods used in the embodiments are all conventional methods; the materials and reagents used are all commercially available.

[0035] Specifically, flexible pyrolytic boron nitride thin films were prepared using ammonia as the nitrogen source and boron chloride and boron bromide as the boron source.

[0036] Example 1

[0037] Flexible pyrolytic boron nitride thin films were prepared by chemical vapor deposition using boron chloride (BCl3) as the boron source. The specific process is as follows:

[0038] Step (1): Place 2-3 inch graphite (from a graphene research institute) into the reactor (GSL-1700X-F3LV);

[0039] Step (2): The above substrate is preheated at 1200°C for 12 hours in a reactor, with a heating rate of 2°C / min.

[0040] Step (3): Introduce NH3 into step (2) at a flow rate of 400 scc / min;

[0041] Step (4): BCl3 is introduced into step (3) at a flow rate of 400 scc / min and mixed with ammonia. The molar ratio of NH3 to BCl3 is 4:1.

[0042] Step (5): Calcine NH3 and BCl3 at a temperature of 1200℃ to 1700℃ at a rate of 2℃ / min. After holding at 1700℃ for 3 hours, the mixture is naturally cooled to room temperature to obtain a flexible pyrolytic boron nitride film with gaseous boron halide as BCl3.

[0043] Figure 1 This is a physical image of the flexible pyrolytic boron nitride thin film in Embodiment 1 of the present invention.

[0044] like Figure 1 As shown, the flexible pyrolytic boron nitride film in Example 1 was bent, and the bending shape demonstrated the excellent flexibility of the prepared pyrolytic boron nitride film.

[0045] Figure 2 This is a cross-sectional scanning electron microscope image of the flexible pyrolytic boron nitride thin film in Example 1 of the present invention.

[0046] like Figure 2 As shown, the flexible pyrolytic boron nitride film in Embodiment 1 of the present invention has a layered structure, with each layer of boron nitride having a thickness of 20~30μm and a relatively uniform thickness. The thickness of the obtained flexible pyrolytic boron nitride film is 80μm~240μm.

[0047] Figure 3 This is a high-resolution transmission electron microscope (TEM) image of the flexible pyrolytic boron nitride thin film in Embodiment 1 of the present invention.

[0048] like Figure 3 As shown in the figure, the lattice stripes of the (001) plane can be observed, indicating that its structure is simple and relatively pure.

[0049] Figure 4 This is an X-ray diffraction (XRD) pattern of the flexible pyrolytic boron nitride thin film in Example 1 of the present invention.

[0050] like Figure 4As shown, the flexible pyrolytic boron nitride film in Example 1 exhibits a characteristic diffraction peak at 25.98°, corresponding to the (002) crystal plane. Furthermore, the XRD test results of the front and back sides of the flexible pyrolytic boron nitride film in Example 1 are the same, indicating that the flexible pyrolytic boron nitride film prepared in Example 1 has good uniformity.

[0051] Figure 5 This is the Raman spectrum of the flexible pyrolytic boron nitride thin film in Example 1 of the present invention.

[0052] like Figure 5 As shown, the flexible pyrolytic boron nitride film in Example 1 was subjected to a temperature of 1367 cm⁻¹. -1 A Raman peak appears, which is due to boron nitride E. 2g This is caused by vibrational modes. Furthermore, the presence of carbon-free characteristic peaks further confirms the purity of the product.

[0053] Example 2

[0054] Using the same method and reaction parameters as in Example 1, pyrolytic boron nitride films were prepared at BCl3 gas flow rates of 300 scc / min, 350 scc / min, 400 scc / min, and 500 scc / min, and ammonia gas flow rate of 400 scc / min. The test structures of the prepared pyrolytic boron nitride films are shown in Table 1.

[0055] Table 1

[0056]

[0057] Table 1 shows that, under the same nitrogen source flow rate, changing the BCl3 gas flow rate alters the uniformity, flexibility, and brittleness of the obtained pyrolytic boron nitride films. Specifically, at a BCl3 gas flow rate of 300 scc / min, the obtained pyrolytic boron nitride films cannot be bonded together, and grain boundaries exist between the films. The presence of these grain boundaries hinders lateral growth and prevents film formation, while also increasing the film's brittleness and resulting in poor flexibility. Under BCl3 gas flow rates of 350–400 scc / min, the obtained pyrolytic boron nitride films exhibit good flexibility and uniform film formation. At a BCl3 gas flow rate of 500 scc / min, the thickness of the obtained pyrolytic boron nitride films increases, leading to decreased flexibility and increased brittleness.

[0058] Example 3

[0059] Flexible pyrolytic boron nitride thin films were prepared by chemical vapor deposition using boron bromide (BBr3) as the boron source. The specific process is as follows:

[0060] Step (1): Place 2-3 inch graphite (from a graphene research institute) into the reactor (GSL-1700X-F3LV);

[0061] Step (2): The above substrate is preheated at 1200°C for 12 hours in a reactor, with a heating rate of 2°C / min.

[0062] Step (3): Introduce NH3 into step (2) at a flow rate of 400 scc / min;

[0063] Step (4): BBr3 is introduced into step (3) at a flow rate of 350 scc / min and mixed with ammonia. The molar ratio of NH3 to BBr3 is 5:1.

[0064] Step (5): Calcine NH3 and BBr3 at a temperature of 1200℃ to 1700℃ at a rate of 1℃ / min. After holding at 1700℃ for 3 hours, the mixture is naturally cooled to room temperature to obtain a flexible pyrolytic boron nitride film with gaseous boron halide as BBr3.

[0065] Figure 6 This is a cross-sectional scanning electron microscope image of the flexible pyrolytic boron nitride thin film in Example 3 of the present invention.

[0066] like Figure 6 As shown in the figure, the grown flexible pyrolytic boron nitride film is a layered material with a thickness of 40-50 μm for each boron nitride layer. The thickness of each boron nitride layer is relatively uniform, and the thickness of the obtained flexible pyrolytic boron nitride film is 80 μm-240 μm.

[0067] Example 4

[0068] Using the same method and reaction parameters as in Example 3, pyrolytic boron nitride films were prepared at BBr3 gas flow rates of 300 scc / min, 350 scc / min, 400 scc / min, and 500 scc / min, and ammonia gas flow rate of 400 scc / min. The test structures of the prepared pyrolytic boron nitride films are shown in Table 2.

[0069] Table 2

[0070]

[0071] Table 2 shows that, under the same nitrogen source flow rate, changing the BBr3 gas flow rate alters the uniformity, flexibility, and brittleness of the continuously formed pyrolytic boron nitride film. Specifically, under the condition of a BBr3 gas flow rate of 300–350 scc / min, the obtained pyrolytic boron nitride film exhibits good flexibility, uniform film formation, and moderate film thickness. Further increasing the BBr3 gas flow rate leads to an increase in the thickness of the pyrolytic boron nitride film and a decrease in its flexibility.

[0072] Comparative Example 1

[0073] Flexible pyrolytic boron nitride thin films were prepared by chemical vapor deposition using boron chloride (BCl3) as the boron source. The specific process is as follows:

[0074] Step (1): Place 2-3 inch graphite (from a graphene research institute) into the reactor (GSL-1700X-F3LV);

[0075] Step (2): The above substrate is preheated at 1200°C for 12 hours in a reactor, with a heating rate of 2°C / min.

[0076] Step (3): Introduce NH3 into step (2) at a flow rate of 400 scc / min;

[0077] Step (4): BCl3 is introduced into step (3) at a flow rate of 400 scc / min and mixed with ammonia. The molar ratio of NH3 to BCl3 is 10:1.

[0078] Step (5): Calcine NH3 and BCl3 at a temperature of 1200℃ to 1700℃ at a rate of 2℃ / min. After holding at 1700℃ for 3 hours, the mixture is naturally cooled to room temperature to obtain a flexible pyrolytic boron nitride film with gaseous boron halide as BCl3.

[0079] Figure 7 This is a scanning electron microscope image of the flexible pyrolytic boron nitride thin film in Comparative Example 1 of the present invention.

[0080] like Figure 7 As shown, the flexible pyrolytic boron nitride film prepared by the method in Comparative Example 1 is no longer uniform in thickness.

[0081] Example 5

[0082] Using the same method and reaction parameters as in Example 1, the calcination temperature was set to 1400℃, 1500℃, 1600℃ and 1700℃ in step (5) to prepare different pyrolytic boron nitride films. The test structures of the prepared pyrolytic boron nitride films are shown in Table 3.

[0083] Table 3

[0084]

[0085] Example 6

[0086] Using the same method and reaction parameters as in Example 1, pyrolytic boron nitride films were prepared at ammonia gas flow rates of 100 scc / min, 300 scc / min, 400 scc / min, 500 scc / min, and 700 scc / min, and a BCl3 gas flow rate of 400 scc / min. The test structures of the prepared pyrolytic boron nitride films are shown in Table 4.

[0087] Table 4

[0088]

[0089] Example 7

[0090] Flexible pyrolytic boron nitride thin films were prepared by chemical vapor deposition using boron chloride (BCl3) as the boron source. The specific process is as follows:

[0091] Step (1): Place a 2-3 inch polished single-crystal silicon substrate (from a certain semiconductor technology company) into the reactor (GSL-1700X-F3LV);

[0092] Step (2): In the reactor, the substrate from step (1) is preheated at 1200℃ for 12h, with a heating rate of 2℃ / min;

[0093] Step (3): Introduce NH3 into step (2) at a flow rate of 400 scc / min;

[0094] Step (4): BCl3 is introduced into step (3) at a flow rate of 400 scc / min and mixed with ammonia. The molar ratio of NH3 to BCl3 is 4:1.

[0095] Step (5): Calcine NH3 and BCl3 at a temperature of 1200℃ to 1700℃ at a rate of 2℃ / min. After holding at 1700℃ for 3 hours, the mixture is naturally cooled to room temperature to obtain a flexible pyrolytic boron nitride film with gaseous boron halide as BCl3.

[0096] Figure 8 This is a cross-sectional scanning electron microscope image of the flexible pyrolytic boron nitride thin film in Example 7 of the present invention.

[0097] like Figure 8As shown, using Si as a substrate, NH3 and BCl3 react under calcination conditions. The interlayer boundaries of the pyrolytic boron nitride film grown on the Si substrate become less clear, and the thickness of each layer is between 40 and 60 μm. However, it is still possible to obtain a continuous film with a certain degree of flexibility.

[0098] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a flexible pyrolytic boron nitride thin film, comprising the following steps: The substrate is placed in a reactor and preheated to 1200~1300°C; After preheating, a nitrogen source is introduced into the reactor; After introducing a nitrogen source, gaseous boron halide is introduced, and the molar ratio of the nitrogen source to the gaseous boron halide is controlled to be 2:1 to 8:

1. After introducing gaseous boron halide, the mixture is calcined at a temperature of 1500~1700℃ to obtain a flexible pyrolytic boron nitride film deposited on the substrate. The substrate is selected from a graphite substrate or a single-crystal silicon substrate; The flow rates of the nitrogen source and gaseous boron halide are 300~600 scc / min.

2. The preparation method according to claim 1, wherein, The nitrogen source is ammonia, and the gaseous boron halide is selected from at least one of boron chloride and boron bromide.

3. The preparation method according to claim 2, wherein, The substrate is preheated in an air atmosphere; The substrate has a size of 2 to 3 inches and a thickness of 5 μm to 5 mm.

4. The preparation method according to claim 1, wherein, The temperature is increased to the preheating temperature at a heating rate of 1~5℃ / min, and the preheating temperature is increased to the calcination temperature at a heating rate of 1~5℃ / min.

5. The preparation method according to claim 3, wherein, The substrate is a graphite substrate with a thickness of 5~20μm.

6. The preparation method according to claim 5, wherein, The gas flow rate of the nitrogen source is 400~500 scc / min, the gas flow rate of boron chloride is 350~400 scc / min, and the gas flow rate of boron bromide is 300~350 scc / min. The molar ratio of the nitrogen source to the gaseous boron halide is 3:1 to 6:1; The calcination temperature is 1600~1700℃.

7. The preparation method according to claim 1, wherein, When a nitrogen source is introduced, the vacuum level of the reactor is 1*10. -2 ~9*10 -2 The outer diameter of the furnace chamber of the reactor is 80~100mm.

8. A flexible pyrolytic boron nitride thin film prepared by the preparation method according to any one of claims 1-7, wherein, The flexible pyrolytic boron nitride film is a multilayer stacked pyrolytic boron nitride film.

9. The flexible pyrolytic boron nitride thin film according to claim 8, wherein, In the flexible pyrolytic boron nitride film, the thickness of each layer of flexible pyrolytic boron nitride is 20μm~60μm, and the thickness of the flexible pyrolytic boron nitride film is 80μm~240μm.

10. The application of the flexible pyrolytic boron nitride thin film according to any one of claims 8-9 in the fabrication of electronic devices or energy storage.

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