Method for preparing boron nitride self-supporting film by electrospinning and film

Abstract

The application provides a method for preparing a boron nitride self-supporting film by electrospinning and the film, and comprises the following steps: S1: preparing a mixed powder of boron nitride nanotubes and boron nitride nanosheets; S2: obtaining a hydroxylated boron nitride mixed powder; S3: the obtained hydroxylated boron nitride mixed powder is soaked in a silane coupling agent, and stirring is performed to obtain an amidated boron nitride modified by polydopamine, and the silane coupling agent is 3-ureidopropyl trimethoxysilane; S4: after ultrasonic treatment, a boron nitride aramid nanofiber suspension is obtained, the mass percentage of aramid nanofibers in an aramid nanofiber ethanol solution is 3-8 wt%; S5: the boron nitride aramid nanofiber suspension obtained in step S4 is electrospun to obtain a film, and the film is subjected to high-temperature hot pressing treatment to obtain a boron nitride self-supporting film. The boron nitride self-supporting film prepared by the application has the characteristics of high thermal conductivity, ultra-lightness, high toughness, high wave permeability, excellent dielectric performance and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of nanometer ceramic film material, and particularly relates to a method for preparing a boron nitride self-supporting film by electrospinning and the film. BACKGROUND

[0002] Electrospinning is a special fiber manufacturing process, in which a polymer solution or melt is jetted in a strong electric field. Under the action of an electric field, the droplet at the needle tip will change from a spherical shape to a conical shape (i.e., a "Taylor cone"), and a fiber filament is obtained from the conical tip. This way can produce polymer filaments with nanometer diameter.

[0003] Boron nitride and graphite have extremely similar structures, and both layered or tubular boron nitride and graphene or carbon nanotubes have excellent thermal conductivity and mechanical properties. However, compared with graphene or carbon nanotubes, boron nitride has superior thermal stability, insulation and wave transmission performance. The thermal conductivity of the self-supporting film of graphite is as high as 1500 W / mK, which has great application value in the field of heat conduction. However, the self-supporting film of graphite has strong conductivity and great shielding effect on electromagnetic waves, which makes it difficult to be widely used in the fields of insulation, heat conduction and wave transmission such as 5G base stations and mobile phone antennas. The boron nitride self-supporting film has good heat conduction capacity, and also has excellent insulation and wave transmission performance. The traditional boron nitride self-supporting film is prepared by using boron nitride nanosheets as the base body and by means of filtration. The boron nitride self-supporting film prepared by this method has low strength due to the lack of strong fiber cooperation. SUMMARY

[0004] Therefore, the present application aims to provide a method for preparing a boron nitride self-supporting film by electrospinning and the film to solve at least one technical problem in the background art.

[0005] To achieve the above-mentioned purposes, the technical scheme of the present application is as follows:

[0006] The method for preparing a boron nitride self-supporting film by electrospinning and the film comprise the following steps:

[0007] S1: dispersing boron nitride nanotubes and boron nitride nanosheets in an organic solution to prepare boron nitride slurry, and obtaining a mixed powder of boron nitride nanotubes and boron nitride nanosheets by ultrasonic peeling and centrifugation of the boron nitride slurry, and then freeze-drying the sediment;

[0008] S2: performing oxygen plasma treatment on the mixed powder of boron nitride nanotubes and boron nitride nanosheets obtained in step S1 to obtain a hydroxylated boron nitride mixed powder;

[0009] S3: The hydroxylated boron nitride mixed powder obtained in step S2 is soaked in a silane coupling agent and stirred to obtain hydroxylated boron nitride amidation. The hydroxylated boron nitride amidation is soaked in polydopamine and stirred to obtain polydopamine-modified amidated boron nitride.

[0010] S4: The polydopamine-modified amidated boron nitride obtained in step S3 is mixed with an aramid nanofiber ethanol solution and ultrasonicated to obtain a boron nitride aramid nanofiber suspension.

[0011] S5: The boron nitride aramid nanofiber suspension obtained in step S4 is electrospun to obtain a film, and the film is subjected to high-temperature hot pressing treatment to obtain a boron nitride self-supporting film.

[0012] Furthermore, in step S1, the length of the boron nitride nanotube is 50~150μm, preferably, the length of the boron nitride nanotube is 150μm.

[0013] And / or, the diameter of the boron nitride nanotubes in step S1 is 50~150nm, preferably, the diameter of the boron nitride nanotubes is 50nm.

[0014] In step S1, the wall thickness of the boron nitride nanotubes is 10~30nm, preferably 10nm.

[0015] And / or, the median diameter of the boron nitride nanotubes in step S1 is 50~150nm, preferably, the median diameter of the boron nitride nanotubes in step S1 is 50nm.

[0016] And / or, in step S1, the lateral length of the boron nitride nanosheets is 50~200nm, preferably 200nm.

[0017] The thickness of the boron nitride nanosheets is 30~50nm, preferably 30nm.

[0018] Further, the solid content of the boron nitride slurry in step S1 is 30% to 70%, preferably, the solid content of the boron nitride slurry in step S1 is 60%.

[0019] And / or, the organic solution in step S1 includes one or more of ethanol, dimethyl sulfoxide, dichloromethane, tetrahydrofuran, toluene, and dimethylformamide. Preferably, the organic solution in step S1 is one of tetrahydrofuran or dimethylformamide.

[0020] And / or, the time for ultrasonic stripping of the boron nitride slurry in step S1 is 24 to 72 hours;

[0021] And / or, the boron nitride slurry after ultrasonication in step S1 is centrifuged, including low-speed centrifugation followed by high-speed centrifugation, wherein the low-speed centrifugation speed is 1000-3000 r / min and the low-speed centrifugation time is 10-25 min; preferably, the low-speed centrifugation speed is 3000 r / min and the low-speed centrifugation time is 15 min, the high-speed centrifugation speed is 8000-20000 r / min and the high-speed centrifugation time is 15-45 min, preferably, the high-speed centrifugation speed is 11000 r / min and the high-speed centrifugation time is 30 min.

[0022] And / or, the freeze-drying temperature in step S1 is -78~-82℃, preferably, the freeze-drying temperature is 80℃ and the time is 24~48h.

[0023] And / or, the ultrasonic time for ultrasonic stripping of the boron nitride slurry in step S1 is 48 hours.

[0024] Furthermore, the oxygen plasma treatment time in step S2 is 20 to 60 minutes, preferably 30 minutes.

[0025] Furthermore, the silane coupling agent in step S3 is 3-ureapropyltrimethoxysilane;

[0026] And / or, in step S3, the hydroxylated boron nitride mixed powder is soaked in the silane coupling agent for 1 to 5 hours, preferably for 3 hours.

[0027] And / or, in step S3, after the hydroxylated boron nitride mixed powder is soaked in a silane coupling agent, it is stirred at a speed of 100-500 r / min, preferably 300 r / min, at a temperature of 40-80°C, preferably 60°C, for a time of 30-60 min.

[0028] And / or, the concentration of polydopamine in step S3 is 1 to 4%, preferably, the concentration of polydopamine in step S3 is 2%.

[0029] The hydroxylated boron nitride amidation is immersed in polydopamine at room temperature for 1 to 5 hours, preferably for 3 hours.

[0030] Further, the preparation method of the aramid nanofiber ethanol solution in step S4 includes the following steps: dissolving and soaking aramid nanofibers in ethanol to obtain the aramid nanofiber ethanol solution, wherein the soaking temperature of the aramid nanofibers in ethanol is 50~90℃, preferably 70℃, and the soaking time is 1.8-2.2h.

[0031] In step S4, the mass percentage of the aramid nanofiber ethanol solution is 3-8 wt%, preferably 5 wt%.

[0032] The soaking time is 1.8-2.2 hours, preferably 2 hours.

[0033] And / or, in step S4, the ultrasonic time after mixing the polydopamine-modified amidated boron nitride with the aramid nanofiber ethanol solution is 1-2 h;

[0034] The solid content of the boron nitride aramid nanofiber suspension in step S4 is 30-70%, preferably 50%.

[0035] Further, in step S5, the prepared boron nitride aramid nanofiber suspension is divided into 20 portions and electrospun in a 10-vertical-10-horizontal staggered pattern.

[0036] Furthermore, in step S5, the surface of the receiving disc in the electrospinning process is coated with polytetrafluoroethylene, and the rotation speed of the receiving disc is 1000-3000 r / min, preferably 2500 r / min.

[0037] The electrospinning time is 0.5 to 3 hours, preferably 3 hours.

[0038] And / or, the resulting film is subjected to hot pressing at a temperature of 200°C, within a range of 100–300°C.

[0039] Compared with existing technologies, the method and film for preparing boron nitride self-supporting thin films by electrospinning described in this invention have the following advantages:

[0040] 1. This application utilizes nanoscale ultralight and high-strength boron nitride nanotubes as the substrate, uses boron nitride nanosheets to fill the gaps, and provides a low-cost, large-scale technical route for preparing ultra-high-strength boron nitride self-supporting films through a vertical alternating spinning method.

[0041] 2. This application avoids the significant drawback of low tensile strength in traditional wet-process preparation of thermally conductive films using boron nitride nanosheets. By functionalizing and modifying the surface of boron nitride, strong interfacial bonding between boron nitride nanotubes is achieved, significantly reducing the thermal resistance between boron nitride interfaces. Ordered cross-weaving of nanotubes greatly enhances the strength of the thermally conductive and wave-transparent film. Aramid nanofibers are used to improve the viscosity and density of boron nitride.

[0042] 3. The electrospinning method used in this invention is a large-area, low-cost process preparation technology. At the same time, the boron nitride self-supporting thin film prepared by this method has the characteristics of high thermal conductivity, ultralight weight, high strength and toughness, high wave transmission and excellent dielectric properties. Attached Figure Description

[0043] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0044] Figure 1 This is a diagram of the thermally conductive and wave-transparent thin film prepared by electrospinning of boron nitride nanotubes and boron nitride nanosheets as described in Example 1 of this invention;

[0045] Figure 2 This is a schematic diagram of the internal structure of the thermally conductive and wave-transparent composite film described in Embodiment 1 of the present invention;

[0046] Figure 3 The images shown are microscopic SEM images of the thermally conductive and wave-transparent composite film described in Embodiment 1 of the present invention (sEM magnification of a is 1000x, b is 1800x, c is 10000x, and d is 18000x). Detailed Implementation

[0047] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0048] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0049] Example 1

[0050] Boron nitride nanotubes with a diameter of 50 nm, a length of 150 μm, and a wall thickness of 10 nm, and boron nitride nanosheets with a transverse length of 200 nm and a thickness of 30 nm were selected as raw materials. Equal masses of boron nitride nanotubes and nanosheets were added to dimethylformamide to prepare a slurry with a solid content of 60%. The boron nitride slurry was then ultrasonically exfoliated for 48 h. The ultrasonically exfoliated slurry was then centrifuged at low speed (3000 rpm) for 15 min, followed by high-speed centrifugation at 11000 rpm for 30 min. The supernatant was then decanted to obtain boron nitride nanotube and nanosheet precipitates. The slurry was then freeze-dried at -80 °C for 48 h. The freeze-dried boron nitride nanotube and nanosheet mixed powder was then subjected to oxygen plasma treatment for 30 min to obtain hydroxylated boron nitride mixed powder. The hydroxylated boron nitride mixed powder was then soaked in 3-ureapropyltrimethoxysilane for 3 hours, and stirred for 45 minutes at 300 rpm and 60 °C to amidate the hydroxylated boron nitride. The hydroxylated boron nitride nanosheets s-OH interacted with the silanol obtained from the hydrolysis of 3-ureapropyltrimethoxysilane to yield boron nitride nanosheets s-CONH2 with amide groups at the ends.

[0051] Boron nitride slurry was modified by adding 2% polydopamine, and the mixture was soaked at room temperature for 3 hours with stirring. Then, 5 wt% aramid nanofibers were dissolved and soaked in ethanol at 70℃ for 2 hours. The soaked aramid nanofiber ethanol solution was then added to the polydopamine-modified amidotropic boron nitride to prepare a boron nitride-aramid nanofiber suspension of approximately 50%, which was ultrasonicated for 2 hours. The prepared boron nitride nanotube / boron nitride nanosheet / aramid nanofiber suspension was divided into 20 portions and electrospun in a 10-vertical-10-horizontal staggered pattern. A polytetrafluoroethylene coating was applied to the surface of the receiving disc, the spinning speed was adjusted to 2000 r / min, and the spinning time was 3 hours. The resulting film was then subjected to a high-temperature hot-pressing treatment at 200℃ to obtain a self-supporting boron nitride film. The obtained film had a strength of 30 MPa, a thermal conductivity of 60 W / mK, and a film density of 50 g / m³. 2 With a porosity of 70%, the finished thermally conductive and wave-transparent thin film is as follows: Figure 1 As shown, the internal structure of the thermally conductive and wave-transparent composite film is as follows: Figure 2 As shown, the microstructure of the thermally conductive and wave-transparent composite film is as follows: Figure 3 As shown.

[0052] Example 2

[0053] Boron nitride nanotubes with a diameter of 50 nm, a length of 50 μm, and a wall thickness of 10 nm, and boron nitride nanosheets with a transverse length of 200 nm and a thickness of 30 nm were selected as raw materials. Equal masses of boron nitride nanotubes and nanosheets were added to tetrahydrofuran to prepare a slurry with a solid content of 60%. The boron nitride slurry was then ultrasonically exfoliated for 48 h. The ultrasonically exfoliated slurry was then centrifuged at a low speed of 3000 r / min for 15 min, followed by high-speed centrifugation at 11000 r / min for 30 min. The supernatant was then decanted to obtain boron nitride nanotube and nanosheet precipitates. The slurry was then freeze-dried at -80 °C for 48 h. The freeze-dried boron nitride nanotube and nanosheet mixed powder was then subjected to oxygen plasma treatment for 30 min to obtain hydroxylated boron nitride mixed powder. The hydroxylated boron nitride mixed powder was then soaked in 3-ureapropyltrimethoxysilane for 3 hours, and stirred for 45 minutes at 300 rpm and 60°C to amidate the boron nitride. The hydroxylated boron nitride nanosheets (s-OH) interacted with the silanol obtained from the hydrolysis of 3-ureapropyltrimethoxysilane to obtain boron nitride nanosheets (s-CONH2) with amide groups at the ends. 2% polydopamine was added to the boron nitride slurry to modify the amidated boron nitride, and the mixture was soaked at room temperature for 3 hours with thorough stirring. Then, 5 wt% aramid nanofibers were dissolved and soaked in ethanol at 70°C for 2 hours. The soaked aramid nanofiber ethanol solution was added to the polydopamine-modified amidated boron nitride to prepare a suspension of approximately 50% boron nitride aramid nanofibers, which was then sonicated for 2 hours. The prepared boron nitride nanotube / boron nitride nanosheet / aramid nanofiber suspension was divided into 20 portions and electrospun in a 10-vertical-10-horizontal staggered pattern. A polytetrafluoroethylene (PTFE) coating was applied to the surface of the receiving disk, the spinning speed was adjusted to 2000 r / min, and the spinning time was 3 h. The resulting film was then subjected to a high-temperature hot-pressing treatment at 200℃ to obtain a self-supporting boron nitride film. The obtained film had a strength of 15 MPa, a thermal conductivity of 35 W / mK, and a film density of 70 g / m³. 2 The porosity is 60%.

[0054] Example 3

[0055] Boron nitride nanotubes with a diameter of 50 nm, a length of 50 μm, and a wall thickness of 10 nm, and boron nitride nanosheets with a transverse length of 200 nm and a thickness of 30 nm were selected as raw materials. Equal masses of boron nitride nanotubes and nanosheets were added to dimethylformamide to prepare a slurry with a solid content of 60%. The boron nitride slurry was then ultrasonically exfoliated for 48 h. The ultrasonically exfoliated slurry was then centrifuged at low speed (3000 rpm) for 15 min, followed by high-speed centrifugation at 11000 rpm for 30 min. The supernatant was then decanted to obtain boron nitride nanotube and nanosheet precipitates. The slurry was then freeze-dried at -80 °C for 48 h. The freeze-dried boron nitride nanotube and nanosheet mixed powder was then subjected to oxygen plasma treatment for 30 min to obtain hydroxylated boron nitride mixed powder. The hydroxylated boron nitride mixed powder was then soaked in 3-ureapropyltrimethoxysilane for 3 hours, and stirred for 45 minutes at 300 rpm and 60°C to amidate the boron nitride. The hydroxylated boron nitride nanosheets (s-OH) interacted with the silanol obtained from the hydrolysis of 3-ureapropyltrimethoxysilane to obtain boron nitride nanosheets (s-CONH2) with amide groups at the ends. 2% polydopamine was added to the boron nitride slurry to modify the amidated boron nitride, and the mixture was soaked at room temperature for 3 hours with thorough stirring. Then, 5 wt% aramid nanofibers were dissolved and soaked in ethanol at 70°C for 2 hours. The soaked aramid nanofiber ethanol solution was added to the polydopamine-modified amidated boron nitride to prepare a suspension of approximately 50% boron nitride aramid nanofibers, which was then sonicated for 2 hours. The prepared boron nitride nanotube / boron nitride nanosheet / aramid nanofiber suspension was divided into 20 portions and electrospun in a 10-vertical-10-horizontal staggered pattern. A polytetrafluoroethylene (PTFE) coating was applied to the surface of the receiving disk, the spinning speed was adjusted to 2000 r / min, and the spinning time was 3 h. The resulting film was then subjected to a high-temperature hot-pressing treatment at 200℃ to obtain a self-supporting boron nitride film. The obtained film had a strength of 20 MPa, a thermal conductivity of 40 W / mK, and a film density of 60 g / m³. 2 The porosity is 65%.

[0056] Example 4

[0057] Boron nitride nanotubes with a diameter of 50 nm, a length of 150 μm, and a wall thickness of 10 nm, and boron nitride nanosheets with a transverse length of 200 nm and a thickness of 30 nm were selected as raw materials. Equal masses of boron nitride nanotubes and nanosheets were added to dimethylformamide to prepare a slurry with a solid content of 60%. The boron nitride slurry was then ultrasonically exfoliated for 48 h. The ultrasonically exfoliated slurry was then centrifuged at low speed (2000 rpm) for 30 min, followed by high-speed centrifugation at 2000 rpm for 20 min. The supernatant was then decanted to obtain boron nitride nanotube and nanosheet precipitates. This slurry was then freeze-dried at -80 °C for 48 h. The freeze-dried boron nitride nanotube and nanosheet mixed powder was then subjected to oxygen plasma treatment for 30 min to obtain hydroxylated boron nitride mixed powder. The hydroxylated boron nitride mixed powder was then soaked in 3-ureapropyltrimethoxysilane for 3 hours, and stirred for 45 minutes at 300 rpm and 50°C to amidate the boron nitride. The hydroxylated boron nitride nanosheets (s-OH) interacted with the silanol obtained from the hydrolysis of 3-ureapropyltrimethoxysilane to obtain boron nitride nanosheets (s-CONH2) with amide groups at the ends. 2% polydopamine was added to the boron nitride slurry to modify the amidated boron nitride, and the mixture was soaked at room temperature for 1 hour and stirred until homogeneous. Then, 3 wt% aramid nanofibers were dissolved and soaked in ethanol at 70°C for 2 hours. The soaked aramid nanofiber ethanol solution was added to the polydopamine-modified amidated boron nitride to prepare a suspension of approximately 50% boron nitride aramid nanofibers, which was then sonicated for 2 hours. The prepared boron nitride nanotube / boron nitride nanosheet / aramid nanofiber suspension was divided into 20 portions and electrospun in a 10-vertical-10-horizontal staggered pattern. A polytetrafluoroethylene (PTFE) coating was applied to the surface of the receiving disk, the spinning speed was adjusted to 3000 r / min, and the spinning time was 3 h. The resulting film was then subjected to a high-temperature hot-pressing treatment at 200℃ to obtain a self-supporting boron nitride film. The obtained film had a strength of 40 MPa, a thermal conductivity of 60 W / mK, and a film density of 65 g / m³. 2 The porosity is 50%.

[0058] The above description is only a preferred embodiment of the present invention and is 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 boron nitride self-supporting thin films by electrospinning, characterized in that: Includes the following steps: S1: Preparation of a mixed powder of boron nitride nanotubes and boron nitride nanosheets; S2: The mixed powder of boron nitride nanotubes and boron nitride nanosheets obtained in step S1 is subjected to oxygen plasma treatment to obtain hydroxylated boron nitride mixed powder. S3: The hydroxylated boron nitride mixed powder obtained in step S2 is soaked in a silane coupling agent and stirred to obtain hydroxylated boron nitride amidation. The hydroxylated boron nitride amidation is soaked in polydopamine and stirred to obtain polydopamine-modified amidated boron nitride. The silane coupling agent is 3-ureapropyltrimethoxysilane. S4: The polydopamine-modified amidated boron nitride obtained in step S3 is mixed with an aramid nanofiber ethanol solution, and after sonication, a boron nitride aramid nanofiber suspension is obtained. The mass percentage of aramid nanofibers in the aramid nanofiber ethanol solution is 3~8 wt%. S5: Electrospinning the boron nitride aramid nanofiber suspension obtained in step S4 to obtain a thin film, and then subjecting the thin film to high-temperature hot pressing to obtain a boron nitride self-supporting thin film. The preparation of the mixed powder of boron nitride nanotubes and boron nitride nanosheets in step S1 includes the following steps: dispersing boron nitride nanotubes and boron nitride nanosheets in an organic solution to prepare a boron nitride slurry; subjecting the boron nitride slurry to ultrasonication and centrifugation to obtain a precipitate; and freeze-drying the precipitate to obtain the mixed powder of boron nitride nanotubes and boron nitride nanosheets. The boron nitride nanotubes in step S1 have a tube length of 50~150μm, a diameter of 50~150nm, and a wall thickness of 10~30nm. In step S1, the lateral length of the boron nitride nanosheets is 50~200nm, and the thickness of the boron nitride nanosheets is 30~50nm. In step S5, the prepared boron nitride aramid nanofiber suspension is divided into 20 portions and electrospun in a 10-vertical-10-horizontal staggered pattern. In step S5, the surface of the receiving disc is coated with polytetrafluoroethylene, the rotation speed of the receiving disc is 1000-3000 r / min, and the electrospinning time is 0.5-3 h. The resulting film was subjected to hot pressing at a temperature of 100–300°C.

2. The method for preparing boron nitride self-supporting thin films by electrospinning according to claim 1, characterized in that: The solid content of the boron nitride slurry in step S1 is 30%–70%; And / or, the organic solution in step S1 includes one or more of ethanol, dimethyl sulfoxide, dichloromethane, tetrahydrofuran, toluene, and dimethylformamide; And / or, the time for ultrasonication of the boron nitride slurry in step S1 is 24 to 72 hours; And / or, the boron nitride slurry after ultrasonication in step S1 is centrifuged, including low-speed centrifugation and high-speed centrifugation, wherein the low-speed centrifugation speed is 1000~3000 r / min and the low-speed centrifugation time is 10~25 min, and the high-speed centrifugation speed is 8000~20000 r / min and the high-speed centrifugation time is 15~45 min. And / or, the freeze-drying temperature in step S1 is -78~-82℃, and the time is 24~48h.

3. The method for preparing boron nitride self-supporting thin films by electrospinning according to claim 1, characterized in that: The solid content of the boron nitride slurry in step S1 is 70%; And / or, the organic solution in step S1 is tetrahydrofuran and dimethylformamide; And / or, the time for ultrasonication of the boron nitride slurry in step S1 is 48 hours.

4. The method for preparing boron nitride self-supporting thin films by electrospinning according to claim 1, characterized in that: The oxygen plasma treatment time in step S2 is 20–60 min.

5. The method for preparing boron nitride self-supporting thin films by electrospinning according to claim 1, characterized in that: In step S3, the hydroxylated boron nitride mixed powder is soaked in silane coupling agent for 1 to 5 hours; And / or, in step S3, the hydroxylated boron nitride mixed powder is soaked in a silane coupling agent and then stirred, wherein the stirring speed is 100-500 r / min, the stirring temperature is 40-80℃, and the stirring time is 30-60 min; And / or, in step S3, the concentration of polydopamine is 1-4%, and the hydroxylated boron nitride amidation is immersed in polydopamine at room temperature for 1-5 hours.

6. The method for preparing boron nitride self-supporting thin films by electrospinning according to claim 1, characterized in that: The preparation method of the aramid nanofiber ethanol solution in step S4 includes the following steps: dissolving and soaking aramid nanofibers in ethanol to obtain the aramid nanofiber ethanol solution. The soaking temperature of the aramid nanofibers in ethanol is 50~90℃ and the soaking time is 1.8-2.2h.

7. The method for preparing boron nitride self-supporting thin films by electrospinning according to claim 5, characterized in that: In step S4, the ultrasonication time after mixing polydopamine-modified amidated boron nitride with aramid nanofiber ethanol solution is 1-2 hours. The solid content of the boron nitride aramid nanofiber suspension in step S4 is 30-70%.

8. The boron nitride self-supporting film obtained by the electrospinning method for preparing boron nitride self-supporting films according to any one of claims 1-7.

Images