A method for preparing a boron nitride nanosheet having a large aspect ratio
Boron nitride nanosheets with high aspect ratio were successfully prepared by plasma torch heating and ultrasonic dispersion, which solved the problems of complexity and low yield in the existing technology, realized efficient and controllable nanosheet preparation, and improved the performance of dielectric energy storage materials.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANGHAI SECOND POLYTECHNIC UNIVERSITY
- Filing Date
- 2024-09-27
- Publication Date
- 2026-05-29
AI Technical Summary
Existing technologies struggle to efficiently and controllably prepare high-quality, high-purity, and high-performance two-dimensional boron nitride nanosheets, and the preparation process is complex with low yields.
Hexagonal boron nitride powder was heated by a plasma spray gun. By controlling the power, airflow ratio and flow rate of the plasma spray gun, the interlayer expansion of boron nitride was achieved. After rapid cooling in an ice-water bath, it was ultrasonically dispersed to obtain boron nitride nanosheets with a large aspect ratio.
We have achieved a simple and efficient preparation of boron nitride nanosheets with high aspect ratio, which have excellent electrical insulation properties and high thermal conductivity, making them suitable for dielectric energy storage materials and enhancing the energy storage density and thermal stability of dielectric composite materials.
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Figure CN119409145B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of nanomaterial preparation technology, and in particular to a method for preparing boron nitride nanosheets with a high aspect ratio. Background Technology
[0002] With the continuous advancement of power electronics technology, 5G technology is increasingly widely used in communications and other fields. Simultaneously, microelectronic devices are evolving towards greater lightness and smaller size. This trend places higher demands on the electrical and thermal conductivity properties of electronic components and energy storage materials. Among numerous potential material options, two-dimensional (2D) materials have attracted significant attention and become a research hotspot due to their unique electrical, thermal, physical, and chemical properties. The utilization of 2D materials has gained popularity in several disciplines due to their special thermal, electrical, and mechanical properties. Compared to zero-dimensional (0D) and one-dimensional (1D) fillers, 2D fillers are more effective in improving the dielectric and energy storage performance of polymer-based composite materials. Two-dimensional materials with high aspect ratios have a significant impact and important role in the field of dielectric energy storage, mainly in the following aspects: (1) promoting charge injection and inhibiting electrical tree growth: Two-dimensional materials with high aspect ratios can inhibit the growth of electrical trees through the interface barrier effect, thereby enhancing the breakdown resistance of dielectric materials; (2) improving energy storage density: Due to their unique structural characteristics, two-dimensional materials with high aspect ratios can effectively improve the energy storage density of dielectric composite materials by reducing filler agglomeration and hindering the formation of conductive pathways. The introduction of these materials can increase the dielectric constant of the material, thereby generating stronger polarization under the action of an electric field and storing more energy. However, how to prepare high-quality, high-purity, high-performance, and high-yield two-dimensional nanosheets is a technical problem that urgently needs to be solved.
[0003] Current methods for preparing two-dimensional layered materials such as boron nitride nanosheets (BNNSs) mainly include mechanical exfoliation and chemical exfoliation. While mechanical ball milling is simple to operate and has low environmental requirements, it has limitations such as difficulty in precise control, insufficient selectivity, and low crystallinity of the prepared BNNSs. Chemical exfoliation includes liquid-phase ultrasonic exfoliation and ion-intercalation exfoliation. Although effective, liquid-phase ultrasonic exfoliation uses expensive and potentially toxic solvents; furthermore, BNNSs exhibit poor dispersibility in solvents, which can lead to re-aggregation during solvent removal, reducing the yield of the final product. Ion-intercalation exfoliation requires strict environmental conditions during the ion-intercalation stage, undoubtedly increasing the complexity of the preparation process; during the removal of the intercalated material, BNNSs may also re-aggregate, further affecting the yield. To improve efficiency and quality, the preparation process urgently needs further optimization and improvement. Summary of the Invention
[0004] The purpose of this invention is to provide a method for preparing boron nitride nanosheets with a high aspect ratio, thereby solving the aforementioned problems in the prior art. This invention develops a simple, efficient, easy-to-operate, and controllable method for exfoliating boron nitride using a plasma spray gun. It can efficiently and controllably prepare high aspect ratio BNNSs from large-size hexagonal boron nitride, thus providing a material suitable for preparing dielectric capacitors with excellent properties such as high aspect ratio, ultra-high thermal conductivity, and high-temperature stability.
[0005] To achieve the above objectives, the present invention provides the following technical solution:
[0006] One of the technical solutions of this invention is to provide a method for preparing boron nitride nanosheets with a high aspect ratio, comprising the following steps:
[0007] Boron nitride powder was heated and sprayed out using a plasma spray gun to obtain expanded boron nitride, which was then cooled in a coolant to obtain a precursor solution. The precursor solution was then sonicated, centrifuged, and the supernatant was collected and filtered to obtain the high aspect ratio boron nitride nanosheets.
[0008] Preferably, the boron nitride powder is added to the plasma spray gun by using a discrete nozzle for internal feeding. The discrete nozzle ensures that the powder feed gas flow does not interfere with the arc plasma process, and the powder beam does not scour the anode.
[0009] Preferably, the coolant is isopropanol and water in a mass ratio of 4-5:5-6, more preferably 4:6.
[0010] Preferably, the boron nitride powder is hexagonal boron nitride powder with an average size of 18-22 μm (abbreviated as h-BN).
[0011] Preferably, the cooling includes the following steps: directly spraying the expanded boron nitride ejected from the plasma spray gun into the coolant, wherein the temperature of the coolant is 0-5°C.
[0012] Preferably, the distance between the nozzle of the plasma spray gun and the coolant is 1.5-2.5m, more preferably 2.2m.
[0013] Preferably, the parameters of the plasma spray gun are as follows: plasma gas Ar flow rate of 90-180 SLPM, plasma gas N2 flow rate of 30-80 SLPM, plasma gas H2 flow rate of 10-50 SLPM, boron nitride powder feeding rate of 15-30 g / min, powder carrier gas Ar flow rate of 9-30 SLPM, and spraying power of 50-100 kW.
[0014] More preferably, the parameters of the plasma spray gun are as follows: plasma gas Ar flow rate of 90-176 SLPM, plasma gas N2 flow rate of 50-60 SLPM, plasma gas H2 flow rate of 20-25 SLPM, boron nitride powder feeding rate of 17-30 g / min, powder carrier gas Ar flow rate of 9-20 SLPM, and spraying power of 80-95 kW.
[0015] Preferably, the ultrasonic power is 25-30 kHz and the duration is 30-120 min.
[0016] More preferably, the power of the ultrasound is 25-30 kHz and the duration is 40-50 min.
[0017] Preferably, the centrifuge speed is 1500-3000 rpm and the time is 5-30 min.
[0018] More preferably, the centrifuge speed is 1500-2000 rpm and the time is 8-10 min.
[0019] Preferably, the filtration is performed by filtering through gauze with a pore size of 4-5 μm.
[0020] More preferably, the filtration is performed by filtering through gauze with a pore size of 4 μm.
[0021] Preferably, the filtration process further includes a drying step; the drying temperature is 70-80°C, and the drying time is 12-24 hours. More preferably, the drying temperature is 80°C, and the drying time is 24 hours.
[0022] The second technical solution of the present invention provides a boron nitride nanosheet with a large aspect ratio obtained according to the above preparation method.
[0023] The third technical solution of the present invention provides an application of the above-mentioned high aspect ratio boron nitride nanosheets in the field of dielectric energy storage.
[0024] The technical principle of this invention is as follows:
[0025] During the heating and ejection stage, this invention controls the temperature range of the plasma spray gun by adjusting its power, airflow ratio, and flow rate. Under the influence of high temperature and high-speed plasma impact, boron nitride powder undergoes interlayer expansion, resulting in expanded boron nitride. The nozzle of the spray gun is aligned with an ice-water bath, allowing the high-temperature expanded boron nitride to be directly sprayed into the ice water for rapid cooling. After cooling to room temperature, it is ultrasonically dispersed to obtain a BNNSs suspension.
[0026] This invention utilizes a high-temperature, high-speed plasma jet generated by a plasma gun to heat hexagonal boron nitride (BNNSs), causing thermal expansion of the boron nitride and thus weakening the van der Waals forces between the boron nitride layers. Finally, the boron nitride is exfoliated using ultrasonic aqueous phase, thereby preparing BNNSs with a high aspect ratio. By adjusting the temperature and powder feed rate, boron nitride nanosheets with different aspect ratios can be obtained. A powder feed rate of 28 g / min at 2100℃–2450℃ yields boron nitride nanosheets with an average aspect ratio of 2302. A powder feed rate of 30 g / min at 2450℃–2650℃ yields boron nitride nanosheets with an average aspect ratio of 2480. A powder feed rate of 15 g / min at 1534℃–1692℃ yields boron nitride nanosheets with an average aspect ratio of 1521. Boron nitride nanosheets with an average aspect ratio of 1730 can be obtained at a powder feed rate of 17 g / min within the range of 1692℃ to 1837℃. Boron nitride nanosheets with an average aspect ratio of 1840 can be obtained at a powder feed rate of 20 g / min within the range of 1837℃ to 1950℃. Boron nitride nanosheets with an average aspect ratio of 2020 can be obtained at a powder feed rate of 25 g / min within the range of 2100℃.
[0027] The beneficial technical effects of the present invention are as follows:
[0028] This invention develops a simple, efficient, easy-to-operate, and controllable method for exfoliating boron nitride using a plasma spray gun. It can efficiently and controllably prepare high-aspect-ratio boron nitride nanosheets (BNNSs) from large-size hexagonal boron nitride, thus providing a material suitable for preparing dielectric capacitors with excellent properties such as high aspect ratio, ultra-high thermal conductivity, and high-temperature stability. Furthermore, the boron nitride nanosheets prepared by this invention also exhibit excellent electrical insulation properties; the high aspect ratio means a larger surface area per unit volume, which enhances its application potential in catalysis, adsorption, and sensors.
[0029] The method involves first heating hexagonal boron nitride using a supersonic plasma torch, then directly spraying the heated boron nitride into an ice-water bath. Following ultrasonic dispersion and centrifugation to remove precipitate, the supernatant is filtered and finally dried to obtain the target product. The boron nitride nanosheets prepared using this method exhibit uniform size and thickness, with a high aspect ratio, surpassing similar products in existing technologies. Furthermore, the prepared boron nitride nanosheets possess excellent dielectric and thermal conductivity properties, making them suitable for applications in high-energy-storage, wide-temperature-frequency dielectric capacitors. Attached Figure Description
[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0031] Figure 1 This is a schematic diagram of the preparation process for Examples 1-6.
[0032] Figure 2 Atomic force microscopy (A), height (B), and lateral dimension (C) images of the product of Example 1.
[0033] Figure 3 This is a statistical distribution diagram of the lateral dimensions and thickness data of the product of Example 1.
[0034] Figure 4 This is a photograph of the boron nitride nanosheet supernatant from Example 1.
[0035] Figure 5 The diagram shows the experimental equipment used in Examples 1-6.
[0036] Figure 6 The graph shows the thermal conductivity of boron nitride nanosheets with different aspect ratios in Examples 1-6. Detailed Implementation
[0037] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.
[0038] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.
[0039] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.
[0040] The terms “comprising,” “including,” “having,” “containing,” etc., used in this invention are all open-ended terms, meaning that they include but are not limited to.
[0041] The layered boron nitride powder used in the following embodiments and comparative examples of this invention is hexagonal boron nitride powder (product name: BN-HS) with an average lateral size of 20 μm, purchased from Dandong Chemical Research Institute Co., Ltd. The isopropanol used was purchased from Shanghai Titan Technology Co., Ltd. (Adamas). Atomic force microscopy (AFM) images were obtained using an atomic force microscope (Park-XE7).
[0042] All raw materials used in the following embodiments and comparative examples of the present invention are commercially available products.
[0043] Figure 1 This is a schematic diagram of the preparation process for Examples 1-6.
[0044] Example 1
[0045] A method for preparing boron nitride nanosheets:
[0046] 80 mL of isopropanol and 120 mL of deionized water were mixed, and the solution temperature was adjusted to 4 °C to obtain a coolant, which was placed 2.2 m below the plasma spray gun for later use. Boron nitride powder was heated and sprayed out using the plasma spray gun, and the expanded boron nitride was directly sprayed into the coolant to obtain a precursor solution. The parameters of the plasma spray gun were as follows: plasma gas Ar flow rate of 140 SLPM, plasma gas N2 flow rate of 55 SLPM, plasma gas H2 flow rate of 24 SLPM, powder carrier gas Ar flow rate of 15 SLPM, powder feed rate of 25 g / min, and spraying power of 90 kW. Under these parameters, the particle temperature was between 1950 °C and 2100 °C, and the aspect ratio of the boron nitride nanosheets could reach 2020.
[0047] The precursor solution was ultrasonically dispersed at 30 kHz for 40 min to obtain a boron nitride nanosheet suspension, and then centrifuged at 2000 rpm for 10 min to obtain the boron nitride nanosheet supernatant.
[0048] The supernatant of the obtained boron nitride nanosheets was filtered through gauze with a pore size of 4 μm, and the filtered product was dried at 80 °C for 24 h to obtain boron nitride nanosheets.
[0049] Figure 2 Atomic force microscopy (A), height (B), and lateral dimension (C) images of the product of Example 1.
[0050] Depend on Figure 2 As can be seen from (a), the present invention has successfully prepared BNNSs with a large aspect ratio.
[0051] Twenty-five groups of boron nitride nanosheets were prepared repeatedly according to the method in Example 1, and the lateral dimensions and thickness data of the products were statistically analyzed. The test results are as follows: Figure 3As shown.
[0052] Figure 3 This is a statistical distribution diagram of the lateral dimensions and thickness data of the product of Example 1.
[0053] Figure 4 This is a photograph of the boron nitride nanosheet supernatant from Example 1.
[0054] Example 2
[0055] A method for preparing boron nitride nanosheets:
[0056] 80 mL of isopropanol and 120 mL of deionized water were mixed, and the solution temperature was adjusted to 4 °C to obtain a coolant, which was placed 2.2 m below the plasma spray gun for later use. Boron nitride powder was heated and sprayed out using the plasma spray gun, and the expanded boron nitride was directly sprayed into the coolant to obtain a precursor solution. The parameters of the plasma spray gun were as follows: plasma gas Ar flow rate of 102 SLPM, plasma gas N2 flow rate of 50 SLPM, plasma gas H2 flow rate of 35 SLPM, powder carrier gas Ar flow rate of 17 SLPM, powder feed rate of 28 g / min, and spraying power of 92 kW. Under these parameters, the particle temperature was between 2100 °C and 2450 °C, and the aspect ratio of the boron nitride nanosheets could reach 2302.
[0057] The precursor solution was ultrasonically dispersed at 30 kHz for 40 min to obtain a boron nitride nanosheet suspension, and then centrifuged at 2000 rpm for 10 min to obtain the boron nitride nanosheet supernatant.
[0058] The supernatant of the obtained boron nitride nanosheets was filtered through gauze with a pore size of 4 μm, and the filtered product was dried at 80 °C for 24 h to obtain boron nitride nanosheets.
[0059] Example 3
[0060] A method for preparing boron nitride nanosheets:
[0061] 80 mL of isopropanol and 120 mL of deionized water were mixed, and the solution temperature was adjusted to 4 °C to obtain a coolant. This coolant was placed 2.2 m below the plasma spray gun for later use. Boron nitride powder was heated and sprayed out using the plasma spray gun, and the expanded boron nitride was directly sprayed into the coolant to obtain a precursor solution. The parameters of the plasma spray gun were as follows: plasma gas Ar flow rate of 90 SLPM, plasma gas N2 flow rate of 48 SLPM, plasma gas H2 flow rate of 49 SLPM, powder carrier gas Ar flow rate of 20 SLPM, powder feed rate of 30 g / min, and spraying power of 95 kW. Under these parameters, the particle temperature was between 2450 °C and 2650 °C, and the aspect ratio of the boron nitride nanosheets could reach 2480.
[0062] The precursor solution was ultrasonically dispersed at 30 kHz for 40 min to obtain a boron nitride nanosheet suspension, and then centrifuged at 2000 rpm for 10 min to obtain the boron nitride nanosheet supernatant.
[0063] The supernatant of the obtained boron nitride nanosheets was filtered through gauze with a pore size of 4 μm, and the filtered product was dried at 80 °C for 24 h to obtain boron nitride nanosheets.
[0064] Example 4
[0065] A method for preparing boron nitride nanosheets:
[0066] 80 mL of isopropanol and 120 mL of deionized water were mixed, and the solution temperature was adjusted to 4 °C to obtain a coolant, which was placed 2.2 m below the plasma spray gun for later use. Boron nitride powder was heated and sprayed out using the plasma spray gun, and the expanded boron nitride was directly sprayed into the coolant to obtain a precursor solution. The parameters of the plasma spray gun were as follows: plasma gas Ar flow rate of 176 SLPM, plasma gas N2 flow rate of 63 SLPM, plasma gas H2 flow rate of 17 SLPM, powder carrier gas Ar flow rate of 9 SLPM, powder feed rate of 15 g / min, and spraying power of 87 kW. Under these parameters, the particle temperature was between 1534 °C and 1692 °C, and the aspect ratio of the boron nitride nanosheets could reach 1521.
[0067] The precursor solution was ultrasonically dispersed at 30 kHz for 40 min to obtain a boron nitride nanosheet suspension, and then centrifuged at 2000 rpm for 10 min to obtain the boron nitride nanosheet supernatant.
[0068] The supernatant of the obtained boron nitride nanosheets was filtered through gauze with a pore size of 4 μm, and the filtered product was dried at 80 °C for 24 h to obtain boron nitride nanosheets.
[0069] Example 5
[0070] A method for preparing boron nitride nanosheets:
[0071] 80 mL of isopropanol and 120 mL of deionized water were mixed, and the solution temperature was adjusted to 4 °C to obtain a coolant, which was placed 2.2 m below the plasma spray gun for later use. Boron nitride powder was heated and sprayed out using the plasma spray gun, and the expanded boron nitride was directly sprayed into the coolant to obtain a precursor solution. The parameters of the plasma spray gun were as follows: plasma gas Ar flow rate of 163 SLPM, plasma gas N2 flow rate of 60 SLPM, plasma gas H2 flow rate of 19 SLPM, powder carrier gas Ar flow rate of 10 SLPM, powder feed rate of 17 g / min, and spraying power of 87 kW. Under these parameters, the particle temperature was between 1692 °C and 1837 °C, and the aspect ratio of the boron nitride nanosheets could reach 1730.
[0072] The precursor solution was ultrasonically dispersed at 30 kHz for 40 min to obtain a boron nitride nanosheet suspension, and then centrifuged at 2000 rpm for 10 min to obtain the boron nitride nanosheet supernatant.
[0073] The supernatant of the obtained boron nitride nanosheets was filtered through gauze with a pore size of 4 μm, and the filtered product was dried at 80 °C for 24 h to obtain boron nitride nanosheets.
[0074] Example 6
[0075] A method for preparing boron nitride nanosheets:
[0076] 80 mL of isopropanol and 120 mL of deionized water were mixed, and the solution temperature was adjusted to 4 °C to obtain a coolant, which was placed 2.2 m below the plasma spray gun for later use. Boron nitride powder was heated and sprayed out using the plasma spray gun, and the expanded boron nitride was directly sprayed into the coolant to obtain a precursor solution. The parameters of the plasma spray gun were as follows: plasma gas Ar flow rate of 151 SLPM, plasma gas N2 flow rate of 57 SLPM, plasma gas H2 flow rate of 21 SLPM, powder carrier gas Ar flow rate of 13 SLPM, powder feed rate of 20 g / min, and spraying power of 89 kW. Under these parameters, the particle temperature was between 1837 °C and 1950 °C, and the aspect ratio of the boron nitride nanosheets could reach 1840.
[0077] The precursor solution was ultrasonically dispersed at 30 kHz for 40 min to obtain a boron nitride nanosheet suspension, and then centrifuged at 2000 rpm for 10 min to obtain the boron nitride nanosheet supernatant.
[0078] The supernatant of the obtained boron nitride nanosheets was filtered through gauze with a pore size of 4 μm, and the filtered product was dried at 80 °C for 24 h to obtain boron nitride nanosheets.
[0079] Figure 5 The diagram shows the experimental equipment used in Examples 1-6.
[0080] The thermal conductivity of the products from Examples 1-6 was measured, and the test results are as follows: Figure 6 As shown.
[0081] Figure 6 The graph shows the thermal conductivity of boron nitride nanosheets with different aspect ratios in Examples 1-6.
[0082] Comparative Example 1 (Vacuum-phase stripping method)
[0083] A method for preparing two-dimensional hexagonal boron nitride nanosheets using liquid nitrogen vaporization:
[0084] (1) Weigh 1g of commercial grade hexagonal boron nitride (h-BN, average size about 5μm) and place it in an alumina crucible. Then transfer it to a high-temperature furnace and heat it to 600℃ in air atmosphere. Hold it at this temperature for 30 minutes.
[0085] (2) Quickly remove the heated hexagonal boron nitride and rapidly transfer it to a Dewar flask (-196℃) containing liquid nitrogen. The volume ratio of liquid nitrogen to h-BN is 1:50 until the liquid nitrogen is completely vaporized.
[0086] (3) Transfer the h-BN in the Dewar flask to a high-temperature furnace and heat it to 600°C for 30 minutes;
[0087] (4) Repeat steps (2) and (3) 20 times to obtain boron nitride nanosheets.
[0088] The product was measured to have a radial dimension of 50–500 nm, fewer than 10 layers, and a thickness of less than 4 nm.
[0089] Comparative Example 2 (Chemical Stripping Method)
[0090] A method for preparing boron nitride nanosheets:
[0091] Mix 1g of hexagonal boron nitride powder with 100mL of sulfuric acid and stir until homogeneous. Then add 0.5g of potassium permanganate and continue stirring to form a mixture. Place the mixture in an ice bath and stir for 12 hours. Then remove the remaining potassium permanganate by adding hydrogen peroxide dropwise. Finally, wash the reaction product with water until the pH value is 6-8, then dissolve it in anhydrous ethanol to separate and remove the unpeeled boron nitride powder to obtain boron nitride nanosheets.
[0092] Comparative Example 3 (Liquid Phase Ultrasonic Exfoliation Method)
[0093] A method for preparing boron nitride nanosheets:
[0094] 0.3 g of hexagonal boron nitride was added to a 300 mL Erlenmeyer flask, followed by 100 mL of thionyl chloride. The flask was sealed and placed in an ultrasonic cleaner, where it was ultrasonically cleaned at 210 W for 5 hours, and then allowed to stand for 24 hours. The upper milky white dispersion was carefully collected by pouring. The thionyl chloride in the upper dispersion was recovered by rotary evaporation. The obtained boron nitride nanosheets were then dried in a vacuum drying oven at 70 °C for 24 hours to obtain pure boron nitride nanosheets, weighing 60 mg, with a yield of 20%.
[0095] Comparative Example 4 (Mechanical Ball Milling Method)
[0096] A method for preparing boron nitride nanosheets:
[0097] 1) Weigh 0.25g of hexagonal boron nitride raw material and 1.25g of tannic acid into a ball mill jar, and ball mill them at room temperature on a planetary ball mill. The media balls are stainless steel balls, the ball-to-material mass ratio is 60:1, the rotation speed is 300rpm, and the ball milling time is 20h.
[0098] 2) The ball milling product obtained in step 1) is thoroughly washed with deionized water and ethanol, and then dried in a forced-air drying oven to obtain a light yellow powder.
[0099] 3) The pale yellow powder obtained in step 2) is dispersed in isopropanol, sonicated for 30 min, centrifuged at 2000 rpm for 30 min, and the supernatant is taken to obtain boron nitride nanosheets.
[0100] Comparative Example 5 (Ion Insertion Stripping Method)
[0101] A method for preparing boron nitride nanosheets:
[0102] (1) Prepare a mixed solution of 60 mL deionized water and 40 mL isopropanol as a dispersant; (2) Add 1 g of hexagonal boron nitride powder to the mixed solution obtained in step (1) and stir thoroughly to disperse the boron nitride evenly; (3) Place the dispersion obtained in step (2) in an ultrasonic cleaner for ultrasonic treatment for 6 h; (4) Pour the dispersion obtained in step (3) into a hydrothermal reactor and carry out a high-temperature hydrothermal reaction at 180 °C; (5) Perform the same centrifugation treatment on the dispersion obtained in step (4) 3 times, with a centrifugation rate of 1000 rpm and a centrifugation time of 5 min; (6) Take the supernatant of step (5) and vacuum filter it 3 times with a large amount of deionized water to remove salt impurities; (7) Dry the product obtained in step (6) under vacuum at 60 °C for 12 h to obtain boron nitride nanosheets.
[0103] The aspect ratio data of Example 1 and Comparative Examples 1-5 are shown in Table 1 (the average aspect ratio is the average value after repeating the relevant preparation method 3 times).
[0104] Table 1
[0105]
[0106] As shown in Table 1, Example 1 has a larger aspect ratio than Comparative Examples 1-5, which helps to reduce filler agglomeration and hinder the formation of conductive pathways.
[0107] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.
Claims
1. A method for preparing boron nitride nanosheets with a high aspect ratio, characterized in that, Includes the following steps: Boron nitride powder was heated and sprayed out using a plasma spray gun to obtain expanded boron nitride, which was then cooled in a coolant to obtain a precursor solution. The precursor solution was then sonicated, centrifuged, and the supernatant was collected and filtered to obtain the high aspect ratio boron nitride nanosheets. The boron nitride powder is a hexagonal boron nitride powder with an average size of 18-22 μm; The cooling process includes the following steps: directly spraying the expanded boron nitride ejected from the plasma spray gun into the coolant, wherein the temperature of the coolant is 0-5℃; The parameters of the plasma spray gun are as follows: plasma gas Ar flow rate is 90-180 SLPM, plasma gas N2 flow rate is 30-80 SLPM, plasma gas H2 flow rate is 10-50 SLPM, boron nitride powder feeding rate is 15-30 g / min, powder carrier gas Ar flow rate is 9-30 SLPM, and spraying power is 50-100 kW.
2. The preparation method according to claim 1, characterized in that, The ultrasonic power is 25-30 kHz, and the duration is 30-120 min.
3. The preparation method according to claim 1, characterized in that, The centrifuge speed is 1500-3000 rpm, and the time is 5-30 min.
4. The preparation method according to claim 1, characterized in that, The filtration is performed by filtering through gauze with a pore size of 4-5 μm.
5. A boron nitride nanosheet with a high aspect ratio obtained by the preparation method according to any one of claims 1-4.
6. An application of the high aspect ratio boron nitride nanosheets of claim 5 in the field of dielectric energy storage.