Hexagonal boron nitride nanosheets, methods of making and applications thereof

Abstract

In the preparation method of the hexagonal boron nitride nanosheet provided in the application, an organic polymer containing at least one functional group of a hydroxyl group or a carbonyl group is used as an intercalation agent, and a "viscous entanglement effect" generated by a polymer molecular chain in a ball milling medium is used to overcome an "impact crushing effect" caused by violent impact energy between grinding balls or between a grinding ball and a grinding tank in the ball milling process, and to stabilize the shearing energy in the ball milling process, so that the size of the prepared hexagonal boron nitride nanosheet is large, which meets the high-performance application of the hexagonal boron nitride nanosheet, and the lattice defects of the hexagonal boron nitride nanosheet are reduced. Further, the preparation method provided in the application is simple, safe, low in cost, safe and efficient, has a good industrial production basis, and has a wide application prospect.

Description

Technical Field

[0001] This application relates to the field of nanomaterial preparation, specifically to a hexagonal boron nitride nanosheet, its preparation method, and its application. Background Technology

[0002] Hexagonal boron nitride (BON) is a typical two-dimensional material with high thermal conductivity, high barrier properties, high hydrophobicity, high strength, large specific surface area, thermal / chemical stability, resistance to microbial contamination, and abrasion resistance, making it widely applicable in fields such as metal corrosion protection, thermal management, energy storage, and biopharmaceuticals. However, the strong intermolecular forces and ionic bonds between boron nitride layers make the exfoliation and fabrication of large-size, high-quality hexagonal boron nitride nanosheets extremely difficult, becoming a key scientific challenge restricting the commercial application of boron nitride.

[0003] Currently, hexagonal boron nitride nanosheets are mainly prepared using mechanical exfoliation techniques such as ball milling, ultrasonication, high-speed stirring, water jetting, and air jet milling. Among these, ball milling has been the mainstream exfoliation technique due to its significant advantages in process operation, large-scale preparation, overall performance, and cost. The current ball milling exfoliation method involves filling a grinding jar with hexagonal boron nitride raw material, an intercalating agent, and grinding balls. The enormous impact and shear energy generated by the high-speed rotation of the grinding balls is used to exfoliate the hexagonal boron nitride layers, thus preparing hexagonal boron nitride nanosheets. However, this method suffers from a "crushing effect" caused by the intense impact energy between grinding balls or between the grinding balls and the grinding jar, typically resulting in hexagonal boron nitride nanosheets with a diameter of less than 1 μm, making them too small to meet the requirements of high-performance applications. Summary of the Invention

[0004] Based on this, this application provides a hexagonal boron nitride nanosheet, its preparation method, and its application. This hexagonal boron nitride nanosheet has a relatively large size and exhibits good dispersibility in various polar solvents, making it easy to prepare on a large scale.

[0005] A first aspect of this application provides a method for preparing hexagonal boron nitride nanosheets, comprising the following steps:

[0006] Hexagonal boron nitride powder, intercalating agent and ball milling media were mixed and then ball milled to prepare hexagonal boron nitride nanosheets.

[0007] The intercalating agent comprises an organic polymer containing at least one functional group, either hydroxyl or carbonyl.

[0008] In one embodiment, the relative number-average molecular weight of the organic polymer is 300 g / mol to 10000 g / mol.

[0009] In one embodiment, the intercalating agent includes one or more of polylactic acid, polyacrylic acid, polyvinyl alcohol, polyethylene glycol, polypropylene glycol, polybutylene glycol, polypentylene glycol, polyoctyl glycol, nanocellulose, carboxymethyl cellulose, and sodium carboxymethyl cellulose.

[0010] In one embodiment, the mass ratio of the hexagonal boron nitride powder to the intercalating agent is 1:1 to 500; the mass-to-volume ratio of the hexagonal boron nitride powder to the ball milling media is 1g:1 to 100mL.

[0011] In one embodiment, the milling media includes one or more of water, methanol, ethanol, ethylene glycol, glycerol, isopropanol, n-butanol, tetrahydrofuran, dimethylformamide, dimethyl sulfoxide, dimethylacetamide, and N-methylpyrrolidone.

[0012] In one embodiment, the process parameters of the ball milling process include: a ball milling rate of 50 rpm to 500 rpm and a ball milling time of 1 h to 100 h.

[0013] A second aspect of this application provides a hexagonal boron nitride nanosheet, which is prepared by the method for preparing hexagonal boron nitride nanosheets described in the first aspect.

[0014] In one embodiment, the surface and / or edges of the hexagonal boron nitride nanosheets contain hydroxyl groups.

[0015] In one embodiment, the diameter of the hexagonal boron nitride nanosheets is 1 μm to 15 μm.

[0016] A third aspect of this application provides the application of the hexagonal boron nitride nanosheets described in the second aspect of this application in thermally conductive materials, barrier functional fillers, catalyst supports, polymer filler materials, metal corrosion protection, energy storage, and biopharmaceuticals.

[0017] The method for preparing hexagonal boron nitride nanosheets provided in this application uses an organic polymer containing at least one functional group, either hydroxyl or carbonyl, as an intercalating agent. It utilizes the "viscous entanglement effect" generated by the polymer molecular chains in the ball milling medium to overcome the "impact crushing effect" caused by the intense impact energy between grinding balls or between grinding balls and the grinding jar during ball milling. Simultaneously, it stabilizes the shear energy during the ball milling process, thereby enabling the prepared hexagonal boron nitride nanosheets to have a larger size, meeting the requirements for high-performance applications of hexagonal boron nitride nanosheets; and it also reduces lattice defects in the hexagonal boron nitride nanosheets.

[0018] Furthermore, the preparation method provided in this application is simple, safe, low-cost, and highly efficient, possessing a solid foundation for industrial production and broad application prospects. Attached Figure Description

[0019] Figure 1 This is a SEM image of the hexagonal boron nitride nanosheets prepared in Example 1 of this application;

[0020] Figure 2 The image shows the HRTEM spectrum of the hexagonal boron nitride nanosheets prepared in Example 1 of this application.

[0021] Figure 3 The infrared spectrum of the hexagonal boron nitride nanosheets prepared in Example 1 of this application;

[0022] Figure 4 The energy spectrum of the hexagonal boron nitride nanosheets prepared in Example 1 of this application shows that the OH groups are mainly located at the edges of the BNNS.

[0023] Figure 5 The enthalpy of the grafting of hydroxyl groups at the edges of boron and nitrogen atoms in the hexagonal boron nitride nanosheets of this application are: nitrogen edge (left side, enthalpy of reaction is -3.86 eV) and boron edge (right side, enthalpy of reaction is -6.36 eV);

[0024] Figure 6 These are optical images of the boron nitride nanosheets prepared in Example 1 of this application dispersed in different solvents. Detailed Implementation

[0025] The following detailed embodiments provide a more complete and clear description of the hexagonal boron nitride nanosheets, their preparation method, and their applications. This application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0027] In this article, "one or more" refers to any one, two or more of the listed items.

[0028] In this application, terms such as "first aspect," "second aspect," "third aspect," "fourth aspect," and "fifth aspect" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, terms such as "first," "second," "third," "fourth," and "fifth" serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0029] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0030] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0031] Unless otherwise specified, the percentage content mentioned in this application refers to mass percentage for solid-liquid mixtures and solid-phase-solid mixtures, and volume percentage for liquid-phase-liquid mixtures.

[0032] Unless otherwise specified, all percentage concentrations mentioned in this application refer to the final concentration. The final concentration refers to the proportion of the added component in the system after the addition of that component.

[0033] Unless otherwise specified, the temperature parameters in this application may be either constant temperature processing or processing within a certain temperature range. The constant temperature processing allows for temperature fluctuations within the precision range controlled by the instrument.

[0034] Unless otherwise specified, the term "sheet diameter" in this application refers to the lateral dimension of hexagonal boron nitride nanosheets.

[0035] This application provides a method for preparing hexagonal boron nitride nanosheets, comprising the following steps:

[0036] Hexagonal boron nitride powder, intercalating agent and ball milling media were mixed and then ball milled to prepare hexagonal boron nitride nanosheets.

[0037] The intercalating agent comprises an organic polymer containing at least one functional group, either hydroxyl or carbonyl.

[0038] The method for preparing hexagonal boron nitride nanosheets provided in this application uses an organic polymer containing at least one functional group, either hydroxyl or carbonyl, as an intercalating agent. This method leverages the "viscous entanglement effect" generated by the polymer molecular chains in the ball milling media to overcome the "impact pulverization effect" caused by the intense impact energy between grinding balls or between grinding balls and the grinding jar during ball milling. Simultaneously, it stabilizes the shear energy during ball milling, resulting in larger-sized hexagonal boron nitride nanosheets, thus meeting the high-performance application requirements of hexagonal boron nitride nanosheets. Furthermore, the preparation method of this application can also reduce lattice defects in the hexagonal boron nitride nanosheets.

[0039] Furthermore, the preparation method provided in this application has the advantages of being recyclable, pollution-free, low-cost, high-yield, simple and safe, and easy to mass-produce and scale up, thus having a good industrial production foundation and broad application prospects.

[0040] Meanwhile, the hexagonal boron nitride nanosheets obtained by the ball milling exfoliation method provided in this application are relatively large in size and have hydroxyl groups modified at the edges. They are of high quality, with few defects, low impurity content, and good dispersibility, and have broad application prospects.

[0041] In one example, the relative number-average molecular weight of the organic polymer is 300 g / mol to 10000 g / mol.

[0042] Understandably, the relative number-average molecular weight of the organic polymer described in this application can be selected from any value between 300 g / mol and 10000 g / mol. Specifically, the relative number-average molecular weight of the organic polymer includes, but is not limited to, 300 g / mol, 400 g / mol, 500 g / mol, 600 g / mol, 700 g / mol, 800 g / mol, 900 g / mol, 1000 g / mol, 1500 g / mol, 2000 g / mol, 2500 g / mol, 3000 g / mol, 3500 g / mol, 4000 g / mol, 4500 g / mol, 5000 g / mol, 5500 g / mol, 6000 g / mol, 6500 g / mol, 7000 g / mol, 7500 g / mol, 8000 g / mol, 8500 g / mol, 9000 g / mol, 9500 g / mol, or 10000 g / mol.

[0043] In one example, the relative number-average molecular weight of the organic polymer may be selected from 300–400 g / mol, 400–500 g / mol, 500–600 g / mol, 600–700 g / mol, 700–800 g / mol, 800–900 g / mol, 900–1000 g / mol, 1000–1500 g / mol, 1500–2000 g / mol, 2000–2500 g / mol. 2500~3000g / mol, 3000~3500g / mol, 3500~4000g / mol, 4000~4500g / mol, 4500~5000g / mol, 5000~550 0g / mol, 5500~6000g / mol, 6000~7000g / mol, 7000~8000g / mol, 8000~9000g / mol, 9000~10000g / mol.

[0044] In one example, the intercalating agent includes one or more of polylactic acid, polyacrylic acid, polyvinyl alcohol, polyethylene glycol, polypropylene glycol, polybutanediol, polypentyl glycol, polyoctyl glycol, nanocellulose, carboxymethyl cellulose, and sodium carboxymethyl cellulose. This application, by selecting an organic polymer containing at least one functional group of hydroxyl or carbonyl groups, can overcome the impact and crushing effect under strong mechanical exfoliation and stabilize shear energy. Simultaneously, the introduction of hydroxyl groups enables the prepared hexagonal boron nitride nanosheets to possess good compatibility and interfacial interaction. Furthermore, this application uses an organic polymer containing at least one functional group of hydroxyl or carbonyl groups as the intercalating agent, avoiding the use of strong acids, strong bases, and strong oxidants, resulting in low production costs and facilitating batch and large-scale production.

[0045] In one example, the mass ratio of the hexagonal boron nitride powder to the intercalating agent is 1:1 to 500. It is understood that the mass ratio of the hexagonal boron nitride powder to the intercalating agent can be selected from any value between 1:1 and 500. Specifically, the mass ratio of the hexagonal boron nitride powder to the intercalating agent includes, but is not limited to, 1:1, 1:5, 1:10, 1:20, 1:30, 1:40, 1:50, 1:100, 1:200, 1:300, 1:400, or 1:500.

[0046] In one example, the mass-to-volume ratio of the hexagonal boron nitride powder to the milling media is 1 g: 1 to 100 mL. It is understood that the mass-to-volume ratio of the hexagonal boron nitride powder to the milling media can be selected from any value between 1 g: 1 and 100 mL. Specifically, the mass-to-volume ratio of the hexagonal boron nitride to the milling media includes, but is not limited to, 1 g: 1 mL, 1 g: 5 mL, 1 g: 10 mL, 1 g: 20 mL, 1 g: 25 mL, 1 g: 30 mL, 1 g: 40 mL, 1 g: 50 mL, 1 g: 60 mL, 1 g: 70 mL, 1 g: 80 mL, 1 g: 90 mL, and 1 g: 100 mL.

[0047] In one example, the viscosity (25°C) of the mixture of hexagonal boron nitride powder, intercalating agent, and milling media is 0.1–200 Pa·s. Specifically, the viscosity of the mixture of hexagonal boron nitride powder, intercalating agent, and milling media includes, but is not limited to, 0.1 Pa·s, 0.2 Pa·s, 0.5 Pa·s, 1 Pa·s, 2 Pa·s, 5 Pa·s, 10 Pa·s, 20 Pa·s, 50 Pa·s, 100 Pa·s, 150 Pa·s, or 200 Pa·s.

[0048] In one example, the milling media includes one or more of water, methanol, ethanol, ethylene glycol, glycerol, isopropanol, n-butanol, tetrahydrofuran, dimethylformamide, dimethyl sulfoxide, dimethylacetamide, and N-methylpyrrolidone.

[0049] In one example, during the ball milling process, the mass ratio of the hexagonal boron nitride powder to the grinding balls is 1:50 to 200. By adjusting the mass ratio of the hexagonal boron nitride powder to the grinding balls during the ball milling process, the uniformity and thoroughness of the grinding can be ensured.

[0050] Understandably, this application does not limit the material of the grinding balls used in the ball milling process. Examples of materials for the grinding balls include agate, zirconium dioxide, corundum, silicon nitride, polytetrafluoroethylene, nylon, polyurethane, cemented carbide, or 304 stainless steel.

[0051] In one example, during the ball milling process, the grinding balls include small grinding balls and large grinding balls in a mass ratio of 1:1 to 7, the large grinding balls having a diameter of 8 mm to 12 mm, and the small grinding balls having a diameter of 2 mm to 6 mm.

[0052] In one example, the process parameters for the ball milling treatment include a ball milling time of 1 hour to 100 hours. Specifically, the ball milling time includes, but is not limited to, 1 hour, 2 hours, 4 hours, 8 hours, 12 hours, 16 hours, 18 hours, 20 hours, 24 hours, 30 hours, 35 hours, 40 hours, 50 hours, 60 hours, 70 hours, 80 hours, 90 hours, or 100 hours.

[0053] This application does not limit the ball milling process mode, but the ball milling process mode can be exemplified by continuous ball milling mode and intermittent ball milling mode.

[0054] In one specific example, the ball milling process is a continuous ball milling mode.

[0055] In one specific example, the ball milling process is an intermittent ball milling mode of 1h to 3h, followed by a 0.5h to 1h pause.

[0056] In one example, the process parameters for the ball milling process include a ball milling rate of 50 rpm to 500 rpm. Specifically, the ball milling rate includes, but is not limited to, 50 rpm, 100 rpm, 150 rpm, 200 rpm, 250 rpm, 270 rpm, 300 rpm, 350 rpm, 370 rpm, 400 rpm, 450 rpm, 470 rpm, or 500 rpm.

[0057] In one example, the process parameters of the ball milling process include a ball milling frequency of 1 kHz to 60 kHz. Specifically, the ball milling frequency includes, but is not limited to, 1 kHz, 2 kHz, 3 kHz, 5 kHz, 8 kHz, 9 kHz, 10 kHz, 15 kHz, 20 kHz, 25 kHz, 30 kHz, 35 kHz, 40 kHz, 45 kHz, 50 kHz, 55 kHz, 58 kHz, 59 kHz, or 60 kHz.

[0058] In one specific example, the method for preparing the hexagonal boron nitride nanosheets includes the following steps:

[0059] Hexagonal boron nitride powder, intercalating agent and ball milling media were mixed and then ball milled to prepare hexagonal boron nitride dispersion;

[0060] The hexagonal boron nitride dispersion was filtered to recover the organic polymer solution; after washing with anhydrous ethanol, it was dried to obtain hexagonal boron nitride nanosheets. Understandably, the organic polymer solution is a solution of an organic polymer containing at least one functional group (hydroxyl or carbonyl) used as an intercalating agent; recovery is beneficial for cost savings and reuse.

[0061] In one specific example, the drying equipment is a vacuum oven, and the drying temperature is 20°C to 90°C.

[0062] This application also provides a hexagonal boron nitride nanosheet, which is prepared by the preparation method of hexagonal boron nitride nanosheet described in any of the above examples.

[0063] In one example, the surface and / or edges of the hexagonal boron nitride nanosheets contain hydroxyl groups. The hexagonal boron nitride nanosheets prepared in this application contain hydroxyl groups on their surface or edges. The introduction of hydroxyl groups enables the prepared hexagonal boron nitride nanosheets to have good compatibility and interfacial interactions. Furthermore, the hexagonal boron nitride nanosheets prepared in this application exhibit good dispersibility in various polar solvents. These polar solvents include, but are not limited to, water, ethanol, isopropanol, and DMF.

[0064] In one example, the hexagonal boron nitride nanosheets have a diameter of 1 μm to 15 μm. The hexagonal boron nitride nanosheets obtained according to the method provided in this application have a larger diameter, fewer defects, and better dispersibility, and can be used as barrier fillers in thermally conductive sheets, thermally conductive composite materials, polyesters, or anti-corrosion coatings.

[0065] In one example, the thickness of the hexagonal boron nitride nanosheets is 0.5 nm to 5 nm.

[0066] This application also provides the application of the hexagonal boron nitride nanosheets described in any of the above examples in thermally conductive materials, barrier functional fillers, catalyst supports, polymer filler materials, metal corrosion protection, energy storage, and biopharmaceuticals.

[0067] The following are specific examples. Unless otherwise specified, the raw materials used in the examples are all commercially available products.

[0068] Example 1

[0069] 1 g of polyvinyl alcohol with a relative number average molecular weight of 10000 g / mol was weighed and placed in a 250 mL agate ball mill jar along with 5 mL of deionized water, 1 g of hexagonal boron nitride powder, and 100 g of agate abrasive (80 g of 10 mm diameter and 20 g of 2 mm diameter abrasive). The system viscosity was 5 Pa·s. The ball mill jar was sealed and fixed on a planetary ball mill. The ball mill was started and the system was milled at 250 rpm for 12 h at room temperature. After milling, the hexagonal boron nitride dispersion was filtered, the polymer solution was recovered, washed with anhydrous ethanol, and then dried in a vacuum oven at 30 °C to obtain milled hexagonal boron nitride nanosheets with a yield of 74%.

[0070] Figure 1 This is a SEM image of the hexagonal boron nitride nanosheets obtained in this embodiment. The diameter of the obtained hexagonal boron nitride nanosheets is greater than 5 μm. Figure 2 This is a high-magnification TEM image of the hexagonal boron nitride nanosheets obtained in this embodiment. The TEM image shows that the prepared hexagonal boron nitride nanosheets have a thickness of 0.7 nm and a layer count of 1. Figure 3 The image shows an FTIR image of the hexagonal boron nitride nanosheets obtained in this embodiment. The FTIR image shows the grafted hydroxyl groups in the structure of the hexagonal boron nitride nanosheets. Figure 4 The electron energy loss spectrum of the hexagonal boron nitride nanosheets obtained in this embodiment confirms that hydroxyl groups tend to be grafted onto the edges of the hexagonal boron nitride nanosheets. Figure 5 The density functional theory (DFT) plot of the hexagonal boron nitride nanosheets prepared in this application confirms that hydroxyl groups tend to graft onto boron atoms at the edge of the hexagonal boron nitride nanosheets. Figure 6 The image shows a dispersion of hexagonal boron nitride nanosheets at a concentration of 5 mg / ml in this embodiment, confirming that hexagonal boron nitride nanosheets have good dispersibility in various polar solvents.

[0071] Example 2

[0072] 100g of polylactic acid with a relative number-average molecular weight of 1000g / mol was weighed and placed in a 250mL agate ball mill jar along with 40mL of anhydrous ethanol, 2g of boron nitride powder, and 120g of agate abrasive (80g of 10mm diameter abrasive, 15g of 5mm diameter abrasive, and 25g of 2mm diameter abrasive). The system viscosity was 0.7Pa·s. The ball mill jar was sealed and fixed on a planetary ball mill. The ball mill was started and milled at 250rpm for 12h. During the milling process, the mill was stopped for 0.5h every 2h to ensure a suitable temperature for the milling system. After milling, the hexagonal boron nitride dispersion was filtered, the polymer solution was recovered, washed with anhydrous ethanol, and then dried in a vacuum oven at 30℃ to obtain milled hexagonal boron nitride nanosheets with a yield of 69%.

[0073] Example 3

[0074] 500g of polylactic acid with a relative number-average molecular weight of 1000g / mol was weighed and placed in a 250mL agate ball mill jar along with 100mL of anhydrous ethanol, 1g of boron nitride powder, and 100g of zirconia abrasive (80g of 10mm diameter and 20g of 2mm diameter). The system viscosity was 59Pa·s. The ball mill jar was sealed and fixed on a planetary ball mill, which was then started and milled at 250rpm for 4 hours. During the milling process, the mill was stopped for 0.5 hours every 3 hours to ensure that the milling system maintained a suitable temperature. After milling, the hexagonal boron nitride dispersion was filtered, the polymer solution was recovered, washed with anhydrous ethanol, and then dried in a vacuum oven at 30℃ to obtain milled hexagonal boron nitride nanosheets with a yield of 53%.

[0075] Example 4

[0076] 200g of polylactic acid with a relative number average molecular weight of 5000g / mol was weighed and placed in a 250mL zirconia ball mill jar along with 50mL of deionized water, 1g of boron nitride powder, and 130g of zirconia abrasive (80g of 10mm diameter abrasive, 25g of 5mm diameter abrasive, and 25g of 2mm diameter abrasive). The system viscosity was 4.2Pa·s. The ball mill jar was sealed and fixed on a planetary ball mill. The mill was started and milled at 250rpm for 12h. During milling, the mill was stopped for 1h every 3h to ensure a suitable temperature for the system. After milling, the hexagonal boron nitride dispersion was filtered, the polymer solution was recovered, washed with anhydrous ethanol, and then dried in a vacuum oven at 30℃ to obtain milled hexagonal boron nitride nanosheets with a yield of 63%.

[0077] Example 5

[0078] 50g of polyvinyl alcohol with a relative number average molecular weight of 10000g / mol was weighed and placed in a 250mL agate ball mill jar along with 40mL of deionized water, 1g of boron nitride powder, and 100g of agate abrasive (80g of 10mm diameter and 20g of 2mm diameter abrasive). The system viscosity was 126Pa·s. The ball mill jar was sealed and fixed on a planetary ball mill, which was then started and milled at 300rpm for 12h. During the milling process, the mill was stopped for 1h every 2h to ensure that the milling system maintained a suitable temperature. After milling, the hexagonal boron nitride dispersion was filtered, the polymer solution was recovered, washed with anhydrous ethanol, and then dried in a vacuum oven at 30℃ to obtain milled hexagonal boron nitride nanosheets with a yield of 40%.

[0079] Example 6

[0080] 100g of polyvinyl alcohol with a relative number average molecular weight of 10000g / mol was weighed and placed in a 250mL agate ball milling jar along with 40mL of deionized water, 2g of boron nitride powder, and 100g of agate abrasive (80g of 10mm diameter and 20g of 2mm diameter abrasive). The system viscosity was 78Pa·s. The ball milling jar was sealed and fixed on a planetary ball mill, which was then started and milled at 300rpm for 12h. During the milling process, the milling was stopped for 1h every 2h to ensure that the milling system maintained a suitable temperature. After milling, the hexagonal boron nitride dispersion was filtered, the polymer solution was recovered, washed with anhydrous ethanol, and then dried in a vacuum oven at 30℃ to obtain milled hexagonal boron nitride nanosheets with a yield of 43%.

[0081] Example 7

[0082] 100g of polyethylene glycol with a relative number-average molecular weight of 10000g / mol was weighed and placed in a 250mL zirconia ball mill jar along with 40mL of anhydrous ethanol, 1g of boron nitride powder, and 100g of zirconia abrasive (80g of 10mm diameter and 20g of 2mm diameter). The system viscosity was 81Pa·s. The ball mill jar was sealed and fixed on a planetary ball mill, which was then started and milled at 300rpm for 20h. During the milling process, the mill was stopped for 1h every 3h to ensure a suitable temperature for the milling system. After milling, the hexagonal boron nitride dispersion was filtered, the polymer solution was recovered, washed with anhydrous ethanol, and then dried in a vacuum oven at 30℃ to obtain milled hexagonal boron nitride nanosheets with a yield of 53%.

[0083] Example 8

[0084] 100g of polyethylene glycol with a relative number-average molecular weight of 10000g / mol was weighed and placed in a 250mL zirconia grinding jar along with 80mL of anhydrous ethanol, 3g of boron nitride powder, and 150g of zirconia abrasive (80g of 10mm diameter and 20g of 2mm diameter). The system viscosity was 33Pa·s. The grinding jar was sealed and fixed on a planetary ball mill, which was then started and milled at 250rpm for 24h. During the milling process, the mill was stopped for 0.5h every 2h to ensure a suitable temperature for the grinding system. After milling, the hexagonal boron nitride dispersion was filtered, the polymer solution was recovered, washed with anhydrous ethanol, and then dried in a vacuum oven at 30℃ to obtain milled hexagonal boron nitride nanosheets with a yield of 58%.

[0085] Example 9

[0086] 100g of nanocellulose with a relative number-average molecular weight of 5000g / mol was weighed and placed in a 250mL zirconia grinding jar along with 25mL of anhydrous ethanol, 2g of boron nitride powder, and 150g of zirconia abrasive (100g of 10mm diameter and 50g of 2mm diameter). The system viscosity was 72Pa·s. The grinding jar was sealed and fixed on a planetary ball mill, which was then started and milled at 250rpm for 24h. During the milling process, the mill was stopped for 1h every 2h to ensure a suitable temperature for the grinding system. After milling, the hexagonal boron nitride dispersion was filtered, the polymer solution was recovered, washed with anhydrous ethanol, and then dried in a vacuum oven at 30℃ to obtain milled hexagonal boron nitride nanosheets with a yield of 48%.

[0087] Example 10

[0088] 100g of nanocellulose with a relative number-average molecular weight of 5000g / mol was weighed and placed in a 250mL zirconia grinding jar along with 40mL of anhydrous ethanol, 2g of boron nitride powder, and 100g of zirconia abrasive (80g of 10mm diameter and 20g of 2mm diameter). The system viscosity was 39Pa·s. The grinding jar was sealed and fixed on a planetary ball mill, which was then started and milled at 200rpm for 24h. During the milling process, the mill was stopped for 1h every 2h to ensure a suitable temperature for the grinding system. After milling, the hexagonal boron nitride dispersion was filtered, the polymer solution was recovered, washed with anhydrous ethanol, and then dried in a vacuum oven at 30℃ to obtain milled hexagonal boron nitride nanosheets with a yield of 50%.

[0089] Comparative Example 1

[0090] 100g of xylitol with a relative number-average molecular weight of 152g / mol was weighed and placed in a 250mL zirconia grinding jar along with 50mL of deionized water, 2g of boron nitride powder, and 100g of zirconia abrasive (80g of 10mm diameter and 20g of 2mm diameter). The system viscosity was 7.3Pa·s. The grinding jar was sealed and fixed on a planetary ball mill, which was then started and milled at 200rpm for 24h. During the milling process, the mill was stopped for 1h every 2h to ensure that the grinding system maintained a suitable temperature. After milling, the hexagonal boron nitride dispersion was filtered, the polymer solution was recovered, washed with anhydrous ethanol, and then dried in a vacuum oven at 30℃ to obtain milled hexagonal boron nitride nanosheets with a yield of 17%.

[0091] Comparative Example 2

[0092] 100g of citric acid with a relative number-average molecular weight of 192g / mol was weighed and placed in a 250mL agate ball mill jar along with 20mL of deionized water, 2g of boron nitride powder, and 150g of zirconia abrasive (100g of 10mm diameter and 50g of 2mm diameter). The system viscosity was 39Pa·s. The ball mill jar was sealed and fixed on a planetary ball mill, which was then started and milled at 300rpm for 20h. During the milling process, the mill was stopped for 1h every 2h to ensure that the milling system maintained a suitable temperature. After milling, the hexagonal boron nitride dispersion was filtered, the polymer solution was recovered, washed with anhydrous ethanol, and then dried in a vacuum oven at 30℃ to obtain milled hexagonal boron nitride nanosheets with a yield of 22%.

[0093] Comparative Example 3

[0094] 100g of tannic acid with a relative number-average molecular weight of 170g / mol was weighed and added to 100mL of anhydrous ethanol, 2g of boron nitride powder, and 150g of zirconia abrasive (100g of 10mm diameter and 50g of 2mm diameter). The mixture was placed in a 250mL zirconia grinding jar, resulting in a system viscosity of 3.3 Pa·s. The grinding jar was sealed and fixed on a planetary ball mill. The mill was started and milled at 250rpm for 24 hours. During milling, the mill was stopped for 1 hour every 2 hours to ensure a suitable temperature for the system. After milling, the hexagonal boron nitride dispersion was filtered, and the polymer solution was recovered. After washing with anhydrous ethanol, the polymer was dried in a vacuum oven at 30℃ to obtain milled hexagonal boron nitride nanosheets with a yield of 14%.

[0095] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0096] The embodiments described above are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing hexagonal boron nitride nanosheets, characterized in that, Includes the following steps: Hexagonal boron nitride powder, intercalating agent, and ball milling media are mixed and then ball milled to prepare hexagonal boron nitride nanosheets; the mass ratio of hexagonal boron nitride powder to intercalating agent is 1:1~500; The intercalating agent is polylactic acid; The relative number-average molecular weight of the polylactic acid is 1000 g / mol to 10000 g / mol; During the ball milling process, the grinding balls include small grinding balls and large grinding balls with a mass ratio of 1:1 to 7. The diameter of the large grinding balls is 8 mm to 12 mm, and the diameter of the small grinding balls is 2 mm to 6 mm. The process parameters of the ball milling process include: a ball milling rate of 50 rpm to 500 rpm and a ball milling time of 1 h to 100 h. The diameter of the hexagonal boron nitride nanosheets is greater than 5 μm.

2. The method for preparing hexagonal boron nitride nanosheets according to claim 1, characterized in that, The viscosity of the mixture of hexagonal boron nitride powder, intercalating agent and ball milling media at 25°C is 0.1~200 Pa·s; And / or, the ball milling process is an intermittent ball milling mode of 1h to 3h, followed by a 0.5h to 1h stop; And / or, the process parameters of the ball milling process include: a ball milling frequency of 1kHz to 60kHz.

3. The method for preparing hexagonal boron nitride nanosheets according to claim 1, characterized in that, The mass-to-volume ratio of the hexagonal boron nitride powder to the ball milling media is 1g:1~100mL.

4. The method for preparing hexagonal boron nitride nanosheets according to any one of claims 1 to 3, characterized in that, The ball milling media include one or more of water, methanol, ethanol, ethylene glycol, glycerol, isopropanol, n-butanol, tetrahydrofuran, dimethylformamide, dimethyl sulfoxide, dimethylacetamide, and N-methylpyrrolidone.

5. The method for preparing hexagonal boron nitride nanosheets according to any one of claims 1 to 3, characterized in that, The preparation method includes the following steps: 100g of polylactic acid with a relative number average molecular weight of 1000g / mol was weighed and mixed with 40 mL of anhydrous ethanol, 2g of boron nitride powder, and 120g of agate abrasive, wherein the agate abrasive included 80g of agate abrasive with a diameter of 10mm, 15g of agate abrasive with a diameter of 5mm, and 25g of agate abrasive with a diameter of 2mm. The mixture was placed in a 250mL agate ball mill jar, and the system viscosity was 0.7 Pa·S. The ball mill jar was sealed and fixed on a planetary ball mill, and the ball mill was started and ball milled at 250rpm for 12h. During the ball milling process, the ball milling was stopped for 0.5h every 2h to ensure that the ball milling system had a suitable temperature. After ball milling, the hexagonal boron nitride dispersion was filtered, the polymer solution was recovered, washed with anhydrous ethanol, and dried in a vacuum oven at 30℃ to obtain ball-milled hexagonal boron nitride nanosheets with a yield of 69%.

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