A ball milling modification method for thin-layer hexagonal boron nitride modified with bifunctional groups

Abstract

This invention belongs to the field of inorganic nanoparticle preparation technology, and relates to a ball milling modification method for bifunctionalized thin-layer hexagonal boron nitride: Hexagonal boron nitride powder, guanidine hydrochloride, and urea are continuously heated and stirred to obtain a homogeneous mixture of a eutectic solvent formed by guanidine hydrochloride and urea and the hexagonal boron nitride powder; this mixture is poured into a ball mill jar containing grinding balls and a liner, and a certain amount of ethanol and water are added as dispersants for high-energy ball milling; after the material is separated from the grinding balls, the milled material is vacuum filtered, dried, and the resulting powder is dispersed in water, then ultrasonicated, allowed to stand, vacuum filtered, and dried to obtain bifunctionalized thin-layer hexagonal boron nitride. This invention not only has the advantages of readily available raw materials and simple process, but also high efficiency, environmental friendliness, and low energy consumption. The hexagonal boron nitride obtained by this method has thinner layers, good biocompatibility, low relative density, and good thermal conductivity.

Description

Technical Field

[0001] This invention belongs to the field of inorganic nanoparticle preparation technology, and relates to a ball milling modification method for thin-layer hexagonal boron nitride modified with bifunctional groups. Background Technology

[0002] With the rapid development of the electronics industry, the introduction of high frequencies, upgrades to hardware components, and the exponential increase in the number of antennas have led to increasingly higher integration of electronic components, resulting in continuously increasing power consumption and heat generation. Therefore, heat dissipation has become a bottleneck in this field. Thermal interface materials, as elastic materials filling the space between a heat source and a heat sink, play a crucial role in dissipating air and accelerating heat dissipation, making them key materials in microelectronic thermal management. Common thermal interface materials are based on polymers such as epoxy resin, rubber, and silicone grease; however, polymers themselves have poor thermal conductivity, making it difficult to meet the heat dissipation requirements of the electronics industry. Research shows that filled thermally conductive and insulating polymer materials, prepared by blending high thermal conductivity insulating inorganic ceramic fillers (such as alumina, aluminum nitride, and boron nitride) with polymers, can improve the thermal conductivity of thermally conductive materials. Furthermore, they are low-cost, simple to process, suitable for large-scale production, and represent a major method for improving the thermal conductivity of polymer materials.

[0003] Hexagonal boron nitride nanosheets are a novel two-dimensional sheet nanomaterial similar to graphene, obtained through the exfoliation of hexagonal boron nitride. They retain the low resistivity and coefficient of thermal expansion, as well as good chemical stability of hexagonal boron nitride, while exhibiting excellent thermal conductivity (1700-2000 W / m·K within a single layer) and mechanical properties. Furthermore, their high aspect ratio and sheet-like structure facilitate the formation of thermally conductive pathways within polymer substrates. Therefore, hexagonal boron nitride nanosheets are considered the best filler for high thermal conductivity and insulating polymer-based composites. However, hexagonal boron nitride nanosheets have few surface active sites, making them prone to aggregation. This leads to phonon scattering when heat flows through the two-phase interface, resulting in significant heat loss and limiting the improvement of the composite material's thermal conductivity. Researchers have found that surface functionalization of hexagonal boron nitride can effectively improve its dispersibility in polymers and its interfacial compatibility with polymers, further enhancing the thermal conductivity of the composite material.

[0004] Existing methods for preparing thin-layer hexagonal boron nitride (HBN) can be broadly categorized into two types: bottom-up synthesis and top-down exfoliation. Bottom-up synthesis constructs the h-BN structure through atomic or molecular-level assembly, primarily including chemical vapor deposition (CVD) and physical vapor deposition (PVD). Its advantages include high product crystallinity, but its disadvantages include demanding conditions, high cost, difficulty in functionalization, and potential side reactions, making it impractical. Top-down exfoliation methods are divided into physical exfoliation and chemical exfoliation. Physical exfoliation is considered practically applicable due to its simplicity and low cost, but existing techniques suffer from poor dispersion, structural fragmentation, and low functionalization of the resulting HBN. Summary of the Invention

[0005] Purpose of the invention

[0006] To address the aforementioned shortcomings of existing technologies, the present invention aims to propose a ball milling modification method for thin-layer hexagonal boron nitride modified with bifunctional groups. This method simultaneously achieves ultra-thin exfoliation and bifunctionalization of hexagonal boron nitride powder during ball milling, enabling the preparation of thin-layer hexagonal boron nitride modified with bifunctional groups that exhibits good dispersibility in water.

[0007] Technical solution

[0008] A ball milling modification method for a thin layer of hexagonal boron nitride modified with bifunctional groups, specifically including the following steps:

[0009] (1) Weigh a certain amount of hexagonal boron nitride powder, guanidine hydrochloride and urea and place them in a container. Put the container in a water bath and heat and stir continuously to obtain a uniform mixture of eutectic solvent formed by guanidine hydrochloride and urea and hexagonal boron nitride powder.

[0010] (2) Pour the homogeneous mixture obtained in step (1) into a ball mill jar containing grinding balls and a liner, add a certain amount of ethanol and water as dispersants, and perform high-energy ball milling.

[0011] (3) After separating the ball-milled material from the grinding balls in step (2), the ball-milled material is vacuum filtered, dried, and the resulting powder is dispersed in water, then sonicated, allowed to stand, vacuum filtered, and dried to obtain a thin layer of hexagonal boron nitride modified with bifunctional groups.

[0012] Furthermore, in step (1), the molar ratio of guanidine hydrochloride to urea in the eutectic solvent formed by guanidine hydrochloride and urea is 1:2, and the mass ratio of hexagonal boron nitride powder to eutectic solvent is 1:5-1:50.

[0013] Furthermore, in step (1), the water bath heating temperature is 65-70℃, and after the sample begins to become a liquid mixture during the water bath heating process, it is continuously stirred at a speed of 400-600 rpm for 10-30 minutes.

[0014] Furthermore, in step (2), the grinding balls are zirconia grinding balls, which are composed of three sizes: large balls with a diameter of 8-10 mm, medium balls with a diameter of 3-5 mm, and small balls with a diameter of 1-2 mm. The mass ratio of the large, medium, and small balls is (15-17):(35-37):(20-22). The internal volume ratio of the grinding balls to the inner lining of the grinding jar is 3 / 5-2 / 3. The internal volume ratio of the eutectic solvent formed by guanidine hydrochloride and urea and the uniform mixture of hexagonal boron nitride powder to the inner lining of the grinding jar is 1 / 10-1 / 5.

[0015] Furthermore, in step (2), the mass ratio of ethanol and water to hexagonal boron nitride powder is 2:1-16:1, and the volume ratio of ethanol to water is 3:1-3:2.5.

[0016] Furthermore, in step (2), the ball milling time is 10-40 hours and the ball milling speed is 600-1200 rpm.

[0017] Furthermore, in step (3), the vacuum filtration requires the use of excess deionized water to remove the residual guanidine hydrochloride and urea, and the dried product directly yields boron nitride powder.

[0018] Furthermore, the boron nitride powder obtained directly by drying is mixed with deionized water at a mass ratio of 1:(950-1050), ultrasonicated for 1-2 hours, and then left to stand for ≥24 hours.

[0019] Furthermore, when vacuum filtering the settled liquid, only the upper 3 / 4 to 4 / 5 of the liquid is filtered, and finally, the bifunctional modified thin layer of hexagonal boron nitride is obtained directly by drying.

[0020] Furthermore, both drying steps in step (3) are carried out in an oven at 80°C for a drying time of 12 hours or more.

[0021] Advantages and Effects: 1. To date, hydroxyl functionalization and amino functionalization are the two main methods for modifying hexagonal boron nitride. Therefore, this invention uses amino-rich urea and guanidine hydrochloride as ball milling aids. The eutectic solvent formed by urea and guanidine hydrochloride has certain adhesive properties. During ball milling, by coating the hexagonal boron nitride powder, the vertical impact force of the grinding balls on the homogeneous mixture of the eutectic solvent formed by guanidine hydrochloride and urea and the hexagonal boron nitride powder can be buffered, reducing the damage to the hexagonal boron nitride caused by the collision of the grinding balls, thereby obtaining a thin layer of hexagonal boron nitride with a more complete structure and larger lateral dimensions. Furthermore, the amino groups rich in the eutectic solvent can achieve amino functionalization of the B atoms in the hexagonal boron nitride.

[0022] 2. This invention employs wet ball milling, using ethanol and water as dispersants. Mixing these with a eutectic solvent keeps the abrasive in a liquid state, improving milling efficiency. Furthermore, the ethanol and water mixture, acting as a polar solvent, maintains the dispersion of the thin-layer hexagonal boron nitride, preventing re-stacking. The abundant hydroxyl groups in the dispersant functionalize the hexagonal boron nitride and increase its interlayer spacing, thereby accelerating the exfoliation process and preventing re-stacking.

[0023] 3. This invention uses a zirconia grinding jar liner and zirconia grinding balls. Compared with steel balls, using a zirconia liner and grinding balls can avoid the generation of iron powder during the ball milling process, which would affect the stripping of hexagonal boron nitride. In addition, the acid washing step is eliminated after ball milling, saving costs and being more environmentally friendly.

[0024] 4. In this invention, after ball milling, an ultrasonic treatment and a settling period are performed to allow the unfunctionalized thick hexagonal boron nitride to settle to the bottom while only the upper 3 / 4 of the liquid in the solution is filtered out, thus obtaining successfully functionalized hexagonal boron nitride with a thinner layer.

[0025] 5. Thin-layer hexagonal boron nitride with hydroxyl and amino functionalization has the advantages of good biocompatibility, low relative density, and good thermal conductivity. Attached Figure Description

[0026] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. The scope of protection of the present invention is not limited to the descriptions below.

[0027] Figure 1 This is a SEM image of the raw material, hexagonal boron nitride powder;

[0028] Figure 2 The SEM image angle 1 of the thin layer of hexagonal boron nitride modified with bifunctional groups in Embodiment 1 of the present invention;

[0029] Figure 3 The SEM image angle 2 of the thin hexagonal boron nitride modified with bifunctional groups in Embodiment 1 of the present invention;

[0030] Figure 4 This is the XRD spectrum of the thin-layer hexagonal boron nitride and hexagonal boron nitride powder modified with bifunctional groups in Example 1 of this invention;

[0031] Figure 5 This is the FTIR spectrum of the thin-layer hexagonal boron nitride and hexagonal boron nitride powder modified with bifunctional groups in Example 1 of this invention. Detailed Implementation

[0032] A ball milling modification method for a thin layer of hexagonal boron nitride modified with bifunctional groups, specifically including the following steps:

[0033] (1) Weigh a certain amount of hexagonal boron nitride powder (commercially available conventional hexagonal boron nitride), guanidine hydrochloride and urea and place them in a container. Place the container in a water bath and heat the water bath at 65-70℃. Stir continuously at 400-600 rpm for 10-30 minutes. After the sample begins to become a liquid mixture during the water bath heating process, a homogeneous mixture of guanidine hydrochloride and urea eutectic solvent and hexagonal boron nitride powder is obtained. In the eutectic solvent formed by guanidine hydrochloride and urea, the molar ratio of guanidine hydrochloride and urea is 1:2, and the mass ratio of hexagonal boron nitride powder and eutectic solvent is 1:5-1:50, with the optimal ratio being 1:39-1:41.

[0034] (2) Pour the homogeneous mixture obtained in step (1) into a grinding jar containing grinding balls and a liner. The grinding balls are zirconia grinding balls, which consist of three sizes: large balls with a diameter of 8-10 mm, medium balls with a diameter of 3-5 mm, and small balls with a diameter of 1-2 mm. The mass ratio of the large, medium, and small balls is (15-17):(35-37):(20-22). The internal volume ratio of the grinding balls to the liner of the grinding jar is 3 / 5-2 / 3. Guanidine hydrochloride and urea form... The volume ratio of the homogeneous mixture of the eutectic solvent and hexagonal boron nitride powder to the inner lining of the ball mill jar is 1 / 10-1 / 5. A certain amount of ethanol and water are added as dispersants, with the mass ratio of ethanol and water to hexagonal boron nitride powder being 2:1-16:1, the preferred weight ratio of ethanol and water to hexagonal boron nitride powder being 14:1, and the volume ratio of ethanol to water being 3:1-3:2.5. High-energy ball milling is then performed for 10-40 hours at a speed of 600-1200 rpm.

[0035] (3) After separating the ball-milled material from the grinding balls in step (2), the ball-milled material is vacuum filtered. Excess deionized water is used to remove the residual guanidine hydrochloride and urea. The material is dried in an oven at 80°C. The resulting powder is dispersed in deionized water. The mass ratio of boron nitride powder to deionized water is 1:(950-1050). The material is then sonicated for 1-2 hours and then removed. It is left to stand for ≥24 hours. At this time, the unfunctionalized thick hexagonal boron nitride has poor dispersibility in water. After standing for 24 hours, it will sink to the bottom of the beaker. The liquid after standing is vacuum filtered, and only the upper 3 / 4-4 / 5 of the liquid is filtered. Finally, it is dried in an oven at 80°C for ≥12 hours to directly obtain the bifunctional modified thin-layer hexagonal boron nitride.

[0036] The following examples are provided to better understand the present invention and are not intended to limit the preferred embodiments described. They do not constitute a limitation on the content or scope of protection of the present invention. Any product identical or similar to the present invention derived by any person under the guidance of the present invention or by combining features of the present invention with other prior art falls within the scope of protection of the present invention. Where specific experimental steps or conditions are not specified in the examples, they can be performed according to the conventional experimental steps or conditions described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0037] The present invention will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed by the present invention.

[0038] Example 1

[0039] A ball milling modification method for a thin layer of hexagonal boron nitride modified with bifunctional groups, specifically including the following steps:

[0040] (1) Weigh a certain amount of hexagonal boron nitride powder, guanidine hydrochloride and urea and place them in a container. Place the container in a water bath and heat it at 66°C. Stir continuously at 500 rpm for 20 minutes. After the sample begins to become a liquid mixture during the water bath heating process, a uniform mixture of guanidine hydrochloride and urea eutectic solvent and hexagonal boron nitride powder is obtained. In the eutectic solvent formed by guanidine hydrochloride and urea, the molar ratio of guanidine hydrochloride and urea is 1:2, and the mass ratio of hexagonal boron nitride powder and eutectic solvent is 1:39.

[0041] (2) Pour the homogeneous mixture obtained in step (1) into a ball mill jar containing grinding balls and a liner. The grinding balls are zirconia grinding balls, which are composed of three sizes: large balls with a diameter of 8-10 mm, medium balls with a diameter of 3-5 mm, and small balls with a diameter of 1-2 mm. The mass ratio of the large, medium, and small balls is 16:36:21. The internal volume ratio of the grinding balls to the liner of the ball mill jar is 3 / 5. The internal volume ratio of the homogeneous mixture of the eutectic solvent formed by guanidine hydrochloride and urea and the hexagonal boron nitride powder to the liner of the ball mill jar is 1 / 5. Add a certain amount of ethanol and water as dispersants. The mass ratio of ethanol and water to the hexagonal boron nitride powder is 14:1, and the volume ratio of ethanol to water is 3:2. Perform high-energy ball milling for 20 hours and at a speed of 900 rpm.

[0042] (3) After separating the ball-milled material from the grinding balls in step (2), the ball-milled material is vacuum filtered. Excess deionized water is used to remove the residual guanidine hydrochloride and urea. The material is dried in an oven at 80°C. The resulting powder is dispersed in deionized water (the mass ratio of boron nitride powder to deionized water is 1:1000). After sonication for 1.5 hours, the material is taken out and left to stand for ≥24 hours. At this time, the unfunctionalized thick hexagonal boron nitride has poor dispersibility in water and will sink to the bottom of the beaker after standing for 24 hours. The liquid after standing is vacuum filtered, and only the upper 3 / 4 of the liquid is filtered. Finally, the material is dried in an oven at 80°C for ≥12 hours to directly obtain the thin layer of hexagonal boron nitride modified with bifunctional groups.

[0043] The structure of the bifunctional modified thin-layer hexagonal boron nitride prepared in this embodiment was characterized using field emission scanning electron microscopy (FEM). The morphology of the bifunctional modified thin-layer hexagonal boron nitride prepared in Example 1 was characterized. The scanning electron microscope images clearly show obvious exfoliation marks on the ball-milled hexagonal boron nitride. Figure 1 These are scanning electron microscope images of the raw material, hexagonal boron nitride. The raw material, hexagonal boron nitride, has a bulk structure. Figure 2 and Figure 3 These are scanning electron microscope (SEM) images of the thin-layer hexagonal boron nitride modified with bifunctional groups prepared in Example 1, and... Figure 1 compared to, Figure 2 and Figure 3 The thickness of the raw material hexagonal boron nitride decreases, and its shape changes from blocky to sheet-like, with bending occurring at the edges of the sheets. This is an effect caused by ball milling. The thin-layer material referred to in this patent is hexagonal boron nitride modified with bifunctional groups that has undergone ball milling, changing its shape from blocky to sheet-like. Hexagonal boron nitride that has become sheet-like is defined as a thin-layer material.

[0044] The XRD pattern of the bifunctional modified thin-layer hexagonal boron nitride prepared in Example 1 was obtained using X-ray diffraction. The analysis focused on whether the ball milling process in Example 1 would damage the crystal structure of hexagonal boron nitride. Figure 4 Comparison of XRD patterns for bifunctional modified thin-layer hexagonal boron nitride and hexagonal boron nitride powder. Figure 4 The diffraction peaks of the bifunctionalized thin-layer hexagonal boron nitride prepared in Example 1 are highly consistent with those of the hexagonal boron nitride powder, proving that Example 1 successfully prepared high-quality thin-layer hexagonal boron nitride with well-preserved crystal structure. The decreased peak intensity and increased full width at half maximum (FWHM) both indicate that the thin-layer hexagonal boron nitride was successfully exfoliated.

[0045] like Figure 5The infrared spectrum of the bifunctionalized thin-layer hexagonal boron nitride prepared in Example 1 was obtained using Fourier transform infrared spectroscopy, and the chemical bond structure of the thin-layer boron nitride prepared in Example 1 was analyzed. The BN and BNB vibrational peaks in the spectrum confirm that the final product is boron nitride, and the amino and hydroxyl functional groups in the spectrum indicate that the thin-layer boron nitride was successfully functionalized by amino and hydroxyl groups.

[0046] Example 2

[0047] A ball milling modification method for a thin layer of hexagonal boron nitride modified with bifunctional groups, specifically including the following steps:

[0048] (1) Weigh a certain amount of hexagonal boron nitride powder, guanidine hydrochloride and urea and place them in a container. Place the container in a water bath and heat it at 68°C. Stir continuously at 550 rpm for 24 minutes. After the sample begins to become a liquid mixture during the water bath heating process, a uniform mixture of guanidine hydrochloride and urea eutectic solvent and hexagonal boron nitride powder is obtained. In the eutectic solvent formed by guanidine hydrochloride and urea, the molar ratio of guanidine hydrochloride and urea is 1:2, and the mass ratio of hexagonal boron nitride powder and eutectic solvent is 1:41.

[0049] (2) Pour the homogeneous mixture obtained in step (1) into a ball mill jar containing grinding balls and a liner. The grinding balls are zirconia grinding balls, which are composed of three sizes: large balls with a diameter of 8-10 mm, medium balls with a diameter of 3-5 mm, and small balls with a diameter of 1-2 mm. The mass ratio of the large, medium, and small balls is 15:37:20. The internal volume ratio of the grinding balls to the liner of the ball mill jar is 2 / 3. The internal volume ratio of the homogeneous mixture of the eutectic solvent formed by guanidine hydrochloride and urea and the hexagonal boron nitride powder to the liner of the ball mill jar is 1 / 10. Add a certain amount of ethanol and water as dispersants. The mass ratio of ethanol and water to the hexagonal boron nitride powder is 8:1, and the volume ratio of ethanol to water is 3:1. Perform high-energy ball milling for 30 hours and at a speed of 800 rpm.

[0050] (3) After separating the ball-milled material from the grinding balls in step (2), the ball-milled material is vacuum filtered. The residual guanidine hydrochloride and urea need to be removed by excess deionized water. The material is dried in an oven at 80°C. The resulting powder is dispersed in deionized water. The mass ratio of boron nitride powder to deionized water is 1:1010. After sonication for 1.4 hours, the material is taken out and left to stand for more than 24 hours. At this time, the unfunctionalized thick hexagonal boron nitride has poor dispersibility in water. After standing for 24 hours, it will sink to the bottom of the beaker. The liquid after standing is vacuum filtered, and only the upper 4 / 5 of the liquid is filtered. Finally, the material is dried in an oven at 80°C for more than 12 hours to directly obtain the thin layer of hexagonal boron nitride modified with bifunctional groups.

[0051] Example 3

[0052] A ball milling modification method for a thin layer of hexagonal boron nitride modified with bifunctional groups, specifically including the following steps:

[0053] (1) Weigh a certain amount of hexagonal boron nitride powder, guanidine hydrochloride and urea and place them in a container. Place the container in a water bath and heat it at 65°C. Stir continuously at 400 rpm for 30 minutes. After the sample begins to become a liquid mixture during the water bath heating process, a uniform mixture of guanidine hydrochloride and urea eutectic solvent and hexagonal boron nitride powder is obtained. In the eutectic solvent formed by guanidine hydrochloride and urea, the molar ratio of guanidine hydrochloride and urea is 1:2, and the mass ratio of hexagonal boron nitride powder and eutectic solvent is 1:5.

[0054] (2) Pour the homogeneous mixture obtained in step (1) into a ball mill jar containing grinding balls and a liner. The grinding balls are zirconia grinding balls, which are composed of three sizes: large balls with a diameter of 8-10 mm, medium balls with a diameter of 3-5 mm, and small balls with a diameter of 1-2 mm. The mass ratio of the large, medium, and small balls is 17:36:22. The internal volume ratio of the grinding balls to the liner of the ball mill jar is 3 / 5. The internal volume ratio of the homogeneous mixture of the eutectic solvent formed by guanidine hydrochloride and urea and the hexagonal boron nitride powder to the liner of the ball mill jar is 1 / 5. Add a certain amount of ethanol and water as dispersants. The mass ratio of ethanol and water to the hexagonal boron nitride powder is 2:1, and the volume ratio of ethanol to water is 3:2.5. Perform high-energy ball milling for 10 hours and at a speed of 1200 rpm.

[0055] (3) After separating the ball-milled material from the grinding balls in step (2), the ball-milled material is vacuum filtered. The residual guanidine hydrochloride and urea need to be removed by excess deionized water. The material is dried in an oven at 80°C. The resulting powder is dispersed in deionized water. The mass ratio of boron nitride powder to deionized water is 1:950. After ultrasonication for 2 hours, the material is taken out and left to stand for ≥24 hours. At this time, the unfunctionalized thick hexagonal boron nitride has poor dispersibility in water. After standing for 24 hours, it will sink to the bottom of the beaker. The liquid after standing is vacuum filtered, and only the upper 3 / 4 of the liquid is filtered. Finally, the material is dried in an oven at 80°C for ≥12 hours to directly obtain the thin layer of hexagonal boron nitride modified with bifunctional groups.

[0056] Example 4

[0057] A ball milling modification method for a thin layer of hexagonal boron nitride modified with bifunctional groups, specifically including the following steps:

[0058] (1) Weigh a certain amount of hexagonal boron nitride powder, guanidine hydrochloride and urea and place them in a container. Place the container in a water bath and heat it at 70°C. Stir continuously at 600 rpm for 10 minutes. After the sample begins to become a liquid mixture during the water bath heating process, a uniform mixture of guanidine hydrochloride and urea eutectic solvent and hexagonal boron nitride powder is obtained. In the eutectic solvent formed by guanidine hydrochloride and urea, the molar ratio of guanidine hydrochloride and urea is 1:2, and the mass ratio of hexagonal boron nitride powder and eutectic solvent is 1:50.

[0059] (2) Pour the homogeneous mixture obtained in step (1) into a ball mill jar containing grinding balls and a liner. The grinding balls are zirconia grinding balls, which are composed of three sizes: large balls with a diameter of 8-10 mm, medium balls with a diameter of 3-5 mm, and small balls with a diameter of 1-2 mm. The mass ratio of the large, medium, and small balls is 15:35:21. The internal volume ratio of the grinding balls to the liner of the ball mill jar is 2 / 3. The internal volume ratio of the homogeneous mixture of the eutectic solvent formed by guanidine hydrochloride and urea and the hexagonal boron nitride powder to the liner of the ball mill jar is 1 / 9. Add a certain amount of ethanol and water as dispersants. The mass ratio of ethanol and water to the hexagonal boron nitride powder is 16:1, and the volume ratio of ethanol to water is 3:1.5. Perform high-energy ball milling for 40 hours and at a speed of 600 rpm.

[0060] (3) After separating the ball-milled material from the grinding balls in step (2), the ball-milled material is vacuum filtered. Excess deionized water is used to remove the residual guanidine hydrochloride and urea. The material is dried in an oven at 80°C. The resulting powder is dispersed in deionized water. The mass ratio of boron nitride powder to deionized water is 1:1050. After sonication for 1 hour, the material is taken out and left to stand for ≥24 hours. At this time, the unfunctionalized thick hexagonal boron nitride has poor dispersibility in water. After standing for 24 hours, it will sink to the bottom of the beaker. The liquid after standing is vacuum filtered, and only the upper 4 / 5 of the liquid is filtered. Finally, the material is dried in an oven at 80°C for ≥12 hours to directly obtain the thin layer of hexagonal boron nitride modified with bifunctional groups.

[0061] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all embodiments here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for ball milling modification of bi-functional modified thin-layer hexagonal boron nitride, characterized in that: The specific steps are as follows: (1) Weigh a certain amount of hexagonal boron nitride powder, guanidine hydrochloride and urea and place them in a container. Place the container in a water bath and heat and stir continuously to obtain a uniform mixture of eutectic solvent formed by guanidine hydrochloride and urea and hexagonal boron nitride powder. In the eutectic solvent formed by guanidine hydrochloride and urea, the molar ratio of guanidine hydrochloride and urea is 1:2, and the mass ratio of hexagonal boron nitride powder and eutectic solvent is 1:5-1:

50. (2) Pour the homogeneous mixture obtained in step (1) into a ball mill jar containing grinding balls and a liner, add a certain amount of ethanol and water as dispersants, and perform high-energy ball milling; the grinding balls are zirconia grinding balls, which are composed of three sizes of grinding balls, namely large balls with a diameter of 8-10 mm, medium balls with a diameter of 3-5 mm, and small balls with a diameter of 1-2 mm. The mass ratio of large balls, medium balls and small balls is (15-17): (35-37): (20-22). The internal volume ratio of grinding balls to the liner of the ball mill jar is 3 / 5-2 / 3. The internal volume ratio of the homogeneous mixture of guanidine hydrochloride and urea eutectic solvent and hexagonal boron nitride powder to the liner of the ball mill jar is 1 / 10-1 / 5. (3) After separating the ball-milled material from the grinding balls in step (2), the ball-milled material is vacuum filtered, dried, and the resulting powder is dispersed in water, then sonicated, allowed to stand, vacuum filtered, and dried to obtain a thin layer of hexagonal boron nitride modified with bifunctional groups.

2. The method of ball milling of bifunctionally modified thin-layer hexagonal boron nitride according to claim 1, characterized in that: In step (1), the water bath heating temperature is 65-70℃. After the sample begins to become a liquid mixture during the water bath heating process, it is continuously stirred at a speed of 400-600 rpm for 10-30 minutes.

3. The method of claim 1, wherein the ball-milling modification of the bi- functionalized thin-layer hexagonal boron nitride is characterized by: In step (2), the mass ratio of ethanol and water to hexagonal boron nitride powder is 2:1-16:1, and the volume ratio of ethanol to water is 3:1-3:2.

5.

4. The method of claim 1, wherein the ball-milling modification of the bi- functionalized thin-layer hexagonal boron nitride is characterized by: In step (2), the ball milling time is 10-40 hours and the ball milling speed is 600-1200 rpm.

5. The method of claim 1, wherein the ball-milling modification of the bi- functionalized thin-layer hexagonal boron nitride is characterized by: In step (3), the vacuum filtration requires the use of excess deionized water to remove the residual guanidine hydrochloride and urea, and the dried product directly yields boron nitride powder.

6. The ball milling modification method for thin-layer hexagonal boron nitride modified with bifunctional groups according to claim 5, characterized in that: The boron nitride powder obtained directly by drying is mixed with deionized water at a mass ratio of 1:(950-1050). After sonication for 1-2 hours, the mixture is removed and left to stand for ≥24 hours.

7. The ball milling modification method for thin-layer hexagonal boron nitride modified with bifunctional groups according to claim 6, characterized in that: When the liquid after standing is vacuum filtered, only the upper 3 / 4 to 4 / 5 of the liquid is filtered, and finally the bifunctional modified thin layer of hexagonal boron nitride is obtained directly by drying.

8. The ball milling modification method for thin-layer hexagonal boron nitride modified with bifunctional groups according to claim 7, characterized in that: Both drying steps in step (3) are carried out in an oven at 80°C for a drying time of 12 hours or more.

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