Three-dimensional boron nitride skeleton, high-thermal-conductivity insulating composite material and preparation method and application thereof

Abstract

The invention relates to a three-dimensional boron nitride skeleton, a high-thermal-conductivity insulating composite material and a preparation method and application thereof, and belongs to the technical field of composites.The preparation method of the three-dimensional boron nitride skeleton comprises the steps that S1, hydroxylation treatment is conducted on boron nitride, and hydroxylated boron nitride is obtained; s2, carrying out surface modification on the hydroxylated boron nitride by adopting a silane coupling agent to obtain modified boron nitride; s3, uniformly mixing the modified boron nitride with saccharides, and performing compression molding to obtain a prefabricated blank; and S4, putting the prefabricated blank in water, and dissolving to remove saccharides, thereby obtaining the three-dimensional boron nitride skeleton. The preparation method of the three-dimensional boron nitride skeleton provided by the invention is simple in process, environment-friendly and low in cost, and the prepared three-dimensional boron nitride skeleton has relatively good structural strength and stability.

Description

Technical Field

[0001] This invention relates to the field of composite material technology, and in particular to a three-dimensional boron nitride skeleton, a high thermal conductivity insulating composite material, its preparation method, and its application. Background Technology

[0002] As electronic technology evolves towards miniaturization and multifunctional integration, integrated circuit components have entered the nanoscale era. Against this backdrop, the heat generated during the operation of high-power devices accumulates rapidly, leading to a continuous increase in chip heat flux density and posing a severe challenge to device stability. Simultaneously, with technological innovations in smart grids, new energy, and rail transportation, high-voltage power equipment is also accelerating its transformation towards miniaturization and high power density. However, the heat accumulation generated by high-voltage equipment during high-power operation can easily cause aging of insulating materials, affecting their dielectric properties and the operational stability of the high-voltage equipment. Therefore, achieving efficient heat dissipation in insulation scenarios has become a core issue urgently needing breakthroughs in the high-voltage power field. This demand is also driving research and development breakthroughs in insulating materials that combine excellent dielectric properties and high thermal conductivity.

[0003] Currently, polymer materials dominate the semiconductor packaging field due to their lightweight, easy processing, and excellent insulation properties. For example, epoxy resin (EP) is widely used in printing, coating, potting, and electrical insulation due to its excellent electrical insulation, mechanical properties, and adhesion. However, the low thermal conductivity of epoxy resin limits its development in high-power electronic devices. To solve this problem, the following methods are usually adopted: (1) By introducing insulating and highly thermally conductive fillers (e.g., ceramics, metal oxides, metals, and carbonaceous materials) into epoxy resin, composite materials with continuous thermally conductive networks can be constructed, which can significantly improve the thermal conductivity and insulation properties of epoxy resin. (2) By constructing oriented boron nitride (BN) structures and three-dimensional BN skeletons, epoxy resin can be encapsulated to prepare composite materials that take into account both thermal conductivity and insulation properties. In recent years, the technology for constructing three-dimensional boron nitride skeletons involves many methods such as self-assembly, freeze drying, CVD, and chemical crosslinking. However, these methods require relatively strict experimental conditions (such as special temperatures, pressures, and crosslinking agents) and cumbersome process flows, resulting in poor industrial scalability.

[0004] Therefore, there is an urgent need to provide a method for preparing three-dimensional boron nitride frameworks that is simple, environmentally friendly, and low-cost. Summary of the Invention

[0005] To address one or more technical problems existing in the prior art, this invention provides a three-dimensional boron nitride framework, a high thermal conductivity insulating composite material, its preparation method, and its application. The preparation method of the three-dimensional boron nitride framework provided by this invention is simple, environmentally friendly, and low in cost, and the obtained three-dimensional boron nitride framework has good structural strength and stability.

[0006] The present invention provides a method for preparing a three-dimensional boron nitride framework in a first aspect, comprising: S1. Boron nitride is hydroxylated to obtain hydroxylated boron nitride; S2. The hydroxylated boron nitride is surface modified using a silane coupling agent to obtain modified boron nitride; S3. The modified boron nitride is mixed evenly with sugars and then pressed into shape to obtain a preform. S4. Place the preform in water and remove sugars by dissolving to obtain a three-dimensional boron nitride framework.

[0007] In a second aspect, the present invention provides a three-dimensional boron nitride framework, which is prepared using the preparation method described in the first aspect.

[0008] In a third aspect, the present invention provides a high thermal conductivity insulating composite material, which is obtained by impregnating a polymer matrix material with the three-dimensional boron nitride skeleton described in the second aspect and then curing it.

[0009] In a fourth aspect, the present invention provides an application of the high thermal conductivity insulating composite material described in the third aspect, which is applied in the field of high voltage electrical insulation.

[0010] Compared with the prior art, the present invention has at least the following beneficial effects: This invention first introduces hydroxyl groups onto the surface of boron nitride by hydroxylating it. Then, it modifies the surface of boron nitride by using a silane coupling agent to form chemical bonds with the hydroxyl groups through hydrolysis. Finally, it creates pores using sugars as self-sacrificing templates and removes the sugars by washing with water, thus preparing a three-dimensional boron nitride framework. The method for preparing the three-dimensional boron nitride framework provided by this invention is simple, environmentally friendly, and low-cost, and the resulting three-dimensional boron nitride framework exhibits good structural strength and stability.

[0011] This invention employs a silane coupling agent to modify the surface of boron nitride, improving its dispersion uniformity and interfacial compatibility within the polymer matrix. This effectively avoids the agglomeration problem of boron nitride at high filler contents, thereby enhancing the processability of the composite material. By using sucrose as a sacrificial template, a triple effect of pore formation, structural stabilization, and boron nitride oxygen functionalization is simultaneously achieved, resulting in a structurally stable, high-strength three-dimensional boron nitride framework.

[0012] This invention utilizes a method for preparing composite materials by impregnating a polymer matrix material with a three-dimensional boron nitride framework and then curing it. This method can significantly improve the thermal conductivity and volume resistivity of the composite material with low boron nitride content, and synergistically enhance the thermal conductivity and insulation properties of the polymer matrix material.

[0013] The composite material preparation method provided by this invention is simple, environmentally friendly, and low in cost. The resulting composite material has both excellent thermal conductivity and insulation properties, which can meet the application requirements in the field of high-voltage electrical insulation and has strong industrial application potential. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a flowchart illustrating the preparation process of a three-dimensional boron nitride framework provided by the present invention; Figure 2 These are FTIR images of hexagonal boron nitride (h-BN), modified boron nitride (BN-KH), and the three-dimensional boron nitride framework (3D BN-KH-3) provided in Example 3; Figure 3 The XPSO1s spectra of the modified boron nitride (BN-KH) and the three-dimensional boron nitride framework (3D BN-KH-3) provided in Example 3 are shown. Figure 4 These are SEM images of the three-dimensional boron nitride framework provided in Examples 1-3; Figure 5 These are SEM images of the high thermal conductivity insulating composite materials provided in Examples 1-3; Figure 6 This is a comparison chart of the thermal conductivity of pure EP and the high thermal conductivity insulating composite materials provided in Examples 1-3; Figure 7 This is a comparison chart of the dielectric properties of pure EP and the high thermal conductivity insulating composite materials provided in Examples 1-3; Figure 8 This is a comparison chart of the volume resistivity of pure EP and the high thermal conductivity insulating composite materials provided in Examples 1-3 within 60 seconds at 100V. Figure 9 These are structural stability test diagrams of the three-dimensional boron nitride framework (3D BN-KH-3) provided in Example 3 and the three-dimensional boron nitride framework (3D BN-KH-D1) provided in Comparative Example 1. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0017] In a first aspect, this invention provides a method for preparing a three-dimensional boron nitride framework, such as... Figure 1 As shown, it includes: S1. Boron nitride is hydroxylated to obtain hydroxylated boron nitride (denoted as BN-OH). S2. Surface modification of hydroxylated boron nitride was performed using a silane coupling agent to obtain modified boron nitride (denoted as BN-KH). S3. Mix the modified boron nitride with sugars evenly, and press them into shape to obtain a preform; S4. Place the preform in water and remove sugars by dissolving to obtain a three-dimensional boron nitride framework (denoted as 3D BN-KH).

[0018] This invention first introduces hydroxyl groups onto the surface of boron nitride by hydroxylating it. Then, it modifies the surface of boron nitride by using a silane coupling agent to form chemical bonds with the hydroxyl groups through hydrolysis. Finally, it creates pores using sugars as self-sacrificing templates and removes the sugars by washing with water, thus preparing a three-dimensional boron nitride framework. The method for preparing the three-dimensional boron nitride framework provided by this invention is simple, environmentally friendly, and low-cost, and the resulting three-dimensional boron nitride framework exhibits good structural strength and stability.

[0019] This invention employs a silane coupling agent to modify the surface of boron nitride, improving its dispersion uniformity and interfacial compatibility within the polymer matrix. This effectively avoids the agglomeration problem of boron nitride at high filler contents, thereby enhancing the processability of the composite material. By using sucrose as a sacrificial template, a triple effect of pore creation, structural stabilization, and oxygen functionalization modification of boron nitride (introducing hydroxyl groups onto the boron nitride surface) is simultaneously achieved, resulting in a structurally stable, high-strength three-dimensional boron nitride framework.

[0020] In some preferred embodiments of the present invention, boron nitride is preferably hexagonal boron nitride (h-BN) with high thermal conductivity, excellent electrical insulation properties and low cost.

[0021] According to some preferred embodiments, the hydroxylation treatment includes: mixing boron nitride with a sodium hydroxide solution and reacting at 60-80°C for 2-6 hours; The amount of boron nitride used is 1 to 5% of the mass of the sodium hydroxide solution (for example, it can be 1%, 2%, 3%, 4% or 5%).

[0022] According to some preferred embodiments, the amount of silane coupling agent is 3 to 7% of the mass of hydroxylated boron nitride (e.g., 3%, 4%, 5%, 6% or 7%).

[0023] According to some preferred embodiments, the silane coupling agent is selected from one or more of KH550, KH560, and KH570.

[0024] According to some preferred embodiments, the silane coupling agent is further hydrolyzed before surface modification, at a temperature of 45-70°C. In some preferred embodiments of the present invention, the hydrolysis of the silane coupling agent is carried out in a mixture of ethanol and water, wherein the mass ratio of ethanol to water in the mixture is 90-95:5-10.

[0025] According to some preferred embodiments, the surface modification temperature is 50~70°C.

[0026] When the silane coupling agent is KH550, the hydrolysis temperature is 50~70℃ and the time is 1~2h; the surface modification temperature is 50~70℃ and the time is 2~6h.

[0027] When the silane coupling agent is KH560, because its structure contains epoxy, in order to avoid ring-opening side reactions, it is necessary to appropriately control the hydrolysis temperature and the surface modification temperature. Specifically: the hydrolysis temperature is 50~60℃ and the time is 0.5~1.5h; the surface modification temperature is 50~70℃ and the time is 2~6h.

[0028] When the silane coupling agent is KH570, because its structure contains double bonds, in order to avoid double bond side reactions, it is necessary to appropriately control the hydrolysis temperature and the surface modification temperature. Specifically: the hydrolysis temperature is 45~60℃ and the hydrolysis time is 0.5~2h; the surface modification temperature is 50~60℃ and the time is 2~6h.

[0029] According to some preferred embodiments, the mass ratio of modified boron nitride to sugar is 3:4~6; According to some preferred embodiments, the sugar is selected from one or more of glucose, sucrose, and maltose.

[0030] According to some preferred embodiments, the particle size of the sugar is 0.14~2.50 mm, preferably 0.28~0.80 mm.

[0031] This invention can utilize sucrose granules of different sizes as needed, such as fine sucrose (0.14mm~0.45mm), medium sucrose (0.45mm~1.25mm), and coarse sucrose (0.80mm~2.50mm). It should be noted that the above ranges of fine, small, medium, and coarse sucrose conform to the national standard GB / T317-2018 White Granulated Sugar.

[0032] According to some preferred embodiments, the compression molding pressure is 10~30MPa.

[0033] According to some preferred embodiments, the dissolution temperature is 60~95°C.

[0034] The dissolution temperature varies slightly when using different sugars as self-sacrificing templates for pore creation: when using sucrose as a self-sacrificing template, sucrose is dissolved in an aqueous system at 60-80°C; when using glucose as a self-sacrificing template, glucose is dissolved in an aqueous system at 75-90°C; and when using maltose as a self-sacrificing template, maltose is dissolved in an aqueous system at 80-95°C.

[0035] In some specific embodiments of the present invention, the method for preparing a three-dimensional boron nitride framework includes: (1) Hydroxylation treatment of boron nitride First, add hexagonal boron nitride (h-BN) powder to a 5 mol / L sodium hydroxide solution (the amount of hexagonal boron nitride is 1-5% of the mass of the sodium hydroxide solution), and stir in a water bath at 60-80℃ for 2-6 hours to achieve full adhesion of hydroxyl groups. Then filter, wash the precipitate repeatedly with deionized water until neutral, and dry at 80℃ for 12 hours to obtain hydroxylated boron nitride (denoted as BN-OH).

[0036] (2) Surface modification of hydroxylated boron nitride Add silane coupling agent KH550 (5% of the mass of hydroxylated boron nitride) to an ethanol / water mixed solution (ethanol to water mass ratio of 90-95:5-10), and stir in a water bath at 50-70°C for 1-2 hours to allow the silane coupling agent to fully hydrolyze. Then, disperse the hydroxylated boron nitride (BN-OH) in the above solution, stir in a water bath at 50-70°C for 2-6 hours, filter, and repeatedly wash the precipitate with deionized water. After washing, dry at 80°C for 12 hours to obtain KH550 modified boron nitride (denoted as BN-KH).

[0037] (3) Preparation of a three-dimensional boron nitride framework.

[0038] Modified boron nitride powder and sucrose (particle size 0.28~0.8mm) were mixed at a mass ratio of 3:4~6 and placed into a square mold for pressing (held at 10~30MPa pressure for 10min) to obtain a preform. The pressed preform was repeatedly washed at 60~80℃ to remove sugars from the sample. Finally, it was dried to obtain a three-dimensional boron nitride framework (denoted as 3D BN-KH).

[0039] In a second aspect, the present invention provides a three-dimensional boron nitride framework, which is prepared using the method of the first aspect.

[0040] In a third aspect, the present invention provides a high thermal conductivity insulating composite material, which is obtained by impregnating a polymer matrix material with a three-dimensional boron nitride skeleton as described in the second aspect and then curing it.

[0041] This invention utilizes a method for preparing composite materials by impregnating a polymer matrix material with a three-dimensional boron nitride framework and then curing it. This method can significantly improve the thermal conductivity and volume resistivity of the composite material with low boron nitride content, and synergistically enhance the thermal conductivity and insulation properties of the polymer matrix material.

[0042] The composite material preparation method provided by this invention is simple, environmentally friendly, and low in cost. The resulting composite material has both excellent thermal conductivity and insulation properties, which can meet the application requirements in the field of high-voltage electrical insulation and has strong industrial application potential.

[0043] According to some preferred embodiments, the polymer matrix material is selected from one or more of epoxy resin, phenolic resin, polylactic acid, and paraffin phase change materials.

[0044] The preparation conditions of the composite material vary depending on the polymer matrix material used in this invention: When the polymer matrix material is epoxy resin (e.g., EP51), it is first melted at 60-80°C, then the three-dimensional boron nitride framework is filled by vacuum impregnation, and finally, it is cured in stages: first cured at 80-100°C for 1-3 hours, and then cured at 110-130°C for 1-3 hours. When the polymer matrix material is a phase change material (e.g., paraffin wax), the paraffin wax is first melted into a liquid at 50-70°C, then the three-dimensional boron nitride framework is filled by vacuum impregnation, and finally, it is cooled to 20-30°C for curing and shaping. When the polymer matrix material is a thermosetting resin (e.g., phenolic resin), the viscosity of the phenolic resin is first reduced at 60-80°C, then a three-dimensional boron nitride framework is filled by vacuum impregnation, and finally, segmented curing is performed: first, curing at 110-130°C for 1-3 hours, and then curing at 150-180°C for 1-3 hours. When the polymer matrix material is a thermoplastic resin (e.g., polylactic acid PLA), it is first heated to a molten state at 190-230°C, then a three-dimensional boron nitride framework is filled by vacuum impregnation, and finally, it is cooled to 20-30°C for curing and shaping.

[0045] In a fourth aspect, the present invention provides an application of the high thermal conductivity insulating composite material of the third aspect, which is applied in the field of high voltage electrical insulation.

[0046] The composite material provided by this invention has both excellent thermal conductivity and insulation properties, which can meet the application requirements in the field of high-voltage electrical insulation.

[0047] To more clearly illustrate the technical solution and advantages of the present invention, the present invention will be further described below with reference to embodiments. The present invention does not specifically limit the source of the reagents used in the embodiments and comparative examples; they can be directly purchased or synthesized in-house. Example 1

[0048] A method for preparing a three-dimensional boron nitride framework, comprising: (1) Hydroxylation treatment of boron nitride First, hexagonal boron nitride (h-BN) powder was added to a 5 mol / L sodium hydroxide solution (the amount of hexagonal boron nitride was 2% of the mass of the sodium hydroxide solution), and stirred in a water bath at 70°C for 3 hours. Then, the mixture was filtered, and the precipitate was repeatedly washed with deionized water until neutral. Finally, it was dried at 80°C for 12 hours to obtain hydroxylated boron nitride (denoted as BN-OH).

[0049] (2) Surface modification of hydroxylated boron nitride Silane coupling agent KH550 (5% of the mass of hydroxylated boron nitride (BN-OH)) was added to an ethanol / water mixed solution (ethanol to water mass ratio of 95:5) and stirred in a 60°C water bath for 1 h to allow the silane coupling agent to be fully hydrolyzed. Subsequently, the hydroxylated boron nitride (BN-OH) was dispersed in the above solution and stirred in a 60°C water bath for 3 h. After filtration, the precipitate was repeatedly washed with deionized water and then dried at 80°C for 12 h to obtain KH550 modified boron nitride (denoted as BN-KH).

[0050] (3) Preparation of a three-dimensional boron nitride framework.

[0051] Modified boron nitride powder (BN-KH) and sucrose (particle size 0.28~0.8mm) were mixed at a mass ratio of 3:6 and placed into a square mold for pressing (held at 30MPa pressure for 10min) to obtain a preform. The pressed preform was repeatedly washed at 70℃ to remove sucrose from the sample, and finally dried to obtain a three-dimensional boron nitride framework (denoted as 3D BN-KH-1).

[0052] A method for preparing a high thermal conductivity insulating composite material, comprising: Weigh 20g of E51 epoxy resin (EP) and pour it into a beaker. Seal the beaker and maintain the temperature at 70℃ for 10 minutes to reduce the viscosity of the epoxy resin. Then add 1g of polyetheramine (D-230) to the epoxy resin, stir at a constant temperature to form a homogeneous mixture, and degas under vacuum for 30 minutes. Completely immerse the prepared three-dimensional boron nitride skeleton (3D BN-KH-1) into the mixture and place it at room temperature for 30 minutes. Then transfer it to a vacuum drying oven and maintain a vacuum to ensure that the epoxy resin completely impregnates the voids in the skeleton. Finally, cure the mixture (first at 90℃ for 2 hours, then at 120℃ for 2 hours to obtain a high thermal conductivity insulating composite material (denoted as 3D BN-KH / EP-1). Example 2

[0053] This embodiment is basically the same as Embodiment 1, except that: In the process of preparing the three-dimensional boron nitride framework, modified boron nitride powder (BN-KH) powder and sucrose (particle size of 0.28~0.8mm) are mixed at a mass ratio of 3:5. The resulting three-dimensional boron nitride framework is denoted as 3D BN-KH-2, and the resulting high thermal conductivity insulating composite material is denoted as 3D BN-KH / EP-2. Example 3

[0054] This embodiment is basically the same as Embodiment 1, except that: In the process of preparing the three-dimensional boron nitride framework, modified boron nitride powder (BN-KH) powder and sucrose (particle size of 0.28~0.8mm) are mixed at a mass ratio of 3:4. The resulting three-dimensional boron nitride framework is denoted as 3D BN-KH-3, and the resulting high thermal conductivity insulating composite material is denoted as 3D BN-KH / EP-3.

[0055] As Figure 2 It can be seen that the infrared spectrum of pure hexagonal boron nitride (h-BN) only shows a value of 1379 cm⁻¹. -1 and 816cm -1 The absorption peaks at 2919 cm⁻¹ are generated by the stretching vibrations of in-plane BN and the bending vibrations of out-of-plane BN, respectively. The BN-KH surface modified with KH550 exhibits characteristic peaks belonging to KH550, with a peak at 2919 cm⁻¹. -1 and 2849cm -1 A stretching vibration peak of the CH bond appears at 1102 cm⁻¹. -1 and 3467cm -1 Stretching vibration peaks of Si-O and NH appear at 3400-3600 cm⁻¹, respectively. -1Stretching vibrations of hydroxyl groups were observed nearby. These results demonstrate that hexagonal boron nitride (h-BN) has been successfully hydroxylated, and silane molecules have been successfully grafted onto the surface of hexagonal boron nitride (h-BN). Pore formation using BN-KH composites with sucrose yielded a three-dimensional boron nitride framework (3D BN-KH-3) at 3400-3600 cm⁻¹. -1 Characteristic peaks of silane molecules and stretching vibration peaks of hydroxyl groups were observed nearby, and these peaks were in the range of 1000-1100 cm⁻¹. -1 Nearby and 1700cm -1 The absence of characteristic peaks for CO and C=O nearby indicates that sucrose molecules were removed during the dissolution step. Furthermore, the three-dimensional boron nitride framework (3D BN-KH-3) of Example 3 showed peak values ​​in the 2000-3500 cm⁻¹ range. -1 The presence of a broad peak may be related to the hydroxyl groups left after sucrose pore formation.

[0056] To further verify the hydroxyl groups left after sucrose pore formation, this invention used X-ray photoelectron spectroscopy (XPS) to further analyze the elemental composition (as shown in Table 1) and chemical composition (as shown in Table 2) of the modified boron nitride powder (BN-KH) and the three-dimensional boron nitride framework (3D BN-KH-3). Figure 3 The analysis was performed. Table 1 shows that, compared to modified boron nitride, the oxygen content in the three-dimensional boron nitride framework increased (from 2.71% to 4.67%). Figure 3 The XPS O1s peak fitting curve shows that the BO component content in the three-dimensional boron nitride framework increased (from 25% to 37.4%). Combined with the above FTIR, elemental, and XPS analyses, it is evident that during the water washing process of the preform, the three-dimensional boron nitride framework gradually forms as sucrose dissolves. Simultaneously, the sucrose also performs oxygen functionalization modification on the 3D BN-KH surface, leaving hydroxyl groups. This hydroxyl modification by sucrose improves the polarity and wettability of the BN surface, thereby improving the interfacial compatibility between BN components and between BN and the polar resin EP. Furthermore, during the subsequent impregnation and curing processes of EP, these hydroxyl groups may undergo ring-opening or hydrogen bonding with the epoxy, enhancing the interfacial bonding between the BN filler and the polymer matrix.

[0057]

[0058] Depend on Figure 4It can be seen that the three-dimensional boron nitride frameworks (denoted as 3D BN-KH-1, 3D BN-KH-2, and 3D BN-KH-3, respectively) prepared in Examples 1-3 of this invention all exhibit a honeycomb structure in cross-section. Furthermore, as the mass ratio of BN-KH to sucrose increases, the porosity inside the three-dimensional boron nitride framework decreases, and the overall mesh connection becomes more regular. From the magnified images of the pore wall structures of the three three-dimensional boron nitride frameworks, it can be seen that all three frameworks exhibit interconnected porous thermal conduction pathways. As the mass ratio of modified boron nitride to sucrose increases, the pore wall thickness gradually increases, the framework integrity is strengthened, the connectivity between pores gradually improves, and the phenomenon of pore breakage or collapse decreases. These results indicate that as the mass ratio of modified boron nitride to sucrose in the composite material increases, the pore structure shape in the three-dimensional boron nitride framework gradually becomes more regular, the connectivity improves, and the framework strength gradually increases. This is beneficial for the subsequent impregnation of the polymer matrix EP in the framework and for efficient heat conduction relying on interconnected thermal channels.

[0059] Figure 5 SEM images of the composite materials prepared in Examples 1-3 (3D BN-KH / EP-1, 3D BN-KH / EP-2, and 3D BN-KH / EP-3, respectively) show that all three composite materials exhibit smooth surfaces, indicating that KH550 modification did not disrupt the crystal structure of BN. Furthermore, EP uniformly fills the voids in the porous framework without delamination, demonstrating good interfacial compatibility. As the proportion of BN-KH in the composite materials increases, the lamellar size gradually increases, and the lamellar structure gradually transforms from fragmented small-sized structures to large-sized complete structures, which is beneficial for constructing continuous, directional thermal conductivity pathways.

[0060] Depend on Figure 4 and Figure 5 It is known that, within a certain range, increasing the mass ratio of BN-KH to sucrose can optimize the pore connectivity of the three-dimensional boron nitride framework, promote the formation of large-size BN sheet structures, facilitate directional and complete thermal conduction pathways, and also improve the mechanical properties of composite materials.

[0061] Depend on Figure 6It is known that the thermal conductivity of pure EP is only 0.20 W / (m·K), while the thermal conductivity of the composite material in Example 1 is 3.4 W / (m·K), which is 16 times higher than that of EP; the thermal conductivity of the composite material in Example 2 is 3.79 W / (m·K), which is 17.95 times higher than that of EP; and the thermal conductivity of the composite material in Example 3 is 4.25 W / (m·K), which is 20.25 times higher than that of EP. The significant improvement in the thermal conductivity of the above composite materials is due to the excellent thermal conductivity pathway formed by the three-dimensional boron nitride network. As the proportion of BN-KH in the composite material increases, the contact between BN-KH lamellars increases, and the degree of structural densification improves, but no agglomeration occurs. A continuous three-dimensional thermally conductive network can be formed, which significantly improves the thermal conductivity of the composite material.

[0062] This invention further explores the application potential of composite materials in high-voltage and ultra-high-voltage scenarios, and tests the dielectric properties and volume resistivity of the composite materials. The results are as follows: Figure 7 As shown. By Figure 7 (a) It can be seen that, compared with pure EP, the room temperature dielectric constants of the composite materials prepared in Examples 1-3 (3D BN-KH / EP-1, 3D BN-KH / EP-2, and 3D BN-KH / EP-3, respectively) are all improved to a certain extent. Furthermore, the room temperature dielectric constant gradually increases with the increase of the proportion of BN-KH in the composite material. This is mainly because boron nitride itself has a high dielectric constant. When the proportion of BN-KH in the composite material increases, the interface between BN-KH and EP also increases. Under the action of an electric field, the interfacial polarization between the two is also strengthened, leading to an increase in the dielectric constant of the prepared composite material. Although the room temperature dielectric constants of the composite materials prepared in Examples 1-3 are higher than those of pure EP, they are still at a relatively low level (less than 4), exhibiting good insulation properties. Figure 7 (b) It can be seen that, compared with pure EP, the dielectric losses of the composite materials prepared in Examples 1-3 (3D BN-KH / EP-1, 3D BN-KH / EP-2, and 3D BN-KH / EP-3, respectively) are significantly lower than those of EP, indicating that the composite materials have better insulation performance and lower energy loss. In summary, the composite materials prepared in Examples 1-3 of this invention have low dielectric constants and dielectric losses, and possess good insulation performance.

[0063] Depend on Figure 8 It can be seen that the volume resistivity of the composite materials (3D BN-KH / EP-1, 3D BN-KH / EP-2 and 3D BN-KH / EP-3, respectively) obtained in Examples 1-3 of the present invention is 6.70 × 10⁻⁶. 15 Ω·cm, 6.87×10 15 Ω·cm and 6.95×10 15The Ω·cm values ​​are significantly higher than the volume resistivity of pure EP (5.43 × 10⁻⁶ Ω·cm). 15 (Ω·cm). This shows that as the BN-KH content in the composite material increases, the volume resistivity of the composite material also increases, remaining at around 10 Ω·cm. 15 The volume resistivity is on the order of Ω·cm. This ultra-high volume resistivity can meet the requirements of high-voltage insulation, making the composite material a promising candidate for application in the field of high-voltage electrical insulation (for example, it can be used in integrated circuit packaging in electronic packaging, LED heat dissipation substrates, high-temperature resistant insulating structural components in aerospace, and solid insulating components suitable for AC GIS (gas-insulated switchgear), etc.).

[0064] Comparative Example 1 This is essentially the same as Example 3, except that sodium chloride is used instead of sucrose to prepare the three-dimensional boron nitride framework (denoted as 3D BN-KH-D1).

[0065] The structural stability of the three-dimensional boron nitride frameworks prepared in Example 3 and Comparative Example 1 was tested by placing a 1kg weight on their surfaces. The results are as follows: Figure 9 As shown, the three-dimensional boron nitride framework (3D BN-KH-3) of Example 3 remained intact, while the three-dimensional boron nitride framework (3D BN-KH-D1) of Comparative Example 1 was destroyed. It is evident that the stability of the three-dimensional boron nitride framework prepared by using a sucrose sacrificial template in Example 3 is significantly better than that of the three-dimensional boron nitride framework prepared by using a sodium chloride sacrificial template in Comparative Example 1. This further verifies that sucrose can stabilize the boron nitride framework structure during dissolution. The reason for this phenomenon may be the introduction of hydroxyl groups on the BN surface, which facilitates the formation of hydrogen bonds between BN particles, helps disperse the stress generated during sucrose dissolution, or inhibits particle slippage, thereby enhancing bulk stability. Furthermore, sucrose becomes viscous when dissolved in hot water; this property also allows sucrose to play a local binding role within the bulk, strengthening the adhesion between particles and thus stabilizing the three-dimensional boron nitride framework structure.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a three-dimensional boron nitride framework, characterized in that, include: S1. Boron nitride is hydroxylated to obtain hydroxylated boron nitride; S2. The hydroxylated boron nitride is surface modified using a silane coupling agent to obtain modified boron nitride; S3. The modified boron nitride is mixed evenly with sugars and then pressed into shape to obtain a preform. S4. Place the preform in water and remove sugars by dissolving to obtain a three-dimensional boron nitride framework.

2. The preparation method according to claim 1, characterized in that, The hydroxylation treatment includes: mixing boron nitride with sodium hydroxide solution and reacting at 60-80°C for 2-6 hours; The amount of boron nitride used is 1 to 5% of the mass of the sodium hydroxide solution.

3. The preparation method according to claim 1, characterized in that, The amount of the silane coupling agent is 3-7% of the mass of the hydroxylated boron nitride; and / or The silane coupling agent is selected from one or more of KH550, KH560, and KH570.

4. The preparation method according to claim 1, characterized in that, Prior to the surface modification, the silane coupling agent is hydrolyzed at a temperature of 45–70°C; and / or The surface modification temperature is 50~70℃.

5. The preparation method according to claim 1, characterized in that, The mass ratio of the modified boron nitride to the sugar is 3:4~6; The sugars are selected from one or more of glucose, sucrose, and maltose; and / or The sugar has a particle size of 0.14~2.50 mm, preferably 0.28~0.80 mm.

6. The preparation method according to claim 1, characterized in that, The compression molding pressure is 10~30MPa; and / or The melting temperature is 60~95℃.

7. A three-dimensional boron nitride framework, characterized in that, It is prepared by the preparation method according to any one of claims 1-6.

8. A high thermal conductivity insulating composite material, characterized in that, It is obtained by impregnating a polymer matrix material with the three-dimensional boron nitride framework as described in claim 7 and then curing it.

9. The high thermal conductivity insulating composite material according to claim 8, characterized in that, The polymer matrix material is selected from one or more of epoxy resin, phenolic resin, polylactic acid, and paraffin phase change materials.

10. An application of the high thermal conductivity insulating composite material according to claim 8 or 9, characterized in that, It is used in the field of high-voltage electrical insulation.

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