Boron nitride setter plate with high thermal conductivity and preparation method thereof

Abstract

The invention relates to the technical field of boron nitride load bearing plates, in particular to a high-thermal-conductivity boron nitride load bearing plate and a preparation method thereof.The preparation method comprises the following steps of S1, base material preparation, S2, boron nitride combined powder preparation, S3, powder A preparation, S4, powder B preparation, S5, powder C preparation and S6, finished product preparation. According to the invention, through the arrangement of the multi-particle-size combined powder in the boron nitride combined powder and three-stage particle gradation, the closest packing is realized, through the treatment of the coarse particle boron nitride powder, the graphene oxide can adsorb graphene on the surface of the coarse particle and enhance the heat transfer of the cross section, and through the treatment of the medium particle boron nitride powder, the heat transfer of the cross section is enhanced. According to the preparation method, the thermal stress is effectively buffered, the contact area is increased, fine-particle boron nitride powder is treated, sol is sintered to form a glass phase, the fine particles are wrapped, the grain boundary is filled, meanwhile, boron nitride whiskers are interspersed among the particles, an additional heat conduction path is constructed, and the heat conduction performance of the boron nitride setter plate is effectively improved.

Description

Technical Field

[0001] This invention relates to the field of boron nitride sintering plate technology, specifically to a high thermal conductivity boron nitride sintering plate and its preparation method. Background Technology

[0002] Sintering plates are key auxiliary components used in high-temperature sintering processes to support sintered materials such as electronic ceramic components. They need to have good structural stability and durability at high temperatures. Boron nitride ceramics are widely used in the preparation of high-performance sintering plates due to their excellent high-temperature resistance, thermal shock resistance and chemical stability.

[0003] Currently, in the preparation of boron nitride sintering plates, the surface of boron nitride powder is chemically inert, and there is a lack of effective connections between particles. Therefore, phonons are severely scattered when crossing the interfaces between different particles. Even if a high physical packing density is achieved, heat flow is mainly limited to short-range conduction within a single particle or local area, failing to form an efficient and stable long-range heat transport path throughout the material. This severely restricts a breakthrough in improving its overall thermal conductivity. Based on this, the present invention provides a high thermal conductivity boron nitride sintering plate and its preparation method. Summary of the Invention

[0004] The purpose of this invention is to provide a high thermal conductivity boron nitride sintering plate and its preparation method. The boron nitride sintering plate prepared by this invention not only has good thermal conductivity but also good mechanical properties, ensuring that the boron nitride sintering plate maintains excellent stability and durability in harsh sintering environments.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a boron nitride sintering plate with high thermal conductivity, comprising the following steps: S1: Base material preparation. The raw materials of the base material include solvent, boron nitride combined powder, sintering aid and binder. The mass ratio of solvent, boron nitride combined powder, sintering aid and binder is 90-100:80-90:2-4:3-5. The solvent is prepared by mixing propyl acetate and isobutanol in a volume ratio of 4:1. The sintering aid is yttrium oxide and the binder is polyvinyl alcohol. S2: Preparation of boron nitride composite powder, which is prepared by mixing powder A, powder B and powder C; S3: Preparation of powder A, wherein the raw material for powder A is coarse boron nitride powder with a particle size of 10-15 μm; S4: Preparation of powder B, wherein the raw material for powder B is medium-particle boron nitride powder with a particle size of 3-8 μm; S5: Preparation of powder C, wherein the raw material for powder C is fine boron nitride powder with a particle size of 0.2-0.8 μm, and the mass ratio of powder A, powder B and powder C is 1:0.6-0.8:0.2-0.3; S6: Finished product preparation, further processing of the base material to obtain a high thermal conductivity boron nitride sintering plate.

[0006] Preferably, the method for preparing powder A is as follows: coarse boron nitride powder and treated powder are fed into a mixer, which is set to 60-100 rpm and stirred for 20-40 minutes to obtain a coarse mixture. The coarse mixture is then fed into a tube furnace and heated to 400-440°C in an air atmosphere at a heating rate of 2-4°C / min. The temperature is held for 45-55 minutes, and then cooled to room temperature. The resulting product is washed with deionized water and then dried in an oven at 70-90°C for 4-6 hours to obtain a preparatory material. The preparatory material is added to a dispersion and heated in an ice-water bath at 500-70°C. The product was ultrasonically dispersed at 0W for 40–60 min, then PVP and ethanol solution were added, and ultrasonic dispersion was performed at 300–400W for 20–40 min. The resulting product was transferred to a reaction vessel, and the reaction vessel was set at 140–180℃ and 200–400 rpm for constant temperature stirring for 4–6 h. The resulting product was centrifuged to obtain a precipitate, which was then washed alternately with ethanol and deionized water. After that, it was freeze-dried at -50℃ for 10–20 h. The resulting product was then heat-treated in a tube furnace and naturally cooled to room temperature to obtain powder A.

[0007] Preferably, the mass ratio of coarse boron nitride powder to treated powder is 1:0.15-0.2, the mass of dispersion is 4-6 times the mass of preparative material, the mass ratio of PVP to ethanol solution is 1:0.1-0.2, the mass concentration of ethanol solution is 20-40%, and the mass of ethanol solution is 6-8 times the mass of preparative material.

[0008] Preferably, the treatment powder is prepared by mixing sodium hydroxide and potassium hydroxide in a mass ratio of 1:1, and the dispersion is prepared by mixing graphene oxide and deionized water in a mass ratio of 1:80-100.

[0009] Preferably, the heat treatment method is as follows: set the heating rate to 3-5℃ / min to raise the temperature to 450-500℃, and then set the heating rate to 8-10℃ / min to raise the temperature to 1800-2200℃.

[0010] Preferably, the method for preparing powder B is as follows: medium-particle boron nitride powder is dispersed in a treatment liquid, and ultrasonically dispersed at 600-800W for 1.5-2 hours. The resulting product is centrifuged to obtain a solid. The solid is then placed in an oven and dried at 70-90℃ for 2-4 hours to obtain powder B. The mass of the treatment liquid is 3-4 times the mass of the medium-particle boron nitride powder, and the treatment liquid is prepared by mixing isopropanol and deionized water in a mass ratio of 4:6.

[0011] Preferably, the method for preparing powder C is as follows: fine boron nitride powder and sol are added to a mixer, stirred at 400-600 rpm for 20-40 min, the resulting product is spray-dried, and the resulting product is pre-calcined at 600°C for 45-55 min to obtain powder C, wherein the mass ratio of fine boron nitride powder to sol is 1:0.25-0.35.

[0012] Preferably, the sol is prepared by the following method: Yttrium nitrate and aluminum isopropoxide are dissolved in anhydrous ethanol to obtain a first excipient, which is set aside for later use. Boron nitride whiskers are dispersed in anhydrous ethanol at a mass ratio of 1:50 and ultrasonically dispersed at 200-300W for 20-40 minutes. Then, 60-80% of the ethanol mass of deionized water is added and mixed to obtain a second excipient. The first and second excipients are fed into a mixer and stirred at 60-100rpm for 20-40 minutes to obtain the sol. The mass ratio of yttrium nitrate, aluminum isopropoxide and anhydrous ethanol is 1:1:15-20, and the mass ratio of the first excipient to the second excipient is 1:3-4.

[0013] Preferably, the method for preparing the finished product is as follows: Solvent, boron nitride combined powder, sintering aid, and binder are weighed as needed and added to a mixer. The mixer is set to 60-100 rpm and stirred for 30-50 minutes to obtain a slurry. The slurry is spray-dried, sieved through a 100-120 mesh, and then placed into a mold. It is then subjected to static pressing under a pressure of 80-90 MPa to obtain a green blank. The green blank is sent to a sintering furnace, and under nitrogen atmosphere protection, the heating rate is set to 5-10℃ / min, and the temperature is raised to 1700-1900℃ while applying a pressure of 200T. The temperature and pressure are maintained for 3-4 hours. After cooling, a substrate is obtained. The substrate is cut, ground, and polished to obtain a high thermal conductivity boron nitride sintering plate.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. In this invention, by setting up multi-size composite powder in the boron nitride composite powder, coarse particles serve as the skeleton, providing the main heat conduction pathways; medium particles fill the gaps between coarse particles, increasing the packing density and reducing porosity; and fine particles fill the tiny gaps and enhance sintering density through surface activity. Through three-level particle gradation, the densest packing is achieved, reducing porosity and thus improving the overall thermal conductivity. By treating the coarse boron nitride powder, graphene oxide can adsorb graphene on the surface of the coarse particles, forming a coating layer after high-temperature treatment, forming a thermally conductive connection between the boron nitride particles and enhancing cross-sectional heat transfer. By treating the medium boron nitride powder, its liquid phase can be exfoliated, increasing its aspect ratio and playing a supporting role, effectively buffering thermal stress and increasing the contact area. By treating the fine boron nitride powder, the sol forms a glassy phase after sintering, encapsulating the fine particles and filling the grain boundaries. At the same time, boron nitride whiskers interweave between the particles, constructing additional heat conduction paths, effectively improving the thermal conductivity of the boron nitride sintering plate.

[0015] 2. In this invention, the optimized solvent system and binder compatibility of propyl acetate and isobutanol ensure that the slurry has good fluidity and dispersion stability, thereby enabling the specially treated powders at all levels to be evenly distributed. By combining spray drying and precisely controlled hot pressing sintering process, the sintering aid yttrium oxide is effectively promoted to form a liquid phase, accelerating the densification process. The overall process is stable, and at the same time, it lays the foundation for obtaining a high-quality sintering plate with stable performance.

[0016] 3. In this invention, the tough coating layer formed by graphene oxide on the surface of coarse particles not only optimizes the heat conduction path, but also acts as a highly efficient reinforcing phase, significantly improving the bending strength and fracture toughness of the material through bridging and crack deflection mechanisms. The glass phase formed at the grain boundaries during sintering can effectively fill micro-defects and passivate stress concentration at crack tips. At the same time, the interpenetration of boron nitride whiskers between particles further strengthens the matrix. The synergistic effect of these components ensures that the sintering plate exhibits excellent structural stability and durability in the harsh high-temperature sintering environment. Attached Figure Description

[0017] Figure 1 The present invention provides a flowchart of a high thermal conductivity boron nitride sintering plate and its preparation method. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] It should be noted that the raw materials used in the following embodiments are all commercially available.

[0020] Example 1:

[0021] A method for preparing a boron nitride sintering plate with high thermal conductivity includes the following steps: S1: Base material preparation. The raw materials of the base material include solvent, boron nitride combined powder, sintering aid and binder. The mass ratio of solvent, boron nitride combined powder, sintering aid and binder is 90:80:2:3. The solvent is prepared by mixing propyl acetate and isobutanol in a volume ratio of 4:1. Yttrium oxide is selected as the sintering aid and polyvinyl alcohol is selected as the binder. S2: Preparation of boron nitride composite powder, which is prepared by mixing powder A, powder B and powder C; S3: Preparation of powder A, the raw material for powder A is coarse boron nitride powder with a particle size of 10μm; S4: Preparation of powder B, the raw material of powder B is medium-particle boron nitride powder with a particle size of 3μm; S5: Preparation of powder C. The raw material for powder C is fine boron nitride powder with a particle size of 0.2μm. The mass ratio of powder A, powder B and powder C is 1:0.6:0.2. S6: Finished product preparation, further processing of the base material to obtain a high thermal conductivity boron nitride sintering plate.

[0022] The method for preparing powder A is as follows: Coarse boron nitride powder and treated powder are fed into a mixer at a mass ratio of 1:0.15. The mixer is set to 60 rpm and stirred for 20 minutes to obtain a coarse mixture. The coarse mixture is then fed into a tube furnace and heated to 400℃ in an air atmosphere at a heating rate of 2℃ / min. The temperature is held for 45 minutes, and then cooled to room temperature. The resulting product is washed with deionized water and then dried in an oven at 70℃ for 4 hours to obtain a preparatory material. This preparatory material is added to a dispersion and heated in an ice-water bath. The product was ultrasonically dispersed at 500W for 40 minutes, then PVP and ethanol solution were added, and ultrasonic dispersion was performed at 300W for 20 minutes. The resulting product was transferred to a reaction vessel, which was set to 140℃ and 200rpm for constant temperature stirring for 4 hours. The resulting product was centrifuged to obtain a precipitate, which was then washed alternately with ethanol and deionized water. After that, it was freeze-dried at -50℃ for 10 hours. The resulting product was then heat-treated in a tube furnace and naturally cooled to room temperature to obtain powder A.

[0023] The dispersion was 4 times the mass of the preparative material, the mass ratio of PVP to ethanol solution was 1:0.1, the mass concentration of the ethanol solution was 20%, and the mass of the ethanol solution was 6 times the mass of the preparative material.

[0024] The treatment powder is prepared by mixing sodium hydroxide and potassium hydroxide in a mass ratio of 1:1, and the dispersion is prepared by mixing graphene oxide and deionized water in a mass ratio of 1:80.

[0025] The heat treatment method is as follows: set the heating rate to 3℃ / min to raise the temperature to 450℃, and then set the heating rate to 8℃ / min to raise the temperature to 1800℃.

[0026] The method for preparing powder B is as follows: medium-particle boron nitride powder is dispersed in a treatment solution and ultrasonically dispersed at 600W for 1.5h. The resulting product is centrifuged to obtain a solid. The solid is then placed in an oven and dried at 70℃ for 2h to obtain powder B. The mass of the treatment solution is three times the mass of the medium-particle boron nitride powder. The treatment solution is prepared by mixing isopropanol and deionized water in a mass ratio of 4:6.

[0027] The method for preparing powder C is as follows: fine boron nitride powder and sol are added to a mixer and stirred at 400 rpm for 20 min. The resulting product is spray-dried and pre-calcined at 600℃ for 45 min to obtain powder C. The mass ratio of fine boron nitride powder to sol is 1:0.25.

[0028] The sol was prepared by the following method: Yttrium nitrate and aluminum isopropoxide were dissolved in anhydrous ethanol to obtain the first excipient, which was set aside for later use. Boron nitride whiskers were dispersed in anhydrous ethanol at a mass ratio of 1:50 and ultrasonically dispersed at 200W for 20 minutes. Then, 60% of the ethanol mass of deionized water was added and mixed to obtain the second excipient. The first and second excipients were fed into a mixer and stirred at 60rpm for 20 minutes to obtain the sol. The mass ratio of yttrium nitrate, aluminum isopropoxide and anhydrous ethanol was 1:1:15, and the mass ratio of the first excipient to the second excipient was 1:3.

[0029] The method for preparing the finished product is as follows: the solvent, boron nitride combined powder, sintering aid and binder are weighed as needed and added to the mixer. The mixer is set to 60 rpm and stirred for 30 min to obtain a slurry. The slurry is spray dried and sieved through a 100-mesh sieve. Then it is loaded into a mold and statically pressed under a pressure of 80 MPa to obtain a green blank. The green blank is sent into a sintering furnace and heated to 1700℃ under a nitrogen atmosphere protection with a heating rate of 5℃ / min. At the same time, a pressure of 200T is applied and the temperature and pressure are held for 3 h. After cooling, the substrate is obtained. The substrate is cut, ground and polished to obtain a high thermal conductivity boron nitride sintering plate.

[0030] Example 2:

[0031] A method for preparing a boron nitride sintering plate with high thermal conductivity includes the following steps: S1: Base material preparation. The raw materials of the base material include solvent, boron nitride combined powder, sintering aid and binder. The mass ratio of solvent, boron nitride combined powder, sintering aid and binder is 95:85:3:4. The solvent is prepared by mixing propyl acetate and isobutanol in a volume ratio of 4:1. Yttrium oxide is selected as the sintering aid and polyvinyl alcohol is selected as the binder. S2: Preparation of boron nitride composite powder, which is prepared by mixing powder A, powder B and powder C; S3: Preparation of powder A, the raw material for powder A is coarse boron nitride powder with a particle size of 13μm; S4: Preparation of powder B, the raw material for powder B is medium-particle boron nitride powder with a particle size of 5μm; S5: Preparation of powder C. The raw material for powder C is fine boron nitride powder with a particle size of 0.5μm. The mass ratio of powder A, powder B and powder C is 1:0.7:0.25. S6: Finished product preparation, further processing of the base material to obtain a high thermal conductivity boron nitride sintering plate.

[0032] The method for preparing powder A is as follows: Coarse boron nitride powder and treated powder are fed into a mixer at a mass ratio of 1:0.18. The mixer is set to 80 rpm and stirred for 30 minutes to obtain a coarse mixture. The coarse mixture is then fed into a tube furnace and heated to 420°C in an air atmosphere at a heating rate of 3°C / min. The temperature is held for 50 minutes, then cooled to room temperature. The resulting product is washed with deionized water and then dried in an oven at 80°C for 5 hours to obtain a preparatory material. This preparatory material is added to a dispersion and heated in an ice-water bath. The product was ultrasonically dispersed at 600W for 50 min, then PVP and ethanol solution were added, and ultrasonic dispersion was performed at 350W for 30 min. The resulting product was transferred to a reaction vessel, which was set to 160℃ and 300rpm for 5 h of constant temperature stirring. The resulting product was centrifuged to obtain a precipitate, which was then washed alternately with ethanol and deionized water. After that, it was freeze-dried at -50℃ for 15 h. The resulting product was then heat-treated in a tube furnace and naturally cooled to room temperature to obtain powder A.

[0033] The dispersion was 5 times the mass of the preparative material, the mass ratio of PVP to ethanol solution was 1:0.15, the ethanol solution had a mass concentration of 30%, and the ethanol solution was 7 times the mass of the preparative material.

[0034] The treatment powder is prepared by mixing sodium hydroxide and potassium hydroxide in a mass ratio of 1:1, and the dispersion is prepared by mixing graphene oxide and deionized water in a mass ratio of 1:90.

[0035] The heat treatment method is as follows: set the heating rate to 4℃ / min to raise the temperature to 480℃, and then set the heating rate to 9℃ / min to raise the temperature to 2000℃.

[0036] The method for preparing powder B is as follows: medium-particle boron nitride powder is dispersed in a treatment solution and ultrasonically dispersed at 700W for 1.8h. The resulting product is centrifuged to obtain a solid. The solid is then placed in an oven and dried at 80℃ for 3h to obtain powder B. The mass of the treatment solution is 3.5 times the mass of the medium-particle boron nitride powder. The treatment solution is prepared by mixing isopropanol and deionized water in a mass ratio of 4:6.

[0037] The method for preparing powder C is as follows: fine boron nitride powder and sol are added to a mixer and stirred at 500 rpm for 30 min. The resulting product is spray-dried and pre-calcined at 600℃ for 50 min to obtain powder C. The mass ratio of fine boron nitride powder to sol is 1:0.3.

[0038] The sol was prepared by the following method: Yttrium nitrate and aluminum isopropoxide were dissolved in anhydrous ethanol to obtain the first excipient, which was set aside for later use. Boron nitride whiskers were dispersed in anhydrous ethanol at a mass ratio of 1:50 and ultrasonically dispersed at 250W for 30 minutes. Then, 70% of the ethanol mass of deionized water was added and mixed to obtain the second excipient. The first and second excipients were fed into a mixer and stirred at 80rpm for 30 minutes to obtain the sol. The mass ratio of yttrium nitrate, aluminum isopropoxide and anhydrous ethanol was 1:1:18, and the mass ratio of the first excipient to the second excipient was 1:3.5.

[0039] The method for preparing the finished product is as follows: the solvent, boron nitride combined powder, sintering aid and binder are weighed as needed and added to the mixer. The mixer is set to 80 rpm and stirred for 40 min to obtain a slurry. The slurry is spray dried and sieved through a 110 mesh. Then it is loaded into a mold and statically pressed under a pressure of 85 MPa to obtain a green blank. The green blank is sent into a sintering furnace and heated to 1800℃ under a nitrogen atmosphere protection, with a heating rate of 8℃ / min. At the same time, a pressure of 200T is applied and the temperature and pressure are maintained for 3.5 h. After cooling, the matrix is ​​obtained. The matrix is ​​cut, ground and polished to obtain a high thermal conductivity boron nitride sintering plate.

[0040] Example 3:

[0041] A method for preparing a boron nitride sintering plate with high thermal conductivity includes the following steps: S1: Base material preparation. The raw materials of the base material include solvent, boron nitride combined powder, sintering aid and binder. The mass ratio of solvent, boron nitride combined powder, sintering aid and binder is 100:90:4:5. The solvent is prepared by mixing propyl acetate and isobutanol in a volume ratio of 4:1. Yttrium oxide is selected as the sintering aid and polyvinyl alcohol is selected as the binder. S2: Preparation of boron nitride composite powder, which is prepared by mixing powder A, powder B and powder C; S3: Preparation of powder A, the raw material for powder A is coarse boron nitride powder with a particle size of 15μm; S4: Preparation of powder B, the raw material for powder B is medium-particle boron nitride powder with a particle size of 8μm; S5: Preparation of powder C. The raw material for powder C is fine boron nitride powder with a particle size of 0.8μm. The mass ratio of powder A, powder B and powder C is 1:0.8:0.3. S6: Finished product preparation, further processing of the base material to obtain a high thermal conductivity boron nitride sintering plate.

[0042] The method for preparing powder A is as follows: Coarse boron nitride powder and treated powder are fed into a mixer at a mass ratio of 1:0.2. The mixer is set to 100 rpm and stirred for 40 minutes to obtain a coarse mixture. The coarse mixture is then fed into a tube furnace and heated to 440°C in an air atmosphere at a heating rate of 4°C / min. The temperature is held for 55 minutes, then cooled to room temperature. The resulting product is washed with deionized water and then dried in an oven at 90°C for 6 hours to obtain a preparatory material. This preparatory material is added to a dispersion and heated in an ice-water bath. The product was ultrasonically dispersed at 700W for 60 min, then PVP and ethanol solution were added, and ultrasonic dispersion was performed at 400W for 40 min. The resulting product was transferred to a reactor, which was set to 180℃ and 400rpm, and stirred at a constant temperature for 6 h. The resulting product was centrifuged to obtain a precipitate, which was then washed alternately with ethanol and deionized water. After that, it was freeze-dried at -50℃ for 20 h. The resulting product was then heat-treated in a tube furnace and naturally cooled to room temperature to obtain powder A.

[0043] The mass of the dispersion is 6 times the mass of the preparatory material, the mass ratio of PVP to ethanol solution is 1:0.2, the mass concentration of ethanol solution is 40%, and the mass of ethanol solution is 8 times the mass of the preparatory material.

[0044] The treatment powder is prepared by mixing sodium hydroxide and potassium hydroxide in a mass ratio of 1:1, and the dispersion is prepared by mixing graphene oxide and deionized water in a mass ratio of 1:100.

[0045] The heat treatment method is as follows: set the heating rate to 500℃ at 5℃ / min, and then set the heating rate to 2200℃ at 10℃ / min.

[0046] The method for preparing powder B is as follows: medium-particle boron nitride powder is dispersed in a treatment solution and ultrasonically dispersed at 800W for 2 hours. The resulting product is centrifuged to obtain a solid. The solid is then placed in an oven and dried at 90℃ for 4 hours to obtain powder B. The mass of the treatment solution is 4 times the mass of the medium-particle boron nitride powder. The treatment solution is prepared by mixing isopropanol and deionized water in a mass ratio of 4:6.

[0047] The method for preparing powder C is as follows: fine boron nitride powder and sol are added to a mixer and stirred at 600 rpm for 40 min. The resulting product is spray-dried and pre-calcined at 600℃ for 55 min to obtain powder C. The mass ratio of fine boron nitride powder to sol is 1:0.35.

[0048] The sol was prepared by the following method: Yttrium nitrate and aluminum isopropoxide were dissolved in anhydrous ethanol to obtain the first excipient, which was set aside for later use. Boron nitride whiskers were dispersed in anhydrous ethanol at a mass ratio of 1:50 and ultrasonically dispersed at 300W for 40 minutes. Then, 80% of the ethanol mass of deionized water was added and mixed to obtain the second excipient. The first and second excipients were fed into a mixer and stirred at 100rpm for 40 minutes to obtain the sol. The mass ratio of yttrium nitrate, aluminum isopropoxide and anhydrous ethanol was 1:1:20, and the mass ratio of the first excipient to the second excipient was 1:4.

[0049] The method for preparing the finished product is as follows: the solvent, boron nitride combined powder, sintering aid and binder are weighed as needed and added to the mixer. The mixer is set to 100 rpm and stirred for 50 min to obtain a slurry. The slurry is spray dried and sieved through a 120 mesh. Then it is loaded into a mold and statically pressed under a pressure of 90 MPa to obtain a green blank. The green blank is sent into a sintering furnace and heated to 1900℃ under a nitrogen atmosphere protection, with a heating rate of 10℃ / min. At the same time, a pressure of 200T is applied and the temperature and pressure are maintained for 4 h. After cooling, the matrix is ​​obtained. The matrix is ​​cut, ground and polished to obtain a high thermal conductivity boron nitride sintering plate.

[0050] Comparative Example 1: The difference between this comparative example and Example 1 is that the raw materials for powder A, powder B, and powder C in this comparative example are all boron nitride powder with a particle size of 12 μm.

[0051] Comparative Example 2 differs from Example 1 in that an equal amount of coarse boron nitride powder is used to replace powder A in this comparative example.

[0052] Comparative Example 3 differs from Example 1 in that an equal amount of fine-particle boron nitride powder is used to replace powder C in this comparative example.

[0053] Performance testing: The performance of the boron nitride sintered plates prepared in Examples 1-3 and Comparative Examples 1-3 was tested; Performance testing: The performance of the boron nitride sintered plates prepared in Examples 1-3 and Comparative Examples 1-3 was tested; Bulk density: The bulk density (g / cm³) was tested according to GB / T 25995-2010 standard and recorded in Table 1; Bending strength: The bending strength (MPa) was tested according to GB / T 6569-2006 standard and recorded in Table 1; Compressive strength: The compressive strength (MPa) was tested according to GB / T 8489-2006 standard and recorded in Table 1; Thermal conductivity: The thermal conductivity [(W / (m·K)] was tested according to GB / T 22588-2008 standard and recorded in Table 1; Thermal shock resistance cycle count: The number of thermal shock resistance cycles was tested according to GB / T 37246-2018 and recorded in Table 1.

[0054] Table 1: Analysis and comparison of the data in the table above show that the boron nitride sintering plates prepared using the methods in Examples 1-3 have better performance than those in Comparative Examples 1-3, and the performance data are more stable. The high bulk density and thermal conductivity indicate that the boron nitride powder adopts a multi-scale gradation of powders A, B, and C, achieving close packing, reducing porosity, and providing a smoother path for phonon propagation, thus obtaining higher and more stable thermal conductivity. At the same time, after powder A is coated with graphene oxide, it forms an efficient thermally conductive bridge between coarse particles, further reducing interfacial thermal resistance and making a positive contribution to improving thermal conductivity. The excellent mechanical and thermal shock resistance properties indicate that the sol and boron nitride whiskers introduced in the preparation of powder C can effectively fill grain boundaries, passivate crack tips, and bridge cracks, thereby enhancing the toughness and strength of the material. These enhancement mechanisms work together to enable the sintering plate to resist thermal stress damage during severe alternating heating and cooling.

[0055] Further analysis and comparison revealed that Comparative Example 1, due to the lack of multi-size particle gradation, suffered from an unstable basic framework, resulting in comprehensive performance limitations and a significant decrease in bulk density. This indicates that single-size boron nitride powder cannot be tightly packed, leading to low green body density, numerous internal pores, and consequently, a decline in various properties, as well as an unstable foundation for the firing plate. In contrast, Comparative Example 2 had a bulk density close to that of the example, indicating relatively good basic packing. However, its thermal conductivity and flexural strength were significantly lower than those of the example, suggesting that the absence of the graphene oxide coating layer resulted in a lack of effective inter-particle bonding between boron nitride particles. The "thermal bridge" increases the interfacial thermal resistance and loses the reinforcing and toughening effect of graphene. Its thermal shock resistance is better than that of comparative examples 1 and 3, but worse than that of the example, indicating that the basic framework is still there, but the interfacial bonding force is insufficient. The volume density and thermal conductivity of comparative example 3 are less affected, but its compressive strength and thermal shock resistance cycles are significantly weaker. The sol and boron nitride whiskers in the surface powder C mainly contribute to grain boundary strengthening and toughening. After their absence, the grain boundary bonding force is weakened, and the material is more prone to crack initiation and propagation when subjected to pressure and high-frequency thermal stress.

[0056] By comparing and analyzing the relevant data in the table, it can be seen that the boron nitride sintering plate prepared by this invention not only has good thermal conductivity but also good mechanical properties, ensuring that the boron nitride sintering plate maintains excellent stability and durability in harsh sintering environments. This indicates that the high thermal conductivity boron nitride sintering plate provided by this invention has a broader market prospect and is more suitable for widespread application.

[0057] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0058] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a boron nitride sintering plate with high thermal conductivity, characterized in that: Includes the following steps: S1: Base material preparation. The raw materials of the base material include solvent, boron nitride combined powder, sintering aid and binder. The mass ratio of solvent, boron nitride combined powder, sintering aid and binder is 90-100:80-90:2-4:3-5. The solvent is prepared by mixing propyl acetate and isobutanol in a volume ratio of 4:

1. The sintering aid is yttrium oxide and the binder is polyvinyl alcohol. S2: Preparation of boron nitride composite powder, which is prepared by mixing powder A, powder B and powder C; S3: Preparation of powder A, wherein the raw material for powder A is coarse boron nitride powder with a particle size of 10-15 μm; S4: Preparation of powder B, wherein the raw material for powder B is medium-particle boron nitride powder with a particle size of 3 to 8 μm; S5: Preparation of powder C, wherein the raw material for powder C is fine boron nitride powder with a particle size of 0.2-0.8 μm, and the mass ratio of powder A, powder B and powder C is 1:0.6-0.8:0.2-0.3; S6: Finished product preparation, further processing of the base material to obtain a high thermal conductivity boron nitride sintering plate.

2. The method for preparing the high thermal conductivity boron nitride sintering plate according to claim 1, characterized in that, The method for preparing powder A is as follows: coarse boron nitride powder and treated powder are fed into a mixer, which is set to 60-100 rpm and stirred for 20-40 minutes to obtain a coarse mixture. The coarse mixture is then fed into a tube furnace and heated to 400-440°C at a rate of 2-4°C / min under an air atmosphere. The temperature is held for 45-55 minutes, and then cooled to room temperature. The resulting product is washed with deionized water and then placed in an oven at 70-90°C for 4-6 hours to obtain a preparatory material. The preparatory material is added to a dispersion and heated in an ice-water bath at 500-700 W. Under the specified conditions, the product was ultrasonically dispersed for 40–60 min, then PVP and ethanol solution were added, and ultrasonic dispersion was performed at 300–400 W for 20–40 min. The resulting product was transferred to a reaction vessel, and the reaction vessel was set at a temperature of 140–180 °C and a rotation speed of 200–400 rpm. The mixture was stirred at a constant temperature for 4–6 h. The resulting product was centrifuged to obtain a precipitate, which was then washed alternately with ethanol and deionized water. After that, it was freeze-dried at -50 °C for 10–20 h. The resulting product was then heat-treated in a tube furnace and naturally cooled to room temperature to obtain powder A.

3. The method for preparing the high thermal conductivity boron nitride sintering plate according to claim 2, characterized in that, The mass ratio of coarse boron nitride powder to treated powder is 1:0.15-0.2, the mass of dispersion is 4-6 times the mass of preparative material, the mass ratio of PVP to ethanol solution is 1:0.1-0.2, the mass concentration of ethanol solution is 20-40%, and the mass of ethanol solution is 6-8 times the mass of preparative material.

4. The method for preparing the high thermal conductivity boron nitride sintering plate according to claim 2, characterized in that, The treatment powder is prepared by mixing sodium hydroxide and potassium hydroxide in a mass ratio of 1:1, and the dispersion is prepared by mixing graphene oxide and deionized water in a mass ratio of 1:80-100.

5. The method for preparing the high thermal conductivity boron nitride sintering plate according to claim 2, characterized in that, The heat treatment method is as follows: set the heating rate to 3-5℃ / min to raise the temperature to 450-500℃, and then set the heating rate to 8-10℃ / min to raise the temperature to 1800-2200℃.

6. The method for preparing the high thermal conductivity boron nitride sintering plate according to claim 1, characterized in that, The method for preparing powder B is as follows: medium-particle boron nitride powder is dispersed in a treatment solution and ultrasonically dispersed at 600-800W for 1.5-2 hours. The resulting product is centrifuged to obtain a solid. The solid is then placed in an oven and dried at 70-90℃ for 2-4 hours to obtain powder B. The mass of the treatment solution is 3-4 times the mass of the medium-particle boron nitride powder. The treatment solution is prepared by mixing isopropanol and deionized water in a mass ratio of 4:

6.

7. The method for preparing the high thermal conductivity boron nitride sintering plate according to claim 1, characterized in that, The method for preparing powder C is as follows: fine boron nitride powder and sol are added to a mixer, stirred at 400-600 rpm for 20-40 min, the resulting product is spray-dried, and the resulting product is pre-calcined at 600℃ for 45-55 min to obtain powder C, wherein the mass ratio of fine boron nitride powder to sol is 1:0.25-0.

35.

8. The method for preparing the high thermal conductivity boron nitride sintering plate according to claim 7, characterized in that, The sol is prepared by the following method: Yttrium nitrate and aluminum isopropoxide are dissolved in anhydrous ethanol to obtain the first excipient, which is set aside for later use. Boron nitride whiskers are dispersed in anhydrous ethanol at a mass ratio of 1:50 and ultrasonically dispersed at 200-300W for 20-40 minutes. Then, 60-80% of the ethanol mass of deionized water is added and mixed to obtain the second excipient. The first and second excipients are fed into a mixer and stirred at 60-100rpm for 20-40 minutes to obtain the sol. The mass ratio of yttrium nitrate, aluminum isopropoxide and anhydrous ethanol is 1:1:15-20, and the mass ratio of the first excipient to the second excipient is 1:3-4.

9. The method for preparing a high thermal conductivity boron nitride sintering plate according to claim 1, characterized in that, The method for preparing the finished product is as follows: Solvent, boron nitride powder, sintering aid, and binder are weighed as needed and added to a mixer. The mixer is set to 60-100 rpm and stirred for 30-50 minutes to obtain a slurry. The slurry is then spray-dried, sieved through a 100-120 mesh, and then placed into a mold. It is then subjected to static pressing at 80-90 MPa to obtain a green blank. The green blank is then placed in a sintering furnace. Under a nitrogen atmosphere, the heating rate is set to 5-10℃ / min, and the temperature is raised to 1700-1900℃ while applying a pressure of 200T. The temperature and pressure are maintained for 3-4 hours. After cooling, the substrate is obtained. The substrate is then cut, ground, and polished to produce a high thermal conductivity boron nitride sintering plate.

10. A high thermal conductivity boron nitride sintering plate, characterized in that, It is prepared by the method for preparing high thermal conductivity boron nitride sintering plate according to any one of claims 1 to 9.

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