High-thermal-conductivity silicon nitride ceramic material, preparation method and application thereof

Abstract

This invention relates to the field of silicon nitride ceramic materials, specifically to a high thermal conductivity silicon nitride ceramic material, its preparation method, and its applications, addressing the problem of low thermal conductivity in existing silicon nitride ceramic materials. The high thermal conductivity silicon nitride ceramic material is obtained by ball milling and dispersing α-silicon nitride powder, yttrium oxide, alumina, polyvinylpyrrolidone, polydopamine / silane coupling agent-modified hexagonal boron nitride, and graphene@alumina composite powder, followed by dry pressing and sintering. The high thermal conductivity silicon nitride ceramic material prepared by this method possesses high thermal conductivity, excellent insulation properties, stable mechanical properties, and high-temperature resistance, and can be applied in the fields of electronic information, new energy, and aerospace.

Description

Technical Field

[0001] This invention relates to the field of silicon nitride ceramic materials, specifically to a high thermal conductivity silicon nitride ceramic material, its preparation method, and its application. Background Technology

[0002] Silicon nitride ceramics, as a high-performance advanced inorganic non-metallic material, have been widely used in structural fields such as aerospace engine components, mechanical seal rings, and cutting tools, as well as functional fields such as ceramic substrates and sensor elements, thanks to their excellent high-temperature resistance, superior chemical corrosion resistance, and high strength and hardness. However, the limitation of its intrinsic thermal conductivity has become a key bottleneck restricting further development. The thermal conductivity of pure silicon nitride ceramics at room temperature is much lower than that of traditional metal heat dissipation materials such as copper and aluminum. With the rapid development of high-power-density electronic devices, high-heat-generating devices such as insulated-gate bipolar transistor modules and 5G power amplifiers cannot dissipate the large amount of heat generated during operation, leading to a sharp increase in chip junction temperature, which in turn causes problems such as device performance degradation, decreased reliability, and even failure.

[0003] Therefore, it is of great significance to develop a silicon nitride ceramic material with high thermal conductivity, its preparation method, and its application. Summary of the Invention

[0004] In order to overcome the above-mentioned technical problems, the purpose of this invention is to provide a high thermal conductivity silicon nitride ceramic material, its preparation method and application.

[0005] The objective of this invention can be achieved through the following technical solutions: In a first aspect, this application provides a high thermal conductivity silicon nitride ceramic material, comprising the following components in parts by weight: The composition includes 3-4 parts of polydopamine / silane coupling agent co-modified hexagonal boron nitride, 0.1-0.5 parts of graphene@alumina composite powder, 150-160 parts of mixed solvent, 40-42 parts of α-silicon nitride powder, 2-3 parts of yttrium oxide, 1-1.5 parts of alumina, and 0.24-0.26 parts of polyvinylpyrrolidone. In a preferred embodiment of the present invention, the mixed solvent is a solution of anhydrous ethanol and deionized water mixed in a volume ratio of 1:1; the CAS number of the α-silicon nitride powder is 12033-89-5; the particle size of the yttrium oxide is 1-3 μm; the particle size of the alumina is 0.5-1 μm; and the CAS number of the polyvinylpyrrolidone is 9003-39-8. The polydopamine / silane coupling agent co-modified hexagonal boron nitride is prepared by the following steps: Step a1: Add hexagonal boron nitride powder to anhydrous ethanol and ultrasonically disperse it for 25-30 min at a power of 370-400W. Then centrifuge it for 15-17 min at a speed of 7500-8000 r / min. Discard the supernatant and wash the lower layer with deionized water and centrifuge it 2-3 times. Finally, wash it once with anhydrous ethanol and place it in a vacuum drying oven at a temperature of 55-60℃ for 12-14 h. Grind it through a 100-mesh sieve to obtain pretreated hexagonal boron nitride. Step a2: Add tris(hydroxymethyl)aminomethane to deionized water and stir for 15-25 min at a stirring rate of 200-300 r / min. Adjust the pH to 8.5 with hydrochloric acid, then add pretreated hexagonal boron nitride and ultrasonically disperse for 20-22 min at a power of 270-300 W. Then add dopamine hydrochloride and magnetically stir for 10-12 h at a stirring rate of 400-450 r / min. Then centrifuge for 15-17 min at a speed of 7500-8000 r / min, collect the lower solid and wash it alternately with deionized water and anhydrous ethanol 3-4 times. Then place it in a vacuum drying oven and dry it at a temperature of 65-70℃ for 8-9 h. Grind it through a 100-mesh sieve to obtain polydopamine-coated hexagonal boron nitride. Step a3: Add the silane coupling agent to anhydrous ethanol and stir for 10-12 min at a stirring rate of 200-300 r / min. Add deionized water dropwise and continue stirring for 30-35 min. Then add polydopamine-coated hexagonal boron nitride and ultrasonically disperse for 20-23 min at a power of 270-300 W. Heat to 55℃ and magnetically stir at a stirring rate of 300-350 r / min for 4-6 h. Then centrifuge at a speed of 7500-8000 r / min for 15-17 min. Collect the solid and wash it 3-4 times with anhydrous ethanol. Then place it in a vacuum drying oven and dry it at a temperature of 60-65℃ for 10-12 h. Grind it through a 100-mesh sieve to obtain polydopamine / silane coupling agent co-modified hexagonal boron nitride.

[0006] In a preferred embodiment of the present invention, the ratio of hexagonal boron nitride powder to anhydrous ethanol in step a1 is 10-11g: 500-550mL.

[0007] In a preferred embodiment of the present invention, the hexagonal boron nitride powder in step a1 has a particle size of 3-5 μm and a purity of ≥99%.

[0008] In a preferred embodiment of the present invention, the ratio of tris(hydroxymethyl)aminomethane, deionized water, pretreated hexagonal boron nitride, and dopamine hydrochloride in step a2 is 2.4-3.3g: 200-280mL: 10-14g: 0.5-0.7g.

[0009] In a preferred embodiment of the present invention, the molar concentration of hydrochloric acid in step a2 is 0.1 mol / L.

[0010] In a preferred embodiment of the present invention, the ratio of the amount of silane coupling agent, anhydrous ethanol, deionized water and polydopamine-coated hexagonal boron nitride in step a3 is 1.5-1.7g: 100-120mL: 2-3mL: 5-6g.

[0011] In a preferred embodiment of the present invention, the silane coupling agent in step a3 is KH590.

[0012] The graphene@alumina composite powder is prepared by the following steps: Step b1: Add graphene and mixed acid to a beaker and place it in an ice-water bath at 0-4℃. Stir magnetically for 30-35 min at a stirring rate of 200-300 r / min. Then transfer it to an oil bath and stir at a constant temperature of 45-50℃ for 4-5 h to obtain a mixture. Pour the mixture into deionized water and stir to dilute. Filter with a 0.22 μm filter membrane. Wash the filter cake with deionized water until the pH of the filtrate is 6-7. Then place the filter cake in a vacuum drying oven and dry at 55-60℃ for 8-9 h. Grind it through a 100-mesh sieve to obtain acidified graphene. Step b2: Add aluminum isopropoxide and anhydrous ethanol to a three-necked flask equipped with a stirrer, thermometer, gas delivery tube and constant pressure dropping funnel. Purge with nitrogen for protection and magnetically stir for 30-35 minutes at a temperature of 25-30℃ and a stirring rate of 200-300 r / min. Then, add deionized water dropwise while stirring, controlling the dropping rate to 1-2 drops / s. At the same time, add dilute nitric acid to adjust the pH to 3.5-4.0. After the addition is complete, raise the temperature to 60℃ and continue stirring for 2-3 hours to form an alumina sol. Step b3: Add the acidified graphene to the alumina sol and ultrasonically disperse it for 30-32 minutes at a power of 400W using intermittent ultrasonication (3 seconds on, 2 seconds off). Then transfer it to a constant-temperature magnetic stirrer and stir for 4-5 hours at 75-80℃. After cooling to room temperature, centrifuge at 7500-8000 r / min for 15-17 minutes. Collect the lower solid layer and wash it 3-5 times with anhydrous ethanol. Place the solid in a muffle furnace and heat it to 500℃ at a heating rate of 2℃ / min. Hold it at this temperature for 2 hours. After cooling, grind it through a 100-mesh sieve to obtain graphene@alumina composite powder.

[0013] In a preferred embodiment of the present invention, the ratio of graphene, mixed acid and deionized water used in step b1 is 2-3g: 100-150mL: 500-750mL.

[0014] In a preferred embodiment of the present invention, the graphene in step b1 has 5-10 layers, a sheet diameter of 3-5 μm, and a purity of ≥99%; the mixed acid is a solution of concentrated sulfuric acid and concentrated nitric acid mixed in a volume ratio of 3:1; the concentration of the concentrated sulfuric acid is 80%; and the concentration of the concentrated nitric acid is 66%.

[0015] In a preferred embodiment of the present invention, the ratio of aluminum isopropoxide, anhydrous ethanol and deionized water in step b2 is 5-6g: 50-60mL: 5-6mL.

[0016] In a preferred embodiment of the present invention, the molar concentration of the dilute nitric acid in step b2 is 0.1 mol / L.

[0017] In a preferred embodiment of the present invention, the ratio of acidified graphene to alumina sol in step b3 is 2-3g: 55-82mL.

[0018] Secondly, this application provides a method for preparing a high thermal conductivity silicon nitride ceramic material, comprising the following steps: Step 1: The polydopamine / silane coupling agent co-modified hexagonal boron nitride, graphene@alumina composite powder, and mixed solvent are ultrasonically dispersed for 20-22 min. Then, the powder is added to a planetary ball mill and ball-milled for 2-3 h at a ball-to-particle ratio of 4:1 with silicon nitride balls at a speed of 200 r / min. Then, α-silicon nitride powder, yttrium oxide, alumina, and polyvinylpyrrolidone are added, and ball milling continues for 4-6 h. The slurry after ball milling is transferred to a vacuum degassing tank and degassed for 20-23 min under a vacuum of -0.09 MPa to remove bubbles and obtain silicon nitride composite slurry. Step 2: The silicon nitride composite slurry is treated with a spray dryer with an inlet temperature of 180℃ and an outlet temperature of 80℃. It is then passed through a 200-mesh sieve and placed into a graphite mold. It is then pressed at 25MPa for 8 minutes using an electric press. After that, it is vacuum sealed with plastic film and placed in a cold isostatic press at 180MPa for 12 minutes. Then, it is placed in an oven and dried at 75-80℃ for 6-7 hours. It is then placed in a high-temperature atmosphere sintering furnace and nitrogen gas is introduced at a flow rate of 200mL / min. The temperature is first increased to 700℃ at a rate of 5℃ / min and held for 3 hours. Then, the temperature is increased to 1800-1900℃ at a rate of 10℃ / min and held for 2-3 hours. Finally, the temperature is reduced to room temperature at a rate of 8℃ / min. The slurry is then cut and polished with a diamond wheel to obtain a high thermal conductivity silicon nitride ceramic material.

[0019] Thirdly, this application provides an application of a high thermal conductivity silicon nitride ceramic material in aerospace engine components, mechanical seal rings, and cutting tools.

[0020] The beneficial effects of this invention are: This invention discloses a high thermal conductivity silicon nitride ceramic material, its preparation method, and its application. The method involves ball milling and dispersing α-silicon nitride powder, yttrium oxide, alumina, polyvinylpyrrolidone, polydopamine / silane coupling agent-modified hexagonal boron nitride, and graphene@alumina composite powder, followed by dry pressing and sintering to obtain the high thermal conductivity silicon nitride ceramic material. This preparation method uses α-silicon nitride powder as the main raw material. By adding sintering aids (yttrium oxide and alumina), the sintering temperature can be significantly reduced, the compaction of the green body can be promoted, and the phase transformation and microstructure of silicon nitride can be controlled. Hexagonal boron nitride is co-modified with polydopamine / silane coupling agent to reduce interfacial phonon scattering and improve thermal conductivity, resulting in excellent mechanical and thermal properties. The addition of graphene@alumina composite powder further enhances the thermal conductivity of silicon nitride ceramics. The alumina insulating shell addresses the conductivity issue of graphene, making it more suitable for applications requiring both high thermal conductivity and insulation, such as electronic packaging and heat dissipation substrates. This results in high thermal conductivity silicon nitride ceramic materials with high thermal conductivity, excellent insulation, stable mechanical properties, and high-temperature resistance, applicable to fields such as electronics, new energy, and aerospace.

[0021] In the preparation of high thermal conductivity silicon nitride ceramic materials, a polydopamine / silane coupling agent co-modified hexagonal boron nitride was first prepared. First, hexagonal boron nitride powder was cleaned to remove impurities, resulting in pretreated hexagonal boron nitride. Then, a polydopamine coating layer was polymerized on the surface of the pretreated hexagonal boron nitride to form polydopamine-coated hexagonal boron nitride. Subsequently, it was modified using a silane coupling agent. The siloxane on the silane coupling agent KH590 hydrolyzed to form silanols, which then dehydrated, condensed, and grafted onto the surface of the polydopamine-coated hexagonal boron nitride. Simultaneously, thiol groups were introduced to enhance its reactivity. By improving the interfacial bonding, polydopamine / silane coupling agent co-modified hexagonal boron nitride was obtained. Hexagonal boron nitride has excellent thermal conductivity, and its addition to ceramic materials can significantly improve their thermal conductivity. After dual modification with polydopamine and silane coupling agent KH590, it can be uniformly dispersed during ball milling, and the large number of amino, hydroxyl, and mercapto groups on it can form chemical bonds, thus enabling it to be well distributed in the ceramic material and fully exert its thermal conductivity. At the same time, it can significantly improve the internal density of the ceramic material, thereby improving the overall performance of the ceramic material.

[0022] A graphene@alumina composite powder was prepared during the fabrication of high thermal conductivity silicon nitride ceramic materials. First, graphene was oxidized and etched using concentrated sulfuric acid and concentrated nitric acid, generating numerous hydroxyl and carboxyl groups on its surface. Aluminum isopropoxide was then hydrolyzed to prepare alumina sol. The hydroxyl and carboxyl groups on the graphene surface chemically bonded to the Al-OH groups in the alumina sol, forming a core-shell structure with alumina coating the graphene surface. Graphene forms the core and alumina the shell, resulting in the graphene@alumina composite powder. Graphene possesses ultra-high thermal conductivity, and its addition to ceramic materials significantly enhances their thermal conductivity. The dense alumina coating completely isolates graphene from external electrical contact, effectively blocking conductivity and meeting insulation requirements. Graphene@alumina improves the volume resistivity and thermal conductivity of ceramic materials, optimizes the thermal conductivity network, enhances interfacial compatibility with the silicon nitride matrix, and balances mechanical properties, making it a core candidate material for high-end heat dissipation components in fields such as electronics, new energy, and aerospace. Detailed Implementation

[0023] 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.

[0024] Example 1:

[0025] This embodiment describes a method for preparing a high thermal conductivity silicon nitride ceramic material, including the following steps: Step s1: Add 10g of hexagonal boron nitride powder (particle size of hexagonal boron nitride powder is 3μm, purity ≥99%) to 500mL of anhydrous ethanol, ultrasonically disperse for 25min at a power of 370W, then centrifuge for 15min at a speed of 7500r / min, discard the supernatant, wash the lower layer with deionized water and centrifuge twice, and finally wash once with anhydrous ethanol. Then place it in a vacuum drying oven and dry at a temperature of 55℃ for 12h. Grind it through a 100-mesh sieve to obtain pretreated hexagonal boron nitride. Step s2: Add 2.4g of tris(hydroxymethyl)aminomethane to 200mL of deionized water and stir for 15min at a stirring rate of 200r / min. Adjust the pH to 8.5 with 0.1mol / L hydrochloric acid. Then add 10g of pretreated hexagonal boron nitride and ultrasonically disperse for 20min at a power of 270W. Then add 0.5g of dopamine hydrochloride and magnetically stir for 10h at a stirring rate of 400r / min. Then centrifuge for 15min at a speed of 7500r / min. Collect the lower solid and wash it three times alternately with deionized water and anhydrous ethanol. Then place it in a vacuum drying oven and dry it at a temperature of 65℃ for 8h. Grind it through a 100-mesh sieve to obtain polydopamine-coated hexagonal boron nitride. Step s3: Add 1.5g of silane coupling agent (KH590) to 100mL of anhydrous ethanol, stir for 10min at a stirring rate of 200r / min, add 2mL of deionized water, continue stirring for 30min, then add 5g of polydopamine-coated hexagonal boron nitride, ultrasonically disperse for 20min at a power of 270W, heat to 55℃, and magnetically stir at a stirring rate of 300r / min for 4h. Then centrifuge at a speed of 7500r / min for 15min, collect the solid and wash it 3 times with anhydrous ethanol, then place it in a vacuum drying oven and dry it at a temperature of 60℃ for 10h. Grind it through a 100-mesh sieve to obtain polydopamine / silane coupling agent co-modified hexagonal boron nitride. Step s4: Add 2g of graphene (graphene with 5 layers, a sheet diameter of 3μm, and a purity ≥99%) and 100mL of mixed acid (mixed acid is a solution of concentrated sulfuric acid and concentrated nitric acid mixed in a volume ratio of 3:1; the concentration of concentrated sulfuric acid is 80%; the concentration of concentrated nitric acid is 66%) to a beaker, place it in an ice-water bath at 0℃, and magnetically stir for 30min at a stirring rate of 200r / min. Then transfer it to an oil bath and stir at a constant temperature of 45℃ for 4h to obtain a mixed solution. Pour the mixed solution into 500mL of deionized water, stir to dilute, filter through a 0.22μm filter membrane, wash the filter cake with deionized water until the pH of the filtrate is 6, then place the filter cake in a vacuum drying oven and dry at 55℃ for 8h. Grind it through a 100-mesh sieve to obtain acidified graphene. Step s5: Add 5g of aluminum isopropoxide and 50mL of anhydrous ethanol to a three-necked flask equipped with a stirrer, thermometer, gas delivery tube and constant pressure dropping funnel. Purge with nitrogen for protection and magnetically stir for 30min at 25℃ and 200r / min. Then, while stirring, add 5mL of deionized water dropwise at a rate of 1 drop / s. Simultaneously, add 0.1mol / L dilute nitric acid to adjust the pH to 3.5. After the addition is complete, raise the temperature to 60℃ and continue stirring for 2h to form an alumina sol. Step s6: Add 2g of acidified graphene to 55mL of alumina sol and ultrasonically disperse it for 30min at a power of 400W. Use intermittent ultrasonication, working for 3s and stopping for 2s. Then transfer it to a constant temperature magnetic stirrer and stir at 75℃ for 4h. After cooling to room temperature, centrifuge at 7500r / min for 15min. Collect the lower solid and wash it 3 times with anhydrous ethanol. Put the solid into a muffle furnace and heat it to 500℃ at a heating rate of 2℃ / min. Hold it at this temperature for 2h. After cooling, grind it through a 100-mesh sieve to obtain graphene@alumina composite powder. Step s7: 3 parts of polydopamine / silane coupling agent co-modified hexagonal boron nitride, 0.1 parts of graphene@alumina composite powder, and 150 parts of mixed solvent (a solution of anhydrous ethanol and deionized water in a volume ratio of 1:1) were ultrasonically dispersed for 20 min. Then, the mixture was added to a planetary ball mill and ball-milled for 2 h at a ball-to-material ratio of 4:1 using silicon nitride balls at a speed of 200 r / min. After that, 40 parts of α-silicon nitride powder (CAS No. 12033-89-5), 2 parts of yttrium oxide (particle size 1 μm), 1 part of alumina (particle size 0.5 μm), and 0.24 parts of polyvinylpyrrolidone (CAS No. 9003-39-8) were added, and ball milling continued for 4 h. The ball-milled slurry was transferred to a vacuum degassing tank and degassed for 20 min under a vacuum of -0.09 MPa to remove bubbles and obtain silicon nitride composite slurry. Step s8: The silicon nitride composite slurry is treated with a spray dryer with an inlet temperature of 180℃ and an outlet temperature of 80℃. It is then passed through a 200-mesh sieve and loaded into a graphite mold. It is then pressed at 25MPa for 8 minutes using an electric press. After that, it is vacuum sealed with plastic film and placed in a cold isostatic press at 180MPa for 12 minutes. After that, it is placed in an oven and dried at 75℃ for 6 hours. Then, it is placed in a high-temperature atmosphere sintering furnace and nitrogen gas is introduced at a flow rate of 200mL / min. The temperature is first increased to 700℃ at a heating rate of 5℃ / min and held for 3 hours. Then, the temperature is increased to 1800℃ at a heating rate of 10℃ / min and held for 2 hours. Finally, the temperature is reduced to room temperature at a cooling rate of 8℃ / min. The slurry is then cut and polished with a diamond wheel to obtain a high thermal conductivity silicon nitride ceramic material.

[0026] Example 2:

[0027] This embodiment describes a method for preparing a high thermal conductivity silicon nitride ceramic material, including the following steps: Step s1: Add 10.5g of hexagonal boron nitride powder (particle size of hexagonal boron nitride powder is 4μm, purity ≥99%) to 530mL of anhydrous ethanol, ultrasonically disperse for 27min at a power of 380W, then centrifuge for 16min at a speed of 7700r / min, discard the supernatant, wash the lower layer with deionized water and centrifuge twice, and finally wash once with anhydrous ethanol. Then place it in a vacuum drying oven and dry at a temperature of 57℃ for 13h. Grind it through a 100-mesh sieve to obtain pretreated hexagonal boron nitride. Step s2: Add 2.8g of tris(hydroxymethyl)aminomethane to 240mL of deionized water and stir for 20min at a stirring rate of 250r / min. Adjust the pH to 8.5 with 0.1mol / L hydrochloric acid. Then add 12g of pretreated hexagonal boron nitride and ultrasonically disperse for 21min at a power of 280W. Then add 0.6g of dopamine hydrochloride and magnetically stir for 11h at a stirring rate of 430r / min. Then centrifuge for 16min at a speed of 7700r / min. Collect the lower solid and wash it three times alternately with deionized water and anhydrous ethanol. Then place it in a vacuum drying oven and dry it at a temperature of 68℃ for 8.5h. Grind it through a 100-mesh sieve to obtain polydopamine-coated hexagonal boron nitride. Step s3: Add 1.6g of silane coupling agent (KH590) to 110mL of anhydrous ethanol, stir for 11min at a stirring rate of 250r / min, add 2.5mL of deionized water dropwise, continue stirring for 33min, then add 5.5g of polydopamine-coated hexagonal boron nitride, ultrasonically disperse for 22min at a power of 280W, heat to 55℃, and magnetically stir at a stirring rate of 330r / min for 5h. Then centrifuge at a speed of 7800r / min for 16min, collect the solid and wash it 4 times with anhydrous ethanol, then place it in a vacuum drying oven and dry it at a temperature of 63℃ for 11h. Grind it through a 100-mesh sieve to obtain polydopamine / silane coupling agent co-modified hexagonal boron nitride. Step s4: Add 2.5g of graphene (7 layers, 4μm diameter, purity ≥99%) and 130mL of mixed acid (a solution of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1; the concentration of concentrated sulfuric acid is 80%; the concentration of concentrated nitric acid is 66%) to a beaker and place it in an ice-water bath at 2℃. Stir magnetically for 33min at a stirring rate of 250r / min. Then transfer it to an oil bath and stir at a constant temperature of 47℃ for 4.5h to obtain a mixed solution. Pour the mixed solution into 700mL of deionized water and stir to dilute. Filter through a 0.22μm filter membrane. Wash the filter cake with deionized water until the pH of the filtrate is 6. Then place the filter cake in a vacuum drying oven and dry at 57℃ for 8.5h. Grind it through a 100-mesh sieve to obtain acidified graphene. Step s5: Add 5.5g of aluminum isopropoxide and 55mL of anhydrous ethanol to a three-necked flask equipped with a stirrer, thermometer, gas delivery tube and constant pressure dropping funnel. Purge with nitrogen for protection and magnetically stir for 33min at 27℃ and 250r / min. Then, while stirring, add 5.5mL of deionized water dropwise at a rate of 1 drop / s. Simultaneously, add 0.1mol / L dilute nitric acid to adjust the pH to 3.7. After the addition is complete, continue stirring at 60℃ for 2.5h to form an alumina sol. Step s6: Add 2.5g of acidified graphene to 75mL of alumina sol and ultrasonically disperse it for 31min at a power of 400W. Use intermittent ultrasonication, working for 3s and stopping for 2s. Then transfer it to a constant temperature magnetic stirrer and stir at 77℃ for 4.5h. After cooling to room temperature, centrifuge at 7800r / min for 16min. Collect the lower solid and wash it 4 times with anhydrous ethanol. Put the solid into a muffle furnace and heat it to 500℃ at a heating rate of 2℃ / min. Hold it at this temperature for 2h. After cooling, grind it through a 100-mesh sieve to obtain graphene@alumina composite powder. Step s7: 3.5 parts of polydopamine / silane coupling agent co-modified hexagonal boron nitride, 0.3 parts of graphene@alumina composite powder, and 155 parts of mixed solvent (a solution of anhydrous ethanol and deionized water in a 1:1 volume ratio) were ultrasonically dispersed for 21 min. Then, the mixture was added to a planetary ball mill and ball-milled for 2.5 h at a ball-to-material ratio of 4:1 using silicon nitride balls at 200 r / min. Afterward, 41 parts of α-coupling agent were added. - Silicon nitride powder (CAS No. 12033-89-5), 2.5 parts yttrium oxide (particle size 1-3 μm), 1.2 parts alumina (particle size 0.8 μm) and 0.25 parts polyvinylpyrrolidone (CAS No. 9003-39-8) were ball-milled for 5 hours. The ball-milled slurry was then transferred to a vacuum degassing tank and degassed for 21 minutes under a vacuum of -0.09 MPa to remove bubbles and obtain a silicon nitride composite slurry. Step s8: The silicon nitride composite slurry is treated with a spray dryer with an inlet temperature of 180℃ and an outlet temperature of 80℃. It is then passed through a 200-mesh sieve, loaded into a graphite mold, and pressed at 25MPa for 8 minutes using an electric press. After that, it is vacuum sealed with plastic film and placed in a cold isostatic press at 180MPa for 12 minutes. Then, it is placed in an oven and dried at 77℃ for 6.5 hours. It is then placed in a high-temperature atmosphere sintering furnace, and nitrogen gas is introduced at a flow rate of 200mL / min. The temperature is first increased to 700℃ at a rate of 5℃ / min and held for 3 hours. Then, the temperature is increased to 1850℃ at a rate of 10℃ / min and held for 2.5 hours. Finally, the temperature is reduced to room temperature at a rate of 8℃ / min. The slurry is then cut and polished with a diamond wheel to obtain a high thermal conductivity silicon nitride ceramic material.

[0028] Example 3:

[0029] This embodiment describes a method for preparing a high thermal conductivity silicon nitride ceramic material, including the following steps: Step s1: Add 11g of hexagonal boron nitride powder (particle size of hexagonal boron nitride powder is 5μm, purity ≥99%) to 550mL of anhydrous ethanol, ultrasonically disperse for 30min at a power of 400W, then centrifuge for 17min at a speed of 8000r / min, discard the supernatant, wash the lower layer with deionized water and centrifuge 3 times, and finally wash once with anhydrous ethanol. Then place it in a vacuum drying oven and dry at a temperature of 60℃ for 14h. Grind it through a 100-mesh sieve to obtain pretreated hexagonal boron nitride. Step s2: Add 3.3g of tris(hydroxymethyl)aminomethane to 280mL of deionized water and stir for 25min at a stirring rate of 300r / min. Adjust the pH to 8.5 with 0.1mol / L hydrochloric acid. Then add 14g of pretreated hexagonal boron nitride and ultrasonically disperse for 22min at a power of 300W. Then add 0.7g of dopamine hydrochloride and magnetically stir for 12h at a stirring rate of 450r / min. Then centrifuge for 17min at a speed of 8000r / min. Collect the lower solid and wash it 4 times alternately with deionized water and anhydrous ethanol. Then place it in a vacuum drying oven and dry it at a temperature of 70℃ for 9h. Grind it through a 100-mesh sieve to obtain polydopamine-coated hexagonal boron nitride. Step s3: Add 1.7g of silane coupling agent (KH590) to 120mL of anhydrous ethanol, stir for 12min at a stirring rate of 300r / min, add 3mL of deionized water dropwise, continue stirring for 35min, then add 6g of polydopamine-coated hexagonal boron nitride, ultrasonically disperse for 23min at a power of 300W, heat to 55℃, and magnetically stir at a stirring rate of 350r / min for 6h, then centrifuge at a speed of 8000r / min for 17min, collect the solid and wash it 4 times with anhydrous ethanol, then place it in a vacuum drying oven and dry it at a temperature of 65℃ for 12h, grind it through a 100-mesh sieve to obtain polydopamine / silane coupling agent co-modified hexagonal boron nitride; Step s4: Add 3g of graphene (10 layers, 5μm diameter, purity ≥99%) and 150mL of mixed acid (a solution of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1; the concentration of concentrated sulfuric acid is 80%; the concentration of concentrated nitric acid is 66%) to a beaker and place it in an ice-water bath at 4℃. Stir magnetically for 35min at a stirring rate of 300r / min. Then transfer it to an oil bath and stir at a constant temperature of 50℃ for 5h to obtain a mixed solution. Pour the mixed solution into 750mL of deionized water and stir to dilute. Filter through a 0.22μm filter membrane. Wash the filter cake with deionized water until the pH of the filtrate is 7. Then place the filter cake in a vacuum drying oven and dry at 60℃ for 9h. Grind it through a 100-mesh sieve to obtain acidified graphene. Step s5: Add 6g of aluminum isopropoxide and 60mL of anhydrous ethanol to a three-necked flask equipped with a stirrer, thermometer, gas delivery tube and constant pressure dropping funnel. Purge with nitrogen for protection and magnetically stir for 35min at 30℃ and 300r / min. Then, while stirring, add 6mL of deionized water dropwise at a rate of 2 drops / s. Simultaneously, add 0.1mol / L dilute nitric acid to adjust the pH to 4.0. After the addition is complete, raise the temperature to 60℃ and continue stirring for 3h to form an alumina sol. Step s6: Add 3g of acidified graphene to 82mL of alumina sol and ultrasonically disperse it for 32min at a power of 400W. Use intermittent ultrasonication, working for 3s and stopping for 2s. Then transfer it to a constant temperature magnetic stirrer and stir at 80℃ for 5h. After cooling to room temperature, centrifuge at 8000r / min for 17min. Collect the lower solid and wash it 5 times with anhydrous ethanol. Put the solid into a muffle furnace and heat it to 500℃ at a heating rate of 2℃ / min. Hold it at this temperature for 2h. After cooling, grind it through a 100-mesh sieve to obtain graphene@alumina composite powder. Step s7: 4 parts of polydopamine / silane coupling agent co-modified hexagonal boron nitride, 0.5 parts of graphene@alumina composite powder, and 160 parts of mixed solvent (a solution of anhydrous ethanol and deionized water in a volume ratio of 1:1) were ultrasonically dispersed for 22 min. Then, the mixture was added to a planetary ball mill and ball-milled for 3 h at a ball-to-material ratio of 4:1 using silicon nitride balls at a speed of 200 r / min. After that, 42 parts of α-silicon nitride powder (CAS No. 12033-89-5), 3 parts of yttrium oxide (particle size 3 μm), 1.5 parts of alumina (particle size 1 μm), and 0.26 parts of polyvinylpyrrolidone (CAS No. 9003-39-8) were added, and ball milling continued for 6 h. The ball-milled slurry was transferred to a vacuum degassing tank and degassed for 23 min under a vacuum of -0.09 MPa to remove bubbles and obtain silicon nitride composite slurry. Step s8: The silicon nitride composite slurry is treated with a spray dryer with an inlet temperature of 180℃ and an outlet temperature of 80℃. It is then passed through a 200-mesh sieve, loaded into a graphite mold, and pressed at 25MPa for 8 minutes using an electric press. After that, it is vacuum sealed with plastic film and placed in a cold isostatic press at 180MPa for 12 minutes. Then, it is placed in an oven and dried at 80℃ for 7 hours. It is then placed in a high-temperature atmosphere sintering furnace, and nitrogen gas is introduced at a flow rate of 200mL / min. The temperature is first increased to 700℃ at a rate of 5℃ / min and held for 3 hours. Then, the temperature is increased to 1900℃ at a rate of 10℃ / min and held for 3 hours. Finally, the temperature is reduced to room temperature at a rate of 8℃ / min. The slurry is then cut and polished with a diamond wheel to obtain a high thermal conductivity silicon nitride ceramic material.

[0030] Comparative Example 1: This comparative example illustrates a method for preparing a high thermal conductivity silicon nitride ceramic material, comprising the following steps: Step s1: Add 10g of hexagonal boron nitride powder (particle size of hexagonal boron nitride powder is 3μm, purity ≥99%) to 500mL of anhydrous ethanol, ultrasonically disperse for 25min at a power of 370W, then centrifuge for 15min at a speed of 7500r / min, discard the supernatant, wash the lower layer with deionized water and centrifuge twice, and finally wash once with anhydrous ethanol. Then place it in a vacuum drying oven and dry at a temperature of 55℃ for 12h. Grind it through a 100-mesh sieve to obtain pretreated hexagonal boron nitride. Step s2: Add 2.4g of tris(hydroxymethyl)aminomethane to 200mL of deionized water and stir for 15min at a stirring rate of 200r / min. Adjust the pH to 8.5 with 0.1mol / L hydrochloric acid. Then add 10g of pretreated hexagonal boron nitride and ultrasonically disperse for 20min at a power of 270W. Then add 0.5g of dopamine hydrochloride and magnetically stir for 10h at a stirring rate of 400r / min. Then centrifuge for 15min at a speed of 7500r / min. Collect the lower solid and wash it three times alternately with deionized water and anhydrous ethanol. Then place it in a vacuum drying oven and dry it at a temperature of 65℃ for 8h. Grind it through a 100-mesh sieve to obtain polydopamine-coated hexagonal boron nitride. Step s3: Add 1.5g of silane coupling agent (KH590) to 100mL of anhydrous ethanol, stir for 10min at a stirring rate of 200r / min, add 2mL of deionized water, continue stirring for 30min, then add 5g of polydopamine-coated hexagonal boron nitride, ultrasonically disperse for 20min at a power of 270W, heat to 55℃, and magnetically stir at a stirring rate of 300r / min for 4h. Then centrifuge at a speed of 7500r / min for 15min, collect the solid and wash it 3 times with anhydrous ethanol, then place it in a vacuum drying oven and dry it at a temperature of 60℃ for 10h. Grind it through a 100-mesh sieve to obtain polydopamine / silane coupling agent co-modified hexagonal boron nitride. Step s4: 3 parts of polydopamine / silane coupling agent co-modified hexagonal boron nitride and 150 parts of mixed solvent (the mixed solvent is a solution of anhydrous ethanol and deionized water mixed in a volume ratio of 1:1) are ultrasonically dispersed for 20 min. Then, they are added to a planetary ball mill and ball-milled for 2 h at a ball-to-material ratio of 4:1 with silicon nitride balls at a speed of 200 r / min. Then, 40 parts of α-silicon nitride powder (CAS No. 12033-89-5), 2 parts of yttrium oxide (particle size 1 μm), 1 part of alumina (particle size 0.5 μm) and 0.24 parts of polyvinylpyrrolidone (CAS No. 9003-39-8) are added, and ball milling continues for 4 h. The ball-milled slurry is transferred to a vacuum degassing tank and degassed for 20 min under a vacuum of -0.09 MPa to remove bubbles and obtain silicon nitride composite slurry. Step s5: The silicon nitride composite slurry is treated with a spray dryer with an inlet temperature of 180℃ and an outlet temperature of 80℃. It is then passed through a 200-mesh sieve and loaded into a graphite mold. It is then pressed at 25MPa for 8 minutes using an electric press. After that, it is vacuum sealed with plastic film and placed in a cold isostatic press at 180MPa for 12 minutes. After that, it is placed in an oven and dried at 75℃ for 6 hours. Then, it is placed in a high-temperature atmosphere sintering furnace and nitrogen gas is introduced at a flow rate of 200mL / min. The temperature is first increased to 700℃ at a heating rate of 5℃ / min and held for 3 hours. Then, the temperature is increased to 1800℃ at a heating rate of 10℃ / min and held for 2 hours. Finally, the temperature is reduced to room temperature at a cooling rate of 8℃ / min. The slurry is then cut and polished with a diamond wheel to obtain a high thermal conductivity silicon nitride ceramic material.

[0031] Comparative Example 2: This comparative example illustrates a method for preparing a high thermal conductivity silicon nitride ceramic material, comprising the following steps: Step s1: Add 2g of graphene (graphene with 5 layers, a sheet diameter of 3μm, and a purity ≥99%) and 100mL of mixed acid (mixed acid is a solution of concentrated sulfuric acid and concentrated nitric acid mixed in a volume ratio of 3:1; the concentration of concentrated sulfuric acid is 80%; the concentration of concentrated nitric acid is 66%) to a beaker, place it in an ice-water bath at 0℃, and magnetically stir for 30min at a stirring rate of 200r / min. Then transfer it to an oil bath and stir at a constant temperature of 45℃ for 4h to obtain a mixed solution. Pour the mixed solution into 500mL of deionized water, stir to dilute, filter with a 0.22μm filter membrane, wash the filter cake with deionized water until the pH of the filtrate is 6, then place the filter cake in a vacuum drying oven and dry at a temperature of 55℃ for 8h. Grind it through a 100-mesh sieve to obtain acidified graphene. Step s2: Add 5g of aluminum isopropoxide and 50mL of anhydrous ethanol to a three-necked flask equipped with a stirrer, thermometer, gas delivery tube and constant pressure dropping funnel. Purge with nitrogen for protection and magnetically stir for 30min at 25℃ and 200r / min. Then, while stirring, add 5mL of deionized water dropwise at a rate of 1 drop / s. Simultaneously, add 0.1mol / L dilute nitric acid to adjust the pH to 3.5. After the addition is complete, raise the temperature to 60℃ and continue stirring for 2h to form an alumina sol. Step s3: Add 2g of acidified graphene to 55mL of alumina sol and ultrasonically disperse it for 30min at a power of 400W. Use intermittent ultrasonication, working for 3s and stopping for 2s. Then transfer it to a constant temperature magnetic stirrer and stir for 4h at a temperature of 75℃. After cooling to room temperature, centrifuge at a speed of 7500r / min for 15min. Collect the lower solid and wash it 3 times with anhydrous ethanol. Put the solid into a muffle furnace and heat it to 500℃ at a heating rate of 2℃ / min. Hold it at this temperature for 2h. After cooling, grind it through a 100-mesh sieve to obtain graphene@alumina composite powder. Step s4: 0.1 parts of graphene@alumina composite powder and 150 parts of mixed solvent (the mixed solvent is a solution of anhydrous ethanol and deionized water mixed in a volume ratio of 1:1) are ultrasonically dispersed for 20 min. Then, the mixture is added to a planetary ball mill and ball-milled for 2 h at a ball-to-material ratio of 4:1 using silicon nitride balls at a speed of 200 r / min. After that, 40 parts of α-silicon nitride powder (CAS No. 12033-89-5), 2 parts of yttrium oxide (particle size 1 μm), 1 part of alumina (particle size 0.5 μm) and 0.24 parts of polyvinylpyrrolidone (CAS No. 9003-39-8) are added, and ball milling continues for 4 h. The ball-milled slurry is transferred to a vacuum degassing tank and degassed for 20 min under a vacuum of -0.09 MPa to remove bubbles and obtain silicon nitride composite slurry. Step s5: The silicon nitride composite slurry is treated with a spray dryer with an inlet temperature of 180℃ and an outlet temperature of 80℃. It is then passed through a 200-mesh sieve and loaded into a graphite mold. It is then pressed at 25MPa for 8 minutes using an electric press. After that, it is vacuum sealed with plastic film and placed in a cold isostatic press at 180MPa for 12 minutes. After that, it is placed in an oven and dried at 75℃ for 6 hours. Then, it is placed in a high-temperature atmosphere sintering furnace and nitrogen gas is introduced at a flow rate of 200mL / min. The temperature is first increased to 700℃ at a heating rate of 5℃ / min and held for 3 hours. Then, the temperature is increased to 1800℃ at a heating rate of 10℃ / min and held for 2 hours. Finally, the temperature is reduced to room temperature at a cooling rate of 8℃ / min. The slurry is then cut and polished with a diamond wheel to obtain a high thermal conductivity silicon nitride ceramic material.

[0032] Comparative Example 3: This comparative example illustrates a method for preparing a high thermal conductivity silicon nitride ceramic material, comprising the following steps: Step s1: Add 150 parts of mixed solvent (a solution of anhydrous ethanol and deionized water in a volume ratio of 1:1) to a planetary ball mill. Use silicon nitride balls with a ball-to-material ratio of 4:1. Add 40 parts of α-silicon nitride powder (CAS No. 12033-89-5), 2 parts of yttrium oxide (particle size 1 μm), 1 part of alumina (particle size 0.5 μm), and 0.24 parts of polyvinylpyrrolidone (CAS No. 9003-39-8). Ball mill for 4 hours. Transfer the ball-milled slurry to a vacuum degassing tank and degas for 20 minutes under a vacuum of -0.09 MPa to remove bubbles and obtain silicon nitride composite slurry. Step s2: The silicon nitride composite slurry was treated with a spray dryer with an inlet temperature of 180℃ and an outlet temperature of 80℃. It was then passed through a 200-mesh sieve and placed into a graphite mold. It was then pressed at 25MPa for 8 minutes using an electric press. After that, it was vacuum sealed with plastic film and placed in a cold isostatic press at 180MPa for 12 minutes. After that, it was placed in an oven and dried at 75℃ for 6 hours. Then, it was placed in a high-temperature atmosphere sintering furnace and nitrogen gas was introduced at a flow rate of 200mL / min. The temperature was first increased to 700℃ at a rate of 5℃ / min and held for 3 hours. Then, the temperature was increased to 1800℃ at a rate of 10℃ / min and held for 2 hours. Finally, the temperature was reduced to room temperature at a rate of 8℃ / min. The slurry was then cut and polished with a diamond wheel to obtain a high thermal conductivity silicon nitride ceramic material.

[0033] Performance testing: The thermal conductivity of the high thermal conductivity silicon nitride ceramic materials of Examples 1-3 and Comparative Examples 1-3 was determined according to GB / T 22588-2008 "Determination of Thermal Diffusion Coefficient of Solid Materials by Flash Method"; the flexural strength was determined according to GB / T 6569-2006 "Test Method for Bending Strength of Fine Ceramics"; the relative density was determined according to GB / T 25995-2010 "Test Method for Density and Apparent Porosity of Fine Ceramics"; the Vickers hardness was determined according to GB / T 16534-2009 "Test Method for Vickers Hardness of Fine Ceramics"; and the volume resistivity was determined according to GB / T1410-2006 "Test Method for Volume Resistivity and Surface Resistivity of Solid Insulating Materials".

[0034] The test results are shown in the table below:

[0035] Referring to the table above, based on the comparison between Examples 1-3 and Comparative Examples 1-3, it can be seen that a high thermal conductivity silicon nitride ceramic material has high thermal conductivity, excellent insulation properties, and stable mechanical properties.

[0036] Based on the comparison between Example 1 and Comparative Example 1, it can be seen that polydopamine / silane coupling agent co-modified hexagonal boron nitride can reduce interfacial phonon scattering and improve thermal conductivity, giving it excellent mechanical and thermal properties. Graphene@alumina can improve the volume resistivity and thermal conductivity of ceramic materials. The ceramic material obtained by adding polydopamine / silane coupling agent co-modified hexagonal boron nitride and graphene@alumina composite powder to silicon nitride has better performance than the ceramic material obtained by adding polydopamine / silane coupling agent co-modified hexagonal boron nitride to silicon nitride. Based on the comparison between Example 1 and Comparative Example 2, it can be seen that the ceramic material obtained by adding polydopamine / silane coupling agent to silicon nitride to modify hexagonal boron nitride and graphene@alumina composite powder has better performance than the ceramic material obtained by adding graphene@alumina composite powder to silicon nitride. Based on the comparison between Example 1 and Comparative Example 3, it can be seen that the ceramic material obtained by co-modifying hexagonal boron nitride and graphene@alumina composite powder by adding polydopamine / silane coupling agent to silicon nitride has better performance than the ceramic material obtained by silicon nitride.

[0037] 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.

[0038] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in this application, they should all fall within the protection scope of the present invention.

Claims

1. A high thermal conductivity silicon nitride ceramic material, characterized in that, Includes the following components by weight: The composition includes 3-4 parts of polydopamine / silane coupling agent co-modified hexagonal boron nitride, 0.1-0.5 parts of graphene@alumina composite powder, 150-160 parts of mixed solvent, 40-42 parts of α-silicon nitride powder, 2-3 parts of yttrium oxide, 1-1.5 parts of alumina, and 0.24-0.26 parts of polyvinylpyrrolidone. The polydopamine / silane coupling agent co-modified hexagonal boron nitride is prepared by the following steps: Step a1: Add hexagonal boron nitride powder to anhydrous ethanol, disperse by ultrasonication, centrifuge, wash and centrifuge repeatedly, dry, grind and sieve to obtain pretreated hexagonal boron nitride; Step a2: Tris(hydroxymethyl)aminomethane was added to deionized water, stirred and reacted, pH was adjusted, pretreated hexagonal boron nitride was added, ultrasonic dispersion was performed, dopamine hydrochloride was added, magnetic stirring was performed, centrifuged, washed, dried, ground and sieved to obtain polydopamine-coated hexagonal boron nitride. Step a3: Add the silane coupling agent to anhydrous ethanol and stir, add deionized water dropwise, continue stirring, add polydopamine-coated hexagonal boron nitride, ultrasonically disperse, heat, magnetically stir, centrifuge, wash, dry, grind and sieve to obtain polydopamine / silane coupling agent co-modified hexagonal boron nitride.

2. The high thermal conductivity silicon nitride ceramic material according to claim 1, characterized in that, The mixed solvent is a solution of anhydrous ethanol and deionized water mixed in a volume ratio of 1:1; the CAS number of the α-silicon nitride powder is 12033-89-5; the particle size of the yttrium oxide is 1-3 μm; the particle size of the alumina is 0.5-1 μm; and the CAS number of the polyvinylpyrrolidone is 9003-39-8. In step a1, the ratio of hexagonal boron nitride powder to anhydrous ethanol is 10-11g: 500-550mL; the particle size of the hexagonal boron nitride powder is 3-5μm, and the purity is ≥99%.

3. The high thermal conductivity silicon nitride ceramic material according to claim 1, characterized in that, In step a2, the ratio of tris(hydroxymethyl)aminomethane, deionized water, pretreated hexagonal boron nitride, and dopamine hydrochloride is 2.4-3.3 g: 200-280 mL: 10-14 g: 0.5-0.7 g; the molar concentration of the hydrochloric acid is 0.1 mol / L.

4. The high thermal conductivity silicon nitride ceramic material according to claim 1, characterized in that, In step a3, the ratio of the silane coupling agent, anhydrous ethanol, deionized water, and polydopamine-coated hexagonal boron nitride is 1.5-1.7g: 100-120mL: 2-3mL: 5-6g; the silane coupling agent is KH590.

5. The high thermal conductivity silicon nitride ceramic material according to claim 1, characterized in that, The graphene@alumina composite powder is prepared by the following steps: Step b1: Add graphene and mixed acid to a beaker, stir to obtain a mixture, pour the mixture into deionized water, stir to dilute, filter, wash, dry, grind and sieve to obtain acidified graphene; Step b2: Stir aluminum isopropoxide and anhydrous ethanol magnetically, add deionized water, adjust the pH, heat and continue stirring to form an alumina sol; Step b3: Add acidified graphene to alumina sol for ultrasonic dispersion, stir, then cool, centrifuge, wash, sinter, cool, grind and sieve to obtain graphene@alumina composite powder.

6. The high thermal conductivity silicon nitride ceramic material according to claim 5, characterized in that, In step b1, the ratio of graphene, mixed acid, and deionized water is 2-3g: 100-150mL: 500-750mL; the graphene has 5-10 layers, a sheet diameter of 3-5μm, and a purity ≥99%; the mixed acid is a solution of concentrated sulfuric acid and concentrated nitric acid mixed in a volume ratio of 3:1; the concentration of the concentrated sulfuric acid is 80%; and the concentration of the concentrated nitric acid is 66%.

7. The high thermal conductivity silicon nitride ceramic material according to claim 5, characterized in that, The ratio of aluminum isopropoxide, anhydrous ethanol, and deionized water used in step b2 is 5-6g: 50-60mL: 5-6mL.

8. The high thermal conductivity silicon nitride ceramic material according to claim 5, characterized in that, The ratio of acidified graphene to alumina sol in step b3 is 2-3g: 55-82mL.

9. A method for preparing a high thermal conductivity silicon nitride ceramic material, characterized in that, The preparation of the high thermal conductivity silicon nitride ceramic material as described in any one of claims 1-8 includes the following steps: Step 1: Ultrasonic dispersion of polydopamine / silane coupling agent co-modified hexagonal boron nitride, graphene@alumina composite powder and mixed solvent, ball milling, then addition of α-silicon nitride powder, yttrium oxide, alumina and polyvinylpyrrolidone, ball milling continued, degassing, to obtain silicon nitride composite slurry; Step 2: The silicon nitride composite slurry is treated with a spray dryer, sieved, then placed into a graphite mold for pressure holding, then placed in a cold isostatic press for pressure holding, drying, sintering, cooling, cutting, and polishing to obtain a high thermal conductivity silicon nitride ceramic material.

10. The application of a high thermal conductivity silicon nitride ceramic material as described in any one of claims 1-8 in the fields of aerospace engine components, mechanical seal rings, and cutting tools.

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