Silicon nitride ceramic and preparation method thereof

Abstract

The invention discloses a silicon nitride ceramic and a preparation method thereof, and relates to the technical field of mechanical industry material preparation, and the silicon nitride ceramic comprises the following raw material components: Y2O3, YF3, ZrO2 and alpha-Si3N4. The silicon nitride ceramic provided by the invention has high strength and high toughness.

Description

Technical Field

[0001] This application relates to the field of materials preparation technology in the machinery industry, and in particular to a silicon nitride ceramic and its preparation method. Background Technology

[0002] As modern manufacturing develops towards high speed, precision, and efficiency, the demand for high-performance, high-temperature structural components (such as high-end bearings and cutting tools) is becoming increasingly urgent. Especially when machining difficult-to-machine materials such as high-strength alloys and composite materials, traditional cemented carbide and tool steel, due to their limited heat resistance, wear resistance, and high-temperature hardness, are no longer able to meet the stringent machining requirements.

[0003] Silicon nitride ceramics, due to their excellent high-temperature mechanical properties, outstanding thermal stability, good chemical inertness, and high fracture toughness, have become a promising high-temperature structural ceramic material, and are currently widely used in precision bearings, cutting tools, aerospace engine components, and other fields. However, the brittleness of ceramic materials greatly limits their application in these fields. Therefore, it is necessary to research ceramic materials that combine good toughness with excellent high strength to broaden their application range. Summary of the Invention

[0004] This application provides a silicon nitride ceramic and a method for preparing the same, wherein the silicon nitride ceramic has both high toughness and high strength.

[0005] In a first aspect, this application provides a silicon nitride ceramic, wherein the raw material components of the silicon nitride ceramic include: Y2O3, YF3, ZrO2 and α-Si3N4.

[0006] In some embodiments, the mass percentage of Y2O3 is 3-5% based on the total mass of the raw material components of the silicon nitride ceramic.

[0007] In some embodiments, the mass percentage of YF3 is 4-6% based on the total mass of the raw material components of the silicon nitride ceramic.

[0008] In some embodiments, the ZrO2 mass percentage is 1-2% based on the total mass of the raw material components of the silicon nitride ceramic.

[0009] In some embodiments, the Y2O3 has a purity of 99.9% and a D50 particle size of less than 50 μm.

[0010] In some embodiments, the α-Si3N4 has a purity of 99%, a D50 particle size of less than 10 μm, an α-phase content of more than 90%, and an oxygen content of less than 1 wt%.

[0011] In some embodiments, the YF3 has a purity of 99.99% and a D50 particle size of less than 100 μm.

[0012] In some embodiments, the ZrO2 has a purity of 99.9% and a D50 particle size of less than 10 μm.

[0013] In some embodiments, the raw material components of the silicon nitride ceramic also include binders and solvents.

[0014] In some embodiments, the adhesive comprises polyvinyl butyral.

[0015] In some embodiments, the solvent includes ethanol.

[0016] Secondly, this application provides a method for preparing the silicon nitride ceramic described in the first aspect, comprising: After mixing α-Si3N4, Y2O3, YF3, ZrO2, binder and solvent, the mixture was ball-milled and dried for the first time to obtain a mixture. The mixture is sieved, pressed into shape, and dried a second time to obtain a silicon nitride ceramic intermediate. Silicon nitride ceramic intermediates are sintered to obtain silicon nitride ceramics.

[0017] In some embodiments, the grinding balls of the ball mill include ZrO2 grinding balls.

[0018] In some embodiments, the ZrO2 ball milling tool includes ZrO2 ball milling tools with a diameter of 4-6 mm and ZrO2 ball milling tools with a diameter of 8-12 mm.

[0019] In some embodiments, the mass ratio of the ball mill, dry mix, and solvent is 10:1:(1.2-1.8), wherein the mass of the dry mix is ​​the total mass of α-Si3N4, Y2O3, YF3, ZrO2, and binder.

[0020] In some embodiments, the temperature of the first drying is 60-100°C.

[0021] In some embodiments, the first drying time is 12-24 hours.

[0022] In some embodiments, the pressure of the compression is 25-35 MPa.

[0023] In some embodiments, the pressing time is 1-2 minutes.

[0024] In some embodiments, the temperature of the second drying is 60-100°C.

[0025] In some embodiments, the second drying time is 12-24 hours.

[0026] In some embodiments, the sintering temperature is 1700-1900°C.

[0027] In some embodiments, the sintering atmosphere includes nitrogen.

[0028] In some embodiments, the sintering pressure is 40-50 MPa.

[0029] In some embodiments, the sintering time is 5-8 hours.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This application achieves a multi-component synergistic effect by using a specific raw material system composed of Y2O3, YF3, ZrO2 and α-Si3N4. Among them, Y2O3, as an effective sintering aid, can promote liquid phase generation and mass migration, and accelerate the densification process; the introduction of YF3 can significantly reduce the sintering temperature, reduce energy consumption and inhibit abnormal grain growth; the combined use of Y2O3 and YF3 further enhances the sintering synergistic effect, and achieves more complete densification and microstructure control. At the same time, the addition of ZrO2 effectively improves the fracture toughness and strength of ceramics through phase transformation toughening, microcrack toughening and other mechanisms. In addition, the α-phase → β-phase transformation that occurs in α-Si3N4 during sintering promotes the formation of long columnar β grains, and further enhances the mechanical properties of the material through crack deflection, bridging and other mechanisms. Therefore, this invention prepares high-strength and high-toughness silicon nitride ceramic materials by mixing Y2O3, YF3 and ZrO2 with α-Si3N4, which significantly improves the mechanical properties of silicon nitride ceramics and gives them good thermal and chemical stability, making them applicable to the mechanical industry.

[0031] (2) The present invention significantly improves the density of silicon nitride ceramic materials through processes such as ball milling, drying, sieving, pressing and hot pressing sintering, so that the relative density reaches more than 99.5%, realizing the uniform distribution and structural stability of each component in the matrix, and finally obtaining silicon nitride ceramic products with excellent mechanical properties and thermal stability.

[0032] (3) The silicon nitride ceramics prepared by the present invention have significant comprehensive advantages: the preparation process is characterized by high efficiency, short process and no pollution; the resulting products have high purity, long life and strong performance controllability, showing broad application potential. Detailed Implementation

[0033] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application are clearly and completely described. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0034] With the development of modern manufacturing, the demand for high-temperature components such as bearings and cutting tools is rapidly increasing, especially for components used in machining high-strength and high-toughness materials. Traditional materials such as cemented carbide and steel are increasingly insufficient for efficient application in modern machining. Silicon nitride ceramics are a key engineering material, possessing excellent mechanical properties, thermal stability, and chemical stability, giving them significant advantages in high-temperature processing. They are currently widely used in the machinery industry, aerospace, and other fields.

[0035] Silicon nitride is a covalently bonded material with low self-diffusion rate. Therefore, sintering densification of silicon nitride requires the addition of sintering aids. Common sintering aids include Al2O3, MgO, and rare earth oxides. Generally, sintering aids promote the formation of elongated β-Si3N4 crystals. These β-Si3N4 crystals promote grain bridging and crack deflection, which are beneficial for enhancing the strength and fracture toughness of Si3N4 ceramics. Therefore, by selecting appropriate sintering aids, high-strength, high-toughness, high-performance silicon nitride ceramics applicable to various high-temperature processing fields can be prepared. Compared with traditional materials, these ceramics can be used more precisely in manufacturing and have a longer service life.

[0036] In view of this, this application provides a silicon nitride ceramic and a method for preparing the same, wherein the silicon nitride ceramic has both high toughness and high strength.

[0037] In a first aspect, this application provides a silicon nitride ceramic, wherein the raw material components of the silicon nitride ceramic include: Y2O3, YF3, ZrO2 and α-Si3N4.

[0038] This application achieves a multi-component synergistic effect by employing a specific raw material system composed of Y₂O₃, YF₃, ZrO₂, and α-Si₃N₄. Y₂O₃, as an effective sintering aid, promotes liquid phase generation and mass migration, accelerating the densification process. The introduction of YF₃ significantly reduces sintering temperature, decreases energy consumption, and inhibits abnormal grain growth. The combined use of Y₂O₃ and YF₃ further enhances the sintering synergistic effect, achieving more complete densification and microstructure control. Simultaneously, the addition of ZrO₂ effectively improves the fracture toughness and strength of the ceramic through mechanisms such as phase transformation toughening and microcrack toughening. Furthermore, α-Si₃N₄ undergoes an α-phase → β-phase transformation during sintering, promoting the formation of long columnar β grains, further enhancing the mechanical properties of the material through crack deflection and bridging mechanisms. Therefore, through the synergistic effect of the components, silicon nitride ceramics with both high strength and high toughness can be obtained.

[0039] In conjunction with the first aspect, in some embodiments provided in this application, the mass percentage of Y2O3 is 3-5% based on the total mass of the raw material components of the silicon nitride ceramic. Limiting the mass percentage of Y2O3 within the above range ensures sufficient liquid-phase sintering to promote densification, thereby improving the strength of the ceramic.

[0040] As an example, the mass percentage of Y2O3 can be 3%, 4%, 5%, etc.

[0041] In conjunction with the first aspect, in some embodiments provided in this application, the Y2O3 has a purity of 99.9% and a D50 particle size of less than 50 μm. Limiting the purity and D50 particle size of Y2O3 within the above range allows for sufficient contact between the raw material powders, providing greater sintering driving force and resulting in denser ceramic sintering.

[0042] It should be noted that the purity of Y2O3 refers to the percentage of the mass of the main component Y2O3 in the total mass. For example, a purity of 99.9% means that in 1000 grams of Y2O3, Y2O3 itself accounts for 999 grams, while the total of all other impurities does not exceed 1 gram.

[0043] In conjunction with the first aspect, in some embodiments provided in this application, the α-Si3N4 has a purity of 99%, a D50 particle size of less than 10 μm, an α-phase content of greater than 90%, and an oxygen content of less than 1 wt%. Using α-Si3N4 with the above-mentioned parameters allows for sufficient contact between the raw material powders, providing greater sintering driving force, resulting in denser ceramic sintering. Furthermore, the Si3N4 raw material with lower oxygen content can produce Si3N4 ceramics with better thermal properties.

[0044] It should be noted that the explanation of "the purity of α-Si3N4" can be found in the above description, and will not be elaborated further here.

[0045] In conjunction with the first aspect, in some embodiments provided in this application, the mass percentage of YF3 is 4-6% based on the total mass of the raw material components of the silicon nitride ceramic. Limiting the mass percentage of YF3 within the above range can effectively reduce the sintering temperature and promote ceramic sintering.

[0046] In conjunction with the first aspect, in some embodiments provided in this application, the YF3 has a purity of 99.99% and a D50 particle size of less than 100 μm. Using YF3 with the above-mentioned parameters allows for sufficient contact between the raw material powders, providing greater sintering driving force and resulting in denser ceramic sintering.

[0047] It should be noted that the explanation of "YF3 purity" can be found in the above description, and will not be elaborated further here.

[0048] In conjunction with the first aspect, in some embodiments provided in this application, the ZrO2 mass percentage is 1-2% based on the total mass of the raw material components of the silicon nitride ceramic. Limiting the ZrO2 mass percentage within the above range can provide a reinforcing phase to the Si3N4 ceramic, thereby enhancing its strength.

[0049] In conjunction with the first aspect, in some embodiments provided in this application, the ZrO2 has a purity of 99.9% and a D50 particle size of less than 10 μm. Using ZrO2 with the above-mentioned parameters ensures that the reinforcing phase is uniformly distributed within the Si3N4 ceramic, avoiding cracks and other issues caused by uneven strength.

[0050] It should be noted that the explanation of "purity of ZrO2" can be found in the above description, and will not be elaborated further here.

[0051] In conjunction with the first aspect, in some embodiments provided in this application, the raw material components of the silicon nitride ceramic further include a binder and a solvent. Introducing a binder and solvent system helps to regulate the rheological properties and dispersion stability of the slurry, resulting in a more uniform stress distribution in the ceramic green body during drying and binder removal, and reducing defect generation. The binder indirectly affects sintering behavior and grain growth by influencing the uniformity and particle arrangement of the sintering precursor, ultimately achieving control over the microstructure of the silicon nitride ceramic, thereby improving the macroscopic properties of the ceramic, such as mechanical strength and fracture toughness.

[0052] In conjunction with the first aspect, in some embodiments provided in this application, the mass percentage of the binder is 1% based on the total mass of the raw material components of the silicon nitride ceramic. Limiting the mass percentage of the binder within the above range can effectively promote the formation of ceramic green bodies, reduce the generation of internal defects, and promote the densification of ceramic sintering.

[0053] In conjunction with the first aspect, in some embodiments provided in this application, the binder includes polyvinyl butyral. Using the above-mentioned binder can optimize the formability, strength, and microstructure uniformity of ceramic green bodies, thereby improving the strength and toughness of the ceramics.

[0054] Optionally, the solvent includes, but is not limited to, ethanol.

[0055] Secondly, this application provides a method for preparing the silicon nitride ceramic described in the first aspect, comprising: S100: α-Si3N4, Y2O3, YF3, ZrO2, binder and solvent are mixed and ball-milled, then dried for the first time to obtain a mixture.

[0056] In this step, ball milling is performed after mixing α-Si3N4, Y2O3, YF3, ZrO2, binder and solvent to achieve uniform mixing and refinement of raw materials. The first drying removes the solvent to facilitate subsequent processing and creates a uniform material basis for subsequent reaction sintering, thereby ensuring the uniformity of the final ceramic material composition and structure.

[0057] In conjunction with the second aspect, in some embodiments provided in this application, the grinding balls of the ball mill include ZrO2 grinding balls. Using ZrO2 grinding balls for ball milling avoids introducing impurities other than the formulation components, and ZrO2 grinding balls have extremely high hardness and wear resistance, resulting in minimal wear during the ball milling process, thus ensuring the purity of the raw material mixture. Simultaneously, their high density effectively improves the impact efficiency and mixing uniformity of the ball mill.

[0058] In conjunction with the second aspect, in some embodiments provided in this application, the ZrO2 ball mill includes ZrO2 ball mills with a diameter of 4-6 mm and ZrO2 ball mills with a diameter of 8-12 mm. By using ZrO2 ball mills of different diameters (4-6 mm and 8-12 mm) in combination, the synergistic effect of the large and small ball mills is utilized to achieve a more efficient and uniform grinding effect on the mixed materials.

[0059] As an example, the diameter of the ZrO2 ball milling tool with a diameter of 4-6mm can be 4mm, 5mm, 6mm, etc.; the diameter of the ZrO2 ball milling tool with a diameter of 8-12mm can be 8mm, 10mm, 12mm, etc.

[0060] In conjunction with the second aspect, in some embodiments provided in this application, the mass ratio of the ball mill, dry mix, and solvent is 10:1:(1.2-1.8), wherein the mass of the dry mix is ​​the total mass of α-Si3N4, Y2O3, YF3, ZrO2, and the binder. Sufficient ball milling ensures adequate collision and shearing forces, effectively breaking up agglomerates and refining the powder; an appropriate amount of solvent forms a suitable slurry viscosity, ensuring good powder dispersibility to prevent re-agglomeration, and ensuring effective grinding and transport of the material by the ball milling media, thereby facilitating the acquisition of highly uniform and dense silicon nitride ceramic blanks.

[0061] As an example, the mass ratio of the ball mill, dry mix, and solvent can be 10:1:1.2, 10:1:1.5, 10:1:1.8, etc.

[0062] In conjunction with the second aspect, in some embodiments provided in this application, the temperature of the first drying step is 60-100°C. This temperature range can effectively remove the solvent in the mixed slurry, avoiding binder migration, surface skinning, or component segregation caused by excessively rapid drying (excessively high temperature), thereby ensuring that the mixed powder obtained after drying still maintains a uniform component distribution and good loose flowability.

[0063] As an example, the temperature of the first drying can be 60°C, 70°C, 80°C, 90°C, 100°C, etc.

[0064] In conjunction with the second aspect, in some embodiments provided in this application, the first drying time is 12-24 hours. Limiting the first drying time to the above range ensures that the solvent is removed sufficiently, uniformly, and slowly, effectively preventing the binder from migrating to the surface of the blank and forming a hard shell or cracks due to excessively rapid drying, thereby ensuring good looseness and flowability of the mixed powder after drying.

[0065] As an example, the first drying time can be 12h, 15h, 18h, 20h, 24h, etc.

[0066] S200. After sieving the mixture, press it into shape and dry it a second time to obtain a silicon nitride ceramic intermediate.

[0067] In this step, the mixture is sieved, pressed, and dried to obtain a silicon nitride ceramic intermediate. Sieving ensures the uniformity of the powder used for molding. Pressing gives the green body the required shape and initial strength. Then, a second drying process completely removes residual solvents and volatile components from the binder, thereby obtaining a silicon nitride ceramic intermediate with a complete structure and suitable strength. This provides a green body base with dimensional stability and no internal defects for subsequent high-temperature sintering.

[0068] In conjunction with the second aspect, in some embodiments provided in this application, the pressing pressure is 25-35 MPa. Limiting the pressing pressure within the above range ensures that the powder is fully compacted, obtaining an intermediate with sufficient green strength to maintain its shape and facilitate subsequent handling and processing, while also avoiding defects such as increased density gradient between the inside and outside of the green body or the appearance of layered cracks due to excessive pressure.

[0069] As an example, the pressing pressure can be 25MPa, 30MPa, 35MPa, etc.

[0070] In conjunction with the second aspect, in some embodiments provided in this application, the pressing time is 1-2 minutes. Limiting the pressing time to the above range provides sufficient time for the powder particles to fully rearrange, deform, and compact, thereby obtaining a green blank with high green density and strength; it also avoids the risk of low production efficiency due to excessive holding time or defects such as microcracks in the green blank due to excessive stress relaxation.

[0071] In conjunction with the second aspect, in some embodiments provided in this application, the temperature of the second drying is 60-100°C. Limiting the temperature of the second drying to the above range can remove residual solvents and most of the organic binders in the compact, avoiding defects such as bubbles and cracks caused by rapid volatilization or decomposition of organic matter due to excessively high temperatures, thereby ensuring the structural integrity of the intermediate.

[0072] As an example, the temperature for the second drying can be 60°C, 70°C, 80°C, 90°C, 100°C, etc.

[0073] In conjunction with the second aspect, in some embodiments provided in this application, the second drying time is 12-24 hours. Limiting the second drying time to the above range can effectively remove residual solvent and volatile components of binder inside the pressed green body, while avoiding cracking or deformation of the green body due to excessively rapid drying. This ensures that the silicon nitride ceramic intermediate has sufficient green body strength and complete geometry, which is beneficial for obtaining ceramics with dense structure and uniform properties.

[0074] As an example, the second drying time can be 12h, 15h, 18h, 20h, 24h, etc.

[0075] S300. Sinter the silicon nitride ceramic intermediate to obtain silicon nitride ceramic.

[0076] In this step, silicon nitride ceramic is obtained by sintering the silicon nitride ceramic intermediate.

[0077] In conjunction with the second aspect, in some embodiments provided in this application, the sintering temperature is 1700-1900°C. Limiting the sintering temperature within the above range can provide sufficient sintering driving force and prevent liquid phase volatilization, thereby preparing dense Si3N4 ceramics.

[0078] As an example, the sintering temperature can be 1700℃, 1800℃, 1900℃, etc.

[0079] In conjunction with the second aspect, in some embodiments provided in this application, the sintering atmosphere includes nitrogen. Using nitrogen as the sintering atmosphere can effectively prevent the silicon-based raw materials from being oxidized at high temperatures.

[0080] In conjunction with the second aspect, in some embodiments provided in this application, the applied pressure during sintering is 40-50 MPa. Limiting the applied pressure during sintering to the above range can effectively promote particle rearrangement and mass transport, thereby densifying the ceramic during sintering.

[0081] As an example, the applied pressure during sintering can be 40 MPa, 45 MPa, 50 MPa, etc.

[0082] In conjunction with the second aspect, in some embodiments provided in this application, the sintering time is 5-8 hours. Limiting the sintering time to this range allows for sufficient ceramic grain growth and uniform distribution of intergranular phases, thereby affecting the macroscopic properties of the ceramic. As an example, the sintering time can be 5h, 6h, 7h, 8h, etc.

[0083] The technical solutions provided in this application will be described in detail below with reference to the embodiments.

[0084] Example 1 (1) Weigh 27.6g α-Si3N4, 0.9g Y2O3, 1.2g YF3, 0.3g ZrO2 and 0.3g polyvinyl butyral and put them into a nylon ball mill jar. Add 45g anhydrous ethanol, 150g ZrO2 ball milling pellets with a diameter of 6mm and 150g ZrO2 ball milling pellets with a diameter of 10mm, and put them into a planetary ball mill for ball milling. The ball mill speed is 500RPM and the ball milling time is 12h to obtain a slurry mixture, in which the mass ratio of α-Si3N4 is 92%. The purity of α-Si3N4 is 99%, the D50 particle size is less than 10 μm, the α phase content in α-Si3N4 is greater than 90%, and the oxygen content is less than 1 wt%; the mass percentage of Y2O3 is 3%, the purity of Y2O3 is 99.9%, the D50 particle size is less than 50 μm; the mass percentage of YF3 is 4%, the purity of YF3 is 99.99%, the D50 particle size is less than 100 μm; the mass percentage of ZrO2 is 1%, the purity of ZrO2 is 99.9%, and the D50 particle size is less than 10 μm.

[0085] (2) The slurry mixture obtained in (1) is placed in a vacuum oven for drying. The oven temperature is 60°C and the drying time is 12 hours to obtain the mixture.

[0086] (3) Pass the mixture obtained in (2) through a 100-mesh sieve. After sieving, take 1.5g of the powder and pour it into a stainless steel mold for pressing. The single-axis pressure is 30MPa and the holding time is 1min. After pressing, put the green body into a vacuum oven for drying. The temperature is set to 60℃ and the drying time is 24h to obtain silicon nitride ceramic intermediate.

[0087] (4) The silicon nitride ceramic intermediate obtained in (3) is placed in a hot press sintering furnace for sintering at a temperature of 1800℃, with nitrogen atmosphere introduced, pressure of 40MPa, and holding time of 6h to obtain silicon nitride ceramic.

[0088] Example 2 (1) Weigh 26.1g of α-Si3N4 powder, 1.5g of Y2O3 powder, 1.8g of YF3, 0.6g of ZrO2 powder and 0.3g of polyvinyl butyral and put them into a nylon ball mill jar. Add 45g of anhydrous ethanol, 150g of ZrO2 ball milling tool with a diameter of 6mm and 150g of ZrO2 ball milling tool with a diameter of 10mm, and put them into a planetary ball mill for ball milling. The ball mill speed is 500RPM and the ball milling time is 12h to obtain a slurry mixture, in which the mass ratio of α-Si3N4 is 8%. The composition of α-Si3N4 is 7%, with a purity of 99%, a D50 particle size of less than 10 μm, an α-phase content of greater than 90%, and an oxygen content of less than 1 wt%. The composition of Y2O3 is 5%, with a purity of 99.9% and a D50 particle size of less than 50 μm. The composition of YF3 is 6%, with a purity of 99.99% and a D50 particle size of less than 100 μm. The composition of ZrO2 is 2%, with a purity of 99.9% and a D50 particle size of less than 10 μm.

[0089] (2) The slurry mixture obtained in (1) is placed in a vacuum oven for drying. The oven temperature is 60°C and the drying time is 24 hours to obtain the mixture.

[0090] (3) The mixture obtained in (2) is passed through a 100-mesh sieve. After passing through the sieve, 2g of the powder is poured into a stainless steel mold for pressing. The single-axis pressure is 30MPa and the holding time is 1min. After pressing, the green body is placed in a vacuum oven for drying. The temperature is set to 60℃ and the drying time is 24h to obtain silicon nitride ceramic intermediate.

[0091] (4) The silicon nitride ceramic intermediate obtained in (3) is placed in a hot press sintering furnace for sintering at a temperature of 1750°C, with nitrogen gas introduced into the atmosphere, a pressure of 50 MPa, and a holding time of 5 h to obtain silicon nitride ceramic.

[0092] Example 3 (1) Weigh 26.7g of α-Si3N4 powder, 1.5g of Y2O3 powder, 1.5g of YF3, 0.3g of ZrO2 powder and 0.3g of polyvinyl butyral and put them into a nylon ball milling jar. Add 45g of anhydrous ethanol, 150g of ZrO2 ball milling tool with a diameter of 6mm and 150g of ZrO2 ball milling tool with a diameter of 10mm, and put them into a planetary ball mill for ball milling. The ball mill speed is 500RPM and the ball milling time is 12h. A slurry mixture was obtained, wherein α-Si3N4 accounted for 89% by mass, with a purity of 99% and a D50 particle size of less than 10 μm, the α-phase content in α-Si3N4 was greater than 90%, and the oxygen content was less than 1 wt%; Y2O3 accounted for 5% by mass, with a purity of 99.9% and a D50 particle size of less than 50 μm; YF3 accounted for 5% by mass, with a purity of 99.99% and a D50 particle size of less than 100 μm; and ZrO2 accounted for 1% by mass, with a purity of 99.9% and a D50 particle size of less than 10 μm.

[0093] (2) The slurry mixture obtained in (1) is placed in a vacuum oven for drying. The oven temperature is 60°C and the drying time is 12 hours.

[0094] (3) Pass the mixture obtained in (2) through a 100-mesh sieve. After sieving, take 1.8g of the powder and pour it into a stainless steel mold for pressing. The single-axis pressure is 30MPa and the holding time is 1min. After pressing, put the green body into a vacuum oven for drying. The temperature is set to 60℃ and the drying time is 24h to obtain silicon nitride ceramic intermediate.

[0095] (4) The silicon nitride ceramic intermediate obtained in (3) is placed in a hot press sintering furnace for sintering at a temperature of 1850℃, with nitrogen atmosphere introduced, pressure of 40MPa, and holding time of 8h to obtain silicon nitride ceramic.

[0096] Comparative Example 1 Comparative Example 1 of this application provides a silicon nitride ceramic, similar to Example 1, except that it does not contain YF3.

[0097] Comparative Example 2 Comparative Example 2 of this application provides a silicon nitride ceramic, similar to Example 1, except that it does not contain Y2O3.

[0098] Comparative Example 3 Comparative Example 3 of this application provides a silicon nitride ceramic, similar to Example 1, except that it does not contain ZrO2.

[0099] Comparative Example 4 Comparative Example 5 of this application provides a hot-pressed silicon nitride, which is prepared by a hot-pressing sintering process.

[0100] Performance testing The silicon nitride ceramics of Examples 1-3 and Comparative Examples 1-4 were subjected to performance tests, including flexural strength, fracture toughness, and hardness. The performance testing methods and procedures are as follows: Bending strength test: The bending strength of each sample was determined using a universal testing machine. The three-point bending method was employed, and the critical load (F) at which the sample fractured was recorded by the universal testing machine. The span (L) was set to 20 mm. The height (h) and width (b) of the long strip sample were measured. The bending strength of each sample was obtained using the bending strength calculation formula. The strength of each group of samples was calculated by averaging the strengths of at least three samples.

[0101] Fracture toughness test: The fracture toughness of the samples was determined using the single-sided notched beam method. The notch depth was approximately 1 mm, and the grinding radius was approximately 0.2 mm. A universal testing machine was used with the three-point bending method. The span L was set to 20 mm, the indenter speed was set to 0.1 mm / min, and the sample width b (mm) and height h (mm) were measured. The maximum load P (N) at the time of fracture was recorded, and the crack depth a was 1 mm. Each group of samples underwent at least three fracture toughness tests, and the average value was taken. The fracture toughness KIC of the samples was calculated using the following formula:

[0102] Hardness test: The load F (N) is recorded by the hardness tester, and the indentation area S (m²) is measured. 2 The average indentation length d (m) was calculated. The load and loading time were 196 N and 10 s, respectively. At least three indentations were measured in different areas for each sample. The hardness (Hv) was calculated using the formula, and the average value was taken. The formula is:

[0103] The specific test results are shown in Table 1: Table 1 Performance of Examples 1-3 and Comparative Example 4

[0104] As shown in Table 1, compared with the silicon nitride ceramic of Comparative Example 4, the silicon nitride ceramic materials prepared by Y2O3, YF3 and ZrO2 (Examples 1-3) can significantly improve the flexural strength, fracture toughness and hardness of the ceramic materials, with flexural strength of 1077~1205 MPa and fracture toughness of 8.55~11.23 MPa / m. 1 / 2 Its hardness is 1707~1975H. V .

[0105] In summary, by employing a specific raw material system composed of Y₂O₃, YF₃, ZrO₂, and α-Si₃N₄, a multi-component synergistic effect was achieved. Y₂O₃, as an effective sintering aid, promotes liquid phase generation and mass migration, accelerating the densification process. The introduction of YF₃ significantly reduces sintering temperature, decreases energy consumption, and inhibits abnormal grain growth. The combined use of Y₂O₃ and YF₃ further enhances the sintering synergistic effect, achieving more complete densification and microstructure control. Simultaneously, the addition of ZrO₂ effectively improves the fracture toughness and strength of the ceramic through mechanisms such as phase transformation toughening and microcrack toughening. Furthermore, α-Si₃N₄ undergoes an α-phase → β-phase transformation during sintering, promoting the formation of long columnar β grains, further enhancing the mechanical properties of the material through crack deflection and bridging mechanisms. Therefore, through the synergistic effect of each component, silicon nitride ceramics possessing both high strength and high toughness can be obtained.

[0106] In the description of this specification, the references to terms such as "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[0107] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In this application, "a plurality of" means at least two, such as two, three, etc., unless otherwise expressly specified.

[0108] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A silicon nitride ceramic, characterized in that, The raw material components of the silicon nitride ceramic include: Y2O3, YF3, ZrO2 and α-Si3N4.

2. The silicon nitride ceramic as described in claim 1, characterized in that, Based on the total mass of the raw material components of the silicon nitride ceramic, the mass percentage of Y₂O₃ is 3-5%; and / or, Based on the total mass of the raw material components of the silicon nitride ceramic, the mass percentage of YF3 is 4-6%; and / or, Based on the total mass of the raw material components of the silicon nitride ceramic, the mass percentage of ZrO2 is 1-2%.

3. The silicon nitride ceramic as described in claim 1 or 2, characterized in that, The Y₂O₃ has a purity of 99.9% and a D50 particle size of less than 50 μm; and / or, The α-Si3N4 has a purity of 99%, a D50 particle size of less than 10 μm, an α-phase content of greater than 90%, and an oxygen content of less than 1 wt%; and / or, The YF3 has a purity of 99.99% and a D50 particle size of less than 100 μm; and / or, The purity of the ZrO2 is 99.9%, and the D50 particle size is less than 10 μm.

4. The silicon nitride ceramic as described in claim 1 or 2, characterized in that, The raw material components of the silicon nitride ceramic also include binders and solvents.

5. The silicon nitride ceramic as described in claim 4, characterized in that, The adhesive comprises polyvinyl butyral; and / or, The solvent includes ethanol.

6. A method for preparing silicon nitride ceramic as described in any one of claims 1-5, characterized in that, include: After mixing α-Si3N4, Y2O3, YF3, ZrO2, binder and solvent, the mixture was ball-milled and dried for the first time to obtain a mixture. The mixture is sieved, pressed into shape, and dried a second time to obtain a silicon nitride ceramic intermediate. Silicon nitride ceramic intermediates are sintered to obtain silicon nitride ceramics.

7. The preparation method according to claim 6, characterized in that, The grinding balls of the ball mill include ZrO2 grinding balls; and / or, The ZrO2 ball milling tool includes ZrO2 ball milling tools with a diameter of 4-6 mm and ZrO2 ball milling tools with a diameter of 8-12 mm; and / or, The mass ratio of the ball mill, dry mix, and solvent is 10:1:(1.2-1.8), wherein the mass of the dry mix is ​​the total mass of α-Si3N4, Y2O3, YF3, ZrO2, and binder.

8. The preparation method according to claim 6, characterized in that, The temperature for the first drying step is 60-100℃; and / or, The first drying time is 12-24 hours.

9. The preparation method according to claim 6, characterized in that, The pressing pressure is 25-35 MPa; and / or, The pressing time is 1-2 minutes; and / or, The temperature for the second drying is 60-100℃; and / or, The second drying time is 12-24 hours.

10. The preparation method according to claim 6, characterized in that, The sintering temperature is 1700-1900℃; and / or, The sintering atmosphere includes nitrogen; and / or, The sintering pressure is 40-50 MPa; and / or, The sintering time is 5-8 hours.

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