A high-toughness silicon nitride ceramic and its preparation method

Abstract

This invention belongs to the field of silicon nitride ceramic technology, specifically relating to a high-toughness silicon nitride ceramic and its preparation method, comprising the following steps: mixing α-Si3N4, sintering aid, and additives in a mass ratio of 85-95:5-10:1-5, and performing wet ball milling; the sintering aid is MgO and / or Y2O3; the additive is nano-ZrO2 or TiO2; after ball milling, drying, grinding, and sieving to obtain fine powder; pre-pressing the fine powder into shape and hot-pressing sintering to obtain Si3N4 ceramic; and heat-treating the Si3N4 ceramic under an inert atmosphere to obtain the final product. This invention combines additive regulation with heat treatment processes, constructing an in-situ synergistic reinforcement mechanism by changing the glass phase composition and crystallization state. This not only solves the adverse effects of the glass phase on the mechanical properties of silicon nitride ceramics but also avoids the dispersion problem caused by directly introducing the toughening phase.

Description

Technical Field

[0001] This invention belongs to the field of silicon nitride ceramic technology, specifically relating to a high-toughness silicon nitride ceramic and its preparation method. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] Silicon nitride (Si3N4), as a high-performance structural ceramic, is widely used in machinery manufacturing, aerospace, and new energy equipment due to its high fracture toughness, thermal stability, wear resistance, and corrosion resistance. While existing technologies such as hot pressing and sintering have achieved high strength and high density in the material, they still face four major bottlenecks:

[0004] Firstly, during liquid-phase sintering of silicon nitride ceramics, although sintering aids can form a liquid phase to promote sintering, they easily form a glassy phase at the grain boundaries after cooling. The presence of the glassy phase weakens the grain boundaries, making the material more susceptible to crack propagation and resulting in decreased toughness. At the same time, the high-temperature softening of the glassy phase affects the high-temperature service performance of silicon nitride ceramics, becoming a key issue restricting the improvement of silicon nitride ceramic performance and the expansion of its applications.

[0005] Secondly, the toughening phase can be introduced to improve the toughness of silicon nitride ceramics to a certain extent. However, the toughening phase is prone to uneven dispersion, and particle aggregation can easily cause local stress concentration in silicon nitride ceramics, accelerating crack formation. If the amount of toughening phase added is too high, it will destroy the continuity of the matrix and reduce the overall strength.

[0006] Third, the interwoven structure of long columnar β-Si3N4 grains is key to improving toughness. However, in existing processes, there is a contradiction between the conversion efficiency of the α phase to the β phase and the control of the grain aspect ratio. For example, increasing the conversion temperature can promote the growth of the β phase, but it can easily lead to abnormal grain coarsening; while decreasing the temperature results in insufficient conversion and difficulty in forming an effective toughening microstructure. In addition, directional grain growth can easily induce anisotropy, leading to uneven toughness performance of the material under complex stress fields.

[0007] Fourth, the high-temperature and high-pressure preparation process is costly, and prolonged heating can cause abnormal growth of Si3N4 grains, which in turn leads to a decrease in its mechanical properties. Summary of the Invention

[0008] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a high-toughness silicon nitride ceramic and its preparation method.

[0009] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing high-toughness silicon nitride ceramics, comprising the following steps:

[0011] α-Si3N4, sintering aid and additive are mixed in a mass ratio of 85-95:5-10:1-5 and then wet ball milled; the sintering aid is MgO and / or Y2O3; the additive is nano ZrO2 or TiO2.

[0012] After ball milling, drying, grinding, and sieving, fine powder is obtained;

[0013] Si3N4 ceramics are obtained by pre-pressing fine powder into shape and hot-pressing sintering.

[0014] The Si3N4 ceramic is obtained by heat-treating it in an inert atmosphere at a temperature of 1200-1400℃ for 20-30 hours.

[0015] Secondly, the present invention provides a high-toughness silicon nitride ceramic, which is prepared by the aforementioned preparation method.

[0016] The beneficial effects achieved by one or more embodiments of the present invention described above are as follows:

[0017] This invention innovatively combines additive regulation with heat treatment processes. By altering the composition and crystallization state of the glass phase, it constructs an in-situ synergistic reinforcement mechanism. This not only solves the adverse effects of the glass phase on the mechanical properties of silicon nitride ceramics but also avoids the dispersion problems caused by directly introducing the toughening phase. Through precise control of the type and amount of additives and matching optimized gradient heat treatment parameters, the orderly construction of the ceramic's internal microstructure is achieved. This fully leverages the synergistic effect of additive-induced crystal phase evolution and heat treatment-regulated glass phase crystallization, significantly improving the toughness and performance stability of silicon nitride ceramics. Attached Figure Description

[0018] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0019] Figure 1 The XRD patterns of Si3N4 ceramics prepared in Examples 1-2 and Comparative Example 1 before and after heat treatment are shown below.

[0020] Figure 2 The images shown in Example 1 of this invention are (a) corrosion morphology and (b) bimodal grain size statistics of ZMY after heat treatment with ZrO2 additive.

[0021] Figure 3 The graph shows a comparison of the mechanical properties of Si3N4 ceramics prepared in Examples 1-2 and Comparative Example 1 of this invention, where (a) fracture toughness and (b) hardness are represented. Detailed Implementation

[0022] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0023] In a first aspect, the present invention provides a method for preparing high-toughness silicon nitride ceramics, comprising the following steps:

[0024] α-Si3N4, sintering aid and additive are mixed in a mass ratio of 85-95:5-10:1-5 and then wet ball milled; the sintering aid is MgO and / or Y2O3; the additive is nano ZrO2 or TiO2.

[0025] After ball milling, drying, grinding, and sieving, fine powder is obtained;

[0026] Si3N4 ceramics are obtained by pre-pressing fine powder into shape and hot-pressing sintering.

[0027] The Si3N4 ceramic is obtained by heat treatment under an inert atmosphere.

[0028] The silicon nitride ceramic prepared by this invention, through the regulatory effect of additives, achieves crystalline phase control and the formation of bimodal grains during a specific heat treatment process. This largely realizes the toughening effect of silicon nitride ceramic.

[0029] Compared to silicon nitride ceramic materials regulated by a single additive, this invention, through the synergistic effect of additive regulation and heat treatment, can precisely control the content and distribution of long columnar β-Si3N4 grains in bimodal grains. This improves toughness while avoiding performance fluctuations caused by structural inhomogeneity, resulting in higher material reliability.

[0030] The silicon nitride ceramic preparation method provided by this invention combines diffusion-guided additives with grain growth driven by heat treatment, which can shorten the time to achieve the ideal microstructure and suppress the formation of harmful phases during densification. Under the premise of ensuring a significant improvement in toughness, it broadens the range of adaptability to different performance requirements.

[0031] In some embodiments, α-Si3N4, sintering aids and additives are in a mass ratio of 87-93:5-8:1-3.

[0032] In some embodiments, the sintering aid is a mixture of MgO and Y2O3, with a mass ratio of MgO to Y2O3 of 1-1.5:1. The grain control effect of MgO can avoid the grain boundary weakening problem caused by excessive liquid phase due to the excessive introduction of Y2O3. At the same time, the liquid phase sintering effect of Y2O3 can compensate for the slow densification rate when MgO is used alone, forming a synergistic effect of "refining grains - accelerating densification", ultimately obtaining ceramic materials with high density, uniform grain distribution, and superior mechanical and thermal properties.

[0033] In some embodiments, anhydrous ethanol is used as the solvent in wet ball milling.

[0034] In some embodiments, the material is sieved through a 60-mesh sieve.

[0035] In some embodiments, the pre-compression pressure is 5-15 MPa, preferably 7-13 MPa.

[0036] In some embodiments, the sintering procedure for hot pressing sintering is as follows: 20-30℃ to 750-850℃, heating time 5-15 min; 750-850℃ to 1570-1620℃, heating time 10-20 min; 1570-1620℃ to 1680-1750℃, heating time 2-5 min; holding at 1680-1750℃ for 8-15 min, pressure 25-35 MPa; after holding, natural cooling.

[0037] In some embodiments, the heat treatment temperature is 1200-1400℃, and the holding time is 20-30h.

[0038] Preferably, the heat treatment temperature is 1200-1300℃, and the holding time is 20-25h.

[0039] Secondly, the present invention provides a high-toughness silicon nitride ceramic, which is prepared by the aforementioned preparation method.

[0040] The present invention will be further described below with reference to the embodiments.

[0041] Example 1

[0042] This embodiment prepares the Si3N4 ceramic product ZMY, and the preparation method includes the following steps:

[0043] (1) The raw material powders were weighed strictly according to the component ratio, including 90 parts by mass of α-Si3N4 powder (purity ≥99.9%, particle size D50=0.5μm), 3 parts by mass of Y2O3 powder (purity ≥99.9%, particle size 1μm), 3.5 parts by mass of MgO powder (purity ≥99.9%, particle size 1μm) and 1.5 parts by mass of monoclinic nanoparticle ZrO2 (purity ≥99.9%, particle size 100nm); and an appropriate amount of anhydrous ethanol was used as the dispersion solvent, and Si3N4 balls were used as grinding balls. The ball milling process was carried out in a planetary ball mill at a speed of 300r / min and a milling time of 12h to obtain a uniformly mixed slurry.

[0044] (2) Pour the well-mixed slurry into an evaporating dish, then place it in a drying oven and evaporate the anhydrous ethanol completely at 80°C to obtain coarse powder. Grind the coarse powder repeatedly with a mortar and pestle and then pass it through a 60-mesh sieve to obtain fine powder with uniform particle size.

[0045] (3) The fine powder is loaded into a graphite mold and placed on a tablet press. Pre-pressing is performed under a pre-pressing pressure of 10 MPa to obtain the precursor.

[0046] (4) The precursor was placed in a rapid hot pressing sintering furnace for sintering. The sintering procedure was as follows: room temperature to 800℃, heating time 10 min, pressure 6 MPa; 800℃ to 1600℃, heating time 16 min, pressure 30 MPa; 1600℃ to 1700℃, heating time 3 min, pressure 30 MPa; 1700℃ for 10 min, pressure 30 MPa; after sintering, it was allowed to cool naturally. The sintering process of Si3N4 ceramic ZMY was carried out entirely in a vacuum environment.

[0047] (5) After sintering, allow it to cool naturally and then demold to obtain Si3N4 ceramic;

[0048] (6) Heat treatment of Si3N4 ceramic: heat up to 1250℃ at a rate of 5℃ / min from room temperature and hold for 24h. After heat treatment, cool naturally to room temperature to obtain Si3N4 ceramic ZMY sample.

[0049] In this embodiment, the fracture toughness and hardness of Si3N4 ceramic before and after heat treatment are as follows: Figure 3 As shown in (a) and (b), the fracture toughness after heat treatment reaches 11.72 MPa·m. 1 / 2 The hardness was increased by 31.6% compared to before heat treatment, and the hardness after heat treatment reached 13.43 GPa.

[0050] Example 2

[0051] This embodiment prepares the Si3N4 ceramic product TMY, and the preparation method includes the following steps:

[0052] (1) The raw material powders were weighed strictly according to the component ratio, including 90 parts by weight of α-Si3N4 powder (purity ≥99.9%, particle size D50=0.5μm), 3 parts by weight of Y2O3 powder (purity ≥99.9%, particle size 1μm), 3.5 parts by weight of MgO powder (purity ≥99.9%, particle size 1μm), and 1.5 parts by weight of rutile phase nanoparticles TiO2 (purity ≥99.9%, particle size 100nm); and an appropriate amount of anhydrous ethanol was used as the dispersion solvent, and Si3N4 balls were used as grinding balls. The ball milling process was carried out in a planetary ball mill at a speed of 300r / min and a milling time of 12h to obtain a uniformly mixed slurry.

[0053] (2) Pour the well-mixed slurry into an evaporating dish, then place it in a drying oven. Under 80°C, completely evaporate the anhydrous ethanol to obtain coarse powder. Use a mortar and pestle to repeatedly grind the coarse powder and then pass it through a 60-mesh sieve to obtain fine powder with uniform particle size.

[0054] (3) The fine powder is loaded into a graphite mold and placed on a tablet press. Pre-pressing is performed under a pre-pressing pressure of 10 MPa to obtain the precursor.

[0055] (4) The precursor was placed in a rapid hot pressing sintering furnace for sintering. The sintering program was as follows: room temperature to 800℃, heating time 10 min, pressure 6 MPa; 800℃ to 1600℃, heating time 16 min, pressure 30 MPa; 1600℃ to 1700℃, heating time 3 min, pressure 30 MPa; 1700℃ for holding time 10 min, pressure 30 MPa; after sintering, it was naturally cooled. The sintering process of Si3N4 ceramic TMY was carried out in a vacuum environment throughout.

[0056] (5) After sintering, allow it to cool naturally and then demold to obtain Si3N4 ceramic;

[0057] (6) Heat treatment of Si3N4 ceramic: heat up to 1250℃ at a rate of 5℃ / min from room temperature and hold for 24h. After heat treatment, cool naturally to room temperature to obtain Si3N4 ceramic TMY sample.

[0058] In this embodiment, the fracture toughness and hardness of Si3N4 ceramic before and after heat treatment are as follows: Figure 3 As shown in (a) and (b), the fracture toughness after heat treatment reaches 10.3 MPa·m. 1 / 2 The hardness increased by 18.2% compared to before heat treatment, reaching 13.37 GPa.

[0059] Example 3

[0060] This embodiment prepares the Si3N4 ceramic product ZMY1. The preparation method includes the following steps:

[0061] (1) The raw material powders were weighed strictly according to the component ratio, including 90 parts by weight of α-Si3N4 powder (purity ≥99.9%, particle size D50=0.5μm), 3 parts by weight of Y2O3 powder (purity ≥99.9%, particle size 1μm), 4 parts by weight of MgO powder (purity ≥99.9%, particle size 1μm), and 1 part by weight of monoclinic nanoparticle ZrO2 (purity ≥99.9%, particle size 100nm); and an appropriate amount of anhydrous ethanol was used as the dispersion solvent, and Si3N4 balls were used as grinding balls. The ball milling process was carried out in a planetary ball mill at a speed of 300r / min for 12h to obtain a uniformly mixed slurry.

[0062] (2) Pour the well-mixed slurry into an evaporating dish, then place it in a drying oven and evaporate the anhydrous ethanol completely at 80°C to obtain coarse powder. Grind the coarse powder repeatedly with a mortar and pestle and then pass it through a 60-mesh sieve to obtain fine powder with uniform particle size.

[0063] (3) The fine powder after grinding and sieving is loaded into a graphite mold and placed on a tablet press. It is pre-pressed at a pre-pressing pressure of 10MPa to obtain the precursor.

[0064] (4) The precursor was placed in a rapid hot pressing sintering furnace for sintering. The sintering program was as follows: room temperature to 800℃, heating time 10 min, pressure 6 MPa; 800℃ to 1600℃, heating time 16 min, pressure 30 MPa; 1600℃ to 1700℃, heating time 3 min, pressure 30 MPa; 1700℃ for 10 min, pressure 30 MPa; after sintering, it was allowed to cool naturally. The entire sintering process was carried out in a vacuum environment.

[0065] (5) After sintering, allow it to cool naturally and then demold to obtain Si3N4 ceramic;

[0066] (6) Heat treatment of Si3N4 ceramic: heat up to 1250℃ at a rate of 5℃ / min from room temperature and hold for 24h. After heat treatment, cool naturally to room temperature to obtain Si3N4 ceramic ZMY1 sample.

[0067] In this embodiment, the fracture toughness of Si3N4 ceramic after heat treatment reaches 10.9 MPa·m. 1 / 2 After heat treatment, the hardness reaches 13.31 GPa.

[0068] Example 4

[0069] This embodiment prepares the Si3N4 ceramic product TMY1. The preparation method includes the following steps:

[0070] (1) The raw material powders were weighed strictly according to the component ratio, including 90 parts by mass of α-Si3N4 powder (purity ≥99.9%, particle size D50=0.5μm), 3 parts by mass of Y2O3 powder (purity ≥99.9%, particle size 1μm), 4 parts by mass of MgO powder (purity ≥99.9%, particle size 1μm), and 1 part by mass of rutile nanoparticle powder TiO2 (purity ≥99.9%, particle size 100nm); and an appropriate amount of anhydrous ethanol was used as the dispersion solvent, and Si3N4 balls were used as grinding balls. The ball milling process was carried out in a planetary ball mill at a speed of 300r / min and a milling time of 12h to obtain a uniformly mixed slurry.

[0071] (2) Pour the well-mixed slurry into an evaporating dish, then place it in a drying oven and evaporate the anhydrous ethanol completely at 80°C to obtain coarse powder. Grind the coarse powder multiple times using a mortar and pestle and then pass it through a 60-mesh sieve to obtain fine powder with uniform particle size.

[0072] (3) The fine powder is loaded into a graphite mold and placed on a tablet press. Pre-pressing is performed under a pre-pressing pressure of 10 MPa to obtain the precursor.

[0073] (4) The precursor was placed in a rapid hot pressing sintering furnace for sintering. The sintering program was as follows: room temperature to 800℃, heating time 10 min, pressure 6 MPa; 800℃ to 1600℃, heating time 16 min, pressure 30 MPa; 1600℃ to 1700℃, heating time 3 min, pressure 30 MPa; 1700℃ for 10 min, pressure 30 MPa; after sintering, it was allowed to cool naturally. The entire sintering process was carried out in a vacuum environment.

[0074] (5) After sintering, allow it to cool naturally and then demold to obtain Si3N4 ceramic;

[0075] (6) Heat treatment of Si3N4 ceramic: heat up to 1250℃ at a rate of 5℃ / min from room temperature and hold for 24h. After heat treatment, cool naturally to room temperature to obtain Si3N4 ceramic TMY1 sample.

[0076] In this embodiment, the fracture toughness of the Si3N4 ceramic TMY1 after heat treatment reaches 9.8 MPa·m. 1 / 2 Its hardness reaches 13.28 GPa.

[0077] Comparative Example 1

[0078] This comparative example prepares Si3N4 ceramic product MY, and the preparation method includes the following steps:

[0079] (1) The raw material powders were weighed strictly according to the component ratio, including 90 parts by mass of α-Si3N4 powder (purity ≥99.9%, particle size D50=0.5μm), 3 parts by mass of Y2O3 powder (purity ≥99.9%, particle size 1μm), and 5 parts by mass of MgO powder (purity ≥99.9%, particle size 1μm); and an appropriate amount of anhydrous ethanol was used as the dispersion solvent, and Si3N4 balls were used as the grinding balls. The ball milling process was carried out in a planetary ball mill at a speed of 300 r / min for 12 h to obtain a uniformly mixed slurry.

[0080] (2) Pour the well-mixed slurry into an evaporating dish, then place it in a drying oven. Under 80°C, completely evaporate the anhydrous ethanol to obtain coarse powder. Grind the coarse powder multiple times using a mortar and pestle, and then pass it through a 60-mesh sieve to obtain fine powder with uniform particle size.

[0081] (3) The fine powder is loaded into a graphite mold and placed on a tablet press. Pre-pressing is performed under a pre-pressing pressure of 10 MPa to obtain the precursor.

[0082] (4) The precursor was placed in a rapid hot pressing sintering furnace for sintering. The sintering program was as follows: room temperature to 800℃, heating time 10 min, pressure 6 MPa; 800℃ to 1600℃, heating time 16 min, pressure 30 MPa; 1600℃ to 1700℃, heating time 3 min, pressure 30 MPa; 1700℃ for holding time 10 min, pressure 30 MPa; after sintering, it was allowed to cool naturally. The sintering process of Si3N4 ceramic MY was carried out in a vacuum environment throughout.

[0083] (5) After sintering, allow it to cool naturally and then demold to obtain Si3N4 ceramic;

[0084] (6) Heat treatment of Si3N4 ceramic: heat up to 1250℃ at a rate of 5℃ / min from room temperature and hold for 24h. After heat treatment, cool naturally to room temperature to obtain Si3N4 ceramic sample MY.

[0085] The fracture toughness and hardness of the Si3N4 ceramic MY sample after heat treatment are as follows: Figure 3 As shown in (a) and (b), the fracture toughness after heat treatment reaches 9.1 MPa·m. 1 / 2 The hardness increased by only 4.6% compared to before heat treatment, reaching 14.32 GPa.

[0086] Comparative Example 2

[0087] The difference from Example 1 is that MgO powder is replaced with Y2O3 powder in equal amounts, that is, 6.5 parts by mass of Y2O3 powder and 0 parts by mass of MgO powder, and the rest are the same as in Example 1.

[0088] Comparative Example 3

[0089] The difference from Example 1 is that Y2O3 powder is replaced with MgO powder in equal amounts, that is, 6.5 parts by mass of MgO powder and 0 parts by mass of Y2O3 powder, and the rest are the same as in Example 1.

[0090] Comparative Example 4

[0091] The difference from Example 1 is that the heat treatment method is as follows: the temperature is increased from room temperature to 1150°C at a rate of 5°C / min, and held at that temperature for 24 hours. All other aspects are the same as in Example 1.

[0092] Comparative Example 5

[0093] The difference from Example 1 is that the heat treatment method is as follows: the temperature is increased from room temperature to 1450°C at a rate of 5°C / min, and held at that temperature for 24 hours. All other aspects are the same as in Example 1.

[0094] Table 1 summarizes the relevant properties of the Si3N4 ceramics prepared in Examples 1-4 and Comparative Examples 1-5.

[0095] Table 1

[0096]

[0097] As shown in Table 1, with the addition of 1.5 wt% ZrO2, the fracture toughness after heat treatment reached 11.7 MPa·m. 1 / 2 The MY value increased by 31.6% compared to the untreated sample and by 28.8% compared to the heat-treated sample without additives. With the addition of 1.5 wt% TiO2, the fracture toughness reached 10.3 MPa·m after heat treatment. 1 / 2 Compared to the untreated sample, the MY was increased by 18.2%, and compared to the heat-treated sample without additives, it was increased by 13.1%. At the same time, by optimizing the heat treatment process parameters, such as temperature, time, and heating rate, the crystallization process was precisely controlled, which further enhanced the optimization effect of the microstructure and achieved a high efficiency improvement in the toughness of silicon nitride ceramics.

[0098] To verify the above experimental results, a series of analyses and characterizations were performed on the samples. The XRD patterns of the Si3N4 ceramic ZMY prepared in Example 1, the Si3N4 ceramic TMY prepared in Example 2, and the Si3N4 ceramic MY prepared in Comparative Example 1 are shown below. Figure 1As shown, in ZMY, TMY, and MY, Si3N4 exists as β-Si3N4, and α-Si3N4 is absent, indicating that the introduced sintering aids Y2O3 and MgO can promote the α / β phase transformation during the liquid-phase sintering of Si3N4. Before heat treatment, only the β-Si3N4 phase was present in the samples; after heat treatment, different crystalline phases precipitated in ZMY, TMY, and MY, demonstrating that heat treatment and the addition of additives achieved in-situ control of the crystallization of silicon nitride ceramics, and different properties were controlled by precipitating different crystalline phases.

[0099] To determine the grain size of the samples, the sample surface was polished and then etched using a sodium hydroxide (NaOH) solution at 400℃ for 1 minute. A 2000x image of the surface was then captured using a scanning electron microscope, and the results are as follows. Figure 2 As described in (a), the length distribution data of β-Si3N4 grains were statistically analyzed. The grain statistical results of the Si3N4 ceramic ZMY prepared in Example 1 are as follows: Figure 2 As shown in (b).

[0100] from Figure 2 As can be seen from the above, the Si3N4 ceramic ZMY prepared in Example 1 exhibits obvious bimodal grain size after heat treatment. The synergistic effect of this bimodal grain size can more effectively absorb external energy compared to a single grain structure, greatly improving the fracture toughness of silicon nitride ceramics and making them less prone to brittle fracture when subjected to impact or load.

[0101] In summary, this invention provides a method for preparing silicon nitride ceramics based on the synergistic effect of additive regulation and heat treatment. Through precise coordination of these two methods, it effectively enhances the toughness of the ceramic while ensuring good density and structural stability; and achieves a significant improvement in fracture toughness without compromising strength. In terms of process, utilizing the sintering system of this invention, sintering at 1700℃, 30MPa, and a nitrogen atmosphere under vacuum, combined with heat treatment, enables the preparation of high-performance Si3N4 ceramics. This method offers high production speed and low consumption, facilitating product commercialization and mass production.

[0102] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing high-toughness silicon nitride ceramic, characterized in that: Includes the following steps: α-Si3N4, sintering aid, and additives were mixed in a mass ratio of 85-95:5-10:1-5 and then wet ball-milled. The sintering aid was a mixture of MgO and Y2O3, with a mass ratio of MgO to Y2O3 of 1-1.5:

1. The additives were nano ZrO2 or TiO2. After ball milling, drying, grinding, and sieving, fine powder is obtained; Si3N4 ceramics are obtained by pre-pressing fine powder into shape and hot-pressing sintering. Si3N4 ceramic is obtained by heat treatment in an inert atmosphere at a temperature of 1200-1400℃ for 20-30 hours.

2. The method for preparing high-toughness silicon nitride ceramic according to claim 1, characterized in that: The mass ratio of α-Si3N4, sintering aids and additives is 87-93:5-8:1-3.

3. The method for preparing high-toughness silicon nitride ceramic according to claim 1, characterized in that: The solvent used in wet ball milling is anhydrous ethanol.

4. The method for preparing high-toughness silicon nitride ceramic according to claim 1, characterized in that: When sieving, pass through a 60-mesh sieve.

5. The method for preparing high-toughness silicon nitride ceramic according to claim 1, characterized in that: The pre-compression pressure is 5-15 MPa.

6. The method for preparing high-toughness silicon nitride ceramic according to claim 5, characterized in that: The pre-compression pressure is 7-13 MPa.

7. The method for preparing high-toughness silicon nitride ceramic according to claim 1, characterized in that: The sintering procedure for hot pressing sintering is as follows: 20-30℃ to 750-850℃, heating time 5-15min; 750-850℃ to 1570-1620℃, heating time 10-20min; 1570-1620℃ to 1680-1750℃, heating time 2-5min; holding at 1680-1750℃ for 8-15min, pressure 25-35MPa; after holding, cooling.

8. The method for preparing high-toughness silicon nitride ceramic according to claim 1, characterized in that: The heat treatment temperature is 1200-1300℃, and the holding time is 20-25h.

9. A high-toughness silicon nitride ceramic, characterized in that: It is prepared by any one of the preparation methods described in claims 1-8.

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