A solid solution strengthened silicon nitride-based network structure ceramic material and a preparation method and application thereof

Abstract

This invention relates to the field of silicon nitride composite materials, specifically to a solid solution reinforced silicon nitride-based network structure ceramic material, its preparation method, and its application. The invention involves a first mixing and coating of silicon nitride powder and a sintering aid, followed by a first sintering to obtain a single-layer shell-coated powder. A second mixing and coating with TiC is then performed, followed by a third mixing and coating with ZrB2. After pre-pressing and shaping, a second sintering is conducted to obtain a silicon nitride-based titanium carbide-zirconium boride solid solution network ceramic. By sequentially coating TiC and ZrB2, this invention achieves direct physical contact between TiC and ZrB2, significantly shortening the atomic diffusion path during sintering and forming a high-performance (Ti,Zr)(C,N) solid solution phase. Utilizing the solid solution strengthening effect and unique network structure of the TiC-ZrB2 system, the technical barrier of difficult physical contact and solid solution reaction between multiple reinforcing phases is successfully overcome, achieving a synergistic improvement in the material's strength and toughness.

Description

Technical Field

[0001] This invention relates to the field of silicon nitride composite materials technology, specifically to a solid solution reinforced silicon nitride-based network structure ceramic material, its preparation method, and its application. Background Technology

[0002] Silicon nitride (Si3N4) ceramics, as a typical high-temperature structural material, occupy an important position in mechanical engineering, aerospace, and automotive industries due to their high strength, chemical stability, corrosion resistance, and excellent thermal shock resistance. However, the inherent brittleness of covalently bonded silicon nitride ceramics limits their reliability under extremely complex stress environments. To improve this issue, introducing second-phase particles (such as carbides and borides) into the silicon nitride matrix to prepare multiphase ceramics is a common approach. Studies have shown that promoting solid solution reactions between reinforcing phases can significantly improve the strengthening and toughening effect of the material. However, achieving this goal in the silicon nitride system faces severe challenges. On the one hand, some reinforcing phases (such as TiC) readily produce undesirable byproducts (such as N2) with the silicon nitride matrix during high-temperature sintering, ultimately leaving micropores inside the ceramic and severely impairing the material's mechanical properties.

[0003] To overcome the above problems, one improvement approach is to introduce multiple mutually soluble reinforcing phases and promote their solid solution reaction, thereby forming a composite reinforcing phase with excellent mechanical properties without damaging the Si3N4 matrix. However, in traditional ball milling processes, multiple additive phase powders can only be uniformly dispersed in the Si3N4 matrix. This dispersion state makes it difficult for different types of reinforcing phases to achieve effective physical contact, ultimately hindering atomic diffusion and making it difficult for solid solution reactions between multiple phases to occur, thus failing to form the expected solid solution strengthening effect.

[0004] Therefore, it is urgent to solve the fundamental problem of "difficulty in contact and reaction" between multi-component reinforcing phases in order to ultimately achieve a synergistic improvement in the strength and toughness of silicon nitride ceramics. Summary of the Invention

[0005] Therefore, the purpose of this invention is to provide a solid solution reinforced silicon nitride-based network structure ceramic material, its preparation method, and its applications. The preparation method provided by this invention introduces a novel isolated network structure, successfully overcoming the technical barriers of difficult physical contact and solid solution reaction between multiple reinforcing phases, ultimately achieving a synergistic improvement in the material's strength and toughness.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a solid solution reinforced silicon nitride-based network structure ceramic material, comprising the following steps: Silicon nitride powder and sintering aid are first mixed and coated, and then sintered to obtain a single-layer shell coated powder. The single-shell coated powder and TiC are mixed and coated a second time to obtain a double-shell coated powder; The double-shell coated powder and ZrB2 are mixed and coated a third time to obtain a triple-shell coated powder; After pre-pressing and shaping the three-shell coated powder, a second sintering is performed to obtain a silicon nitride-based titanium carbide-zirconium boride solid solution network ceramic.

[0007] Preferably, the silicon nitride has a particle size of 30~100μm; The sintering aids include Al2O3 and Y2O3; the mass ratio of Al2O3 to Y2O3 is 1:1.5~4; The mass ratio of silicon nitride to sintering aid is 85~95:5~15.

[0008] Preferably, the mass ratio of the single-layer shell-coated powder to TiC is 85~90:4~10.

[0009] Preferably, the mass ratio of TiC to ZrB2 is 1:0.5~1.5.

[0010] Preferably, the mass ratio of the single-layer shell-coated powder to the total mass of TiC and ZrB2 is 85~90:10~15.

[0011] Preferably, the time for the first, second, and third mixing coatings is 6 to 10 hours, and the first, second, and third mixing coatings are carried out under stirring conditions, with the stirring speed being 60 to 85 r / min.

[0012] Preferably, the temperature of the first sintering is 1400~1500℃ and the time is 0.5~1h.

[0013] Preferably, the second sintering includes spark plasma sintering, wherein the conditions for spark plasma sintering include: a sintering temperature of 1750~1850℃, a sintering time of 13min, a sintering pressure of 40MPa, a sintering atmosphere of nitrogen, and a gauge pressure of 0.7~0.9kPa.

[0014] The present invention also provides a solid solution reinforced silicon nitride-based network structure ceramic material prepared by the preparation method described in the above technical solution.

[0015] The present invention also provides the application of the solid solution reinforced silicon nitride-based network structure ceramic material described above in aerospace hot-end structural components, precision bearings, cutting tools or semiconductor support components.

[0016] This invention optimizes interfacial wettability and reduces interfacial defects caused by differences in thermal expansion coefficients between phases by coating the surface of Si3N4 with a sintering aid. By sequentially coating TiC and ZrB2, this invention achieves direct physical contact between TiC and ZrB2, significantly shortening the atomic diffusion path during sintering and forming a high-performance (Ti,Zr)(C,N) solid solution phase. The solid solution phase is connected in a three-dimensional continuous network within the Si3N4 matrix. When cracks propagate in the material, this network structure effectively induces crack deflection, bridging, and pinning, greatly dissipating fracture energy and thus significantly improving the fracture toughness of the material. Simultaneously, the load-bearing capacity of the network skeleton ensures the high strength of the material.

[0017] Furthermore, this invention uses Al2O3 and Y2O3 as sintering aids, which can form a low-melting-point eutectic liquid phase to further promote densification, optimize interfacial wettability, and reduce interfacial defects caused by differences in thermal expansion coefficients between the phases.

[0018] The preparation method provided by this invention utilizes the solid solution strengthening effect and unique network structure of the TiC-ZrB2 system to successfully overcome the technical barrier of difficult physical contact and solid solution reaction between multiple reinforcing phases, thereby achieving a synergistic improvement in the strength and toughness of the material and enhancing the mechanical properties and service reliability of silicon nitride ceramics.

[0019] The preparation method provided by this invention requires no treatment or processing of the powder raw materials, and the mixing process does not require any other mixing medium, which greatly improves production efficiency and provides the possibility for industrial mass production of silicon nitride-based composite materials. Attached Figure Description

[0020] Figure 1 Scanning electron microscope image and elemental analysis results of the solid solution reinforced silicon nitride-based network structure ceramic material prepared in Example 1; Figure 2 This is a scanning electron microscope image of the surface of the solid solution reinforced silicon nitride-based network structure ceramic material prepared in Example 2 after polishing. Figure 3 Scanning electron microscope (SEM) image and elemental analysis diagram of the polished surface of the solid solution reinforced silicon nitride-based network structure ceramic material prepared in Example 3. Detailed Implementation

[0021] This invention also provides a method for preparing a solid solution reinforced silicon nitride-based network structure ceramic material, comprising the following steps: Silicon nitride powder and sintering aid are first mixed and coated, and then sintered to obtain a single-layer shell coated powder. The single-shell coated powder and TiC are mixed and coated a second time to obtain a double-shell coated powder; The double-shell coated powder and ZrB2 are mixed and coated a third time to obtain a triple-shell coated powder; After pre-pressing and shaping the three-shell coated powder, a second sintering is performed to obtain a silicon nitride-based titanium carbide-zirconium boride solid solution network ceramic.

[0022] Unless otherwise specified, the materials and equipment used in this invention are all commercially available products in the field.

[0023] This invention involves first mixing and coating silicon nitride powder with a sintering aid, followed by a first sintering, to obtain a single-layer coated powder. In this invention, the particle size of the silicon nitride can be 30-100 μm, or 40-80 μm, or even 50-60 μm. In this invention, the sintering aid can include Al₂O₃ and Y₂O₃; the mass ratio of Al₂O₃ to Y₂O₃ can be 1:1.5-4, or 1:2-3, or even 1:2-2.5, or specifically 3:7. In this invention, the mass ratio of silicon nitride to the sintering aid can be 85-95:5-15, or 88-92:8-12, or specifically 90:10. In this invention, the first mixing and coating time can be 6-10 hours, 7-10 hours, 8-10 hours, or specifically 9 hours or 10 hours; the first mixing and coating can be carried out under stirring conditions, and the stirring speed can be specifically 60-85 r / min, 70-85 r / min, or specifically 80-85 r / min. In this invention, the first sintering temperature can be specifically 1400-1500℃, 1450-1500℃, or specifically 1480-1500℃; the first sintering time can be specifically 30-60 minutes, 40-60 minutes, or specifically 50-60 minutes.

[0024] After obtaining the single-shell coated powder, the present invention performs a second mixing and coating process with TiC to obtain a double-shell coated powder. In this invention, the mass ratio of the single-shell coated powder to TiC can be 85~90:4~10, or 85~90:4~8, specifically 85:7.5, 90:6.6, 90:5, or 90:4. In this invention, the second mixing and coating time can be 10 hours, and the second mixing and coating can be carried out under stirring conditions, specifically at a stirring speed of 85 r / min.

[0025] After obtaining the double-shell coated powder, the present invention performs a third mixing and coating with ZrB2 to obtain a triple-shell coated powder. In this invention, the mass ratio of TiC to ZrB2 can be 1:0.5~1.5, specifically 6.6:3.4, 1:1, or 1:1.5. In this invention, the third mixing and coating time can be 10 hours, and the third mixing and coating can be carried out under stirring conditions, specifically at a stirring speed of 85 r / min.

[0026] After obtaining the three-shell coated powder, the present invention pre-presses and shapes the powder before a second sintering to obtain a silicon nitride-based titanium carbide-zirconium boride solid solution network ceramic. In this invention, the pre-pressing and shaping time can be specifically 2-5 minutes, or 3-5 minutes, or even 4-5 minutes; the present invention does not have a specific limitation on the pre-pressing and shaping pressure, as long as the pre-pressed and shaped material does not shed powder when moved to the sintering equipment; the pre-pressing and shaping can be performed in a graphite mold. In this invention, the second sintering can include spark plasma sintering (SPS), and the conditions for spark plasma sintering can include: a sintering temperature of 1750-1850℃, or 1800-1850℃; a sintering time of 13 minutes; a sintering pressure of 40 MPa; a sintering atmosphere of nitrogen; and a gauge pressure of 0.7-0.9 kPa, or 0.7-0.8 kPa. The present invention enables the slow decomposition of silicon nitride during high-temperature sintering by sintering under a nitrogen atmosphere. After the second sintering is completed, the present invention may further include cooling the system after the second sintering to room temperature, wherein the cooling rate may be 80~120℃ / min, or 90~110℃ / min, or specifically 100℃ / min.

[0027] This invention also provides a solid solution-reinforced silicon nitride-based network structure ceramic material prepared by the preparation method described above. By designing a special multilayer coated powder structure, this invention introduces a high-performance (Ti,Zr)(C,N) solid solution phase into the Si3N4 matrix to form an isolation network structure, successfully overcoming the technical barrier of difficult physical contact and solid solution reaction between multiple reinforcing phases. Furthermore, the (Ti,Zr)(C,N) solid solution phase can effectively inhibit crack propagation, ultimately achieving a synergistic improvement in the strength and toughness of silicon nitride ceramics.

[0028] This invention also provides the application of the solid solution-reinforced silicon nitride-based network structure ceramic material described above in aerospace hot-end structural components, precision bearings, cutting tools, or semiconductor support components. In this invention, the aerospace hot-end structural component may include turbine blades or rotors; the precision bearing may include engine bearings, machine tool spindle bearings, or high-speed train bearings.

[0029] To further illustrate the present invention, the solid solution reinforced silicon nitride-based network structure ceramic materials, their preparation methods, and applications provided by the present invention are described in detail below with reference to embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0030] In the following embodiments, the mixing and coating are carried out in a mixer.

[0031] Example 1 (1) Spherical silicon nitride powder, Al2O3 and Y2O3 with a mass ratio of 90:3:7 were mixed and coated at 85 r / min for 10 h, and then sintered at 1400℃ without pressure for 30 min to fix the sintering aid on the surface of silicon nitride microspheres and obtain a single-layer shell coated powder.

[0032] (2) TiC and single-shell coated powder with a mass ratio of 6.6:90 were mixed and coated at 85 r / min for 10 h to obtain double-shell coated powder.

[0033] (3) Mix ZrB2 and double-shell coated powder in a mass ratio of 3.4:96.6 at 85 r / min for 10 h to obtain triple-shell coated powder.

[0034] (4) The three-shell coated powder was placed into a graphite mold and pre-pressed under a hydraulic press for 5 min. It was then sintered in a nitrogen atmosphere at 1800℃, 40MPa for 13 min and cooled to room temperature at a cooling rate of 100℃ / min before demolding to obtain silicon nitride-based titanium carbide-zirconium boride solid solution network ceramic.

[0035] Figure 1 The image shows the scanning electron microscope (SEM) image of the powder obtained in step (3) of Example 1 and its elemental analysis results. The Ti and Zr element signals appearing on the silicon nitride spherical powder indicate the formation of a double core-shell coating structure.

[0036] The solid solution-reinforced silicon nitride-based network structure ceramic material prepared in Example 1 has a flexural strength of 508.5 MPa and a fracture toughness of 7.5 MPa·m. 1 / 2 Its Vickers hardness is 15.3 GPa.

[0037] Example 2 The only difference from Example 1 is that the mass ratio of TiC to single-shell coated powder is 5:90; and the mass ratio of ZrB2 to double-shell coated powder is 5:95.

[0038] Figure 2 The image shows a scanning electron microscope (SEM) image of the surface of the solid solution-reinforced silicon nitride-based network structure ceramic material prepared in Example 2 after polishing. The dark phase is Si3N4, while the continuous bright phase is identified as (Ti,Zr)(C,N), which is generated by the in-situ reaction of TiC and ZrB2.

[0039] The solid solution-reinforced silicon nitride-based network structure ceramic material prepared in Example 2 has a flexural strength of 490.3 MPa and a fracture toughness of 8.0 MPa·m. 1 / 2 Its Vickers hardness is 15.2 GPa.

[0040] Example 3 The only difference from Example 1 is that the mass ratio of TiC to single-shell coated powder is 4:90; and the mass ratio of ZrB2 to double-shell coated powder is 6:94.

[0041] Figure 3 The image shows a scanning electron microscope (SEM) image and elemental analysis diagram of the polished surface of the solid solution reinforced silicon nitride-based network structure ceramic material prepared in Example 3. It can be seen that the signals of Zr, C and Ti elements overlap in the network region, indicating the formation of (Ti,Zr)(C,N).

[0042] The solid solution-reinforced silicon nitride-based network structure ceramic material prepared in Example 3 exhibits a flexural strength of 393.5 MPa and a fracture toughness of 6.4 MPa·m. 1 / 2 Its Vickers hardness is 17.0 GPa.

[0043] Example 4 The only difference from Example 1 is that the mass ratio of TiC to single-shell coated powder is 7.5:85; the mass ratio of ZrB2 to double-shell coated powder is 7.5:92.5; and the sintering temperature is 1850℃.

[0044] The solid solution-reinforced silicon nitride-based network structure ceramic material prepared in Example 4 has a flexural strength of 414.2 MPa and a fracture toughness of 7.0 MPa·m. 1 / 2 Its Vickers hardness is 13.9 GPa.

[0045] Comparative Example 1 The only difference from Example 1 is that the single-layer shell coated powder obtained in step (1) is directly sintered in SPS at 1750°C, 40MPa and nitrogen atmosphere for 13 minutes to obtain ceramic material.

[0046] The ceramic material prepared in Comparative Example 1 has a flexural strength of 592.8 MPa and a fracture toughness of 4.7 MPa·m. 1 / 2 The ceramic material prepared in this comparative proportion has low fracture toughness.

[0047] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a solid solution reinforced silicon nitride-based network structure ceramic material, comprising the following steps: Silicon nitride powder and sintering aid are first mixed and coated, and then sintered to obtain a single-layer shell coated powder. The single-shell coated powder and TiC are mixed and coated a second time to obtain a double-shell coated powder; The double-shell coated powder and ZrB2 are mixed and coated a third time to obtain a triple-shell coated powder; After pre-pressing and shaping the three-shell coated powder, a second sintering is performed to obtain a silicon nitride-based titanium carbide-zirconium boride solid solution network ceramic.

2. The preparation method according to claim 1, characterized in that, The silicon nitride has a particle size of 30~100μm; The sintering aids include Al2O3 and Y2O3; the mass ratio of Al2O3 to Y2O3 is 1:1.5~4; The mass ratio of silicon nitride to sintering aid is 85~95:5~15.

3. The preparation method according to claim 1, characterized in that, The mass ratio of the single-layer shell-coated powder to TiC is 85~90:4~10.

4. The preparation method according to claim 1, characterized in that, The mass ratio of TiC to ZrB2 is 1:0.5~1.

5.

5. The preparation method according to claim 1, characterized in that, The mass ratio of the single-layer shell-coated powder to the total mass of TiC and ZrB2 is 85~90:10~15.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The first, second, and third mixing coatings are carried out over a period of 6 to 10 hours, and are performed under stirring conditions at a speed of 60 to 85 r / min.

7. The preparation method according to claim 1 or 2, characterized in that, The first sintering temperature is 1400~1500℃ and the time is 30~60min.

8. The preparation method according to any one of claims 1 to 5, characterized in that, The second sintering includes spark plasma sintering, and the conditions for spark plasma sintering include: sintering temperature of 1750~1850℃, sintering time of 13min, sintering pressure of 40MPa, sintering atmosphere of nitrogen, and gauge pressure of 0.7~0.9kPa.

9. A solid solution reinforced silicon nitride-based network structure ceramic material prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the solid solution reinforced silicon nitride-based network structure ceramic material according to claim 9 in aerospace hot-end structural components, precision bearings, cutting tools or semiconductor support components.

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