Silicon nitride-molybdenum composite and method for producing the same

Abstract

This application relates to the field of inorganic non-metallic materials and discloses a novel high-strength and high-toughness silicon nitride-molybdenum composite material and its preparation method. The preparation method includes: mixing α-Si3N4, a molybdenum-containing metal phase, and a sintering aid to obtain a mixture; sintering the mixture to obtain the silicon nitride-molybdenum composite material; wherein the mass ratio of the molybdenum-containing metal phase to α-Si3N4 satisfies: 0 < molybdenum-containing metal phase / (α-Si3N4 + molybdenum-containing metal phase) ≤ 25%; the silicon nitride-molybdenum composite material includes a matrix and a second phase, wherein the matrix is ​​β-Si3N4, and the second phase includes a silicon-molybdenum compound, wherein the silicon-molybdenum compound includes Mo5Si3, and the mass ratio of Mo5Si3 in the silicon-molybdenum compound is > 50%. The fracture toughness of the composite material obtained by this application can reach 1-13 MPa·m. 1 / 2 The flexural strength can reach 210-920 MPa. In addition, the introduction of Mo5Si3 increases the Vickers hardness of the composite material to 1340-2100 HV, which is significantly higher than that of traditional silicon nitride ceramic composite materials.

Description

Technical Field

[0001] This application relates to the field of inorganic non-metallic materials, specifically to a silicon nitride-molybdenum composite material and its preparation method. Background Technology

[0002] Silicon nitride (Si3N4) ceramics possess high strength, high Vickers hardness, excellent thermal shock resistance, and high-temperature stability, making them a key material in aerospace, energy equipment, and precision manufacturing.

[0003] Because N-Si bonds are covalent, silicon nitride is a brittle material, limiting its practical applications. To improve its inherent brittleness, molybdenum is often introduced as a toughening phase, for example, by utilizing molybdenum's plastic deformation and interfacial bonding with the matrix to enhance the toughness of the composite material. However, during high-temperature sintering or service, molybdenum readily reacts with silicon in the silicon nitride matrix, generally forming MoSi2 and Mo5Si3. Current technology considers MoSi2 to be a stable phase, and the toughness of pure MoSi2 silicon nitride-molybdenum composites can reach 7.6 MPa·m. 1 / 2 The compressive strength is about 3000 MPa - 4500 MPa, but there are a lot of Si-Si covalent bonds in MoSi2, which is a brittle phase, resulting in low bending strength (about 300 MPa).

[0004] Therefore, it is necessary to develop a silicon nitride-molybdenum composite material that can significantly improve the flexural strength and fracture toughness of the composite material without sacrificing the material strength, overcome the performance bottlenecks in the existing technology, and broaden the application range. Summary of the Invention

[0005] This application provides a novel high-strength and high-toughness silicon nitride-molybdenum composite material and its preparation method. The silicon nitride-molybdenum composite material prepared by this method has advantages such as high flexural strength, high Vickers hardness, good fracture toughness, and high density.

[0006] In particular, this invention relates to a silicon nitride ceramic composite material whose mechanical strength and fracture toughness are significantly enhanced by adding metallic molybdenum and rare earth oxides to regulate the phase composition of Si3N4-Mo, and its preparation method.

[0007] To address the aforementioned technical problems, the first aspect of this application proposes a method for preparing a silicon nitride-molybdenum composite material, comprising the following steps: α-Si3N4, molybdenum-containing metallic phase, and sintering aids were mixed to obtain a mixture; The mixture is sintered to obtain the silicon nitride-molybdenum composite material; The mass ratio of molybdenum-containing metal phase to α-Si3N4 satisfies the following condition: 0 < molybdenum-containing metal phase / (α-Si3N4 + molybdenum-containing metal phase) < 25%; The silicon nitride-molybdenum composite material includes a matrix and a second phase. The matrix is ​​β-Si3N4, and the second phase includes a silicon-molybdenum compound, which includes Mo5Si3, and the mass ratio of Mo5Si3 in the silicon-molybdenum compound is >50%.

[0008] Optionally, the sintering aid includes rare earth oxides, said rare earth oxides including at least one of yttrium oxide, lanthanum oxide, aluminum oxide, and lutetium oxide.

[0009] Optionally, the particle size of the sintering aid is 50 nm to 5 μm.

[0010] Optionally, the particle size of α-Si3N4 is 50 nm to 5 μm.

[0011] Optionally, the amount of the sintering aid added is 1 to 10 mol of the metal phase.

[0012] Further, the mixing process includes: ball milling and mixing α-Si3N4, the molybdenum-containing metal phase, and the sintering aid to obtain a mixture; The ball mill rotates at a speed of 100 to 300 rpm, and the milling time is 4 to 48 hours.

[0013] The sintering process includes: drying and grinding the mixture, then loading it into a graphite mold, and performing the sintering process in an SPS sintering furnace (discharge plasma sintering furnace) to obtain the silicon nitride-molybdenum composite material.

[0014] Optionally, the sintering temperature is 1500 ~ 1700 °C; The sintering process takes 240 to 1800 seconds. The heating rate of the sintering process is 50 ~ 300 °C / min; The atmosphere for the sintering process is a vacuum or N2; The sintering process is performed at a pressure of 40 to 100 MPa.

[0015] In a second aspect of this application, a silicon nitride-molybdenum composite material obtained by the above-described method for preparing the silicon nitride-molybdenum composite material is provided.

[0016] The fracture toughness of the silicon nitride-molybdenum composite material described above is 1~13 MPa·m. 1 / 2 ; The flexural strength of the aforementioned silicon nitride-molybdenum composite material is 210 ~ 920 MPa; The Vickers hardness of the above silicon nitride-molybdenum composite material is 1340 ~ 2100 HV.

[0017] Compared with the prior art, the embodiments of this application have the following beneficial effects: This application uses an appropriate amount of rare earth oxides as a sintering aid to promote the preferential conversion of a large amount of α-Si3N4 raw material into β-Si3N4, thereby reducing the silicon source participating in the Mo reaction and inhibiting the formation of Si-rich MoSi2 phase. At the same time, a Mo-rich Mo5Si3 phase is obtained. Mo-rich Mo5Si3 has a metallic property, thus exhibiting superior toughness and effectively absorbing stress, thereby improving the fracture toughness and flexural strength of the ceramic.

[0018] A third aspect of this application proposes an application of the aforementioned silicon nitride-molybdenum composite material in the fields of aerospace, energy equipment, and precision manufacturing. Attached Figure Description

[0019] Figure 1 The X-ray diffraction patterns of the silicon nitride-molybdenum composite materials prepared in Examples 1 and 7 of this application are compared with the standard card.

[0020] Figure 2 This is a sample image of the silicon nitride-molybdenum composite material prepared in Example 7 of this application.

[0021] Figure 3 This is a sample image of the silicon nitride-molybdenum composite material prepared in Example 1 of this application.

[0022] Figure 4 The image shows the Vickers hardness test indentation results of the silicon nitride-molybdenum composite material prepared in Example 1 of this application. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0024] Example 1 A novel high-strength and high-toughness silicon nitride-molybdenum composite material and its preparation method are disclosed, comprising the following steps: Si3N4 (particle size 50 nm), molybdenum-containing metal phase (particle size 50 nm), and La2O3 (particle size 50 nm) are ball-milled and mixed, wherein the mass ratio of Si3N4 to molybdenum-containing metal phase is 9:1, and the amount of La2O3 added is 10 mol% of molybdenum-containing metal phase. The ball milling parameters are 100 rpm / min and 4 h to obtain a mixture. After drying and grinding, the mixture is placed in a graphite mold and sintered in SPS at a sintering temperature of 1650 °C, a sintering time of 240 s, a sintering pressure of 100 MPa, a sintering heating rate of 300 °C / min, and a sintering atmosphere of N2. After sintering, the product is naturally cooled and removed, and polished to obtain the novel high-strength and high-toughness silicon nitride-molybdenum composite material.

[0025] Example 2 A novel high-strength and high-toughness silicon nitride-molybdenum composite material and its preparation method are disclosed, comprising the following steps: Si3N4 (particle size 50 nm), a molybdenum-containing metal phase (particle size 5 μm), and Lu2O3 (particle size 50 nm) are ball-milled and mixed, wherein the mass ratio of Si3N4 to the molybdenum-containing metal phase is 99:1, and the amount of La2O3 added is 1 mol% of the molybdenum-containing metal phase. The ball milling parameters are 300 rmp / min and 4 h to obtain a mixture. After drying and grinding, the mixture is placed in a graphite mold and sintered in SPS at a sintering temperature of 1650 °C, a sintering time of 240 s, a sintering pressure of 40 MPa, a sintering heating rate of 300 °C / min, and a sintering atmosphere of N2. After sintering, the product is naturally cooled and removed, and polished to obtain the novel high-strength and high-toughness silicon nitride-molybdenum composite material.

[0026] Example 3 A novel high-strength and high-toughness silicon nitride-molybdenum composite material and its preparation method are disclosed, comprising the following steps: Si3N4 (particle size 50 nm), a molybdenum-containing metal phase (particle size 50 nm), and La2O3 (particle size 5 μm) are ball-milled and mixed, wherein the mass ratio of Si3N4 to the molybdenum-containing metal phase is 75:25, and the amount of La2O3 added is 10 mol% of the molybdenum-containing metal phase. The ball milling parameters are 100 rpm / min and 48 h to obtain a mixture. After drying and grinding, the mixture is placed in a graphite mold and sintered in SPS at a sintering temperature of 1650 °C, a sintering time of 240 s, a sintering pressure of 40 MPa, a sintering heating rate of 300 °C / min, and sintering is carried out under vacuum conditions. After sintering, the product is naturally cooled and removed, and polished to obtain the novel high-strength and high-toughness silicon nitride-molybdenum composite material.

[0027] Example 4 A novel high-strength and high-toughness silicon nitride-molybdenum composite material and its preparation method are disclosed, comprising the following steps: Si3N4 (particle size 5 μm), a molybdenum-containing metal phase (particle size 5 μm), and sintering aids (La2O3, Y2O3, Al2O3, and Lu2O3, all with a particle size of 50 nm) are ball-milled and mixed. The mass ratio of Si3N4 to the molybdenum-containing metal phase is 90:10, and the amount of sintering aid added is 9 mol% of the molybdenum-containing metal phase. The molar ratio of La2O3, Y2O3, Al2O3, and Lu2O3 is 2:2:2:3. The ball milling parameters are 100 rmp / min for 4 h to obtain the mixture. After drying and grinding, the mixture is placed in a graphite mold and sintered in SPS at a sintering temperature of 1700 °C, a sintering time of 240 s, a sintering pressure of 40 MPa, and a sintering heating rate of 300 °C. The product was removed by sintering at °C / min under N2 atmosphere and allowed to cool naturally. After polishing, a novel high-strength and high-toughness silicon nitride-molybdenum composite material was obtained.

[0028] Example 5 A novel high-strength and high-toughness silicon nitride-molybdenum composite material and its preparation method are disclosed, comprising the following steps: Si3N4 (particle size 50 nm), molybdenum-containing metal phase (particle size 5 μm) and Al2O3 (particle size 5 μm) are ball-milled and mixed, wherein the mass ratio of Si3N4 to molybdenum-containing metal phase is 9:1, and the amount of Al2O3 added is 8 mol% of molybdenum-containing metal phase. The ball milling parameters are 100 rmp / min and 4 h to obtain a mixture. After drying and grinding, the mixture is placed in a graphite mold and sintered in SPS at a sintering temperature of 1500 °C, a sintering time of 1800 s, a sintering pressure of 100 MPa, a sintering heating rate of 50 °C / min, and a sintering atmosphere of N2. After natural cooling, the product is removed and polished to obtain the novel high-strength and high-toughness silicon nitride-molybdenum composite material.

[0029] Example 6 A novel high-strength and high-toughness silicon nitride-molybdenum composite material and its preparation method are disclosed, comprising the following steps: Si3N4 (particle size 5 μm), molybdenum-containing metal phase (particle size 50 nm), and Lu2O3 (particle size 5 μm) are ball-milled and mixed, wherein the mass ratio of Si3N4 to molybdenum-containing metal phase is 9:1, and the amount of Lu2O3 added is 5 mol% of molybdenum-containing metal phase. The ball milling parameters are 100 rmp / min and 4 h to obtain a mixture. After drying and grinding, the mixture is placed in a graphite mold and sintered in SPS at a sintering temperature of 1650 °C, a sintering time of 240 s, a sintering pressure of 40 MPa, a sintering heating rate of 300 °C / min, and sintering is carried out under vacuum conditions. After natural cooling, the product is removed and polished to obtain the novel high-strength and high-toughness silicon nitride-molybdenum composite material.

[0030] Example 7 A novel high-strength and high-toughness silicon nitride-molybdenum composite material and its preparation method are disclosed, comprising the following steps: weighing Si3N4 (particle size 5 μm), molybdenum-containing metal phase (particle size 5 μm), and Y2O3 (particle size 5 μm) and ball milling them together, wherein the mass ratio of Si3N4 to molybdenum-containing metal phase is 9:1, and the amount of Y2O3 added is 2 mol% of the molybdenum-containing metal phase, the ball milling parameters are 100 rpm / min and 4 h to obtain a mixture, the mixture is dried and ground and then placed into a graphite mold, sintered in SPS at a sintering temperature of 1650 °C, a sintering time of 240 s, a sintering pressure of 40 MPa, a sintering heating rate of 300 °C / min, and a sintering atmosphere of N2, the product is removed by natural cooling, and the novel high-strength and high-toughness silicon nitride-molybdenum composite material is obtained after polishing.

[0031] Example 8 A novel high-strength and high-toughness silicon nitride-molybdenum composite material and its preparation method are disclosed, comprising the following steps: Si3N4 (particle size 5 μm), molybdenum-containing metal phase (particle size 5 μm) and La2O3 (particle size 5 μm) are ball-milled and mixed, wherein the mass ratio of Si3N4 to molybdenum-containing metal phase is 9:1, and the amount of La2O3 added is 1 mol% of molybdenum-containing metal phase. The ball milling parameters are 100 rmp / min and 4 h to obtain a mixture. After drying and grinding, the mixture is placed in a graphite mold and sintered in SPS at a sintering temperature of 1650 °C, a sintering time of 240 s, a sintering pressure of 40 MPa, a sintering heating rate of 300 °C / min, and sintering is carried out under vacuum conditions. After natural cooling, the product is removed and polished to obtain the novel high-strength and high-toughness silicon nitride-molybdenum composite material.

[0032] Comparative Example 1 Same as Example 1, the main difference being the absence of a molybdenum-containing metal phase.

[0033] Test methods The fracture toughness test method for silicon nitride-molybdenum composites is GB / T44547-2024 "Test Method for Fracture Toughness of Fine Ceramics - Single-sided V-beam (SEVNB) Method".

[0034] Vickers hardness test method for silicon nitride-molybdenum composite materials: GB / T16534-2009 "Test method for Vickers hardness of fine ceramics at room temperature" is adopted.

[0035] The method for testing the flexural strength of silicon nitride-molybdenum composite materials is GB / T 6569-2006 "Test Method for Flexural Strength of Fine Ceramics".

[0036] Test Analysis: XRD analysis was performed on the silicon nitride-molybdenum composite materials prepared in Examples 1 and 7, and the results are as follows: Figure 1 As shown, the sample of Example 1 contains β-Si3N4 and Mo5Si3 phases, while the sample of Example 7 contains β-Si3N4, Mo5Si3 and MoSi2 phases. The proportions of MoSi2 and Mo5Si3 in the XRD of the other examples and comparative examples are shown in Table 1. Specifically, the proportions of MoSi2 and Mo5Si3 in the sample can be obtained by XRD, and thus the MoSi2:Mo5Si3 ratio in the sample can be obtained.

[0037] The performance of the samples prepared in Examples 1-8 and Comparative Example 1 was tested and analyzed, and the results are shown in Table 1. Table 1: List of sample composition and performance parameters for Examples 1-8 and Comparative Example 1

[0038] Based on Examples 1-8 above, and as shown in Comparative Example 1, increasing the molybdenum-containing metal phase can improve Vickers hardness, fracture toughness, and flexural strength. Comparing Example 1 with Examples 4-8, it is evident that the content of Mo5Si3 increases with the increase of oxide content. Preferably, the higher the Mo5Si3 content, the higher the Vickers hardness, fracture toughness, and flexural strength of the material; preferably, the Mo5Si3 content is greater than or equal to 90%.

[0039] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above descriptions are merely specific embodiments of this application and are not intended to limit the scope of protection of this application. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application for those skilled in the art.

Claims

1. A method for preparing a silicon nitride-molybdenum composite material, characterized in that, Includes the following steps: α-Si3N4, molybdenum-containing metallic phase, and sintering aids were mixed to obtain a mixture; The mixture is sintered to obtain the silicon nitride-molybdenum composite material; The mass ratio of molybdenum-containing metal phase to α-Si3N4 satisfies the following condition: 0 < molybdenum-containing metal phase / (α-Si3N4 + molybdenum-containing metal phase) ≤ 25%; The silicon nitride-molybdenum composite material includes a matrix and a second phase. The matrix is ​​β-Si3N4, and the second phase includes a silicon-molybdenum compound, which includes Mo5Si3, and the mass ratio of Mo5Si3 in the silicon-molybdenum compound is >50%.

2. The preparation method according to claim 1, characterized in that, At least one of the following conditions must be met: The mass ratio of Mo5Si3 in the silicon-molybdenum compound is >90%; The particle size of the α-Si3N4 is 50 nm to 5 μm; The molybdenum-containing metal phase has a particle size of 50 nm to 5 μm; The sintering aid includes rare earth oxides, which include at least one of yttrium oxide, lanthanum oxide, aluminum oxide, and lutetium oxide. The particle size of the sintering aid is 50 nm to 5 μm.

3. The preparation method according to claim 1, characterized in that, The amount of the sintering aid added is 1 mol% to 10 mol% of the molybdenum-containing metal phase.

4. The preparation method according to claim 1, characterized in that, The mixing process includes: α-Si3N4, the molybdenum-containing metal phase, and the sintering aid were ball-milled to obtain a mixture. The ball mill operates at a speed of 100 rpm to 300 rpm, and the milling time is 4 h to 48 h.

5. The preparation method according to claim 1, characterized in that, The sintering process includes: The mixture is dried and ground, then placed into a graphite mold and sintered in an SPS sintering furnace to obtain the silicon nitride-molybdenum composite material.

6. The preparation method according to claim 1, characterized in that, At least one of the following conditions must be met: The sintering temperature is 1500 ~ 1700 ℃; The sintering process takes 240 to 1800 seconds. The heating rate of the sintering process is 50 ~ 300 °C / min; The sintering process is carried out in a vacuum or N2 atmosphere.

7. The preparation method according to claim 1, characterized in that, The sintering process is performed at a pressure of 40 to 100 MPa.

8. A silicon nitride-molybdenum composite material, characterized in that, It is obtained by the preparation method described in any one of claims 1 to 7.

9. The silicon nitride-molybdenum composite material according to claim 8, characterized in that, At least one of the following conditions must be met: The fracture toughness of the silicon nitride-molybdenum composite material is 1~13 MPa·m. 1 / 2 ; The flexural strength of the silicon nitride-molybdenum composite material is 210~920 MPa; The Vickers hardness of the silicon nitride-molybdenum composite material is 1340 ~ 2100 HV.

10. The application of a silicon nitride-molybdenum composite material as described in any one of claims 8 to 9 in the fields of aerospace, energy equipment, and precision manufacturing.

Images