High-performance silicon nitride ceramic composite material and preparation method thereof

Abstract

The invention discloses a high-performance silicon nitride ceramic composite material and a preparation method thereof, and particularly relates to the technical field of preparation of ceramic composite materials. The composite material is prepared from the following components in percentage by mass: 70 to 85 percent of silicon nitride, 5 to 15 percent of carbon fiber, 3 to 10 percent of sintering aid, 5 to 10 percent of zirconium oxide, 3 to 8 percent of yttrium oxide stabilized zirconium oxide, 1 to 5 percent of graphene and 2 to 6 percent of barium titanate. The silicon nitride is high-purity submicron particles, the carbon fiber has a specific length-diameter ratio and a specific diameter, the sintering aid is selected from specific substances, and the preparation method comprises the following steps: weighing the raw materials in proportion, adding a dispersing agent, a binding agent and a defoaming agent, carrying out ball milling by taking ethanol or methanol as a medium to prepare ceramic slurry, and molding by adopting an injection molding process. And drying the green body, and sintering under a specific nitrogen atmosphere condition. The composite material has the advantages of high strength, high toughness, favorable dielectric properties, excellent high-temperature resistance and high adaptability of the preparation process, and has wide application prospects in the fields of silicon nitride ceramic cutters, silicon nitride ceramic substrates, aerospace and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic composite material preparation, and more specifically, to a high-performance silicon nitride ceramic composite material and a preparation method thereof. Background Art

[0002] Silicon nitride ceramics occupy an important position in many advanced material fields due to their excellent mechanical properties, high thermal stability, low dielectric constant and dielectric loss. However, traditional single-phase silicon nitride ceramic materials still face many challenges in practical applications. On the one hand, their dielectric constant and dielectric loss tangent need to be further optimized in some scenarios with high-performance requirements, and they cannot fully meet the stringent requirements for material dielectric properties such as high-frequency electronic devices and precision communication devices. On the other hand, in complex working conditions, the comprehensive performance of single-phase silicon nitride ceramics has limitations. For example, in environments with high temperature, high pressure and strong stress, such as the applications of silicon nitride ceramic cutting tools and silicon nitride ceramic substrates, their mechanical properties and structural stability may not be sufficient to support long-term reliable operation.

[0003] To overcome these problems, many explorations have been carried out in the prior art. For example, CN101555156A discloses a boron nitride whisker / silicon nitride ceramic composite material and a preparation method thereof. The composite material has excellent mechanical properties, good dielectric properties, good heat resistance and ablation resistance, and can be used for the preparation of high-performance radomes; at the same time, the preparation method of the material is simple and easy to operate and suitable for mass production, but the toughness performance of the material is poor. At the same time, CN107903070A provides a preparation method of a high-performance piezoelectric ceramic composite material, which has certain advantages in dielectric properties and temperature stability, but the mechanical properties and ablation resistance of the material are relatively weak, which limits its application in some fields with high requirements for structural strength.

[0004] In addition, with the rapid development of modern technology, the demand for high-performance ceramic composite materials in the fields of aerospace, silicon nitride ceramic cutting tools, silicon nitride ceramic substrates, etc. is increasing and becoming more diverse. In the aerospace field, the high-speed flight and extreme environmental conditions of aircraft require materials to have high strength, high toughness, high temperature resistance, ablation resistance and good dielectric properties to ensure the reliability of aircraft structural components and the normal operation of communication and navigation systems; in the field of electronic communication, the trend of miniaturization, high frequency and high performance of electronic devices puts forward higher requirements for the dielectric constant, dielectric loss and dimensional accuracy of ceramic materials; in the energy field, such as high-temperature fuel cells, nuclear reactors, etc., materials need to maintain stable performance in high-temperature and strongly corrosive environments. Therefore, there is an urgent need to develop a high-performance silicon nitride ceramic composite material with more excellent comprehensive performance and capable of adapting to a variety of complex application scenarios and a preparation method thereof. Summary of the Invention

[0005] To overcome the above-mentioned defects of the prior art, the present invention provides a high-performance silicon nitride ceramic composite material and a preparation method thereof to solve the problems raised in the above background art.

[0006] To achieve the above object, the present invention provides the following technical solution: A high-performance silicon nitride ceramic composite material is composed of the following raw materials in mass percentages: 70-85 wt.% of silicon nitride, 5-15 wt.% of carbon fiber, 3-10 wt.% of sintering aid, 5-10 wt.% of zirconia, 3-8 wt.% of yttria-stabilized zirconia, 1-5 wt.% of graphene, and 2-6 wt.% of barium titanate.

[0007] Among them, the silicon nitride is high-purity submicron particles, the content of α-phase silicon nitride is not less than 93%, the content of free silicon is not more than 0.3%, and the average particle size is 0.4-0.6 microns.

[0008] The carbon fiber has an aspect ratio of 30-80 and a diameter of 1-3 microns, which can improve the toughness and dielectric properties of the material. Its microstructure can hinder crack propagation, consume oxygen during sintering, promote sintering and improve densification.

[0009] The sintering aid is selected from one or more of yttria, alumina, and yttrium aluminum garnet, and the particle size is 0.5-1 micron.

[0010] Preferably, 75-82 wt.% of silicon nitride, 8-12 wt.% of carbon fiber, 5-8 wt.% of sintering aid, 6-8 wt.% of zirconia, 4-6 wt.% of yttria-stabilized zirconia, 2-4 wt.% of graphene, and 3-5 wt.% of barium titanate.

[0011] In this technical solution, silicon nitride serves as the basic component, providing a basic structural and performance framework. The addition of carbon fiber helps to improve the toughness and dielectric properties of the material. Its special aspect ratio and microstructure can effectively hinder crack propagation, enhance the overall stability of the material. At the same time, during sintering, it can consume more oxygen, cooperate with the sintering aid to promote the sintering process, reduce the sintering temperature, and improve the densification of the material. The introduction of zirconia and yttria-stabilized zirconia can, on the one hand, enhance the strength and hardness of the material, and on the other hand, further optimize the thermal and dielectric properties of the material, enabling it to have better performance in high-temperature environments.

[0012] Among them, the added graphene has excellent electrical properties and ultra-high strength. In this composite material, graphene and carbon fiber are intertwined with each other to form a more stable and efficient conductive network. On the one hand, in terms of dielectric properties, by adjusting the content and distribution of graphene and carbon fiber, the dielectric constant and dielectric loss of the material can be precisely controlled, enabling lower signal transmission loss and more stable electromagnetic performance in high-frequency electronic device applications. On the other hand, in terms of mechanical properties, the high-strength characteristics of graphene are superimposed on the strengthening effect of carbon fiber, significantly improving the overall strength and modulus of the material and enhancing the material's resistance to external stress.

[0013] The added barium titanate has good piezoelectric properties and a relatively high dielectric constant. In the composite material system, barium titanate undergoes an interfacial reaction with silicon nitride, zirconia, etc. during the high-temperature sintering process to form a composite phase with a special crystal structure. While this composite phase improves the dielectric properties of the material, it endows the material with certain piezoelectric characteristics. When subjected to an external force, the material can generate a weak electrical signal, and this characteristic can be applied in the field of smart structural materials to achieve the self-sensing function of the material. For example, in the structural health monitoring of aerospace aircraft, it can real-time feedback the stress and damage conditions of the structure, providing additional guarantee for flight safety.

[0014] A method for preparing a high-performance silicon nitride ceramic composite material, comprising the following steps:

[0015] (1) Weigh and mix silicon nitride, carbon fiber, sintering aids, zirconia, yttria-stabilized zirconia, graphene, and barium titanate in proportion, add a dispersant accounting for 0.5 - 1.5% of the total weight of the raw materials and a binder accounting for 0.3 - 1.0%, use ethanol or methanol as the medium, and ball-mill and mix for 1.5 - 3 h to prepare a ceramic slurry with a solid content of 45 - 75 wt%; the dispersant is ammonium polyacrylate, and the binder is polyvinyl alcohol;

[0016] (2) Form the ceramic slurry by injection molding process, with an injection temperature of 150 - 200 °C and an injection pressure of 80 - 150 MPa;

[0017] (3) After the formed green body is dried, sinter and hold for 1 - 4 hours at 1700 - 1900 °C under a nitrogen atmosphere pressure of 5 - 10 MPa, and then naturally cool to room temperature with the furnace to obtain a high-performance silicon nitride ceramic composite material.

[0018] Preferably, in step (1), an antifoaming agent accounting for 0.1 - 0.5% of the total weight of the raw materials is further added to the ball-milling medium, and the antifoaming agent is an organosilicon antifoaming agent.

[0019] Preferably, in step (3), a segmented heating method is adopted during the sintering process. First, the temperature is raised at a heating rate of 5-10 °C / min to 1200-1500 °C and held for 0.5-1.5 hours, and then the temperature is raised to the sintering temperature at a heating rate of 3-8 °C / min.

[0020] In this technical solution, first, raw materials are mixed and ball-milled. The raw material ratio is precisely controlled, and a dispersant and a binder are added for ball-milling. The dispersant can make the raw materials better dispersed during ball-milling, prevent agglomeration, and ensure the uniform distribution of each component. The binder helps to maintain the shape integrity of the green body during the subsequent forming process. The reasonable setting of parameters such as ball-milling time, solid content, and ball-milling medium ensures the full mixing of raw materials and the preliminary progress of chemical reactions, laying a foundation for obtaining high-quality ceramic slurry.

[0021] Secondly, injection molding is carried out. The injection molding process is adopted. By controlling the injection temperature and pressure, the ceramic slurry can accurately fill the mold cavity to obtain a formed green body with complex shapes and precise dimensions. The injection molding process has the advantages of high production efficiency and good product quality consistency, and is suitable for large-scale industrial production.

[0022] Finally, sintering is carried out. The formed green body is sintered under specific conditions of nitrogen atmosphere pressure, temperature, and holding time. The adoption of the segmented heating method helps to reduce the thermal stress of the green body during sintering and avoid the generation of defects such as cracking. The various parameters during the sintering process act synergistically to make the material reach the ideal densification degree and form a stable microstructure, thereby achieving excellent comprehensive performance.

[0023] The technical effects and advantages of the present invention:

[0024] 1. The high-performance silicon nitride ceramic composite material of the present invention exhibits the characteristics of high strength and high toughness through a reasonable raw material formula and a unique preparation process. Among them, the addition of carbon fiber forms an effective crack propagation obstacle and a spatial interlocking structure, significantly improving the fracture toughness of the material. At the same time, the introduction of zirconia and its stable phase further enhances the overall strength of the material by using its phase transformation toughening mechanism, enabling it to withstand greater external forces and stress impacts and having higher reliability in structural applications. For example, in actual tests, the flexural strength of the composite material can reach above 1150 MPa, and the fracture toughness can reach 7.0 MPa·m 1 / 2 Above, which is significantly improved compared with traditional silicon nitride ceramic materials.

[0025] 2. It has good dielectric properties. By precisely regulating the content and distribution of graphene and carbon fiber, the optimization of dielectric constant and dielectric loss is achieved, which can significantly reduce the energy loss of signal transmission, improve the transmission efficiency and quality, ensure the stable and efficient operation of electronic devices, and meet the development trend of miniaturization, high frequency, and high performance in the field of electronic communication.

[0026] 3. The high melting point and thermal stability of silicon nitride, combined with the high temperature resistance characteristics of components such as zirconia, endow the material with excellent high temperature oxidation and thermal shock resistance. In high temperature environments, it can firmly maintain the structural integrity and performance stability, ensuring the safe and continuous operation of equipment under high temperature conditions.

[0027] 4. Using the injection molding process, products with various complex shapes and high-precision dimensions can be accurately prepared. This process is of great significance for meeting the diverse shape and size requirements of high-performance ceramic components in modern industry. It has obvious advantages in the manufacturing of micro ceramic components in electronic devices, special-shaped structural components in aerospace, etc. At the same time, the injection molding process has high production efficiency, is suitable for large-scale industrial production, can effectively reduce production costs, and improve the market competitiveness of products.

[0028] 5. During the raw material mixing process, the added dispersant, binder, and defoamer can effectively improve the dispersibility, formability, and processing performance of the raw materials. The dispersant ensures that each raw material particle is evenly dispersed, avoiding agglomeration, making the material composition more uniform. The binder helps to maintain the shape integrity of the green body during the forming process and improve the strength of the green body. The defoamer reduces the generation of bubbles, further improving the densification and quality stability of the material. In addition, the optimized ball milling process parameters and the stepwise heating method during the sintering process ensure the full mixing reaction of the raw materials and the smooth progress of the sintering process, reducing the formation of defects and improving the performance uniformity and stability of the material. Detailed implementation mode

[0029] Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0030] Example 1

[0031] Weigh 70wt.% of silicon nitride, 15wt.% of carbon fiber, 8wt.% of sintering aids (yttrium oxide and alumina are mixed in a ratio of 1:1), 5wt.% of zirconia, 2wt.% of yttria-stabilized zirconia, 3wt.% of graphene, and 4wt.% of barium titanate by mass percentage. Add 1.0% of ammonium polyacrylate dispersant, 0.5% of polyvinyl alcohol binder, and 0.3% of silicone defoamer based on the total weight of the raw materials, and ball mill and mix for 2h with ethanol as the medium to make a ceramic slurry with a solid content of 50wt%.

[0032] The ceramic slurry is injection molded at an injection temperature of 160 °C and an injection pressure of 100 MPa.

[0033] After the formed green body is dried, under a nitrogen atmosphere pressure of 6 MPa, it is first heated to 1300 °C at a heating rate of 8 °C / min and held for 1 hour, then heated to 1800 °C at a heating rate of 5 °C / min and held for 2 hours, and then naturally cooled to room temperature in the furnace to obtain a high-performance silicon nitride ceramic composite material.

[0034] Example 2

[0035] Weigh 78 wt.% of silicon nitride, 8 wt.% of carbon fiber, 5 wt.% of sintering aid (yttrium aluminum garnet), 6 wt.% of zirconia, 3 wt.% of yttria-stabilized zirconia, 2 wt.% of graphene, and 5 wt.% of barium titanate. Add 1.2% of ammonium polyacrylate dispersant, 0.8% of polyvinyl alcohol binder, and 0.2% of silicone defoamer based on the total weight of the raw materials, and ball-mill and mix for 2.5 h using methanol as the medium to prepare a ceramic slurry with a solid content of 60 wt%.

[0036] Adopt injection molding, with an injection temperature of 180 °C and an injection pressure of 120 MPa.

[0037] After the green body is dried, under a nitrogen atmosphere pressure of 8 MPa, it is first heated to 1400 °C at a heating rate of 6 °C / min and held for 1.5 hours, then heated to 1850 °C at a heating rate of 4 °C / min and held for 3 hours, and then cooled in the furnace to obtain a composite material.

[0038] Example 3

[0039] Take 83 wt.% of silicon nitride, 5 wt.% of carbon fiber, 3 wt.% of sintering aid (yttrium oxide), 5 wt.% of zirconia, 4 wt.% of yttria-stabilized zirconia, 4 wt.% of graphene, and 3 wt.% of barium titanate. Add 0.8% of ammonium polyacrylate dispersant, 0.3% of polyvinyl alcohol binder, and 0.1% of silicone defoamer based on the total weight of the raw materials, and ball-mill and mix for 3 h using ethanol as the medium to prepare a ceramic slurry with a solid content of 70 wt%.

[0040] Injection molding, with an injection temperature of 150 °C and an injection pressure of 80 MPa.

[0041] After the green body is dried, under a nitrogen atmosphere pressure of 5 MPa, it is first heated to 1200 °C at a heating rate of 10 °C / min and held for 0.5 hour, then heated to 1900 °C at a heating rate of 3 °C / min and held for 4 hours, and then cooled in the furnace to obtain a composite material.

[0042] Performance test

[0043] The high-performance silicon nitride ceramic composites prepared in Examples 1-3 were subjected to mechanical property tests (such as flexural strength, fracture toughness, etc.), dielectric property tests (dielectric constant), and thermal property tests (heat resistance temperature, coefficient of thermal expansion, etc.). The results are shown in Table 1.

[0044] Table 1 Performance test table of high-performance silicon nitride ceramic composites

[0045]

[0046] The test results show that, as shown in Table 1, the composite materials of the present invention have excellent comprehensive properties. For example, in Example 1, the flexural strength of the composite material reaches 1000 MPa, the fracture toughness is 6.5 MPa·m 1 / 2 , the dielectric constant is 4.2, and the coefficient of thermal expansion at 1000 °C is 3.2×10 -6 / °C, meeting the application requirements of high-performance materials in related fields.

[0047] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A high performance silicon nitride ceramic composite material, characterized in that: The invention is composed of the following raw materials in percentage by mass: 70-85wt.% of silicon nitride, 5-15wt.% of carbon fiber, 3-10wt.% of sintering aid, 5-10wt.% of zirconium oxide, 3-8wt.% of yttria-stabilized zirconium oxide, 1-5wt.% of graphene and 2-6wt.% of barium titanate; Wherein, the silicon nitride is a high-purity submicron particle, the α-phase silicon nitride content is not less than 93%, the free silicon content is not more than 0.3%, and the average particle size is 0.4-0.6 microns; The carbon fiber has an aspect ratio of 30-80 and a diameter of 1-3 microns, and is used to increase the toughness and dielectric properties of the composite material; The sintering aid is selected from one or more of yttrium oxide, aluminum oxide, and yttrium aluminum garnet, with a particle size of 0.5-1 micron.

2. The high performance silicon nitride ceramic composite material according to claim 1, characterized in that: Silicon nitride 75-82wt.%, carbon fiber 8-12wt.%, sintering aid 5-8wt.%, zirconium oxide 6-8wt.%, yttria-stabilized zirconium oxide 4-6wt.%, graphene 2-4wt.% and barium titanate 3-5wt.%.

3. A method for preparing the high-performance silicon nitride ceramic composite material according to claim 2, characterized in that: The following steps are involved: (1) Silicon nitride, carbon fiber, sintering aid, zirconium oxide, yttria-stabilized zirconium oxide, graphene and barium titanate are weighed and mixed in proportion, 0.5-1.5% of the total weight of the raw materials as a dispersant and 0.3-1.0% of a binder are added, ethanol or methanol is used as a medium, and ball milling is performed for 1.5-3 hours to prepare a ceramic slurry with a solid content of 45-75wt%; the dispersant is ammonium polyacrylate, and the binder is polyvinyl alcohol; (2) molding the ceramic slurry by injection molding, with an injection temperature of 150-200° C. and an injection pressure of 80-150 MPa; (3) After the formed green body is dried, it is sintered and kept warm for 1-4 hours at 1700-1900° C. in a nitrogen atmosphere at a pressure of 5-10 MPa, and then naturally cooled to room temperature in the furnace to obtain a high-performance silicon nitride ceramic composite material.

4. The preparation method according to claim 3, characterized in that: In step (1), a defoamer accounting for 0.1-0.5% of the total weight of the raw materials is also added to the ball milling medium, and the defoamer is an organosilicon defoamer.

5. The preparation method according to claim 3, characterized in that: In step (3), the sintering process adopts a staged heating method, firstly heating to 1200-1500°C at a heating rate of 5-10°C / min, keeping the temperature for 0.5-1.5 hours, and then heating to the sintering temperature at a heating rate of 3-8°C / min.

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