A SiC-TiC composite ceramic, its preparation method and application
By introducing TiC and metal titanium into SiC ceramics, dense sintering at low temperatures using a reactive sintering process, the problem of insufficient mechanical properties of SiC ceramics was solved, and SiC-TiC composite-phase ceramics with excellent friction resistance and mechanical properties were prepared.
Patent Information
- Application Number
- CN202311835968.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-28
- Publication Date
- 2025-06-10
- Estimated Expiration
- 2043-12-28
AI Technical Summary
Existing SiC ceramics are difficult to densely sinter at low temperatures, resulting in insufficient mechanical properties, especially after reaching the melting point of silicon, which reduces its application temperature.
By mixing silicon nitride, carbon black and metal titanium, after cold isostatic molding, reacting and sintering under vacuum, TiC is introduced as the second phase, and the liquid phase metal titanium promotes the density of SiC-TiC ceramics and improves its mechanical properties.
The SiC-TiC composite-phase ceramics are prepared at low temperatures, with excellent friction resistance and mechanical properties. The dimensional hardness at room temperature is 25-30 GPa, the fracture toughness is 3-5MPa·m1/2, and the flexural strength is 450-650MPa.
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of ceramic materials, and more specifically, relates to a SiC-TiC composite ceramic and its preparation method and application. Background Art
[0002] SiC ceramics have excellent properties such as high hardness, wear resistance, corrosion resistance, oxidation resistance, high temperature resistance, and high high-temperature strength. They are not only applied to traditional industrial fields such as high-temperature kiln furniture, combustion nozzles, heat exchangers, sealing rings, and sliding bearings, but also can be used as bulletproof armor materials, space reflectors, fixture materials in semiconductor wafer preparation, and nuclear fuel cladding materials. Since SiC is a three-dimensional crystal with a very strong covalent bond composed of Si-C tetrahedrons and has a diamond-type structure, the diffusion rate during sintering is quite low. At the same time, the oxide layer covering the particle surface plays a role of diffusion barrier, hindering diffusion. Therefore, it is very difficult to sinter pure SiC densely. To prepare dense samples, processes such as hot pressing, hot isostatic pressing, reaction sintering, and normal pressure sintering with sintering aids are usually used. Among them, due to equipment limitations, it is very difficult to prepare large-size and complex-shaped products by hot pressing and hot isostatic pressing sintering processes; during normal pressure sintering, the products shrink greatly, easily causing deformation and cracking of the products, and it is difficult to prepare large-size and complex-shaped products; the reaction sintering process realizes the densification of products at a relatively low temperature (usually above the melting point of silicon, 1410 °C), and the volume of the products hardly changes during the sintering process. Therefore, the reaction sintering process is the most effective method for preparing large-size and complex-shaped silicon carbide products. The silicon carbide prepared by the reaction sintering method is widely used in industrial production due to its advantages such as low temperature and net size, and is widely used in industrial fields such as petrochemical industry, aerospace, mechanical manufacturing, microelectronics, laser, automobile, steel, and nuclear industry. Since there will inevitably be unreacted silicon phases in the finished products of reaction-sintered silicon carbide, it greatly affects its mechanical properties, especially the product performance drops sharply after reaching the melting point of silicon during use, which limits the working temperature of reaction-sintered silicon carbide. Therefore, in recent years, researchers have carried out various experiments on how to improve the mechanical properties of reaction-sintered silicon carbide, including adjusting the raw material content, trying different forming methods, changing the sintering system, etc., so as to solve a series of problems such as low product density, incomplete product sintering, and incomplete reaction, and finally improve its mechanical properties. Summary of the Invention
[0003] In order to solve the above-mentioned deficiencies and drawbacks of the prior art, the primary object of the present invention is to provide a preparation method of a SiC-TiC composite ceramic, which can be prepared at a low temperature, and at the same time, the composite ceramic has excellent friction resistance and mechanical properties.
[0004] Another object of the present invention is to provide a SiC-TiC composite ceramic prepared by the above method.
[0005] Another object of the present invention is to provide the application of the above SiC-TiC composite ceramic.
[0006] The object of the present invention is achieved by the following technical solutions:
[0007] A preparation method of SiC-TiC composite ceramic, comprising the following specific steps:
[0008] S1. Mix silicon nitride, carbon black and metallic titanium, add a solvent and a ball-milling medium, and perform mixing, ball-milling, drying and sieving to obtain a mixed powder;
[0009] S2. Cold isostatically press the mixed powder at 100-300 MPa to form a ceramic green body;
[0010] S3. Brush a layer of BN on the inner surface of the crucible, place the ceramic green body in the crucible, under vacuum conditions, heat up to 1500-1600 °C for heat preservation, and then heat up to 1800-1900 °C for heat preservation to obtain the SiC-TiC composite ceramic.
[0011] Preferably, in step S1, the particle size of the silicon nitride is 1-3 μm, the purity of the silicon nitride is above 99%, the particle size of the carbon black is 100-300 nm, the purity of the carbon black is above 99.9%, and the particle size of the metallic titanium is 1 μm.
[0012] Preferably, in step S1, the ball-milling medium is SiC balls and the solvent is anhydrous ethanol.
[0013] Preferably, in step S1, the molar ratio of silicon nitride:carbon black:metallic titanium is (0.8-1):(3-5):(1-3); the mass ratio of the ball-milling medium, the solvent and the mixed powder is (5-10):(10-20):1.
[0014] Preferably, in step S2, the thickness of the ceramic green body is 4-5 mm.
[0015] Preferably, in step S3, the vacuum degree of the vacuum is below 10 Pa.
[0016] A SiC-TiC composite ceramic, which is prepared by the above method.
[0017] Preferably, the Vickers hardness of the composite ceramic at room temperature is 25-30 GPa, the fracture toughness is 3-5 MPa·m 1 / 2 , and the flexural strength is 450-650 MPa.
[0018] The application of the above SiC-TiC composite ceramic in the field of cutting or friction.
[0019] Compared with the prior art, the present invention has the following beneficial effects:
[0020] 1. The present invention uses silicon nitride, carbon black, and titanium metal as raw materials, introduces TiC as the second phase, and obtains SiC-TiC composite ceramics through reaction sintering under low-temperature vacuum conditions. Among them, heating to 1500-1600 °C is to synthesize silicon carbide and titanium carbide, and raising the temperature to 1800-2000 °C is to use liquid-phase titanium metal to promote the densification of SiC-TiC ceramics and improve the comprehensive performance of reaction-sintered silicon carbide ceramics.
[0021] 2. The present invention generates SiC-TiC composite ceramics through reaction sintering, and uses excessive titanium metal to generate a liquid phase to promote the densification of the ceramics, thereby improving the performance of reaction-sintered silicon carbide.
[0022] 3. The SiC-TiC composite ceramics prepared by the present invention have properties such as wear resistance and excellent mechanics. Specific Embodiments
[0023] The following further illustrates the content of the present invention in conjunction with specific embodiments, but should not be construed as a limitation to the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well-known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the technical field.
[0024] Example 1
[0025] 1. Mix silicon nitride (purity 99.9%, particle size 1 μm): carbon black C (purity 99.9%, particle size 200 nm): Ti (purity 99.9%, particle size 1 μm) with a molar ratio of 1:4:5, and perform ball milling, drying, and sieving according to the total mass ratio of SiC grinding balls to the above powder of 5:1 to obtain a mixed powder.
[0026] 2. Take an appropriate amount of the mixed powder and put it into a mold, press it into shape at 80 MPa with an electric dry press, and then perform cold isostatic pressing at a pressure of 200 MPa to obtain a ceramic green body;
[0027] 3. Brush a layer of BN on the inner surface of the crucible, put the ceramic green body into the crucible, put it into a vacuum sintering furnace (the vacuum degree is maintained at about 10 Pa), first keep it at 1400 °C for 30 min, then raise the temperature to 1800 and keep it for 60 min, and the cooling rate is the same as the heating rate to obtain SiC-TiC composite ceramics.
[0028] The Vickers hardness of the carbon SiC-TiC composite ceramics obtained in this example is 25 GPa (Hv0.2), and the fracture toughness is 3.2 MPa·m 1 / 2 , and the flexural strength is 450 MPa.
[0029] Example 2
[0030] 1. Mix silicon nitride (purity 99.9%, particle size 1 μm), C (purity 99.9%, particle size 200 nm), and Ti (purity 99.9%, particle size 1 μm) in a molar ratio of 1:4:5. Perform ball milling, drying, and sieving according to the total mass ratio of SiC grinding balls to the above powder being 5:1 to obtain a mixed powder.
[0031] 2. Take an appropriate amount of the mixed powder and put it into a mold. Use an electric dry press to compact it at 80 MPa, and then perform cold isostatic pressing at a pressure of 200 MPa to obtain a ceramic green body.
[0032] 3. Brush a layer of BN on the inner surface of the crucible. Put the ceramic green body into the crucible and place it in a vacuum sintering furnace (the vacuum degree is maintained at about 10 Pa). First, keep it at 1400 °C for 60 min, then raise the temperature to 1900 °C and keep it for 60 min. The cooling rate is the same as the heating rate to obtain a SiC-TiC composite ceramic.
[0033] The Vickers hardness of the SiC-TiC composite ceramic prepared in this example is 26 GPa (Hv0.2), and the fracture toughness is 3.8 MPa·m 1 / 2 , and the flexural strength is 500 MPa.
[0034] Example 3
[0035] 1. Mix silicon nitride (purity 99.9%, particle size 1 μm), C (purity 99.9%, particle size 200 nm), and Ti (purity 99.9%, particle size 1 μm) in a molar ratio of 1:4:5. Perform ball milling, drying, and sieving according to the total mass ratio of SiC grinding balls to the above powder being 5:1 to obtain a mixed powder.
[0036] 2. Take an appropriate amount of the mixed powder and put it into a mold. Use an electric dry press to compact it at 80 MPa, and then perform cold isostatic pressing at a pressure of 200 MPa to obtain a ceramic green body.
[0037] 3. Brush a layer of BN on the inner surface of the crucible. Put the ceramic green body into the crucible and place it in a vacuum sintering furnace (the vacuum degree is maintained at about 10 Pa). First, keep it at 1500 °C for 60 min, then raise the temperature to 1900 °C and keep it for 120 min. The cooling rate is the same as the heating rate to obtain a SiC-TiC composite ceramic.
[0038] The Vickers hardness of the SiC-TiC composite ceramic prepared in this example is 30 GPa (Hv0.2), and the fracture toughness is 4.5 MPa·m 1 / 2 , and the flexural strength reaches 600 MPa.
[0039] The Vickers hardness of the composite ceramic of the present invention at room temperature is 25-30 GPa, and the fracture toughness is 3-5 MPa·m 1 / 2 , the flexural strength is 450-650 MPa, and it has properties such as wear resistance and excellent mechanical properties, and can be applied in the fields of cutting or friction.
[0040] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.
Claims
1. Preparation method of SiC-TiC composite ceramics, characterized in that, it includes the following specific steps: S1. Mix silicon nitride, carbon black and metallic titanium, add a solvent and milling media, and perform mixing, ball milling, drying, and sieving to obtain a mixed powder; the molar ratio of silicon nitride:carbon black:metallic titanium is (0.8 - 1):(3 - 5):(1 - 3); S2. Cold isostatically press the mixed powder at 100 - 300 MPa to form a ceramic green body; S3. Brush a layer of BN on the inner surface of the crucible, place the ceramic green body in the crucible, under vacuum conditions, heat to 1500 - 1600 °C for heat preservation, and then heat to 1800 - 1900 °C for heat preservation to obtain SiC-TiC composite ceramics.
2. The preparation method of SiC-TiC composite ceramics according to claim 1, characterized in that, in step S1, the particle size of the silicon nitride is 1 - 3 μm, the purity of the silicon nitride is above 99%, the particle size of the carbon black is 100 - 300 nm, the purity of the carbon black is above 99.9%, and the particle size of the metallic titanium is 1 μm.
3. The preparation method of SiC-TiC composite ceramics according to claim 1, characterized in that, in step S1, the milling media is SiC balls and the solvent is anhydrous ethanol.
4. The preparation method of SiC-TiC composite ceramics according to claim 1, characterized in that, in step S1, the mass ratio of the milling media, solvent and mixed powder is (5 - 10):(10 - 20):
1.
5. The preparation method of SiC-TiC composite ceramics according to claim 1, characterized in that, in step S2, the thickness of the ceramic green body is 4 - 5 mm.
6. The preparation method of SiC-TiC composite ceramics according to claim 1, characterized in that, in step S3, the vacuum degree of the vacuum is below 10 Pa.
7. A SiC-TiC composite ceramic, characterized in that, the composite ceramic is prepared by the method according to any one of claims 1 - 6.
8. The SiC-TiC composite ceramic according to claim 7, characterized in that, The Vickers hardness of the composite ceramic at room temperature is 25 - 30 GPa, and the fracture toughness is 3 - 5 MPa·m 1 / 2 , and the flexural strength is 450 - 650 MPa.
9. Application of the SiC-TiC composite ceramic according to claim 7 or 8 in the field of cutting or friction.