A directional structure silicon carbide composite ceramic material and a preparation method thereof
By mixing silicon carbide whiskers, titanium carbide powder, alumina powder, and yttrium oxide powder to form oriented silicon carbide composite ceramics, the problem of insufficient toughness and high-temperature strength of silicon carbide ceramics in the prior art is solved, and the high toughness and high-temperature performance of the material are improved, while the preparation process is simplified.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- LANZHOU INST OF TECH
- Filing Date
- 2024-07-09
- Publication Date
- 2026-06-05
Smart Images
Figure CN118851786B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of silicon carbide ceramic preparation technology, and particularly to a directional silicon carbide composite ceramic material and its preparation method. Background Technology
[0002] Silicon carbide ceramics possess excellent high-temperature mechanical properties and are widely used in high-temperature bearings, nozzles, and high-temperature corrosion-resistant components. However, their inherent brittleness makes them prone to microcracks under vibration or impact loads, leading to failure. While commonly used methods such as adding toughening metal binders, carbon fibers, or resin binders can improve the toughness of ceramics to some extent, they also reduce their high-temperature resistance.
[0003] Chinese Patent CN115677351A discloses a multi-layered boron carbide composite ceramic with a strong bonding interface and its preparation method. The method involves using a single-phase boron carbide ceramic with high hardness and high elastic modulus as the surface layer, a B4C-TiB2-SiC ternary composite ceramic with high strength and high toughness as the base layer, and a TiC-B4C-Si active reaction system as the transition layer. The materials of each unit layer are prepared into thin strips of different thicknesses using a low-temperature rolling method. These unit layers are then stacked in a designed order in a high-strength graphite sintering mold and sintered at high temperature and pressure in a vacuum atmosphere sintering furnace to obtain the multi-layered boron carbide composite ceramic with a strong bonding interface. The prepared multi-layered composite material has no soft interface layer, high interfacial bonding strength, and the overall material exhibits high hardness, high modulus, high strength, and high fracture toughness. However, the entire process is complex and requires strict technical specifications, and it does not improve the high-temperature strength and toughness of silicon carbide composite ceramics. Summary of the Invention
[0004] This invention addresses the engineering problem of the difficulty in effectively improving the toughness of silicon carbide ceramics using existing methods, and provides a directional silicon carbide composite ceramic material and its preparation method. The preparation method of the directional silicon carbide composite ceramic material provided by this invention can effectively improve the high-temperature strength and toughness of the material, and the preparation process is simple and low-cost.
[0005] To achieve the above objectives, the present invention adopts the following technical solution:
[0006] In a first aspect, the present invention provides a method for preparing a directional silicon carbide composite ceramic material, comprising the following steps:
[0007] Take silicon carbide whiskers, titanium carbide powder, alumina powder and yttrium oxide powder, mix them evenly and add plasticizer to obtain a plastic blank;
[0008] Plastic billets are rolled into oriented structural billets, which are then dried, cut into shape, have a transition layer laid, and undergo multi-layer stacking to obtain multi-layer oriented structural billets.
[0009] Degreasing and sintering of multi-layer oriented structure blanks yield oriented structure silicon carbide composite ceramic materials.
[0010] As a further improvement of the present invention, the mass percentage of silicon carbide whiskers, titanium carbide powder, alumina powder and yttrium oxide powder is 72-78:20-26:1-3:1-3.
[0011] As a further improvement of the present invention, the silicon carbide whisker has the following dimensions: diameter 230-340 nm, length 35-42 μm, and average particle sizes of titanium carbide powder, alumina powder and yttrium oxide powder are 80-110 nm, 120-140 nm and 110-130 nm, respectively.
[0012] As a further improvement of the present invention, the term "uniform mixing" refers to:
[0013] The mixture is ultrasonically mixed in anhydrous ethanol at a frequency of 70–90 Hz for 75–94 minutes, and then vacuum dried at 65–75°C for 120–140 minutes.
[0014] As a further improvement of the present invention, the addition of plasticizer refers to: mixing the mixed powder with 10% PVA solution at a mass percentage ratio of 89-92:8-11.
[0015] As a further improvement of the present invention, the method of rolling the plastic billet into an oriented structure billet includes:
[0016] The first pressing down of the roll is 50% of the thickness of the billet. After folding the double layer in half, it is pressed down another 50%. This process is repeated 4 to 6 times.
[0017] As a further improvement of the present invention, the oriented structure blank is sequentially subjected to drying, cutting and shaping, laying a transition layer, and multi-layer stacking, including:
[0018] After rolling, the billet is dried at 140-155℃ for 15-21 minutes. The billet is then cut to the required size. A 35-45 micrometer thick layer of silicon nitride powder with an average particle size of 50-70nm is laid on its surface. A second layer is then added, followed by another layer of silicon nitride powder and a third layer. This process is repeated for 5-7 layers.
[0019] As a further improvement of the present invention, the degreasing and sintering treatment of the multi-layer oriented structure billet includes:
[0020] The multi-layer oriented structural billet was placed in a pressure sintering furnace at a temperature of 0.5 × 10⁻⁶. 5 ~1×105 Degreased at argon pressure and 360–410°C for 12–15 minutes, then at 6 × 10⁻⁶ ppm. 5 ~1.3×10 6 Degrease at argon pressure and 1560-1630℃ for 21-25 minutes.
[0021] Secondly, the present invention provides a directional silicon carbide composite ceramic material, which is prepared by the aforementioned preparation method.
[0022] Optionally, the prepared silicon carbide composite ceramic material has an oriented structure, and the fracture toughness of the material is greater than or equal to 16.3 MPa·m. 1 / 2 The bending strength is greater than or equal to 1030 MPa, the room temperature hardness is greater than or equal to 23.4 GPa, and the high temperature hardness at 1000℃ is greater than or equal to 19.7 GPa.
[0023] Compared with the prior art, the present invention has the following features and advantages:
[0024] This invention involves uniformly mixing silicon carbide whiskers, titanium carbide powder, alumina powder, and yttrium oxide powder, and adding a plasticizer to obtain a plastic preform. The plastic preform is then rolled into an oriented structure preform. The preform undergoes drying, cutting, layering a transition layer, and multi-layer stacking. Finally, the resulting multi-layer oriented structure preform is degreased and sintered. Alumina and yttrium oxide are introduced to form a glassy phase, bonding the silicon carbide matrix phase and the titanium carbide reinforcing phase, thus improving sintering density. The mixed powder, after plasticizing, ensures repeated plastic deformation without fracture. After multiple rolling processes, the silicon carbide whiskers align along the rolling direction, laying the foundation for the oriented structure. The layering of the transition layer and multi-layer stacking ensures easy sintering of the multi-layer structure while meeting predetermined dimensional requirements.
[0025] The silicon carbide composite ceramic material prepared by this invention has an oriented structure and a fracture toughness greater than or equal to 16.3 MPa·m. 1 / 2 The bending strength is greater than or equal to 1030 MPa, the room temperature hardness is greater than or equal to 23.4 GPa, and the high temperature hardness at 1000℃ is greater than or equal to 19.7 GPa. Attached Figure Description
[0026] Figure 1 This is a flowchart of a method for preparing a directional silicon carbide composite ceramic material. Detailed Implementation
[0027] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.
[0028] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.
[0029] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.
[0030] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.
[0031] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.
[0032] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass in the embodiments of this application can be a well-known unit of mass in the chemical industry, such as μg, mg, g, or kg.
[0033] The terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. For example, without departing from the scope of the embodiments of this application, "first XX" may also be referred to as "second XX," and similarly, "second XX" may also be referred to as "first XX." Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature.
[0034] The first objective of this invention is to provide a method for preparing a directional silicon carbide composite ceramic material, comprising the following steps:
[0035] S1, take silicon carbide whiskers, titanium carbide powder, alumina powder and yttrium oxide powder, mix them evenly and add plasticizer to obtain plastic blank;
[0036] S2, the plastic billet is rolled into an oriented structure billet, and the oriented structure billet is successively dried, cut into shape, laid with a transition layer, and multi-layer stacked to obtain a multi-layer oriented structure billet;
[0037] S3, the multi-layer oriented structure blank is degreased and sintered to obtain oriented structure silicon carbide composite ceramic material.
[0038] Using titanium carbide as the reinforcing phase and alumina and yttrium oxide as the glass phases, a series of techniques including plasticizing, directional rolling, multilayer stacking, and sintering are key methods to simultaneously improve the high-temperature strength and toughness of silicon carbide composite ceramics.
[0039] Specifically, the principles for material selection in this invention are as follows:
[0040] Silicon carbide whiskers: Silicon carbide whiskers have high strength, high modulus, high temperature resistance, and corrosion resistance, making them an ideal reinforcing phase material.
[0041] Titanium carbide powder: As a reinforcing phase, titanium carbide's high melting point, high strength, high hardness, and excellent chemical stability can effectively improve the overall performance of composite ceramic materials.
[0042] Alumina powder: Alumina is a common ceramic material with good thermal and chemical stability. As a glass phase, it can fill the gaps between silicon carbide whiskers and titanium carbide particles, thereby improving the density of the material.
[0043] Yttrium oxide powder: As a sintering aid, yttrium oxide can lower the sintering temperature of ceramic materials, increase the sintering density, and improve the mechanical properties of the materials.
[0044] The main methods are:
[0045] Plasticizing process: By adding a plasticizer, silicon carbide whiskers, titanium carbide powder, alumina powder, and yttrium oxide powder are mixed evenly to obtain a plastic blank. The role of the plasticizer is to give the mixed powder a certain degree of plasticity and fluidity, facilitating subsequent processing.
[0046] Directional rolling: This process uses rolling to produce oriented billets from plastic raw materials. Directional rolling aligns silicon carbide whiskers and titanium carbide particles in a specific direction within the billet, creating an oriented structure. This oriented structure helps improve the mechanical properties and thermal stability of the material.
[0047] Multi-layer stacking: After drying, cutting and shaping, and laying a transition layer, multi-layer stacking is performed. Multi-layer stacking can further improve the density and mechanical properties of the material, and the material properties can also be optimized by controlling the number and method of stacking.
[0048] Degreasing and Sintering: Degreasing removes plasticizers and other organic impurities from the raw material, preparing it for the subsequent sintering process. Sintering is a crucial step in the preparation of ceramic materials, using high-temperature treatment to bond the particles together to form a dense ceramic body. During sintering, alumina and yttrium oxide act as glassy phases, filling the spaces between silicon carbide whiskers and titanium carbide particles, forming a strong bond.
[0049] Due to the reinforcing effect of silicon carbide whiskers and titanium carbide particles, as well as the glass phase filling effect of alumina and yttrium oxide, oriented silicon carbide composite ceramic materials can still maintain high strength at high temperatures.
[0050] Directional rolling and multilayer stacking processes align silicon carbide whiskers and titanium carbide particles in a specific direction within the material, forming an oriented structure. This oriented structure helps improve the material's toughness, enabling it to better resist deformation and fracture under external forces.
[0051] Materials such as silicon carbide, titanium carbide, alumina, and yttrium oxide all have good thermal stability, so oriented silicon carbide composite ceramic materials can still maintain stable performance under high temperature environments.
[0052] Therefore, the preparation method of this invention combines a series of techniques including plasticizing, directional rolling, multilayer stacking, and sintering, which can simultaneously improve the high-temperature strength and toughness of silicon carbide composite ceramic materials. At the same time, this method also has the advantages of simple process, ease of operation, and low cost.
[0053] Furthermore, in the preparation of silicon carbide composite ceramics, this invention addresses the engineering problem of existing methods' inability to effectively improve the toughness of silicon carbide ceramics. Using titanium carbide as the reinforcing phase and alumina and yttrium oxide as the glassy phases, a series of techniques including plasticizing, directional rolling, multilayer stacking, and sintering are employed. The relationship between component ratios, mixing and plasticizing process parameters, powder rolling process parameters, cutting and stacking processes, sintering processes, and the mechanical properties of silicon carbide composite ceramics is investigated. Specifically, the optimal component ratios, mixing and plasticizing process parameters, powder rolling process parameters, cutting and stacking processes, and sintering processes are identified to maintain high mechanical properties in silicon carbide composite ceramic materials. This method features high precision in component control, strong process stability and repeatability, and can simultaneously improve the high-temperature strength and toughness of silicon carbide composite ceramic materials.
[0054] This invention discloses a method for preparing a directional silicon carbide composite ceramic material, comprising the following detailed steps:
[0055] 1) Weigh silicon carbide whiskers (diameter 230-340nm × length 35-42μm), titanium carbide powder (80-110nm), alumina powder (120-140nm), and yttrium oxide powder (110-130nm) in anhydrous ethanol at a mass percentage of 72-78:20-26:1-3:1-3. The powders are ultrasonically mixed in anhydrous ethanol at a frequency of 70-90 Hz for 75-94 minutes and vacuum dried at 65-75℃ for 120-140 minutes. Then, they are mixed with 10% PVA solution at a mass percentage of 89-92:8-11.
[0056] 2) The obtained plastic billet is rolled. The first reduction of the roll is 50% of the billet thickness. After folding it in half, it is reduced by another 50%. This process is repeated 4 to 6 times. After rolling, the billet is dried at 140 to 155°C for 15 to 21 minutes. The billet is then cut to the required size. A 35 to 45 micrometer thick layer of silicon nitride powder with an average particle size of 50 to 70 nm is spread on its surface. A second layer is then added, followed by another layer of silicon nitride powder and a third layer. This process is repeated 5 to 7 times.
[0057] 3) Place the multi-layer oriented structural billet in a gas pressure sintering furnace at 0.5×10 5 ~1×10 5 Degreased at argon pressure and 360–410°C for 12–15 minutes, then at 6 × 10⁻⁶ ppm. 5 ~1.3×10 6 Degreasing was performed at argon pressure and 1560–1630℃ for 21–25 minutes to finally obtain oriented silicon carbide composite ceramic materials.
[0058] The mechanical properties of the oriented silicon carbide composite ceramic materials and their preparation methods prepared in the following examples are shown in Table 1.
[0059] Example 1
[0060] 1) Weigh silicon carbide whiskers (diameter 340nm × length 35μm), titanium carbide powder (110nm), alumina powder (120nm) and yttrium oxide powder (110nm) in a mass ratio of 72:26:1:1. The powders are ultrasonically mixed in anhydrous ethanol at a frequency of 70 Hz for 75 minutes and vacuum dried at 65°C for 120 minutes. Then they are mixed with 10% PVA solution in a mass ratio of 89:11.
[0061] 2) The obtained plastic billet is rolled. The first reduction of the roll is 50% of the billet thickness. After double-folding, it is reduced by another 50%, and this process is repeated 6 times. After rolling, the billet is dried at 140℃ for 21 minutes. The billet is then cut to the required size. A 35-micron thick layer of silicon nitride powder with an average particle size of 50nm is spread on its surface. A second layer is then added, followed by a third layer of silicon nitride powder, and so on, up to 5 layers.
[0062] 3) Place the multi-layer oriented structural billet in a gas pressure sintering furnace at a depth of 1×10 5 Degreased at 360°C for 12 minutes under argon pressure, then at 6×10 5 The silicon carbide composite ceramic material with directional structure was finally obtained by degreasing under argon pressure and 1560℃ for 21 minutes.
[0063] Example 2
[0064] 1) Weigh silicon carbide whiskers (diameter 340nm × length 42μm), titanium carbide powder (110nm), alumina powder (140nm) and yttrium oxide powder (110nm) in a mass ratio of 78:20:1:1. The powders are ultrasonically mixed in anhydrous ethanol at a frequency of 90 Hz for 75 minutes and vacuum dried at 75°C for 120 minutes. Then they are mixed with 10% PVA solution in a mass ratio of 92:8.
[0065] 2) The obtained plastic billet is rolled. The first reduction of the roll is 50% of the billet thickness. After double-folding, it is reduced by another 50%, and this process is repeated 5 times. After rolling, the billet is dried at 155℃ for 18 minutes. The billet is then cut to the required size. A 39-micron thick layer of silicon nitride powder with an average particle size of 60nm is spread on its surface. A second layer is then added, followed by a third layer of silicon nitride powder, and so on, up to a total of 6 layers.
[0066] 3) Place the multi-layer oriented structural billet in a gas pressure sintering furnace at a temperature of 0.8 × 10⁻⁶. 5 Degreased at 410°C for 14 minutes under argon pressure, then at 1.3 × 10⁻⁶ ℃. 6 The silicon carbide composite ceramic material with directional structure was finally obtained by degreasing under argon pressure and at 1630℃ for 25 minutes.
[0067] Example 3
[0068] 1) Weigh silicon carbide whiskers (diameter 290nm × length 39μm), titanium carbide powder (100nm), alumina powder (130nm) and yttrium oxide powder (120nm) in a mass ratio of 74:22:2:2. The powders are ultrasonically mixed in anhydrous ethanol at 80 Hz for 92 minutes and vacuum dried at 75°C for 130 minutes. Then they are mixed with 10% PVA solution in a mass ratio of 90:10.
[0069] 2) The obtained plastic billet is rolled. The first reduction of the roll is 50% of the billet thickness. After double-folding, it is reduced by another 50%, and this process is repeated 6 times. After rolling, the billet is dried at 155℃ for 15 minutes. The billet is then cut to the required size. A 37-micron thick layer of silicon nitride powder with an average particle size of 70nm is spread on its surface. A second layer is then added, followed by a third layer of silicon nitride powder, and so on, up to a total of 7 layers.
[0070] 3) Place the multi-layer oriented structural billet in a gas pressure sintering furnace at a depth of 1×10 5 Degreased at 380°C for 14 minutes under argon pressure, then at 1.1×10⁻⁶ ppm. 6 The silicon carbide composite ceramic material with directional structure was finally obtained by degreasing under argon pressure and 1620℃ for 24 minutes.
[0071] Example 4
[0072] 1) Weigh silicon carbide whiskers (diameter 320nm × length 40μm), titanium carbide powder (110nm), alumina powder (135nm) and yttrium oxide powder (130nm) in a mass ratio of 75:22:2:1. The powders are ultrasonically mixed in anhydrous ethanol at a frequency of 84 Hz for 94 minutes and vacuum dried at 75°C for 140 minutes. Then they are mixed with 10% PVA solution in a mass ratio of 91:9.
[0073] 2) The obtained plastic billet is rolled. The first reduction of the roll is 50% of the billet thickness. After double-folding, it is reduced by another 50%, and this process is repeated 5 times. After rolling, the billet is dried at 155℃ for 15 minutes. The billet is then cut to the required size. A 35-micron thick layer of silicon nitride powder with an average particle size of 50nm is spread on its surface. A second layer is then added, followed by another layer of silicon nitride powder and a third layer. This process is repeated up to 7 layers.
[0074] 3) Place the multi-layer oriented structural billet in a gas pressure sintering furnace at a temperature of 0.7 × 10⁻⁶. 5 Degreased at 370°C under argon pressure for 15 minutes, then at 9×10 5 The silicon carbide composite ceramic material with directional structure was finally obtained by degreasing under argon pressure and 1560℃ for 21 minutes.
[0075] The performance parameters of the silicon carbide composite ceramic materials prepared in Examples 1-4 are shown in Table 1:
[0076] Table 1
[0077]
[0078] As can be seen from the table above, the silicon carbide composite ceramic material prepared by this invention has an oriented structure, and the fracture toughness of the material is greater than or equal to 16.3 MPa·m. 1 / 2 The bending strength is greater than or equal to 1030 MPa, the room temperature hardness is greater than or equal to 23.4 GPa, and the high temperature hardness at 1000℃ is greater than or equal to 19.7 GPa.
[0079] Example 5
[0080] 1) Weigh silicon carbide whiskers (diameter 250nm × length 40μm), titanium carbide powder (90nm), alumina powder (125nm) and yttrium oxide powder (120nm) in a mass ratio of 73:25:1:1. The powders are ultrasonically mixed in anhydrous ethanol at a frequency of 75 Hz for 78 minutes and vacuum dried at 68℃ for 125 minutes. Then they are mixed with 10% PVA solution in a mass ratio of 90:10.
[0081] 2) The obtained plastic billet is rolled. The first reduction of the roll is 50% of the billet thickness. After double-folding, it is reduced by another 50%, and this process is repeated 4 times. After rolling, the billet is dried at 145℃ for 16 minutes. The billet is then cut to the required size. A 38-micron thick layer of silicon nitride powder with an average particle size of 58nm is spread on its surface. A second layer is then added, followed by a third layer of silicon nitride powder, and so on, up to a total of 6 layers.
[0082] 3) Place the multi-layer oriented structural billet in a gas pressure sintering furnace at a temperature of 0.6 × 10⁻⁶. 5 Degreased at 370°C for 12 minutes under argon pressure, then at 7×10 5 The silicon carbide composite ceramic material with directional structure was finally obtained by degreasing under argon pressure and 1580℃ for 22 minutes.
[0083] Example 6
[0084] 1) Weigh silicon carbide whiskers (diameter 260nm × length 40μm), titanium carbide powder (95nm), alumina powder (135nm) and yttrium oxide powder (118nm) in a mass ratio of 74:22:2:2. The powders are ultrasonically mixed in anhydrous ethanol at a frequency of 81 Hz for 82 minutes and vacuum dried at 78°C for 130 minutes. Then they are mixed with 10% PVA solution in a mass ratio of 91:9.
[0085] 2) The obtained plastic billet is rolled. The first reduction of the roll is 50% of the billet thickness. After double-folding, it is reduced by another 50%, and this process is repeated 5 times. After rolling, the billet is dried at 150°C for 18 minutes. The billet is then cut to the required size. A 40-micron thick layer of silicon nitride powder with an average particle size of 62nm is spread on its surface. A second layer is then added, followed by another layer of silicon nitride powder and a third layer. This process is repeated up to 7 layers.
[0086] 3) Place the multi-layer oriented structural billet in a gas pressure sintering furnace at a temperature of 0.8 × 10⁻⁶. 5 Degreased at 400°C for 13 minutes under argon pressure, then at 9×10 5 The silicon carbide composite ceramic material with directional structure was finally obtained by degreasing under argon pressure and 1590℃ for 23 minutes.
[0087] Example 7
[0088] 1) Weigh silicon carbide whiskers (diameter 280nm × length 41μm), titanium carbide powder (95nm), alumina powder (135nm) and yttrium oxide powder (125nm) in a mass ratio of 76:22:1:1. The powders are ultrasonically mixed in anhydrous ethanol at a frequency of 85 Hz for 90 minutes and vacuum dried at 72°C for 135 minutes. Then, they are mixed with 10% PVA solution in a mass ratio of 92:8.
[0089] 2) The obtained plastic billet is rolled. The first reduction of the roll is 50% of the billet thickness. After double-folding, it is reduced by another 50%, and this process is repeated 6 times. After rolling, the billet is dried at 150°C for 20 minutes. The billet is then cut to the required size. A 41-micron thick layer of silicon nitride powder with an average particle size of 65nm is spread on its surface. A second layer is then added, followed by a third layer of silicon nitride powder, and so on, up to a total of 5 layers.
[0090] 3) Place the multi-layer oriented structural billet in a gas pressure sintering furnace at a temperature of 0.9 × 10⁻⁶. 5 Degreased at 400°C for 14 minutes under argon pressure, then at 1.1×10⁻⁶ ppm. 6 The silicon carbide composite ceramic material with directional structure was finally obtained by degreasing under argon pressure and 1590℃ for 24 minutes.
[0091] Example 8
[0092] 1) Weigh silicon carbide whiskers (diameter 330nm × length 41μm), titanium carbide powder (100nm), alumina powder (135nm) and yttrium oxide powder (128nm) in a mass ratio of 77:20:2:1. The powders are ultrasonically mixed in anhydrous ethanol at a frequency of 85 Hz for 93 minutes and vacuum dried at 74°C for 135 minutes. Then they are mixed with 10% PVA solution in a mass ratio of 91:9.
[0093] 2) The obtained plastic billet is rolled. The first reduction of the roll is 50% of the billet thickness. After folding it in half, it is reduced by another 50%, and this process is repeated 4 times. After rolling, the billet is dried at 152℃ for 20 minutes. The billet is then cut to the required size. A 42-micron thick layer of silicon nitride powder with an average particle size of 65nm is spread on its surface. A second layer is then added, followed by another layer of silicon nitride powder and a third layer. This process is repeated up to 5 layers.
[0094] 3) Place the multi-layer oriented structural billet in a gas pressure sintering furnace at a temperature of 0.8 × 10⁻⁶. 5 Degreased at 400°C for 14 minutes under argon pressure, then at 1.2 × 10⁻⁶ ppm. 6 The silicon carbide composite ceramic material with directional structure was finally obtained by degreasing under argon pressure and 1600℃ for 24 minutes.
[0095] Tests in Examples 5-8 also show that the silicon carbide composite ceramic material prepared by this invention has an oriented structure and a fracture toughness greater than or equal to 16.3 MPa·m. 1 / 2 The bending strength is greater than or equal to 1030 MPa, the room temperature hardness is greater than or equal to 23.4 GPa, and the high temperature hardness at 1000℃ is greater than or equal to 19.7 GPa.
[0096] 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 directional silicon carbide composite ceramic material, characterized in that, Includes the following steps: Take silicon carbide whiskers, titanium carbide powder, alumina powder and yttrium oxide powder, mix them evenly and add plasticizer to obtain a plastic blank; Plastic billets are rolled into oriented structural billets, which are then dried, cut into shape, have a transition layer laid, and undergo multi-layer stacking to obtain multi-layer oriented structural billets. Degreasing and sintering of multi-layer oriented structured preforms yields oriented structured silicon carbide composite ceramic materials. The mass percentages of the silicon carbide whiskers, titanium carbide powder, alumina powder, and yttrium oxide powder are 72~78:20~26:1~3:1~3; The silicon carbide whiskers have the following dimensions: diameter 230~340nm, length 35~42μm, and average particle sizes of titanium carbide powder, alumina powder, and yttrium oxide powder are 80~110nm, 120~140nm, and 110~130nm, respectively. The degreasing and sintering treatment of the multi-layer oriented structure billet includes: The multi-layer oriented structural billet was placed in a pressure sintering furnace at a temperature of 0.5 × 10⁻⁶. 5 ~1×10 5 Degreased at argon pressure and 360-410℃ for 12-15 minutes, then at 6×10 5 ~1.3×10 6 Sinter at argon gas pressure and 1560~1630℃ for 21~25 minutes.
2. The method for preparing the oriented silicon carbide composite ceramic material as described in claim 1, characterized in that, The term "uniform mixing" means: The mixture is ultrasonically mixed in anhydrous ethanol at a frequency of 70-90 Hz for 75-94 minutes, and then vacuum dried at 65-75℃ for 120-140 minutes after homogeneity.
3. The method for preparing the oriented silicon carbide composite ceramic material as described in claim 1, characterized in that, The addition of plasticizer refers to the mixing of powder and 10% PVA solution at a mass percentage ratio of 89~92:8~11.
4. The method for preparing the oriented silicon carbide composite ceramic material as described in claim 1, characterized in that, The process of rolling a plastic preform into an oriented preform includes: The first pressing down of the roll is 50% of the billet thickness. After folding the double layer in half, it is pressed down another 50%. This process is repeated 4 to 6 times.
5. The method for preparing the oriented silicon carbide composite ceramic material as described in claim 1, characterized in that, The oriented structural blank undergoes sequential drying, cutting and shaping, laying of transition layers, and multi-layer stacking, including: After rolling, the billet is dried at 140~155℃ for 15~21 minutes. The billet is then cut to the required size. A 35~45 micrometer thick layer of silicon nitride powder with an average particle size of 50~70nm is laid on its surface. Then a second layer is added, followed by another layer of silicon nitride powder and a third layer. This process is repeated until 5~7 layers are added.
6. A directional silicon carbide composite ceramic material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 5.
7. The directional silicon carbide composite ceramic material according to claim 6, characterized in that, The prepared silicon carbide composite ceramic material has an oriented structure and a fracture toughness greater than or equal to 16.3 MPa·m. 1 / 2 The bending strength is greater than or equal to 1030 MPa, the room temperature hardness is greater than or equal to 23.4 GPa, and the high temperature hardness at 1000℃ is greater than or equal to 19.7 GPa.