A silicon carbide fiber-bonded ceramic, its preparation method, and application

Abstract

The present invention discloses a silicon carbide fiber-bonded ceramic, its preparation method and application. The preparation method uses silicon carbide fibers, rare earth materials and a molten salt medium as raw materials, and prepares a rare earth carbide coating on the surface of the silicon carbide fibers by the molten salt method; then, through hot pressing sintering, the silicon carbide fiber-bonded ceramic is prepared. The present invention uses any silicon carbide fiber as the raw material, effectively solves the limitation of the existing preparation of bonded ceramics on the fiber raw material, and can also significantly reduce the sintering temperature of the bonded ceramics. In addition, the preparation method of the present invention has simple process, short cycle, and wide sources and easy access of raw materials such as silicon carbide fibers and metal sources, and can be extended to industrial production. The silicon carbide fiber-bonded ceramic has excellent oxidation resistance, high interlayer bonding strength, low porosity, and high fiber volume fraction, and can be applied in the high-temperature gas environment of aeroengines.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic material preparation, and particularly to a silicon carbide fiber-bonded ceramic, a preparation method thereof, and an application thereof. Background Art

[0002] With the increase in the thrust-to-weight ratio of aeroengines, the temperature in front of the engine turbine also rises accordingly. In the future, it will approach 2000 °C, which poses a great challenge to the temperature resistance of the materials of turbine hot-end components. Silicon carbide fiber-bonded ceramics (SiC fiber-bonded ceramics, FBCs) are new high-temperature resistant materials obtained by directly hot-pressing and sintering SiC fibers at high temperature. In recent years, silicon carbide fiber-bonded ceramics have attracted much attention due to their excellent high-temperature properties and are considered excellent candidate materials for high-temperature components of high-thrust-to-weight-ratio aeroengines. Compared with traditional SiC f / SiC materials, silicon carbide fiber-bonded ceramics have no matrix phase and have characteristics such as extremely low porosity and high fiber volume fraction (>80%). The extremely few pores in the bonded ceramics can avoid the rapid diffusion of high-temperature oxidation gases inside the material, enabling the bonded ceramics to have excellent strength retention ability at high temperatures, and its strength does not decrease significantly at 1500 °C; in addition, the extremely high fiber volume fraction is conducive to fully exerting the high strength, creep resistance and other characteristics of the fibers. Therefore, silicon carbide fiber-bonded ceramics have excellent high-temperature oxidation resistance and are beneficial for long-term use in the high-temperature gas environment of aeroengines.

[0003] At present, the types of silicon carbide fiber-bonded ceramics are very few, only including Tyrannohex type bonded ceramics and SA-Tyrannohex type bonded ceramics, and their preparations all require amorphous silicon carbide fibers containing heteroelements (Ti or Al) as raw materials. At present, it is still impossible to prepare bonded ceramics using any silicon carbide fiber. In addition, the existing bonded ceramics also have defects such as relatively high sintering temperature (1750-1900 °C) and weak interlayer bonding strength. Summary of the Invention

[0004] The present invention provides a silicon carbide fiber-bonded ceramic, a preparation method thereof, and an application thereof, which are used to overcome the need for amorphous silicon carbide fibers containing heteroelements (Ti or Al) as raw materials in the prior art, and can also overcome the defects of relatively high sintering temperature and weak interlayer bonding strength of the existing bonded ceramics.

[0005] To achieve the above object, the present invention proposes a preparation method of a silicon carbide fiber-bonded ceramic, comprising the following steps:

[0006] S1: Using silicon carbide fibers, rare earth materials, and molten salt medium as raw materials, a rare earth carbide coating is prepared on the surface of silicon carbide fibers by the molten salt method; the rare earth materials are rare earth metals or rare earth metal hydrides; the rare earth metal elements in the rare earth materials are at least one of Y, Dy, and Pr; the rare earth carbide coating is RE 3 Si 2 C 2 , where RE is at least one of Y, Dy, and Pr; the molar ratio of the silicon carbide fibers, rare earth materials, and molten salt medium is (2.5 - 4):1:(50 - 110);

[0007] S2: Stack and arrange the silicon carbide fibers with rare earth carbide coatings prepared in S1, and hot press sinter in an inert atmosphere to obtain silicon carbide fiber bonding ceramics.

[0008] To achieve the above object, the present invention also provides a silicon carbide fiber bonding ceramic prepared by the above preparation method; the silicon carbide fiber bonding ceramic includes silicon carbide fibers and rare earth compounds, and the rare earth compounds are located at the interfaces of the silicon carbide fibers; the rare earth metal elements in the rare earth compounds are at least one of Y, Dy, and Pr; the volume content of the silicon carbide fibers in the silicon carbide fiber bonding ceramic is 80 - 99% and the porosity is less than 3%.

[0009] To achieve the above object, the present invention also provides an application of the silicon carbide fiber bonding ceramic. The silicon carbide fiber bonding ceramic prepared by the above preparation method or the above silicon carbide fiber bonding ceramic is applied to high-temperature structural components of aeroengines, thermal protection structural components of hypersonic aircraft, and other high-temperature structural material fields.

[0010] Compared with the prior art, the beneficial effects of the present invention are:

[0011] 1. The preparation method of the silicon carbide fiber - bonded ceramic provided by the present invention uses silicon carbide fibers, rare - earth materials, and molten - salt medium as raw materials. By the molten - salt method, a rare - earth carbide coating is prepared on the surface of the silicon carbide fibers. The rare - earth carbide coating, as a sintering aid, can significantly reduce the sintering and bonding temperature and densification temperature of the silicon carbide fibers, and improve the oxidation resistance and inter - layer bonding strength of the bonded ceramic. In addition, through the molten - salt medium, the prepared coating can be uniform and continuous, so as to achieve good structural consistency and high density after the sintering and bonding of the silicon carbide fibers, and further improve the comprehensive performance of the bonded ceramic. Then, through hot - press sintering at a lower temperature, the silicon carbide fiber - bonded ceramic is prepared. The present invention uses any silicon carbide fiber (including those with and without hetero - elements, partially crystallized and fully crystallized ones) as raw materials, effectively solving the limitation of the existing preparation of bonded ceramics on fiber raw materials, and can also significantly reduce the sintering temperature of the bonded ceramic (the sintering temperature of traditional bonded ceramics is 1750 - 1900 °C, while the sintering temperature of the bonded ceramic provided by the present invention is 1500 - 1700 °C). In addition, the preparation method of the present invention has simple technology, short cycle, and the raw materials such as silicon carbide fibers and metal sources are widely sourced and easily obtained, and can be promoted to industrial production.

[0012] 2. The silicon carbide fiber - bonded ceramic prepared by the present invention includes silicon carbide fibers and rare - earth compounds. The rare - earth compounds are located at the interface of the silicon carbide fibers. The rare - earth compounds have a strong binding force with the fibers, making the bonded ceramic have a high inter - layer bonding strength. At the same time, the rare - earth compound interface has good oxidation resistance, which can protect itself and the silicon carbide fibers from oxidation, and finally enables the silicon carbide fiber - bonded ceramic to have excellent oxidation resistance. In addition, the silicon carbide fiber - bonded ceramic has low porosity and high fiber volume fraction, and can be applied in the high - temperature gas environment of an aero - engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following - described drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0014] Figure 1 It is the process flow chart of the preparation method of the silicon carbide fiber - bonded ceramic proposed by the present invention;

[0015] Figure 2 It is the XRD spectrum of the rare - earth carbide (Y 3 Si 2 C 2 ) coating prepared on the surface of the silicon carbide fiber in Example 1;

[0016] Figure 3 SEM photograph of the rare earth carbide (Y 3 Si 2 C 2 ) coating prepared on the surface of silicon carbide fiber in Example 2; wherein, a is the cross-section of the silicon carbide fiber, b is the surface of the silicon carbide fiber, and c is the partially enlarged photograph of the surface of the silicon carbide fiber;

[0017] Figure 4 Optical photograph and SEM photograph of the silicon carbide fiber bonding ceramic prepared in Example 2; wherein, a is the optical photograph and b is the SEM photograph;

[0018] Figure 5 Optical photograph and SEM photograph of the silicon carbide fiber bonding ceramic prepared in Example 3; wherein, a is the optical photograph and b is the SEM photograph;

[0019] Figure 6 Optical photograph and SEM photograph of the silicon carbide fiber bonding ceramic prepared in Example 4; wherein, a is the optical photograph and b is the SEM photograph.

[0020] The realization, functional features and advantages of the object of the present invention will be further described in conjunction with the embodiments with reference to the accompanying drawings. Detailed implementation manners

[0021] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts belong to the scope of protection of the present invention.

[0022] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0023] Unless otherwise specified, the drugs / reagents used are all commercially available.

[0024] The present invention provides a method for preparing a silicon carbide fiber bonding ceramic, as Figure 1 shown, which includes the following steps:

[0025] S1: Using silicon carbide fibers, rare earth materials, and molten salt medium as raw materials, a rare earth carbide coating is prepared on the surface of silicon carbide fibers by the molten salt method; the rare earth materials are rare earth metals or rare earth metal hydrides; the rare earth metal element (RE) in the rare earth materials is at least one of yttrium (Y), dysprosium (Dy), and praseodymium (Pr); the rare earth carbide coating is RE 3 Si 2 C 2 , where RE is at least one of Y, Dy, and Pr.

[0026] The molar ratio of the silicon carbide fibers, rare earth materials, and molten salt medium is (2.5 - 4):1:(50 - 110). The control of the reaction conditions and raw material ratio of the molten salt method is to ensure that a rare earth carbide with a certain thickness grows on the surface of the silicon carbide fibers in the liquid molten salt medium while ensuring that the silicon carbide fibers retain high mechanical strength; the high-temperature environment, chemical reaction corrosion, and molten salt corrosion during the reaction process will damage the fibers. Therefore, it is necessary to reduce the reaction temperature of the molten salt method process as much as possible and shorten the reaction time; in addition, affected by the liquid buoyancy in the high-temperature molten salt, floating will inevitably occur. If the molar ratio of the SiC fibers, rare earth materials, and molten salt is unreasonable, it will be difficult to prepare a rare earth carbide coating with a controllable thickness, good bonding, and uniform and continuous structure on the surface of the SiC fibers. For example, if the molar ratio of the molten salt is too large or too small, it will lead to the unfavorable phenomenon that the coating thickness of the SiC fibers and their fabrics is significantly non-uniform; therefore, it is necessary to simultaneously study reducing the reaction temperature of the molten salt method process, shortening the reaction time, and adjusting the molar ratio of the SiC fibers, rare earth materials, and molten salt.

[0027] The purpose of using the molten salt method is to in-situ grow rare earth carbide (RE 3 Si 2 C 2 , where RE is at least one of Y, Dy, and Pr) on the surface of the silicon carbide fibers, thereby laying the foundation for the subsequent sintering and bonding of the silicon carbide fibers; at the same time, by adjusting the molar ratio of the SiC fibers, rare earth materials, and molten salt, reducing the reaction temperature of the molten salt method, and shortening the reaction time, the damage to the silicon carbide fibers caused by the reactants and molten salt can be reduced, and finally the bonding ceramic has good mechanical properties.

[0028] S2: Arrange the silicon carbide fibers with a rare earth carbide coating on the surface prepared in S1, and hot press sinter in an inert atmosphere to obtain a silicon carbide fiber bonding ceramic.

[0029] Preferably, in step S1, the thickness of the rare earth carbide coating is 0.1 - 1 μm. The control basis for this thickness range is to achieve the sintering densification of the fibers while maintaining the high mechanical strength of the fibers; therefore, the thickness of the coating cannot be too thick.

[0030] Preferably, the silicon carbide fiber is a one-dimensional tow or a two-dimensional woven structure; the molten salt medium is at least one of sodium chloride, potassium chloride, lithium chloride, magnesium chloride, and calcium chloride.

[0031] Preferably, step S1 is specifically as follows:

[0032] Weigh silicon carbide fibers, rare earth materials, and molten salt medium in proportion, mix them evenly, heat and react under an inert atmosphere, and wash with water after cooling to obtain silicon carbide fibers with rare earth carbide coatings on the surface.

[0033] Preferably, the temperature of the heating reaction is 900 - 1050 °C, and the time is 10 - 100 min. Controlling the high-temperature reaction process conditions aims to control the growth of rare earth carbides on the surface of silicon carbide fibers and reduce the damage of silicon carbide fibers by adjusting the reaction rate of rare earth materials and silicon carbide and the nucleation and growth rate of reaction products.

[0034] Preferably, the inert atmosphere is argon or nitrogen.

[0035] Preferably, in step S2, the temperature of the hot pressing sintering is 1500 - 1700 °C, the pressure is 20 - 70 MPa, and the time is 60 - 120 min. Hot pressing sintering is to promote the rapid sintering and bonding between silicon carbide fibers with rare earth carbide coatings, and finally obtain a silicon carbide fiber bonded ceramic with a high fiber content and high density.

[0036] The present invention also provides a silicon carbide fiber bonded ceramic, which is prepared by the above preparation method; the silicon carbide fiber bonded ceramic includes silicon carbide fibers and rare earth compounds, and the rare earth compounds are located at the interfaces of the silicon carbide fibers; the rare earth metal elements in the rare earth compounds are at least one of Y, Dy, and Pr; the volume content of silicon carbide fibers in the silicon carbide fiber bonded ceramic is 80 - 99%, and the porosity is less than 3%. On the one hand, this content of silicon carbide fibers can achieve the effects of high temperature resistance and toughening of the bonded ceramic, and on the other hand, it can fully exert the effects of sintering aids and oxidation resistance at the interfaces of rare earth compounds, ultimately enabling the bonded ceramic to simultaneously possess synergistic properties such as high temperature resistance, oxidation resistance, high strength, and toughness.

[0037] The present invention also provides an application of the silicon carbide fiber bonded ceramic, applying the silicon carbide fiber bonded ceramic prepared by the above preparation method or the above silicon carbide fiber bonded ceramic to high-temperature structural components of aeroengines, thermal protection structural components of hypersonic aircraft, and other high-temperature structural material fields.

[0038] Example 1

[0039] This example provides a preparation method of a silicon carbide fiber bonded ceramic:

[0040] (1) Using domestic KD-II type silicon carbide fiber as the reference raw material, weigh sodium chloride and potassium chloride with a molar ratio of 1:1, and add yttrium metal with a molar ratio of 1:60 to sodium chloride and potassium chloride. Put them into a mortar and grind to mix evenly to obtain a mixed powder. Uniformly embed silicon carbide fiber products with a molar ratio of 5:2 to yttrium metal into the mixed powder of yttrium metal, sodium chloride and potassium chloride, load them into a graphite crucible, and cover the crucible lid. Place the graphite crucible in a high-temperature pyrolysis furnace, introduce an argon atmosphere, heat up to 600 °C at a rate of 10 °C / min, then heat up to 1050 °C at a rate of 5 °C / min, keep it at 1050 °C for 60 min, then cool down to 500 °C at a rate of 20 °C / min, and then cool down with the furnace. Wash and dry the product to obtain silicon carbide fiber with a Y 3 Si 2 C 2 coated on its surface.

[0041] Figure 2 This is the XRD pattern of preparing rare earth carbide coating on the surface of silicon carbide fiber in this example. As can be seen from the figure, the main components of the coating are Y 3 Si 2 C 2 .

[0042] (2) Using silicon carbide fiber with a Y 3 Si 2 C 2 coated on its surface as the reference raw material, cut it evenly and stack it, and install graphite paper on its upper and lower surfaces respectively, and then install them together into a graphite mold. Place the graphite mold in a high-temperature hot pressing furnace, introduce an argon atmosphere, heat up to 1200 °C at a rate of 10 °C / min, then heat up to 1700 °C at a rate of 5 °C / min, and apply a pressure of 50 MPa. Keep it at 1700 °C for heat preservation and pressure holding for 60 min, then cool down to 500 °C at a rate of 20 °C / min, and then cool down with the furnace to obtain silicon carbide fiber bonding ceramics.

[0043] Example 2

[0044] This example provides a method for preparing silicon carbide fiber bonding ceramics:

[0045] (1) Using domestic KD-II type silicon carbide fiber as the reference raw material, weigh sodium chloride and potassium chloride with a molar ratio of 1:1, and add yttrium metal with a molar ratio of 1:70 to sodium chloride and potassium chloride. Put them into a mortar and grind to mix evenly to obtain a mixed powder. Uniformly embed the silicon carbide fiber product with a molar ratio of 3:1 to yttrium metal into the mixed powder of yttrium metal, sodium chloride and potassium chloride, load it into a graphite crucible, and cover the crucible lid. Place the graphite crucible in a high-temperature pyrolysis furnace, introduce an argon atmosphere, heat it to 600 °C at a rate of 10 °C / min, then heat it to 1000 °C at a rate of 5 °C / min, hold it at 1000 °C for 30 min, then cool it to 500 °C at a rate of 20 °C / min, and then cool it with the furnace. Wash and dry the product to obtain silicon carbide fibers with a surface of Y 3 Si 2 C 2 coated silicon carbide fibers.

[0046] Figure 3 This is the SEM photograph of preparing rare earth carbide (Y 3 Si 2 C 2 ) coating on the surface of silicon carbide fibers. Among them, a is the cross-section of silicon carbide fibers, b is the surface of silicon carbide fibers, and c is the partial enlarged photograph of the surface of silicon carbide fibers. It can be seen from the figure that the thickness of the coating is relatively thin, the grains of rare earth carbide are relatively small, and the coating on the fiber surface is evenly distributed and well combined.

[0047] (2) Using the silicon carbide fibers with Y 3 Si 2 C 2 coating as the reference raw material, cut it evenly and stack it, and install graphite paper on its upper and lower sides respectively, and then install them together into a graphite mold; place the graphite mold in a high-temperature hot pressing furnace, introduce an argon atmosphere, heat it to 1200 °C at a rate of 10 °C / min, then heat it to 1500 °C at a rate of 5 °C / min, and apply a pressure of 40 MPa. Hold it at 1500 °C for heat preservation and pressure holding for 120 min, then cool it to 500 °C at a rate of 20 °C / min, and then cool it with the furnace to obtain the silicon carbide fiber bonding ceramic.

[0048] Figure 4 This is the optical photograph and SEM photograph of the bonding ceramic prepared in this example. It can be seen from the figure that the bonding ceramic is mainly composed of silicon carbide fibers and rare earth compounds, and the two are evenly distributed.

[0049] Example 3

[0050] This example provides a preparation method of a silicon carbide fiber bonding ceramic:

[0051] (1) Using domestic KD-II type silicon carbide fiber as the reference raw material, weigh sodium chloride and potassium chloride with a molar ratio of 1:1, and add yttrium metal with a molar ratio of 1:80 to sodium chloride and potassium chloride. Put them into a mortar and grind to mix evenly to obtain a mixed powder. Uniformly bury the silicon carbide fiber product with a molar ratio of 4:1 to yttrium metal into the mixed powder of yttrium metal, sodium chloride and potassium chloride, load it into a graphite crucible, and cover the crucible lid. Place the graphite crucible in a high-temperature pyrolysis furnace, introduce an argon atmosphere, heat it to 600 °C at a rate of 10 °C / min, then heat it to 1000 °C at a rate of 5 °C / min, hold it at 1000 °C for 20 min, then cool it to 500 °C at a rate of 20 °C / min, and then cool it with the furnace. Wash and dry the product to obtain silicon carbide fiber with a surface of Y 3 Si 2 C 2 coated.

[0052] (2) Using the silicon carbide fiber with Y 3 Si 2 C 2 coated as the reference raw material, cut it evenly and stack it, and install graphite paper on both the upper and lower sides respectively, and then load it into a graphite mold together. Place the graphite mold in a high-temperature hot pressing furnace, introduce an argon atmosphere, heat it to 1200 °C at a rate of 10 °C / min, then heat it to 1700 °C at a rate of 5 °C / min, and apply a pressure of 50 MPa. Hold it at 1700 °C for heat and pressure for 60 min, then cool it to 500 °C at a rate of 20 °C / min, and then cool it with the furnace to obtain the silicon carbide fiber bonding ceramic. Figure 5 Figure 17 is the optical photo and SEM photo of the bonding ceramic prepared in this example. As can be seen from the figure, some fibers are deformed into hexagons, forming a dense "honeycomb" structure.

[0053] Example 4

[0054] This example provides a method for preparing a silicon carbide fiber bonding ceramic:

[0055] (1) Using domestic KD-SA type silicon carbide fiber as the reference raw material, weigh sodium chloride and potassium chloride with a molar ratio of 1:1, and add yttrium metal with a molar ratio of 1:100 to sodium chloride and potassium chloride. Put them into a mortar and grind to mix evenly to obtain a mixed powder. Uniformly bury the silicon carbide fiber product with a molar ratio of 4:1 to yttrium metal into the mixed powder of yttrium metal, sodium chloride and potassium chloride, load it into a graphite crucible, and cover the crucible lid. Place the graphite crucible in a high-temperature pyrolysis furnace, introduce an argon atmosphere, heat it to 600 °C at a rate of 10 °C / min, then heat it to 1000 °C at a rate of 5 °C / min, hold it at 1000 °C for 20 min, then cool it to 500 °C at a rate of 20 °C / min, and then cool it with the furnace. Wash and dry the product to obtain silicon carbide fiber with a surface of Y 3 Si 2 C2 Coated silicon carbide fiber.

[0056] (2) Using the silicon carbide fiber with Y 3 Si 2 C 2 coated as the reference raw material, cut it evenly and stack it, then install graphite paper on both the upper and lower sides respectively, and then put them into a graphite mold together; place the graphite mold in a high-temperature hot-pressing furnace, introduce argon atmosphere, heat it to 1200 °C at a rate of 10 °C / min, then heat it to 1700 °C at a rate of 5 °C / min, and apply pressure up to 45 MPa, keep the temperature and pressure at 1700 °C for 60 min, then cool it to 500 °C at a rate of 20 °C / min, and then cool it with the furnace to obtain the silicon carbide fiber bonding ceramic. Figure 6 The optical photo and SEM photo of the bonding ceramic prepared in this example are shown. It can be seen from the figure that the bonding ceramic has an extremely high fiber content and a uniform and dense structure.

[0057] The bending strength of the silicon carbide fiber bonding ceramic prepared in this example can reach 242 MPa. Using the kerosene drainage method, the apparent density is calculated to be 3.16 g / cm 3 and the porosity is less than 3%.

[0058] Example 5

[0059] This example provides a preparation method of a silicon carbide fiber bonding ceramic:

[0060] (1) Using domestic KD-II type silicon carbide fiber as the reference raw material, weighing sodium chloride and calcium chloride with a molar ratio of 1:1, and adding dysprosium metal with a molar ratio of 1:60 to sodium chloride and calcium chloride, put them into a mortar and grind them to mix evenly to obtain a mixed powder; the silicon carbide fiber product with a molar ratio of 3.5:1 to dysprosium metal is evenly buried in the mixed powder of dysprosium metal, sodium chloride and calcium chloride, put into a graphite crucible, and cover the crucible lid; place the graphite crucible in a high-temperature pyrolysis furnace, introduce argon atmosphere, heat it to 600 °C at a rate of 10 °C / min, then heat it to 1000 °C at a rate of 5 °C / min, keep it at 1000 °C for 60 min, then cool it to 500 °C at a rate of 20 °C / min, and then cool it with the furnace; wash and dry the product to obtain silicon carbide fiber with a surface of Dy 3 Si 2 C 2 coated.

[0061] (2) Using the silicon carbide fiber with Dy 3 Si 2 C 2Using coated silicon carbide fibers as the reference raw material, cut them evenly and stack them, then install graphite paper on their upper and lower surfaces respectively, and then install them together in a graphite mold; place the graphite mold in a high-temperature hot press furnace, introduce an argon atmosphere, heat it to 1200 °C at a rate of 10 °C / min, then heat it to 1700 °C at a rate of 5 °C / min, and apply a pressure of 60 MPa. Keep the temperature and pressure at 1700 °C for 60 min, then cool it to 500 °C at a rate of 20 °C / min, and then cool it with the furnace to obtain silicon carbide fiber bonding ceramics.

[0062] Example 6

[0063] This example provides a method for preparing silicon carbide fiber bonding ceramics:

[0064] (1) Using domestic KD-II type silicon carbide fibers as the reference raw material, weigh lithium chloride and calcium chloride with a molar ratio of 1:1, and add praseodymium metal with a molar ratio of 1:80 to lithium chloride and calcium chloride. Put them into a mortar and grind them to mix evenly to obtain a mixed powder; uniformly bury the silicon carbide fiber product with a molar ratio of 4:1 to praseodymium metal into the mixed powder of praseodymium metal, lithium chloride and calcium chloride, put it into a graphite crucible, and cover the crucible lid; place the graphite crucible in a high-temperature pyrolysis furnace, introduce an argon atmosphere, heat it to 500 °C at a rate of 10 °C / min, then heat it to 900 °C at a rate of 5 °C / min, keep it at 900 °C for 100 min, then cool it to 400 °C at a rate of 20 °C / min, and then cool it with the furnace; wash and dry the product to obtain silicon carbide fibers with a surface of Pr 3 Si 2 C 2 coated silicon carbide fibers.

[0065] (2) Using silicon carbide fibers with a Pr 3 Si 2 C 2 coated surface as the reference raw material, cut them evenly and stack them, then install graphite paper on their upper and lower surfaces respectively, and then install them together in a graphite mold; place the graphite mold in a high-temperature hot press furnace, introduce an argon atmosphere, heat it to 1200 °C at a rate of 10 °C / min, then heat it to 1500 °C at a rate of 5 °C / min, and apply a pressure of 30 MPa. Keep the temperature and pressure at 1500 °C for 60 min, then cool it to 500 °C at a rate of 20 °C / min, and then cool it with the furnace to obtain silicon carbide fiber bonding ceramics.

[0066] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structural transformation made under the inventive concept of the present invention, or direct / indirect application in other related technical fields is included in the patent protection scope of the present invention.

Claims

1. A preparation method of a silicon carbide fiber-bonded ceramic, characterized in that: It includes the following steps: S1: Using silicon carbide fibers, rare earth materials and molten salt medium as raw materials, a rare earth carbide coating is prepared on the surface of silicon carbide fibers by the molten salt method; The silicon carbide fiber is a one-dimensional tow or a two-dimensional woven structure; the rare earth material is a rare earth metal or a rare earth metal hydride; the rare earth metal element in the rare earth material is at least one of Y, Dy, and Pr; the rare earth carbide coating is RE 3 Si 2 C 2 , where RE is at least one of Y, Dy, and Pr; the molten salt medium is at least one of sodium chloride, potassium chloride, lithium chloride, magnesium chloride, and calcium chloride; the molar ratio of the silicon carbide fiber, the rare earth material, and the molten salt medium is (2.5~4):1:(50~110); The thickness of the rare earth carbide coating is 0.1~1 μm; For the preparation of the rare earth carbide coating on the surface of silicon carbide fibers by the molten salt method, weigh silicon carbide fibers, rare earth materials and molten salt medium in proportion, mix evenly, heat and react in an inert atmosphere, the temperature is 900~1050 °C, the time is 10~100 min, and after cooling, wash with water to obtain silicon carbide fibers with a rare earth carbide coating on the surface; S2: Stack and arrange the silicon carbide fibers with a rare earth carbide coating prepared in S1, and perform hot pressing and sintering in an inert atmosphere. The temperature of the hot pressing and sintering is 1500~1700 °C, the pressure is 20~70 MPa, and the time is 60~120 min to obtain a silicon carbide fiber-bonded ceramic. The silicon carbide fiber-bonded ceramic includes silicon carbide fibers and rare earth compounds, and the rare earth compounds are located at the interfaces of the silicon carbide fibers; The rare earth metal element in the rare earth compound is at least one of Y, Dy, and Pr; the volume content of silicon carbide fibers in the silicon carbide fiber-bonded ceramic is 80~99%, and the porosity is less than 3%.

2. The preparation method of a silicon carbide fiber-bonded ceramic according to claim 1, characterized in that: The inert atmosphere is argon or nitrogen.

3. A silicon carbide fiber-bonded ceramic, characterized in that: Prepared by the preparation method of a silicon carbide fiber-bonded ceramic according to claim 1 or 2; the silicon carbide fiber-bonded ceramic includes silicon carbide fibers and rare earth compounds, and the rare earth compounds are located at the interfaces of the silicon carbide fibers; The rare earth metal element in the rare earth compound is at least one of Y, Dy, and Pr; the volume content of silicon carbide fibers in the silicon carbide fiber-bonded ceramic is 80~99%, and the porosity is less than 3%.

4. An application of a silicon carbide fiber-bonded ceramic, characterized in that: The silicon carbide fiber-bonded ceramic according to claim 3 is applied to high-temperature structural components of aeroengines and thermal protection structural components of hypersonic aircraft.

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