Silicon carbide fiber sintered ceramic and method of making same

Abstract

This invention discloses a silicon carbide fiber sintered ceramic and its preparation method. The silicon carbide fiber sintered ceramic comprises hexagonal prism-shaped silicon carbide fibers and a graphite interface layer, wherein the graphite layer is uniformly filled in the middle of the hexagonal prism-shaped silicon carbide fibers, forming a completely dense structure. The preparation method mainly includes two steps: first, a graphite interface layer is prepared on the surface of the silicon carbide fibers using in-situ self-generation technology; then, the silicon carbide fibers with the graphite layer are laid in a graphite mold and hot-pressed and sintered in an inert atmosphere to finally obtain the silicon carbide fiber sintered ceramic. This silicon carbide fiber sintered ceramic has characteristics such as high fiber content, high density, and high strength. The preparation method has the advantages of simple and controllable process, low cost, and broad development prospects.

Description

Technical Field

[0001] This invention belongs to the field of ceramic material preparation technology, specifically relating to a silicon carbide fiber sintered ceramic and its preparation method. Background Technology

[0002] Developing high thrust-to-weight ratio aero-engines with faster flight speeds, longer service life, and lower energy consumption is a goal pursued by aerospace companies worldwide. However, as the thrust-to-weight ratio of aero-engines increases, the turbine inlet temperature also rises, potentially approaching 2000℃ in the future. This poses a significant challenge to the temperature resistance of turbine materials. In recent years, silicon carbide fiber sintered ceramics have attracted considerable attention due to their excellent high-temperature performance and are considered important candidate materials for high-thrust-to-weight ratio aero-engine high-temperature components.

[0003] SiC fiber-bonded ceramics (FBCs) are a new type of high-temperature resistant material obtained by directly hot-pressing and sintering SiC fibers at high temperatures. Compared to traditional SiC... f SiC (Silicon C) materials, sintered ceramics, lack a matrix phase and possess extremely low porosity and an extremely high fiber volume fraction (>80%). The minimal porosity of sintered ceramics prevents the rapid diffusion of high-temperature oxidizing gases within the material, resulting in excellent room-temperature strength retention; its strength does not decrease at 1600℃. Furthermore, the extremely high fiber volume fraction allows for the full utilization of the high strength and creep resistance properties of the fibers. Therefore, SiC fiber sintered ceramics exhibit excellent high-temperature oxidation resistance, making them suitable for long-term use in the high-temperature exhaust environments of aero-engines.

[0004] Currently, only UBE Corporation of Japan has mastered the preparation technology of SiC fiber sintered ceramics and has formed two types of SiC fiber sintered ceramic grades: Tyrannohex and SA-Tyrannohex. See reference 1: Kajii S, Ishikawa T, Matsunaga K, et al. A New Type of Fiber-bonded-ceramic Material Synthesized from Pre-oxidized Si-Ti-CO Fiber. Adv Perform Mater. 1994; 1(2):145-55. Reference 2: Ishikawa T, Kajii S, Matsunaga K, et al. A. Tough, Thermally Conductive Silicon Carbide Composite with High Strength up to 1600℃ in air. Science. 1998; 282(5392):1295-7. Patent reference 1: Ishikawa T, Kajii S, Matsunaga K, et al. Fiber Bonded Ceramics and Its Production [P].: JPH0952776, 1997-02-25., and Patent Document 2: Ishikawa T, Kajii S, Matsunaga K, et al. Sintered SiC Fibers Bonded Material: US Patent 6,132,856 [P]. 2000-10-17.

[0005] UBE has developed two types of SiC fiber sintered ceramics, both of which are hot-pressed and sintered from intermediate SiC fibers (Si-Ti-CO fibers and Si-Al-CO fibers). These intermediate fibers are rich in O and C elements and contain small amounts of Ti or Al elements. During the high-temperature hot-pressing process, the fibers easily sinter together, forming strong interfaces, resulting in low fracture toughness and fracture energy. Furthermore, the deoxidation and decarburization process, which transforms the intermediate fibers into SiC fibers, needs to be completed during hot-pressing and sintering. This process is difficult to control, has a narrow process window, and leads to significant fluctuations in material properties. Summary of the Invention

[0006] To address the challenges of high process control, narrow process window, and significant material property fluctuations in existing SiC fiber sintered ceramics during hot-pressing sintering, which involves the deoxidation and decarburization process transforming intermediate-state fibers into SiC fibers, this invention provides a silicon carbide fiber sintered ceramic and its preparation method. This fills the gap in SiC fiber sintered ceramic materials and preparation technology, and simultaneously solves the technical problems of narrow process window, large material property fluctuations, and low fracture toughness encountered in the preparation of sintered ceramics using intermediate-state SiC fibers as raw materials internationally.

[0007] To achieve the above objectives, the present invention proposes a silicon carbide fiber sintered ceramic, wherein the sintered ceramic has a high silicon carbide content and a fully dense structure, comprising hexagonal prism-shaped silicon carbide fibers and a graphite interface layer.

[0008] To achieve the above objectives, the present invention also proposes a method for preparing silicon carbide fiber sintered ceramics, comprising the following steps:

[0009] S1: Using silicon carbide fiber as raw material, a graphite layer is prepared on the surface of silicon carbide fiber using in-situ self-generation technology;

[0010] S2: The silicon carbide fibers with graphite layers are laid in a graphite mold and then hot-pressed and sintered to obtain a silicon carbide fiber sintered ceramic with high silicon carbide fiber content and complete density.

[0011] The objective of this invention is achieved through the following technical solution:

[0012] A method for preparing silicon carbide fiber sintered ceramics includes the following steps:

[0013] S1. Using silicon carbide fiber as raw material, a graphite layer is prepared on the surface of silicon carbide fiber using in-situ self-generation technology;

[0014] The silicon carbide fiber is one of a one-dimensional structure, a two-dimensional plain weave fabric, or a two-dimensional satin weave fabric.

[0015] The in-situ self-generation technology involves subjecting silicon carbide fibers to high-temperature heat treatment in a high-temperature vacuum furnace at a temperature of 1600–2000°C for 5–30 minutes, with a vacuum degree of 10. -3 The silicon carbide fiber is subjected to a high-temperature decomposition reaction at a pressure of ~1 Pa, thereby preparing a graphite layer in situ on the surface of the silicon carbide fiber; the thickness of the graphite layer is 100~500 nm.

[0016] S2. The silicon carbide fibers with graphite layers are laid out in a graphite mold and then hot-pressed and sintered at a temperature of 1600–2000℃, a pressure of 30–80 MPa, and a time of 10–100 min in an argon atmosphere to obtain silicon carbide fiber sintered ceramic. The silicon carbide fiber sintered ceramic has a high silicon carbide content and a completely dense structure, comprising hexagonal prism-shaped silicon carbide fibers and a graphite interface layer. The volume content of silicon carbide fibers in the silicon carbide fiber sintered ceramic is 90–98%, and the density reaches 3.10–3.20 g / cm³. 3 With a porosity of less than 1%, silicon carbide fiber sintered ceramics exhibit a flexural strength of 310-328 MPa and a fracture toughness of 9.1-10.1 MPa·m. 1 / 2 The fracture work is 1104-1221 J·m -2 .

[0017] In this invention:

[0018] The purpose of using in-situ self-generating technology in step S1 is to prepare a graphite layer on the surface of silicon carbide fibers, thereby laying the foundation for the subsequent sintering deformation of silicon carbide fibers and the high toughness of silicon carbide fiber sintered ceramics. At the same time, the in-situ self-generating technology is simple and has a short processing time, which is conducive to the rapid preparation of a graphite layer with controllable thickness on the surface of silicon carbide fibers, ultimately giving silicon carbide fiber sintered ceramics good mechanical properties.

[0019] Furthermore, the in-situ self-generation technology involves subjecting silicon carbide fibers to high-temperature heat treatment in a high-temperature vacuum furnace at a temperature of 1700–1800°C for 5–20 minutes, with a vacuum degree of 10. -3 The temperature is increased to ~1 Pa, causing a high-temperature decomposition reaction, thereby preparing a graphite layer in situ on the surface of silicon carbide fibers.

[0020] The purpose of controlling the process conditions of in-situ self-generation technology is to control the growth of graphite layer on the surface of silicon carbide fibers by regulating the saturated vapor pressure of silicon atoms and the high-temperature decomposition reaction rate of silicon carbide, thereby achieving controllable preparation of graphite layer thickness.

[0021] The hot pressing sintering described in step S2 is to promote the deformation of silicon carbide fibers and the rapid densification of silicon carbide fiber sintered ceramics, ultimately obtaining silicon carbide fiber sintered ceramics with high fiber content and complete density.

[0022] Furthermore, the hot pressing sintering is one of the following: traditional hot pressing sintering, hot isostatic pressing sintering, and electric field-assisted hot pressing sintering; the sintering process parameters are: temperature 1850~1950℃, pressure 50~80MPa, time 30~90min; the sintering atmosphere is argon.

[0023] The control of hot pressing sintering process conditions is to promote the deformation of silicon carbide fibers and the rapid densification of silicon carbide fiber sintered ceramics, ultimately obtaining hexagonal prism silicon carbide fibers and fully dense silicon carbide fiber sintered ceramics. The silicon carbide fiber sintered ceramics are high in silicon carbide content and have a fully dense structure, comprising hexagonal prism silicon carbide fibers and a graphite interface layer.

[0024] This invention also relates to a silicon carbide fiber sintered ceramic, obtained by the aforementioned method for preparing silicon carbide fiber sintered ceramic. The silicon carbide fiber sintered ceramic has a high silicon carbide content and a fully dense structure, comprising hexagonal prism-shaped silicon carbide fibers and a graphite interface layer. The volume content of silicon carbide fibers in the silicon carbide fiber sintered ceramic is 90-98%, and the density reaches 3.10-3.20 g / cm³. 3 With a porosity of less than 1%, silicon carbide fiber sintered ceramics exhibit a flexural strength of 310-322 MPa and a fracture toughness of 9.1-10.1 MPa·m. 1 / 2 The fracture work is 1104-1184 J·m -2 The silicon carbide fiber content can, on the one hand, give full play to the high temperature resistance, oxidation resistance and high strength of silicon carbide fiber sintered ceramics, and on the other hand, give full play to the role of graphite interface layer in improving toughness. Ultimately, silicon carbide fiber sintered ceramics have synergistic properties such as high temperature resistance, oxidation resistance and high strength and toughness.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] 1. The present invention discloses a silicon carbide fiber sintered ceramic, comprising hexagonal prism-shaped silicon carbide fibers and a graphite interface layer. Compared to traditional silicon carbide fiber sintered ceramics, which require intermediate-state silicon carbide fibers as raw materials, the present invention uses third-generation silicon carbide fibers as raw materials, partially solving the limitation on fiber raw materials in the preparation of silicon carbide fiber sintered ceramics, and also enabling controllable preparation of the graphite interface layer thickness. Furthermore, a graphite layer of optimal thickness can enhance the toughness of the silicon carbide fiber sintered ceramic, ultimately significantly improving its fracture toughness and solving the problem of high brittleness in silicon carbide fiber sintered ceramics.

[0027] 2. The method for preparing silicon carbide fiber sintered ceramics according to the present invention includes two steps: in-situ self-generated graphite layer on the surface of silicon carbide fibers and hot-pressing sintering. The in-situ self-generated graphite layer on the surface of silicon carbide fibers has advantages such as simple process and low cost, and allows for precise control of the graphite layer thickness. The hot-pressing sintering process is a mature process with no special requirements, and the entire preparation process is simple and has a short cycle time. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0029] Figure 1 This is a process flow diagram of a method for preparing silicon carbide fiber sintered ceramics according to the present invention.

[0030] Figure 2 The image shows the XRD pattern of the graphite layer prepared in situ on the surface of silicon carbide fiber in Example 1 of this invention.

[0031] Figure 3 This is a SEM image of an in-situ graphite layer prepared on the surface of silicon carbide fiber in Example 1 of the present invention;

[0032] Figure 4 The XRD pattern of the silicon carbide fiber sintered ceramic prepared in Example 1 of this invention;

[0033] Figure 5 Optical and SEM images of the silicon carbide fiber sintered ceramic prepared in Example 1 of this invention;

[0034] Figure 6 Optical and SEM images of the silicon carbide fiber sintered ceramic prepared in Example 2 of this invention;

[0035] Figure 7 Optical photographs and SEM images of the fracture surfaces of the silicon carbide fiber sintered ceramic prepared in Example 3 of the present invention.

[0036] Figure 8 Optical photographs and SEM images of the fracture surfaces of the silicon carbide fiber sintered ceramic prepared in Example 4 of this invention. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0038] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0039] Unless otherwise specified, all medicines / reagents used are commercially available.

[0040] Example 1:

[0041] A method for preparing silicon carbide fiber sintered ceramics includes the following steps:

[0042] (1) Using domestic KD-SA type silicon carbide fiber as the reference raw material, the silicon carbide fiber was placed in a high-temperature vacuum furnace, the initial vacuum degree was kept below 20 Pa, the temperature was raised to 1750℃ at 10℃ / min, and the vacuum degree was kept below 1 Pa. The temperature was then held for 20 min, and then cooled to 500℃ at 20℃ / min. The temperature was then cooled with the furnace to obtain silicon carbide fiber with a graphite layer on the surface.

[0043] Figure 2 The figure shows the XRD pattern of the graphite layer prepared in situ on the surface of silicon carbide fiber in this embodiment. As can be seen from the figure, the diffraction peaks of the graphite layer are relatively weak, indicating that its thickness is relatively thin. Figure 3 These are SEM images of the in-situ graphite layer prepared on the surface of silicon carbide fibers in this embodiment. Figure 2 It can be seen that the graphite layer is well bonded to the silicon carbide fiber, and its thickness is about 300-400 nm.

[0044] (2) Using silicon carbide fiber containing graphite layer as the reference raw material, cut it evenly and stack it, and put graphite paper into the upper and lower sides respectively, and then put it into a graphite mold; place the graphite mold in a high temperature hot press furnace, introduce argon atmosphere, heat up to 1200℃ at 10℃ / min, then heat up to 1900℃ at 5℃ / min, and pressurize to 60MPa, keep at 1900℃ and pressurize for 60min, then cool down to 500℃ at 20℃ / min, and then cool with the furnace to obtain the silicon carbide fiber sintered ceramic.

[0045] Figure 4 The image shows the XRD pattern of the silicon carbide fiber sintered ceramic prepared in this embodiment. Figure 4 It can be seen that the diffraction peaks of the graphite interface layer inside the silicon carbide fiber sintered ceramic are relatively weak, indicating that its thickness is relatively thin.

[0046] Figure 5 These are SEM images of the silicon carbide fiber sintered ceramics prepared in this embodiment. Figure 5 It can be seen that the silicon carbide fibers are all deformed into hexagonal prisms, and the graphite layer is evenly distributed at the interface between the silicon carbide fibers, forming a completely dense structure.

[0047] The density of the prepared silicon carbide fiber sintered ceramic reached 3.15 g / cm³. 3With a porosity of less than 1%, silicon carbide fiber sintered ceramics exhibit flexural strength, fracture toughness, and fracture energy reaching 328 MPa, 10.1 MPa·m, and 10.1 MPa·m, respectively. 1 / 2 With 1221 J·m -2 The volume content of silicon carbide fiber in silicon carbide fiber sintered ceramics is 93%.

[0048] Example 2:

[0049] A method for preparing silicon carbide fiber sintered ceramics includes the following steps:

[0050] (1) Using domestic KD-SA type silicon carbide fiber as the reference raw material, the silicon carbide fiber was placed in a high-temperature vacuum furnace, the initial vacuum degree was kept below 20 Pa, the temperature was raised to 1700℃ at 10℃ / min, and the vacuum degree was kept below 1 Pa. The temperature was then held for 10 min, and then cooled to 500℃ at 20℃ / min. The temperature was then cooled with the furnace to obtain silicon carbide fiber with a graphite layer on the surface.

[0051] (2) Using silicon carbide fiber containing graphite layer as the reference raw material, cut it evenly and stack it, and put graphite paper into the upper and lower sides respectively, and then put it into a graphite mold; place the graphite mold in a high temperature hot press furnace, introduce argon atmosphere, heat up to 1200℃ at 10℃ / min, then heat up to 1950℃ at 5℃ / min, and pressurize to 30MPa, keep at 1950℃ and pressurize for 30min, then cool down to 500℃ at 20℃ / min, and then cool with the furnace to obtain the silicon carbide fiber sintered ceramic.

[0052] Figure 6 These are SEM images of the silicon carbide fiber sintered ceramics prepared in this embodiment. Figure 6 It can be seen that the silicon carbide fibers are all deformed into hexagonal prisms, and the graphite layer is evenly distributed at the interface between the silicon carbide fibers, forming a completely dense structure.

[0053] The density of the prepared silicon carbide fiber sintered ceramic reached 3.19 g / cm³. 3 With a porosity of less than 1%, the flexural strength of silicon carbide fiber sintered ceramics can reach 311 MPa; the volume content of silicon carbide fibers in silicon carbide fiber sintered ceramics is 98%.

[0054] Example 3:

[0055] A method for preparing silicon carbide fiber sintered ceramics includes the following steps:

[0056] (1) Using domestic KD-SA type silicon carbide fiber as the reference raw material, the silicon carbide fiber was placed in a high-temperature vacuum furnace, the initial vacuum degree was kept below 20 Pa, the temperature was raised to 1800℃ at 10℃ / min, and the vacuum degree was kept below 1 Pa. The temperature was then held for 5 min, and then cooled to 500℃ at 20℃ / min. The temperature was then cooled with the furnace to obtain silicon carbide fiber with a graphite layer on the surface.

[0057] (2) Using silicon carbide fiber containing graphite layer as the reference raw material, cut it evenly and stack it, and put graphite paper into the upper and lower sides respectively, and then put it into a graphite mold; place the graphite mold in a high temperature hot press furnace, introduce argon atmosphere, heat up to 1200℃ at 10℃ / min, then heat up to 1850℃ at 5℃ / min, and pressurize to 70MPa, keep at 1850℃ and pressurize for 90min, then cool down to 500℃ at 20℃ / min, and then cool with the furnace to obtain the silicon carbide fiber sintered ceramic.

[0058] Figure 7 The images shown are SEM images of the fracture surfaces of the silicon carbide fiber sintered ceramics prepared in this embodiment. Figure 7 It can be seen that the silicon carbide fibers are all deformed into hexagonal prisms and there is fiber pull-out phenomenon, indicating that silicon carbide fiber sintered ceramics exhibit good toughness.

[0059] The density of the prepared silicon carbide fiber sintered ceramic reached 3.11 g / cm³. 3 With a porosity of less than 1%, silicon carbide fiber sintered ceramics can achieve flexural strength, fracture toughness, and fracture energy of 310 MPa, 9.1 MPa·m, respectively. 1 / 2 With 1104 J·m -2 The volume content of silicon carbide fiber in silicon carbide fiber sintered ceramics is 90%.

[0060] Example 4:

[0061] A method for preparing silicon carbide fiber sintered ceramics includes the following steps:

[0062] (1) Using domestic KD-SA type silicon carbide fiber as the reference raw material, the silicon carbide fiber was placed in a high-temperature vacuum furnace, the initial vacuum degree was kept below 20 Pa, the temperature was raised to 1750℃ at 10℃ / min, and the vacuum degree was kept below 1 Pa. The temperature was then held for 15 min, and then cooled to 500℃ at 20℃ / min. The temperature was then cooled with the furnace to obtain silicon carbide fiber with a graphite layer on the surface.

[0063] (2) Using silicon carbide fiber containing graphite layer as the reference raw material, cut it evenly and stack it, and put graphite paper into the upper and lower sides respectively, and then put it into a graphite mold; place the graphite mold in a high temperature hot press furnace, introduce argon atmosphere, heat up to 1200℃ at 10℃ / min, then heat up to 1900℃ at 5℃ / min, and pressurize to 80MPa, keep at 1900℃ and pressurize for 90min, then cool down to 500℃ at 20℃ / min, and then cool with the furnace to obtain the silicon carbide fiber sintered ceramic.

[0064] Figure 8 The images shown are SEM images of the fracture surfaces of the silicon carbide fiber sintered ceramics prepared in this embodiment. Figure 8 It can be seen that the silicon carbide fibers deform into hexagonal prisms and exhibit fiber pull-out phenomena, indicating that silicon carbide fiber sintered ceramics exhibit good toughness.

[0065] The density of the silicon carbide fiber sintered ceramic prepared by the above process reaches 3.17 g / cm³. 3 With a porosity of less than 1%, silicon carbide fiber sintered ceramics exhibit flexural strength, fracture toughness, and fracture energy reaching 322 MPa, 9.4 MPa·m, and 1%, respectively. 1 / 2 With 1184 J·m -2 The volume content of silicon carbide fiber in silicon carbide fiber sintered ceramics is 96%.

[0066] Comparative Example 1:

[0067] The preparation method of silicon carbide fiber sintered ceramics includes the following steps:

[0068] Using domestically produced KD-SA type silicon carbide fiber as the base material, it is laid in a graphite mold and then hot-pressed and sintered to obtain interface-free silicon carbide fiber sintered ceramic.

[0069] The obtained silicon carbide fiber sintered ceramics have the following properties:

[0070] The fracture toughness and fracture work are 5.5 MPa·m. 1 / 2 With 55 J·m -2 .

[0071] Compared with Example 1, the fracture toughness is significantly lower.

[0072] Comparative Example 2:

[0073] The preparation method of silicon carbide fiber sintered ceramics includes the following steps:

[0074] Using Si-Al-CO fibers as the base material, they are laid out in a graphite mold and then hot-pressed and sintered to obtain silicon carbide fiber sintered ceramics containing only 20-40nm graphite interfaces.

[0075] The obtained silicon carbide fiber sintered ceramics have the following properties:

[0076] The bending strength and fracture toughness fracture energy are 290 MPa and 4.2 MPa·m, respectively. 1 / 2 .

[0077] Compared to Example 1, this shows that the bending strength and fracture toughness are significantly lower.

[0078] The results show that:

[0079] 1. By comparing Examples 1-4 and Comparative Example 1, it is shown that the graphite layer prepared on the surface of silicon carbide fiber using in-situ self-generated technology plays a very important role in improving the toughness of silicon carbide fiber sintered ceramics, and can significantly improve its fracture toughness and fracture work.

[0080] 2. By comparing Examples 1-4 and Comparative Example 2, it is shown that the graphite layer prepared on the surface of silicon carbide fiber using in-situ self-generation technology can achieve thickness control, reaching 100-500 nm, which is much larger than the graphite interface thickness (20-40 nm) of silicon carbide fiber sintered ceramics prepared with Si-Al-CO fiber, thereby significantly improving its fracture toughness.

[0081] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for preparing silicon carbide fiber sintered ceramics, characterized in that: Includes the following steps: S1. Using silicon carbide fiber as raw material, a graphite layer is prepared on the surface of silicon carbide fiber using in-situ self-generation technology; The silicon carbide fiber is one of a one-dimensional structure, a two-dimensional plain weave fabric, or a two-dimensional satin weave fabric. The in-situ self-generation technology involves subjecting silicon carbide fibers to high-temperature heat treatment in a high-temperature vacuum furnace at a temperature of 1600–2000°C for 5–30 minutes, with a vacuum degree of 10. -3 The silicon carbide fiber is subjected to a high-temperature decomposition reaction at a pressure of ~1 Pa, thereby preparing a graphite layer in situ on the surface of the silicon carbide fiber; the thickness of the graphite layer is 100~500 nm. S2. The silicon carbide fibers with graphite layers are laid out in a graphite mold and then hot-pressed and sintered at a temperature of 1600–2000℃, a pressure of 30–80 MPa, and a time of 10–100 min in an argon atmosphere to obtain silicon carbide fiber sintered ceramic. The silicon carbide fiber sintered ceramic has a high silicon carbide content and a completely dense structure, comprising hexagonal prism-shaped silicon carbide fibers and a graphite interface layer. The volume content of silicon carbide fibers in the silicon carbide fiber sintered ceramic is 90–98%, and the density reaches 3.10–3.20 g / cm³. 3 With a porosity of less than 1%, silicon carbide fiber sintered ceramics exhibit a flexural strength of 310-328 MPa and a fracture toughness of 9.1-10.1 MPa·m. 1 / 2 The fracture work is 1104-1221 J·m -2 .

2. The method for preparing silicon carbide fiber sintered ceramics according to claim 1, characterized in that: The in-situ self-generation technology described in step S1 involves subjecting silicon carbide fibers to high-temperature heat treatment in a high-temperature vacuum furnace at a temperature of 1700–1800°C for 5–20 minutes and a vacuum degree of 10. -3 ~1Pa.

3. The method for preparing silicon carbide fiber sintered ceramics according to claim 1, characterized in that: The hot pressing sintering described in step S2 is one of the following: traditional hot pressing sintering, hot isostatic pressing sintering, and electric field assisted hot pressing sintering; the sintering process parameters are: temperature 1850~1950℃, pressure 50~80MPa, and time 30~90min.

4. A silicon carbide fiber sintered ceramic, characterized in that: The silicon carbide fiber sintered ceramic is prepared by any one of the methods described in claims 1-3. The silicon carbide fiber sintered ceramic has a high silicon carbide content and a completely dense structure, comprising hexagonal prism-shaped silicon carbide fibers and a graphite interface layer. The volume content of silicon carbide fibers in the silicon carbide fiber sintered ceramic is 90-98%, and the density reaches 3.10-3.20 g / cm³. 3 With a porosity of less than 1%, silicon carbide fiber sintered ceramics exhibit a flexural strength of 310-328 MPa and a fracture toughness of 9.1-10.1 MPa·m. 1 / 2 The fracture work is 1104-1221 J·m -2 .

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