Silicon nitride fiber monolithic ceramic and method for preparing silicon nitride fiber monolithic ceramic based on wet spinning

Abstract

The application belongs to the field of ceramic materials, and particularly relates to a silicon nitride fiber monolithic ceramic and a method for preparing the silicon nitride fiber monolithic ceramic based on wet spinning, which comprises the following steps: preparing a silicon nitride fiber monolithic precursor, modifying an interface of the silicon nitride fiber, pre-pressing, drying a green body, degassing the green body, and hot-pressing and sintering to obtain the silicon nitride fiber monolithic ceramic, wherein the bending strength of the silicon nitride fiber monolithic ceramic can reach more than 580 MPa, and the fracture toughness can reach 13 MPa.m 1 / 2 The application successfully prepares the silicon nitride fiber by using the wet spinning technology, effectively improves the bending strength and the fracture toughness of the silicon nitride fiber monolithic ceramic material, and has excellent comprehensive performance.

Description

Technical Field

[0001] The present invention relates to a ceramic material, in particular to a silicon nitride fiber monolithic ceramic and a method for preparing the silicon nitride fiber monolithic ceramic based on wet spinning. Background Art

[0002] Silicon nitride ceramics are an important structural ceramic material. Their excellent properties, including high thermal stability, strong oxidation resistance, high hardness, wear resistance, high temperature resistance, and high dimensional precision, have led to their widespread application in aerospace, chemical engineering, machining, biomedicine, and other fields. With the rapid development of aerospace in recent years, silicon nitride ceramics have attracted considerable research attention and become a promising material. However, their critical weakness is brittleness. When stressed, they can crack or even fracture, leading to material failure, thus limiting their application in these fields and presenting a significant challenge. Therefore, to ensure the reliability and safety of silicon nitride materials during use, it is imperative to improve their brittleness without compromising their performance. Further research into ceramic materials has revealed that, according to current research approaches, achieving higher performance requires increasingly complex and difficult-to-control structures and compositions. Inspired by the unique organizational structures of some biological materials found in nature, the concept of biomimetic structural design has been introduced into material design and research. In 1988, Coblenz proposed the idea of ​​fiber monolithic structure design. Fiber monolithic ceramic composite materials simulate the fiber structure characteristics of bamboo. First, the powder is made into a ceramic fiber precursor, then a certain thickness of interface layer is coated on its surface, and then hot-pressed and sintered. Baskaran et al. prepared SiC / graphite fiber monolithic ceramics with a bending strength of 220 MPa and a fracture work of 1300 J / m 2 . Summary of the Invention

[0003] In response to the shortcomings of the existing technology, the present invention provides a silicon nitride fiber monolithic ceramic and a method for preparing silicon nitride fiber monolithic ceramic based on wet spinning. The process is simple, easy to operate, low in cost, and highly designable. The obtained silicon nitride fiber has excellent machinability, and the prepared silicon nitride fiber monolithic ceramic material has excellent bending strength and fracture toughness, and excellent comprehensive performance.

[0004] The technical solution provided by the present invention is as follows:

[0005] The present invention provides a method for preparing silicon nitride fiber monolithic ceramics based on wet spinning, comprising the following steps:

[0006] A ceramic powder containing silicon nitride, aluminum oxide, and yttrium oxide is mixed with anhydrous ethanol, ball-milled, dried, ground, and sieved to obtain a mixed powder, a mixed solution consisting of a dispersant, a binder, a plasticizer, and an organic solvent is added, and ball-milled again to obtain a spinning solution. The spinning solution is then sprayed into a coagulation bath through a nozzle, and a silicon nitride fiber precursor is obtained after coagulation;

[0007] The silicon nitride fiber precursor is modified by immersing it in an interface layer slurry obtained by mixing boron nitride and aluminum oxide powders using an immersion method, and the thickness of the interface layer is controlled by the immersion time to obtain a silicon nitride fiber precursor having an interface layer;

[0008] The dried silicon nitride fiber precursor with the interface layer is cut according to the size of the pre-pressing mold, arranged uniaxially or crosswise in the mold, and then pre-pressed to obtain a fiber monolith pre-pressed green body;

[0009] The fiber monolith pre-pressed green body is naturally dried;

[0010] Debinding the dried green body;

[0011] The debinding green body is hot pressed and sintered to obtain a silicon nitride fiber monolithic ceramic material.

[0012] Furthermore, the mass ratio of silicon nitride, aluminum oxide, and yttrium oxide in the ceramic powder is 90-100:3-5:7-12, and the particle size of silicon nitride is 0.5 μm.

[0013] Furthermore, the binder is polyethylene glycol butyral, the dispersant is polyethylene glycol, the plasticizer is glycerol, the organic solvent is anhydrous ethanol, and the mass ratio of the binder, dispersant, plasticizer and organic solvent is 10~20:10:3~5:70~75.

[0014] Furthermore, the coagulation bath is water, the temperature of the coagulation bath is 0-10° C., and the diameter of the obtained silicon nitride fiber precursor is 500-800 μm.

[0015] Furthermore, the boron nitride and aluminum oxide powders are mixed in a mass ratio of 1:3, and the particle size of the boron nitride is 1-5 μm.

[0016] Furthermore, the silicon nitride fiber precursor is immersed in the interface layer slurry for 10 to 15 minutes, and the thickness of the interface layer is 5 to 20 μm.

[0017] Furthermore, when a hydraulic press is used for pre-pressing, the pre-pressing pressure is 10-15 MPa and the holding time is 10-20 minutes.

[0018] Further, the glue removal condition is: room temperature, the temperature rising rate is 0.5-5.0 ℃ / min, and the temperature is raised to 600-700 ℃, and the temperature is kept for 1-2 h.

[0019] Further, the sintering condition is: room temperature, the temperature rising rate is 10-15 ℃ / min, and the temperature is raised to 1780-1800 ℃, and the temperature is kept for 1-2 h, and the furnace is cooled down.

[0020] The application further provides a silicon nitride fiber monolithic ceramic prepared by the method, the silicon nitride fiber monolithic ceramic has a bending strength of 500-600 MPa and a fracture toughness of 10-15 MPa·m 1 / 2 .

[0021] Advantages

[0022] The application provides a method for preparing a silicon nitride fiber monolithic ceramic based on wet spinning, and the method has simple process and low cost, and realizes synchronous improvement of the strength and toughness of the ceramic material.

[0023] Specifically, the application has the following outstanding advantages compared with the prior art.

[0024] (1) The wet spinning technology is used to prepare the silicon nitride fiber precursor, the process is simple, easy to operate and low in cost, the preparation time of the fiber is greatly shortened, and the preparation efficiency is improved.

[0025] (2) A certain amount of glycerol is added to the spinning dope to increase the flowability of the spinning dope, the spinning dope will not be blocked when entering the coagulation through the spinning nozzle, and the prepared fiber has better toughness and is easier to process.

[0026] (3) The coagulation bath used in the method is water, and the temperature of the coagulation bath is room temperature, so that the cost is greatly reduced.

[0027] (4) The BN interface is uniformly coated on the surface of the fiber precursor, which is more conducive to crack deflection and branching at the interface during the stress process, and improves the fracture toughness of the ceramic material.

[0028] (5) The bending strength and fracture toughness of silicon nitride fiber monolithic ceramic materials prepared by this method reached 500~600 MPa and 10~15 MPa·m 1 / 2 . BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Scanning electron microscope images of the silicon nitride fiber precursor before and after coating in Example 1 of the present invention show that the silicon nitride fiber precursor has a smooth surface and a diameter of approximately 550 μm. After BN coating, the BN is evenly distributed on the surface of the silicon nitride fiber.

[0030] Figure 2 This is the microstructure of the Si3N4 / BN fiber monolith ceramic material after sintering in Example 1 of the present invention. The black phase is the Si3N4 cell, and the white phase surrounding the Si3N4 cell is the BN interface. The Si3N4 cell width is approximately 450 μm, and the BN thickness is approximately 10 μm. DETAILED DESCRIPTION

[0031] The present invention will be further explained in detail below with reference to the accompanying drawings and specific embodiments. However, it should be understood that the protection scope of the present invention is not limited to the specific embodiments.

[0032] An embodiment of the present invention provides a method for preparing silicon nitride fiber monolithic ceramics based on wet spinning, comprising the following steps:

[0033] 1) Preparation of silicon nitride fiber precursor: Ceramic powders containing silicon nitride, aluminum oxide, and yttrium oxide are mixed with anhydrous ethanol, ball-milled, dried, ground, and sieved to obtain a mixed powder. A mixture consisting of a dispersant, a binder, a plasticizer, and an organic solvent is added, and the mixture is ball-milled again to obtain a spinning solution. The spinning solution is then sprayed into a coagulation bath through a nozzle, and coagulated to obtain a silicon nitride fiber precursor.

[0034] 2) Silicon nitride fiber interface modification: The silicon nitride fiber precursor is modified by the impregnation method. Boron nitride and aluminum oxide powders are stirred in deionized water to obtain an interface layer slurry. The thickness of the interface layer is controlled by the immersion time to obtain a silicon nitride fiber precursor with an interface layer.

[0035] 3) Pre-pressing: Cut the dried silicon nitride fiber precursor with the interface layer according to the size of the pre-pressing mold, arrange it uniaxially or crosswise in the mold, and then pre-press it to obtain a fiber monolith pre-pressed green body;

[0036] 4) Green body drying: The fiber monolith pre-pressed green body is naturally dried;

[0037] 5) Debinding of green body: Debinding of the dried green body;

[0038] 6) Hot pressing and sintering: The debinding green body is hot pressed and sintered to obtain silicon nitride fiber monolithic ceramic material.

[0039] In this embodiment, step 1) is specifically as follows: first, silicon nitride, aluminum oxide and yttrium oxide are mixed with anhydrous ethanol in a mass ratio of 90-100:3-5:7-12, and a planetary ball mill is used for ball milling for 48 hours to obtain a uniform wet mixed powder, the wet mixed powder is dried using a rotary evaporator, and the dried mixed powder is ground and sieved to finally obtain a fine and uniform mixed powder, a dispersant, a binder, a plasticizer and an organic solvent are mixed, and dissolved using mechanical stirring to obtain a mixed solution, and then the mixed powder and the solution are mixed in a mass ratio of 1:1, and ball milled for 48 hours to obtain a spinning solution, which is passed through a spinning nozzle into a coagulation bath, and after coagulation, a silicon nitride fiber monolith precursor is obtained, wherein the diameter of the silicon nitride fiber precursor is 500-800 μm, the curing agent is polyethylene glycol butyral, the binder is polyethylene glycol, the plasticizer is glycerol, and the coagulation bath is water.

[0040] In this embodiment, step 2) is specifically as follows: the silicon nitride fiber precursor is modified by an immersion method, firstly, boron nitride is mixed in deionized water and mechanically stirred for 3 hours, then alumina powder is added and stirred for 6 hours to obtain a uniformly mixed interface layer slurry, wherein boron nitride and alumina are mixed in a mass ratio of 1:3, and the silicon nitride fiber monolith precursor is immersed in the interface layer slurry for 10 to 15 minutes. The thickness of the interface layer of the fiber monolith precursor is changed by the immersion time, and the thickness of the interface layer is 5 to 20 μm.

[0041] In this embodiment, step 3) is specifically as follows: first, the impregnated fiber monolith precursor is dried in an oven at a drying temperature of 60°C, the impregnated silicon nitride fiber monolith precursor is cut according to the size of the pre-pressing mold, and uniaxially or cross-arranged in the mold, and pre-pressed using a hydraulic press at room temperature, and maintained at a pressure of 10-20 MPa for 10-20 minutes to obtain a fiber monolith pre-pressed green body.

[0042] In this embodiment, step 4) specifically includes placing the fiber monolith pre-pressed green body in a room for natural drying for 14 days until the quality of the fiber monolith green body no longer changes, and the green body is dried.

[0043] In this embodiment, step 5) is specifically as follows: the dried green body is placed in a box-type resistance furnace for debinding, the debinding temperature is 600-700°C, the holding time is 1-5 hours, and the heating rate is 0.5-5°C / min.

[0044] In this embodiment, step 6) is specifically as follows: the green body after debinding is hot-pressed and sintered in a hot-pressing sintering furnace, with the temperature rising at a rate of 10-15°C / min to a sintering temperature of 1780-1800°C, the holding time being 1-2 hours, the pressure being 30 MPa, and the silicon nitride fiber monolithic ceramic material being obtained after cooling in the furnace.

[0045] This embodiment also provides a silicon nitride fiber monolithic ceramic, which is prepared according to the above method. The silicon nitride fiber monolithic ceramic has a bending strength of 500-600 MPa and a fracture toughness of 10-15 MPa·m 1 / 2 .

[0046] Example 1

[0047] A method for preparing silicon nitride fiber monolithic ceramics based on wet spinning comprises the following steps:

[0048] (1) Preparation of silicon nitride fiber precursor: 90 g silicon nitride, 3 g aluminum oxide and 7 g yttrium oxide were mixed with anhydrous ethanol for wet mixing. The slurry was ball milled for 48 h, and then dried using a rotary evaporator. The dried powder was ground and sieved to obtain a fine and uniform mixed powder. Then, a mixed solution of 10 g polyethylene glycol butyral, 10 g polyethylene glycol, 5 g propylene glycol and 75 g anhydrous ethanol was prepared. The solution was mechanically stirred for 8 h to fully dissolve the solution. After dissolution, the mixed powder was added. After ball milling for 48 h, a spinning solution was obtained. The spinning solution was sprayed into a coagulation bath using a spinning nozzle. After soaking in the coagulation bath for 20 min, a silicon nitride fiber precursor was obtained. The coagulation bath was deionized water and the temperature was room temperature. The diameter of the silicon nitride fiber precursor was 550 μm.

[0049] (2) Silicon nitride interface modification: The silicon nitride fiber precursor was modified by the impregnation method. 3.75 g of boron nitride was mixed in deionized water and mechanically stirred for 3 h. Then 1.25 g of alumina powder was added and stirred for 6 h to obtain a uniformly mixed interface layer slurry. Boron nitride and alumina were mixed in a mass percentage of 1:3. The silicon nitride fiber monolith precursor was immersed in the interface layer slurry for 10 min. The interface layer thickness of the fiber monolith precursor was changed by changing the immersion time. The thickness of the BN interface layer was 10.14 μm.

[0050] (3) Pre-pressing: First, the coated fiber monolith precursor is dried in an oven at a drying temperature of 60 °C. The impregnated silicon nitride fiber precursor is cut according to the size of the pre-pressing mold. The fibers are cut into uniform lengths and arranged uniaxially or crosswise in the mold. A hydraulic press is used to pre-press at room temperature and the pressure is maintained at 10 MPa for 20 min to obtain a fiber monolith pre-pressed green body.

[0051] (4) Green body drying: the fiber monolithic pre-pressed green body is placed indoors for natural drying, the drying time is 14 days, until the mass of the fiber monolithic green body no longer changes, the green body drying is completed;

[0052] (5) Green body glue removal: the dried green body is placed in a box-type resistance furnace for glue removal, the glue removal temperature is 600 ℃, the holding time is 1 h, and the heating rate is 0.5 ℃ / min;

[0053] (6) Hot-pressing sintering: the green body after glue removal is subjected to hot-pressing sintering in a hot-pressing sintering furnace, the temperature is increased to 1780 ℃ at a heating rate of 10 ℃ / min, the holding time is 1 h, the pressure is 30 MPa, and the silicon nitride fiber monolithic ceramic material is obtained after furnace cooling, the bending strength and the fracture toughness thereof are 567.17 MPa and 11.76 MPa·m 1 / 2 .

[0054] Example 2

[0055] A method for preparing a silicon nitride fiber monolithic ceramic based on a wet spinning process, comprising the following steps:

[0056] (1) Preparation of silicon nitride fiber precursor: 100 g of silicon nitride, 5 g of aluminum oxide and 12 g of yttrium oxide are mixed with anhydrous ethanol for wet mixing, the slurry is ball milled for 48 h using a ball mill, and then dried using a rotary evaporator. The dried powder is ground and sieved to obtain fine and uniform mixed powder. A mixed solution of 15 g of polyethylene glycol butylal, 10 g of polyethylene glycol, 3 g of glycerol and 70 g of anhydrous ethanol is prepared, and the solution is fully dissolved by mechanical stirring for 10 h. After dissolution, the mixed powder is added, and the spinning stock solution is obtained by ball milling for 48 h. The spinning stock solution is introduced into the coagulation bath through a spinning nozzle, and the spinning nozzle is used to spray the spinning stock solution into the coagulation bath. After soaking in the coagulation bath for 20 min, the silicon nitride fiber precursor is obtained. The coagulation bath is deionized water, and the temperature is room temperature. The diameter of the silicon nitride fiber precursor is 650 μm;

[0057] (2) Silicon nitride interface modification: the silicon nitride fiber precursor is modified by immersion method. 5.25 g of boron nitride is mixed in deionized water and mechanically stirred for 2 h. Then 1.75 g of aluminum oxide powder is added and stirred for another 8 h to obtain a uniformly mixed interface layer slurry. The boron nitride and aluminum oxide are mixed in a mass ratio of 1:3. The silicon nitride fiber monolithic precursor is soaked in the interface layer slurry for 15 min. By changing the soaking time, the thickness of the interface layer of the fiber monolithic precursor can be changed. The thickness of the BN interface layer is 12.57 μm;

[0058] (3) Pre-pressing: First, the coated fiber monolith precursor is dried in an oven at a drying temperature of 60 °C. The impregnated silicon nitride fiber precursor is cut according to the size of the pre-pressing mold. The fibers are cut into uniform lengths and arranged uniaxially or crosswise in the mold. A hydraulic press is used to pre-press at room temperature and the pressure is maintained at 15 MPa for 20 min to obtain a fiber monolith pre-pressed green body.

[0059] (4) Body drying: The fiber monolith pre-pressed body is placed in a room for natural drying for 14 days until the quality of the fiber monolith body no longer changes. The body drying is completed.

[0060] (5) Debinding of green body: The dried green body is placed in a box-type resistance furnace for debinding. The debinding temperature is 600 °C, the holding time is 1 h, and the heating rate is 2.0 °C / min.

[0061] (6) Hot pressing sintering: The green body after debinding was hot pressed and sintered in a hot pressing furnace. The temperature was raised to 1800 °C at a heating rate of 15 °C / min, the holding time was 1.5 h, and the pressure was 30 MPa. After cooling in the furnace, the silicon nitride fiber monolithic ceramic material was obtained. Its flexural strength and fracture toughness were 589.32 MPa and 13.93 MPa·m, respectively. 1 / 2 .

[0062] Example 3

[0063] A method for preparing silicon nitride fiber monolithic ceramics based on wet spinning comprises the following steps:

[0064] (1) Preparation of silicon nitride fiber precursor: 90g silicon nitride, 3g aluminum oxide and 7g yttrium oxide were wet mixed with anhydrous ethanol, and the slurry was ball milled for 48 hours, and then dried using a rotary evaporator. The dried powder was ground and sieved to obtain a fine and uniform mixed powder. 20g polyethylene glycol butyral, 10g polyethylene glycol, 5g propylene glycol and 75g anhydrous ethanol were mixed and mechanically stirred for 6 hours to fully dissolve the solution. After dissolution, the mixed powder was added and ball milled for 48 hours to obtain a spinning solution. The spinning solution was sprayed into a coagulation bath using a spinning nozzle. After soaking in the coagulation bath for 20 minutes, a silicon nitride fiber precursor was obtained. The coagulation bath was deionized water and the temperature was room temperature. The diameter of the silicon nitride fiber precursor was 700 μm.

[0065] (2) Silicon nitride interface modification: The silicon nitride fiber precursor was modified by the impregnation method. 6.75 g of boron nitride was mixed in deionized water and mechanically stirred for 4 h. Subsequently, 2.25 g of alumina powder was added and stirred for 8 h to obtain a uniformly mixed interface layer slurry. Boron nitride and alumina were mixed in a mass percentage of 1:3. The silicon nitride fiber monolith precursor was immersed in the interface layer slurry for 20 min. The interface layer thickness of the fiber monolith precursor was changed by changing the immersion time. The thickness of the BN interface layer was 16.32 μm.

[0066] (3) Pre-pressing: First, the coated fiber monolith precursor is dried in an oven at a drying temperature of 70 °C. The impregnated silicon nitride fiber precursor is cut according to the size of the pre-pressing mold. The fibers are cut into uniform lengths and arranged uniaxially or crosswise in the mold. A hydraulic press is used to pre-press at room temperature and the pressure is maintained at 15 MPa for 10 min to obtain a fiber monolith pre-pressed green body.

[0067] (4) Body drying: The fiber monolith pre-pressed body is placed in a room for natural drying for 14 days until the quality of the fiber monolith body no longer changes. The body drying is completed.

[0068] (5) Debinding of green body: The dried green body is placed in a box-type resistance furnace for debinding. The debinding temperature is 600 °C, the holding time is 2 h, and the heating rate is 5.0 °C / min.

[0069] (6) Hot pressing sintering: The green body after debinding was hot pressed and sintered in a hot pressing furnace. The temperature was raised to 1800 °C at a heating rate of 10 °C / min, the holding time was 2 h, and the pressure was 30 MPa. After cooling in the furnace, the silicon nitride fiber monolithic ceramic material was obtained. Its flexural strength and fracture toughness were 520.39 MPa and 14.65 MPa·m, respectively. 1 / 2 .

[0070] Table 1 shows the performance parameters of silicon nitride fiber monolithic ceramics in embodiments 1, 2, and 3 of the method of the present invention.

[0071] Table 1

[0072]

[0073] The table above shows that higher sintering temperatures lead to superior mechanical properties of the prepared ceramics. When sintered at 1800°C and held for 1.5 hours, the silicon nitride / boron nitride fiber monolithic ceramics exhibit excellent flexural strength and fracture toughness. A thicker BN interface layer increases fracture toughness, but flexural strength decreases.

[0074] Figure 2This is the microstructure of the Si3N4 / BN fiber monolithic ceramic material after sintering in Example 1 of the method of the present invention. Figure 2 a is the microscopic morphology of the longitudinal section of the ceramic. It can be found that the black phase is the Si3N4 cell body, and the white phase around the Si3N4 cell body is the BN interface. It can be found that the width of the Si3N4 cell body is about 450 μm. In order to analyze the thickness of the BN interface layer, Figure 2 The rectangular box in a is enlarged, such as Figure 2 As shown in b. The thickness of BN was determined to be approximately 10 μm by measurement. Figure 2 Scan the line in the direction of the blue arrow in b, and the result is as follows Figure 2 As shown in c. Figure 2 In c, it was found that the content of Si element was the lowest when the content of BN element was the highest, which indicated that the interface in the middle was BN. Figure 2 (d and e) are transmission bright field images and high-resolution images, confirming the presence of silicon nitride and boron nitride through morphology and interplanar spacing. Figure 2 Scan the positions of A and B in d, and the results are as follows Figure 2 As shown. It is found that A is boron nitride and B is silicon nitride. Figure 2 The results of f are used to prove Figure 2 Results of (d and e).

[0075] The above are only preferred embodiments of the present invention, and the present invention is not limited to the contents of the embodiments. For those skilled in the art, various changes and modifications can be made within the scope of the technical solution of the present invention, and any changes and modifications made are within the scope of protection of the present invention.

Claims

1. A method for preparing silicon nitride fiber monolithic ceramics based on wet spinning, characterized in that: The following steps are involved: A ceramic powder comprising silicon nitride, aluminum oxide, and yttrium oxide is mixed with anhydrous ethanol, ball-milled, dried, ground, and sieved to obtain a mixed powder, a mixed solution consisting of a dispersant, a binder, a plasticizer, and an organic solvent is added, and ball-milled again to obtain a spinning solution, which is then sprayed into a coagulation bath through a nozzle, and coagulated to obtain a silicon nitride fiber precursor; the binder is polyethylene glycol butyral, the dispersant is polyethylene glycol, the plasticizer is glycerol, and the organic solvent is anhydrous ethanol, and the mass ratio of the binder, dispersant, plasticizer, and organic solvent is 10-20:10:3-5:70-75; The silicon nitride fiber precursor is modified by immersing it in an interface layer slurry obtained by mixing boron nitride and aluminum oxide powders using an immersion method, and the thickness of the interface layer is controlled by the immersion time to obtain a silicon nitride fiber precursor having an interface layer; The dried silicon nitride fiber precursor with the interface layer is cut according to the size of the pre-pressing mold, arranged uniaxially or crosswise in the mold, and then pre-pressed to obtain a fiber monolith pre-pressed green body; Naturally drying the fiber monolith pre-pressed green body; Debinding the dried green body; The debinding green body is hot pressed and sintered to obtain a silicon nitride fiber monolithic ceramic material.

2. The method for preparing silicon nitride fiber monolithic ceramics based on wet spinning according to claim 1, characterized in that: The mass ratio of silicon nitride, aluminum oxide, and yttrium oxide in the ceramic powder is 90-100:3-5:7-12, and the particle size of silicon nitride is 0.5 μm.

3. The method for preparing silicon nitride fiber monolithic ceramics based on wet spinning according to claim 1, characterized in that: The coagulation bath is water, the temperature of the coagulation bath is 0-10° C., and the diameter of the obtained silicon nitride fiber precursor is 500-800 μm.

4. The method for preparing silicon nitride fiber monolithic ceramics based on wet spinning according to claim 1, characterized in that: The boron nitride and aluminum oxide powders are mixed in a mass ratio of 1:3, and the particle size of the boron nitride is 1-5 μm.

5. The method for preparing silicon nitride fiber monolithic ceramics based on wet spinning according to claim 1, characterized in that: The silicon nitride fiber precursor is immersed in the interface layer slurry for 10 to 15 minutes, and the thickness of the interface layer is 5 to 20 μm.

6. The method for preparing silicon nitride fiber monolithic ceramics based on wet spinning according to claim 1, characterized in that: When using a hydraulic press for pre-pressing, the pre-pressing pressure is 10~15MPa and the holding time is 10~20min.

7. The method for preparing silicon nitride fiber monolithic ceramics based on wet spinning according to claim 1, characterized in that: The debinding conditions are as follows: heating from room temperature to 600-700 °C at a heating rate of 0.5-5.0 °C / min and keeping the temperature for 1-2 h.

8. The method for preparing silicon nitride fiber monolithic ceramics based on wet spinning according to claim 1, characterized in that: The sintering conditions are as follows: heating from room temperature to 1780~1800℃ at a heating rate of 10~15℃ / min, keeping the temperature for 1~2 hours, and cooling with the furnace.

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