Preparation method and application of a continuous fiber reinforced silicon nitride-based composite ceramic material with a sandwich structure

Abstract

The present invention relates to the technical field of functional materials, and particularly to a preparation method and application of a continuous fiber reinforced silicon nitride-based composite ceramic material with a sandwich structure. The preparation method includes the following steps: mixing silicon nitride powder with a solvent and a sintering aid and performing ball milling to obtain a silicon nitride suspension; drying the silicon nitride suspension to obtain a silicon nitride composite powder; pre-sintering the silicon nitride composite powder to obtain a composite ceramic powder; mixing lithium aluminosilicate powder with water, a surfactant, and a thickening agent uniformly to obtain a lithium aluminosilicate impregnating solution; impregnating carbon fibers with the lithium aluminosilicate impregnating solution to obtain a fiber impregnated body; drying and carbon removal treating the fiber impregnated body to obtain a 2D fiber impregnated body; sintering the 2D fiber impregnated body and the composite ceramic powder by means of powder embedding to obtain a continuous fiber reinforced silicon nitride-based composite ceramic material with a sandwich structure. The method of the present invention has the advantages of simplicity, high efficiency, and low cost.

Description

Technical Field

[0001] The present invention relates to the technical field of functional materials, and particularly to a preparation method and application of a continuous fiber-reinforced silicon nitride-based composite ceramic material with a sandwich structure. Background Art

[0002] Silicon nitride is a high-performance ceramic material with excellent physical properties such as high hardness, high wear resistance, and high-temperature stability. Therefore, it is widely used in the fields of aviation, aerospace, automotive, electronics, etc. However, the brittle drawback of silicon nitride also limits its application scope. To overcome this drawback, researchers have adopted fiber toughening technology. The basic principle of this technology is to introduce fibers into the silicon nitride matrix and increase the toughness of silicon nitride through the interaction between the fibers and the matrix. Among them, factors such as the selection and distribution of fibers and the interfacial structure between the matrix and the fibers will affect the toughening effect. At present, most domestic and foreign studies use methods such as CVD, CVI, and PIP to regulate the interface of fibers to improve the toughness of silicon nitride-based composites. However, the fracture toughness of the fiber-reinforced silicon nitride-based composites prepared by the above methods needs to be further improved. Summary of the Invention

[0003] Based on the above, the present invention provides a preparation method and application of a continuous fiber-reinforced silicon nitride-based composite ceramic material with a sandwich structure.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] One of the technical solutions of the present invention, a preparation method of a continuous fiber-reinforced silicon nitride-based composite ceramic material with a sandwich structure, includes the following steps:

[0006] Mix silicon nitride powder with a solvent and a sintering aid and ball mill to obtain a silicon nitride suspension;

[0007] Dry the silicon nitride suspension to obtain a silicon nitride composite powder;

[0008] Pre-sinter the silicon nitride composite powder to obtain a composite ceramic powder;

[0009] Mix lithium aluminosilicate powder with water, a surfactant, and a thickener uniformly to obtain a lithium aluminosilicate impregnating solution;

[0010] Impregnate carbon fibers with the lithium aluminosilicate impregnating solution to obtain a fiber impregnated body;

[0011] Dry and carbon-remove the fiber impregnated body to obtain a 2D fiber impregnated body;

[0012] The 2D fiber impregnated body and the composite ceramic powder are sintered by means of powder embedding to obtain the continuous fiber reinforced silicon nitride-based composite ceramic material with a sandwich structure.

[0013] The second technical solution of the present invention is a continuous fiber reinforced silicon nitride-based composite ceramic material with a sandwich structure prepared according to the above preparation method.

[0014] The third technical solution of the present invention is the application of the above continuous fiber reinforced silicon nitride-based composite ceramic material with a sandwich structure in the fields of aerospace, automobiles, electronics, and functional materials.

[0015] The technical concept of the present invention:

[0016] The present invention creatively proposes to use a lithium aluminosilicate system to physically modify the interface of carbon fibers. At the same time, a thickening agent and a surfactant are used to impregnate the carbon fibers. After impregnation, the space between the carbon fibers is filled with lithium aluminosilicate microcrystalline ceramics. At this time, a layer of composite ceramic powder is evenly laid on the impregnated carbon fibers. The lithium aluminosilicate is in direct contact with SiBON in the composite ceramic powder, which can greatly reduce the sintering temperature and control the sintering temperature below 1400 °C. Based on the in-situ reaction, the lithium aluminosilicate will promote the crystallization of silicon oxynitride ceramics on the surface of SiBON. Since the crystal structure of silicon oxynitride ceramics is hexagonal and the precipitated silicon oxynitride ceramic crystals have a certain aspect ratio, they can prevent cracks from penetrating when cracks propagate, effectively improving the fracture toughness of silicon nitride. Compared with other commonly used substances in the art such as polysilazane, this method can reduce the sintering temperature, achieve large-size continuous rapid sintering, and improve the fracture toughness of silicon nitride.

[0017] The present invention discloses the following technical effects:

[0018] The present invention provides a preparation method for a continuous fiber reinforced silicon nitride-based composite ceramic material with a sandwich structure that is simple, efficient, low-cost, and highly tough. By combining slurry impregnation and powder embedding sintering, the present invention can effectively improve the toughness of the silicon nitride-based composite material and has high superiority in the production process. In addition, the method of the present invention can also reduce the production cost of the material and improve the production efficiency, thereby better exerting the fiber toughening effect. Therefore, the present invention has broad application prospects and is expected to become an important technology in the field of preparation of silicon nitride-based composite materials.

[0019] The present invention uses a lithium aluminosilicate system as an impregnating solution to physically modify and prepare a 2D carbon fiber impregnated body. Physically modifying carbon fibers does not damage the carbon fibers, and the process is simple and low-cost, enabling mass production. The fiber arrangement method of the sandwich structure can effectively exert the mechanism of fiber toughening and achieve a better toughening effect.

[0020] The continuous fiber-reinforced silicon nitride-based composite ceramic material (composite material) with a sandwich structure prepared by the present invention exhibits a yield plateau during the fracture process and has certain toughness. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] 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 use in the embodiments. Obviously, the drawings in the following description 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 these drawings.

[0022] Figure 1 The physical and microscopic views of the composite material prepared in Example 1, where a is the top view of the surface of the composite material, b is the macroscopic view of the sandwich structure of the composite material, c is the microscopic surface view of the composite material, and d is the microscopic view of the sandwich structure of the composite material.

[0023] Figure 2 XRD diagrams of the silicon nitride composite powder (before sintering) and the composite ceramic powder (after sintering) in Step 2 of Example 1.

[0024] Figure 3 The microscopic structure diagram of the fracture surface of the composite material prepared in Example 1; where the left figure is a schematic diagram of fiber debonding and pulling out, and the right figure is a schematic diagram of the propagation of stepped cracks.

[0025] Figure 4 The load-stress curve of the fracture toughness of the composite material prepared in Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0027] It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention. In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0028] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this invention pertains. Although this invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of this invention.

[0029] Without departing from the scope or spirit of this invention, various improvements and changes can be made to the specific embodiments of the description of this invention, which are obvious to those skilled in the art. Other embodiments obtained from the description of this invention are obvious to those skilled in the art. The description and examples of this invention are merely exemplary.

[0030] Regarding "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0031] The first aspect of this invention provides a method for preparing a continuous fiber-reinforced silicon nitride-based composite ceramic material with a sandwich structure, comprising the following steps:

[0032] Mix silicon nitride powder with a solvent and a sintering aid by ball milling to obtain a silicon nitride suspension;

[0033] Dry the silicon nitride suspension to obtain silicon nitride composite powder;

[0034] Pre-sinter the silicon nitride composite powder to obtain a composite ceramic powder;

[0035] Mix lithium aluminosilicate powder with water, a surfactant, and a thickening agent uniformly to obtain a lithium aluminosilicate impregnating solution;

[0036] Impregnate carbon fiber with the lithium aluminosilicate impregnating solution to obtain a fiber impregnated body;

[0037] Dry and carbon-remove the fiber impregnated body to obtain a 2D fiber impregnated body;

[0038] Sinter the 2D fiber impregnated body and the composite ceramic powder by powder embedding to obtain the continuous fiber-reinforced silicon nitride-based composite ceramic material with a sandwich structure.

[0039] In a preferred embodiment of this invention, the ball milling is carried out in a stirred ball mill for 1 - 6 hours.

[0040] In a preferred embodiment of this invention, the solvent is n-hexane; the sintering aid is boric acid; the mass-volume ratio of the silicon nitride powder to the sintering aid is 5:2; the solvent is added according to the addition amounts of the above two, and the specific mass-volume ratio of the silicon nitride powder to the solvent is 10g:35 - 100mL.

[0041] Excessive boric acid can promote low-temperature forming and easy shaping. However, the reaction and sintering result in a glass-ceramic of the silicon-boron-oxygen-nitrogen system with a relatively high overall structural hardness and strength, which will weaken the silicon nitride content. Therefore, the above ratio is selected. If there is too little boric acid, the boric acid in the sintering process becomes boron gangue and forms a liquid phase, which is insufficient to fill the voids and will lead to poor densification in the final sintering, and will also weaken the mechanical properties.

[0042] In a preferred embodiment of the present invention, the drying temperature is 75 °C and the time is 2 h;

[0043] In a preferred embodiment of the present invention, the temperature of the pre-sintering is 600 °C and the time is 2 h.

[0044] During this pre-sintering process, boric acid decomposes into boron oxide, and then boron oxide reacts in-situ with silicon nitride powder to obtain a silicon nitride-based composite ceramic SiBON.

[0045] The pre-sintering temperature is set at 450-700 °C. The purpose is to dehydrate the boric acid in the material as much as possible and remove volatile metaboric acid, so as to avoid internal closed pores caused by rising gas inside the material during the sintering process. In the present invention, it is preferably pre-sintered at 600 °C for 2 h, which can save energy while ensuring the product effect. If the pre-sintering temperature is too low or the time is too short, the residual water and metaboric acid will cause gas evolution. Too high a pre-sintering temperature will cause the decomposition of boron oxide, which is not conducive to the occurrence of in-situ reaction.

[0046] In a preferred embodiment of the present invention, the mass ratio of the lithium aluminosilicate powder, water, surfactant, and thickener is (12.5-32.5):37.5:1:1; the surfactant is polyethylene glycol; the thickener is methyl cellulose.

[0047] The direct contact between the lithium aluminosilicate powder and SiBON in the composite ceramic powder can significantly reduce the sintering temperature and control the sintering temperature below 1400 °C. Based on the in-situ reaction, lithium aluminosilicate will promote the crystallization of silicon oxynitride ceramics on the surface of SiBON. Since the crystal structure of silicon oxynitride ceramics is hexagonal and the precipitated silicon oxynitride ceramic crystals have a certain aspect ratio, they can prevent crack penetration during crack propagation and effectively improve the fracture toughness of silicon nitride. However, the proportion of lithium aluminosilicate should not be too high, otherwise excessive precipitation of silicon oxynitride ceramics will cause SiBON grains to penetrate and the toughness to decrease. Water, surfactant, and thickener are used to smoothly make lithium aluminosilicate into an impregnating solution with a certain fluidity and combine it with the fiber.

[0048] In a preferred embodiment of the present invention, a winding machine is used to impregnate the carbon fiber with the lithium aluminosilicate impregnating solution to obtain a fiber impregnated body; the rotation speed of the winding machine is 70 r / min.

[0049] In a preferred embodiment of the present invention, the drying temperature is 50 °C and the time is 2 h; the carbon removal treatment temperature is 400 °C and the time is 2 h.

[0050] The temperature and time of drying and carbon removal treatment should not exceed the values described above. Excessive drying temperature, carbon removal temperature, and too long treatment time will damage the normal combination of lithium aluminosilicate and carbon fiber, which is not conducive to the formation of the 2D fiber impregnated body.

[0051] In a preferred embodiment of the present invention, before sintering the 2D fiber impregnated body and the composite ceramic powder by powder embedding method, it further includes the step of cutting the 2D fiber impregnated body.

[0052] In a preferred embodiment of the present invention, the sintering by powder embedding method is specifically as follows: Put the 2D fiber impregnated body and the composite ceramic powder into a sintering mold, and the placement method is in turn: 4.5 - 5 mm thick composite ceramic powder, 0.7 mm thick 2D fiber impregnated body, 1.5 - 2 mm thick composite ceramic powder, 0.7 mm thick 2D fiber impregnated body, 1.5 - 2 mm thick composite ceramic powder, 0.7 mm thick 2D fiber impregnated body, 4.5 - 5 mm thick composite ceramic powder; then sinter at 1300 °C for 0.5 h under a pressure of 5 Mpa in a nitrogen atmosphere.

[0053] If the fiber impregnated body is cut thicker and the composite ceramic powder is laid thicker, the fracture toughness of a single layer will also increase within a certain range. However, too thick impregnated body and powder layer are not conducive to the full contact between lithium aluminosilicate and SiBON during sintering, and at the same time will increase the difficulty of connection between layers. Therefore, for military anti - ballistic requirements, the preferred implementation plan is: 5 mm thick composite ceramic powder, 0.7 mm thick 2D fiber impregnated body, 2 mm thick composite ceramic powder, 0.7 mm thick 2D fiber impregnated body, 2 mm thick composite ceramic powder, 0.7 mm thick 2D fiber impregnated body, 5 mm thick composite ceramic powder; then sinter at 1300 °C for 0.5 h under a pressure of 5 Mpa in a nitrogen atmosphere. At this time, the fracture toughness is relatively high, and the mass ratio of the 2D fiber impregnated body to the composite ceramic powder is 1:5; for other application scenarios with smaller requirements, such as the photovoltaic thermal field support cylinder, the thickness of the composite ceramic powder on the upper and lower surfaces can be appropriately reduced to 2.5 mm per layer.

[0054] The second aspect of the present invention provides a continuous fiber - reinforced silicon nitride - based composite ceramic material with a sandwich structure prepared by the above - mentioned preparation method.

[0055] The third aspect of the present invention provides the application of the above - mentioned continuous fiber - reinforced silicon nitride - based composite ceramic material with a sandwich structure in the fields of aerospace, automotive, electronics, and functional materials.

[0056] In the embodiments of the present invention and the comparative examples, the raw materials used, unless otherwise specified, can be obtained through commercial channels.

[0057] The instruments and equipment used in the embodiments of the present invention and the comparative examples are common instruments and equipment in the art.

[0058] The carbon fiber used in the embodiments of the present invention and the comparative examples is T300-3K carbon fiber (1. Carbon fiber specification: 3K; 2. Carbon fiber diameter: about 7-10 microns; 3. Carbon fiber length: usually ranging from a few millimeters to a few centimeters; 4. Fiber density: about 1.75-1.85 g / cm 3 ; 5. Strength: 3000-4000 MPa), purchased from Guangwei Composite Materials Co., Ltd., n-hexane was purchased from Shandong Zhengji Chemical Co., Ltd., silicon nitride powder and boric acid were purchased from Hubei Yongkuo Technology Co., Ltd.

[0059] The lithium aluminosilicate powder used in the embodiments of the present invention was prepared by the following steps: 1 mol of Al(NO3)3·9H2O was dissolved in 500 mL of deionized water (2 mol / L), heated to 75 °C, and ammonia water was added dropwise with mechanical stirring until boehmite sol was formed; 1 mol of LiNO3 was dissolved in 500 mL of deionized water (2 mol / L), added to the boehmite sol, and the stirring was accelerated to obtain a lithium-aluminum solution; 400 mg of SiO2 sol was slowly added dropwise to the lithium-aluminum solution, and the stirring speed was accelerated to obtain a lithium aluminosilicate sol, and the stirring was continued for 4 h; dried at 100 °C for 48 h to obtain a LAS precursor powder; heat-treated at 800 °C for 12 h to remove nitrate and water to obtain a lithium aluminosilicate (Li2O-Al2O3-SiO2, LAS) gel powder (abbreviation: lithium aluminosilicate powder).

[0060] Example 1

[0061] (1) 500 mL of n-hexane, 100 g of silicon nitride powder, 40 g of boric acid and 300 g of zirconia grinding balls were successively added to a ball mill jar, and ball milled and stirred in a stirred ball mill for 1 h and then filtered to obtain a uniformly mixed silicon nitride suspension.

[0062] (2) The above silicon nitride suspension was dried in an oven at 75 °C for 2 h to obtain a silicon nitride composite powder; the silicon nitride composite powder was pre-sintered at 600 °C for 2 hours to obtain a silicon nitride-based composite phase ceramic SiBON powder (abbreviation: composite phase ceramic powder).

[0063] (3) Prepare the lithium aluminosilicate powder into an impregnating solution. Specifically, mix lithium aluminosilicate powder, deionized water, polyethylene glycol, and methyl cellulose in a mass ratio of 22.5:37.5:1:1 and stir for 0.5 h to obtain a lithium aluminosilicate impregnating solution with certain fluidity. Put this lithium aluminosilicate impregnating solution into the winding machine mold, and slowly pass the carbon fiber through the above-mentioned lithium aluminosilicate impregnating solution by the winding machine. Set the winding speed at 70 r / min to obtain a fiber impregnated body.

[0064] (4) Dry and decarbonize the above-mentioned fiber impregnated body. Specifically, place the fiber impregnated body in an oven for drying. Set the drying temperature at 50 °C and the heat preservation time at 2 h. Then carry out decarbonization in an electric resistance furnace. Set the decarbonization temperature at 400 °C and the heat preservation time at 2 h. Finally, obtain a 2D fiber impregnated body.

[0065] (5) Cut the above-mentioned 2D fiber impregnated body into a square with a side length of 0.25 m, and then put it into a sintering mold together with the above-mentioned composite ceramic powder. The placement method is as follows: 5 mm thick composite ceramic powder, 0.7 mm thick 2D fiber impregnated body, 2 mm thick composite ceramic powder, 0.7 mm thick 2D fiber impregnated body, 2 mm thick composite ceramic powder, 0.7 mm thick 2D fiber impregnated body, 5 mm thick composite ceramic powder; then sinter at 1300 °C for 0.5 h under a nitrogen atmosphere at a pressure of 5 Mpa. Finally, obtain a continuous fiber-reinforced silicon nitride-based composite ceramic material with a sandwich structure showing a stepped fracture (abbreviation: composite material).

[0066] Example 2

[0067] (1) Add 500 mL of n-hexane, 100 g of silicon nitride powder, 40 g of boric acid, and 300 g of zirconia grinding balls into a ball mill tank in sequence. Ball mill and stir in a stirring ball mill for 1 h and then filter to obtain a silicon nitride suspension with uniformly mixed materials.

[0068] (2) Dry the above-mentioned silicon nitride suspension in an oven at 75 °C for 2 h to obtain a silicon nitride composite powder; pre-sinter the silicon nitride composite powder at 600 °C for 2 hours to obtain a silicon nitride-based composite ceramic SiBON powder (abbreviation: composite ceramic powder).

[0069] (3) Prepare the lithium aluminosilicate powder into an impregnating solution. Specifically, mix lithium aluminosilicate powder, deionized water, polyethylene glycol, and methyl cellulose in a mass ratio of 20.5:37.5:1:1 and stir for 0.5 h to obtain a lithium aluminosilicate impregnating solution with certain fluidity. Put this lithium aluminosilicate impregnating solution into the winding machine mold, and slowly pass the carbon fiber through the above-mentioned lithium aluminosilicate impregnating solution by the winding machine. Set the winding speed at 70 r / min to obtain a fiber impregnated body.

[0070] (4) The above fiber impregnated body is dried and carbon removed, specifically: the fiber impregnated body is placed in an oven for drying, the drying temperature is set at 50 °C, and the heat preservation time is 2 h. Subsequently, carbon removal is carried out in an electric resistance furnace, the carbon removal temperature is set at 400 °C, and the heat preservation time is 2 h. Finally, a 2D fiber impregnated body is obtained.

[0071] (5) The above 2D fiber impregnated body is cut into a square with a side length of 0.25 m, and then put into a sintering mold together with the above composite ceramic powder. The placement method is as follows: 5 mm thick composite ceramic powder, 0.7 mm thick 2D fiber impregnated body, 2 mm thick composite ceramic powder, 0.7 mm thick 2D fiber impregnated body, 2 mm thick composite ceramic powder, 0.7 mm thick 2D fiber impregnated body, 5 mm thick composite ceramic powder; then sintering is carried out at 1300 °C for 0.5 h under a pressure of 5 Mpa in a nitrogen atmosphere. Finally, a continuous fiber reinforced silicon nitride based composite ceramic material with a sandwich structure showing stepped fracture (abbreviation: composite material) is obtained.

[0072] Example 3

[0073] (1) 500 mL of n-hexane, 100 g of silicon nitride powder, 40 g of boric acid, and 300 g of zirconia grinding balls are successively added to a ball milling tank, and ball milling and stirring are carried out in a stirring ball mill for 1 h, and then filtered to obtain a silicon nitride suspension with uniformly mixed materials.

[0074] (2) The above silicon nitride suspension is dried in an oven at 75 °C for 2 h to obtain a silicon nitride composite powder; the silicon nitride composite powder is pre-sintered at 600 °C for 2 hours to obtain a silicon nitride based composite ceramic SiBON powder (abbreviation: composite ceramic powder).

[0075] (3) Prepare a lithium aluminosilicate impregnating solution, specifically: mix lithium aluminosilicate powder, deionized water, polyethylene glycol, and methyl cellulose in a mass ratio of 32.5:37.5:1:1 and stir for 0.5 h to obtain a lithium aluminosilicate impregnating solution with a certain fluidity. Put the lithium aluminosilicate impregnating solution into a winding machine mold, and slowly pass the carbon fiber through the above lithium aluminosilicate impregnating solution, and set the winding speed at 70 r / min to obtain a fiber impregnated body.

[0076] (4) The above fiber impregnated body is dried and carbon removed, specifically: the fiber impregnated body is placed in an oven for drying, the drying temperature is set at 50 °C, and the heat preservation time is 2 h. Subsequently, carbon removal is carried out in an electric resistance furnace, the carbon removal temperature is set at 400 °C, and the heat preservation time is 2 h. Finally, a 2D fiber impregnated body is obtained.

[0077] (5) Cut the above 2D fiber impregnated body into a square with a side length of 0.25 m, and then put it into a sintering mold together with the above composite ceramic powder, 5 mm thick composite ceramic powder, 0.7 mm thick 2D fiber impregnated body, 2 mm thick composite ceramic powder, 0.7 mm thick 2D fiber impregnated body, 2 mm thick composite ceramic powder, 0.7 mm thick 2D fiber impregnated body, 5 mm thick composite ceramic powder; then sinter at 1300 °C for 0.5 h under a pressure of 5 Mpa in a nitrogen atmosphere. Finally, a continuous fiber-reinforced silicon nitride-based composite ceramic material with a sandwich structure showing stepped fracture (abbreviation: composite material) is obtained.

[0078] Example 4

[0079] (1) Add 500 mL of n-hexane, 100 g of silicon nitride powder, 40 g of boric acid, and 300 g of zirconia grinding balls into a ball mill in sequence, and ball mill and stir for 1 h in a stirring ball mill, and then filter to obtain a silicon nitride suspension with uniformly mixed materials.

[0080] (2) Dry the above silicon nitride suspension in an oven at 75 °C for 2 h to obtain a silicon nitride composite powder, and pre-sinter the silicon nitride composite powder at 600 °C for 2 hours to obtain a silicon nitride-based composite ceramic SiBON powder (abbreviation: composite ceramic powder).

[0081] (3) Prepare a lithium aluminosilicate impregnating solution, specifically: mix lithium aluminosilicate powder, deionized water, polyethylene glycol, and methyl cellulose in a mass ratio of 12.5:37.5:1:1 and stir for 0.5 h to obtain a lithium aluminosilicate impregnating solution with a certain fluidity. Put the lithium aluminosilicate impregnating solution into a winding machine mold, and slowly pass the carbon fiber through the above lithium aluminosilicate impregnating solution, and set the winding speed to 70 r / min to obtain a fiber impregnated body.

[0082] (4) Perform drying and carbon removal treatment on the above fiber impregnated body, specifically: place the fiber impregnated body in an oven for drying, set the drying temperature to 50 °C, and keep the temperature for 2 h. Then perform carbon removal in an electric resistance furnace, set the carbon removal temperature to 400 °C, and keep the temperature for 2 h. Finally, a 2D fiber impregnated body is obtained.

[0083] (5) Cut the above 2D fiber impregnated body into a square with a side length of 0.25 m, and then put it into a sintering mold together with the above composite ceramic powder, 5 mm thick composite ceramic powder, 0.7 mm thick 2D fiber impregnated body, 2 mm thick composite ceramic powder, 0.7 mm thick 2D fiber impregnated body, 2 mm thick composite ceramic powder, 0.7 mm thick 2D fiber impregnated body, 5 mm thick composite ceramic powder; then sinter at 1300 °C for 0.5 h under a pressure of 5 Mpa in a nitrogen atmosphere. Finally, a continuous fiber-reinforced silicon nitride-based composite ceramic material with a sandwich structure showing stepped fracture (abbreviation: composite material) is obtained.

[0084] Figure 1 The physical and microscopic images of the composite material prepared in Example 1. Among them, a is the top view of the surface of the composite material, b is the macroscopic performance diagram of the sandwich structure of the composite material, c is the microscopic surface diagram of the composite material, and d is the microscopic diagram of the sandwich structure of the composite material. It can be seen from a and b in the figure that the surface of the composite material prepared in Example 1 is smooth; it can be known from c and d in the figure that after sintering at a low temperature (1300 °C), the prepared composite material has a high density.

[0085] Figure 2 XRD patterns of the silicon nitride composite powder (before sintering) and the multiphase ceramic powder (after sintering) in step 2 of Example 1; Figure 2 It can be seen that the main crystal forms of the silicon nitride composite powder are boric acid and β-Si3N4; boric acid disappears in the multiphase ceramic powder, and the main crystal phase is β-Si3N4. There also appears a part of amorphous phase and cristobalite phase, indicating that boric acid decomposes into boron oxide, and boron oxide reacts in-situ with β-Si3N4 to form amorphous SiBON, and SiO2 segregation and crystallization occur during the cooling process, resulting in the cristobalite phase.

[0086] Figure 3 Microstructural diagram of the fracture surface of the composite material prepared in Example 1; among them, the left figure is a schematic diagram of fiber debonding and pulling out, and the right figure is a schematic diagram of the propagation of stepped cracks. Figure 3 It shows that fiber debonding and pulling out and the propagation of stepped cracks occur in the microstructure of the composite material.

[0087] Figure 4 Load-stress curve for measuring the fracture toughness of the composite material prepared in Example 1 by the single-edge notched beam method. Figure 4 It can be seen that the fracture toughness of the composite material prepared in Example 1 is significantly higher than that of ordinary silicon nitride, which is 5 - 7 MPa·m 1 / 2 significantly improved.

[0088] Comparative Example 1

[0089] The difference from Example 1 is only that the pre-sintering step in step (2) is omitted.

[0090] Comparative Example 2

[0091] The difference from Example 1 is only that the laying method in step (5) is specifically: 7 mm thick multiphase ceramic powder, 2.1 mm thick 2D fiber impregnated body, 7 mm thick multiphase ceramic powder.

[0092] Comparative Example 3

[0093] The difference from Example 1 is only that the lithium aluminosilicate impregnating solution in step (3) is replaced by polysilazane.

[0094] Comparative Example 4

[0095] The difference from Example 1 is only that the embedded sintering in step (5) is changed to general atmospheric pressure sintering. The atmosphere of the atmospheric pressure sintering is air, the pressure is one atmospheric pressure, the temperature is 1300 °C, and the time is 0.5 h.

[0096] The fracture toughness test and the room temperature tensile strength test were carried out on the products in Examples 1-4 and Comparative Examples 1-4. The fracture toughness test method was the single-edge notch beam method, and the test results are as follows:

[0097] Table 1 Fracture Toughness Test

[0098]

[0099]

[0100] As can be seen from Table 1, compared with the fracture toughness of general silicon nitride of 5-7 MPa·m 1 / 2 and the room temperature tensile strength of about 900 MPa, the fracture toughness of the composite material is significantly improved, and the filling amount of lithium aluminosilicate is appropriate. Too much or too little will affect the toughening degree of the material; from the comparison between Example 1 and Comparative Example 1, it can be seen that after canceling the pre-sintering step, the volatilization of the participating water and metaboric acid will cause internal closed pores, resulting in a decrease in the toughening degree; from the comparison between Example 1 and Comparative Example 2, it can be seen that the number of layers of the 2D fiber impregnated body in the sandwich structure is very important for the improvement of both fracture toughness and room temperature tensile strength; from the comparison between Example 1 and Comparative Example 3, the superiority of lithium aluminosilicate ceramics in toughening can be reflected; from the comparison between Example 1 and Comparative Example 4, the superiority of embedded sintering in toughening silicon nitride can be reflected.

[0101] The above-described embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A preparation method of a continuous fiber reinforced silicon nitride-based composite ceramic material with a sandwich structure, characterized in that, It includes the following steps: Mix silicon nitride powder with a solvent and a sintering aid, and perform ball milling to obtain a silicon nitride suspension; Dry the silicon nitride suspension to obtain silicon nitride composite powder; Perform pre-sintering on the silicon nitride composite powder to obtain a multiphase ceramic powder; Mix lithium aluminosilicate powder with water, a surfactant, and a thickening agent evenly to obtain a lithium aluminosilicate impregnating solution; Use the lithium aluminosilicate impregnating solution to impregnate carbon fibers to obtain a fiber impregnated body; Perform drying and carbon removal treatment on the fiber impregnated body to obtain a 2D fiber impregnated body; Sinter the 2D fiber impregnated body and the multiphase ceramic powder by powder embedding to obtain the continuous fiber reinforced silicon nitride-based multiphase ceramic material with a sandwich structure; The solvent is n-hexane; the sintering aid is boric acid; the mass ratio of the silicon nitride powder to the sintering aid is 5:2; The specific method of sintering by powder embedding is as follows: Place the 2D fiber impregnated body and the multiphase ceramic powder into a sintering mold, and the placement method is in turn: 2.5 - 3 mm thick multiphase ceramic powder, 0.7 mm thick 2D fiber impregnated body, 2.5 - 3 mm thick multiphase ceramic powder, 0.7 mm thick 2D fiber impregnated body, 2.5 - 3 mm thick multiphase ceramic powder, 0.7 mm thick 2D fiber impregnated body, 2.5 - 3 mm thick multiphase ceramic powder; then sinter at 1300 °C for 0.5 h under a nitrogen atmosphere at a pressure of 5 Mpa.

2. The preparation method according to claim 1, characterized in that, The drying temperature is 75 °C and the time is 2 h; the pre-sintering temperature is 800 °C and the time is 2 h.

3. The preparation method according to claim 1, wherein, The mass ratio of the lithium aluminosilicate powder to water, the surfactant, and the thickening agent is (12.5 - 32.5):37.5:1:1; the surfactant is polyethylene glycol; the thickening agent is methyl cellulose.

4. The preparation method according to claim 1, characterized in that, The drying temperature is 50 °C and the time is 2 h; the carbon removal treatment temperature is 400 °C and the time is 2 h.

5. The preparation method according to claim 1, characterized in that, Before sintering the 2D fiber impregnated body and the multiphase ceramic powder by powder embedding, it also includes the step of cutting the 2D fiber impregnated body.

6. A continuous fiber reinforced silicon nitride-based multiphase ceramic material with a sandwich structure prepared by the preparation method according to any one of claims 1 - 5.

7. Application of the continuous fiber reinforced silicon nitride-based multiphase ceramic material with a sandwich structure according to claim 6 in the fields of aerospace, automotive, electronics, and functional materials.

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