Lightweight anti-ablation nitride fiber reinforced ceramic-based composite material and preparation method thereof

Abstract

The invention provides a light anti-ablation nitride fiber reinforced ceramic-based composite material and a preparation method thereof, and relates to the field of ceramic materials. The preparation method of the light anti-ablation fiber reinforced ceramic matrix composite material comprises the following steps: preparing a composite preform, carrying out first-round compounding, carrying out second-round compounding and carrying out final-round compounding. According to the preparation method of the light anti-ablation nitride fiber reinforced ceramic-based composite material, the contradiction between the properties of wave-transparent materials can be effectively balanced, and the prepared composite material has the characteristics of light weight, low dielectric, ablation resistance and high compactness and also has the characteristic of low thermal conductivity.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials, and in particular to a lightweight, ablation-resistant nitride fiber-reinforced ceramic matrix composite material and its preparation method. Background Technology

[0002] In the field of high-temperature microwave-transparent materials, existing nitride fiber-reinforced ceramic matrix composites possess the characteristics of flexible material composition design, excellent mechanical properties, outstanding dielectric properties, and superior high-temperature resistance. They are gradually becoming important candidate materials for high-temperature microwave-transparent composites and are the best choice for high-temperature microwave-transparent materials used in new high-speed aircraft, high-speed flying objects, and aerospace equipment. Currently, nitride fiber-reinforced ceramic matrix microwave-transparent composites mainly include three material systems (including fibers and matrix): Si3N4, BN, and SiBN. These form a performance hierarchy, progressing from pursuing high strength (Si3N4 material system), to extreme microwave transmission and thermal shock resistance (BN material system), and finally to a comprehensive balance and high temperature resistance (SiBN material system). This provides the material basis for high-speed aircraft and aerospace equipment to maintain normal operation of their communication, navigation, and detection systems even under extreme environments involving multiple fields such as thermal barrier, vibration, and electromagnetic windows.

[0003] As high-speed aircraft and aerospace equipment evolve towards lightweight and low-cost designs, wave-transparent materials, while meeting requirements for high-temperature resistance and ablation resistance, are also facing higher demands for low density and low dielectric properties. Generally speaking, the higher the density of a material, the better its ablation performance and the higher its dielectric constant; conversely, a lower density results in a lower dielectric constant, an increased degree of porosity and defects, and a decreased ablation resistance. It can be seen that there is a certain contradictory relationship among the performance indicators of wave-transparent materials, making it impossible to achieve an effective balance.

[0004] Existing technologies disclose a low-density, high-temperature resistant insulation layer material prepared using a layup process with phosphate adhesives, hollow glass microspheres, and hollow quartz fibers as main raw materials. This material can withstand 1200℃ and can therefore be applied in the field of integrated load-bearing and thermal insulation. However, due to the use of foaming agents in the preparation process, the material itself has a large number of pore defects; in addition, the addition of hollow glass microspheres in the raw materials also affects the dielectric properties of the material, thus making it unsuitable for use as an ablation-resistant wave-transparent material.

[0005] Based on this, a method for preparing lightweight ablation-resistant nitride fiber reinforced ceramic matrix composite material is provided, which can effectively balance the contradiction between the properties of wave-transparent materials. The prepared composite material has lightweight, low dielectric, ablation-resistant and high density properties, while also having low thermal conductivity, which has important technical significance and research value. Summary of the Invention

[0006] To address the technical problems existing in the prior art, this invention provides a method for preparing a lightweight ablation-resistant nitride fiber reinforced ceramic matrix composite material, which can effectively balance the contradiction between the properties of wave-transparent materials. The resulting composite material has lightweight, low dielectric, ablation-resistant, and high density characteristics, while also having low thermal conductivity. This invention also provides a lightweight ablation-resistant nitride fiber reinforced ceramic matrix composite material prepared by the aforementioned method.

[0007] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A method for preparing a lightweight, ablation-resistant fiber-reinforced ceramic matrix composite material, characterized by comprising the following steps: preparing a composite preform, first-round composite, second-round composite, and final-round composite; The method for preparing the composite preform is as follows: continuous nitride ceramic fibers are made into a preform, the preform is soaked in an organic solvent and then heat-treated, and a Si3N4-BN composite coating is prepared on the fiber surface of the preform by chemical vapor infiltration to obtain the composite preform. The first-round composite method involves uniformly mixing silica hollow sphere powder with silica sol to obtain an impregnation slurry; after impregnating the composite preform with the impregnation slurry, it is dried and heat-treated to complete the first-round composite; the first-round composite is repeated 2-3 times to obtain the first-round composite intermediate. The first-round composite intermediate was then subjected to a second-round composite and a final-round composite to obtain a lightweight, ablation-resistant fiber-reinforced ceramic matrix composite material.

[0008] Furthermore, the method of the second round of composite is as follows: after the first round of composite intermediate is impregnated with Si3N4 precursor slurry or SiBN precursor slurry, it is cured and pyrolyzed in an inert gas environment to complete the second round of composite. The second round of composite is repeated 3-4 times to obtain the second round of composite intermediate. The final composite method is as follows: the intermediate of the second composite is impregnated with BN precursor slurry, and then cured and pyrolyzed in an inert gas environment to complete the final composite. The final composite is repeated 1-2 times to obtain a lightweight ablation-resistant fiber-reinforced ceramic matrix composite material.

[0009] Preferably, in the preparation of the composite preform, the continuous nitride ceramic fiber is one of the following: continuous BN fiber; a combination of continuous BN fiber and continuous Si3N4 fiber; a combination of continuous BN fiber and continuous SiBN fiber; a combination of continuous BN fiber, continuous Si3N4 fiber and continuous SiBN fiber; The precast structure can be one of the following: fabric stitching structure, orthogonal triaxial structure, or 2.5D structure; The volume percentage content of continuous nitride ceramic fibers in the preform is 30-40%.

[0010] Furthermore, in the preparation of the composite preform, the Si3N4-BN composite coating is prepared on the fiber surface of the preform by chemical vapor infiltration. This is achieved by placing the heat-treated preform in a chemical vapor infiltration furnace, continuously introducing BCl3, SiCl4, and ammonia as reaction gases under vacuum conditions, controlling the vapor infiltration pressure at 100-500 Pa, the vapor infiltration temperature at 900-920 °C, and the vapor infiltration time at 3-5 h, thereby completing the preparation of the Si3N4-BN composite coating.

[0011] Preferably, the total flow rate of the reacting gases is 5-6 L / min; The volumetric flow rate ratio of BCl3, SiCl4, and ammonia is 0.7-0.75:0.25-0.3:4-6; The thickness of the Si3N4-BN composite coating obtained on the fiber surface of the preform is 0.1-1 μm.

[0012] Preferably, in the first round of compounding, the particle size of the silica hollow sphere powder is 0.3-1.2 μm, and the wall thickness of the silica hollow spheres is 12 nm-50 nm; The concentration of silica sol is 5-10 wt%; The mass ratio of silica hollow sphere powder to silica sol in the impregnation slurry is 10-30:100.

[0013] Preferably, in the first round of composite impregnation, the composite preform is impregnated with the impregnation slurry by completely immersing the composite preform in the impregnation slurry, controlling the vacuum degree at 0.095-0.099MPa and the vibration frequency at 50-200Hz, and then performing vacuum vibration impregnation for 5-10 hours; followed by high-pressure impregnation at 6-8MPa for 1-3 hours. The heat treatment temperature is 300-400℃, and the heat treatment time is 0.5-1.5h.

[0014] Preferably, in the secondary compounding process, the concentration of polysilazane in the Si3N4 precursor slurry is 45-50 wt%; and the concentration of polyborosilicate in the SiBN precursor slurry is 40-45 wt%. The impregnation is vacuum impregnation, with a vacuum degree of 0.095-0.099 MPa and an impregnation time of 5-10 hours; The curing temperature is 250-300℃, and the curing time is 4-6h; the pyrolysis temperature is 750-950℃, and the pyrolysis time is 2-5h.

[0015] Preferably, in the final compounding process, the polyboron alkane concentration in the BN precursor slurry is 35-40 wt%. The impregnation is vacuum impregnation, with a vacuum degree of 0.095-0.099 MPa and an impregnation time of 5-10 hours; The curing temperature is 200-250℃, and the curing time is 4-6h; the pyrolysis temperature is 750-950℃, and the pyrolysis time is 2-5h.

[0016] A lightweight, ablation-resistant fiber-reinforced ceramic matrix composite material prepared by the aforementioned method.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The method for preparing lightweight ablation-resistant fiber-reinforced ceramic matrix composite material of the present invention, in the step of preparing composite preform, uses continuous BN fiber as the main fiber raw material to make preform, laying the foundation for low dielectric constant and low dielectric loss of composite material. After the preform is soaked in organic solvent and subjected to high temperature heat treatment, Si3N4-BN composite coating is prepared on the fiber surface of the preform by chemical vapor infiltration process. While improving the strength and toughness of the preform, it also improves the matching between the subsequent fiber preform and the first-round composite material, realizing an effective transition between the fiber preform and the first-round composite material. In the first-stage composite process, submicron-sized hollow silica spheres are introduced through an impregnation slurry. This effectively reduces the density of the composite material while densifying it, resulting in a lightweight and ablation-resistant material. Simultaneously, the temperature resistance and low thermal conductivity of the hollow silica spheres in the impregnation slurry effectively lower the thermal conductivity of the composite, further preventing heat diffusion into the material. Furthermore, the low dielectric constant and low loss of the hollow silica spheres effectively improve the dielectric properties of the composite. In the second-stage composite process, impregnation, curing, and pyrolysis using Si3N4 or SiBN precursor slurry further fill the pores of the composite and encapsulate the hollow silica spheres introduced in the first stage, improving the density and strength of the composite and enhancing its ablation resistance. In the final-stage composite process, impregnation, curing, and pyrolysis using BN precursor slurry form a BN sealing protective layer on the outer layer and the surface of the pores of the composite, further improving the stability and ablation resistance of the composite. The aforementioned technologies work together synergistically to effectively balance the contradictions between the properties of wave-transparent materials. The resulting composite material is lightweight, has low dielectric, ablation resistance, and high density, while also having low thermal conductivity.

[0018] (2) The lightweight, ablation-resistant fiber-reinforced ceramic matrix composite material of the present invention has a density of 1.51-1.63 g / cm³. 3 The thermal conductivity is 0.19-0.27 W / (m·k); the dielectric constant is 3.08-3.34; and the loss tangent is 0.0027-0.0035.

[0019] (3) The preparation method of the lightweight ablation-resistant fiber-reinforced ceramic matrix composite material of the present invention is not limited by the structure, shape and size of the preform, the raw materials are easy to obtain, the preparation process is easy to control, and it is conducive to large-scale industrial production. Detailed Implementation

[0020] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific embodiments are now described. It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0021] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, "first," "second," etc., are used to distinguish similar objects and are not used to describe a particular order or sequence. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0022] This invention provides a method for preparing a lightweight, ablation-resistant fiber-reinforced ceramic matrix composite material, comprising the following steps: preparing a composite preform, first-round composite, second-round composite, and final-round composite.

[0023] The method for preparing the composite preform is as follows: continuous nitride ceramic fibers are made into preforms with different structures. After the preforms are soaked in organic solvent and heat-treated, a Si3N4-BN composite coating with a thickness of 0.1-1 μm is prepared on the fiber surface of the preforms by chemical vapor infiltration process to obtain the composite preform.

[0024] In the preparation of the composite preform, the continuous nitride ceramic fiber is one of the following: continuous BN fiber, continuous Si3N4 fiber, and / or a combination of continuous SiBN fiber and continuous BN fiber. When the continuous nitride ceramic fiber is a combination of continuous Si3N4 fiber and / or continuous SiBN fiber and continuous BN fiber, the weight percentage of continuous BN fiber is not less than 50%.

[0025] In the preparation of the composite preform, the structure of the preform is one of the following: fabric stitching structure, orthogonal triaxial structure and 2.5D structure; the volume percentage content of continuous nitride ceramic fibers in the preform is 30-40% (i.e. the porosity of the preform is 60-70%).

[0026] In the preparation of the composite preform, the organic solvent used for the organic solvent immersion treatment is at least one of the following: ethanol, acetone, or petroleum ether; the organic solvent immersion temperature is 25-60℃, and the organic solvent immersion time is 24-72h.

[0027] In the preparation of the composite preform, the heat treatment temperature is 350-650℃ and the heat treatment time is 2-5h.

[0028] In the preparation of the composite preform, the Si3N4-BN composite coating is prepared on the fiber surface of the preform by placing the heat-treated preform in a chemical vapor infiltration furnace. Under vacuum conditions, BCl3, SiCl4, and ammonia are continuously introduced as reaction gases at a volume flow rate ratio of 0.7-0.75:0.25-0.3:4-6. The total flow rate of the reaction gases is controlled at 5-6 L / min, the vapor infiltration pressure is 100-500 Pa, the vapor infiltration temperature is 900-920 °C, and the vapor infiltration time is 3-5 h. A Si3N4-BN composite coating with a thickness of 0.1-1 μm is prepared on the fiber surface of the preform.

[0029] The first-round composite method is as follows: silicon dioxide hollow sphere powder and silica sol are mixed evenly to prepare an impregnation slurry; the composite preform is completely immersed in the impregnation slurry, and after vacuum vibration impregnation and high pressure impregnation, the composite preform is taken out, and then dried and heat-treated to complete the first-round composite of the impregnation slurry and the composite preform; the first-round composite is repeated 2-3 times until the weight gain of the composite preform is 3-8%, and the first-round composite intermediate is obtained.

[0030] In the first round of compounding, the particle size of the silica hollow sphere powder is 0.3-1.2μm, the wall thickness of the silica hollow sphere is 12nm-50nm, the concentration of silica sol is 5-10wt%, and the mass ratio of silica hollow sphere powder to silica sol in the impregnation slurry is 10-30:100.

[0031] In the first round of composite formation, the volume of the impregnation slurry used must be sufficient to completely submerge the composite preform during vacuum vibration (i.e., to keep the liquid level of the impregnation slurry above the top of the composite preform during vacuum vibration).

[0032] In the first round of composite process, during vacuum vibration impregnation, the impregnation vacuum degree is controlled at 0.095-0.099 MPa, the vibration frequency is 50-200 Hz, and the vacuum vibration impregnation time is 5-10 h.

[0033] In the first round of compounding, during high-pressure impregnation, the impregnation pressure is controlled at 6-8 MPa, and the high-pressure impregnation time is 1-3 hours.

[0034] In the first round of compounding, the drying temperature is 80-120℃ and the drying time is 5-10h.

[0035] In the first round of composite treatment, the heat treatment temperature is 300-400℃ and the heat treatment time is 0.5-1.5h.

[0036] The method for secondary composite is as follows: the primary composite intermediate is placed in a Si3N4 precursor slurry or a SiBN precursor slurry, vacuum impregnated, and then cured and pyrolyzed in an inert gas environment to complete the secondary composite. The secondary composite is repeated 3-4 times to obtain the secondary composite intermediate.

[0037] In the second round of compounding, the concentration of polysilazane in the Si3N4 precursor slurry is 45-50 wt%; the concentration of polyborosilicate in the SiBN precursor slurry is 40-45 wt%.

[0038] In the second round of compounding, the volume of Si3N4 precursor slurry or SiBN precursor slurry used must be sufficient to completely submerge the first round of compounding intermediate during the vacuum impregnation process (i.e., the liquid level of the precursor slurry must be kept above the top of the first round of compounding intermediate during the vacuum impregnation process).

[0039] In the second round of compounding, during vacuum impregnation, the vacuum degree is controlled at 0.095-0.099 MPa, and the vacuum impregnation time is 5-10 hours.

[0040] In the second round of lamination, the curing temperature is 250-300℃ and the curing time is 4-6h.

[0041] In the second round of compounding, the pyrolysis temperature is 750-950℃ and the pyrolysis time is 2-5h.

[0042] The final composite method involves placing the secondary composite intermediate in a BN precursor slurry, vacuum impregnating it, then heating and curing it in an inert gas environment, followed by pyrolysis to complete the final composite. This final composite process is repeated 1-2 times to obtain a lightweight, ablation-resistant fiber-reinforced ceramic matrix composite material.

[0043] In the final compounding process, the concentration of polyboron alkane in the BN precursor slurry is 35-40 wt%.

[0044] In the final stage of the composite process, the volume of the BN precursor slurry must be sufficient to completely submerge the intermediate in the secondary stage of the composite process during the vacuum impregnation process (i.e., the liquid level of the precursor slurry must be kept above the top of the intermediate in the secondary stage of the composite process during the vacuum impregnation process).

[0045] In the final wheel compounding process, during vacuum impregnation, the vacuum degree is controlled at 0.095-0.099 MPa, and the vacuum impregnation time is 5-10 hours.

[0046] In the final composite process, the curing temperature is 200-250℃ and the curing time is 4-6 hours.

[0047] In the final compounding process, the pyrolysis temperature is 750-950℃ and the pyrolysis time is 2-5h.

[0048] The method for preparing lightweight, ablation-resistant fiber-reinforced ceramic matrix composites according to embodiments of the present invention involves using continuous BN fibers as the main fiber raw material to form a preform in the preform preparation step. This lays the foundation for the low dielectric constant and low dielectric loss of the composite material. After the preform is treated with organic solvent immersion and high-temperature heat treatment, a Si3N4-BN composite coating is prepared on the fiber surface of the preform using a chemical vapor infiltration process. This improves the strength and toughness of the preform while enhancing the compatibility between the subsequent fiber preform and the first-round composite material, achieving an effective transition between the fiber preform and the first-round composite material. In the first-round composite step, submicron-sized silica hollow sphere powder is introduced through the impregnation slurry. This effectively reduces the density of the material while achieving densification, giving the composite material both lightweight and ablation-resistant characteristics. Simultaneously, the temperature resistance and low thermal conductivity of the silica hollow sphere powder in the impregnation slurry effectively reduce the thermal conductivity of the composite material, further preventing heat diffusion into the material. Furthermore, the low dielectric constant and low loss of the silica hollow sphere powder effectively improve the dielectric properties of the composite material. In the second-stage composite process, impregnation, curing, and pyrolysis using Si3N4 or SiBN precursor slurry further fills the pores of the composite material and encapsulates and fixes the silica hollow spheres introduced in the first-stage composite process, improving the density and strength of the composite material and enhancing its ablation resistance. In the final-stage composite process, impregnation, curing, and pyrolysis using BN precursor slurry forms a BN sealing protective layer on the outer layer of the composite material and the outer surface of the open pores, further improving the stability and ablation resistance of the composite material. The aforementioned techniques work together synergistically to effectively balance the contradictions between the properties of the wave-transparent materials. The resulting composite material possesses lightweight, low dielectric, ablation resistance, and high density characteristics, while also exhibiting low thermal conductivity.

[0049] The present invention also provides a lightweight ablation-resistant fiber-reinforced ceramic matrix composite material prepared by the aforementioned preparation method.

[0050] The present invention will be further described below with reference to some specific embodiments.

[0051] Example 1 This embodiment provides a method for preparing a lightweight, ablation-resistant fiber-reinforced ceramic matrix composite material, specifically as follows: 1. Preparation of composite preforms A preform with a fabric-stitched structure was made from continuous nitride ceramic fibers. The volume percentage of continuous nitride ceramic fibers in the preform was controlled to be 35%. The preform was soaked in an organic solvent (acetone) at 25°C for 24 hours, followed by heat treatment at 350°C for 3 hours. The preform after high-temperature treatment was placed in a chemical vapor infiltration furnace. Under vacuum conditions, BCl3, SiCl4, and ammonia were continuously introduced as reaction gases at a volume flow rate ratio of 0.7:0.3:4. The total flow rate of the reaction gases was controlled to be 5 L / min, the vapor infiltration pressure to be 280 Pa, the vapor infiltration temperature to be 900°C, and the vapor infiltration time to be 3 hours. A Si3N4-BN composite coating with a thickness of 0.5 μm was prepared on the fiber surface of the preform to obtain the composite preform.

[0052] Among them, the continuous nitride ceramic fibers are continuous BN fibers and continuous Si3N4 fibers; the weight ratio of continuous BN fibers to continuous Si3N4 fibers is 6:4.

[0053] 2. First round of compound Silica hollow sphere powder and silica sol were mixed evenly to prepare an impregnation slurry. The composite preform was completely immersed in the impregnation slurry, and the vacuum degree was controlled at 0.095 MPa, the vibration frequency at 50 Hz, and the vacuum vibration impregnation time was 5 h. Then, the pressure was controlled at 6 MPa and high pressure impregnation was carried out for 1.5 h. After that, the composite preform was taken out, dried at 95 ℃ for 10 h, and heat-treated at 300 ℃ for 1 h to complete the first round of composite between the impregnation slurry and the composite preform. The first round of composite was repeated 3 times until the weight gain of the composite preform was 5.6%, and the first round of composite intermediate was obtained.

[0054] The median particle size of the silica hollow sphere powder is 0.4 μm, the wall thickness of the silica hollow spheres is 20 nm, the silica sol concentration is 8 wt%, and the mass ratio of silica hollow sphere powder to silica sol in the impregnation slurry is 20:100.

[0055] 3. Secondary compound The first-round composite intermediate was placed in a Si3N4 precursor slurry, and the vacuum degree was controlled at 0.095 MPa. After vacuum impregnation for 5 hours, it was taken out. Then, it was cured at 250°C for 6 hours in a nitrogen environment and then pyrolyzed at 850°C for 3 hours to complete the second-round composite. The second-round composite was repeated 4 times to obtain the second-round composite intermediate.

[0056] The Si3N4 precursor slurry contains 45wt% polysilazane; the SiBN precursor slurry contains 40wt% polyborosilicate.

[0057] 4. Final wheel compound The intermediate of the second-round composite was placed in a BN precursor slurry, and the vacuum degree was controlled at 0.095 MPa. After vacuum impregnation for 5 hours, it was taken out. Then, it was cured at 200℃ for 6 hours in a nitrogen environment and then pyrolyzed at 850℃ for 3 hours to complete the final round composite. The final round composite was repeated twice to obtain a lightweight ablation-resistant fiber-reinforced ceramic matrix composite material.

[0058] The concentration of polyboron alkane in the BN precursor slurry is 38 wt%.

[0059] This embodiment also provides a lightweight, ablation-resistant fiber-reinforced ceramic matrix composite material prepared by the aforementioned method.

[0060] Testing revealed that the lightweight, ablation-resistant fiber-reinforced ceramic matrix composite material of this embodiment has a density of 1.63 g / cm³. 3 The thermal conductivity is 0.22 W / (m·K); the dielectric constant is 3.34; and the loss tangent is 0.0035.

[0061] Example 2 This embodiment provides a method for preparing a lightweight, ablation-resistant fiber-reinforced ceramic matrix composite material, specifically as follows: 1. Preparation of composite preforms A 2.5D preform was fabricated using continuous nitride ceramic fibers, with the volume percentage of continuous nitride ceramic fibers in the preform controlled at 35%. The preform was then immersed in an organic solvent (acetone) at 30℃ for 36 hours, followed by heat treatment at 450℃ for 3 hours. The preform after high-temperature treatment was placed in a chemical vapor infiltration furnace. Under vacuum conditions, BCl3, SiCl4, and ammonia were continuously introduced as reaction gases at a volume flow rate ratio of 0.72:0.28:5.5. The total flow rate of the reaction gases was controlled at 5.7 L / min, the vapor infiltration pressure at 350 Pa, the vapor infiltration temperature at 910℃, and the vapor infiltration time at 4 hours. A Si3N4-BN composite coating with a thickness of 0.6 μm was then prepared on the fiber surface of the preform to obtain the composite preform.

[0062] Among them, the continuous nitride ceramic fibers are continuous BN fibers and continuous SiBN fibers; the weight ratio of continuous BN fibers to continuous SiBN fibers is 6.5:3.5.

[0063] 2. First round of compound Silica hollow sphere powder and silica sol were mixed evenly to prepare an impregnation slurry. The composite preform was completely immersed in the impregnation slurry, and the vacuum degree was controlled at 0.099 MPa and the vibration frequency at 150 Hz for 8 hours. Then, the pressure was controlled at 7.5 MPa for 2 hours of high-pressure impregnation. The composite preform was then removed, dried at 110℃ for 8 hours, and heat-treated at 350℃ for 1.2 hours to complete the first round of composite bonding between the impregnation slurry and the composite preform. The first round of bonding was repeated 3 times until the weight gain of the composite preform was 5.1%, thus obtaining the first round of composite intermediate.

[0064] The median particle size of the silica hollow sphere powder is 0.4 μm, and the wall thickness of the silica hollow spheres is 20 nm; the silica sol concentration is 8 wt%; and the mass ratio of silica hollow sphere powder to silica sol in the impregnation slurry is 24:100.

[0065] 3. Secondary compound The first-round composite intermediate was placed in a SiBN precursor slurry, and the vacuum degree was controlled at 0.099 MPa. After vacuum impregnation for 8 hours, it was taken out. Then, it was cured at 270℃ for 5 hours in a nitrogen environment and then pyrolyzed at 850℃ for 4 hours to complete the second-round composite. The second-round composite was repeated 3 times to obtain the second-round composite intermediate.

[0066] The Si3N4 precursor slurry contains 45wt% polysilazane; the SiBN precursor slurry contains 40wt% polyborosilicate.

[0067] 4. Final wheel compound The intermediate of the second-round composite was placed in a BN precursor slurry, and the vacuum degree was controlled at 0.099 MPa. After vacuum impregnation for 8 hours, it was taken out. Then, it was cured at 240℃ for 5 hours in a nitrogen environment and then pyrolyzed at 850℃ for 4 hours to complete the final round composite. The final round composite was repeated once to obtain a lightweight ablation-resistant fiber-reinforced ceramic matrix composite material.

[0068] The concentration of polyboron alkane in the BN precursor slurry is 38 wt%.

[0069] This embodiment also provides a lightweight, ablation-resistant fiber-reinforced ceramic matrix composite material prepared by the aforementioned method.

[0070] Testing revealed that the lightweight, ablation-resistant fiber-reinforced ceramic matrix composite material of this embodiment has a density of 1.51 g / cm³. 3 The thermal conductivity is 0.19 W / (m·K); the dielectric constant is 3.08; and the loss tangent is 0.0027.

[0071] Example 3 This embodiment provides a method for preparing a lightweight, ablation-resistant fiber-reinforced ceramic matrix composite material, which consists of the following steps: preparing a composite preform, first-round composite, and second-round composite.

[0072] 1. Preparation of composite preforms A preform with an orthogonal triaxial structure was prepared by continuous nitride ceramic fibers. The volume percentage content of continuous nitride ceramic fibers in the preform was controlled to be 35%. The preform was immersed in an organic solvent (ethanol) at 40℃ for 48h, followed by heat treatment at 500℃ for 2.5h. The preform after high-temperature treatment was placed in a chemical vapor infiltration furnace. Under vacuum conditions, BCl3, SiCl4 and ammonia were continuously introduced as reaction gases at a volume flow rate ratio of 0.75:0.25:6. The total flow rate of the reaction gases was controlled to be 6L / min, the vapor infiltration pressure was 350Pa, the vapor infiltration temperature was 920℃ and the vapor infiltration time was 4.5h. A Si3N4-BN composite coating with a thickness of 0.7μm was prepared on the fiber surface of the preform to obtain the composite preform.

[0073] Among them, the continuous nitride ceramic fiber is a continuous BN fiber.

[0074] 2. First round of compound Silica hollow sphere powder and silica sol were mixed evenly to prepare an impregnation slurry. The composite preform was completely immersed in the impregnation slurry, and the vacuum degree was controlled at 0.099 MPa and the vibration frequency at 200 Hz for 5 hours. Then, the pressure was controlled at 8 MPa for 1 hour of high-pressure impregnation. The composite preform was then removed, dried at 120℃ for 5 hours, and heat-treated at 400℃ for 0.5 hours to complete the first round of composite bonding between the impregnation slurry and the composite preform. The first round of bonding was repeated 3 times until the weight gain of the composite preform was 6%, thus obtaining the first round of composite intermediate.

[0075] The median particle size of the silica hollow sphere powder is 0.4 μm, the wall thickness of the silica hollow spheres is 20 nm, the silica sol concentration is 8 wt%, and the mass ratio of silica hollow sphere powder to silica sol in the impregnation slurry is 25:100.

[0076] 3. Secondary compound The first-round composite intermediate was placed in a SiBN precursor slurry, and the vacuum degree was controlled at 0.099 MPa. After vacuum impregnation for 7 hours, it was taken out. Then, it was cured at 300℃ for 4 hours in a nitrogen environment and then pyrolyzed at 900℃ for 2.5 hours to complete the second-round composite. The second-round composite was repeated 4 times to obtain the second-round composite intermediate.

[0077] The Si3N4 precursor slurry contains 45wt% polysilazane; the SiBN precursor slurry contains 40wt% polyborosilicate.

[0078] 4. Final wheel compound The intermediate of the second-round composite was placed in a BN precursor slurry, and the vacuum degree was controlled at 0.099 MPa. After vacuum impregnation for 7 hours, it was taken out. Then, it was cured at 250°C for 4 hours in a nitrogen environment and then pyrolyzed at 900°C for 2.5 hours to complete the final round composite. The final round composite was repeated once to obtain a lightweight ablation-resistant fiber-reinforced ceramic matrix composite material.

[0079] The concentration of polyboron alkane in the BN precursor slurry is 38 wt%.

[0080] This embodiment also provides a lightweight, ablation-resistant fiber-reinforced ceramic matrix composite material prepared by the aforementioned method.

[0081] Testing revealed that the lightweight, ablation-resistant fiber-reinforced ceramic matrix composite material of this embodiment has a density of 1.58 g / cm³. 3 The thermal conductivity is 0.27 W / (m·K); the dielectric constant is 3.20; and the loss tangent is 0.0030.

[0082] Unless otherwise stated, all percentages used in this invention are mass percentages.

[0083] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a lightweight, ablation-resistant fiber-reinforced ceramic matrix composite material, characterized in that, It consists of the following steps: preparation of composite preform, first-round composite, second-round composite, and final-round composite; The method for preparing the composite preform is as follows: continuous nitride ceramic fibers are made into a preform, the preform is soaked in an organic solvent and then heat-treated, and a Si3N4-BN composite coating is prepared on the fiber surface of the preform by chemical vapor infiltration to obtain the composite preform. The first-round composite method involves uniformly mixing silica hollow sphere powder with silica sol to obtain an impregnation slurry; after impregnating the composite preform with the impregnation slurry, it is dried and heat-treated to complete the first-round composite; the first-round composite is repeated 2-3 times to obtain the first-round composite intermediate. The first-round composite intermediate was then subjected to a second-round composite and a final-round composite to obtain a lightweight, ablation-resistant fiber-reinforced ceramic matrix composite material.

2. The method for preparing the lightweight ablation-resistant fiber-reinforced ceramic matrix composite material according to claim 1, characterized in that, The method of the second-round composite is as follows: the first-round composite intermediate is impregnated with Si3N4 precursor slurry or SiBN precursor slurry, and then cured and pyrolyzed in an inert gas environment to complete the second-round composite. The second-round composite is repeated 3-4 times to obtain the second-round composite intermediate. The final composite method is as follows: the intermediate of the second composite is impregnated with BN precursor slurry, and then cured and pyrolyzed in an inert gas environment to complete the final composite. The final composite is repeated 1-2 times to obtain a lightweight ablation-resistant fiber-reinforced ceramic matrix composite material.

3. The method for preparing the lightweight ablation-resistant fiber-reinforced ceramic matrix composite material according to claim 1, characterized in that, In the preparation of the composite preform, the continuous nitride ceramic fiber is one of the following: continuous BN fiber; a combination of continuous BN fiber and continuous Si3N4 fiber; a combination of continuous BN fiber and continuous SiBN fiber; a combination of continuous BN fiber, continuous Si3N4 fiber and continuous SiBN fiber. The precast structure can be one of the following: fabric stitching structure, orthogonal triaxial structure, or 2.5D structure; The volume percentage content of continuous nitride ceramic fibers in the preform is 30-40%.

4. The method for preparing the lightweight ablation-resistant fiber-reinforced ceramic matrix composite material according to claim 1, characterized in that, In the preparation of the composite preform, the Si3N4-BN composite coating is prepared on the fiber surface of the preform by chemical vapor infiltration. The heat-treated preform is placed in a chemical vapor infiltration furnace, and BCl3, SiCl4 and ammonia are continuously introduced as reaction gases under vacuum conditions. The vapor infiltration pressure is controlled at 100-500 Pa, the vapor infiltration temperature is controlled at 900-920℃, and the vapor infiltration time is controlled at 3-5 h to complete the preparation of the Si3N4-BN composite coating.

5. The method for preparing the lightweight ablation-resistant fiber-reinforced ceramic matrix composite material according to claim 4, characterized in that, The total flow rate of the reacting gases is 5-6 L / min; The volumetric flow rate ratio of BCl3, SiCl4, and ammonia is 0.7-0.75:0.25-0.3:4-6; The thickness of the Si3N4-BN composite coating obtained on the fiber surface of the preform is 0.1-1 μm.

6. The method for preparing the lightweight ablation-resistant fiber-reinforced ceramic matrix composite material according to claim 1, characterized in that, In the first round of composite formation, the particle size of the silica hollow sphere powder is 0.3-1.2μm, and the wall thickness of the silica hollow sphere is 12nm-50nm. The concentration of silica sol is 5-10 wt%; The mass ratio of silica hollow sphere powder to silica sol in the impregnation slurry is 10-30:

100.

7. The method for preparing the lightweight ablation-resistant fiber-reinforced ceramic matrix composite material according to claim 1, characterized in that, In the first round of composite impregnation, the composite preform is impregnated with the impregnation slurry by completely immersing the composite preform in the impregnation slurry, controlling the vacuum degree to 0.095-0.099MPa and the vibration frequency to 50-200Hz, and then performing vacuum vibration impregnation for 5-10 hours; then controlling the pressure to 6-8MPa and performing high-pressure impregnation for 1-3 hours. The heat treatment temperature is 300-400℃, and the heat treatment time is 0.5-1.5h.

8. The method for preparing the lightweight ablation-resistant fiber-reinforced ceramic matrix composite material according to claim 2, characterized in that, In the second round of compounding, the concentration of polysilazane in the Si3N4 precursor slurry is 45-50 wt%; the concentration of polyborosilicate in the SiBN precursor slurry is 40-45 wt%. The impregnation is vacuum impregnation, with a vacuum degree of 0.095-0.099 MPa and an impregnation time of 5-10 hours; The curing temperature is 250-300℃, and the curing time is 4-6h; the pyrolysis temperature is 750-950℃, and the pyrolysis time is 2-5h.

9. The method for preparing the lightweight ablation-resistant fiber-reinforced ceramic matrix composite material according to claim 2, characterized in that, In the final compounding process, the polyboron alkane concentration in the BN precursor slurry is 35-40 wt%. The impregnation is vacuum impregnation, with a vacuum degree of 0.095-0.099 MPa and an impregnation time of 5-10 hours; The curing temperature is 200-250℃, and the curing time is 4-6h; the pyrolysis temperature is 750-950℃, and the pyrolysis time is 2-5h.

10. A lightweight, ablation-resistant fiber-reinforced ceramic matrix composite material prepared by the preparation method according to any one of claims 1-9.