A method for preparing a carbon fiber reinforced SiC-SiBC(N / O) composite material

Abstract

This invention belongs to the field of ceramic preparation technology and relates to a method for preparing carbon fiber reinforced SiC-SiBC(N / O) composite materials. The method for preparing carbon fiber reinforced SiC-SiBC(N / O) composite materials provided by this invention involves impregnating a carbon fiber preform with a boron-containing ceramic precursor and a SiC ceramic precursor, either sequentially or alternately, using a pyrolysis step to control the boron content and boron-containing phase distribution in the composite material. The resulting composite material exhibits excellent mechanical properties and self-healing capabilities.

Description

Technical Field

[0001] This invention belongs to the field of ceramic preparation technology and relates to a method for preparing carbon fiber reinforced SiC-SiBC (N / O) composite materials. Background Technology

[0002] As a new type of strategic material that is high-temperature resistant, strong, and lightweight, C f Ceramic matrix composites, represented by SiC, are considered the best candidate materials for high-temperature structures such as aero-engines, gas turbines, and brake discs. However, the long-term stability of ceramic matrix composites under high-temperature and oxidizing conditions is one of the major challenges in contemporary technological development. Due to thermal stress generated during the manufacturing process and impacts from various sources, the ceramic matrix is ​​prone to microcrack formation. If left unchecked, the crack damage area exceeding a critical value will lead to potentially catastrophic structural damage. The presence of microcracks provides diffusion pathways for oxidizing substances (O2 and H2O), causing oxidation of the interfacial phases and fibers in the ceramic matrix composite components, ultimately leading to material failure and severely impacting its long service life requirements under high-temperature oxidizing environments. The self-healing capability of materials becomes particularly important. Crack self-healing can not only reverse the propagation of structural damage and prevent the inward diffusion of oxidizing substances, but also improve oxidation resistance, thereby extending the service life of the material and improving the reliability, repairability, and reusability of silicon carbide ceramic matrix composites.

[0003] Currently, the main approaches to achieving self-healing include introducing multilayer boron-modified coatings. The French company Snecma has researched and developed this technology into a relatively mature multi-element, multilayer coating self-healing material. Professor P. Goursat's team at the University of Limoges, France, and Snecma, representing the French company, were the first to propose and prepare (SiC) materials with multilayer matrices. f / C / (SiBC) m The composite material matrix consists of alternating layers of Si-BC and SiC, forming a multi-element, multi-layered microstructure. A drawback of self-healing coatings and multi-layered matrices is the relatively concentrated borosilicate phase, which is prone to volatilization and detachment under prolonged environmental erosion, leading to self-healing failure. It only exhibits good sealing effects at lower temperatures, and the preparation process is complex and time-consuming. In recent years, self-healing matrices with dispersed self-healing component particles have been developed, primarily using B4C and SiB4 as self-repairing fillers. The Key Laboratory of Ultra-High Temperature Structural Composite Materials at Northwestern Polytechnical University is one of the earliest teams in China to conduct research on multi-element dispersed self-healing composite materials, and has prepared C... f / SiC-SiB4、C f / SiC-ZrB2 and C fVarious multi-component dispersion matrix materials such as SiC-SiBC (CN 106431452 B) are used. However, traditional solid-phase boron sources are introduced into the ceramic matrix through slurry infiltration, which makes it difficult to achieve uniform dispersion of boron-containing particles. Furthermore, current technology cannot design and control the distribution of boron-containing self-healing components, which severely restricts the self-healing effect of composite materials. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for preparing carbon fiber reinforced SiC-SiBC (N / O) composite materials. By performing impregnation-pyrolysis steps with boron-containing ceramic precursors and SiC ceramic precursors sequentially or alternately, the boron content and boron-containing phase distribution in the composite material are controlled, resulting in a composite material with excellent mechanical properties and self-healing function.

[0005] The first objective of this invention is achieved through the following technical solution:

[0006] A method for preparing carbon fiber reinforced SiC-SiBC (N / O) composite material includes the following steps:

[0007] S1. The boron-containing ceramic precursor is immersed in the carbon fiber preform under vacuum conditions. The carbon fiber preform is then removed, compressed, cross-linked, and cured. The cured carbon fiber preform is then pyrolyzed.

[0008] S2. The product from the previous step is immersed in a boron-containing ceramic precursor, impregnated under vacuum conditions, removed, crosslinked and cured, and then pyrolyzed.

[0009] S3. Repeat step S2 0 to 20 times;

[0010] The product from the previous step was immersed in S4 and SiC ceramic precursors under vacuum conditions, then removed, crosslinked and cured, and then pyrolyzed.

[0011] S5. Repeat step S4 until the weight gain of the composite material is ≤1%.

[0012] In this article, SiC-SiBC(N / O) represents SiC-SiBCN, SiC-SiBCO, SiC-SiBCNO, or SiC-SiBC, depending on the type of boron-containing ceramic precursor being impregnated.

[0013] In this paper, the steps from impregnation to pyrolysis completion in steps S2 to S5 are referred to as an impregnation-pyrolysis step. The weight gain rate of the composite material refers to the increase in weight of the composite material obtained in the latest impregnation-pyrolysis step relative to the composite material in the previous impregnation-pyrolysis step.

[0014] In this preparation method, boron-containing ceramic precursors are impregnated in the first few impregnation-pyrolysis cycles, and SiC ceramic precursors are impregnated in subsequent impregnation-pyrolysis cycles, resulting in a ceramic matrix composite material with a boron-containing phase distribution closer to the fiber distribution, which greatly improves the self-healing effect of the composite material cracks.

[0015] Preferably, the boron-containing ceramic precursor is one or more of polyborosilicate, boron-modified polysiloxane, boron-modified polycarbosilane, and SiBCO ceramic precursor; more preferably, the boron-containing ceramic precursor is polyborosilicate.

[0016] Optionally, the boron-containing ceramic precursor is a liquid boron-containing ceramic precursor.

[0017] Preferably, the SiC ceramic precursor is one or more of polycarbosilane and polycarbosilane containing heterogeneous elements; optionally, the heterogeneous elements include one or more of aluminum, iron, titanium, zirconium, cobalt, nickel, lanthanum, yttrium, and niobium.

[0018] Optionally, the SiC ceramic precursor is a liquid SiC ceramic precursor.

[0019] Preferably, the SiC ceramic precursor is a polycarbosilane containing heterogeneous elements.

[0020] The boron-containing ceramic precursor used for impregnation can be a liquid boron-containing ceramic precursor or a solution formed by dissolving a solid boron-containing ceramic precursor in solvent I. Solvent I can be any organic solvent that can dissolve the boron-containing ceramic precursor. The SiC ceramic precursor used for impregnation can be a liquid SiC ceramic precursor or a solution formed by dissolving a solid SiC ceramic precursor in solvent II. Solvent II can be any organic solvent that can dissolve the boron-containing ceramic precursor, such as xylene, cyclohexane, or tetrahydrofuran.

[0021] Preferably, the boron-containing ceramic precursor is a liquid boron-containing ceramic precursor, and the SiC ceramic precursor is a liquid SiC ceramic precursor.

[0022] Preferably, the carbon fiber preform is a chopped carbon fiber preform, which is prepared into a certain three-dimensional shape by using chopped carbon fibers as raw materials through steps such as weaving.

[0023] Preferably, in the chopped carbon fiber preform, the length of the chopped carbon fiber is 0.1–100 mm, more preferably 0.5–50 mm, even more preferably 1–30 mm, and most preferably, the length of the chopped carbon fiber is 5–10 mm; the volume fraction of the chopped carbon fiber in the chopped carbon fiber preform is 5–25 vol%, more preferably 10–20 vol%.

[0024] Preferably, the impregnation time is 3 to 100 hours, more preferably 4 to 50 hours, and even more preferably 6 to 30 hours. The impregnation can be carried out at room temperature.

[0025] Preferably, in step S1, the step of compressing the carbon fiber preform includes: placing the carbon fiber preform in a flat plate fixture, applying pressure, and compressing the carbon fiber preform to a certain thickness.

[0026] Preferably, the pressure applied during the compression step is 0.5 to 50 MPa, more preferably 1 to 30 MPa, and even more preferably 1 to 10 MPa.

[0027] Preferably, in the compression step, the certain thickness is 20-80% of the thickness of the carbon fiber preform, more preferably 25-60%. Compressing the carbon fiber preform reduces its thickness; the smaller the thickness, the greater the volume fraction of carbon fiber in the final composite material, and the better its mechanical properties.

[0028] In steps S2 to S5, the carbon fiber preform is no longer compressed.

[0029] Preferably, the cross-linking curing temperature is 70–200°C, more preferably 80–150°C; and the cross-linking curing time is 1–30 hours, more preferably 2–15 hours.

[0030] Preferably, the pyrolysis is carried out under an inert atmosphere, the pyrolysis temperature is 800-1500℃, more preferably 900-1200℃, and the pyrolysis time is 0.2-10 hours, preferably 0.5-5 hours.

[0031] Preferably, step S2 is repeated at least once, and more preferably, step S2 is repeated at least twice.

[0032] The specific impregnation time, cross-linking curing temperature and time, and pyrolysis temperature and time can be the same or different in each of the above steps.

[0033] The second objective of this invention is achieved through the following technical solution:

[0034] A method for preparing carbon fiber reinforced SiC-SiBC (N / O) composite material includes the following steps:

[0035] The SiC ceramic precursor is immersed in the carbon fiber preform under vacuum conditions. The carbon fiber preform is then removed, compressed, cross-linked, and cured. The cured carbon fiber preform is then pyrolyzed.

[0036] The product from the previous step is immersed in S2 and SiC ceramic precursors under vacuum conditions, then removed, crosslinked and cured, and then pyrolyzed.

[0037] S3. Repeat step S2 0 to 20 times;

[0038] S4. The product from the previous step is immersed in a boron-containing ceramic precursor, impregnated under vacuum conditions, removed, crosslinked and cured, and then pyrolyzed.

[0039] S5. Repeat step S4 until the weight gain of the composite material is ≤1%.

[0040] The second objective of this invention provides a method for preparing carbon fiber reinforced SiC-SiBC(N / O) composite material, in which the specific limitations of each step are the same as those provided in the first objective of this invention.

[0041] The third objective of this invention is achieved through the following technical solution:

[0042] A method for preparing carbon fiber reinforced SiC-SiBC (N / O) composite material includes the following steps:

[0043] S1. The boron-containing ceramic precursor is immersed in the carbon fiber preform under vacuum conditions. The carbon fiber preform is then removed, compressed, cross-linked, and cured. The cured carbon fiber preform is then pyrolyzed.

[0044] The product from the previous step is immersed in S2 and SiC ceramic precursors under vacuum conditions, then removed, crosslinked and cured, and then pyrolyzed.

[0045] S3. The product from the previous step is immersed in a boron-containing ceramic precursor, impregnated under vacuum conditions, removed, crosslinked and cured, and then pyrolyzed.

[0046] S4. Alternately repeat steps S2 and S3 until the weight gain of the composite material is ≤1%.

[0047] In steps S2 to S4, the steps from impregnation to pyrolysis completion are referred to as an impregnation-pyrolysis step. Step S2 can be the last impregnation-pyrolysis step, or step S3 can be the last impregnation-pyrolysis step.

[0048] In this preparation method, a boron-containing ceramic precursor is first impregnated, followed by a SiC ceramic precursor, and this process is repeated alternately to obtain a ceramic matrix composite material with a boron phase distribution closer to the fiber distribution, which greatly improves the self-healing effect of cracks in the composite material.

[0049] The preparation method of carbon fiber reinforced SiC-SiBC(N / O) composite material provided by the third objective of this invention has the same specific limitations for each step as the preparation method of carbon fiber reinforced SiC-SiBC(N / O) composite material provided by the first objective of this invention.

[0050] The fourth objective of this invention is achieved through the following technical solution:

[0051] A method for preparing carbon fiber reinforced SiC-SiBC (N / O) composite material includes the following steps:

[0052] The SiC ceramic precursor is immersed in the carbon fiber preform under vacuum conditions. The carbon fiber preform is then removed, compressed, cross-linked, and cured. The cured carbon fiber preform is then pyrolyzed.

[0053] S2. The product from the previous step is immersed in a boron-containing ceramic precursor, impregnated under vacuum conditions, removed, crosslinked and cured, and then pyrolyzed.

[0054] The product from the previous step was immersed in S3 and SiC ceramic precursors under vacuum conditions, then removed, crosslinked and cured, and then pyrolyzed.

[0055] S4. Alternately repeat steps S2 and S3 until the weight gain of the composite material is ≤1%.

[0056] In steps S2 to S4, the steps from impregnation to pyrolysis completion are referred to as an impregnation-pyrolysis step. Step S2 can be the last impregnation-pyrolysis step, or step S3 can be the last impregnation-pyrolysis step.

[0057] The preparation method of carbon fiber reinforced SiC-SiBC(N / O) composite material provided by the fourth objective of this invention has the same specific limitations for each step as the preparation method of carbon fiber reinforced SiC-SiBC(N / O) composite material provided by the first objective of this invention.

[0058] The fifth objective of this invention is achieved through the following technical solution:

[0059] A carbon fiber reinforced SiC-SiBC (N / O) composite material, which is prepared by the preparation method of the first objective, the second objective, the third objective, or the fourth objective.

[0060] The carbon fiber reinforced SiC-SiBC(N / O) composite material has an elemental gradient distribution and a self-healing function.

[0061] Compared with the prior art, the present invention has the following beneficial effects:

[0062] 1. This invention enables simple control of the fiber volume fraction in carbon fiber reinforced SiC-SiBC (N / O) composite materials by controlling the pressure applied by the flat plate clamp. The volume fraction of the carbon fiber preform increases after compression, which is beneficial to improving the mechanical properties of the composite material.

[0063] 2. This invention controls the order and number of impregnation-pyrolysis of boron-containing ceramic precursors and SiC ceramic precursors to regulate the boron content and boron-containing phase distribution in boron-modified ceramic matrix composites, thereby achieving microstructure design and fine control of the composite material and effectively improving the self-healing effect of cracks in the composite material.

[0064] 3. In the first few impregnation-pyrolysis cycles of this invention, a boron-containing ceramic precursor is impregnated, and in the subsequent impregnation-pyrolysis cycles, a SiC ceramic precursor is impregnated; or, a boron-containing ceramic precursor is impregnated first, and then a SiC ceramic precursor is impregnated, and so on, to obtain a ceramic matrix composite material with a boron phase distribution closer to the fiber distribution, which greatly improves the self-healing effect of the composite material cracks.

[0065] 4. When the SiC ceramic precursor impregnated in this invention is a polycarbosilane containing heterogeneous elements, it is more beneficial to improve the mechanical properties of the composite material and the retention rate of mechanical properties after high-temperature treatment. Attached Figure Description

[0066] Figure 1 The image shows a scanning electron microscope (SEM) image of the microstructure of the carbon fiber reinforced SiC-SiBCN composite material prepared in Example 1. Detailed Implementation

[0067] The technical solution of the present invention will be further described and illustrated below with specific embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are only for the purpose of helping to understand the present invention and are not intended to limit the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are within the scope of protection of the present invention. Furthermore, the specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to limit themselves to the specific values ​​in the examples below. In addition, the accompanying drawings used herein are merely for better illustration of the disclosed content of the present invention and do not limit the scope of protection. Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commonly used raw materials in the art, and the methods used in the embodiments are all conventional methods in the art.

[0068] In the following examples and comparative examples:

[0069] Liquid polyborosilazane precursors were prepared by the following method: 1,1,3,3-tetramethyl-1,3-divinyldisilazane was dissolved in anhydrous tetrahydrofuran, and a boron dimethyl sulfide complex was added under high-purity argon protection. The reaction was carried out at room temperature for 12 hours, and the solvent was removed in a rotary evaporator at 70°C. Liquid polymer poly[imino(methylmethylenesilyl)] and a caster catalyst were added, and the mixture was stirred at room temperature for 1 hour to synthesize the liquid polyborosilazane precursors.

[0070] Liquid polycarbosilane precursors are prepared by the following method: using alkoxyhalosilanes, dihalomethanes, and metallic magnesium as raw materials, a polymerization reaction is carried out at 100℃ for 40 hours to synthesize liquid polycarbosilane precursors.

[0071] The SiBCO ceramic precursor was prepared by the following method: SiBCO ceramic precursor was synthesized by dehydrogenation coupling of 1,3,5,7-tetramethyl-1,3,5,7-tetracyclotetrasiloxane and boric acid in ethanol at 78°C for 24 hours.

[0072] Polyaluminosilicate was prepared by the following method: dichlorosilane was dechlorinated and condensed under potassium metal catalysis to synthesize polydimethylsilane, which was then pyrolyzed at 480°C to obtain polysiloxane. Polysiloxane and Al(AcAc)3 were then reacted in a high-temperature and high-pressure reactor at 420°C to synthesize polyaluminosilicate.

[0073] Example 1

[0074] The preparation method of the carbon fiber reinforced SiC-SiBCN composite material provided in this embodiment is as follows:

[0075] S1. Place the chopped carbon fiber preform (chopped carbon fiber length is 5mm, chopped carbon fiber volume fraction is 10Vol%) in an impregnation tank, immerse the chopped carbon fiber preform in liquid polyborosilazane precursor, and impregnate for 6 hours under vacuum conditions (pressure is 5Pa); remove the chopped carbon fiber preform and place it in a flat fixture, apply a pressure of 5MPa to the flat fixture, compress the chopped carbon fiber preform to 50% of the original thickness and fix it with nuts, place it in an oven and heat it to 120℃ to crosslink and cure for 2 hours, remove the cured preform from the fixture and place it in a high-temperature tube furnace and heat it to 1000℃ to pyrolyze it in an argon atmosphere for 1 hour;

[0076] S2. The product from the previous step is immersed in liquid polyborosilazane precursor and impregnated under vacuum conditions (pressure of 5 Pa) for 6 hours. The preform is then removed and placed in an oven to be heated to 120°C for cross-linking and curing for 2 hours. Then it is placed in a high-temperature tube furnace and heated to 1000°C for pyrolysis in an argon atmosphere for 1 hour to complete one impregnation-pyrolysis step.

[0077] S3. Repeat the impregnation-pyrolysis step of step S2 twice;

[0078] S4. Immerse the product from the previous step in liquid polycarbosilane precursor and impregnate it under vacuum conditions (pressure of 5 Pa) for 6 hours; take out the preform and place it in an oven to heat to 120°C for cross-linking and curing for 2 hours, and then place it in a high-temperature tube furnace to heat to 1000°C and decompose it in an argon atmosphere for 1 hour.

[0079] S5. Repeat step S4 until the weight gain of the composite material is ≤1%.

[0080] Figure 1 The image shows a scanning electron microscope (SEM) image of the microstructure of the carbon fiber reinforced SiC-SiBCN composite material prepared in Example 1, where the black area represents carbon fiber, the gray area represents the SiBCN phase, and the grayish-white area represents the SiC phase.

[0081] Example 2

[0082] The only difference between Example 2 and Example 1 is that the liquid polyborosilazane precursor is replaced with a SiBCO ceramic precursor solution (solid SiBCO ceramic precursor is dissolved in xylene to form a 60% by weight solution), otherwise it is the same as Example 1. Carbon fiber reinforced SiC-SiBCO composite material was prepared.

[0083] Example 3

[0084] The only difference between Example 3 and Example 1 is that in step S1 of Example 3, the chopped carbon fiber preform is compressed to 25% of its original thickness, while the rest is the same as in Example 1.

[0085] Example 4

[0086] The only difference between Example 4 and Example 1 is that in Example 4, step S3 is a repetition of step S2 (impregnation-pyrolysis) zero times; all other steps are the same as in Example 1. The specific steps are as follows:

[0087] S1. Place the chopped carbon fiber preform (chopped carbon fiber length is 5mm, chopped carbon fiber volume fraction is 10Vol%) in an impregnation tank, immerse the chopped carbon fiber preform in liquid polyborosilazane precursor, and impregnate for 6 hours under vacuum conditions (pressure is 5Pa); remove the chopped carbon fiber preform and place it in a flat fixture, apply a pressure of 5MPa to the flat fixture, compress the chopped carbon fiber preform to 50% of the original thickness and fix it with nuts, place it in an oven and heat it to 120℃ to crosslink and cure for 2 hours, remove the cured preform from the fixture and place it in a high-temperature tube furnace and heat it to 1000℃ to pyrolyze it in an argon atmosphere for 1 hour;

[0088] S2. The product from the previous step is immersed in liquid polyborosilazane precursor and impregnated under vacuum conditions (pressure of 5 Pa) for 6 hours. The preform is then removed and placed in an oven to be heated to 120°C for cross-linking and curing for 2 hours. Then it is placed in a high-temperature tube furnace and heated to 1000°C for pyrolysis in an argon atmosphere for 1 hour to complete one impregnation-pyrolysis step.

[0089] S3. Immerse the product from the previous step in liquid polycarbosilane precursor and impregnate it under vacuum conditions (pressure of 5 Pa) for 6 hours; take out the preform and place it in an oven to heat to 120°C for cross-linking and curing for 2 hours, and then place it in a high-temperature tube furnace to heat to 1000°C for pyrolysis in an argon atmosphere for 1 hour.

[0090] S4. Repeat step S3 until the weight gain of the composite material is ≤1%.

[0091] Example 5

[0092] The difference between Example 5 and Example 1 is that in Example 5, the first four impregnation-pyrolysis steps impregnate with liquid polycarbosilane precursors, and the subsequent impregnation-pyrolysis steps impregnate with liquid polyborosilazane precursors. The other steps are the same as in Example 1. The specific steps are as follows:

[0093] S1. Place the chopped carbon fiber preform (chopped carbon fiber length is 5mm, chopped carbon fiber volume fraction is 10Vol%) in an impregnation tank, immerse the chopped carbon fiber preform in liquid polycarbosilane precursor, and impregnate under vacuum conditions (pressure is 5Pa) for 6 hours; take out the chopped carbon fiber preform and place it in a flat fixture, apply a pressure of 5MPa to the flat fixture, compress the chopped carbon fiber preform to 50% of the original thickness and fix it with nuts, place it in an oven and heat it to 120℃ to crosslink and cure for 2 hours, take out the cured preform from the fixture and place it in a high temperature tube furnace and heat it to 1000℃ to pyrolyze it in an argon atmosphere for 1 hour;

[0094] S2. The product from the previous step is immersed in liquid polycarbosilane precursor and impregnated under vacuum conditions (pressure of 5 Pa) for 6 hours. The preform is then removed and placed in an oven to be heated to 120°C for cross-linking and curing for 2 hours. Then it is placed in a high-temperature tube furnace and heated to 1000°C for pyrolysis in an argon atmosphere for 1 hour to complete one impregnation-pyrolysis step.

[0095] S3. Repeat the impregnation-pyrolysis step of step S2 twice;

[0096] S4. Immerse the product from the previous step in liquid polyborosilazane precursor and impregnate it under vacuum conditions (pressure of 5 Pa) for 6 hours; take out the preform and place it in an oven to heat to 120°C for cross-linking and curing for 2 hours, and then place it in a high-temperature tube furnace to heat to 1000°C for pyrolysis in an argon atmosphere for 1 hour.

[0097] S5. Repeat step S4 until the weight gain of the composite material is ≤1%.

[0098] Example 6

[0099] The only difference between Example 6 and Example 1 is that the length of the chopped carbon fiber in Example 6 is 10 mm and the volume fraction of the chopped carbon fiber is 20 Vol%. The rest is the same as in Example 1.

[0100] Example 7

[0101] The preparation method of the carbon fiber reinforced SiC-SiBCN composite material provided in this embodiment is as follows:

[0102] S1. Place the chopped carbon fiber preform (chopped carbon fiber length is 10mm, chopped carbon fiber volume fraction is 10Vol%) in an impregnation tank, immerse the chopped carbon fiber preform in liquid polyborosilazane precursor, and impregnate for 6 hours under vacuum conditions (pressure is 5Pa); remove the chopped carbon fiber preform and place it in a flat fixture, apply a pressure of 5MPa to the flat fixture, compress the chopped carbon fiber preform to 50% of its original thickness and fix it with nuts, place it in an oven and heat it to 120℃ to crosslink and cure for 2 hours, remove the cured preform from the fixture and place it in a high-temperature tube furnace and heat it to 1000℃ to pyrolyze it in an argon atmosphere for 1 hour;

[0103] S2. Immerse the product from the previous step in liquid polycarbosilane precursor and impregnate it under vacuum conditions (pressure of 5 Pa) for 6 hours; take out the preform and place it in an oven to heat to 120°C for cross-linking and curing for 2 hours, and then place it in a high-temperature tube furnace to heat to 1000°C for pyrolysis in an argon atmosphere for 1 hour.

[0104] S3. Immerse the product from the previous step in liquid polyborosilazane precursor and impregnate it under vacuum conditions (pressure of 5 Pa) for 6 hours; take out the preform and place it in an oven to heat to 120°C for cross-linking and curing for 2 hours, and then place it in a high-temperature tube furnace to heat to 1000°C for pyrolysis in an argon atmosphere for 1 hour.

[0105] S4. Alternately repeat steps S2 and S3 until the weight gain of the composite material is ≤1%. The last impregnation-pyrolysis step is step S2.

[0106] Example 8

[0107] The only difference between Example 8 and Example 7 is that in Example 8, liquid polycarbosilane is replaced with a polyaluminosilane solution (solid polyaluminosilane solution is dissolved in xylene to form a solution with a weight fraction of 60%), otherwise it is the same as Example 1.

[0108] Example 9

[0109] The only difference between Example 9 and Example 7 is that Example 9 first impregnates the liquid polycarbosilane precursor, and then impregnates the liquid polyborosilazane precursor solution. The specific steps are as follows:

[0110] S1. Place the chopped carbon fiber preform (chopped carbon fiber length is 10mm, chopped carbon fiber volume fraction is 10Vol%) in an impregnation tank, immerse the chopped carbon fiber preform in liquid polycarbosilane precursor, and impregnate for 6 hours under vacuum conditions (pressure is 5Pa); take out the chopped carbon fiber preform and place it in a flat fixture, apply a pressure of 5MPa to the flat fixture, compress the chopped carbon fiber preform to 50% of the original thickness and fix it with nuts, place it in an oven and heat it to 120℃ to crosslink and cure for 2 hours, take out the cured preform from the fixture and place it in a high-temperature tube furnace and heat it to 1000℃ to pyrolyze it in an argon atmosphere for 1 hour;

[0111] S2. Immerse the product from the previous step in the liquid polyborosilazane precursor and impregnate it under vacuum conditions (pressure of 5 Pa) for 6 hours. Take out the preform and place it in an oven to heat to 120°C for cross-linking and curing for 2 hours. Then place it in a high-temperature tube furnace and heat to 1000°C for pyrolysis in an argon atmosphere for 1 hour.

[0112] S3. Immerse the product from the previous step in liquid polycarbosilane precursor and impregnate it under vacuum conditions (pressure of 5 Pa) for 6 hours; take out the preform and place it in an oven to heat to 120°C for cross-linking and curing for 2 hours, and then place it in a high-temperature tube furnace to heat to 1000°C for pyrolysis in an argon atmosphere for 1 hour.

[0113] S4. Alternately repeat steps S2 and S3 until the weight gain of the composite material is ≤1%. The last impregnation-pyrolysis step is step S2.

[0114] Comparative Example 1

[0115] The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 was entirely impregnated with the liquid polyborosilazane precursor of Example 1, while the rest was the same as Example 1.

[0116] Comparative Example 2

[0117] The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 was entirely impregnated with the liquid polycarbosilane precursor of Example 1, while the rest was the same as Example 1.

[0118] Comparative Example 3

[0119] The difference between Comparative Example 3 and Example 1 is that the short-cut carbon fiber preform in Comparative Example 3 was not compressed, but otherwise it was the same as Example 1.

[0120] The properties of the composite materials in Examples 1-9 and Comparative Examples 1-3 were tested. The self-healing effect test included: polishing the surface of the prepared ceramic matrix composite samples; using a diamond indenter of a Vickers hardness tester to create a cross-shaped indentation at the center of the sample to generate a pre-crack at the center of the tensile surface of each specimen; annealing the indented specimens in a high-temperature air environment to activate the crack repair ability of the composite material; and observing the crack repair using a scanning electron microscope. The strength retention rate test included: treating the prepared ceramic matrix composite samples in an oxidizing environment at 1000℃ for 20 hours, then testing the flexural strength and comparing it with the flexural strength of the samples not treated at 1000℃. The performance results are shown in Table 1.

[0121] Table 1. Relevant properties of the composite materials in the examples and comparative examples.

[0122]

[0123] By comparing Example 1 and Comparative Example 3, it can be seen that using a flat plate clamp to compress the carbon fiber preform after the first impregnation is beneficial to improving the flexural strength of the composite material and the strength retention rate after high-temperature treatment.

[0124] Comparative Example 1, with its fully impregnated liquid polyborosilazane precursor, yielded a composite material that, while achieving full healing, exhibited significantly reduced flexural strength, making it difficult to apply in practice. In contrast, Comparative Example 2, with its fully impregnated liquid polycarbosilane precursor, produced a composite material with high flexural strength, but the cracks could not heal. The composite materials prepared using the method protected in Examples 1, 3, and 6-8 all achieved full healing and possessed high flexural strength.

[0125] Compared to Example 1, Example 5 involves impregnating the first four impregnation-pyrolysis steps with a liquid polycarbosilane precursor, followed by impregnation with a liquid borosilicate precursor in subsequent impregnation-pyrolysis steps. Compared to Example 7, Example 9 involves impregnation with a liquid polycarbosilane precursor followed by impregnation with a liquid borosilicate precursor. In the composite materials of Examples 5 and 9, the boron phase is not distributed close to the chopped carbon fibers, which adversely affects the self-healing effect of the composite material and also reduces its mechanical properties.

[0126] By comparing Examples 7 and 8, it can be seen that when the SiC ceramic precursor is a polycarbosilane containing heterogeneous elements, it is beneficial to improve the flexural strength of the composite material and the strength retention rate after high-temperature treatment.

[0127] All aspects, embodiments, and features of this invention should be considered illustrative in all respects and not limiting of the invention; the scope of the invention is defined only by the claims. Other embodiments, modifications, and uses will become apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0128] In the preparation method of this invention, the order of the steps is not limited to the listed order. For those skilled in the art, variations in the order of the steps without creative effort are also within the scope of protection of this invention. Furthermore, two or more steps or actions can be performed simultaneously.

[0129] Finally, it should be noted that the specific embodiments described herein are merely illustrative examples of the invention and are not intended to limit the implementation of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them; it is neither necessary nor possible to exemplify all embodiments here. However, these obvious variations or modifications derived from the essential spirit of the invention still fall within the scope of protection of the invention, and interpreting them as any additional limitation would contradict the spirit of the invention.

Claims

1. A method for preparing carbon fiber reinforced SiC-SiBCN composite material, characterized in that, Includes the following steps: S1. The carbon fiber preform is immersed in liquid polyboron silazane precursor under vacuum conditions, the carbon fiber preform is removed and compressed, then crosslinked and cured, and the cured carbon fiber preform is pyrolyzed. S2. The product from the previous step is immersed in liquid polyborosilazane precursor under vacuum conditions, then removed, crosslinked and cured, and then pyrolyzed. S3. Repeat step S2 0~20 times; The product from the previous step was immersed in S4 and SiC ceramic precursors under vacuum conditions, then removed, crosslinked and cured, and then pyrolyzed. S5. Repeat step S4 until the weight gain of the composite material is ≤1%; The SiC ceramic precursor is a polycarbosilane containing heterogeneous elements; The pyrolysis is carried out under an inert atmosphere at a temperature of 800-1500°C for 0.2-10 hours.

2. The preparation method according to claim 1, characterized in that, The heterogeneous element is one or more of aluminum, iron, titanium, zirconium, cobalt, nickel, lanthanum, yttrium, and niobium.

3. The preparation method according to claim 1, characterized in that, The carbon fiber preform is a chopped carbon fiber preform; In the chopped carbon fiber preform, the length of the chopped carbon fiber is 0.1~100mm, and the volume fraction of the chopped carbon fiber is 5~25Vol.

4. The preparation method according to claim 1, characterized in that, In step S1, the step of compressing the carbon fiber preform includes: placing the carbon fiber preform in a flat fixture, applying pressure, and compressing the carbon fiber preform to a certain thickness. The applied pressure is 0.5~50MPa, and the certain thickness is 20~80% of the thickness of the carbon fiber preform.

5. The preparation method according to claim 1, characterized in that, The soaking time is 3 to 100 hours.

6. The preparation method according to claim 1, characterized in that, The cross-linking curing temperature is 70~200℃, and the cross-linking curing time is 1~30 hours.

7. The preparation method according to claim 1, characterized in that, Repeat step S2 at least twice.

8. The preparation method according to claim 1, characterized in that, The pyrolysis is carried out under an inert atmosphere at a temperature of 900-1200℃ for 0.5-5 hours.

9. A carbon fiber reinforced SiC-SiBCN composite material, characterized in that, The carbon fiber reinforced SiC-SiBCN composite material is prepared by any one of the preparation methods described in claims 1-8.

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