Fiber-reinforced silicon carbide ceramic matrix composite and method of making same

Abstract

The application provides a fiber-reinforced silicon carbide ceramic matrix composite material and a preparation method thereof, and relates to the technical field of ceramic matrix composite materials.The preparation method comprises the following steps: pre-densification treatment;mixing a silicon source and a phenolic resin to obtain an impregnation solution;carrying out one-time impregnation on the obtained pre-densified preform;subjecting the preform after the one-time impregnation to one-time solidification and one-time heat treatment to obtain a first carbonization product;carrying out two-time impregnation on the first carbonization product;subjecting the first carbonization product after the two-time impregnation to two-time solidification and two-time heat treatment to obtain a second carbonization product;carrying out a molten silicon infiltration treatment on the second carbonization product to obtain the fiber-reinforced silicon carbide ceramic matrix composite material.The application adopts a step-by-step impregnation-carbonization process mode, compared with a traditional RMI (reactive melt infiltration) method, can effectively avoid the problem of high-temperature damage of fibers caused by the low melting point of silicon, and significantly improves the structural stability and mechanical properties of the composite material.

Description

Technical Field

[0001] This invention relates to the field of ceramic matrix composites, and in particular to a fiber-reinforced silicon carbide ceramic matrix composite and its preparation method. Background Technology

[0002] Carbon fiber and silicon carbide fiber, as novel high-performance fiber materials, possess excellent strength, modulus, and high-temperature resistance, making them ideal reinforcing materials for the preparation of high-performance ceramic matrix composites. Compared with traditional high-temperature alloy materials, carbon fiber reinforced silicon carbide matrix composites (C / SiC) exhibit superior properties such as low density, oxidation resistance, corrosion resistance, and thermal shock resistance, giving them broad application prospects in aerospace, automotive lightweighting, and high-temperature chemical industries.

[0003] However, current processes for preparing C / SiC composites still face some challenges. While traditional chemical vapor infiltration (CVI) and precursor impregnation pyrolysis (PIP) methods are mature, they suffer from drawbacks such as high manufacturing costs, long production cycles, and low material density. Reactive infiltration (RMI), on the other hand, offers advantages like short preparation cycles, low costs, and low residual porosity. However, the low melting point of silicon during preparation can easily damage fibers, affecting the material's mechanical properties.

[0004] To address these issues, researchers have been exploring new preparation processes. Among these, the use of silicon alloys as a method to lower the reaction melting temperature has attracted widespread attention. Furthermore, optimizing process parameters, such as impregnating Si-containing powders with mixed phenolic resins, can effectively improve the density and properties of the material. However, how to reduce manufacturing costs and improve production efficiency while ensuring material performance remains a pressing technical challenge.

[0005] Regarding solutions to the problems of complex and costly preparation processes for fiber-reinforced C / SiC matrix composites, several invention patents have been reported.

[0006] For example, CN107266075A discloses a C / C–SiC composite material and its preparation method, using chopped carbon fibers, carbon fiber plain weave fabric, phenolic resin, and industrial silicon powder as raw materials, which are obtained through molding, curing, carbonization, and melt infiltration processes. Although this method can achieve high density, the low fiber and high SiC design of the material surface results in high hardness and brittleness, making machining difficult, causing severe tool wear, and significantly increasing the cost and cycle of finishing, which is not conducive to large-scale mass production.

[0007] Patent CN103342570B discloses a low-cost molten silicon infiltration process for preparing C / SiC composite materials: First, carbon felt / graphite felt is pretreated by calcination at 400-600℃, then sequentially coated with a boron nitride protective layer, impregnated with carbon / silicon carbide slurry, and subjected to a single molten silicon infiltration at 1600-1800℃; subsequently, it is impregnated with phenolic resin and carbonized in an inert atmosphere at 800-1000℃, and finally subjected to a second molten silicon infiltration to obtain the C / SiC composite material. This material exhibits high density, low porosity and free silicon content, and excellent strength, toughness, and tribological properties, making it suitable for brake pad manufacturing. However, its process is lengthy and cumbersome, and mass production consistency control is difficult, requiring improvement.

[0008] In summary, existing technologies still have the following common drawbacks: 1. Traditional chemical vapor infiltration (CVI) and precursor impregnation pyrolysis (PIP) methods for preparing C / SiC composites suffer from problems such as high manufacturing costs, long production cycles, and low material density. 2. During the reactive infiltration (RMI) process, the low melting point of silicon can easily damage the fibers, affecting the mechanical properties of the material. 3. In the existing preparation process, the curing and carbonization process of carbon fiber reinforced resin composites needs to be further optimized in order to improve the carbon fiber content and performance. Summary of the Invention

[0009] One of the objectives of this invention is to provide a method for preparing fiber-reinforced silicon carbide ceramic matrix composites, so as to at least solve one of the technical problems existing in the prior art.

[0010] The second objective of this invention is to develop fiber-reinforced silicon carbide ceramic matrix composites.

[0011] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In a first aspect, the present invention provides a method for preparing fiber-reinforced silicon carbide ceramic matrix composite materials, comprising the following steps: (A) Pre-densification treatment of continuous carbon fiber braided preforms was carried out using chemical vapor infiltration; (B) Preparation of impregnation solution: The silicon source and phenolic resin are mixed to obtain the impregnation solution; (C) The pre-densified preform obtained in step (A) is impregnated once with the impregnation liquid obtained in step (B), and the preform after the first impregnation is subjected to a first curing and a first heat treatment to obtain the first carbonized product. (D) The first carbonized product is impregnated a second time, and the first carbonized product after the second impregnation is subjected to a second curing and a second heat treatment in sequence to obtain a second carbonized product; (E) The second carbide product is subjected to melt infiltration treatment to obtain the fiber-reinforced silicon carbide ceramic matrix composite material.

[0012] Furthermore, the deposition temperature for the pre-densification treatment is 1000-1050℃, the deposition time is 400-500 h, and the vacuum degree is 10. -2 -10 -3 Pa; Preferably, the gas used in the pre-densification process includes one or more of CH4, Ar and C2H2; the total flow rate of the gas used in the pre-densification process is 100-150 sccm.

[0013] Furthermore, step (A) also includes: performing a pretreatment before the pre-densification treatment; the pretreatment temperature is 1100-1300℃, and the pretreatment time is 1-3 h.

[0014] Furthermore, the silicon source includes at least one of silicon powder and silica powder; Preferably, the preparation process of the impregnation solution includes at least one of (a) to (f): (a) The silicon powder has a purity ≥99.9%, a particle size ≤1 μm, and a specific surface area of ​​20-30 m². 2 / g; (b) The silica powder has a purity ≥99.9%, a particle size ≤200 nm, and a specific surface area of ​​80-120 m². 2 / g; (c) The molecular weight of the phenolic resin is 350-400, and the free phenol content is ≤5%; (d) The mass ratio of the silicon powder to the silica powder is 65-75:25-35; (e) The raw materials for preparing the impregnation solution also include a dispersant, which includes at least one of a titanate coupling agent and a silane coupling agent; the amount of the titanate coupling agent added is 0.5%-1% of the total mass of the silica powder and phenolic resin mixture; the amount of the silane coupling agent added is 0.5%-1% of the total mass of the silica powder, silica powder and phenolic resin mixture. (f) The solid content of the impregnation solution is 60%-70%.

[0015] Furthermore, the primary impregnation is either vacuum impregnation or pressure impregnation; wherein, the vacuum degree of vacuum impregnation is 10. -2 -10 -1 The impregnation time is 2-3 h; the pressure of the pressure impregnation is 2-3 MPa, and the heat and pressure holding time is 40-80 min.

[0016] Furthermore, the primary curing temperature is 170-200℃ and the time is 1-3h; or, the primary curing is segmented curing, the first stage of the primary curing temperature is 100-150℃ and the time is 0.5-2h, and the second stage of the primary curing temperature is 160-200℃ and the time is 1-3h. Preferably, the temperature of the first heat treatment is 1600-1800℃, and the time is 1-3h.

[0017] Furthermore, the secondary impregnation is either vacuum impregnation or pressure impregnation; wherein, the vacuum degree of vacuum impregnation is 10. -2 -10 -1 The impregnation time is 1-2 hours; the pressure of the pressure impregnation is 2-3 MPa, and the heat and pressure holding time is 40-60 minutes.

[0018] Furthermore, the secondary curing temperature is 170-200℃, and the time is 1-3 hours; Preferably, the temperature of the secondary heat treatment is 1800-2000℃, and the time is 1-3h.

[0019] Furthermore, the fused silica treatment employs a powder embedding method; the silicon particle size is 1-3 mm; and the vacuum degree is 10. -4 -10 - 3 Pa; the temperature of the molten silicon infiltration treatment is 1600-1900℃; the holding time is 1-2h.

[0020] Secondly, the present invention provides a fiber-reinforced silicon carbide ceramic matrix composite material, which is prepared by the aforementioned preparation method.

[0021] Compared with the prior art, the present invention has the following beneficial effects: The method for preparing fiber-reinforced silicon carbide ceramic matrix composite material provided by the present invention first performs chemical vapor infiltration pre-densification on a continuous carbon fiber woven preform, then performs two cycles of impregnation-curing-heat treatment, and finally performs melt infiltration, thereby achieving synergistic densification of CVI process and reaction precursor impregnation pyrolysis.

[0022] The pre-densification treatment constructs a stable carbon skeleton between fiber bundles, preventing localized accumulation or pore blockage caused by uneven capillary forces during subsequent resin impregnation, and providing mechanical support for the carbonization products. The silicon, silica, and carbon sources are integrated into the impregnation solution, enabling them to synergistically react and generate silicon carbide during subsequent heat treatment. The first impregnation and corresponding heat treatment achieve initial filling of the impregnation solution and cross-linking and curing of the resin. Heat treatment also carbonizes some phenolic resin and induces in-situ reactions between Si and SiO2, forming the initial silicon carbide phase and carbon network. The second impregnation and corresponding heat treatment replenish the carbon source content, further filling residual pores, increasing the degree of carbonization and silicon carbide formation, and enhancing the compactness and structural integrity of the preform. Finally, the second carbonization product undergoes melt infiltration treatment, using the previously formed continuous porous carbide skeleton to guide the directional infiltration and full reaction of liquid silicon, ultimately obtaining a fiber-reinforced silicon carbide ceramic matrix composite. The resulting composite material exhibits high density, structural stability, and excellent mechanical properties, with a short preparation cycle and good process repeatability. Detailed Implementation

[0023] Unless otherwise defined herein, the scientific and technical terms used in conjunction with this invention shall have the meanings commonly understood by one of ordinary skill in the art. The meaning and scope of terms shall be clear; however, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or foreign definitions. In this application, unless otherwise stated, the use of "or" means "and / or". Furthermore, the use of the term "comprising" and other forms is non-limiting.

[0024] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] In a first aspect, the present invention provides a method for preparing fiber-reinforced silicon carbide ceramic matrix composite materials, comprising the following steps: (A) The continuous carbon fiber braided preform is pre-densified by chemical vapor infiltration. The core function of this step is to construct the initial C matrix skeleton. Optionally, the density of the preform can reach 45%~55%, which provides stable support for the subsequent impregnation process and avoids excessive shrinkage of the fiber during the subsequent high-temperature treatment. (B) Preparation of impregnation solution: Silicon powder, silica powder and phenolic resin are mixed to obtain impregnation solution; this step can avoid Si source agglomeration by controlling the particle size of Si source and dispersion process, and ensure the sufficiency of subsequent reactions.

[0026] (C) The pre-densified preform obtained in step (A) is impregnated once with the impregnation liquid obtained in step (B), and the preform after the first impregnation is subjected to a first curing and a first heat treatment to obtain the first carbonized product. (D) The first carbonized product is impregnated a second time, and the first carbonized product after the second impregnation is subjected to a second curing and a second heat treatment in sequence to obtain a second carbonized product; (E) The second carbide product is subjected to melt infiltration treatment to obtain the fiber-reinforced silicon carbide ceramic matrix composite material.

[0027] This invention adopts a step-by-step process route of "impregnation-carbonization-secondary impregnation-carbonization-molten silicon infiltration". Compared with the traditional CVI (chemical vapor infiltration) and PIP (polymer impregnation pyrolysis) methods, it significantly reduces manufacturing costs, significantly improves production efficiency, and effectively solves the technical problems of high cost and long production cycle of traditional processes.

[0028] In this invention, a pre-densification treatment is performed using chemical vapor infiltration (CVI) technology. During the densification process, a pyrolytic carbon (PyC) layer of controllable thickness can be formed on the carbon fiber surface, which builds a reliable initial protective barrier for the carbon fiber and effectively avoids early damage to the fiber caused by subsequent processes.

[0029] This invention also optimizes process parameters by using a mixture of phenolic resin and Si-containing powder for impregnation treatment. This not only effectively improves the density of the composite material and reduces the internal porosity, but also builds a dense protective barrier for the carbon fiber, effectively blocking the erosion of the carbon fiber by molten Si during the melt infiltration process, thereby significantly improving the mechanical properties of the material.

[0030] Furthermore, the present invention adopts a step-by-step impregnation-carbonization process mode, which, compared with the traditional RMI (reactive infiltration) method, can effectively avoid the problem of high-temperature fiber damage caused by the low melting point of silicon, and significantly improve the structural stability and mechanical properties of the composite material.

[0031] In some preferred embodiments, the continuous carbon fiber is of T300 or T700 grade.

[0032] In some preferred embodiments, the deposition temperature of the pre-densification treatment is 1000-1050℃, for example, 1000℃, 1010℃, 1020℃, 1030℃, 1040℃, 1050℃, etc., and the deposition time is 400-500 h, for example, 400 h, 450 h, 500 h, etc., with a vacuum degree of 10. -2 -10 -3 Pa.

[0033] Preferably, the gas used in the pre-densification process includes one or more of CH4, Ar and C2H2; the total flow rate of the gas used in the pre-densification process is 100-150 sccm, for example, it can be 100 sccm, 110 sccm, 120 sccm, 130 sccm, 140 sccm, 150 sccm, etc.

[0034] In some preferred embodiments, step (A) further includes: performing a pretreatment before the pre-densification treatment; the temperature of the pretreatment is 1100-1300℃, for example, 1100℃, 1200℃, 1300℃, etc., and the time of the pretreatment is 1-3 h, for example, 1 h, 2 h, 3 h, etc.

[0035] In some preferred embodiments, the preparation process of the impregnation solution includes at least one of (a) to (f): (a) The silicon powder has a purity ≥99.9%, a particle size ≤1 μm, and a specific surface area of ​​20-30 m². 2 / g.

[0036] (b) The silica powder has a purity ≥99.9%, a particle size ≤200 nm, and a specific surface area of ​​80-120 m². 2 / g.

[0037] (c) The molecular weight of the phenolic resin is 350-400, and the free phenol content is ≤5%.

[0038] (d) The mass ratio of the silicon powder to the silica powder is 65-75:25-35; where “65-75” can be, for example, 65, 70, 75, etc., and “25-35” can be, for example, 25, 30, 35, etc.

[0039] (e) The raw materials for preparing the impregnation solution also include a dispersant, which includes at least one of a titanate coupling agent and a silane coupling agent; the amount of the titanate coupling agent added is 0.5%-1% of the total mass of the mixture of silica powder and phenolic resin, for example, it can be 0.5%, 0.75%, 1%, etc.; the amount of the silane coupling agent added is 0.5-1% of the total mass of the mixture of silica powder, silica powder and phenolic resin, for example, it can be 0.5%, 0.75%, 1%, etc.

[0040] (f) The solid content of the impregnation liquid is 60%-70%, for example, it can be 60%, 65%, 70%, etc.

[0041] This invention uses large and small particle size powders to disperse Si powder (particle size ≤ 1 μm, specific surface area ceramic 20-30 m²). 2 / g) and SiO2 powder with a purity ≥99.9% (particle size ≤200nm, specific surface area 80-120m²). 2 Large-diameter powder particles form gaps, which small-diameter powder particles can fill, preventing particle agglomeration due to gaps. Simultaneously, increased bulk density allows phenolic resin to more uniformly coat the powder surface, reducing van der Waals forces between particles and improving dispersion stability. Furthermore, mixing different particle sizes reduces interparticle friction, resulting in better resin slurry flowability and easier uniform dispersion. Additionally, small-diameter powder particles can fill the interfacial gaps between large-diameter powder and phenolic resin, increasing the contact area between powder and resin, reducing interfacial defects, and improving the material's mechanical strength.

[0042] In some preferred embodiments, the primary impregnation is vacuum impregnation or pressure impregnation, which can improve the filling effect of the impregnation liquid on micropores.

[0043] The vacuum degree of vacuum impregnation is 10. -2 -10 -1 The impregnation time is 2-3 hours, for example, 2 hours, 2.5 hours, 3 hours, etc.; the pressure of the pressurized impregnation is 2-3 MPa, for example, 2 MPa, 2.5 MPa, 3 MPa, etc.; the heat and pressure holding time is 40-80 minutes, for example, 40 minutes, 50 minutes, 60 minutes, 70 minutes, 80 minutes, etc.

[0044] In some preferred embodiments, the temperature of the first curing is 170-200℃, for example, 170℃, 180℃, 190℃, 200℃, etc., and the time is 1-3h, for example, 1h, 2h, 3h, etc.

[0045] As an alternative implementation, the primary curing temperature is staged curing, with the first stage temperature being 100-150℃ and the time being 0.5-2h, and the second stage temperature being 160-200℃ and the time being 1-3h.

[0046] In some preferred embodiments, the temperature of the first heat treatment is 1600-1800℃, for example, 1600℃, 1700℃, 1800℃, etc., and the time is 1-3h, for example, 1h, 2h, 3h, etc.

[0047] In some preferred embodiments, the secondary impregnation is vacuum impregnation or pressure impregnation.

[0048] The vacuum degree of vacuum impregnation is 10. -2 -10 -1Pa, the impregnation time is 1-2h, for example, 1h, 1.5h, 2h, etc.; the pressure of the pressurized impregnation is 2-3 MPa, for example, 2 MPa, 2.5 MPa, 3 MPa, etc., and the heat and pressure holding time is 40-60 min, for example, 40 min, 50 min, 60 min, etc.

[0049] In some preferred embodiments, the secondary curing temperature is 170-200℃, for example, 170℃, 180℃, 190℃, 200℃, etc., and the time is 1-3h, for example, 1h, 2h, 3h, etc.

[0050] In some preferred embodiments, the temperature of the secondary heat treatment is 1800-2000℃, for example, 1800℃, 1900℃, 2000℃, etc., and the time is 1-3h, for example, 1h, 2h, 3h, etc.

[0051] In some preferred embodiments, the fused silica treatment employs a powder embedding method; the silicon particle size is 1-3 mm, for example, 1 mm, 2 mm, 3 mm, etc.; the vacuum degree is 10. -4 -10 -3 Pa; the temperature of the molten silicon infiltration treatment is 1600-1900℃, for example, it can be 1600℃, 1700℃, 1800℃, 1900℃, etc.; the holding time is 1-2h, for example, it can be 1h, 1.5h, 2h, etc.

[0052] A second aspect of the present invention provides a fiber-reinforced silicon carbide ceramic matrix composite material, which is prepared by the aforementioned preparation method.

[0053] The present invention will be further illustrated by the following examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0054] Example 1 This embodiment provides a fiber-reinforced silicon carbide ceramic matrix composite material, the preparation process of which is as follows: Step 1: Pretreatment and CVI pre-densification of carbon fiber preforms: Select T700 grade carbon fiber woven preforms and pretreat them at 1200℃ in an Ar atmosphere for 2 hours; place them in a CVI furnace with a vacuum degree of 10. -2 Pa, deposition time 480h, CH4:Ar:C2H2=20:40:5 (volume ratio), deposition temperature 1020℃, heating rate 5℃ / min, total gas flow rate 120sccm, pre-densification preform density 50% (i.e., relative to the fully densified sample, density is 50%, 50% is porosity).

[0055] Step 2, Preparation of impregnation solution: Si powder with a purity of 99.99% (particle size 0.8μm, specific surface area 25m²) was selected. 2 / g) and SiO2 powder with a purity of 99.99% (particle size 180nm, specific surface area 100m²) 2 / g) was used as the Si source, and the mass ratio of the two was controlled at 70:30; thermosetting liquid phenolic resin (molecular weight 380, free phenol content 3.2%) was selected as the solvent and C source.

[0056] First, add liquid phenolic resin to a high-speed mixing tank, start stirring and slowly add Si powder, while simultaneously adding 0.8% (by mass) of titanate coupling agent (NDZ-101) to the mixture (Si powder + phenolic resin). Adjust the stirring speed to 1500 r / min and continue stirring for 30 min to initially disperse the Si powder. Then, reduce the stirring speed to 800 r / min and slowly add SiO2 powder, while simultaneously adding 0.7% (by mass) of silane coupling agent (Si powder + SiO2 powder + phenolic resin) to the mixture. KH-560), close the mixing tank, transfer the material to the ultrasonic disperser, set the power to 300W and the frequency to 40kHz, and ultrasonically disperse for 20min; after ultrasonication, put the material into a planetary ball mill, select zirconia balls as the grinding medium, control the ball-to-material ratio to 5:1 and the rotation speed to 300r / min, and ball mill for 2h to ensure that Si / SiO2 powder is uniformly dispersed in the resin solution, and obtain a Si / SiO2 / phenolic resin impregnation solution with a solid content of 65%. Place the impregnation solution in a vacuum drying oven and let it stand for 2h to remove bubbles, and set aside for later use.

[0057] Step 3, Vacuum Impregnation: Fix the preform after CVI pre-densification in Step 1 onto the bracket inside the impregnation tank, close the impregnation tank and start the vacuum pump to evacuate the vacuum inside the tank to 8×10⁻⁶. -2 Maintain this vacuum level for 30 minutes to ensure that all air is expelled from the pores inside the preform. Then, slowly inject the impregnation solution prepared in step 2 through the infusion pipeline. After injection, maintain the vacuum state and continue impregnation for 2.5 hours to ensure that the impregnation solution fully fills the pores inside the preform. After impregnation, stop vacuuming, slowly release the pressure to normal atmospheric pressure, remove the preform, and use a scraper to remove excess impregnation solution from the surface.

[0058] Step 4, Curing and Heat Treatment: Place the impregnated preform into a forced-air oven, set the temperature to 180℃, and cure at a constant temperature for 2 hours. Monitor the temperature inside the oven in real time during the curing process to ensure temperature uniformity. After curing, take out the sample and place it in a normal pressure graphite furnace. Introduce Ar gas as a protective atmosphere, control the heating rate to 5℃ / min, raise the temperature to 1700℃, hold for 2 hours, and then allow it to cool naturally to room temperature to complete the high-temperature heat treatment.

[0059] Step 5, Vacuum Impregnation: Fix the sample from Step 4 onto the support inside the impregnation tank, close the impregnation tank and start the vacuum pump to evacuate the tank to a vacuum level of 8 × 10⁻⁶. -2 The vacuum level was maintained at 280 Pa for 20 minutes to ensure that all air was expelled from the pores inside the preform. Then, thermosetting liquid phenolic resin (molecular weight 380, free phenol content 3.2%) was slowly injected through an infusion line as the impregnation solution. After injection, the vacuum was maintained for 1 hour to ensure that the impregnation solution fully filled the pores inside the preform. After impregnation, the vacuum was stopped, and the pressure was slowly released to atmospheric pressure. The preform was then removed, and excess impregnation solution was removed from the surface using a scraper.

[0060] Step 6, Curing and Heat Treatment: Place the impregnated preform into a forced-air oven, set the temperature to 180℃, and cure at a constant temperature for 2 hours. During the curing process, monitor the temperature inside the oven in real time to ensure temperature uniformity. After curing, take out the sample and place it in a normal pressure graphite furnace. Introduce Ar gas as a protective atmosphere, control the heating rate to 5℃ / min, raise the temperature to 1900℃, hold for 2 hours, and then allow it to cool naturally to room temperature to complete the high-temperature heat treatment.

[0061] Step 7, Melt Infiltration: Si particle size 2mm (purity 99.99%), vacuum infiltration furnace 10 -3 Pa, held at 1750℃ for 1.5h, heating rate 9℃ / min, cooling rate 2℃ / min, and after cooling, surface impurities were removed to obtain fiber-reinforced C / SiC material.

[0062] Example 2 This embodiment provides a fiber-reinforced silicon carbide ceramic matrix composite material, which differs from Embodiment 1 in that: Step 3 involves pressurized impregnation: The preform with CVI pre-densification is placed in an impregnation tank, and the impregnation solution prepared in Step 2 is injected to ensure that the preform is completely submerged in the solution. High-purity nitrogen is then introduced into the impregnation tank, and the pressure is slowly increased to 2.5 MPa while maintaining the tank temperature at room temperature. This pressure and temperature hold time is maintained for 70 minutes to enhance the filling effect of the impregnation solution on the micropores. After impregnation, the pressure is slowly released to atmospheric pressure, the preform is removed, and excess impregnation solution is removed from the surface. Step 5 involves pressurized impregnation: The sample from Step 4 is fixed in an impregnation tank, and then thermosetting liquid phenolic resin (molecular weight 360, free phenol content 4.0%) is slowly injected through an infusion pipeline as the impregnation solution, ensuring that the preform is completely submerged in the impregnation solution; then, high-purity nitrogen gas is introduced into the impregnation tank, and the pressure is slowly increased to 2.5 MPa, while maintaining the temperature inside the tank at room temperature, and the pressure is maintained for 45 minutes. After impregnation is completed, the pressure is slowly released to atmospheric pressure, the preform is removed, and excess impregnation solution is removed from the surface.

[0063] Example 3 This embodiment provides a fiber-reinforced silicon carbide ceramic matrix composite material, which differs from Embodiment 1 in that: In step 1, the deposition temperature is 1000℃, the total gas flow rate is 150 sccm, and the density of the preform after pre-densification is 55%. In step 2, the mass ratio of Si powder to SiO2 powder is 75:25; an impregnation solution with a solid content of 70% is obtained. In step 3, the soaking time is 2 hours; In step 4, the product is cured in a forced-air oven at 170°C for 3 hours and then heat-treated at 1800°C for 1 hour. In step 5, the soaking time is 2 hours; In step 6, heat treatment is performed at 1800℃ for 3 hours; In step 7, maintain the temperature at 1900℃ for 1 hour.

[0064] Example 4 This embodiment provides a fiber-reinforced silicon carbide ceramic matrix composite material, which differs from Embodiment 1 in that: In step 1, the deposition temperature was 1050℃, the total gas flow rate was 100 sccm, and the density of the preform after pre-densification was 48%. In step 2, the mass ratio of Si powder to SiO2 powder is 65:35; an impregnation solution with a solid content of 60% is obtained. In step 3, the soaking time is 3 hours; In step 4, the product is cured in a forced-air oven at 200°C for 1 hour and then heat-treated at 1600°C for 3 hours. In step 5, the soaking time is 1 hour; In step 6, heat treatment is performed at 2000℃ for 1 hour; In step 7, maintain the temperature at 1600℃ for 2 hours.

[0065] Example 5 This embodiment provides a fiber-reinforced silicon carbide ceramic matrix composite material, which differs from Embodiment 2 in that: In step 1, the carbon fiber woven preform is of grade T300; In step 2, the Si powder has a particle size of 0.9 μm and a specific surface area of ​​22 m². 2 / g, SiO2 powder with a particle size of 150nm and a specific surface area of ​​100m² 2 / g; add titanate coupling agent (NDZ-101) accounting for 0.9% of the mass fraction of the mixed system (Si powder + phenolic resin); add silane coupling agent (KH-560) accounting for 0.8% of the mass fraction of the mixed system (Si powder + SiO2 powder + phenolic resin); and prepare an impregnation solution with a solid content of 68%. In step 3, pressurize to 3MPa and maintain the pressure and temperature for 40 minutes; In step 5, pressurize to 2 MPa and maintain the pressure and temperature for 60 minutes.

[0066] Example 6 This embodiment provides a fiber-reinforced silicon carbide ceramic matrix composite material, which differs from Embodiment 2 in that: in step 3, the pressure is increased to 2MPa and held at temperature and pressure for 80min; in step 5, the pressure is increased to 3MPa and held at temperature and pressure for 40min.

[0067] Example 7 This embodiment provides a fiber-reinforced silicon carbide ceramic matrix composite material, which differs from Embodiment 1 in that the Si powder has a particle size of 1.5 μm and a specific surface area of ​​15 m². 2 / g.

[0068] Example 8 This embodiment provides a fiber-reinforced silicon carbide ceramic matrix composite material, which differs from Embodiment 1 in that the SiO2 powder has a particle size of 400 nm and a specific surface area of ​​70 m². 2 / g.

[0069] Example 9 This embodiment provides a fiber-reinforced silicon carbide ceramic matrix composite material, which differs from Embodiment 1 in that: in step 2, SiO2 powder is not added to the impregnation liquid raw material.

[0070] Comparative Example 1 This comparative example provides a fiber-reinforced silicon carbide ceramic matrix composite material, which differs from Example 1 in that: in step 3, the impregnation time is 3 hours; and steps 5 and 6 are omitted, i.e., only one impregnation is performed.

[0071] Comparative Example 2 This comparative example provides a fiber-reinforced silicon carbide ceramic matrix composite material, which differs from Example 2 in that: in step 3, the impregnation time is 2 hours; and steps 5 and 6 are omitted, i.e., only one impregnation is performed.

[0072] Test case The composite materials prepared in the above embodiments and comparative examples were tested.

[0073] Test method: The bending strength is tested by the three-point bending method using a universal testing machine.

[0074] The test results are shown in Table 1.

[0075] Table 1

[0076] As shown in Table 1, Examples 1 and 2 exhibit superior performance, representing excellent results under vacuum impregnation and pressure impregnation processes, respectively, thus verifying the effectiveness of the overall route of double impregnation-carbonization-melt infiltration. Examples 3-6 show moderate strength, and their differences reflect that CVI pre-densification parameters (such as deposition temperature and gas flow rate), heat treatment regime (such as primary / secondary heat treatment temperature and time), and carbon fiber grade (such as T700 and T300) are key factors in performance control.

[0077] The strength of Examples 7, 8, and 9 further decreased, indicating that the particle size distribution, specific surface area matching, and synergistic reaction design of Si powder and SiO2 powder in the impregnation solution play an important role in the in-situ generation of a uniform silicon carbide phase, suppression of agglomeration, and improvement of resin coating and pore filling.

[0078] Comparative Examples 1 and 2 showed the lowest strength, significantly lower than all other examples, clearly demonstrating that a single impregnation could not provide sufficient carbon source replenishment and skeletal reinforcement, resulting in severely inadequate final mechanical properties.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a fiber-reinforced silicon carbide ceramic matrix composite material, characterized in that, Includes the following steps: (A) Pre-densification treatment of continuous carbon fiber braided preforms was carried out using chemical vapor infiltration; (B) Preparation of impregnation solution: The silicon source and phenolic resin are mixed to obtain the impregnation solution; (C) The pre-densified preform obtained in step (A) is impregnated once with the impregnation liquid obtained in step (B), and the preform after the first impregnation is subjected to a first curing and a first heat treatment to obtain the first carbonized product. (D) The first carbonized product is impregnated a second time, and the first carbonized product after the second impregnation is subjected to a second curing and a second heat treatment in sequence to obtain a second carbonized product; (E) The second carbide product is subjected to melt-infiltrating silicon treatment to obtain the fiber-reinforced silicon carbide ceramic matrix composite material.

2. The preparation method according to claim 1, characterized in that, The pre-densification treatment was carried out at a deposition temperature of 1000-1050℃, a deposition time of 400-500 h, and a vacuum degree of 10. -2 -10 -3 Pa; Preferably, the gas used in the pre-densification process includes one or more of CH4, Ar and C2H2; the total flow rate of the gas used in the pre-densification process is 100-150 sccm.

3. The preparation method according to claim 1, characterized in that, Step (A) further includes: performing a pretreatment before the pre-densification treatment; the temperature of the pretreatment is 1100-1300℃, and the time of the pretreatment is 1-3 h.

4. The preparation method according to claim 1, characterized in that, The silicon source includes at least one of silicon powder and silica powder; Preferably, the preparation process of the impregnation solution includes at least one of (a) to (f): (a) The silicon powder has a purity of ≥99.9%, a particle size of ≤1 μm, and a specific surface area of ​​20-30 m². 2 / g; (b) The silica powder has a purity ≥99.9%, a particle size ≤200 nm, and a specific surface area of ​​80-120 m². 2 / g; (c) The molecular weight of the phenolic resin is 350-400, and the free phenol content is ≤5%; (d) The mass ratio of the silicon powder to the silica powder is 65-75:25-35; (e) The raw materials for preparing the impregnation solution also include a dispersant, which includes at least one of a titanate coupling agent and a silane coupling agent; the amount of the titanate coupling agent added is 0.5%-1% of the total mass of the silica powder and phenolic resin mixture; the amount of the silane coupling agent added is 0.5%-1% of the total mass of the silica powder, silica powder and phenolic resin mixture. (f) The solid content of the impregnation solution is 60%-70%.

5. The preparation method according to claim 1, characterized in that, The first impregnation is either vacuum impregnation or pressure impregnation; wherein, the vacuum degree of vacuum impregnation is 10. -2 -10 -1 The impregnation time is 2-3 hours; the pressure for the pressurized impregnation is 2-3 MPa, and the heat and pressure holding time is 40-80 minutes.

6. The preparation method according to claim 1, characterized in that, The primary curing temperature is 170-200℃ and the time is 1-3 hours; or, the primary curing is a staged curing, the first stage of the primary curing is 100-150℃ and the time is 0.5-2 hours, and the second stage of the primary curing is 160-200℃ and the time is 1-3 hours. Preferably, the temperature of the first heat treatment is 1600-1800℃, and the time is 1-3h.

7. The preparation method according to claim 1, characterized in that, The secondary impregnation is either vacuum impregnation or pressure impregnation; wherein, the vacuum degree of vacuum impregnation is 10. -2 -10 -1 The impregnation time is 1-2 hours; the pressure for the pressurized impregnation is 2-3 MPa, and the heat and pressure holding time is 40-60 minutes.

8. The preparation method according to claim 1, characterized in that, The secondary curing temperature is 170-200℃, and the time is 1-3 hours; Preferably, the temperature of the secondary heat treatment is 1800-2000℃, and the time is 1-3h.

9. The preparation method according to claim 1, characterized in that, The fused silica treatment employs a powder embedding method; the silicon particle size is 1-3 mm; and the vacuum degree is 10. -4 -10 -3 Pa; the temperature of the molten silicon infiltration treatment is 1600-1900℃; the holding time is 1-2h.

10. A fiber-reinforced silicon carbide ceramic matrix composite material, characterized in that, It is prepared by the preparation method according to any one of claims 1-9.

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