Method for improving mechanical property of silicon carbide fiber reinforced silicon carbide ceramic matrix composite material through high-temperature time-domain heat treatment

Abstract

The invention discloses a method for improving the mechanical property of a silicon carbide fiber reinforced silicon carbide ceramic-based composite material through high-temperature time-domain heat treatment, and belongs to the technical field of high-temperature heat treatment of ceramic-based composite materials. A PyC interface phase is prepared on the surface of a silicon carbide fiber through a chemical vapor deposition method, then a SiC matrix is prepared through a chemical vapor infiltration method for further densification, then the SiCf / SiC composite material is subjected to 1350 DEG C thermal scouring through high-temperature liquid oxygen-kerosene gas, and finally the SiCf / SiC ceramic-based composite material with better mechanical properties is obtained. The material can be applied to hot end parts (nose cones, front edges, spray pipes, flaps and the like) of aircrafts.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature heat treatment technology for ceramic matrix composites, and more specifically relates to a method for improving the mechanical properties of silicon carbide fiber-reinforced silicon carbide ceramic matrix composites through high-temperature time-domain heat treatment. Background Technology

[0002] With the development of thermal structural composite materials in the aerospace field, especially the rapidly increasing demand for ceramic matrix composites, the ever-increasing cruise speed of aircraft has brought new challenges to ceramic matrix composites. Hot-end components of aircraft, such as the nose cone, leading edge, nozzle, and flaps, require higher mechanical properties from ceramic matrix composites under dynamic thermal environments. f SiC composite materials are mainly composed of silicon carbide fibers, interface phases, and a SiC ceramic matrix. Silicon carbide fibers, acting as reinforcement, are the primary load-bearing unit of the ceramic material, providing mechanical strength and improving toughness, effectively mitigating the inherent brittleness caused by the short critical crack length and limited internal lattice slip systems. The SiC ceramic matrix, as the outer layer structure, primarily functions to transfer loads, protect the inner structure, and maintain the structural integrity of the ceramic material. f SiC composite thermal structural components are susceptible to erosion from combustion gases during long-term service in ultra-high-speed environments, which exacerbates oxidation damage and failure of internal components, leading to the degradation of SiC. f The mechanical properties of SiC composites decline sharply. Therefore, improving the mechanical properties of SiC... f The mechanical properties of SiC composites, and the impact of SiC f The design and engineering application of SiC composite materials are of great significance.

[0003] Based on this, the present invention is proposed. Summary of the Invention

[0004] The purpose of this invention is to provide a method for improving the mechanical properties of silicon carbide fiber-reinforced silicon carbide ceramic matrix composites through high-temperature time-domain heat treatment, thereby solving the problems existing in the prior art. This invention prepares a PyC interface phase on the surface of silicon carbide fibers using chemical vapor deposition, then further densifies the SiC matrix using chemical vapor infiltration, and finally densifies the SiC matrix using high-temperature liquid oxygen-kerosene fuel gas treatment. f The SiC composite material was subjected to hot scouring at 1350℃, ultimately yielding SiC with improved mechanical properties. f / SiC ceramic matrix composites.

[0005] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of this invention is to provide a method for improving the mechanical properties of silicon carbide fiber-reinforced silicon carbide ceramic matrix composites through high-temperature time-domain heat treatment, comprising the following steps: Silicon carbide fibers were woven into 2.5D plate-shaped preform samples and then heat-treated to obtain silicon carbide fiber preforms. A PyC interface phase is deposited on the surface of the silicon carbide fiber preform by chemical vapor deposition, resulting in a silicon carbide fiber preform sample with the PyC interface phase deposited. A SiC matrix was prepared by chemical vapor infiltration based on the silicon carbide fiber preform sample with deposited PyC interface phase, and then further densified to obtain SiC. f / PyC / SiC ceramic matrix composites; For the SiC f High-temperature time-domain heat treatment of PyC / SiC ceramic matrix composites yields silicon carbide fiber-reinforced silicon carbide ceramic matrix composites with improved mechanical properties.

[0006] Furthermore, the 2.5D plate-shaped precast specimen includes a 2.5D plate-shaped precast material-grade specimen or a 2.5D plate-shaped precast component-grade specimen.

[0007] Preferably, the heat treatment includes: heat treatment for 4 to 10 hours under an argon atmosphere and at a temperature of 300 to 500°C.

[0008] Preferably, the chemical vapor deposition includes: heating to 1000-1200°C at a heating rate of 5-7°C / min, introducing methane at a flow rate of 100-500 mL / min, introducing hydrogen at a flow rate of 100-300 mL / min, introducing argon at a flow rate of 200-450 mL / min, maintaining a vacuum of 1-5 kPa, and depositing for 1-3 hours.

[0009] Furthermore, the chemical vapor deposition includes: heating to 1100°C at a heating rate of 7°C / min, introducing methane at a flow rate of 500 mL / min, introducing hydrogen at a flow rate of 200 mL / min, introducing argon at a flow rate of 200 mL / min, maintaining a vacuum of 1~5 kPa, and depositing for 3 hours.

[0010] Preferably, the chemical vapor infiltration includes: heating to 1000-1400°C at a heating rate of 6-10°C / min, introducing trichloromethylsilane gas at a flow rate of 0.1-0.8 g / min, introducing hydrogen gas at a flow rate of 1-3 L / min, introducing argon gas at a flow rate of 200-400 mL / min, maintaining a vacuum of 1-5 kPa, and infiltrating for 10-20 h.

[0011] Furthermore, the chemical vapor infiltration includes: heating to 1200°C at a heating rate of 8°C / min, introducing trichloromethylsilane gas at a flow rate of 0.3 g / min, introducing hydrogen gas at a flow rate of 200 mL / min, introducing argon gas at a flow rate of 200 mL / min, maintaining a vacuum of 1~5 kPa, and infiltrating for 15 h.

[0012] Preferably, the high-temperature time-domain heat treatment includes a high-temperature thermal scouring treatment at 1350°C in liquid oxygen-kerosene fuel gas. Due to the high testing cost, the long-term service limit temperature of 1350°C for SiCf / SiC composite materials is used as the heat treatment temperature, which is also backward compatible.

[0013] Preferably, the parameters for the high-temperature thermal scouring treatment are set as follows: temperature is 1350℃, liquid oxygen partial pressure is 1~1.9 MPa, liquid oxygen flow rate is 250~290 L / min; kerosene partial pressure is 0.6~0.8 MPa, kerosene flow rate is 6~9 L / h, and time is 1~5 h.

[0014] The second technical solution of the present invention provides a silicon carbide fiber-reinforced silicon carbide ceramic matrix composite material with improved mechanical properties prepared by the above method.

[0015] The third technical solution of the present invention provides the application of silicon carbide fiber-reinforced silicon carbide ceramic matrix composite material with improved mechanical properties in the field of aircraft.

[0016] Furthermore, the application of silicon carbide fiber-reinforced silicon carbide ceramic matrix composites with improved mechanical properties in the field of aircraft specifically refers to the application of such composites in the hot-end parts of aircraft (nose cone, leading edge, nozzle, and flaps, etc.).

[0017] This invention first prepares a PyC interface phase on the surface of silicon carbide fibers using chemical vapor deposition. The formed PyC interface phase, through controllable weak interfacial effects, achieves toughening mechanisms such as crack deflection and fiber pull-out in the composite material, while simultaneously protecting the fibers and optimizing load transfer. Its selection is based on comprehensive performance, process controllability, and compatibility with CMC systems. Although oxidation resistance is a weakness, it can be mitigated through multilayer structural design (such as PyC / SiC). nLayering can effectively compensate for this, therefore PyC remains an irreplaceable interfacial phase in non-oxide CMCs. Further densification is achieved by preparing a SiC matrix using chemical vapor infiltration (CVI). The densification of the SiC matrix prepared by CVI is essentially a chemical vapor deposition process controlled by gas diffusion and surface reaction kinetics. Its core technology lies in precisely controlling temperature, pressure, gas flow, and chemical environment to allow SiC to slowly and uniformly deposit from the gas phase into every corner of the fiber preform's pores, achieving gradual filling from the pore walls to the center. Despite the challenge of lower efficiency, CVI remains a key method for preparing high-performance SiC due to its low damage to fibers and excellent microstructure controllability. f The irreplaceable key technology of SiC composite materials. Finally, SiC is processed using high-temperature liquid oxygen-kerosene fuel gas. f SiC composite materials were subjected to hot scouring at 1350℃. At 1350℃, a hot scouring time of 2-3 hours was considered the optimal process window, achieving a synergistic optimization of material strength and toughness. [The last sentence appears to be incomplete and possibly refers to a separate, unrelated statement about SiC hot scouring at 1350℃.] f The performance evolution of PyC / SiC composites is a multi-scale coupling result of the time-domain evolution of "PyC interface layer integrity-pore defect connectivity" and "micro-stress transfer-macro-mechanical response." This law clarifies the critical time domain for high-temperature performance degradation, providing experimental and theoretical basis for the micro-macro correlation in the high-temperature service life assessment of composites. This ensures that SiC with better mechanical properties is ultimately obtained. f / SiC ceramic matrix composites.

[0018] The present invention discloses the following technical effects: This invention utilizes high-temperature liquid oxygen-kerosene fuel gas to process SiC f PyC / SiC ceramic matrix composites were subjected to high-temperature time-domain treatment at 1350℃ to enhance the performance of SiC. f Mechanical properties of PyC / SiC ceramic matrix composites. The SiC composites containing a PyC interfacial phase prepared by this invention. f SiC ceramic matrix composites are relatively dense and exhibit good material properties. Furthermore, research indicates that high-temperature liquid oxygen-kerosene time-domain treatment at 1350℃ significantly improves the properties of SiC. f The PyC / SiC composite material exhibits a promoting effect on the improvement of mechanical properties. The tensile strength of the specimen after 2.5 hours in the time domain is significantly higher than that of the untreated SiC. f The PyC / SiC composite material (381.73±9.01MPa) was improved to 396.02±4.67MPa. The composite material prepared by this invention has a dense structure, excellent performance, controllable microstructure and composition, short preparation cycle, simple process, and low cost of high-temperature time-domain heat treatment. Attached Figure Description

[0019] Figure 1 Physical images of the high-temperature liquid oxygen-kerosene gas platform and high-temperature fixture used for thermal scouring of SiC / SiC ceramic matrix composite samples containing PyC interface phase. Figure 2 Cross-sectional SEM images (a, b) of a SiC / SiC ceramic matrix composite sample containing a PyC interface phase before thermal scouring, and the proportion of each component (c). Figure 3 The tensile stress-strain curves of SiC / SiC ceramic matrix composite samples containing PyC interface phase prepared in Examples 1 to 3 before and after hot scouring are shown. Among them, (a) is the tensile stress-strain curve of SiC / SiC ceramic matrix composite containing PyC interface phase without hot scouring, and (b) is the tensile stress-strain curve of SiC / SiC ceramic matrix composite containing PyC interface phase after hot scouring. Figure 4 The tensile stress-strain curve of the SiC / SiC ceramic matrix composite sample containing the PyC interface phase prepared for Comparative Example 1 after 10 hours of thermal scouring. Detailed Implementation

[0020] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0021] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0022] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0023] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0024] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0025] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0026] Unless otherwise specified, all raw materials used in the following embodiments and comparative examples of this invention are commercially available products, and the source of these commercially available products does not affect the technical effect of this invention.

[0027] Unless otherwise specified, the room temperature involved in this invention is 25±5℃.

[0028] Example 1 The 2.5D fiber preform is woven from silicon carbide fiber cloth (selected from Fujian Liya Company's third-generation silicon carbide fiber), and the initial dimensions of the 2.5D fiber preform are 200×150×4mm. 3 The fiber volume fraction was 25-30%. The 2.5D fiber preform was subjected to argon protection at 400℃ for 4 hours to remove the cured adhesive from the fiber surface. The preform was suspended in a vertical chemical vapor deposition (CVI) furnace using carbon rope. The furnace was heated to 1100℃ at a rate of 7℃ / min under Ar gas flow rate of 300 mL / min. The PyC interface phase was deposited using a CH4-H2-Ar system. The CVI process conditions for the PyC interface phase were: deposition chamber pressure 5 kPa, CH4 (99.99% purity), H2 (99.99% purity), and Ar (99.99% purity) gas flow rates of 500 mL / min, 200 mL / min, and 200 mL / min, respectively, with a deposition time of 3 hours. After deposition, the CH4 and H2 inlets were closed, and the Ar flow rate was adjusted to 100 mL / min to ensure the furnace chamber cooled under vacuum. Once the temperature drops below 500℃, turn off the furnace switch, shut off the Ar inlet, turn off the mechanical pump, and turn off the cooling water. After the temperature drops to room temperature, open the furnace to take a sample, and you will get a composite material sample with the PyC interface phase.

[0029] The composite material sample with the PyC interface phase was suspended in a silicon carbide deposition furnace. The furnace was heated to 1200℃ at a heating rate of 8℃ / min under Ar gas flow rate of 200 mL / min. The SiC matrix was deposited using a CH3Cl3Si(MTS)-H2-Ar system, where MTS volatilized into the deposition chamber. The CVI process conditions for the SiC matrix were: deposition chamber pressure 3 kPa; MTS flow rate 0.3 g / min; carrier gas H2 flow rate 2000 mL / min; dilution gas Ar flow rate 200 mL / min; deposition time 15 h. After deposition, the MTS inlet was closed, and the Ar flow rate was adjusted to 100 mL / min to ensure the furnace chamber cooled under vacuum. Once the temperature drops below 800℃, turn off the furnace switch, shut off the Ar inlet, turn off the mechanical pump, and turn off the cooling water. Keep the furnace chamber under vacuum. After the temperature drops to room temperature, open the furnace body to take a sample, and you will get a SiC / SiC ceramic matrix composite sample containing the PyC interface phase.

[0030] The prepared SiC / SiC ceramic matrix composite sample containing the PyC interface phase was placed in a fixture and passed through... Figure 1 The platform shown underwent high-temperature thermal scouring treatment at 1350℃ using liquid oxygen-kerosene fuel gas. The thermal scouring process conditions were: thermal scouring temperature 1350℃; liquid oxygen partial pressure 1.45 MPa, liquid oxygen flow rate 270 L / min; kerosene partial pressure 0.73 MPa, kerosene flow rate 7.9 L / h; thermal scouring time 2.5 h. After the thermal scouring time was completed, the heating switch was turned off, and the liquid oxygen and kerosene inlets were closed. Samples were taken after the temperature cooled to room temperature, yielding SiC with improved performance containing the PyC interface phase. f / SiC ceramic matrix composite sample.

[0031] Example 2 The 2.5D fiber preform is woven from silicon carbide fiber cloth (selected from Fujian Liya Company's third-generation silicon carbide fiber), and the initial dimensions of the 2.5D fiber preform are 200×150×4mm. 3The fiber volume fraction was 25-30%. The 2.5D fiber preform was subjected to argon protection at 400℃ for 4 hours to remove the cured adhesive from the fiber surface. The preform was suspended in a vertical chemical vapor deposition (CVI) furnace using carbon rope. The furnace was heated to 1100℃ at a rate of 7℃ / min under Ar gas flow rate of 300 mL / min. The PyC interface phase was deposited using a CH4-H2-Ar system. The CVI process conditions for the PyC interface phase were: deposition chamber pressure 5 kPa, CH4 (99.99% purity), H2 (99.99% purity), and Ar (99.99% purity) gas flow rates of 500 mL / min, 200 mL / min, and 200 mL / min, respectively, with a deposition time of 3 hours. After deposition, the CH4 and H2 inlets were closed, and the Ar flow rate was adjusted to 100 mL / min to ensure the furnace chamber cooled under vacuum. Once the temperature drops below 500℃, turn off the furnace switch, shut off the Ar inlet, turn off the mechanical pump, and turn off the cooling water. After the temperature drops to room temperature, open the furnace to take a sample, and you will get a composite material sample with the PyC interface phase.

[0032] The composite material sample with the PyC interface phase was suspended in a silicon carbide deposition furnace. The furnace was heated to 1200℃ at a heating rate of 8℃ / min under Ar gas flow rate of 200 mL / min. The SiC matrix was deposited using a CH3Cl3Si(MTS)-H2-Ar system, where MTS volatilized into the deposition chamber. The CVI process conditions for the SiC matrix were: deposition chamber pressure 3 kPa; MTS flow rate 0.3 g / min; carrier gas H2 flow rate 2000 mL / min; dilution gas Ar flow rate 200 mL / min; deposition time 15 h. After deposition, the MTS inlet was closed, and the Ar flow rate was adjusted to 100 mL / min to ensure the furnace chamber cooled under vacuum. Once the temperature drops below 800℃, turn off the furnace switch, shut off the Ar inlet, turn off the mechanical pump, and turn off the cooling water. Keep the furnace chamber under vacuum. After the temperature drops to room temperature, open the furnace body to take a sample, and you will get a SiC / SiC ceramic matrix composite sample containing the PyC interface phase.

[0033] The prepared SiC / SiC ceramic matrix composite sample containing the PyC interface phase was placed in a fixture and passed through... Figure 1The platform shown underwent high-temperature thermal scouring treatment at 1350℃ using liquid oxygen-kerosene fuel gas. The thermal scouring process conditions were: thermal scouring temperature 1350℃; liquid oxygen partial pressure 1.45 MPa, liquid oxygen flow rate 270 L / min; kerosene partial pressure 0.73 MPa, kerosene flow rate 7.9 L / h; thermal scouring time 1 hour. After the thermal scouring time was completed, the heating switch was turned off, and the liquid oxygen and kerosene inlets were closed. Samples were taken after cooling to room temperature to obtain SiC with improved performance containing the PyC interface phase. f / SiC ceramic matrix composite sample.

[0034] Example 3 The 2.5D fiber preform is woven from silicon carbide fiber cloth (selected from Fujian Liya Company's third-generation silicon carbide fiber), and the initial dimensions of the 2.5D fiber preform are 200×150×4mm. 3 The fiber volume fraction was 25-30%. The 2.5D fiber preform was subjected to argon protection at 400℃ for 4 hours to remove the cured adhesive from the fiber surface. The preform was suspended in a vertical chemical vapor deposition (CVI) furnace using carbon rope. The furnace was heated to 1100℃ at a rate of 7℃ / min under Ar gas flow rate of 300 mL / min. The PyC interface phase was deposited using a CH4-H2-Ar system. The CVI process conditions for the PyC interface phase were: deposition chamber pressure 5 kPa, CH4 (99.99% purity), H2 (99.99% purity), and Ar (99.99% purity) gas flow rates of 500 mL / min, 200 mL / min, and 200 mL / min, respectively, with a deposition time of 3 hours. After deposition, the CH4 and H2 inlets were closed, and the Ar flow rate was adjusted to 100 mL / min to ensure the furnace chamber cooled under vacuum. Once the temperature drops below 500℃, turn off the furnace switch, shut off the Ar inlet, turn off the mechanical pump, and turn off the cooling water. After the temperature drops to room temperature, open the furnace to take a sample, and you will get a composite material sample with the PyC interface phase.

[0035] The composite material sample with the PyC interface phase was suspended in a silicon carbide deposition furnace. The furnace was heated to 1200℃ at a heating rate of 8℃ / min under Ar gas flow rate of 200 mL / min. The SiC matrix was deposited using a CH3Cl3Si(MTS)-H2-Ar system, where MTS volatilized into the deposition chamber. The CVI process conditions for the SiC matrix were: deposition chamber pressure 3 kPa; MTS flow rate 0.3 g / min; carrier gas H2 flow rate 2000 mL / min; dilution gas Ar flow rate 200 mL / min; deposition time 15 h. After deposition, the MTS inlet was closed, and the Ar flow rate was adjusted to 100 mL / min to ensure the furnace chamber cooled under vacuum. Once the temperature drops below 800℃, turn off the furnace switch, shut off the Ar inlet, turn off the mechanical pump, and turn off the cooling water. Keep the furnace chamber under vacuum. After the temperature drops to room temperature, open the furnace body to take a sample, and you will get a SiC / SiC ceramic matrix composite sample containing the PyC interface phase.

[0036] The prepared SiC / SiC ceramic matrix composite sample containing the PyC interface phase was placed in a fixture and passed through... Figure 1 The platform shown underwent high-temperature thermal scouring treatment at 1350℃ using liquid oxygen-kerosene fuel gas. The thermal scouring process conditions were: thermal scouring temperature 1350℃; liquid oxygen partial pressure 1.45 MPa, liquid oxygen flow rate 270 L / min; kerosene partial pressure 0.73 MPa, kerosene flow rate 7.9 L / h; thermal scouring time 5 h. After the thermal scouring time was completed, the heating switch was turned off, and the liquid oxygen and kerosene inlets were closed. Samples were taken after cooling to room temperature to obtain SiC with improved performance containing the PyC interface phase. f / SiC ceramic matrix composite sample.

[0037] Figure 2 SEM images (a, b) of the cross section of the SiC / SiC ceramic matrix composite sample containing the PyC interface phase before thermal scouring, and the proportion of each component (c).

[0038] Tensile tests were conducted on the SiC / SiC ceramic matrix composite samples containing the PyC interface phase prepared in Examples 1-3 before and after thermal scouring: Reinforcing plates were attached to both ends of the specimen before the tensile test. The specimen was placed in a muffle furnace and cured at 60℃ for 2 hours. The specimen length was 150 mm. The tensile test was conducted on a general mechanical testing machine (UTM5105, SUNS, Shenzhen, China) at room temperature. The tensile speed was 0.2 mm / min, and the effective range of the tension sensor was 0~95000 N. The mechanical properties of the specimen after heat treatment were tested by room temperature tensile tests, and compared with the tensile properties of the specimen before heat treatment. Stress-strain curves were collected during the test, as shown in the figure. Figure 3 As shown.

[0039] Figure 3 The tensile stress-strain curves of the SiC / SiC ceramic matrix composite samples containing the PyC interface phase prepared in Examples 1-3 are shown before and after thermal scouring. (a) is the tensile stress-strain curve of the SiC / SiC ceramic matrix composite sample containing the PyC interface phase without thermal scouring, and (b) is the tensile stress-strain curve of the SiC / SiC ceramic matrix composite sample containing the PyC interface phase after thermal scouring. Figure 3 In (a), SC0-1 represents Example 1, SC0-2 represents Example 2, and SC0-3 represents Example 3. Figure 3 (b) In this example, SC1-1 represents Example 1, SC1-2 represents Example 2, and SC1-3 represents Example 3.

[0040] Depend on Figure 3 It can be seen that the SC0-1 specimen exhibits an "inflection point" at approximately 0.1% strain during the initial loading stage, indicating a change in the slope. This suggests that SiC... f The PyC / SiC composite matrix can effectively withstand the load in this stage. With increasing load, the matrix fractures, forming a second linear region characterized by stiffness degradation. Subsequently, the fibers are subjected to stress until peak flexural strength is reached. At this point, the SC0-1 curve drops sharply, indicating brittle fracture failure of the specimen. However, with time-domain thermal erosion treatment, the first linear segment of the stress-strain curves of SC1-1, SC1-2, and SC1-3 shows significant changes. Their "inflection point" shifts significantly forward, and the modulus of the first linear segment decreases significantly, seemingly approaching parallel to the second linear segment curve, only fluctuating with changes in the thermal erosion time domain. Furthermore, the changes in the fracture strain values ​​of the specimens were collected, which also reflects the changes in SiC with time-domain thermal erosion. fThe toughness variation of the PyC / SiC composite material was observed. After 1 hour of hot scouring, the toughness of the SC1-2 specimen significantly improved, with an average fracture strain of 0.78%. However, as the time domain increased, the toughness of the SC2 and SC3 specimens decreased significantly. Notably, in the figure, the tensile strengths of the SC1-2 specimen (393.04±8.46 MPa) after 1 hour of hot scouring and the SC1-1 specimen (396.02±4.67 MPa) after 2.5 hours of hot scouring were quite similar, higher than those of the SC1-3 specimen (387.65±5.63 MPa) after 5 hours of hot scouring, and both higher than those of the un-hot-scouring SC0-1 specimen (378.40±2.34 MPa). This is mainly because after heat treatment, the PyC layer begins to slightly graphitize, making its structure more ordered, possibly moderately reducing the interfacial bonding strength, making it closer to the ideal "weak interface" state, and releasing some internal stress, thus improving the mechanical properties of SC1-1. However, in Comparative Example 1, sample SC1-4, which underwent high-temperature heat scouting treatment for 10 hours, Figure 4 The performance degradation is clearly visible, which may be because the long-term heat treatment at 1350℃ may cause the PyC interface layer to react chemically with the SiC fiber or matrix, generating a brittle phase, which leads to a decrease in the strength and modulus of the fiber itself. This causes the stress-strain curve to revert to a shape similar to brittle ceramics, with almost no "plateau region".

[0041] Comparative Example 1 (the high-temperature heat scouring treatment time was adjusted to 10 hours) The 2.5D fiber preform is woven from silicon carbide fiber cloth (selected from Fujian Liya Company's third-generation silicon carbide fiber), and the initial dimensions of the 2.5D fiber preform are 200×150×4mm. 3 The fiber volume fraction was 25-30%. The 2.5D fiber preform was subjected to argon protection at 400℃ for 4 hours to remove the cured adhesive from the fiber surface. The preform was suspended in a vertical chemical vapor deposition (CVI) furnace using carbon rope. The furnace was heated to 1100℃ at a rate of 7℃ / min under Ar gas flow rate of 300 mL / min. The PyC interface phase was deposited using a CH4-H2-Ar system. The CVI process conditions for the PyC interface phase were: deposition chamber pressure 5 kPa, CH4 (99.99% purity), H2 (99.99% purity), and Ar (99.99% purity) gas flow rates of 500 mL / min, 200 mL / min, and 200 mL / min, respectively, with a deposition time of 3 hours. After deposition, the CH4 and H2 inlets were closed, and the Ar flow rate was adjusted to 100 mL / min to ensure the furnace chamber cooled under vacuum. Once the temperature drops below 500℃, turn off the furnace switch, shut off the Ar inlet, turn off the mechanical pump, and turn off the cooling water. After the temperature drops to room temperature, open the furnace to take a sample, and you will get a composite material sample with the PyC interface phase.

[0042] The composite material sample with the PyC interface phase was suspended in a silicon carbide deposition furnace. The furnace was heated to 1200℃ at a heating rate of 8℃ / min under Ar gas flow rate of 200 mL / min. The SiC matrix was deposited using a CH3Cl3Si(MTS)-H2-Ar system, where MTS volatilized into the deposition chamber. The CVI process conditions for the SiC matrix were: deposition chamber pressure 3 kPa; MTS flow rate 0.3 g / min; carrier gas H2 flow rate 2000 mL / min; dilution gas Ar flow rate 200 mL / min; deposition time 15 h. After deposition, the MTS inlet was closed, and the Ar flow rate was adjusted to 100 mL / min to ensure the furnace chamber cooled under vacuum. Once the temperature drops below 800℃, turn off the furnace switch, shut off the Ar inlet, turn off the mechanical pump, and turn off the cooling water. Keep the furnace chamber under vacuum. After the temperature drops to room temperature, open the furnace body to take a sample, and you will get a SiC / SiC ceramic matrix composite sample containing the PyC interface phase.

[0043] The prepared SiC / SiC ceramic matrix composite sample containing the PyC interface phase was placed in a fixture and passed through... Figure 1 The platform shown underwent high-temperature thermal scouring treatment at 1350℃ using liquid oxygen-kerosene fuel gas. The thermal scouring process conditions were: thermal scouring temperature 1350℃; liquid oxygen partial pressure 1.45 MPa, liquid oxygen flow rate 270 L / min; kerosene partial pressure 0.73 MPa, kerosene flow rate 7.9 L / h; thermal scouring time 10 h. After the thermal scouring time was completed, the heating switch was turned off, and the liquid oxygen and kerosene inlets were closed. Samples were taken after the temperature cooled to room temperature, yielding SiC containing the PyC interface phase. f / SiC ceramic matrix composite sample.

[0044] After preparation, a tensile test was performed, and the result was 259.56 ± 9.34 MPa, showing a significant decrease. This indicates that SiC... f After prolonged thermal scouring (more than 5 hours), the SiC composite material undergoes excessive oxidative degradation at the interface, resulting in an abnormally high fiber-matrix bonding strength, damage to the deep fiber structure, severe loosening of the matrix, and enhanced pore connectivity. This leads to the collapse of the fiber-interface-matrix synergistic load-bearing system, causing a severe decline in material performance.

[0045] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0046] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for improving the mechanical properties of silicon carbide fiber-reinforced silicon carbide ceramic matrix composites through high-temperature time-domain heat treatment, characterized in that, Includes the following steps: Silicon carbide fibers were woven into 2.5D plate-shaped preform samples and then heat-treated to obtain silicon carbide fiber preforms. A PyC interface phase is deposited on the surface of the silicon carbide fiber preform by chemical vapor deposition, resulting in a silicon carbide fiber preform sample with the PyC interface phase deposited. A SiC matrix was prepared by chemical vapor infiltration based on the silicon carbide fiber preform sample with deposited PyC interface phase, and then further densified to obtain SiC. f / PyC / SiC ceramic matrix composites; For the SiC f High-temperature time-domain heat treatment of PyC / SiC ceramic matrix composites yields silicon carbide fiber-reinforced silicon carbide ceramic matrix composites with improved mechanical properties.

2. The method according to claim 1, characterized in that, The heat treatment includes: heat treatment for 4 to 10 hours under an argon atmosphere and at a temperature of 300 to 500°C.

3. The method according to claim 1, characterized in that, The chemical vapor deposition process includes: heating to 1000-1200°C at a heating rate of 5-7°C / min, introducing methane at a flow rate of 100-500 mL / min, introducing hydrogen at a flow rate of 100-300 mL / min, introducing argon at a flow rate of 200-450 mL / min, maintaining a vacuum of 1-5 kPa, and depositing for 1-3 hours.

4. The method according to claim 3, characterized in that, The chemical vapor deposition process includes: heating to 1100°C at a heating rate of 7°C / min, introducing methane at a flow rate of 500 mL / min, introducing hydrogen at a flow rate of 200 mL / min, introducing argon at a flow rate of 200 mL / min, maintaining a vacuum of 1~5 kPa, and depositing for 3 hours.

5. The method according to claim 1, characterized in that, The chemical vapor infiltration process includes: heating to 1000-1400℃ at a heating rate of 6-10℃ / min, introducing trichloromethylsilane gas at a flow rate of 0.1-0.8 g / min, introducing hydrogen gas at a flow rate of 1-3 L / min, introducing argon gas at a flow rate of 200-400 mL / min, maintaining a vacuum of 1-5 kPa, and infiltrating for 10-20 h.

6. The method according to claim 5, characterized in that, The chemical vapor infiltration process includes: heating to 1200°C at a heating rate of 8°C / min, introducing trichloromethylsilane gas at a flow rate of 0.3 g / min, introducing hydrogen gas at a flow rate of 200 mL / min, introducing argon gas at a flow rate of 200 mL / min, maintaining a vacuum of 1~5 kPa, and infiltrating for 15 h.

7. The method according to claim 1, characterized in that, The high-temperature time-domain heat treatment includes a high-temperature thermal scouring treatment at 1350°C in liquid oxygen-kerosene gas.

8. The method according to claim 7, characterized in that, The parameters for the high-temperature thermal scouring treatment are set as follows: temperature is 1350℃, liquid oxygen partial pressure is 1~1.9Mpa, liquid oxygen flow rate is 250~290L / min; kerosene partial pressure is 0.6~0.8Mpa, kerosene flow rate is 6~9L / h, and time is 1~5h.

9. The silicon carbide fiber-reinforced silicon carbide ceramic matrix composite material with improved mechanical properties prepared by the method according to any one of claims 1 to 8.

10. The application of the silicon carbide fiber-reinforced silicon carbide ceramic matrix composite material with improved mechanical properties as described in claim 9 in the field of aircraft.

Images