Silicon carbide fiber-reinforced silicon carbide composite material and method of making the same

Abstract

The application provides a preparation method of a silicon carbide fiber reinforced silicon carbide composite material, comprising the following steps: step 1: taking a silicon carbide fiber cloth, and using a CVI deposition furnace to prepare a fiber surface interface layer, step 2: laying and sewing the fiber cloth with the surface deposition interface layer in step 1 to obtain a fiber preform, step 3: using a CVI process to deposit the fiber preform to obtain a part of SiC matrix, fill the pores in the fiber bundle with the SiC matrix to obtain a SiC / SiC (SiC) porous blank, and step 4: densifying the SiC / SiC (SiC) porous blank through slurry infusion and silicon infiltration to obtain the silicon carbide fiber reinforced silicon carbide composite material. In the application, the silicon carbide fiber cloth is directly used as a deposition object of the interface layer, the interface layer is first deposited on the silicon carbide fiber cloth, and then the fiber preform is obtained through laying and sewing, so that the problem of uneven deposition of the interface layer in the fiber preform can be effectively avoided, the consistency of the performance in the preform is ensured, and the mechanical property uniformity of the composite material is improved.

Description

Technical Field

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

[0002] Currently, silicon carbide fiber-reinforced silicon carbide composites are prepared using a composite process combining CVI (Cryogenic Fiber Interchange) with RMI (Reverse Motion Injection) or PIP (Polymerization Injection) processes. This composite process avoids the drawbacks of single-process methods and yields composites with superior performance. The traditional process for preparing ceramic matrix composite components involves: first, weaving fiber cloth or fiber bundles to obtain a fiber preform; then, using the CVI process to deposit a fiber surface interface layer; finally, using the RMI or PIP process to densify the sample, ultimately preparing the SiC / SiC composite material. Patents such as CN117865700A, CN113800915A, and CN112079646A all involve first preparing a fiber preform with the corresponding structure, and then using the CVI process to prepare an interface layer that meets the usage requirements. When using this process to prepare the interface layer, for samples with a thick fiber preform (>8mm), the steric hindrance effect of the fibers within the preform makes it difficult or only a small amount of deposited gas to enter the preform during the CVI preparation process. This results in the absence of fiber surfaces inside the preform or a very thin interface layer, thus affecting the homogeneity of the silicon carbide fiber-reinforced silicon carbide composite material. Furthermore, there is an optimal thickness for the interface layer; an interface layer that is too thick or too thin will adversely affect the performance of the composite material, leading to significant differences in the internal and external properties of the prepared sample and affecting the service life of the SiC / SiC composite material.

[0003] Furthermore, for ceramic matrix composite materials prepared by first preparing an interface layer on the surface of silicon carbide fiber cloth, such as the patent application number CN202311762669.X, the interface layer is relatively thin and the patent does not effectively protect the interface layer, which will cause the interface layer to be eroded by liquid silicon in subsequent processes, thereby damaging the fiber properties and reducing the mechanical properties of the composite material. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, one of the objectives of this invention is to provide a method for preparing silicon carbide fiber reinforced silicon carbide composite material, so that the prepared composite material has a uniform interface layer thickness, consistent internal and external mechanical properties, and the interface layer is not subject to erosion by liquid silicon.

[0005] Another object of the present invention is to provide a silicon carbide fiber reinforced silicon carbide composite material.

[0006] This invention is achieved using the following technical solution:

[0007] This invention provides a method for preparing silicon carbide fiber-reinforced silicon carbide composite material, comprising the following preparation steps:

[0008] Step 1: Take silicon carbide fiber cloth and prepare the fiber surface interface layer using a CVI deposition furnace;

[0009] Step 2: The fiber cloth with the interface layer deposited on the surface in Step 1 is laid up and sewn to obtain a fiber preform;

[0010] Step 3: Deposit a partial SiC matrix on the fiber preform using the CVI process. The partial SiC matrix fills the pores in the fiber cloth to obtain a SiC / SiC (SiC) porous preform.

[0011] Step 4: The SiC / SiC (SiC) porous preform is densified by slurry injection and silicon infiltration to obtain silicon carbide fiber reinforced silicon carbide composite material.

[0012] The innovative advantage of this invention lies in that it does not use silicon carbide fiber preforms as the interface layer deposition target, but directly uses silicon carbide fiber cloth as the interface layer deposition target. An interface layer is first deposited on the silicon carbide fiber cloth, and then the silicon carbide fiber cloth with the deposited interface layer is laid up and sewn to obtain the fiber preform. Simultaneously, this invention uses the CVI process to deposit a partial SiC matrix on the fiber preform, which can fill the pores within the fiber bundles of the silicon carbide fiber cloth. This effectively protects the fibers and interface layer from being eroded by liquid silicon during the subsequent silicon infiltration process. This solves the problem of uneven fiber deposition in the interface layer of the fiber preform affecting the performance of silicon carbide fiber-reinforced silicon carbide composites, effectively ensuring the consistency of the internal and external properties of silicon carbide fiber-reinforced silicon carbide composites and improving their mechanical properties.

[0013] Preferably, the preparation of the fiber surface interface layer using a CVI deposition furnace in step 1 specifically involves placing silicon carbide fibers in the CVI deposition furnace and preparing an interface layer on the surface of the silicon carbide fibers. The interface layer is either C or BN, and its thickness is 0.2–1 μm, preferably 0.3–0.6 μm, and even more preferably 0.4–0.5 μm. An interface layer thickness that is too high or too low will lead to a decrease in the overall mechanical properties of the SiC / SiC composite material.

[0014] Preferably, a protective coating is also prepared outside the interface layer. The protective coating is one of SiC or Si3N4, and the thickness of the protective coating is 0.1 to 1 μm, preferably 0.1 to 0.5 μm, and even more preferably 0.1 to 0.3 μm.

[0015] Preferably, the total thickness of the interface layer and the protective coating is ≤1μm, and more preferably ≤0.8μm.

[0016] The inventors discovered that when only a single layer of BN (silicon carbide) is deposited as the interface layer, BN is prone to hydrolysis in air, leading to the disappearance of the interface layer. Preparing a protective interface layer on the surface of the BN interface layer can prevent it from contacting air and undergoing hydrolysis. If the protective layer is too thin, its air-isolation effect is poor, and it cannot completely prevent hydrolysis of the BN interface layer, affecting the mechanical properties of the final silicon carbide fiber-reinforced silicon carbide composite material. Conversely, if both the interface layer and the protective layer are too thick, it will increase the stiffness of the fiber cloth, making the coating prone to large-scale peeling during subsequent layup processes, thus reducing the performance of the composite material.

[0017] Preferably, the CVI process deposition in step 3 involves placing a stitched preform with a porous graphite mold into a silicon carbide deposition furnace, depositing a portion of the SiC matrix within the fiber preform, and obtaining a SiC / SiC porous preform after demolding after deposition. The content of the deposited matrix is ​​between 20 and 30 vol%, preferably between 24 and 26 vol%.

[0018] The inventors discovered that depositing a portion of the SiC matrix can prevent the fibers and interface layer from being eroded by liquid silicon during the subsequent silicon infiltration process, thereby improving the mechanical properties of the composite material. The amount of deposited SiC matrix needs to be controlled between 20% and 30% vol% of the total volume of the SiC / SiC (SiC) porous preform. If the content is too low, the protection effect on the fibers and interface layer will be poor; if the content is too high, SiC will not be able to penetrate into the sample during the subsequent slurry pouring process, affecting the uniformity of slurry pouring.

[0019] Preferably, the infusion in step 4 is carried out in a vacuum infusion device. Specifically, a slurry containing SiC particles is poured into the vacuum infusion device to immerse the SiC / SiC porous preform, and vacuum infusion is performed. After the infusion is completed, a SiC / SiC (SiC) porous preform is obtained.

[0020] Preferably, the SiC particles in the slurry have a particle size of 0.1–10 μm, more preferably 0.5–2 μm, and the SiC particle content in the slurry is 30–80 wt%, more preferably 40–70%, and even more preferably 55%–65%.

[0021] If the SiC particle size is too fine, the sample will not be sufficiently infiltrated with silica; if the particle size is too coarse, the slurry will have poor stability and will easily settle. If the SiC content is too high, the slurry viscosity will be too high, the fluidity will be poor, and the slurry pouring will be affected; if the content is too low, the slurry pouring efficiency will be low.

[0022] Preferably, the silicon infiltration in step 4 involves placing a SiC / SiC (SiC) porous preform in a graphite mold coated with a BN layer for silicon infiltration. After silicon infiltration, a SiC / SiC composite material structural part is obtained. The silicon infiltration temperature is 1430℃~1500℃, preferably 1430℃~1470℃, more preferably 1440℃~1460℃, and the silicon infiltration time is 0.5~4h, preferably 0.5~2h, and even more preferably 0.5~1h. Silicon infiltration temperatures above 1500℃ will cause severe damage to the fibers, reducing the mechanical properties of the final sample. Silicon infiltration temperatures below 1400℃ result in high viscosity of the silicon liquid, insufficient capillary force during silicon infiltration, and poor macroscopic silicon infiltration effect.

[0023] As a general inventive concept, the present invention also provides a silicon carbide fiber reinforced silicon carbide composite material, which is prepared by the aforementioned preparation method.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1) This invention provides a method for preparing silicon carbide fiber-reinforced silicon carbide composite materials. The method directly uses silicon carbide fiber cloth as the interface layer deposition target, and then prepares a fiber preform through layup and stitching. The preform prepared by this method has a basically consistent thickness of the inner and outer interface layers, resulting in consistent mechanical properties inside and outside the final SiC / SiC composite structural component, significantly extending the service life of the component. Using traditional processes to prepare a silicon carbide fiber preform first and then deposit it results in a large difference in flexural strength between the inner and outer samples. Using the method for preparing SiC / SiC composite structural components provided by this invention, the difference in tensile strength between the inner and outer samples is small, and the performance uniformity is greatly improved.

[0026] 2) The method for preparing silicon carbide fiber reinforced silicon carbide composite material provided by the present invention deposits a portion of SiC matrix in the preform before the silicon infiltration process, which can effectively protect the fiber and interface layer from being eroded by liquid silicon in the subsequent silicon infiltration process, thereby improving the mechanical properties of the composite material. Attached Figure Description

[0027] Figure 1 Flowchart of the preparation process for silicon carbide fiber-reinforced silicon carbide composites Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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. Example 1:

[0029] This embodiment describes a method for preparing silicon carbide fiber-reinforced silicon carbide composite material, comprising the following steps:

[0030] Step 1: Select an areal density of 185 g / m³ 2 A silicon carbide fiber cloth with a satin weave and 0.5K bundles was placed in a CVI deposition furnace containing BN to deposit a BN interface layer with a thickness of approximately 325 nm. Then, it was placed in a SiC deposition furnace to deposit a SiC protective layer with a thickness of approximately 114 nm.

[0031] Step 2: The silicon carbide fiber cloth with an interface layer and a protective layer was laid in a porous graphite mold. The thickness of the layup sample was 12 mm. After the layup was completed, it was secured with bolts, and then the sample was sewn together along the holes of the porous graphite mold.

[0032] Step 3: After stitching, a portion of the SiC matrix is ​​deposited onto the silicon carbide fiber preform with the mold, resulting in a SiC / SiC (SiC) porous preform with a density of 1.75 g / cm³. 3 (The volume of the sedimentary matrix is ​​approximately 25 vol%);

[0033] Step 4: The obtained SiC / SiC (SiC) porous preform is subjected to slurry pouring. The SiC particles in the slurry have a particle size of 1μm and a SiC particle content of 30wt%. The SiC / SiC (SiC) porous preform after slurry pouring is placed in a graphite crucible coated with BN coating for silicon infiltration treatment. The silicon infiltration temperature is set at 1430℃ and the holding time is 30min. After cooling, silicon carbide fiber reinforced silicon carbide composite material is obtained.

[0034] Samples were taken along the thickness direction of the prepared silicon carbide fiber reinforced silicon carbide composite material samples. The flexural strength of the samples inside and outside was tested using the standard ASTM C1341-13. The internal flexural strength was 558 MPa, the external flexural strength was 561 MPa, and the difference in tensile strength between the internal and external samples was 3 MPa. Example 2:

[0035] This embodiment describes a method for preparing silicon carbide fiber-reinforced silicon carbide composite material, comprising the following steps:

[0036] Step 1: Select an areal density of 185 g / m³ 2 A silicon carbide fiber cloth with a satin weave and 0.5K bundles was placed in a CVI deposition furnace containing BN to deposit a BN interface layer with a thickness of approximately 415 nm. Then, it was placed in a SiC deposition furnace to deposit a SiC protective layer with a thickness of approximately 152 nm.

[0037] Step 2: The silicon carbide fiber cloth with an interface layer and a protective layer was laid in a porous graphite mold. The thickness of the laid sample was 12 mm. After the layup was completed, it was fastened with bolts, and then the sample was sewn together along the holes of the porous graphite mold.

[0038] Step 3: After stitching, a portion of the SiC matrix is ​​deposited onto the silicon carbide fiber preform with the mold, resulting in a SiC / SiC (SiC) porous preform with a density of 1.81 g / cm³. 3 Afterwards (the volume of the deposited SiC substrate was 27 vol%),

[0039] Step 4: The obtained SiC / SiC (SiC) porous preform is subjected to slurry pouring. The slurry contains SiC particles with a particle size of 1 μm and a SiC particle content of 30 wt%. The SiC / SiC (SiC) porous preform after slurry pouring is placed in a graphite crucible coated with BN. The silicon infiltration temperature is set to 1430℃, and the holding time is 30 min. After cooling, silicon carbide fiber reinforced silicon carbide composite material is obtained.

[0040] Samples were taken along the thickness direction of the prepared silicon carbide fiber reinforced silicon carbide composite material samples. The flexural strength of the samples inside and outside was tested using the standard ASTM C1341-13. The internal flexural strength was 542 MPa, the external flexural strength was 538 MPa, and the difference in tensile strength between the internal and external samples was 4 MPa. Example 3:

[0041] This embodiment provides a method for preparing silicon carbide fiber-reinforced silicon carbide composite material, including the following steps:

[0042] Step 1: Select an areal density of 185 g / m³ 2 A silicon carbide fiber cloth with a satin weave and 0.5K bundle was placed in a BN deposition furnace to deposit a BN interface layer with a thickness of 712 nm. Then, it was placed in a SiC deposition furnace to deposit a SiC protective layer with a thickness of 524 nm.

[0043] Step 2: Then, the silicon carbide fiber cloth with the prepared interface layer + protective layer is laid in the porous graphite mold. The thickness of the laid sample is 12mm. After the layup is completed, it is tightened with bolts, and then the sample is sewn together along the holes of the porous graphite mold.

[0044] Step 3: After stitching, a portion of the SiC matrix is ​​deposited onto the silicon carbide fiber preform with the mold, resulting in a SiC / SiC (SiC) porous preform with a density of 1.75 g / cm³. 3 Afterwards (the volume of the deposited matrix is ​​approximately 25 vol%);

[0045] Step 4: The obtained SiC / SiC (SiC) porous preform is subjected to slurry pouring. The SiC particles in the slurry have a particle size of 1μm and a SiC particle content of 30wt%. The SiC / SiC (SiC) porous preform obtained after slurry pouring is placed in a graphite crucible coated with BN coating. The silicon infiltration temperature is set to 1430℃ and the holding time is 30min. After cooling, silicon carbide fiber reinforced silicon carbide composite material is obtained.

[0046] Samples were taken along the thickness direction of the prepared silicon carbide fiber reinforced silicon carbide composite material samples, and the flexural strength inside and outside the samples was tested using the standard ASTM C1341-13. The internal flexural strength was 478 MPa, and the external flexural strength was 486 MPa. Example 4:

[0047] This embodiment provides a method for preparing silicon carbide fiber-reinforced silicon carbide composite material, including the following steps: Step 1: Select an areal density of 185 g / m³ 2 A silicon carbide fiber cloth with a satin weave and 0.5K bundles was placed in a BN deposition furnace to deposit a BN interface layer with a thickness of 358 nm. Then, it was placed in a SiC deposition furnace to deposit a SiC protective layer with a thickness of 152 nm.

[0048] Step 2: Then, the silicon carbide fiber cloth with the prepared interface layer + protective layer is laid in the porous graphite mold. The thickness of the laid sample is 12mm. After the layup is completed, it is tightened with bolts, and then the sample is sewn together along the holes of the porous graphite mold.

[0049] Step 3: After stitching, a portion of the SiC matrix is ​​deposited onto the silicon carbide fiber preform with the mold, resulting in a SiC / SiC (SiC) porous preform with a density of 2.05 g / cm³. 3 Afterwards (the sedimentary matrix volume was approximately 35 vol%),

[0050] Step 4: The obtained SiC / SiC (SiC) porous preform is subjected to slurry pouring. The SiC particles in the slurry have a particle size of 1μm and a SiC particle content of 30wt%. After slurry pouring, the SiC / SiC (SiC) porous preform is obtained and placed in a graphite crucible coated with BN coating. The silicon infiltration temperature is set to 1430℃ and the holding time is 30min. After cooling, silicon carbide fiber reinforced silicon carbide composite material is obtained.

[0051] Samples were taken along the thickness direction of the prepared silicon carbide fiber reinforced silicon carbide composite material samples, and the flexural strength inside and outside the samples was tested using the standard ASTM C1341-13. The internal flexural strength was 413 MPa, and the external flexural strength was 422 MPa. Comparative Example 1:

[0052] A method for preparing silicon carbide fiber-reinforced silicon carbide composite material is provided, comprising the following steps:

[0053] Step 1: Select an areal density of 185 g / m³ 2 A silicon carbide fiber cloth with a satin weave and 0.5K bundles was cut into fiber cloths of a certain size, then laid in a graphite mold to a thickness of 12mm. The cloth was then placed in a BN deposition furnace, and a BN interface layer was deposited according to the process described in Example 1.

[0054] Step 2: Then continue to deposit part of the SiC substrate. After reaching the specified density, after slurry pouring, place the sample in a graphite crucible coated with BN coating, set the silicon diffusion temperature to 1450℃, the holding time to 60min, and obtain the sample after cooling.

[0055] A cross-section of the sample was taken, and the thickness of the BN interface layer inside and outside the sample was observed using SEM. Samples were taken along the thickness direction of the sample, and the flexural strength inside and outside the sample was tested using the standard ASTM C1341-13. The internal flexural strength was 435 MPa, and the external flexural strength was 548 MPa. The difference in tensile strength between the internal and external samples was 113 MPa.

[0056] The interface layer thickness and internal and external flexural strength test results of the samples in Example 1 and Comparative Example 1 show that the silicon carbide fiber reinforced silicon carbide composite material prepared by the SiC / SiC composite material preparation method of the present invention has a tensile strength difference between the internal and external samples within 5 MPa, which significantly improves the consistency of the mechanical properties of the samples compared with Comparative Document 1.

[0057] Comparing Example 1 and Comparative Example 1, it can be seen that the sample of Comparative Example 1, which first prepares the preform and then prepares the interface layer, has a large difference in internal and external mechanical properties. The external flexural strength is 548 MPa, which is basically the same as that of Example 1, but its internal flexural strength is only 435 MPa, which is significantly different from that of Example 1. This shows that the preparation method of SiC / SiC composite material provided by this patent can effectively improve the uniformity of the internal and external mechanical properties of the sample. Comparative Example 2:

[0058] A method for preparing silicon carbide fiber-reinforced silicon carbide composite material is provided, comprising the following steps:

[0059] Step 1: Select an areal density of 185 g / m³2 A silicon carbide fiber cloth with a satin weave and 0.5K bundles was placed in a BN deposition furnace to deposit a BN interface layer with a thickness of 325 nm. Then, it was placed in a SiC deposition furnace to deposit a SiC protective layer with a thickness ranging from 157 nm.

[0060] Step 2: The silicon carbide fibers with the prepared interface layer and protective layer are immersed in a slurry containing SiC particles, resin binder, and plasticizer. After complete immersion, the fibers are removed and dried to obtain silicon carbide fiber prepreg. The carbon fiber prepreg is cut into the required size and stacked in a mold, with a total thickness of 12 mm. The mold and sample are placed on a hot press at 150°C for 2 hours to obtain silicon carbide fiber reinforced resin matrix composite material.

[0061] Step 3: Place the silicon carbide fiber-reinforced resin matrix composite material in a high-temperature pyrolysis furnace. The pyrolysis temperature is 1000℃, the pyrolysis time is 1 hour, and the atmosphere is flowing nitrogen to obtain a SiC / C preform.

[0062] Step 4: Place the SiC / C preform into a graphite crucible, cover it, and place it in a vacuum silicon infiltration furnace. The silicon infiltration temperature is 1450℃, and the holding time is 30 minutes. After cooling, a silicon-infiltrated silicon carbide reinforced silicon carbide fiber sample is obtained.

[0063] The flexural strength of the sample, both internally and externally, was tested using the standard ASTM C1341-13. The measured flexural strength of the sample was 435 MPa.

[0064] Comparing Example 1 and Comparative Example 2, it can be seen that the flexural strength of the sample with partial SiC matrix deposited inside the preform reaches 560 MPa, while the flexural strength of the sample without SiC matrix deposited is only 435 MPa. By using the SiC / SiC composite material preparation method of the present invention, the interface layer can be effectively protected from subsequent liquid silicon erosion, thereby significantly improving the mechanical properties of the composite material.

Claims

1. A method for preparing a silicon carbide fiber-reinforced silicon carbide composite material, characterized in that, The preparation steps include the following: Step 1: Take silicon carbide fiber cloth and prepare the fiber surface interface layer using a CVI deposition furnace. Step 2: The fiber cloth with the interface layer deposited in Step 1 is laid up and sewn to obtain a fiber preform. Step 3: Deposit SiC onto the fiber preform using the CVI process to partially fill the pores within the fiber cloth with SiC matrix, thus obtaining a SiC / SiC (SiC) porous preform. Step 4: The SiC / SiC (SiC) porous preform is densified by slurry injection and silicon infiltration to obtain silicon carbide fiber reinforced silicon carbide composite material.

2. The method for preparing a silicon carbide fiber-reinforced silicon carbide composite material according to claim 1, characterized in that, The fiber surface interface layer mentioned in step 1 is prepared by placing silicon carbide fiber cloth in a CVI deposition furnace and preparing an interface layer on the surface of the silicon carbide fiber cloth. The interface layer is one of C or BN and the thickness of the interface layer is 0.2~1μm.

3. The method for preparing a silicon carbide fiber-reinforced silicon carbide composite material according to claim 2, characterized in that, A protective coating is also prepared outside the interface layer. The protective coating is either SiC or Si3N4, and the thickness of the protective coating is 0.1~1μm. The total thickness of the interface layer and the protective coating is ≤1μm.

4. The method for preparing a silicon carbide fiber-reinforced silicon carbide composite material according to claim 1, characterized in that, In step 3, the CVI process deposition involves placing a fiber preform with a porous graphite mold into a silicon carbide deposition furnace, where a portion of the SiC matrix is ​​deposited within the fiber preform, with the matrix content being 20-30 vol.

5. The method for preparing a silicon carbide fiber-reinforced silicon carbide composite material according to claim 1, characterized in that, The infusion described in step 4 is carried out in a vacuum infusion device. Specifically, the slurry containing SiC particles is poured into the vacuum infusion device to immerse the SiC / SiC porous preform and then vacuum infusion is performed.

6. The method for preparing a silicon carbide fiber-reinforced silicon carbide composite material according to claim 5, characterized in that, The slurry contains 30-80 wt% SiC particles with a particle size of 0.1-10 μm.

7. The method for preparing a silicon carbide fiber-reinforced silicon carbide composite material according to claim 1, characterized in that, In step 4, silicon infiltration involves placing the SiC / SiC (SiC) porous preform in a graphite mold coated with a BN layer and performing silicon infiltration treatment at a temperature of 1430℃~1500℃ for 0.5~4h.

8. A silicon carbide fiber-reinforced silicon carbide composite material, prepared by the preparation method according to any one of claims 1 to 7.

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