A preparation method of SiC / SiC composite material and the composite material

Abstract

The present invention relates to a method for preparing a SiC / SiC composite material, which comprises the following steps: S1, forming a single layer or multiple layers of interfaces on SiC fibers; S2, providing an impregnating slurry comprising rare earth silicate, immersing the fibers after forming the interfaces in the impregnating slurry for vacuum impregnation, heating up for curing to make the slurry adhere, heating up for pyrolysis to remove organic substances and simultaneously form a porous structure to obtain a SiC / SiC composite material with a porous matrix; and S3, performing matrix densification treatment by generating SiC through polymer precursor impregnation pyrolysis. The present invention also relates to a composite material obtained by the above preparation method. According to the method for preparing a SiC / SiC composite material of the present invention, only a simple slurry impregnation process is used to modify the composite material matrix, the process is simple, the cost is low, the oxidation resistance of the material can be improved, and at the same time, the negative influence of reaction thermal stress on the material can be reduced.

Description

Technical Field

[0001] The present invention relates to composite materials, and more specifically to a preparation method of SiC / SiC composite materials and the composite materials thereof. Background Art

[0002] SiC / SiC composite materials are high-performance materials with a complex structure composed of fibers, interfaces, and matrices. Due to their excellent mechanical properties, light weight, high temperature resistance, etc., they can be used as hot-end components of aeroengines in the aerospace field. However, the working environment of aeroengines is extremely harsh, facing the coupling effects of high-temperature loads, cyclic stresses, gas erosion, corrosive environments, etc., resulting in premature failure of the materials. Among them, high-temperature oxidation erosion has a serious impact on the material properties. The SiC matrix oxidizes into gaseous components such as Si(OH) 4 etc. After volatilization, pores are formed, which destroys the protective effect of the dense matrix on the composite material interface and fibers, causing serious degradation of the material's mechanical properties and premature failure of components. Therefore, improving the high-temperature oxidation resistance of SiC / SiC composite materials, especially the oxidation resistance of the matrix, is an important way to reduce the risk of material failure.

[0003] Currently, there is little research on modifying the SiC matrix to improve the antioxidant performance of materials. Usually, the method of in-situ reaction to introduce a second-phase material with antioxidant or self-healing ability is used for improvement. CN202211419352 discloses a preparation method of SiC / SiC-SiBYYb composite materials. By impregnating YbB 6 powder and reacting with molten infiltrated Si-Y alloy, a quaternary matrix with YbB 4 , YB 4 , Si, and YSi 2 phases is in-situ generated inside the porous SiC / SiC composite material embryo. By consuming corrosive gases during the oxidation process and in-situ generating a water-oxygen-resistant phase, the water-oxygen corrosion resistance and self-healing performance of the composite material are improved. However, the in-situ preparation process involves complex reactions, there are uneven thermal stresses, which are prone to cause microcracks inside the material, is not conducive to application in the service environment, and the preparation process is complex and costly. Summary of the Invention

[0004] In order to solve the problems such as the complexity of the process of introducing multi-phase materials by in-situ reaction in the above-mentioned prior art, the present invention provides a preparation method of SiC / SiC composite materials and the composite materials thereof.

[0005] The preparation method of the SiC / SiC composite material according to the present invention comprises the following steps: S1, forming a single layer or multiple layers of interfaces on the SiC fibers; S2, providing an impregnation slurry comprising rare earth silicate, immersing the fibers after forming the interfaces in the impregnation slurry for vacuum impregnation, heating and curing to make the slurry adhere, heating and pyrolyzing to remove organic substances and simultaneously form a porous structure to obtain a SiC / SiC composite material with a porous matrix; and S3, performing matrix densification treatment by generating SiC through polymer precursor infiltration and pyrolysis method.

[0006] In a preferred embodiment, the interface is a BN interface, a PyC interface, or a BN / SiC multi-layer interface.

[0007] In a preferred embodiment, the thickness of the interface is 50 - 2000 nm.

[0008] In a preferred embodiment, in step S1, the interface is deposited by chemical vapor deposition (CVD). In a preferred embodiment, the SiC fibers are placed in a reaction furnace, using ammonia (NH 3 ), boron trichloride (BCl 3 ) as reaction gases, hydrogen (H 2 ) as a diluent gas, the deposition pressure is 0.1 - 10 KPa, the deposition temperature is 700 - 1100 °C, the deposition time is 10 - 300 min, and the gas flow ratio is BCl 3 :NH 3 = 1:(0.5 - 5), BCl 3 :H 2 = 1:(1 - 20).

[0009] In a preferred embodiment, the rare earth silicate is one or more of Yb 2 Si 2 O 7 , Y 2 Si 2 O 7 , Ho 2 Si 2 O 7 , Yb 2 SiO 5 , Y 2 SiO 5 , or Ho 2 SiO 5 .

[0010] In a preferred embodiment, in step S2, SiC powder and rare earth silicate powder are mixed in a mass ratio of 1:(0.05 - 10) to obtain a mixed powder, and the mixed powder: solvent: dispersant: binder: curing agent = 1:(0.5 - 3):(0.02 - 0.3):(0.02 - 0.2):(0.02 - 0.2) are ball-milled and mixed to obtain an impregnation slurry.

[0011] In a preferred embodiment, in a polytetrafluoroethylene ball-milling tank, ball-milling and mixing for 12 - 120 h to obtain an impregnation slurry, and the ball-milling medium is SiC balls.

[0012] In a preferred embodiment, in step S2, vacuum impregnation is carried out in a vacuum impregnation tank for 0.5 - 5 h, cured at 80 - 120 °C in a high-temperature oven for 10 - 30 h, and pyrolyzed at 700 - 1100 °C in a vacuum carbon tube furnace for 0.5 - 3 h.

[0013] In a preferred embodiment, the precursor is polycarbosilane (PCS) or polydimethylsilane (PDMS).

[0014] In a preferred embodiment, in step S3, the SiC / SiC composite material is vacuum impregnated with the precursor, and the precursor is pyrolyzed under an inert gas to obtain SiC to increase the density.

[0015] In a preferred embodiment, the pyrolysis conditions of the precursor are 800 - 1200 °C, 0.5 - 5 h.

[0016] In a preferred embodiment, step S3 is repeated 5 - 20 times.

[0017] The composite material according to the present invention is obtained by the above-mentioned preparation method of the SiC / SiC composite material.

[0018] According to the preparation method of the SiC / SiC composite material of the present invention, the composite material matrix is modified only by a simple slurry impregnation process, that is, antioxidant components are directly introduced into the material through the slurry impregnation process. The process is simple and the cost is low, which can improve the antioxidant property of the material, that is, improve the antioxidant erosion ability of the material, and at the same time reduce the negative impact of the reaction thermal stress on the material. Specifically, the rare earth silicate introduced thereby has a similar thermal expansion coefficient to the SiC matrix and small thermal stress. Brief Description of the Drawings

[0019] Figure 1 is a process flow diagram of the preparation method of the SiC / SiC composite material according to the present invention.

[0020] Figure 2 is SiC / SiC-Yb according to Example 1 of the present invention 2 Si 2 O7 Cross-sectional morphology diagram of the composite material.

[0021] Figure 3 It is SiC / SiC-Yb according to Embodiment 1 of the present invention 2 Si 2 O 7 Fracture morphology diagram of the composite material after being subjected to hydrothermal oxidation at 1200 °C for 80 h.

[0022] Figure 4 It is SiC / SiC-Yb according to Embodiment 2 of the present invention 2 Si 2 O 7 Cross-sectional morphology diagram of the composite material.

[0023] Figure 5 It is the fracture morphology diagram of the SiC / SiC composite material according to Comparative Example 1 of the present invention after being subjected to hydrothermal oxidation at 1200 °C for 80 h. Detailed implementation manners

[0024] The following combines the accompanying drawings to give the preferred embodiments of the present invention and describes them in detail.

[0025] As Figure 1 shown, the preparation method of the SiC / SiC composite material according to the present invention first includes forming a single layer or multiple layers of interfaces on the SiC fibers. In a preferred embodiment, the interface is a BN interface, a PyC interface, or a BN / SiC multi-layer interface. In a preferred embodiment, the interface is formed by chemical vapor deposition (CVD). In a preferred embodiment, the thickness of the interface is 50 - 2000 nm. Specifically, the SiC fibers are placed in a reaction furnace, using ammonia (NH 3 ), boron trichloride (BCl 3 ), as reaction gases, and hydrogen (H 2 ) as a diluent gas, a BN interface with a thickness of 50 - 2000 nm is deposited by chemical vapor deposition (CVD), the deposition pressure is 0.1 - 10 KPa, the deposition temperature is 700 - 1100 °C, the deposition time is 10 - 300 min, and the gas flow ratio is BCl 3 : NH 3 = 1: (0.5 - 5), BCl 3 : H 2 = 1: (1 - 20).

[0026] The preparation method of the SiC / SiC composite material according to the present invention then includes providing an impregnation slurry including rare earth silicate and treating the fibers with the formed interface using the impregnation slurry. In a preferred embodiment, the rare earth silicate is Yb 2 Si 2 O7 , Y 2 Si 2 O 7 , Ho 2 Si 2 O 7 , Yb 2 SiO 5 , Y 2 SiO 5 , or Ho 2 SiO 5 One or more of those above. It should be understood that by adjusting the proportion of rare earth silicate in the impregnation slurry, the introduction amount of the second-phase material (i.e., rare earth silicate) in the SiC / SiC composite material can be controlled, thereby controlling the antioxidant effect of the SiC / SiC composite material.

[0027] Specifically, SiC powder (particle size of 300 - 1000 nm) and Yb 2 Si 2 O 7 powder (300 - 1000 nm) are mixed in a mass ratio of 1:(0.05 - 10) to obtain a mixed powder. According to the mass ratio of mixed powder:solvent (such as absolute ethanol):dispersant (such as fish oil):binder (such as polyvinyl butyral PVB):curing agent (such as phenolic resin) = 1:(0.5 - 3):(0.02 - 0.3):(0.02 - 0.2):(0.02 - 0.2), they are added into a polytetrafluoroethylene ball mill pot, and ball milled for 12 - 120 h to obtain an impregnation slurry, with the ball milling medium being SiC balls.

[0028] Specifically, the fibers after forming the interface are immersed in the impregnation slurry and vacuum impregnated in a vacuum impregnation tank for 0.5 - 5 h. Subsequently, curing is carried out in a high-temperature oven, with the curing time being 10 - 30 h and the curing temperature being 80 - 120 °C. Finally, pyrolysis is carried out in a vacuum carbon tube furnace to remove organic substances and form a porous structure to obtain a SiC / SiC composite material with a porous matrix. The pyrolysis atmosphere is an inert atmosphere, the pyrolysis temperature is 700 - 1100 °C, and the pyrolysis time is 0.5 - 3 h.

[0029] The preparation method of the SiC / SiC composite material according to the present invention finally includes densifying the matrix by generating SiC through polymer precursor infiltration and pyrolysis. In a preferred embodiment, the precursor is polycarbosilane (PCS) or polydimethylsilane (PDMS). Specifically, the SiC / SiC composite material is vacuum impregnated with the precursor and pyrolyzed under an inert atmosphere, with the pyrolysis conditions being 800 - 1200 °C and 0.5 - 5 h. In order to increase the density of the material, the impregnation and pyrolysis process is repeated 5 - 20 times to obtain SiC / SiC - Yb 2 Si 2O 7 Composite material

[0030] Example 1

[0031] Place the SiC fibers in a reaction furnace, using ammonia (NH 3 ), boron trichloride (BCl 3 ) as reaction gases, and hydrogen (H 2 ) as a diluent gas. Deposit a BN interface layer with a thickness of 300 nm by chemical vapor deposition (CVD). The deposition pressure is 2 KPa, the deposition temperature is 900 °C, and the deposition time is 180 min. The B source is BCl 3 , the gas flow rate is 20 mL / min, the N source is NH 3 , the gas flow rate is 60 mL / min, and the H 2 gas flow rate is 180 mL / min.

[0032] Mix 10 g of SiC powder (particle size 300 nm), 20 g of Yb 2 Si 2 O 7 powder (particle size 300 nm), 45 g of absolute ethanol, 3 g of fish oil, 1.5 g of polyvinyl butyral, and 1.5 g of phenolic resin. After continuous ball milling for 24 h, an impregnation slurry is obtained.

[0033] Immerse the fibers with the deposited interface in the slurry, and perform 1 h of vacuum impregnation in a vacuum impregnation tank. Place the impregnated fibers together with the slurry in an oven at 100 °C for curing, and the curing time is 12 h. Subsequently, pyrolyze in a vacuum carbon tube furnace at 1100 °C for 1 h to obtain a SiC / SiC composite material with a porous matrix.

[0034] Using polycarbosilane (PCS) as a precursor, immerse the SiC / SiC composite material with a porous matrix in PCS, and perform 1 h of vacuum impregnation in a vacuum impregnation tank. Subsequently, pyrolyze at 1100 °C for 2 h under an Ar atmosphere. After PCS pyrolysis, SiC is formed. Repeat the PCS impregnation and pyrolysis process 8 times to obtain a SiC / SiC-Yb 2 Si 2 O 7 composite material.

[0035] The SiC / SiC-Yb 2 Si 2 O 7 composite material prepared in this example has a dense structure, a flexural strength of 470 MPa, and a strength retention rate of 85.8% after 80 h of hydrothermal oxidation at 1200 °C.

[0036] Figure 2SiC / SiC-Yb prepared in this example 2 Si 2 O 7 Cross-sectional morphology diagram of the composite material. It can be seen from the figure that the SiC / SiC-Yb 2 Si 2 O 7 composite material shows a relatively dense structure.

[0037] Figure 3 SiC / SiC-Yb prepared in this example 2 Si 2 O 7 Fracture morphology diagram of the composite material after water-oxygen oxidation at 1200 °C for 80 h. It can be seen from the figure that fiber pull-out and crack deflection are still exhibited after oxidation.

[0038] Example 2

[0039] The difference from Example 1 lies in the preparation of the impregnation slurry: 15 g of SiC powder (300 nm particle size), 15 g of Yb 2 Si 2 O 7 powder (300 nm particle size), 45 g of absolute ethanol, 3 g of fish oil, 1.5 g of polyvinyl butyral, and 1.5 g of phenolic resin are mixed.

[0040] The SiC / SiC-Yb 2 Si 2 O 7 composite material prepared in this example has a dense structure and a flexural strength of 474 MPa.

[0041] Figure 4 SiC / SiC-Yb prepared in this example 2 Si 2 O 7 Cross-sectional morphology diagram of the composite material. It can be seen from the figure that the SiC / SiC-Yb 2 Si 2 O 7 composite material shows a relatively dense structure.

[0042] Comparative Example 1

[0043] The difference from Example 1 lies in the preparation of the impregnation slurry: 30 g of SiC powder (300 nm particle size), 45 g of absolute ethanol, 3 g of fish oil, 1.5 g of polyvinyl butyral, and 1.5 g of phenolic resin are mixed.

[0044] The bending strength of the SiC / SiC composite material prepared in this comparative example is 477 MPa, and the strength retention rate after 80 h of hydrothermal oxidation at 1200 °C is 63.3%.

[0045] Figure 5 This is the fracture morphology diagram of the SiC / SiC composite material prepared in this comparative example after 80 h of hydrothermal oxidation at 1200 °C. It can be seen from the figure that the fiber pull-out after oxidation is significantly shorter.

[0046] The above are only the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various changes can be made to the above embodiments of the present invention. That is, all simple, equivalent changes and modifications made according to the claims and the content of the specification of the present invention application fall within the scope of the claims of the present invention patent. Those not described in detail in the present invention are all conventional technical contents.

Claims

1. A method for preparing a SiC / SiC composite material, characterized in that: The preparation method comprises the following steps: S1, forming a single layer or multilayer interface on SiC fiber; S2, SiC powder and rare earth silicate powder are mixed in a mass ratio of 1: (0.05-10) to obtain a mixed powder, and mixed by ball milling in a mass ratio of mixed powder: solvent: dispersant: binder: curing agent = 1: (0.5-3): (0.02-0.3): (0.02-0.2): (0.02-0.2) to provide an impregnation slurry, and the fiber after the interface is formed is immersed in the impregnation slurry in a vacuum impregnation tank for vacuum impregnation for 0.5-5 h, and the temperature is raised to 80-120 ° C in a high temperature oven and cured for 10-30 h to fix the slurry, and the temperature is raised to 700-1100 ° C in a vacuum carbon tube furnace to crack for 0.5-3 h to remove organic matter and form a porous structure to obtain a SiC / SiC composite material with a porous matrix; as well as S3, generating SiC by polymer precursor impregnation pyrolysis method for matrix densification.

2. The preparation method according to claim 1, characterized in that: The interface is a BN interface, a PyC interface, or a BN / SiC multilayer interface.

3. The preparation method according to claim 1, characterized in that: The rare earth silicate is one or more of Yb2Si2O7, Y2Si2O7, Ho2Si2O7, Yb2SiO5, Y2SiO5, or Ho2SiO5.

4. The preparation method according to claim 1, characterized in that: The impregnation slurry is obtained by ball milling the mixture for 12 to 120 h in a polytetrafluoroethylene ball mill, and the ball milling medium is SiC ball.

5. The preparation method according to claim 1, characterized in that: The precursor is polycarbosilane or polydimethylsilane.

6. The preparation method according to claim 1, characterized in that: In step S3, the SiC / SiC composite material is vacuum impregnated with a precursor, and the precursor is cracked under an inert gas to obtain SiC to increase density.

7. The preparation method according to claim 6, characterized in that: The pyrolysis conditions of the precursor are 800~1200 ℃, 0.5~5 h.

8. A composite material obtained by the preparation method according to any one of claims 1 to 7.

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