Fiber preform with gradient SiBN interface coating deposited on outer surface as well as preparation method and application of fiber preform

Abstract

The invention relates to a fiber preform with a gradient SiBN interface coating deposited on the outer surface as well as a preparation method and application of the fiber preform. In the gradient SiBN interface coating structure, the content of the Si element is gradually increased from inside to outside, and the content of the B element is gradually decreased from inside to outside. The gradient SiBN interface coatings with different element contents are continuously prepared on the surface of the fiber by adopting a chemical vapor infiltration method, and accurate control of the element contents and continuous controllable preparation of the multifunctional gradient SiBN interface coating fiber preform are realized by adjusting the proportion and process parameters of different SiBN interface layer precursors; the inner-layer SiBN interface coating is mainly used for mechanical strengthening and toughening, and the middle-layer SiBN interface coating and the outer-layer SiBN interface coating are mainly used for oxidation resistance and self-healing protection. The gradient SiBN interface coating prepared by the method can be applied to preparation of a fiber reinforced ceramic matrix composite material, and can achieve good mechanical reinforcing and toughening and anti-oxidation protection effects on the material.

Description

TECHNICAL FIELD

[0001] The present application relates to a fiber preform with a gradient SiBN interface coating deposited on the outer surface and a preparation method and application thereof, and belongs to the technical field of ceramic matrix composites and preparation thereof. BACKGROUND

[0002] Fiber-reinforced ceramic matrix composites are a new type of high-temperature thermal structural material. In recent years, they have been widely concerned and applied in the fields of aviation, aerospace, nuclear energy and mechanical transportation due to their excellent high specific strength, specific modulus, low density, high temperature resistance and thermal chemical stability. However, the fibers and interface phases in fiber-reinforced ceramic matrix composites, especially the interface phases, are easily oxidized at high temperatures, which greatly limits their use in high-temperature oxidation environments. Therefore, improving the oxidation resistance of fiber-reinforced ceramic matrix composites is of great significance to promote their application in the thermal structural components of aero-engine (such as sealing sheets, regulating sheets, guide vanes), aerospace vehicles (such as nose cones, leading edges, wings, etc.).

[0003] At present, the main means to improve the oxidation resistance of fiber-reinforced ceramic matrix composites include the preparation of interface coatings (such as PyC interface, BN interface, etc.), oxidation-resistant coatings (SiC coating, B4C coating, etc.), and oxidation-resistant matrix (such as B4C matrix, SiBC matrix, etc.). However, for oxidation-resistant coatings, they basically exist only on the surface of the material, and once the coating peels off, the protection of the internal material is lost. For oxidation-resistant matrix, the matrix mostly exists only on the periphery of the fiber bundle, and there is little matrix inside the fiber bundle, mostly interface phase, so the oxidation-resistant protection is limited. For interface coatings, PyC interface coating has poor high-temperature oxidation resistance, and starts to oxidize in large quantities at about 400 o C, and BN interface coating will be oxidized and hydrolyzed and volatilized at about 500 o C. Therefore, the above means are not conducive to the long-term application of C / SiC materials and SiC / SiC materials in high-temperature oxidation environments. SiBN ceramics have excellent high-temperature oxidation resistance and stability, and good physical and chemical compatibility with inorganic fibers. Studies have shown that the oxidation resistance of SiBN interface layer is better than that of BN interface and PyC interface, making it a promising candidate material for the interface phase of ceramic matrix composites.

[0004] There are few reports on the preparation of SiBN ceramics at present, and the main methods include precursor impregnation pyrolysis, mechanical alloying and chemical vapor deposition (CVD method) and so on. As one of the methods for preparing SiBN ceramics, the interface coating prepared by CVD method has good continuity and high purity, and causes little damage to the fiber, which is an ideal method for preparing fiber surface interface coating. However, there are few relevant reports at home and abroad. S. Stockel et al. successfully prepared SiBN interface coating on the surface of Nextel, Nicalon and SiBCN fibers using tetramethylsilane (TMS), N,N,N-trimethylborane and ammonia as reaction precursors. The SiBN interface coating has good high-temperature oxidation resistance. A.W. Moore et al. used BCl3 as boron source, HSiCl3 as silane, NH3 as nitrogen source, and hydrogen or argon as dilution gas to prepare SiBN interface coating on the surface of SiC fiber at 1400 o C in SiC fiber bundle, and the oxidation resistance of SiBN interface coating is better than that of BN interface. LIU. Y. S et al. successfully prepared SiBN interface on the surface of SiC fiber bundle using BCl3-NH3-SiCl4-H2-Ar as the reaction system. The tensile strength of SiBN interface fiber bundle with different thicknesses obeys the Weibull distribution and shows typical non-brittle fracture characteristics, but no oxidation resistance data is given. Although the above precursors are used to obtain SiBN interface phase, the composition of SiBN interface coating on the surface of fiber bundle is prepared under single condition, and the content of Si, B and N elements in the fiber surface interface coating is also single component, which cannot realize the synergistic development of mechanical strengthening and toughening of interface phase and the oxidation protection of fiber. In addition, the above interface phase deposition is easy to produce a large amount of by-products at high temperature, which affects the deposition quality of the interface coating and limits the further use in the interior of the fiber preform. In addition, the Chinese patent with application number 201711312460.8 discloses a method for preparing wave-transparent BN fiber toughened Si-B-N ceramic matrix composite by CVD / CVI method. However, in this method, SiBN is used for the matrix phase, and the main function is wave absorption. The interface phase is BN interface, and the material is still enhanced and toughened by BN interface phase, not SiBN interface. At the same time, this method does not disclose how to realize the regulation and change of Si element content in SiBN interface phase and how to realize the maximum performance of the material by regulating the direct contact between SiBN interface phase and fiber, and the method also does not disclose that controlling the content of Si element in what range can be beneficial to the full play of the mechanical properties of the material. SUMMARY

[0005] In view of the problems and deficiencies of the single-component SiBN interface coating at the present stage, the application provides a fiber preform with an outer surface deposited gradient SiBN interface coating which is uniform, dense, has good high-temperature stability, greatly improves the oxidation resistance, and takes into account the mechanical properties of the material. Meanwhile, the application also provides a preparation method of the fiber preform, which has simple preparation process, strong operability, low equipment requirement, less by-products, is suitable for large-size complex structural parts, and meets the engineering application requirements, thereby providing a new research idea and method for further development of fiber-reinforced ceramic matrix composite interface phase.

[0006] In the first aspect, the application provides a fiber preform with an outer surface deposited gradient SiBN interface coating, which comprises: a fiber preform and a multilayer structure gradient SiBN interface coating deposited on the surface of the fiber preform; the Si element content of the multilayer structure gradient SiBN interface coating presents a gradient increase from the inside to the outside, and the B element content presents a gradient decrease from the inside to the outside.

[0007] Preferably, the Si element content of the innermost SiBN interface coating is 10 at.% or less, preferably 8 at.% or less; the Si element content of the intermediate layer SiBN interface coating is 10 at.% to 15 at.%, preferably 12 at.% to 15 at.%; and the Si element content of the outermost SiBN interface coating is 15 at.% or more, preferably 18 at.% or more, more preferably 20 at.% or more.

[0008] Preferably, the B element content of the innermost SiBN interface coating is 35 at.% or more, preferably 38 at.% or more; the B element content of the intermediate layer SiBN interface coating is 30 at.% to 35 at.%; and the B element content of the outermost SiBN interface coating is 30 at.% or less, preferably 28 at.% or less.

[0009] Preferably, the gradient change of the Si element content of the gradient SiBN interface coating is realized by at least one of the following ways: controlling the deposition temperature by a chemical vapor deposition process, and controlling the molar ratio of the two gases of the silicon source and the nitrogen source in the precursor. The gradient change of the B element content in the gradient SiBN interface coating is realized by at least one of the following ways: controlling the deposition temperature by a chemical vapor deposition process, and controlling the molar ratio of the two gases of the boron source and / or the nitrogen source in the precursor.

[0010] Preferably, the gradient SiBN interface coating is prepared by in-situ continuous multiple deposition on the surface of the fiber preform through a chemical vapor infiltration process, using a nitrogen source, a boron source and a silicon source as raw materials. The nitrogen source includes but is not limited to NH3. The boron source includes but is not limited to BCl3. The silicon source includes but is not limited to SiCl4.

[0011] Preferably, the gradient SiBN interface coating has a layer number n³2, preferably 2-10 layers, more preferably a 3-layer structure; for example, the gradient SiBN interface coating has a 3-layer structure divided into an inner layer, a middle layer and an outer layer; the inner layer SiBN interface coating has a thickness of 20 nm-10 µm, preferably 300 nm-1200 nm; the middle layer SiBN interface coating has a thickness of 20 nm-5 µm, and the outer layer SiBN interface coating has a thickness of 20 nm-5 µm; the total thickness of the inner layer, middle layer and outer layer is 60 nm-20 µm, preferably 340 nm-1500 nm.

[0012] Preferably, the fibers include at least one of carbon fibers, SiC fibers, silicon nitride fibers, alumina fibers, boron nitride fibers, SiCN fibers, and SiBN fibers; the structural form of the fiber preform includes at least one of a fiber stitched preform, a fiber needled preform, a fiber two-dimensional cloth stacked preform, 2.5D weaving, a fiber three-dimensional four-way, a three-dimensional five-way, and a three-dimensional six-way weaving.

[0013] In a second aspect, the present application provides a method for preparing a fiber preform with a gradient SiBN interface coating on the outer surface, comprising the following steps: (1) placing the fiber preform in the furnace inner constant temperature zone of the deposition system, performing vacuum flushing operation, and then raising the furnace inner temperature to 700-950 o C and maintaining the temperature; (2) after the temperature maintaining is completed, adjusting the furnace inner temperature to the interface coating process deposition temperature, introducing process gas into the furnace, and obtaining a fiber preform with a preliminary SiBN interface coating modification through deposition; (3) after step (2) is completed, cutting off the process gas, replacing it with dilution gas, and then continuing to introduce process gas into the furnace, and obtaining a fiber preform with a secondary SiBN interface coating modification through deposition; (4) after step (3) is completed, cutting off the process gas, replacing it with dilution gas, and then continuing to introduce process gas into the furnace, and continuously depositing on the surface of the fiber preform deposited in step (3) under constant temperature and pressure to obtain a fiber preform with a final gradient SiBN interface coating modification.

[0014] Preferably, in step (1), the vacuum flushing operation is performed 2-4 times, and the furnace inner set vacuum degree is 3 Pa or less.

[0015] Preferably, in step (2), the process gases are SiCl4, BCl3, NH3, H2, and Ar, with the molar ratio of NH3 to BCl3 being 0.5~3, the molar ratio of BCl3 to SiCl4 being 0.3~10, the molar ratio of H2 to Ar being 0.5~10, and the molar ratio of NH3 to H2 being 0.25~1.5; the deposition temperature of the interface layer is 650~800℃, the deposition time is 0.5~20 hours, and the deposition pressure is 0.5~3KPa. Under the same temperature and pressure, the volume of a gas is directly proportional to its amount of substance (moles). Therefore, the molar ratio of the process gases is equal to their flow rate ratio.

[0016] Preferably, in step (3), the process gases are SiCl4, BCl3, NH3, H2 and Ar, the molar ratio of NH3 to BCl3 is 3~100, preferably 3~12, the molar ratio of BCl3 to SiCl4 is 0.1~3, the molar ratio of H2 to Ar is 0.5~10, and the molar ratio of NH3 to H2 is 1.5~6; the deposition temperature of the interface layer is 650~950℃, the deposition time is 0.5~12 hours, and the deposition pressure is 0.5~3KPa.

[0017] Preferably, in step (4), the process gases are SiCl4, BCl3, NH3, H2 and Ar, the molar ratio of NH3 to BCl3 is 3~30, the molar ratio of BCl3 to SiCl4 is 0.05~3, the molar ratio of H2 to Ar is 0.5~10, and the molar ratio of NH3 to H2 is 1.5~15; the deposition temperature of the interface layer is 650~950℃, the deposition time is 0.5~12 hours, and the deposition pressure is 0.5~3KPa.

[0018] Thirdly, the present invention provides a fiber-reinforced ceramic matrix composite material containing a gradient SiBN interfacial coating deposited on its outer surface. The SiC matrix of the fiber preform with the aforementioned gradient SiBN interfacial coating is densified using at least one of chemical vapor infiltration (CVI), precursor impregnation pyrolysis (PIP), and reactive infiltration (RMI) methods to obtain a gradient interfacial coating-reinforced SiC matrix composite material; wherein the gradient interfacial coating-reinforced SiC matrix composite material has a flexural strength of ≥200 MPa and a porosity ≤10%.

[0019] The present invention has the following beneficial effects: (1) The present invention uses a multi-layer gradient SiBN interface to modify the structure of the fiber preform. The multi-layer structure gives the fiber preform flexibility in the service environment. The gradient interface can be optimized according to the changes in the service environment of the fiber preform. By precisely cutting and designing the gradient structure, the environmental applicability of the fiber preform can be effectively improved.

[0020] (2) By using a gradient SiBN interface coating to modify the surface of the fiber preform, the present invention can effectively improve the operating temperature range of the original fiber preform and realize the stable use of the fiber preform in a wide temperature range (500~1500℃). The presence of the gradient SiBN interface coating can effectively slow down the oxidation failure rate of the fiber preform in a high-temperature oxidizing environment and protect the integrity of the fiber skeleton in the fiber preform.

[0021] (3) By regulating the distribution of Si element content in the gradient SiBN interface coating from the inside to the outside of the entire coating, the inner SiBN interface coating is mainly composed of low Si element content, which is conducive to crack deflection and can effectively modify the defects on the fiber surface, effectively ensuring the mechanical properties of the single fiber in the fiber preform, and thus realizing the high mechanical properties of the material. The middle and outer SiBN interface coatings are mainly composed of high Si element content, which improves the resistance of the single fiber to water and oxygen erosion, slows down the volatilization rate of the interface phase, and thus realizes the high resistance of the overall fiber preform to high temperature water and oxygen erosion, and finally realizes the synergistic development of the material's mechanical properties and antioxidant properties.

[0022] (4) In this invention, since the Si element content is achieved by controlling the deposition temperature and the molar ratio of the two gases, silicon source (e.g., SiCl4) and nitrogen source (e.g., NH3), the gradient structure coating can be continuously prepared in the furnace without the sample needing to be removed, which greatly improves the preparation efficiency of fiber preforms with different layers of gradient structure coating. At the same time, the method of this invention is applicable to large-size complex structural parts, and the prepared materials can meet the requirements of engineering applications. Attached Figure Description

[0023] Figure 1The images shown are: (a) X-ray photoelectron spectroscopy (XPS) spectrum of SiC fibers sampled from the SiC fiber preform after depositing four layers of gradient SiBN interfaces inside the preform in Example 1 of the present invention; (b) XPS spectrum of SiC fibers sampled from the SiC fiber preform after depositing four layers of gradient SiBN interfaces inside the preform in Example 1 of the present invention, showing that the interface is mainly composed of NB, N-Si, and NO bonds; and (c) Infrared spectroscopy spectrum of SiC fibers sampled from the SiC fiber preform after depositing four layers of gradient SiBN interfaces inside the preform in Example 1 of the present invention, showing that the prepared SiBN interface is mainly composed of NB, N-Si, and NO bonds. The peaks should include BNB and Si-N-Si asymmetric stretching vibrations, corresponding to the vibration peaks of BN and Si3N4 ceramic phases, respectively; (c) is a scanning electron microscope image of SiC fibers sampled from inside the SiC fiber preform after the deposition of four layers of gradient SiBN interfaces inside the preform in Example 1 of this invention. It can be seen from the image that the prepared gradient SiBN interface coating completely encapsulates the fibers, and the surface of each fiber bundle has achieved interface phase deposition. From the arrow in the first SiBN-1 interface layer, it can be seen that by controlling the structure of the inner SiBN interface phase, there is an obvious boundary line inside the inner SiBN interface phase, which is beneficial for subsequent crack deflection at this point, thereby improving the mechanical properties of the material.

[0024] Figure 2 This is a high-magnification scanning electron microscope image of the four-layer gradient SiBN interface deposited inside the fiber preform in Example 1 of the present invention. As can be seen from the arrows in the image, the thickness of the prepared gradient SiBN interface coating is at the micrometer level, the prepared gradient SiBN interface coatings are very tightly bonded, and the morphology of the prepared gradient SiBN interface coatings is obviously different, indicating that the elemental composition content of the different interface layers is different.

[0025] Figure 3 This is a high-magnification scanning electron microscope image of the three-layer gradient SiBN interface deposited inside the fiber preform in Example 2 of the present invention. As can be seen from the image, the thickness of the prepared gradient SiBN interface coating is at the micrometer level. After changing the process parameters and conditions, the prepared gradient SiBN interface coatings are still very tightly bonded, and the morphologies of the prepared gradient SiBN interface coatings are also completely different, indicating that the elemental composition content of different interface layers is different. It also shows that changing the process parameters can significantly and effectively improve the morphology and structure of the interface phase.

[0026] Figure 4The image shows a high-magnification scanning electron microscope (SEM) image of the three-layer gradient SiBN interface deposited inside the fiber preform in Example 3 of this invention. As can be seen from the image, the thickness of the prepared gradient SiBN interface coating is at the nanometer level, and the bonding between the prepared gradient SiBN interface coatings is very tight. Although the interface thickness is very thin, the morphology of the prepared gradient SiBN interface coatings is still significantly different, indicating that the elemental composition content of the different interface layers is different.

[0027] Figure 5 The images show high-magnification cross-sectional scanning electron microscope (SEM) images and corresponding energy dispersive spectroscopy (EDS) analysis diagrams of the three-layer gradient SiBN interface deposited inside the fiber preform in Example 4 of this invention. As can be seen from the images, the thickness of the prepared gradient SiBN interface coating is at the nanometer level, and the bonding between the prepared gradient SiBN interface coatings is very tight. From the intensity results of the B and Si peaks in the EDS, it can be seen that the elemental composition content of the different interface layers is different.

[0028] Figure 6 The SiC fiber preform containing a 3-layer gradient SiBN interface coating prepared in Example 4 of this invention was subjected to 1200... o The fiber surface morphology photograph and corresponding energy dispersive spectroscopy point and surface analysis diagrams after 20 hours of high-temperature oxidation show that the surface of the interfacial coating still has obvious B element peaks after 20 hours of high-temperature oxidation. At the same time, there are obvious bubbling marks on the surface of the interfacial phase, indicating that the interfacial phase exhibits extremely strong stability in the high-temperature water and oxygen environment and has not been completely hydrolyzed and volatilized.

[0029] Figure 7 The figure shows the stress-displacement curve of the SiC fiber preform with a 3-layer gradient SiBN interface coating prepared in Example 5 of the present invention, applied to the preparation of SiC / SiC composite materials in ceramic matrix composites. As can be seen from the figure, the prepared gradient structure SiBN interface phase coating exhibits a good mechanical strengthening and toughening effect on the material, with a flexural strength of 283 MPa and a modulus of 189 GPa. Detailed Implementation

[0030] The present invention will be further described below with reference to the accompanying drawings and the following embodiments. It should be understood that the drawings and the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0031] To address the problems and shortcomings of using single-component SiBN interface coatings at present, this invention provides a fiber preform with an external surface deposition gradient SiBN interface coating that is uniform and dense, has good high-temperature stability, significantly improves oxidation resistance, and takes into account the mechanical properties of the material.

[0032] The fiber preform with an outer surface deposited gradient SiBN interface coating includes: a fiber preform and a multilayer gradient SiBN interface coating deposited on the surface of the fiber preform.

[0033] In optional embodiments, the fibers include, but are not limited to, carbon fibers, SiC fibers, silicon nitride fibers, alumina fibers, boron nitride fibers, SiCN fibers, SiBN fibers, etc.

[0034] In optional embodiments, the structural forms of the fiber preform include, but are not limited to, at least one of the following fiber preforms: fiber stitched preform, fiber needle-punched preform, fiber two-dimensional fabric laminated preform, 2.5D braid, fiber three-dimensional four-dimensional, three-dimensional five-dimensional, and three-dimensional six-dimensional braid.

[0035] For example, the fiber preform includes at least one of the following: carbon fiber bundle, carbon fiber two-dimensional cloth, carbon fiber two-dimensional cloth laminated preform, carbon fiber two-dimensional cloth stitched body, carbon fiber three-dimensional four-dimensional preform, carbon fiber needle-punched preform, SiC fiber cloth, SiC fiber two-dimensional laminated preform, SiC fiber two-dimensional stitched preform, SiC fiber three-dimensional braided preform, and 2.5D carbon fiber preform.

[0036] In this invention, the SiBN interface coating primarily serves to strengthen and toughen the material. As an interface phase, it must meet the material's requirements for mechanical strength. Secondly, it must also meet the interface's requirements for oxidation resistance. Therefore, the functional roles of the SiBN interface phase differ in different locations. To this end, this invention designs the gradient SiBN interface coating where the Si content increases gradually from the inside out, and the B content decreases gradually from the inside out.

[0037] In optional embodiments, the Si content of the innermost SiBN interface coating is 10 at.% or less, preferably 8 at.% or less. The innermost SiBN interface layer is dominated by the BN phase and secondarily by the Si3N4 phase, primarily functioning as a mechanical reinforcement and toughening agent. The Si content of the intermediate SiBN interface layer is 10 at.% to 15 at.%, preferably 12 at.% to 15 at.%. The intermediate layer primarily serves as a transition layer, providing both mechanical transfer and antioxidant protection. The Si content of the outermost SiBN interface layer is 15 at.% or more, preferably 18 at.% or more, and more preferably 20 at.% or more. The Si content in the outermost interface phase is significantly higher than that in the innermost layer, primarily serving as an antioxidant protection agent. The high Si content helps to minimize the volatilization rate of the interface phase under high temperature and humidity conditions.

[0038] In an optional embodiment, the boron content of the innermost SiBN interface coating is 35 at.% or more, preferably 38 at.% or more; the boron content of the middle SiBN interface coating is 30 at.% to 35 at.%; and the boron content of the outermost SiBN interface coating is 30 at.% or less, preferably 28 at.% or less.

[0039] In an optional embodiment, the gradient SiBN interface coating is prepared by in-situ continuous deposition of silicon, boron, and nitrogen sources on the surface of the fiber preform using a chemical vapor infiltration process. Nitrogen sources include, but are not limited to, NH3. Silicon sources include, but are not limited to, BCl3. Silicon sources include, but are not limited to, SiCl4. The interface layer is a SiBN interface coating with a multi-layered structure from the inside out. In the SiBN gradient interface coating, the Si content gradually increases from the inside out, while the B content gradually decreases from the inside out.

[0040] It should be understood that any method that causes the Si element content in the gradient SiBN interface coating to exhibit the aforementioned variation pattern is applicable to the present invention. In an optional embodiment, the gradient change in the Si element content in the gradient SiBN interface coating is achieved by controlling the deposition temperature during the chemical vapor deposition process and controlling at least one method of controlling the molar ratio of silicon and nitrogen source gases in the entire precursor. That is, satisfying one of the above two methods will result in the gradient change in the Si element content in the gradient SiBN interface coating. In an optional embodiment, the deposition temperature of each layer in the gradient SiBN interface coating increases sequentially from the inside to the outside. In an optional embodiment, the molar ratio of nitrogen source to silicon source in the process gas of each layer in the gradient SiBN interface coating increases sequentially from the inside to the outside (or exhibits an overall increasing trend, i.e., the molar ratio of nitrogen source to silicon source in the process gas of the outermost Nth layer is the same as that of the (N-1)th layer). In an optional embodiment, the deposition temperature of each layer in the gradient SiBN interface coating increases sequentially from the inside to the outside, and the molar ratio of nitrogen source to silicon source of process gas increases sequentially from the inside to the outside of each layer (or the overall trend is increasing, that is, the molar ratio of nitrogen source to silicon source of process gas of the Nth layer, which is the outermost layer, is the same as that of the (N-1)th layer).

[0041] It should be understood that any method that causes the boron content in the gradient SiBN interface coating to exhibit the aforementioned variation pattern is applicable to the present invention. In an optional embodiment, the gradient change in the boron content in the gradient SiBN interface coating is achieved by controlling at least one method of the chemical vapor deposition process, specifically controlling the deposition temperature and the molar ratio of boron and nitrogen source gases in the entire precursor. That is, satisfying one of the above two methods will result in the gradient change in the boron content in the gradient SiBN interface coating. In an optional embodiment, the deposition temperature of each layer in the gradient SiBN interface coating increases sequentially from the inside to the outside. In an optional embodiment, the molar ratio of boron source to nitrogen source in the process gas decreases sequentially from the inside to the outside of each layer in the gradient SiBN interface coating (or exhibits a decreasing trend overall, i.e., the molar ratio of boron source to nitrogen source in the process gas of the outermost Nth layer is the same as that of the (N-1)th layer). In an optional embodiment, the deposition temperature of each layer in the gradient SiBN interface coating increases sequentially from the inside to the outside, while the molar ratio of boron source / nitrogen source of the process gas decreases sequentially from the inside to the outside of each layer (or shows a decreasing trend overall, that is, the molar ratio of boron source / nitrogen source of the process gas of the Nth layer, which is the outermost layer, is the same as that of the (N-1)th layer).

[0042] In an optional embodiment, the gradient interface coating has a multilayer structure (n³²), preferably 2 to 10 layers, more preferably 3 layers, consisting of inner, middle, and outer layers. That is, the SiBN interface phase preferably has 2 to 10 layers, more preferably 3 layers.

[0043] In an optional embodiment, the thickness of the innermost SiBN interface layer in the multilayer structure is 20 nm to 10 μm, preferably 300 nm to 1200 nm, the thickness of each SiBN interface layer in the middle layer is independently 20 nm to 5 μm, the thickness of the outermost SiBN interface layer is 20 nm to 5 μm, and the total thickness of the inner, middle, and outer interface phases is 60 nm to 20 μm, preferably 340 nm to 1500 nm.

[0044] As an example, in the three-layer structure, the thickness of the inner SiBN interface layer is 20 nm to 10 μm, preferably 300 nm to 1200 nm, the thickness of the middle SiBN interface layer is 20 nm to 5 μm, the thickness of the outermost SiBN interface layer is 20 nm to 5 μm, and the total thickness of the inner, middle, and outer interface phases is 60 nm to 20 μm, preferably 340 nm to 1500 nm.

[0045] The following will describe in detail the preparation method of the fiber preform with the outer surface deposition gradient SiBN interface coating of the present invention.

[0046] The method includes: (1) firstly, a SiBN interface coating with a low Si content of Si element of a certain thickness is deposited on the fiber surface inside the fiber preform using chemical vapor infiltration method to obtain an interface layer protecting the SiC fiber preform; (2) based on the fiber preform obtained in step (1), a SiBN interface coating with a medium Si content of Si element of a certain thickness is deposited; (3) based on step (2), a SiBN interface coating with a high Si content of Si element of a certain thickness is deposited to finally obtain a fiber preform with a gradient SiBN interface coating on the outer surface.

[0047] In the gradient SiBN interface coating structure, the Si element content increases progressively from the inside out, while the B element content decreases progressively from the inside out. This invention employs chemical vapor infiltration to continuously prepare gradient SiBN interface coatings with different element contents on the fiber surface. By adjusting the proportions of different SiBN interface layer precursors and process parameters, precise control of element content and continuous, controllable preparation of multifunctional gradient SiBN interface coating fiber preforms are achieved. The inner SiBN interface coating primarily provides mechanical reinforcement and toughening, while the middle and outer SiBN interface coatings primarily provide antioxidant and self-healing protection.

[0048] The gradient SiBN interfacial coating prepared by this invention has good bonding with fibers, good physicochemical compatibility and thermal stability. During the preparation of the interfacial phase, the gradient coating can be prepared continuously without removing the sample, which improves the preparation efficiency of the interfacial coating. The preparation process of the interfacial coating is simple to operate and highly repeatable. The prepared gradient SiBN interfacial coating can be applied to the preparation of fiber-reinforced ceramic matrix composites, which can play a good role in mechanical reinforcement, toughening and antioxidant protection of the material.

[0049] As an example, a fiber preform with an outer surface deposited with a gradient SiBN interface coating includes the following steps: Step (1): Place the fiber preform into the constant temperature zone of the furnace, perform multiple vacuum rinsing operations, and after reaching the set vacuum level, raise the furnace temperature to 700~950°C. o C and keep warm for a period of time. The warming time can be 30~120 minutes.

[0050] In step (1), the vacuum rinsing operation is performed 2 to 4 times, and the vacuum level inside the furnace is set to below 3 Pa.

[0051] Step (2): After the heat preservation is completed, the temperature inside the furnace is adjusted to the deposition temperature of the interface coating process. A certain flow rate and proportion of SiCl4, BCl3, NH3, H2 and Ar are introduced into the furnace. The material is deposited for a period of time under a certain temperature and pressure. The fiber preform modified with the preliminary SiBN interface coating is then taken out.

[0052] In step (2), the molar ratio of NH3 to BCl3 is 0.5~3, the molar ratio of BCl3 to SiCl4 is 0.3~10, the molar ratio of H2 to Ar is 0.5~10, and the molar ratio of NH3 to H2 is 0.25~1.5. The deposition temperature of the interface layer is 650~800℃, the deposition time is 0.5~20 hours, and the deposition pressure is 0.5~3 kPa.

[0053] Step (3): After step (2) is completed, the process gas is cut off, and after a period of replacement with dilution gas, a certain flow rate and proportion of SiCl4, BCl3, NH3, H2 and Ar are introduced into the furnace. The material is deposited under constant temperature and pressure for a period of time, and then the fiber preform modified with secondary SiBN interface coating is obtained.

[0054] In step (3), the molar ratio of NH3 to BCl3 is 3~100, preferably 3~12; the molar ratio of BCl3 to SiCl4 is 0.1~3; the molar ratio of H2 to Ar is 0.5~10; and the molar ratio of NH3 to H2 is 1.5~6. The deposition temperature of the interface layer is 650~950℃, the deposition time is 0.5~12 hours, and the deposition pressure is 0.5~3 KPa.

[0055] Step (4): After step (3) is completed, the process gas is cut off, and after a period of replacement with dilution gas, a certain flow rate and proportion of SiCl4, BCl3, NH3, H2 and Ar are introduced into the furnace. Under constant temperature and pressure, the fiber preform deposited in step (3) continues to be deposited for a period of time. The fiber preform modified with the final gradient SiBN interface coating is then obtained.

[0056] In step (4), the molar ratio of NH3 to BCl3 is 3~30, the molar ratio of BCl3 to SiCl4 is 0.05~3, the molar ratio of H2 to Ar is 0.5~10, and the molar ratio of NH3 to H2 is 1.5~15. The deposition temperature of the interface layer is 650~950℃, the deposition time is 0.5~12 hours, and the deposition pressure is 0.5~3 KPa.

[0057] It's important to understand that the gas flow rate can be adjusted based on the coating thickness, and the proportions of each gas flow rate can also be adjusted based on the coating composition. Furthermore, since the number of layers in a gradient interface coating is unlimited, appropriate deposition steps can be set based on the number of layers in the gradient interface coating.

[0058] The fiber preform with an externally deposited gradient SiBN interfacial coating prepared by this invention can be used to prepare fiber-reinforced ceramic matrix composites. The fiber-reinforced ceramic matrix composite containing the externally deposited gradient SiBN interfacial coating is densified in the SiC matrix using at least one of chemical vapor infiltration (CVI), precursor impregnation pyrolysis (PIP), and reactive infiltration (RMI) methods, ultimately obtaining the gradient interfacial coating-reinforced SiC matrix composite. The material exhibits a flexural strength exceeding 200 MPa and a porosity ≤10%. Chemical vapor infiltration (CVI), precursor impregnation pyrolysis (PIP), and reactive infiltration (RMI) methods for SiC matrix densification are conventional techniques in this field and will not be elaborated upon here.

[0059] In summary, the Si content in the SiBN gradient interface coating gradually increases from the inside to the outside. The Si content in the inner SiBN interface coating is below 10 at.%, the Si content in the middle SiBN interface layer is 10 at.% to 15 at.%, and the Si content in the outermost SiBN interface layer is above 15 at.%. This gradient change in Si content is achieved by controlling at least one method: the deposition temperature during chemical vapor deposition (CVD) and the molar ratio of SiCl4 and NH3 gases in the precursor. The deposition temperature controls the Si content; with other process parameters remaining constant, the Si content gradually increases with increasing deposition temperature. Both deposition temperature and the molar ratio of SiCl4 and NH3 gases in the precursor can be used to control the Si content.

[0060] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0061] Example 1

[0062] A fiber preform with an outer surface deposited with a gradient SiBN interface and its preparation method are disclosed. In this gradient coating, the SiBN interface coating is continuously deposited on the fiber surface four times. The thickness of the SiBN interface coating gradually decreases from the inside to the outside, and the coating thickness is in the micrometer range. In this embodiment, the raw material of the fiber preform is SiC fiber. From the inside to the outside, the thickness of the first inner layer SiBN interface coating is 1.44 μm, the thickness of the second middle layer SiBN interface coating is 910 nm, the thickness of the third middle layer SiBN interface coating is 753 nm, and the thickness of the fourth outermost layer SiBN interface coating is 178 nm.

[0063] The method for preparing the gradient interface coating in the above embodiments includes the following steps: (1) Place the fiber preform into the constant temperature zone of the reaction chamber, evacuate the equipment of the deposition reaction chamber to about 10 Pa, then flush the equipment, fill it with inert gas Ar until the pressure inside the furnace is 10 kPa, and then continue to evacuate. Repeat the above operation 3 times until the vacuum degree inside the furnace reaches 0 Pa. (2) After the vacuum degree inside the furnace reaches 0 Pa, the temperature is first raised to 700°C at a rate of 10°C / min, and then raised to 770°C at a rate of 5°C / min. (3) After the temperature reaches 770℃, keep it at that temperature for 60 minutes, close all pipeline valves, and introduce argon gas until the pressure inside the furnace is about 2.5KPa. Then open the valves and introduce SiCl4, BCl3, NH3, H2, and Ar into the reaction chamber to deposit the first inner layer SiBN coating. The flow rate of SiCl4 is controlled at 400 ml / min and the purity is above 99.9%; the flow rate of BCl3 is controlled at 120 ml / min and the purity is 99.99%; the flow rate of NH3 is controlled at 360 ml / min and the purity is 99.99%; the flow rate of H2 is controlled at 360 ml / min and the purity is 99.999%; the flow rate of Ar is controlled at 360 ml / min and the purity is 99.999%; the deposition temperature is 800℃, the deposition pressure is 2.5 KPa, and the deposition time of the first inner layer SiBN interface layer is 8h. After the deposition is completed, cut off the process gas and introduce argon gas to replace it for 30min. (4) After the replacement is completed, the temperature is raised to 850℃ at a heating rate of 5℃ / min. SiCl4, BCl3, NH3, H2 and Ar are introduced into the furnace into the reaction chamber to deposit the second intermediate SiBN coating. The flow rate of SiCl4 is controlled at 400 ml / min and the purity is above 99.9%; the flow rate of BCl3 is controlled at 120 ml / min and the purity is 99.99%; the flow rate of NH3 is controlled at 1000 ml / min and the purity is 99.99%; the flow rate of H2 is 500 ml / min and the purity is 99.999%; the flow rate of Ar is 1000 ml / min and the purity is 99.999%; the deposition temperature is 850℃, the deposition pressure is 2 KPa, and the deposition time of the second intermediate SiBN interface layer is 6h. After the deposition is completed, the process gas is cut off and argon gas is introduced for replacement for 30min. (5) After the replacement is completed, the temperature is raised to 900℃ at a heating rate of 5℃ / min. SiCl4, BCl3, NH3, H2 and Ar are introduced into the furnace into the reaction chamber to deposit the third intermediate SiBN coating. The flow rate of SiCl4 is controlled at 300 ml / min and the purity is above 99.9%; the flow rate of BCl3 is controlled at 300 ml / min and the purity is 99.99%; the flow rate of NH3 is controlled at 3000 ml / min and the purity is 99.99%; the flow rate of H2 is 500 ml / min and the purity is 99.999%; the flow rate of Ar is 1000 ml / min and the purity is 99.999%; the deposition temperature is 900℃, the deposition pressure is 2 KPa, and the deposition time of the third intermediate SiBN interface layer is 5h. After the deposition is completed, the process gas is cut off and argon gas is introduced for replacement for 30min. (6) After the replacement is completed, the temperature is increased to 920°C at a heating rate of 5°C / min. SiCl4, BCl3, NH3, H2 and Ar are introduced into the furnace into the reaction chamber to deposit the fourth outermost SiBN coating. The flow rate of SiCl4 is controlled at 300 ml / min and the purity is above 99.9%; the flow rate of BCl3 is controlled at 500 ml / min and the purity is 99.99%; the flow rate of NH3 is controlled at 4000 ml / min and the purity is 99.99%; the flow rate of H2 is 800 ml / min and the purity is 99.999%; the flow rate of Ar is 1000 ml / min and the purity is 99.999%; the deposition temperature is 920°C and the deposition pressure is 2 KPa. The deposition time of the fourth outermost SiBN interface layer is 1 hour. After the deposition is completed, the process gas is cut off and the equipment begins to cool down naturally. When the temperature drops below 300°C, all equipment is shut down and the equipment is allowed to cool down naturally to room temperature.

[0064] After deposition, the SiC fiber preform was removed, and the elemental composition of the deposited gradient SiBN interface phase cross-section was analyzed using scanning electron microscopy. The Si atomic content in the first layer (innermost layer) of the SiBN interface phase was 5.84%, and the B atomic content was 38.42%. The Si atomic content in the second layer (middle layer) of the SiBN interface phase was 12.97%, and the B atomic content was 33.65%. The Si atomic content in the third layer (second outermost layer) of the SiBN interface phase was 19.91%, and the B atomic content was 26.38%. The Si atomic content in the fourth layer (outermost layer) of the SiBN interface phase was 24.71%, and the B atomic content was 12.89%.

[0065] The surface of the prepared SiBN interfacial phase was analyzed using X-ray photoelectron spectroscopy, such as... Figure 1 As shown in (a), the SiBN interface is mainly composed of NB, N-Si, and NO bonds. The XPS spectra show that the NB bond peak content is significantly higher than the N-Si bond peak content, indicating that the prepared SiBN interface phase is mainly composed of BN ceramic phase and supplemented by Si3N4 ceramic phase. Infrared spectroscopy was used to analyze the prepared SiBN interface phase, as shown in... Figure 1 As shown in (b), the prepared SiBN interface phase mainly includes BNB and Si-N-Si asymmetric stretching vibration peaks, which correspond to the vibration peaks of BN and Si3N4 ceramic phases, respectively, indicating that the prepared SiBN interface phase is mainly composed of BN and Si3N4 ceramic phases.

[0066] Example 2

[0067] A fiber preform with an outer surface deposited with a gradient SiBN interface and its preparation method are disclosed. In this gradient coating, the SiBN interface coating is continuously deposited on the fiber surface three times. The thickness of the SiBN interface coating gradually decreases from the inside to the outside, and the coating thickness is in the micrometer range. In this embodiment, the raw material of the fiber preform is SiC fiber. From the inside to the outside, the thickness of the first inner layer SiBN interface coating is 3.21 μm, the thickness of the second middle layer SiBN interface coating is 1.74 μm, and the thickness of the third outermost layer SiBN interface coating is 1.58 μm.

[0068] The method for preparing the gradient interface coating in the above embodiments includes the following steps: (1) Place the fiber preform into the constant temperature zone of the reaction chamber, evacuate the equipment of the deposition reaction chamber to about 10 Pa, then flush the equipment, fill it with inert gas Ar until the pressure inside the furnace is 10 kPa, and then continue to evacuate. Repeat the above operation 3 times until the vacuum degree inside the furnace reaches 0 Pa. (2) After the vacuum degree inside the furnace reaches 0 Pa, the temperature is first raised to 700°C at a rate of 10°C / min, and then raised to 780°C at a rate of 5°C / min. (3) After the temperature reaches 780℃, keep it at that temperature for 60 minutes, close all pipeline valves, and introduce argon gas until the furnace pressure is about 2.5KPa. Then open the valves and introduce SiCl4, BCl3, NH3, H2, and Ar into the reaction chamber to deposit the first inner layer SiBN coating. The flow rate of SiCl4 is controlled at 400 ml / min and the purity is above 99.9%; the flow rate of BCl3 is controlled at 200 ml / min and the purity is 99.99%; the flow rate of NH3 is controlled at 500 ml / min and the purity is 99.99%; the flow rate of H2 is 360 ml / min and the purity is 99.999%; the flow rate of Ar is 360 ml / min and the purity is 99.999%; the deposition temperature is 800℃, the deposition pressure is 2 KPa, and the deposition time of the first inner layer SiBN interface layer is 17.8h. After the deposition is completed, cut off the process gas and introduce argon gas to replace it for 30min. (4) After the replacement is completed, the temperature is raised to 870℃ at a heating rate of 5℃ / min. SiCl4, BCl3, NH3, H2 and Ar are introduced into the furnace into the reaction chamber to deposit the second intermediate SiBN coating. The flow rate of SiCl4 is controlled at 400 ml / min and the purity is above 99.9%; the flow rate of BCl3 is controlled at 200 ml / min and the purity is 99.99%; the flow rate of NH3 is controlled at 1000 ml / min and the purity is 99.99%; the flow rate of H2 is 500 ml / min and the purity is 99.999%; the flow rate of Ar is 1000 ml / min and the purity is 99.999%; the deposition temperature is 870℃, the deposition pressure is 2 KPa, and the deposition time of the second intermediate SiBN interface layer is 11.5h. After the deposition is completed, the process gas is cut off and argon gas is introduced for replacement for 30min. (5) After the replacement is completed, the temperature is increased to 930°C at a heating rate of 5°C / min. SiCl4, BCl3, NH3, H2 and Ar are introduced into the furnace into the reaction chamber to deposit the third outermost SiBN coating. The flow rate of SiCl4 is controlled at 300 ml / min and the purity is above 99.9%; the flow rate of BCl3 is controlled at 500 ml / min and the purity is 99.99%; the flow rate of NH3 is controlled at 4000 ml / min and the purity is 99.99%; the flow rate of H2 is 800 ml / min and the purity is 99.999%; the flow rate of Ar is 1000 ml / min and the purity is 99.999%; the deposition temperature is 930°C and the deposition pressure is 2 KPa. The deposition time of the third outermost SiBN interface layer is 10.5h. After the deposition is completed, the process gas is cut off and the equipment begins to cool down naturally. When the temperature drops below 300°C, all equipment is shut down and the equipment is allowed to cool down to room temperature naturally.

[0069] After deposition, the SiC fiber preform was removed, and the elemental composition of the deposited gradient SiBN interface phase cross-section was analyzed using scanning electron microscopy. The Si atomic content in the first layer (innermost layer) of the SiBN interface phase was 6.12%, and the B atomic content was 39.46%. The Si atomic content in the second layer (middle layer) of the SiBN interface phase was 13.86%, and the B atomic content was 32.95%. The Si atomic content in the third layer (outermost layer) of the SiBN interface phase was 19.91%, and the B atomic content was 26.38%.

[0070] Example 3

[0071] A fiber preform with an outer surface deposition gradient SiBN interface and its preparation method are disclosed. In this gradient coating, the SiBN interface coating is continuously deposited on the fiber surface three times. The thickness of the SiBN interface coating gradually decreases from the inside to the outside, and the coating thickness is at the nanometer level. In this embodiment, the raw material of the fiber preform is SiC fiber. From the inside to the outside, the thickness of the first inner layer SiBN interface coating is 92.3 nm, the thickness of the second middle layer SiBN interface coating is 113 nm, and the thickness of the third outermost layer SiBN interface coating is 76.8 nm.

[0072] The method for preparing the gradient interface coating in the above embodiments includes the following steps: (1) Place the fiber preform into the constant temperature zone of the reaction chamber, evacuate the equipment of the deposition reaction chamber to about 10 Pa, then flush the equipment, fill it with inert gas Ar until the pressure inside the furnace is 10 kPa, and then continue to evacuate. Repeat the above operation 3 times until the vacuum degree inside the furnace reaches 0 Pa. (2) After the vacuum degree inside the furnace reaches 0 Pa, the temperature is first raised to 700°C at a rate of 10°C / min, and then raised to 800°C at a rate of 5°C / min. (3) After the temperature reaches 800℃, keep it at that temperature for 60 minutes, close all pipeline valves, and introduce argon gas until the pressure inside the furnace is about 2.5KPa. Then open the valves and introduce SiCl4, BCl3, NH3, H2, and Ar into the reaction chamber to deposit the first inner layer SiBN coating. The flow rate of SiCl4 is controlled at 100 ml / min and the purity is above 99.9%; the flow rate of BCl3 is controlled at 200 ml / min and the purity is 99.99%; the flow rate of NH3 is controlled at 500 ml / min and the purity is 99.99%; the flow rate of H2 is 360 ml / min and the purity is 99.999%; the flow rate of Ar is 360 ml / min and the purity is 99.999%; the deposition temperature is 800℃, the deposition pressure is 2 KPa, and the deposition time of the first inner layer SiBN interface layer is 0.5h. After the deposition is completed, cut off the process gas and introduce argon gas to replace it for 30min. (4) After the replacement is completed, the temperature is raised to 870°C at a heating rate of 5°C / min. SiCl4, BCl3, NH3, H2 and Ar are introduced into the reaction chamber to deposit the second intermediate SiBN coating. The flow rate of SiCl4 is controlled at 100 ml / min and the purity is above 99.9%; the flow rate of BCl3 is controlled at 200 ml / min and the purity is 99.99%; the flow rate of NH3 is controlled at 1000 ml / min and the purity is 99.99%; the flow rate of H2 is 500 ml / min and the purity is 99.999%; the flow rate of Ar is 1000 ml / min and the purity is 99.999%; the deposition temperature is 870°C, the deposition pressure is 2 KPa, and the deposition time of the second intermediate SiBN interface layer is 45 min. After the deposition is completed, the process gas is cut off and argon gas is introduced for replacement for 30 min. (5) After the replacement is completed, the temperature is increased to 930°C at a heating rate of 5°C / min. SiCl4, BCl3, NH3, H2 and Ar are introduced into the furnace into the reaction chamber to deposit the third outermost SiBN coating. The flow rate of SiCl4 is controlled at 400 ml / min and the purity is above 99.9%; the flow rate of BCl3 is controlled at 500 ml / min and the purity is 99.99%; the flow rate of NH3 is controlled at 4000 ml / min and the purity is 99.99%; the flow rate of H2 is 800 ml / min and the purity is 99.999%; the flow rate of Ar is 1000 ml / min and the purity is 99.999%; the deposition temperature is 930°C and the deposition pressure is 2 KPa. The deposition time of the third outermost SiBN interface layer is 31 min. After the deposition is completed, the process gas is cut off and the equipment begins to cool down naturally. When the temperature drops below 300°C, all equipment is shut down and the equipment is allowed to cool down to room temperature naturally.

[0073] After deposition, the SiC fiber preform was removed, and the elemental composition of the deposited gradient SiBN interface phase cross-section was analyzed using scanning electron microscopy. The Si atomic content in the first layer (innermost layer) of the SiBN interface phase was 6.2%, and the B atomic content was 40.44%. The Si atomic content in the second layer (middle layer) of the SiBN interface phase was 13.12%, and the B atomic content was 32.57%. The Si atomic content in the third layer (outermost layer) of the SiBN interface phase was 20.59%, and the B atomic content was 23.28%.

[0074] Example 4

[0075] A fiber preform with an outer surface deposition gradient SiBN interface and its preparation method are disclosed. In this gradient coating, the SiBN interface coating is continuously deposited on the fiber surface three times. The thickness of the SiBN interface coating gradually decreases from the inside to the outside, and the coating thickness is in the micrometer range. In this embodiment, the raw material of the fiber preform is SiC fiber. From the inside to the outside, the thickness of the first inner layer SiBN interface coating is 1.80 μm, the thickness of the second middle layer SiBN interface coating is 1.04 μm, and the thickness of the third outermost layer SiBN interface coating is 904.6 nm.

[0076] The method for preparing the gradient interface coating in the above embodiments includes the following steps: (1) Place the fiber preform into the constant temperature zone of the reaction chamber, evacuate the equipment of the deposition reaction chamber to about 10 Pa, then flush the equipment, fill it with inert gas Ar until the pressure inside the furnace is 10 kPa, and then continue to evacuate. Repeat the above operation 3 times until the vacuum degree inside the furnace reaches 0 Pa. (2) After the vacuum degree inside the furnace reaches 0 Pa, the temperature is first raised to 700°C at a rate of 10°C / min, and then raised to 800°C at a rate of 5°C / min. (3) After the temperature reaches 800℃, keep it at that temperature for 60 minutes, close all pipeline valves, and introduce argon gas until the pressure inside the furnace is about 2.5KPa. Then open the valves and introduce SiCl4, BCl3, NH3, H2, and Ar into the reaction chamber to deposit the first inner layer SiBN coating. The flow rate of SiCl4 is controlled at 200 ml / min and the purity is above 99.9%; the flow rate of BCl3 is controlled at 200 ml / min and the purity is 99.99%; the flow rate of NH3 is controlled at 500 ml / min and the purity is 99.99%; the flow rate of H2 is 360 ml / min and the purity is 99.999%; the flow rate of Ar is 360 ml / min and the purity is 99.999%; the deposition temperature is 800℃, the deposition pressure is 2 KPa, and the deposition time of the first inner layer SiBN interface layer is 18.4h. After the deposition is completed, cut off the process gas and introduce argon gas to replace it for 30min. (4) After the replacement is completed, the temperature is raised to 880℃ at a heating rate of 5℃ / min. SiCl4, BCl3, NH3, H2 and Ar are introduced into the furnace into the reaction chamber to deposit the second intermediate SiBN coating. The flow rate of SiCl4 is controlled at 100 ml / min and the purity is above 99.9%; the flow rate of BCl3 is controlled at 200 ml / min and the purity is 99.99%; the flow rate of NH3 is controlled at 1000 ml / min and the purity is 99.99%; the flow rate of H2 is 500 ml / min and the purity is 99.999%; the flow rate of Ar is 1000 ml / min and the purity is 99.999%; the deposition temperature is 880℃, the deposition pressure is 2 KPa, and the deposition time of the second intermediate SiBN interface layer is 6.8h. After the deposition is completed, the process gas is cut off and argon gas is introduced for replacement for 30min. (5) After the replacement is completed, the temperature is increased to 940°C at a heating rate of 5°C / min. SiCl4, BCl3, NH3, H2 and Ar are introduced into the furnace into the reaction chamber to deposit the third outermost SiBN coating. The flow rate of SiCl4 is controlled at 400 ml / min and the purity is above 99.9%; the flow rate of BCl3 is controlled at 500 ml / min and the purity is 99.99%; the flow rate of NH3 is controlled at 4000 ml / min and the purity is 99.99%; the flow rate of H2 is 800 ml / min and the purity is 99.999%; the flow rate of Ar is 1000 ml / min and the purity is 99.999%; the deposition temperature is 940°C and the deposition pressure is 2 KPa. The deposition time of the third outermost SiBN interface layer is 6h. After the deposition is completed, the process gas is cut off and the equipment begins to cool down naturally. When the temperature drops below 300°C, all equipment is shut down and the equipment is allowed to cool down naturally to room temperature.

[0077] After deposition, the SiC fiber preform was removed, and the elemental composition of the deposited gradient SiBN interface phase cross section was analyzed using scanning electron microscopy. The Si atomic content in the first layer (innermost layer) of the SiBN interface phase was 7.06%, and the B atomic content was 41.38%. The Si atomic content in the second layer (middle layer) of the SiBN interface phase was 14.16%, and the B atomic content was 32.69%. The Si atomic content in the third layer (outermost layer) of the SiBN interface phase was 21.87%, and the B atomic content was 22.46%.

[0078] Example 5

[0079] A fiber preform with an outer surface-deposited gradient SiBN interfacial coating is used to prepare SiC / SiC composite materials. The material has a flexural strength of 283 MPa and a modulus of 189 GPa. The method for preparing the SiC / SiC composite material in the above embodiment includes the following steps: (1) The preparation method and process of the gradient interface coating on the outer surface are the same as those in Example 3 above; (2) The prepared functional gradient interface coating fiber preform was placed in the reaction chamber of the furnace for SiC matrix densification. The vacuum was purged three times. After the vacuum reached 0 Pa, the temperature was increased to 990℃ at a heating rate of 5℃ / min. MTS, H2 and Ar were introduced into the furnace to deposit the SiC matrix in the reaction chamber. The flow rate of MTS was controlled at 200 ml / min and the purity was above 99.8%. The flow rate of H2 was controlled at 2000 ml / min and the purity was 99.99%. The flow rate of Ar was 500 ml / min and the purity was 99.999%. The deposition temperature was 990℃, the deposition pressure was 3 KPa, and the deposition time was 50h. After the deposition was completed, the process gas was cut off, and the substrate was taken out after cooling to room temperature. (3) Further densification of the initially densified material is carried out using a precursor impregnation pyrolysis method. Liquid polycarbonylsilane with a molecular weight of 1600 is used for impregnation, and pyrolysis is carried out under an Ar protective atmosphere. The impregnation vacuum degree is 10 kPa, the impregnation time is 120 minutes, and the curing temperature is 200°C. o C, curing time is 12 hours, pyrolysis temperature is 1200℃. o C, the time is 3 hours, the impregnation pyrolysis process is repeated 6 times until the material weight gain is less than 1%, and then SiC / SiC material is obtained after removal.

[0080] Table 1 SiC f / SiBN1 / SiBN2 / SiBN3 / SiC materials and SiC f / SiBN / SiC material 1000 o Comparison of bending strength retention rate data after 100 hours of oxygenation in water.

[0081] Table 1 shows the results of 1000 hours of toughening protection of SiC / SiC composite materials using the three-layer gradient SiBN interface coating of this invention and SiC / SiC composite materials using only the SiBN interface as the interface phase. o The table shows the flexural strength retention rate after 100 hours of oxidation in water. As can be seen from the table, the flexural strength retention rate of the material with a 3-layer gradient SiBN interface coating after high temperature and long-term oxidation is 105.62%, which is significantly higher than that of the material with a single SiBN interface phase, SiC / SiC.

[0082] Comparative Example 1 A fiber preform with an outer surface-deposited gradient SiBN interfacial coating was used to prepare SiC / SiC composite materials. The Si content in the SiBN interfacial phase gradually decreased from the inside to the outside. Three-point bending strength testing was performed on the prepared material, and the bending strength was 164.55 MPa, significantly lower than the mechanical properties of the material in Example 5. In this comparative example, the fiber preform raw material was SiC fiber. From the inside to the outside, the thickness of the first inner SiBN interfacial coating layer was 76.8 nm, the second middle SiBN interfacial coating layer was 113 nm, and the third outermost SiBN interfacial coating layer was 92.3 nm.

[0083] The method for preparing SiC / SiC composite materials in the above embodiments includes the following steps: (1) Place the fiber preform into the constant temperature zone of the reaction chamber, evacuate the equipment of the deposition reaction chamber to about 10 Pa, then flush the equipment, fill it with inert gas Ar until the pressure inside the furnace is 10 kPa, and then continue to evacuate. Repeat the above operation 3 times until the vacuum degree inside the furnace reaches 0 Pa. (2) After the vacuum degree inside the furnace reaches 0 Pa, the temperature is first raised to 700°C at a rate of 10°C / min, and then raised to 930°C at a rate of 5°C / min. (3) After the temperature reaches 930℃, keep it at that temperature for 60 minutes, close all pipeline valves, and introduce argon gas until the pressure inside the furnace is about 2.5KPa. Then open the valves and introduce SiCl4, BCl3, NH3, H2, and Ar into the reaction chamber to deposit the innermost layer of the first SiBN coating. The flow rate of SiCl4 is controlled at 400 ml / min and the purity is above 99.9%; the flow rate of BCl3 is controlled at 500 ml / min and the purity is 99.99%; the flow rate of NH3 is controlled at 4000 ml / min and the purity is 99.99%; the flow rate of H2 is 800 ml / min and the purity is 99.999%; the flow rate of Ar is 1000 ml / min and the purity is 99.999%; the deposition temperature is 930℃ and the deposition pressure is 2KPa. The deposition time of the outermost SiBN interface layer is 31 minutes. After the deposition is completed, cut off the process gas and introduce argon gas to replace it for 30 minutes. (4) After the argon purging is completed, the temperature is cooled down. When the temperature drops to 870℃, it is held for 60 minutes. SiCl4, BCl3, NH3, H2 and Ar are introduced into the furnace into the reaction chamber to deposit the second intermediate SiBN coating. The flow rate of SiCl4 is controlled at 100 ml / min and the purity is above 99.9%; the flow rate of BCl3 is controlled at 200 ml / min and the purity is 99.99%; the flow rate of NH3 is controlled at 1000 ml / min and the purity is 99.99%; the flow rate of H2 is 500 ml / min and the purity is 99.999%; the flow rate of Ar is 1000 ml / min and the purity is 99.999%; the deposition temperature is 870℃, the deposition pressure is 2KPa, and the deposition time of the second intermediate SiBN interface layer is 45 minutes. After the deposition is completed, the process gas is cut off and argon is introduced for purging for 30 minutes. (5) After the argon gas replacement is completed, the temperature is cooled down. When the temperature drops to 800℃, it is kept at that temperature for 60 minutes. SiCl4, BCl3, NH3, H2 and Ar are introduced into the furnace into the reaction chamber to deposit the first inner layer SiBN coating. The flow rate of SiCl4 is controlled at 100 ml / min and the purity is above 99.9%; the flow rate of BCl3 is controlled at 200 ml / min and the purity is 99.99%; the flow rate of NH3 is controlled at 500 ml / min and the purity is 99.99%; the flow rate of H2 is 360 ml / min and the purity is 99.999%; the flow rate of Ar is 360 ml / min and the purity is 99.999%; the deposition temperature is 800℃ and the deposition pressure is 2KPa. The deposition time of the third inner layer SiBN interface layer is 0.5h. After the deposition is completed, the process gas is cut off and the equipment begins to cool down naturally. When the temperature drops below 300℃, all equipment is turned off and the equipment is allowed to cool down naturally to room temperature. (6) The prepared functional gradient interface coating fiber preform was placed in the reaction chamber of the furnace for SiC matrix densification. The vacuum was purged three times. After the vacuum reached 0 Pa, the temperature was increased to 990 °C at a heating rate of 5 °C / min. MTS, H2 and Ar were introduced into the furnace to deposit the SiC matrix in the reaction chamber. The flow rate of MTS was controlled at 200 ml / min and the purity was above 99.8%. The flow rate of H2 was controlled at 2000 ml / min and the purity was 99.99%. The flow rate of Ar was 500 ml / min and the purity was 99.999%. The deposition temperature was 990 °C, the deposition pressure was 3 KPa, and the deposition time was 50 h. After the deposition was completed, the process gas was cut off, and the substrate was taken out after cooling to room temperature. (7) Further densification of the initially densified material is carried out using a precursor impregnation pyrolysis method. Liquid polycarbonylsilane with a molecular weight of 1600 is used for impregnation, and pyrolysis is carried out under an Ar protective atmosphere. The impregnation vacuum degree is 10 kPa, the impregnation time is 120 minutes, and the curing temperature is 200°C. o C, curing time is 12 hours, pyrolysis temperature is 1200℃. o C, the time is 3 hours, the impregnation pyrolysis process is repeated 6 times until the material weight gain is less than 1%, and then SiC / SiC material is obtained after removal.

[0084] After deposition, the SiC fiber preform was removed, and the elemental composition of the deposited gradient SiBN interface phase cross-section was analyzed using scanning electron microscopy. The Si atomic content in the first layer (innermost layer) of the SiBN interface phase was 20.59%, and the B atomic content was 23.28%. The Si atomic content in the second layer (middle layer) of the SiBN interface phase was 13.12%, and the B atomic content was 32.57%. The Si atomic content in the third layer (outermost layer) of the SiBN interface phase was 6.2%, and the B atomic content was 40.44%.

Claims

1. A fiber preform with an outer surface deposited with a gradient SiBN interfacial coating, characterized in that, include: Fiber preform and a multilayer structured gradient SiBN interface coating deposited on the surface of the fiber preform; The Si content of the multilayer gradient SiBN interface coating increases gradually from the inside to the outside, while the B content decreases gradually from the inside to the outside.

2. The fiber preform with an outer surface deposited with a gradient SiBN interface coating according to claim 1, characterized in that, The Si content of the innermost SiBN interface coating is less than 10 at.%, preferably less than 8 at.%; the Si content of the middle SiBN interface coating is 10 at.% to 15 at.%, preferably 12 at.% to 15 at.%; and the Si content of the outermost SiBN interface coating is more than 15 at.%, preferably more than 18 at.%.

3. The fiber preform with an outer surface deposited with a gradient SiBN interface coating according to claim 1 or 2, characterized in that, The innermost SiBN interface coating has a boron content of 35 at.% or more, preferably 38 at.% or more; the middle SiBN interface coating has a boron content of 30 at.% to 35 at.%; and the outermost SiBN interface coating has a boron content of less than 30 at.%, preferably less than 28 at.%.

4. The fiber preform with an outer surface deposited with a gradient SiBN interface coating according to any one of claims 1 to 3, characterized in that, The gradient change in Si element content of the gradient SiBN interface coating is achieved by controlling the deposition temperature and the molar ratio of silicon source and nitrogen source gases in the precursor through chemical vapor deposition process at least one method; the gradient change in B element content of the gradient SiBN interface coating is achieved by controlling the deposition temperature and the molar ratio of boron source and / or nitrogen source gases in the precursor through chemical vapor deposition process at least one method.

5. The fiber preform with an outer surface deposited with a gradient SiBN interface coating according to any one of claims 1 to 4, characterized in that, The gradient SiBN interface coating has n³² layers, preferably 2 to 10 layers, and more preferably 3 layers. For example, the gradient SiBN interface coating has a 3-layer structure consisting of an inner layer, a middle layer, and an outer layer. In the 3-layer structure, the thickness of the inner SiBN interface coating is 20 nm to 10 µm, preferably 300 nm to 1200 nm; the thickness of the middle SiBN interface coating is 20 nm to 5 μm; and the thickness of the outer SiBN interface coating is 20 nm to 5 μm. The total thickness of the three interface phases (inner, middle, and outer layers) is 60 nm to 20 μm, preferably 340 nm to 1500 nm.

6. The fiber preform with an outer surface deposited with a gradient SiBN interface coating according to any one of claims 1 to 5, characterized in that, The fiber includes at least one of carbon fiber, SiC fiber, silicon nitride fiber, alumina fiber, boron nitride fiber, SiCN fiber, and SiBN fiber; the structural form of the fiber preform includes at least one of fiber stitched preform, fiber needle-punched preform, fiber two-dimensional fabric laminated preform, 2.5D braiding, fiber three-dimensional four-dimensional, three-dimensional five-dimensional, and three-dimensional six-dimensional braiding.

7. A method for preparing a fiber preform with an outer surface deposited with a gradient SiBN interface coating according to any one of claims 1 to 6, comprising the following steps: (1) Place the fiber preform in the constant temperature zone of the furnace in the deposition system. After vacuum rinsing, raise the furnace temperature to 700~950°C after reaching the set vacuum level. o C and maintain at that temperature; (2) After the heat preservation is completed, the temperature inside the furnace is adjusted to the deposition temperature of the interface coating process, and the process gas is introduced into the furnace to obtain the fiber preform modified by the initial SiBN interface coating through deposition. (3) After step (2) is completed, the process gas is cut off, and the process gas is continued to be introduced into the furnace after being replaced with dilution gas. The fiber preform modified with secondary SiBN interface coating is obtained by deposition. (4) After step (3) is completed, the process gas is cut off, and the process gas is continued to be introduced into the furnace after being replaced with dilution gas. Under constant temperature and pressure, the fiber preform deposited in step (3) continues to be deposited to obtain the final gradient SiBN interface coating modified fiber preform.

8. The preparation method according to claim 7, characterized in that, In step (2), the process gases include SiCl4, BCl3, NH3, H2 and Ar, with the molar ratio of NH3 to BCl3 being 0.5~3, the molar ratio of BCl3 to SiCl4 being 0.3~10, the molar ratio of H2 to Ar being 0.5~10, and the molar ratio of NH3 to H2 being 0.25~1.5; the deposition temperature of the interface coating is 650~800℃, the deposition time is 0.5~20 hours, and the deposition pressure is 0.5~3KPa.

9. The preparation method according to claim 7 or 8, characterized in that, In step (3), the process gases include SiCl4, BCl3, NH3, H2 and Ar, the molar ratio of NH3 to BCl3 is 3~100, preferably 3~12, the molar ratio of BCl3 to SiCl4 is 0.1~3, the molar ratio of H2 to Ar is 0.5~10, and the molar ratio of NH3 to H2 is 1.5~6; the deposition temperature of the interface coating is 650~950℃, the deposition time is 0.5~12 hours, and the deposition pressure is 0.5~3KPa.

10. The preparation method according to any one of claims 7 to 9, characterized in that, In step (4), the process gases include SiCl4, BCl3, NH3, H2 and Ar, with the molar ratio of NH3 to BCl3 being 3~30, the molar ratio of BCl3 to SiCl4 being 0.05~3, the molar ratio of H2 to Ar being 0.5~10, and the molar ratio of NH3 to H2 being 1.5~15; the deposition temperature of the interface coating is 650~950℃, the deposition time is 0.5~12 hours, and the deposition pressure is 0.5~3KPa.

11. A fiber-reinforced ceramic matrix composite material, characterized in that, The fiber-reinforced ceramic matrix composite material comprises a fiber preform with an outer surface deposited with a gradient SiBN interfacial coating according to any one of claims 1 to 6; preferably, the fiber preform with the outer surface deposited with the gradient SiBN interfacial coating is densified into a SiC matrix using at least one of chemical vapor infiltration, precursor impregnation pyrolysis, and reactive melt infiltration methods to obtain a gradient interfacial coating reinforced SiC matrix composite material; wherein the gradient interfacial coating reinforced SiC matrix composite material has a flexural strength of ≥200 MPa and a porosity ≤10%.

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