Interface phase preparation method based on low-temperature chemical vapor deposition and instant online high-temperature heat treatment

Abstract

The invention relates to a continuous preparation method of an interface phase with uniformity and high thermal stability, and belongs to the technical field of ceramic matrix composite material preparation. In order to solve the problems that an interface phase prepared by low-temperature chemical vapor deposition is uniform but poor in stability, and interface phase pollution is easily caused by off-line high-temperature heat treatment, the invention provides a continuous preparation method. The method comprises the steps that a flexible fiber substrate firstly penetrates through a low-temperature chemical vapor deposition area, and a uniform initial interface phase is obtained; and then directly entering a real-time online high-temperature heat treatment area without passing through an atmospheric environment, and carrying out real-time online high-temperature crystallization treatment at 1350-1800 DEG C. According to the method, through series integration of low-temperature deposition and online high-temperature heat treatment, online continuous completion of the whole deposition-crystallization process of the interface phase is achieved, water and oxygen pollution in the interface phase transfer process is fundamentally avoided, and finally the interface phase has excellent uniformity and high thermal stability; and a reliable base interface phase preparation technology is provided for the high-performance ceramic-based composite material.

Description

Technical Field

[0001] This invention relates to the preparation of interfacial phases for reinforcing fibers in ceramic matrix composites, and particularly to a method for preparing interfacial phases based on low-temperature chemical vapor deposition and instantaneous online high-temperature heat treatment. Background Technology

[0002] The properties of ceramic matrix composites (CMCs) largely depend on the interfacial phase between the fibers and the matrix. An ideal interfacial phase possesses suitable chemical stability, a layered structure, and good compatibility with both the fibers and the matrix. Boron nitride (BN) interfacial phases are widely used as interfacial materials for high-performance CMCs because they meet these requirements. The mechanical fracturing effect and corrosion resistance of the BN interfacial phase are closely related to its degree of crystallinity. In ceramic matrix composites used in aerospace propulsion, a high degree of crystallinity in the BN interfacial phase is generally desirable, resulting in good mechanical fracturing effect and resistance to oxidation and corrosion. In particular, under certain conditions, such as long-term service environments exceeding the preparation temperature of the BN interfacial phase, high-temperature stability of the BN interfacial phase is also required; the BN interfacial phase must not undergo adverse changes such as decomposition or shrinkage at high temperatures.

[0003] Chemical vapor deposition (CVD) is the most commonly used technique for preparing BN interfacial phases. Based on the application of continuous fiber reinforcements, the CVD preparation processes for BN interfacial phases can be mainly divided into three categories: the first category is fiber preforms with millimeter-level thickness and defined three-dimensional geometry; the second category is two-dimensional fiber fabrics; and the third category is continuous fiber bundles.

[0004] For the first type of fiber preform, since it can only be placed in a CVD reaction chamber, a low-temperature CVD method with a slow deposition rate is used. The deposition temperature should not exceed 900℃, and the deposition rate should be controlled at only a few nanometers to tens of nanometers per hour to deposit BN into the internal pores of the fiber preform. The BN interface phase deposited using this method is amorphous, containing numerous defects such as dangling bonds, and exhibits poor chemical and thermal stability. After deposition, subsequent ex-situ or in-situ high-temperature treatment is necessary to obtain a BN interface phase with certain high-temperature stability and crystallinity, achieving interfacial mechanical fusing and oxidation corrosion resistance. This method has become one of the typical technologies in the field of ceramic matrix composites.

[0005] For the second type of two-dimensional fiber fabric and the third type of continuous fiber bundle, since they are flexible thin substrates that can be wound, they can be continuously moved through the CVD reaction chamber by winding to prepare the BN interface phase on the fiber surface. Considering the deposition efficiency, the deposition process with a very low deposition rate, which is typical for the first type, is generally not used when preparing the BN interface phase by continuous winding. On the other hand, to obtain a BN interface phase with good high-temperature stability and crystallinity, high-temperature chemical vapor deposition with a high deposition rate is generally used in the case of continuous winding, with deposition temperatures reaching over 1400℃, and in some cases even 1600℃. However, due to the high reaction rate at high temperatures (reaching tens or even hundreds of micrometers per hour), it is very easy to cause excessive deposition on the outer surface of the fiber bundle and insufficient deposition inside the fiber bundle, resulting in a very uneven distribution of the interface phase inside and outside the fiber bundle, thus affecting the subsequent performance of ceramic matrix composites.

[0006] Appropriately lowering the CVD temperature can effectively alleviate the uneven deposition inside and outside the fiber bundle, improving the uniform deposition. However, a negative effect is insufficient thermal stability and poor crystallinity of the obtained BN interface phase. To improve the high-temperature stability and crystallinity of the BN interface phase, after deposition, the fibers with the deposited BN interface phase on the winding mechanism can be removed from the reactor and wound onto a high-temperature resistant graphite or C / C tooling, then placed in another high-temperature furnace for high-temperature heat treatment (due to the inclusion of electronic components in the winding structure and the material's poor heat resistance, the winding mechanism and the coated fiber substrate on it cannot be simply moved into the high-temperature furnace for heat treatment). This "offline heat treatment" mode has a fatal flaw: BN materials with poor crystallinity, especially amorphous BN obtained by low-temperature deposition, are extremely prone to moisture absorption and oxidation in the air. During sample transfer and unwinding, the interface phase will be exposed to the atmospheric environment for a long time, leading to the formation of boron-oxygen hydrates on its surface. The oxygen content of the interface phase obtained after heat treatment is too high, severely degrading the interface phase properties, and thus damaging the mechanical properties and service life of the composite material. At the same time, this method also significantly increases workload and cost, and reduces efficiency.

[0007] Patent (CN 119265550 A, Continuous Chemical Vapor Deposition Equipment and Method) proposes an apparatus and method potentially applicable to SiC material deposition. This involves setting up a deposition preparation chamber, a deposition chamber, and a heat treatment chamber within a vacuum apparatus. Specifically, the reactor in the deposition chamber can be moved to the heat treatment chamber for high-temperature heat treatment or cooling after deposition is completed within the deposition chamber. However, this apparatus and method are only potentially applicable to fixed substrates, and they are merely a simple upgrade or modification of traditional fixed-substrate chemical vapor deposition apparatus or methods. It only involves intermittently moving the reactor between the three regions to prepare for the next step, thus remaining a traditional intermittent chemical vapor deposition process and not a typical continuous chemical vapor deposition. On the other hand, due to the inclusion of electronic components in the winding structure of continuous fibers and the fact that the material is not resistant to high temperatures, and the fact that the winding mechanism is mechanically and electrically connected to the outside of the closed reaction system, it is not possible to simply move the winding mechanism along with the fiber substrate with the coating deposited on it into the high-temperature chamber of the device for heat treatment. Furthermore, the device requires valves to isolate the different areas from each other, while the continuous fibers need to be connected to each other during the deposition process. Therefore, the device and method are not suitable for the continuous preparation of BN interface phase on continuous fiber substrates that require continuous movement.

[0008] Therefore, there is an urgent need in this field for a preparation method that can balance the uniformity of the continuous fiber interface phase with high thermal stability. The ideal solution would be to achieve seamless online integration of "deposition" and "crystallization" during the continuous manufacturing process of the fiber interface phase, avoiding water- and oxygen-based contamination and damage to the interface phase caused by intermediate steps. However, existing technologies lack effective means to rapidly and efficiently perform high-temperature heat treatment on moving fiber substrates that are compatible with continuous winding systems. Developing an innovative online heat treatment technology is key to overcoming these technological bottlenecks. Summary of the Invention

[0009] To address the shortcomings of existing technologies, such as low-temperature chemical vapor deposition (LCVD) producing boron nitride interfacial phases that are uniform but unstable, and subsequent offline high-temperature heat treatment that easily leads to interfacial phase contamination and degradation, this invention provides an interfacial phase preparation method based on low-temperature deposition and online high-temperature heat treatment. The core of this method lies in the following: during the continuous movement of the flexible substrate, deposition is first performed in the low-temperature LCVD reaction zone to obtain a relatively uniform interfacial phase inside and outside the fiber bundle. Subsequently, the phase is immediately passed through an instant high-temperature heat treatment zone, thereby achieving an online transformation of the interfacial phase from a "uniform, amorphous state" or "high-temperature unstable state" to a "uniform, crystalline state" or "high-temperature stable state" without interrupting the process flow or exposing it to the atmosphere.

[0010] The method for preparing an interface phase based on low-temperature deposition and instant online high-temperature heat treatment includes: setting up a winding device in a closed reaction system and loading a flexible fiber substrate onto the winding device; the unwinding element of the winding device is configured at the inlet end of the low-temperature chemical vapor deposition zone, and the winding element of the winding device is configured at the outlet end of the high-temperature heat treatment zone; the low-temperature chemical vapor deposition zone and the high-temperature heat treatment zone are connected in series in the closed reaction system; the winding device is started to make the flexible fiber substrate move continuously through the low-temperature chemical vapor deposition zone at a set speed, and after the chemical vapor deposition is completed, the flexible fiber substrate with the initial interface phase deposited is continuously moved and immediately enters the high-temperature heat treatment zone without contacting the atmosphere; the flexible fiber substrate after instant online high-temperature heat treatment is cooled and wound up in an atmosphere-isolated environment to obtain an interface phase with both uniformity and high thermal stability.

[0011] In some technical solutions, the flexible fiber substrate is selected from one or a composite of SiC fiber, carbon fiber, SiBCN fiber, SiCN fiber, SiBN fiber, BN fiber, and Si3N4 fiber.

[0012] In some technical solutions, the deposition temperature of low-temperature chemical vapor deposition is 600℃~1300℃, preferably 800℃~1250℃.

[0013] In some technical solutions, the online high-temperature heat treatment temperature is 1350℃~1800℃; the online high-temperature heat treatment time is 5 seconds~150 seconds.

[0014] In some technical solutions, the online high-temperature heat treatment device is selected from any one of the following: DC electric heating device, AC electric heating device, induction heating device, ultra-high temperature radiation heating device, Joule heating device, and microwave heating device.

[0015] In some technical solutions, the interface phase is a ceramic matrix composite reinforced fiber interface phase, preferably a boron nitride-based interface phase, and more preferably a hexagonal boron nitride-based interface phase with a layered structure.

[0016] In some technical solutions, the boron nitride-based interface phase is an undoped boron nitride interface phase, a silicon-doped boron nitride-based interface phase, or a silicon-carbon co-doped boron nitride-based interface phase.

[0017] In some technical solutions, the interface phase is an undoped boron nitride interface phase, and the process gas includes a precursor process gas and an auxiliary process gas; the precursor process gas includes a boron source and a nitrogen source in gaseous form; for example, the boron source is boron trichloride, and the nitrogen source is ammonia; for example, the auxiliary process gas is hydrogen, nitrogen, or a hydrogen-nitrogen mixture.

[0018] In some technical solutions, the interface phase is a silicon-doped boron nitride-based interface phase, and the process gas includes a precursor process gas and an auxiliary process gas; the precursor process gas includes a boron source, a nitrogen source, and a silicon source in gaseous form; for example, the boron source is boron trichloride, the nitrogen source is ammonia, and the silicon source is one or a mixture of silicon tetrachloride, trichlorosilane, and silane; for example, the auxiliary process gas is hydrogen, nitrogen, or a hydrogen-nitrogen mixture.

[0019] In some technical solutions, the interface phase is a silicon-carbon co-doped boron nitride-based interface phase, and the process gas includes a precursor process gas and an auxiliary process gas; wherein, the precursor process gas includes a boron source, a nitrogen source, a silicon source, and a carbon source in gaseous form; for example, the boron source is boron trichloride, the nitrogen source is ammonia, the silicon source is one or a mixture of trichloromethylsilane, silicon tetrachloride, and trichlorosilane, and the carbon source is one or a mixture of trichloromethylsilane and methane; for example, the auxiliary process gas is hydrogen, nitrogen, or a hydrogen-nitrogen mixture.

[0020] In some technical solutions, the oxygen content of the interface phase is below 10 at%.

[0021] The present invention has the following beneficial effects: This invention integrates low-temperature deposition with real-time online high-temperature heat treatment, realizing a continuous and automated "deposition-crystallization" process for high-quality BN interface phases on flexible fiber substrates. It effectively solves the key technical problems of difficulty in achieving both deposition uniformity and thermal stability in traditional methods, as well as interface phase contamination caused by offline processing. It provides a reliable interface phase preparation technology based on continuous fiber bundles or two-dimensional fiber cloth for the development of high-performance ceramic matrix composites. Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating the principle of the interface phase preparation method based on low-temperature deposition and high-temperature heat treatment described in this invention. Figure 2 The cross-sectional morphology of the BN interface phase obtained in Embodiment 1 of the present invention is shown in a scanning electron microscope image. The obtained BN interface phase has a typical layered structure of crystalline hexagonal BN. Figure 3 The cross-sectional morphology of the BN interface phase obtained in Embodiment 2 of the present invention is shown in a scanning electron microscope image. The obtained BN interface phase has a typical layered structure of crystalline hexagonal BN. Figure 4 A cross-sectional scanning electron microscope image of the Si and C doped BN interface phase obtained in Example 3 of the present invention is shown. The obtained interface phase has the layered structure characteristics of crystalline hexagonal BN. Figure 5a and Figure 5bThe cross-sectional scanning electron microscope (SEM) images of the silicon-doped BN interface phase obtained by Comparative Example 1 using conventional offline heat treatment (i.e., the sample is removed from the furnace after deposition and then placed in another high-temperature furnace for treatment) are shown before and after heat treatment. Detailed Implementation

[0023] The present invention will be further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0024] This invention primarily addresses the problems of poor interfacial phase stability in boron nitride obtained through single low-temperature deposition and the tendency for interfacial phase contamination during traditional offline high-temperature heat treatment. The core of this invention lies in constructing an integrated continuous system and continuous processing method. During the movement of the flexible fiber substrate, the interfacial phase is first uniformly deposited in the low-temperature chemical vapor deposition zone, and then stabilized and crystallized through real-time online high-temperature heat treatment without contact with the atmosphere. This results in a single process obtaining an interfacial phase that combines uniform deposition inside and outside the fiber bundle with high thermal stability.

[0025] The following combination Figure 1 This paper exemplifies an interface phase preparation method based on low-temperature chemical vapor deposition (LCV) and real-time online high-temperature heat treatment. The figure illustrates the core components of the entire reaction system, the workflow, and the series relationship between the low-temperature LCV deposition zone and the high-temperature heat treatment zone.

[0026] System preparation. A closed reaction system is provided, in which a low-temperature chemical vapor deposition device (low-temperature chemical vapor deposition reaction zone, low-temperature chemical vapor deposition reaction chamber) and an online high-temperature heat treatment device (online high-temperature heat treatment zone) are sequentially arranged along the movement direction of the flexible fiber substrate.

[0027] Any commercially available chemical vapor deposition (CVD) apparatus can be used. The CVD apparatus can be a typical thermochemical vapor deposition (TCVD) apparatus or an external field-assisted CVD apparatus (UV light, plasma, etc.). The reactor can be a closed reactor. The inlet and outlet channels of the CVD apparatus are conventional in the art and will not be described further. It should be understood that the outlet channel of the CVD apparatus is located outside the high-temperature heat treatment zone.

[0028] A winding device is also provided within the closed reaction system. The structure of the winding device is not limited, as long as it can continuously and stably wind up or unwind the flexible substrate. The winding device includes an unwinding element (unwinding mechanism) and a winding element (winding mechanism). The unwinding element is located at the inlet end of the low-temperature chemical vapor deposition zone. The winding element is located at the outlet end of the high-temperature heat treatment zone. Correspondingly, the outlet end of the low-temperature chemical vapor deposition zone and the inlet end of the high-temperature heat treatment zone are connected in series. In other words, the outlet end of the low-temperature chemical vapor deposition zone and the inlet end of the high-temperature heat treatment zone maintain a series connection.

[0029] The winding device can be a roller-shaped winding device. As an example, the winding device includes an unwinding roller, a guide roller, and a take-up roller. The unwinding roller is located at the inlet end of the low-temperature chemical vapor deposition reaction zone, and the take-up roller is located at the outlet end of the online high-temperature heat treatment zone. Pairs of guide rollers are also placed at the inlet end of the low-temperature chemical vapor deposition reaction zone and the outlet end of the online high-temperature heat treatment zone, respectively. Furthermore, the guide rollers are closer to the inlet end of the low-temperature chemical vapor deposition reaction zone and the outlet end of the online high-temperature heat treatment zone than the unwinding roller and the take-up roller. The function of the guide rollers is to change direction and generate tension. The number of guide rollers can be adjusted as needed. Preferably, there are four guide rollers. For example, the first pair of guide rollers is located at the inlet end of the low-temperature chemical vapor deposition reaction zone, and the second pair of guide rollers is located at the outlet end of the online high-temperature heat treatment zone. In an embodiment of the invention, a flexible substrate is loaded onto the unwinding roller, pulled sequentially through the low-temperature chemical vapor deposition zone and the online high-temperature heat treatment zone by the guide rollers, and finally fixed to the take-up roller.

[0030] A flexible fiber substrate is loaded onto a winding device. The flexible fiber substrate is a high-temperature resistant, windable material.

[0031] The flexible fiber substrate can take the form of, but is not limited to, continuous fibers, two-dimensional fiber cloth, etc.

[0032] The flexible fiber substrate may be made of any one or a combination of SiC fiber, carbon fiber, SiBCN fiber, SiCN fiber, SiBN fiber, BN fiber, and Si3N4 fiber.

[0033] Pretreatment. Shut down the reaction system and isolate it from the atmosphere. Evacuate the system. As an example, the vacuum level of the reaction system can be 0.1~2 Pa. After evacuation, purge the system with an inert gas. The number of purgings includes, but is not limited to, 2~3 times. The inert gas includes, but is not limited to, nitrogen or argon.

[0034] Low-temperature chemical vapor deposition. The low-temperature chemical vapor deposition apparatus is heated. The deposition area is heated to a predetermined deposition temperature. The deposition temperature can be 600°C to 1300°C. For example, the reaction zone is heated and maintained at a low-temperature deposition temperature of 600°C to 1300°C. Under these deposition conditions, a uniform amorphous initial BN interface phase is deposited on the surface of a continuously moving flexible fiber substrate. The deposition pressure can be 20 to 2000 Pa. The deposition time can be adjusted as needed. Including but not limited to this, the deposition time can be 10 to 40 minutes.

[0035] In the chemical vapor deposition process, process gases are introduced into the reaction chamber of the low-temperature chemical vapor deposition apparatus. Once the temperature of the reaction chamber reaches a predetermined temperature, process gases are introduced into the reaction chamber. The process gases include precursor process gases and auxiliary process gases. The precursor process gas is a process gas that provides at least some of the elements of the deposited product. The precursor process gas includes a gaseous element source. The composition of the precursor process gas can be adjusted adaptively according to the composition of the interfacial phase. For example, a precursor that is liquid or solid at room temperature can be heated to form precursor vapor to obtain the precursor process gas. The auxiliary process gas is a process gas that provides a carrier gas, reducing or oxidizing atmosphere, etc. Auxiliary process gases include, but are not limited to, hydrogen, nitrogen, argon, or mixtures thereof.

[0036] Parameters for chemical vapor deposition include, but are not limited to, one or more of the following: process gas composition (gas ratio), process gas flow rate, deposition pressure (reaction chamber pressure), and deposition temperature (reaction chamber temperature). The process gas composition includes the types and proportions of process gases. When the process gas is a mixture of multiple process gases, the process gas composition can be the proportions of each process gas.

[0037] In an optional embodiment, the interfacial phase is a boron nitride-based interfacial phase. The precursor process gas includes a boron source and a nitrogen source. The boron source includes, but is not limited to, boron trichloride (BCl3). The nitrogen source includes, but is not limited to, ammonia (NH3).

[0038] In an optional embodiment, to improve the corrosion resistance of the boron nitride-based interface phase, the boron nitride-based interface phase can also be doped and modified. This can be achieved by introducing the doping-modified component of the boron nitride-based interface phase into the process gas.

[0039] In an optional embodiment, the interface phase is a silicon-doped boron nitride-based interface phase (Si-BN system). The precursor process gas includes a boron source, a nitrogen source, and a silicon source. The boron source includes, but is not limited to, boron trichloride (BCl3). The nitrogen source includes, but is not limited to, ammonia (NH3). The silicon source includes, but is not limited to, one or a mixture of silicon tetrachloride (SiCl4), trichlorosilane (SiHCl3), and silane (SiH4).

[0040] In an optional embodiment, the interface phase is a silicon-carbon co-doped boron nitride-based interface phase (Si-BCN system). The precursor process gas includes a boron source, a nitrogen source, a silicon source, and a carbon source. The boron source includes, but is not limited to, boron trichloride (BCl3). The nitrogen source includes, but is not limited to, ammonia (NH3). The silicon source includes, but is not limited to, one or a mixture of several of silicon tetrachloride (SiCl4), trichlorosilane (SiHCl3), silane (SiH4), and trichloromethylsilane (CH3SiCl3). The carbon source includes, but is not limited to, one or a mixture of several of trichloromethylsilane (CH3SiCl3) and methane.

[0041] Instantaneous online high-temperature heat treatment. After low-temperature chemical vapor deposition (LCVD), the (precursor) gas in the LCVD zone is removed. The flexible fiber substrate with the initial interface phase deposited is immediately placed into the online high-temperature heat treatment zone by a winding device. The purpose of the online high-temperature heat treatment is to heat the interface phase to the crystallization temperature, stabilizing the amorphous to crystalline structure. The temperature of the online high-temperature heat treatment can be 1350℃~1800℃. The duration of the online high-temperature heat treatment can be 5 seconds~150 seconds. The atmosphere for the online high-temperature heat treatment is a vacuum atmosphere.

[0042] The temperature and time of the instantaneous online heat treatment jointly determine the final degree of stable crystallization of the interfacial phase. By controlling the temperature of the high-temperature heat treatment zone and adjusting its effective length (which, for a given fiber substrate moving speed, determines the high-temperature heat treatment time), the stability or crystallization degree of the boron nitride-based interfacial phase can be effectively controlled. Controlling the final high-temperature stability or crystallization degree of the boron nitride-based interfacial phase optimizes its function as an interfacial phase in ceramic matrix composites.

[0043] The online high-temperature heat treatment device can be any device that can heat the fiber substrate, such as conventional DC heating devices, AC heating devices, induction heating devices, ultra-high temperature radiation heating devices, Joule heating devices that can achieve rapid temperature rise, microwave heating devices, etc.

[0044] Post-processing and sampling. After undergoing real-time online high-temperature heat treatment, the flexible fiber substrate is cooled under isolated atmospheric conditions and then the sample is collected by a take-up roller. The final product is a continuous fiber or two-dimensional fabric with a crystallized, structurally stable boron nitride-based interface phase uniformly coated inside and outside the fiber bundle. This interface phase exhibits excellent compositional and structural uniformity along the radial direction of the fiber bundle (sample thickness direction).

[0045] In some technical solutions, the temperature and time of high-temperature heat treatment can be controlled according to the thickness of the boron nitride-based interface phase. The movement speed of the flexible substrate affects the time of high-temperature heat treatment. The flexible substrate can continuously pass through the reaction zone at a constant or variable set speed. Including but not limited to this, the movement speed of the flexible substrate can be 0.01~1.5 m / min, for example 0.5 m / min or 1 m / min.

[0046] The boron nitride-based interface phase prepared by the method described in this invention has a typical layered structure of (hexagonal) BN-based interface phases. The boron nitride-based interface phase also exhibits uniformity in radial distribution along the fiber substrate (sample thickness direction) and high thermal stability.

[0047] In an optional embodiment, an unwinding mechanism, a low-temperature chemical vapor deposition (LCV) reaction zone, an instant online high-temperature heat treatment zone, and a winding mechanism are sequentially arranged along the movement direction of the flexible fiber substrate. The flexible fiber substrate (such as SiC fiber bundles or SiC fiber two-dimensional cloth) is loaded onto the unwinding mechanism. The reaction system is shut down, a vacuum is drawn, and then the system is flushed with a high-purity inert gas (such as nitrogen or argon). The winding device is started, and the flexible fiber substrate undergoes LCV deposition in the low-temperature LCV reaction chamber. The flexible substrate, with the initial interface phase deposited, immediately and continuously moves into the online high-temperature heat treatment zone. Simultaneously with LCV deposition and high-temperature heat treatment, the heat-treated flexible fiber substrate is fixed to the winding mechanism. After instant high-temperature heat treatment, the flexible fiber substrate is cooled and wound under isolated atmospheric conditions to obtain an interface phase with both uniformity and high thermal stability. The isolated atmospheric conditions can be a vacuum environment.

[0048] In summary, this invention relates to a continuous preparation method for a matrix interface phase that combines uniformity and high crystallinity, belonging to the field of ceramic matrix composite material preparation technology. Addressing the problems of poor stability in uniform interface phases prepared by low-temperature chemical vapor deposition (LVCD) and the tendency for interface phase contamination during offline high-temperature heat treatment, this invention provides a continuous preparation method. The method involves first passing a flexible fiber substrate through a low-temperature deposition zone under atmospheric isolation to obtain a uniform initial interface phase; then, without passing through an atmospheric environment, it directly enters an instant online high-temperature heat treatment zone for instant online high-temperature crystallization treatment at 1350–1800°C. This method, through the tandem integration of low-temperature deposition and online high-temperature heat treatment, achieves the continuous online completion of the entire interface phase "deposition-crystallization" process, fundamentally avoiding contamination during interface phase transfer. Ultimately, this results in an interface phase with both excellent uniformity and high thermal stability, providing a reliable matrix interface phase preparation technology for high-performance ceramic matrix composites.

[0049] The present invention will be further described in detail below with reference to embodiments. It should also be understood that the following embodiments are only for further illustration 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.

[0050] Example 1

[0051] Methods for preparing interfacial phases based on low-temperature deposition and real-time online high-temperature heat treatment include: (1) Using continuous silicon carbide fiber bundles as substrates. The continuous silicon carbide fiber bundle substrate is loaded into a winding device. The chemical vapor deposition system is evacuated to a background vacuum level better than 2 Pa, and then the system is flushed with nitrogen three times until the background vacuum level is better than 0.5 Pa.

[0052] (2) BCl3, NH3, H2, and N2 were introduced into the reaction chamber of the chemical vapor deposition system. A continuous silicon carbide fiber bundle substrate was continuously passed through the reaction chamber of the chemical vapor deposition system at a speed of 50 cm / min. The deposition zone temperature was controlled at 1100 ℃, the deposition pressure was maintained at 200 Pa, and the deposition time was 30 minutes. The flow rates of BCl3, NH3, H2, and N2 were 0.15 L / min, 0.3 L / min, 0.15 L / min, and 0.6 L / min, respectively.

[0053] (3) After the fiber substrate is deposited in the chemical vapor deposition zone, the continuous silicon carbide fiber bundle substrate loaded with the deposited product continues to pass through the online high-temperature heat treatment zone at a speed of 50 cm / min. The temperature of the online high-temperature heat treatment zone is controlled at 1500℃ and the heat treatment time is 140 seconds.

[0054] (4) After the continuous silicon carbide fiber bundle substrate is subjected to real-time online high-temperature heat treatment, it is cooled and wound up in an isolated atmospheric environment to obtain a BN interface phase with both uniformity and high thermal stability.

[0055] Figure 2 The image shows a cross-sectional morphology electron microscope (EM) image of the BN interface phase prepared in this embodiment. It can be seen that the obtained BN interface phase exhibits a typical layered structure of crystalline hexagonal BN. EDS analysis revealed that the oxygen content of the obtained BN interface phase was 9 at% to 10 at%.

[0056] Example 2

[0057] Methods for preparing interfacial phases based on low-temperature deposition and real-time online high-temperature heat treatment include: (1) Using continuous silicon carbide fiber bundles as substrates. The continuous silicon carbide fiber bundle substrate is loaded into a winding device. The chemical vapor deposition system is evacuated to a background vacuum level better than 2 Pa, and then the system is flushed with nitrogen three times until the background vacuum level is better than 0.5 Pa.

[0058] (2) BCl3, NH3, H2, and N2 were introduced into the reaction chamber of the chemical vapor deposition system. A continuous silicon carbide fiber bundle substrate was continuously passed through the reaction chamber of the chemical vapor deposition system at a speed of 50 cm / min. The deposition zone temperature was controlled at 1080 ℃, the deposition pressure was maintained at 200 Pa, and the deposition time was 30 minutes. The flow rates of BCl3, NH3, H2, and N2 were 0.15 L / min, 0.3 L / min, 0.15 L / min, and 0.6 L / min, respectively.

[0059] (3) After the fiber substrate is deposited in the chemical vapor deposition zone, the continuous silicon carbide fiber bundle substrate loaded with the deposited product continues to pass through the online high-temperature heat treatment zone at a speed of 50 cm / min. The temperature of the online high-temperature heat treatment zone is controlled at 1500℃ and the heat treatment time is 80 seconds.

[0060] (4) After the continuous silicon carbide fiber bundle substrate is subjected to real-time online high-temperature heat treatment, it is cooled and wound up in an isolated atmospheric environment to obtain a BN interface phase with both uniformity and high thermal stability.

[0061] Figure 3 The image shows a cross-sectional morphology electron microscope (EM) image of the BN interface phase prepared in this embodiment. It can be seen that the obtained BN interface phase exhibits a typical layered structure of crystalline hexagonal BN. EDS analysis revealed that the oxygen content of the obtained BN interface phase was 9 at% to 10 at%.

[0062] Example 3

[0063] Methods for preparing interfacial phases based on low-temperature deposition and real-time online high-temperature heat treatment include: (1) Using continuous silicon carbide fiber bundles as substrates. The continuous silicon carbide fiber bundle substrate is loaded into a winding device. The chemical vapor deposition system is evacuated to a background vacuum level better than 2 Pa, and then the system is flushed with nitrogen three times until the background vacuum level is better than 0.5 Pa.

[0064] (2) BCl3, NH3, H2, and N2 were introduced into the reaction chamber of the chemical vapor deposition system. A continuous silicon carbide fiber bundle substrate was continuously passed through the reaction chamber of the chemical vapor deposition system at a speed of 50 cm / min. The deposition zone temperature was controlled at 1050 °C, the deposition pressure was maintained at 200 Pa, and the deposition time was 30 minutes. The flow rates of BCl3, NH3, MTS, H2, and N2 were 0.15 L / min, 0.60 L / min, 0.12 L / min, 0.45 L / min, and 0.6 L / min, respectively.

[0065] (3) After the fiber substrate is deposited in the chemical vapor deposition zone, the continuous silicon carbide fiber bundle substrate loaded with the deposited product continues to pass through the online high-temperature heat treatment zone at a speed of 100 cm / min. The temperature of the online high-temperature heat treatment zone is controlled at 1550℃ and the heat treatment time is 70 seconds.

[0066] (4) After the continuous silicon carbide fiber bundle substrate is subjected to real-time online high-temperature heat treatment, it is cooled and wound up in an isolated atmospheric environment to obtain a Si and C doped BN interface phase with both uniformity and high thermal stability.

[0067] Figure 4 The image shows an electron microscope (EM) image of the cross-sectional morphology of the Si and C-doped BN interface phase prepared in this embodiment. It can be seen that the obtained BN interface phase exhibits a crystalline hexagonal layered BN structure. EDS analysis revealed that the oxygen content of the obtained BN interface phase is 2 at% to 10 at%.

[0068] Comparative Example 1 Methods for preparing interfacial phases based on low-temperature deposition and offline high-temperature heat treatment include: (1) Using continuous silicon carbide fiber bundles as substrates. The continuous silicon carbide fiber bundle substrate is loaded into a winding device. The chemical vapor deposition system is evacuated to a background vacuum level better than 2 Pa, and then the system is flushed with nitrogen three times until the background vacuum level is better than 0.5 Pa.

[0069] (2) BCl3, NH3, H2, and N2 were introduced into the reaction chamber of the chemical vapor deposition system. A continuous silicon carbide fiber bundle substrate was continuously passed through the reaction chamber of the chemical vapor deposition system at a speed of 50 cm / min. The deposition zone temperature was controlled at 1100 ℃, the deposition pressure was maintained at 200 Pa, and the deposition time was 30 minutes. The flow rates of BCl3, NH3, H2, and N2 were 0.15 L / min, 0.3 L / min, 0.15 L / min, and 0.6 L / min, respectively.

[0070] (3) After chemical deposition, the continuous silicon carbide fiber bundle substrate after chemical vapor deposition is cooled and wound up in an isolated atmospheric environment. The continuous silicon carbide fiber bundle substrate loaded with the deposited product is taken out, placed in a sealed plastic bag, and then transferred to a high-temperature vacuum carbon tube furnace for high-temperature heat treatment at 1350℃ for 1 hour to obtain the BN interface phase.

[0071] Figure 5a and Figure 5b The images show SEM images of the cross-sectional morphology of the BN interface phase prepared in this comparative example before and after offline heat treatment. It can be seen that the interface phase before heat treatment exhibits obvious amorphous characteristics, while the BN interface phase obtained after heat treatment has a typical layered structure of crystalline hexagonal BN. EDS analysis revealed that the oxygen content of the obtained heat-treated BN interface phase was 15 at%~20 at%. Compared with this comparative example, the BN-based interface phases obtained in Examples 1, 2, and 3 have significantly lower oxygen contents, highlighting the advantage of the tandem integration of low-temperature chemical vapor deposition and in-situ online heat treatment in achieving lower oxygen content.

Claims

1. A method for preparing interfacial phases based on low-temperature deposition and immediate in-line high-temperature heat treatment, characterized in that, The application relates to a method for preparing a flexible fiber substrate with a uniform and high-thermal-stability interface phase. The method comprises the following steps: arranging a winding device in a closed reaction system and loading a flexible fiber substrate on the winding device; arranging an unwinding element of the winding device at an inlet end side of a low-temperature chemical vapor deposition zone and arranging a winding element of the winding device at an outlet end side of a high-temperature heat treatment zone; arranging the low-temperature chemical vapor deposition zone and the high-temperature heat treatment zone in series in the closed reaction system; starting the winding device to continuously move the flexible fiber substrate through the low-temperature chemical vapor deposition zone at a set speed; after the chemical vapor deposition is completed, continuously moving the flexible fiber substrate with the initial interface phase to the high-temperature heat treatment zone immediately under the condition of not contacting the atmosphere; and cooling and winding the flexible fiber substrate after the immediate online high-temperature heat treatment under the condition of isolating the atmosphere to obtain the flexible fiber substrate with the uniform and high-thermal-stability interface phase. The flexible fiber substrate is selected from one of SiC fiber, carbon fiber, SiBCN fiber, SiCN fiber, SiBN fiber, BN fiber and Si3N4 fiber or a composite thereof.

2. The method of preparing an interfacial phase according to claim 1, wherein, The deposition temperature of the low-temperature chemical vapor deposition is 600 DEG C to 1300 DEG C, preferably 800 DEG C to 1250 DEG C.

3. The method for producing an interfacial phase according to claim 1 or 2, characterized in that, The temperature of the online high-temperature heat treatment is 1350 DEG C to 1800 DEG C; and the time of the online high-temperature heat treatment is 5 seconds to 150 seconds.

4. The interfacial phase production method according to any one of claims 1 to 3, characterized in that, The online high-temperature heat treatment device is selected from any one of a direct-current heating device, an alternating-current heating device, an induction heating device, an ultrahigh-temperature radiation heating device, a Joule heat device and a microwave heating device.

5. The interfacial phase production method according to any one of claims 1 to 4, characterized in that, The interface phase is a ceramic matrix composite reinforcing fiber interface phase, preferably a boron nitride-based interface phase, more preferably a hexagonal boron nitride-based interface phase with a layered structure.

6. The interfacial phase production method according to any one of claims 1 to 5, characterized in that, The boron nitride-based interface phase is an undoped boron nitride interface phase, a silicon-doped boron nitride-based interface phase or a silicon-carbon co-doped boron nitride-based interface phase.

7. The method of claim 6, wherein the interface phase is prepared by a method comprising: The interface phase is an undoped boron nitride interface phase, and the process gas comprises a precursor process gas and an auxiliary process gas; the precursor process gas comprises a boron source and a nitrogen source in a gaseous form; for example, the boron source is boron trichloride, and the nitrogen source is ammonia; for example, the auxiliary process gas is hydrogen, nitrogen or hydrogen-nitrogen mixed gas.

8. The interfacial phase production method according to any one of claims 1 to 7, characterized in that, The interface phase is a silicon-doped boron nitride-based interface phase, and the process gas comprises a precursor process gas and an auxiliary process gas; the precursor process gas comprises a boron source, a nitrogen source and a silicon source in a gaseous form; for example, the boron source is boron trichloride, the nitrogen source is ammonia, and the silicon source is a mixture of one or more of silicon tetrachloride, trichlorosilane and silane; for example, the auxiliary process gas is hydrogen, nitrogen or hydrogen-nitrogen mixed gas.

9. The interfacial phase production method according to any one of claims 1 to 6, characterized in that, The interface phase is a silicon-carbon co-doped boron nitride-based interface phase, and the process gas comprises a precursor process gas and an auxiliary process gas; wherein the precursor process gas comprises a boron source, a nitrogen source, a silicon source and a carbon source in a gaseous form; for example, the boron source is boron trichloride, the nitrogen source is ammonia, the silicon source is one or a mixture of trichloromethylsilane, silicon tetrachloride and trichlorosilane, and the carbon source is one or a mixture of trichloromethylsilane and methane; for example, the auxiliary process gas is hydrogen, nitrogen or hydrogen-nitrogen mixed gas.

10. The interfacial phase production method according to any one of claims 1 to 6, characterized in that, ​

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