A boron nitride interface coating for a fibrous radome fabric and a method of making the same

Abstract

The application provides a boron nitride interface coating of a fiber radome fabric and a preparation method thereof, and comprises the following steps: weaving the fiber radome fabric; depositing the interface coating on the fiber radome fabric in stages through first and second deposition stages; the first deposition stage comprises the following steps: positively hoisting the fiber radome fabric in a deposition furnace, vacuumizing the furnace to maintain the pressure in the furnace at a preset pressure, and introducing a reaction gas from a cavity formed on the inner surface of the fiber radome fabric; the second deposition stage comprises the following steps: inversely hoisting the fiber radome fabric in the deposition furnace, sleeving a separation mold on the outer surface of the fiber radome fabric to form a separation space between the separation mold and the outer surface of the fiber radome fabric, vacuumizing the furnace to maintain the pressure in the furnace at a preset pressure, and introducing a reaction gas from the separation space. The interface coating is deposited in stages, and is deposited in a mode of from inside to outside, from outside to inside and in cooperation with the pressure difference between the inside and the outside, the boron nitride interface coating has good uniformity and consistency, and the radome has high use reliability.

Description

Technical Field

[0001] This invention relates to the field of interface coating technology, and more specifically, to a boron nitride interface coating for fiber radome fabric and its preparation method. Background Technology

[0002] For fiber-reinforced ceramic matrix composites, the interface control technology between the fiber and the matrix is ​​crucial for preparing high-performance fiber-reinforced composites. In existing technologies, the preparation processes for boron nitride interface coatings of nitride fiber-reinforced ceramic matrix composites mainly include liquid phase method (also known as impregnation-coating method), chemical vapor deposition (CVD), and carbothermal reduction method. Among these, the CVD method produces a uniform and dense boron nitride interface coating with a tight bond between the coating and the matrix, a fast deposition rate, stable and easily controllable quality, and minimal damage to the matrix fibers. Therefore, the CVD / CVI method is widely used for preparing high-quality boron nitride interface coatings. However, current research on the preparation process of boron nitride interface coatings using the CVD / CVI method mainly focuses on fiber-reinforced composites with fibers or fiber fabrics as the substrate. Research on the preparation of interface coatings for products with specific shapes and structures is limited. Furthermore, the use of the CVD / CVI method to prepare boron nitride interface coatings on product components with special structures, especially in fiber radome fabrics with structural and dimensional requirements (such as...), is particularly challenging. Figure 1 The boron nitride interface coating prepared on the fabric (as shown) suffers from poor uniformity and consistency, severely affecting the reliability of the radome in later use. Therefore, how to prepare a boron nitride interface coating with good uniformity and consistency on the fiber radome fabric has become an urgent technical problem to be solved in this field. Summary of the Invention

[0003] This invention provides a boron nitride interface coating on fiber radome fabric and its preparation method, in order to solve the problem that the boron nitride interface coating prepared on fiber radome fabric in the prior art has poor uniformity and consistency, which seriously affects the reliability of the radome in later use.

[0004] On one hand, the present invention provides a method for preparing a boron nitride interface coating on a fiber radome fabric, comprising the following steps: obtaining a fiber radome fabric based on nitride fiber weaving according to preset structure and size requirements; depositing a boron nitride interface coating on the fiber radome fabric in stages through a first deposition stage and a second deposition stage based on chemical vapor deposition; wherein, the first deposition stage includes: suspending the fiber radome fabric upright in a deposition furnace, evacuating the furnace until the pressure inside the furnace is maintained at a preset pressure, and introducing a reactive gas into a cavity formed on the inner surface of the fiber radome fabric to complete the first deposition stage; the second deposition stage includes: suspending the fiber radome fabric upside down in a deposition furnace, fitting an isolation mold around the fiber radome fabric to form an isolation space between the isolation mold and the outer surface of the fiber radome fabric, evacuating the furnace until the pressure inside the furnace is maintained at a preset pressure, and introducing a reactive gas into the isolation space to complete the second deposition stage.

[0005] In some embodiments of the present invention, the surface of the nitride fiber is coated with a surface wetting agent before weaving the fiber radome fabric; the fiber radome fabric is pretreated before deposition; the specific process of the pretreatment is as follows: the fiber radome fabric is placed on a ceramic-like fixture, and the ceramic-like fixture carrying the fiber radome fabric is placed in an air atmosphere and kept at a temperature of 400-600°C for 1-6 hours.

[0006] In some embodiments of the present invention, during the first deposition stage, the fiber radome fabric is placed on a first conforming fixture, and the fiber radome fabric is suspended upright in the deposition furnace with the large end facing down and the tip facing up. The furnace pressure is evacuated until it is maintained at a preset pressure, and a reaction gas is introduced into the cavity formed on the inner surface of the fiber radome fabric. The first conforming fixture is adapted to the shape and size of the inner surface of the fiber radome fabric, and the first conforming fixture is provided with a plurality of openings. The large end of the first conforming fixture extends out of the large end of the fiber radome fabric.

[0007] In some embodiments of the present invention, during the first deposition stage, a first conforming device with a fiber radome fabric is placed on the gas inlet base of the deposition furnace, and the fiber radome fabric is covered by a cylindrical graphite separator. A sealing ring is provided between the bottom of the cylindrical graphite separator and the bottom of the fiber radome fabric, and a reaction gas is introduced from the gas inlet base of the deposition furnace into the cavity formed on the inner surface of the fiber radome fabric; the upper and lower ends of the cylindrical graphite separator are open ends.

[0008] In some embodiments of the present invention, during the first deposition stage, a graphite limiting member is provided around the outer surface of the large end of the fiber radome fabric to restrict the displacement of the fiber radome fabric.

[0009] In some embodiments of the present invention, during the second deposition stage, a second contouring fixture is placed on the fiber radome fabric, keeping the large end of the fiber radome fabric facing upwards and the tip facing downwards. The fiber radome fabric is then inverted and suspended inside the deposition furnace using the second contouring fixture. An isolation mold is fitted over the second contouring fixture, forming an isolation space between the isolation mold and the second contouring fixture. A vacuum is drawn until the pressure inside the furnace is maintained at a preset pressure, and a reaction gas is introduced through the isolation space. The second contouring fixture is adapted to the shape and size of the outer surface of the fiber radome fabric, and has several openings. The large end of the second contouring fixture extends beyond the large end of the fiber radome fabric. The isolation mold has an air inlet opening, and the air inlet opening on the isolation mold corresponds to the position of the air inlet opening on the deposition furnace air inlet base.

[0010] In some embodiments of the present invention, during the second deposition stage, a first conforming tool is also placed inside the fiber antenna radome fabric.

[0011] In some embodiments of the present invention, the preset pressure is 100-1000 Pa, and the reaction gas includes BCl3, NH3, H2 and Ar; the deposition temperature of the first deposition stage is 500-900℃, and the deposition time is 6-15 h; the deposition temperature of the second deposition stage is 500-900℃, and the deposition time is 6-12 h.

[0012] In some embodiments of the present invention, after the first deposition stage and the second deposition stage, the deposited fiber radome fabric is subjected to nitriding treatment to obtain a boron nitride interface coating on the fiber radome fabric; the nitriding treatment is carried out in a nitrogen atmosphere with a pressure of 0.1 to 0.5 MPa, the nitriding temperature is 1200 to 1500°C, and the nitriding time is 1 to 5 hours.

[0013] In some embodiments of the present invention, the nitride fibers are modified before being woven into a fiber antenna radome fabric; the modified nitride fibers and unmodified nitride fibers are woven together to obtain the fiber antenna radome fabric.

[0014] In some embodiments of the present invention, the fiber radome fabric includes an inner layer fiber, an outer layer fiber, and an intermediate layer fiber located between the inner layer fiber and the outer layer fiber; the inner layer fiber and the outer layer fiber are both modified nitride fibers, and the intermediate layer fiber is an unmodified nitride fiber.

[0015] In some embodiments of the present invention, the process of modifying nitride fibers involves preparing a fiber modification solution; the fiber modification solution comprises BO2, an adhesive, and a solvent in a mass ratio of (1-2):(0.5-1):(8-10);

[0016] The nitride fiber is impregnated in a fiber modification solution and then dried to obtain the modified nitride fiber.

[0017] In some embodiments of the present invention, the binder includes one of furan resin, phenolic resin, and sodium carboxymethyl cellulose; the solvent includes methanol or ethanol.

[0018] The beneficial effect of adopting the above-mentioned further technical solution is that BO2 is attached to the surface of the nitride fibers of the inner and outer layers of the fiber radome fabric. This enables the reaction of NH3 in the reaction gas with the nitride fibers when the boron nitride interface coating is deposited on the fiber radome fabric, thereby improving the bonding strength between the boron nitride interface coating generated by the reaction and the fiber radome fabric. It also reduces the porosity of the fiber radome fabric from both sides to the middle, making the thickness of the coating and fiber layer bonding controllable, while avoiding a significant reduction in the porosity of the fiber radome fabric.

[0019] In some embodiments of the present invention, before depositing a boron nitride interface coating on the nitride fiber radome preform, the nitride fiber radome preform is heat-treated in a nitrogen atmosphere at a temperature of 800-1100°C.

[0020] The beneficial effect of adopting the above-mentioned further technical solution is that boron nitride is attached to the inner and outer fiber surfaces of the fiber radome fabric, thereby reducing the porosity of the fiber radome fabric from both sides to the middle, making the thickness of the coating and fiber layer bonded controllable, while avoiding a significant reduction in the porosity of the fiber radome fabric.

[0021] Furthermore, the adhering boron nitride exhibits a certain degree of activity before the boron nitride interface coating is deposited on the fiber radome fabric, which is beneficial for the high bonding strength between the boron nitride interface coating generated by the subsequent reaction and the fiber radome fabric. On the other hand, the present invention also provides a boron nitride interface coating for fiber radome fabric, prepared according to the preparation method of the boron nitride interface coating for fiber radome fabric described in any of the preceding claims.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) In the preparation process of this invention, an interface coating is deposited on the fiber radome fabric in stages. In the first deposition stage, the deposition is carried out from the inside out. During the deposition process, the pressure inside the deposition furnace is controlled to be maintained at a preset pressure. When the reactive gas is introduced, the gas directly enters the cavity formed on the inner surface of the fiber radome fabric in the first deposition stage. The cavity and the deposition furnace cavity form a pressure difference. The cavity is in a high-pressure state, which is conducive to the gas passing through the fiber radome fabric from the inside to the outside. In the second deposition stage, the deposition is carried out from the outside to the inside. During the deposition process, the pressure inside the deposition furnace is controlled to be maintained at a preset pressure. When the reactive gas is introduced, the gas directly enters the isolation space. The isolation space and the deposition furnace cavity form a pressure difference. The isolation space is in a high-pressure state, which is conducive to the gas passing through the fiber radome fabric from the outside to the inside. The deposition efficiency is high, the boron nitride interface coating has good uniformity and consistency, and the mechanical properties of the radome prepared in this way are consistent. There are no relatively weak areas in the mechanical properties. The mechanical properties are good, the bending strength is high, and the reliability of the radome is high.

[0024] (2) The nitride fibers used in the weaving of the fiber radome fabric of the present invention are coated with a surface wetting agent, which facilitates weaving. Before depositing the fiber radome fabric, the fiber radome fabric is pretreated. The design of the ceramic tooling can avoid the deformation of the fiber radome fabric during the pretreatment process. The temperature setting of 400 to 600°C can effectively remove the surface wetting agent while avoiding carbonization of the surface wetting agent, and avoid the carbonization of the organic wetting agent in subsequent heat treatment processes, which would weaken the electrical performance.

[0025] (3) In the first deposition stage of the present invention, the fiber antenna radome fabric is supported by the first contouring tool. The design of the opening facilitates the reaction gas to pass through the fiber antenna radome fabric from the inside to the outside along a certain trajectory. The large end of the first contouring tool extends out of the large end of the fiber antenna radome fabric, which facilitates the hoisting of the fiber antenna radome fabric. The cylindrical graphite isolation component covers the fiber antenna radome fabric and guides the gas coming out of the fiber antenna radome fabric. The sealing ring plays a sealing role to prevent the reaction gas entering the deposition furnace from spreading. The design of the graphite limiting component plays a limiting role to the fiber antenna radome fabric to prevent it from being displaced unnecessarily. In addition, the graphite limiting component can also be used in conjunction with the hoisting to suspend the large end face of the fiber antenna radome fabric in the air to avoid affecting the end face deposition.

[0026] (4) In the second deposition stage of the present invention, the fiber antenna radome fabric is supported by the second contour tooling. The design of the opening facilitates the reaction gas to pass through the fiber antenna radome fabric from the outside to the inside in a certain trajectory. The large end of the second contour tooling extends out of the large end of the fiber antenna radome fabric, which facilitates the hoisting of the fiber antenna radome fabric. The design of the isolation mold forms an isolation space between the isolation mold and the second contour tooling, which separates the isolation space from the deposition furnace cavity, which facilitates the formation of the pressure difference between the inside and outside after the reaction gas is introduced. The use of the first contour tooling prevents the fiber antenna radome fabric from shrinking and deforming in the second deposition stage.

[0027] (5) When depositing the boron nitride interface coating of the present invention, BCl3, NH3, H2 and Ar are used as reaction gases, and deposition is carried out at a deposition temperature of 500 to 900°C and a gas pressure of 100 to 1000 Pa in the deposition furnace. When the reaction gas is introduced into the cavity or isolation space formed on the inner surface of the fiber antenna radome fabric, a stable gas pressure difference can be easily obtained by reasonably adjusting the gas pressure, so that the deposition process is easy to control and the deposition uniformity and consistency are good. After the deposition is completed, the coating is nitrided at a nitriding temperature of 1200 to 1500°C in a nitrogen atmosphere with a pressure of 0.1 to 0.5 MPa to complete the transformation of the coating from an amorphous phase to a crystalline phase. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments of the present invention will be described below.

[0029] Figure 1 A schematic diagram of the structure of a fiber optic radome fabric;

[0030] Figure 2 This is a flowchart illustrating a method for preparing a boron nitride interface coating on a fiber optic radome fabric according to an embodiment of the present invention.

[0031] Figure 3 This is a schematic diagram of the structure of the first contouring tool used in the method for preparing a boron nitride interface coating on a fiber radome fabric according to an embodiment of the present invention.

[0032] Figure 4 This is a schematic diagram of the structure of the second contouring tool used in the method for preparing a boron nitride interface coating on a fiber radome fabric according to an embodiment of the present invention.

[0033] Figure 5 This is a schematic diagram of the first deposition stage in the method for preparing a boron nitride interface coating on a fiber radome fabric according to an embodiment of the present invention.

[0034] Figure 6 This is a schematic diagram of the second deposition stage in the method for preparing a boron nitride interface coating on a fiber radome fabric according to an embodiment of the present invention.

[0035] Figure 7 SEM image of a single fiber cut from the inner surface of a fiber radome fabric with a boron nitride interface coating prepared according to an embodiment of the present invention.

[0036] Figure 8 SEM image of a single fiber taken from the middle of a fiber radome fabric with a boron nitride interface coating prepared according to an embodiment of the present invention.

[0037] Figure 9SEM image of a single fiber taken from the outer surface of a fiber radome fabric with a boron nitride interface coating prepared according to an embodiment of the present invention. Detailed Implementation

[0038] To make the objectives, technical solutions and advantages of the present invention clearer, the various aspects of the present invention will be described in detail below with reference to specific embodiments. However, these specific embodiments are only used to illustrate the present invention and do not constitute any limitation on the scope of protection and the substantive content of the present invention.

[0039] Example 1

[0040] This embodiment provides a method for preparing a boron nitride interface coating on a fiber optic radome fabric, such as... Figure 2 As shown, it includes the following steps:

[0041] S1. A fiber radome fabric is woven from nitride fibers according to preset structural and dimensional requirements. Before weaving the fiber radome fabric, the surface of the nitride fibers is coated with a surface wetting agent. Before deposition on the fiber radome fabric, it is pretreated. The specific pretreatment process is as follows: The fiber radome fabric is placed on a contour ceramic fixture (designed according to the structural and dimensional requirements of the fiber radome fabric to prevent deformation during pretreatment). The contour ceramic fixture carrying the fiber radome fabric is placed in an air atmosphere and kept at 400–600°C for 1–6 hours to remove the surface wetting agent. In this embodiment, the surface of the contour ceramic fixture has several openings to facilitate full contact between the fiber radome fabric and the atmosphere. Preferably, the contour ceramic fixture and... Figure 3 The first contouring tooling structure is the same.

[0042] S2. Based on chemical vapor deposition, a boron nitride interface coating is deposited on the fiber radome fabric in stages through a first deposition stage and a second deposition stage.

[0043] The first deposition stage includes: suspending the fiber radome fabric upright in the deposition furnace, evacuating the furnace until the pressure is maintained at a preset level, and introducing reactive gas into a cavity formed on the inner surface of the fiber radome fabric to complete the first deposition stage. Specifically, in this embodiment, as follows... Figure 5 As shown, in the first deposition stage, the fiber radome fabric 1 is placed in the first contouring fixture 2 (e.g., Figure 3As shown, the first contouring fixture is designed according to the structural and dimensional requirements of the fiber radome fabric (preferably a high-temperature resistant contouring graphite fixture). The fiber radome fabric 1 is kept in a state where the large end is facing down and the tip is facing up. A molybdenum wire passes through the bottom of the first contouring fixture 2 and is suspended upright in the deposition furnace. The furnace is evacuated until the pressure inside the furnace is maintained at a preset pressure. The reaction gas is introduced into the cavity formed on the inner surface of the fiber radome fabric 1. The shape and size of the first contouring fixture 2 are adapted to the inner surface of the fiber radome fabric 1. The first contouring fixture 2 is provided with several openings. Preferably, the large end of the first contouring fixture 2 extends out of the large end of the fiber radome fabric 1. Further, in this embodiment, during the first deposition stage, a first contouring fixture 2 with a fiber radome fabric 1 is placed on the deposition furnace inlet base 3. The fiber radome fabric 1 is covered by a cylindrical graphite separator 7. A sealing ring 8 is provided between the bottom of the cylindrical graphite separator 7 and the bottom of the fiber radome fabric 1. Reactive gas is introduced from the deposition furnace inlet base 3 into the cavity formed on the inner surface of the fiber radome fabric 1. In this embodiment, the upper and lower ends of the cylindrical graphite separator 7 are open ends. The deposition furnace inlet base 3 is provided with an inlet opening 31. The reactive gas enters the cavity formed on the inner surface of the fiber radome fabric 1 through the inlet opening 31. A pressure difference is formed between the cavity and the deposition furnace cavity. The cavity is under high pressure, which facilitates the gas to pass through the fiber radome fabric from the inside to the outside. In this embodiment, during the first deposition stage, a graphite limiting member 4 is provided around the outer surface of the large end of the fiber radome fabric 1 to restrict the displacement of the fiber radome fabric 1.

[0044] The second deposition stage includes: inverting the fiber radome fabric 180° and suspending it inside the deposition furnace; fitting an isolation mold over the fiber radome fabric to form an isolation space between the isolation mold and the outer surface of the fiber radome fabric; evacuating the furnace until the pressure inside is maintained at a preset pressure; and introducing reactive gas through the isolation space to complete the second deposition stage. Specifically, in this embodiment, as shown... Figure 6 As shown, in the second deposition stage, the second contouring tool 5 (such as...) Figure 4As shown, the second contouring fixture is designed according to the structural and dimensional requirements of the fiber radome fabric (preferably a high-temperature resistant contouring graphite fixture) and placed on the fiber radome fabric 1, keeping the large end of the fiber radome fabric 1 facing upwards and the pointed end facing downwards. A molybdenum wire passes through the bottom of the large end side of the second contouring fixture 5, inverting and suspending the fiber radome fabric 1 inside the deposition furnace. An isolation mold 6 is fitted over the second contouring fixture 5, forming an isolation space between the isolation mold 6 and the second contouring fixture 5. A vacuum is drawn until the furnace pressure is maintained at a preset pressure, and reactive gas is introduced through the isolation space. The second contouring fixture 5 is adapted to the shape and size of the outer surface of the fiber radome fabric 1. The second contouring fixture 5 has several openings perpendicular to the wall of the fiber radome fabric. The large end of the second contouring fixture 5 extends beyond the large end of the fiber radome fabric 1. The isolation mold 6 has an air inlet 61, which corresponds to the air inlet 31 on the deposition furnace air inlet base 3. The reaction gas enters the isolation space through the opening 61, creating a pressure difference between the isolation space and the deposition furnace chamber. The isolation space is under high pressure, facilitating the gas to pass through the fiber radome fabric 1 from the outside in. In this embodiment, during the second deposition stage, the first contouring fixture 2 is also placed inside the fiber radome fabric 1.

[0045] In this embodiment, the preset pressure is 100-1000 Pa, and the reactant gases include BCl3, NH3, H2, and Ar; the deposition temperature in the first deposition stage is 500-900℃, and the deposition time is 6-15 h; the deposition temperature in the second deposition stage is 500-900℃, and the deposition time is 6-12 h. In this embodiment, the reaction gas introduction rate and gas pressure can be reasonably adjusted according to actual conditions.

[0046] S3. After the first and second deposition stages, the deposited fiber radome fabric is subjected to nitriding treatment to obtain a boron nitride interface coating on the fiber radome fabric. The nitriding treatment is carried out in a nitrogen atmosphere with a pressure of 0.1 to 0.5 MPa, a nitriding temperature of 1200 to 1500 °C, and a nitriding time of 1 to 5 h.

[0047] This embodiment also provides a boron nitride interface coating for a fiber radome fabric, which is prepared according to the preparation method of the boron nitride interface coating for the fiber radome fabric in this embodiment.

[0048] Example 2

[0049] This embodiment provides a boron nitride interface coating for a fiber radome fabric and its preparation method. This embodiment differs from Example 1 only in the pretreatment, deposition, and nitriding process parameters. Here, only the differences are described; the similarities are not repeated.

[0050] The specific pretreatment process in this embodiment is as follows: the fiber radome fabric is placed on the ceramic-shaped fixture, the ceramic-shaped fixture carrying the fiber radome fabric is placed in an air atmosphere and kept at 400°C for 6 hours to remove the surface wetting agent.

[0051] In this embodiment, the preset pressure during the deposition process is 100 Pa, and the reaction gases include BCl3, NH3, H2 and Ar; the deposition temperature of the first deposition stage is 500℃ and the deposition time is 15 h; the deposition temperature of the second deposition stage is 500℃ and the deposition time is 12 h.

[0052] In this embodiment, the nitriding treatment was carried out under a nitrogen atmosphere with a pressure of 0.1 MPa, a nitriding temperature of 1200°C, and a nitriding time of 5 hours.

[0053] Example 3

[0054] This embodiment provides a boron nitride interface coating for a fiber radome fabric and its preparation method. This embodiment differs from Example 1 only in the pretreatment, deposition, and nitriding process parameters. Here, only the differences are described; the similarities are not repeated.

[0055] The specific pretreatment process in this embodiment is as follows: the fiber radome fabric is placed on the ceramic mold, the ceramic mold containing the fiber radome fabric is placed in an air atmosphere and kept at 500°C for 3 hours to remove the surface wetting agent.

[0056] In this embodiment, the preset pressure during the deposition process is 600 Pa, and the reaction gases include BCl3, NH3, H2 and Ar; the deposition temperature of the first deposition stage is 700℃ and the deposition time is 10 h; the deposition temperature of the second deposition stage is 700℃ and the deposition time is 9 h.

[0057] In this embodiment, the nitriding treatment was carried out under a nitrogen atmosphere with a pressure of 0.3 MPa, a nitriding temperature of 1300°C, and a nitriding time of 3 hours.

[0058] Example 4

[0059] This embodiment provides a boron nitride interface coating for a fiber radome fabric and its preparation method. This embodiment differs from Example 1 only in the pretreatment, deposition, and nitriding process parameters. Here, only the differences are described; the similarities are not repeated.

[0060] The specific pretreatment process in this embodiment is as follows: the fiber radome fabric is placed on the ceramic mold, the ceramic mold containing the fiber radome fabric is placed in an air atmosphere and kept at 600°C for 1 hour to remove the surface wetting agent.

[0061] In this embodiment, the preset pressure during the deposition process is 1000 Pa, and the reaction gases include BCl3, NH3, H2 and Ar; the deposition temperature of the first deposition stage is 900℃ and the deposition time is 6h; the deposition temperature of the second deposition stage is 900℃ and the deposition time is 6h.

[0062] In this embodiment, the nitriding treatment was carried out under a nitrogen atmosphere with a pressure of 0.5 MPa, a nitriding temperature of 1500°C, and a nitriding time of 1 hour.

[0063] Example 5

[0064] This embodiment provides a boron nitride interface coating for a nitride fiber radome preform and its preparation method. This embodiment differs from Embodiment 1. Here, only the differences will be described, and the similarities will not be repeated.

[0065] Before the nitride fibers are woven into the fiber radome fabric, the nitride fibers are modified; the modified nitride fibers and unmodified nitride fibers are woven together to obtain the fiber radome fabric; the fiber radome fabric includes inner layer fibers, outer layer fibers, and intermediate layer fibers located between the inner layer fibers and the outer layer fibers; the inner layer fibers and the outer layer fibers are both modified nitride fibers, and the intermediate layer fibers are unmodified nitride fibers.

[0066] The process of modifying nitride fibers involves preparing a fiber modification solution; the fiber modification solution includes BO2, an adhesive, and a solvent in a mass ratio of 1.6:0.8:9.5; the nitride fibers are impregnated in the fiber modification solution and then dried to obtain modified nitride fibers; the adhesive includes furan resin; and the solvent includes ethanol.

[0067] Example 6

[0068] This embodiment provides a boron nitride interface coating for a nitride fiber radome preform and its preparation method. This embodiment differs from Embodiment 4. Here, only the differences will be described, and the similarities will not be repeated.

[0069] Before depositing a boron nitride interface coating on the nitride fiber radome preform, the nitride fiber radome preform is heat-treated in a nitrogen atmosphere at a temperature of 900°C.

[0070] The boron nitride interface coating of the fiber radome fabric prepared in Examples 1-6 of this application has good uniformity and consistency. The mechanical properties of each part of the radome prepared in this way are uniform, there are no relatively weak areas in mechanical properties, the mechanical properties are good, the bending strength is high, and the radome has high reliability in use. Figure 7-9 The boron nitride interface coating on the fiber radome fabric prepared in Example 4 is shown. Figure 7This is a SEM image of a single fiber taken from the inner surface of the fiber radome fabric. Figure 8 This is a SEM image of a single fiber taken from the middle of the fiber radome fabric. Figure 9 The image shows a SEM image of a single fiber taken from the outer surface of the fiber radome fabric. It can be seen that the fiber surface is coated with a uniformly thick boron nitride interface coating. The thickness of the boron nitride interface coating on the inner surface of a single fiber is 1.40 μm, on the middle surface it is 0.93 μm, and on the outer surface it is 1.21 μm. The thickness of the boron nitride interface coating deposited throughout the fiber radome fabric is relatively uniform and consistent. Bending strength tests were conducted on samples taken from the root of the radome samples made from the fiber radome fabrics with deposited boron nitride interface coatings of Examples 2-4, according to GB / T6569-2006 "Test Method for Bending Strength of Fine Ceramics". The bending strength corresponding to Example 2 was 87.2 MPa, Example 3 was 90.3 MPa, and Example 4 was 93.8 MPa, demonstrating excellent mechanical properties and high bending strength.

[0071] The present invention has been described above with reference to specific embodiments. These specific embodiments are merely exemplary and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make various modifications, changes, or substitutions without departing from the essence of the present invention. Therefore, various equivalent variations made according to the present invention still fall within the scope of the present invention.

Claims

1. A method for preparing a boron nitride interface coating on a fiber optic radome fabric, characterized in that, Includes the following steps: According to the preset structural and dimensional requirements, a fiber antenna radome fabric is obtained by weaving nitride fibers. Based on chemical vapor deposition, a boron nitride interface coating is deposited on the fiber radome fabric in stages through a first deposition stage and a second deposition stage. The first deposition stage includes: suspending the fiber radome fabric upright in the deposition furnace, evacuating the furnace until the pressure inside the furnace is maintained at a preset pressure, and introducing reactive gas into the cavity formed on the inner surface of the fiber radome fabric to complete the first deposition stage. The second deposition stage includes: inverting and suspending the fiber radome fabric inside the deposition furnace, fitting an isolation mold over the fiber radome fabric, forming an isolation space between the isolation mold and the outer surface of the fiber radome fabric, evacuating the furnace until the pressure inside the furnace is maintained at a preset pressure, and introducing a reaction gas through the isolation space to complete the second deposition stage.

2. The method for preparing the boron nitride interface coating on the fiber radome fabric as described in claim 1, characterized in that, Before weaving the fiber radome fabric, the surface of the nitride fibers is coated with a surface wetting agent; the fiber radome fabric is pretreated before deposition. The specific process of the pretreatment is as follows: the fiber radome fabric is placed on the ceramic tooling, and the ceramic tooling with the fiber radome fabric is placed in an air atmosphere and kept at a temperature of 400~600℃ for 1~6 hours.

3. The method for preparing the boron nitride interface coating on the fiber radome fabric as described in claim 1, characterized in that, In the first deposition stage, the fiber radome fabric is placed on the first contouring fixture, and the fiber radome fabric is hoisted in the deposition furnace with the large end facing down and the tip facing up. The furnace pressure is evacuated until it is maintained at a preset pressure, and the reaction gas is introduced into the cavity formed on the inner surface of the fiber radome fabric. The first conforming tool is adapted to the shape and size of the inner surface of the fiber radome fabric, and the first conforming tool is provided with several openings; the large end of the first conforming tool extends out of the large end of the fiber radome fabric.

4. The method for preparing the boron nitride interface coating on the fiber radome fabric as described in claim 3, characterized in that, In the first deposition stage, a first conforming device with fiber antenna radome fabric is placed on the gas inlet base of the deposition furnace. The fiber antenna radome fabric is covered by a cylindrical graphite separator. A sealing ring is set between the bottom of the cylindrical graphite separator and the bottom of the fiber antenna radome fabric. Reaction gas is introduced from the gas inlet base of the deposition furnace into the cavity formed on the inner surface of the fiber antenna radome fabric. The cylindrical graphite separator has open ends at both the top and bottom.

5. The method for preparing the boron nitride interface coating on the fiber radome fabric as described in claim 3, characterized in that, In the first deposition stage, a graphite limiting element is provided around the outer surface of the large end of the fiber antenna radome fabric to restrict the displacement of the fiber antenna radome fabric.

6. The method for preparing the boron nitride interface coating on the fiber radome fabric as described in claim 1, characterized in that, In the second deposition stage, the second contouring fixture is placed on the fiber radome fabric, keeping the large end of the fiber radome fabric facing up and the tip facing down. The fiber radome fabric is then inverted and suspended in the deposition furnace by the second contouring fixture. An isolation mold is fitted outside the second contouring fixture, forming an isolation space between the isolation mold and the second contouring fixture. The furnace pressure is evacuated until it is maintained at a preset pressure, and the reaction gas is introduced through the isolation space. The second contouring fixture is adapted to the shape and size of the outer surface of the fiber radome fabric, and has several openings. The large end of the second contouring fixture extends out of the large end of the fiber radome fabric. The isolation mold has an air inlet opening. The air inlet opening on the isolation mold corresponds to the position of the air inlet opening on the deposition furnace air inlet base.

7. The method for preparing the boron nitride interface coating on the fiber radome fabric as described in claim 6, characterized in that, In the second deposition stage, a first contouring fixture is also placed inside the fiber antenna radome fabric.

8. The method for preparing the boron nitride interface coating on the fiber radome fabric as described in claim 1, characterized in that, The preset pressure is 100-1000 Pa, and the reaction gases include BCl3, NH3, H2 and Ar; The deposition temperature in the first deposition stage is 500~900℃, and the deposition time is 6~15h; The deposition temperature in the second deposition stage is 500~900℃, and the deposition time is 6~12h.

9. The method for preparing the boron nitride interface coating on the fiber radome fabric as described in claim 1, characterized in that, After the first and second deposition stages, the deposited fiber radome fabric is subjected to nitriding treatment to obtain a boron nitride interface coating on the fiber radome fabric. The nitriding treatment is carried out in a nitrogen atmosphere with a pressure of 0.1~0.5 MPa, a nitriding temperature of 1200~1500℃, and a nitriding time of 1~5 h.

10. The method for preparing the boron nitride interface coating on the fiber radome fabric as described in claim 1, characterized in that, Before the nitride fibers are woven into the fiber radome fabric, the nitride fibers are modified; the modified nitride fibers and the unmodified nitride fibers are woven together to obtain the fiber radome fabric.

11. The method for preparing the boron nitride interface coating on the fiber radome fabric as described in claim 10, characterized in that, The fiber radome fabric includes an inner layer of fibers, an outer layer of fibers, and an intermediate layer of fibers located between the inner and outer layers of fibers; the inner and outer layers of fibers are modified nitride fibers, and the intermediate layer of fibers are unmodified nitride fibers.

12. The method for preparing the boron nitride interface coating on the fiber radome fabric as described in claim 11, characterized in that, Before depositing a boron nitride interface coating on the nitride fiber radome preform, the nitride fiber radome preform is heat-treated in a nitrogen atmosphere at a temperature of 800-1100℃.

13. A boron nitride interface coating for a fiber optic radome fabric, characterized in that, The boron nitride interface coating of the fiber radome fabric is prepared by any one of claims 1-12.

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