A nitride fiber-reinforced nitride ceramic radome and a method of manufacturing the same

Abstract

The application provides a nitride fiber reinforced nitride ceramic radome and a preparation method thereof, and comprises the following steps: S1, braiding a nitride fiber radome preform; S2, depositing a boron nitride interface coating on the nitride fiber radome preform to obtain an intermediate; S3, placing the intermediate in a limiting mold tooling provided with a plurality of through holes, setting an impregnation mold tooling outside the limiting mold tooling, injecting a nitride ceramic precursor between the limiting mold tooling and the impregnation mold tooling, and repeating impregnation molding and cracking to obtain a radome blank; and S4, ceramming the radome blank to obtain the nitride fiber reinforced nitride ceramic radome. The preparation method of the application completes the compounding of the nitride ceramic precursor and the preform based on the limiting mold tooling provided with a plurality of through holes and the impregnation mold tooling after the coating is prepared on the preform, the impregnation molding and cracking process is not prone to deformation, the mold is easy to demold, the amount of the precursor is saved, the cost is low, and the radome has good comprehensive performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of antenna covers, in particular to a nitride fiber reinforced nitride ceramic antenna cover and a preparation method thereof. BACKGROUND

[0002] At present, the main preparation processes of the matrix suitable for the nitride fiber reinforced ceramic matrix composite are CVI method and PIP method. The CVI method has the advantages of low preparation temperature, small thermal damage to the reinforcing fiber, etc., and is suitable for preparing complex components, but it has problems of long preparation cycle, poor deposition uniformity, high production cost, etc. The PIP method has the advantages of designable precursor molecules, small thermal damage to the fiber, near net shape forming, etc., and is suitable for preparing three-dimensional complex components, but it has problems of incomplete densification, density gradient in some positions, etc., which will lead to the decline of the material performance. At present, the technical personnel try to prepare the nitride fiber reinforced ceramic matrix antenna cover with specific shape and structure by combining the CVI method with the PIP method, but for the antenna cover with structure and size requirements, there is still a big difference in the density uniformity of different parts of the antenna cover, and the PIP precursor impregnation forming process has problems of easy deformation of the antenna cover, difficult demolding, high waste rate of the precursor, high cost, etc., which affect the comprehensive performance of the antenna cover. SUMMARY

[0003] The present application provides a nitride fiber reinforced nitride ceramic antenna cover and a preparation method thereof to solve the above technical problems.

[0004] In one aspect, the present application provides a preparation method of a nitride fiber reinforced nitride ceramic antenna cover, comprising the following steps: S1, obtaining a nitride fiber antenna cover preform by weaving nitride fibers; S2, depositing a boron nitride interface coating on the nitride fiber antenna cover preform based on the CVI process to obtain an intermediate; S3, placing the intermediate in a limiting mold tool provided with a plurality of through holes, setting an impregnation mold tool outside the limiting mold tool, injecting a nitride ceramic precursor between the limiting mold tool and the impregnation mold tool, and repeating the impregnation forming and cracking processes to obtain an antenna cover blank; S4, performing ceramic treatment on the antenna cover blank to obtain the nitride fiber reinforced nitride ceramic antenna cover.

[0005] Compared with the prior art, the present application has the following beneficial effects: the preparation method of the present application completes the compounding of the nitride ceramic precursor and the preform based on the limiting mold tool provided with a plurality of through holes and the impregnation mold tool after preparing the boron nitride interface coating on the nitride fiber antenna cover preform, the impregnation forming and cracking processes are not easy to deform, easy to demold, and the nitride ceramic precursor is only injected between the limiting mold tool and the impregnation mold tool, which saves the additional loss amount of the precursor, has low cost, and has good comprehensive performance of the antenna cover.

[0006] In some embodiments of the present application, the nitride fiber surface is coated with a surface wetting agent before weaving the nitride fiber radome preform; the nitride fiber radome preform is pretreated before the S2 step, and the specific process of the pretreatment is as follows: the nitride fiber radome preform is placed on a profiled ceramic tooling, and the profiled ceramic tooling loaded with the nitride fiber radome preform is placed in an air atmosphere and kept at a temperature of 500-600℃ for 1-6h.

[0007] The beneficial effects of the above further technical solutions are that the nitride fiber radome preform used in the present application is coated with a surface wetting agent, which facilitates weaving; the nitride fiber radome preform is pretreated before deposition, the design of the profiled ceramic tooling can avoid deformation of the nitride fiber radome preform during the pretreatment process, and the temperature setting of 500-600℃ can effectively remove the surface wetting agent while avoiding carbonization of the surface wetting agent, thereby avoiding weakening of the electrical properties caused by carbonization of the organic wetting agent in the subsequent heat treatment process.

[0008] In some embodiments of the present application, the S2 step includes: based on the CVI process, depositing a boron nitride interface coating on the nitride fiber radome preform in stages through a first deposition stage and a second deposition stage; wherein the first deposition stage includes: placing the nitride fiber radome preform on a first profiled tooling, keeping the nitride fiber radome preform in a state of large end downward and sharp end upward, vertically hanging in the deposition furnace, vacuumizing to maintain the pressure in the furnace at a preset pressure, introducing a reaction gas from the cavity formed on the inner surface of the nitride fiber radome preform, and completing the first deposition stage; the second deposition stage includes: placing a second profiled tooling on the nitride fiber radome preform, keeping the nitride fiber radome preform in a state of large end upward and sharp end downward, inverting the nitride fiber radome preform in the deposition furnace through the second profiled tooling, sleeving an isolation mold outside the second profiled tooling, forming an isolation space between the isolation mold and the second profiled tooling, vacuumizing to maintain the pressure in the furnace at a preset pressure, introducing a reaction gas from the isolation space, and completing the second deposition stage; the preset pressure is 100-1000Pa, and the reaction gas includes BCl3, NH3, H2 and Ar; the deposition temperature of the first deposition stage and the second deposition stage is 600-800℃, and the deposition time is 12-20h.

[0009] The beneficial effects of the further technical solutions are that, in the preparation process, the interface coating is deposited on the nitride fiber radome preform in stages, the first deposition stage is deposited from the inside to the outside, the pressure in the deposition furnace is controlled to maintain a preset pressure during the deposition process, when the reaction gas is introduced, the gas directly enters the cavity formed on the inner surface of the nitride fiber radome preform 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 beneficial to the gas passing through the nitride fiber radome preform from the inside to the outside, the second deposition stage is deposited from the outside to the inside, the pressure in the deposition furnace is controlled to maintain a preset pressure during the deposition process, when the reaction 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 beneficial to the gas passing through the nitride fiber radome preform from the outside to the inside, the deposition efficiency is high, the boron nitride interface coating is uniform and consistent, and the mechanical properties of the radome prepared in this way are consistent, there is no relatively weak area of mechanical properties, the mechanical properties are good, the bending strength is high, and the radome has high reliability.

[0010] When the boron nitride interface coating is deposited, BCl3, NH3, H2 and Ar are used as reaction gases, the deposition temperature is 600-800℃, the gas pressure in the deposition furnace is 100-1000Pa, when the reaction gas is introduced into the cavity or the isolation space formed on the inner surface of the nitride fiber radome preform, a stable pressure difference is obtained by reasonable adjustment of the gas pressure, so that the deposition process is easy to control, and the deposition uniformity and consistency are good.

[0011] In some embodiments of the present application, the first profiling tool is adapted to the shape and size of the inner surface of the nitride fiber radome preform, and a plurality of openings are provided on the first profiling tool; the large end of the first profiling tool extends out of the large end of the nitride fiber radome preform; in the first deposition stage, the first profiling tool with the nitride fiber radome preform is arranged on the deposition furnace inlet base, the nitride fiber radome preform is covered by a cylindrical graphite spacer, a sealing ring is arranged between the bottom of the cylindrical graphite spacer and the bottom of the nitride fiber radome preform, and the reaction gas is introduced into the cavity formed on the inner surface of the nitride fiber radome preform from the deposition furnace inlet base; the upper and lower ends of the cylindrical graphite spacer are open; in the first deposition stage, a graphite limiting piece is arranged around the outer surface of the large end of the nitride fiber radome preform to limit the displacement of the nitride fiber radome preform; the second profiling tool is adapted to the shape and size of the outer surface of the nitride fiber radome preform, and a plurality of openings are provided on the second profiling tool; the large end of the second profiling tool extends out of the large end of the nitride fiber radome preform; the isolation mold is provided with an inlet opening; the inlet opening of the isolation mold corresponds to the position of the inlet opening on the deposition furnace inlet base; in the second deposition stage, the first profiling tool is further arranged in the nitride fiber radome preform.

[0012] The beneficial effects of adopting the above further technical solutions are that in the first deposition stage of the present application, the first profiling tool supports the nitride fiber radome preform, the design of the openings facilitates the reaction gas to pass through the nitride fiber radome preform along a certain trajectory from inside to outside, and the large end of the first profiling tool extending out of the large end of the nitride fiber radome preform facilitates hoisting the nitride fiber radome preform; the cylindrical graphite spacer covers the nitride fiber radome preform, which plays a guiding role for the gas coming out of the nitride fiber radome preform; the sealing ring plays a packaging role to prevent the reaction gas entering the deposition furnace from scattering; the design of the graphite limiting piece plays a limiting role for the nitride fiber radome preform to prevent unnecessary displacement, and in addition, the graphite limiting piece can also cooperate with hoisting to suspend the large end face of the nitride fiber radome preform, avoiding affecting the end face deposition.

[0013] In the second deposition stage of the present application, the second profiling tool supports the nitride fiber radome preform, the design of the openings facilitates the reaction gas to pass through the nitride fiber radome preform along a certain trajectory from outside to inside, and the large end of the second profiling tool extending out of the large end of the nitride fiber radome preform facilitates hoisting the nitride fiber radome preform; the design of the isolation mold forms an isolation space between the isolation mold and the second profiling tool, which isolates the isolation space from the deposition furnace cavity, facilitating the formation of the internal and external pressure difference after the reaction gas is introduced; the use of the first profiling tool prevents the nitride fiber radome preform from shrinking and deforming in the second deposition stage.

[0014] In some embodiments of the present application, the intermediate obtained after deposition is subjected to nitriding treatment before the S3 step, the nitriding treatment is carried out under a nitrogen atmosphere with a pressure of 0.1-0.5 MPa, the nitriding temperature is 1200-1500°C, and the nitriding time is 1-5 h.

[0015] The beneficial effects of the above further technical solutions are that the intermediate is subjected to nitriding treatment under a nitrogen atmosphere with a pressure of 0.1-0.5 MPa at a nitriding temperature of 1200-1500°C after deposition, and the conversion process of the coating from amorphous phase to crystalline phase is completed.

[0016] In some embodiments of the present application, the nitride ceramic precursor is a polysilazane precursor, a silicon boron nitride precursor, or a boron nitride precursor; the limiting mold tooling includes a porous inner mold tooling and a split porous outer mold tooling, the shape of the porous inner mold tooling is adapted to the intermediate, the shape of the split porous outer mold tooling is adapted to the intermediate, and the intermediate is placed between the porous inner mold tooling and the split porous outer mold tooling; the impregnation mold tooling includes a core mold tooling and an outer mold tooling, the shape of the outer surface of the core mold tooling is adapted to the inner surface of the porous inner mold tooling, the shape of the inner surface of the outer mold tooling is adapted to the outer surface of the split porous outer mold tooling, the limiting mold tooling is arranged between the core mold tooling and the outer mold tooling, and the core mold tooling and the porous inner mold tooling, the outer mold tooling and the split porous outer mold tooling are left with an injection space; the porous inner mold tooling, the split porous outer mold tooling, the intermediate, and the core mold tooling are positioned by means of a positioning disc provided with a plurality of communication openings through their large ends; the open end of the outer mold tooling faces upward so that the intermediate is arranged in the outer mold tooling in an inverted state, the impregnation mold tooling further includes a sealing cover, the size of the sealing cover is adapted to the size of the open end of the outer mold tooling for sealing the opening of the outer mold tooling, the sealing cover is provided with a gas passage, a precursor injection passage, a vacuum table interface, and an observation window; and the outer surface of the outer mold tooling is connected to a plurality of support legs.

[0017] The beneficial effects of the further technical scheme are that the limiting die tooling includes a porous inner die tooling and a split porous outer die tooling, the intermediate body is arranged between the porous inner die tooling and the split porous outer die tooling, the deformation of the intermediate body is limited, the porous structure provides a channel for the precursor to enter the intermediate body, and the split porous outer die tooling facilitates subsequent removal; the impregnation die tooling includes a core die tooling and an outer die tooling, the limiting die tooling is arranged between the core die tooling and the outer die tooling, and the core die tooling and the outer die tooling are respectively arranged with the porous inner die tooling and the split porous outer die tooling, and an injection space is left between the core die tooling and the porous inner die tooling and between the outer die tooling and the split porous outer die tooling; when the precursor is impregnated, the precursor is impregnated into the intermediate body from the injection space, most of the waste of the precursor is the remaining precursor in the injection space, the waste rate of the precursor is low, and the raw material cost is reduced; the positioning disc has a positioning function, and facilitates the formation of the injection space after positioning; the sealing cover has a sealing function, the gas passage provides a channel for the gas to enter and exit, the precursor injection passage provides a channel for the precursor to be injected, the vacuum gauge interface is connected with the vacuum gauge to facilitate the observation of the air pressure in the sealed space, and the observation window facilitates the observation of the amount of the precursor injected into the sealed space, and thus facilitates the implementation of subsequent impregnation molding and cracking processes.

[0018] In some embodiments of the present application, the specific steps of S3 are as follows: S31, the porous inner die tooling is arranged in the intermediate body, the intermediate body is arranged in the split porous outer die tooling, the core die tooling is arranged in the porous inner die tooling after the outer surface of the core die tooling is coated with a release agent, the positioning disc is used to position the porous inner die tooling, the split porous outer die tooling, the intermediate body and the core die tooling, and the porous inner die tooling and the split porous outer die tooling are tightly attached to the intermediate body, and an injection space is left between the core die tooling and the porous inner die tooling; S32, the outer die tooling is arranged in the product assembled in step S31 after the inner surface of the outer die tooling is coated with a release agent, and the positioning disc is used to leave an injection space between the outer die tooling and the split porous outer die tooling; S33, the sealing cover is assembled to the opening end of the outer die tooling assembled in step S32, the impregnation molding and cracking processes are repeated, and the radome blank is obtained.

[0019] The beneficial effects of the further technical scheme are that the coating of the release agent facilitates subsequent demolding.

[0020] In some embodiments of the present application, the impregnation molding comprises the following steps: controlling the air pressure in the impregnation mold tool through a gas passage, keeping the vacuum degree at -0.90 to -0.1 Mpa for 30 to 120 min, then siphoning the nitride ceramic precursor through a precursor injection passage, and then keeping the vacuum degree at -0.90 to -0.1 Mpa for 120 to 240 min, so that the nitride ceramic precursor is fully filled into the inside of the radome fabric; then, the impregnation mold tool is put into a high-pressure reaction kettle, the gas passage valve is opened, and the pressure is increased to 6 to 10 Mpa and kept for 12 to 20 h, then the pressure is released to 2 to 4 Mpa, the temperature in the high-pressure kettle is increased to 200 to 300 DEG C, the pressure is increased to 4 to 8 Mpa, and kept for 4 to 10 h.

[0021] In some embodiments of the present application, the specific process of the cracking is as follows: after the intermediate after impregnation molding is demolded and surface processed, it is kept at a temperature of 700 to 900 DEG C in an NH3 atmosphere for 2 to 4 h; the impregnation molding and the cracking process are repeated for 4 to 7 times; and the ceramization treatment is carried out under a pressure of 0.5 to 1 Mpa and a nitrogen atmosphere, the treatment temperature is 1100 to 1300 DEG C, and the treatment time is 1 to 5 h.

[0022] The beneficial effects of the above further technical solutions are that small molecule gases are released during the precursor solidification process, the impregnation molding system of the present application, especially the high-pressure stage, can inhibit the appearance of large pores and inhibit the deformation and thickness increase phenomenon caused by gas discharge; on this basis, the cracking system is carried out under normal pressure to avoid the use of ammonia gas under high pressure to cause danger.

[0023] In some embodiments of the present application, the nitride fiber is modified by a fiber modification solution before being woven; the modified nitride fiber and the unmodified nitride fiber are woven together to obtain the nitride fiber radome preform.

[0024] In some embodiments of the present application, the nitride fiber radome preform comprises inner layer fibers, outer layer fibers, and intermediate layer fibers 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.

[0025] In some embodiments of the present application, the fiber modification solution comprises BO2, a binder, and a solvent in a mass ratio of (1-2):(0.5-1):(8-10).

[0026] The process of modifying the nitride fiber by the fiber modification solution is that the nitride fiber is immersed in the fiber modification solution and then dried to obtain the modified nitride fiber.

[0027] In some embodiments of the present application, the binder comprises one of furan resin, phenolic resin, sodium carboxymethyl cellulose; and the solvent comprises methanol or ethanol.

[0028] The beneficial effects of the above further technical solutions are that the nitride fiber surface of the inner layer and the outer layer of the nitride fiber antenna radome preform is attached with BO2, so that when the boron nitride interface coating is deposited on the nitride fiber antenna radome preform, NH3 in the reaction gas reacts with the nitride fiber, thereby improving the bonding strength of the boron nitride interface coating generated by the reaction with the nitride fiber antenna radome preform, and reducing the porosity of the nitride fiber antenna radome preform from both sides to the middle, realizing the controllable thickness of the coating and the fiber layer combination, and avoiding the significant reduction of the porosity of the nitride fiber antenna radome.

[0029] In some embodiments of the present application, before the boron nitride interface coating is deposited on the nitride fiber antenna radome preform, the nitride fiber antenna radome preform is heat treated in a nitrogen atmosphere, and the heat treatment temperature is 800-1100℃.

[0030] The beneficial effects of the above further technical solutions are that the nitride fiber surface of the inner layer and the outer layer of the nitride fiber antenna radome preform is attached with BO2, so that when the boron nitride interface coating is deposited on the nitride fiber antenna radome preform, NH3 in the reaction gas reacts with the nitride fiber, thereby improving the bonding strength of the boron nitride interface coating generated by the reaction with the nitride fiber antenna radome preform, and reducing the porosity of the nitride fiber antenna radome preform from both sides to the middle, realizing the controllable thickness of the coating and the fiber layer combination, and avoiding the significant reduction of the porosity of the nitride fiber antenna radome.

[0031] And before the boron nitride interface coating is deposited on the nitride fiber antenna radome preform, the attached boron nitride has a certain activity, which is conducive to the high bonding strength of the boron nitride interface coating generated by the subsequent reaction with the nitride fiber antenna radome preform.

[0032] On the other hand, the present application also provides a nitride fiber reinforced nitride ceramic antenna radome prepared according to the preparation method of the nitride fiber reinforced nitride ceramic antenna radome of any one of the above.

[0033] Compared with the prior art, the present application has the following beneficial effects: the nitride fiber reinforced nitride ceramic antenna radome prepared by the present application has high density, good uniformity and consistency, no uneven area, high mechanical properties, the root sampling tensile strength reaches 65-75MPa, the compressive strength reaches 150-162MPa, the mechanical properties of different parts of the antenna radome are consistent, the linear ablation rate of the antenna radome at 2100℃ is 0.7-0.8 of that of the quartz fiber reinforced composite material antenna radome, and the ablation resistance is high. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiments of the present application will be described below.

[0035] Figure 1 Flow chart of the method for preparing nitride fiber reinforced nitride ceramic radome of one embodiment of the present application;

[0036] Figure 2 Structural schematic diagram of the first profiling tool of one embodiment of the present application;

[0037] Figure 3 Structural schematic diagram of the second profiling tool of one embodiment of the present application;

[0038] Figure 4 Structural schematic diagram of the first deposition stage in the process of depositing boron nitride interface coating of one embodiment of the present application;

[0039] Figure 5 Structural schematic diagram of the second deposition stage in the process of depositing boron nitride interface coating of one embodiment of the present application;

[0040] Figure 6 SEM image of a single fiber taken from the inner surface of the intermediate body on which boron nitride interface coating is deposited, prepared by one embodiment of the present application;

[0041] Figure 7 SEM image of a single fiber taken from the middle of the intermediate body on which boron nitride interface coating is deposited, prepared by one embodiment of the present application;

[0042] Figure 8 SEM image of a single fiber taken from the outer surface of the intermediate body on which boron nitride interface coating is deposited, prepared by one embodiment of the present application;

[0043] Figure 9 Structural schematic diagram of the porous inner mold tool and the split type porous outer mold tool of the limiting mold tool of one embodiment of the present application; wherein, Figure 9 (a) is a structural schematic diagram of the porous inner mold tool, Figure 9 (b) is a structural schematic diagram of the split type porous outer mold tool;

[0044] Figure 10 Structural schematic diagram of the core mold tool and the outer mold tool of the impregnation mold tool of one embodiment of the present application; wherein, Figure 10 (a) is a structural schematic diagram of the core mold tool, Figure 10 (b) is a structural schematic diagram of the outer mold tool;

[0045] Figure 11 Structural schematic diagram of the positioning disc of one embodiment of the present application;

[0046] Figure 12 Structural schematic diagram of the sealing cover of one embodiment of the present application;

[0047] Figure 13 An assembly state side view of an impregnation mold tool, a limiting mold tool and an intermediate body according to an embodiment of the present application;

[0048] Figure 14 A CT test image of a nitride fiber reinforced nitride ceramic radome prepared according to an embodiment of the present application; wherein, Figure 14 (a) is a CT test image of the entire radome, Figure 14 (b) - (e) are CT test images of different sections of the radome. DETAILED DESCRIPTION

[0049] In order to make the objectives, technical solutions and advantages of the present application clearer, each aspect of the present application will be described in detail below in combination with specific embodiments, but these specific embodiments are only used to illustrate the present application and do not constitute any limitation on the scope and substance of the present application.

[0050] Embodiment 1

[0051] The present embodiment provides a preparation method of a nitride fiber reinforced nitride ceramic radome, as shown in the following steps: Figure 1

[0052] S1, according to the predetermined structure and size requirements, nitride fiber is woven to obtain a nitride fiber radome preform; wherein, before weaving the nitride fiber radome preform, a surface wetting agent is coated on the surface of the nitride fiber; before depositing the nitride fiber radome preform, the nitride fiber radome preform is pretreated first, and the specific process of the pretreatment is as follows: the nitride fiber radome preform is placed on a profiled ceramic tool (the profiled ceramic tool is designed according to the structure and size requirements of the nitride fiber radome preform, which can prevent the nitride fiber radome preform from deforming during the pretreatment process), and the profiled ceramic tool loaded with the nitride fiber radome preform is placed in an air atmosphere, and the surface wetting agent is removed at a temperature of 500-600℃ for 1-6h. In the present embodiment, the profiled ceramic tool is provided with a plurality of openings to facilitate the nitride fiber radome preform to be in full contact with the atmosphere. Preferably, the profiled ceramic tool is the same as the first profiled tool in the first embodiment. Figure 2

[0053] S2, based on the CVI process, a boron nitride interface coating is deposited on the nitride fiber radome preform to obtain an intermediate body. Specifically, based on the CVI process, the boron nitride interface coating is deposited on the nitride fiber radome preform in stages through a first deposition stage and a second deposition stage.

[0054] ​​The first deposition stage comprises: hoisting the nitride fiber radome preform vertically in a deposition furnace, vacuumizing the furnace to maintain the pressure in the furnace at a preset pressure, introducing reaction gas into the cavity formed on the inner surface of the nitride fiber radome preform, and completing the first deposition stage. In the embodiment, as shown in Figure 4 In the first deposition stage, the nitride fiber radome preform 1 is placed on the first profiling tool 2 coated with boron nitride slurry, the first profiling tool is designed according to the structure and size requirements of the nitride fiber radome preform, and is preferably a high-temperature-resistant profiling graphite tool, the nitride fiber radome preform 1 is kept in a state with the large end downward and the pointed end upward, the molybdenum wire is passed through the bottom of the first profiling tool 2 and hoisted vertically in the deposition furnace, the furnace is vacuumized to maintain the pressure in the furnace at a preset pressure, and the reaction gas is introduced into the cavity formed on the inner surface of the nitride fiber radome preform 1. Figure 2 The first profiling tool 2 is adapted to the shape and size of the inner surface of the nitride fiber radome preform 1, and a plurality of openings are provided on the first profiling tool 2. Preferably, the large end of the first profiling tool 2 protrudes out of the large end of the nitride fiber radome preform 1. Further, in the first deposition stage, the first profiling tool 2 with the nitride fiber radome preform 1 is placed on the deposition furnace gas inlet base 3, the nitride fiber radome preform 1 is covered by the cylindrical graphite isolation piece 7, a sealing ring 8 is arranged between the bottom of the cylindrical graphite isolation piece 7 and the bottom of the nitride fiber radome preform 1, and the reaction gas is introduced into the cavity formed on the inner surface of the nitride fiber radome preform 1 from the deposition furnace gas inlet base 3. In the embodiment, the upper and lower ends of the cylindrical graphite isolation piece 7 are open, the gas inlet opening 31 is provided on the deposition furnace gas inlet base 3, the reaction gas is introduced into the cavity formed on the inner surface of the nitride fiber radome preform 1 from the gas inlet opening 31, the cavity is in a high-pressure state due to the pressure difference between the cavity and the deposition furnace cavity, and the gas is beneficial to pass through the nitride fiber radome preform from the inside to the outside. In the first deposition stage, the graphite limiting piece 4 is arranged around the outer surface of the large end of the nitride fiber radome preform 1 to limit the displacement of the nitride fiber radome preform 1.

[0055] The second deposition stage comprises: hoisting the nitride fiber radome preform upside down by 180° in the deposition furnace, sleeving the isolation mold on the nitride fiber radome preform to form an isolation space between the isolation mold and the outer surface of the nitride fiber radome preform, vacuumizing the furnace to maintain the pressure in the furnace at a preset pressure, introducing reaction gas into the isolation space, and completing the second deposition stage. In the embodiment, as shown in Figure 5 In the second deposition stage, the second profiling tool 5 coated with boron nitride slurry is placed on the isolation mold, the second profiling tool is designed according to the structure and size requirements of the nitride fiber radome preform, and is preferably a high-temperature-resistant profiling graphite tool, the nitride fiber radome preform is kept in a state with the large end upward and the pointed end downward, the molybdenum wire is passed through the bottom of the second profiling tool 5 and hoisted vertically in the deposition furnace, the furnace is vacuumized to maintain the pressure in the furnace at a preset pressure, and the reaction gas is introduced into the cavity formed on the inner surface of the nitride fiber radome preform. Figure 3As shown, the second profiling tool is designed according to the structure and size requirements of the nitride fiber radome preform, and is preferably a high-temperature-resistant profiling graphite tool. The second profiling tool is placed on the nitride fiber radome preform 1, keeping the nitride fiber radome preform 1 in an upside-down state with the large end up and the pointed end down. The molybdenum wire is passed through the bottom of the large end of the second profiling tool 5, and the nitride fiber radome preform 1 is inverted and hoisted in the deposition furnace. The isolation mold 6 is fitted outside the second profiling tool 5, forming an isolation space between the isolation mold 6 and the second profiling tool 5. The pressure in the furnace is maintained at a preset pressure after vacuumizing, and the reaction gas is introduced from the isolation space. The shape and size of the second profiling tool 5 are adapted to the outer surface of the nitride fiber radome preform 1, and a plurality of openings perpendicular to the wall of the nitride fiber radome preform are provided on the second profiling tool 5. The large end of the second profiling tool 5 protrudes from the large end of the nitride fiber radome preform 1. The isolation mold 6 is provided with a gas inlet opening 61, which corresponds to the gas inlet opening 31 on the deposition furnace gas inlet base 3. The reaction gas enters the isolation space from the opening 61, and the isolation space and the deposition furnace cavity form a pressure difference, keeping the isolation space in a high-pressure state, which is conducive to the gas passing through the nitride fiber radome preform 1 from the outside to the inside. In this embodiment, the first profiling tool 2 is also placed in the nitride fiber radome preform 1 during the second deposition stage.

[0056] In this embodiment, 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 and the second deposition stage is 600-800℃, and the deposition time is 12-20h. In this embodiment, the introduction rate and gas pressure of the reaction gas can be reasonably adjusted according to actual conditions.

[0057] After deposition, the intermediate obtained after deposition is first subjected to nitriding treatment. 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 1-5h.

[0058] S3, densification and composite molding: placing the intermediate in a limiting mold tool provided with a plurality of through holes, and setting an impregnation mold tool outside the limiting mold tool, injecting a nitride ceramic precursor between the limiting mold tool and the impregnation mold tool, and repeating the impregnation molding and cracking process to obtain a radome blank. In this embodiment, the specific selection of the nitride ceramic precursor is not limited, for example, the nitride ceramic precursor can be a polysilazane precursor, a silicon boron nitride precursor or a boron nitride precursor.

[0059] As Figures 9-13As shown, the limiting mold tool includes a porous inner mold tool 100 and a split porous outer mold tool 200, the porous inner mold tool 100 is shaped to adapt to the intermediate body, the split porous outer mold tool 200 is shaped to adapt to the intermediate body, and the intermediate body 700 is disposed between the porous inner mold tool 100 and the split porous outer mold tool 200.

[0060] The dip mold tool includes a core mold tool 300 and an outer mold tool 400, the outer surface of the core mold tool 300 is shaped to adapt to the inner surface of the porous inner mold tool 100, the inner surface of the outer mold tool 400 is shaped to adapt to the outer surface of the split porous outer mold tool 200, the limiting mold tool is disposed between the core mold tool 300 and the outer mold tool 400, and the core mold tool 300 and the outer mold tool 400 are spaced apart from the porous inner mold tool 100 and the split porous outer mold tool 200 to form an injection space. In the embodiment, the width of the injection space (i.e. the distance between the core mold tool 300 and the porous inner mold tool 100, and the distance between the outer mold tool 400 and the split porous outer mold tool 200) is 1-2 mm.

[0061] The porous inner mold tool 100, the split porous outer mold tool 200, the intermediate body 700 and the core mold tool 300 are positioned by a positioning disc 500 provided with a plurality of through holes 503. In the embodiment, the through holes 503 provide a channel for precursor injection. In the embodiment, the porous inner mold tool 100 is provided with a first connecting seat 101, the split porous outer mold tool 200 is provided with a second connecting seat 201, the positioning disc 500 is provided with a limiting mold tool connecting hole 502, and the porous inner mold tool 100 and the split porous outer mold tool 200 are positioned by cooperating the first connecting seat 101 and the second connecting seat 201 with the limiting mold tool connecting hole 502, respectively. The core mold tool 300 can be a solid structure, and is provided with a first mounting hole at the large end, and the positioning disc 500 is provided with a second mounting hole 501, and the core mold tool 300 is positioned by cooperating the first mounting hole with the second mounting hole 501.

[0062] The opening end of the outer mold tool 400 faces upward to allow the intermediate body 700 to be disposed in the outer mold tool 400 in an inverted state, and the dip mold tool further includes a sealing cover 600, the size of the sealing cover 600 is adapted to the size of the opening end of the outer mold tool 400, and the sealing cover 600 is used to seal the opening of the outer mold tool 400, the sealing cover 600 is provided with a gas passage 602, a precursor injection passage 603, a vacuum gauge interface 601 and an observation window 604, and the outer surface of the outer mold tool 400 is connected with a plurality of support legs 401.

[0063] In the embodiment, the specific steps of S3 are as follows:

[0064] S31, place the porous inner mold tool 100 into the intermediate body 700, place the intermediate body 700 into the split porous outer mold tool 200, coat the outer surface of the core mold tool 300 with a layer of release agent and place it into the porous inner mold tool 100, position the porous inner mold tool 100, the split porous outer mold tool 200, the intermediate body 700 and the core mold tool 300 by the positioning disc 500, and make the porous inner mold tool 100 and the split porous outer mold tool 200 respectively tightly adhere to the intermediate body 700, and leave an injection space between the core mold tool 300 and the porous inner mold tool 100;

[0065] S32, coat the inner surface of the outer mold tool 400 with a layer of release agent, then invert the product assembled in step S31 into the outer mold tool 400, and make the outer mold tool 400 and the split porous outer mold tool 200 leave an injection space by the positioning disc 500;

[0066] S33, assemble the sealing cover 600 to the opening end of the outer mold tool 400 assembled in step S32, repeat the impregnation molding and pyrolysis process to obtain the radome blank.

[0067] In this embodiment, the impregnation molding includes the following steps: controlling the gas pressure in the impregnation mold tool through the gas passage, maintaining the vacuum degree at -0.90 to -0.1 Mpa for 30 to 120 min, then siphoning the nitride ceramic precursor through the precursor injection passage, and then maintaining the vacuum degree at -0.90 to -0.1 Mpa for 120 to 240 min, so that the nitride ceramic precursor is fully filled into the radome fabric; then, place the impregnation mold tool into a high-pressure reaction kettle, open the control valve of the gas passage, pressurize to 6 to 10 Mpa and maintain for 12 to 20 h, then release the pressure to 2 to 4 Mpa, raise the temperature in the high-pressure reaction kettle to 200 to 300 ℃, pressurize to 4 to 8 MPa, and maintain for 4 to 10 h.

[0068] In this embodiment, the specific process of pyrolysis is as follows: after the impregnation molding intermediate body is demolded and surface processed, it is placed into a graphite mold, and is kept at a temperature of 700 to 900 ℃ in an NH3 atmosphere for 2 to 4 h. In this embodiment, the impregnation molding and pyrolysis process is repeated for 4 to 7 cycles.

[0069] S4, perform ceramic treatment on the radome blank to obtain a nitride fiber reinforced nitride ceramic radome. In this embodiment, the ceramic treatment is performed under a pressure of 0.5 to 1 Mpa and a nitrogen atmosphere, the treatment temperature is 1100 to 1300 ℃, and the treatment time is 1 to 5 h.

[0070] This embodiment also provides a nitride fiber reinforced nitride ceramic radome, which is prepared according to the preparation method of the nitride fiber reinforced nitride ceramic radome of this embodiment.

[0071] Example 2

[0072] The present embodiment provides a nitride fiber reinforced nitride ceramic radome and a preparation method thereof. The present embodiment is different from the embodiment 1 only in the process parameters of the pretreatment, deposition, nitriding treatment, impregnation molding, cracking and ceramization. Here, only the differences are described, and the same parts are not described again.

[0073] The specific process of the pretreatment in the present embodiment is as follows: the nitride fiber radome preform is placed on the profiled ceramic tooling, and the profiled ceramic tooling loaded with the nitride fiber radome preform is placed in an air atmosphere, and kept at a temperature of 500℃ for 6h to remove the surface wetting agent.

[0074] In the deposition process of the present embodiment, the preset pressure is 100Pa, and the reaction gas includes BCl3, NH3, H2 and Ar; the deposition temperature of the first deposition stage and the second deposition stage is 600℃, and the deposition time is 20h.

[0075] The nitriding treatment in the present embodiment is carried out in a nitrogen atmosphere with a pressure of 0.1Mpa, and the nitriding temperature is 1200℃ and the nitriding time is 5h.

[0076] The specific process of the impregnation molding in the present embodiment is as follows: the gas pressure in the impregnation mold tooling is controlled through the gas passage, and kept at a vacuum degree of-0.90Mpa for 120min, then the nitride ceramic precursor is injected through the precursor injection passage, and kept at a vacuum degree of-0.90Mpa for 240min to siphon the nitride ceramic precursor; then, the impregnation mold tooling is placed into a high-pressure reaction kettle, the control valve of the gas passage is opened, and the pressure is increased to 6Mpa and kept for 20h, then the pressure is released to 2Mpa, the temperature in the high-pressure reaction kettle is increased to 200℃, the pressure is increased to 4MPa, and kept for 10h.

[0077] The specific process of the cracking in the present embodiment is as follows: after the intermediate after impregnation molding is demolded and surface processed, it is placed in a graphite mold, kept at a temperature of 700℃ for 4h in an NH3 atmosphere. In the present embodiment, the impregnation molding and cracking process are repeated for 7 times.

[0078] The ceramization treatment in the present embodiment is carried out in a nitrogen atmosphere with a pressure of 0.5Mpa, and the treatment temperature is 1100℃ and the treatment time is 5h.

[0079] Example 3

[0080] The present embodiment provides a boron nitride interface coating of a nitride fiber radome preform and a preparation method thereof. The present embodiment is different from the embodiment 1 only in the process parameters of the pretreatment, deposition, nitriding treatment, impregnation molding, cracking and ceramization. Here, only the differences are described, and the same parts are not described again.

[0081] The specific process of the pre-treatment of this embodiment is as follows: the nitride fiber radome preform is placed on a profiled ceramic tooling, the profiled ceramic tooling loaded with the nitride fiber radome preform is placed in an air atmosphere, and the surface sizing agent is removed by keeping the temperature at 550 DEG C for 3 h.

[0082] In the deposition process of this embodiment, the preset pressure is 600 Pa, the reaction gas includes BCl3, NH3, H2 and Ar, the deposition temperature of the first deposition stage and the second deposition stage is 700 DEG C, and the deposition time is 15 h.

[0083] The nitriding treatment of this embodiment is carried out in a nitrogen atmosphere with a pressure of 0.3 MPa, the nitriding temperature is 1300 DEG C, and the nitriding time is 3 h.

[0084] The specific process of the impregnation molding of this embodiment is as follows: the gas pressure in the impregnation mold tooling is controlled through a gas passage, the vacuum degree is kept at-0.50 MPa for 80 min, the nitride ceramic precursor is injected through a precursor injection passage, the vacuum degree is kept at-0.50 MPa for 200 min, and the nitride ceramic precursor is siphoned; then, the impregnation mold tooling is placed in a high-pressure reaction kettle, the control valve of the gas passage is opened, the pressure is increased to 8 MPa and kept for 17 h, the pressure is released to 3 MPa, the temperature in the high-pressure reaction kettle is increased to 250 DEG C, the pressure is increased to 6 MPa, and kept for 8 h.

[0085] The specific process of the cracking of this embodiment is as follows: after the intermediate after impregnation molding is demolded and surface processed, it is placed in a graphite mold, kept at a temperature of 800 DEG C for 3 h in an NH3 atmosphere. In this embodiment, the impregnation molding and the cracking process are repeated for 5 times.

[0086] The ceramization treatment of this embodiment is carried out in a nitrogen atmosphere with a pressure of 0.7 MPa, the treatment temperature is 1200 DEG C, and the treatment time is 3 h.

[0087] Embodiment 4

[0088] This embodiment provides a nitride fiber radome preform boron nitride interface coating and a preparation method thereof. This embodiment is different from embodiment 1 only in the process parameters of pre-treatment, deposition, nitriding treatment, impregnation molding, cracking and ceramization treatment. Here, only the differences are described, and the same parts are not described again.

[0089] The specific process of the pre-treatment of this embodiment is as follows: the nitride fiber radome preform is placed on a profiled ceramic tooling, the profiled ceramic tooling loaded with the nitride fiber radome preform is placed in an air atmosphere, and the surface sizing agent is removed by keeping the temperature at 600 DEG C for 1 h.

[0090] In the deposition process of this embodiment, the preset pressure is 1000 Pa, the reaction gas includes BCl3, NH3, H2 and Ar; the deposition temperature of the first deposition stage and the second deposition stage is 800℃, and the deposition time is 12h.

[0091] The nitriding treatment in this embodiment is carried out in a nitrogen atmosphere with a pressure of 0.5 MPa, the nitriding temperature is 1500℃, and the nitriding time is 1h.

[0092] The specific process of the impregnation molding in this embodiment is as follows: the gas pressure in the impregnation mold tool is controlled through the gas passage, and the vacuum degree is kept at-0.1 MPa for 30 min; then the nitride ceramic precursor is injected through the precursor injection passage, and the vacuum degree is kept at-0.1 MPa for 120 min to siphon the nitride ceramic precursor; then, the impregnation mold tool is placed into a high-pressure reaction kettle, the control valve of the gas passage is opened, the pressure is increased to 10 MPa and kept for 12h, then the pressure is released to 4 MPa, the temperature in the high-pressure reaction kettle is increased to 300℃, the pressure is increased to 8 MPa, and kept for 4h.

[0093] The specific process of the impregnation molding in this embodiment is as follows: the gas pressure in the impregnation mold tool is controlled through the gas passage, and the vacuum degree is kept at-0.1 MPa for 30 min; then the nitride ceramic precursor is injected through the precursor injection passage, and the vacuum degree is kept at-0.1 MPa for 120 min to siphon the nitride ceramic precursor; then, the impregnation mold tool is placed into a high-pressure reaction kettle, the control valve of the gas passage is opened, the pressure is increased to 10 MPa and kept for 12h, then the pressure is released to 4 MPa, the temperature in the high-pressure reaction kettle is increased to 300℃, the pressure is increased to 8 MPa, and kept for 4h.

[0094] The ceramicization treatment in this embodiment is carried out in a nitrogen atmosphere with a pressure of 1 MPa, the treatment temperature is 1300℃, and the treatment time is 1h.

[0095] Figure 6 Figure 6 shows the SEM image of a single fiber taken from the inner surface of the intermediate body with deposited boron nitride interface coating prepared in Example 4, Figure 7 Figure 7 shows the SEM image of a single fiber taken from the middle of the intermediate body with deposited boron nitride interface coating prepared in Example 4, Figure 8 Figure 8 shows the SEM image of a single fiber taken from the outer surface of the intermediate body with deposited boron nitride interface coating prepared in Example 4. As can be seen from the figure, the fiber surface is coated with a boron nitride interface coating with uniform thickness, the thickness of the boron nitride interface coating on the inner surface of the single fiber is 1.40 μm, the thickness of the boron nitride interface coating on the middle of the single fiber is 0.93 μm, and the thickness of the boron nitride interface coating on the outer surface of the single fiber is 1.21 μm. The thickness of the boron nitride interface coating deposited at different positions of the nitride fiber radome preform is not much different, and the uniformity and consistency are good. Figure 14 Figure 9 shows the CT test image of the nitride fiber reinforced nitride ceramic radome prepared in Example 4, wherein, Figure 14 (a) is the CT test image of the entire radome, Figure 14(b) -14(e) are CT test figures of different parts of the radome, from which it can be seen that the uniformity and consistency of the radome are good, and there is no uneven area. In addition, the tensile strength and compressive strength of the nitride fiber reinforced nitride ceramic radome root samples prepared in Examples 2-4 were tested by GB / T 23805-2009 "Fine Ceramic Room Temperature Tensile Strength Test Method" and GB / T 8489-2006 "Fine Ceramic Compression Strength Test Method", respectively. The tensile strength of Example 2 is 65Mpa, and the compressive strength is 150Mpa. The tensile strength of Example 3 is 70Mpa, and the compressive strength is 156Mpa. The tensile strength of Example 4 is 75Mpa, and the compressive strength is 162Mpa. The mechanical properties are excellent, and the mechanical properties of different parts of the radome are good. The line ablation test of the nitride fiber reinforced nitride ceramic radome prepared in Examples 2-4 shows that the line ablation rate of the radome of Example 2 at 2100℃ is 0.8 times that of the quartz fiber reinforced composite material radome, the line ablation rate of the radome of Example 3 at 2100℃ is 0.75 times that of the quartz fiber reinforced composite material radome, and the line ablation rate of the radome of Example 4 at 2100℃ is 0.7 times that of the quartz fiber reinforced composite material radome. High ablation resistance.

[0096] Example 5

[0097] The present embodiment provides a boron nitride interface coating of a nitride fiber radome preform and a preparation method thereof. The present embodiment is different from Example 1. Here, only the differences are described, and the same parts are not described again.

[0098] The nitride fiber is modified by a fiber modification solution before being woven; the modified nitride fiber and the unmodified nitride fiber are woven together to obtain the nitride fiber radome preform.

[0099] The nitride fiber radome preform comprises inner layer fibers, outer layer fibers, and intermediate layer fibers 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.

[0100] The fiber modification solution comprises BO2, an adhesive, and a solvent in a mass ratio of 1.2:0.9:8.5; the adhesive comprises phenolic resin; and the solvent comprises methanol.

[0101] The process of modifying the nitride fiber by the fiber modification solution is to immerse the nitride fiber in the fiber modification solution and then dry to obtain the modified nitride fiber.

[0102] Example 6

[0103] The embodiment provides a boron nitride interface coating of a nitride fiber radome preform and a preparation method thereof, and the embodiment is different from the embodiment 5. Herein, only the differences are described, and the same parts are not described again.

[0104] The fiber modification solution comprises BO2, a binder and a solvent in a mass ratio of 1.5:0.8:9; the binder comprises furan resin; and the solvent comprises ethanol.

[0105] Before the boron nitride interface coating is deposited on the nitride fiber radome preform, the nitride fiber radome preform is subjected to heat treatment in a nitrogen atmosphere, and the heat treatment temperature is 850 DEG C.

[0106] The application is described in combination with the specific embodiments, and the specific embodiments are only exemplary and cannot limit the protection scope of the application, and various modifications, changes or replacements can be made by those skilled in the art without departing from the essence of the application. Therefore, various equivalent changes made according to the application still belong to the scope covered by the application.

Claims

1. A method for preparing a nitride fiber reinforced nitride ceramic radome, characterized in that, Includes the following steps: S1. A nitride fiber radome preform is obtained by weaving nitride fibers; S2. Based on the CVI process, a boron nitride interface coating is deposited on the nitride fiber radome preform to obtain an intermediate; S3. The intermediate is placed in a limiting mold fixture with several through holes. An impregnation mold fixture is set outside the limiting mold fixture. Nitride ceramic precursor is injected between the limiting mold fixture and the impregnation mold fixture. The impregnation molding and pyrolysis process is repeated to obtain the radome blank. S4. The radome blank is subjected to ceramic treatment to obtain the nitride fiber reinforced nitride ceramic radome; Step S2 includes: based on the CVI process, depositing a boron nitride interface coating on the nitride fiber radome preform in stages through a first deposition stage and a second deposition stage. The first deposition stage includes: placing the nitride fiber radome preform on a first contouring fixture, hoisting the nitride fiber radome preform into the deposition furnace with the large end facing down and the tip facing up, evacuating the furnace until the pressure inside the furnace is maintained at a preset pressure, and introducing a reaction gas into the cavity formed on the inner surface of the nitride fiber radome preform to complete the first deposition stage. The second deposition stage includes: placing a second contouring fixture on the nitride fiber radome preform, keeping the large end of the nitride fiber radome preform facing upwards and the tip facing downwards, and then inverting and suspending the nitride fiber radome preform in the deposition furnace using the second contouring fixture; fitting an isolation mold around the second contouring fixture to form an isolation space between the isolation mold and the second contouring fixture; 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. The preset pressure is 100-1000 Pa, and the reaction gases include BCl3, NH3, H2 and Ar; the deposition temperature of the first deposition stage and the second deposition stage are both 600-800℃, and the deposition time is both 12-20h.

2. The method for preparing a nitride fiber reinforced nitride ceramic radome as described in claim 1, characterized in that, Before weaving the nitride fiber radome preform, the surface of the nitride fiber is coated with a surface wetting agent; Before step S2, the nitride fiber radome preform is pretreated. The specific pretreatment process is as follows: the nitride fiber radome preform is placed on a ceramic molding fixture, and the ceramic molding fixture carrying the nitride fiber radome preform is placed in an air atmosphere and kept at a temperature of 500~600℃ for 1~6 hours.

3. The method for preparing a nitride fiber reinforced nitride ceramic radome as described in claim 1, characterized in that, The first contouring fixture is adapted to the shape and size of the inner surface of the nitride fiber radome preform, and has several openings. The large end of the first contouring fixture extends beyond the large end of the nitride fiber radome preform. In the first deposition stage, the first contouring fixture with the nitride fiber radome preform is placed on the gas inlet base of the deposition furnace. The nitride fiber radome preform 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 nitride fiber radome preform. Reaction gas is introduced from the gas inlet base of the deposition furnace into the cavity formed on the inner surface of the nitride fiber radome preform. The upper and lower ends of the cylindrical graphite separator are open ends. In the first deposition stage, a graphite limiting member is provided around the outer surface of the large end of the nitride fiber radome preform to restrict the displacement of the nitride fiber radome preform. The second contouring tool is adapted to the shape and size of the outer surface of the nitride fiber radome preform, and the second contouring tool is provided with several openings; the large end of the second contouring tool extends out of the large end of the nitride fiber radome preform; the isolation mold is provided with an air inlet; the air inlet on the isolation mold corresponds to the position of the air inlet on the deposition furnace air inlet base; in the second deposition stage, the first contouring tool is also placed inside the nitride fiber radome preform.

4. The method for preparing a nitride fiber reinforced nitride ceramic radome as described in claim 1, characterized in that, Before proceeding with step S3, the intermediate obtained after deposition is subjected to nitriding treatment. 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.

5. The method for preparing a nitride fiber reinforced nitride ceramic radome as described in claim 1, characterized in that, The nitride ceramic precursor is a polyboronsilazane precursor, a silicon boron nitrogen precursor, or a boron nitride precursor. The limiting mold fixture includes a multi-hole inner mold fixture and a split multi-hole outer mold fixture. The shape of the multi-hole inner mold fixture is adapted to the intermediate body, and the shape of the split multi-hole outer mold fixture is adapted to the intermediate body. The intermediate body is placed between the multi-hole inner mold fixture and the split multi-hole outer mold fixture. The impregnation mold fixture includes a core mold fixture and an outer mold fixture. The shape of the outer surface of the core mold fixture is adapted to the inner surface of the porous inner mold fixture, and the shape of the inner surface of the outer mold fixture is adapted to the outer surface of the split porous outer mold fixture. The limiting mold fixture is located between the core mold fixture and the outer mold fixture. An injection space is provided between the core mold fixture and the porous inner mold fixture, and between the outer mold fixture and the split porous outer mold fixture. The multi-hole inner mold tooling, the split multi-hole outer mold tooling, the intermediate body and the core mold tooling are positioned by means of a positioning plate with several connecting openings at their large ends. The opening end of the outer mold fixture faces upward so that the intermediate body is placed in the outer mold fixture in an inverted state. The immersion mold fixture also includes a sealing cover. The size of the sealing cover is adapted to the size of the opening end of the outer mold fixture and is used to seal the opening of the outer mold fixture. The sealing cover is provided with a gas passage, a precursor injection passage, a vacuum gauge interface and an observation window. Several support legs are connected to the outer surface of the outer mold fixture.

6. The method for preparing a nitride fiber reinforced nitride ceramic radome as described in claim 5, characterized in that, The specific steps for S3 are as follows: S31. Insert the multi-hole inner mold tooling into the intermediate body, place the intermediate body into the split multi-hole outer mold tooling, coat the outer surface of the core mold tooling with a layer of release agent and place it into the multi-hole inner mold tooling, position the multi-hole inner mold tooling, the split multi-hole outer mold tooling, the intermediate body and the core mold tooling by the positioning plate, and make the multi-hole inner mold tooling and the split multi-hole outer mold tooling tightly attached to the intermediate body, leaving an injection space between the core mold tooling and the multi-hole inner mold tooling; S32. After coating the inner surface of the outer mold fixture with a layer of release agent, the product assembled in step S31 is placed upside down inside the outer mold fixture. The positioning plate leaves an injection space between the outer mold fixture and the split multi-hole outer mold fixture. S33. Assemble the sealing cap onto the opening end of the outer mold tooling assembled in step S32, and repeat the immersion molding and pyrolysis process to obtain the radome blank.

7. The method for preparing a nitride fiber reinforced nitride ceramic radome as described in claim 6, characterized in that, The impregnation molding process includes the following steps: controlling the gas pressure inside the impregnation mold tooling through a gas passage, maintaining a vacuum of -0.90 to -0.1 MPa for 30 to 120 minutes, then siphoning the nitride ceramic precursor through the precursor injection passage, and maintaining a vacuum of -0.90 to -0.1 MPa for 120 to 240 minutes to ensure that the nitride ceramic precursor is fully filled into the radome fabric; then, placing the impregnation mold tooling into a high-pressure reactor, opening the gas passage valve, pressurizing to 6 to 10 MPa and maintaining for 12 to 20 hours, then venting to 2 to 4 MPa, raising the temperature inside the high-pressure reactor to 200 to 300°C, pressurizing to 4 to 8 MPa, and maintaining for 4 to 10 hours.

8. The method for preparing a nitride fiber reinforced nitride ceramic radome as described in claim 1, characterized in that, The specific process of the pyrolysis is as follows: after demolding and surface processing of the intermediate after impregnation and molding, it is kept at a temperature of 700~900℃ for 2~4h in NH3 atmosphere; The impregnation molding and pyrolysis process is repeated 4 to 7 times. The ceramicization treatment is carried out under a pressure of 0.5~1 MPa and a nitrogen atmosphere, at a temperature of 1100~1300℃, for a time of 1~5 hours.

9. The method for preparing a nitride fiber reinforced nitride ceramic radome as described in claim 1, wherein its features are as follows: The characteristic is that the nitride fibers are modified by a fiber modification solution before being woven; the modified nitride fibers and the unmodified nitride fibers are woven together to obtain the nitride fiber radome preform.

10. The method for preparing a nitride fiber reinforced nitride ceramic radome as described in claim 9, characterized in that, The nitride fiber radome preform includes an inner layer fiber, an outer layer fiber, and an intermediate layer fiber located between the inner and outer layer fibers; the inner and outer layer fibers are modified nitride fibers, and the intermediate layer fiber is an unmodified nitride fiber.

11. A nitride fiber reinforced nitride ceramic radome, characterized in that, The nitride fiber reinforced nitride ceramic radome is prepared according to any one of claims 1-10.

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