阅读说明：本技术 氮化物纤维增强陶瓷基透波复合材料及其精密成型方法 (Nitride fiber reinforced ceramic-based wave-transparent composite material and precision forming method thereof ) 是由 马新 邱海鹏 梁艳媛 王晓猛 赵禹良 陈明伟 谢巍杰 王岭 刘善华 于 2020-12-13 设计创作，主要内容包括：本发明属于先进复合材料制备技术领域,具体公开了一种氮化物纤维增强陶瓷基透波复合材料及其精密成型方法。本发明的精密成型方法中材料制备与构件成型一次完成,不仅能保证复合材料的完整性能,还能缩短生产周期,降低制造成本。本发明采用低粘度的聚硅氮烷/正己烷成型胶液,能较好地浸润氮化物纤维预制体,并在低温下发生交联固化反应,首轮交联固化后,聚硅氮烷在氨气气氛中生成的氮化物在纤维束间均匀分布,残碳量低,介电性能适中,并与纤维粘附性好,对构件定型起到关键性作用；配合热模压工艺,可以控制构件的尺寸精度和型面,得到尺寸精度高的构件坯体。实验证明,本发明制备的透波复合材料构件厚度均匀,尺寸精度高,型面光洁度好。(The invention belongs to the technical field of advanced composite material preparation, and particularly discloses a nitride fiber reinforced ceramic matrix wave-transparent composite material and a precision forming method thereof. The precise forming method of the invention completes material preparation and member forming at one time, not only can ensure the integrity of the composite material, but also can shorten the production period and reduce the manufacturing cost. According to the invention, the low-viscosity polysilazane/n-hexane molding glue solution is adopted, the nitride fiber preform can be well infiltrated, and a crosslinking curing reaction is carried out at low temperature, after the first round of crosslinking curing, the nitride generated by polysilazane in the ammonia atmosphere is uniformly distributed among fiber bundles, the residual carbon content is low, the dielectric property is moderate, the adhesion with the fiber is good, and a key effect on component shaping is achieved; the size precision and the molded surface of the component can be controlled by matching with a hot die pressing process, and a component blank with high size precision is obtained. Experiments prove that the wave-transparent composite material member prepared by the invention has uniform thickness, high dimensional precision and good surface finish.)

1. A precision forming method of a nitride fiber reinforced ceramic matrix wave-transparent composite material is characterized in that: the method comprises the following steps:

(1) preparing a nitride fiber preform: forming the nitride fiber into a nitride fiber preform by adopting a fabric forming process;

(2) and (3) nitride fiber preform treatment: cleaning the nitride fiber preform to remove impurities to obtain a treated nitride fiber preform;

(3) preparing a BN interface layer: by BCl₃-NH₃-Ar-H₂A precursor gas system, preparing a BN interface layer on the surface of the fiber on the treated nitride fiber preform by a chemical vapor infiltration process to obtain the nitride fiber preform with the BN interface layer;

(4) vacuum impregnation molding glue solution: immersing the nitride fiber preform with the BN interface layer into a forming glue solution containing a polysilazane precursor for vacuum impregnation to obtain a nitride fiber preform subjected to vacuum impregnation;

(5) hot die pressing and forming: heating the nitride fiber preform subjected to vacuum impregnation to 180-200 ℃, keeping the temperature and pressure at 1-10 Mpa for 20-40 min, and obtaining a formed nitride fiber preform;

(6) high-temperature cracking: cracking the formed nitride fiber preform at high temperature in an ammonia atmosphere to obtain an inorganic composite material;

(7) densification of the composite material: and (3) adopting a precursor conversion process, immersing the inorganic composite material into a glue solution containing a polysilazane precursor for vacuum impregnation, then cracking at high temperature in an ammonia atmosphere, and repeating densification circulation to obtain the nitride fiber reinforced ceramic-based wave-transmitting composite material.

2. The precision molding method according to claim 1, characterized in that: in the step (1), the volume fraction of the nitride fibers in the nitride fiber preform is 35-60%, and the nitride fibers are selected from one or more of silicon nitride fibers, silicon boron nitrogen fibers and boron nitride fibers.

3. The precision molding method according to claim 1, characterized in that: and (2) putting the nitride fiber preform into water for ultrasonic cleaning, then putting the nitride fiber preform into a muffle furnace, heating the nitride fiber preform to 400-600 ℃ in air, preserving the heat for 1-3 hours, and then cooling to obtain the treated nitride fiber preform.

4. The precision molding method according to claim 1, characterized in that: in step (3), BCl₃Flow rate of 100-300 mL/min, NH₃Flow rate of 200-600 mL/min, Ar flow rate of 200-400 mL/min, H₂The flow rate is 500-1000 mL/min.

5. The precision molding method according to claim 1 or 4, characterized in that: and (3) putting the treated nitride fiber preform into a BN deposition furnace, setting the pressure in the furnace to be 2-3 kPa, the deposition temperature to be 600-1000 ℃, and the deposition time to be 20-50 h to obtain the nitride fiber preform with the BN interface layer.

6. The precision molding method according to claim 1, characterized in that: in the step (4), taking the mixture with the mass ratio of 1: (1-9) preparing a forming glue solution from a polysilazane precursor and n-hexane; and completely immersing the nitride fiber preform with the BN interface layer into the molding glue solution for 3-5 hours under the condition that the vacuum degree is less than 100Pa to obtain the nitride fiber preform after vacuum impregnation.

7. The precision molding method according to claim 1, characterized in that: in the step (5), drying the nitride fiber preform subjected to vacuum impregnation, then placing the dried nitride fiber preform into a lower die cavity, raising the temperature to 70-90 ℃ without die closing, and preserving the temperature for 10-15 min; then, heating to 120-140 ℃, keeping the temperature for 10-30 min, closing the mold, and slowly pressurizing to the pressure of 1-10 MPa; and finally, heating to 180-200 ℃, and maintaining the temperature and the pressure for 20-40 min to obtain the formed nitride fiber preform.

8. The precision molding method according to claim 1, characterized in that: in the step (6), the temperature of the formed nitride fiber preform is raised to 800-1200 ℃ at the heating rate of 10-20 ℃/min under the protection of ammonia atmosphere, and the temperature is maintained for 0.5-1 hour, so as to obtain the inorganic composite material.

9. The precision molding method according to claim 1, characterized in that: in the step (7), the inorganic composite material is vacuum-impregnated in a mass ratio of 1: (0.5-2.5) drying the mixed solution of the polyborosilazane precursor and n-hexane for 3-5 hours, then cracking at high temperature in an ammonia atmosphere, and repeating for 10-15 cycles to obtain the nitride fiber reinforced ceramic matrix wave-transmitting composite material.

10. A nitride fiber reinforced ceramic matrix wave-transparent composite material prepared by the precision molding method according to any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of advanced composite material preparation, relates to a nitride fiber reinforced composite material and a preparation method thereof, and particularly relates to a nitride fiber reinforced ceramic matrix wave-transparent composite material and a precision forming method thereof.

Background

The high-temperature-resistant wave-transmitting material is a multifunctional medium material widely applied to aircrafts such as precision guidance missiles, aerospace planes, carrier rockets and the like, and mainly has the functions of protecting the complete structure of the aircrafts in high-speed flight, realizing efficient transmission and effective communication of electromagnetic waves, and ensuring flight trajectory control, attitude adjustment, precision guidance and efficient damage of various aerospace aircrafts in severe environments. With the rapid development of hypersonic aircrafts and the research and development of reusable vehicles, higher requirements are put forward on the temperature resistance, wave transmission and bearing performance of wave-transmitting material structural members (antenna covers, antenna windows, wave-transmitting skins and the like), and the following performance requirements must be met: (1) long-term high temperature bearing capacity; (2) low room and high temperature dielectric constants and loss tangents; (3) excellent thermal shock resistance; (4) good ablation resistance; (5) lower thermal conductivity and coefficient of thermal expansion; (6) environmental resistance, etc.

The continuous fiber reinforced ceramic matrix composite has excellent performances of low density, high specific strength, high melting point, high temperature oxidation resistance, high fracture toughness, thermal shock resistance and the like, and is considered as a main development direction of a high temperature resistant structure-function integrated composite. For the wave-transparent composite material, the used fiber and the matrix must also have low dielectric constant and loss, excellent high-temperature mechanical property and oxidation resistance. The nitride ceramic matrix belongs to a covalent bond compound, has excellent mechanical properties such as high specific strength and high specific mode, has excellent high-temperature stability and lower dielectric property, and has great application prospect in wave-transparent ceramic materials. In recent years, novel silicon nitride fibers have been developed at home and abroad, and a foundation is laid for researching and developing the radome made of the continuous silicon nitride fiber reinforced ceramic-based wave-transparent composite material.

The wave-transparent radome belongs to a large-size thin-wall component, and the size precision of the radome wall directly influences the electrical thickness of the radome body, thereby influencing the transmission and aiming errors of signals, so that the precise forming preparation technology of the wave-transparent ceramic matrix composite thin-wall component is the premise and guarantee for realizing the excellent performance of the radome, and is also the difficulty of current research. The existing ceramic matrix composite material preparation process is difficult to realize the accurate control of the size of a component, for example, a slurry dipping hot-pressing method is difficult to prepare a component with large size and complex shape; the production period of the ceramic matrix composite thin-wall component prepared by the chemical vapor infiltration method is long, the cost is high, and the components and the sizes of the materials in the component are locally distributed unevenly. The components prepared by the traditional process can reach the required dimensional accuracy only by later machining, so that the size and the shape of the thin-wall component are limited, the preparation period and the cost are increased, and the machining can damage the interior of the component and easily generate the defects of cracks and the like, thereby reducing the material strength. Therefore, the development of new precise forming technology for ceramic-based wave-transparent composite material members, especially the preparation technology for precise forming of thin-wall members, is imperative.

The precursor impregnation-cracking (PIP) process is a new process for preparing a material which develops very rapidly in recent ten years, and the process is widely applied to the preparation of ceramic matrix composite materials. The PIP process can prepare large components with complex shapes and can realize near-net shape, but also has the problem that a large amount of small molecules escape in the pyrolysis process, so that the local size of the components is easily uneven. Aiming at the ceramic matrix wave-transparent composite material, the ideal wave-transparent precursor is easy to crosslink and solidify, has high ceramic yield, and does not contain impurity elements which influence the wave-transparent performance, particularly carbon elements, or the impurity elements can be completely removed in the ceramic process, so that the obtained ceramic matrix has high purity and excellent performance. Polysilazane is a nitride ceramic precursor, which contains a large amount of unsaturated carbon groups in its side chains, is easy to crosslink and cure, and has the characteristics of low molding temperature and high ceramic yield, but it has difficulty in efficiently removing impurity carbon elements even if it is cracked in an ammonia atmosphere because the molecular chains sharply increase and carbon-containing groups are entangled therein during crosslinking, and thus it has been difficult to obtain a nitride substrate having high purity and excellent dielectric properties. Currently, only perhydropolysilazane (PHPS) and Borazine (Borazine) can meet the use requirements. However, the total hydrogen precursor is a dangerous chemical which is easy to volatilize, flammable and explosive, is very sensitive to water and oxygen, is expensive and is not easy to store, so that the total hydrogen precursor is not suitable for engineering application. The novel Polysilazane (PBSZ) combines the advantages of the boron nitride ceramic precursor and the silicon nitride ceramic precursor, and the side chain of the novel Polysilazane (PBSZ) only contains a small amount of saturated carbon groups and can be cracked in an ammonia environment to effectively remove impurity carbon elements. However, the precursor cannot be cured and crosslinked at low temperature, and although a silicon boron nitrogen ceramic matrix with low impurity content and more excellent temperature resistance can be obtained, the matrix is relatively loose, size rebound is easy to occur due to release of internal stress after demolding, and precise molding of a high-performance ceramic-based wave-transmitting composite material component is difficult to realize.

Through the development of recent decades, the forming process of the Polymer Matrix Composite (PMC) is quite mature, several forming methods which are widely applied at present mainly include winding forming, vacuum bag pressure forming, resin transfer molding forming, compression molding forming and the like, and the prepared resin matrix composite is high in dimensional precision. Therefore, the special advantages of preparing the ceramic matrix composite by the PIP process can be tried to be utilized, a proper forming glue solution is selected, the mature forming process of the polymer matrix composite is used for reference, the prefabricated part is subjected to auxiliary forming in advance to form a composite material biscuit, a good foundation is laid for the precise forming of the component, the biscuit is subjected to densification treatment, and the near-net-shape thin-wall component is finally obtained.

Disclosure of Invention

First, technical problem to be solved

Aiming at the technical problem that the ceramic matrix wave-transparent composite thin-wall component is difficult to precisely form and the defects of the prior art are avoided, the invention provides a precise forming method of a nitride fiber reinforced ceramic matrix wave-transparent composite, so as to solve the problems that the size of the ceramic matrix wave-transparent composite thin-wall component is difficult to precisely control, the preparation process is complex, the overall performance of the component is easily reduced and the like in the prior art.

Second, technical scheme

In order to solve the technical problems, the invention adopts the technical scheme that:

a precision forming method of a nitride fiber reinforced ceramic matrix wave-transparent composite material comprises the following steps:

(1) preparing a nitride fiber preform: forming the nitride fiber into a nitride fiber preform by adopting a fabric forming process;

(2) and (3) nitride fiber preform treatment: cleaning the nitride fiber preform to remove impurities to obtain a treated nitride fiber preform;

(3) preparing a BN interface layer: by BCl₃-NH₃-Ar-H₂A precursor gas system, preparing a BN interface layer on the surface of the fiber on the treated nitride fiber preform by a chemical vapor infiltration process to obtain the nitride fiber preform with the BN interface layer;

(4) vacuum impregnation molding glue solution: immersing the nitride fiber preform with the BN interface layer into a forming glue solution containing a polysilazane precursor for vacuum impregnation to obtain a nitride fiber preform subjected to vacuum impregnation;

(5) hot die pressing and forming: heating the nitride fiber preform subjected to vacuum impregnation to 180-200 ℃, keeping the temperature and pressure at 1-10 Mpa for 20-40 min, and obtaining a formed nitride fiber preform;

(6) high-temperature cracking: cracking the formed nitride fiber preform at high temperature in an ammonia atmosphere to obtain an inorganic composite material;

(7) densification of the composite material: and (3) adopting a precursor conversion process, immersing the inorganic composite material into a glue solution containing a polysilazane precursor for vacuum impregnation, then cracking at high temperature in an ammonia atmosphere, and repeating densification circulation to obtain the nitride fiber reinforced ceramic-based wave-transmitting composite material.

As a preferred embodiment, in step (1), the nitride fiber is selected from one or more of silicon nitride fiber, silicon boron nitrogen fiber, and boron nitride fiber. More preferably, silicon nitride fibers.

In a preferred embodiment, in the step (1), the volume fraction of the nitride fibers in the nitride fiber preform is 35 to 60%.

As a preferred embodiment, in the step (1), a fabric forming process is adopted to form the nitride fibers into fiber preforms with different structures, and one or more of chopped strand mats, continuous fiber mats, fiber cloth and non-wrinkle fabrics are selected as the reinforcing materials; and then, according to the performance requirements, obtaining fiber preforms with different structures by adopting one or more three-dimensional fabric forming processes of braiding, weaving, knitting and sewing.

As a preferred embodiment, in the step (2), the nitride fiber preform is put into water (deionized water such as deionized water) to be ultrasonically cleaned, so as to remove surface contaminants; and then putting the fiber into a muffle furnace, heating the fiber to 400-600 ℃ in air, preserving the heat for 1-3 h, cooling the fiber along with the furnace, removing a fiber surface sizing agent, and obtaining the nitride fiber preform after cleaning and impurity removal treatment.

As a preferred embodiment, in the step (3), the treated nitride fiber preform is put into a BN deposition furnace using BCl₃-NH₃-Ar-H₂Precursor gas system, preparing a BN interface layer on the surface of the fiber by a chemical vapor infiltration process, wherein BCl₃Flow rate of 100-300 mL/min, NH₃Flow rate of 200-600 mL/min, Ar flow rate of 200-400 mL/min, H₂The flow rate is 500-1000 mL/min, the pressure in the furnace is 2-3 kPa, the deposition temperature is 600-1000 ℃, and the deposition time is 20-50 h, so that the nitride fiber preform with the BN interface layer with a certain thickness is obtained.

As a preferred embodiment, in the step (4), the mass ratio of 1: (1-9) fully stirring the polysilazane precursor and n-hexane until the polysilazane precursor is completely dissolved to obtain a forming glue solution; and then placing the nitride fiber preform with the BN interface layer in an impregnation tank, vacuumizing until the vacuum degree is less than 100Pa, adding the prepared molding glue solution into the impregnation tank, and completely impregnating the fiber preform below the liquid level for 3-5 hours to obtain the nitride fiber preform after vacuum impregnation. The Polysilazane (PSZ) precursor is an organosilicon compound with a main chain formed by alternating C, Si and N atoms, the average molecular weight of the organosilicon compound is 1200-1800, the softening point is 180-200 ℃, and the oxygen content is about 2 wt%; is light yellow at normal temperature, is a yellow brown brittle solid at normal temperature, and can be dissolved in organic solvents such as n-hexane, divinylbenzene, toluene, xylene and the like.

As a preferred embodiment, in the step (5), drying the nitride fiber preform subjected to vacuum impregnation at 70 ℃ for 2-4 h, naturally cooling, placing the nitride fiber preform into a lower mold cavity, raising the temperature to 70-90 ℃ without closing the mold, and keeping the temperature for 10-15 min; then, heating to 120-140 ℃, keeping the temperature for 10-30 min, closing the mold, and slowly pressurizing to the pressure of 1-10 MPa; and finally, heating to 180-200 ℃, preserving heat and pressure for 20-40 min, and cooling to obtain the formed nitride fiber preform. Further preferably, in the hot die pressing process, the temperature rise rate is 2-4 ℃/min.

In a preferable embodiment, in the step (6), the formed nitride fiber preform is placed into a pyrolysis furnace, heated to 800-1200 ℃ at a heating rate of 5-15 ℃/min under the protection of ammonia atmosphere, and kept at the temperature for 0.5-1 hour to obtain the inorganic composite material.

As a preferred embodiment, in the step (7), the inorganic composite material is vacuum-impregnated in a mass ratio of 1: (0.5-2.5) drying the mixed solution of the polyborosilazane precursor and n-hexane for 3-5 hours at 70 ℃ after dipping for 2-4 hours, then cracking at high temperature in an ammonia atmosphere, and repeating for 10-15 cycles to obtain the densified nitride fiber reinforced ceramic matrix wave-transparent composite material. The Polysilazane (PBSZ) precursor is in a solid state, is an organic silicon compound with a main chain formed by alternating C, Si, B and N atoms, and has the average molecular weight of 1400-2000, the softening point of 90-100 ℃ and the oxygen content of about 0.8 wt%; is light yellow at normal temperature, is a yellow brown brittle solid at normal temperature, and can be dissolved in organic solvents such as n-hexane, divinylbenzene, toluene, xylene and the like.

Firstly, removing a sizing agent on the surface of a fiber preform by adopting an ultrasonic cleaning and air heat treatment mode; then using BCl₃-NH₃-Ar-H₂A precursor gas system, wherein a BN interface with a certain thickness is prepared by a chemical vapor infiltration process; then adopting a precursor dipping and cracking process, taking a polysilazane precursor/n-hexane solution as a forming glue solution, dipping the fiber preform in vacuum, taking out and drying the fiber preform, forming the fiber preform to a designed size by utilizing a hot die pressing process, and then putting the fiber preform into an ammonia cracking furnace for high-temperature cracking to obtain a composite material biscuit with high size precision; and finally, preparing the near-net-shape nitride fiber reinforced ceramic-based wave-transmitting composite material member by using the polysilazane precursor/n-hexane glue solution through the process steps of repeated vacuum impregnation, pyrolysis and the like. The forming preparation process provided by the invention has wide application range, and can be used for preparing nitride fiber reinforced ceramic matrix wave-transparent composite components with controllable dimensional precision for various prefabricated bodies with complex structures by adopting the method.

The nitride fiber reinforced ceramic matrix wave-transparent composite material prepared by the precise forming method.

The invention utilizes the characteristics that the molding glue solution can be crosslinked and cured at low temperature and has small volume shrinkage after high-temperature cracking, and the composite material biscuit prepared by combining the hot die pressing process has high dimensional precision and basically has no change in dimension in the subsequent densification process. The preparation process of the nitride fiber reinforced ceramic-based wave-transparent composite material provided by the invention is also the generation process of the whole product, the final product has high molding size precision (the tolerance is less than or equal to 2 percent), uniform thickness and high surface finish degree, and does not need processing or a small amount of processing, thereby not only maintaining the integrity of the composite material, but also shortening the production period of components and reducing the manufacturing cost. Meanwhile, the preparation temperature of the composite material is low, the nitride ceramic matrix is uniform and compact, the residual carbon content is low, and the composite material has excellent mechanical property and wave-transmitting property.

Third, beneficial effect

Compared with the prior art, the precision forming method of the nitride fiber reinforced ceramic matrix wave-transparent composite material provided by the invention has the following advantages:

(1) the polysilazane/n-hexane glue has excellent moldability. The polysilazane/normal hexane solution adopted by the invention has lower viscosity at room temperature, and can well infiltrate the nitride fiber preform; the glue solution can generate crosslinking curing reaction at low temperature (less than 200 ℃), so that the component can be subjected to hot die pressing at lower temperature to obtain a component blank with high dimensional precision; after the first round of crosslinking and curing, the nitride matrix generated after the polysilazane is cracked at high temperature in the ammonia atmosphere is uniformly distributed among fiber bundles, the residual carbon content is low, the dielectric property is moderate, the adhesion with the fibers is good, a continuous framework structure is formed, a key effect is played on the shaping of the component, the stress in the prefabricated body is reduced, the size rebound in the high-temperature treatment process of the component is avoided, and the accurate and controllable size of the component can be ensured.

(2) The hot die pressing process is adopted, the pressure range is large, the large composite material component with a complex shape and high fiber volume fraction can be prepared, the dimensional precision and the molded surface of the component can be controlled, and meanwhile, the equipment is simple, the repeatability of a molded product is high, and the production efficiency is high.

(3) The material preparation and the component forming are completed at one time. The preparation process of the nitride fiber reinforced ceramic-based wave-transparent composite material provided by the invention is also the generation process of the whole product, the final product has uniform thickness, high dimensional precision (the tolerance is less than or equal to 2 percent), high surface finish degree, no need of processing or a small amount of processing, not only can maintain the integrity of the composite material, but also shortens the production period of components and reduces the manufacturing cost.

(4) The forming preparation process has wide application range, and the precision forming method can be adopted to prepare the nitride fiber reinforced ceramic matrix wave-transparent composite material component with controllable dimensional precision for various prefabricated bodies with complex structures.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly described below. It is obvious that the drawings described below are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.

FIG. 1 is a schematic view of a graphite mold for press molding in an embodiment of the present invention;

FIG. 2 is a diagram of a graphite mold used for compression molding in the example of the present invention;

FIG. 3 is a schematic representation of a silicon nitride fiber reinforced ceramic matrix wave-transparent composite material according to example 1 of the present invention;

FIG. 4 is an XRD pattern of the silicon nitride fiber reinforced ceramic matrix wave-transparent composite material in example 1 of the present invention.

Detailed Description

The following examples are given to further illustrate the embodiments of the present invention. The following detailed description of the embodiments is only for illustrating the technical solutions of the present invention, but not for limiting the scope of the present invention, i.e., the present invention is not limited to the specific embodiments described in the embodiments. Any modification, replacement or improvement of the raw materials and means is covered without departing from the spirit of the present invention.

It should be noted that the embodiments of the present invention and features of the embodiments may be combined with each other without conflict. The raw materials, equipment and the like used in the following examples and comparative examples are commercially available.

Example 1

In the embodiment, the silicon nitride fiber reinforced ceramic matrix wave-transparent composite thin-wall component has the size requirement of 200 × 200 × 2mm, and the mold is designed as shown in fig. 1 (a) is a front view with the size, and (b) is a schematic structural diagram), and fig. 2, and the preparation method of the component comprises the following steps:

(1) preparing a silicon nitride fiber preform: weaving silicon nitride fibers into a 2.5D preform of 200X 2mm, wherein the volume fraction of the silicon nitride fibers is 45.2%;

(2) and (3) fiber preform treatment: putting the fiber preform into deionized water, performing ultrasonic cleaning to remove surface pollutants, then putting the fiber preform into a muffle furnace, heating the fiber preform to 400 ℃ in air, preserving the heat for 3 hours, cooling the fiber preform along with the furnace, and removing a fiber surface sizing agent;

(3) preparing a BN interface layer: placing the treated fiber preform into a BN deposition furnace by adopting BCl₃-NH₃-Ar-H₂Precursor gas system, preparing a BN interface layer on the surface of the fiber by a chemical vapor infiltration process, wherein BCl₃Flow rate of 100mL/min, NH₃The flow rate is 200mL/min, the Ar flow rate is 200mL/min, H₂The flow rate is 500mL/min, the pressure in the furnace is 2kPa, the deposition temperature is 600 ℃, and the deposition time is 50h, so that a BN interface layer with a certain thickness is obtained;

(4) vacuum impregnation molding glue solution: preparing a polysilazane precursor and n-hexane into uniform molding glue solution according to the mass ratio of 1:3, then putting a silicon nitride fiber preform with a BN interface layer into an impregnation tank, vacuumizing until the vacuum degree is less than 100Pa, and then adding the prepared molding glue solution into the impregnation tank to ensure that the fiber preform is completely impregnated below the liquid level for 3 hours;

(5) hot die pressing and forming: drying the vacuum-impregnated fiber preform at 70 ℃ for 2h, naturally cooling, putting into a lower die cavity, raising the temperature to 80 ℃ without die closing, and preserving the temperature for 15 min; then, heating to 140 ℃, preserving heat for 10min, closing the die and slowly pressurizing, and maintaining the pressure when the pressure of a press table shows 3 MPa; finally, heating to 180 ℃, preserving heat and pressure for 30min, and cooling after shutdown; the whole temperature rise rate is 2 ℃/min;

(6) high-temperature cracking: placing the molded fiber preform into a pyrolysis furnace, rapidly heating to 800 ℃ at a heating rate of 5 ℃/min under the protection of ammonia atmosphere, and preserving heat for 1 hour to obtain an inorganic composite material;

(7) densification of materials and components: adopting a precursor conversion process, carrying out vacuum impregnation on an inorganic composite material into a polyborosilazane precursor/n-hexane (mass ratio is 1:1) mixed solution for 3 hours, then drying at 70 ℃ for 2 hours, carrying out pyrolysis in an ammonia atmosphere (pyrolysis conditions are the same as the step (6)), and repeating for 15 cycles to obtain the densified silicon nitride fiber reinforced ceramic matrix wave-transparent composite material thin-wall component (a physical diagram is shown in figure 3, and an XRD (X-ray diffraction) diagram is shown in figure 4).

Experiments show that the average value of the thickness dimension of the large-size thin-wall component made of the silicon nitride fiber reinforced ceramic-based wave-transparent composite material prepared in the embodiment is 2.00mm, the tolerance is 2%, and the density is 1.81g/cm³Tensile strength of 67.5MPa, bending strength of 152.7MPa, and fracture toughness of 15.2 MPa.m^1/2Dielectric loss tangent of 8.28X 10^-3And a dielectric constant of 4.12.

Example 2

In this embodiment, the silicon nitride fiber reinforced ceramic matrix wave-transparent composite thin-walled component has a size requirement of 200 × 200 × 2mm, and the mold is designed as shown in fig. 1 and 2, and the preparation method of the component includes the following steps:

(1) preparing a silicon nitride fiber preform: laminating 10 layers of silicon nitride fiber cloth with the plane size of 200 multiplied by 200mm, preforming the silicon nitride fiber cloth with the thickness of 2mm, and hooking a needle by using a 1K silicon nitride fiber bundle to obtain a two-dimensional preform (the volume fraction of the silicon nitride fiber is 49.4%);

(2) and (3) fiber preform treatment: putting the fiber preform into deionized water, performing ultrasonic cleaning to remove surface pollutants, then putting the fiber preform into a muffle furnace, heating the fiber preform to 500 ℃ in air, preserving the heat for 2 hours, cooling the fiber preform along with the furnace, and removing a fiber surface sizing agent;

(3) preparing a BN interface layer: placing the treated fiber preform into a BN deposition furnace by adopting BCl₃-NH₃-Ar-H₂Precursor gas system, preparing a BN interface layer on the surface of the fiber by a chemical vapor infiltration process, wherein BCl₃Flow rate of 200mL/min, NH₃The flow rate is 400mL/min, the Ar flow rate is 300mL/min, H₂The flow rate is 700mL/min, the pressure in the furnace is 2.5kPa, the deposition temperature is 800 ℃, and the deposition time is 30 hours, so that a BN interface layer with a certain thickness is obtained;

(4) vacuum impregnation molding glue solution: preparing a polysilazane precursor and n-hexane into uniform molding glue solution according to the mass ratio of 1:4, then putting a silicon nitride fiber preform with a BN interface layer into an impregnation tank, vacuumizing until the vacuum degree is less than 100Pa, and then adding the prepared molding glue solution into the impregnation tank to ensure that the fiber preform is completely impregnated below the liquid level for 4 hours;

(5) hot die pressing and forming: drying the vacuum-impregnated fiber preform at 70 ℃ for 3h, naturally cooling, putting into a lower die cavity, raising the temperature to 70 ℃ without die closing, and keeping the temperature for 15 min; then, heating to 140 ℃, preserving heat for 30min, closing the die and slowly pressurizing, and maintaining the pressure when the pressure of a press table shows 2 MPa; finally, heating to 180 ℃, preserving heat and pressure for 40min, and cooling after shutdown; the whole temperature rise rate is 3 ℃/min;

(6) high-temperature cracking: placing the molded fiber preform into a vacuum cracking furnace, rapidly heating to 1200 ℃ at a heating rate of 15 ℃/min under the protection of ammonia atmosphere, and preserving heat for 1 hour to obtain an inorganic composite material;

(7) densification of the composite material: adopting a precursor conversion process, carrying out vacuum impregnation on the inorganic composite material into a polyborosilazane precursor/n-hexane (mass ratio is 1:1) mixed solution for 4 hours, then drying for 3 hours at 70 ℃, then carrying out pyrolysis in an ammonia atmosphere (the pyrolysis condition is the same as the step (6)), and repeating for 15 cycles to obtain the densified silicon nitride fiber reinforced ceramic matrix wave-transparent composite material thin-wall component.

Experiments show that the average value of the thickness dimension of the large-size thin-wall component made of the silicon nitride fiber reinforced ceramic matrix wave-transparent composite material prepared in the embodiment is 1.98mm, the tolerance is 2%, and the density is 1.82g/cm³Tensile strength of 75MPa, bending strength of 175.8MPa, and fracture toughness of 17.2 MPa.m^1/2Dielectric loss tangent of 8.83X 10^-3And a dielectric constant of 4.53.

Example 3

In this embodiment, the silicon nitride fiber reinforced ceramic matrix wave-transparent composite thin-walled component has a size requirement of 200 × 200 × 2mm, and the mold is designed as shown in fig. 1 and 2, and the preparation method of the component includes the following steps:

(1) preparing a silicon nitride fiber preform: laminating 11 layers of silicon nitride fiber cloth with the plane size of 200 multiplied by 200mm, preforming the silicon nitride fiber cloth with the thickness of 2mm, and hooking a needle by using a 1K silicon nitride fiber bundle to obtain a two-dimensional preform (the volume fraction of the silicon nitride fiber is 53.8%);

(2) and (3) fiber preform treatment: putting the fiber preform into deionized water, performing ultrasonic cleaning to remove surface pollutants, then putting the fiber preform into a muffle furnace, heating the fiber preform to 600 ℃ in air, preserving the heat for 1 hour, cooling the fiber preform along with the furnace, and removing a fiber surface sizing agent;

(3) preparing a BN interface layer: placing the treated fiber preform into a BN deposition furnace by adopting BCl₃-NH₃-Ar-H₂Precursor gas system, preparing a BN interface layer on the surface of the fiber by a chemical vapor infiltration process, wherein BCl₃Flow rate 300mL/min, NH₃The flow rate is 600mL/min, the Ar flow rate is 400mL/min, H₂The flow rate is 1000mL/min, the pressure in the furnace is 3kPa, the deposition temperature is 1000 ℃, and the deposition time is 25 hours, so that a BN interface layer with a certain thickness is obtained;

(4) vacuum impregnation molding glue solution: preparing a polysilazane precursor and n-hexane into uniform molding glue solution according to the mass ratio of 1:1, then putting a silicon nitride fiber preform with a BN interface layer into an impregnation tank, vacuumizing until the vacuum degree is less than 100Pa, and then adding the prepared molding glue solution into the impregnation tank to ensure that the fiber preform is completely impregnated below the liquid level for 5 hours;

(5) hot die pressing and forming: drying the vacuum-impregnated fiber preform at 70 ℃ for 4h, naturally cooling, putting into a lower die cavity, raising the temperature to 80 ℃ without die closing, and preserving the temperature for 10 min; then, the temperature is increased to 140 ℃, the temperature is kept for 15min, the die is closed, the pressure is slowly increased, and the pressure of a press table is 10 MPa; finally, heating to 200 ℃, and keeping the temperature and the pressure for 30 min; the whole temperature rise rate is 3 ℃/min;

(6) high-temperature cracking: placing the molded fiber preform into a vacuum cracking furnace, rapidly heating to 1200 ℃ at a heating rate of 10 ℃/min under the protection of ammonia atmosphere, and preserving heat for 1 hour to obtain an inorganic composite material;

(7) densification of the composite material: adopting a precursor conversion process, carrying out vacuum impregnation on the inorganic composite material into a polyborosilazane precursor/n-hexane (mass ratio is 1:1) mixed solution for 5 hours, then drying at 70 ℃ for 4 hours, carrying out pyrolysis in an ammonia atmosphere (the pyrolysis condition is the same as the step (6)), and repeating for 15 cycles to obtain the densified silicon nitride fiber reinforced ceramic matrix wave-transparent composite material large-size thin-wall component.

Experiments show that the nitridation prepared in this exampleThe average value of the thickness dimension of the large-size thin-wall component made of the silicon fiber reinforced ceramic matrix wave-transparent composite material is 2.02mm, the tolerance is 1.1 percent, and the density is 1.84g/cm³Tensile strength of 82.3MPa, bending strength of 198.6MPa, and fracture toughness of 19.1 MPa.m^1/2Dielectric loss tangent of 7.93X 10^-3And a dielectric constant of 4.23.

Comparative example 1

In the comparative example, the silicon nitride fiber reinforced ceramic matrix wave-transparent composite thin-wall component has the size requirement of 200 × 200 × 2mm, and the mold is designed as shown in fig. 1 and fig. 2, and the preparation method of the component comprises the following steps:

(1) this step was the same as step (1) of example 1;

(2) this step was the same as step (2) of example 1;

(3) this step was the same as step (3) of example 1;

(4) vacuum impregnation of precursor: placing the fiber preform in an impregnation tank, vacuumizing until the vacuum degree is less than 100Pa, adding a mixed solution of a polyborosilazane precursor/n-hexane (the mass ratio is 1:1) into the impregnation tank, and completely impregnating the fiber preform below the liquid level for 3 hours;

(5) high-temperature cracking: drying the fiber preform subjected to vacuum impregnation at 70 ℃ for 2h, naturally cooling, then placing the fiber preform into a mold, placing the fiber preform into a pyrolysis furnace, rapidly heating the fiber preform to 800 ℃ at a heating rate of 5 ℃/min under the protection of ammonia atmosphere, and preserving the heat for 1 hour;

(6) this step was the same as step (7) of example 1.

Experiments show that the average value of the thickness dimension of the large-size thin-wall component made of the silicon nitride fiber reinforced ceramic matrix wave-transparent composite material prepared by the comparative example is 2.7 +/-0.03 mm, and the density after densification is 1.77g/cm³Tensile strength of 46MPa, bending strength of 110.5MPa, fracture toughness of 11.3 MPa.m^1/2Dielectric loss tangent of 7.53X 10^-3And a dielectric constant of 4.74.

Therefore, compared with the comparative example 1, the thin-wall member of the silicon nitride fiber reinforced ceramic matrix wave-transparent composite material prepared in the embodiment 1 of the invention has higher dimensional accuracy, excellent mechanical property and dielectric property, and completely meets the requirements of engineering application.

The experimental results show that the precision forming method provided by the invention overcomes the problems that the size of the ceramic matrix wave-transparent composite thin-wall component in the prior art is difficult to accurately control, the preparation process is complex, the integral performance of the component is easy to reduce and the like, shortens the production period of the component, reduces the manufacturing cost, ensures that the final product has uniform thickness, high size precision (the tolerance is less than or equal to 2 percent), high surface smoothness, does not need to be processed or processed in a small amount, and keeps the integral performance of the composite material.

In the above examples and comparative examples, the performance test methods are shown in table 1.

TABLE 1 Performance test methods

Content of test	Test method
		Thickness of	Vernier caliper measurement
Density of	GB/T 255995
		Tensile strength	GJB 6475-2008
Bending strength	GB/T 6569-2006
		Fracture toughness	GB/T 23806-2009
Dielectric properties	GB/T 5597-1999

The above are merely examples of the present invention, and do not limit the scope of the present invention. It will be apparent to those skilled in the art that various modifications and variations can be made in the embodiments of the present invention without departing from the technical spirit of the invention. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.