Wave-absorbing stealth ceramic structure and manufacturing method

Abstract

The invention relates to a wave-absorbing stealth ceramic structure and a preparation method, and belongs to the technical field of electromagnetic wave absorbing materials, the wave-absorbing ceramic structure is composed of continuous silicon carbide fiber and PBO fiber composite materials, silicon carbide fiber cloth and PBO fibers are arranged in a 90-degree staggered mode in a multi-layer stacking mode, and the wave-absorbing stealth ceramic structure is prepared through a high-temperature pressureless sintering technology. The ceramic structure has good wave absorbing performance in the frequency band of 8 GHz to 18 GHz, the bandwidth range of 6.5 GHz to 10 GHz when the reflectivity is lower than-8 dB, and the density is lower than 3 g / cm < 3 >, the ceramic structure has the characteristics of light weight, thin thickness, high strength, high temperature resistance, oxidation resistance and the like, and the preparation method is simple in process, low in cost, suitable for batch production and suitable for industrial production. The material is widely applicable to stealth equipment such as aircrafts and missiles and other application scenes requiring electromagnetic wave shielding and wave absorbing functions.

Description

Technical Field

[0001] The invention relates to a wave-absorbing stealth ceramic structure and a manufacturing method. Background Art

[0002] The radar absorbing ceramic materials currently developed mainly use ceramic micropowder as radar absorbent and are prepared by hot pressing process, such as Si / C / N ceramic particle reinforced LAS glass, mullite, Si3N4 and other ceramic materials, but such materials have the following shortcomings: 1) It is difficult to achieve gradient distribution of dielectric properties, and the radar absorbing frequency band is narrow; 2) Particle reinforced ceramic materials have poor toughness and are prone to catastrophic damage; 3) Hot pressing process is difficult to prepare large and complex components. Continuous fiber reinforced ceramic matrix composites have the advantages of high temperature resistance, oxidation resistance, high specific strength, high specific modulus, high toughness, etc., and are easy to form large and complex components. However, the continuous silicon carbide fiber reinforced silicon carbide (SiCf / SiC) composites currently developed are mainly used for thermal protection and thermal structures. Due to the lack of necessary dielectric property modification, the radar absorbing performance is poor.

[0003] At the same time, as my country's defense budget expenditure continues to grow and the risk of war in various regions of the world increases, the stealth capability of advanced weapons and equipment is crucial. Since stealth material technology involves the development of major military materials, the independent control of stealth materials has also become an important part of ensuring the development of my country's military equipment, with broad market prospects and a long life cycle.

[0004] Therefore, there is a need for a radar-absorbing stealth ceramic structure and a manufacturing method that has simple process, low cost, stable quality, and is suitable for batch and large-scale production. Summary of the invention

[0005] The purpose of the present invention is to solve the deficiencies of the above prior art, to provide a microwave-absorbing stealth ceramic structure with simple structure, wide absorption frequency band, light weight, thin thickness, good mechanical properties and excellent heat protection function, and to provide a preparation method of the microwave-absorbing stealth ceramic structure with simple process, low cost, stable quality and suitable for batch and large-scale production. The following is a specific scheme:

[0006] On the one hand, a wave-absorbing stealth ceramic structure includes a fiber structure, wherein the fiber structure is composed of silicon carbide fiber and PBO fiber, the ratio of the silicon carbide fiber to the PBO fiber is 5:1, the fiber structures are aligned up and down, and there are equidistant gaps between the fiber structures, and silicon carbide powder and slurry are arranged in the gaps, and the slurry is prepared by polycarbosilane, divinylbenzene, xylene and silicon carbide micropowder in a mass ratio of 1: (0.4-0.6): (0.1-0.3): (0.6-0.8), and a PBO unidirectional fiber layer is arranged on the upper side of the fiber structure. The density of the ceramic structure is 3g / cm 3 the following.

[0007] The absorbing ceramic is mainly composed of a composite material of continuous silicon carbide fiber and PBO fiber. The absorbing ceramic uses multi-layered stacked silicon carbide fiber cloth and PBO fiber as reinforcement, and the multi-layered stacked silicon carbide fiber cloth and PBO fiber are connected into a whole by high-temperature pressureless sintering in an equal-proportion intermittent arrangement in a 90° direction. The bandwidth of the absorbing ceramic with a reflectivity lower than -8dB in the frequency band of 8GHz to 18GHz at room temperature is 6.5GHz to 10GHz; the density of the absorbing ceramic is 3g / cm 3 the following.

[0008] PBO, or poly(p-phenylene benzobisoxazole) fiber, is an organic fiber with excellent comprehensive properties. Its molecular structure is highly symmetrical, and it has ultra-high strength, ultra-high modulus, high temperature resistance, and high environmental stability. PBO fiber has excellent dielectric properties, and its wave transmittance can reach more than 98%, which means that it allows electromagnetic waves to pass through while absorbing less electromagnetic waves. In terms of wave absorption performance, PBO fiber exhibits good electromagnetic wave absorption capacity, and the electromagnetic wave absorption performance of PBO fiber / epoxy structural functional composite materials is between -10dB and -15dB. This shows that the material can effectively absorb electromagnetic waves, reduce the penetration and reflection of electromagnetic waves, and thus has potential application value in electromagnetic shielding and absorption.

[0009] Silicon carbide fiber is a high-performance ceramic material with carbon and silicon as the main components. It is divided into whiskers and continuous silicon carbide fibers in terms of morphology. It has the advantages of high-temperature oxidation resistance, high hardness, high strength, high thermal stability, corrosion resistance and low density. Compared with carbon fiber, silicon carbide fiber can maintain good performance under extreme conditions. It not only has excellent mechanical properties, oxidation resistance and longer high-temperature service life, but also has good wave absorption performance.

[0010] On the other hand, a method for manufacturing a wave-absorbing stealth ceramic structure comprises the following steps: preparing polycarbosilane, divinylbenzene, xylene and silicon carbide powder in a ratio of 1: (0.4-0.6): (0.1-

[0011] The slurry is prepared in a mass ratio of 0.3)∶(0.6~0.8); the PBO fiber is evenly spread to the bottom of the mold, and then the PBO fiber and the silicon carbide fiber are arranged in a ratio of 1:5 and placed into the mold; the silicon carbide powder and slurry are filled in the empty space; polycarbosilane is used as a precursor, and the product is repeatedly densified by a pressureless sintering process to obtain a microwave absorbing ceramic of a silicon carbide composite material.

[0012] The electric heating pressureless sintering process is adopted. The principle of pressureless sintering is: under the condition of no external pressure, a green body with a certain shape is placed under certain temperature and atmosphere conditions to undergo a physical and chemical process to become a dense, volume-stable, consolidated and dense block with certain properties. Pressureless sintering is a process of densification through the bonding between powder particles, and its driving force is mainly the reduction of pore surface free energy. Therefore, the densification process is also the process of reducing the pore surface area in the powder pressed part, and of course, the process of reducing the pore volume. For metal powder pressed parts, since the metal particles can be deformed during the pressing process, the density of 90% can be directly achieved. At this time, the porosity that needs to be removed is very small. It only needs to be sintered at a very low temperature for a period of time to eliminate the residual porosity and establish a coherent grain boundary.

[0013] Beneficial effect: Through the composite of PBO fiber and silicon carbide fiber, the density of the material is lower than 3g / cm 3 , with lightweight characteristics, the combination of silicon carbide and PBO fiber provides high strength and toughness, reduces the weight of the structure, and is easy to use in weight-sensitive equipment such as aircraft and missiles;

[0014] The pressureless sintering process simplifies the manufacturing process, reduces production costs, and improves the stability of product quality. The process is suitable for batch and large-scale production and is conducive to industrial application and promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The schematic diagram of the structure of a wave-absorbing stealth ceramic structure is shown in FIG. 1 , wherein 1 is PBO fiber, 2 is silicon carbide powder, and 3 is silicon carbide fiber;

[0016] Figure 2 It is a schematic diagram of the three-dimensional structure of a wave-absorbing stealth ceramic structure, where 4 is a PBO unidirectional fiber layer and 5 is a fiber structure;

[0017] Figure 3 It is a schematic diagram of the manufacturing steps of a radar-absorbing stealth ceramic structure. DETAILED DESCRIPTION

[0018] In order to deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with embodiments and drawings. The embodiments are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention.

[0019] Please see Figure 1-2A wave-absorbing stealth ceramic structure includes a fiber structure, the fiber structure is composed of silicon carbide fiber and PBO fiber, the ratio of silicon carbide fiber to PBO fiber is 5:1, the fiber structures are aligned up and down, and there are equidistant gaps between the fiber structures. Silicon carbide powder and slurry are arranged in the gaps. The slurry is prepared by polycarbosilane, divinylbenzene, xylene and silicon carbide micropowder in a mass ratio of 1: (0.4-0.6): (0.1-0.3): (0.6-0.8). A PBO unidirectional fiber layer is arranged on the upper side of the fiber structure. The density of the ceramic structure is 3g / cm 3 the following.

[0020] Please see Figure 3 A method for manufacturing a wave-absorbing stealth ceramic structure comprises the following steps: preparing polycarbosilane, divinylbenzene, xylene and silicon carbide powder in a ratio of 1: (0.4-0.6): (0.1-0.3):

[0021] The slurry is prepared with a mass ratio of (0.6-0.8); the PBO fiber is evenly spread to the bottom of the mold, and then the PBO fiber and the silicon carbide fiber are arranged in a ratio of 1:5 and placed into the mold; the silicon carbide powder and slurry are filled in the empty space; polycarbosilane is used as a precursor, and the product is repeatedly densified by a pressureless sintering process to obtain a microwave absorbing ceramic of a silicon carbide composite material.

[0022] The design of this absorbing stealth ceramic structure forms a dense fiber composite material structure through the composite reinforcement of silicon carbide fiber and PBO fiber, combined with silicon carbide powder and slurry filling; firstly, the mechanical strength and durability of the ceramic material in a specific direction are enhanced by the staggered arrangement of fiber cloth and fiber layers in equal proportions; secondly, silicon carbide fiber provides higher oxidation resistance and high temperature resistance, while PBO fiber has excellent wave transmission performance and electromagnetic wave absorption capacity. The synergistic effect of the two enables the ceramic structure to have a wide-band electromagnetic wave absorption effect while maintaining high strength. The pressureless sintering process further improves the densification and stability of the ceramic structure, giving it better stealth and electromagnetic shielding effects.

[0023] The radar-absorbing stealth ceramic structure manufactured by this method is light in weight and thin in thickness, and has good mechanical strength, impact resistance and efficient electromagnetic wave absorption capability. It is widely used in application scenarios such as aircraft and missiles that have strict requirements on radar stealth.

[0024] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A radar-absorbing stealth ceramic structure, characterized in that: The invention comprises a fiber structure, wherein the fiber structure is composed of silicon carbide fiber and PBO fiber, wherein the ratio of the silicon carbide fiber to the PBO fiber is 5:1, the fiber structures are aligned up and down, and an equidistant gap is provided between the fiber structures, wherein silicon carbide powder and slurry are provided in the gap, wherein the slurry is prepared by polycarbosilane, divinylbenzene, xylene and silicon carbide micropowder in a mass ratio of 1:(0.4-0.6):(0.1-0.3):(0.6-0.8), a PBO unidirectional fiber layer is provided on the upper side of the fiber structure, and the density of the ceramic structure is 3g / cm 3 the following.

2. A method for manufacturing a microwave-absorbing stealth ceramic structure, used to manufacture a microwave-absorbing stealth ceramic structure as claimed in claim 1, characterized in that: The following steps are involved: The slurry is prepared by using polycarbosilane, divinylbenzene, xylene and silicon carbide powder in a mass ratio of 1:(0.4-0.6):(0.1-0.3):(0.6-0.8); PBO fibers are evenly spread on the bottom surface of the mold, and then PBO fibers and silicon carbide fibers are arranged in a ratio of 1:5 and placed in the mold; Silicon carbide powder and slurry are filled in the vacant space; polycarbosilane is used as a precursor, and the product is repeatedly densified by a pressureless sintering process to obtain a microwave absorbing ceramic of a silicon carbide composite material.

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