A high-temperature, broadband stealth silicon carbide continuous fiber composite material for aviation nozzles

Abstract

The application discloses a high-temperature wide-frequency stealth silicon carbide continuous fiber composite material for an aerojet, and belongs to the field of aeroengine and structure wave-absorbing composite materials. A preform with a certain structure and thickness is prepared by taking silicon carbide fibers as raw materials; then, a boron nitride (BN) interface layer is deposited on the surface of the preform, a silicon carbide layer is continuously deposited on the surface of the preform with the boron nitride (BN) interface layer, and finally, protrusions are arranged on the surface of the material, so that the final high-temperature wide-frequency stealth silicon carbide continuous fiber composite material for an aerojet is obtained. The high-temperature wide-frequency stealth silicon carbide continuous fiber composite material for an aerojet prepared by the application has the characteristics of high-temperature resistance, corrosion resistance, oxidation resistance, wide-frequency absorption and good load bearing.

Description

TECHNICAL FIELD

[0001] The application relates to a high-temperature wide-band stealth silicon carbide continuous fiber composite material for an aero-engine nozzle, and belongs to the field of aero-engine and structural wave-absorbing composite materials. BACKGROUND

[0002] An engine is the heart of an aircraft, and a tail nozzle is one of the most important components of an aero-engine. For high-temperature components such as an engine tail nozzle, the service temperature can reach 1000 DEG C or above, and the components are subjected to harsh environments such as oxidation and corrosion. Therefore, designing and preparing a structure-function integrated wave-absorbing material which is thin, light, wide and strong is a hot research topic at present.

[0003] Traditional coating type wave-absorbing materials have the problems of performance decline and decomposition under high temperature, oxidation and corrosion, and cannot meet the requirements of wave absorption under high temperature, oxidation and corrosion. Structural type wave-absorbing materials are dual-functional composite materials developed on the basis of advanced composite materials, and have the advantages of strong designability, good performance stability and small environmental influence. The structural type wave-absorbing materials simultaneously have excellent wave-absorbing performance and bearing performance through the synergistic effect of structural design and material properties. Metals, ceramics and their composite materials can simultaneously meet the requirements of high temperature resistance and bearing, but must have suitable electrical properties to have good wave-absorbing performance. Good impedance matching can make electromagnetic waves enter the material as much as possible, and excellent electromagnetic loss can loss the electromagnetic waves entering the material, and the two often cannot be satisfied simultaneously. Metal materials have strong electromagnetic wave loss capacity, but the impedance mismatch between the material and free air causes strong reflection of electromagnetic waves. Therefore, the contradiction between the two can be relieved through the regulation of material electrical properties and structural design, which is an effective way to improve the wave-absorbing performance of the composite material. SUMMARY

[0004] [TECHNICAL PROBLEM]

[0005] The traditional coating type wave-absorbing material has the problems of poor wave-absorbing performance under high temperature, oxidation and corrosion, and easy falling off, and has simple preparation and low cost;

[0006] The metal material in the structural type wave-absorbing material has excellent electromagnetic loss capacity, but has poor impedance matching; the ceramic material has high temperature resistance and easy adjustable electrical properties, but has large brittleness and poor bearing capacity;

[0007] It can be seen that the existing wave-absorbing material cannot simultaneously meet the basic service requirements and realize good wave-absorbing performance under high temperature, oxidation and corrosion, strong bearing capacity and good impedance matching.

[0008] [TECHNICAL SCHEME]

[0009] To solve the above problems, the application provides a high-temperature wide-frequency stealth silicon carbide continuous fiber composite material for an aviation nozzle and a preparation method thereof. Specifically, the application prepares a preform with a certain structure and thickness from silicon carbide fibers; then deposits a boron nitride (BN) interface layer on the surface of the preform, continues to deposit a silicon carbide layer on the surface of the preform containing the boron nitride (BN) interface layer, and finally sets a protrusion on the surface of the material, thereby obtaining the final high-temperature wide-frequency stealth silicon carbide continuous fiber composite material for the aviation nozzle. The high-temperature wide-frequency stealth silicon carbide continuous fiber composite material prepared by the application has the characteristics of high-temperature resistance, corrosion resistance, oxidation resistance, wide-frequency absorption, and good load bearing.

[0010] A first object of the application is to provide a method for preparing a high-temperature wide-frequency stealth silicon carbide continuous fiber composite material, comprising the following steps:

[0011] (1) Preparing a preform:

[0012] Weaving low-dielectric-constant silicon carbide long fibers to obtain a low-dielectric-constant fabric as a matching layer;

[0013] Weaving high-dielectric-constant silicon carbide long fibers to obtain a high-dielectric-constant fabric as a loss layer;

[0014] Stacking the low-dielectric-constant fabric and the high-dielectric-constant fabric together according to a layer ratio of 9:6-8 and sewing them to obtain a preform;

[0015] (2) Depositing a boron nitride (BN) interface layer:

[0016] Using an impregnation-coating method to deposit a boron nitride (BN) interface layer on the surface of the preform to obtain a material containing a boron nitride interface layer;

[0017] (3) Depositing silicon carbide:

[0018] Using a precursor impregnation pyrolysis (PIP) method to deposit silicon carbide on the surface of the preform containing the boron nitride interface layer to obtain a material deposited with boron nitride and silicon carbide;

[0019] (4) Preparing a protrusion:

[0020] Preparing a square protrusion structure on the surface of the matching layer of the material deposited with boron nitride and silicon carbide to obtain the high-temperature wide-frequency stealth silicon carbide continuous fiber composite material.

[0021] In an embodiment of the application, the fineness of the silicon carbide long fibers in step (1) is 160-200 tex.

[0022] In an embodiment of the application, the low-dielectric-constant in step (1) refers to a dielectric constant of 3-6, and the high-dielectric-constant refers to a dielectric constant of 8-12.

[0023] In one embodiment of the present invention, the weaving in step (1) is plain weaving to obtain plain fabric.

[0024] In one embodiment of the present invention, the stacking method in step (1) is that the upper layer is a low dielectric constant fabric as a matching layer, and the lower layer is a high dielectric constant fabric as a loss layer.

[0025] In one embodiment of the present invention, in step (1), the warp yarn density of the low dielectric constant fabric and the high dielectric constant fabric is 65-75 yarns / 10 cm; and the weft yarn density is 65-75 yarns / 10 cm.

[0026] In one embodiment of the present invention, the stitching in step (1) is performed by using a mold, specifically placing a high dielectric constant fabric on the lower layer of the mold and a low dielectric constant fabric on the upper layer of the mold, and stitching is performed through the holes of the mold; the stitching density is 2-3 stitches / cm.

[0027] In one embodiment of the present invention, the dipping-coating method in step (2) is specifically:

[0028] Mixing urea, water, and ethanol uniformly to obtain a mixed solution; then adding boric acid to the mixed solution and dissolving it to obtain a precursor solution; then immersing the preform in the precursor solution, removing it, drying it, keeping it warm, and performing a cracking and curing reaction to obtain a material containing a boron nitride interface layer;

[0029] The dosage ratio of urea, water, ethanol and boric acid is 0.5-0.6 mol: 90-120 mL: 180-210 mL: 0.04-0.05 mol;

[0030] The impregnation is carried out at room temperature for 8-12 minutes; the impregnation requires vacuum assistance; the drying is carried out at 105-115°C for 0.5-1.5 hours; the insulation is carried out at 115-125°C under a nitrogen atmosphere for 30-40 minutes; the cracking and curing reaction is carried out at 155-165°C for 90-120 minutes to crack the urea; and then the reaction is carried out at 200-220°C for 90-120 minutes to allow the boric acid and urea to react.

[0031] In one embodiment of the present invention, the precursor impregnation pyrolysis (PIP) method in step (3) is specifically:

[0032] The material containing the boron nitride interface layer is immersed in a polycarbosilane (PCS) precursor solution under nitrogen protection, and is subjected to immersion cracking to obtain a material having deposited boron nitride and silicon carbide;

[0033] The polycarbosilane (PCS) precursor solution is a mixed solution of polycarbosilane and xylene, and the mass ratio of polycarbosilane to xylene is 1:1-2; the immersion cracking is cracking at 1000°C for 2 hours as a cycle; and the cracking cycles are 5-15.

[0034] In one embodiment of the present invention, the parameters of the square raised structure in step (4) are: the raised height is 0.5-1.5 mm, the side length is 7-8 mm, and the distance between the edges of adjacent raised structures is 1-2 mm.

[0035] In one embodiment of the present invention, the square protrusion structure in step (4) is obtained by cutting.

[0036] The second object of the present invention is a high-temperature, broadband, stealth silicon carbide continuous fiber composite material prepared by the method of the present invention.

[0037] The third object of the present invention is to apply the high-temperature, broadband, stealth silicon carbide continuous fiber composite material described in the present invention in the field of aerospace.

[0038] In one embodiment of the present invention, the application is for an aviation nozzle.

[0039] A fourth object of the present invention is to provide an aviation nozzle, which adopts the high-temperature, broadband stealth silicon carbide continuous fiber composite material described in the present invention.

[0040] A fifth object of the present invention is to provide a method for improving the microwave absorption, broadband absorption and load-bearing performance of a silicon carbide continuous fiber composite material under high temperature, oxidation and corrosion conditions, comprising the following steps:

[0041] (1) Preparation of preform:

[0042] A low dielectric constant fabric is obtained by weaving long silicon carbide fibers with a low dielectric constant as a matching layer;

[0043] A high dielectric constant fabric is obtained by weaving long silicon carbide fibers with a high dielectric constant as a loss layer;

[0044] The low dielectric constant fabric and the high dielectric constant fabric are stacked and sewn together in a layer ratio of 9:6-8 to obtain a preform;

[0045] (2) Deposition of boron nitride (BN) interface layer:

[0046] A boron nitride (BN) interface layer is deposited on the surface of the preform by a dip-coating method to obtain a material containing a boron nitride interface layer;

[0047] (3) Deposition of silicon carbide:

[0048] Silicon carbide is deposited on the surface of a preform containing a boron nitride interface layer by using a precursor infusion pyrolysis (PIP) method to obtain a material having deposited boron nitride and silicon carbide;

[0049] (4) Preparation of protrusions:

[0050] A square protruding structure is prepared on the upper surface of the matching layer of the deposited boron nitride and silicon carbide material to obtain the high-temperature, broadband stealth silicon carbide continuous fiber composite material.

[0051] [Beneficial Effects]

[0052] (1) Compared with traditional coated absorbing materials, the high-temperature broadband stealth silicon carbide continuous fiber composite material of the present invention still has good performance stability at a high temperature of 800°C and is not easy to delaminate or fall off.

[0053] (2) Compared with metal materials, the high-temperature, broadband stealth silicon carbide continuous fiber composite material of the present invention improves the problem of poor impedance matching of metal materials by rationally mixing fibers with different dielectric constants, and enables more electromagnetic waves to enter the interior of the composite material and be lost.

[0054] (3) Compared with pure ceramic materials, the high-temperature, broadband stealth silicon carbide continuous fiber composite material of the present invention improves its problems of high brittleness and poor machinability, and improves its toughness and load-bearing capacity.

[0055] (4) The present invention combines low-dielectric and high-dielectric silicon carbide fibers, so that the composite material can not only achieve impedance matching with free air, but also has excellent electromagnetic loss capability, effectively balancing the contradiction between the two absorbing conditions and improving the overall absorbing performance of the composite material.

[0056] (5) The present invention deposits a BN interface layer on the surface of the silicon carbide fiber preform, which can improve the mechanical properties of the composite material without affecting the electrical properties of the composite material, and also has good oxidation resistance.

[0057] (6) The material prepared by the PIP method of the present invention has many pores with non-uniform distribution and non-uniform size. These pores greatly extend the propagation path of electromagnetic waves inside the composite material, increase the scattering and reflection of electromagnetic waves, and further improve the wave absorbing performance of the composite material.

[0058] (7) The raised structures cut on the surface of the composite material of the present invention not only improve the impedance matching between the composite material and free air, but the raised edges also increase the scattering effect on electromagnetic waves, further improving its wave absorbing performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1Schematic diagram of the structure of the silicon carbide fiber preform in Example 1, wherein 1 is a low dielectric constant silicon carbide fiber and 2 is a high dielectric constant silicon carbide fiber.

[0060] Figure 2 This is the square raised structure after cutting in Example 1. DETAILED DESCRIPTION

[0061] The following describes preferred embodiments of the present invention. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0062] Test method:

[0063] 1. Test of wave absorption performance at room temperature and high temperature:

[0064] The bow method was used to test the composite material's reflection loss in the 4-18 GHz range at room temperature and at 800°C, and the effective absorption bandwidth (RL < -10dB) was calculated. The test standard was GJB 2038-94, "Test Method for Reflectivity of Radar Absorbing Materials."

[0065] 2. Compression strength test:

[0066] The three-point bending method was used to test the flexural strength of the composite materials. The test was carried out on a CSC-1101 electronic universal testing machine, and three groups of tests were conducted in total.

[0067] 3. Test of microwave absorption performance under oxidation:

[0068] In the 4-18 GHz range, the bow method was used to test the reflection loss of composite materials under air oxidation, and the effective absorption bandwidth (RL < -10 dB) was calculated. The test standard is GJB 2038-94, "Test Method for Reflectivity of Radar Absorbing Materials."

[0069] 4. Test of wave absorption performance under corrosion:

[0070] In the 4-18 GHz range, the bow method was used to test the reflection loss of composite materials exposed to hydrogen sulfide and sulfur dioxide gas corrosion, and the effective absorption bandwidth (RL < -10 dB) was calculated. The test standard is GJB 2038-94, "Test Method for Reflectivity of Radar Absorbing Materials."

[0071] The raw materials used in the embodiment are:

[0072] Silicon carbide fiber: commercial cansas3301 silicon carbide fiber from Fujian Jianya New Materials Co., Ltd., with a fineness of 185tex;

[0073] Carbon fiber: Japan Toray T700-6k carbon fiber, fineness is 396tex;

[0074] Aramid fiber: Taihe New Materials K-29 aramid fiber, fineness is 110tex;

[0075] Boric acid: analytically pure, white crystalline powder;

[0076] Urea: analytical grade, white crystalline powder;

[0077] Polycarbosilane: pale yellow glass, Suzhou Sailifei Ceramic Fiber Co., Ltd.

[0078] The solutions mentioned in the Examples and Comparative Examples without specifying the solvent are water; the % mentioned without specifying the meaning refers to the mass percentage; the reaction temperature without specifying the reaction temperature refers to the reaction at room temperature.

[0079] Example 1

[0080] A method for preparing a high-temperature, broadband, stealth silicon carbide continuous fiber composite material comprises the following steps:

[0081] (1) Preparation of preform:

[0082] A low dielectric constant fabric is obtained by plain weaving silicon carbide long fibers with a low dielectric constant of 4 and a fineness of 185 tex, with a warp density of 70 yarns / 10 cm and a weft density of 70 yarns / 10 cm;

[0083] A high dielectric constant fabric is obtained by plain weaving silicon carbide long fibers with a high dielectric constant of 10 and a fineness of 185 tex, with a warp density of 70 yarns / 10 cm and a weft density of 70 yarns / 10 cm;

[0084] The fabrics were laid into the mold in the order of nine low-dielectric-constant fabrics as the matching layer on the top and eight high-dielectric-constant fabrics as the lossy layer on the bottom. The 17 layers of silicon carbide fiber cloth were then sewn together using long silicon carbide fibers through the holes in the mold to prevent subsequent delamination of the composite material. The stitching density was 2 stitches / cm.

[0085] (2) Deposition of boron nitride (BN) interface layer:

[0086] 0.5 mol of urea, 100 mL of water, and 200 mL of anhydrous ethanol were mixed to obtain a mixed solution; 0.05 mol of boric acid was then added to the mixed solution, and the boric acid was dissolved by continuous stirring to obtain a precursor solution;

[0087] The preform is then placed in a precursor solution, vacuum-assisted, immersed at room temperature for 10 minutes, and then taken out; dried in an oven at 110°C for 1 hour; kept at 120°C for 35 minutes under nitrogen protection; cracked and cured at 160°C for 120 minutes to crack the urea, and reacted at 210°C for 120 minutes to react boric acid and urea to obtain a material containing a boron nitride interface layer;

[0088] (3) Precursor impregnation pyrolysis (PIP) deposition of silicon carbide:

[0089] 200 g of polycarbosilane was dissolved in 200 g of xylene to obtain a polycarbosilane (PCS) precursor solution;

[0090] The material containing the boron nitride interface layer was immersed in a polycarbosilane (PCS) precursor solution under nitrogen protection and subjected to immersion cracking at 1000°C for 2 hours as a cycle. A total of 10 cracking cycles were performed to obtain a material with deposited boron nitride and silicon carbide.

[0091] (4) Preparation of protrusions:

[0092] A square raised structure is obtained by cutting on the upper surface of the matching layer of the deposited boron nitride and silicon carbide material. The raised structure has a height of 1 mm, a side length of 7 mm, and a distance of 1.2 mm between the edges of adjacent raised structures, thereby obtaining the high-temperature, broadband stealth silicon carbide continuous fiber composite material (thickness of 5 mm).

[0093] Example 2

[0094] The low dielectric constant in step (1) of Example 1 was adjusted to 3, and the high dielectric constant was adjusted to 12; the other steps remained the same as in Example 1, to obtain a composite material.

[0095] Example 3

[0096] The high dielectric constant fabric in step (1) of Example 1 was adjusted to 6 layers; the rest of the steps remained the same as in Example 1 to obtain a composite material.

[0097] Example 4

[0098] The height of the protrusions in step (4) of Example 1 was adjusted to 0.5 mm, the side length was adjusted to 8 mm, and the distance between the edges of adjacent protrusion structures was adjusted to 1 mm; the rest was kept consistent with Example 1 to obtain a composite material.

[0099] Comparative Example 1

[0100] The low dielectric constant fabric in step (1) of Example 1 was omitted, and 17 layers of high dielectric constant fabric were used. Other details were the same as in Example 1 to obtain a composite material.

[0101] Comparative Example 2

[0102] The high dielectric constant fabric in step (1) of Example 1 was omitted, and 17 layers of low dielectric constant fabric were used. Other steps were the same as in Example 1 to obtain a composite material.

[0103] Comparative Example 3

[0104] Adjust the silicon carbide fiber in step (1) of Example 1 to carbon fiber, the dielectric constant is consistent with the silicon carbide fiber, and the other is consistent with Example 1, to obtain a composite material.

[0105] Comparative Example 4

[0106] Adjust the silicon carbide fiber in step (1) of Example 1 to aramid fiber, the dielectric constant is consistent with the silicon carbide fiber, and the other is consistent with Example 1, to obtain a composite material.

[0107] Comparative Example 5

[0108] Adjust the high dielectric constant fabric in step (1) of Example 1 to be on the upper layer, and the low dielectric constant fabric to be on the lower layer, and the other is consistent with Example 1, to obtain a composite material.

[0109] Comparative Example 6

[0110] Adjust the number of layers of the low dielectric constant fabric in step (1) of Example 1 to 5 layers, and the other is consistent with Example 1, to obtain a composite material.

[0111] Comparative Example 7

[0112] Omit the stitching in step (1) of Example 1, and the other is consistent with Example 1, to obtain a composite material.

[0113] Comparative Example 8

[0114] Adjust the boron nitride layer in step (2) of Example 1 to a silicon carbide layer, and the specific operation is as follows: take H2 as the carrier gas, Ar as the dilution gas, and trichloromethylsilane (CH3SiCl3, MTS) as the raw material, place the preform in the reaction chamber, and deposit at a high temperature of 1100°C for 1h; the other is consistent with Example 1, to obtain a composite material.

[0115] Comparative Example 9

[0116] Adjust the precursor impregnation pyrolysis method (PIP) in step (3) of Example 1 to chemical vapor deposition (CVI), and the specific operation is as follows: take H2:Ar=1:10 as the protective gas, and bring trichloromethylsilane into the reaction chamber by bubbling; place the material containing the boron nitride interface layer in the reaction chamber, and deposit at a high temperature of 1000°C for 16h; the other is consistent with Example 1, to obtain a composite material.

[0117] Comparative Example 10

[0118] Adjust the protrusion height in step (4) of Example 1 to 2mm; the other is consistent with Example 1, to obtain a composite material.

[0119] Comparative Example 11

[0120] Step (2) of Example 1 was omitted, and the rest of the steps were kept the same as in Example 1 to obtain a composite material.

[0121] Comparative Example 12

[0122] Omit step (3) of Example 1, and keep the rest the same as in Example 1 to obtain the material.

[0123] Comparative Example 13

[0124] Step (4) of Example 1 was omitted, and the rest of the steps were kept the same as in Example 1 to obtain a composite material.

[0125] Comparative Example 14

[0126] The square protrusion in step (4) of Example 1 was adjusted to an equilateral triangle with a side length of 7 mm and a height of 1.5 mm. Other aspects remained the same as in Example 1 to obtain a composite material.

[0127] The obtained composite material was subjected to performance testing, and the test results are as follows:

[0128] Table 1

[0129]

[0130] From Table 1 we can see that:

[0131] The composite materials prepared in Examples 1-4 have an effective absorption bandwidth of over 80% at room temperature, an effective absorption bandwidth of over 69% in an oxidizing environment, an effective absorption bandwidth of over 60% at a high temperature of 800°C, and an effective absorption bandwidth of over 71% in a corrosive environment. The compressive strength reaches over 540 MPa, demonstrating excellent absorption performance and reliable load-bearing capacity under various environments.

[0132] Compared with Example 1, in Comparative Example 1, the entire composite material preform is woven with high dielectric constant silicon carbide fibers, resulting in an impedance mismatch between the composite material and free air, causing strong reflection of electromagnetic waves.

[0133] Compared with Example 1, in Comparative Example 2, the entire composite preform is woven entirely from low-dielectric-constant silicon carbide fibers, which creates a good impedance match with free air, allowing a large amount of electromagnetic waves to enter the composite. However, the electromagnetic loss capability of the low-dielectric-constant fibers is relatively poor, and the composite cannot effectively dissipate electromagnetic waves entering the material.

[0134] Compared with Example 1, in Comparative Example 3, the carbon fiber has a higher overall dielectric constant, which easily forms a strong reflection of electromagnetic waves, and its high-temperature performance stability is not as good as that of silicon carbide fiber, so the wave absorption performance is reduced.

[0135] Compared with Example 1, the aramid fiber in Comparative Example 4 has better flexibility, which can improve the compressive strength of the composite material, but the aramid fiber has poor high-temperature performance stability and can only withstand a high-temperature environment of 200°C;

[0136] Compared with Example 1, the wave-absorbing performance of the composite material in Comparative Example 5 has greatly decreased, because the high-dielectric silicon carbide fiber is placed in the upper layer to form strong reflection of electromagnetic waves, reducing the amount of electromagnetic waves entering the composite material; and the low-dielectric silicon carbide fiber is placed in the lower layer, which cannot form good loss effect on the small amount of electromagnetic waves entering the interior of the composite material;

[0137] Compared with Example 1, the impedance matching between the composite material and the free air has decreased due to the reduction of the number of layers of the low-dielectric silicon carbide fiber in the upper layer in Comparative Example 6, so that the electromagnetic waves entering the interior of the composite material have decreased;

[0138] Compared with Example 1, the compressive strength of the composite material in Comparative Example 7 has decreased, because the preform formed by the two-dimensional plain cloth layers is prone to delamination after the stitching operation is cancelled, resulting in a decrease in mechanical properties;

[0139] Compared with Example 1, the wave-absorbing performance and the compressive strength of the composite material in Comparative Example 8 have decreased, because the silicon carbide fiber often contains a small amount of free carbon, which is prone to chemical reaction with the oxide interface phase of SiO2, resulting in a decrease in fiber strength;

[0140] Compared with Example 1, the wave-absorbing performance and the compressive strength of the composite material in Comparative Example 9 have decreased; this is because the composite material prepared by the CVI method often forms a carbon-rich interface phase, causing strong reflection of electromagnetic waves, and the method is prone to bottleneck effect when preparing the silicon carbide matrix, causing blockage;

[0141] Compared with Example 1, the wave-absorbing performance of the composite material in Comparative Example 10 has greatly decreased; this is because when the protrusion height is 2 mm, the matching between the gradient impedance and the free air is not as good as that when the protrusion height is 1 mm;

[0142] Compared with Example 1, the wave-absorbing performance and the mechanical properties of the composite material in Comparative Example 11 have decreased after the BN interface disappears, because the BN interface can deflect and expand the crack in a benign manner, and also has certain oxidation resistance;

[0143] Compared with Example 1, the mechanical properties of the composite material in Comparative Example 12 have greatly decreased, because it loses the load transfer and protection provided by the matrix;

[0144] Compared with example 1, the wave-absorbing performance of the composite material of comparative example 13 is reduced because the scattering effect of the composite material on electromagnetic waves is reduced by removing the protruding design on the surface of the composite material; however, the mechanical performance of the composite material is improved because of the more balanced cubic structure.

[0145] Compared with example 1, the wave-absorbing performance of the composite material of comparative example 14 is reduced because the scattering effect of the triangular structure is not as good as that of the square structure.

[0146] In summary, the effective wave-absorbing bandwidth of the composite material prepared by the method of the present application accounts for more than 80% at room temperature, more than 69% in an oxidation environment, more than 60% at a high temperature of 800 DEG C, and more than 71% in a corrosion environment, and the compressive strength is more than 540 MPa, that is, the composite material has excellent wave-absorbing performance and reliable load-bearing performance in different environments and can be used in the field of aerospace.

[0147] Although the present application has been disclosed with reference to the preferred embodiments, it is not intended to limit the present application, and any person skilled in the art can make various modifications and modifications without departing from the spirit and scope of the present application, and therefore the protection scope of the present application should be defined by the claims.

Claims

1. A method for preparing a high-temperature, broadband, stealth silicon carbide continuous fiber composite material, characterized in that: The steps include: (1) Preparation of preform: A low dielectric constant fabric is obtained by weaving long silicon carbide fibers with a low dielectric constant as a matching layer; A high dielectric constant fabric is obtained by weaving long silicon carbide fibers with a high dielectric constant as a loss layer; The low dielectric constant fabric and the high dielectric constant fabric are stacked and sewn together in a layer ratio of 9:6-8 to obtain a preform; Among them, low dielectric constant refers to a dielectric constant of 3-6, and high dielectric constant refers to a dielectric constant of 8-12; (2) Deposition of boron nitride interface layer: Depositing a boron nitride interface layer on the surface of the preform by a dip-coating method to obtain a material containing a boron nitride interface layer; (3) Deposition of silicon carbide: Depositing silicon carbide on the surface of a preform containing a boron nitride interface layer by a precursor impregnation and cracking method to obtain a material having deposited boron nitride and silicon carbide; (4) Preparation of protrusions: A square protruding structure is prepared on the upper surface of the matching layer of the deposited boron nitride and silicon carbide material to obtain the high-temperature, broadband stealth silicon carbide continuous fiber composite material.

2. The method according to claim 1, characterized in that The weaving in step (1) is plain weaving to obtain plain fabric.

3. The method according to claim 1, characterized in that The dipping-coating method in step (2) is: Urea, water and ethanol are mixed evenly to obtain a mixed solution; boric acid is then added to the mixed solution and dissolved to obtain a precursor solution; the preform is then immersed in the precursor solution, taken out, dried, kept warm, and subjected to cracking and curing reaction to obtain a material containing a boron nitride interface layer.

4. The method according to claim 1, wherein The precursor impregnation cracking method in step (3) is: The material containing the boron nitride interface layer is immersed in a polycarbosilane precursor solution under nitrogen protection, and is immersed and cracked to obtain a material with deposited boron nitride and silicon carbide.

5. The method according to claim 1, wherein The parameters of the square raised structure in step (4) are: a raised height of 0.5-1.5 mm, a side length of 7-8 mm, and a distance between the edges of adjacent raised structures of 1-2 mm.

6. A high-temperature, broadband, stealth silicon carbide continuous fiber composite material prepared by the method according to any one of claims 1 to 5.

7. Application of the high-temperature, broadband, stealth silicon carbide continuous fiber composite material according to claim 6 in the field of aerospace.

8. An aviation nozzle, characterized in that: The high-temperature, broadband, stealth silicon carbide continuous fiber composite material described in claim 6 is used.

9. A method for improving the wave absorption, broadband absorption and load-bearing performance of silicon carbide continuous fiber composite materials under high temperature, oxidation and corrosion, characterized in that: The steps include: (1) Preparation of preform: A low dielectric constant fabric is obtained by weaving long silicon carbide fibers with a low dielectric constant as a matching layer; A high dielectric constant fabric is obtained by weaving long silicon carbide fibers with a high dielectric constant as a loss layer; The low dielectric constant fabric and the high dielectric constant fabric are stacked and sewn together in a layer ratio of 9:6-8 to obtain a preform; Among them, low dielectric constant refers to a dielectric constant of 3-6, and high dielectric constant refers to a dielectric constant of 8-12; (2) Deposition of boron nitride interface layer: Depositing a boron nitride interface layer on the surface of the preform by a dip-coating method to obtain a material containing a boron nitride interface layer; (3) Deposition of silicon carbide: Depositing silicon carbide on the surface of a preform containing a boron nitride interface layer by a precursor impregnation and cracking method to obtain a material having deposited boron nitride and silicon carbide; (4) Preparation of protrusions: A square protruding structure is prepared on the upper surface of the matching layer of the deposited boron nitride and silicon carbide material to obtain the high-temperature, broadband stealth silicon carbide continuous fiber composite material.

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