A wide-temperature-range structural microwave absorbing ceramic matrix composite material and its preparation method

Abstract

This invention relates to a wide-temperature-range structural microwave-absorbing ceramic matrix composite material with a PyC / BN embedded nano-interface and its preparation method. The preparation method of the composite material includes: laminating and shaping a multilayer fiber cloth, depositing a PyC interface on it, introducing Ni particles to etch the continuous PyC interface to form a discontinuous PyC interface, depositing a BN interface to obtain a PyC / BN nano-embedded interface structure, and finally depositing a matrix to obtain the wide-temperature-range structural microwave-absorbing ceramic matrix composite material. This invention, by controlling the PyC / BN nano-embedded interface structure, can reduce conductivity loss and enhance interface polarization loss. The changes in these two losses cancel each other out during heating, resulting in relatively stable electromagnetic wave absorption performance of the ceramic matrix composite material during heating. This achieves excellent electromagnetic wave absorption of over 90% in the X-band across a wide temperature range of room temperature to 1000℃.

Description

Technical Field

[0001] This invention belongs to the field of structural microwave absorbing materials technology, specifically relating to a wide-temperature-range structural microwave absorbing ceramic matrix composite material with PyC / BN embedded nano-interface and its preparation method. Background Technology

[0002] Microwave absorbing materials can be categorized into absorbing coatings and integrated load-bearing and absorbing materials (i.e., structural absorbing materials) based on their application. Among these, structural absorbing materials have attracted widespread attention due to their greater design flexibility in absorbing functions and the fact that, unlike absorbing coatings, they do not require consideration of compatibility with the substrate material. For high-temperature applications, ceramic matrix composites (CMCs) have become suitable candidates for high-temperature structural absorbing materials due to their excellent strength, toughness, high-temperature stability, and electromagnetic tunability. When the ambient temperature changes, the dielectric constant of absorbing CMCs typically changes, thus affecting their absorption performance. Therefore, developing CMC technology with stable absorption performance over a wide temperature range is a current research challenge and focus in the field of high-temperature absorbing materials.

[0003] Currently, most microwave absorbing ceramic matrix composites (CMCs) are based on a single structural design, with their loss units mainly consisting of fibers, matrix, or interfaces, exhibiting excellent microwave absorption performance at room temperature. Examples include high-temperature resistant integrated ceramic matrix composites (Yang Haitang, Luo Heng. A high-temperature resistant integrated ceramic matrix composite and its preparation method, China, CN112876273B[P]) and multi-scale toughened plywood-structured microwave absorbing ceramic matrix composites (Luo Ruiying, Cui Guangyuan. Multi-scale toughened plywood-structured microwave absorbing ceramic matrix composite and its preparation method, China, CN113754455B[P]). However, the aforementioned patents and related research have not reported on the high-temperature microwave absorption performance of ceramic matrix composites, and their potential for wide-temperature applications remains unclear. Some studies have shown that as temperature increases, the conductivity of fibers and the matrix, which have a high volume fraction in the CMC, both increase, leading to increased conductivity loss, a continuously increasing dielectric constant, and a subsequent decrease in microwave absorption performance. For example, Mu et al. (Temperature-dependent diel ectr ic and microwave absorpt i on properties of S iC f(The microwave absorption properties of SiC / SiC-Al2O3 composites modified by thermal cross-linking procedure. Journal of the European Ceramic Society, 2015, 35, 2991-3003.) This study investigated the microwave absorption properties of SiC / SiC-Al2O3 in the range of room temperature to 700℃. It was found that the dielectric constant of the composite material increases with increasing temperature, leading to a drastic change in the reflection loss (RL, a parameter expressing the microwave absorption performance) with temperature. At 400℃, the effective absorption bandwidth (EAB, where RL ≤ -10dB, meaning an absorption level ≥90%) of the composite material reaches its maximum (EAB = 4GHz). In comparison, the EAB decreases by 33% and 81% at room temperature and 700℃, respectively.

[0004] As mentioned earlier, the sharp increase in conductivity loss during heating is the main reason for the continuous increase in the dielectric constant of CMC. If the increase in conductivity loss caused by high temperature can be reduced or offset, the temperature dependence of CMC dielectric properties can be effectively reduced, and high-temperature stable control of CMC microwave absorption performance can be achieved. Tsangaris (Electrical modules and interfacial polarization in composite polymeric systems. Journal of Materials Science, 1998; 33: 2027-37.) and Banaszak (Nanostructured materials for microwave receptors. Progress in Materials Science, 2017, 87: 221-245.) found that in the microwave band, interfacial polarization shows a monotonically decreasing trend with increasing temperature. Therefore, for a loss material mainly composed of electrical conduction loss and interfacial polarization loss, the material will exhibit a relatively weakened temperature dependence of its microwave absorption performance because the changes in the two losses cancel each other out during the heating process. This inspires the design concept of a wide-temperature-range microwave absorption CMC. Summary of the Invention

[0005] In view of the above-mentioned situation of the prior art, the present invention proposes a wide temperature range structural microwave absorbing ceramic matrix composite material with PyC / BN embedded nano-interface and its preparation method, so as to achieve wide temperature range electromagnetic wave absorption of CMC.

[0006] According to one aspect of the present invention, a wide-temperature-range structural microwave absorbing ceramic matrix composite material is provided, characterized by comprising a preform formed by laminating and shaping multiple layers of low-loss fiber cloth, wherein the lamination and shaping specifically includes sewing quartz glass fiber yarn through the multiple layers of low-loss fiber cloth in the thickness direction of the preform to ensure that the final composite material does not exhibit delamination. The composite material further includes a pyrolytic carbon (PyC) interface deposited on the preform, wherein Ni particles are uniformly distributed on the surface of the PyC interface. The composite material also includes a boron nitride (BN) interface deposited on the PyC interface and a low-loss matrix prepared on the BN interface.

[0007] A wide-temperature-range structural microwave absorbing ceramic matrix composite material is characterized by comprising a preform formed by laminating and shaping multiple layers of low-loss fiber cloth, a pyrolytic carbon interface deposited on the preform, Ni particles uniformly distributed on the surface of the pyrolytic carbon interface, a boron nitride interface deposited on the pyrolytic carbon interface, and a low-loss matrix prepared on the BN interface.

[0008] The low-loss fiber cloth uses fibers including: SiC fiber, Si3N4 fiber, SiO2 fiber, Al2O3 fiber, etc., with resistivity greater than 10. 6 Fibers with a density of Ω·cm.

[0009] The low-loss substrates mentioned above include ceramic substrates such as Si3N4, SiCN, and SiBCN with dielectric constants below 7 and dielectric losses below 0.1.

[0010] According to another aspect of the present invention, a method for preparing a wide-temperature-range structural microwave absorbing ceramic matrix composite material as described above is provided, comprising the following steps: firstly, a multilayer low-loss fiber cloth is laminated and shaped to form a preform; then, a PyC interface is deposited on the preform, and Ni particles are introduced to etch the continuous PyC interface to form a discontinuous PyC interface; then, a BN interface is deposited on the PyC interface to obtain a PyC / BN nano-mosaic interface structure; finally, a low-loss matrix is ​​deposited on the BN interface to realize the preparation of the wide-temperature-range structural microwave absorbing ceramic matrix composite material.

[0011] Specifically, including:

[0012] Step 1: Lay multiple layers of low-damage fiber cloth onto a perforated graphite mold, and clamp the mold's four sides with graphite bolts to secure it. First, use quartz glass fiber yarn to sew through the holes in the graphite mold in the thickness direction onto the preform at a certain density to ensure that the final composite material will not delaminate.

[0013] Step 2: Deposit the PyC interface on the preform using chemical vapor infiltration (CVI) process. Place the sample to be deposited into a CVI furnace, evacuate the furnace and heat it to 900-1000°C, then introduce the carbon source into the furnace. The deposition time is 10-60 minutes.

[0014] Step 3: Precursor impregnation pyrolysis (PIP) is used to prepare uniformly distributed Ni particles on the PyC surface. An organic solution of Ni(NO3)2·6H2O is prepared, and the sample to be impregnated is placed in the prepared solution. The sample is then placed in a high-temperature furnace and heated to 500℃ under an Ar atmosphere, held for 1.5 h to ensure complete pyrolysis of Ni(NO3)2·6H2O to NiO. In the final 0.5 h, H2 is introduced to reduce NiO to elemental Ni. The temperature is then further increased to 600–1200℃ (annealing temperature) and held for 0.5–3 h. After annealing, Ni is used to etch PyC, resulting in discontinuous PyC.

[0015] Step 4: Deposit the BN interface using the CVI process. Place the sample to be deposited into the CVI BN furnace. First, evacuate the CVI furnace and heat it to 600-1000℃. Then, introduce BCl3, NH3, H2, and Ar into the furnace, controlling their flow ratio to be 1:3:5:5. BCl3 is the boron source, NH3 is the nitrogen source, H2 is the carrier gas and reactant gas, and Ar is the dilution gas. The deposition time is 10-30 hours.

[0016] Step 5: Finally, a low-loss matrix is ​​prepared using the CVI process to obtain a wide-temperature-range structural microwave absorbing ceramic matrix composite material with a PyC / BN embedded nano-interface.

[0017] In step 1, the low-loss fiber cloth uses fibers including: SiC fiber, Si3N4 fiber, SiO2 fiber, Al2O3 fiber, etc., with resistivity greater than 10. 6 Fibers with a density of Ω·cm.

[0018] In step 2, the carbon source is methane, acetylene, ethanol, propane, propylene, etc.

[0019] In step 3, the mass fraction of solute Ni(NO3)2·6H2O in the Ni(NO3)2·6H2O organic solution is 0.05-0.5 wt.%, and the solvent is an organic solvent such as methanol, ethanol, or acetone.

[0020] In step 4, the low-loss substrate includes ceramic substrates such as Si3N4, SiCN, and SiBCN with a dielectric constant of less than 7 and a dielectric loss of less than 0.1.

[0021] A further technical solution of the present invention is: when the low-loss substrate is Si3N4, the CVI process parameters are limited to: deposition temperature of 800-1200℃, deposition time of 180-300h, and the introduced gas is NH3, Ar, carrier gas H2 and reactant gas H2, and their flow ratio is controlled to be 7:10:8:4, wherein the carrier gas H2 carries SiCl4 in.

[0022] A further technical solution of the present invention is: when the low-loss substrate is SiCN, the CVI process parameters are limited to: deposition temperature of 800-1200℃, deposition time of 180-300h, and the introduced gas is C3H6, NH3, Ar, carrier gas H2 and reaction gas H2, and their flow ratio is controlled to be 4:6:12:150:20, wherein the carrier gas H2 carries SiCl4.

[0023] A further technical solution of the present invention is: when the low-loss substrate is Si BCN, the CVI process parameters are limited to: deposition temperature of 900-1200℃, deposition time of 180-300h, and the introduced gases are BCl3, NH3, Ar, carrier gas H2 and reaction gas H2, and their flow ratio is controlled to be 1:3:23:15:80, wherein the carrier gas H2 carries SiCl4.

[0024] This invention controls the dielectric properties and temperature dependence of the mosaic interface by adjusting parameters such as the microstructure, thickness, mosaic structure, and deposition substrate structure of PyC and BN, thereby achieving wide-temperature-range electromagnetic wave absorption of CMC.

[0025] The beneficial effects of this invention are as follows:

[0026] (1) Based on the objective law of the change of conductivity loss and interface polarization loss during the heating process, a loss-type interface composed of conductivity loss and interface polarization loss is proposed to be constructed. It is intended to achieve mutual cancellation of the two loss changes during heating through the optimization of the interface structure, thereby reducing the temperature sensitivity of CMC dielectric properties, realizing high temperature stability control of CMC absorption performance, and achieving the beneficial effect of CMC wide temperature range absorption. In a wide temperature range from room temperature to 1000℃, the absorption of X-band electromagnetic waves is greater than 90% (i.e., the reflectivity RL is less than -10dB).

[0027] (2) The PyC / BN embedded nano-interface has the characteristics of large heterogeneous interface area, which can significantly enhance interface polarization and improve the dispersion characteristics of dielectric constant. Thus, CMC can not only absorb waves strongly in the X-band, but also have good absorption performance in other frequency bands, taking into account broadband absorption.

[0028] (3) The ingenious design and precise preparation of the PyC / BN embedded nano-interface can improve the high-temperature oxidation resistance of PyC, achieve high-temperature long-term stability of the CMC interface, protect the fiber from environmental erosion, and continuously exert its toughening function. Attached Figure Description

[0029] Figure 1 This is a flowchart of the preparation method of the wide-temperature-range structural microwave absorbing ceramic matrix composite material of the present invention.

[0030] Figure 2 This is the microstructure of PyC after being etched by Ni nanoparticles in Example 1 of the present invention.

[0031] Figure 3 This is the microstructure of PyC after being etched by Ni nanoparticles in Example 1 of the present invention.

[0032] Figure 4 This is a schematic diagram of the structure of the wide-temperature-range structural microwave absorbing ceramic matrix composite material with PyC / BN embedded nano-interface of the present invention.

[0033] Figure 5 The images show the RL curves of the wide-temperature-range structural microwave absorbing ceramic matrix composite material prepared according to Example 4 of the present invention at different temperatures.

[0034] Figure 6 The figures show the RL curves of the wide-temperature-range structural microwave absorbing ceramic matrix composite material prepared according to Comparative Example 1 of the present invention at different temperatures. Detailed Implementation

[0035] To better understand the purpose, technical solution, and advantages of this invention, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0036] To address the problem of efficient electromagnetic wave absorption over a wide temperature range, this invention constructs a conductivity loss-interface polarization loss system. Low-loss fibers and ceramics are used as the preform and substrate, respectively, and an equivalent dielectric layer with a pyrolytic carbon / boron nitride (PyC / BN) nano-embedded structure is designed as the interface (electromagnetic wave loss unit). PyC is a good conductor, with conductivity loss being dominant, while BN is an insulator. This significant difference in electrical properties not only helps reduce the conductivity of the PyC / BN interface and improve impedance matching but also enhances the interfacial polarization intensity. Furthermore, considering the high conductivity of continuous PyC, to further control the conductivity loss and interfacial polarization loss to the target characteristics, Ni nanoparticles are introduced to etch PyC, forming discontinuous PyC with distinct nano-etched pits. When combined with BN, BN embeds into the etched structure of PyC, thereby increasing the interfacial polarization loss and reducing the conductivity loss. This technical solution controls the dielectric properties and temperature dependence of the mosaic interface by adjusting parameters such as the microstructure, thickness, mosaic structure, and deposition substrate structure of PyC and BN, thereby achieving wide-temperature-range electromagnetic wave absorption of CMC. Figure 1 This is a flowchart of the preparation method of the wide-temperature-range structural microwave absorbing ceramic matrix composite material of the present invention.

[0037] Example 1:

[0038] (1) Lay multilayer SiC low-loss fiber cloth on a perforated graphite mold, and clamp the four sides of the mold with graphite bolts and fix it. First, quartz glass fiber yarn is inserted and sewn through the holes in the graphite mold in the thickness direction at a certain density to make the thickness direction of the preform firm and ensure that no delamination occurs in the final composite material.

[0039] (2) A PyC interface was deposited on the preform using a chemical vapor infiltration (CVI) process. The sample to be deposited was placed in a CVI PyC furnace, the deposition temperature was 1000℃, the deposition time was 30 min, and the carbon source was methane.

[0040] (3) A precursor impregnation pyrolysis (PIP) process was used to prepare uniformly distributed Ni particles on the PyC surface. A 0.1 wt.% Ni(NO3)2·6H2O solution was prepared, and the sample to be impregnated was placed in the prepared solution. The sample was then placed in a high-temperature furnace and heated to 500℃. After pyrolysis and reduction, elemental Ni was obtained. Subsequently, the temperature was further increased to 800℃ (annealing temperature) and held for 1 h. After annealing, Ni etched PyC to obtain discontinuous PyC. The microstructure of the etched PyC is shown in the figure. Figure 2 As shown in the figure, obvious wear can be seen on its surface. This is because Ni and PyC will undergo eutectic reaction at high temperature to form a new phase, thereby achieving the etching of continuous PyC.

[0041] (4) The BN interface was deposited using the CVI process. The sample to be deposited was placed in the CVI BN furnace, the deposition temperature was 800℃, the deposition time was 20h, and the gas introduced was BC l3, NH3, H2 and Ar, and the flow rate ratio was controlled to be 1:3:5:5.

[0042] (5) Finally, the Si3N4 matrix was prepared using the CVI process at a deposition temperature of 800℃ for 240 h. The introduced gases were NH3, Ar, carrier gas H2, and reactant gas H2, with a flow rate ratio of 7:10:8:4. Ultimately, a wide-temperature-range structural microwave-absorbing ceramic matrix composite material with a PyC / BN embedded nano-interface was obtained. Its microstructure schematic diagram is shown below. Figure 3 As shown.

[0043] The ceramic matrix composite material prepared in this embodiment was subjected to RL testing using the bow-shaped frame method. At room temperature, its X-band electromagnetic wave absorption was less than 90%, and its absorption performance gradually improved with increasing temperature.

[0044] Example 2:

[0045] (1) Lay multilayer SiC low-loss fiber cloth on a perforated graphite mold, and clamp the four sides of the mold with graphite bolts and fix it. First, quartz glass fiber yarn is inserted and sewn through the holes in the graphite mold in the thickness direction at a certain density to make the thickness direction of the preform firm and ensure that no delamination occurs in the final composite material.

[0046] (2) A PyC interface was deposited on the preform using a chemical vapor infiltration (CVI) process. The sample to be deposited was placed in a CVI PyC furnace, the deposition temperature was 1000℃, the deposition time was 30 min, and the carbon source was ethanol.

[0047] (3) Ni particles were uniformly distributed on the PyC surface using a precursor impregnation pyrolysis (PIP) process. A Ni(NO3)2·6H2O solution with a concentration of 0.1 wt.% was prepared. The sample to be impregnated was placed in the prepared solution and then placed in a high-temperature furnace. After heating to 500℃, elemental Ni was obtained through pyrolysis and reduction. Subsequently, the temperature was further increased to 800℃ (annealing temperature) and held for 1 h. After annealing, Ni was used to etch PyC, resulting in discontinuous PyC.

[0048] (4) The BN interface was deposited using the CVI process. The sample to be deposited was placed in the CVI BN furnace, the deposition temperature was 800℃, the deposition time was 20h, and the gas introduced was BC l3, NH3, H2 and Ar, and the flow rate ratio was controlled to be 1:3:5:5.

[0049] (5) Finally, the Si3N4 matrix was prepared using the CVI process at a deposition temperature of 800℃ and a deposition time of 240h. The introduced gases were NH3, Ar, carrier gas H2, and reactant gas H2, and their flow rates were controlled at a ratio of 7:10:8:4. Ultimately, a wide-temperature-range structural microwave absorbing ceramic matrix composite material with a PyC / BN embedded nano-interface was obtained.

[0050] Compared to Example 1, this embodiment adjusted the type of carbon source, and the prepared ceramic matrix composite material was subjected to RL testing using the bow-shaped frame method. At room temperature, its X-band electromagnetic wave absorption was greater than 90%, and the absorption performance gradually deteriorated with increasing temperature.

[0051] Example 3:

[0052] (1) Lay multilayer SiC low-loss fiber cloth on a perforated graphite mold, and clamp the four sides of the mold with graphite bolts and fix it. First, quartz glass fiber yarn is inserted and sewn through the holes in the graphite mold in the thickness direction at a certain density to make the thickness direction of the preform firm and ensure that no delamination occurs in the final composite material.

[0053] (2) A PyC interface was deposited on the preform using a chemical vapor infiltration (CVI) process. The sample to be deposited was placed in a CVI PyC furnace, the deposition temperature was 1000℃, the deposition time was 30 min, and the carbon source was ethanol.

[0054] (3) A precursor impregnation pyrolysis (PIP) process was used to prepare uniformly distributed Ni particles on the PyC surface. A 0.2 wt.% Ni(NO3)2·6H2O solution was prepared, and the sample to be impregnated was placed in the prepared solution. The sample was then placed in a high-temperature furnace and heated to 500℃. After pyrolysis and reduction, elemental Ni was obtained. Subsequently, the temperature was further increased to 800℃ (annealing temperature) and held for 1 h. After annealing, Ni etched PyC to obtain discontinuous PyC. The microstructure of the etched PyC is shown in the figure. Figure 3 As shown in the figure, its surface exhibits a difference compared to Figure 2 The increased consumption is due to the increased Ni particle content, which expands the etched area of ​​PyC.

[0055] (4) The BN interface was deposited using the CVI process. The sample to be deposited was placed in the CVI BN furnace, the deposition temperature was 800℃ (annealing temperature), the deposition time was 20h, and the introduced gases were BC l3, NH3, H2 and Ar, and their flow ratio was controlled to be 1:3:5:5.

[0056] (5) Finally, the Si3N4 matrix was prepared using the CVI process at a deposition temperature of 800℃ and a deposition time of 240h. The introduced gases were NH3, Ar, carrier gas H2, and reactant gas H2, and their flow rates were controlled at a ratio of 7:10:8:4. Ultimately, a wide-temperature-range structural microwave absorbing ceramic matrix composite material with a PyC / BN embedded nano-interface was obtained.

[0057] Compared to Example 2, the concentration of the Ni(NO3)2·6H2O solution was adjusted in this embodiment. The prepared ceramic matrix composite material was tested for reflection loss (RL) using the bow-shaped frame method. At room temperature, its X-band electromagnetic wave absorption was less than 90%, and its absorption performance gradually improved with increasing temperature.

[0058] Example 4:

[0059] (1) Lay multi-layer low-loss SiC fiber cloth on a perforated graphite mold, and clamp the four sides of the mold with graphite bolts and fix it. First, quartz glass fiber yarn is inserted and sewn through the holes in the graphite mold in the thickness direction at a certain density to make the thickness direction of the preform firm and ensure that no delamination occurs in the final composite material.

[0060] (2) A PyC interface was deposited on the preform using a chemical vapor infiltration (CVI) process. The sample to be deposited was placed in a CVI PyC furnace, the deposition temperature was 1000℃, the deposition time was 30 min, and the carbon source was ethanol.

[0061] (3) Ni particles were uniformly distributed on the PyC surface using a precursor impregnation pyrolysis (PIP) process. A Ni(NO3)2·6H2O solution with a concentration of 0.1 wt.% was prepared. The sample to be impregnated was placed in the prepared solution and then placed in a high-temperature furnace. After heating to 500℃, elemental Ni was obtained through pyrolysis and reduction. Subsequently, the temperature was further increased to 900℃ (annealing temperature) and held for 1 h. After annealing, Ni was used to etch PyC, resulting in discontinuous PyC.

[0062] (4) The BN interface was deposited using the CVI process. The sample to be deposited was placed in the CVI BN furnace, the deposition temperature was 800℃, the deposition time was 20h, and the gas introduced was BC l3, NH3, H2 and Ar, and the flow rate ratio was controlled to be 1:3:5:5.

[0063] (5) Finally, the Si3N4 matrix was prepared using the CVI process at a deposition temperature of 800℃ and a deposition time of 240h. The introduced gases were NH3, Ar, carrier gas H2, and reactant gas H2, and their flow rates were controlled at a ratio of 7:10:8:4. Ultimately, a wide-temperature-range structural microwave absorbing ceramic matrix composite material with a PyC / BN embedded nano-interface was obtained.

[0064] Compared to Example 2, the Ni annealing temperature was adjusted in this embodiment. The prepared ceramic matrix composite material was subjected to RL testing using the bow-shaped frame method. At room temperature, its X-band electromagnetic wave absorption was less than 90%, and the absorption performance changed little with increasing temperature. Within a wide temperature range of room temperature to 1000℃, the X-band electromagnetic wave absorption was greater than 90% (RL < -10dB). Figure 5 As shown.

[0065] Example 5:

[0066] (1) Lay multilayer low-loss Si3N4 fiber cloth on a perforated graphite mold, and clamp the four sides of the mold with graphite bolts to fix it. First, quartz glass fiber yarn is inserted and sewn through the holes in the graphite mold in the thickness direction at a certain density to make the thickness direction of the preform firm and ensure that no delamination occurs in the final composite material.

[0067] (2) A PyC interface was deposited on the preform using a chemical vapor infiltration (CVI) process. The sample to be deposited was placed in a CVI PyC furnace, the deposition temperature was 1000℃, the deposition time was 30 min, and the carbon source was ethanol.

[0068] (3) Ni particles were uniformly distributed on the PyC surface using a precursor impregnation pyrolysis (PIP) process. A Ni(NO3)2·6H2O solution with a concentration of 0.1 wt.% was prepared. The sample to be impregnated was placed in the prepared solution and then placed in a high-temperature furnace. After heating to 500℃, elemental Ni was obtained through pyrolysis and reduction. Subsequently, the temperature was further increased to 900℃ and held for 1 h. After annealing, Ni was used to etch PyC, resulting in discontinuous PyC.

[0069] (4) The BN interface was deposited using the CVI process. The sample to be deposited was placed in the CVI BN furnace, the deposition temperature was 800℃, the deposition time was 20h, and the gas introduced was BC l3, NH3, H2 and Ar, and the flow rate ratio was controlled to be 1:3:5:5.

[0070] (5) Finally, Si BCN matrix was prepared by CVI process, with a deposition temperature of 900℃ and a deposition time of 240h. The introduced gases were BCl3, NH3, Ar, carrier gas H2 and reaction gas H2, and their flow ratio was controlled to be 1:3:23:15:80, in which carrier gas H2 introduced SiCl4.

[0071] Compared with Example 4, this embodiment adjusted the fiber and matrix types. The prepared ceramic matrix composite material was subjected to RL testing by the bow frame method, and its wave absorption performance was not significantly different from that of the ceramic matrix composite material prepared in Example 4.

[0072] Comparative Example 1:

[0073] (1) Lay multi-layer low-loss SiC fiber cloth on a perforated graphite mold, and clamp the four sides of the mold with graphite bolts and fix it. First, quartz glass fiber yarn is inserted and sewn through the holes in the graphite mold in the thickness direction at a certain density to make the thickness direction of the preform firm and ensure that no delamination occurs in the final composite material.

[0074] (2) A PyC interface was deposited on the preform using a chemical vapor infiltration (CVI) process. The sample to be deposited was placed in a CVI PyC furnace, the deposition temperature was 1000℃, the deposition time was 30 min, and the carbon source was ethanol.

[0075] (3) The BN interface was deposited using the CVI process. The sample to be deposited was placed in the CVI BN furnace, the deposition temperature was 800℃, the deposition time was 20h, and the gas introduced was BC l3, NH3, H2 and Ar, and the flow rate ratio was controlled to be 1:3:5:5.

[0076] (4) Finally, the Si3N4 matrix was prepared using the CVI process at a deposition temperature of 800℃ and a deposition time of 240h. The introduced gases were NH3, Ar, carrier gas H2, and reactant gas H2, and their flow rates were controlled at 7:10:8:4. Ultimately, a wide-temperature-range structural microwave absorbing ceramic matrix composite material with a PyC / BN nano-interface was obtained.

[0077] Compared to Example 5, this comparative example reduced the Ni etching process steps. The prepared ceramic matrix composite material was subjected to RL testing using the bow-shaped frame method, and the results are as follows: Figure 6 As shown, at room temperature, its X-band electromagnetic wave absorption is less than 90% (RL>-10dB), and the absorption performance gradually deteriorates with increasing temperature. This result indicates that the PyC / BN embedded nano-interface plays an important role in wide-temperature-range electromagnetic wave absorption.

Claims

1. A wide-temperature-range structural microwave absorbing ceramic matrix composite material, characterized in that... The invention includes a preform formed by laminating and shaping multiple layers of low-loss fiber cloth, a pyrolytic carbon interface deposited on the preform, Ni particles uniformly distributed on the surface of the pyrolytic carbon interface, a boron nitride interface deposited on the pyrolytic carbon interface, and a low-loss matrix prepared on the BN interface. Preparation steps: Step 1: Lay out and shape multiple layers of low-damage fiber cloth to form a preform; Step 2: A pyrolytic carbon interface is deposited on the preform using a chemical vapor infiltration process; Step 3: Using a precursor impregnation pyrolysis process, uniformly distributed Ni particles are prepared on the surface of the deposited pyrolytic carbon interface. This includes immersing the preform to be impregnated in an organic solution of Ni(NO3)2·6H2O, heating it under an inert atmosphere to the temperature at which Ni(NO3)2·6H2O is completely pyrolyzed into NiO, holding it at that temperature and reducing NiO to elemental Ni, and then continuing to heat it to 600–1200 °C and holding it for 0.5–3 h to achieve Ni etching of the pyrolytic carbon interface and obtain a discontinuous pyrolytic carbon interface. Step 4: Deposit the BN interface on the discontinuous pyrolysis carbon interface using a chemical vapor infiltration process; Step 5: Finally, a low-loss matrix is ​​deposited on the BN interface using a chemical vapor infiltration process.

2. The wide-temperature-range structural microwave absorbing ceramic matrix composite material according to claim 1, wherein the low-loss fiber cloth uses fibers selected from those with resistivity greater than 10... 6 SiC fibers, Si3N4 fibers, SiO2 fibers or Al2O3 fibers with Ω·cm.

3. The wide-temperature-range structural microwave absorbing ceramic matrix composite material according to claim 1, wherein the low-loss matrix is ​​selected from Si3N4, SiCN or SiBCN ceramic matrices with a dielectric constant of less than 7 and a dielectric loss of less than 0.

1.

4. A method for preparing a wide-temperature-range structural microwave absorbing ceramic matrix composite material according to claim 1, comprising the following steps: Step 1: Lay out and shape multiple layers of low-damage fiber cloth to form a preform; Step 2: A pyrolytic carbon interface is deposited on the preform using a chemical vapor infiltration process; Step 3: Using a precursor impregnation pyrolysis process, uniformly distributed Ni particles are prepared on the surface of the deposited pyrolytic carbon interface. This includes immersing the preform to be impregnated in an organic solution of Ni(NO3)2·6H2O, heating it under an inert atmosphere to the temperature at which Ni(NO3)2·6H2O is completely pyrolyzed into NiO, holding it at that temperature and reducing NiO to elemental Ni, and then continuing to heat it to 600–1200 °C and holding it for 0.5–3 h to achieve Ni etching of the pyrolytic carbon interface and obtain a discontinuous pyrolytic carbon interface. Step 4: Deposit the BN interface on the discontinuous pyrolysis carbon interface using a chemical vapor infiltration process; Step 5: Finally, a low-loss matrix is ​​deposited on the BN interface using a chemical vapor infiltration process.

5. The method according to claim 4, wherein in step 1, the layering and shaping includes sewing the multilayer low-loss fiber cloth through quartz glass fiber yarn in the thickness direction of the preform.

6. The method according to claim 4, wherein in step 1, the fibers used in the low-loss fiber cloth are selected from fibers with a resistivity greater than 10. 6 SiC fibers, Si3N4 fibers, SiO2 fibers or Al2O3 fibers with Ω·cm.

7. The method according to claim 4, wherein in step 4, the low-loss substrate is selected from Si3N4, SiCN or SiBCN ceramic substrates with a dielectric constant of less than 7 and a dielectric loss of less than 0.

1.

8. According to the method of claim 7, when the low-loss substrate is Si3N4, the parameters of the chemical vapor infiltration process are set as follows: deposition temperature 800-1200℃, deposition time 180-300 h, the introduced gas is NH3, Ar, carrier gas H2 and reactant gas H2, and the flow rate ratio is controlled to be 7:10:8:4, wherein the carrier gas H2 carries SiCl4 in.

9. The method according to claim 7, wherein when the low-loss substrate is SiCN, the parameters of the chemical vapor infiltration process are set as follows: deposition temperature 800-1200℃, deposition time 180-300 h, and the introduced gas is C3H6, NH3, Ar, carrier gas H2 and reactant gas H2, and their flow ratio is controlled to be 4:6:12:150:20, wherein the carrier gas H2 carries SiCl4.

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