High-temperature-resistant wave-absorbing honeycomb ceramic, preparation method and application thereof

Abstract

This invention discloses a high-temperature resistant microwave absorbing honeycomb ceramic, its preparation method, and its applications, relating to the field of porous ceramic materials technology. The process includes obtaining a honeycomb skeleton; introducing a porous structural material onto the honeycomb skeleton to obtain a honeycomb structure preform; introducing a ceramic phase onto the honeycomb structure preform to obtain a porous composite; and removing the honeycomb skeleton from the porous composite to obtain the high-temperature resistant microwave absorbing honeycomb ceramic. The ceramic prepared by this invention has a porous wall structure and a hollow skeleton, mainly solving the shortcomings of existing high-temperature resistant microwave absorbing honeycomb ceramics, such as complex preparation processes, poor microwave absorption performance, and difficulty in control.

Description

Technical Field

[0001] This invention relates to the field of porous ceramic materials technology, specifically to a high-temperature resistant microwave absorbing honeycomb ceramic, its preparation method, and its application. Background Technology

[0002] Honeycomb structure absorbing materials have attracted widespread attention in the field of microwave absorption due to their combination of low density, large specific surface area, and wide effective absorption bandwidth. However, currently common honeycomb structure absorbing materials are usually resin-based, which makes it difficult to meet the requirements of high-temperature applications.

[0003] Existing technologies disclose honeycomb-shaped high-temperature absorbing microwave structures, which consist of a silicone rubber absorbing layer, an aluminum alloy honeycomb structure layer, and an isocyanate composite material layer. While this structure offers the advantage of controllable dielectric properties, its microwave absorption performance primarily depends on the silicone rubber absorbing layer, significantly limiting its operating temperature. Existing technologies also disclose methods for preparing honeycomb ceramic materials through compression molding and die extrusion molding. The advantages of these two methods are that they can yield honeycomb structures with high ceramic phase content and excellent high-temperature resistance. However, their disadvantages include complex fabrication processes and difficulty in controlling dielectric properties. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a high-temperature resistant microwave absorbing honeycomb ceramic, its preparation method, and its applications. This ceramic features a porous wall structure and a hollow framework, primarily overcoming the drawbacks of existing high-temperature resistant microwave absorbing honeycomb ceramics, such as complex preparation processes, poor absorption performance, and difficulty in control.

[0005] The first objective of this invention is to provide a method for preparing high-temperature resistant microwave absorbing honeycomb ceramics, comprising the following steps:

[0006] Obtain the honeycomb skeleton;

[0007] A porous structural material is introduced onto the honeycomb skeleton to obtain a honeycomb structure preform;

[0008] A ceramic phase was introduced onto a honeycomb structure preform to obtain a porous composite.

[0009] The honeycomb skeleton in the porous composite is removed to obtain high-temperature absorbing honeycomb ceramic.

[0010] Preferably, the porous structure material includes carbon nanotube foam, graphene foam or MXenes foam, and SiC, SiOC or SiCN porous ceramic structures.

[0011] Preferably, the ceramic phase is SiC ceramic, Si3N4 ceramic, or SiCN ceramic.

[0012] Preferably, the honeycomb skeleton includes paper honeycomb, resin honeycomb, aluminum honeycomb, or glass cloth honeycomb.

[0013] Preferably, the method for removing the honeycomb skeleton in the porous composite includes oxidation or etching.

[0014] Preferably, the method for introducing the ceramic phase includes chemical vapor infiltration or precursor impregnation pyrolysis.

[0015] More preferably, the chemical vapor infiltration method introduces a ceramic phase, comprising:

[0016] The honeycomb structure preform is placed in a deposition furnace, vacuumed to a pressure of <300Pa, heated to 1000-1100℃, and the gas required for chemical vapor infiltration is introduced in proportion. The temperature is maintained for 70-80h, and a ceramic matrix is ​​uniformly deposited on the honeycomb structure preform to obtain a porous composite.

[0017] The second objective of this invention is to provide a high-temperature resistant absorbing honeycomb ceramic.

[0018] Preferably, the honeycomb ceramic is composed of a wave-transparent hollow skeleton and a wave-absorbing honeycomb wall, and the honeycomb wall has a porous structure.

[0019] The third objective of this invention is to provide an application of high-temperature resistant absorbing honeycomb ceramics in microwave absorption.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] This invention provides a method for preparing high-temperature resistant absorbing honeycomb ceramics. Compared with existing honeycomb ceramic preparation methods, the preparation process of the high-temperature resistant absorbing honeycomb ceramics described in this invention is simple, and the structure is easy to control. By using aramid honeycombs with different pore sizes or thicknesses, the final pore size and thickness of the honeycomb can be controlled. It exhibits excellent high-temperature resistance and is easy to industrialize. Furthermore, through the design of the wave-transmitting hollow skeleton and the wave-absorbing porous honeycomb wall, the wave absorption performance of the honeycomb ceramics is controllable, achieving excellent broadband wave absorption performance.

[0022] The high-temperature absorbing honeycomb ceramic provided by this invention has a physical structure between the ceramic phase and the honeycomb, and the microstructure is similar to a sandwich structure. By introducing a high-temperature resistant ceramic phase on the surface of the honeycomb structure, it can protect and support the honeycomb skeleton, while improving the strength and high-temperature resistance of the honeycomb. Attached Figure Description

[0023] Figure 1 This is a photograph of the SiC absorbing honeycomb ceramic prepared in Example 1.

[0024] Figure 2 The image shows a scanning electron microscope (SEM) image of the SiC absorbing honeycomb ceramic prepared in Example 1.

[0025] Figure 3 The image shows the microwave absorption performance of the SiC absorbing honeycomb ceramic prepared in Example 1.

[0026] Figure 4 The diagram shows the high-temperature microwave absorption performance of the SiC absorbing honeycomb ceramic prepared in Example 1. Detailed Implementation

[0027] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention, but the embodiments are not intended to limit the present invention.

[0028] This invention provides a method for preparing high-temperature resistant microwave absorbing honeycomb ceramic, comprising the following steps:

[0029] Obtain the honeycomb skeleton;

[0030] A porous structural material is introduced onto the honeycomb skeleton to obtain a honeycomb structure preform;

[0031] A ceramic phase was introduced onto a honeycomb structure preform to obtain a porous composite.

[0032] The honeycomb skeleton in the porous composite is removed to obtain high-temperature absorbing honeycomb ceramic.

[0033] The honeycomb ceramic material prepared by this invention has a porous wall structure and a hollow skeleton, which mainly solves the shortcomings of existing high-temperature resistant microwave absorbing ceramic honeycomb, such as complex preparation process, poor microwave absorption performance and difficulty in control.

[0034] The porous structure material includes carbon nanotube foam, graphene foam or MXenes foam, and SiC, SiOC or SiCN porous ceramic structures.

[0035] In this invention, the honeycomb structure preform is prepared as follows: the honeycomb preform can be a carbon honeycomb preform obtained by heat treatment of aramid paper honeycomb, or a high-temperature resistant honeycomb structure material such as glass cloth honeycomb. A porous structure is introduced onto the honeycomb surface by freeze-drying or impregnation-drying methods to obtain the honeycomb structure preform. The final pore structure of the honeycomb ceramic is determined by the pore structure of the honeycomb preform.

[0036] The porous structure can be carbon nanotube foam, graphene foam, or MXenes foam obtained by freeze-drying. Alternatively, it can be a SiOC or SiC ceramic porous structure obtained by impregnating ceramic precursors such as PSO or PCS and then curing and pyrolyzing them.

[0037] The ceramic phase is SiC ceramic, Si3N4 ceramic, or SiCN ceramic.

[0038] In this invention, the ceramic matrix is ​​introduced by depositing the ceramic matrix via chemical vapor infiltration. The obtained preform is placed in a deposition furnace, evacuated to a pressure <300 Pa, heated to 1000–1100 °C, and a gaseous precursor required for chemical vapor infiltration is introduced in proportion; the temperature is maintained for 70–80 h to allow the ceramic matrix to be uniformly deposited within the porous structure; or the precursor is impregnated and decomposed.

[0039] The honeycomb skeleton includes paper honeycomb, resin honeycomb, aluminum honeycomb, or glass cloth honeycomb.

[0040] It should be noted that the honeycomb skeleton used in this invention is mainly aramid paper honeycomb or glass cloth honeycomb. The aramid paper honeycomb is obtained by heat treatment to produce carbon honeycomb before use, followed by freeze-drying or impregnation-drying to introduce a porous structure onto the honeycomb surface, resulting in a honeycomb structure preform. The final pore structure of the honeycomb ceramic is determined by the pore structure of the honeycomb preform.

[0041] Methods for removing the honeycomb skeleton in porous composites include oxidation or etching.

[0042] In this invention, the removal of the honeycomb preform skeleton is carried out using different methods depending on the material of the honeycomb preform. For carbon or resin-based honeycomb preform skeletons, oxidation can be used to remove the skeleton. For honeycomb preforms such as glass cloth, HF etching can be used to remove the skeleton.

[0043] Methods for introducing ceramic phases include chemical vapor infiltration or precursor impregnation pyrolysis.

[0044] Specifically, the chemical vapor infiltration method introduces a ceramic phase, including:

[0045] The honeycomb structure preform is placed in a deposition furnace, vacuumed to a pressure of <300Pa, heated to 1000-1100℃, and the gas required for chemical vapor infiltration is introduced in proportion. The temperature is maintained for 70-80h, and a ceramic matrix is ​​uniformly deposited on the honeycomb structure preform to obtain a porous composite.

[0046] In one embodiment, the preparation method for honeycomb ceramic materials is simple, the honeycomb structure is controllable, and it is easy to achieve large-scale preparation. The specific preparation process is as follows:

[0047] Aramid paper honeycomb was pyrolyzed at 900℃ to obtain a carbon honeycomb framework. Then, a porous carbon nanotube foam structure was introduced onto the carbon honeycomb framework using freeze-drying to obtain a honeycomb structure preform. The honeycomb framework can be obtained by high-temperature pyrolysis of paper honeycomb or resin honeycomb, or it can be a high-temperature resistant honeycomb structure such as glass cloth honeycomb. The porous structure can be carbon nanotube foam, graphene foam, MXenes foam, or porous ceramic structures such as SiOC and SiCN.

[0048] A ceramic phase is introduced onto a honeycomb skeleton using chemical vapor deposition. The preform is placed in a deposition furnace, evacuated to a pressure <300 Pa, and heated to 1000–1100 °C. The gas precursor required for chemical vapor infiltration is introduced in proportion. The mixture is held at this temperature for 70–80 hours to allow the ceramic matrix to be uniformly deposited within the porous structure. The ceramic phase can be SiC ceramic, Si3N4 ceramic, etc.

[0049] Different methods are used to remove the honeycomb preform skeleton depending on the material. For carbon or resin-based honeycomb preform skeletons, oxidation can be used. For honeycomb preforms such as glass cloth, HF etching can be used to remove the honeycomb preform skeleton.

[0050] This invention provides a high-temperature absorbing honeycomb ceramic prepared by the above method.

[0051] The honeycomb ceramic is composed of a wave-transparent hollow skeleton and a wave-absorbing honeycomb wall, and the honeycomb wall has a porous structure.

[0052] This invention provides an application of high-temperature resistant absorbing honeycomb ceramics in microwave absorption.

[0053] It should be noted that, unless otherwise specified, the experimental methods used in this invention are all conventional methods; and the reagents and materials used, unless otherwise specified, are all commercially available.

[0054] Example 1

[0055] A method for preparing high-temperature resistant microwave absorbing honeycomb ceramic includes the following steps:

[0056] Aramid paper honeycomb structure was heat-treated at 900℃ to obtain a carbon honeycomb preform; 10g of multi-walled carbon nanotubes were placed in 100g of deionized water and ultrasonically dispersed for 12h to obtain a uniformly dispersed multi-walled carbon nanotube aqueous dispersion; the carbon honeycomb preform was immersed in the multi-walled carbon nanotube aqueous dispersion for 10min, and then frozen in liquid nitrogen; the alternating immersion and freezing was repeated three times, and the preform was vacuum dried to obtain a carbon honeycomb / CNT foam preform;

[0057] The obtained preform was placed in a CVD deposition furnace to deposit SiC matrix for 120 h to obtain C / CNT / SiC ceramic honeycomb composite material.

[0058] The SiC substrate deposition was carried out under an argon atmosphere, with trichloromethylsilane (MTS) as the ceramic precursor and H2 as the carrier gas and dilution gas. To ensure that MTS could enter the deposition furnace uniformly, MTS was introduced by bubbling. The deposition temperature was 1000℃, and the flow rates of argon, carrier gas H2, and dilution gas H2 were 3.0 L / min, 2.0 L / min, and 1.0 L / min, respectively. The dilution ratio of H2 to MTS was 10, and the total system pressure was maintained at 8 kPa.

[0059] Finally, the obtained C / CNT / SiC honeycomb structure was oxidized at 600℃ for 20h to remove the carbon honeycomb preform skeleton, thus obtaining SiC microwave absorbing honeycomb ceramic.

[0060] See Figure 1 The image shown is a physical picture of SiC absorbing honeycomb ceramic; see also... Figure 2 As shown, scanning electron microscope images of SiC absorbing honeycomb ceramics are obtained from... Figures 1-2 It can be seen that the material produced has a honeycomb structure. Figure 3 This is a curve showing the RL (resonance ratio) of SiC absorbing honeycomb ceramic as a function of frequency. From... Figure 3 As can be seen, its bandwidth with RL less than -10dB can cover 3 to 40GHz.

[0061] Figure 4 This is a graph showing the high-temperature microwave absorption performance of the SiC absorbing honeycomb ceramic prepared in Example 1. From... Figure 4 It can be seen that stable absorption of the entire X-band can be achieved from room temperature to 600℃. Figure 4 The minimum reflectance can reach -40.8dB at 4.1GHz.

[0062] Example 2

[0063] A method for preparing high-temperature resistant microwave absorbing honeycomb ceramic includes the following steps:

[0064] 5g of graphene oxide was placed in 100g of deionized water and ultrasonically dispersed for 12h to obtain a uniformly dispersed graphene oxide aqueous dispersion. Glass cloth honeycomb was immersed in the graphene oxide aqueous dispersion for 10min, then frozen in liquid nitrogen. This process of alternating immersion and freezing was repeated three times. After vacuum drying, a glass cloth / graphene foam prefabricated honeycomb was obtained. A Si3N4 substrate was introduced by chemical vapor infiltration. The Si3N4 substrate deposition was carried out under an argon atmosphere, using SiCl4 and NH3 as gas sources and Ar and H2 as diluent gases. The reaction temperature was 800℃, the holding time was 120h, and the furnace pressure was 3KPa. Finally, the glass cloth honeycomb structure was etched away using HF to obtain Si3N4 microwave absorbing honeycomb ceramic.

[0065] The honeycomb ceramic structure prepared in this embodiment is similar to the SiC honeycomb ceramic structure prepared in Example 1.

[0066] Example 3

[0067] A method for preparing high-temperature resistant microwave absorbing honeycomb ceramic includes the following steps:

[0068] A SiOC ceramic precursor, PSO, was introduced onto the surface of an aramid paper honeycomb using the PIP process, followed by the introduction of a SiCN ceramic precursor via impregnation. The mixture was then held at 220°C for 12 hours, followed by pyrolysis at 1000°C to obtain a carbon / SiOC / SiCN ceramic precursor. Finally, it was oxidized at 600°C for 20 hours to obtain a SiOC / SiCN high-temperature resistant microwave-absorbing honeycomb ceramic material. The PIP process involved preparing a precursor solution with a 1:1 mass ratio of polysiloxane (PSO) as the precursor and xylene as the solvent. The composite material was then vacuum-impregnated in the precursor solution for 2 hours, followed by holding at 220°C for 12 hours. This impregnation process was repeated 1–5 times, followed by pyrolysis at 1000°C for 2 hours under an Ar atmosphere to break down the resin framework into a carbon skeleton, thus obtaining the carbon / SiOC ceramic honeycomb.

[0069] The carbon / SiOC ceramic cell ceramic material obtained in this embodiment is similar to the SiC cell ceramic prepared in Example 1.

[0070] In summary, this invention selects a mature honeycomb structure as a template, which can add wave-absorbing functionality to the already applied honeycomb structure, making it more conducive to widespread application. Thanks to the in-situ molding process, complex structures, such as porous foam structures, can be introduced into the honeycomb coating, which is beneficial to improving the wave-absorbing performance of ceramic honeycomb.

[0071] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing high-temperature resistant microwave absorbing honeycomb ceramic, characterized in that, Includes the following steps: Obtain the honeycomb skeleton; A porous structural material is introduced onto the honeycomb skeleton to obtain a honeycomb structure preform; A ceramic phase was introduced onto a honeycomb structure preform to obtain a porous composite. The honeycomb skeleton in the porous composite is removed to obtain high-temperature absorbing honeycomb ceramic; The porous structure material includes carbon nanotube foam, graphene foam or MXenes foam, and SiC, SiOC or SiCN porous ceramic structures. The ceramic phase is SiC ceramic, Si3N4 ceramic or SiCN ceramic; The honeycomb skeleton includes paper honeycomb, resin honeycomb, aluminum honeycomb, or glass cloth honeycomb; Methods for removing the honeycomb skeleton in porous composites include oxidation or etching. Methods for introducing ceramic phases include chemical vapor infiltration or precursor impregnation pyrolysis; The chemical vapor infiltration method introduces a ceramic phase, including: The honeycomb structure preform is placed in a deposition furnace, vacuumed to a pressure of <300Pa, heated to 1000-1100ºC, and the gas required for chemical vapor infiltration is introduced in proportion. The temperature is maintained for 70-80h, and a ceramic matrix is ​​uniformly deposited on the honeycomb structure preform to obtain a porous composite.

2. A high-temperature absorbing honeycomb ceramic prepared by the method of claim 1.

3. The high-temperature resistant absorbing honeycomb ceramic according to claim 2, characterized in that, The honeycomb ceramic consists of a wave-transparent hollow skeleton and a wave-absorbing honeycomb wall, the honeycomb wall having a porous structure.

4. The application of the high-temperature resistant absorbing honeycomb ceramic as described in claim 2 in microwave absorption.

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