High-temperature-resistant porous silicon carbide-based wave-absorbing composite material and preparation method thereof
By introducing an interface layer into the silicon carbide nanowire composite material and optimizing the structural design, the shortcomings of existing materials in impedance matching and electromagnetic loss are solved, and the effect of a high-temperature resistant, wide-band, and strongly absorbing absorbing material is achieved.
Patent Information
- Application Number
- CN202410275785.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-12
- Publication Date
- 2025-09-12
AI Technical Summary
Existing silicon carbide nanowire composite absorbing materials are difficult to achieve impedance matching and electromagnetic loss capability matching design, resulting in a narrow effective absorption bandwidth that is difficult to meet application requirements.
Through macro/micro integrated structural design, interface layers (such as silicon carbide interface and boron nitride interface) are introduced to optimize the impedance matching capability of the material, and the absorption performance is improved through multiple loss mechanisms (ohmic loss, polarization loss, etc.).
A composite absorbing material with high temperature resistance, wide bandwidth, strong absorption and lightweight has been achieved. The effective absorption bandwidth is significantly improved, the reflection loss is reduced, and the material still maintains good absorbing performance at high temperatures.
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Figure CN120622948A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of wave-absorbing composite materials, and relates to a high-temperature resistant porous silicon carbide-based wave-absorbing composite material and a preparation method thereof, and specifically relates to a porous silicon carbide-based wave-absorbing composite material with silicon carbide nanowires as a skeleton. Background Art
[0002] With the rapid development of wireless communication and radar detection technologies, high-performance materials are of great significance for enhancing the battlefield survivability, penetration, and combat capabilities of weaponry. High-temperature thermal structures such as engine tail nozzles can operate at temperatures exceeding 800°C. Therefore, high-performance, high-temperature absorbing composite materials are attracting widespread attention worldwide. High-temperature ceramic absorbing materials, with their advantages of low density, high temperature resistance, and strong absorption, have become key candidate materials for addressing electromagnetic pollution and military stealth technology. Silicon carbide nanowires, on the other hand, possess the inherent advantages of high twin density, oxidation resistance, and high specific surface area. They also possess excellent dielectric properties and moderate electrical conductivity, providing strong dielectric loss. They are attracting widespread attention in lightweight, high-temperature resistant, and efficient electromagnetic wave absorption applications.
[0003] However, silicon carbide nanowires also have certain application limitations. The electromagnetic parameters of silicon carbide nanowires make it difficult to achieve impedance matching characteristics; at the same time, their electromagnetic loss mechanism is single and the dielectric loss capacity is insufficient, resulting in a narrow effective absorption bandwidth, which is difficult to meet application requirements; existing silicon carbide nanowire composite absorbing materials are difficult to achieve a matching design between the impedance matching degree and the electromagnetic loss capacity. Summary of the Invention
[0004] To address these issues, the present invention optimizes the material's impedance matching capabilities through a macroscopic / microscopic integrated structural design. Furthermore, by introducing interface layers (e.g., silicon carbide interfaces and boron nitride interfaces) within the porous silicon carbide nanowire network framework, multiple loss mechanisms are introduced. This effectively compensates for the single electromagnetic loss mechanism of a single type of silicon carbide nanowire, optimizing the composite's absorption performance through multiple loss mechanisms, including ohmic loss and polarization loss. Therefore, the combination of silicon carbide nanowires and interface layers facilitates the preparation of high-temperature-resistant, broadband, highly absorbing, and lightweight composite absorbers for both military and civilian applications.
[0005] On the one hand, the present invention provides a high-temperature resistant porous silicon carbide-based absorbing composite material, which includes: a lightweight porous network skeleton structure formed by one-dimensional silicon carbide nanowires oriented and arranged parallel to the 3D printing direction, and an interface layer in situ grown on the surface of the silicon carbide nanowires, wherein the interface layer is uniformly coated on the surface of the silicon carbide nanowires; the interface layer is a silicon carbide interface layer or a boron nitride interface layer.
[0006] The interface layer introduced into the porous silicon carbide nanowire network skeleton of the present invention must possess the performance characteristics of a reflective layer or a matching layer. The silicon carbide interface layer has reflective layer characteristics, and its introduction can increase the dielectric constant of the composite material, causing electromagnetic waves to produce multiple reflections and losses at the interface of the composite material. The boron nitride interface layer has matching layer characteristics, and its extremely low dielectric constant allows electromagnetic waves to pass through the interface, improving the impedance matching of the composite material and causing incident electromagnetic waves to enter the material and suffer losses. At the same time, the introduction of the interface layer can achieve dielectric loss of electromagnetic waves based on interfacial polarization. The combination of the interface layer and the silicon carbide nanowires can achieve multiple impedance mutations, causing multiple scattering and losses of electromagnetic waves.
[0007] Preferably, the high-temperature-resistant porous silicon carbide-based absorbing composite material has a macroscopic periodic structure and a microscopic porous structure. The macroscopic periodic structure refers to a rectangular grid structure with 3D-printed strips arranged parallel to each other within a layer and orthogonally stacked between printed layers. The microscopic porous network structure is composed of silicon carbide nanowires and the pores between the interface layer and the nanowires. This microscopic porous network structure facilitates multiple scattering and absorption of electromagnetic waves incident on the material, preventing direct reflection of electromagnetic waves from the surface of the porous silicon carbide-based absorbing composite material.
[0008] Preferably, the silicon carbide nanowires have a diameter of 100 to 500 nm and a length of 50 to 100 μm.
[0009] Preferably, the interface layer is a silicon carbide interface layer or a boron nitride interface layer, preferably a silicon carbide interface layer; The thickness of the silicon carbide interface layer is 167.6 to 400.7 nm; the silicon carbide nanowires and the silicon carbide interface layer form a local conductive network structure; The thickness of the boron nitride interface layer is 145.3-353.6 nm.
[0010] Preferably, when the interface layer is a silicon carbide interface layer, the porosity of the high-temperature resistant porous silicon carbide-based absorbing composite material is 64.1% to 92.5%; When the interface layer is a boron nitride interface layer, the porosity of the high-temperature resistant porous silicon carbide-based wave-absorbing composite material is 70.5% to 93.4%.
[0011] In another aspect, the present invention provides a method for preparing a high-temperature-resistant porous silicon carbide-based absorbing composite material. The method uses hydroxypropyl methylcellulose as a binder to prepare a silicon carbide nanowire composite slurry, utilizes 3D printing technology to prepare a macroscopic periodic gel structure, and constructs a microscopic porous network structure through freeze casting. Finally, chemical vapor infiltration technology is used to in situ grow an interface layer to prepare a high-temperature-resistant porous silicon carbide-based absorbing composite material. To ensure that incident electromagnetic waves are absorbed within the material rather than directly passing through it, the 3D printing spacing within the layer is set to match the needle size, and the printed layers are arranged orthogonally to ensure that the printed strips are in close contact with no macroscopic gaps.
[0012] In one embodiment, the method for preparing the high temperature resistant porous silicon carbide-based microwave absorbing composite material provided by the present invention comprises: (1) uniformly dispersing silicon carbide nanowires and hydroxypropyl methylcellulose in a solvent to obtain a composite printing slurry; (2) obtaining a hydrogel skeleton structure by 3D printing the composite printing slurry; (3) A lightweight porous aerogel skeleton structure is obtained by freeze drying and vacuum drying; (4) Chemical vapor infiltration is used to in situ grow an interface layer in the obtained lightweight porous aerogel skeleton structure to obtain a high-temperature resistant porous silicon carbide-based absorbing composite material.
[0013] The present invention firstly disperses silicon carbide nanowires and hydroxypropyl methylcellulose uniformly in deionized water to prepare a composite slurry, wherein the hydroxypropyl methylcellulose serves as a binder and can also improve the surface activity of the silicon carbide nanowires; uses 3D printing technology to prepare a macroscopic periodic gel structure, and constructs a microscopic porous network structure through freeze casting; finally, uses chemical vapor infiltration technology to in-situ grow an interface layer to prepare a high-temperature resistant porous silicon carbide-based absorbing composite material.
[0014] Preferably, in step (1), the mass ratio of the silicon carbide nanowires to hydroxypropyl methylcellulose is 3:2 to 9:1, preferably 4:1; and the concentration of the silicon carbide nanowires in the composite printing slurry is 0.5 to 40 vol%.
[0015] Preferably, in step (2), the diameter of the 3D printing needle is 0.4-0.6 mm, the needle movement speed is 10-30 mm / s, and the printing pressure is 0.3-0.6 MPa. Preferably, the printing needle diameter is consistent with the printing spacing and the printing layer thickness.
[0016] Preferably, in step (3), the freeze-drying temperature is -40°C to -80°C, and the time is 12 to 36 hours; the vacuum drying time is 24 to 72 hours.
[0017] Preferably, in step (4), the reaction gas for in-situ growth of the silicon carbide interface layer by chemical vapor infiltration is methyltrichlorosilane, the flow rate of the reaction gas is 220 to 360 mL / min, the reaction temperature is 1000 to 1200° C., and the reaction time is 0.5 to 5 hours; The reaction gases for in-situ growth of the boron nitride interface layer by the chemical vapor infiltration method are boron trichloride and ammonia, the flow rates of the boron trichloride are 10 to 50 mL / min, the flow rate of the ammonia is 20 to 100 mL / min, the reaction temperature is 700 to 1000° C., and the reaction time is 0.5 to 4 hours.
[0018] Beneficial effects:
[0019] The high-temperature resistant porous silicon carbide-based absorbing composite material prepared by the present invention has a macroscopically ordered, microscopically porous structure and excellent thermal stability. 3D printing and freeze casting construct a uniform porous structure, which can achieve multiple scattering of incident electromagnetic waves. The interconnected network structure composed of silicon carbide nanowires and the interface layer can enhance the conductivity loss of the composite material. The multiphase interface can introduce impedance mutations and a large number of dipoles, enhance the interface polarization and dipole polarization loss of the composite material, and effectively improve the absorbing performance of the composite material. Therefore, the silicon carbide nanowire / silicon carbide absorbing composite material has a maximum effective absorption bandwidth of 5.9 GHz and a minimum reflection loss of -41.4 dB at a matching thickness of 2.4 mm. Based on the intrinsic high-temperature resistance and oxidation resistance of silicon carbide, the composite material has good thermal stability. After being heat-treated in air at 1000°C for 4 hours, the effective absorption bandwidth remains at 5.4 GHz at a matching thickness of 2 mm. At a matching thickness of 2.2 mm, the silicon carbide nanowire / boron nitride absorbing composite material has a maximum effective absorption bandwidth of 5.6 GHz and a minimum reflection loss of -25.9 dB. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 Schematic diagram and actual picture of the macroscopic periodic structure of the porous network skeleton of silicon carbide nanowire aerogel in Example 1; Figure 2 This is a surface SEM image of the porous network skeleton of silicon carbide nanowire aerogel in Example 1; Figure 3 : This is a cross-sectional SEM image of the silicon carbide nanowire / silicon carbide composite material in Example 1; Figure 4 is the reflection loss value of the silicon carbide nanowire / silicon carbide composite material at different simulated thicknesses in Example 1; Figure 5 is the reflection loss value of the silicon carbide nanowire / boron nitride composite material at different simulated thicknesses in Example 5; Figure 6The maximum effective absorption bandwidth variation trend of the composite materials prepared in Examples 1 to 5 and Comparative Examples 1 to 2 is shown. DETAILED DESCRIPTION
[0021] To further illustrate the content, features and practical effects of the present invention, the present invention is described in detail below in conjunction with the embodiments. It should be noted that the modification method of the design of the present invention is not limited to these specific embodiments. Without departing from the spirit and connotation of the design of the present invention, equivalent replacements and modifications made by those skilled in the art based on the content of the present invention are also within the scope of the present invention.
[0022] In this paper, silicon carbide nanowires and hydroxypropyl methylcellulose are ultrasonically dispersed in deionized water to create a uniformly dispersed composite slurry. A porous network framework is constructed using 3D printing and freeze-casting techniques. A high-purity interface layer is in situ grown using chemical vapor infiltration to create a high-temperature-resistant porous silicon carbide-based microwave-absorbing composite material. The multiple absorption mechanisms introduced by the in-situ grown interface layer, combined with the intrinsic thermal stability of silicon carbide, make this composite material potentially applicable in the field of high-temperature, broadband microwave-absorbing composite materials.
[0023] The following is an exemplary description of the preparation method of the high-temperature resistant porous silicon carbide-based microwave-absorbing composite material provided by the present invention.
[0024] Preparation of composite printing slurry. Silicon carbide nanowires and hydroxypropyl methylcellulose were added to deionized water and uniformly dispersed using ultrasound. The addition of hydroxypropyl methylcellulose helped to form a gel-like slurry. This system exhibited shear-thinning properties at room temperature, ensuring the stability and continuity of the 3D printing process.
[0025] In an optional embodiment, the diameter of the silicon carbide nanowires may be 5 to 500 nm, and the aspect ratio may be greater than 10. The mass ratio of silicon carbide nanowires to hydroxypropyl methylcellulose may be 3:2 to 9:1, and the concentration of silicon carbide nanowires in the slurry may be 0.5 to 40 vol%.
[0026] Preparation of the hydrogel skeleton structure: The composite printing slurry is added to the barrel of the 3D printing device. The printing parameters, including printing pressure and printing speed, are set according to the designed model to produce the hydrogel skeleton structure.
[0027] In an optional embodiment, during the 3D printing process, the printing pressure is 0.3 to 0.6 MPa, the needle diameter is 0.4 to 0.6 mm, the needle movement speed is 10 to 30 mm / s, and the printing spacing within and between layers is 0.4 to 0.6 mm.
[0028] Preparation of a lightweight, porous aerogel skeleton. The printed hydrogel skeleton is placed in a freeze dryer. Through a freeze-casting process, the network skeleton is micromanipulated. The sublimation of ice crystals under vacuum conditions ensures the formation of a porous structure. This microscopic porous network enhances multiple scattering of electromagnetic waves, facilitating their absorption within the network structure.
[0029] In an optional embodiment, the temperature of the freeze casting process is -40°C to -80°C and the time is 24 to 72 hours. The freezing temperature controls the ice crystal formation process and determines the pore size of the porous structure, and the freezing time ensures that the ice crystals are completely sublimated.
[0030] Preparation of high-temperature resistant porous silicon carbide-based microwave-absorbing composite materials. In-situ introduction of an interface layer into the porous network skeleton is achieved by chemical vapor infiltration.
[0031] In an optional embodiment, the interface layer is a silicon carbide interface layer or a boron nitride interface layer, preferably a silicon carbide interface layer. The introduction of the silicon carbide interface layer introduces a large number of dipoles, enhancing both interface and dipole relaxation losses. Furthermore, the silicon carbide interface uniformly wraps around the surface of the silicon carbide nanowires, jointly constructing a large number of local conductive network structures and enhancing the ohmic loss process. The combination of multiple loss mechanisms can effectively improve the composite material's absorption performance.
[0032] The reaction gas for the in-situ growth of the silicon carbide interface layer by the chemical vapor infiltration method is methyltrichlorosilane, the flow rate is 220-360 mL / min, the reaction temperature is 1000-1200°C, and the reaction time is 0.5-6 hours. The reaction gases for the in-situ growth of the boron nitride interface layer by the chemical vapor infiltration method are boron trichloride and ammonia, the flow rate of boron trichloride is 10-50 mL / min, the flow rate of ammonia is 20-100 mL / min, the reaction temperature is 700-1000°C, and the reaction time is 0.5-4 hours. If the reaction time is too short, it is difficult to form a uniform and connected interface layer, and the performance optimization effect cannot be achieved. If the reaction time is too long, the in-situ grown interface layer will fill the pores of the composite material in large quantities, which will greatly reduce the porosity of the material. The electromagnetic wave will be reflected on the surface of the material and it will be difficult for it to be incident on the material for absorption.
[0033] The following examples are further given to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention all fall within the scope of protection of the present invention. The specific process parameters and the like in the following examples are only examples within a suitable range, that is, those skilled in the art can make selections within a suitable range through the description herein, and are not limited to the specific numerical values exemplified below.
[0034] Example 1
[0035] (1) 2 g of silicon carbide nanowires and 0.5 g of hydroxypropyl methylcellulose were added to 20 mL of deionized water and ultrasonically dispersed at a power of 400 W for 1 hour to obtain a uniformly dispersed composite printing slurry. (2) The resulting composite printing slurry was transferred to the barrel of a 3D printing device. The printing needle diameter was 0.51 mm, the printing speed was set to 20 mm / s, the printing pressure was set to 0.5 MPa, the printed rectangular model size was 15 mm × 10 mm × 2 mm, and the printing spacing and layer thickness were 0.51 mm. Macroscopically periodic and repeatable hydrogel skeleton structures were constructed by 3D printing. (3) The printed hydrogel skeleton structure was placed in a freeze dryer, frozen at -60 °C for 24 hours, and vacuum dried for 48 hours to obtain a lightweight porous aerogel skeleton structure. (4) The obtained lightweight porous aerogel skeleton structure was placed in a horizontal quartz tube furnace, and methyltrichlorosilane was used as the reaction gas with a flow rate of 320 mL / min to in situ grow a silicon carbide interface on the surface of the silicon carbide nanowires. The reaction temperature was 1100 ° C and the reaction time was 1 hour to obtain a silicon carbide nanowire / silicon carbide composite material.
[0036] A circular ring structure with an inner diameter of 3 mm and an outer diameter of 7 mm was cut out from the composite material using a laser cutting machine. The dielectric constant of the composite material was measured using the coaxial cable method of a vector network analyzer, and the reflection loss value RL of the sample at different thicknesses and frequencies was calculated. The frequency band where the reflection loss value is less than -10 is the effective absorption bandwidth.
[0037] Example 2
[0038] The preparation method of the silicon carbide nanowire / silicon carbide composite material in this Example 2 refers to that in Example 1, with the only difference being that in step (4), the in-situ growth time of the silicon carbide interface is 2 hours.
[0039] Example 3
[0040] The preparation method of the silicon carbide nanowire / silicon carbide composite material in this Example 3 refers to that in Example 1, except that after step (4), the prepared silicon carbide nanowire / silicon carbide composite material is heat-treated in air at 800°C for 4 hours.
[0041] Example 4
[0042] The preparation method of the silicon carbide nanowire / silicon carbide composite material in this Example 4 refers to that in Example 1, except that after step (4), the prepared silicon carbide nanowire / silicon carbide composite material is heat-treated in air at 1000° C. for 4 hours.
[0043] Example 5
[0044] (1) 2 g of silicon carbide nanowires and 0.5 g of hydroxypropyl methylcellulose were added to 20 mL of deionized water and ultrasonically dispersed at a power of 400 W for 1 hour to obtain a uniformly dispersed composite printing slurry. (2) The resulting composite printing slurry was transferred to the barrel of a 3D printing device. The printing needle diameter was 0.51 mm, the printing speed was set to 20 mm / s, the printing pressure was set to 0.5 MPa, the printed rectangular model size was 15 mm × 10 mm × 2 mm, and the printing spacing and layer thickness were 0.51 mm. Macroscopically periodic and repeatable hydrogel skeleton structures were constructed by 3D printing. (3) The printed hydrogel skeleton structure was placed in a freeze dryer, frozen at -60 °C for 24 hours, and vacuum dried for 48 hours to obtain a lightweight porous aerogel skeleton structure. (4) The obtained lightweight porous aerogel skeleton structure was placed in a horizontal quartz tube furnace, and boron trichloride and ammonia were used as reaction gases with flow rates of 15 mL / min and 50 mL / min, respectively, to in situ grow a boron nitride interface on the surface of the silicon carbide nanowires. The reaction temperature was 800 ° C and the reaction time was 2 hours to obtain a silicon carbide nanowire / boron nitride composite material.
[0045] Comparative Example 1
[0046] The preparation method of the silicon carbide nanowire / silicon carbide composite material in Comparative Example 1 refers to that in Example 1, with the only difference being that no silicon carbide interface is in situ grown on the surface of the silicon carbide nanowire.
[0047] Comparative Example 2
[0048] The preparation method of the silicon carbide nanowire / silicon carbide composite material in this comparative example 2 refers to that in Example 1, with the only difference being that in step (4), the in-situ growth time of the silicon carbide interface is 6 hours.
[0049] Figure 1 Schematic diagram and actual image of the macroscopic periodic structure of the porous network skeleton of the silicon carbide nanowire aerogel in Example 1. As can be seen, the 3D printing slurry strips are in close contact and arrangement, preventing incident electromagnetic waves from directly penetrating the material. The self-supporting nature of the 3D printing slurry ensures the stability, repeatability, and dimensional accuracy of the composite material's macrostructure.
[0050] Figure 2 This is a surface SEM image of the porous network skeleton of the silicon carbide nanowire aerogel in Example 1. During the 3D printing process, due to shear compression, the high-aspect-ratio SiC nanowires tend to align along the printing direction. The numerous microscopic pores between the silicon carbide nanowires increase the multiple scattering of the incident electromagnetic wave.
[0051] Figure 3This is a cross-sectional SEM image of the silicon carbide nanowire / silicon carbide composite material in Example 1. It can be seen that a silicon carbide interface is in situ grown on the surface of the silicon carbide nanowire, and the interface thickness is about 167.6 nm.
[0052] Figure 4 The reflection loss values of the silicon carbide nanowire / silicon carbide composite material at different simulated thicknesses in Example 1 are shown. It can be found that when the composite material has a thickness of 2.4 mm, it exhibits excellent broadband absorption performance, with an effective absorption band (reflection loss value less than -10 dB) from 12.1 GHz to 18.0 GHz and a bandwidth of 5.9 GHz. When the composite material has a thickness of 2.7 mm, it exhibits excellent electromagnetic wave loss strength, with a minimum reflection loss value of -41.4 dB.
[0053] Figure 5 The reflection loss values of the silicon carbide nanowire / boron nitride composite material at different simulated thicknesses in Example 5 are shown. It can be found that when the composite material has a thickness of 2.2 mm, it exhibits excellent broadband absorption performance, with an effective absorption band (reflection loss value less than -10 dB) from 12.1 GHz to 17.7 GHz and a bandwidth of 5.6 GHz. When the composite material has a thickness of 2.1 mm, it exhibits excellent electromagnetic wave loss strength, with a minimum reflection loss value of -25.9 dB.
[0054] Figure 6The maximum effective absorption bandwidth variation trend of the composite materials prepared in Examples 1 to 5 and Comparative Examples 1 to 2 is shown. It can be seen that compared with Comparative Example 1, the increase in the effective absorption bandwidth of Example 1 is attributed to the introduction of the silicon carbide interface. The in-situ grown silicon carbide interface not only forms a microscopic local conductive network with the silicon carbide nanowires, increasing ohmic loss, but also introduces a large number of dipoles, enhancing polarization loss. As the in-situ growth time of the silicon carbide interface increases, the effective absorption bandwidth of Example 2 decreases compared with that of Example 1. As the in-situ growth time of the silicon carbide interface further increases, the effective absorption bandwidth of Comparative Example 2 decreases significantly compared with that of Example 1. This is attributed to the increase in the in-situ growth time of the silicon carbide interface, the decrease in the surface porosity of the composite material, the decrease in the impedance matching ability of the composite material, and the reflection of part of the incident electromagnetic wave. In Examples 3 and 4, based on Example 1, the silicon carbide nanowire / silicon carbide composite material was subjected to high-temperature air heat treatment. Compared to Example 1, the composite material showed only a slight decrease in effective absorption bandwidth after high-temperature heat treatment, and maintained an effective absorption bandwidth of 5.4 GHz after high-temperature heat treatment at 1000°C, demonstrating good thermal stability and high-temperature absorption performance. Compared to Example 1, the composite material in Example 5, which incorporated an in-situ boron nitride interface, showed less improvement in absorption performance. This is due to boron nitride's low dielectric constant, making it difficult to participate in the formation of microscopic local conductive networks, resulting in weak ohmic loss capacity. However, compared to Comparative Example 1, the performance of Example 5 was significantly improved, indicating that the polarization loss and relaxation loss introduced by the boron nitride interface can still optimize the material's electromagnetic wave absorption performance.
Claims
1. A high temperature resistant porous silicon carbide based microwave absorbing composite material, characterized in that: The high-temperature resistant porous silicon carbide-based absorbing composite material includes: a lightweight porous network skeleton structure formed by one-dimensional silicon carbide nanowires oriented and arranged parallel to the 3D printing direction, and an interface layer in situ grown on the surface of the silicon carbide nanowires, wherein the interface layer is uniformly coated on the surface of the silicon carbide nanowires; the interface layer is a silicon carbide interface layer or a boron nitride interface layer.
2. The high temperature resistant porous silicon carbide based microwave absorbing composite material according to claim 1, characterized in that: The high-temperature resistant porous silicon carbide-based absorbing composite material has a macroscopic periodic structure and a microscopic porous structure; wherein the macroscopic periodic structure refers to a rectangular grid structure in which 3D-printed strips are arranged in parallel within a layer and orthogonally stacked between printed layers; the microscopic porous network structure is a porous network structure composed of silicon carbide nanowires, the interface layer and the pores between the nanowires.
3. The high temperature resistant porous silicon carbide based wave absorbing composite material according to claim 1 or 2, characterized in that: The silicon carbide nanowires have a diameter of 100 to 500 nm and a length of 50 to 100 μm.
4. The high temperature resistant porous silicon carbide based microwave absorbing composite material according to any one of claims 1 to 3, characterized in that: The thickness of the silicon carbide interface layer is 167.6 to 400.7 nm; the silicon carbide nanowires and the silicon carbide interface layer form a local conductive network structure; The thickness of the boron nitride interface layer is 145.3-353.6 nm.
5. The high temperature resistant porous silicon carbide based microwave absorbing composite material according to any one of claims 1 to 4, characterized in that: When the interface layer is a silicon carbide interface layer, the porosity of the high-temperature resistant porous silicon carbide-based wave-absorbing composite material is 64.1% to 92.5%; When the interface layer is a boron nitride interface layer, the porosity of the high-temperature resistant porous silicon carbide-based wave-absorbing composite material is 70.5% to 93.4%.
6. A method for preparing a high temperature resistant porous silicon carbide-based microwave absorbing composite material according to any one of claims 1 to 5, characterized in that: include: (1) uniformly dispersing silicon carbide nanowires and hydroxypropyl methylcellulose in a solvent to obtain a composite printing slurry; (2) obtaining a hydrogel skeleton structure by 3D printing the composite printing slurry; (3) A lightweight porous aerogel skeleton structure is obtained by freeze drying and vacuum drying; (4) Chemical vapor infiltration is used to in situ grow an interface layer in the obtained lightweight porous aerogel skeleton structure to obtain a high-temperature resistant porous silicon carbide-based absorbing composite material.
7. The preparation method according to claim 6, characterized in that In step (1), the mass ratio of the silicon carbide nanowires to hydroxypropyl methylcellulose is 3:2 to 9:1, preferably 4:1; and the concentration of the silicon carbide nanowires in the composite printing slurry is 0.5 to 40 vol%.
8. The preparation method according to claim 6 or 7, characterized in that In step (2), the diameter of the 3D printing needle is 0.4 to 0.6 mm, the needle movement speed is 10 to 30 mm / s, and the printing pressure is 0.3 to 0.6 MPa.
9. The preparation method according to any one of claims 6 to 8, characterized in that In step (3), the freeze-drying temperature is -40°C to -80°C, and the time is 12 to 36 hours; the vacuum drying time is 24 to 72 hours.
10. The preparation method according to any one of claims 6 to 9, characterized in that: In step (4), the reaction gas for in-situ growth of the silicon carbide interface layer by chemical vapor infiltration is methyltrichlorosilane, the flow rate of the reaction gas is 220 to 360 mL / min, the reaction temperature is 1000 to 1200° C., and the reaction time is 0.5 to 5 hours; The reaction gases for in-situ growth of the boron nitride interface layer by the chemical vapor infiltration method are boron trichloride and ammonia, the flow rate of boron trichloride is 10-50 mL / min, the flow rate of ammonia is 20-100 mL / min, the reaction temperature is 700-1000° C., and the reaction time is 0.5-4 hours.