A composite aerogel with tunable effective electromagnetic wave absorption band, its preparation method, and its applications.

Abstract

This application relates to the field of electromagnetic wave absorbing materials technology, and discloses a composite aerogel that combines thermal conductivity and tunable effective electromagnetic wave absorption band, its preparation method, and its applications. The composite aerogel consists of composite nanosheets, magnetic nanorods, and a binder; the composite nanosheets form a continuously oriented layered structure through the binder, and the magnetic nanorods are loaded onto the composite nanosheets; the composite nanosheets are composed of Ti3C2T... x The composite aerogel is composed of MXene nanosheets and reduced graphene oxide through hydrogen bonding; the magnetic nanorods are iron oxide nanorods; and the binder is a one-dimensional fiber. The unique layered oriented arrangement of this composite aerogel improves the impedance matching at the aerogel / air interface, reduces electromagnetic wave surface reflection, and allows electromagnetic waves entering the aerogel to be gradually converted into heat energy through multiple reflections and absorption processes. Furthermore, its layered oriented arrangement facilitates directional heat conduction. Through the synergistic effect of its structure and materials, it possesses both electromagnetic wave absorption and high thermal conductivity.

Description

Technical Field

[0001] This application relates to the field of electromagnetic wave absorbing materials technology, and in particular to a composite aerogel that combines thermal conductivity and tunable effective electromagnetic wave absorption band, its preparation method, and its application. Background Technology

[0002] Electromagnetic wave absorbing materials are materials that can convert incident electromagnetic wave energy into heat or other forms of energy and significantly reduce reflectivity. They are widely used in military stealth, 5G communications, medical equipment, electromagnetic shielding of electronic equipment, and electromagnetic protection for personnel. For specific civilian and military applications, electromagnetic wave absorbing materials need to meet requirements such as a wide effective absorption bandwidth, strong absorption, and selectivity for specific frequency bands. At the same time, they also need to possess a series of new requirements, such as high thermal conductivity, low density, good mechanical elasticity, and thermal stability.

[0003] Electromagnetic wave absorbing aerogels possess advantages such as ultra-lightweight, wide-bandwidth high efficiency, multifunctional integration, and customizable structure, making them one of the most promising next-generation microwave absorbing materials. However, most current electromagnetic wave absorbing aerogels operate primarily in the Ku band (12-18 GHz), exhibiting poor compatibility in lower frequency bands such as the X-band (8-12 GHz) and C-band (4-8 GHz). Furthermore, few existing electromagnetic wave absorbing aerogels simultaneously meet the minimum reflection loss (RLmin) and maximum absorption bandwidth (EAB) at the same thickness. In addition, due to their porous structure, existing electromagnetic wave absorbing aerogels have low intrinsic thermal conductivity, resulting in insufficient heat dissipation from absorbed electromagnetic waves, impacting the efficiency and lifespan of electronic devices. Moreover, existing electromagnetic wave absorbing aerogels suffer from poor mechanical elasticity, making it difficult to return to their original shape after external forces. These shortcomings limit the widespread application of electromagnetic wave absorbing aerogels.

[0004] Therefore, there is an urgent need to develop a new electromagnetic wave absorbing material to solve the problems of poor high-frequency-low-frequency absorption compatibility, difficulty in achieving the lowest reflection loss and maximum absorption bandwidth at the same thickness, and poor thermal conductivity, while also possessing good mechanical properties, thereby broadening the application range of the material. Summary of the Invention

[0005] This application provides a composite aerogel with adjustable effective electromagnetic wave absorption bands, its preparation method, and its application. It aims to solve the technical problems of poor high-frequency-low-frequency absorption compatibility, difficulty in achieving the lowest reflection loss and maximum absorption bandwidth at the same thickness, and poor thermal conductivity of existing electromagnetic wave absorbing aerogels.

[0006] To achieve the above objectives, the present application adopts the following technical solution.

[0007] In a first aspect, this application provides a composite aerogel that combines thermal conductivity and tunable electromagnetic wave absorption bands, comprising composite nanosheets, magnetic nanorods, and a binder; wherein the composite nanosheets are formed into a continuously oriented sheet structure by the binder, and the magnetic nanorods are loaded on the composite nanosheets; The composite nanosheets are made of Ti3C2T x MXene nanosheets are composed of reduced graphene oxide and MXene through hydrogen bonding. The magnetic nanorods are iron oxide nanorods; The binder is a one-dimensional fiber.

[0008] Preferably, the composite aerogel comprises, by mass percentage, 60-80 wt% composite nanosheets, 10-30 wt% magnetic nanorods, and 1-10 wt% binder.

[0009] A second aspect of this application provides a method for preparing the aforementioned composite aerogel, comprising: S1, FeOOH hydroxyl oxide nanorods were prepared by hydrothermal method and then surface modified to carry a positive charge; S2, Ti3C2T x MXene nanosheet dispersion and graphene oxide nanosheet dispersion are mixed to obtain MXene / GO mixed dispersion; The hydroxyl iron oxide nanorods were added to the MXene / GO mixed dispersion and shaken to adsorb, thus obtaining the MXene / GO / FeOOH composite dispersion. S3, add the binder to the MXene / GO / FeOOH composite dispersion, homogenize it, and then freeze and freeze-dry it to obtain MXene / GO / FeOOH aerogel; S4, the MXene / GO / FeOOH aerogel is thermally reduced to obtain MXene / RGO / Fe3O4 nanorod composite aerogel, which is a composite aerogel with both thermal conductivity and tunable electromagnetic wave absorption band.

[0010] Preferably, step S1 includes: The FeCl3 aqueous solution was kept at 85-95℃ for 16-24h under sealed conditions. After washing, the solid phase was collected and dried to obtain FeOOH nanorods. The FeOOH nanorods were added to an aqueous solution of hexadecyltrimethylammonium bromide and ultrasonically vibrated to make their surface positively charged.

[0011] Preferably, the binder comprises at least one of poly(p-phenylene-2,6-benzobisoxazole) nanofibers, nanoaramid fibers, or polyimide.

[0012] Preferably, the Ti3C2T x The thickness of MXene nanosheets is 1~10 nm, and the sheet size is 0.5~10 µm; The thickness of the graphene oxide nanosheets is 1~5nm, and the sheet size is 5~50µm; The FeOOH nanorods have a length of 0.5~2µm and a diameter of 0.1~0.2µm.

[0013] Preferably, the Ti3C2T x The mass ratio of MXene nanosheets, graphene oxide nanosheets, and FeOOH nanorods is (5~50):(5~50):(5~30); The mass ratio of the binder to the MXene / GO / FeOOH composite nanosheets is (1~10):(90~99).

[0014] Preferably, the directional freezing described in S3 specifically includes: The MXene / GO / FeOOH composite dispersion was added to a mold, and the mold was placed on a copper bridge with liquid nitrogen at the bottom for gradient freezing.

[0015] Preferably, the thermal reduction in S4 specifically refers to: Under a hydrogen atmosphere, the MXene / GO / FeOOH aerogel was heated to 350~400℃ and held for 2~4 hours.

[0016] A third aspect of this application provides the application of the above-described composite aerogel or the composite aerogel prepared by the above-described preparation method in 5G base station devices and military equipment.

[0017] Compared with the prior art, the beneficial effects of this application are as follows: The directional composite aerogel of this application is composed of composite nanosheets, magnetic nanorods, and a binding agent. The composite nanosheets are made of Ti3C2T x MXene and reduced graphene oxide are composited via interfacial hydrogen bonding, forming a continuously oriented sheet structure through a linker. This unique structure creates a directional thermal pathway and allows for the regulation of electromagnetic wave absorption performance through its tunable dielectric properties, such as interfacial polarization and dipole polarization. The magnetic nanorods are tunable aspect ratio tetroxide nanorods loaded on the composite nanosheets. Their anisotropy effectively modulates the electromagnetic wave absorption towards lower frequencies. The abundant interfacial polarization and space charge polarization losses formed with the composite nanosheets help improve impedance matching and broaden the electromagnetic wave absorption bandwidth. The linker enhances the performance of Ti3C2T. x The connection between MXene and reduced graphene nanosheets improves the mechanical elasticity and thermal conductivity of the aerogel.

[0018] The unique layered oriented arrangement structure of the composite aerogel in this application further improves the impedance matching at the aerogel / air interface, reduces electromagnetic wave surface reflection, and gradually converts electromagnetic waves entering the aerogel into heat energy through multiple reflections and absorption processes. Furthermore, its layered oriented arrangement structure facilitates directional heat conduction. Through the synergistic effect of structure and materials, this multi-scale aerogel, designed from micro to macro levels, possesses both electromagnetic wave absorption and high thermal conductivity. The composite aerogel of this application achieves a thermal conductivity of up to 1.0 W / m. . K has an effective electromagnetic wave absorption bandwidth covering the Ku (12-18 GHz), X (8-12 GHz), and C (4-8 GHz) bands, and is tunable within these bands; its density is only 9~10 mg / cm³. 3 Under pressure of 6~10 kPa and 100 cycles of compression, the deformation exceeds 50%, and under the maximum pressure of 22 kPa, the deformation is 70%. After the external force is removed, it can return to its original shape, exhibiting good mechanical elasticity and having wide practical application value. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A cross-sectional scanning electron microscope image of the composite aerogel prepared in Example 1; Figure 2 The measured electromagnetic wave reflection loss of the composite aerogel prepared in Example 1 is shown in the figure. Figure 3 The above is a measured image of the electromagnetic wave reflection loss of the composite aerogel prepared in Example 2. Figure 4 The image shows the measured electromagnetic wave reflection loss of the composite aerogel prepared in Example 3. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0022] In the following description of this embodiment, the terms "including", "comprising", "having", and "containing" are all open-ended terms, meaning that they include but are not limited to.

[0023] In the following description of this embodiment, the term "and / or" is used to describe the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, B existing alone, and A and B existing simultaneously. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0024] In the following description of this embodiment, the term "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0025] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms "a" and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0026] Those skilled in the art should understand that, in the following description of the embodiments of this application, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0027] Those skilled in the art will understand that the numerical ranges in the embodiments of this application should be understood as each intermediate value between the upper and lower limits of the specifically disclosed range. Each smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this application. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0028] Unless otherwise stated, the technical / scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. While this application describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this application. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0029] This application provides a composite aerogel with adjustable thermal conductivity and effective electromagnetic wave absorption band, which is composed of composite nanosheets, magnetic nanorods and a binder; the composite nanosheets are formed into a continuously oriented sheet structure by the binder, and the magnetic nanorods are loaded on the composite nanosheets.

[0030] The composite nanosheets are made of Ti3C2T x The MXene nanosheets are composed of reduced graphene oxide and MXene through hydrogen bonding; the magnetic nanorods are iron oxide nanorods; and the binder is a one-dimensional fiber.

[0031] The composite aerogel comprises, by weight percentage, 60% to 80 wt% composite nanosheets, 10% to 30% wt% magnetic nanorods, and 1% to 10 wt% binder.

[0032] In the composite aerogel of this application, MXene has customizable physicochemical properties and abundant surface functional groups (such as -OH, -F), which can enhance interfacial polarization, improve electromagnetic wave absorption, and also have high electrical and thermal conductivity. RGO can be used as a basic building block for constructing 3D materials with extremely low density. RGO interacts with MXene to construct a layered oriented structure, enhances mechanical properties, can adjust the impedance matching of MXene materials, reduce the density of absorbing materials, and can also improve the chemical stability of MXenes.

[0033] In the composite aerogel of this application, Fe3O4 nanorods are loaded onto composite nanosheets. The anisotropy of the nanorods, with adjustable aspect ratio, can effectively modulate the electromagnetic wave absorption towards lower frequencies. The abundant interfacial polarization and space charge polarization loss formed with the composite nanosheets help improve impedance matching and broaden the electromagnetic wave absorption bandwidth. The linker can enhance the absorption of Ti3C2T... x The connection between MXene and reduced graphene nanosheets improves the mechanical elasticity and thermal conductivity of the aerogel.

[0034] The composite aerogel of this application has a layered, oriented structure with interlayer spacing of 15–35 micrometers. This unique structure forms a directional heat conduction pathway and allows for the adjustment of electromagnetic wave absorption performance through its tunable dielectric properties, such as interfacial polarization and dipole polarization. This structure improves the impedance matching at the aerogel-air interface, reduces electromagnetic wave surface reflection, and allows electromagnetic waves entering the aerogel to be gradually converted into heat energy through multiple reflections and absorption processes. The layered, oriented structure further facilitates directional heat conduction. Through the synergistic effect of structure and materials, this multi-scale aerogel, designed from micro to macro levels, possesses both electromagnetic wave absorption and high thermal conductivity.

[0035] A second aspect of this application provides a method for preparing the aforementioned composite aerogel, comprising: S1, FeOOH hydroxyl oxide nanorods were prepared by hydrothermal method and then surface modified to carry a positive charge; Specifically, an aqueous solution of FeCl3 is kept at 85–95°C for 16–24 h under sealed conditions. After washing, the solid phase is collected and dried to obtain FeOOH nanorods. The preferred concentration of FeCl3 is 30–120 mM. The FeOOH nanorods prepared in this step have a length of 0.5–2 µm and a diameter of 0.1–0.2 µm.

[0036] The FeOOH nanorods were added to an aqueous solution of hexadecyltrimethylammonium bromide (CTAB) and ultrasonically vibrated to thoroughly mix the CTAB and FeOOH nanorods, thereby giving the FeOOH nanorods a positive charge on their surface. The concentration of the hexadecyltrimethylammonium bromide aqueous solution was preferably 2-10 mg / ml.

[0037] S2, Ti3C2T x MXene nanosheet dispersion and graphene oxide nanosheet dispersion were mixed and vortexed for 3-5 min to obtain MXene / GO mixed dispersion; The hydroxyl iron oxide nanorods were added to the MXene / GO mixed dispersion and shaken to adsorb, thus obtaining the MXene / GO / FeOOH composite dispersion. In this application, the Ti3C2T x MXene nanosheet dispersion is Ti3C2T x Aqueous dispersions of MXene nanosheets, preferably Ti3C2T x The thickness of MXene nanosheets is 1~10 nm, and the sheet size is 0.5~10 µm; The graphene oxide nanosheet dispersion is an aqueous dispersion of graphene oxide nanosheets, preferably with a thickness of 1~5 nm and a sheet size of 5~50 µm.

[0038] The Ti3C2T x The preferred mass ratio of MXene nanosheets, graphene oxide nanosheets, and FeOOH nanorods is (5~50):(5~50):(5~30).

[0039] S3, add the binder to the MXene / GO / FeOOH composite dispersion, homogenize it, and then freeze and freeze-dry it to obtain MXene / GO / FeOOH aerogel; In this application, the binder is a one-dimensional fiber, which may be selected from at least one of poly(p-phenylene-2,6-benzobisoxazole) nanofibers, nano-aramid fibers, or polyimide. Preferably, the mass ratio of the binder to the MXene / GO / FeOOH composite nanosheets is (1~10):(90~99).

[0040] The homogenization process is performed using a homogenizer or ultrasonic treatment, preferably by stirring in a homogenizer for 3-5 minutes.

[0041] The directional freezing involves gradient freezing of the composite dispersion from bottom to top. Specifically, the MXene / GO / FeOOH composite dispersion is added to a mold, and the mold is placed on a copper bridge immersed in liquid nitrogen at the bottom for gradient freezing; the copper bridge is used to transfer heat.

[0042] After the directional freezing is completed, the gel is freeze-dried to obtain MXene / GO / FeOOH aerogel.

[0043] S4, the MXene / GO / FeOOH aerogel is thermally reduced to obtain MXene / RGO / Fe3O4 nanorod composite aerogel, which is a composite aerogel with both thermal conductivity and tunable electromagnetic wave absorption band.

[0044] The thermal reduction specifically involves heating the MXene / GO / FeOOH aerogel to 350-400℃ and holding it at that temperature for 2-4 hours under a hydrogen atmosphere to carry out a reduction reaction, thereby obtaining Ti3C2T with a directional structure. x MXene / RGO / Fe3O4 nanorod aerogel.

[0045] The unique layered oriented arrangement structure of the composite aerogel in this application further improves the impedance matching of the aerogel / air interface, reduces electromagnetic wave surface reflection, and the electromagnetic waves entering the aerogel are gradually converted into heat energy in the process of multiple reflection and absorption. Moreover, its layered oriented arrangement structure is conducive to directional heat conduction. Under the synergistic effect of structure and material, this aerogel with multi-scale design from micro to macro has both electromagnetic wave absorption and high thermal conductivity.

[0046] The composite aerogel of this application has a thermal conductivity of up to 1.0 W / m. . K has an effective electromagnetic wave absorption bandwidth covering the Ku (12-18 GHz), X (8-12 GHz), and C (4-8 GHz) bands, and is tunable within these bands. Its density is only 9~10 mg / cm³. 3 Under pressures of 6-10 kPa and 100 cycles of compression, the deformation exceeds 50%, and under a maximum pressure of 22 kPa, the deformation reaches 70%. It can return to its original shape after the external force is removed, exhibiting excellent mechanical elasticity. It has broad practical application value and can be used in 5G base station devices and military equipment.

[0047] The present application will be further described below through specific embodiments.

[0048] In the embodiments of this application, Ti3C2T is used.x The MXene nanosheets have a thickness of 1~10nm and a sheet size of 0.5~10µm; the GO nanosheets used have a thickness of 1~5nm and a sheet size of 5~50µm.

[0049] Example 1 This embodiment provides a method for preparing composite aerogel, including: S1. 400 ml of 100 mM FeCl3·6H2O aqueous solution was reacted at 87 °C for 18 h under sealed conditions. After washing with deionized water, centrifuging and screening, and vacuum drying at 60 °C, FeOOH nanorods with a length of 0.8~1.2 µm and a diameter of 0.15~0.2 µm were obtained.

[0050] S2, take 1 mL of Ti3C2T with a concentration of 10 mg / mL. x An aqueous dispersion of MXene was mixed with 4 mL of an aqueous dispersion of GO at a concentration of 10 mg / mL using a homogenizer to obtain Ti3C2T. x MXene / GO nanosheet dispersion; 10 mg of FeOOH nanorods prepared by S1 were added to a hexadecyltrimethylammonium bromide (CTAB) aqueous solution and ultrasonically vibrated for surface modification; then they were reacted with Ti3C2T x MXene / GO nanosheet dispersion was mixed and adsorbed by shaking to obtain Ti3C2T. x MXene / GO / FeOOH composite nanosheet dispersion.

[0051] S3, 1.2g of poly(p-phenylene-2,6-benzobisoxazole) nanofibers and 400 μl of polyamic acid were added to Ti3C2T x The MXene / GO / FeOOH composite nanosheets were mixed in a homogenizer for 5 minutes. The mixture was then poured into a silicone mold and placed on a copper bridge connected to liquid nitrogen at the bottom for directional freezing. After freeze-drying, Ti3C2T with a directional structure was obtained. x MXene / GO / FeOOH aerogel.

[0052] S4, Ti3C2T x MXene / GO / FeOOH aerogel was heated to 380 °C and held for 3 h in a hydrogen atmosphere to obtain Ti3C2T with a directional structure. x MXene / RGO / Fe3O4 nanorod aerogel.

[0053] Example 2 This embodiment provides a method for preparing composite aerogel, including: S1. 400 ml of 60 mM FeCl3·6H2O aqueous solution was reacted at 87 °C for 20 h under sealed conditions. After washing with deionized water, centrifuging and screening, and vacuum drying at 60 °C, FeOOH nanorods with a length of 0.6~0.9 µm and a diameter of 0.1~0.15 µm were obtained.

[0054] S2, take 2 mL of Ti3C2T with a concentration of 10 mg / mL. x MXene aqueous dispersion and 3 mL of GO aqueous dispersion with a concentration of 10 mg / mL were mixed using a homogenizer to obtain Ti3C2T. x MXene / GO nanosheet dispersion; 10 mg of FeOOH nanorods prepared by S1 were added to a hexadecyltrimethylammonium bromide (CTAB) aqueous solution and ultrasonically vibrated to perform surface modification; then, they were combined with the Ti3C2T... x MXene / GO nanosheet dispersion was mixed and adsorbed by shaking to obtain Ti3C2T. x MXene / GO / FeOOH composite nanosheet dispersion.

[0055] S3, 1.2g of aramid nanofibers and 200 μl of polyamic acid were added to Ti3C2T x The MXene / GO / FeOOH composite nanosheets were mixed in a homogenizer for 5 minutes. The mixture was then poured into a silicone mold and placed on a copper bridge connected to liquid nitrogen at the bottom for directional freezing. After freeze-drying, Ti3C2T with a directional structure was obtained. x MXene / GO / FeOOH aerogel.

[0056] S4, Ti3C2T x MXene / GO / FeOOH aerogel was heated to 380 °C and held for 3 h in a hydrogen atmosphere to obtain Ti3C2T with a directional structure. x MXene / RGO / Fe3O4 nanorod aerogel.

[0057] Example 3 This embodiment provides a method for preparing composite aerogel, including: S1. 400 ml of 40 mM FeCl3·6H2O aqueous solution was reacted at 87 °C for 20 h under sealed conditions. After washing with deionized water, centrifuging and screening, and vacuum drying at 60 °C, FeOOH nanorods with a length of 0.6~0.9 µm and a diameter of 0.1~0.15 µm were obtained.

[0058] S2, take 3 mL of Ti3C2T with a concentration of 10 mg / mL. xMXene aqueous dispersion and 2 mL of GO aqueous dispersion with a concentration of 10 mg / mL were mixed using a homogenizer to obtain Ti3C2T. x MXene / GO nanosheet dispersion; 20 mg of FeOOH nanorods prepared by S1 were added to a hexadecyltrimethylammonium bromide (CTAB) aqueous solution and ultrasonically vibrated for surface modification; then they were reacted with Ti3C2T x MXene / GO nanosheet dispersion was mixed and adsorbed by shaking to obtain Ti3C2T. x MXene / GO / FeOOH composite nanosheet dispersion.

[0059] S3, 1.2g of aramid nanofibers and 400 μl of polyamic acid were added to Ti3C2T x The MXene / GO / FeOOH composite nanosheets were mixed in a homogenizer for 5 minutes. The mixture was then poured into a silicone mold and placed on a copper bridge connected to liquid nitrogen at the bottom for directional freezing. After freeze-drying, Ti3C2T with a directional structure was obtained. x MXene / GO / FeOOH aerogel.

[0060] S4, Ti3C2T x MXene / GO / FeOOH aerogel was heated to 400 °C and held for 2 h in a hydrogen atmosphere to obtain Ti3C2T with a directional structure. x MXene / RGO / Fe3O4 nanorod aerogel.

[0061] Example 4 This embodiment provides a method for preparing composite aerogel, including: S1. 400 ml of 40 mM FeCl3·6H2O aqueous solution was reacted at 87 °C for 20 h under sealed conditions. After washing with deionized water, centrifuging and screening, and vacuum drying at 60 °C, FeOOH nanorods with a length of 0.8~1.2 µm and a diameter of 0.15~0.2 µm were obtained.

[0062] S2, take 2.5 mL of Ti3C2T with a concentration of 10 mg / mL. x An aqueous dispersion of MXene was mixed with 2.5 mL of an aqueous dispersion of GO at a concentration of 10 mg / mL using a homogenizer to obtain Ti3C2T. x MXene / GO nanosheet dispersion; 30 mg of FeOOH nanorods prepared by S1 were added to a hexadecyltrimethylammonium bromide (CTAB) aqueous solution and ultrasonically vibrated for surface modification; then they were reacted with Ti3C2T xMXene / GO nanosheet dispersion was mixed and adsorbed by shaking to obtain Ti3C2T. x MXene / GO / FeOOH composite nanosheet dispersion.

[0063] S3, add 1 mL of polyamic acid to Ti3C2T x The MXene / GO / FeOOH composite nanosheets were mixed in a homogenizer for 5 minutes. The mixture was then poured into a silicone mold and placed on a copper bridge connected to liquid nitrogen at the bottom for directional freezing. After freeze-drying, Ti3C2T with a directional structure was obtained. x MXene / GO / FeOOH aerogel.

[0064] S4, Ti3C2T x MXene / GO / FeOOH aerogel was heated to 380 °C and held for 3 h in a hydrogen atmosphere to obtain Ti3C2T with a directional structure. x MXene / RGO / Fe3O4 nanorod aerogel.

[0065] The morphology and performance of the composite aerogel prepared in this application were analyzed and tested, as follows: Ti3C2T prepared in Example 1 x Cross-sectional scanning electron microscope image of MXene / RGO / Fe3O4 nanorod aerogel as shown below Figure 1 As shown in the figure, the internal lamellar spacing of the composite aerogel material is about 25µm, exhibiting a directional arrangement structure. This structure reduces the strong reflection of incident waves on the surface, which is beneficial for impedance matching, extends the effective propagation path of waves within the material, facilitates multiple reflections and dissipation of electromagnetic waves within the material, and also enhances the longitudinal thermal conductivity of the aerogel.

[0066] Ti3C2T prepared in Examples 1-4 x The thermal conductivity data of MXene / RGO / Fe3O4 nanorod aerogels are shown in Table 1: Table 1 Ti3C2T x Thermal conductivity of MXene / RGO / Fe3O4 nanorod aerogel

[0067] As shown in Table 1, the Ti3C2T prepared in this application x MXene / RGO / Fe3O4 nanorod aerogels all exhibit excellent thermal conductivity, reaching up to 1 W / m. . K.

[0068] Figure 2 Ti3C2T prepared in Example 1 xMeasured electromagnetic wave reflection loss of MXene / RGO / Fe3O4 nanorod aerogel. From... Figure 2 It is known that it has a broadband strong absorption effect in the C-band (4-8 GHz), with an effective absorption bandwidth (EAB) of 3.4 GHz and the lowest reflection loss (RL). min The value is -49 dB.

[0069] Figure 3 Ti3C2T prepared in Example 2 x Measured electromagnetic wave reflection loss of MXene / RGO / Fe3O4 nanorod aerogel. From... Figure 3 It is known that it exhibits broadband strong absorption in the X-band and part of the Ku-band (8-13.4 GHz), with an effective absorption bandwidth (EAB) of 5.4 GHz and the lowest reflection loss (RL). min The value is -54 dB.

[0070] Figure 4 Ti3C2T prepared in Example 3 x Measured electromagnetic wave reflection loss of MXene / RGO / Fe3O4 nanorod aerogel. From... Figure 4 It can be seen that it has broadband strong absorption in the Ku band (12-17 GHz), with an effective absorption bandwidth (EAB) of 5 GHz and the lowest reflection loss (RL). min The value is -47 dB.

[0071] Ti3C2T prepared in Example 4 x MXene / RGO / Fe3O4 nanorod aerogels exhibit an effective absorption bandwidth (EAB) of 4.5 GHz in part of the C-band and X-band (7.5-12 GHz) and the lowest reflection loss (RL). min The value is -50 dB.

[0072] The test results show that the Ti3C2T of this application... x The MXene / RGO / Fe3O4 nanorod aerogel exhibits an effective electromagnetic wave absorption bandwidth covering the Ku (12-18 GHz), X (8-12 GHz), and C (4-8 GHz) bands. Depending on specific requirements, this application can utilize Ti3C2T... x The mass ratio of MXene nanosheets, GO nanosheets, and FeOOH nanorods was adjusted to modify the composition of Ti3C2T. x The electromagnetic wave absorption band of MXene / RGO / Fe3O4 nanorod aerogel can be tuned. It is particularly suitable for electromagnetic wave absorption in military equipment stealth and 5G base station components, reducing radiation and interference and improving device efficiency.

[0073] Although this application has been described in detail in this specification with general descriptions and specific embodiments, some modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, such modifications or improvements made without departing from the spirit of this application are all within the scope of protection claimed in this application.

Claims

1. A composite aerogel with adjustable effective electromagnetic wave absorption band, characterized in that, It is composed of composite nanosheets, magnetic nanorods and a binder; the composite nanosheets are formed into a continuously oriented sheet structure by the binder, and the magnetic nanorods are loaded on the composite nanosheets; The composite nanosheets are made of Ti3C2T x MXene nanosheets are composed of reduced graphene oxide and MXene through hydrogen bonding. The magnetic nanorods are iron oxide nanorods; The binder is a one-dimensional fiber.

2. The composite aerogel according to claim 1, characterized in that, The composite aerogel comprises, by weight percentage, 60-80 wt% composite nanosheets, 10-30 wt% magnetic nanorods, and 1-10 wt% binder.

3. The method for preparing the composite aerogel according to claim 1, characterized in that, include: S1, FeOOH hydroxyl oxide nanorods were prepared by hydrothermal method and then surface modified to carry a positive charge; S2, Ti3C2T x MXene nanosheet dispersion and graphene oxide nanosheet dispersion are mixed to obtain MXene / GO mixed dispersion; The hydroxyl iron oxide nanorods were added to the MXene / GO mixed dispersion and shaken to adsorb, thus obtaining the MXene / GO / FeOOH composite dispersion. S3, add the binder to the MXene / GO / FeOOH composite dispersion, homogenize it, and then freeze and freeze-dry it to obtain MXene / GO / FeOOH aerogel; S4, the MXene / GO / FeOOH aerogel is thermally reduced to obtain MXene / RGO / Fe3O4 nanorod composite aerogel, which is a composite aerogel with both thermal conductivity and tunable electromagnetic wave absorption band.

4. The preparation method according to claim 3, characterized in that, Step S1 includes: The FeCl3 aqueous solution was kept at 85-95℃ for 16-24h under sealed conditions. After washing, the solid phase was collected and dried to obtain FeOOH nanorods. The FeOOH nanorods were added to an aqueous solution of hexadecyltrimethylammonium bromide and ultrasonically vibrated to make their surface positively charged.

5. The preparation method according to claim 3, characterized in that, The binder includes at least one of poly(p-phenylene-2,6-benzobisoxazole) nanofibers, nano-aramid fibers, or polyimide.

6. The preparation method according to claim 3, characterized in that, The Ti3C2T x The thickness of MXene nanosheets is 1~10 nm, and the sheet size is 0.5~10 µm; The thickness of the graphene oxide nanosheets is 1~5nm, and the sheet size is 5~50µm; The FeOOH nanorods have a length of 0.5~2µm and a diameter of 0.1~0.2µm.

7. The preparation method according to claim 3, characterized in that, The Ti3C2T x The mass ratio of MXene nanosheets, graphene oxide nanosheets, and FeOOH nanorods is (5~50):(5~50):(5~30); The mass ratio of the binder to the MXene / GO / FeOOH composite nanosheets is (1~10):(90~99).

8. The preparation method according to claim 3, characterized in that, The directional freezing described in S3 specifically includes: The MXene / GO / FeOOH composite dispersion was added to a mold, and the mold was placed on a copper bridge with liquid nitrogen at the bottom for gradient freezing.

9. The preparation method according to claim 3, characterized in that, The thermal reduction described in S4 specifically refers to: Under a hydrogen atmosphere, the MXene / GO / FeOOH aerogel was heated to 350~400℃ and held for 2~4 hours.

10. The application of the composite aerogel according to claims 1-2 or the composite aerogel prepared by the preparation method according to any one of claims 3-9 in 5G base station devices and military equipment.

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