A microwave absorbing material, its preparation method and application

Abstract

This invention belongs to the field of electromagnetic wave absorbing materials technology, specifically relating to an absorbing material, its preparation method, and its application. This invention uses multi-walled carbon nanotubes (MWCNTs), potassium permanganate (KMnO4), and divalent manganese as raw materials, based on Mn... 2+ With MnO4 ‑ The redox reaction between the two components allows for in-situ uniform loading of MnO2 nanoparticles onto the MWCNT surface through simple stirring in a room-temperature liquid environment, resulting in microwave absorption performance superior to most similar absorbing materials. Compared to traditional methods for preparing absorbing materials, the technical route of this invention offers significant advantages, including simple preparation process, no pollutant emissions, energy-saving and environmentally friendly process, adjustable and controllable material structure, excellent microwave absorption performance, and scalability. This method effectively overcomes the technical limitations in the preparation of absorbing materials, providing a scalable new paradigm for the green and large-scale production of high-performance absorbing materials.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave absorbing materials technology, and particularly relates to a wave absorbing material, its preparation method and application. Background Technology

[0002] Electromagnetic waves, as the core carrier of modern communication, navigation, radar, and medical imaging, have driven technological innovation while also creating control requirements in specific scenarios. For example, precision electronic equipment needs to reduce signal interference caused by electromagnetic wave reflection; in the field of stealth technology, it is necessary to reduce the intensity of radar wave reflection from targets. These scenarios all rely on high-performance electromagnetic wave absorbing (EMWA) materials, which achieve efficient attenuation by converting electromagnetic waves into forms such as heat energy.

[0003] While traditional microwave absorbing materials (such as ferrites and magnetic metals) can achieve a certain degree of attenuation, they generally suffer from problems such as high density, large matching thickness (>1.5 mm), and high filler content (>15%), making it difficult to meet the urgent needs of 5G communications, aerospace, and other fields for "lightweight, thin, broadband, and strong absorption" materials. Therefore, developing high-efficiency microwave absorbing materials with low filler content (<15%) and ultra-thin (<1.5 mm) characteristics remains a key challenge that urgently needs to be overcome in this field.

[0004] Currently, traditional methods for preparing microwave absorbing materials mainly include hydrothermal-calcination, template methods, and sol-gel methods. These methods generally suffer from problems such as complex preparation processes, high energy consumption, long reaction times, and high solvent toxicity, which severely restrict the large-scale production and application of microwave absorbing materials. Therefore, there is an urgent need for a microwave absorbing material, its preparation method, and its application to solve the above problems. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this invention provides a microwave absorbing material, its preparation method, and its applications. This invention offers advantages such as excellent microwave absorption performance, simple preparation process, high efficiency, and environmental friendliness.

[0006] To achieve one of the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing a microwave absorbing material includes the following steps:

[0008] S1. At room temperature, place carbon material, divalent manganese salt solution, and potassium permanganate (KMnO4) solution in a beaker and stir magnetically to disperse the raw materials evenly and obtain a mixed solution.

[0009] S2. The reaction products in step S1 are sequentially vacuum filtered, washed with deionized water until the filtrate is colorless, and finally dried to obtain a microwave absorbing material containing 4-10% MnO2 by mass.

[0010] Preferably, Mn in divalent manganese salt solutions 2+ MnO4 in KMnO4 solution - The molar ratio is 3:2.

[0011] Preferably, the carbon material is one or more of graphite, carbon black, multi-walled carbon nanotubes (MWCNTs), graphene, and MXene.

[0012] Preferably, the divalent manganese salt solution is one or more of manganese carbonate solution, manganese chloride solution, manganese sulfate solution, manganese acetate solution, and manganese nitrate solution.

[0013] Preferably, in step S1, the concentration of the divalent manganese salt solution is 0.1-0.5 mol / L.

[0014] Preferably, in step S1, the concentration of the KMnO4 solution is 0.5-1.5 mol / L.

[0015] Preferably, the stirring time is 0.5-24 h.

[0016] Preferably, the drying temperature is 70-90 ℃ and the drying time is 12-24 h.

[0017] To achieve the second objective mentioned above, the present invention provides a microwave absorbing material, which is a composite material of MnO2 and carbon materials, wherein the mass fraction of MnO2 is 4-10%.

[0018] To achieve the third objective mentioned above, this invention provides an application of a microwave absorbing material, which is applied to the fields of electromagnetic protection, 5G communication, or stealth technology.

[0019] The advantages of this invention are:

[0020] (1) This invention uses MWCNT, KMnO4 and divalent manganese source as raw materials, based on Mn 2+ With MnO4 -The redox reaction between MnO2 and MWCNT nanoparticles can be achieved in situ uniformly loaded onto the MWCNT surface through simple stirring in a room-temperature liquid phase environment, resulting in microwave absorption performance superior to most existing similar materials. Compared to traditional microwave absorbing material preparation methods, the method of this invention only requires a simple one-step stirring process in a room-temperature liquid phase to achieve in situ uniform loading of MnO2 nanoparticles onto the MWCNT surface, eliminating the need for high-temperature and high-pressure equipment and pretreatment steps. This significantly reduces energy and reagent consumption, with a reaction time of <1 h and a reagent utilization rate of >95%. Furthermore, the raw materials are readily available and inexpensive, offering significant advantages such as energy-saving and environmentally friendly processes, adjustable and controllable material structure, excellent microwave absorption performance, and scalability. Compared to traditional processes, this invention offers significant advantages, a simplified process route, eliminates reliance on complex equipment, and is environmentally friendly with no pollution. It also boasts low cost and high efficiency, making it highly potential for large-scale production.

[0021] (2) Compared with existing preparation methods, the present invention prepares microwave absorbing material by combining MnO2 with MWCNT nanocomposite with adjustable dielectric constant, optimizes impedance matching and enhances interface polarization, thereby improving the microwave absorbing performance of the material.

[0022] (3) This invention can achieve in-situ uniform loading of MnO2 nanoparticles on the surface of MWCNT without complicated pretreatment process, construct hierarchical heterogeneous interface, significantly enhance interface polarization effect, promote multiple reflection / scattering, and reduce its filling amount and material thickness. The MWCNT used has low density, adjustable dielectric properties, large specific surface area, high mechanical strength and good chemical stability, which further improves the electromagnetic wave absorption performance of the material. Attached Figure Description

[0023] Figure 1 The diagram shows the microwave absorption performance of the microwave absorbing materials prepared in Examples 1-4 and Comparative Examples 1-2 of this invention.

[0024] Figure 2 This is a morphological scan of the microwave absorbing material prepared in Example 2 of the present invention.

[0025] Figure 3 This is an elemental mapping diagram of the microwave absorbing material prepared in Example 2 of the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0027] Example 1

[0028] Step 1: Disperse 0.05 g MWCNT in 25 mL of 0.17 mol / L manganese acetate tetrahydrate (Mn(Ac)2·4H2O) solution and stir at room temperature for 0.5 h;

[0029] Step 2: Add 5 mL of 0.58 mol / L KMnO4 solution dropwise and stir at room temperature for 0.5 h to obtain a mixed solution;

[0030] Step 3: The reaction product from Step 2 is vacuum filtered and washed with deionized water until the filtrate is colorless. After drying at 80°C for 12 hours, a MnO2 / MWCNT composite microwave absorbing material 1 with a mass fraction of 4% MnO2 is obtained.

[0031] Example 2

[0032] Step 1: Disperse 0.05 g MWCNT in 25 mL of 0.26 mol / L Mn(Ac)2·4H2O solution and stir at room temperature for 0.5 h;

[0033] Step 2: Add 5 mL of 0.87 mol / L KMnO4 solution dropwise and stir at room temperature for 0.5 h to obtain a mixed solution;

[0034] Step 3: The reaction product from step 2 is vacuum filtered and washed with deionized water until the filtrate is colorless. After drying at 80°C for 12 hours, a MnO2 / MWCNT composite microwave absorbing material 2 with a mass fraction of 6% MnO2 is obtained.

[0035] Example 3

[0036] Step 1: Disperse 0.05 g MWCNT in 25 mL of 0.35 mol / L Mn(Ac)2·4H2O solution and stir at room temperature for 0.5 h;

[0037] Step 2: Add 5 mL of 1.16 mol / L KMnO4 solution dropwise and stir at room temperature for 0.5 h to obtain a mixed solution;

[0038] Step 3: The reaction product in Step 2 is vacuum filtered and washed with deionized water until the filtrate is colorless. After drying at 80°C for 12 hours, a MnO2 / MWCNT composite microwave absorbing material 3 with a mass fraction of 8% MnO2 is obtained.

[0039] Example 4

[0040] Step 1: Disperse 0.05 g MWCNT in 25 mL of 0.44 mol / L Mn(Ac)2·4H2O solution and stir at room temperature for 0.5 h;

[0041] Step 2: Add 5 mL of 1.45 mol / L KMnO4 solution dropwise and stir at room temperature for 0.5 h to obtain a mixed solution;

[0042] Step 3: Vacuum filter the reaction product from Step 2 and wash it with deionized water until the filtrate is colorless. After drying at 80 °C for 12 h, a MnO2 / MWCNT composite microwave absorbing material 4 with a MnO2 mass fraction of 10% is obtained.

[0043] Comparative Example 1

[0044] Step 1: Weigh 0.05 g of MWCNT into a beaker, add 30 mL of deionized water, and then stir magnetically to disperse evenly to obtain a mixed solution;

[0045] Step 2: The reaction product from Step 1 is vacuum filtered and washed with deionized water until the filtrate is colorless. After drying at 80°C for 12 hours, MWCNT absorbing material 5 is obtained.

[0046] Comparative Example 2

[0047] Step 1: Weigh 1.5 g Mn(Ac)2·4H2O and 0.7 g KMnO4 into a beaker, add deionized water and stir magnetically to disperse evenly to obtain a mixed solution;

[0048] Step 2: The reaction product from Step 1 is vacuum filtered and washed with deionized water until the filtrate is colorless. After drying at 80°C for 12 hours, MnO2 microwave absorbing material 6 with a mass fraction of 6% is obtained.

[0049] The electromagnetic absorption performance of the absorbing materials obtained in Examples 1-4 and Comparative Examples 1-2 was tested, and the results are as follows: Figure 1 As shown.

[0050] Depend on Figure 1 It can be seen that the minimum reflection loss (RL) of the absorbing material prepared in Example 1 is... min The effective absorption bandwidth (EAB) is -44.82 dB, and the effective absorption bandwidth (EAB) is 4.56 GHz.

[0051] The microwave absorbing material prepared in Example 2 has an RL value of 1.4 mm. min It is -52.57 dB, and the EAB is 4.60 GHz (almost completely covering the Ku band).

[0052] RL of the microwave absorbing material prepared in Example 3 min The value is -23.80 dB, and the EAB is 3.36 GHz.

[0053] RL of the microwave absorbing material prepared in Example 4 minThe value is -29.37 dB, and the EAB value is 2.48 GHz.

[0054] RL of MWCNT prepared in Comparative Example 1 min It has a strength of only -11.04 dB and an effective absorption bandwidth of 2.2 GHz, which is much lower than the MnO2 / MWCNT composite absorbing materials prepared in Examples 1-4.

[0055] RL of MnO2 prepared in Comparative Example 2 min It is only -6.85 dB, which is much lower than the MnO2 / MWCNT composite absorbing materials prepared in Examples 1-4.

[0056] pass Figure 1 The comparative results show that the MnO2 / MWCNT composite absorbing material prepared in Example 2 exhibits the best absorption performance. With increasing MnO2 content (4%→10%), the absorption performance of the composite absorbing material first increases and then decreases. The MnO2 / MWCNT composite absorbing material with a MnO2 content of 6% demonstrates the best overall performance, with its strong absorption (-52.57 dB) and wideband characteristics (4.60 GHz) attributed to impedance matching optimization caused by the introduction of MnO2. In contrast, the MWCNT in Comparative Example 1 and the MnO2 in Comparative Example 2 show significantly poor absorption performance.

[0057] The morphology scanning image of the MnO2 / MWCNT composite microwave absorbing material prepared in Example 2 is shown below. Figure 2 As shown. By Figure 2 It is evident that the staggered structure in the MnO2 / MWCNT composite absorbing material prepared in Example 2 facilitates the formation of a conductive network, providing a low-impedance path for electromagnetic wave transmission and thus improving conductive loss. The surface of the absorbing material is uniformly loaded with MnO2 nanoparticles with a diameter of approximately 10-20 nm. The MnO2 loading on the MWCNT surface effectively enhances interfacial polarization and multiple scattering effects, contributing to improved electromagnetic wave absorption performance.

[0058] The elemental mapping diagram of the MnO2 / MWCNT composite microwave absorbing material prepared in Example 2 is shown below. Figure 3 As shown. By Figure 3 It can be seen that C, O, Mn and N elements are uniformly distributed in the MnO2 / MWCNT composite microwave absorbing material, which further confirms that MnO2 nanoparticles are uniformly loaded on the MWCNT surface.

[0059] The comprehensive performance of the MnO2 / MWCNT composite microwave absorbing materials prepared in Examples 1 and 2 was compared with that of other carbon-based composite microwave absorbing materials. The results are shown in Table 1.

[0060] Table 1

[0061] ;

[0062] As shown in Table 1, the MnO2 / MWCNT composite absorbing material prepared by the present invention is thin and has a low filling amount. Furthermore, the MnO2 / MWCNT composite absorbing material prepared in Example 2 can achieve excellent EMWA performance with a low filling amount (10%) and a thin thickness (1.4 mm), and its overall performance exceeds that of 90% of similar absorbing materials.

[0063] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a microwave absorbing material, characterized in that, Includes the following steps: Step 1: Disperse 0.05 g MWCNT in 25 mL of 0.17 mol / L manganese acetate tetrahydrate solution and stir at room temperature for 0.5 h; Step 2: Add 5 mL of 0.58 mol / L KMnO4 solution dropwise and stir at room temperature for 0.5 h to obtain a mixed solution; Step 3: The reaction product from Step 2 is vacuum filtered and washed with deionized water until the filtrate is colorless. After drying at 80°C for 12 hours, a MnO2 / MWCNT composite microwave absorbing material with a mass fraction of 4% is obtained.

2. A method for preparing a microwave absorbing material, characterized in that, Includes the following steps: Step 1: Disperse 0.05 g MWCNT in 25 mL of 0.26 mol / L Mn(Ac)2·4H2O solution and stir at room temperature for 0.5 h; Step 2: Add 5 mL of 0.87 mol / L KMnO4 solution dropwise and stir at room temperature for 0.5 h to obtain a mixed solution; Step 3: The reaction product from step 2 is vacuum filtered and washed with deionized water until the filtrate is colorless. After drying at 80°C for 12 hours, a MnO2 / MWCNT composite microwave absorbing material with a mass fraction of 6% is obtained.

3. A microwave absorbing material prepared by the method described in claim 1 or 2.

4. An application of the microwave absorbing material as described in claim 3, characterized in that: This absorbing material can be applied to electromagnetic protection, 5G communication, or stealth technology.

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