Iron-cobalt-nickel / nitrogen-doped carbon-based composite wave-absorbing material with adjustable wave-absorbing frequency band and preparation method of iron-cobalt-nickel / nitrogen-doped carbon-based composite wave-absorbing material

Abstract

The invention discloses an iron-cobalt-nickel / nitrogen-doped carbon-based composite wave-absorbing material with an adjustable wave-absorbing frequency band and a preparation method of the iron-cobalt-nickel / nitrogen-doped carbon-based composite wave-absorbing material. The preparation method comprises the following steps: step 1, dispersing dimethyl imidazole cobalt and nickel nitrate hexahydrate into an ethanol solution to react to prepare a product A; 2, dispersing the product A and iron nitrate nonahydrate into an ethanol solution to react to prepare a product B; and step 3, performing high-temperature pyrolysis on the product B in an inert gas atmosphere to prepare the iron-cobalt-nickel / nitrogen-doped carbon-based composite wave-absorbing material. The composite wave-absorbing material has a hollow polyhedral frame structure, and has an electromagnetic wave absorbing property with an adjustable wave-absorbing frequency band in a C-Ku wave band. The method for preparing the iron-cobalt-nickel / nitrogen-doped carbon-based composite wave-absorbing material is simple, low in cost and suitable for large-scale production.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite wave-absorbing materials, and in particular relates to an iron-cobalt-nickel / nitrogen-doped carbon-based composite wave-absorbing material with adjustable wave-absorbing frequency band and a preparation method thereof. Background Art

[0002] The rapid development of wireless communication technology and the widespread use of electronic products have greatly promoted social progress. However, the resulting electromagnetic radiation problem is becoming increasingly serious, even being considered the fourth largest source of pollution in society today, after water pollution, air pollution, and noise pollution. It not only affects people's health but also interferes with the normal operation of electronic products. Therefore, there is a huge market demand for the development of electromagnetic attenuation absorbing materials to reduce or even eliminate electromagnetic pollution, and it has attracted widespread attention from researchers.

[0003] The electromagnetic attenuation performance of an absorbing material is determined by its composition and structure. While traditional absorbing materials, such as carbonyl iron powder, ferroferric oxide, and carbon nanotubes, exhibit strong electromagnetic attenuation performance, their limited composition and structure lead to problems such as high density, high fill ratios, large matching thicknesses, and a narrow effective absorption bandwidth. Therefore, developing new absorbing materials to address these issues is of great research significance. For example, published patent CN117285036A reports a MOF-74 / melamine-derived iron-cobalt-nickel-based composite. Leveraging the tunable composition and structure of ZIF-67, the composite achieves tailored impedance matching and electromagnetic wave attenuation. Results show that the composite exhibits a minimum reflection loss of nearly -60 dB at 1.44 mm. Also published patent CN116623318A reports a FeCoNi@C / SiC-C fiber composite absorber. By combining SiC-C fibers with MOF and then pyrolyzing them, a unique core / shell microstructure is constructed to optimize impedance matching and enhance electromagnetic wave attenuation. Results show that the composite absorber achieves an effective absorption bandwidth of 11.66 GHz and a minimum reflection loss of -19.56 dB. Given the significant room for optimization in the preparation process, absorption frequency band, and attenuation performance of these iron-cobalt-nickel-based composite absorbers, it is necessary to propose a simpler composite absorber derived from dimethylimidazolium cobalt derivatives and its preparation method, which combines the advantages of adjustable absorption frequency band and strong attenuation performance. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the present invention provides an iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material with adjustable absorption frequency band and a preparation method thereof. The prepared iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material has excellent electromagnetic wave absorption performance and can meet a series of requirements such as adjustable absorption frequency band, thin matching thickness and low filling ratio.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides a method for preparing an iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material with an adjustable absorbing frequency band, comprising the following steps:

[0007] Step 1: Dispersing dimethylimidazolium cobalt (ZIF-67) and nickel nitrate hexahydrate in an ethanol solution to react and prepare product A (ZIF-67@CoNi BHs);

[0008] Step 2: Disperse product A and ferric nitrate nonahydrate into an ethanol solution to react and prepare product B (ZIF-

[0009] 67@FeCoNi THs);

[0010] Step 3: The product B is pyrolyzed at high temperature in an inert gas atmosphere to prepare an iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material (FeCoNi@NCMs).

[0011] Furthermore, step 1 is specifically as follows: dispersing dimethyl imidazole cobalt and nickel nitrate hexahydrate in an ethanol solution and stirring at room temperature. After the reaction is completed, filtering to obtain a precipitate, and then washing the precipitate with water and vacuum drying to obtain product A.

[0012] Furthermore, in step 1, the ratio of dimethylimidazole cobalt, nickel nitrate hexahydrate and ethanol is 1 g: (1-5) g: 500-3000 mL.

[0013] Furthermore, in step 1, the stirring time at room temperature is 10 to 60 minutes, and the vacuum drying temperature is 40 to 60°C.

[0014] Furthermore, step 2 is specifically as follows: dispersing product A and ferric nitrate nonahydrate in an ethanol solution and stirring at room temperature. After the reaction is completed, filtering to obtain a precipitate, and then washing the precipitate with water and vacuum drying to obtain product B.

[0015] Furthermore, in step 2, the ratio of product A, ferric nitrate nonahydrate and ethanol is 1 g: (0.1-5) g: 500-3000 mL.

[0016] Furthermore, in step 2, the stirring time at room temperature is 30 to 180 minutes, and the vacuum drying temperature is 40 to 60°C.

[0017] Furthermore, step 3 is specifically as follows: placing product B in a tube furnace, and preparing an iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material through programmed temperature pyrolysis, with nitrogen as the protective gas.

[0018] Furthermore, in step 3, the heating rate is 1-4°C / min, the pyrolysis temperature is 700-900°C, and the pyrolysis time is 1-4h.

[0019] The present invention provides an iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material prepared by the preparation method.

[0020] Compared with the prior art, the technical effects of the present invention are embodied in the following aspects:

[0021] (1) The present invention utilizes the reaction of transition metal ions with dimethylimidazolium cobalt and a high-temperature pyrolysis process to prepare an iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material. The operation method is simple and easy to prepare on a large scale.

[0022] (2) The iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material prepared by the present invention has excellent absorbing performance and the characteristic of adjustable absorbing frequency band. The minimum reflection loss (RL) at 5.3 GHz is min ) and effective absorption bandwidth (EAB) are -46.2dB and 1.62GHz respectively, the minimum reflection loss and effective absorption bandwidth at 7.5GHz are -46.6dB and 3.45GHz respectively, and the minimum reflection loss and effective absorption bandwidth at 11.4GHz are -53.1dB and 3.5GHz respectively, involving C~Ku bands.

[0023] (3) The iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material prepared based on the Kirkendall effect of the present invention has a hollow structure, which is beneficial to impedance matching control and electromagnetic energy loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The scanning electron microscopy (SEM) images of ZIF-67, ZIF-67@CoNiBHs and ZIF-67@FeCoNiTHs prepared in Example 1 and the transmission electron microscopy (TEM) image of FeCoNi@NCMs-700 are shown;

[0025] Figure 2 is the XRD pattern of ZIF-67, ZIF-67@CoNiBHs and ZIF-67@FeCoNiTHs prepared in Example 1;

[0026] Figure 3 are the XRD patterns of FeCoNi@NCMs-700 (a), FeCoNi@NCMs-800 (b) and FeCoNi@NCMs-900 (c) prepared in Examples 1 to 3;

[0027] Figure 4 is a reflection loss-frequency graph of FeCoNi@NCM-700 (20 wt.%) prepared in Example 1;

[0028] Figure 5 is a reflection loss-frequency graph of FeCoNi@NCM-800-1 (20 wt.%) prepared in Example 2;

[0029] Figure 6 is a reflection loss-frequency graph of FeCoNi@NCM-900 (20 wt.%) prepared in Example 3;

[0030] Figure 7 This is the reflection loss-frequency diagram of FeCoNi@NCM-800-2 (20 wt.%) prepared in Example 4. DETAILED DESCRIPTION

[0031] The present invention will be further described in detail below with reference to specific embodiments and drawings, which are intended to explain the present invention rather than to limit the scope of protection of the claims.

[0032] The experimental methods used in the following examples are conventional methods unless otherwise specified, and the reagents and equipment used are conventional reagents and equipment in the art unless otherwise specified.

[0033] Example 1

[0034] (1) Dispersing dimethylimidazole cobalt and nickel nitrate hexahydrate in an ethanol solution to react and prepare product A: 320 mg of dimethylimidazole cobalt and 640 mg of nickel nitrate hexahydrate were dispersed in 200 mL of ethanol solution, stirred for 30 minutes, and then filtered to obtain a precipitate. Finally, the precipitate was washed with water and vacuum-dried at 50° C. to obtain product A.

[0035] (2) Product A and ferric nitrate nonahydrate were dispersed in an ethanol solution to react and prepare product B: 400 mg of product A and 160 mg of ferric nitrate nonahydrate were dispersed in 200 mL of ethanol solution, stirred for 50 minutes, and then filtered to obtain a precipitate. Finally, the precipitate was washed with water and vacuum-dried at 50°C to obtain product B.

[0036] (3) Product B was pyrolyzed at high temperature in an inert gas atmosphere to prepare an iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material: Product B was placed in a tubular furnace, and then nitrogen was introduced into the tubular furnace. The temperature was raised to 700°C at 2°C / min and then pyrolyzed for 2h to obtain an iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material (FeCoNi@NCMs-700).

[0037] Figure 1 The SEM images of ZIF-67, ZIF-67@CoNiBHs, and ZIF-67@FeCoNi THs, as well as the TEM image of FeCoNi@NCMs-700, prepared in Example 1. Compared with ZIF-67, it can be seen that ZIF-67@CoNi BHs still has a relatively smooth surface, while the surface of ZIF-67@FeCoNi THs becomes rough, and FeCoNi@NCMs-700 has a hollow structure.

[0038] Figure 2 The XRD patterns of ZIF-67, ZIF-67@CoNi BHs and ZIF-67@FeCoNi THs prepared in Example 1 show that the diffraction peaks of the prepared samples correspond to those of ZIF-67, indicating that Ni 2+ and Fe 3+ Etching of ZIF-67 cannot completely destroy its crystal structure.

[0039] Figure 3 (a) is the XRD pattern of FeCoNi@NCMs-700 prepared in Example 1. The diffraction peaks at 43.7°, 50.9° and 74.9° are attributed to the (111), (200) and (220) crystal planes of the FeCoNi alloy, respectively.

[0040] Figure 4 This is the reflection loss-frequency diagram of FeCoNi@NCMs-700 (20 wt.%) prepared in Example 1. Its minimum reflection loss and effective absorption bandwidth at 8.0 GHz are -17.5 dB and 2.05 GHz, respectively.

[0041] Example 2

[0042] (1) Dispersing cobalt dimethyl imidazole and nickel nitrate hexahydrate in an ethanol solution to react and prepare product A: 320 mg of cobalt dimethyl imidazole and 640 mg of nickel nitrate hexahydrate were dispersed in 300 mL of ethanol solution, stirred for 30 minutes, and filtered to obtain a precipitate. Finally, the precipitate was washed with water and vacuum-dried at 50° C. to obtain product A.

[0043] (2) Product A and ferric nitrate nonahydrate were dispersed in an ethanol solution to react and prepare product B: 400 mg of product A and 200 mg of ferric nitrate nonahydrate were dispersed in 250 mL of ethanol solution, stirred for 60 minutes, and then filtered to obtain a precipitate. Finally, the precipitate was washed with water and vacuum-dried at 50°C to obtain product B.

[0044] (3) Product B was pyrolyzed at high temperature in an inert gas atmosphere to prepare an iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material: Product B was placed in a tube furnace, and then nitrogen was introduced into the tube furnace. The temperature was raised to 800°C at 2°C / min and pyrolyzed for 2h to obtain an iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material (FeCoNi@NCMs-800-1).

[0045] Figure 3 (b) is the XRD pattern of FeCoNi@NCMs-800-1 prepared in Example 2. The diffraction peaks at 43.7°, 50.9° and 74.9° are attributed to the (111), (200) and (220) crystal planes of the FeCoNi alloy, respectively.

[0046] Figure 5 This is the reflection loss-frequency diagram of FeCoNi@NCMs-800-1 (20 wt.%) prepared in Example 2. Its minimum reflection loss and effective absorption bandwidth at 5.3 GHz are -46.2 dB and 1.62 GHz, respectively.

[0047] Example 3

[0048] (1) Dispersing dimethylimidazolium cobalt and nickel nitrate hexahydrate in an ethanol solution to react and prepare product A: 320 mg of dimethylimidazolium cobalt and 840 mg of nickel nitrate hexahydrate were dispersed in 300 mL of ethanol solution, stirred for 40 minutes, and filtered to obtain a precipitate. Finally, the precipitate was washed with water and vacuum-dried at 60° C. to obtain product A.

[0049] (2) Product A and ferric nitrate nonahydrate were dispersed in an ethanol solution to react and prepare product B: 400 mg of product A and 180 mg of ferric nitrate nonahydrate were dispersed in 250 mL of ethanol solution, stirred for 50 minutes, and filtered to obtain a precipitate. Finally, the precipitate was washed with water and vacuum-dried at 60°C to obtain product B.

[0050] (3) Product B is pyrolyzed at high temperature in an inert gas atmosphere to prepare an iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material: Product B is placed in a tubular furnace, and then nitrogen is introduced into the tubular furnace. The temperature is raised to 900°C at 2°C / min and then pyrolyzed for 2h to obtain an iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material (FeCoNi@NCMs-900).

[0051] Figure 3 (c) is the XRD pattern of FeCoNi@NCMs-900 prepared in Example 3. The diffraction peaks at 43.7°, 50.9° and 74.9° are attributed to the (111), (200) and (220) crystal planes of the FeCoNi alloy, respectively.

[0052] Figure 6 This is the reflection loss-frequency diagram of FeCoNi@NCMs-900 (20 wt.%) prepared in Example 3, wherein the minimum reflection loss and effective absorption bandwidth at 11.4 GHz are -53.1 dB and 3.5 GHz, respectively.

[0053] Example 4

[0054] (1) Dispersing cobalt dimethyl imidazole and nickel nitrate hexahydrate in an ethanol solution to react and prepare product A: 320 mg of cobalt dimethyl imidazole and 740 mg of nickel nitrate hexahydrate were dispersed in 350 mL of ethanol solution, stirred for 40 minutes, and filtered to obtain a precipitate. Finally, the precipitate was washed with water and vacuum-dried at 60° C. to obtain product A.

[0055] (2) Product A and ferric nitrate nonahydrate were dispersed in an ethanol solution to react and prepare product B: 400 mg of product A and 80 mg of ferric nitrate nonahydrate were dispersed in 300 mL of ethanol solution, stirred for 60 minutes, and filtered to obtain a precipitate. Finally, the precipitate was washed with water and vacuum-dried at 60°C to obtain product B.

[0056] (3) Product B was pyrolyzed at high temperature in an inert gas atmosphere to prepare an iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material: Product B was placed in a tube furnace, and then nitrogen was introduced into the tube furnace. The temperature was raised to 800°C at 3°C / min and then pyrolyzed for 2h to obtain an iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material (FeCoNi@NCMs-

[0057] 800-2).

[0058] Figure 7 This is the reflection loss-frequency diagram of FeCoNi@NCMs-800-2 (20 wt.%) prepared in Example 4. Its minimum reflection loss and effective absorption bandwidth at 7.5 GHz are -46.6 dB and 3.45 GHz, respectively.

[0059] The FeCoNi@NCMs-700, FeCoNi@NCMs-800-1, FeCoNi@NCMs-900 and FeCoNi@NCMs-800-2 prepared in the above Examples 1 to 4 were used as absorbers, and paraffin was used as a molding agent; the absorber and paraffin were accurately weighed in a weight ratio of 1:4, and then the paraffin was melted and mixed evenly with the absorber and pressed into circular ring samples, named FeCoNi@NCMs-700 (20wt.%), FeCoNi@NCMs-800-1 (20wt.%), FeCoNi@NCMs-900 (20wt.%) and FeCoNi@NCMs-800-2 (20wt.%).

[0060] The above are only preferred embodiments of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. Improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A method for preparing an iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material with adjustable absorbing frequency band, characterized in that: The following steps are involved: Step 1: Dispersing dimethylimidazolium cobalt (ZIF-67) and nickel nitrate hexahydrate in an ethanol solution to react and prepare product A (ZIF-67@CoNi BHs); Step 2: Product A and ferric nitrate nonahydrate are dispersed in an ethanol solution to react and prepare product B (ZIF-67@FeCoNiTHs); Step 3: The product B is pyrolyzed at high temperature in an inert gas atmosphere to prepare an iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material (FeCoNi@NCMs).

2. The method for preparing an iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material with adjustable absorbing frequency band according to claim 1, characterized in that: Step 1 is specifically as follows: dispersing dimethyl imidazole cobalt and nickel nitrate hexahydrate in an ethanol solution and stirring at room temperature. After the reaction is completed, filtering to obtain a precipitate, then washing the precipitate with water and vacuum drying to obtain product A.

3. The method for preparing an iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material with adjustable absorbing frequency band according to claim 2, characterized in that: The feeding ratio of dimethylimidazole cobalt, nickel nitrate hexahydrate and ethanol in step 1 is 1g: (1-5)g: 500-3000mL.

4. The method for preparing an iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material with adjustable absorbing frequency band according to claim 2, characterized in that: In step 1, the reaction time of dimethylimidazole cobalt and nickel nitrate hexahydrate is 10 to 60 minutes, and the vacuum drying temperature is 40 to 60°C.

5. The method for preparing an iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material with adjustable absorbing frequency band according to claim 1, characterized in that: Step 2 is specifically as follows: Product A and ferric nitrate nonahydrate are dispersed in an ethanol solution and stirred at room temperature. After the reaction is completed, the precipitate is filtered to obtain a precipitate, and the precipitate is washed with water and vacuum-dried to obtain Product B.

6. The method for preparing an iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material with adjustable absorbing frequency band according to claim 5, characterized in that: The feed ratio of the product A, ferric nitrate nonahydrate and ethanol in step 2 is 1 g: (0.1-5) g: 500-3000 mL.

7. The method for preparing an iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material with adjustable absorbing frequency band according to claim 5, characterized in that: In step 2, the reaction time of product A and ferric nitrate nonahydrate is 30 to 180 minutes, and the vacuum drying temperature is 40 to 60°C.

8. The method for preparing an iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material with adjustable absorbing frequency band according to claim 1, characterized in that: Step 3 is specifically as follows: placing product B in a tube furnace, and preparing an iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material by programmed temperature pyrolysis, with nitrogen as the protective gas.

9. The method for preparing an iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material with adjustable absorbing frequency band according to claim 8, characterized in that: In step 3, the heating rate is 1-4°C / min, the pyrolysis temperature is 700-900°C, and the pyrolysis time is 1-4h.

10. Iron-cobalt-nickel / nitrogen-doped carbon-based composite absorbing material prepared by the preparation method according to any one of claims 1 to 9.

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