Electromagnetic composite absorbing material and preparation method thereof

Abstract

The present invention provides a method for preparing an electromagnetic composite absorbing material, specifically comprising the following steps: dissolving Co(NO3)2·6H2O and FeCl3·6H2O in water to prepare a solution A, and dissolving 2-methylimidazole and sodium hydroxide in water to prepare a solution B; dropwise adding the solution in step A to the continuously stirred solution B to obtain a mixed solution; after the dropwise addition is completed, continuing to stir the mixed solution and then allowing it to stand; and after the standing period, sequentially centrifuging, washing, and drying to obtain a precursor; and calcining the precursor under an inert atmosphere, and then cooling to obtain an electromagnetic composite absorbing material. The present invention also provides an electromagnetic composite absorbing material prepared using the above preparation method. The present invention uses a simple two-step method to synthesize iron-doped ZIF in water at room temperature, precipitates and dries the resulting material, and then calcines and carbonizes it at high temperature in an oxygen-isolated environment. The obtained iron-doped ZIF is reduced at high temperature to a sea urchin-shaped electromagnetic composite absorbing material having a regular dodecahedral skeleton / Co / Fe with carbon nanotubes grown on the surface.

Description

Technical Field

[0001] The present invention relates to the technical field of composite materials, and in particular to an electromagnetic composite absorbing material and a preparation method thereof. Background Art

[0002] With the development of human science and technology, electromagnetic radiation, especially man-made electromagnetic radiation, has become the fourth largest pollution after water pollution, air pollution and noise pollution, which is more polluting and difficult to protect.

[0003] Electromagnetic radiation not only affects the normal operation of industrial equipment and interferes with the normal transmission of electromagnetic signals, but also disrupts human life. For example, severe electromagnetic pollution can cause plant growth problems, genetic mutations, and even death; it can also weaken the human immune system and cause symptoms such as headaches, insomnia, and vision loss.

[0004] Therefore, controlling electromagnetic radiation pollution has become a pressing issue in today's society. The most effective measure to control electromagnetic radiation pollution is shielding and absorbing electromagnetic waves, keeping their intensity within a safe range. Absorbing materials are materials that absorb or significantly attenuate electromagnetic energy incident on their surfaces, thereby reducing electromagnetic interference. To protect against the hazards of electromagnetic radiation, the theoretical research on practical absorbing material technologies and the development of absorbing materials for various applications are urgent issues. Summary of the Invention

[0005] The present invention aims to provide a method for preparing an electromagnetic composite absorbing material. The prepared electromagnetic composite absorbing material has an extremely low density and an effective absorbing bandwidth of 5.14 GHz. The method has simple steps, a short cycle, is easily repeatable, and can be easily scaled up. Using water as a solvent can save costs. The method is universal and representative, and is convenient for large-scale industrial production.

[0006] A method for preparing an electromagnetic composite absorbing material, the method comprising the following steps:

[0007] S1. Dissolve Co(NO3)2·6H2O and FeCl3·6H2O in water to prepare solution A, and dissolve 2-methylimidazole and sodium hydroxide in water to prepare solution B;

[0008] S2, adding the solution A obtained in step S1 dropwise to the continuously stirred solution B to obtain a mixed solution, and after the dropwise addition is completed, continuing to stir the mixed solution and then allowing it to stand. After the standing period, centrifuging, washing, and drying are performed in sequence to obtain a precursor;

[0009] S3. calcining the precursor obtained in step S2 under an inert atmosphere, and then cooling to obtain an electromagnetic composite absorbing material.

[0010] The present invention uses a simple two-step method to synthesize iron-doped ZIF in water at room temperature. After precipitation and drying, it is calcined and carbonized at high temperature in an oxygen-isolated environment. The obtained iron-doped ZIF is reduced at high temperature to a sea urchin-shaped electromagnetic composite absorbing material with a regular dodecahedral skeleton / Co / Fe with carbon nanotubes grown on the surface.

[0011] Preferably, in the prepared solution A in step S1, Co 2+ and Fe 3+ The sum of the concentrations is 0.1-0.22 mol / L.

[0012] Preferably, in the prepared solution A in step S1, Co 2+ and Fe 3+ The sum of the concentrations is 0.166 mol / L.

[0013] Preferably, in the step S1, in the prepared solution B, the concentration of 2-methylimidazole is 1-2 mol / L, and the concentration of sodium hydroxide is 0.2-1 mol / L.

[0014] Preferably, in the step S1, in the prepared solution B, the concentration of 2-methylimidazole is 1.683 mol / L, and the concentration of sodium hydroxide is 0.5 mol / L.

[0015] Preferably, in step S2, the volume ratio of solution A to solution B is 1:(1-2).

[0016] Preferably, in step S2, the stirring time is 1-6 hours, and the standing time is 12-48 hours.

[0017] Preferably, in step S2, in the mixed solution, Co 2+ and Fe 3+ The ratio of the sum of the moles of 2-methylimidazole to the mole of 2-methylimidazole is 1:16.8.

[0018] Preferably, in step S2, the washing solvent is methanol, and the number of washes is three. The synthesis method of the present invention is to synthesize iron-doped ZIF in water. This method can simply and cost-effectively prepare a large number of iron-doped ZIF precursor particles. Only a small amount of methanol is used for washing the ZIF, which greatly saves methanol usage, not only reducing costs but also reducing the potential for environmental pollution caused by the use of methanol.

[0019] Preferably, in step S3, the calcination conditions are as follows: the calcination temperature is 600-900° C., and the calcination time is 1-6 hours.

[0020] Another object of the present invention is to provide an electromagnetic composite absorbing material prepared by the above preparation method.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] First, the present invention uses a simple two-step method to synthesize iron-doped ZIF in water at room temperature. After the precipitation is dried, it is calcined and carbonized at high temperature in an oxygen-free environment. The obtained iron-doped ZIF is reduced at high temperature to a sea urchin-shaped electromagnetic composite absorbing material with a regular dodecahedral skeleton / Co / Fe with carbon nanotubes grown on the surface.

[0023] Secondly, the present invention can change the diameter of the obtained CNT by adjusting the input amount of iron ions. Increasing the input amount of iron ions can reduce the overall conductivity and dielectric loss of the material; at the same time, increasing the input amount of iron ions can increase the magnetic loss of the material. In this case of trade-off, the material can achieve impedance matching, and ultimately achieve an improvement in the overall wave absorption ability of the material.

[0024] Third, during the carbonization process of the material, the carbon skeleton of the ZIF grains serves as the carbon source of CNTs. In the process of forming CNTs, the metal particles consume the carbon skeleton to form CNTs, forming a large number of holes inside and on the surface of the material. This will cause electromagnetic waves to be repeatedly refracted inside and on the surface, which is beneficial to the overall loss of electromagnetic waves by the material.

[0025] Fourthly, due to the existence of pores, many C / Co, C / Fe, and C / Air interfaces are formed inside and outside the material, which greatly increases the specific surface area of ​​the material and is beneficial to the loss of electromagnetic waves due to interface polarization of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a scanning electron microscope image of the precursor prepared in Example 2 of the present invention;

[0027] Figure 2 This is a scanning electron microscope image of the electromagnetic composite absorbing material prepared in Example 2 of the present invention;

[0028] Figure 3 This is the X-ray diffraction pattern of the electromagnetic composite absorbing material prepared in Example 2 of the present invention;

[0029] Figure 4 This is a reflection loss diagram of the electromagnetic composite absorbing material prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0030] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. It should be noted that the following embodiments are only intended to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter ranges described in the present invention. Reasonable variations derived therefrom are still within the scope of protection of the claims of the present invention.

[0031] It should be noted that the endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein.

[0032] An embodiment of the present invention provides a method for preparing an electromagnetic composite absorbing material, the method comprising the following steps:

[0033] S1. Dissolve Co(NO3)2·6H2O and FeCl3·6H2O in water to prepare solution A, and dissolve 2-methylimidazole and sodium hydroxide in water to prepare solution B. In solution A: Co 2+ and Fe 3+ The sum of the concentrations of is 0.1-0.22 mol / L, in solution B: the concentration of 2-methylimidazole is 1-2 mol / L, and the concentration of sodium hydroxide is 0.2-1 mol / L;

[0034] S2. Add solution A obtained in step S1 dropwise to the continuously stirred solution B to obtain a mixed solution, wherein the volume ratio of solution A to solution B is 1:(1-2). After the dropwise addition is completed, the mixed solution is further stirred for 1-6 hours and then allowed to stand for 12-48 hours. After the standing period, the mixture is centrifuged, washed with methanol three times, and dried to obtain a precursor;

[0035] S3. calcining the precursor obtained in step S2 at 600-900° C. for 1-6 hours under an inert atmosphere, and then cooling to obtain an electromagnetic composite absorbing material.

[0036] The present invention will be described in detail below through specific examples.

[0037] Example 1

[0038] A method for preparing an electromagnetic composite absorbing material comprises the following steps:

[0039] S1. Dissolve Co(NO3)2·6H2O and FeCl3·6H2O in water to prepare solution A, and dissolve 2-methylimidazole and sodium hydroxide in water to prepare solution B. In solution A: Co 2+ and Fe 3+ The sum of the concentrations of is 0.1 mol / L. In solution B: the concentration of 2-methylimidazole is 1 mol / L, and the concentration of sodium hydroxide is 0.2 mol / L.

[0040] S2. Add solution A obtained in step S1 dropwise to the continuously stirred solution B to obtain a mixed solution, wherein the volume ratio of solution A to solution B is 1:1. After the dropwise addition is completed, the mixed solution is further stirred for 1 hour and then allowed to stand for 12 hours. After the standing period, centrifugation, washing with methanol three times, and drying are performed in sequence to obtain a precursor;

[0041] S3. calcining the precursor obtained in step S2 at 600° C. for 1 h under an inert atmosphere, and then cooling the precursor to obtain an electromagnetic composite absorbing material.

[0042] Example 2

[0043] A method for preparing an electromagnetic composite absorbing material comprises the following steps:

[0044] S1. Dissolve Co(NO3)2·6H2O and FeCl3·6H2O in water to prepare solution A, and dissolve 2-methylimidazole and sodium hydroxide in water to prepare solution B. In solution A: Co 2+ and Fe 3+ The concentration ratio is 3:2, Co 2+ and Fe 3+ The sum of the concentrations of is 0.1663 mol / L. In solution B: the concentration of 2-methylimidazole is 1.683 mol / L, and the concentration of sodium hydroxide is 0.5 mol / L.

[0045] S2. Add solution A obtained in step S1 dropwise to the continuously stirred solution B to obtain a mixed solution, wherein the volume ratio of solution A to solution B is 1:1.667. After the dropwise addition is completed, the mixed solution is stirred for 4 hours and then allowed to stand for 24 hours. After the standing period, centrifugation, washing with methanol three times, and drying are performed in sequence to obtain a precursor;

[0046] S3. calcining the precursor obtained in step S2 at 800° C. for 2 h under an inert atmosphere, and then cooling the precursor to obtain an electromagnetic composite absorbing material.

[0047] Example 3

[0048] A method for preparing an electromagnetic composite absorbing material comprises the following steps:

[0049] S1. Dissolve Co(NO3)2·6H2O and FeCl3·6H2O in water to prepare solution A, and dissolve 2-methylimidazole and sodium hydroxide in water to prepare solution B. In solution A: Co 2+ and Fe 3+ The concentration ratio is 2:3, and Co 2+ and Fe 3+ The sum of the concentrations of is 0.1663 mol / L. In solution B: the concentration of 2-methylimidazole is 1.683 mol / L, and the concentration of sodium hydroxide is 0.5 mol / L.

[0050] S2. Add solution A obtained in step S1 dropwise to the continuously stirred solution B to obtain a mixed solution, wherein the volume ratio of solution A to solution B is 1:1.667. After the dropwise addition is completed, the mixed solution is stirred for 4 hours and then allowed to stand for 24 hours. After the standing period, centrifugation, washing with methanol three times, and drying are performed in sequence to obtain a precursor;

[0051] S3. calcining the precursor obtained in step S2 at 800° C. for 2 h under an inert atmosphere, and then cooling the precursor to obtain an electromagnetic composite absorbing material.

[0052] Example 4

[0053] A method for preparing an electromagnetic composite absorbing material comprises the following steps:

[0054] S1. Dissolve Co(NO3)2·6H2O and FeCl3·6H2O in water to prepare solution A, and dissolve 2-methylimidazole and sodium hydroxide in water to prepare solution B. In solution A: Co 2+ and Fe 3+ The concentration ratio is 4:1, and Co 2+ and Fe 3+ The sum of the concentrations of is 0.1663 mol / L. In solution B: the concentration of 2-methylimidazole is 1.683 mol / L, and the concentration of sodium hydroxide is 0.5 mol / L.

[0055] S2. Add solution A obtained in step S1 dropwise to the continuously stirred solution B to obtain a mixed solution, wherein the volume ratio of solution A to solution B is 1:1.667. After the dropwise addition is completed, the mixed solution is stirred for 4 hours and then allowed to stand for 24 hours. After the standing period, centrifugation, washing with methanol three times, and drying are performed in sequence to obtain a precursor;

[0056] S3. calcining the precursor obtained in step S2 at 800° C. for 2 h under an inert atmosphere, and then cooling the precursor to obtain an electromagnetic composite absorbing material.

[0057] Example 5

[0058] A method for preparing an electromagnetic composite absorbing material comprises the following steps:

[0059] S1. Dissolve Co(NO3)2·6H2O and FeCl3·6H2O in water to prepare solution A, and dissolve 2-methylimidazole and sodium hydroxide in water to prepare solution B. In solution A: Co 2+ and Fe 3+ The sum of the concentrations of is 0.22 mol / L. In solution B: the concentration of 2-methylimidazole is 2 mol / L, and the concentration of sodium hydroxide is 1.0 mol / L.

[0060] S2. Add solution A obtained in step S1 dropwise to the continuously stirred solution B to obtain a mixed solution, wherein the volume ratio of solution A to solution B is 1:2. After the dropwise addition is completed, the mixed solution is further stirred for 6 hours and then allowed to stand for 48 hours. After the standing period, the mixture is centrifuged, washed with methanol three times, and dried to obtain a precursor;

[0061] S3. calcining the precursor obtained in step S2 at 900° C. for 6 h under an inert atmosphere, and then cooling the precursor to obtain an electromagnetic composite absorbing material.

[0062] The precursors and electromagnetic composite absorbing materials prepared in Examples 1-5 were subjected to performance tests, and the test results are shown in Table 1:

[0063] Table 1: Performance test results of electromagnetic composite absorbing materials prepared in Examples 1-5

[0064] <![CDATA[Density (g / cm 3 )]]> Effective absorption bandwidth (GHz) Maximum return loss (dB) Example 1 0.5 0 -3 Example 2 0.454 5.14 -24.83 Example 3 0.45 0 -5.2 Example 4 0.45 4.5 -13 Example 5 0.6 2 -14

[0065] Therefore, the density of the composite absorbing material obtained by this application is only 0.454 g / cm 3 , the effective absorption bandwidth can reach 5.14GHz, the maximum reflection loss can reach -24.83dB, and it has excellent absorption performance. The inventors further tested the precursor and electromagnetic composite absorbing material of Example 2, and the test results are as follows Figure 1-4 As shown, it can be seen that the material prepared by the present invention can be used to synthesize electromagnetic wave absorbing agents economically, greenly, simply and efficiently, and the magnetic properties and wave absorbing capabilities can be changed by changing the synthesis ratio, and it has strong maneuverability.

[0066] Although the present disclosure is disclosed as above, the protection scope of the present disclosure is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A method for preparing an electromagnetic composite absorbing material, characterized in that: The preparation method specifically comprises the following steps: S1. Dissolve Co(NO3)2·6H2O and FeCl3·6H2O in water to prepare solution A, and dissolve 2-methylimidazole and sodium hydroxide in water to prepare solution B; S2, adding the solution A obtained in step S1 dropwise to the continuously stirred solution B to obtain a mixed solution, and after the dropwise addition is completed, continuing to stir the mixed solution and then allowing it to stand. After the standing period, centrifuging, washing, and drying are performed in sequence to obtain a precursor; In step S2, in the mixed solution, Co 2+ and Fe 3+ The ratio of the sum of the moles of to the mole of 2-methylimidazole is 1:16.8; S3. calcining the precursor obtained in step S2 under an inert atmosphere, and then cooling to obtain an electromagnetic composite absorbing material, wherein the electromagnetic composite absorbing material is a sea urchin-shaped electromagnetic composite absorbing material having a regular dodecahedral skeleton of carbon nanotubes / Co / Fe grown on the surface.

2. The method for preparing the electromagnetic composite absorbing material according to claim 1, wherein: In the step S1, in the prepared solution A, Co 2+ and Fe 3+ The sum of the concentrations is 0.1-0.22 mol / L.

3. The method for preparing the electromagnetic composite absorbing material according to claim 1, wherein: In the step S1, in the prepared solution A, Co 2+ and Fe 3+ The sum of the concentrations is 0.166 mol / L.

4. The method for preparing the electromagnetic composite absorbing material according to claim 1, wherein: In the step S1, in the prepared solution B, the concentration of 2-methylimidazole is 1-2 mol / L, and the concentration of sodium hydroxide is 0.2-1 mol / L.

5. The method for preparing the electromagnetic composite absorbing material according to claim 1, wherein: In step S1, in the prepared solution B, the concentration of 2-methylimidazole is 1.683 mol / L, and the concentration of sodium hydroxide is 0.5 mol / L.

6. The method for preparing the electromagnetic composite absorbing material according to claim 1, wherein: In step S2, the volume ratio of solution A to solution B is 1:(1-2).

7. The method for preparing the electromagnetic composite absorbing material according to claim 1, wherein: In step S2, the stirring time is 1-6 hours, and the standing time is 12-48 hours.

8. The method for preparing the electromagnetic composite absorbing material according to claim 1, wherein: In step S3, the calcination conditions are as follows: the calcination temperature is 600-900° C., and the calcination time is 1-6 hours.

9. An electromagnetic composite absorbing material, characterized in that: The method is prepared according to any one of claims 1 to 8.

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