Hollow carbon / co efficient electromagnetic wave absorbing material and preparation method and application thereof

Abstract

The application provides a hollow carbon / Co efficient electromagnetic wave absorbing material and a preparation method and application thereof, and comprises the following steps: step 1, dissolving cobalt nitrate hexahydrate, tetradecyl trimethyl ammonium bromide, 2-methyl imidazole and zinc nitrate hexahydrate in water, stirring and reacting to obtain solution C; step 2, washing solution C, separating and drying a solid product to obtain a hollow ZIF-8 / ZIF-67 precursor; and step 3, carbonizing the hollow ZIF-8 / ZIF-67 precursor under an inert atmosphere to obtain the hollow carbon / Co efficient electromagnetic wave absorbing material. The preparation process is simple, the material can be prepared on a large scale, and the prepared composite material has excellent electromagnetic wave absorbing performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of material science and relates to a hollow carbon / Co efficient electromagnetic wave absorbing material with a hierarchical pore structure and a preparation method and application thereof. BACKGROUND

[0002] With the wide application of electromagnetic waves in the field of wireless communication and the popularization of 5G technology, people's life and work are facilitated, but serious electromagnetic pollution is also caused. Adopting electromagnetic wave absorbing materials to absorb and attenuate these harmful electromagnetic waves is an effective means to solve electromagnetic pollution. Hollow carbon materials with a porous shell structure have high specific surface area, strong dielectric loss, excellent impedance matching characteristics and good chemical stability, and are a high-efficiency electromagnetic wave absorbing material with application prospects. At present, the preparation of hollow carbon materials with a porous shell structure is mainly based on SiO2 hard template method (ACS Applied Materials & Interfaces, 2018, 10, 51, 44483-44493; ACS Applied Materials & Interfaces, 2017, 9, 7, 6332-6341; Dalton Transactions, 2019, 48(27), 10145-10150; Carbon, 2020, 167, 843-851), which has a relatively complex preparation process and needs HF and NaOH to remove the template, so the preparation process is complex, the required time is long, and large-scale preparation is difficult. SUMMARY

[0003] The application aims to provide a hollow carbon / Co efficient electromagnetic wave absorbing material and a preparation method and application thereof, which have a simple preparation process, can be prepared on a large scale, and the prepared composite material has excellent electromagnetic wave absorbing performance.

[0004] The application is achieved by the following technical solutions.

[0005] A preparation method of a hollow carbon / Co efficient electromagnetic wave absorbing material, comprising the following steps:

[0006] (1) First, add cobalt nitrate hexahydrate to a tetradecyltrimethylammonium bromide (CTAB) solution and stir to obtain solution A; 14 TAB) solution, and stir to obtain solution A;

[0007] (2) Add 2-methylimidazole to solution A and continuously stir to obtain solution B;

[0008] (3) Add zinc nitrate hexahydrate to solution B and continue to stir to obtain solution C;

[0009] (4) centrifugal washing of solution C with DMF and methanol respectively, drying to obtain solid D;

[0010] (5) carbonization treatment of solid D under argon atmosphere to obtain hollow carbon / Co high-efficiency electromagnetic wave absorbing material with hierarchical pore structure in shell layer.

[0011] Preferably, the stirring time in step (1) is 10-20 min, the stirring time in step (2) is 30-50 min, and the stirring time in step (1) is 30-60 min.

[0012] Preferably, the cobalt nitrate hexahydrate, zinc nitrate hexahydrate, C 14 The mass ratio of TAB and 2-methylimidazole is 1:(0.5-4.3):19.6:35.8.

[0013] Preferably, in the step (4), the rotation speed of centrifugal washing is 5000-8000 r·min -1 , and the centrifugal washing time is 2-6 min.

[0014] Preferably, in the step (4), the temperature of vacuum drying is 50-80℃, and the holding time is 24 h.

[0015] Preferably, in the step (5), the temperature is raised to 500℃ at 0.5℃ / min, and the holding time is 20-50 min.

[0016] Compared with the prior art, the present application has the following beneficial effects:

[0017] Different from the mechanism of morphology control in the patents CN107722046A and CN111554896B, which controls the growth rate of ZIF-67 crystal face by cationic surfactant (CTAB), the preparation method of the present application uses the spherical micelles formed by tetradecyl trimethyl ammonium bromide in aqueous solution as a template, and the oligomeric complex of Zn 2+ , Co 3+ and 2-methylimidazole is aggregated and grown on the surface of the micelles to prepare ZIF-8 / ZIF-67 composite organic framework structure, and then the Zn metal is removed by a simple inert atmosphere in-situ carbonization process using the difference in thermal stability of ZIF-8 and ZIF-67 and the volatility of Zn metal, to prepare hollow carbon / Co composite material with hierarchical pore structure in shell layer, which has excellent electromagnetic wave absorption performance; by adjusting the content of Zn in the hollow ZIF-8 / ZIF-67 precursor, the control of the pore structure in the shell layer of the hollow carbon / Co composite material with hierarchical pore structure in shell layer prepared by the present application can be realized. At the same time, this method has low requirements for equipment operation, simple process, low energy consumption, and easy control of reaction conditions, and can be operated continuously, which is suitable for large-scale industrial production.

[0018] The hollow carbon / Co shell prepared by this invention has a hierarchical pore structure, and Co nanoparticles are generated in situ in the shell, which is beneficial to the multiple scattering of electromagnetic waves and magnetic loss. At the same time, zinc can adjust the pore size, and the synergistic effect of the two is beneficial to the improvement of electromagnetic wave absorption performance. Attached Figure Description

[0019] Figure 1 X-ray diffraction patterns of hollow carbon / Co high-efficiency electromagnetic wave absorbing materials with hierarchical pore structure in the shell obtained by the method described in Examples 1-3, wherein: (a) Example 1, (b) Example 2, (c) Example 3;

[0020] Figure 2 SEM images of hollow carbon / Co high-efficiency electromagnetic wave absorbing materials with hierarchical pore structure in the shell obtained by the method described in Examples 1-3, wherein: (a) Example 1, (b) Example 2, (c) Example 3;

[0021] Figure 3 The images are TEM images of hollow carbon / Co high-efficiency electromagnetic wave absorbing materials with hierarchical porous shells prepared by the methods described in Examples 1-3, where: (a) Example 1, (b) Example 2, (c) Example 3;

[0022] Figure 4 The absorption and reflection loss diagrams of hollow carbon / Co high-efficiency electromagnetic wave absorbing materials with hierarchical pore structure in the shell prepared by the method described in Examples 1-3 are shown when the filling amount in the paraffin matrix is ​​30wt% and the matching thickness is 3.7mm. Among them: (a) Example 1, (b) Example 2, (c) Example 3. Detailed Implementation

[0023] To further understand the present invention, the present invention will be described below with reference to embodiments. These descriptions are only for further explaining the features and advantages of the present invention and are not intended to limit the claims of the present invention.

[0024] Example 1

[0025] (1) First, add 7.5 mL of cobalt nitrate hexahydrate solution (0.0915 g / mL) to 200 mL of C 14 In a TAB solution (0.0673 g / mL), stir for 10 min to obtain solution A;

[0026] (2) Then add 150 mL of 2-methylimidazole solution (0.164 g / mL) to solution A and stir continuously for 30 min to obtain solution B;

[0027] (3) 5 mL of zinc nitrate hexahydrate solution (0.0744 g / mL) was added to solution B, and after continuous stirring for 30 min, solution C was obtained;

[0028] (4) Solution C was centrifugally washed once with DMF and three times with methanol, and then dried at 60°C for 24 h to obtain solid D (hollow ZIF-8 / ZIF-67 precursor); the rotation speed for each centrifugal washing was 6000 r·min -1 , and the centrifugal time was 4 min;

[0029] (5) After solid D was heated to 500°C at a rate of 0.5°C / min under an argon atmosphere and then kept at 500°C for 30 min, a hollow carbon / Co composite material with a hierarchical pore structure in the shell layer was obtained.

[0030] As can be seen from Figure 1 (a), the hollow carbon / Co composite material was successfully prepared by the method described in Example 1. As can be seen from Figure 2 (a) and Figure 3 (a), the hollow carbon / Co composite material prepared by the method described in Example 1 had a clear hollow structure, a particle size of 312-331 nm, a pore size of 13-55 nm in the shell layer, and in-situ grown cobalt nanoparticles in the porous carbon shell skeleton.

[0031] As can be seen from Figure 4 (a), the hollow carbon / Co composite material with a hierarchical pore structure in the shell layer prepared by the method described in Example 1 had an effective absorption width (<-10 dB) of 8 GHz, and the maximum reflection loss was located at 11.68 GHz, which was -56.7 dB.

[0032] Example 2

[0033] (1) First, 7.5 mL of cobalt nitrate hexahydrate solution (0.0915 g / mL) was added to 200 mL of C 14 TAB solution (0.0673 g / mL), and stirred for 10 min to obtain solution A;

[0034] (2) Then, 150 mL of 2-methylimidazole solution (0.164 g / mL) was added to solution A, and continuously stirred for 30 min to obtain solution B;

[0035] (3) 5 mL of zinc nitrate hexahydrate solution (0.2975 g / mL) was added to solution B, and after continuous stirring for 30 min, solution C was obtained;

[0036] (4) The solution C was centrifugally washed once with DMF and three times with methanol, and then dried at 60°C for 24h to obtain solid D (hollow ZIF-8 / ZIF-67 precursor); the rotation speed of each centrifugal washing was 6000r·min -1 , and the centrifugal time was 4min;

[0037] (5) The solid D was heated to 500°C at 0.5°C / min under argon atmosphere, and then kept for 30min to obtain the hollow carbon / Co high-efficiency electromagnetic wave absorbing material with hierarchical pore structure in the shell layer.

[0038] As can be seen from Figure 1 (b), the carbon / Co composite material was prepared by the method described in Example 2. As can be seen from Figure 2 (b) and Figure 3 (b), the carbon / Co composite material prepared by the method described in Example 2 has a hollow structure, a particle size of 306-325nm, a pore size of 20-60nm in the shell layer, and in-situ grown cobalt nanoparticles in the porous carbon shell skeleton.

[0039] As can be seen from Figure 4 (b), the hollow carbon / Co composite material with hierarchical pore structure in the shell layer prepared by the method described in Example 2 has an effective absorption width of 5.04GHz, and the maximum reflection loss is located at 12.64GHz, which is -55.5dB.

[0040] Example 3

[0041] (1) First, 7.5mL of cobalt nitrate hexahydrate solution (0.0915g / mL) was added to 200mL of C 14 TAB solution (0.0673g / mL), and stirred for 10min to obtain solution A;

[0042] (2) Then, 150mL of 2-methylimidazole solution (0.164g / mL) was added to solution A, and continuously stirred for 30min to obtain solution B;

[0043] (3) 5mL of zinc nitrate hexahydrate solution (0.595g / mL) was added to solution B, and continuously stirred for 30min to obtain solution C;

[0044] (4) The solution C was centrifugally washed once with DMF and three times with methanol, and then dried at 60°C for 24h to obtain solid D (hollow ZIF-8 / ZIF-67 precursor); the rotation speed of each centrifugal washing was 6000r·min -1 , and the centrifugal time was 4min;

[0045] (5) The solid D is heated to 500℃ at 0.5℃ / min under an argon atmosphere, and then kept for 30 min, to obtain the hollow carbon / Co high-efficiency electromagnetic wave absorbing material with a hierarchical pore structure in the shell layer.

[0046] From Figure 1 (c) it can be seen that the carbon / Co composite material is prepared by the method described in Example 3. From Figure 2 (c) and Figure 3 (c) it can be seen that the carbon / Co composite material prepared by the method described in Example 3 has a hollow structure, the particle size is 375-393 nm, the pore size in the shell layer is 23-110 nm, and there are in-situ grown cobalt nanoparticles in the porous carbon shell skeleton. From Comparative Examples 1-3 it can be seen that the pore size in the shell layer of the finally obtained product gradually increases with the increase of the zinc addition amount, which shows that by adjusting the Zn content in the hollow ZIF-8 / ZIF-67 precursor, the pore structure in the shell layer of the hollow carbon / Co composite material with a hierarchical pore structure prepared by the method of the present application can be controlled.

[0047] From Figure 4 (c) it can be seen that the effective absorption width of the hollow carbon / Co composite material with a hierarchical pore structure prepared by the method described in Example 3 is 4.72 GHz, and the maximum reflection loss is located at 16.87 GHz, which is -52.3 dB.

[0048] Example 4

[0049] (1) First, 7.5 mL of a cobalt nitrate hexahydrate solution (0.0915 g / mL) is added to 200 mL of a C 14 TAB solution (0.0673 g / mL), and stirred for 20 min to obtain solution A;

[0050] (2) Then, 150 mL of a 2-methylimidazole solution (0.164 g / mL) is added to solution A, and continuously stirred for 40 min to obtain solution B;

[0051] (3) 5 mL of a zinc nitrate hexahydrate solution (0.595 g / mL) is added to solution B, and continuously stirred for 50 min to obtain solution C;

[0052] (4) Solution C is centrifugally washed once with DMF and three times with methanol, and then dried at 50℃ for 24 h to obtain solid D (hollow ZIF-8 / ZIF-67 precursor); the rotation speed for each centrifugal washing is 5000 r·min -1 , and the centrifugal time is 2 min;

[0053] (5) After solid D is heated to 500℃ at 0.5℃ / min under argon atmosphere, and then kept for 20min, the hollow carbon / Co high-efficiency electromagnetic wave absorbing material with hierarchical pore structure in the shell layer can be obtained.

[0054] Example 5

[0055] (1) First, 7.5mL of cobalt nitrate hexahydrate solution (0.0915g / mL) is added to 200mL of C 14 TAB solution (0.0673g / mL), and stirred for 20min to obtain solution A;

[0056] (2) Then, 150mL of 2-methylimidazole solution (0.164g / mL) is added to solution A, and continuously stirred for 50min to obtain solution B;

[0057] (3) 5mL of zinc nitrate hexahydrate solution (0.595g / mL) is added to solution B, and continuously stirred for 60min to obtain solution C;

[0058] (4) Solution C is centrifugally washed once with DMF and three times with methanol, and then dried at 80℃ for 24h to obtain solid D (hollow ZIF-8 / ZIF-67 precursor);

[0059] (5) After solid D is heated to 500℃ at 0.5℃ / min under argon atmosphere, and then kept for 50min, the hollow carbon / Co high-efficiency electromagnetic wave absorbing material with hierarchical pore structure in the shell layer can be obtained.

[0060] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Various modifications and changes can be made by those skilled in the art based on the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a hollow carbon / Co high-efficiency electromagnetic wave absorbing material, characterized in that, Comprising the following steps: Step 1, dissolving cobalt nitrate hexahydrate, tetradecyl trimethyl ammonium bromide, 2-methyl imidazole and zinc nitrate hexahydrate in water, stirring the reaction to obtain solution C; the mass ratio of cobalt nitrate hexahydrate, zinc nitrate hexahydrate, tetradecyl trimethyl ammonium bromide and 2-methyl imidazole is 1: (0.5-4.3): 19.6: 35.8; Step 1 specifically comprises: (1) adding cobalt nitrate hexahydrate into tetradecyl trimethyl ammonium bromide solution, stirring to obtain solution A; (2) adding 2-methyl imidazole into solution A, stirring to obtain solution B; (3) adding zinc nitrate hexahydrate into solution B, stirring to obtain solution C; Step 2, washing solution C, separating solid product and drying to obtain hollow ZIF-8 / ZIF-67 precursor; Step 3, carbonizing the hollow ZIF-8 / ZIF-67 precursor under inert atmosphere to obtain hollow carbon / Co high-efficiency electromagnetic wave absorbing material.

2. The method of claim 1, wherein the hollow carbon / Co high-performance electromagnetic wave absorbing material is prepared by the following steps. The stirring time in step (1) is 10-20 min, the stirring time in step (2) is 30-50 min, and the stirring time in step (3) is 30-60 min.

3. The preparation method of the hollow carbon / Co high-efficiency electromagnetic wave absorbing material according to claim 1, characterized in that, The specific steps of washing are centrifugal washing with DMF and methanol in sequence.

4. The method of claim 3, wherein the hollow carbon / Co high-performance electromagnetic wave absorbing material is prepared by the following steps of: The centrifugal washing speed is 5000-8000 r·min -1 , and the centrifugal time is 2-6 min.

5. The method of claim 1, wherein the hollow carbon / Co high-performance electromagnetic wave absorbing material is prepared by the steps of: The temperature of drying is 50-80 ℃.

6. The method of claim 1, wherein the hollow carbon / Co high-performance electromagnetic wave absorbing material is prepared by the steps of: The temperature of carbonization treatment is 500 ℃, and the time is 20-50 min.

7. Hollow carbon / Co high-efficiency electromagnetic wave absorbing material obtained by the preparation method of any one of claims 1-6.

8. Application of the hollow carbon / Co high-efficiency electromagnetic wave absorbing material of claim 7 in absorbing electromagnetic wave.

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