CN113597252B - A kind of preparation method of carbon/magnetic electromagnetic wave absorbing material of sandwich structure - Google Patents

Abstract

The invention discloses a carbon/magnetic and electromagnetic wave absorbing material with a sandwich structure and a preparation method thereof. It uses iron salt to prepare flake iron ferric oxide; 5-10g of flake iron ferric oxide is coated with polydopamine to obtain a flake material , and then carbonize the polydopamine-coated sheet material in a nitrogen atmosphere at 450-600°C for 1 hour to obtain the material, add it to 100ml of distilled water, and then add ferric chloride and ferrous chloride with a molar ratio of 2:1 Mix 5g of the blend, stir to dissolve, gradually add 8ml of ammonia water dropwise, react in a 50°C water bath for 1 hour, and then wash. The sandwich structure carbon/magnetic and electromagnetic wave absorbing material has a structure of ferroferric oxide as the inner layer, the middle layer as a carbon layer, and the outermost layer as nanometer ferroferric oxide particles, which can significantly improve the electromagnetic wave absorbing performance of the material, and has Dielectric loss and magnetic loss performance, and light weight, has very broad application prospects.

Description

A kind of preparation method of carbon/magnetic electromagnetic wave absorbing material of sandwich structure

technical field

The invention belongs to the technical field of electromagnetic materials, and in particular relates to a carbon/magnetic electromagnetic wave absorbing material with a sandwich structure and a preparation method thereof.

Background technique

With the rapid development of electronics and electrical technology, the scope of electromagnetic energy utilization continues to expand, followed by electromagnetic radiation pollution. Electromagnetic pollution has become the fifth largest public hazard after wastewater, waste gas, solid waste and noise. Relevant reports indicate that electromagnetic pollution will replace noise pollution in this century and become one of the five major physical pollutions. At present, using electromagnetic wave absorbing materials to weaken or eliminate electromagnetic wave pollution is an effective method.

At present, ferrite or carbon materials are commonly used as electromagnetic wave absorbing materials in the market. Fe3iron tetroxide, carbonyl iron and magnetic electromagnetic wave absorbing materials are heavy in weight, and the prepared materials are thick and heavy, which limits their application range. On the other hand, carbon-based electromagnetic wave absorbing materials have the advantages of light weight, adjustable frequency range, and good compatibility with the organic/inorganic phase interface of the matrix. Graphite powder, carbon black, carbon nanotubes, chopped carbon fibers and activated carbon fibers have been reported as carbon-based electromagnetic wave protection functional fillers. However, the main factor determining the absorbing characteristics of carbon materials is electrical resistance, but its high conductivity makes it easy to reflect electromagnetic waves and affect the absorption efficiency. For this reason, many researchers load magnetic particles on carbon materials, including nickel-plated graphite powder, nickel-plated carbon nanotubes, and loaded nano-ferrite particles to improve the electromagnetic wave absorption performance of the material. Electromagnetic wave absorbing materials are also improved by means of dielectric loss materials, a layer of magnetic loss materials, etc. Patents CN109936974B and CN110028931A proposed methods for preparing electromagnetic wave absorbing materials with a sandwich structure, but there are still certain defects in the preparation process. It is not an obvious multi-layer structure, but a hybrid material, and the number of layers cannot be freely controlled. It cannot independently control the electromagnetic wave absorption performance.

Contents of the invention

In order to overcome the problems of heavy product quality, difficult molding, and single electromagnetic wave loss mechanism in the prior art, the present invention prepares a carbon/magnetic electromagnetic wave absorbing material with a sandwich structure, which forms a carbon layer, a magnetic Micron flake particles with a multi-layer structure such as layers can effectively absorb electromagnetic waves and have very broad application prospects.

In order to achieve the above object, the technical solution provided by the present invention: a carbon/magnetic and electromagnetic wave absorbing material with a sandwich structure, the sandwich structure carbon/magnetic and electromagnetic wave absorbing material, the inner layer is ferric oxide, the middle layer is a carbon layer, The outermost layer is nano ferric oxide particles.

Preferably, the inner layer is ferric oxide, the middle layer is carbon layer, and the outer layer is nano ferric oxide particles as a combined layer, and the sandwich structure carbon/magnetic electromagnetic wave absorbing material has at least 2 combined layers.

As another aspect of the present invention, the present invention provides a method for preparing a sandwich structure carbon/magnetic and electromagnetic wave absorbing material, which includes the following steps, (1) dissolving iron salt in diethylene glycol, and preparing a mass fraction of 8% -10% metal salt solution S1; (2) Add buffer to the S1 solution, stir to dissolve and let it stand for 5 minutes to prepare solution S2; (3) Transfer the S2 solution to the autoclave, and pass through the protective gas, kept at 200°C for 8 hours, and vibrated once every 30 minutes to prevent the agglomeration of particles, then took it out and washed it with deionized water and dried it to obtain flaky ferric oxide; (4) configure 1-2g/ L dopamine hydrochloride and adjust the pH to 8.5 to prepare solution S3; (5) put the flaky iron ferric oxide prepared in step (3) into solution S3, the mass fraction of the flaky ferric ferric oxide is 9% -11%, then shake and react in a water bath at 30°C for 10-24 hours to obtain a polydopamine-coated sheet material; (6) Put the polydopamine-coated sheet material into a 450-600°C nitrogen atmosphere for carbonization treatment 1 hour to obtain material S4; (7) Add every 10g of material S4 to 100ml of distilled water, then add 5g of ferric chloride and ferrous chloride blend with a molar ratio of 2:1 and stir to dissolve, then gradually drop 8ml of ammonia water, React in a 50°C water bath for 1 hour, then wash.

Preferably, the iron salt is selected from ferric sulfate and ferric chloride.

Preferably, the sandwich structure carbon/magnetic and electromagnetic wave absorbing material has an inner layer of ferric oxide, a middle layer of carbon, and an outer layer of nano ferric oxide particles.

Preferably, steps (4)-(7) are repeated to prepare a multi-layer electromagnetic wave absorbing material.

The beneficial effects of the present invention are as follows:

The sheet-like carbon/magnetic electromagnetic wave absorbing material of sandwich structure prepared by the cross-hybridization of ferroferric oxide and carbon in the present invention can significantly improve the electromagnetic wave absorbing performance of the material, has both dielectric loss and magnetic loss performance, and is light in weight, It can be used as an electromagnetic wave absorber and combined with textiles, polymer adhesives, etc. to prepare light and soft electromagnetic wave absorbing composite materials, and has very broad application prospects.

Description of drawings

Fig. 1 is the SEM picture of the carbon-magnetic electromagnetic wave absorbing material of the sandwich structure prepared by the present invention;

Fig. 2 is the carbon-magnetic electromagnetic wave absorbing material electromagnetic wave absorption performance figure of the sandwich structure that the embodiment 1 of the present invention makes;

Fig. 3 is the carbon-magnetic electromagnetic wave absorbing material electromagnetic wave absorption performance diagram of the sandwich structure that the embodiment of the present invention 2 makes;

Fig. 4 is a diagram of the electromagnetic wave absorption performance of the sandwich-structured carbon-magnetic electromagnetic wave absorbing material prepared in Example 3 of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings.

Example 1:

(1) Dissolve 2g of anhydrous ferric chloride into 20ml of diethylene glycol to prepare a metal salt solution;

(2) Add 2g of citric acid-sodium citrate buffer (pH=10) to the solution in step 1, stir to dissolve and let stand for 5 minutes to prepare the solution;

(3) Transfer the solution prepared in step 2 to a Teflon-lined stainless steel autoclave and keep it at 200°C for 8 hours. Vibrate once in 30 minutes to prevent the agglomeration of particles; then take it out and wash it with deionized water and dry it to obtain flake ferric oxide;

(4) Prepare 1g/L dopamine hydrochloride, and adjust the pH of the solution to 8.5 with citric acid-sodium citrate buffer;

(5) Put 5g of flaky iron ferric oxide into 50ml of the solution prepared in step 4, and then shake and react in a water bath at 30°C for 10 hours to obtain a sheet material coated with polydopamine, the thickness of which is 5nm;

(6) Place the material prepared in step 5 into a nitrogen atmosphere at 450°C for carbonization treatment for 1 hour, and then take it out;

(7) Add 10g of the material prepared in step 6 to 100ml of distilled water, then add 5g of the blend of ferric chloride and ferrous chloride with a molar ratio of 2:1, stir and dissolve, and gradually add 8ml of ammonia water, at 50℃ React in a water bath for 1 hour, then wash and set aside;

(8) The prepared material is ferroferric oxide as the inner layer, the middle layer is carbon layer, and the outermost layer is nano-ferric oxide particles, with a conductivity of 0.2 S/cm. The special sandwich structure has certain electromagnetic wave absorption performance, as shown in Figure 2 below.

Example 2:

(1) Dissolve 10g of anhydrous ferric chloride into 80ml of diethylene glycol to prepare a metal salt solution;

(2) Add 5g of citric acid-sodium citrate buffer (pH=10) into the solution in step 1, stir to dissolve and let stand for 5 minutes to prepare the solution;

(3) Transfer the solution prepared in step 2 to a Teflon-lined stainless steel autoclave and keep it at 200°C for 8 hours. Vibrate once in 30 minutes to prevent the agglomeration of particles; then take it out and wash it with deionized water and dry it to obtain flake ferric oxide;

(4) Prepare 2g/L dopamine hydrochloride, and adjust the pH of the solution to 8.5 with citric acid-sodium citrate buffer;

(5) Put 10g of flaky iron ferric oxide into 80ml of the solution prepared in step 4, and then shake and react in a water bath at 30°C for 24 hours to obtain a sheet-like material coated with polydopamine. The thickness of polydopamine is 10nm;

(6) Place the material prepared in step 5 into a nitrogen atmosphere at 600°C for carbonization treatment for 1 hour, and then take it out;

(7) Add 10g of the material prepared in step 6 to 100ml of distilled water, then add 5g of the blend of ferric chloride and ferrous chloride with a molar ratio of 2:1, stir and dissolve, and gradually add 8ml of ammonia water, at 50℃ React in a water bath for 1 hour, then wash and set aside;

(8) The prepared material is ferroferric oxide as the inner layer, the middle layer is carbon layer, and the outermost layer is nanometer ferric oxide particles, with a conductivity of 0.8 S/cm. The special sandwich structure has good electromagnetic wave Absorption performance, controlling the carbonization temperature of dopamine can effectively improve the electromagnetic wave absorption performance of the material, as shown in Figure 3 below.

Example 3:

(1) Dissolve 10g of anhydrous ferric chloride into 80ml of diethylene glycol to prepare a metal salt solution;

(2) Add 5 g of citric acid-sodium citrate buffer (pH=10) to the solution in step 1, stir to dissolve and let stand for 5 minutes to prepare the solution;

(3) Transfer the solution prepared in step 2 to a Teflon-lined stainless steel autoclave and keep it at 200°C for 8 hours. Vibrate once in 30 minutes to prevent the agglomeration of particles; then take it out and wash it with deionized water and dry it to obtain flake ferric oxide;

(4) Prepare 2g/L dopamine hydrochloride, and adjust the pH of the solution to 8.5 with citric acid-sodium citrate buffer;

(5) Put 10g of flaky iron ferric oxide into 80ml of the solution prepared in step 4, and then shake and react in a water bath at 30°C for 24 hours to obtain a sheet-like material coated with polydopamine. The thickness of polydopamine is 10nm;

(6) Place the material prepared in step 5 into a nitrogen atmosphere at 600°C for carbonization treatment for 1 hour, and then take it out;

(7) Add 10g of the material prepared in step 6 to 100ml of distilled water, then add 5g of the blend of ferric chloride and ferrous chloride with a molar ratio of 2:1, stir and dissolve, and gradually add 8ml of ammonia water, at 50℃ React in a water bath for 1 hour, then wash and set aside;

(8) Repeat steps 4-7 once again to coat and carbonize polydopamine and load the outermost layer of iron tetroxide;

(9) The prepared material is ferroferric oxide as the inner layer, and the outer layer is alternately loaded with carbon layer and nanometer ferric oxide particle layer. The conductivity is 0.85 S/cm. The special multi-layer sandwich structure has excellent electromagnetic wave absorption Performance, we found that the electromagnetic wave absorption performance of the material becomes stronger, the minimum loss reaches -19dB, and the bandwidth of the effective loss (<-10dB) in the 2-18GHz band reaches 12GHz, as shown in Figure 4 below.

The coating, carbonization and other preparation processes involved in the present invention generate a carbon layer in situ on the surface of the sheet-shaped ferroferric oxide, so that the structure of the produced product is more stable, and the carbonization rate of dopamine is controlled by the carbonization temperature. At the same time, it can be passed The preparation process controls the number of layers in order to achieve the maximum absorption performance under different electromagnetic wave frequency bands. Compared with the blending and hybridization of various materials by other technologies, the dispersion of various materials prepared by it is not stable, and the stability is not good. However, this patent is loaded layer by layer, and the thickness of each layer is controllable. The prepared material has stable performance. The carbon layer has a great influence on the performance of the material. This patent uses dopamine coating and carbonization technology to prepare carbon layers with different conductivity to control the electromagnetic wave impedance matching and coordinated electromagnetic wave loss of the material as a whole.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications are also possible. It should be regarded as the protection scope of the present invention.

Claims (4)

1. A preparation method of sandwich structure carbon/magnetic electromagnetic wave absorbing material, is characterized in that: comprise the following steps, (1) dissolving the iron salt into diethylene glycol to prepare a metal salt solution S1 with a mass fraction of 8%-10%; (2) adding a buffering agent to the S1 solution, stirring and dissolving, and standing for 5 minutes to prepare a solution S2; (3) Transfer the solution S2 to an autoclave, pass in a protective gas, keep it at 200°C for 8 hours, shake it once every 30 minutes to prevent the agglomeration of particles, then take it out and wash it with deionized water and dry it , to obtain flaky ferric oxide; (4) Prepare 1-2g/L dopamine hydrochloride and adjust the pH to 8.5 to prepare solution S3; (5) Put the flaky iron ferric oxide prepared in step (3) into solution S3, the mass fraction of the flaky ferric oxide is 9%-11%, then shake and react in a water bath at 30°C for 10- 24 hours, obtain the sheet material of coating polydopamine; (6) carbonizing the polydopamine-coated sheet material in a nitrogen atmosphere at 450-600°C for 1 hour to obtain material S4; (7) Add every 10g of material S4 to 100ml of distilled water, then add 5g of ferric chloride and ferrous chloride blend with a molar ratio of 2:1, stir to dissolve, then gradually drop 8ml of ammonia water, and react in a water bath at 50°C After washing for 1 hour, a sandwich structure carbon/magnetic electromagnetic wave absorbing material is obtained. 2. The preparation method of sandwich structure carbon/magnetic and electromagnetic wave absorbing material as claimed in claim 1, characterized in that: the iron salt in step (1) is selected from ferric sulfate and ferric chloride. 3. the preparation method of sandwich structure carbon/magnetic electromagnetic wave absorbing material as claimed in claim 1 is characterized in that: the sandwich structure carbon/magnetic electromagnetic wave absorbing material that step (7) obtains, its inner layer is ferroferric oxide, middle The layer is a carbon layer, and the outer layer is nanometer ferric oxide particles. 4. The method for preparing a sandwich structure carbon/magnetic electromagnetic wave absorbing material as claimed in claim 3, characterized in that: repeating steps (4)-(7) can prepare a multi-layer electromagnetic wave absorbing material.