CN113708085B - A kind of preparation method of nanoporous carbon-coated magnetic nanoparticle composite - Google Patents

Abstract

The invention provides a preparation method of a nanoporous carbon-coated magnetic nanoparticle composite, which belongs to the technical field of composite materials. Firstly, graphite phase carbon nitride is synthesized, mixed with magnesium powder and carbonized at high temperature, and the product is washed with hydrochloric acid to obtain nanoporous carbon; secondly, metal salts of iron, cobalt and nickel are dissolved in methanol and added to nanoporous carbon, mixed and dried. and finally, the mixture is calcined at high temperature to obtain a nanoporous carbon-coated nanoparticle composite wave absorbing material. The invention utilizes a two-step nanoporous carbon-coated magnetic nanoparticle composite wave absorbing material, and exhibits good electromagnetic wave absorption ability; the preparation method is simple to operate, and the product has good electromagnetic parameters and electromagnetic wave absorption ability.

Description

A kind of preparation method of nanoporous carbon-coated magnetic nanoparticle composite

technical field

The invention belongs to the technical field of composite materials, and relates to a preparation method of a nanoporous carbon-coated magnetic nanoparticle composite wave absorbing material.

Background technique

Nowadays, with the rapid development of electronic communication technology, human life is increasingly dependent on various electronic products, which brings great convenience to people's daily life but also brings serious electromagnetic pollution. Long-term exposure to excessive electromagnetic radiation will cause irreversible damage to the human immune system, nervous system, etc., and seriously threaten the physical and mental health of human beings. In addition, in the fields of ship manufacturing and electromagnetic stealth of fighters, the preparation of efficient electromagnetic wave absorbing materials is also a hot research topic.

Carbon materials have low cost and good electrical conductivity. However, high electrical conductivity makes single-component carbon materials have poor impedance matching and cannot fully absorb electromagnetic waves. Therefore, it has gradually become the mainstream direction to make composite absorbing materials with new magnetic particles and carbon materials. As a special structure of nanoporous carbon-coated magnetic particle composite absorbing, due to the introduction of magnetic particles with good impedance matching performance, it is beneficial for electromagnetic waves to enter the material, reduce electromagnetic wave reflection, and increase the magnetic loss of the material. absorb.

Therefore, the present invention designs and synthesizes a nanoporous carbon-coated magnetic nanoparticle composite for electromagnetic wave absorption.

SUMMARY OF THE INVENTION

In view of the problems existing in the prior art, the present invention provides a simple and feasible method for preparing nanoporous carbon-coated magnetic nanoparticle composites.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A preparation method of a nanoporous carbon-coated magnetic nanoparticle composite, the method obtains nanoporous carbon by reducing gC ₃ N ₄ with magnesium powder, and adsorbs metal salts through the pores of the nanoporous carbon to obtain a metal salt-loaded nanoporous carbon composite Finally, the intermediate 3 is calcined at high temperature to obtain nanoporous carbon-coated magnetic nanoparticles. Specifically include the following steps:

1) Prepare gC ₃ N ₄ by calcining melamine (C ₃ N ₆ H ₆ ) at high temperature as intermediate 1; mix intermediate 1 and magnesium powder evenly, calcin at high temperature, and wash the obtained product with hydrochloric acid and deionized water until neutral , filter and dry to obtain nanoporous carbon, namely intermediate 2. The mass ratio of the gC ₃ N ₄ to magnesium is 1:0.5-3.5, the calcination temperature is 700-900° C., and the calcination time is 1-3h.

2) Dissolving the metal salt in methanol to prepare a solution, adding the intermediate 2 nanoporous carbon, and magnetically stirring for 30 min, drying the mixed solution to obtain the metal salt-loaded nanoporous carbon composite, namely the intermediate 3. The mass ratio of C to metal salt in the intermediate 3 is controlled at 1:0.2-2.

3) The intermediate 3 powder is placed in a tube furnace, and calcined at a high temperature in an inert atmosphere, the calcination temperature is 300-700° C., and the calcination time is 1-4 h to obtain a nanoporous carbon-coated magnetic nanoparticle composite.

Further, the process of preparing gC ₃ N ₄ in the step 1) is as follows: placing melamine in a tube furnace and calcining at high temperature in the air, the calcination temperature is 480-650 ° C, and the optimal temperature is 550 ° C; the calcination time is 1-5h, the optimal time is 3h.

Further, in the step 1), the calcination temperature is preferably 750° C., and the calcination time is preferably 2 h.

Further, in the step 2), the mass ratio of nanoporous carbon to metal salt is preferably 3:1.

Further, the metal salts include iron acetylacetonate, ferrous acetylacetonate, nickel acetylacetonate, cobalt acetylacetonate, cobalt nitrate, iron nitrate, nickel nitrate, iron acetate, cobalt acetate, nickel acetate, iron chloride, chloride One of nickel and cobalt chloride and a combination thereof.

Further, in the step 3), the calcination temperature is preferably 500°C, and the calcination time is preferably 2h.

The beneficial effects of the present invention are:

In the preparation process, the present invention utilizes magnesium and gC ₃ N ₄ to calcine, and the product is washed with hydrochloric acid to obtain nano-porous carbon; the pores of the nano-porous carbon are used to adsorb the metal salt in the methanol solution of the metal salt, and finally the metal salt is reduced to magnetic properties by high temperature. The obtained product is a composite of nanoporous carbon-coated magnetic nanoparticles.

Scanning electron microscopy, Raman spectroscopy and X-ray diffraction all showed that the nanoporous carbon-coated magnetic nanoparticles were successfully prepared by this method, and the structures were consistent with expectations. The pre-test of the network vector analyzer and the later simulation with matlab can well prove that it has good wave-absorbing performance, which shows the feasibility of this method. The prepared nanoporous carbon-coated magnetic nanoparticle has good impedance matching and attenuation performance, and can fully attenuate electromagnetic waves.

Description of drawings

Figure 1 is a scanning electron microscope image of the C@Fe ₃ O ₄ -1 composite absorbing material:

Figure 2 shows the Raman spectrum of the C@Fe ₃ O ₄ -1 composite absorber:

Figure 3 shows the Raman spectrum of the X-ray diffraction pattern of the C@Fe ₃ O ₄ -1 composite absorber:

Figure 4 is the reflection loss curve of the C@Fe ₃ O ₄ -1 composite absorbing material.

Detailed ways

The present invention will be further described below with reference to specific embodiments.

Example 1 Preparation method of nanoporous carbon-coated magnetic Fe ₃ O ₄ composite wave absorbing particles C@Fe ₃ O ₄ -1:

(1) Preparation of nanoporous carbon C-1:

8.0 g of melamine was placed in a tube furnace and calcined at 550° C. for 3 hours in an air atmosphere. Mix 2.0g _gC3N4 and _4.0g magnesium powder evenly, calcinate at 750℃ for 2h under argon atmosphere, wash the product with hydrochloric acid and deionized water until neutral, filter and dry, the product is nanoporous carbon C-1 .

(2) Preparation of C@Fe(acc) _3-1 :

3.0 g of the nanoporous carbon obtained above was added to 40 ml of methanol solution dissolved with 1.0 g of Fe(acc) , and after magnetic stirring for 30 min, the resulting mixed solution was dried, and the obtained powder was C@Fe(acc _{) 3} -1.

(3) Preparation of C@Fe ₃ O ₄ -1:

The C@Fe(acc) ₃ -1 was placed in a tube furnace and calcined at 500 °C for 2 h in an argon atmosphere to obtain nanoporous carbon-coated magnetic Fe ₃ O ₄ composite absorbing particles C@Fe ₃ O ₄ -1.

(4) The test results are as follows:

Fig. 1 is the scanning electron microscope image of C@Fe ₃ O ₄ -1. It can be seen from the figure that there are a large number of particles on the surface of porous carbon;

Figure 2 is the Raman spectrum of C@Fe ₃ O ₄ -1. It can be seen from the figure that there are obviously D peaks and G peaks of graphitic carbon. The final product C@Fe ₃ O ₄ -1 contains graphitic carbon;

Figure 3 is the X-ray diffraction pattern of C@Fe ₃ O ₄ -1, the diffraction peak at 26.1 ⁰ is the diffraction peak of graphitic carbon, and the diffraction peaks at 46.6 ⁰ and 53.8 ⁰ are the diffraction peaks of Fe ₃ O ₄ . Explain that the composition of C@Fe ₃ O ₄ -1 is graphitic carbon and Fe ₃ O ₄ .

Figure 4 is the absorbing performance diagram of C@Fe ₃ O ₄ -1. It can be seen from the figure that the reflection loss of the composite absorbing material C@Fe ₃ O ₄ -1 is -73.93dB at the frequency of 7.37GHz, and the effective absorption is The bandwidth is 5.44GHz and the thickness is 1.9mm.

Example 2 Preparation method of nanoporous carbon-coated magnetic Fe ₃ O ₄ composite absorbing particles C@Fe ₃ O ₄ -2:

(1) Preparation of nanoporous carbon C-2:

8.0 g of melamine was placed in a tube furnace and calcined at 480° C. for 1 h in an air atmosphere. Mix 2.0g gC ₃ N ₄ and 1.0g magnesium powder evenly, calcinate at 800°C for 3h under argon atmosphere, wash the product with hydrochloric acid and deionized water until neutral, filter and dry, and the product is nanoporous carbon C-2 .

(2) Preparation of C@Fe(acc) _3-2 :

1.5g of the nanoporous carbon obtained above was added to 40ml _of methanol solution in which 3.0g Fe(acc) was dissolved, and after magnetic stirring for 30min, the obtained mixed solution was dried, and the obtained powder was C@Fe(acc ₎ . -2.

(3) Preparation of C@Fe ₃ O ₄ -2:

The C@Fe(acc) ₃ -2 was placed in a tube furnace and calcined at 700 °C for 4 h in an argon atmosphere to obtain nanoporous carbon-coated magnetic Fe ₃ O ₄ composite absorbing particles C@Fe ₃ O ₄ -2.

Example 3 Preparation method of nanoporous carbon-coated magnetic Fe ₃ O ₄ composite absorbing particles C@Fe ₃ O ₄ -3:

(1) Preparation of nanoporous carbon C-3:

8.0 g of melamine was placed in a tube furnace, and calcined at 600° C. for 5 hours in an air atmosphere. Mix 1.0g _gC3N4 and 3.0g magnesium powder evenly, calcinate at 700℃ for 1h under argon atmosphere, wash the product with hydrochloric acid and deionized water until neutral, filter and dry, the product is nanoporous carbon C- ₃ .

(2) Preparation of C@Fe(acc) _3-3 :

2.0g of the nanoporous carbon obtained above was added to 40ml of methanol solution dissolved with 1.0g of Fe(acc) , and after magnetic stirring for 30 min, the resulting mixed solution was dried, and the obtained powder was C@Fe(acc _{) 3} -3.

(3) Preparation of C@Fe ₃ O ₄ -3:

The C@Fe(acc) ₃ -3 was placed in a tube furnace and calcined at 400 °C for 1 h in an argon atmosphere to obtain nanoporous carbon-coated magnetic Fe ₃ O ₄ composite absorbing particles C@Fe ₃ O ₄ -3.

Example 4 Preparation method of nanoporous carbon-coated magnetic Fe ₃ O ₄ composite absorbing particles C@Fe ₃ O ₄ -4:

(1) Preparation of nanoporous carbon C-4:

8.0 g of melamine was placed in a tube furnace and calcined at 650° C. for 4 hours in an air atmosphere. Mix 1.0g gC ₃ N ₄ and 3.5g magnesium powder uniformly, calcinate at 900℃ for 2h under argon atmosphere, wash the product with hydrochloric acid and deionized water until neutral, filter and dry, the product is nanoporous carbon.

(2) Preparation of C@Fe(acc) _3-4 :

2.0 g of the nanoporous carbon obtained above was added to 40 ml of methanol solution dissolved with 0.4 g of Fe(acc) , and after magnetic stirring for 30 min, the resulting mixed solution was dried, and the obtained powder was C@Fe(acc _{) 3} -4.

(3) Preparation of C@Fe ₃ O ₄ -4:

The C@Fe(acc) ₃ -4 was placed in a tube furnace and calcined at 300 °C for 1.5 h in an argon atmosphere to obtain nanoporous carbon-coated magnetic Fe ₃ O ₄ composite absorbing particles C@Fe ₃ O _4-4 .

Example 5 Preparation method of nanoporous carbon-coated magnetic Fe ₃ O ₄ composite absorbing particles C@Fe ₃ O ₄ -5:

(1) Preparation of nanoporous carbon C-5:

8.0 g of melamine was placed in a tube furnace, and calcined at 500° C. for 2 hours in an air atmosphere. Mix _{2.0g gC3N4} and 2.0g magnesium powder evenly, calcinate at 850℃ for 2h under argon atmosphere, wash the product with hydrochloric acid and deionized water until neutral, filter and dry, the product is nanoporous carbon C-5 .

(2) Preparation of C@Fe(acc) _3-5 :

2.0g of the nanoporous carbon obtained above was added to 40ml of methanol solution dissolved with 2.5g Fe(acc) ₃ , and after magnetic stirring for 30min, the obtained mixed solution was dried, and the obtained powder was C@Fe(acc) ₃ -5.

(3) Preparation of C@Fe ₃ O ₄ -5:

The C@Fe(acc) ₃ -5 was placed in a tube furnace, calcined at 600 °C for 3 h in an argon atmosphere, and the nanoporous carbon-coated magnetic Fe ₃ O ₄ composite absorbing particles C@Fe ₃ O ₄ were obtained. -5.

The above-mentioned embodiments only represent the embodiments of the present invention, but should not be construed as a limitation on the scope of the present invention. It should be pointed out that for those skilled in the art, without departing from the concept of the present invention, Several modifications and improvements can also be made, which all belong to the protection scope of the present invention.

Claims (6)

1. a preparation method of nanoporous carbon-coated magnetic nanoparticle composite, is characterized in that, comprises the steps: 1) Prepare gC ₃ N ₄ by calcining melamine C ₃ N ₆ H ₆ at high temperature as intermediate 1; mix intermediate 1 and magnesium powder uniformly and then calcinate at high temperature, the calcination temperature is 700-900 ° C, and the calcination time is 1-3 h The obtained product is washed with hydrochloric acid, washed with deionized water to neutrality, filtered and dried to obtain nanoporous carbon, namely intermediate 2; the mass ratio of the gC ₃ N ₄ to magnesium powder is 1:0.5-3.5; 2) Dissolving the metal salt in methanol to prepare a solution, and adding the nanoporous carbon as the intermediate 2, after magnetic stirring, drying the mixed solution to obtain the nanoporous carbon composite loaded with the metal salt, namely the intermediate 3; The C in the described intermediate 3 and the metal salt mass ratio are controlled at 1:0.2-2; 3) placing the powdered intermediate 3 in a tube furnace, and calcining at a high temperature in an inert atmosphere, the calcination temperature is 300-700 ° C, and the calcination time is 1-4 h, to obtain a nanoporous carbon-coated magnetic nanoparticle composite . 2. The preparation method of a nanoporous carbon-coated magnetic nanoparticle composite according to claim 1, wherein the step ₁ ) preparing _gC3N4 is as follows: placing melamine in a tubular furnace , calcined at high temperature in air, the calcination temperature is 480-650 ℃, and the optimal temperature is 550 ℃. 3 . The method for preparing a nanoporous carbon-coated magnetic nanoparticle composite according to claim 1 , wherein the calcination temperature in the step 1) is preferably 750° C., and the calcination time is preferably 2h. 4 . 4 . The method for preparing a nanoporous carbon-coated magnetic nanoparticle composite according to claim 1 , wherein in the step 2) the mass ratio of nanoporous carbon to metal salt is preferably 3:1. 5 . 5. the preparation method of a kind of nanoporous carbon-coated magnetic nanoparticle composite according to claim 1, is characterized in that, described metal salt comprises ferric acetylacetonate, ferrous acetylacetonate, nickel acetylacetonate, acetylacetonate One of cobalt, cobalt nitrate, iron nitrate, nickel nitrate, iron acetate, cobalt acetate, nickel acetate, iron chloride, nickel chloride, cobalt chloride, and a combination thereof. 6 . The method for preparing a nanoporous carbon-coated magnetic nanoparticle composite according to claim 1 , wherein in step 3) the calcination temperature is preferably 500° C., and the calcination time is preferably 2h. 7 .

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