CN111807346A

CN111807346A - Preparation method of broadband efficient wave-absorbing macroporous thin-layer carbon material

Info

Publication number: CN111807346A
Application number: CN202010695463.XA
Authority: CN
Inventors: 丁春艳; 吴松松; 张宇; 温广武
Original assignee: Shandong University of Technology
Current assignee: Shandong University of Technology
Priority date: 2020-07-20
Filing date: 2020-07-20
Publication date: 2020-10-23
Anticipated expiration: 2040-07-20
Also published as: CN111807346B

Abstract

The invention provides a preparation method of a broadband high-efficiency wave-absorbing macroporous thin-layer carbon material, which comprises the following steps: adding zinc nitrate and glucose according to a certain mass ratio of the glucose to the zinc nitrate, uniformly stirring, transferring the uniformly mixed solution into a forced air drying oven, and carrying out expansion reaction at 120 ℃ for 12 hours to obtain a precursor. And transferring the precursor into a tubular furnace, and keeping the temperature for 2 hours at 900 ℃ in a nitrogen atmosphere to obtain the zinc oxide/carbon material. And (3) carrying out acid washing and water washing on the prepared zinc oxide/carbon material to remove zinc oxide, thus obtaining the pure macroporous thin-layer carbon material. The method has the advantages of simple process, low raw material price and easy industrial production, and the prepared wave-absorbing material has the advantages of ultrahigh absorption peak value, ultra-wide effective absorption bandwidth, lower filling amount, higher specific surface area and the like.

Description

Preparation method of broadband efficient wave-absorbing macroporous thin-layer carbon material

Technical Field

A preparation method of a broadband high-efficiency wave-absorbing macroporous thin-layer carbon material belongs to the field of preparation of novel wave-absorbing materials.

Background

In recent years, as the problems of electromagnetic interference and pollution are increased, the performance and the service life of electronic devices are affected, and the health of human bodies is harmed. The high-performance wave-absorbing (MA) material plays an important role in protecting human health and normal operation of electronic instruments. The prepared microwave absorbing material with the characteristics of thinness, lightness, width and strength is beneficial to reducing the harm of electromagnetic waves to people in daily life, and more importantly, the prepared microwave absorbing material is used as a special military defense material to enhance the stealth characteristic of weaponry. The ideal MA material not only has the characteristics of wide absorption frequency range, strong absorption performance, light weight, low filling rate, chemical corrosion resistance, high thermal stability and the like. Among a plurality of wave-absorbing materials, carbon-based wave-absorbing materials are receiving more and more attention, especially the light weight, good dielectric property and high chemical corrosion resistance.

However, the MA mechanism of carbon-based materials generally depends on their dielectric properties. For amorphous carbon materials, the conductivity and dielectric properties are poor. Therefore, it is difficult to obtain good MA performance simply by using amorphous carbon as the MA material without further design. At the present time, numerous carbon-based MA materials remain unmarketable due to high production costs and complex process flows, so that there is an urgent need to explore sustainable and economical raw materials to produce versatile carbon materials and convenient synthetic techniques.

Disclosure of Invention

The invention aims to provide a preparation method of a broadband high-efficiency wave-absorbing macroporous thin-layer carbon material, and the prepared carbon material has an obvious macroporous structure, low filling amount and excellent wave-absorbing performance. And the importance of the large pores and the thin layer of carbon to form a good impedance match was verified by adjusting the size and wall thickness of the pores.

In order to achieve the purpose, the technical scheme adopted by the invention comprises the following steps:

step 1) adding 1g of glucose into 10ml of deionized water, and carrying out ultrasonic treatment until the glucose is completely dissolved to form a glucose solution;

step 2) adding zinc nitrate with a certain mass into the solution prepared in the step 1, uniformly stirring, transferring the mixed solution into a forced air drying oven, and drying for 12 hours at 120 ℃ to prepare a precursor;

step 3) transferring the precursor prepared in the step 2 into a tubular furnace, heating to 900 ℃ at the heating rate of 5 ℃/min, and preserving the heat for 2 hours in the nitrogen atmosphere to prepare the zinc oxide/carbon composite material;

and 4) washing and acid washing the zinc oxide/carbon composite material prepared in the step 3 to remove zinc oxide impurities, so as to obtain the pure macroporous thin-layer carbon material.

Compared with the prior art, the invention has the following beneficial technical effects:

1. in the step 1), glucose and zinc nitrate interact at 120 ℃, and the system expands to obtain a precursor with a porous structure. The reaction can be carried out at a lower temperature, so that the resources are saved and the cost is reduced.

2. In the step 3), ZnO and the amorphous carbon are subjected to chemical reaction to generate a pore structure in the carbonization process, and a method for directly carbonizing the precursor at high temperature is adopted, so that the process is simple and environment-friendly. The precursor forms an axial pore channel in the precursor after high-temperature carbonization, partial amorphous carbon is etched on the surface and in the amorphous carbon to generate a porous structure due to the occurrence of an etching reaction, and meanwhile, a product Zn is evaporated in a high-temperature environment and is discharged along with inert gas, so that the macroporous thin-layer carbon is finally formed. Compared with other modes for preparing the macroporous thin-layer carbon, the reaction of zinc oxide and carbon is more thorough, the produced porous structure is more ordered, and impurities are easier to remove.

3. And 3) preserving heat for 2 hours, wherein the heat preservation time is selected to ensure the strength of the carbon skeleton and enhance the stability of the structure.

4. The invention can change the amount of zinc nitrate to adjust the pore size and wall thickness of the macroporous thin-layer carbon, and verifies the importance of the macroporous and thin-layer carbon for forming good impedance matching. The material keeps higher dielectric loss and improves impedance matching at the same time, so that more electromagnetic waves enter the material to participate in loss. The macroporous pore channel is used as a channel of electromagnetic waves, so that the impedance matching characteristic can be met, the electromagnetic waves can smoothly enter the material, and the electromagnetic waves are multiply scattered in the pore channel of the optical cable, so that the entered electromagnetic waves are dissipated to the maximum extent, and the excellent wave absorbing performance is achieved. And the invention has high specific surface area (1806 m) due to the existence of macropores²The filling amount of the invention can be stabilized at an extremely low level (2.3 percent), and the light weight requirement can be well realized.

5. The preparation method has the advantages of better control of the conditions used for preparation, low equipment operation requirement, simple process, low energy consumption, continuous operation and easier batch production.

Drawings

1. Fig. 1 shows the precursor morphology of the macroporous thin-layer carbon material prepared in examples 1, 2 and 3 of the present invention.

2. Fig. 2 is an XRD pattern of the macroporous thin-layer carbon prepared after removing zinc oxide by reaction in nitrogen atmosphere in example 3 of the present invention.

3. Fig. 3 is an SEM image of the macroporous thin layer carbon prepared in example 1.

4. Fig. 4 is an SEM image of the macroporous thin layer carbon prepared in example 2.

5. Fig. 5 is an SEM image of the macroporous thin layer carbon prepared in example 3.

6. FIG. 6 is a wave-absorbing reflection loss diagram of the macroporous thin-layer carbon wave-absorbing material prepared in example 3 of the present invention with a filling amount of 2.3% and thicknesses of 2.5mm and 3.5 mm.

Detailed Description

The present invention will now be described in further detail with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.

1. The invention relates to a preparation method of a broadband high-efficiency wave-absorbing macroporous thin-layer carbon material, which comprises the following specific steps:

step 1) adding 1g of glucose into 10ml of deionized water, and carrying out ultrasonic treatment until the glucose is completely dissolved to form a glucose solution.

And 2) adding zinc nitrate with a certain mass into the solution prepared in the step 1), uniformly stirring, transferring the mixed solution into a forced air drying oven, and drying at 120 ℃ for 12 hours to prepare a precursor.

And 3) transferring the precursor prepared in the step 2) into a tubular furnace, heating to 900 ℃ at the heating rate of 5 ℃/min, and preserving the heat for 2 hours in a nitrogen atmosphere to prepare the zinc oxide/carbon composite material.

And 4) washing and pickling the zinc oxide/carbon composite material prepared in the step 3) to remove zinc oxide impurities, so as to obtain the pure macroporous thin-layer carbon material.

The mass of the zinc nitrate added in the step 2) is 0.5g, 1.5g and 2.5 g. Preferably 2.5 g.

2. Example 1

A preparation method of a broadband high-efficiency wave-absorbing macroporous thin-layer carbon material comprises the following specific steps:

And 2) adding 0.5g of zinc nitrate into the solution prepared in the step 1), uniformly stirring, transferring the mixed solution into a forced air drying oven, and drying at 120 ℃ for 12 hours to prepare a precursor.

3. Example 2

And 2) adding 1.5g of zinc nitrate into the solution prepared in the step 1), uniformly stirring, transferring the mixed solution into a forced air drying oven, and drying at 120 ℃ for 12 hours to prepare a precursor.

4. Example 3

And 2) adding 2.5g of zinc nitrate into the solution prepared in the step 1), uniformly stirring, transferring the mixed solution into a forced air drying oven, and drying at 120 ℃ for 12 hours to prepare a precursor.

The material prepared in example 3 was characterized. Fig. 1 is a morphology diagram of precursors prepared in examples 1, 2 and 3, fig. 2 is an XRD diagram of the macroporous thin-layer carbon wave-absorbing material prepared in example 3, fig. 3 is an SEM diagram of the macroporous thin-layer carbon prepared in example 1, fig. 4 is an SEM diagram of the macroporous thin-layer carbon prepared in example 2, fig. 5 is an SEM diagram of the macroporous thin-layer carbon prepared in example 3, and fig. 6 is a wave-absorbing reflection loss diagram of the macroporous thin-layer carbon wave-absorbing material prepared in example 3 at a filling amount of 2.3% and thicknesses of 2.5mm and 3.5 mm.

1. As can be seen from FIG. 1, the precursor of the present invention exhibits different swelling effects depending on the amount of zinc nitrate added, wherein the swelling effect is the best when the amount of zinc nitrate added is 2.5 g.

2. As can be seen from fig. 2, the macroporous thin-layer carbon of the present invention has characteristic peaks of amorphous carbon.

3. As can be seen from fig. 3, the macroporous thin-layer carbon of the present invention has a significant porous structure, but the pore walls are thicker, and the wall thickness of the pore walls is about 0.393 um.

4. As can be seen from fig. 4, the macroporous thin-layer carbon of the present invention has a distinct porous structure with a pore wall thickness of about 0.125 um.

5. As can be seen from fig. 5, the macroporous thin-layer carbon of the present invention has a distinct porous structure with a pore wall thickness of about 0.069 um.

6. As can be seen from FIG. 6, the macroporous thin-layer carbon wave-absorbing material has excellent wave-absorbing performance, the effective bandwidth respectively reaches 6.00GHz (12.00-18.00GHz) and 4GHz (8.00-12.00GHz) when the thickness is 2.5mm and 3.5mm, the effective bandwidth reaches 6.0GHz when the thickness is 2.5mm, the Ku-band is covered, the effective bandwidth reaches 4.0GHz when the thickness is 3.5mm, the X-band is covered, the X-band and the Ku-band are covered at low thickness, and the superiority of the bandwidth is more favorable for the practical utilization of the invention.

Claims

1. A preparation method of a broadband high-efficiency wave-absorbing macroporous thin-layer carbon material is characterized by comprising the following steps:

2. The preparation method of the broadband efficient wave-absorbing macroporous thin-layer carbon material according to claim 1, characterized in that: 1g of glucose was added to 10ml of deionized water and sonicated to dissolve completely to form a homogeneous glucose solution.

3. The preparation method of the broadband efficient wave-absorbing macroporous thin-layer carbon material according to claim 1, characterized in that: adding zinc nitrate with certain mass into the solution prepared in the step 1), uniformly stirring, transferring the mixed solution into a forced air drying oven, and drying for 12 hours at 120 ℃ to prepare a light porous precursor.

4. The preparation method of the broadband efficient wave-absorbing macroporous thin-layer carbon material according to claim 1, characterized in that: transferring the precursor prepared in the step 2) into a tubular furnace, heating to 900 ℃ at the heating rate of 5 ℃/min in the nitrogen atmosphere, preserving the temperature for 2 hours, and cooling at room temperature to prepare the zinc oxide/carbon composite material.

5. The preparation method of the broadband efficient wave-absorbing macroporous thin-layer carbon material according to claim 1, characterized in that: washing and acid washing the zinc oxide/carbon composite material prepared in the step 3) to remove zinc oxide impurities, thus obtaining the pure macroporous thin-layer carbon material.

6. The preparation method of the broadband efficient wave-absorbing macroporous thin-layer carbon material according to claim 1, characterized in that: heating the macroporous thin-layer carbon material prepared in the step 4) and paraffin according to the mass ratio of 1:58 at 60 ℃ until the materials are uniformly mixed, and pressing the materials into a ring-shaped tube with the outer diameter of 7.0mm and the inner diameter of 3.0mm to test the wave-absorbing performance.

7. The preparation method of the broadband efficient wave-absorbing macroporous thin-layer carbon material according to claim 1, characterized in that: the mass of the zinc nitrate added in the step 2) is 0.5g, 1.5g and 2.5g respectively.