CN108795378B - Hierarchical porous carbon/magnetic electromagnetic wave absorption material and preparation method and application thereof - Google Patents
Hierarchical porous carbon/magnetic electromagnetic wave absorption material and preparation method and application thereof Download PDFInfo
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- CN108795378B CN108795378B CN201810680653.7A CN201810680653A CN108795378B CN 108795378 B CN108795378 B CN 108795378B CN 201810680653 A CN201810680653 A CN 201810680653A CN 108795378 B CN108795378 B CN 108795378B
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Abstract
A hierarchical porous carbon/magnetic electromagnetic wave absorbing material, a preparation method and an application thereof relate to an electromagnetic wave absorbing material. The ratio of the hierarchical porous carbon/magnetic electromagnetic wave absorption material is as follows: nitrate salt: 0.5g or 1 g; gelatin: 1g of a compound; solvent: 20ml of the solution; dissolving gelatin in water, stirring to obtain gelatin solution, adding nitrate into the gelatin solution, and drying to obtain mixture; and calcining the obtained mixture under the condition of nitrogen to perform carbonization reaction, and cooling to room temperature to obtain the hierarchical porous carbon/magnetic electromagnetic wave absorbing material. The hierarchical porous carbon/magnetic electromagnetic wave absorption material can be applied to preparation of stealth materials. The formula of the raw materials has no special requirements on equipment, the production conditions are mild, the production efficiency is high, the process is simple, the raw materials are cheap, the production cost is low, corrosive reagents harmful to human and environment are not needed in the preparation process, acidic byproducts and acidic gases are not generated, and the method is friendly to workers, ecological environment and production equipment.
Description
Technical Field
The invention relates to an electromagnetic wave absorbing material, in particular to a hierarchical pore carbon/magnetic electromagnetic wave absorbing material prepared by taking gelatin and nitrate as raw materials, a preparation method and an application thereof, wherein the hierarchical pore carbon/magnetic electromagnetic wave absorbing material is prepared by using one-step carbonization reaction to enable nitrate to induce gelatin to self-foam to form micropores, and oxides generated by the nitrate in high-temperature calcination react with carbon to form nanopores.
Background
With the rapid development of information technology, ubiquitous electromagnetic waves cause serious harm to human health, electronic safety, national defense safety and the like. In order to effectively eliminate the disadvantageous electromagnetic wave, research has been conducted on an electromagnetic wave absorbent having advantages of strong absorption, a wide frequency band, a light weight thin layer, and the like, in which a porous material is widely used in the field of electromagnetic wave absorption because it has light weight, low price, easily controlled pore structure, remarkably improved electromagnetic wave absorption performance of the material, and the like. However, the porous wave-absorbing materials reported at present still have many problems, such as complex preparation process, high cost, use of reagents harmful to human and environment, poor performance enhancement, etc.
Chinese patent CN 201510292093.4 discloses a worm-like porous carbon/magnetic particle composite wave absorbing agent and a preparation method thereof. The method comprises the steps of mixing polyacrylonitrile and cobalt-doped ferroferric oxide particles coated with silicon dioxide according to a certain proportion in a solution blending mode to obtain polyacrylonitrile/magnetA solution of sex particles; coating the solution on a glass plate, quickly transferring the glass plate to water, soaking, taking out, and drying in the air to obtain a polyacrylonitrile/magnetic particle porous composite membrane; and pre-oxidizing and carbonizing the obtained polyacrylonitrile/magnetic particle porous composite membrane at a certain temperature, and grinding to obtain the porous carbon/magnetic particle composite wave absorbing agent with the worm-like holes. The diameter of a worm-like hole of the material is 40-100 nm, the material has strong electromagnetic wave absorption property, when the thickness is 1.5mm, the effective absorption bandwidth reaches 4GHz, and the material has good absorption on an electromagnetic wave Ku waveband. Chinese patent CN201610268827.X discloses a method for preparing a CuO/porous carbon composite wave-absorbing material by taking ZIF-67 as a template. Synthesizing metal organic framework ZIF-67 powder by a precipitation method; calcining ZIF-67 powder under nitrogen, dissolving the calcined substance in HF solution to obtain a product with metal Co removed, and marking the product as NPC; dissolving NPC in Cu (NO)3)2And in the solution, removing the upper layer solution after reaction, drying the obtained solid, and calcining at 300-600 ℃ in nitrogen to obtain the porous carbon composite wave-absorbing material inlaid with CuO. The product S-300 shows excellent microwave absorption performance, when the frequency is 11GHz and the matching thickness is 2mm, the optimal RL value can reach-27 dB, the bandwidth of RL less than-10 dB is 3.5GHz, and when the matching thickness is 1-5 mm, the frequency of RL less than-10 dB can cover 3-13 GHz.
The article "Micropore Co @ C Nanoparticles Prepared by Dealloying CoAl @ CPrecurrs: Achieving StrongWidebandMicrowaveAbsorption via Controlling carbon Shell Thickness" (ACS Appl. Mater. interfaces 2017,9(51), 44704-. The preparation method comprises the following steps: firstly, preparing a CoAl alloy through arc plasma reaction in a mixed atmosphere, then depositing carbon on the surface of the CoAl alloy by using methane as a carbon source to obtain CoAl @ C, and finally washing the Al by using sodium hydroxide to obtain the Co @ C. The BET specific surface area of the material prepared by the method is 20.4m2The maximum emission loss is-141.1 dB, the effective absorption bandwidth is 7.3GHz, and the thickness is 1.8 nm. Paper "Lightweight and effective microwave absorbing materials based on unwallnut shell-derivednoporous carbon "(Nanoscale, 2017,9, 7408-: placing the washed and dried walnut kernels in a tubular furnace in nitrogen atmosphere for calcining for 1h, then uniformly mixing the carbonized product with KOH, drying, calcining in the tubular furnace at 500-900 ℃ for 2h in the nitrogen atmosphere, and finally washing the activated sample to be neutral by using HCl to obtain the nano porous carbon material. The specific surface area of the material prepared by the method is 736.2-1101.4 m2The total pore volume is between 0.31 and 0.46cm3The maximum emission loss of the material with the best performance is-42.4 dB, the effective absorption bandwidth is 1.76GHz, and the thickness is 2.0 nm.
As can be seen from the above patents and documents, the methods widely used for preparing porous materials mainly include template method and chemical activation method, however, the template method not only requires the use of expensive template, but also requires the use of large amount of agents such as KOH or HF, etc. which are harmful to human body and environment in the post-treatment process for removing the template; the chemical activation method is a process for preparing porous carbon by using KOH activation, and has the advantages of long activation time, high energy consumption, high cost and serious pollution. In addition, the porous carbon materials have poor wave-absorbing performance, which severely limits the development of the porous carbon materials. In conclusion, the development of a new green and environment-friendly production process and the preparation of the electromagnetic wave absorbing material with excellent performance have great economic and ecological significance.
Disclosure of Invention
Aiming at the defects of the existing porous electromagnetic wave absorbing material technology, low material absorption strength, narrow absorption broadband, difficult realization of broadband absorption and the like, the invention aims to provide a production process which is low in cost, simple in preparation process and friendly to human and environment, and the prepared multi-level pore electromagnetic wave absorbing material which has the advantages of super-wide effective absorption bandwidth, high absorption strength and thin thickness, mild condition, no need of corrosive reagents harmful to human and environment, low production cost and good repeatability can greatly reduce equipment investment, reduce the technical difficulty of the process and improve the production efficiency of the process, and the preparation method and the application thereof.
The ratio of the hierarchical pore carbon/magnetic electromagnetic wave absorption material is as follows:
nitrate salt: 0.5g or 1 g; gelatin: 1g of a compound; solvent: 20ml of the solution;
wherein the nitrate and gelatin are calculated by mass and the solvent is calculated by volume.
The nitrate may be selected from one of ferric nitrate, cobalt nitrate, nickel nitrate, etc.
The solvent can be water or the like.
The preparation method of the hierarchical pore carbon/magnetic electromagnetic wave absorption material comprises the following steps:
1) dissolving gelatin in water, stirring to obtain gelatin solution, adding nitrate into the gelatin solution, and drying to obtain mixture;
in the step 1), the water can adopt deionized water at 80 ℃; the temperature of the drying may be 80 ℃.
2) Calcining the mixture obtained in the step 1) under the condition of nitrogen to carry out carbonization reaction, and cooling to room temperature to obtain the hierarchical porous carbon/magnetic electromagnetic wave absorbing material.
In step 2), the mixture is calcined under nitrogen to carry out carbonization reaction, and the mixture can be placed in a tubular furnace and calcined under nitrogen at 600 ℃ for 2 h.
The hierarchical porous carbon/magnetic electromagnetic wave absorption material can be applied to preparation of stealth materials.
Any reagents used in the preparation process do not require pre-treatment.
The application test is given below: and (3) mixing the product and paraffin wax according to the mass ratio of 1: 1 at normal temperature and normal pressure, and testing the electromagnetic parameters of the product by using a vector network analyzer.
The invention has the following advantages and technical effects:
the raw material formula has no special requirements on production equipment, the production condition is mild, the production efficiency is high, the process is simple, the raw materials are cheap, the production cost is low, corrosive reagents harmful to human and environment are not needed in the preparation process, acidic byproducts and acidic gases are not generated, and the method is friendly to workers, ecological environment and production equipment. The invention has excellent performance, the effective absorption bandwidth of the invention is respectively as high as 8.2, 9.8 and 6.3GHz, and the invention can be used in the fields of stealth materials and the like.
Drawings
Fig. 1 is a nitrogen adsorption and desorption isotherm of the hierarchical porous carbon/magnetic material prepared in examples 1 to 3 of the present invention.
Fig. 2 is a graph showing electromagnetic wave absorption properties of the hierarchical porous carbon/magnetic material prepared in example 1 of the present invention.
Fig. 3 is a graph showing electromagnetic wave absorption properties of the hierarchical porous carbon/magnetic material prepared in example 2 of the present invention.
Fig. 4 is a graph showing electromagnetic wave absorption properties of the multi-graded porous carbon/magnetic material prepared in example 3 of the present invention.
Detailed Description
Example 1
The specific surface area is 234.8m2Per g, pore volume 0.32cm3A multi-pore carbon/magnetic material per gram.
The following formulation was used in this example:
iron nitrate: 0.5 g; gelatin: 1g of a compound; water: 20 ml.
The hierarchical porous carbon/magnetic material is prepared by the formula composition according to the following method:
1) firstly, adding weighed gelatin into water, placing the gelatin in an oven at 85 ℃, adding weighed ferric nitrate after the gelatin is completely dissolved, uniformly stirring, and placing the uniformly mixed solution at room temperature until the gelatin is completely dried;
2) heating the dried mixture to 600 ℃ in a nitrogen atmosphere, and carbonizing for 2 hours to obtain a product;
the electromagnetic wave absorption performance curve of the hierarchical porous carbon/magnetic material prepared in example 1 of the present invention is shown in fig. 2.
Example 2
The specific surface area is prepared to be 239.3m2Per g, pore volume 0.32cm3A multi-pore carbon/magnetic material per gram.
The following formulation was used in this example:
cobalt nitrate: 1g of a compound; gelatin: 1g of a compound; water: 20 ml.
The hierarchical porous carbon/magnetic material is prepared by the formula composition according to the following method:
1) firstly, adding weighed gelatin into water, placing the gelatin in an oven at 85 ℃, adding weighed ferric nitrate after the gelatin is completely dissolved, uniformly stirring, and placing the uniformly mixed solution at room temperature until the gelatin is completely dried;
2) heating the dried mixture to 600 ℃ in a nitrogen atmosphere, and carbonizing for 2 hours to obtain a product;
the electromagnetic wave absorption performance curve of the hierarchical porous carbon/magnetic material prepared for example 2 of the present invention is shown in fig. 3.
Example 3
The specific surface area is 220.0m2Per g, pore volume 0.18cm3A multi-pore carbon/magnetic material per gram.
The following formulation was used in this example:
nickel nitrate: 0.5 g; gelatin: 1g of a compound; water: 20 ml.
The hierarchical porous carbon/magnetic material is prepared by the formula composition according to the following method:
1) firstly, adding weighed gelatin into water, placing the gelatin in an oven at 85 ℃, adding weighed ferric nitrate after the gelatin is completely dissolved, uniformly stirring, and placing the uniformly mixed solution at room temperature until the gelatin is completely dried;
2) heating the dried mixture to 600 ℃ in a nitrogen atmosphere, and carbonizing for 2 hours to obtain a product;
the electromagnetic wave absorption performance curve of the hierarchical porous carbon/magnetic material prepared in example 3 of the present invention is shown in fig. 4.
The results of pore structure parameters of the hierarchical porous carbon/magnetic materials obtained in examples 1 to 3 are summarized in Table 1.
TABLE 1
The nitrogen adsorption and desorption isotherms of the hierarchical porous carbon/magnetic material prepared in the embodiments 1 to 3 of the present invention are shown in fig. 1.
The invention discloses a method for producing a hierarchical porous carbon/magnetic composite material by using gelatin and ferric nitrate as raw materials and calcining a mixture of the gelatin and the ferric nitrate. The raw materials of the formula comprise gelatin and ferric nitrate according to a certain proportion. At a lower temperature, ferric nitrate causes gelatin to spontaneously bubble to form micropores, and ferrite formed by decomposing ferric nitrate in the high-temperature calcination process reacts with carbon to generate nanopores, so that a hierarchical pore structure is formed. Furthermore, it has been demonstrated that gelatin with cobalt nitrate or nickel nitrate can promote spontaneous foaming of gelatin. The material is used for electromagnetic wave absorption, and results show that the maximum reflection loss (RLmax) of the material prepared from the gelatin and the ferric nitrate is up to-51.1 dB, and the Effective Absorption Bandwidth (EAB) reaches 8.2 GHz. EAB of the material prepared by gelatin and cobalt nitrate or nickel nitrate respectively reaches 6.3GHz and 9.8 GHz. The preparation method is simple, does not need toxic and harmful chemical reagents, is environment-friendly and equipment-friendly, has low cost, and can be used for industrial production. The material has ultra-wide electromagnetic wave absorption bandwidth, so the material has wide application prospect in the field of stealth materials.
Claims (3)
1. A preparation method of a hierarchical porous carbon/magnetic electromagnetic wave absorption material is characterized in that the hierarchical porous carbon/magnetic electromagnetic wave absorption material comprises the following components in percentage by weight: nitrate salt: 0.5g or 1 g; gelatin: 1g of a compound; solvent: 20ml of the solution; wherein nitrate and gelatin are calculated by mass, and the solvent is calculated by volume; the nitrate is selected from one of ferric nitrate, cobalt nitrate and nickel nitrate;
the preparation method comprises the following steps:
1) dissolving gelatin in deionized water at 80 ℃, stirring until the gelatin is dissolved to obtain a gelatin solution, adding nitrate into the gelatin solution, and drying at 80 ℃ to obtain a mixture;
2) calcining the mixture obtained in the step 1) under the condition of nitrogen to carry out carbonization reaction, and cooling to room temperature to obtain the hierarchical porous carbon/magnetic electromagnetic wave absorbing material; the mixture is calcined under the nitrogen condition to carry out carbonization reaction, and the mixture is placed in a tube furnace and calcined for 2 hours under the nitrogen condition at the temperature of 600 ℃.
2. The method for preparing a hierarchical porous carbon/magnetic electromagnetic wave absorbing material as set forth in claim 1, wherein said solvent is water.
3. The use of the hierarchical porous carbon/magnetic electromagnetic wave absorbing material prepared by the method of claim 1 in the preparation of stealth materials.
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| CN105742072A (en) * | 2016-04-11 | 2016-07-06 | 河南师范大学 | Preparation method for metal embedded porous carbon counter electrode material |
| CN105820796A (en) * | 2016-04-25 | 2016-08-03 | 中国科学院西安光学精密机械研究所 | Preparation method of magnetic-alloy-loaded porous carbon sphere composite wave-absorbing material |
| CN105896099A (en) * | 2016-04-25 | 2016-08-24 | 中国科学院西安光学精密机械研究所 | Method for preparing porous carbon ball composite absorbing material loaded with magnetic metal element |
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| CN105742072A (en) * | 2016-04-11 | 2016-07-06 | 河南师范大学 | Preparation method for metal embedded porous carbon counter electrode material |
| CN105820796A (en) * | 2016-04-25 | 2016-08-03 | 中国科学院西安光学精密机械研究所 | Preparation method of magnetic-alloy-loaded porous carbon sphere composite wave-absorbing material |
| CN105896099A (en) * | 2016-04-25 | 2016-08-24 | 中国科学院西安光学精密机械研究所 | Method for preparing porous carbon ball composite absorbing material loaded with magnetic metal element |
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| Mechanistic insights into the formation of porous carbons from gelatin;A. E. Danks，等;《Journal of Materials Chemistry A》;20170105;第5卷(第23期);第11644-11651页 * |
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