CN115594161A - Polyimide-based porous magnetic carbon material and preparation method thereof - Google Patents
Polyimide-based porous magnetic carbon material and preparation method thereof Download PDFInfo
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- CN115594161A CN115594161A CN202211071336.8A CN202211071336A CN115594161A CN 115594161 A CN115594161 A CN 115594161A CN 202211071336 A CN202211071336 A CN 202211071336A CN 115594161 A CN115594161 A CN 115594161A
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Abstract
The invention provides a preparation method of a porous magnetic carbon material based on polyimide, which is characterized by comprising the following steps: step S1, adding CoCl 2 ·6H 2 Adding O water into the polyamide acid PAA solution to obtain a coating solution; s2, forming a glue film with the thickness of 100 microns on a glass plate by using an aluminum scraper and placing the glue film in a coagulating bath for curing and drying to obtain porous PAA/CoCl 2 Film formation: step S3, the treated porous PAA/CoCl 2 Transferring the film to a tubular furnace, carrying out heat treatment under the protection of argon, and naturally cooling to obtain a product; and S4, washing the product with distilled water for multiple times until the washed liquid is neutral, placing the product in an oven for drying, and grinding the washed product to obtain the porous hollow magnetic carbon material. Compared with the method for preparing the porous carbon material by using a template method, an etching method and the like, the composite wave absorber material has a preparation processSimple, convenient to operate, easy to realize industrial production, low in cost and the like.
Description
Technical Field
The invention relates to the field of electromagnetic wave absorbing materials, in particular to a polyimide-based porous magnetic carbon material and a preparation method thereof.
Background
In various fields of national economy, the development of 5G technology is relied on, and the V2X vehicle networking technology and the IOT Internet of things technology are rapidly growing in recent years. People also need to solve the problems closely related to the environment and health caused by the rapid development of science and technology while fully enjoying the benefits caused by the rapid development of science and technology. With the rapid development of electrical technology and electrical equipment, pollution caused by electromagnetic waves has attracted much attention. Excessive electromagnetic waves may damage electrical equipment while posing a threat to human health. It is therefore an urgent task to find ways to effectively attenuate or shield electromagnetic radiation.
Compared with electromagnetic wave shielding materials, the wave absorbing material can effectively reduce the reflection of electromagnetic waves on the surface of an object and simultaneously effectively attenuate the electromagnetic waves incident into the material. Meanwhile, the electromagnetic wave reflecting device can convert redundant electromagnetic waves into heat energy instead of simply reflecting the electromagnetic waves, and is attracted by attention. The application of the wave-absorbing material can not only effectively solve the problems of electromagnetic pollution protection and electromagnetic compatibility in daily production and life, but also improve the fighting capacity and the fighting life of weaponry. In the aspect of composition, the wave absorbing material mainly comprises a wave absorbing agent material which plays a role in electromagnetic loss and a base material which provides bonding and processing performances. Therefore, the development of high performance electromagnetic wave absorbing materials is the development of wave absorber materials with "thin, light, wide, and strong" electromagnetic loss characteristics.
The magnetic hollow or porous carbon material has the advantages of small density, good electromagnetic matching property and the like, and the interaction between the material and electromagnetic waves can be enhanced due to the porous or hollow structure, so that the magnetic hollow or porous carbon material is widely concerned in the field of high-performance wave-absorbing materials and has great application potential. However, the problems of complex preparation process, difficulty in rapid batch production, high cost and the like exist in the field of development of magnetic hollow or porous carbon wave absorber materials. Along with the continuous improvement of the requirements of wave-absorbing materials, how to rapidly and efficiently produce the wave-absorbing agent material with low cost and high performance is very important.
Disclosure of Invention
The invention provides a preparation method of a porous magnetic carbon material based on polyimide, aiming at solving the technical problem of complex preparation process of the existing magnetic hollow or porous carbon material, and the preparation method is characterized by comprising the following steps:
step S1, adding CoCl 2 ·6H 2 Adding O into the polyamide acid PAA solution to obtain a coating solution;
s2, forming a glue film with the thickness of 100 microns on a glass plate by using an aluminum scraper and placing the glue film in a coagulating bath for curing and drying to obtain porous PAA/CoCl 2 Film formation:
step S3, the treated porous PAA/CoCl 2 Transferring the film into a tube furnace, carrying out heat treatment under the protection of argon, and naturally cooling to obtain a product;
and S4, washing the product with distilled water for multiple times until the washed liquid is neutral, placing the product in an oven for drying, and grinding the washed product to obtain the porous hollow magnetic carbon material.
Further, in step S1, the solid content of the PAA solution is 15wt% to 20wt%; the CoCl 2 ·6H 2 The mass of O is 2.4 g-4.4 g.
Further, in step S2, the composition of the coagulation bath is deionized water.
Further, in step S3, the heat treatment includes the following specific steps:
s3-1, treating for 0-2.5 hours at the temperature of 250-350 ℃;
and S3-2, treating for 1-3 h at 900-1100 ℃.
Further, the heating rate in the heat treatment process is 1-10 ℃/min.
On the other hand, the invention also provides a polyimide-based porous magnetic carbon material which is prepared by the preparation method.
In summary, compared with the prior art, the invention has the beneficial effects that:
the invention has the beneficial effects that: the invention fully utilizes the dissolution characteristic of polyimide acid, designs a method for introducing magnetic metal particles and obtaining a porous hollow structure by combining pretreatment with a high-temperature pyrolysis method, and prepares the magnetic carbon composite wave absorber material with the porous hollow structure. Compared with the preparation of the porous carbon material by using a template method, an etching method and the like, the composite wave absorber material has the advantages of simple preparation process, convenience in operation, easiness in industrial production, low cost and the like. The polyimide-based porous magnetic carbon material prepared by the invention has stronger wave-absorbing performance and wider wave-absorbing frequency band under the condition of smaller thickness, and is more convenient to use.
Drawings
FIG. 1 is a schematic flow chart of the present invention.
Fig. 2 is a scanning electron micrograph of the polyimide-based porous magnetic carbon material prepared in example 1 of the present invention.
Fig. 3 is XRD spectra of the polyimide-based porous magnetic carbon material prepared in examples 1 and 2 of the present invention.
FIG. 4 is a graph showing electromagnetic parameters for preparing a polyimide-based porous magnetic carbon material in example 4 of the present invention.
FIG. 5 is a graph of calculated reflection loss RL data for electromagnetic parameters tested to prepare a polyimide-based porous magnetic carbon material in example 4 of this invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
The present invention will be described in further detail with reference to the following detailed description and accompanying drawings.
According to the invention, polyimide is taken as a raw material, and is subjected to treatment processes of compounding with metal salt, soaking treatment with deionized water, pyrolysis and the like in sequence, so that the magnetic particle filled porous hollow carbon composite wave absorber material is obtained. The composite wave absorbent material has excellent wave absorption performance, when the filling content is 25% and the thickness is 3.4mm, the maximum reflection loss of the composite wave absorbent material to electromagnetic waves reaches-60.3 dB (more than 99.999% of absorption), the frequency bandwidth of the reflection loss exceeding-10 dB (more than 90% of absorption) reaches 6.2GHz, and the composite wave absorbent material has broadband and strong absorption characteristics. In conclusion, the prepared magnetic carbon composite wave absorber material with the porous structure has the electromagnetic wave loss characteristics of thinness, lightness, width and strength.
In an optional embodiment, the porous magnetic carbon composite wave absorbing agent material based on polyimide prepared by the invention is mixed with paraffin to prepare composite materials with different filling amounts, electromagnetic parameters of the materials are tested, and the wave absorbing performance of the materials is calculated, wherein the specific preparation, test and calculation methods are as follows:
(1) Weighing paraffin and a porous magnetic carbon composite wave absorber material based on polyimide, mixing according to the mass fraction of the wave absorber of 10-35%, and fully grinding until the mixture is uniform;
(2) Pressing the paraffin mixture containing the composite wave absorbing agent with a certain mass fraction into a test ring with the outer diameter of 7mm and the inner diameter of 3.04mm through a special die;
(3) And (3) testing the electromagnetic parameters (epsilon ', epsilon', mu) of the sample in the range of 2-18 GHz by using a vector network analyzer, and calculating the wave absorbing performance of the composite wave absorbing agent by using the following formula, namely the reflection loss RL.
In the formula: z 0 Is free space impedance with a magnitude of 377 Ω; mu.s 0 、ε 0 Is the vacuum permeability and dielectric constant, ε 0 ＝8.854187817×10 -12 F/m，μ0＝4π×10 -7 H/m；Z in Is the input impedance of the wave-absorbing material (obtained by calculating the data of epsilon', mu and mu); f is the frequency of the electromagnetic wave (in the range of 2 to 18 GHz); d is the thickness of the wave-absorbing material; c is the propagation speed of electromagnetic wave in free space, equal to 3X 10 of light speed 8 m/s；ε r (ε r = epsilon' -j epsilon ") and mu r (μ r And = mu' -j mu ") is equivalent relative complex dielectric constant and complex permeability of the wave-absorbing material, and j is an imaginary unit of the complex dielectric constant and the complex permeability, and has no practical significance. Experiments can be carried out to determine epsilon ', epsilon ', mu ' of the material under different electromagnetic wave frequencies f.
The specific embodiment is as follows:
example 1
The synthesis method of the porous magnetic carbon material based on polyimide can be realized by the following reaction steps:
(1) 30g,20% wt of the polyamic acid solution (solvent is DMAc) was weighed out, and 2.2g of CoCl was added 2 ·6H 2 Stirring the mixture evenly to obtain a coating solution;
(2) Forming a glue film with the thickness of 100 mu m on a glass plate by using an aluminum scraper, and curing and drying the glue film in a coagulating bath to obtain the porous PAA/CoCl 2 A film;
(3) The treated porous PAA/CoCl is added 2 The film is transferred to a tube furnace and is subjected to heat treatment under the protection of argon. Heating and heat treatment at 30-350 deg.c/min; 60min at 350 ℃; 350-800 ℃ and 10 ℃/min; 60min at 800 ℃; naturally cooling at 800-30 ℃;
(4) And (3) grinding the composite porous carbon subjected to pyrolysis in the step (2) by using an agate mortar to obtain the polyimide-based porous magnetic carbon material.
Example 2
The synthesis method of the polyimide-based porous magnetic carbon material can be realized by the following reaction steps:
(1) 30g,20% by weight of the polyamic acid solution (solvent is DMAc) was weighed, and 2.2g of CoCl was added 2 ·6H 2 Stirring the mixture evenly to obtain a coating solution;
(2) Forming a glue film with the thickness of 100 mu m on a glass plate by using an aluminum scraper, and curing and drying the glue film in a coagulating bath to obtain the porous PAA/CoCl 2 A film;
(3) The treated porous PAA/CoCl 2 The film was transferred to a tube furnace and heat treated under argon. Heating and heat treatment program at 30-350 deg.c and 10 deg.c/min; 60min at 350 ℃; 350-1000 ℃,10 ℃/min; 60min at 1000 ℃; naturally cooling at 1000-30 ℃;
(4) And (3) grinding the composite porous carbon subjected to pyrolysis in the step (2) by using an agate mortar to obtain the polyimide-based porous magnetic carbon material.
Example 3
(1) 30g,20% wt of the polyamic acid solution (solvent is DMAc) was weighed out, and 4.0g of CoCl was added 2 ·6H 2 O, uniformly stirring to obtain a coating liquid;
(2) Forming a glue film with the thickness of 100 mu m on a glass plate by using an aluminum scraper, and curing and drying the glue film in a coagulating bath to obtain the porous PAA/CoCl 2 A film;
(3) The treated porous PAA/CoCl 2 The film was transferred to a tube furnace and heat treated under argon. Heating and heat treatment program at 30-350 deg.c and 10 deg.c/min; 60min at 350 ℃; 350-1000 ℃,10 ℃/min; 60min at 1000 ℃; naturally cooling at 1000-30 ℃;
(4) And (3) grinding the composite porous carbon pyrolyzed in the step (2) by using an agate mortar to obtain the polyimide-based porous magnetic carbon material.
Example 4:
as an application of the polyimide-based porous magnetic carbon composite wave absorber material prepared by the present invention, paraffin was used as a matrix, the polyimide-based porous magnetic carbon composite material prepared in example 1 was used as a wave absorber, and a test sample with a wave absorber filling amount of 25% was prepared, which was achieved by the following steps:
(1) Mixing paraffin and a porous magnetic carbon composite wave absorbing agent material of polyimide according to a certain mass ratio; wherein the mass percent of the wave absorbing agent/(wave absorbing agent + paraffin) is 25%;
(2) Pressing the mixture of the wave absorbing agent and the paraffin into a test ring with the outer diameter of 7mm and the inner diameter of 3.04mm by using an oil press through a die;
(3) And (3) testing the electromagnetic parameters (epsilon ', epsilon ', mu ') of the prepared sample in the range of 2-18 GHz by using a vector network analyzer, and calculating the wave absorbing performance of the composite wave absorbing agent by using a formula, namely the reflection loss RL.
Fig. 1 shows a schematic diagram of a preparation process of a polyimide-based porous magnetic carbon composite carbon material, wherein the preparation process is mainly divided into a metal salt compounding and phase separation treatment process, a pyrolysis process, and corresponding washing and drying processes. The preparation process fully utilizes the dissolution characteristic of the polyamic acid, and forms a hollow structure in the film through the interaction of the deionized water and the organic solvent, and the hollow structure is solidified and formed, so that the magnetic carbon composite wave absorber material with the porous hollow structure is prepared.
FIG. 2 shows a scanning electron micrograph of the material prepared in example 1. As can be seen from a scanning electron microscope image, the prepared porous carbon has an obvious hollow structure, and magnetic particles with a certain quantity and particle size are filled around the hole.
The XRD spectra of example 1 and example 2 are shown in figure 3. It is known from XRD characterization that after high temperature treatment, cobalt chloride is decomposed to produce cobalt particles, which bring magnetic loss components to the material, and polyimide is decomposed to produce carbon, which brings dielectric loss components to the material.
Figure 5 shows the reflection loss data for the samples prepared in example 3. The porous magnetic carbon composite wave absorbing agent based on the polyimide has excellent absorption performance on electromagnetic waves, the maximum reflection loss of the porous magnetic carbon composite wave absorbing agent on the electromagnetic waves reaches-60.3 dB (more than 99.999 percent of absorption) when the filling content is 25 percent and the thickness is 3.4mm, the bandwidth of the reflection loss of more than-10 dB (more than 90 percent of absorption) reaches 6.2GHz, and the porous magnetic carbon composite wave absorbing agent has broadband and strong absorption characteristics. Therefore, the prepared polyimide-based porous magnetic carbon composite wave absorber has the electromagnetic wave absorption characteristics of thinness, lightness, width and strength, and is an electromagnetic wave absorber material with excellent performance. The invention fully utilizes the dissolution characteristic of polyamic acid, designs a method for introducing magnetic metal particles and obtaining a porous hollow structure by combining pretreatment with a high-temperature pyrolysis method, and prepares the magnetic carbon composite wave absorber material with the porous hollow structure. The polyimide-based porous magnetic carbon material prepared by the invention has stronger wave-absorbing performance and wider wave-absorbing frequency band under the condition of smaller thickness, is more convenient to use, has a simple and convenient preparation method, is convenient for batch production, and has larger potential.
The foregoing is a more detailed description of the present invention with reference to specific embodiments thereof, and it is not intended to limit the invention to the specific embodiments thereof. It will be apparent to those skilled in the art that a number of simple derivations or substitutions can be made without departing from the inventive concept.
Claims (6)
1. A preparation method of a porous magnetic carbon material based on polyimide is characterized by comprising the following steps:
step S1, adding CoCl 2 ·6H 2 Adding O into the polyamide acid PAA solution to obtain a coating solution;
s2, forming a glue film with the thickness of 100 microns on a glass plate by using an aluminum scraper and placing the glue film in a coagulating bath for curing and drying to obtain porous PAA/CoCl 2 Film formation:
step S3, the treated porous PAA/CoCl is treated 2 Transferring the film to a tubular furnace, carrying out heat treatment under the protection of argon, and naturally cooling to obtain a product;
and S4, washing the product with distilled water for multiple times until the washed liquid is neutral, placing the product in an oven for drying, and grinding the washed product to obtain the porous hollow magnetic carbon material.
2. The method for preparing a porous magnetic carbon material based on polyimide according to claim 1, wherein in step S1, the solid content of the PAA solution is 15wt% to 20wt%; the CoCl 2 ·6H 2 The mass of O is 2.4g to 4.4g.
3. The method of claim 1, wherein the coagulation bath is deionized water in step S2.
4. The method for preparing a porous magnetic carbon material based on polyimide according to claim 1, wherein in step S3, the heat treatment comprises the following specific steps:
s3-1, treating for 0-2.5 hours at the temperature of 250-350 ℃;
and S3-2, treating for 1-3 h in an environment with the temperature of 900-1100 ℃.
5. The method for preparing a porous magnetic carbon material based on polyimide as claimed in claim 4, wherein the temperature rise rate of the heat treatment process is 1-10 ℃/min.
6. A polyimide-based porous magnetic carbon material, characterized in that it is produced by the production method according to any one of claims 1 to 5.
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| KR20110017536A (en) * | 2009-08-14 | 2011-02-22 | 충남대학교산학협력단 | Manufacturing method for composite of electromagnetic wave shielding and absorption using high-temperature oxidative resistant porous nano silicon carbide |
| WO2014189270A1 (en) * | 2013-05-21 | 2014-11-27 | 한국생산기술연구원 | Electromagnetic wave shielding sheet comprising carbon composite fiber manufactured by electrospinning and method for manufacturing same |
| CN111285344A (en) * | 2020-02-20 | 2020-06-16 | 西安工程大学 | Magnetic microporous carbon composite film and preparation method thereof |
| CN111302324A (en) * | 2020-02-20 | 2020-06-19 | 西安工程大学 | Magnetic microporous carbon-based wave-absorbing composite material and preparation method thereof |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20110017536A (en) * | 2009-08-14 | 2011-02-22 | 충남대학교산학협력단 | Manufacturing method for composite of electromagnetic wave shielding and absorption using high-temperature oxidative resistant porous nano silicon carbide |
| WO2014189270A1 (en) * | 2013-05-21 | 2014-11-27 | 한국생산기술연구원 | Electromagnetic wave shielding sheet comprising carbon composite fiber manufactured by electrospinning and method for manufacturing same |
| CN111285344A (en) * | 2020-02-20 | 2020-06-16 | 西安工程大学 | Magnetic microporous carbon composite film and preparation method thereof |
| CN111302324A (en) * | 2020-02-20 | 2020-06-19 | 西安工程大学 | Magnetic microporous carbon-based wave-absorbing composite material and preparation method thereof |
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