CN113242687B - Porous fibrous carbon/magneto-electromagnetic wave absorbing material and preparation method thereof - Google Patents
Porous fibrous carbon/magneto-electromagnetic wave absorbing material and preparation method thereof Download PDFInfo
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- CN113242687B CN113242687B CN202110660890.9A CN202110660890A CN113242687B CN 113242687 B CN113242687 B CN 113242687B CN 202110660890 A CN202110660890 A CN 202110660890A CN 113242687 B CN113242687 B CN 113242687B
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- H05K9/0073—Shielding materials
- H05K9/0081—Electromagnetic shielding materials, e.g. EMI, RFI shielding
- H05K9/009—Electromagnetic shielding materials, e.g. EMI, RFI shielding comprising electro-conductive fibres, e.g. metal fibres, carbon fibres, metallised textile fibres, electro-conductive mesh, woven, non-woven mat, fleece, cross-linked
Abstract
The invention discloses a porous fibrous carbon/magneto-electromagnetic wave absorbing material and a preparation method thereof, wherein the electromagnetic wave absorbing material takes active carbon fiber as a substrate, the surface of the fiber is provided with pores, and the surface and the inside of the fiber are loaded with a magneto-loss material Fe 3 O 4 . The preparation method comprises the steps of firstly preparing macroporous active carbon fibers, taking the macroporous active carbon fibers as a base material, and loading ferroferric oxide on the surfaces and the interiors of the fibers in the modes of in-situ hybridization, electroplating or magnetron sputtering and the like. The porous fibrous carbon/magneto-electromagnetic wave absorbing material can obviously improve the electromagnetic wave absorbing performance of the material, can be compounded with resin, fabric and the like to prepare an effective electromagnetic wave protection composite material, and has very wide application prospect.
Description
Technical Field
The invention relates to an electromagnetic wave absorber, in particular to a porous fibrous carbon/magneto-electromagnetic wave absorbing material and a preparation method thereof.
Background
With the rapid development of electronic and electric technologies, the electromagnetic energy utilization range is continuously expanded, and electromagnetic radiation pollution is caused. The problem of electromagnetic pollution has become the 5 th major nuisance following wastewater, exhaust gas, solid waste and noise, and reports on the same indicate that electromagnetic pollution will replace noise pollution in this century to become first-time physical pollution. Currently, the use of electromagnetic wave absorbing materials to attenuate or eliminate electromagnetic wave pollution is an effective approach.
Compared with the traditional ferrite, carbonyl iron and magnetic electromagnetic wave absorbing material, the carbon-based electromagnetic wave absorbing material has the advantages of light weight, adjustable frequency range and good compatibility with the organic/inorganic phase interface of the matrix. The graphite powder, carbon black, carbon nano tube, chopped carbon fiber and activated carbon fiber are all reported as carbon-based electromagnetic wave protection functional fillers. The active carbon fiber has a large surface area, which is a non-negligible factor, and the surface of the electromagnetic wave absorbing material has multiple polarization effects due to the existence of a large amount of surface polar groups, so that absorption attenuation is generated due to relaxation effects. The active carbon fiber represented by the porous fiber material has a main factor determining the wave-absorbing characteristic, namely the resistance, but has high conductivity, is easy to reflect electromagnetic waves and affects the absorption efficiency. Meanwhile, the magnetic permeability of carbon materials such as activated carbon fiber is extremely low, so that the magnetic material hardly acts on magnetic signals, and broadband absorption is not easy to realize. For this reason, many researchers load magnetic particles on carbon materials, including graphite powder nickel plating, carbon nanotube nickel plating, and nano ferrite particle loading, to improve electromagnetic wave absorption performance of the materials.
The patent applications CN1512835A, CN101886214A and CN109937618A mainly use ferrite electromagnetic wave absorption powder with magnetic loss as main absorption materials, and then prepare sheet materials by tabletting or compounding with resin, but the problems of heavy mass, difficult folding of the sheet materials and the like exist, and the electromagnetic wave loss is also single magnetic loss.
Patent application CN107072128A, CN104831421a is a wave-absorbing material based on dielectric loss carbon material, and has no magnetic loss material, which causes the defect of single loss mechanism.
The patent application CN111548601a is a preparation of electromagnetic wave absorbing material by mixing metal salt into polyacrylonitrile solution and then using electrostatic spinning technology and carbonization process, and although the patent application combines dielectric loss and magnetic loss mechanisms, it has a certain defect in terms of material structure and simplification of preparation process.
Disclosure of Invention
Aiming at the problems of heavy product quality, difficult molding, single electromagnetic wave loss machining and the like caused by adopting single carbonyl iron, ferroferric oxide, carbon black, graphene and other ferrite and pure carbon materials as electromagnetic wave absorbing materials in the prior art. The invention provides a porous fibrous carbon/magneto-electromagnetic wave absorbing material and a preparation method thereof, wherein the porous fibrous carbon/magneto-electromagnetic wave absorbing material is used for preparing macroporous active carbon fibers, and ferroferric oxide is loaded on the surfaces and the interiors of the fibers by taking the porous fibrous carbon/magneto-electromagnetic wave absorbing material as a base material, so that the electromagnetic wave absorbing performance of the material can be obviously improved, and the porous fibrous carbon/magneto-electromagnetic wave absorbing material can be composited with resin, fabric and the like to prepare an effective electromagnetic wave protection composite material, and has very wide application prospect.
The invention is realized by the following technical scheme:
porous fibrous carbon/magneto-electromagnetic wave absorbing materialThe material comprises active carbon fiber, wherein pores exist on the surface of the fiber, and the surface and the inside of the fiber are loaded with a magnetic loss material Fe 3 O 4 。
A preparation method of a porous fibrous carbon/magneto-electromagnetic wave absorbing material comprises the following steps:
step 1), cleaning and drying a polyacrylonitrile-based pre-oxidized fiber felt by deionized water, and then adopting normal-temperature plasma treatment to prepare a material S1;
step 2) soaking the S1 in a phosphoric acid solution, and drying the soaked S1 to prepare S2;
step 3) under the protection of nitrogen, activating the S2, and then washing and drying the activated S2 by deionized water for standby, so as to prepare S3;
step 4) reaming the S3, and introducing steam into the S3 for activation to prepare a sample S4;
and 5) loading ferroferric oxide on the S4 material in an in-situ hybridization, electroplating or magnetron sputtering mode to obtain the porous fibrous carbon/magneto-electromagnetic wave absorbing material.
Preferably, the plasma treatment in step 1) takes 20 to 100 seconds.
Preferably, the concentration of the phosphoric acid solution in the step 2) is 20% -30%.
Preferably, the soaking time in the step 2) is 5-20 h.
Preferably, the activation in step 3) is carried out at a temperature of 300-600 ℃ for a time of 1-5 hours.
Preferably, the temperature of the activation in step 4) is 700 to 1000 ℃.
Preferably, the time of introducing the water vapor in the step 4) is 1-10 min.
Preferably, the in situ hybridization in step 5) is performed as follows: preparing 1-5 mol/L ferric chloride solution, soaking S4 into the ferric chloride solution for 2h, and then treating for 1h at 450 ℃ under the protection of nitrogen, so as to obtain the porous fibrous carbon/magneto-electromagnetic wave absorbing material.
Preferably, the magnetron sputtering method in step 5) is as follows: and (3) carrying out normal-temperature plasma treatment on the S4 for 50S, and then carrying out magnetron sputtering to load ferroferric oxide, thereby obtaining the porous fibrous carbon/magneto-electromagnetic wave absorbing material.
The beneficial effects of the invention are as follows:
1. compared with patent applications CN1512835A, CN101886214A and CN109937618A, the invention mainly combines polyacrylonitrile activated carbon fiber with dielectric loss and ferroferric oxide with magnetic loss to prepare the flexible fiber felt, and solves the defects of the patent applications.
2. The present invention differs from patent application CN111548601a in that: on one hand, the macroporous activated carbon fiber is prepared by utilizing a fiber activation technology, and a large number of pores and loaded ferroferric oxide can improve the interface polarization effect of the material and enhance the electromagnetic wave loss; on the other hand, the invention has great difference from the preparation process, the preparation process of the invention is to carry out parameter adjustment on the existing mature industrialized process, and meanwhile, the prepared electromagnetic wave absorbing material is flexible and has certain strength, and can be directly put into use only by simple compounding.
3. The invention uses Fe 3 O 4 And activated carbon fibers, which are representative of both magnetic and carbon-based types. This design can incorporate Fe 3 O 4 The advantages of the particles and the activated carbon fibers enable the magnetic and dielectric materials to perform electromagnetic complementary actions. This effect is beneficial to control of Fe 3 O 4 Particles and activated carbon fibers are used for adjusting electromagnetic parameters, so that a microwave absorbing material with better impedance matching characteristics can be obtained; in addition, the weight of the microwave absorbing material is greatly reduced, and the light absorbing material with wide application prospect can be prepared.
4. Compared with the traditional ferrite-coated electromagnetic wave absorbing material, the fibrous electromagnetic wave absorbing material prepared by the invention is lighter in weight, has soft performance, and can more conveniently camouflage aiming at military targets.
5. The secondary activation process is used for adjusting fiber pores, controlling and adjusting ferric oxide loading capacity of ferric chloride solution concentration and the like, so that the excellent electromagnetic wave absorbing material can be prepared.
Drawings
FIG. 1 is an SEM image of the fiber surface of a porous fibrous carbon/magnetic electromagnetic wave absorbing material prepared in example 1;
FIG. 2 is an SEM image of a fiber cross section of a porous fibrous carbon/magnetic electromagnetic wave absorbing material prepared in example 1;
FIG. 3 is an electromagnetic wave loss curve of the porous fibrous carbon/magnetic electromagnetic wave absorbing material prepared in example 1;
FIG. 4 is an electromagnetic wave loss curve of the porous fibrous carbon/magnetic electromagnetic wave absorbing material prepared in example 2;
FIG. 5 is an electromagnetic wave loss curve of the porous fibrous carbon/magnetic electromagnetic wave absorbing material produced in example 3.
Detailed Description
The invention will be described in further detail with reference to the drawings and the specific embodiments.
Example 1
A porous fibrous carbon/magneto-electromagnetic wave absorbing material takes active carbon fiber as a substrate, a large number of pores exist on the surface of the fiber, and a magneto-loss material Fe is loaded on the surface and the inside of the fiber 3 O 4 。
A preparation method of a porous fibrous carbon/magneto-electromagnetic wave absorbing material comprises the following specific steps:
(1) Cleaning and drying Polyacrylonitrile (PAN) based pre-oxidized fiber felt with deionized water, and then treating for 20S by adopting normal-temperature plasma to prepare the PAN based pre-oxidized fiber felt subjected to surface etching (S1).
(2) S1 is soaked in a phosphoric acid solution with the concentration of 20 percent for 20 hours, and the soaked S1 is dried to prepare the PAN-based pre-oxidized fiber felt (S2) containing phosphoric acid.
(3) Under the protection of nitrogen, activating the S2 at 300 ℃ for 5 hours, and then washing and drying the activated carbon fiber felt with deionized water for standby, thus preparing the activated carbon fiber felt (S3).
(4) And (3) reaming the S3, and introducing steam into the S3 at 700 ℃ for 10min for activation to prepare the reamed activated carbon fiber felt (S4).
(5) Preparing 5mol/L ferric chloride solution, soaking S4 in the ferric chloride solution for 2 hours, and then treating the solution for 1 hour at 450 ℃ under the protection of nitrogen to prepare the porous fibrous carbon/magneto-electromagnetic wave absorbing material.
As shown in FIG. 1, the porous fiber material prepared in this embodiment can clearly see that the fiber surface is loaded with granular substances, namely Fe 3 O 4 As shown in FIG. 2, the cross section of the fiber has a plurality of pores, a plurality of pores and supported Fe 3 O 4 Can improve the interface polarization of the material and enhance the electromagnetic wave loss.
The gram weight of each square meter of the porous fiber material prepared by the embodiment is 850g, and the effective frequency band of electromagnetic wave loss < -10dB in the range of 8-18 GHz is 7GHz, as shown in figure 3.
Example 2
A porous fibrous carbon/magneto-electromagnetic wave absorbing material comprises the following specific steps:
(1) And cleaning and drying the PAN-based pre-oxidized fiber felt by deionized water, and then performing plasma treatment at normal temperature for 100 seconds to prepare the PAN-based pre-oxidized fiber felt subjected to surface etching (S1).
(2) S1 is soaked in a phosphoric acid solution with the concentration of 30 percent for 5 hours, and the soaked S1 is dried to prepare the PAN-based pre-oxidized fiber felt (S2) containing phosphoric acid.
(3) Under the protection of nitrogen, activating the S2 at 600 ℃ for 1h, and then washing and drying the activated carbon fiber felt with deionized water for standby, thus preparing the activated carbon fiber felt (S3).
(4) And (3) reaming the S3, and introducing steam into the S3 at 1000 ℃ for 1min for activation to prepare the reamed activated carbon fiber felt (S4).
(5) And (3) carrying out normal-temperature plasma treatment on the S4 for 50S, and then carrying out magnetron sputtering to load ferroferric oxide on the surface of the S4, wherein the mass ratio is 1:1000, so as to prepare the porous fibrous carbon/magneto-electromagnetic wave absorbing material.
The gram weight of each square meter of the porous fiber material prepared by the embodiment is 700g, and the effective frequency band of electromagnetic wave loss < -10dB in the range of 8-18 GHz is 6.5GHz, as shown in figure 4.
Example 3
A porous fibrous carbon/magneto-electromagnetic wave absorbing material comprises the following specific steps:
(1) And cleaning and drying the PAN-based pre-oxidized fiber felt by deionized water, and then treating the PAN-based pre-oxidized fiber felt by normal-temperature plasma for 60S to prepare the PAN-based pre-oxidized fiber felt subjected to surface etching (S1).
(2) S1 is soaked in a phosphoric acid solution with the concentration of 30 percent for 12 hours, and the soaked S1 is dried to prepare the PAN-based pre-oxidized fiber felt (S2) containing phosphoric acid.
(3) Under the protection of nitrogen, activating S2 for 2 hours at 550 ℃, then washing with deionized water, and drying for standby, thus preparing the activated carbon fiber felt (S3).
(4) And (3) reaming the S3, and introducing steam into the S3 at 950 ℃ for 2min for activation to prepare the reamed activated carbon fiber felt (S4).
(5) Preparing 1mol/L ferric chloride solution, soaking S4 in the ferric chloride solution for 2 hours, and then treating the solution for 1 hour at 450 ℃ under the protection of nitrogen to prepare the porous fibrous carbon/magneto-electromagnetic wave absorbing material.
The gram weight of each square meter of the porous fiber material prepared by the embodiment is 750g, and the effective frequency band of electromagnetic wave loss < -10dB in the range of 8-18 GHz is 5.4GHz, as shown in figure 5.
Claims (7)
1. A porous fibrous carbon/magneto-electromagnetic wave absorbing material is characterized by comprising active carbon fibers, wherein pores exist on the surfaces of the fibers, and a magnetically lossy material Fe is loaded on the surfaces and the inside of the fibers 3 O 4 The method comprises the steps of carrying out a first treatment on the surface of the The activated carbon fiber is prepared by using polyacrylonitrile-based pre-oxidized fiber felt as a raw material, activating the activated carbon fiber at a low temperature of 300-600 ℃ and then heating the activated carbon fiber at a temperature of 700-1000 ℃ to Wen Kuokong;
the preparation method comprises the following steps:
step 1), cleaning and drying a polyacrylonitrile-based pre-oxidized fiber felt by deionized water, and then adopting normal-temperature plasma treatment to prepare a material S1;
step 2) soaking the S1 in a phosphoric acid solution, and drying the soaked S1 to prepare S2;
step 3) under the protection of nitrogen, activating the S2 at 300-600 ℃ for 1-5 hours, and then washing with deionized water, drying for standby, so as to prepare the S3;
step 4) reaming the S3, and introducing steam into the S3 for activation, wherein the activation temperature is 700-1000 ℃, so as to prepare a sample S4;
and 5) loading ferroferric oxide on the S4 material in an in-situ hybridization, electroplating or magnetron sputtering mode to obtain the porous fibrous carbon/magneto-electromagnetic wave absorbing material.
2. A porous fibrous carbon/magneto-electromagnetic wave absorbing material according to claim 1, wherein the plasma treatment in step 1) is performed for a time of 20 to 100s.
3. The porous fibrous carbon/magneto-magnetic wave absorbing material of claim 1, wherein the concentration of said phosphoric acid solution in step 2) is 20% to 30%.
4. A porous fibrous carbon/magneto-electromagnetic wave absorbing material according to claim 1, wherein the soaking time of step 2) is 5-20 hours.
5. The porous fibrous carbon/magneto-magnetic wave absorbing material of claim 1, wherein said time of introducing water vapor in step 4) is 1 to 10 minutes.
6. A porous fibrous carbon/magneto-magnetic wave absorbing material according to claim 1, wherein the in situ hybridization of step 5) is as follows: preparing 1-5 mol/L ferric chloride solution, soaking S4 into the ferric chloride solution for 2h, and then treating for 1h at 450 ℃ under the protection of nitrogen, so as to obtain the porous fibrous carbon/magneto-electromagnetic wave absorbing material.
7. A porous fibrous carbon/magneto-magnetic wave absorbing material according to claim 1, wherein the magnetron sputtering in step 5) is performed as follows: and (3) carrying out normal-temperature plasma treatment on the S4 for 50S, and then carrying out magnetron sputtering to load ferroferric oxide, thereby obtaining the porous fibrous carbon/magneto-electromagnetic wave absorbing material.
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