CN117677169A - Carbon-based electromagnetic shielding block material and preparation and application thereof - Google Patents
Carbon-based electromagnetic shielding block material and preparation and application thereof Download PDFInfo
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 65
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- 229910052751 metal Inorganic materials 0.000 claims description 28
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- 239000002184 metal Substances 0.000 claims description 21
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 11
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 10
- 239000002041 carbon nanotube Substances 0.000 claims description 9
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 8
- 238000004321 preservation Methods 0.000 claims description 8
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- JDSHMPZPIAZGSV-UHFFFAOYSA-N melamine Chemical compound NC1=NC(N)=NC(N)=N1 JDSHMPZPIAZGSV-UHFFFAOYSA-N 0.000 claims description 7
- 239000007769 metal material Substances 0.000 claims description 7
- 239000000203 mixture Substances 0.000 claims description 7
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- 238000002490 spark plasma sintering Methods 0.000 claims description 7
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- UFMZWBIQTDUYBN-UHFFFAOYSA-N cobalt dinitrate Chemical compound [Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O UFMZWBIQTDUYBN-UHFFFAOYSA-N 0.000 claims description 2
- 229910001981 cobalt nitrate Inorganic materials 0.000 claims description 2
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- ZMANZCXQSJIPKH-UHFFFAOYSA-N Triethylamine Chemical compound CCN(CC)CC ZMANZCXQSJIPKH-UHFFFAOYSA-N 0.000 description 3
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- 239000013094 zinc-based metal-organic framework Substances 0.000 description 3
- KKEYFWRCBNTPAC-UHFFFAOYSA-N Terephthalic acid Chemical compound OC(=O)C1=CC=C(C(O)=O)C=C1 KKEYFWRCBNTPAC-UHFFFAOYSA-N 0.000 description 2
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Abstract
The invention relates to a carbon-based electromagnetic shielding block material and preparation and application thereof, and belongs to the technical field of electromagnetic shielding materials. The electromagnetic shielding material is prepared by taking porous carbon composite powder as a raw material and adopting a discharge plasma sintering technology. The prepared block material has excellent mechanical, electric and thermal conductivity, can realize good electromagnetic shielding effect in multiple wave bands, and has wide application prospect in the electromagnetic protection fields of aerospace, constructional engineering and the like.
Description
Technical Field
The invention belongs to the field of electromagnetic shielding materials, and particularly relates to a carbon-based electromagnetic shielding block material, and preparation and application thereof.
Background
Electromagnetic technology brings great convenience to life of people, and simultaneously brings a large amount of electromagnetic radiation, so that electromagnetic pollution is caused, normal operation of electronic equipment is influenced, human health is damaged, and electromagnetic information leakage is seriously caused. Therefore, developing electromagnetic shielding materials with high absorption efficiency is one of the most important technical means for solving the problems of electromagnetic radiation and electromagnetic pollution. On the one hand, with the rapid development of aerospace weaponry, wireless base stations and 5G communication technologies, the ideal electromagnetic shielding material should meet the characteristics of light weight, strong absorption, wide frequency, high thermal stability and the like. On the other hand, for the application fields of electronic element protecting shell, construction engineering shielding body, aviation missile antenna protecting cover and the like, the electromagnetic shielding structural member is required to have excellent mechanical properties, and the safety, applicability and durability of the protecting body are prevented from being influenced by external environmental force.
Carbon nanomaterial such as carbon nanotube, carbon fiber, graphene and the like have been widely used in the field of electromagnetic shielding due to their characteristics of ultra-high conductivity, excellent mechanical properties, strong corrosion resistance, low density, easy processing, environmental friendliness and the like. However, the high conductivity of carbon materials tends to cause a large amount of electromagnetic wave reflection, causing secondary pollution. Thus, researchers have often chosen to introduce magnetic components to enhance the impedance matching characteristics to enhance the absorption of electromagnetic waves within the material. Metal-organic frameworks (MOFs) are porous materials that are self-assembled from organic ligands and metal ions or clusters through coordination bonds. Through heat treatment, metal ions are reduced into metal simple substances and uniformly distributed in the organic ligand-derived porous carbon matrix, and the MOF-derived metal/carbon material has better electromagnetic wave absorption capacity based on the synergistic effect of dielectric loss and magnetic loss. However, due to disorder of the derivatized porous carbon structure, electron transport ability is poor, conductivity is low, and carbon material exists mainly in the form of amorphous carbon, graphitization degree is generally low, thereby inhibiting electromagnetic shielding effectiveness thereof. For example, ZHU et al constructed needle Co by simple pyrolysis of ZIF-67 at high temperature 3 O 4 and/C array structure, the electromagnetic shielding effectiveness of the material is only 33dB (reference: novel MOF-modified 3 Dhierucic needleracearracyarc architecture with the thermocellunentEMIshielding, thermal insulation and thermal capacitor performance.nanoscales.2022.). In addition, in the special application fields of aerospace, military industry and the like, besides the requirement that the electromagnetic shielding composite material has high shielding efficiency, the requirement of developing a super-strong bearing and super-light high-performance component with integrated structural and functional functions is also put forward. Therefore, there is a need to develop structural materials having excellent mechanical and electromagnetic shielding effects to satisfy the important equipment in the related artA need.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to solve the technical problems of selecting a metal/carbon material, wherein a carbon component provides dielectric loss, a magnetic metal provides magnetic loss, and a carbon-based electromagnetic shielding block material with dielectric-magnetic dual loss is prepared.
The carbon-based block material is obtained by spark plasma sintering of a precursor containing a metal/carbon material.
The metal/carbon material is metal/carbon derived from a crystalline porous material, wherein the crystalline porous material is a cobalt-based metal-organic framework Co-MOF material.
The metal/carbon material is one of metal/porous carbon or metal/carbon nanotube CNT/porous carbon.
The preparation method of the carbon-based block material comprises the following steps:
(1) Performing heat treatment on the metal organic framework material in an inert atmosphere to obtain a metal/porous carbon material;
or performing heat treatment on the mixture of the metal organic framework material and melamine in a mixed atmosphere to obtain a metal/carbon nano tube CNT/porous carbon material;
(2) And (3) performing spark plasma sintering treatment on the metal/porous carbon material or the metal/carbon nano tube CNT/porous carbon material, and then polishing and polishing to obtain the carbon-based block material.
The preferred mode of the preparation method is as follows:
the metal-organic framework material in the step (1) is a cobalt-based metal-organic framework Co-MOF material.
The preparation method of the cobalt-based metal-organic framework Co-MOF material comprises the following steps: dissolving 2-methylimidazole in a methanol solution containing cobalt nitrate, synthesizing crystals by a solution method, centrifuging, washing and drying; wherein the reaction temperature of the solution method is 20-25 ℃ and the reaction time is 18-24h; the process conditions of centrifugation are: the rotation speed is 10000r/min, and the time is 5-10min; the washing process conditions are as follows: sequentially washing with methanol solution for 3-5 times; the drying process conditions are as follows: drying at 50-80deg.C for 6-10 hr.
And (2) performing heat treatment on the metal organic framework material in the step (1), wherein the heat treatment is as follows: the temperature rising rate is 2-5 ℃/min, the calcining temperature is 600-800 ℃, and the heat preservation time is 1-3h.
The mixture of the metal organic framework material and the melamine in the step (1) is subjected to heat treatment, wherein the heat treatment is as follows: the temperature rising rate is 2-5 ℃/min, the calcining temperature is 600-900 ℃, and the heat preservation time is 0.5-1.5h.
The mixed atmosphere in the step (1) is methane and argon, wherein the flow rate ratio of the methane to the argon is 1: (0.5-2); the metal organic framework material and melamine mixture comprises the following components in percentage by mass: (0.05-0.10).
The technological parameters of the spark plasma sintering treatment in the step (2) are as follows: sintering temperature is 1600-2200 ℃, sintering pressure is 60-100MPa, heating rate is 90-110 ℃/min, and heat preservation time is 4-10min.
And (3) demolding and removing the carbon paper before the grinding and polishing treatment in the step (2).
The invention relates to an application of the carbon-based block material in shielding materials.
The carbon-based block material is applied to the fields of aerospace, military national defense, constructional engineering or electromagnetic protection.
Further, for example, the carbon-based block shielding material can be used as an electromagnetic shielding device in the fields of electromagnetic protection, aerospace and the like.
The method can efficiently convert the porous carbon into the graphite block, not only has excellent electromagnetic shielding effect in multiple wave bands, but also has excellent electric, thermal and mechanical properties, and can be used as a lightweight high-efficiency electromagnetic shielding structural member to be applied to the fields of aerospace, military national defense or electromagnetic protection.
The electromagnetic shielding material is prepared by taking porous carbon composite powder as a raw material and adopting a discharge plasma sintering technology. The prepared block material has excellent mechanical, electric and thermal conductivity, can realize good electromagnetic shielding effect in multiple wave bands, and has wide application prospect in the electromagnetic protection fields of aerospace, constructional engineering and the like.
Advantageous effects
(1) According to the invention, by combining chemical synthesis and industrial sintering technology, porous carbon is efficiently converted into graphite by using a spark plasma sintering method, and the prepared carbon-based block material has the advantages of low density, high density, excellent mechanical property, high conductivity and good thermal stability. Meanwhile, the graphitization degree of the obtained block is up to 98%, and compared with the traditional graphite preparation process, the preparation method does not need to add an adhesive and repeatedly dip and bake, and has shorter preparation period and simpler process flow;
(2) The carbon-based shielding block prepared by the invention has excellent electromagnetic shielding effect, such as SE in the X, ku and K wave bands T 68.26dB, 53.52dB and 32.45dB are respectively achieved, and the shielding performance is mainly absorbed in three wave bands. At the same time, the flexural strength of the carbon-based block is 97MPa, the compressive strength is up to 208MPa, excellent mechanical properties are shown, and the in-plane thermal conductivity is up to 248Wm -1 K -1 The conductivity is as high as 7311S/cm;
(3) The carbon-based electromagnetic shielding block material prepared by the invention has a unique microstructure, and amorphous carbon forms a continuous and regular graphite conductive network after being sintered by spark plasma, so that the shielding efficiency is improved, and the conductivity loss of electromagnetic waves is promoted. And the strong magnetic loss caused by the cooperative magnetic metal improves the overall impedance matching characteristic of the material, so that electromagnetic waves can enter the material. In addition, the presence of a portion of the defects in the carbon material results in an asymmetric distribution of charges forming dipoles, while the abundant heterogeneous interface between C and Co exacerbates the polarization relaxation losses. The coexistence of multiple loss mechanisms promotes the attenuation of electromagnetic waves in the material, and finally, the prepared block material has excellent electromagnetic shielding performance mainly based on absorption.
Drawings
FIG. 1 is an XRD pattern of Co-MOF prepared in example 1;
FIG. 2 is an XRD pattern of C/Co and C/CoB obtained in example 1;
FIG. 3 is a cross-sectional Scanning Electron Microscope (SEM) of the bulk C/CoB prepared in example 1;
FIG. 4 is a graph of the electromagnetic shielding effectiveness of the bulk C/CoB prepared in example 1 in the X-band (8.2-12.4 GHz);
FIG. 5 is a graph of the electromagnetic shielding effectiveness of the bulk C/CoB prepared in example 1 in the Ku band (12.4-18 GHz);
FIG. 6 is a graph of the electromagnetic shielding effectiveness of the bulk C/CoB prepared in example 1 in the K band (18-26.5 GHz);
FIG. 7 is a scanning electron microscope image of powder C/CNT/Co obtained in example 2;
FIG. 8 is a cross-sectional Scanning Electron Microscope (SEM) of the bulk C/CNT/CoB obtained in example 2;
FIG. 9 is a graph of electromagnetic shielding effectiveness of bulk C/CNT/CoB prepared in example 2 in the K-band (18-26.5 GHz);
FIG. 10 is a graph of the total electromagnetic shielding effectiveness of the block C/CoB of example 1 in the X, ku, K bands;
FIG. 11 is an XRD contrast pattern of the block C/CoB prepared in comparative example 1 and the block prepared in example 1;
FIG. 12 is a sectional scanning electron micrograph of bulk C/ZnB prepared in comparative example 2.
Detailed Description
The invention will be further illustrated with reference to specific examples. It is to be understood that these examples are illustrative of the present invention and are not intended to limit the scope of the present invention. Further, it is understood that various changes and modifications may be made by those skilled in the art after reading the teachings of the present invention, and such equivalents are intended to fall within the scope of the claims appended hereto.
Example 1
(1) 8.148gCo (NO) 3 ) 3 ·6H 2 O was dissolved in 350ml of methanol solution and magnetically stirred 400r/min until complete dissolution, resulting in a pale red solution. Then, 9.1952g of 2-methylimidazole was weighed and dissolved in 350ml of methanol solution, followed by magnetic stirring. The organic ligand solution was poured into the metal ion-containing solution and stirred well at 22 ℃ for 24h to give a purple solution. The product was collected by centrifugation and washed 3 times with methanol solution, and finally dried at 80℃for 6 hours to obtain Co-MOF powder.
(2) And (3) placing the Co-MOF powder in a quartz crucible, performing high-temperature pyrolysis in a tube furnace under an argon atmosphere, heating at a rate of 5 ℃/min, calcining at a temperature of 700 ℃, and preserving the temperature for 3 hours to obtain Co/porous carbon powder (C/Co).
(3) Weighing 0.5g, 1.0g and 2.0g of C/Co powder, sequentially loading the powder into high-pressure graphite dies with diameters of 10, 15 and 30mm according to the sequence of carbon paper-sample-carbon paper, sintering at 1800 ℃ under 80MPa, heating at 100 ℃/min, maintaining for 10min, naturally cooling to room temperature after sintering, taking out the dies, demoulding, and removing the carbon paper to obtain the black block sample C/CoB.
The XRD patterns of the Co-MOFs produced in this example are shown in FIG. 1, and the XRD diffraction peaks of the Co-MOFs produced in the example are consistent with the simulated standard Co-MOFXRD diffraction peaks.
The XRD patterns of the C/Co and C/CoB prepared in this example are shown in FIG. 2, and the test results show that the crystal phase mainly comprises Co and graphite phases.
The section electron microscope of the block C/CoB prepared in the embodiment is shown in FIG. 3, the test result shows that the block section is flat, no obvious holes exist, the whole is compact, and the block density is 2.68g/cm through calculation of the formula ρ=m/v 3 The block is cut into small cubes with the length, the width and the height of 1mm, 1mm and 1mm, the compression strength of the block is measured by a compression experiment of a universal mechanical tester, the block is cut into cubes with the length, the width and the height of 12mm, 1mm and 1mm, the bending strength is measured by a three-point bending test and is 97MPa, and the bending strength and the compression strength are measured for 3 times to obtain an average value. Electrical conductivity was 5541S/cm (Z direction) and 7311S/cm (XY direction) by the four-probe method, and thermal conductivity was 91Wm by the laser thermal conductivity meter and the differential scanning calorimeter -1 K -1 (Z direction) and 248Wm -1 K -1 (XY direction).
After the block material prepared in this example was demolded and polished, rectangular parallelepiped samples having a length×width of 10.95mm×4.5mm, 15.9mm×8.03mm and 22.9mm×10.2mm and an unlimited thickness were cut, and the shielding properties of the samples were measured in the ranges of 8.2 to 12.4GHz, 12.4 to 18GHz and 18 to 26.5GHz by a vector network analyzer (Keysight, N5234B). As shown in FIGS. 4, 5 and 6The total shielding effectiveness SE of the C/CoB block in the 8.2-12.4GHz band is shown T =68.26 dB, where SE A ＝51.35dB，SE R =16.91 dB; SE in the 12.4-18GHz band T = 53.52dB, where SE A ＝35.47dB，SE R =18.05db; SE in 18-26.5GHz range T = 32.45dB, where SE A ＝17.61dB，SE R ＝14.84dB。
Example 2
The difference between this example and example 1 is that after Co-MOF is synthesized, melamine with mass fraction of 5wt.% of Co-MOF is weighed and ground and mixed uniformly, and then the mixture is placed in a quartz crucible, and methane and argon are introduced in a ratio of 1: and (3) carrying out high-temperature calcination on the mixed gas with the temperature of 0.5, wherein the heating rate is 5 ℃/min, the calcination temperature is 750 ℃, and the heat preservation time is 1h, so as to prepare the Co/carbon nano tube/porous carbon powder (C/CNT/Co).
Weighing 0.5g, 1.0g and 2.0g of C/CNT/Co powder, sequentially loading the powder into high-pressure graphite dies with diameters of 10, 15 and 30mm according to the sequence of carbon paper-sample-carbon paper, sintering at 1800 ℃, sintering pressure of 80MPa, heating rate of 100 ℃/min and heat preservation time of 10min, naturally cooling to room temperature after sintering, taking out the dies, demoulding, and removing the carbon paper to obtain the block sample C/CNT/CoB.
The scanning electron microscope image of the C/CNT/Co powder prepared in this example is shown in FIG. 7, and the test results show that the grown CNTs are wound in a curved manner and uniformly distributed on the surface of the porous carbon.
A section electron microscope of the block C/CNT/CoB prepared in the embodiment is shown in FIG. 8, and the test result shows that the block section is uneven and the whole is not compact, and the block density is 2.26g/cm through calculation according to the formula ρ=m/v 3 The lighter blocks are more widely used in the fields of military, aerospace and the like. The block was cut into small cubes of length x width x height 1mm x 1mm, and the compressive strength of the block was 92MPa as measured by compression experiments with a universal mechanical tester.
After demoulding and polishing the block material prepared in the embodiment, a cuboid sample with the length multiplied by the width of 10.95mm multiplied by 4.5mm and the thickness not limited is cut, and a screen of the sample within the range of 18-26.5GHz is tested by a vector network analyzer (Keysight, N5234B)The shielding performance. As shown in FIG. 9, the total shielding effectiveness SE of the C/CNT/CoB bulk T =26.24 dB, where SE A ＝13.69dB，SE R ＝12.55dB。
Comparative example 1
The comparative example differs from example 1 in that the C/Co powder was weighed and placed in a high pressure graphite mold, the sintering temperature was changed to 1400℃, and the other sintering conditions and subsequent sample processing steps were unchanged.
As shown in FIG. 11, the XRD pattern of the bulk C/CoB prepared in this comparative example shows that the diffraction peak of the bulk C/CoB-1400 graphite (002) obtained by sintering at 1400 ℃ is lower than that of the bulk prepared at other sintering temperatures, indicating poor graphite crystallinity. The bulk density was calculated to be 2.74g/cm by ρ=m/v 3 The block is cut into small cubes with the length, the width and the height of 1mm multiplied by 1mm, and the compression strength of the block is 157MPa and is lower than 1800 ℃ by a compression experiment of a universal mechanical tester. The comparison shows that the block prepared at the sintering temperature lower than the sintering temperature of the invention can not achieve the effect of the invention.
Comparative example 2
This comparative example differs from example 1 in that Zn-MOF was chosen as precursor and 16.99g of zinc acetate was weighed into 500ml of N, N-dimethylformamide and magnetically stirred 400r/min until completely dissolved. 5.065g of terephthalic acid and 8.5ml of triethylamine were then weighed out and dissolved in 400ml of N, N-dimethylformamide with magnetic stirring until completely dissolved. The organic ligand solution was poured into the metal ion-containing solution and stirred well at 22 ℃ for 24 hours to give a white solution. The product was collected by centrifugation and washed 3 times with methanol solution, and finally dried at 60℃for 12 hours to obtain Zn-MOF powder. The Zn-MOF powder was placed in a quartz crucible and subjected to high-temperature pyrolysis in a tube furnace under an argon atmosphere, and the heat treatment conditions and sintering conditions were the same as those of example 1, to finally prepare a bulk sample C/ZnB. A section electron microscope diagram of the block C/ZnB prepared in the comparative example is shown in figure 12, and test results show that compared with a block prepared by taking Co-MOF as a precursor, the block prepared by the method has poorer compactness due to the change of metal type, and uneven section presents uneven shape. The bulk density was calculated to be 1.46g/cm by the formula ρ=m/v 3 Cutting the block into small cubes with length, width and height of 1mm, 1mm and 1mmThe compressive strength of the block is only 26.24MPa, which is far lower than that of the block C/CoB prepared by taking Co-MOF as a precursor through a compression experiment of a universal mechanical testing machine. The comparison shows that the metal type in the metal organic frame has great influence on the density, mechanical property and the like of the sample, and other metals can not achieve the effect of the invention.
Claims (10)
1. A carbon-based bulk material, characterized in that the carbon-based bulk material is obtained by spark plasma sintering with a precursor comprising a metal/carbon material.
2. The carbon-based bulk material of claim 1, wherein the metal/carbon material is one of metal/porous carbon or metal/carbon nanotube CNT/porous carbon.
3. A method of preparing a carbon-based bulk material, comprising:
(1) Performing heat treatment on the metal organic framework material in an inert atmosphere to obtain a metal/porous carbon material;
or performing heat treatment on the mixture of the metal organic framework material and melamine in a mixed atmosphere to obtain a metal/carbon nano tube CNT/porous carbon material;
(2) And (3) performing spark plasma sintering treatment on the metal/porous carbon material or the metal/carbon nano tube CNT/porous carbon material, and then polishing and polishing to obtain the carbon-based block material.
4. The method of claim 3, wherein the metal-organic framework material in step (1) is a cobalt-based metal-organic framework Co-MOF material.
5. The method of claim 4, wherein the method of preparing the cobalt-based metal-organic framework Co-MOF material comprises: dissolving 2-methylimidazole in a methanol solution containing cobalt nitrate, synthesizing crystals by a solution method, centrifuging, washing and drying.
6. The method according to claim 3, wherein the metal organic frame material in the step (1) is subjected to a heat treatment, wherein the heat treatment is: the temperature rising rate is 2-5 ℃/min, the calcining temperature is 600-800 ℃, and the heat preservation time is 1-3h;
the mixture of the metal organic framework material and melamine is subjected to heat treatment, wherein the heat treatment is as follows: the temperature rising rate is 2-5 ℃/min, the calcining temperature is 600-900 ℃, and the heat preservation time is 0.5-1.5h.
7. The method according to claim 3, wherein the mixed atmosphere in the step (1) is methane and argon, and the flow rate ratio of methane to argon is 1: (0.5-2); the metal organic framework material and melamine mixture comprises the following components in percentage by mass: (0.05-0.10).
8. The method according to claim 3, wherein the spark plasma sintering process parameters in the step (2) are as follows: sintering temperature is 1600-2200 ℃, sintering pressure is 60-100MPa, heating rate is 90-110 ℃/min, and heat preservation time is 4-10min; and (3) demolding and removing the carbon paper before the grinding and polishing treatment in the step (2).
9. Use of the carbon-based bulk material of claim 1 in a shielding material.
10. Use of the carbon-based bulk material of claim 1 in the fields of aerospace, military national defense, construction engineering or electromagnetic protection.
Priority Applications (1)
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