CN113645822A - Porous hollow graphitized carbon electromagnetic wave absorption material and preparation method thereof - Google Patents
Porous hollow graphitized carbon electromagnetic wave absorption material and preparation method thereof Download PDFInfo
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 71
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 61
- 238000002360 preparation method Methods 0.000 title abstract description 14
- 238000010521 absorption reaction Methods 0.000 title description 25
- 239000000463 material Substances 0.000 title description 22
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims abstract description 61
- 238000000034 method Methods 0.000 claims abstract description 28
- 239000011358 absorbing material Substances 0.000 claims abstract description 25
- 238000005520 cutting process Methods 0.000 claims abstract description 4
- 239000000126 substance Substances 0.000 claims abstract description 4
- 239000003575 carbonaceous material Substances 0.000 claims description 24
- 238000010438 heat treatment Methods 0.000 claims description 22
- 238000005530 etching Methods 0.000 claims description 16
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 15
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 12
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 9
- 239000000377 silicon dioxide Substances 0.000 claims description 9
- GHMLBKRAJCXXBS-UHFFFAOYSA-N resorcinol Chemical compound OC1=CC=CC(O)=C1 GHMLBKRAJCXXBS-UHFFFAOYSA-N 0.000 claims description 8
- 238000002156 mixing Methods 0.000 claims description 7
- 239000002243 precursor Substances 0.000 claims description 7
- 238000000967 suction filtration Methods 0.000 claims description 7
- 239000002245 particle Substances 0.000 claims description 6
- 235000012239 silicon dioxide Nutrition 0.000 claims description 6
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 4
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 4
- 238000010000 carbonizing Methods 0.000 claims description 4
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- 229910021641 deionized water Inorganic materials 0.000 claims description 4
- 238000000926 separation method Methods 0.000 claims description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 4
- 229910052681 coesite Inorganic materials 0.000 claims description 3
- 229910052906 cristobalite Inorganic materials 0.000 claims description 3
- WSFSSNUMVMOOMR-NJFSPNSNSA-N methanone Chemical compound O=[14CH2] WSFSSNUMVMOOMR-NJFSPNSNSA-N 0.000 claims description 3
- 229910052682 stishovite Inorganic materials 0.000 claims description 3
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- 231100000331 toxic Toxicity 0.000 abstract description 2
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- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 description 3
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- 238000004519 manufacturing process Methods 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
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- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K9/00—Screening of apparatus or components against electric or magnetic fields
- H05K9/0073—Shielding materials
- H05K9/0081—Electromagnetic shielding materials, e.g. EMI, RFI shielding
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/20—Graphite
- C01B32/205—Preparation
Abstract
A porous hollow graphitized carbon electromagnetic wave absorbing material and a preparation method thereof are disclosed, the electromagnetic wave absorbing material is in a regular spherical shape, the diameter of the spherical shape is 200-400 nm, nano holes with the size of 5-20 nm are randomly distributed on the surface, and the nano holes are etched on the surface of the hollow graphitized carbon by hydrogen peroxide through a chemical bond cutting means. The electromagnetic wave absorbing material can effectively absorb electromagnetic waves with wide frequency bandwidth, does not use highly toxic organic solvents in the preparation process, and has low cost and simple process.
Description
Technical Field
The invention relates to the technical field of electromagnetic wave absorbing materials, in particular to a porous hollow graphitized carbon electromagnetic wave absorbing material and a preparation method thereof.
Background
The application of the electromagnetic technology in the modern military and industrial fields is increasingly wide, the demand for the electromagnetic stealth material is continuously increased, and due to the special hexagonal carbon network structure of the graphene, the graphene has high conductivity and ultralow density, so that the graphene is widely concerned in the research field of the electromagnetic stealth material. However, the raw material price of graphene is expensive, the application cost is high, the graphitized hollow carbon spheres are products obtained by high-temperature carbonization of polymers, have electromagnetic loss performance similar to that of graphene, and are low in density due to the hollow structure, so that the graphitized hollow carbon spheres are a low-cost graphene substitute.
Hitherto, various graphitized carbon spheres have been successfully prepared and applied to the fields of similar energy storage, catalysis and the like, and patent CN 106861618A discloses a nitrogen-doped porous hollow carbon sphere carbon dioxide adsorbing material, and a preparation method and application thereof.
At present, the synthesis of graphitized carbon spheres is mainly realized by a template method, the process is relatively mature, but the method for introducing a pore structure into the carbon material is still rarely researched, and the method mainly has two difficulties for the exploration of the method: 1. the method of introducing the pore structure needs to be relatively mild, controllable and low cost; 2. the introduction of the pore structure does not significantly destroy the original structure. The introduction of a proper and controllable pore structure can balance the impedance matching and dielectric attenuation capacity of the carbon material and enhance the electromagnetic wave absorption performance of the material, and meanwhile, the nanoparticles with special structures can also be applied to various other fields. Therefore, the preparation and development of the porous hollow graphitized carbon electromagnetic wave absorbing material with a simple process and a regular shape and uniform size of the prepared product are very necessary.
Disclosure of Invention
In order to solve the technical problems, the invention provides a porous hollow graphitized carbon electromagnetic wave absorbing material and a preparation method thereof, the electromagnetic wave absorbing material can effectively absorb electromagnetic waves with wider frequency bandwidth, and in the preparation process, no toxic organic solvent is used, so that the cost is low, and the process is simple.
In order to realize the technical purpose, the adopted technical scheme is as follows: a porous hollow graphitized carbon electromagnetic wave absorbing material is in a regular spherical shape, the diameter of the spherical shape is 200-400 nm, nano holes with the size of 5-20 nm are randomly distributed on the surface, and the nano holes are etched on the surface of the hollow graphitized carbon by hydrogen peroxide through means of chemical bond cutting.
A preparation method of a porous hollow graphitized carbon electromagnetic wave absorption material comprises the following steps:
Further, the specific implementation method of step 1 is as follows: adopting 3-8 g of nano SiO with the particle diameter of 200-300 nm2Taking the mixture as a template, respectively adding 1000-2000 ml of ethanol, 40-100 m of formaldehyde, 4-8 g of resorcinol and 50-100 ml of ammonia water, stirring at a constant speed for reacting for 18-24h, performing centrifugal separation, carbonizing at 700-900 ℃, completely immersing the sample by using a sodium hydroxide solution with the concentration of 2mol/L, and performing heat treatment at 80-100 ℃ for at least 8 hours to etch and completely remove nano SiO2To obtain the hollow graphitized carbon.
Further, the diameter of the hollow graphitized carbon material in the step 1 is 200-300 nm.
Further, the mass fraction of the hydrogen peroxide in the step 2 is 30 wt%.
Further, in the step 2, the co-heating temperature of the hydrogen peroxide and the hollow graphitized carbon is 60-90 ℃.
Further, in the step 2, the co-heating time of the hydrogen peroxide and the hollow graphitized carbon is 1-3 h.
The invention has the beneficial effects that: the method for introducing the pore structure into the carbon material is mild and controllable, can retain the integrity of the original structure while introducing the nanoscale pore structure, has the characteristics of wide effective absorption bandwidth and high electromagnetic absorption strength under low filling ratio (10wt%) and low thickness (<2mm) compared with the traditional microwave absorbent, and has better microwave absorption performance; the co-heating time is controlled to be 2-3 h, wider electromagnetic waves can be absorbed, meanwhile, no highly toxic chemical reagent is used in the production process, no complex and expensive synthesis equipment is needed in the preparation method, the process is simple, the cost is low, the yield can be improved by amplifying the reaction times, and the functional coating filler can be used for production and application.
Drawings
FIG. 1 is a transmission electron micrograph of porous hollow graphitized carbon-0;
FIG. 2 is a transmission electron micrograph of porous hollow graphitized carbon-3;
FIG. 3 is a specific surface area and pore distribution diagram of porous hollow graphitized carbon;
fig. 4 is an electromagnetic parameter diagram of porous hollow graphitized carbon;
FIG. 5 is a reflection loss plot of porous hollow graphitized carbon-0;
FIG. 6 is a reflection loss plot of porous hollow graphitized carbon-3;
fig. 7 is a reflection loss diagram of porous hollow graphitized carbon-5.
Detailed Description
The invention is realized by the following technical scheme:
(1) the invention particularly relates to a porous hollow graphitized carbon electromagnetic wave absorbing material which is in a regular spherical shape, the diameter of the spherical shape is 200-400 nm, and nanopores with the size of 5-20 nm are randomly distributed on the surface of the spherical shape. The hydrogen peroxide is used as a pore-forming agent, nano holes can be etched on the surface of the graphitized carbon by means of chemical bond cutting, as shown in fig. 1 and fig. 2, the hollow porous graphitized carbon-0 obtained in comparative example 1 before etching has obvious surface edge and complete structure, the hollow porous graphitized carbon-3 etched by hydrogen peroxide for a certain time can basically keep uniform spherical shape, the edge of the sample is lighter than that of a sample which is not treated by hydrogen peroxide, a large number of white light spots appear on the surface of a single spherical particle, the light spots are nano holes generated by etching under the action of hydrogen peroxide, the existence of the nano holes does not influence the spherical structure, and the particles can keep spherical shape without collapse.
(2) In addition, the specific surface area of the hollow porous graphitized carbon is further improved by etching the hydrogen peroxide, so that the density of the material is further reduced. Fig. 3 is a BET specific surface area and average pore diameter map of the hollow porous graphitized carbon obtained in comparative example 1, examples 2 and 3. According to images, after hydrogen peroxide treatment, the specific surface area of the material is increased, the average pore diameter is increased from 2nm to 8nm, and the specific surface area and the average pore diameter are further improved along with the extension of treatment time.
(3) The introduction of the pore structure regulates and controls the electromagnetic parameters of the material, can effectively regulate impedance matching and enhance dielectric attenuation capability to a certain extent. Fig. 4 is an electromagnetic parameter map of the hollow porous graphitized carbon obtained in comparative example 1, examples 2 and 3. Wherein the filling ratio of the sample to the paraffin wax at the time of the test was 1: 9, which corresponds to a filling ratio of the sample of 10 wt%. According to image display, after hydrogen peroxide treatment, the values of the real part and the imaginary part of the dielectric of the material are reduced, and the values of the real part and the imaginary part of the dielectric are further reduced along with the extension of treatment time, which indicates that the impedance matching performance of the material is optimized and controlled.
(4) The preparation principle of the porous hollow graphitized carbon electromagnetic wave absorbing material comprises the steps of preparing a precursor by using a silicon dioxide template method, wrapping a silicon dioxide template with a polymer to prepare the precursor, converting the precursor into a carbon material by heat treatment, removing the template to obtain hollow graphitized carbon spheres, forming holes on the surfaces of the hollow carbon spheres by using the etching effect of hydrogen peroxide on the carbon material, controlling the etching time to control the hole forming degree, preparing porous hollow graphitized carbon, reducing the density of the carbon material by introducing a hole structure, optimizing impedance matching, and improving the electromagnetic absorption performance.
(5) The porous hollow graphitized carbon electromagnetic wave absorbing material synthesizes nano-carbon by a conventional template method, a pore structure is introduced by utilizing the action of hydrogen peroxide and the hollow graphitized carbon, the reaction condition and the degree are mild and controllable, the introduction of the pore structure not only reduces the density of the material, but also regulates and controls the impedance matching characteristic of the material, optimizes the electromagnetic absorption performance of the material, the effective absorption bandwidth of the synthesized hollow graphitized carbon material-3 can reach 6.3GHz when the thickness of a sample is 2mm, the electromagnetic performance of the material is mainly derived from the dielectric loss of the carbon material and the dipole polarization caused by the structural defects generated by pore forming, the appearance of the material can be regulated and controlled by regulating and controlling the etching time, the electromagnetic parameters of the material can be regulated and controlled, the electromagnetic wave attenuation purpose is achieved, and the low density and the environmental protection of the porous material can ensure that the environmental pollution is reduced in the production and application process, making it possible to apply it to functional coatings.
(6) The invention relates to a porous hollow nano carbon electromagnetic wave absorbing material and a preparation method thereof, comprising the following steps:
different polymer components can be selected within a range, and the etching effect of the prepared hollow graphitized carbon is consistent with that of the hydrogen peroxide material and does not fluctuate greatly.
And 2, mixing the hollow graphitized carbon material obtained in the step 1 with 500ml of hydrogen peroxide, maintaining a certain temperature, continuously stirring for a certain time, performing suction filtration, and washing with deionized water to obtain the porous hollow graphitized carbon electromagnetic wave absorbing material.
The diameter of the hollow graphitized carbon material in the step 1 is 200-300 nm.
The mass fraction of the hydrogen peroxide in the step 2 is 30 wt%.
In the step 2, the co-heating temperature of the hydrogen peroxide and the hollow graphitized carbon is 60-90 ℃, the etching effect of the hydrogen peroxide on the carbon material is consistent in the temperature range, and the temperature of 80 ℃ is fixed as the co-heating temperature in the embodiment. .
In the step 2, the co-heating time of the hydrogen peroxide and the hollow graphitized carbon is 2-3 h.
Embodiments of the present invention are further described below with reference to the accompanying drawings.
Example 1
The porous hollow graphitized carbon electromagnetic wave absorbing material and the preparation method thereof comprise the following steps:
And 2, weighing 500mg of the hollow graphitized carbon material obtained in the step 1, adding the weighed hollow graphitized carbon material into 400-750 ml of hydrogen peroxide solution with the mass fraction of 30wt%, mixing and stirring until the hollow graphitized carbon powder is uniformly dispersed in a liquid phase, continuously stirring, heating the reaction environment to 80 ℃, maintaining the temperature for 1h, extracting the obtained product in a suction filtration manner, and drying to obtain the porous hollow graphitized carbon material-1.
The sample and paraffin are mixed according to the ratio of 1: 9 and pressed into a sample ring with the inner diameter of 3.04mm and the outer diameter of 7.00mm, a vector network analyzer is used for carrying out 2-18 GHz electromagnetic parameter test, the reflectivity of the sample is obtained through test and calculation, and when the thickness of the sample is 2mm, the effective absorption bandwidth is 4.2 GHz.
Example 2
And 2, weighing 500mg of the hollow graphitized carbon material obtained in the step 1, adding the weighed hollow graphitized carbon material into 500ml of hydrogen peroxide solution with the mass fraction of 30%, mixing and stirring until the hollow graphitized carbon powder is uniformly dispersed in a liquid phase, continuously stirring, heating the reaction environment to 80 ℃, maintaining the temperature for 3 hours, extracting and drying the obtained product in a suction filtration mode, and thus obtaining the porous hollow graphitized carbon material-3.
The sample and paraffin are mixed according to the ratio of 1: 9 and pressed into a sample ring with the inner diameter of 3.04mm and the outer diameter of 7.00mm, a vector network analyzer is used for carrying out 2-18 GHz electromagnetic parameter test, the sample reflectivity is obtained through test and calculation, and the result is shown in figure 6, when the thickness of the sample is 2mm, the effective absorption bandwidth is 6.3 GHz.
Example 3
And 2, weighing 500mg of the hollow graphitized carbon material obtained in the step 1, adding the weighed hollow graphitized carbon material into 500ml of hydrogen peroxide solution with the mass fraction of 30%, mixing and stirring until the hollow graphitized carbon powder is uniformly dispersed in a liquid phase, continuously stirring, heating the reaction environment to 80 ℃, maintaining the temperature for 5 hours, extracting and drying the obtained product in a suction filtration mode, and thus obtaining the porous hollow graphitized carbon material-5.
The sample and paraffin are mixed according to the ratio of 1: 9 and pressed into a sample ring with the inner diameter of 3.04mm and the outer diameter of 7.00mm, a vector network analyzer is used for carrying out 2-18 GHz electromagnetic parameter test, the sample reflectivity is obtained through test and calculation, and the result is shown in figure 7, when the thickness of the sample is 2mm, the effective absorption bandwidth is 1.0 GHz.
Comparative example 1
And 2, weighing 500mg of the hollow graphitized carbon material obtained in the step 1, adding 500ml of deionized water, mixing and stirring until the hollow graphitized carbon powder is uniformly dispersed in a liquid phase, continuously stirring, heating the reaction environment to 80 ℃, maintaining the temperature for 3 hours, extracting and drying the obtained product in a suction filtration manner, and thus obtaining the porous hollow graphitized carbon material-0.
The sample and paraffin are mixed according to the ratio of 1: 9 and pressed into a sample ring with the inner diameter of 3.04mm and the outer diameter of 7.00mm, a vector network analyzer is used for carrying out 2-18 GHz electromagnetic parameter test, the sample reflectivity is obtained through test and calculation, and the result is shown in figure 7, when the thickness of the sample is 2mm, the effective absorption bandwidth is 3.9 GHz.
The performance of the sample is improved to a certain extent by regulating and controlling the electromagnetic parameters. Fig. 5, 6 and 7 are reflection loss maps of the samples obtained in comparative example 1, examples 2 and 3, respectively. As can be seen from FIG. 5, the sample of the hollow porous graphitized carbon-0 has certain performance at a filling ratio of 10wt%, but the effective absorption bandwidth is narrow, and is 3.9GHz at a sample thickness of 2 mm.
Under the condition that the filling ratio is 10wt%, when the thickness of a sample is 2mm, the effective absorption bandwidth can be increased to 4.2GHz, the absorption frequency range covers the frequency range of 13.8-18 GHz, and the performance of the hollow porous graphitized carbon-1 is slightly superior to that of the sample which is not treated by hydrogen peroxide.
In all the examples and the comparative examples, the electromagnetic absorption performance of the porous hollow graphitized carbon-3 corresponding to fig. 6 is optimal, when the thickness of the sample is 2mm, the effective absorption bandwidth can reach 6.3GHz, the absorption frequency range covers the frequency range of 11.7-18 GHz, and the minimum reflection loss value can be lower than-30 dB. Under the condition that the filling ratio of the hollow porous graphitized carbon-3 is 10wt%, the sample has relatively better performance, and the performance is superior to that of a sample which is not treated by hydrogen peroxide, because the introduction of the pore structure improves impedance matching on the basis of not damaging the original spherical structure, enhances polarization and effectively improves the electromagnetic wave absorption performance of the material.
Under the condition that the filling ratio of the hollow porous graphitized carbon-5 is 10wt%, the performance of the sample is reduced compared with that of the sample treated for 3 hours, the electromagnetic absorption performance is reduced due to the fact that the spherical structure is damaged due to overlong hydrogen peroxide etching treatment time, and the effective absorption bandwidth of the sample is 1GHz under the condition that the thickness of the sample is 2 mm.
Therefore, the electromagnetic absorption frequency bandwidth of the hollow graphitized carbon can be effectively widened by introducing the pore structure, but the proper etching degree needs to be controlled, the original nanometer material structure can be damaged due to too deep etching process, the performance is reduced, and the electromagnetic wave material with the electromagnetic wave absorption function can be prepared within 0-5 hours of etching.
Claims (7)
1. A porous hollow graphitized carbon electromagnetic wave absorbing material is characterized in that: the electromagnetic wave absorbing material is in a regular spherical shape, the diameter of the spherical shape is 200-400 nm, nano holes with the size of 5-20 nm are randomly distributed on the surface, hydrogen peroxide is used for etching the nano holes on the surface of the hollow graphitized carbon through a chemical bond cutting method.
2. The method for preparing a porous hollow graphitized carbon electromagnetic wave absorbing material as claimed in claim 1, which comprises the following steps:
step 1, preparing a precursor by using a silicon dioxide template method, converting the precursor into a carbon material by heat treatment, and removing the silicon dioxide template to obtain hollow graphitized carbon;
step 2, mixing the hollow graphitized carbon obtained in the step 1 with hydrogen peroxide according to the ratio of 1: 0.8-1.5, maintaining the co-heating temperature, continuously stirring for a certain time, performing suction filtration, and washing with deionized water to obtain the porous hollow graphitized carbon electromagnetic wave absorbing material.
3. The method for preparing a porous hollow graphitized carbon electromagnetic wave absorbing material as claimed in claim 2, wherein the specific implementation method of the step 1 is as follows: adopting 3-8 g of nano SiO with the particle diameter of 200-300 nm2Taking the mixture as a template, respectively adding 1000-2000 ml of ethanol, 40-100 m of formaldehyde, 4-8 g of resorcinol and 50-100 ml of ammonia water, stirring at a constant speed for reacting for 18-24h, performing centrifugal separation, carbonizing at 700-900 ℃, completely immersing the sample by using a sodium hydroxide solution with the concentration of 2mol/L, and performing heat treatment at 80-100 ℃ for at least 8 hours to etch and completely remove nano SiO2To obtain the hollow graphitized carbon.
4. The method for preparing a porous hollow graphitized carbon electromagnetic wave absorbing material as claimed in claim 2, characterized in that: the diameter of the hollow graphitized carbon material in the step 1 is 200-300 nm.
5. The method for preparing a porous hollow graphitized carbon electromagnetic wave absorbing material as claimed in claim 2, characterized in that: the mass fraction of the hydrogen peroxide in the step 2 is 30 wt%.
6. The method for preparing a porous hollow graphitized carbon electromagnetic wave absorbing material as claimed in claim 2, characterized in that: in the step 2, the co-heating temperature of the hydrogen peroxide and the hollow graphitized carbon is 60-90 ℃.
7. The method for preparing a porous hollow graphitized carbon electromagnetic wave absorbing material as claimed in claim 2, characterized in that: in the step 2, the co-heating time of the hydrogen peroxide and the hollow graphitized carbon is 1-3 h.
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