CN116443848B - Preparation method of modified carbon-based wave-absorbing material - Google Patents
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Abstract
The invention relates to the technical field of wave-absorbing materials, and particularly discloses a preparation method of a modified carbon-based wave-absorbing material. The modified carbon-based wave-absorbing material has the advantages of no harmful substances, environmental protection, stronger magnetic loss, favorable improvement of impedance matching characteristics, lower filling quantity, high dielectric loss, nitrogen doped porous carbon, change of the dielectric property of the porous carbon, contribution to expanding the electromagnetic wave absorbing capacity, heteroatom boron, capability of inducing charge delocalization of electrons in the carbon material, modulating defects and disorder of the material, generating more dipole polarization and further improving the wave-absorbing performance.
Description
Technical Field
The invention relates to the technical field of wave-absorbing materials, in particular to a preparation method of a modified carbon-based wave-absorbing material.
Background
The wave absorbing material is a material capable of absorbing and attenuating incident electromagnetic waves, and can convert the absorbed electromagnetic waves into heat energy or other forms of energy to be consumed, so that the electromagnetic waves disappear, and the wave absorbing material is generally applied to the military field, such as military stealth technology, radar, infrared detection and the like are reduced or eliminated. With the rapid development of wireless communication technology and electronic equipment, a large amount of electromagnetic wave pollution is caused, and the wireless communication technology and electronic equipment become a new environment pollution, afflict the daily life of people and have great harm to the bodies of people.
Carbon materials are considered as one of the wave-absorbing materials with the most practical application potential because of the advantages of wide sources, simple preparation, small density, high dielectric loss, excellent physicochemical properties and the like. Chinese patent CN107098332B discloses a method for preparing carbon-based wave-absorbing material by carbonizing organic matter at high temperature, using sugar water thermal carbonization product as precursor, carbonizing at high temperature, uniformly mixing and dispersing with paraffin in acetone, curing and forming, using raw materials with low price and abundant resources, however, single carbon material only has dielectric loss property, and is difficult to achieve matching of ideal electromagnetic parameters, so that it can not be single as an ideal microwave absorbing material, the ferromagnetic wave-absorbing material has good chemical stability, magnetic loss and dielectric loss, and electromagnetic wave still can enter into the material to generate loss at higher frequency, thus being widely applied to various fields of electromagnetic protection, but the ferromagnetic wave-absorbing material has larger density and is not light and thin. The carbon material is used as a main body, other components are used as modification, the carbon-based material is modified, and the carbon-based composite wave-absorbing material formed by combination is focused by a large number of researchers due to the characteristic of complementary advantages, so that the carbon-based composite wave-absorbing material has a wide research prospect.
Disclosure of Invention
In order to solve the technical problems, the invention provides a preparation method of a modified carbon-based wave-absorbing material, and a composite and compatible carbon-based wave-absorbing material with excellent wave-absorbing performance is prepared.
In order to achieve the above object, the present invention discloses a method for preparing a modified carbon-based wave absorbing material, comprising the steps of:
uniformly mixing N, N-dimethylformamide, nanocellulose (NCC), 2- (4-carboxyphenyl) -1,3, 2-dioxaboron, 4-Dimethylaminopyridine (DMAP) and 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride (EDC & HCl), reacting, washing with acetone after the reaction is finished, and freeze-drying to obtain boron-containing cellulose;
step (2) mixing deionized water, boron-containing cellulose and potassium hydroxide, stirring, adding melamine, continuing stirring to obtain a mixed solution, drying the mixed solution in an oven at 80-90 ℃ for 24-36 hours to obtain a boron-nitrogen double-doped porous carbon precursor;
carbonizing a boron-nitrogen double-doped porous carbon precursor in an inert gas atmosphere, washing to neutrality by using a hydrochloric acid aqueous solution after carbonization, and drying at 50-60 ℃ for 12-18h to obtain the boron-nitrogen double-doped porous carbon;
and (4) uniformly mixing ethylene glycol, ferric chloride hexahydrate and ammonium acetate, adding boron-nitrogen double-doped porous carbon to obtain a mixed solution, heating the mixed solution to react, filtering after the reaction is finished, washing with deionized water and ethanol, and drying in a drying oven at 50-60 ℃ for 18-24 hours to obtain the modified carbon-based wave-absorbing material, namely the hollow nano ferroferric oxide/boron-nitrogen double-doped porous carbon material.
Preferably, the nanocellulose in the step (1) is obtained by acidizing microcrystalline cellulose by sulfuric acid, and the specific treatment process comprises the steps of stirring and reacting a 60% sulfuric acid aqueous solution with a mass fraction of 4:1 and microcrystalline cellulose in a water bath at 50 ℃ for 1h, centrifuging, washing the supernatant with deionized water to pH 7, dialyzing, and freeze-drying to obtain the nanocellulose.
Preferably, the mass ratio of N, N-dimethylformamide, nanocellulose, 2- (4-carboxyphenyl) -1,3, 2-dioxaboron, 4-dimethylaminopyridine and 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride in the step (1) is 2100-2500:100:95-145:15-28:32-55.
Preferably, the temperature of the reaction in the step (1) is 0-20 ℃, and the reaction time is 3-6h.
Preferably, the mass ratio of deionized water, boron-containing cellulose, potassium hydroxide and melamine in the step (2) is 1200-1500:100:65-95:350-420.
Preferably, deionized water, boron-containing cellulose and potassium hydroxide in the step (2) are stirred for 1-1.5 hours at 70-80 ℃, melamine is added, and the mixture is stirred for 2-3 hours at 70-80 ℃ to obtain the mixed solution.
Preferably, the carbonization temperature in the step (3) is 750-800 ℃, and the carbonization time is 3-4h.
Preferably, the inert gas in step (3) comprises nitrogen.
Preferably, the mass ratio of the ethylene glycol, the ferric chloride hexahydrate, the ammonium acetate and the boron nitrogen double doped porous carbon in the step (4) is 3000-15000:1-10:3-35:100.
Preferably, the temperature of the reaction in the step (4) is 180-220 ℃ and the reaction time is 12-24h.
In the invention, sulfuric acid is used for acidizing microcrystalline cellulose, amorphous cellulose in the microcrystalline cellulose is removed by acid hydrolysis, and the microcrystalline cellulose is kept tiny and resistantThe preparation method comprises the steps of carrying out esterification reaction on hydroxyl groups on the acid crystalline nanocellulose and carboxyl groups on 2- (4-carboxyphenyl) -1,3, 2-dioxaboron in an N, N-dimethylformamide solvent under the action of 4-dimethylaminopyridine and 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride to obtain boron-containing cellulose, mixing the boron-containing cellulose, potassium hydroxide and melamine, carrying out hydrolysis-crosslinking reaction in a deionized water solvent to obtain a boron-nitrogen double-doped porous carbon precursor, carrying out hydrolysis-crosslinking reaction in an inert gas atmosphere, providing a boron source for boron-containing heterocycle, providing a nitrogen source for melamine, and providing a carbon source for benzene rings on 2- (4-carboxyphenyl) -1,3, 2-dioxaboron and cellulose, carrying out high-temperature carbonization on the boron-nitrogen double-doped porous carbon precursor, washing to neutrality by using a hydrochloric acid aqueous solution to obtain boron-nitrogen double-doped carbon, wherein the porous carbon has higher carbon content, mixing ethylene glycol, ferric chloride hexahydrate and ammonium acetate uniformly, adding the boron-nitrogen double-doped porous carbon precursor into the mixture, carrying out thermal absorption reaction to obtain a hollow carbon-nitrogen-doped carbon-three-doped porous carbon-boron-carbon-absorbing material, and carrying out thermal-absorbing reaction to prepare the hollow carbon-three-doped carbon-absorbing porous carbon-absorbing material, so as to avoid the hollow carbon-doped carbon-absorbing material. During the production of the hollow nano ferroferric oxide, glycol is used as a solvent and a reducing agent, ammonium acetate and FeCl are used under the high temperature condition 3 ·6H 2 The crystal water in O is hydrolyzed to generate OH - And Fe again 3+ React to form Fe (OH) 3 ，Fe 3+ Reduction to form part of Fe 2+ And OH (OH) - Reaction to form Fe (OH) 2 ，Fe(OH) 3 And Fe (OH) 2 The nano ferroferric oxide is generated by reaction, according to the Ostwald ripening theory, the generated crystal grains are agglomerated into loose microspheres initially, the small crystal grains of the inner core have higher surface energy and solubility, the mass migration is converted into the shell by the dissolution-recrystallization process preferentially, and the voids in the sphere are further enlarged along with the prolongation of the ripening process, finally a hollow structure is formed and uniformly grown on the boron-nitrogen double-doped porous carbon matrix.
Compared with the prior art, the invention has the beneficial effects that:
the modified carbon-based wave absorbing material prepared and generated by the method has the advantages that porous carbon and hollow nano ferroferric oxide in the hollow nano ferroferric oxide/boron nitrogen double-doped porous carbon material have rich pore structures with large specific surface areas, reflection and scattering times can be increased for incident electromagnetic waves, a propagation path can be effectively prolonged, a good wave absorbing effect is generated, meanwhile, the modified carbon-based wave absorbing material has an excellent micro-current conduction effect, dielectric loss can be effectively improved, wave absorbing performance is further improved, the hollow nano ferroferric oxide can provide magnetic loss, nitrogen doped porous carbon can effectively change the dielectric performance of the porous carbon, the capability of absorbing electromagnetic waves is enlarged, hetero atom boron with different electronegativity with carbon is doped, charge delocalization of electrons in the carbon material can be induced, defects and disorder of the material are modulated, more dipole polarization is generated, and the wave absorbing performance is further improved.
The cellulose is used as a carbon source, the prepared porous carbon has a series of advantages of light weight, low price, wide sources, reproducibility and the like, does not generate harmful substances in the preparation process, is environment-friendly, has special electromagnetic performance and good wave absorbing effect, has small absorption frequency bandwidth and density, and the prepared modified carbon-based wave absorbing material has the characteristics of light weight and thinness and excellent mechanical property. The nano ferroferric oxide serving as a magnetic ion has larger saturation magnetization intensity, can endow the material with stronger magnetic loss, is favorable for improving impedance matching characteristics, and further achieves the purpose of light weight, and the obtained modified carbon-based wave-absorbing material has lower filling amount, high dielectric loss and excellent wave-absorbing performance.
Drawings
FIG. 1 is a flow chart of the preparation of a modified carbon-based wave-absorbing material in accordance with the present invention;
FIG. 2 is a schematic diagram of the mechanism of the preparation of boron-containing cellulose in the present invention.
Detailed Description
The technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments, and all other embodiments obtained by those skilled in the art without making any inventive effort based on the embodiments of the present invention are within the scope of protection of the present invention.
Example 1
The preparation method of the modified carbon-based wave-absorbing material comprises the following steps:
(1) Uniformly mixing N, N-dimethylformamide, nanocellulose, 2- (4-carboxyphenyl) -1,3, 2-dioxaboron, 4-dimethylaminopyridine and 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride in a mass ratio of 2100:100:95:15:32, reacting at 0 ℃ for 6 hours, washing with acetone after the reaction is finished, and freeze-drying to obtain boron-containing cellulose;
(2) Mixing deionized water, boron-containing cellulose and potassium hydroxide, stirring for 1.5 hours at 70 ℃, adding melamine, and continuing stirring for 3 hours at 70 ℃, wherein the mass ratio of the added deionized water to the added boron-containing cellulose to the added potassium hydroxide to the added melamine is 1200:100:65:350, so as to obtain a mixed solution, drying the mixed solution in an oven at 80 ℃ for 36 hours, and obtaining the boron-nitrogen double-doped porous carbon precursor;
(3) Carbonizing the boron-nitrogen double-doped porous carbon precursor in a nitrogen atmosphere at 750 ℃ for 4 hours, washing to be neutral by using a hydrochloric acid aqueous solution after carbonization, and drying for 18 hours at 50 ℃ to obtain boron-nitrogen double-doped porous carbon;
(4) Uniformly mixing ethylene glycol, ferric chloride hexahydrate and ammonium acetate, adding boron-nitrogen double-doped porous carbon to obtain a mixed solution, wherein the mass ratio of the added ethylene glycol to the added ferric chloride hexahydrate to the added ammonium acetate to the added boron-nitrogen double-doped porous carbon is 3000:1:3:100, transferring the mixed solution into a reaction kettle, heating at 180 ℃ for reaction for 24 hours, filtering after the reaction is finished, washing with deionized water and ethanol, and drying in a 50 ℃ drying box for 24 hours to obtain the modified carbon-based wave absorbing material, namely the hollow nano ferroferric oxide/boron-nitrogen double-doped porous carbon material.
Example 2
The preparation method of the modified carbon-based wave-absorbing material comprises the following steps:
(1) Uniformly mixing N, N-dimethylformamide, nanocellulose, 2- (4-carboxyphenyl) -1,3, 2-dioxaboron, 4-dimethylaminopyridine and 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride in a mass ratio of 2200:100:110:18:38, reacting for 4 hours at 10 ℃, washing with acetone after the reaction is finished, and freeze-drying to obtain boron-containing cellulose;
(2) Mixing deionized water, boron-containing cellulose and potassium hydroxide, stirring for 1.2 hours at 75 ℃, adding melamine, and continuing stirring for 2.5 hours at 75 ℃, wherein the mass ratio of the added deionized water to the added boron-containing cellulose to the added potassium hydroxide to the added melamine is 1280:100:72:375, so as to obtain a mixed solution, drying the mixed solution in a drying oven at 85 ℃ for 32 hours, and obtaining the boron-nitrogen double-doped porous carbon precursor;
(3) Carbonizing the boron-nitrogen double-doped porous carbon precursor in a nitrogen atmosphere at 780 ℃ for 3.5 hours, washing to be neutral by using a hydrochloric acid aqueous solution after carbonization, and drying at 55 ℃ for 15 hours to obtain boron-nitrogen double-doped porous carbon;
(4) Uniformly mixing ethylene glycol, ferric chloride hexahydrate and ammonium acetate, adding boron-nitrogen double-doped porous carbon to obtain a mixed solution, wherein the mass ratio of the added ethylene glycol to the added ferric chloride hexahydrate to the added ammonium acetate to the added boron-nitrogen double-doped porous carbon is 6000:3:12:100, transferring the mixed solution into a reaction kettle, heating at 190 ℃ for reaction for 20 hours, filtering after the reaction is finished, washing with deionized water and ethanol, and drying in a 55 ℃ drying box for 20 hours to obtain the modified carbon-based wave absorbing material, namely the hollow nano ferroferric oxide/boron-nitrogen double-doped porous carbon material.
Example 3
The preparation method of the modified carbon-based wave-absorbing material comprises the following steps:
(1) Uniformly mixing N, N-dimethylformamide, nanocellulose, 2- (4-carboxyphenyl) -1,3, 2-dioxaboron, 4-dimethylaminopyridine and 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride in a mass ratio of 2300:100:125:22:45, reacting for 4 hours at 15 ℃, washing with acetone after the reaction is finished, and freeze-drying to obtain boron-containing cellulose;
(2) Mixing deionized water, boron-containing cellulose and potassium hydroxide, stirring for 1.2 hours at 75 ℃, adding melamine, and continuing stirring for 2.5 hours at 75 ℃, wherein the mass ratio of the added deionized water to the added boron-containing cellulose to the added potassium hydroxide to the added melamine is 1350:100:80:390, so as to obtain a mixed solution, drying the mixed solution in an oven at the temperature of 85 ℃ for 32 hours, and obtaining a boron-nitrogen double-doped porous carbon precursor;
(3) Carbonizing the boron-nitrogen double-doped porous carbon precursor in a nitrogen atmosphere at 780 ℃ for 3.5 hours, washing to be neutral by using a hydrochloric acid aqueous solution after carbonization, and drying at 55 ℃ for 15 hours to obtain boron-nitrogen double-doped porous carbon;
(4) Uniformly mixing ethylene glycol, ferric chloride hexahydrate and ammonium acetate, adding boron-nitrogen double-doped porous carbon to obtain a mixed solution, wherein the mass ratio of the added ethylene glycol to the ferric chloride hexahydrate to the ammonium acetate to the boron-nitrogen double-doped porous carbon is 9000:6:18:100, transferring the mixed solution into a reaction kettle, heating at 200 ℃ for reaction for 18 hours, filtering after the reaction is finished, washing with deionized water and ethanol, and drying in a 55 ℃ drying box for 20 hours to obtain the modified carbon-based wave-absorbing material, namely the hollow nano ferroferric oxide/boron-nitrogen double-doped porous carbon material.
Example 4
The preparation method of the modified carbon-based wave-absorbing material comprises the following steps:
(1) Uniformly mixing N, N-dimethylformamide, nanocellulose, 2- (4-carboxyphenyl) -1,3, 2-dioxaboron, 4-dimethylaminopyridine and 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride in a mass ratio of 2400:100:135:25:50, reacting for 5h at 15 ℃, washing with acetone after the reaction is finished, and freeze-drying to obtain boron-containing cellulose;
(2) Mixing deionized water, boron-containing cellulose and potassium hydroxide, stirring for 1.2 hours at 75 ℃, adding melamine, and continuing stirring for 2.5 hours at 75 ℃, wherein the mass ratio of the added deionized water to the added boron-containing cellulose to the added potassium hydroxide to the added melamine is 1420:100:90:410, so as to obtain a mixed solution, drying the mixed solution in an oven at the temperature of 85 ℃ for 32 hours, and obtaining a boron-nitrogen double-doped porous carbon precursor;
(3) Carbonizing the boron-nitrogen double-doped porous carbon precursor in a nitrogen atmosphere at 780 ℃ for 3.5 hours, washing to be neutral by using a hydrochloric acid aqueous solution after carbonization, and drying at 55 ℃ for 15 hours to obtain boron-nitrogen double-doped porous carbon;
(4) Uniformly mixing ethylene glycol, ferric chloride hexahydrate and ammonium acetate, adding boron-nitrogen double-doped porous carbon to obtain a mixed solution, wherein the mass ratio of the added ethylene glycol to the ferric chloride hexahydrate to the ammonium acetate to the boron-nitrogen double-doped porous carbon is 12000:8:25:100, transferring the mixed solution into a reaction kettle, heating at 210 ℃ for reaction for 15 hours, filtering after the reaction is finished, washing with deionized water and ethanol, and drying in a 55 ℃ drying box for 20 hours to obtain the modified carbon-based wave-absorbing material, namely the hollow nano ferroferric oxide/boron-nitrogen double-doped porous carbon material.
Example 5
The preparation method of the modified carbon-based wave-absorbing material comprises the following steps:
(1) Uniformly mixing N, N-dimethylformamide, nanocellulose, 2- (4-carboxyphenyl) -1,3, 2-dioxaboron, 4-dimethylaminopyridine and 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride in a mass ratio of 2500:100:145:28:55, reacting for 3h at 20 ℃, washing with acetone after the reaction is finished, and freeze-drying to obtain boron-containing cellulose;
(2) Mixing deionized water, boron-containing cellulose and potassium hydroxide, stirring for 1h at 80 ℃, adding melamine, and continuing stirring for 2h at 80 ℃, wherein the mass ratio of the added deionized water to the added boron-containing cellulose to the added potassium hydroxide to the added melamine is 1500:100:95:420, so as to obtain a mixed solution, drying the mixed solution in a drying oven at 90 ℃ for 24h, and obtaining the boron-nitrogen double-doped porous carbon precursor;
(3) Carbonizing the boron-nitrogen double-doped porous carbon precursor in a nitrogen atmosphere at 800 ℃ for 3 hours, washing to neutrality by using a hydrochloric acid aqueous solution after carbonization, and drying at 60 ℃ for 12 hours to obtain boron-nitrogen double-doped porous carbon;
(4) Uniformly mixing ethylene glycol, ferric chloride hexahydrate and ammonium acetate, adding boron-nitrogen double-doped porous carbon to obtain a mixed solution, wherein the mass ratio of the added ethylene glycol to the ferric chloride hexahydrate to the ammonium acetate to the boron-nitrogen double-doped porous carbon is 15000:10:35:100, transferring the mixed solution into a reaction kettle, heating at 220 ℃ for reaction for 12 hours, filtering after the reaction is finished, washing with deionized water and ethanol, and drying in a drying box at 60 ℃ for 18 hours to obtain the modified carbon-based wave-absorbing material, namely the hollow nano ferroferric oxide/boron-nitrogen double-doped porous carbon material.
Comparative example 1
A preparation method of a wave-absorbing material comprises the following steps:
(1) Mixing deionized water, nanocellulose and potassium hydroxide, stirring for 1.2 hours at 75 ℃, adding melamine, and continuing stirring for 2.5 hours at 75 ℃, wherein the mass ratio of the added deionized water to the added boron-containing cellulose to the added potassium hydroxide to the added melamine is 1420:100:90:410, so as to obtain a mixed solution, drying the mixed solution in an oven at the temperature of 85 ℃ for 32 hours, and obtaining a nitrogen-doped porous carbon precursor;
(2) Carbonizing a nitrogen-doped porous carbon precursor in a nitrogen atmosphere at 780 ℃ for 3.5 hours, washing to neutrality by using a hydrochloric acid aqueous solution after carbonization, and drying at 55 ℃ for 15 hours to obtain nitrogen-doped porous carbon;
(3) Uniformly mixing ethylene glycol, ferric chloride hexahydrate and ammonium acetate, adding nitrogen-doped porous carbon to obtain a mixed solution, wherein the mass ratio of the added ethylene glycol to the ferric chloride hexahydrate to the ammonium acetate to the nitrogen-doped porous carbon is 12000:8:25:100, transferring the mixed solution into a reaction kettle, heating at 210 ℃ for reaction for 15 hours, filtering after the reaction is finished, washing with deionized water and ethanol, and drying in a 55 ℃ drying box for 20 hours to obtain the modified carbon-based wave absorbing material, namely the hollow nano ferroferric oxide/nitrogen double-doped porous carbon material.
Comparative example 2
A preparation method of a wave-absorbing material comprises the following steps:
(1) Uniformly mixing N, N-dimethylformamide, nanocellulose, 2- (4-carboxyphenyl) -1,3, 2-dioxaboron, 4-dimethylaminopyridine and 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride in a mass ratio of 2400:100:135:25:50, reacting for 5h at 15 ℃, washing with acetone after the reaction is finished, and freeze-drying to obtain boron-containing cellulose;
(2) Mixing deionized water, boron-containing cellulose and potassium hydroxide, stirring for 1.2 hours at 75 ℃, adding melamine, and continuing stirring for 2.5 hours at 75 ℃, wherein the mass ratio of the added deionized water to the added boron-containing cellulose to the added potassium hydroxide to the added melamine is 1420:100:90:410, so as to obtain a mixed solution, drying the mixed solution in an oven at the temperature of 85 ℃ for 32 hours, and obtaining a boron-nitrogen double-doped porous carbon precursor;
(3) Carbonizing the boron-nitrogen double-doped porous carbon precursor in a nitrogen atmosphere at 780 ℃ for 3.5h, washing to neutrality by using a hydrochloric acid aqueous solution after carbonization, and drying at 55 ℃ for 15h to obtain the boron-nitrogen double-doped porous carbon wave absorbing material.
Microcrystalline cellulose used in examples and comparative examples in the present invention was provided by the photo-complex fine chemical research institute in Tianjin; melamine was purchased from a company of ala Ding Shiji; ferric chloride hexahydrate (FeCl) 3 ·6H 2 O), available from a company of ala Ding Shiji, the remaining reagents are all commercially available.
The performance test was performed on the wave-absorbing materials of examples 1 to 5 and comparative examples 1 to 2, and the specific test is as follows:
(1) The electromagnetic performance test was performed by pressing the wave-absorbing materials of examples 1 to 5 and comparative examples 1 to 2 into concentric rings having an outer diameter of 7mm and an inner diameter of 3mm, the wave-absorbing capacity test was performed on an N5230 type vector network analyzer, the frequency range of the electromagnetic parameters tested was 2.4 to 18GHz, and the reflection loss performance results corresponding to the electromagnetic parameters recorded as 9.2GHz are shown in table 1:
TABLE 1
As can be seen from the test results in Table 1, the corresponding wave-absorbing materials of examples 1 to 5, namely the hollow nano ferroferric oxide/nitrogen double doped porous carbon material, have good wave-absorbing performance, wherein the reflection loss of the wave-absorbing material of example 5 is-52.1 dB when the electromagnetic parameter is 9.2GHz, the porous carbon of comparative example 1 is not doped with boron element, the wave-absorbing performance is affected to a certain extent by-42.0 dB, and the wave-absorbing performance of comparative example 2 is greatly reduced by-32.6 dB due to the fact that the boron nitrogen double doped porous carbon wave-absorbing material is not added with ferroferric oxide.
Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made hereto without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (4)
1. A preparation method of a modified carbon-based wave-absorbing material is characterized by comprising the following steps: the method comprises the following steps:
uniformly mixing N, N-dimethylformamide, nanocellulose, 2- (4-carboxyphenyl) -1,3, 2-dioxaborane, 4-dimethylaminopyridine and 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride, reacting, washing and drying after the reaction is finished to obtain boron-containing cellulose;
the mass ratio of the N, N-dimethylformamide to the nanocellulose to the 2- (4-carboxyphenyl) -1,3, 2-dioxaborane to the 4-dimethylaminopyridine to the 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride in the step (1) is 2100-2500:100:95-145:15-28:32-55;
the reaction temperature in the step (1) is 0-20 ℃, and the reaction time is 3-6h;
step (2) mixing deionized water, boron-containing cellulose and potassium hydroxide, stirring, adding melamine, continuing stirring to obtain a mixed solution, and drying to obtain a boron-nitrogen double-doped porous carbon precursor;
in the step (2), the mass ratio of deionized water, boron-containing cellulose, potassium hydroxide and melamine is 1200-1500:100:65-95:350-420;
carbonizing the boron-nitrogen double-doped porous carbon precursor in an inert gas atmosphere, washing and drying to obtain boron-nitrogen double-doped porous carbon;
the carbonization temperature in the step (3) is 750-800 ℃, and the carbonization time is 3-4 hours;
step (4) mixing ethylene glycol, ferric chloride hexahydrate and ammonium acetate uniformly, adding boron-nitrogen double-doped porous carbon to obtain a mixed solution, heating the mixed solution to react, and after the reaction is finished, performing suction filtration, washing and drying to obtain the modified carbon-based wave-absorbing material;
in the step (4), the mass ratio of the ethylene glycol to the ferric chloride hexahydrate to the ammonium acetate to the boron nitrogen doped porous carbon is 3000-15000:1-10:3-35:100;
the reaction temperature in the step (4) is 180-220 ℃, and the reaction time is 12-24h.
2. The method for preparing a modified carbon-based wave-absorbing material according to claim 1, wherein: the nanocellulose in the step (1) is obtained by acidizing microcrystalline cellulose by sulfuric acid, and the specific treatment process comprises the steps of stirring and reacting a 60% sulfuric acid aqueous solution and microcrystalline cellulose with the mass ratio of 4:1 in a water bath at 50 ℃ for 1h, centrifuging, washing with deionized water until the pH value of the supernatant is 7, dialyzing, and freeze-drying to obtain the nanocellulose.
3. The method for preparing a modified carbon-based wave-absorbing material according to claim 1, wherein: in the step (2), deionized water, boron-containing cellulose and potassium hydroxide are stirred for 1-1.5 hours at 70-80 ℃, melamine is added, and stirring is carried out for 2-3 hours at 70-80 ℃ to obtain a mixed solution.
4. The method for preparing a modified carbon-based wave-absorbing material according to claim 1, wherein: the inert gas in the step (3) comprises nitrogen.
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