Preparation method and application of boron and nitrogen co-doped graphene carbon aerogel wave-absorbing material
By using in-situ synthesis and boron and nitrogen co-doping techniques, the problems of poor dispersion and high density of carbon-based microwave absorbing materials have been solved, and low-density, high-efficiency microwave absorbing materials have been prepared, which are suitable for electromagnetic wave absorption in military and civilian fields.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- LASER FUSION RES CENT CHINA ACAD OF ENG PHYSICS
- Filing Date
- 2024-06-06
- Publication Date
- 2026-06-12
AI Technical Summary
Existing carbon-based microwave absorbing materials suffer from poor dispersion, easy agglomeration, and poor matching performance under working conditions, which cannot fully utilize the comprehensive microwave absorption performance of composite materials. Furthermore, traditional methods result in high material density and heavy weight, which cannot meet the needs of practical applications.
Using in-situ synthesis technology, uniform graphene sheets are dispersed in a carbon aerogel network structure through chemical interaction and co-gel technology between graphene oxide precursor solution and carbon aerogel precursor solution. Boron and nitrogen co-doping is then carried out to form a porous network structure, which improves dielectric loss and impedance matching characteristics.
The prepared boron and nitrogen co-doped graphene/carbon aerogel microwave absorbing material has low density, high absorption intensity and excellent microwave absorption performance, and is suitable for military and civilian applications and large-scale industrial production.
Smart Images
Figure CN118495951B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of microwave absorbing materials technology, specifically to a boron- and nitrogen-doped graphene / carbon aerogel-based composite material, its preparation method, and its application. Background Technology
[0002] Currently, while the development of electronic technology and the widespread use of electronic devices have brought convenience to society, they have also created an increasingly complex electromagnetic environment. In both military and civilian fields, electromagnetic waves with frequencies in the gigahertz (GHz) range are often the cause of electronic device malfunctions and human health problems. Therefore, the development of novel absorbing materials for military penetration, civilian shielding, and electromagnetic pollution has been a focus of close attention for researchers. Electromagnetic wave absorbing materials, or simply absorbing materials, absorb or attenuate incident electromagnetic waves by dissipating them as heat energy within the material through dielectric loss, magnetic loss, and multiple reflection interference cancellation. Compared with traditional electromagnetic shielding materials, absorbing materials have greater advantages. They can convert the electromagnetic energy carried by incident electromagnetic waves into heat energy, protecting targets from electromagnetic interference and radiation while avoiding secondary electromagnetic radiation pollution caused by reflection.
[0003] Ideal and efficient electromagnetic wave absorbing materials should possess characteristics such as strong absorption properties, a wide absorption frequency range, thin matching thickness, and low density. Traditional ceramic-based and metal oxide-based absorbing materials suffer from high density, heavy weight, poor corrosion resistance, high cost, and limited absorption performance, making them unsuitable for practical applications. Carbon materials, due to their light weight, stable physicochemical properties, and excellent electrical conductivity, have attracted widespread attention across various fields. Graphene, as a member of the carbon material family, possesses excellent electrical loss characteristics and ultra-low density; however, pure two-dimensional graphene materials exhibit poor dispersion in the matrix and are prone to agglomeration, significantly reducing their performance. Furthermore, current composite methods typically involve physical mixing, resulting in insufficient contact between the two composite materials and poor matching performance under operating conditions, failing to fully utilize the comprehensive absorption performance of the composite material. Summary of the Invention
[0004] This invention employs in-situ synthesis technology, utilizing the chemical interaction and co-gelling technique between a graphene oxide precursor solution and a carbon aerogel precursor solution. The main principle involves the condensation reaction of resorcinol and formaldehyde under the alkaline catalyst of sodium carbonate. The addition of sodium carbonate enables the formation of COONa groups at the edges of the graphene oxide nanosheets, facilitating the initial formation of resorcinol anions. A large number of resorcinol anions are prepared and simultaneously adsorbed onto the surface of graphene oxide (GO), reacting with added formaldehyde to form a hydroxymethyl intermediate. This forms the basis for the subsequent condensation reaction to form resorcinol-formaldehyde nanoclusters. The hydrophilic resorcinol-formaldehyde organic layer on the graphene oxide surface not only weakens π-π attraction stacking but also forms an internal network structure composed of resorcinol-formaldehyde-graphene oxide nanosheets through cross-linking reactions between overlapping nanosheet layers. After supercritical drying and high-temperature carbonization under an argon atmosphere, the graphene oxide sheets are uniformly "embedded" within the network structure of the carbon aerogel microspheres. Simultaneously, heteroatomic doping effectively adjusts the intrinsic electronic structure. While nitrogen-doped graphene exhibits lower reflectivity, the impedance matching characteristics of single-atom-doped materials remain poor, with low attenuation factors and limited attenuation capabilities. Therefore, this invention introduces boron and nitrogen co-doped graphene / carbon aerogel absorbing materials, enabling them to possess a low-density porous network structure while exhibiting a high attenuation factor and good impedance matching characteristics, thus demonstrating promising application prospects.
[0005] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.
[0006] To achieve these objectives and other advantages according to the present invention, a method for preparing a boron-nitrogen co-doped graphene carbon aerogel microwave absorbing material is provided, comprising the following steps:
[0007] Step 1: Mix the aqueous solution of graphene oxide with boron precursor reagents and nitrogen precursor reagents by ultrasonication and stirring until homogeneous to obtain a boron and nitrogen doped graphene oxide solution.
[0008] Step 2: Prepare precursor solutions with different theoretical densities from the phenolic resin solution. Add the precursor solutions to the boron and nitrogen-doped graphene oxide solution and stir until homogeneous to obtain a mixed precursor solution.
[0009] Step 3: Add the precursor mixture to the mineral oil, stir at high speed and then at low speed, and heat and solidify to obtain an organic particle / mineral oil mixture; mineral oil is an oil phase dispersant that makes the aqueous phase (precursor mixture) uniformly dispersed in the oil phase, forming water-in-oil reaction "droplets".
[0010] Step 4: Filter and separate the organic particles / mineral oil mixture, wash it, dry the obtained sample at room temperature and pressure, and then dry it at a higher temperature to obtain organic composite aerogel powder.
[0011] Step 5: Place the organic composite aerogel powder into a carbonization furnace and sinter and carbonize it under inert gas protection to obtain boron and nitrogen co-doped graphene carbon aerogel microwave absorbing material.
[0012] Preferably, the boron precursor reagent is boric acid, sodium tetraborate, sodium perborate, aminoborane, etc.; and the nitrogen precursor reagent is urea, trihydroxypyridine, melamine, etc.
[0013] Preferably, the concentration of the graphene oxide aqueous solution is 2-20 mg / mL; the mass ratio of the boron precursor reagent to the nitrogen precursor reagent is 1:20-25; and the mass-volume ratio of the boron precursor reagent to the graphene oxide aqueous solution is 0.1-0.5 g:10 mL.
[0014] Preferably, the theoretical density of the precursor solution is 0.1–0.8 g / mL; the phenolic resin solution is a resorcinol-formaldehyde solution; and the volume ratio of the precursor solution to the boron- and nitrogen-doped graphene oxide solution obtained in step one is 1:3 to 1:8.
[0015] Preferably, in step three, the high-speed stirring speed is 800-1000 r / min and the time is 25-35 min; the low-speed stirring speed is 200-400 r / min and the heating temperature is 55-65℃; and the curing is carried out by oil bath curing for 48 h.
[0016] Preferably, the mineral oil contains the emulsifier Span 80, and the content of Span 80 is 2-5% of the mineral oil mass. The addition of Span 80 causes the hydrophobic oil to be surrounded by the hydrophilic groups of Span 80, forming a directional attraction, reducing the work required for the mineral oil to disperse in water, thereby obtaining a well-dispersed emulsion.
[0017] Preferably, in step four, the temperature for heating and drying is 80–100°C.
[0018] Preferably, in step five, the sintering temperature is 800–1100°C and the time is 4–6 hours.
[0019] The present invention also provides an application of boron and nitrogen co-doped graphene carbon aerogel absorbing material prepared by the preparation method described above in electromagnetic wave absorption.
[0020] The present invention offers at least the following advantages: The boron- and nitrogen-doped graphene / carbon aerogel samples obtained by this invention possess a tunable porous network structure, with graphene sheets uniformly dispersed within the carbon aerogel network structure, effectively enhancing the dielectric loss and mechanical strength of the graphene. The boron- and nitrogen-doped graphene / carbon aerogel microwave absorbing material prepared by this invention exhibits a higher attenuation factor and better impedance matching characteristics, enabling the absorption of more electromagnetic waves into the material and subjecting them to multiple reflections and absorptions. Furthermore, the method involves a simple preparation process and mild preparation conditions, making it suitable for large-scale industrial production. It shows promising application prospects in the fields of civilian and military microwave absorbing materials.
[0021] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached image description:
[0022] Figure 1 This is a SEM image of the boron and nitrogen co-doped graphene carbon aerogel microwave absorbing material prepared in Example 1 of this invention.
[0023] Figure 2 The image shows the microwave absorption performance of the boron and nitrogen co-doped graphene carbon aerogel microwave absorbing material prepared in Example 1 of this invention. Detailed implementation method:
[0024] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.
[0025] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not imply the presence or addition of one or more other elements or combinations thereof.
[0026] This invention discloses a method for preparing boron-nitrogen co-doped graphene / carbon aerogel microwave absorbing material. The material employs an in-situ composite technique to uniformly disperse graphene sheets within a carbon aerogel network structure. Simultaneously, by controlling the density of the carbon aerogel precursor solution, the pore structure distribution is modulated, which helps reduce electromagnetic wave reflection and facilitates energy penetration into the material's interior, thereby enhancing its absorption capacity. The introduction of boron and nitrogen co-doping improves conductivity, thus enhancing conductivity loss. The introduced heteroatoms and defects enrich the dielectric polarization loss of the material, improving its impedance matching characteristics. This material exhibits low density, high absorption intensity, and excellent microwave absorption performance. Furthermore, the process is simple and the preparation conditions are mild. The boron and nitrogen non-metallic atom doping not only avoids the loss of lightweight properties caused by the introduction of dielectric or magnetic materials but also overcomes the constraints of structured graphene-based carbon materials, making it suitable for mass industrial production. This method has significant guiding significance for the research and development of lightweight and efficient pure carbon-based electromagnetic wave absorbing materials. Besides military applications such as radar and aircraft stealth, absorbing materials have broad application potential and market prospects in the fields of electromagnetic shielding and electromagnetic security protection for civilian communication equipment.
[0027] Example 1:
[0028] A method for preparing a boron-nitrogen co-doped graphene carbon aerogel microwave absorbing material includes the following steps:
[0029] Step 1: Add 0.3g boric acid to 10ml of 3mg / mL graphene oxide aqueous solution, stir for 30min, then add 6.9g urea, sonicate and stir for 12h to mix evenly, and obtain boron and nitrogen doped graphene oxide solution.
[0030] Step 2: Prepare a resorcinol-formaldehyde solution with a theoretical density of 0.4 g / mL (dissolve 25.88 g of resorcinol in 53.39 mL of deionized water. After complete dissolution, add 0.249 g of sodium carbonate, stir until clear, add 34.85 mL of formaldehyde solution, stir evenly, and then standardize to a volume of 100 mL to obtain 100 mL of phenolic resin precursor solution). Add the resorcinol-formaldehyde solution to the boron and nitrogen-doped graphene oxide solution from Step 1, stir evenly, and obtain a mixed precursor solution.
[0031] Step 3: Add the precursor mixture from Step 2 to 600 ml of mineral oil, emulsify at 800 r / min for 30 min, then reduce the speed to 300 r / min, raise the temperature to 60°C, and solidify in an oil bath for 48 h to obtain an organic particle / mineral oil mixture; the mineral oil contains the emulsifier Span 80, and the content of Span 80 is 3% of the mineral oil mass;
[0032] Step 4: Filter and separate the organic particles / mineral oil mixture to obtain organic solid powder. Wash the sample multiple times with dichloromethane and hot anhydrous ethanol. Dry the obtained sample at room temperature and pressure, and then heat it to dry (85℃) to obtain organic composite aerogel powder.
[0033] Step 5: Place the organic composite aerogel powder into a programmable temperature-controlled carbonization furnace and carbonize it at 1050℃ for 5 hours under inert gas protection to obtain boron and nitrogen co-doped graphene carbon aerogel microwave absorbing material. This material has a three-dimensional network structure of porous carbon and a uniformly dispersed graphene sheet structure.
[0034] Figure 1 This is a SEM image of the boron-nitrogen co-doped graphene carbon aerogel microwave absorbing material prepared in Example 1 of this invention; Figure 1 It can be seen that graphene is uniformly embedded on the resorcinol-formaldehyde porous carbon layer, and the wrinkles on the wall are also faintly visible. The graphene is tightly surrounded by porous carbon microspheres on both sides, forming graphene sheets in an amorphous, porous carbon structure.
[0035] Figure 2 This image shows the microwave absorption performance of the boron-nitrogen co-doped graphene carbon aerogel absorbing material prepared in Example 1 of this invention. Figure 2 It is evident that the absorption performance at different thicknesses shows that the minimum RL value shifts to lower frequencies with increasing aerogel thickness, demonstrating the dependence of the RL value on the thickness of the absorbing material. When the sample thickness increases to a certain value, an increase in absorption peaks occurs. By incorporating graphene oxide sheet structures, a multi-scale three-dimensional porous network structure is constructed within the carbon aerogel, possessing a complex solid-gas interface that provides excellent impedance matching characteristics and abundant loss mechanisms. The complex interface provided by the porous network structure of the carbon aerogel generates strong space charge polarization and significant interfacial polarization losses, which is beneficial for impedance matching, allowing more incident waves to enter the material's interior. Simultaneously, the small-area graphene-like sheets within the aerogel facilitate multiple reflection losses of electromagnetic waves. Furthermore, the abundant carbon atom structural defects and boron and nitrogen heteroatoms within the carbon aerogel provide numerous polarization centers, leading to high dielectric loss polarization relaxation and enhancing its attenuation loss for electromagnetic waves.
[0036] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.
Claims
1. A method for preparing a boron-nitrogen co-doped graphene carbon aerogel microwave absorbing material, characterized in that, Includes the following steps: Step 1: Mix the aqueous solution of graphene oxide with boron precursor reagents and nitrogen precursor reagents by ultrasonication and stirring until homogeneous to obtain a boron and nitrogen doped graphene oxide solution. Step 2: Prepare a precursor solution from the phenolic resin solution, add the precursor solution to the boron and nitrogen-doped graphene oxide solution, and stir until homogeneous to obtain a mixed precursor solution. Step 3: Add the precursor mixture to the mineral oil, stir at high speed and then at low speed, and heat and solidify to obtain an organic particle / mineral oil mixture. Step 4: Filter and separate the organic particles / mineral oil mixture, wash it, dry the obtained sample at room temperature and pressure, and then dry it at a higher temperature to obtain organic composite aerogel powder. Step 5: Place the organic composite aerogel powder into a carbonization furnace and sinter and carbonize it under inert gas protection to obtain boron and nitrogen co-doped graphene carbon aerogel microwave absorbing material. In step three, the high-speed stirring speed is 800~1000 r / min and the time is 25~35 min; the low-speed stirring speed is 200~400 r / min and the temperature is 55~65℃; the curing is carried out by oil bath curing for 48 h. The mineral oil contains the emulsifier Span 80, and the content of Span 80 is 2-5% of the mineral oil mass. The theoretical density of the precursor solution is 0.1~0.8 g / mL; the phenolic resin solution is a resorcinol-formaldehyde solution; the volume ratio of the precursor solution to the boron and nitrogen-doped graphene oxide solution obtained in step one is 1:3~1:
8.
2. The preparation method of the boron and nitrogen co-doped graphene carbon aerogel microwave absorbing material as described in claim 1, characterized in that, The boron precursor reagents are boric acid, sodium tetraborate, sodium perborate, and aminoborane; the nitrogen precursor reagents are urea, trihydroxypyridine, and melamine.
3. The preparation method of the boron and nitrogen co-doped graphene carbon aerogel microwave absorbing material as described in claim 1, characterized in that, The concentration of the graphene oxide aqueous solution is 2~20 mg / mL; the mass ratio of the boron precursor reagent to the nitrogen precursor reagent is 1:20~25; and the mass-volume ratio of the boron precursor reagent to the graphene oxide aqueous solution is 0.1~0.5 g:10 mL.
4. The preparation method of the boron and nitrogen co-doped graphene carbon aerogel microwave absorbing material as described in claim 1, characterized in that, In step four, the temperature for heating and drying is 80~100℃.
5. The preparation method of the boron and nitrogen co-doped graphene carbon aerogel microwave absorbing material as described in claim 1, characterized in that, In step five, the sintering temperature is 800~1100℃ and the time is 4~6h.
6. The application of a boron-nitrogen co-doped graphene carbon aerogel absorbing material prepared by the preparation method according to any one of claims 1 to 5 in electromagnetic wave absorption.