Ni / nitrogen-doped carbon composite wave-absorbing material and preparation method thereof
By preparing Ni/nitrogen-doped carbon composite microwave absorbing materials, the problem of low absorption efficiency of traditional magnetic materials has been solved, achieving thin, light, and wide-band electromagnetic wave absorption performance. Moreover, the preparation process is simple and low-cost.
Patent Information
- Application Number
- CN202511409039.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-29
- Publication Date
- 2025-11-25
AI Technical Summary
Traditional magnetic electromagnetic wave absorbing materials have high permeability and low dielectric constant, resulting in low absorption efficiency and difficulty in achieving wide-band absorption.
A method for preparing Ni/nitrogen-doped carbon composite microwave absorbing materials was adopted. Melamine, terephthalaldehyde, nickel nitrate hexahydrate and terephthalic acid were reacted in a mixed solvent to form a Ni/COF precursor, which was then calcined at high temperature under a nitrogen atmosphere to prepare a Ni/nitrogen-doped carbon composite material with a nanosheet structure, thereby optimizing dielectric loss and impedance matching.
It achieves electromagnetic wave absorption performance with thin thickness, strong absorption and wide bandwidth, with an RLmin value of -55.16 dB and an EAB value of 6.40 GHz, meeting the requirements of lightweight and wide bandwidth, and the fabrication process is simple and low cost.
Smart Images
Figure CN121006201A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of microwave absorbing materials technology, specifically relating to a Ni / nitrogen-doped carbon composite microwave absorbing material and its preparation method. Background Technology
[0002] With the rapid development of communication technology, various electronic products have greatly facilitated people's daily lives. However, the resulting electromagnetic pollution poses a significant threat to human health and the operation of high-precision equipment. To address this issue, researchers have developed a series of absorbing materials that are thin, lightweight, have wide bandwidth, and exhibit strong reflection loss characteristics.
[0003] Traditional microwave absorbing materials are severely limited in practical applications due to drawbacks such as high density, narrow absorption bandwidth, and a single loss mechanism. Magnetic absorbing materials, despite possessing high permeability, suffer from low dielectric constant, leading to strong reflection of electromagnetic waves at their surface and consequently low absorption efficiency. Furthermore, these materials are strictly constrained by the Snoek limit; at high frequencies, the permeability drops sharply, posing a significant challenge to achieving effective absorption over a wide frequency range.
[0004] In recent years, porous materials with low relative density and high specific surface area, such as porous zeolite materials, activated carbon, and metal-organic frameworks (MOFs), have attracted increasing attention in the field of microwave absorption. As an emerging porous material, covalent organic frameworks (COFs) possess advantages such as large specific surface area, tunable pore structure, and designable composition. Furthermore, COFs exhibit good stability through strong covalent bonds and contain only lightweight elements (such as H, B, C, N, and O), giving them the potential for lightweight materials. By combining COFs with traditional magnetic materials, and through the control of porous structures, optimization of interface engineering, and design of chemical composition, wide-bandwidth and high-loss absorption performance has been achieved. For example, Zhu et al. synthesized a hollow core-shell Fe / Fe3O4@porous carbon composite material by calcining Fe3O4@COF composites, achieving a minimum reflectance (RL) of [missing value] at a thickness of 1.80 mm. min The impedance is -50.05 dB, and the effective absorption bandwidth (EAB) reaches 5.20 GHz. The excellent performance stems from the high specific surface area and hollow core-shell porous structure, which promotes multiple reflections and scattering of electromagnetic waves, optimizes impedance matching, and enhances wave absorption performance.
[0005] However, existing magnetic materials have high filler ratios and suffer from high permeability and low dielectric constants. Therefore, it is particularly important to develop simple and convenient methods to prepare composite materials with low filler ratios and wide bandwidths.
[0006] Therefore, developing a Ni / nitrogen-doped carbon composite microwave absorbing material is of great significance. Summary of the Invention
[0007] The technical problem this invention aims to solve is to address the issues of high permeability and low dielectric constant in traditional magnetic electromagnetic wave absorbing materials. This invention provides a Ni / nitrogen-doped carbon composite absorbing material and its preparation method. The dielectric loss mechanism of COF can compensate for the insufficient magnetic loss in the high-frequency band of magnetic absorbing materials, thus broadening the effective absorption bandwidth. This material has the advantages of thinness, strong absorption, and wide absorption bandwidth, and its preparation process is simple, easy to control, and low in cost.
[0008] To address the aforementioned technical problems, this invention discloses a method for preparing a Ni / nitrogen-doped carbon composite microwave absorbing material, comprising the following steps:
[0009] S1. Melamine, terephthalaldehyde, nickel nitrate hexahydrate and terephthalic acid are dissolved in a mixed solvent to obtain a mixed solution; sodium oxyoxide solution is added to the mixed solution, and after mixing evenly, a hydrothermal reaction is carried out. After the reaction is completed, the solution is filtered, washed and dried to obtain the Ni / COF precursor.
[0010] S2. The Ni / COF precursor is calcined under a nitrogen atmosphere to obtain the Ni / nitrogen-doped carbon composite microwave absorbing material.
[0011] In S2, the heating and calcination process has a heating rate of 2-5 °C / min, a calcination temperature of 600-700 °C, and a calcination time of 1-3 h.
[0012] Preferably, in S2, the heating and calcination process has a heating rate of 3 °C / min, a calcination temperature of 650 °C, and a calcination time of 2 h.
[0013] In S1, the molar ratio of melamine to terephthalaldehyde is 1:(1-1.5); the concentration of terephthalaldehyde in the mixed solution is 9.98 mg / mL.
[0014] In S1, the mass ratio of terephthalic acid to nickel nitrate hexahydrate is 1:(1-1.2); the concentration of nickel nitrate hexahydrate in the mixed solution is 2.18 mg / mL.
[0015] In S1, the mixed solvent is a solvent composed of dimethyl sulfoxide and N,N-dimethylformamide; the volume ratio of dimethyl sulfoxide to N,N-dimethylformamide is 1:(3-3.5).
[0016] In S1, the volume ratio of the sodium hydroxide solution to N,N-dimethylformamide is 1:(7.5-15).
[0017] In S1, the concentration of the sodium hydroxide solution is 0.3–0.6 M.
[0018] In S1, the sodium oxyoxide solution is added to the mixed solution while stirring, and the stirring speed is 600-800 rpm.
[0019] In S1, the hydrothermal reaction is carried out under the following conditions: reaction at 100 °C for 10 h.
[0020] In S1, the washing conditions are as follows: alternating washing with anhydrous ethanol and deionized water, and washing is performed 4 to 6 times.
[0021] In S1, the drying conditions are: temperature of 60-80 ℃ and time of 12-14 h.
[0022] Furthermore, the Ni / nitrogen-doped carbon composite microwave absorbing material prepared by the above preparation method is also within the scope of protection of this invention.
[0023] Specifically, in some embodiments of the present invention, Ni / nitrogen-doped carbon composite microwave absorbing materials were successfully prepared by the above preparation method. XRD and SEM characterization proved that the material has a nanosheet structure and COF particles are attached to the surface of the layered structure. Characterization of its microwave absorption performance proved that the Ni / nitrogen-doped carbon composite microwave absorbing material provided by the present invention has excellent electromagnetic wave absorption performance in the X and Ku bands.
[0024] Beneficial effects:
[0025] 1) This invention provides a Ni / nitrogen-doped carbon composite microwave absorbing material and its preparation method. Using Ni / COF as a precursor, the precursor is converted into a Ni / nitrogen-doped carbon composite material through high-temperature carbonization. This method features a simple precursor preparation process, unique morphology, low cost, and repeatable operation. Changing the carbonization temperature provides an effective method for adjusting the dielectric constant. The Ni / nitrogen-doped carbon composite microwave absorbing material prepared by this invention not only optimizes the electromagnetic parameters of the composite material but also achieves a balance between impedance matching and attenuation capability.
[0026] 2) This invention transforms the precursor into an ideal magnetic carbon-based composite material through a high-temperature carbonization method. The prepared composite material exhibits good reflection loss and absorption bandwidth. When the filler content is 35 wt%, the Ni / nitrogen-doped carbon composite material shows a high RL at 2.23 mm. min The value is -55.16 dB, and the EAB value is 6.40 GHz (11.60-18.00 GHz) with a matching thickness of 2.40 mm. Attached Figure Description
[0027] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.
[0028] Figure 1 The images show the X-ray diffraction (XRD) patterns of the Ni / COF precursor and Ni / nitrogen-doped carbon composite microwave absorbing materials prepared in Examples 1-3 of this invention.
[0029] Figure 2 SEM images of the Ni / COF precursor and Ni / nitrogen-doped carbon composite microwave absorbing material prepared in Example 2 of this invention.
[0030] Figure 3 The image shows the RL curves of the Ni / nitrogen-doped carbon composite microwave absorbing material prepared in Example 1 of this invention at thicknesses of 1.00–5.50 mm.
[0031] Figure 4 The image shows the RL curves of the Ni / nitrogen-doped carbon composite microwave absorbing material prepared in Example 2 of this invention at thicknesses of 1.00–5.50 mm.
[0032] Figure 5 The image shows the RL curves of the Ni / nitrogen-doped carbon composite microwave absorbing material prepared in Example 3 of this invention at thicknesses of 1.00–5.50 mm. Detailed Implementation
[0033] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are commercially available.
[0034] Example 1:
[0035] A Ni / nitrogen-doped carbon composite microwave absorbing material and its preparation method, comprising the following steps:
[0036] S1. Dissolve 0.4704 g melamine, 0.7981 g terephthalaldehyde, 0.1661 g terephthalic acid and 0.1745 g nickel nitrate hexahydrate in 80 mL of a solvent consisting of dimethyl sulfoxide and N,N-dimethylformamide in a volume ratio of 1:3 to obtain a mixed solution.
[0037] S2. Add 4 mL (0.4 M) of sodium hydroxide solution to the mixed solution obtained in S1 with stirring. After rapid dropwise addition, continue stirring for 30 min. Transfer the resulting solution to a reaction vessel and hydrothermally react at 100 °C for 10 h. After cooling to room temperature, filter and collect the solid product. Then wash it five times alternately with anhydrous ethanol and deionized water. After drying in a vacuum drying oven at 60 °C for 12 h, the Ni / COF precursor is obtained.
[0038] S3. The dried Ni / COF precursor was placed in a tube furnace and heated to 600 °C at a rate of 3 °C / min under a nitrogen atmosphere. After holding at this temperature for 2 h, the Ni / nitrogen-doped carbon composite material was obtained and denoted as NC-1.
[0039] Example 2:
[0040] A Ni / nitrogen-doped carbon composite microwave absorbing material and its preparation method, comprising the following steps:
[0041] S1. Dissolve 0.4704 g melamine, 0.7981 g terephthalaldehyde, 0.1661 g terephthalic acid and 0.1745 g nickel nitrate hexahydrate in 80 mL of a solvent consisting of dimethyl sulfoxide and N,N-dimethylformamide in a volume ratio of 1:3 to obtain a mixed solution.
[0042] S2. Add 4 mL (0.4 M) of sodium hydroxide solution to the mixed solution obtained in S1 with stirring. After rapid dropwise addition, continue stirring for 30 min. Transfer the resulting solution to a reaction vessel and hydrothermally react at 100 °C for 10 h. After cooling to room temperature, filter and collect the solid product. Then wash it five times alternately with anhydrous ethanol and deionized water. After drying in a vacuum drying oven at 60 °C for 12 h, the Ni / COF precursor is obtained.
[0043] S3. The dried Ni / COF precursor was placed in a tube furnace and heated to 650 °C at a rate of 3 °C / min under a nitrogen atmosphere. After holding at this temperature for 2 h, the Ni / nitrogen-doped carbon composite material was obtained and designated as NC-2.
[0044] Example 3
[0045] A Ni / nitrogen-doped carbon composite microwave absorbing material and its preparation method, comprising the following steps:
[0046] S1. Dissolve 0.4704 g of melamine, 0.7981 g of terephthalaldehyde, 0.1661 g of terephthalic acid and 0.1745 g of nickel nitrate hexahydrate in 80 mL of a solvent consisting of dimethyl sulfoxide and N,N-dimethylformamide in a volume ratio of 1:3 to obtain a mixed solution;
[0047] S2. Add 4 mL (0.4 M) of sodium hydroxide solution to the mixed solution obtained in S1 with stirring. After rapid dropwise addition, continue stirring for 30 min. Transfer the resulting solution to a reaction vessel and hydrothermally react at 100 °C for 10 h. After cooling to room temperature, filter and collect the solid product. Then wash it five times alternately with anhydrous ethanol and deionized water. After drying in a vacuum drying oven at 60 °C for 12 h, the Ni / COF precursor is obtained.
[0048] S3. The dried Ni / COF precursor was placed in a tube furnace and heated to 700 °C at a rate of 3 °C / min under a nitrogen atmosphere. After holding at this temperature for 2 h, the Ni / nitrogen-doped carbon composite material was obtained and designated as NC-3.
[0049] Performance characterization:
[0050] 1. The phase structure of Ni / nitrogen-doped carbon composite microwave absorbing material was analyzed using an XRD instrument.
[0051] Figure 1 The images show the XRD patterns of the Ni / COF precursor and Ni / nitrogen-doped carbon composite microwave absorbing materials prepared in Examples 1-3. Figure 1 In this context, 'a' represents the XRD patterns of the Ni / COF precursors prepared in Examples 1-3; Figure 1 Figure b shows the XRD patterns of the Ni / nitrogen-doped carbon composite microwave absorbing materials prepared in Examples 1-3. The broad peaks observed at approximately 23° for NC-1, NC-2, and NC-3 reveal the presence of amorphous carbon. Simultaneously, the diffraction peaks at 44.50, 51.84, and 76.37° correspond to the (111), (200), and (220) crystal planes of Ni according to the standard PDF card (JCPDS No. 04-0850), respectively. Notably, as the carbonization temperature increases, the intensity of the three Ni diffraction peaks gradually becomes sharper and stronger, indicating an increase in crystallinity. The above analysis demonstrates that Ni / nitrogen-doped carbon composite microwave absorbing materials can be successfully synthesized by adjusting the carbonization temperature.
[0052] 2. The microstructure of the Ni / nitrogen-doped carbon composite microwave absorbing material prepared in Example 2 was analyzed using scanning electron microscopy.
[0053] Figure 2 These are SEM images of the Ni / COF precursor and Ni / nitrogen-doped carbon composite microwave absorbing material prepared in Example 2 of this invention, wherein... Figure 2 (a~c) are SEM images of the prepared Ni / COF precursor. Figure 2 (d~f) are SEM images of the Ni / nitrogen-doped carbon composite microwave absorbing material after carbonization at 650℃. For example... Figure 2 As shown in (a~c), the Ni / COF precursor exhibits a layered structure composed of numerous nanosheets with a size of approximately 3 μm, while COF particles are attached to the surface of the layered structure. Figure 2As shown in (d~f), the surface layered structure of the composite material is significantly affected by the calcination temperature. During pyrolysis, the number of pores on the surface of the composite material continuously increases, some layered structures collapse, and the average size shrinks slightly. This may be related to the increase in pore size, as the enlarged pore size cannot support the framework of the layered structure. Furthermore, this porous layered framework provides a transmission channel for the migration and jumping of free electrons, promoting the attenuation of electromagnetic waves.
[0054] 3. The electromagnetic parameters of the sample are analyzed using a vector network analyzer, and its absorption performance is then calculated.
[0055] Figure 3 The RL curves of the Ni / nitrogen-doped carbon composite material prepared in Example 1 are shown in the range of 1.00–5.50 mm. Figure 4 The RL curves of the Ni / nitrogen-doped carbon composite material prepared in Example 2 are shown in the range of 1.00–5.50 mm. Figure 5 The RL curves for the Ni / nitrogen-doped carbon composite material prepared in Example 3 are shown in the range of 1.00–5.50 mm. Figure 3 As can be seen, NC-1 (the Ni / nitrogen-doped carbon composite material prepared in Example 1) at a thickness of 3.00 mm exhibits high RL. min The value is -18.84 dB, and the EAB value is 5.04 GHz (12.32-17.36 GHz).
[0056] Depend on Figure 4 It can be seen that the RL of NC-2 (the Ni / nitrogen-doped carbon composite material prepared in Example 2) min The EAB value is significantly improved compared to NC-1 at thicknesses of 2.23, 2.40, and 3.00 mm. min The values were -55.16, -44.67, and -32.31 dB, respectively, achieving electromagnetic wave absorption performance in the X and Ku bands. When the thickness was 2.40 mm, the EAB value reached 6.40 GHz (11.60–18.00 GHz), with a larger absorption bandwidth compared to NC-1. The EAB effectively covered the entire Ku band, satisfying both good absorption capability and a wide absorption bandwidth. The improved absorption performance is attributed to strong electromagnetic attenuation and good impedance matching characteristics.
[0057] from Figure 5 As can be seen, the microwave absorption performance of NC-3 (the Ni / nitrogen-doped carbon composite material prepared in Example 3) gradually decreases with increasing carbonization temperature. The RL at 2.29 mm... minThe value is -21.93 dB, and the EAB value at 2.40 mm is 6.00 GHz (11.68–17.68 GHz). The reduced absorption performance is likely due to impedance mismatch. Clearly, the sample's RL... min The EAB value initially increases and then decreases with increasing carbonization temperature. These results indicate that tunable electromagnetic wave absorption can be effectively achieved by adjusting the carbonization temperature, thereby enhancing reflection loss and achieving a wider absorption bandwidth. Ni / nitrogen-doped carbon composite materials exhibit excellent electromagnetic wave absorption performance, fulfilling the requirements of "thin, light, wide, and strong" for microwave absorbing materials.
[0058] This invention provides a Ni / nitrogen-doped carbon composite microwave absorbing material and its preparation method. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.
Claims
1. A method for preparing a Ni / nitrogen-doped carbon composite wave-absorbing material, characterized in that, Includes the following steps: S1. Melamine, terephthalaldehyde, nickel nitrate hexahydrate and terephthalic acid are dissolved in a mixed solvent to obtain a mixed solution; sodium oxyoxide solution is added to the mixed solution, and after mixing evenly, a hydrothermal reaction is carried out. After the reaction is completed, the solution is filtered, washed and dried to obtain the Ni / COF precursor. S2. The Ni / COF precursor is calcined under a nitrogen atmosphere to obtain the Ni / nitrogen-doped carbon composite microwave absorbing material. In S2, the heating and calcination process has a heating rate of 2-5 °C / min, a calcination temperature of 600-700 °C, and a calcination time of 1-3 h.
2. The production method according to claim 1, characterized by, In S1, the molar ratio of melamine to terephthalaldehyde is 1:(1-1.5); the concentration of terephthalaldehyde in the mixed solution is 9.98 mg / mL.
3. The production method according to claim 1, characterized by, In S1, the mass ratio of terephthalic acid to nickel nitrate hexahydrate is 1:(1-1.2); the concentration of nickel nitrate hexahydrate in the mixed solution is 2.18 mg / mL.
4. The method of claim 1, wherein, In S1, the mixed solvent is a solvent composed of dimethyl sulfoxide and N,N-dimethylformamide; the volume ratio of dimethyl sulfoxide to N,N-dimethylformamide is 1:(3-3.5).
5. The preparation method according to claim 4, characterized in that, In S1, the volume ratio of the sodium hydroxide solution to N,N-dimethylformamide is 1:(7.5-15).
6. The production method according to claim 5, wherein In S1, the concentration of the sodium hydroxide solution is 0.3–0.6 M.
7. The preparation method according to claim 1, characterized in that, In S1, the hydrothermal reaction is carried out under the following conditions: reaction at 100°C for 10 h.
8. The preparation method according to claim 1, characterized in that, In S1, the washing conditions are as follows: alternating washing with anhydrous ethanol and deionized water, and washing 4 to 6 times.
9. The preparation method according to claim 1, characterized in that, In S1, the drying conditions are: temperature of 60-80 °C and time of 12-14 h.
10. The Ni / nitrogen-doped carbon composite microwave absorbing material prepared by the preparation method according to any one of claims 1 to 9.