L-lysine regulates the growth of carbon cloth-based wave-absorbing material of NiCo-LDH nanometer array on carbon cloth surface, and its preparation method and application

Abstract

This invention belongs to the technical field of electromagnetic wave absorbing functional materials, specifically relating to a carbon cloth-based microwave absorbing material with L-lysine-controlled growth of NiCo-LDH nanoarrays on a carbon cloth surface, its preparation method, and its application. The invention uses carbon cloth as a substrate. After activation treatment, cobalt chloride hexahydrate, nickel chloride hexahydrate, urea, and L-lysine are added to deionized water. Following ultrasonication and stirring, a hydrothermal reaction is carried out, causing NiCo-LDH nanoarrays to grow in situ on the carbon cloth surface. After washing and drying, the material is obtained. L-lysine can control the arrangement density and orientation of the NiCo-LDH nanoarrays. The obtained material can be used in the field of electromagnetic wave absorbing materials; in a preferred embodiment, when the amount of L-lysine added is 1.0 g, the effective absorption bandwidth of the sample under a matching thickness of 1.09 mm can reach 4.24 GHz.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave absorbing functional materials technology, specifically relating to a carbon cloth-based microwave absorbing material with L-lysine-regulated growth of NiCo-LDH nanoarrays on the surface of carbon cloth, its preparation method, and its application. Background Technology

[0002] With the rapid development of electronic information technology and wireless communication equipment, electromagnetic interference and electromagnetic radiation have attracted increasing attention. Developing lightweight, efficient, broadband, thin-film, and flexible electromagnetic wave absorbing materials has become an important research direction in this field. NiCo-LDH possesses characteristics such as tunable composition, rich interfaces, and strong polarization, showing potential for application in electromagnetic wave absorption. However, its powder materials typically suffer from problems such as easy agglomeration, poor flexibility, and difficulty in direct application to flexible devices, which limits its practical applications.

[0003] Carbon cloth possesses advantages such as light weight, good flexibility, excellent conductivity, and ease of surface loading of active components. Using it as a substrate for in-situ growth of NiCo-LDH nanoarrays is beneficial for constructing flexible, integrated composite microwave absorbing materials. However, achieving a wide effective absorption bandwidth with relatively small matching thicknesses remains challenging for existing carbon cloth-based microwave absorbing materials. Some existing methods require high-temperature calcination, vulcanization, or other post-processing steps, making the processes relatively complex; others require the introduction of surfactants, complexing agents, or multiple auxiliary control components, which hinders process simplification. Simultaneously, the nucleation and growth process of NiCo-LDH on the carbon cloth surface is easily affected by reaction conditions, making it difficult to effectively control the growth direction, arrangement density, and structural uniformity of the resulting nanoarrays, thus affecting the microwave absorption performance of the material.

[0004] L-Lysine is a small molecule of amino acid containing both amino and carboxyl groups. In hydrothermal reaction systems, it may interact with metal ions or crystal growth interfaces, thereby affecting the nucleation and growth behavior of materials. Therefore, developing a carbon cloth-based microwave absorbing material and its preparation method that utilizes L-lysine to regulate the growth of NiCo-LDH nanoarrays on carbon cloth surfaces, with a relatively simple preparation process and the ability to obtain a wide effective absorption bandwidth at a relatively small matching thickness, is of practical significance. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of uneven nucleation, loose array, poor structural continuity, and difficulty in obtaining a wide effective absorption bandwidth under a small matching thickness in the growth process of NiCo-LDH on the surface of carbon cloth in the prior art. The invention provides a carbon cloth-based microwave absorbing material with L-lysine-regulated growth of NiCo-LDH nanoarrays on the surface of carbon cloth, its preparation method, and its application.

[0006] Another objective of this invention is to provide a method for in-situ growth of NiCo-LDH nanoarrays on carbon cloth by introducing L-lysine as a growth regulator.

[0007] Another object of the present invention is to provide a carbon cloth-based microwave absorbing material with a wide effective absorption bandwidth at a relatively small matching thickness.

[0008] To solve the above technical problems, the present invention adopts the following technical solution:

[0009] A method for preparing a microwave absorbing material with L-lysine-regulated growth of NiCo-LDH nanoarrays on carbon cloth surface, characterized by comprising the following steps:

[0010] (1) The carbon cloth was placed in an air atmosphere and heated to 450 ℃ at a heating rate of 5 ℃ / min and held for 2 h to obtain activated carbon cloth.

[0011] (2) 1.1 g cobalt chloride hexahydrate, 0.54 g nickel chloride hexahydrate, 0.55 g urea and L-lysine were added to 60 mL of deionized water, ultrasonically dispersed for 30 min and stirred for 1 h to obtain a homogeneous precursor solution. L-lysine was used as a morphology regulator.

[0012] (3) The activated carbon cloth is immersed in the precursor solution and transferred together to a 100 mL polytetrafluoroethylene-lined stainless steel reactor. The reaction is carried out hydrothermally at 120 °C for 10 h to allow the NiCo-LDH nanoarray to grow in situ on the surface of the carbon cloth.

[0013] (4) After the reaction is completed, the product is naturally cooled to room temperature, taken out, washed repeatedly with deionized water and anhydrous ethanol, and dried in a vacuum oven at 50 °C for 12 h to obtain the carbon cloth-based microwave absorbing material.

[0014] Furthermore, in step (2), the amount of L-lysine added as a morphology regulator is 0.5-2.0g.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] (1) The present invention can realize the in-situ growth of NiCo-LDH nanoarrays on the surface of carbon cloth by a one-step hydrothermal method, and the preparation process is relatively simple.

[0017] (2) The present invention introduces L-lysine as a growth regulator, which can regulate the arrangement density, orientation and structural uniformity of NiCo-LDH nanoarrays.

[0018] (3) After the formation of the NiCo-LDH nanoarray, the present invention does not require high-temperature calcination, sulfidation or other high-temperature post-treatment steps, which helps to reduce post-treatment processes.

[0019] (4) The carbon cloth-based microwave absorbing material obtained by the present invention has good electromagnetic wave absorption performance. In the preferred embodiment, when the amount of L-lysine added is 1.0 g, the effective absorption bandwidth of the material can reach 4.24 GHz under the condition that the matching thickness is only 1.09 mm, which shows the advantage of achieving a wider bandwidth absorption under a smaller matching thickness.

[0020] (5) The material obtained by the present invention has both the flexibility of carbon cloth substrate and surface array structure, and can be used in the field of electromagnetic wave absorbing materials. Attached Figure Description

[0021] Figure 1 This is a schematic diagram illustrating the preparation of carbon cloth-based microwave absorbing materials with L-lysine-regulated nanoarray growth obtained in Examples 1-3.

[0022] Figure 2 (a, b, c) are SEM images of the sample prepared in Comparative Example 1.

[0023] Figure 2 (d, e, f) are SEM images of the samples prepared in Example 1.

[0024] Figure 2 (g, h, i) are SEM images of the samples prepared in Example 2.

[0025] Figure 2 (j, k, l) are SEM images of the samples prepared in Example 3.

[0026] Figure 3 The XRD patterns of the samples prepared in Comparative Example 1 and Examples 1–3 are shown.

[0027] Figure 4 The XPS full spectrum of the sample prepared in Example 2.

[0028] Figure 5 The image shown is a TEM image of the sample prepared in Example 2.

[0029] Figure 6 (a, b) are the three-dimensional plot and two-dimensional contour plot of the reflection loss (RL) of the sample prepared in Comparative Example 1 in the frequency range of 2–18 GHz, respectively.

[0030] Figure 6 (c, d) are three-dimensional and two-dimensional contour plots of the reflection loss (RL) of the sample prepared in Example 1 in the frequency range of 2–18 GHz, respectively.

[0031] Figure 6 (e, f) are the three-dimensional and two-dimensional contour plots of the reflection loss (RL) of the sample prepared in Example 2 in the frequency range of 2–18 GHz, respectively.

[0032] Figure 6 (g, h) are three-dimensional and two-dimensional contour plots of the reflection loss (RL) of the sample prepared in Example 3 in the frequency range of 2–18 GHz, respectively. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to embodiments. Commercially purchased carbon cloth is cut into 1cm × 1cm pieces, and one piece is used for each reaction.

[0034] Comparative Example 1: Preparation of a microwave absorbing material without L-lysine-mediated regulation of NiCo-LDH nanoarray growth on carbon cloth surface, the specific steps are as follows:

[0035] (1) Commercially purchased carbon was placed in a tube furnace and heated to 450°C at a rate of 5°C / min in air atmosphere, and held at that temperature for 2 hours for activation treatment. After cooling, it was taken out and ultrasonically cleaned with anhydrous ethanol and deionized water in sequence, and then dried in a vacuum oven at 60°C for later use.

[0036] (2) Accurately weigh 1.1g of cobalt chloride hexahydrate (CoCl2·6H2O), 0.54g of nickel chloride hexahydrate (NiCl2·6H2O) and 0.55g of urea, dissolve the above reagents in 60 mL of deionized water, sonicate at room temperature for 30 minutes, and then continue to stir magnetically for 1 hour to obtain a clear and homogeneous reaction precursor solution.

[0037] (3) The pretreated carbon cloth from step (1) was completely immersed in the precursor solution prepared in step (2), and the entire system was transferred to a 100 mL stainless steel autoclave lined with polytetrafluoroethylene. After sealing, the autoclave was placed in an oven at 120 °C and heated for 10 hours.

[0038] (4) After the reaction is complete, allow the autoclave to cool naturally to room temperature. Use tweezers to remove the carbon cloth loaded with the product, and rinse it repeatedly with deionized water and anhydrous ethanol several times to remove residual ions and impurities on the surface. Finally, dry the washed product in a vacuum oven at 50 °C for 12 hours to obtain the final product.

[0039] Example 1: Preparation of a microwave absorbing material with L-lysine-regulated growth of NiCo-LDH nanoarrays on carbon cloth surface, the specific steps are as follows:

[0040] (1) Commercially purchased carbon was placed in a tube furnace and heated to 450°C at a rate of 5°C / min in air atmosphere, and held at that temperature for 2 hours for activation treatment. After cooling, it was taken out and ultrasonically cleaned with anhydrous ethanol and deionized water in sequence, and then dried in a vacuum oven at 60°C for later use.

[0041] (2) Accurately weigh 1.1g of cobalt chloride hexahydrate (CoCl2·6H2O), 0.54g of nickel chloride hexahydrate (NiCl2·6H2O), 0.55g of urea and 0.5g of L-lysine, dissolve the above reagents in 60 mL of deionized water, sonicate at room temperature for 30 minutes, and then continue to stir magnetically for 1 hour to obtain a clear and homogeneous reaction precursor solution.

[0042] (3) The pretreated carbon cloth from step (1) was completely immersed in the precursor solution prepared in step (2), and the entire system was transferred to a 100 mL stainless steel autoclave lined with polytetrafluoroethylene. After sealing, the autoclave was placed in an oven at 120 °C and heated for 10 hours.

[0043] (4) After the reaction is complete, allow the autoclave to cool naturally to room temperature. Use tweezers to remove the carbon cloth loaded with the product, and rinse it repeatedly with deionized water and anhydrous ethanol several times to remove residual ions and impurities on the surface. Finally, dry the washed product in a vacuum oven at 50 °C for 12 hours to obtain the final product.

[0044] Example 2: Preparation of a microwave absorbing material with L-lysine-regulated growth of NiCo-LDH nanoarrays on carbon cloth surface, the specific steps are as follows:

[0045] (1) Commercially purchased carbon was placed in a tube furnace and heated to 450°C at a rate of 5°C / min in air atmosphere, and held at that temperature for 2 hours for activation treatment. After cooling, it was taken out and ultrasonically cleaned with anhydrous ethanol and deionized water in sequence, and then dried in a vacuum oven at 60°C for later use.

[0046] (2) Accurately weigh 1.1g of cobalt chloride hexahydrate (CoCl2·6H2O), 0.54g of nickel chloride hexahydrate (NiCl2·6H2O), 0.55g of urea and 1g of L-lysine, dissolve the above reagents in 60 mL of deionized water, sonicate at room temperature for 30 minutes, and then continue to stir magnetically for 1 hour to obtain a clear and homogeneous reaction precursor solution.

[0047] (3) The pretreated carbon cloth from step (1) was completely immersed in the precursor solution prepared in step (2), and the entire system was transferred to a 100 mL stainless steel autoclave lined with polytetrafluoroethylene. After sealing, the autoclave was placed in an oven at 120 °C and heated for 10 hours.

[0048] (4) After the reaction is complete, allow the autoclave to cool naturally to room temperature. Use tweezers to remove the carbon cloth loaded with the product, and rinse it repeatedly with deionized water and anhydrous ethanol several times to remove residual ions and impurities on the surface. Finally, dry the washed product in a vacuum oven at 50 °C for 12 hours to obtain the final product.

[0049] Example 3: Preparation of a microwave absorbing material with L-lysine-regulated growth of NiCo-LDH nanoarrays on carbon cloth surface, the specific steps are as follows:

[0050] (1) Commercially purchased carbon was placed in a tube furnace and heated to 450°C at a rate of 5°C / min in air atmosphere, and held at that temperature for 2 hours for activation treatment. After cooling, it was taken out and ultrasonically cleaned with anhydrous ethanol and deionized water in sequence, and then dried in a vacuum oven at 60°C for later use.

[0051] (2) Accurately weigh 1.1g of cobalt chloride hexahydrate (CoCl2·6H2O), 0.54g of nickel chloride hexahydrate (NiCl2·6H2O), 0.55g of urea and 2g of L-lysine, dissolve the above reagents in 60 mL of deionized water, sonicate at room temperature for 30 minutes, and then continue to stir magnetically for 1 hour to obtain a clear and homogeneous reaction precursor solution.

[0052] (3) The pretreated carbon cloth from step (1) was completely immersed in the precursor solution prepared in step (2), and the entire system was transferred to a 100 mL stainless steel autoclave lined with polytetrafluoroethylene. After sealing, the autoclave was placed in an oven at 120 °C and heated for 10 hours.

[0053] (4) After the reaction is complete, allow the autoclave to cool naturally to room temperature. Use tweezers to remove the carbon cloth loaded with the product, and rinse it repeatedly with deionized water and anhydrous ethanol several times to remove residual ions and impurities on the surface. Finally, dry the washed product in a vacuum oven at 50 °C for 12 hours to obtain the final product.

[0054] 1. Morphological and structural characterization

[0055] The microstructure of the samples from each embodiment was characterized using scanning electron microscopy (SEM), and the results are as follows: Figure 2 As shown: Figure 2 As shown in (a, b, c), in Comparative Example 1, in the reaction system without the addition of L-lysine, the NiCo-LDH grown on the surface of the carbon cloth fiber exhibited a relatively sparse and unevenly sized nanoneedle structure with disordered orientation, failing to form an effective array arrangement. Figure 2As shown in (d, e, f), in Example 1, when the amount of L-lysine added was 0.5 g, the morphology of the NiCo-LDH nanoarray underwent a significant evolution, with a significant increase in the density of the nanoarray units and a decrease in size. Figure 2 As shown in (g, h, i), in Example 2, when the amount of L-lysine added was 1.0 g, a relatively dense array structure with basically perpendicular orientation and relatively uniform size was formed on the surface of the carbon cloth fiber. Figure 2 As shown in (j, k, l), in Example 3, when the amount of L-lysine added was further increased to 2g, the density of the NiCo-LDH nanoarray further increased, but local aggregation occurred, and the structural regularity and vertical orientation decreased.

[0056] To characterize the crystal structure of the samples, X-ray diffraction analysis was performed on the samples obtained in Comparative Example 1 and Examples 1–3. Figure 3 As shown, diffraction peaks were observed near 25.6° and 43.7° in all samples, corresponding to the (002) and (101) crystal planes of graphite, respectively. The diffraction peaks at 17.5°, 26.7°, 30.4°, 33.8°, 35.5°, 36.5°, 39.5°, and 44.7° in Examples 1–3 can be attributed to NiCo-LDH related crystal planes, indicating the formation of the NiCo-LDH phase in the samples. With increasing L-lysine addition, the positions of the diffraction peaks in each sample did not change significantly, while the intensity of some diffraction peaks decreased, indicating that the introduction of L-lysine had a certain impact on the sample structure formation process.

[0057] Figure 4 The image shows the XPS full spectrum of the sample from Example 2. As can be seen from the figure, characteristic peaks for C, O, Co, and Ni elements are present in the sample, indicating the presence of NiCo-LDH related components on the sample surface. Furthermore, a characteristic N 1s peak is observed at approximately 400 eV, indicating the presence of nitrogen-containing species on the sample surface. Considering the introduction of L-lysine into the reaction system and the results after thorough washing of the sample, it can be concluded that this nitrogen-containing signal is related to the introduction of L-lysine.

[0058] Figure 5 This is a TEM image of the sample from Example 2. Figure 5 As shown in (a), localized crystallization regions with a characteristic size of approximately 20 nm can be observed in the sample, indicating that the array is composed of relatively small nanounits. Figure 5 As shown in (b), clear lattice fringes are visible in the HRTEM image, with a crystal plane spacing of approximately 0.27 nm, which can be attributed to the (221) crystal plane of NiCo-LDH, further indicating the formation of the NiCo-LDH phase in the sample. Since L-lysine is a small molecule regulator, it is usually difficult to directly distinguish it as an independent coating layer in TEM.

[0059] 2. Electromagnetic performance testing and analysis

[0060] To evaluate the absorption performance of the samples from each embodiment, their reflection loss values ​​were calculated based on transmission line theory. A ring (outer diameter 7.0 mm, inner diameter 3.0 mm, thickness 2.4 mm) was prepared from 45% of the sample material from each embodiment and 55% paraffin wax, and tested using a vector network analyzer. Figure 6 (ah) displays the three-dimensional (3D) and two-dimensional (2D) contour plots of RL, as a function of frequency and absorber thickness for Comparative Example 1, Example 1, Example 2, and Example 3, respectively. A −10 dB threshold is marked to define the effective absorption bandwidth (EAB), corresponding to 90% absorption efficiency. Furthermore, in practical applications of electromagnetic wave absorbing materials, the effective absorption bandwidth at a specific thickness is usually considered; therefore, this invention primarily analyzes the effective absorption bandwidth of samples at different matching thicknesses. Figure 6 As shown in (a) and (b), in Comparative Example 1, without the introduction of L-lysine, the sample only exhibited electromagnetic wave absorption capability under certain frequency and thickness conditions, with a narrow effective absorption bandwidth and a relatively large matching thickness. After the introduction of L-lysine, the absorption performance of the sample was improved. Figure 6 As shown in (c) and (d), Example 1 achieves an effective absorption bandwidth of 3.28 GHz when the matching thickness is 1.5 mm. Figure 6 As shown in (e, f), Example 2 exhibits superior absorption performance, achieving RL < −10 dB in a certain frequency band corresponding to a thickness range of 1.0–1.5 mm; specifically, with a matched thickness of 1.09 mm, the effective absorption bandwidth reaches 4.24 GHz. Figure 6 As shown in (g, h), the effective absorption bandwidth of Example 3 was not further increased, and the effective absorption bandwidth was 3.84 GHz when the matching thickness was 1.12 mm.

[0061] The above results indicate that the amount of L-lysine added has a significant impact on the microwave absorption performance of the sample. Under the conditions of this invention, when the amount of L-lysine added is 1.0 g, the resulting sample exhibits a wider effective absorption bandwidth at a smaller matching thickness.

Claims

1. A method for preparing a microwave absorbing material with L-lysine-regulated growth of NiCo-LDH nanoarrays on carbon cloth surface, characterized in that, Includes the following steps: (1) The carbon cloth is placed in a tube furnace and heated in an air atmosphere to activate it, thus obtaining activated carbon cloth. (2) Cobalt salt, nickel salt, urea and L-lysine were added to deionized water and stirred and sonicated to obtain a uniform reaction precursor solution, wherein L-lysine was used as a growth regulator. (3) Immerse the activated carbon cloth obtained in step (1) completely in the precursor solution prepared in step (2). (4) The precursor solution containing activated carbon cloth is transferred to a hydrothermal reactor for hydrothermal reaction, so that nickel-cobalt layered bimetallic hydroxide (NiCo-LDH) nanoarrays are grown in situ on the surface of the carbon cloth substrate. (5) After the reaction is complete and the product is cooled, the product is taken out, washed and dried to obtain the electromagnetic wave absorbing material.

2. The preparation method according to claim 1, characterized in that... The heating in step (1) is to heat to 450 ℃ at a heating rate of 5 ℃ / min, and then hold at that temperature for 2 hours to activate the surface.

3. The preparation method according to claim 1, characterized in that: In step (2), the cobalt salt is cobalt chloride hexahydrate, the nickel salt is nickel chloride hexahydrate, the amount of cobalt chloride hexahydrate added is 1.1 g, the amount of nickel chloride hexahydrate added is 0.54 g, the amount of urea added is 0.55 g, and the volume of deionized water is 60 mL.

4. The preparation method according to claim 3, characterized in that: In step (2), the amount of L-lysine added is 0.5–2.0 g.

5. The preparation method according to claim 1 or 3, characterized in that: In step (2), the ultrasonic time is 30 min and the stirring time is 1 h.

6. The preparation method according to claim 1, characterized in that... The heat preservation temperature in step (4) is 120 ℃, and then the heat preservation reaction is carried out for 10 hours.

7. The preparation method according to claim 1, characterized in that... The washing in step (5) is done by alternating between deionized water and ethanol, and the drying is done by drying in a vacuum oven at 50 ℃ for 12 h.

8. A carbon cloth-based microwave absorbing material, characterized in that: The carbon cloth-based microwave absorbing material is prepared by the preparation method according to any one of claims 1 to 7, and includes a carbon cloth substrate and a NiCo-LDH nanoarray grown in situ on the surface of the carbon cloth substrate.

9. The carbon cloth-based microwave absorbing material according to claim 8, characterized in that: The NiCo-LDH nanoarray is densely, uniformly, and basically vertically distributed on the surface of the carbon fiber.

10. The carbon cloth-based microwave absorbing material according to claim 8 or 9, characterized in that: The arrangement density and orientation of the NiCo-LDH nanoarray are regulated by the amount of L-lysine added.

11. The application of the carbon cloth-based absorbing material according to any one of claims 8–10 in the field of electromagnetic wave absorption.

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