Preparation method of hyperbranched polyamide-graphene oxide coating modified double-layer periodic carbon fiber woven body wave-absorbing material

Abstract

The invention discloses a preparation method of a hyperbranched polyamide-graphene oxide coating modified double-layer periodic carbon fiber woven body wave-absorbing material, and belongs to the technical field of preparation of electromagnetic wave absorbing materials. The invention aims to solve the technical problems of weak low-frequency absorption performance, anisotropic electromagnetic absorption performance and uncontrollable graphene oxide content of a carbon fiber single-layer one-way periodic woven body wave-absorbing material. The method comprises the following steps: coating the hyperbranched polyamide organic coating on the surface of the carbon fiber fabric by an impregnation method; and electroplating for 5 minutes under the voltage of 20 V to form an organic matter-graphene oxide coating on the surface of the carbon fiber fabric. According to the invention, the wave-absorbing performance is enhanced by using the organic coating and the graphene oxide with controllable loading capacity. The preparation technology is simple, the raw material cost is low, and large-scale production can be achieved. The modified carbon fiber woven body disclosed by the invention has the characteristics of ultra-light weight, strong absorption, wide frequency band and high mechanical strength, and has a good application prospect in the field of electromagnetic wave absorption.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave absorption and functional electromagnetic wave absorbing composite material preparation. Specifically, it relates to a method for preparing a double-layer periodic carbon fiber braided wave absorbing material modified with a hyperbranched polyamide-graphene oxide coating. Background Technology

[0002] The research and development of electromagnetic wave absorbing materials is key to advancing electromagnetic shielding and stealth technology. Electromagnetic wave absorbing materials effectively absorb incident electromagnetic waves and convert electromagnetic energy into heat, dissipating it without secondary reflection. In increasingly sophisticated electronic devices and other applications, there is a growing demand for electromagnetic protection of flexible, deformable, and modulated components. Therefore, the research and development of high-performance, flexible, and high-strength electromagnetic wave absorbing materials has become a crucial issue. Electromagnetic wave absorbing materials play an indispensable role in 5G networks, satellite communications, artificial intelligence, wearable electronics, autonomous vehicles and aircraft, medical protection, and electromagnetic pollution control. Electromagnetic interference caused by electromagnetic waves to electronic devices leads to signal loss or interruption. Secondary reflections from single shielding materials cause mutual interference between electronic devices, resulting in signal loss or incorrect transmission. This limits the performance of advanced electronic products and causes significant economic losses. Solving these problems depends on the rapid development of functional electromagnetic wave absorbing materials and key breakthroughs in materials that combine strength, absorption, and flexibility.

[0003] The dispersive properties and high conductivity of carbon fiber materials have long been a focus of attention, and their excellent attenuation performance shows promising application prospects in electromagnetic wave absorption. Researchers have conducted a series of studies on chopped fiber modification, fiber hybrid weaving, carbon fiber periodic structure braided bodies, carbon fiber-ceramic composites, and carbon fiber-resin composites. Targeting the strong attenuation characteristics of carbon fiber, surface modification and periodic structure weaving can effectively improve its impedance matching. The strong attenuation provided by the conductive network in the carbon fiber braid, along with the good impedance matching brought about by the periodic structure and interface polarization, greatly improves the electromagnetic wave absorption performance of carbon fiber. Compared with traditional carbon fiber absorbing materials, this material can overcome existing limitations and become a new type of functional absorbing material, while simultaneously meeting the characteristics of ultra-lightweight, thin, wide effective absorption bandwidth, high mechanical strength, and flexibility. Therefore, developing high-performance absorbing materials with excellent broadband performance, focusing on surface-modified double-layer periodic structure carbon fiber braids, is of great significance and economic benefit for the electromagnetic protection of deformable and dynamically adjustable equipment. This invention aims to solve the technical problems of weak low-frequency absorption performance, anisotropic electromagnetic absorption performance, and uncontrollable graphene oxide content in single-layer unidirectional periodic woven carbon fiber microwave absorbing materials. It provides a method for preparing a double-layer periodic carbon fiber woven microwave absorbing material modified with a hyperbranched polyamide-graphene oxide coating.

[0004] To address the aforementioned technical problems, the present invention adopts the following technical solution: The purpose of this invention is to provide a method for preparing a bilayer periodic carbon fiber braided microwave absorbing material modified with a hyperbranched polyamide-graphene oxide coating, which is carried out according to the following steps: Step 1: Add N-aminoethylpiperazine and N,N'-methylenebisacrylamide to deionized water, stir until completely dissolved, heat in a water bath, cool to room temperature, concentrate by rotary evaporation, wash with deionized water and acetone in sequence, and dry under vacuum to obtain an orange-yellow colloid. Step 2: Prepare a solution from the orange-yellow colloid. After removing the colloid from the carbon fiber braid in an acetone solution water bath, immerse the braid in the prepared solution for impregnation treatment, and then dry to obtain a hyperbranched polyamide-coated braid. Step 3: Electroplating the hyperbranched polyamide-coated woven fabric obtained in Step 2 in a graphene oxide solution, washing and drying to obtain the microwave absorbing material. Further specifying, in step one, the molar ratio of N-aminoethylpiperazine and N,N'-methylenebisacrylamide is 1.25:1, wherein the concentration of N-aminoethylpiperazine is 0.4 mol / L.

[0005] To further specify, in step one, the stirring speed is 300 rpm to 500 rpm.

[0006] Further specifying, in step one, the water bath temperature is 60-65 ℃.

[0007] Further specifying, in step one, the concentration is achieved by rotary evaporation at 80-100 ℃.

[0008] Further specifying, in step two, the carbon fiber braid is a double-layer braid, with the upper layer having a braiding pattern of three strands in the transverse direction and one strand in the longitudinal direction per cycle, and the lower layer having a braiding pattern of two strands in the transverse direction and two strands in the longitudinal direction per cycle, with a 5 mm interval between the two layers.

[0009] Furthermore, in step two, the degumming water bath temperature for the carbon fiber braid is 80-90 ℃.

[0010] Further specifying, in step two, the degumming water bath time for the carbon fiber braid is 36-48 hours.

[0011] Further specifying, in step two, the immersion is carried out at 25-30 ℃, and the immersion process is controlled to keep the temperature for 12 h.

[0012] Further specifying, in step two, drying is carried out at 80-100 ℃.

[0013] Further specifying, in step three, the electroplating process uses graphene oxide at a concentration of 0.2-0.35 mg / mL.

[0014] Further specifying, in step three, the electroplating process uses ultrasonic dispersion, with the ultrasonic frequency controlled at 40 kHz, the voltage controlled at 15-25 V, the electroplating distance at 2-3 cm, and the pH value at 9.5-10.5.

[0015] Further specifying, the washing process described in step three requires washing with deionized water three times; drying at 80-100 ℃ for 6 hours.

[0016] The present invention also provides a hyperbranched polyamide-graphene oxide coating modified bilayer periodic carbon fiber braided microwave absorbing material prepared by any of the above methods.

[0017] This invention utilizes the strong attenuation properties of carbon fibers for electromagnetic waves, and the impedance matching brought about by the periodic structure and interface polarization. Optimizing absorption performance through multi-scale control has broad application prospects. Long carbon fibers, compared to short-cut carbon fibers, exhibit significant dispersion characteristics. This greatly facilitates adjusting impedance matching to regulate reflection characteristics. Carbon fibers possess strong reflection properties. Through modification with a hyperbranched polyamide-graphene oxide coating and the design of the periodic unit structure, a gradual transition occurs from strong loss difference matching to effective absorption where loss and matching are consistent across a wide range. This process introduces a small amount of graphene oxide and a relatively thick interface layer. While optimizing impedance matching, more loss mechanisms, such as dipole polarization and interface polarization, are introduced to enhance absorption performance.

[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention uses commercial materials to synthesize composite materials. The synthesis process does not require complex equipment or harsh experimental environments. The preparation process of this invention is low-cost, simple, and can be mass-produced.

[0019] The material prepared by the method of this invention is an ultralight, broadband, highly absorbent, thin, and mechanically strong microwave absorbing material. When the overall thickness is 6 mm, the effective bandwidth is 12.46 GHz (5.54-18 GHz). This invention provides a good theoretical foundation for the development of carbon fiber functional microwave absorbing materials and offers good design ideas for the study of various loss mechanisms of electromagnetic wave absorbing materials.

[0020] The present invention provides a hyperbranched polyamide-graphene oxide coating-modified bilayer periodic carbon fiber braided microwave absorbing material. The carbon fibers in this material are highly conductive and exhibit strong electromagnetic wave attenuation, but also strong reflection, thus failing to achieve good microwave absorption performance. Through appropriate interface treatment, the electrical conductivity of the carbon fibers is reduced from 1×10⁻⁶. 3 Increased to 36.2×10 3Simultaneously, by adjusting the dielectric constant of the system, impedance differences are reduced, and loss capability is adjusted to achieve a balance between impedance matching and loss capability. Furthermore, the periodic unit structure in the carbon fiber braid can introduce more resonant losses, creating multiple refractions and attenuations between the periodic units. In summary, by adjusting the thickness of the hyperbranched polyamide-graphene oxide interface phase and the periodic unit structure, a good conductive network is constructed while simultaneously achieving good impedance matching, thereby obtaining significant electromagnetic wave absorption performance and mechanical strength.

[0021] The hyperbranched polyamide-graphene oxide coating-modified bilayer periodic carbon fiber braided microwave absorbing material prepared by the method of this invention can be applied in the field of electromagnetic wave absorbing materials.

[0022] For a deeper understanding of the features and technical content of this invention, please refer to the accompanying detailed description and drawings. It should be noted that the drawings are provided for illustrative purposes only and are not intended to limit the scope of the invention. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the unit structure of the carbon fiber periodic structure braid obtained in step one of Example 1; Figure 2 The images show the 1H NMR spectra of the hyperbranched polyamide molecule prepared in Example 1 and the control sample. Figure 3 The images show the carbon NMR spectra of the hyperbranched polyamide molecule prepared in Example 1 and the control sample. Figure 4 The infrared spectra of the hyperbranched polyamide molecules prepared in Example 1 and the control sample are shown. Figure 5 These are the XPS total spectra of the hyperbranched polyamide molecules prepared in Example 1 and the control sample; Figure 6 These are the XPS carbon spectra of the hyperbranched polyamide molecules prepared in Example 1 and the control sample; Figure 7 These are the XPS nitrogen spectra of the hyperbranched polyamide molecules prepared in Example 1 and the control sample; Figure 8 This is a scanning electron microscope image of the hyperbranched polyamide-graphene oxide coating-coated carbon fibers prepared in Example 1; Figure 9 This is a high-resolution scanning electron microscope image of the hyperbranched polyamide-graphene oxide coating-coated carbon fibers prepared in Example 1. Figure 10 This is a high-resolution surface morphology image of the carbon fibers coated with hyperbranched polyamide-graphene oxide coating prepared in Example 1. Figure 11 The images show the XPS spectra of the hyperbranched polyamide-graphene oxide coated carbon fibers prepared in Example 1 and their comparative samples. Figure 12 This is the XPS nitrogen spectrum of the hyperbranched polyamide-graphene oxide coating-coated carbon fiber prepared in Example 1; Figure 13 This is a reflection loss diagram of the carbon fibers coated with hyperbranched polyamide-graphene oxide coating prepared in Example 1; Figure 14 This is a reflection loss diagram of the carbon fiber periodic structure braid coated with hyperbranched polyamide-graphene oxide coating prepared in Example 1. Figure 15 The image shows the reflection loss of a comparative sample of the carbon fiber periodic structure braid coated with hyperbranched polyamide-graphene oxide coating prepared in Example 1. Figure 16 This is a polarization performance diagram of the reflection loss in TM mode of the carbon fiber periodic structure braid coated with hyperbranched polyamide-graphene oxide coating prepared in Example 1. Figure 17 This is a polarization performance diagram of the reflection loss in TE mode of the carbon fiber periodic structure braid coated with hyperbranched polyamide-graphene oxide coating prepared in Example 1. Figure 18 It is a three-dimensional diagram of a double-layered woven body; Figure 19 This is a front view of the double-layered woven fabric; Figure 20 This is a picture of the back of the double-layered woven fabric. Detailed Implementation

[0024] The present invention will be described in detail below with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but should not be considered as limiting the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0025] Example 1: The preparation method of the hyperbranched polyamide-graphene oxide coating-modified bilayer periodic carbon fiber braided microwave absorbing material in this embodiment is carried out according to the following steps: Step 1: First, measure 300 mL of deionized water into a 500 mL beaker and stir magnetically at 300 rpm. Weigh 0.12 mol of N,N'-methylenebisacrylamide and 0.15 mol of N-aminoethylpiperazine and dissolve them in the deionized water. Stir the system for 30 min until a white solution is formed. Transfer the solution to a water bath and heat at 60 °C for 12 h. After heating, cool to room temperature to obtain a clear orange-yellow solution. Concentrate the solution by rotary evaporation at 90 °C, and wash it three times each with deionized water and acetone. Dry the solution under vacuum at 60 °C for 12 h to obtain the orange-yellow colloidal HPAA-2. Step 2: Prepare a 10 mg / mL solution of the orange-yellow colloid HPAA-2 obtained in Step 1. After removing the colloid, immerse the carbon fiber braid in the prepared solution and soak it at 30 ℃ for 12 h. After removing it, dry it at 100 ℃ for 2 h to obtain a carbon fiber braid coated with hyperbranched polyamide. Step 3: The hyperbranched polyamide-coated carbon fiber braid obtained in Step 2 was electroplated in a graphene oxide solution with a concentration of 0.3 mg / mL. The electroplating process was carried out by ultrasonic dispersion at a frequency of 40 kHz, an electroplating voltage of 20 V, a solution pH of 10, a distance of 2 cm between the two electrodes, and an electroplating time of 5 min. After washing three times with deionized water, the material was placed in a high-temperature drying oven at 80 ℃ for 6 h to obtain a hyperbranched polyamide-graphene oxide coating modified double-layer periodic carbon fiber braided microwave absorbing material CF@HPAA-GO.

[0026] Preparation of test samples: The hyperbranched polyamide-graphene oxide coating modified carbon fiber prepared in Example 1 was cut into 1 mm lengths and placed in paraffin at a volume ratio of 2 vol. % and ultrasonically heated to 80°C. The temperature was maintained for 15 min, and the sample was placed in a mold to finally obtain a coaxial ring with an outer diameter of 7 mm, an inner diameter of 3.04 mm, and a height of 2 mm.

[0027] The hyperbranched polyamide-graphene oxide coating modified carbon fiber braid prepared in Example 1 was cut into 18cm×18cm square braided boards to obtain large board samples for the bow method test.

[0028] HPAA-1 and HPAA-3 comparison samples: Weigh 0.1 mol of N,N'-methylenebisacrylamide and 0.15 mol of N-aminoethylpiperazine from the orange-yellow colloidal material obtained in step one of Example 1, dissolve them in deionized water, and proceed as in step one. This is designated as HPAA-1 control sample. Weigh 0.15 mol of N,N'-methylenebisacrylamide and 0.15 mol of N-aminoethylpiperazine, dissolve them in deionized water, and proceed as in step one. This is designated as HPAA-3 control sample.

[0029] Comparison of CF@GO and CF@HPAA-GO: The double-layer carbon fiber periodic structure braid obtained in step two of Example 1 is directly subjected to step three without undergoing the impregnation process of hyperbranched polyamide solution. The double-layer periodic structure braid obtained in step two of Example 1, which does not undergo the impregnation process afterward, is the CF@GO control sample.

[0030] The CF@GO control sample was prepared using the same test sample as in Example 1.

[0031] The carbon fiber CF@HPAA-GO modified with the hyperbranched polyamide-graphene oxide coating prepared in Example 1 was tested with a CF@GO control sample.

[0032] The 1H NMR spectra of the HPAA-2 organic compound obtained in step one of Example 1, as well as the HPAA-1 and HPAA-3 control samples, are shown below. Figure 2 As shown, the carbon NMR spectrum is as follows: Figure 3 As shown, the degree of branching of the organic compounds obtained under different ratios is different. The degree of branching of HPAA-1, HPAA-2 and HPAA-3 are 0.13, 0.246 and 0.255, respectively.

[0033] Figure 4 The images show the infrared spectra of HPAA-2 prepared in Example 1, compared with those of HPAA-1 and HPAA-3. The absorption peaks at 1232, 1537, 1640, and 3305 cm⁻¹ correspond to the stretching vibrations of amide III, amide II, amide I, and amine, respectively. The absorption peak gradually sharpens in the wavenumber range of 3200-3500 cm⁻¹, possibly related to hydrogen bonding.

[0034] Figure 5 This is an XPS image of HPAA-2 prepared in Example 1 compared with HPAA-1 and HPAA-3. It can be seen that as the monomer ratio changes, the nitrogen content of HPAA-1, HPAA-2, and HPAA-3 is 2.58%, 8.1%, and 24.11%, respectively. Figure 6 The C spectrum can prove that HPAA-2 has C=C, C=O, CN and other bonding functions; Figure 7The N spectrum can prove that HPAA-2 contains NH, CNC, NC and other bonding interactions, proving the feasibility of the existence of hydrogen bonds.

[0035] The microstructure of the hyperbranched polyamide-graphene oxide-coated carbon fibers prepared in Example 1 is shown in the figure below. Figure 8 As shown, the high-resolution morphology image of the hyperbranched polyamide-graphene oxide-coated carbon fibers prepared in Example 1 is as follows. Figure 9 As shown, the atomic force microscopy image of the surface roughness of the hyperbranched polyamide-graphene oxide-coated carbon fiber prepared in Example 1 is as follows. Figure 10 As shown, the above micrographs characterize the surface morphology and roughness of the hyperbranched polyamide-graphene oxide-coated carbon fibers. The prepared carbon fiber sample has a relatively thick interface layer, and the graphene oxide is attached to the carbon fiber surface in layers. In the high-resolution image, the thickness of the interface layer is approximately 86.3 nm, and the surface roughness is approximately 20.5 nm.

[0036] Figure 11 The above are XPS images of the hyperbranched polyamide-graphene oxide-coated carbon fiber microwave absorbing material prepared in Example 1. The nitrogen spectrum peaks of the hyperbranched polyamide-graphene oxide-coated carbon fiber prepared in Example 1 are shown below. Figure 12 As shown, with the application of HPAA-1, HPAA-2, and HPAA-3 organic compounds to coat the carbon fibers, the nitrogen contents were 1.35%, 1.57%, and 2.16%, respectively. The nitrogen spectrum shows that the carbon fiber surface still possesses NH, CNC, and NC bonds, proving that the organic compounds were successfully coated on the carbon fiber surface.

[0037] The reflection loss diagram of the hyperbranched polyamide-graphene oxide-coated carbon fiber microwave absorbing material prepared in Example 1 is shown below. Figure 13 As shown, the minimum reflection loss of the obtained coaxial ring sample with hyperbranched polyamide-graphene oxide-coated carbon fiber is -47.107 dB, corresponding to a matching thickness of 1.7 mm; the maximum effective bandwidth is 4.84 GHz, corresponding to a matching thickness of 1.5 mm.

[0038] The large-panel reflection loss test curve of CF@HPAA-GO is shown below. Figure 14 As shown, the effective absorption bandwidth is 12.46 GHz, which is highly similar to the simulation results. The absorption performance test curves of the CF@GO large-format board are shown below. Figure 15 As shown, the effective absorption bandwidth is 9.2 GHz. The effective absorption bandwidth of CF@HPAA-GO is more than 40% higher than that of the CF@GO large board comparison sample.

[0039] The two-dimensional statistical graph of the large-plate reflection loss of CF@HPAA-GO as a function of incident angle and TM polarization mode is shown below. Figure 16 As shown in the figure, the two-dimensional statistical graph of the large-plate reflection loss of CF@HPAA-GO as a function of the incident angle and TE polarization mode is as follows. Figure 17 As shown in the figure, the statistical results indicate that the periodic carbon fiber woven plate is insensitive to polarization mode and polarization angle, and has strong applicability.

[0040] The specific embodiments of the present invention have been described in detail above. It should be noted that the present invention is not limited to the specific embodiments described above. Various modifications or alterations can be made by those skilled in the art without departing from the scope of protection defined by the claims, and all such modifications or alterations fall within the scope of the present invention.

Claims

1. A method for preparing a bilayer periodic carbon fiber braided microwave absorbing material modified with a hyperbranched polyamide-graphene oxide coating, characterized in that, Includes the following steps: Step 1: Add N-aminoethylpiperazine and N,N'-methylenebisacrylamide to deionized water, stir until completely dissolved, heat in a water bath, cool to room temperature, concentrate by rotary evaporation, wash with deionized water and acetone in sequence, and dry under vacuum to obtain an orange-yellow colloid. Step 2: Prepare a solution from the orange-yellow colloid, immerse the degummed carbon fiber braid in the prepared solution, perform an impregnation treatment, and dry to obtain a hyperbranched polyamide-coated braid. Step 3: Electroplating the hyperbranched polyamide-coated woven fabric obtained in Step 2 in a graphene oxide solution, washing and drying to obtain the microwave absorbing material.

2. The method according to claim 1, characterized in that, In step one, the molar ratio of N-aminoethylpiperazine and N,N'-methylenebisacrylamide is 1.25:1, and the concentration of N-aminoethylpiperazine is 0.4 mol / L.

3. The method according to claim 1, characterized in that, In step one, the stirring speed is 300 rpm to 500 rpm; the water bath temperature is 55-65 ℃; and the concentration is carried out by rotary evaporation at 80-100 ℃.

4. The method according to claim 1, characterized in that, In step two, the carbon fiber braid is a double-layer braid. The upper layer is woven with three strands in the transverse direction and one strand in the longitudinal direction per cycle, and the lower layer is woven with two strands in the transverse direction and two strands in the longitudinal direction per cycle. The two layers are spaced 5 mm apart.

5. The method according to claim 1, characterized in that, In step two, immersion is carried out at 25-30 ℃.

6. The method according to claim 1, characterized in that, In step two, dry at 90-110 ℃.

7. The method according to claim 1, characterized in that, In step three, the concentration of graphene oxide is 0.2-0.35 mg / mL.

8. The method according to claim 1, characterized in that, In step three, the electroplating process uses ultrasonic dispersion, while controlling the voltage at 15-25 V, the electroplating distance at 2-3 cm, the pH value at 9.5-10.5, and the current value at 190-210 mA.

9. The method according to claim 1, characterized in that, The washing process described in step three involves washing three times with deionized water and drying at 80-100℃.

10. A hyperbranched polyamide-graphene oxide coating-modified bilayer periodic carbon fiber braided microwave absorbing material prepared by the method of any one of claims 1-9.

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