Bamboo charcoal fiber cloth-based composite material, and preparation method and application thereof

Abstract

This invention discloses a bamboo charcoal fiber cloth-based composite material, its preparation method, and its application, belonging to the field of electromagnetic shielding materials technology. The bamboo charcoal fiber cloth-based composite material comprises: a base fabric, wherein the base fabric is a bamboo charcoal fiber cloth that has been oxidized and activated by TEMPO (2,2,6,6-tetramethylpiperidine-1-oxy radical); a gradient copper layer electroplated on the surface of the base fabric; and a nickel layer electroplated on the surface of the gradient copper layer; wherein the density of the copper layer on the base fabric side is less than that of the nickel layer and the copper layer. By performing a special process to modify the surface of the bamboo charcoal fiber cloth, and simultaneously forming a gradient copper layer and a nickel layer on its surface, a bamboo charcoal fiber cloth-based composite material with lightweight properties, structural stability, and excellent electromagnetic shielding performance is prepared to meet the needs of flexible and broadband electromagnetic shielding applications.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic shielding materials technology, specifically relating to a bamboo charcoal fiber cloth-based composite material, its preparation method, and its application. Background Technology

[0002] Electromagnetic interference (EMI) refers to the phenomenon where external electromagnetic energy (such as electromagnetic waves, electric fields, and magnetic fields) enters the interior of electronic equipment, interfering with or disrupting its normal operation. EMI shielding materials, as an effective strategy for EMI protection, utilize special conductive materials to wrap sensitive areas, preventing electromagnetic waves from entering and achieving EMI shielding. However, existing EMI shielding materials generally suffer from drawbacks such as being "thick, heavy, narrow, and weak." For example, metal foils have high density and are easily broken when bent; conductive coatings have narrow shielding bands and are prone to oxidation and failure; and precious metal fillers are costly and have complex manufacturing processes. Therefore, the market urgently needs new shielding materials that are "thin, light, wide, strong," and flexible.

[0003] Biomass materials are considered a potential alternative to traditional metallic electromagnetic shielding materials due to their advantages such as low cost, sustainability, lightweight, and naturally porous structure. Among them, bamboo charcoal fiber cloth, while retaining the advantages of its biomass source, forms a stable carbon skeleton structure after high-temperature carbonization, possessing characteristics such as porosity, high specific surface area, weavability, and good flexibility, making it an ideal lightweight electromagnetic shielding substrate material. However, unlike natural cellulose-based materials, bamboo charcoal fiber cloth experiences a significant reduction in surface polar functional groups such as hydroxyl groups during carbonization, resulting in a predominantly inert carbon structure. For electroless deposition processes such as electroless copper / nickel plating, its metal ion complexing ability and nucleation activity are significantly insufficient, leading to difficulties in metal coating deposition on its surface. Specifically, this manifests as low metal nucleation density, discontinuous deposition, a tendency for the coating to grow in island-like patterns, and weak adhesion to the substrate. These deposition defects not only limit the construction of a continuous conductive network but also cause coating cracking or peeling during material bending or long-term service, ultimately leading to decreased electromagnetic shielding effectiveness and insufficient performance stability.

[0004] Therefore, there is an urgent need to develop a bamboo charcoal fiber cloth-based metallized composite material that combines lightweight, structural stability, and excellent electromagnetic shielding performance to meet the needs of flexible and broadband electromagnetic shielding applications. Summary of the Invention

[0005] To address the aforementioned issues, this invention aims to provide a bamboo charcoal fiber cloth-based composite material. This material undergoes surface treatment modification of the bamboo charcoal fiber cloth using a special process, while simultaneously forming a gradient copper and nickel layer on its surface. This process yields a bamboo charcoal fiber cloth-based composite material that combines lightweight properties, structural stability, and excellent electromagnetic shielding performance.

[0006] The technical solution adopted in this invention is as follows: This invention first discloses a bamboo charcoal fiber cloth-based composite material, which is formed by sequentially plating a copper layer and a nickel layer onto the surface of bamboo charcoal fiber cloth as the base layer. Specifically, the bamboo charcoal fiber cloth-based composite material includes: The base fabric is a bamboo charcoal fiber fabric that has been TEMPO-oxidized and activated; A gradient copper layer is electroplated onto the surface of the base fabric; And a nickel layer plated onto the surface of the gradient copper layer; In this case, the gradient copper layer has a lower density on the base fabric side than on the nickel side.

[0007] This invention also discloses a method for preparing the bamboo charcoal fiber fabric-based composite material described herein, comprising the following steps: Bamboo charcoal fiber cloth is available; The bamboo charcoal fiber cloth was subjected to TEMPO-ultrasound synergistic oxidation modification, followed by palladium-free activation treatment; The activated bamboo charcoal fibers were placed in a chemical copper plating solution and chemical copper plating was performed on their surface in stages. The copper-plated bamboo charcoal fibers are placed in a chemical nickel plating solution, and chemical nickel plating is performed on their surface.

[0008] This invention employs TEMPO oxidation modification synergistically with ultrasonic cavitation to treat the surface of bamboo charcoal fiber cloth. This effectively converts primary hydroxyl groups on the surface of the bamboo charcoal fiber cloth into carboxyl functional groups, significantly enhancing the complexation and loading capacity of the fiber surface for metal ions and improving the adhesion of metal coatings to the bamboo charcoal fiber cloth surface. Simultaneously, a "gradient copper-dense nickel" composite metal structure is formed on the surface of the bamboo charcoal fiber cloth. This not only effectively alleviates the problem of stress concentration within the coating, but also significantly improves the overall conductivity and corrosion resistance of the material. This allows the bamboo charcoal fiber cloth-based composite material to achieve a balance of high conductivity, strong adhesion, and adaptability to extreme environments. Thanks to the three-dimensional conductive network structure synergistically constructed by the lightweight porous conductive skeleton of the bamboo charcoal fiber cloth and the special composite metal layer, while meeting high-efficiency shielding performance, the material's surface density is significantly reduced compared to traditional silver-based or metal plate shielding structures, achieving a balance of "thin, light, wide, and strong" technical characteristics.

[0009] As used in this invention, the bamboo charcoal fiber cloth refers to a flexible fabric-like substrate material with certain mechanical strength and porous structure, made from bamboo charcoal powder as raw material. Specifically, it is made by carbonizing and grinding bamboo to obtain bamboo charcoal powder, then spinning the powder into fibers, and finally weaving them into cloth.

[0010] In some examples of the present invention, the thickness of the bamboo charcoal fiber cloth is in the range of 0.2-0.3 mm, for example, it can be any value or a range between any two values ​​from 0.2 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm, 0.25 mm, 0.26 mm, 0.27 mm, 0.28 mm, 0.29 mm, and 0.3 mm.

[0011] In some examples of the present invention, preferably, the particle size of the bamboo charcoal powder is 60-90 mesh, for example, any value or a range between any two of 60 mesh, 65 mesh, 70 mesh, 75 mesh, 80 mesh, 85 mesh, and 90 mesh. Within the preferred particle size range, while ensuring fiber spinnability and fabric flexibility, the final bamboo charcoal fiber fabric possesses a suitable pore structure and specific surface area, thereby facilitating the subsequent deposition and bonding of the metal layer.

[0012] As described in this invention, the TEMPO oxidation refers to a selective oxidation reaction using 2,2,6,6-tetramethylpiperidine-1-oxygen radical (TEMPO) and its derivatives as catalysts. In this paper, this treatment is mainly applied to the surface modification of bamboo charcoal fiber cloth. In some specific examples, the well-established TEMPO / NaClO / NaBr system is preferably used to selectively oxidize the primary hydroxyl groups on the cellulose molecular chains of the bamboo charcoal fiber cloth surface to carboxyl groups (-COOH). It should be noted that this treatment aims to introduce a large number of negatively charged carboxylate groups onto the surface of the bamboo charcoal fiber cloth. These groups can effectively adsorb metal cations in the solution (such as copper ions, nickel ions, etc. in subsequent activation or electroless plating steps), thereby significantly improving the chemical activity and hydrophilicity of the fiber surface, providing sufficient and uniformly distributed active sites for subsequent targetless activation and electroless plating of metal layers.

[0013] In a preferred embodiment of the present invention, ultrasonic means are introduced during TEMPO oxidation to perform synergistic modification, thereby improving the effect of TEMPO oxidation.

[0014] It should be understood that there are no particular limitations on the composition of the TEMPO oxidation system; it can be configured based on compositions known in the art, and the specific ratios and parameters can be optimized experimentally. In some specific examples, the specific TEMPO oxidation modification steps include: 1g of bamboo charcoal fiber was placed in 50mL of deionized water containing 0.04-0.06g TEMPO and 0.4-0.6g NaBr or KBr, and pretreated with ultrasound at 30-50kHz for 5-15min. Then, 25-35mmol / g NaClO solution was slowly added, and the mixture was reacted at 23-27℃ for 30-50min under continuous ultrasound to obtain oxidized modified bamboo charcoal fiber cloth TBCF. The pH of the system was maintained at 10.3-10.7 during the reaction.

[0015] In this process, ultrasonic pretreatment at a frequency of 30-50 kHz is introduced for 5-15 minutes before the addition of NaClO solution to promote the full wetting of bamboo charcoal fiber cloth and the penetration and uniform distribution of the oxidation system in the fiber. Subsequently, after the addition of NaClO solution, ultrasonic treatment is continued to enhance oxidation kinetics, improve the effect of TEMPO oxidation, and ensure that there are sufficient active sites on the surface of bamboo charcoal fiber cloth.

[0016] As used in this invention, the targetless activation method is distinct from traditional surface activation processes that rely on precious metal (such as palladium) targets for physical vapor deposition (PVD) or precious metal salt solutions for sensitization and activation. In this invention, the targetless activation process refers to immersing the surface of TEMPO-modified bamboo charcoal fiber cloth in a solution containing specific metal ions (e.g., copper ions) without the aid of external precious metal targets. The strong complexation and adsorption of metal ions by the carboxyl groups and other functional groups introduced onto the fiber surface allows the metal ions to firmly adhere to the fiber surface. Subsequently, a reduction treatment (e.g., using sodium borohydride or other reducing agents) reduces these adsorbed metal ions in situ into catalytically active metal nanoparticles (e.g., nano-copper). These nanoparticles can then serve as catalytic centers for subsequent chemical copper plating. This method avoids the use of precious metal palladium, reducing costs and completely eliminating the problems of precious metal dependence, high costs, and environmental pollution associated with traditional Pd / Sn sensitization-activation processes. Furthermore, the catalytic sites originate from the functional groups within the fiber itself, resulting in a more uniform distribution. While ensuring the activation effect, it has achieved green, low-cost and scalable production.

[0017] It should be understood that the composition of the activation solution used in targetless activation is not particularly required, and any known activation solution composition in the art can be used. However, it is preferred to use an activation solution composition with copper ions as the main component, which facilitates the subsequent deposition of a gradient copper layer. Furthermore, specific activation parameters such as temperature can be appropriately optimized or adjusted according to the composition of the activation solution and research needs, and therefore there are no particular limitations. In some specific embodiments of the present invention, the palladium-free activation treatment includes the following steps: placing the TEMPO-oxidized bamboo charcoal fiber cloth into a solution containing 0.18-0.22g CuSO4. Soak the bamboo charcoal fiber cloth (PCF) in a 50 mL aqueous solution of 5H2O at 53-57℃ for 25-35 min, then directly transfer it into a 50 mL aqueous solution containing 0.08-0.12 g NaBH4 and 0.08-0.12 g NaOH, and react at room temperature for 4-6 min to obtain activated bamboo charcoal fiber cloth (PCF).

[0018] As used in this invention, the gradient copper layer refers to a copper layer of varying density deposited on the surface of a substrate (the activated bamboo charcoal fiber cloth in this invention) through a staged chemical plating method. A typical characteristic of this copper layer is that its copper content or crystal structure is not completely uniform in the thickness direction, but rather exhibits a certain gradient variation. Specifically, the density of the copper layer on the substrate side is lower than that on the nickel layer side. The copper layer near the substrate interface may contain more crystal nuclei or a transition structure that is more tightly bonded to the non-metallic substrate, while the surface layer further away from the substrate (nickel layer side) tends to form a dense, continuous pure copper crystalline layer. This gradient structure helps to mitigate the stress caused by the difference in thermal expansion coefficients between the metal layer and the organic / inorganic composite substrate, enhancing the adhesion and peel resistance of the coating.

[0019] In some specific examples, the total thickness of the gradient copper layer is 0.8-2.4 μm, for example, it can be any value among 0.8 μm, 1.0 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2.0 μm, 2.2 μm, and 2.4 μm, or a range between any two values.

[0020] In some specific examples, the staged electroless copper plating of the gradient copper layer includes the following steps: The activated bamboo charcoal fibers were arranged in a chemical copper plating solution and CH2O was added. The first stage was carried out in a water bath at 50℃-55℃ for 5-15 minutes, and the second stage was carried out in a water bath at 55℃-60℃ for 5-30 minutes. The water bath temperature in the first stage was lower than that in the second stage.

[0021] It should be understood that the chemical copper plating solution typically contains the following basic components: a soluble copper salt (such as copper sulfate) as a source of copper ions, a reducing agent (such as formaldehyde, glyoxylic acid, sodium hypophosphite, etc.), a complexing agent (such as potassium sodium tartrate, ethylenediaminetetraacetic acid, etc., used to stabilize copper ions and prevent copper hydroxide precipitation), a pH adjuster (such as sodium hydroxide, used to maintain the solution as strongly alkaline), and a stabilizer (such as potassium ferrocyanide, 2,2'-bipyridine, etc., used to prevent spontaneous decomposition of the solution). There are no specific requirements for its composition; any chemical copper plating solution known in the art or independently developed can be used in this invention. In some specific examples, the chemical copper plating solution is prepared by dissolving 10-12g CuSO4·5H2O, 13-15g NaKC4H4O6·4H2O, 11-13g NaOH, and 0.015-0.025g 2,2'-bipyridine in 1000mL of deionized water.

[0022] As used in this invention, the nickel layer refers to a metallic nickel layer formed by further deposition on the surface of the gradient copper layer through a chemical plating method. The main function of this nickel layer is to provide the outermost protection for the bamboo charcoal fiber cloth-based composite material, preventing the inner copper layer from being corroded or oxidized in specific environments, while further enhancing the stability and durability of the overall conductive network.

[0023] In some specific examples of the present invention, the thickness of the nickel layer ranges from 0.8 to 3.2 μm, for example, it can be any value or a range between any two of the following: 0.8 μm, 1.0 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2.0 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3.0 μm, and 3.2 μm. It should be understood that the thickness of the nickel layer can be selected and optimized within this range according to the specific requirements of the end application for corrosion resistance, conductivity, and cost.

[0024] It should be understood that the electroless nickel plating solution typically contains: nickel salts (such as nickel sulfate, nickel chloride) as a source of nickel ions, reducing agents (such as sodium hypophosphite, whose reduction products may result in a nickel-phosphorus alloy coating), complexing agents (such as sodium citrate, lactic acid, etc.), pH buffers (such as boric acid, sodium acetate), as well as stabilizers and accelerators. There are no specific requirements for its composition; any electroless copper plating solution known in the art or independently developed can be used in this invention. In some specific examples, the electroless nickel plating solution consists of: 28-32g NiSO4·6H2O, 30-34g NaH2PO2·H2O, 23-27g Na3C6H5O7·2H2O, and 18-22g CH3COONa dissolved in 1000mL deionized water, with the pH adjusted to 4.8-5.2.

[0025] Specific process parameters for electroless nickel plating can be optimized experimentally based on research needs and the composition of the electroless nickel plating solution. In some specific examples of this invention, the electroless nickel plating is performed in a water bath at 88-92°C for 5-20 minutes. By adjusting the appropriate reaction temperature and duration, a nickel plating layer with excellent performance can be obtained.

[0026] This invention also discloses the application of the bamboo charcoal fiber cloth-based composite material described in this invention, or the bamboo charcoal fiber cloth-based composite material prepared by the method described in this invention, in electromagnetic shielding.

[0027] Thanks to the three-dimensional conductive network structure synergistically constructed by the lightweight porous conductive skeleton of bamboo charcoal fiber cloth and the gradient metal layer in this invention, the bamboo charcoal fiber cloth-based composite material of this invention can achieve high electromagnetic shielding efficiency of over 80-90dB in both the X-band and Ka-band, with a maximum shielding efficiency of over 90dB and a reflectivity of ≥98%, even with a relatively thin thickness (not exceeding 0.5mm). While meeting the requirements of high-efficiency shielding performance, it also possesses the technical characteristics of being "thin, light, wide, and strong," making it particularly suitable for fields with electromagnetic shielding requirements, such as 5G communication equipment and aerospace electronic systems, where weight and volume are highly sensitive.

[0028] The beneficial effects of this invention are: This invention utilizes a specific surface oxidation modification process combined with chemical plating of a gradient copper layer to form a composite metal layer of "gradient copper + dense nickel" on the surface of bamboo charcoal fiber cloth. This results in a bamboo charcoal fiber cloth-based composite material possessing the technical characteristics of being "thin, light, wide, and strong." Specific advantages are as follows: This invention introduces TEMPO oxidation modification technology and utilizes the ultrasonic cavitation effect to significantly enhance the mass transfer efficiency of the oxidation reaction, enabling the primary hydroxyl groups on the surface of bamboo charcoal fiber to be converted into carboxyl functional groups more efficiently. This significantly improves the complexation and loading capacity of the fiber surface for metal ions, and significantly enhances the adhesion of the subsequent composite metal coating.

[0029] This invention employs a two-stage gradient electroless copper plating process to deposit uniform copper particles on the surface of bamboo charcoal fiber cloth, effectively alleviating the problem of stress concentration within the plating layer. Subsequent dense electroless nickel plating then forms a continuously covering nickel protective layer, constructing a stable "gradient copper-dense nickel" composite metal structure. This structure significantly improves the overall electrical conductivity and corrosion resistance of the material, balancing high conductivity, strong adhesion, and adaptability to extreme environments.

[0030] Thanks to the three-dimensional conductive network structure constructed by the lightweight porous conductive skeleton of bamboo charcoal fiber cloth and the gradient metal layer, the composite material of this invention can achieve high electromagnetic shielding efficiency in both the X-band and Ka-band under extremely thin conditions. Attached Figure Description

[0031] Figure 1 This is a scanning electron microscope image of the bamboo charcoal fiber cloth-based composite material prepared in Example 3 of the present invention.

[0032] Figure 2 This is a scanning electron microscope image of the bamboo charcoal fiber cloth-based composite material prepared in Comparative Example 1 of the present invention.

[0033] Figure 3 This is a scanning electron microscope image of the bamboo charcoal fiber cloth-based composite material prepared in Comparative Example 2 of the present invention.

[0034] Figure 4 The X-ray diffraction patterns of the bamboo charcoal fiber-based composite materials prepared in Examples 1-4 and Comparative Example 2 of this invention are shown below. Figure 4 In Figure A, the X-ray diffraction patterns of the bamboo charcoal fiber cloth-based composite materials in Examples 1-4 and Comparative Example 2 are shown. Figure 4 Image B is the X-ray diffraction pattern of the bamboo charcoal fiber cloth composite material in Example 4.

[0035] Figure 5 The diagrams show the shielding performance of the bamboo charcoal fiber cloth-based composite materials prepared in Examples 1-4 and Comparative Example 2 of this invention. Figure 5 In the diagram, A represents the shielding performance results for the X-band. Figure 5 B represents the shielding performance results for the Ka-band.

[0036] Figure 6 The image shows the Tafel polarization curves of the bamboo charcoal fiber cloth-based composite materials prepared in Example 3 and Comparative Example 2 of this invention in a 3.5wt% NaCl solution.

[0037] Figure 7 The thermogravimetric curves of the bamboo charcoal fiber fabric prepared in Example 3 and Comparative Example 2 of this invention are shown. Detailed Implementation

[0038] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. Furthermore, unless otherwise specified, methods not specifically describing conditions or steps are conventional methods, and the reagents and materials used are commercially available.

[0040] Example 1: Bamboo charcoal fiber cloth-based composite material and its preparation method S1. TEMPO oxidation modification of bamboo charcoal fiber cloth Bamboo charcoal fiber cloth was oxidized and modified in a TEMPO-NaClO-NaBr system. Specifically, 1g of bamboo charcoal fiber cloth was immersed in the oxidization modification solution, then placed in an ultrasonic cleaner for ultrasonic pretreatment. Subsequently, NaClO solution was slowly added, and the reaction was carried out under continuous ultrasonic conditions. The oxidization modification solution was a deionized aqueous solution containing TEMPO and NaBr, with a TEMPO concentration of 0.97 mg / mL, a NaBr concentration of 9.66 mg / mL, and 50 mL of deionized water. The first stage of ultrasonic treatment was performed at a frequency of 40 kHz for 10 min, with a NaClO solution concentration of 0.048 mol / L. The second stage of ultrasonic treatment was performed at a frequency of 40 kHz for 30 min, with the ultrasonic temperature at 25℃. During the reaction, 0.5 mol / L NaOH solution was added dropwise to maintain the pH at 10.5. After the reaction, the cloth was rinsed three times with deionized water and dried at 60℃ for 2 h to obtain the oxidized bamboo charcoal fiber cloth, denoted as TBCF.

[0041] S2, Palladium-free activation treatment of bamboo charcoal fiber cloth The TBCF from step S1 was placed in 50 mL of CuSO4·5H2O solution (concentration 4.0 mg / mL) and soaked in a water bath at 55°C for 30 min. After the soaking, it was directly removed and placed in 50 mL of solution (containing 2.0 mg / mL NaBH4 and 2.0 mg / mL NaOH) and allowed to stand at room temperature for 5 min. After the reaction was completed, it was washed three times with deionized water and dried at 60°C for 2 h to obtain activated bamboo charcoal fiber cloth, denoted as PCF.

[0042] S3, Staged Electroless Copper Plating The PCF from step S2 was placed in a chemical copper plating solution (100 mL) and CH2O (2 mL) was added. The first stage was a 50°C water bath reaction for 15 min, and the second stage was a 60°C water bath reaction for 30 min. Chemical copper plating was performed on the surface of the bamboo charcoal fiber cloth, and the obtained sample was denoted as PCF / Cu.

[0043] The chemical copper plating solution consisted of: 1 L of deionized water, 11 mg / mL CuSO4·5H2O, and C... 10 H 14 N2Na2O8 20g mg / mL, NaKC4H4O6·4H2O 14mg / mL, NaOH 12g mg / mL and 2,2'-bipyridine 0.02mg / mL.

[0044] S4, electroless nickel plating The PCF / Cu from step S3 was placed in 100 mL of electroless nickel plating solution and reacted in a 90 °C water bath for 5 min, followed by drying at 60 °C for 2 h. The resulting sample was denoted as PCF / Cu / Ni5.

[0045] The composition of the electroless nickel plating solution is as follows: 1000 mL of deionized water, 30 mg / mL of NiSO4·6H2O, 32 mg / mL of NaH2PO2·H2O, 25 mg / mL of Na3C6H5O7·2H2O, and 20 mg / mL of CH3COONa, with 60 mL of 10 wt% H2SO4 added (to adjust the pH of the nickel plating solution to 5).

[0046] Example 2: Bamboo charcoal fiber cloth-based composite material and its preparation method S1. TEMPO oxidation modification of bamboo charcoal fiber cloth Same as Example 1.

[0047] S2, Palladium-free activation treatment of bamboo charcoal fiber cloth Same as Example 1.

[0048] S3, Staged Electroless Copper Plating Same as Example 1, except that: the first stage is a 52°C water bath reaction for 15 minutes, and the second stage is a 56°C water bath reaction for 20 minutes.

[0049] S4, electroless nickel plating The PCF / Cu from step S3 was placed in 100 mL of electroless nickel plating solution and reacted in a 90 °C water bath for 10 min, followed by drying at 60 °C for 2 h. The obtained sample was denoted as PCF / Cu / Ni. 10 .

[0050] The composition of the electroless nickel plating solution is the same as in Example 1.

[0051] Example 3: Bamboo charcoal fiber cloth-based composite material and its preparation method S1. TEMPO oxidation modification of bamboo charcoal fiber cloth Same as Example 1.

[0052] S2, Palladium-free activation treatment of bamboo charcoal fiber cloth Same as Example 1.

[0053] S3, Staged Electroless Copper Plating Same as Example 1.

[0054] S4, electroless nickel plating The PCF / Cu from step S3 was placed in 100 mL of electroless nickel plating solution and reacted in a 90 °C water bath for 15 min, followed by drying at 60 °C for 2 h. The obtained sample was denoted as PCF / Cu / Ni. 15 .

[0055] The composition of the electroless nickel plating solution is the same as in Example 1.

[0056] Example 4: Bamboo charcoal fiber cloth-based composite material and its preparation method S1. TEMPO oxidation modification of bamboo charcoal fiber cloth Same as Example 1.

[0057] S2, Palladium-free activation treatment of bamboo charcoal fiber cloth Same as Example 1.

[0058] S3, Staged Electroless Copper Plating Same as Example 1, except that: the first stage is a 55°C water bath reaction for 5 minutes, and the second stage is a 60°C water bath reaction for 15 minutes.

[0059] S4, electroless nickel plating The PCF / Cu from step S3 was placed in 100 mL of electroless nickel plating solution and reacted in a 90 °C water bath for 20 min, followed by drying at 60 °C for 2 h. The obtained sample was denoted as PCF / Cu / Ni. 20 .

[0060] The composition of the electroless nickel plating solution is the same as in Example 1.

[0061] Comparative Example 1 This comparative example uses the same implementation method as Example 1, except that ultrasound was not introduced during the TEMPO oxidation modification process. All other process steps and condition parameters are the same as in Example 1. 。

[0062] Comparative Example 2 This comparative example uses the same implementation method as Example 1, except that only the first stage of copper plating is performed, i.e., no staged copper plating is performed, and the reaction is carried out at 50°C for 15 minutes. All other process steps and condition parameters are the same as in Example 1.

[0063] Performance testing The performance of the bamboo charcoal fiber cloth-based composite materials prepared in Examples 1-4 and Comparative Examples 1-2 was tested: (1) The surface morphology of the bamboo charcoal fiber cloth composite materials prepared in Examples 1-4 and the bamboo charcoal fiber cloth composite materials prepared in Comparative Examples 1-2 were characterized by a high-resolution field emission scanning electron microscope of Hitachi Regulus 8230. The accelerating voltage used was 3kV.

[0064] Figure 1 The scanning electron microscope (SEM) characterization results of the bamboo charcoal fiber-based composite material prepared in Example 3 are presented. It can be seen that the coating on the sample surface is continuous and uniform, the metal particles are fine and densely distributed, and they are tightly bonded to the gradient copper layer. The overall surface is relatively smooth and flat, which is conducive to constructing a continuous and stable conductive network, thereby achieving excellent electromagnetic shielding performance and corrosion resistance. Figure 2 and Figure 3 The surface morphologies of the bamboo charcoal fiber-based composite materials prepared in Comparative Example 1 and Comparative Example 2 are shown respectively. Figure 2 In the corresponding Comparative Example 1, the sample surface was relatively smooth overall, but most of the substrate was exposed, and the metal coating was insufficient, showing obvious discontinuity. Figure 3 In Comparative Example 2 shown, granular or clustered structures can be observed in some parts of the coating, but the overall coverage is discontinuous, the coating distribution is uneven and the density is poor. Only about half of the area is effectively coated, while the remaining areas still have obvious exposure or incomplete coverage, showing significant regional differences.

[0065] The above results indicate that the specific modification treatment of the bamboo charcoal fiber cloth surface combined with the formation of a gradient copper layer in this application can effectively improve the nucleation and growth behavior of the metal coating on the bamboo charcoal fiber cloth surface, which helps to alleviate the stress concentration problem caused by the difference in thermal expansion coefficients between the metal layer and the organic / inorganic composite substrate, thereby significantly improving the coating uniformity and density of the composite metal layer.

[0066] (2) The crystal structure of the sample was characterized and analyzed using an X-ray diffractometer of model X'Pert PRO MPO from Panaco, USA. Figure 4 Figure A shows the XRD pattern of the bamboo charcoal fiber cloth composite material in the example. It was found that the intensity of the copper diffraction peaks decreased with increasing electroless nickel plating time. However, since the deposited nickel particles are amorphous, their diffraction peaks were not very obvious. But through comparison... Figure 4 As can be seen in Figure B, nickel diffraction peaks can be observed at positions of 44.5° and 76.4°, which are consistent with the nickel PDF card (PDF#00-004-0850), indicating that nickel particles were successfully deposited on the basis of electroless copper plating.

[0067] (3) A vector network analyzer of model ROHDE & SCHWARZ was used to test the shielding performance of bamboo charcoal fiber cloth composite materials of Examples 1, 2, 3, 4 and Comparative Example 2 in the frequency ranges of 8-12 GHz and 26.5-40 GHz using the waveguide method. The shielding effectiveness in the X-band and Ka-band was obtained. Figure 5 ).

[0068] pass Figure 5As can be seen, compared with the bamboo charcoal fiber cloth-based composite material of Comparative Example 2, the bamboo charcoal fiber cloth-based composite material of Example 3 achieves an average electromagnetic shielding effectiveness of 86.52dB and 82.36dB in the X-band and Ka-band, respectively, exhibiting extremely high electromagnetic shielding effectiveness. This is mainly because the sample of Comparative Example 2 lacks a gradient copper plating transition layer, resulting in uneven copper plating coverage and difficulty in forming a continuous conductive network, thus limiting the electromagnetic shielding performance. In contrast, the sample of Example 3, through gradient copper plating followed by nickel plating, forms a dense "copper-nickel" composite conductive structure, significantly improving conductivity and electromagnetic wave absorption capability, thereby achieving superior electromagnetic shielding performance. This indicates that the gradient copper plating and subsequent nickel plating processes play a crucial role in constructing an efficient conductive network and improving shielding performance. Its electromagnetic shielding effectiveness (EMI SE value) far exceeds the electromagnetic shielding effectiveness value required for commercial electromagnetic shielding material applications, demonstrating its wide applicability.

[0069] (4) Figure 6 The Tafel polarization curves of the bamboo charcoal fiber cloth-based composite materials in Example 3 and Comparative Example 2 in 3.5 wt% NaCl solution are shown. A three-electrode system was used for the tests, with a saturated calomel electrode as the reference electrode, the test sample as the working electrode, and a platinum sheet as the auxiliary electrode. The results reflect the corrosion resistance of the materials. Table 1 shows the results of calculating the corrosion potential Ecorr and corrosion current Icorr of the two materials using the extrapolation method.

[0070] It can be observed that the bamboo charcoal fiber cloth-based composite material in Example 3 has a higher corrosion potential. Although the corrosion current of this material is also greater than that of Comparative Example 2, the corrosion potential usually dominates when evaluating the corrosion resistance of the material. This indicates that the corrosion resistance of Example 3 is better than that of Comparative Example 2. Ni has good corrosion resistance, and electroless nickel plating can provide additional corrosion protection for the material, but the introduction of a gradient copper layer significantly improves the corrosion resistance of the material.

[0071] Table 1

[0072] (5) To evaluate the thermal stability of the composite material of bamboo charcoal fiber cloth after chemical copper plating and chemical nickel plating, thermogravimetric analysis was performed on Example 3 and Comparative Example 2. The results are as follows: Figure 7 As shown.

[0073] The original bamboo charcoal fiber cloth exhibited significant weight loss during heating, with a residual weight of 1.76% at 800°C. In Comparative Example 2, the initial weight loss temperature of the bamboo charcoal fiber cloth-based composite material was approximately 214°C. Due to the easy oxidation of the copper layer during heating, its thermal stability was relatively reduced, resulting in a final residual weight of 71.92%. In contrast, the initial weight loss temperature of the bamboo charcoal fiber cloth-based composite material in Example 3 increased to approximately 247°C, and the weight loss rate slowed down, indicating that the nickel layer effectively protected the copper layer.

[0074] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A bamboo charcoal fiber cloth-based composite material, characterized in that, include: The base fabric is a bamboo charcoal fiber fabric modified by TEMPO-ultrasound-assisted oxidation and without palladium activation treatment; A gradient copper layer is electroplated onto the surface of the base fabric; And a nickel layer plated onto the surface of the gradient copper layer; The gradient copper layer is formed by staged electroless copper plating, wherein the density of the copper layer on the base fabric side is less than that of the copper layer on the nickel side. The staged electroless copper plating includes the following steps: The activated bamboo charcoal fibers were arranged in a chemical copper plating solution and CH2O was added. The first stage was carried out in a water bath at 50℃-55℃ for 5-15 minutes, and the second stage was carried out in a water bath at 55℃-60℃ for 15-30 minutes. The water bath temperature in the first stage was lower than that in the second stage.

2. The bamboo charcoal fiber cloth-based composite material according to claim 1, characterized in that, The thickness of the bamboo charcoal fiber cloth is 0.2-0.3 mm, and the particle size of the bamboo charcoal powder used to prepare the bamboo charcoal fiber cloth is 60-90 mesh; the thickness of the gradient copper layer is 0.8-2.4 μm, and the thickness of the nickel layer is 0.8-3.2 μm.

3. A method for preparing the bamboo charcoal fiber cloth-based composite material according to claim 1 or 2, characterized in that, Includes the following steps: Bamboo charcoal fiber cloth is available; The bamboo charcoal fiber cloth was subjected to TEMPO-ultrasound synergistic oxidation modification, followed by palladium-free activation treatment; The activated bamboo charcoal fibers were placed in a chemical copper plating solution and chemical copper plating was performed on their surface in stages. The copper-plated bamboo charcoal fibers are placed in a chemical nickel plating solution, and chemical nickel plating is performed on their surface.

4. The method as described in claim 3, characterized in that, The TEMPO-ultrasound synergistic oxidation modification is carried out in a TEMPO oxidation system and includes the following steps: 1g of bamboo charcoal fiber was placed in 50mL of deionized water containing 0.04-0.06g TEMPO and 0.4-0.6g NaBr or KBr, and pretreated with ultrasound at 30-50kHz for 5-15min. Then, 25-35mmol / g NaClO solution was slowly added, and the mixture was reacted at 23-27℃ for 30-50min under continuous ultrasound to obtain oxidized modified bamboo charcoal fiber cloth TBCF. The pH of the system was maintained at 10.3-10.7 during the reaction.

5. The method as described in claim 3, characterized in that, The palladium-free activation treatment includes the following steps: The TEMPO-oxidized bamboo charcoal fiber cloth was placed in a solution containing 0.18-0.22g CuSO4. Soak the bamboo charcoal fiber cloth (PCF) in a 50 mL aqueous solution of 5H2O at 53-57℃ for 25-35 min, then directly transfer it into a 50 mL aqueous solution containing 0.08-0.12 g NaBH4 and 0.08-0.12 g NaOH, and react at room temperature for 4-6 min to obtain activated bamboo charcoal fiber cloth (PCF).

6. The method as described in claim 3, characterized in that, The electroless copper plating solution is prepared by dissolving 10-12g CuSO4·5H2O, 13-15g NaKC4H4O6·4H2O, 11-13g NaOH and 0.015-0.025g 2,2'-bipyridine in 1000mL of deionized water.

7. The method as described in claim 3, characterized in that, The composition of the electroless nickel plating solution is as follows: 28-32g NiSO4·6H2O, 30-34g NaH2PO2·H2O, 23-27g Na3C6H5O7·2H2O, and 18-22g CH3COONa are dissolved in 1000mL of deionized water, and the pH is adjusted to 4.8-5.

2.

8. The method as described in claim 3, characterized in that, The electroless nickel plating is performed by reacting in a water bath at 88-92℃ for 5-20 minutes.

9. The application of the bamboo charcoal fiber cloth-based composite material as described in claim 1 or 2, or the bamboo charcoal fiber cloth-based composite material prepared by the method described in any one of claims 3-8, in electromagnetic shielding.

Images