Metal modified carbon fiber and preparation process thereof

Abstract

The invention relates to the technical field of carbon fiber surface treatment, in particular to a preparation process of metal modified carbon fibers and the metal modified carbon fibers prepared by adopting the preparation process. The preparation process comprises the steps of broadening and dispersing treatment, graphene layer treatment and plating treatment, and the broadening and dispersing treatment comprises the steps that carbon fibers are broadened and thinned, so that carbon fiber filaments are dispersed; the graphene layer treatment comprises the following steps: generating a graphene layer on the surface of the carbon fiber subjected to broadening and dispersing treatment, and thinning the graphene layer; the plating treatment comprises the step of generating a metal plating layer on the surface of the carbon fiber treated by the graphene layer. The monofilaments of the carbon fibers are dispersed through broadening dispersion treatment, the black core phenomenon can be prevented, the area of a graphene layer generated on the surfaces of the monofilaments in the carbon fibers and the area of a metal coating are increased, and the uniformity of the coating is improved. The metal coating is generated after the graphene layer is generated, so that a composite structure of the metal coating and the graphene layer can be formed on the surface of the carbon fiber, and the overall conductivity is improved.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber surface treatment technology, and in particular to a preparation process for metal-modified carbon fiber and a metal-modified carbon fiber prepared using this preparation process. Background Technology

[0002] Carbon fiber possesses excellent properties such as lightweight, high strength, corrosion resistance, and fatigue resistance, and is widely used in high-tech industries such as aerospace, transportation, and new energy. With technological advancements, the demand for functional applications of carbon fiber has significantly increased. Carbon fiber metallization, as a typical surface modification method, can effectively improve the electrical conductivity and surface wettability of carbon fiber. Metallized carbon fiber exhibits good electrical conductivity and shielding properties, and its strength and high-temperature resistance are also enhanced compared to unmodified carbon fiber, making it widely used in conductive fillers, electromagnetic shielding, and microwave absorption. Currently, the mainstream carbon fiber metallization processes are chemical plating and electroplating. Compared to electroplating, electroplating has a faster deposition rate and produces a coating with lower phosphorus content and better ductility. However, it suffers from poor coating uniformity, weaker bonding with carbon fibers, and higher porosity. Electroless plating, on the other hand, requires no continuous power source, produces a coating with stronger bonding, greater uniformity, lower porosity, higher phosphorus content, higher hardness, and better corrosion and wear resistance. However, electroless plating is more expensive, more complex, requires larger amounts of plating solution, has a relatively slower deposition rate, and excessive phosphorus content can lead to brittleness. There is still significant room for improvement in the overall electrical conductivity of carbon fibers through metallization modification. Summary of the Invention

[0003] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is to provide a preparation process for metal-modified carbon fibers, which can obtain metal-modified carbon fibers with significantly improved electrical conductivity.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] This invention provides a process for preparing metal-modified carbon fibers, including a broadening and dispersion treatment, a graphene layer treatment, and a plating treatment. The broadening and dispersion treatment involves broadening and thinning the carbon fibers to disperse them. The graphene layer treatment involves generating a graphene layer on the surface of the broadened and dispersed carbon fibers and then thinning the graphene layer. The plating treatment involves generating a metal coating on the surface of the graphene-treated carbon fibers.

[0006] Preferably, the graphene layer treatment employs a laser-induced method to generate a graphene layer on the surface of carbon fibers.

[0007] Preferably, the graphene layer is thinned using a femtosecond laser.

[0008] Preferably, the broadening and dispersion treatment employs pneumatically assisted plasma electromagnetic broadening.

[0009] Preferably, the plating process is a composite plating process, which involves connecting the carbon fiber to the negative terminal of the power supply, connecting the coating metal to the positive terminal of the power supply, placing the carbon fiber and the coating metal in the plating solution and connecting the current, cutting off the current after a set energizing time, and then removing the coating metal from the plating solution, allowing the carbon fiber to react spontaneously in the plating solution until the plating process is completed, thereby generating a metal coating on the surface of the carbon fiber.

[0010] Preferably, the plating process is electroplating or chemical plating.

[0011] Preferably, nickel plating is applied.

[0012] The present invention also provides a metal-modified carbon fiber, which is prepared by the metal-modified carbon fiber preparation process described above.

[0013] Compared with the prior art, the present invention has significant progress:

[0014] The metal-modified carbon fiber preparation process of this invention disperses the carbon fiber monofilaments through a broadening and dispersion treatment, preventing black core phenomena. This process increases the area of ​​the graphene layer formed on the surface of the carbon fiber monofilaments by graphene layer treatment and the area of ​​the metal coating formed on the surface of the carbon fiber monofilaments by plating treatment, thus improving coating uniformity. By generating a graphene layer followed by a metal coating, a composite structure of metal coating and graphene layer can be formed on the surface of the carbon fiber, which helps to increase the overall conductivity. The graphene is filled and encapsulated by nanoscale metal particles, forming a graphene-metal composite layer, which provides a good pathway for electron movement. Among them, the continuous carbon rings in the graphene layer are the "main trunk" in the good pathway, and the metal layer acts as "branch trunks". Compared with an all-metal coating, the conductivity can be significantly improved. Attached Figure Description

[0015] Figure 1 This is a 10,000x magnified scanning electron microscope image of the surface of the metal-modified carbon fiber prepared in Example 1 of this invention. Detailed Implementation

[0016] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0017] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0018] like Figure 1 The image shows an embodiment of the preparation process of metal-modified carbon fiber provided by the present invention.

[0019] The preparation process of metal-modified carbon fibers in this embodiment includes a broadening and dispersion treatment, a graphene layer treatment, and a plating treatment. The broadening and dispersion treatment involves broadening and thinning the carbon fibers to disperse the fiber filaments. The graphene layer treatment involves forming a graphene layer on the surface of the broadened and dispersed carbon fibers and then thinning the graphene layer. The plating treatment involves forming a metal coating on the surface of the graphene-treated carbon fibers. The metal coating material is not limited and can be any metal material suitable for metallization modification of carbon fibers. Preferably, the plating treatment uses nickel plating, i.e., a nickel layer is formed on the surface of the graphene-treated carbon fibers.

[0020] Therefore, the metal-modified carbon fiber preparation process of this embodiment, by widening and dispersing the carbon fiber monofilaments, can prevent black core phenomenon and increase the area of ​​the graphene layer formed on the surface of the carbon fiber monofilaments by graphene layer treatment and the area of ​​the metal coating formed on the surface of the carbon fiber monofilaments by plating treatment, thereby improving the coating uniformity. By generating a graphene layer and then generating a metal coating, a composite structure of metal coating and graphene layer can be formed on the surface of carbon fiber, which is beneficial to increasing the overall conductivity. Graphene is filled and encapsulated by nanoscale metal particles to form a graphene-metal composite layer, providing a good pathway for electron movement. Among them, the continuous carbon rings in the graphene layer are the "main road" in the good pathway, and the metal layer acts as the "branch road". Compared with an all-metal coating, the conductivity can be significantly improved.

[0021] In this embodiment, preferably, the graphene layer treatment employs a laser-induced method to generate a graphene layer on the surface of the carbon fiber. For example, using a carbon dioxide laser-induced method, in conjunction with carbon fibers having a polyimide slurry film on their surface, a carbon dioxide laser can be used in a nitrogen atmosphere to induce the formation of a graphene layer on the carbon fibers with the polyimide slurry film. The strong bond between the polyimide slurry film and the carbon fiber enhances the interfacial bonding force of the graphene layer. After the graphene layer is generated on the surface of the carbon fiber, the carbon fiber surface is cleaned with an airflow.

[0022] In this embodiment, preferably, the graphene layer is thinned using a femtosecond laser. Femtosecond laser treatment thins the graphene layer on the carbon fiber surface, minimizing the graphene deposition thickness and fully utilizing the advantage of fewer graphene layers for enhanced conductivity. After thinning, the carbon fiber is ultrasonically cleaned with deionized water and then dried.

[0023] In this embodiment, preferably, the broadening and dispersion process employs pneumatically assisted plasma electromagnetic broadening. Pneumatically assisted plasma electromagnetic broadening is accomplished through a combination of a high-voltage discharge plasma electrostatic generator and an airflow blowing device. The carbon fiber is drawn through the positive and negative electrodes of the high-voltage discharge under inert dry gas via an insulating tension roller. After the electrodes are subjected to high-voltage discharge, plasma is generated. Under the influence of high-voltage electrostatics, inert drying, and electromagnetic fields, the carbon fiber itself generates static electricity and expands and loosens. At this point, with the assistance of a fan-shaped airflow from a nozzle, the electrostatically expanded carbon fiber is initially dispersed and shaped. Then, it is drawn by a metal tension roller outside the broadening and dispersion area to achieve final broadening and sizing by eliminating static electricity. This achieves the broadening and thinning of the carbon fiber, ensuring thorough dispersion of the carbon fiber filaments.

[0024] In this embodiment, the preparation process of metal-modified carbon fibers involves carbon fiber selection and cleaning before the broadening and dispersion treatment. Preferably, carbon fibers with a polyimide sizing agent on the surface are selected as the fiber skeleton, i.e., carbon fibers with a polyimide sizing film on the surface are chosen. The cleaning process involves ultrasonic cleaning with ethanol, followed by rinsing with deionized water and drying. This achieves a cleaning effect without damaging the polyimide sizing film on the carbon fiber surface, thus providing conditions for laser-induced graphene layer formation.

[0025] In this embodiment, preferably, the plating process is a composite plating, which involves: connecting the graphene-treated carbon fiber to the negative terminal of a power supply, preferably using a multi-point connection, i.e., leading several connecting wires from the negative terminal of the power supply and connecting them to different positions on the carbon fiber, with each connection position being evenly distributed on the carbon fiber; connecting the plating metal (such as nickel) to the positive terminal of the power supply; placing the carbon fiber and plating metal in the plating solution and connecting the current, then cutting off the current after a set energizing time. This process is an electric field catalytic process, which can be instantaneous. The power is cut off when bubbles are generated on the surface of the carbon fiber in the plating solution; then removing the plating metal from the plating solution, allowing the carbon fiber to react spontaneously in the plating solution. The spontaneous reaction time of the carbon fiber in the plating solution is longer than that of the electric field catalytic process, until the plating is completed, generating a metal plating layer on the surface of the carbon fiber. This plating layer is a composite effect of the fully fused electroplating layer and chemical plating layer. During the plating process, the plating solution is maintained at a set temperature. Composite plating is a metallization and composite modification process for carbon fiber surfaces under electric field catalysis, combining electroplating and chemical plating processes. Compared to simple chemical plating, composite plating can reduce the plating reaction difficulty of chemical plating on carbon fiber surfaces, save chemical plating solution consumption, increase the deposition rate of the coating, and reduce the content of impurity elements in the coating (such as achieving a phosphorus content of less than 3%) while producing the same metal coating thickness. The composite coating generated by composite plating is an effective fusion of electroplating and chemical plating, which can take into account the high ductility and high interfacial fatigue toughness of electroplating and the uniformity, density, high wear resistance and corrosion resistance of chemical plating. It maximizes the preservation of the mechanical properties and flexible weaving characteristics of carbon fiber and significantly improves its conductivity, achieving a breakthrough in conductivity limits across material categories.

[0026] In this embodiment, when the plating process is composite nickel plating, the positive terminal of the power supply is connected to a nickel plate. The plating solution contains: 18g / L-33g / L nickel sulfate, 20g / L-33g / L sodium hypophosphite, 5g / L-15g / L sodium citrate, and 10g / L-35g / L ammonium chloride. Ammonia water is added to the plating solution to adjust the pH value to 9. The voltage is 5V-15V, the energizing time is set to 5s-120s, the temperature of the plating solution during the plating process is 45℃-90℃, and the plating time is 15min-20min.

[0027] In other embodiments, the plating process may also be electroplating or chemical plating.

[0028] Preferably, the preparation process of the metal-modified carbon fiber in this embodiment further includes an activation treatment performed after the graphene layer treatment and before the plating treatment. The activation treatment modifies the surface of the carbon fiber through oxidation before plating, improving surface wettability. Preferably, the activation treatment includes roughening, sensitization, and activation performed sequentially.

[0029] The following provides a specific embodiment 1 of the preparation process of the above-mentioned metal-modified carbon fiber, and provides a comparative example 1 as a comparison. The comparative example 1 does not have the broadening dispersion treatment and graphene layer treatment.

[0030] Comparative Example 1:

[0031] Comparative Example 1 uses simple electroless nickel plating, which includes the following steps:

[0032] Step 1: Place the carbon fiber in analytical grade acetone solution, filter it under constant temperature of 60℃ water bath for 24 hours, wash it repeatedly with anhydrous ethanol and deionized water, and dry it for later use.

[0033] Step 2: Prepare a 15% nitric acid solution, immerse the carbon fiber from Step 1 in the nitric acid solution, heat in a 75°C water bath for 20 minutes, remove it and neutralize it in a 10wt% sodium hydroxide solution for 5 minutes, wash it repeatedly with deionized water and dry it.

[0034] Step 3: Immerse the carbon fiber from Step 2 in a 10 g / L palladium chloride solution (containing 10 ml / L hydrogen chloride), heat at 40°C for 15 min, add 0.1 mol / L sodium citrate and reduce at 40°C for 15 min.

[0035] Step 4: Prepare a plating solution containing 20 g / L nickel sulfate, 24 g / L sodium hypophosphite, 6.5 g / L sodium citrate, and 13.5 g / L ammonium chloride. Adjust the pH of the plating solution to 9 with ammonia. Immerse the carbon fiber treated in Step 3 into the plating solution and maintain the plating solution temperature at 75°C with shaking for 45 minutes. Then, rinse repeatedly with deionized water and dry.

[0036] The linear resistance of the nickel-plated carbon fiber prepared in Comparative Example 1 was measured to be 5.3 Ω / 8cm using a digital multimeter.

[0037] Example 1:

[0038] The preparation process of the metal-modified carbon fiber in Example 1 mainly includes broadening and dispersion treatment, graphene layer treatment, activation treatment, and plating treatment. The plating treatment adopts composite nickel plating, specifically including the following steps in sequence:

[0039] Step 1, Carbon fiber selection: Select carbon fibers with polyimide as the sizing agent on the surface as the fiber skeleton. The carbon fiber surface has a polyimide sizing film.

[0040] Step 2, Cleaning: Clean with 50% ethanol at room temperature using ultrasonic oscillation for 20 minutes; then rinse with deionized water and dry.

[0041] Step 3, Broadening and Dispersion Treatment: The carbon fibers treated in Step 2 are pulled through high-voltage discharge positive and negative plates by an insulating tension roller under inert dry gas. The distance between the plates is 4.5 cm. After the plates are discharged by high voltage, plasma is generated. The plasma generation power is 150W and lasts for 120s. After being subjected to high voltage static electricity, inert drying and electromagnetic fields, the carbon fibers themselves generate static electricity and expand and loosen. At this time, under the cooperation of the fan-shaped airflow of the nozzle, the statically expanded carbon fibers are blown away and initially shaped. The airflow speed is 11m / s. Then, the carbon fibers are pulled by a metal tension roller outside the broadening and dispersion area to achieve static elimination, broadening and final shaping.

[0042] Step 4, Graphene layer treatment: using an energy density of 8 J / cm² 2 A carbon dioxide laser with a scanning speed of 550 mm / s was used to induce the formation of graphene layers on both sides of the carbon fiber after step 3 in a nitrogen atmosphere. The carbon fiber surface was then cleaned with airflow. The carbon fiber double surface with graphene layers was then treated with a femtosecond laser. Each surface was treated with the femtosecond laser twice. The surface was then cleaned with deionized water by ultrasonic oscillation and dried.

[0043] Step 5, Activation Treatment: This includes roughening, sensitization, and activation performed sequentially. Roughening involves immersing the carbon fibers treated in Step 4 in a roughening solution containing 220 g / L ammonium persulfate and 100 ml / L hydrogen chloride at 50°C for 15 minutes; or, alternatively, using a 65% nitric acid solution at 90°C for 30 minutes. After roughening, the carbon fibers are washed with deionized water and dried. Sensitization involves immersing the roughened carbon fibers in a sensitization solution containing 15 g / L stannous chloride and 10 ml / L hydrogen chloride at room temperature for 30 minutes. After sensitization, the carbon fibers are washed with deionized water and dried. Activation involves immersing the sensitized carbon fibers in an activation solution containing 10 g / L silver nitrate solution, clarified with added ammonia, at 40°C for 30 minutes. After activation, the carbon fibers are washed with deionized water and dried.

[0044] Step 6, Plating Treatment: Composite nickel plating. Connect the carbon fiber treated in Step 5 to the negative terminal of the power supply, and connect the positive terminal to the nickel plate. Place the carbon fiber and nickel plate in the plating solution and turn on the current. The plating solution contains: 20 g / L nickel sulfate, 24 g / L sodium hypophosphite, 6.5 g / L sodium citrate, and 13.5 g / L ammonium chloride. Adjust the pH of the plating solution to 9 with ammonia water. The voltage is 5V, and the energizing time is set to 5 seconds. After 5 seconds, turn off the current and remove the nickel plate from the plating solution, allowing the carbon fiber to react spontaneously in the plating solution. Maintain the temperature of the plating solution at 45℃ and the plating time for 15 minutes. After plating, clean and dry the carbon fiber.

[0045] Figure 1 A 10,000x magnified scanning electron microscope image of the surface of the metal-modified carbon fiber prepared in Example 1 is shown. The linear resistance of the metal-modified carbon fiber prepared in Example 1 was measured to be 3.2 Ω / 8 cm using a digital multimeter. Compared with Comparative Example 1, the linear resistance is significantly reduced, indicating a significant improvement in the conductivity of the carbon fiber.

[0046] Based on the preparation process of metal-modified carbon fiber of the present invention, the present invention provides a metal-modified carbon fiber, which is prepared by the above-mentioned preparation process of metal-modified carbon fiber.

[0047] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A process for preparing metal-modified carbon fibers, characterized in that, The process includes a broadening and dispersion treatment, a graphene layer treatment, and a plating treatment. The broadening and dispersion treatment involves broadening and thinning the carbon fibers to disperse them. The graphene layer treatment involves forming a graphene layer on the surface of the carbon fibers after the broadening and dispersion treatment, and then thinning the graphene layer. The plating process involves generating a metal plating layer on the surface of the carbon fibers after the graphene layer treatment.

2. The preparation process of metal-modified carbon fiber according to claim 1, characterized in that, The graphene layer treatment employs a laser-induced method to generate the graphene layer on the surface of carbon fibers.

3. The preparation process of metal-modified carbon fiber according to claim 1, characterized in that, The graphene layer is thinned using a femtosecond laser.

4. The preparation process of metal-modified carbon fiber according to claim 1, characterized in that, The broadening and dispersion process employs pneumatically assisted plasma electromagnetic broadening.

5. The preparation process of metal-modified carbon fiber according to claim 1, characterized in that, The plating process is a composite plating process, which involves connecting the carbon fiber to the negative terminal of a power supply, connecting the coating metal to the positive terminal of a power supply, placing the carbon fiber and the coating metal in a plating solution and connecting the current, cutting off the current after a set energizing time, and then removing the coating metal from the plating solution to allow the carbon fiber to react spontaneously in the plating solution until the plating process is completed, thereby generating a metal coating on the surface of the carbon fiber.

6. The preparation process of metal-modified carbon fiber according to claim 1, characterized in that, The plating process is either electroplating or chemical plating.

7. The preparation process of metal-modified carbon fiber according to claim 1, characterized in that, The plating process involves nickel plating.

8. A metal-modified carbon fiber, characterized in that, It is prepared using the preparation process of metal-modified carbon fiber as described in any one of claims 1 to 7.

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