Metal-modified carbon fibers and their preparation methods

Abstract

This invention relates to the field of carbon fiber surface treatment technology, and particularly to a method for preparing metal-modified carbon fiber and the metal-modified carbon fiber obtained by this method. The preparation method includes a primary plating process, which is a composite plating process. The composite plating process involves connecting the carbon fiber to the negative terminal of a power supply and connecting the plating metal to the positive terminal of the power supply. The carbon fiber and the plating metal are placed in a plating solution and an electric current is applied. After a set energizing time, the current is cut off, and then the plating metal is removed from the plating solution, allowing the carbon fiber to react spontaneously in the plating solution until the plating is completed, resulting in a composite plating layer on the surface of the carbon fiber. Combining electroplating and chemical plating processes reduces the difficulty of the chemical plating reaction on the carbon fiber surface, saves on chemical plating solution consumption, increases the plating deposition rate, and reduces the content of impurity elements in the plating layer, resulting in metal-modified carbon fiber that combines the advantages of both electroplating and chemical plating processes.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber surface treatment technology, and in particular to a method for preparing metal-modified carbon fiber and a metal-modified carbon fiber prepared by the method. 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, uniformity, low porosity, high phosphorus content, high hardness, and excellent corrosion and wear resistance. However, it 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. Both electroplating and electroless plating of carbon fibers still have significant room for improvement in terms of environmental pollution, interfacial bonding quality, production speed, fiber skeleton damage, and electrical conductivity. The current technological landscape, to some extent, restricts the rapid development of integrated structural and functional applications of carbon fibers, particularly in the preservation of carbon fiber mechanical properties, flexibility, and the compatibility of high electrical and thermal conductivity. Further research is needed in these areas. Summary of the Invention

[0003] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is to provide a method for preparing metal-modified carbon fibers, which can obtain metal-modified carbon fibers that have the advantages of both electroplating and chemical plating processes.

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

[0005] This invention provides a method for preparing metal-modified carbon fibers, including a main plating process, which is a composite plating process. The composite plating process 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 is completed, thereby generating a composite coating on the surface of the carbon fiber.

[0006] Preferably, the process further includes a graphene layer treatment performed before the main coating treatment, wherein the graphene layer treatment is performed by generating a graphene layer on the surface of the carbon fiber and thinning the graphene layer.

[0007] Preferably, the graphene layer treatment employs a laser-induced method to generate a graphene layer on the surface of carbon fibers.

[0008] Preferably, the graphene layer is thinned using a femtosecond laser.

[0009] Preferably, it also includes a broadening and dispersion treatment performed before the main coating treatment, wherein the broadening and dispersion treatment is to broaden and thin the carbon fibers to disperse the carbon fiber filaments.

[0010] Preferably, the widening and dispersion treatment employs vibration jet widening.

[0011] Preferably, it also includes a secondary plating process performed before or after the primary plating process, wherein the secondary plating process is electroplating, chemical plating, or composite plating.

[0012] Preferably, the primary plating process involves nickel plating, and the secondary plating process involves silver plating.

[0013] Preferably, the process also includes an activation treatment prior to the main coating treatment, the activation treatment including carbon fiber anodizing.

[0014] The present invention also provides a metal-modified carbon fiber, which is prepared by the metal-modified carbon fiber preparation method described above.

[0015] Compared with the prior art, the present invention has significant progress:

[0016] The method for preparing metal-modified carbon fibers proposed in this invention involves composite plating, which combines electroplating and chemical plating processes to form an electric field-catalyzed metallization composite modification process for carbon fiber surfaces. Compared with simple chemical plating, composite plating, while producing the same coating thickness, can reduce the difficulty of the chemical plating reaction on the carbon fiber surface, save on chemical plating solution consumption, increase the coating deposition rate, and reduce the content of impurity elements in the coating. 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 the electroplating layer and the uniformity, density, high wear resistance, and corrosion resistance of the chemical plating layer. This maximizes the retention of the mechanical properties and flexible weaving characteristics of carbon fibers, as well as significantly improves their conductivity, achieving a breakthrough in conductivity limits across material classes. Attached Figure Description

[0017] Figure 1 This is a 2000x magnified scanning electron microscope image of the surface of the metal-modified carbon fiber prepared in Example 1 of this invention.

[0018] Figure 2This is a 5000x magnified scanning electron microscope image of the surface of the metal-modified carbon fiber obtained in Example 1 of this invention.

[0019] Figure 3 This is a 2000x magnified scanning electron microscope image of the cross-section of the metal-modified carbon fiber prepared in Example 3 of this invention.

[0020] Figure 4 This is a 1000x magnified scanning electron microscope image of the surface of the metal-modified carbon fiber obtained in Example 3 of this invention.

[0021] Figure 5 This is a 10,000x magnified scanning electron microscope image of the surface of the metal-modified carbon fiber obtained in Example 3 of this invention.

[0022] Figure 6 This is a 2000x magnified scanning electron microscope image of the cross-section of the metal-modified carbon fiber prepared in Example 4 of this invention.

[0023] Figure 7 This is a 1000x magnified scanning electron microscope image of the surface of the metal-modified carbon fiber obtained in Example 4 of this invention.

[0024] Figure 8 This is a 10,000x magnified scanning electron microscope image of the surface of the metal-modified carbon fiber prepared in Example 4 of this invention. Detailed Implementation

[0025] 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.

[0026] 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.

[0027] like Figures 1 to 8 The image shows an embodiment of the method for preparing metal-modified carbon fibers provided by the present invention.

[0028] The method for preparing metal-modified carbon fiber in this embodiment includes a primary plating treatment, which is a composite plating process. The composite plating involves: connecting the 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 evenly distributed on the carbon fiber; connecting the plating metal to the positive terminal of the power supply; placing the carbon fiber and the plating metal in a plating solution and applying current, then cutting off the current after a set energizing time (this process is an electric field catalysis 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 solution. The spontaneous reaction time of the carbon fiber in the plating solution is longer than that of the electric field catalysis process, until the plating is completed, generating a composite plating layer on the surface of the carbon fiber. This plating layer is a composite effect resulting from the full fusion of the electroplating layer and the chemical plating layer. During the plating process, the plating solution is maintained at a set temperature. After the primary plating treatment is completed, the carbon fiber is cleaned and dried.

[0029] The metal-modified carbon fiber preparation method proposed in this embodiment is a composite plating process that combines electroplating and chemical plating to form a metallization composite modification process of carbon fiber surface under electric field catalysis. Compared with simple chemical plating, composite plating can reduce the plating reaction difficulty of chemical plating on the carbon fiber surface, 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 generating the same coating thickness (composite 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 retention 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.

[0030] In this embodiment, the coating material for composite plating is not limited and can be any metal material suitable for carbon fiber metallization modification, with nickel being the most preferred. During 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 is added to the plating solution to adjust the pH to 9. The voltage is 5V-15V, the energizing time is set to 5s-120s, the temperature of the plating solution during plating is 45℃-90℃, and the plating time is 15min-20min.

[0031] Preferably, the preparation method of metal-modified carbon fiber in this embodiment further includes a graphene layer treatment before the main plating treatment. The graphene layer treatment involves generating a graphene layer on the surface of the carbon fiber and thinning the graphene layer. By generating a graphene layer and performing a composite plating treatment, a composite structure of a composite plating layer and a graphene layer can be formed on the surface of the carbon fiber, which is beneficial to increasing the overall conductivity. Taking the main plating treatment using composite nickel plating as an example, the graphene is filled and encapsulated by nano-sized nickel particles to form a graphene-nickel 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 nickel layer acts as a "branch trunk". Compared with a full nickel layer, the conductivity can be significantly improved.

[0032] 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.

[0033] 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.

[0034] Preferably, the method for preparing metal-modified carbon fibers in this embodiment further includes a broadening and dispersion treatment performed before the main coating treatment. The broadening and dispersion treatment involves broadening and thinning the carbon fibers to disperse the carbon fiber filaments. This prevents black core formation. The broadening and dispersion treatment disperses the carbon fiber filaments, which helps increase the area of ​​the composite coating formed on the surface of the carbon fiber filaments during the main coating treatment, thus improving coating uniformity. If a graphene layer treatment is performed before the main coating treatment, the broadening and dispersion treatment is performed before the graphene layer treatment. This broadening and dispersion treatment disperses the carbon fiber filaments, which helps increase the area of ​​the graphene layer formed on the surface of the carbon fiber filaments during the graphene layer treatment and the area of ​​the composite coating formed on the surface of the carbon fiber filaments during the main coating treatment, thus improving coating uniformity.

[0035] In this embodiment, preferably, the widening and dispersion treatment employs vibration-jet widening. Vibration-jet widening is accomplished by a vibration-jet device. The carbon fiber is brought into contact with two tension rollers in the device, and subjected to the high-frequency reciprocating action of the intermediate vibration roller relative to the two tension rollers. Simultaneously, the carbon fiber is dispersed by the fan-shaped airflow from the nozzle, causing the carbon fiber filaments to deflect outwards to both sides, and then widened and shaped by the tension rollers. This achieves the widening and thinning of the carbon fiber, ensuring thorough dispersion of the carbon fiber filaments.

[0036] The method for preparing metal-modified carbon fibers in this embodiment involves selecting and cleaning the carbon fibers 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 selected. The cleaning treatment is divided into two cases depending on whether graphene layer treatment is performed: When no graphene layer treatment is performed, the cleaning treatment involves: high-temperature calcination of the carbon fibers, followed by ultrasonic cleaning with ethanol or acetone, then washing with deionized water and drying, thereby achieving the effect of removing glue and oil; When a graphene layer treatment is performed, the cleaning treatment involves: ultrasonic cleaning with ethanol, then washing with deionized water and drying, thereby achieving the cleaning effect without damaging the polyimide sizing film on the carbon fiber surface, providing conditions for laser-induced graphene layer formation.

[0037] Preferably, the method for preparing metal-modified carbon fibers in this embodiment further includes a secondary coating treatment performed before or after the primary coating treatment. The secondary coating treatment is electroplating, chemical plating, or a composite plating. The coating material for the secondary coating treatment is not limited and can be any metal material suitable for metallization modification of carbon fibers, with silver being the most preferred. Adding at least one secondary coating treatment before or after the primary coating treatment can form a multilayer metal coating structure on the carbon fiber surface, which is beneficial for further increasing conductivity. When the secondary coating treatment is performed before the primary coating treatment, it is performed after the broadening and dispersion treatment. If a graphene layer treatment is performed before the primary coating treatment, the secondary coating treatment is performed after the graphene layer treatment.

[0038] In this embodiment, preferably, the primary plating treatment is nickel plating, and the secondary plating treatment is silver plating. Preferably, the secondary plating treatment is performed after the graphene layer treatment and before the primary plating treatment. After the graphene layer treatment and the secondary plating treatment with silver plating, the carbon fiber can be subjected to high-temperature treatment, heating the carbon fiber at high temperature in an inert environment to melt the silver layer into a mesh structure. The primary plating treatment is then performed. This forms a graphene-silver-nickel composite layer on the surface of the carbon fiber. Compared to the graphene-nickel composite layer formed by the graphene layer treatment and the primary plating treatment, the silver mesh layer is attached to the continuous carbon rings of the graphene layer, further increasing the number of pathways on the "main road" and resulting in stronger overall conductivity.

[0039] Preferably, the preparation method of metal-modified carbon fiber in this embodiment further includes an activation treatment before the main plating treatment, so as to perform surface oxidation modification on the carbon fiber before plating and improve surface wettability. Preferably, the activation treatment includes carbon fiber anodizing, which is performed by connecting the carbon fiber to the positive terminal of a power supply and the negative terminal of the power supply to graphite, using a mixture of ammonium persulfate and nitric acid as the electrolyte, placing the carbon fiber and graphite in the electrolyte and connecting the current, which is 0.3A-0.5A, for 15s-20s. Short-time anodizing in the mixture of ammonium persulfate and nitric acid can achieve a combined treatment of carbon fiber dispersion, roughening, and activation, reducing the excessive loss of fiber skeleton mechanical properties caused by the long-term high-temperature activation process. Here, carbon fiber dispersion refers to the further dispersion caused by molecular repulsion between carbon fiber filaments, and roughening refers to the formation of pits and rough structures on the carbon fiber surface, increasing the surface area, roughness, and friction of the carbon fiber. In other embodiments, the activation treatment may also include roughening, sensitization, and activation performed sequentially, or roughening and electrochemical oxidation performed sequentially. The activation treatment is performed after the broadening and dispersion treatment. If the graphene layer treatment is performed before the main coating treatment, the activation treatment is performed after the graphene layer treatment. If the secondary coating treatment is performed before or after the main coating treatment, an activation treatment is performed before the main coating treatment and before the secondary coating treatment. For example, if the secondary coating treatment is performed after the graphene layer treatment and before the main coating treatment, an activation treatment is performed after the graphene layer treatment, followed by the secondary coating treatment and high-temperature treatment, then another activation treatment, and finally the main coating treatment.

[0040] The following provides six specific examples 1-6 of the preparation method of the above-mentioned metal-modified carbon fiber, and also provides a comparative example 1 as a comparison, which is a pure chemical plating.

[0041] Comparative Example 1:

[0042] Comparative Example 1 uses simple electroless nickel plating, which includes the following steps:

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] The linear resistance of the nickel-plated carbon fiber prepared in this comparative example was measured to be 5.3Ω / 8cm using a digital multimeter.

[0048] Example 1:

[0049] The preparation method of metal-modified carbon fibers in Example 1 mainly includes broadening and dispersion treatment, graphene layer treatment, activation treatment, and main coating treatment, specifically including the following steps in sequence:

[0050] 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.

[0051] Step 2, Cleaning: Clean with 50% ethanol at room temperature using ultrasonic oscillation for 20 minutes; then rinse with deionized water and dry.

[0052] Step 3, Broadening and Dispersion Treatment: The carbon fibers treated in Step 2 are brought into contact with two tension rollers in the vibratory blowing device. The intermediate vibrating roller reciprocates at a high frequency relative to the two tension rollers. The vibration frequency of the vibrating roller is 8Hz and the amplitude is 18mm. At the same time, the carbon fibers are dispersed under the cooperation of the fan-shaped airflow from the nozzle. The airflow velocity is 11m / s. The carbon fiber filaments deflect to both sides and move outward, and are broadened and shaped by the tension rollers.

[0053] 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.

[0054] Step 5, Activation treatment: The carbon fiber treated in step 4 is anodized. The carbon fiber is connected to the positive terminal of the power supply, and the negative terminal of the power supply is connected to the graphite. The electrolyte is a mixture of 0.6 wt% ammonium persulfate and 0.5 wt% nitric acid. The carbon fiber and graphite are placed in the electrolyte and the current is turned on. The current is 0.5A and the current-carrying time is 20s.

[0055] Step 6, Main 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 of the power supply 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 of energizing, 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 at 15 minutes. After plating, clean and dry the carbon fiber.

[0056] Figure 1 The image shown is a 2000x magnified scanning electron microscope image of the surface of the metal-modified carbon fiber prepared in Example 1. Figure 2 A 5000x 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, measured using a digital multimeter, is 3.2 Ω / 8 cm. Compared with Comparative Example 1, the linear resistance is significantly reduced, indicating a significant improvement in the conductivity of the carbon fiber.

[0057] Example 2:

[0058] Example 2 is basically the same as Example 1, and the similarities will not be repeated. The difference is that, compared with Example 1, the preparation method of metal-modified carbon fiber in Example 2 adds a secondary coating treatment after the graphene layer treatment and before the main coating treatment. Specifically, the following step ac is added between step 5 and step 6 of Example 1:

[0059] Step a, Secondary plating treatment: The secondary plating treatment is silver plating, which is carried out by electroplating. The carbon fiber treated in step 5 of Example 1 is connected to the negative terminal of the power supply, and the positive terminal of the power supply is connected to the silver plate. The carbon fiber and the silver plate are placed in the silver plating solution and the current is turned on. The silver plating solution contains 20g / L silver nitrate, 35g / L citric acid and 40g / L ammonium sulfate. The pH value of the silver plating solution is adjusted to 9.5 with ammonia water. The voltage is 5V and the current is turned on for 5min. After 5min, the current is turned off, the carbon fiber is taken out, cleaned and dried.

[0060] Step b, high temperature treatment: The carbon fibers treated in step a are heated at 450°C for 20 minutes in an inert nitrogen atmosphere to melt and disperse the silver nanoparticles on the carbon fiber surface into a network.

[0061] Step c, Activation treatment: The carbon fibers treated in step b are subjected to anodizing as described in step 5. Then proceed to step 6 of Example 1.

[0062] The linear resistance of the metal-modified carbon fiber prepared in Example 2 was measured to be 1.1 Ω / 8 cm using a digital multimeter. Compared with Example 1, the linear resistance was significantly reduced, and the conductivity of the carbon fiber was significantly improved.

[0063] Example 3:

[0064] The preparation method of metal-modified carbon fiber in Example 3 mainly includes broadening and dispersion treatment, activation treatment, and main coating treatment, specifically including the following steps in sequence:

[0065] Step 1, Cleaning treatment: The carbon fiber is ignited at a high temperature of 450℃ for 30 minutes; then it is ultrasonically cleaned with 50% ethanol at room temperature for 20 minutes; then it is washed with deionized water and dried.

[0066] Step 2, Broadening and Dispersion Treatment: The carbon fibers treated in Step 1 are brought into contact with two tension rollers in the vibratory blowing device. The intermediate vibrating roller is subjected to high-frequency reciprocating action relative to the two tension rollers. The vibration frequency of the vibrating roller is 8Hz and the amplitude is 18mm. At the same time, the carbon fibers are dispersed under the cooperation of the fan-shaped airflow from the nozzle. The airflow velocity is 11m / s. The carbon fiber filaments deflect to both sides and move outward, and are broadened and shaped by the tension rollers.

[0067] Step 3, Activation Treatment: This includes roughening, sensitization, and activation performed sequentially. Roughening involves immersing the carbon fibers treated in Step 2 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 ammonia, at 40°C for 30 minutes. After activation, the carbon fibers are washed with deionized water and dried.

[0068] Step 4, Main Plating Treatment: Composite nickel plating. Connect the carbon fiber treated in Step 3 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 mass ratio of carbon fiber to plating solution volume is 1g:500ml. The plating solution contains: 20g / L nickel sulfate, 24g / L sodium hypophosphite, 6.5g / L sodium citrate, and 13.5g / L ammonium chloride. Adjust the pH of the plating solution to 9 with ammonia. The voltage is 5V, and the energizing time is set to 10s. After 10s, 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 50℃ and the plating time for 15min. After plating, clean and dry the carbon fiber.

[0069] Figure 3 The image shown is a 2000x magnified scanning electron microscope image of the cross-section of the metal-modified carbon fiber prepared in Example 3. Figure 4 The image shown is a 1000x magnified scanning electron microscope image of the surface of the metal-modified carbon fiber prepared in Example 3. Figure 5 The image shown is a 10,000x magnified scanning electron microscope image of the surface of the metal-modified carbon fiber prepared in Example 3.

[0070] Example 4:

[0071] Example 4 is basically the same as Example 3, and the similarities will not be repeated. The difference is that, compared with Example 3, the preparation method of metal-modified carbon fiber in Example 4 replaces the sensitization and activation in step 3 with electrochemical oxidation. Specifically, step 3 of Example 3 is replaced with: the activation treatment includes roughening and electrochemical oxidation performed sequentially. Roughening involves immersing the carbon fiber treated in step 2 of Example 3 in a roughening solution containing 220 g / L ammonium persulfate and 100 ml / L hydrogen chloride, at a temperature of 50°C for 15 min; or, the roughening solution is a 65% nitric acid solution, at a temperature of 90°C for 30 min. After roughening, the carbon fiber is washed with deionized water and dried. Electrochemical oxidation involves connecting the roughened carbon fiber to the positive terminal of a power source and the negative terminal to graphite. The electrolyte is a 0.6 wt% sulfuric acid solution. The carbon fiber and graphite are placed in the electrolyte and a current of 0.3 A is applied for 15 seconds. After electrochemical oxidation, the carbon fiber is washed with deionized water and dried.

[0072] Figure 6 The image shown is a 2000x magnified scanning electron microscope image of the cross-section of the metal-modified carbon fiber prepared in Example 4. Figure 7 The image shown is a 1000x magnified scanning electron microscope image of the surface of the metal-modified carbon fiber prepared in Example 4. Figure 8 The image shown is a 10,000x magnified scanning electron microscope image of the surface of the metal-modified carbon fiber prepared in Example 4.

[0073] Example 5:

[0074] Example 5 is basically the same as Example 3 or Example 4, and the similarities will not be repeated. The difference is that, compared with Example 3 or Example 4, the preparation method of metal modified carbon fiber in Example 5 replaces the energizing voltage in step 4 with 15V and the energizing time with 15s.

[0075] Example 6:

[0076] Example 6 is basically the same as Example 3 or Example 4, and the similarities will not be repeated. The difference is that, compared with Example 3 or Example 4, the preparation method of metal modified carbon fiber in Example 6 replaces the energizing voltage in step 4 with 10V and the energizing time with 120s.

[0077] Based on the preparation method of metal-modified carbon fiber of the present invention, the present invention provides a metal-modified carbon fiber, which is prepared by the above-described preparation method of metal-modified carbon fiber.

[0078] 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 method for preparing metal-modified carbon fibers, characterized in that, The process includes a primary plating treatment, which is a composite plating process. The composite plating process involves connecting the carbon fiber to the negative terminal of a power supply and connecting the coating metal to the positive terminal of a power supply. The carbon fiber and the coating metal are placed in a plating solution and current is applied. After a set energizing time, the current is cut off. Then, the coating metal is removed from the plating solution, allowing the carbon fiber to react spontaneously in the plating solution until the plating process is completed, resulting in a composite coating on the surface of the carbon fiber.

2. The method for preparing metal-modified carbon fibers according to claim 1, characterized in that, It also includes a graphene layer treatment performed before the main coating process, wherein the graphene layer treatment is performed by generating a graphene layer on the surface of the carbon fiber and thinning the graphene layer.

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

4. The method for preparing metal-modified carbon fibers according to claim 2, characterized in that, The graphene layer is thinned using a femtosecond laser.

5. The method for preparing metal-modified carbon fibers according to claim 1, characterized in that, It also includes a broadening and dispersion treatment performed before the main coating treatment, wherein the broadening and dispersion treatment is to broaden and thin the carbon fibers to disperse the carbon fiber filaments.

6. The method for preparing metal-modified carbon fibers according to claim 5, characterized in that, The widening and dispersion treatment employs vibration jet widening.

7. The method for preparing metal-modified carbon fibers according to claim 1, characterized in that, It also includes a secondary plating process performed before or after the primary plating process, wherein the secondary plating process is electroplating, electroless plating, or the composite plating.

8. The method for preparing metal-modified carbon fibers according to claim 7, characterized in that, The primary plating process involves nickel plating, and the secondary plating process involves silver plating.

9. The method for preparing metal-modified carbon fibers according to claim 1, characterized in that, It also includes an activation process performed prior to the main coating process, the activation process including carbon fiber anodizing.

10. A metal-modified carbon fiber, characterized in that, It is prepared by the method for preparing metal-modified carbon fibers as described in any one of claims 1 to 9.

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