A continuous fiber surface coating system and method

Abstract

This invention discloses a continuous fiber surface coating system and method. The system includes a cleaning unit, a sensitization unit, an activation unit, a coating unit, and a fiber guiding unit. The fiber guiding unit transports the fibers sequentially through the cleaning unit, sensitization unit, activation unit, and coating unit. The method includes S1, cleaning the fibers; S2, sensitizing the fibers; S3, activating the fibers; and S4, coating the fibers. The continuous fiber surface coating system of this invention enables automated coating of continuous fiber surfaces, achieves uniform traction, and uses ultrasonic and aeration to accelerate ion migration in the coating solution, resulting in uniform, controllable thickness single-element or composite coatings. The continuous fiber surface coating method of this invention causes minimal fiber damage, maintains high strength, produces a uniform fiber interface layer, and exhibits low internal loss and no burrs.

Description

Technical Field

[0001] This invention relates to the field of fiber surface treatment technology, and in particular to a low-cost, high-efficiency continuous fiber surface coating system and method that can meet the needs of large-size, multi-filament applications. Background Technology

[0002] With the continuous advancement of aerospace technology, advanced aerospace equipment places higher demands on the lightweight, high-temperature resistance, strength, and modulus properties of materials. High-specific-strength, high-specific-modulus fiber-reinforced aluminum matrix composites have become a superior choice. Silicon carbide fiber, as a typical high-performance ceramic fiber, exhibits good interfacial compatibility with aluminum. Furthermore, silicon carbide fiber possesses excellent high-temperature resistance and oxidation resistance, making its application in aluminum matrix composites effective in improving the material's strength, temperature resistance, corrosion resistance, and fracture toughness. However, due to the poor wettability of silicon carbide fiber with the aluminum alloy matrix, a coating treatment is required on the surface of the silicon carbide fiber when preparing silicon carbide fiber-reinforced aluminum matrix composites using the liquid-phase method. This coating improves the wettability between the fiber and the matrix, enhances the interfacial bonding strength, and inhibits harmful interfacial reactions, which is crucial for improving the overall performance of the composite material.

[0003] Silicon carbide fiber surface coating can be carried out through both physical and chemical methods. Common fiber coating methods include chemical plating, physical vapor deposition (PVD), chemical vapor deposition (CVD), and electroplating. Among them, chemical plating and electroplating are relatively convenient and simple, have low equipment requirements, and have good application prospects.

[0004] However, most existing technologies for preparing surface coatings of silicon carbide fibers can only prepare surface coatings for relatively short fibers in batches. For example, patent application number CN201710061198.8 requires cutting the fibers before electroplating with nickel. The cut fibers are difficult to weave, limiting the size of the fiber reinforcement. Patent application number CN201811608906.6 requires large-scale dedicated magnetron sputtering equipment, which is relatively expensive. There is a lack of corresponding devices and processes on the market that can meet the needs of preparing large-size, multi-tow fiber composite materials. Summary of the Invention

[0005] This invention provides a continuous fiber surface coating system and method to solve the technical problems of fiber size limitations and high device cost in the prior art.

[0006] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows: A continuous fiber surface coating system includes a cleaning unit, a sensitization unit, an activation unit, a coating unit, and a fiber guiding unit. The fiber guiding unit transports the fibers sequentially through the cleaning, sensitization, activation, and coating units. After passing through the fiber guiding unit, the continuous fibers enter the cleaning unit to increase the surface roughness, then enter the sensitization and activation units, and finally enter the coating unit for coating treatment. Through the cooperation of each unit, continuous coating can be achieved while the fibers remain continuous under normal temperature and pressure, resulting in high coating efficiency, good coating uniformity, and controllable thickness.

[0007] As a further preferred embodiment of the above technical solution, the fiber guiding unit includes a yarn feeding device installed before the cleaning unit and a guiding device installed in the cleaning unit, sensitization unit, activation unit and coating unit; the yarn feeding device includes a fiber yarn frame, a yarn collecting plate and a yarn dispensing device arranged sequentially along the fiber transport direction, the fibers placed on the fiber yarn frame are introduced to the yarn dispensing device through the yarn collecting plate, so that the continuous fiber bundle is unfolded and laid out in parallel before being sent into the cleaning unit.

[0008] As a further preferred embodiment of the above technical solution, the fiber yarn frame is composed of transverse keels and longitudinal keels. The longitudinal keels are arranged side by side, and the surfaces of the longitudinal keels are spaced apart with slots for mounting the transverse keels. The transverse keels are spaced apart with fiber spool supports for loading fiber spools. The fiber yarn frame can select multiple transverse keels connected in parallel according to the needs of different fiber bundles, loading multiple fiber spools, thereby controlling the bundle-gathering effect of the fiber bundles. This allows the system of the present invention to select different strands of fiber for filament coating as needed, meeting the requirements for surface coating of large-size, multi-bundle continuous fibers.

[0009] As a further preferred embodiment of the above technical solution, the gap of the fiber collecting plate is wider than the width of the fiber bundle, and its thickness is slightly greater than the thickness of the fiber bundle; rubber rollers are installed in front of and / or behind the fiber collecting plate. The rubber rollers in front of and behind the fiber collecting plate can prevent the fibers from twisting and damaging them.

[0010] As a further preferred embodiment of the above technical solution, the fiber guiding unit further includes a winding machine installed after the coating unit.

[0011] As a further preferred embodiment of the above technical solution, the cleaning unit includes a cleaning tank and a water tank arranged in sequence, and a guide device is installed below the liquid level of both the cleaning tank and the water tank.

[0012] As a further preferred embodiment of the above technical solution, the plating unit includes a chemical plating tank and an electroplating tank arranged sequentially; a conductive wheel with the negative terminal of an external power supply is installed above the liquid level in the electroplating tank, and a metal electrode plate with the positive terminal of an external power supply is also installed inside the electroplating tank. The plating unit can be selected for single-element plating and composite plating as needed.

[0013] As a further preferred embodiment of the above technical solution, the number of metal electrode plates is three, which are symmetrically installed on the inner surface of the front end, the middle section and the inner surface of the rear end of the electroplating tank; the number of conductive wheels is consistent with the number of metal electrode plates.

[0014] As a further preferred embodiment of the above technical solution, an ultrasonic generator is installed at the bottom of the sensitization unit, the activation unit, and the chemical plating tank. The ultrasonic generator is located at the bottom of the container directly below the long, continuous fiber section.

[0015] As a further preferred embodiment of the above technical solution, a washing tank is provided between the sensitization unit and the activation unit, and between the activation unit and the coating unit, for cleaning the sensitized and activated fibers. The washing tank is used to clean the sensitized and activated fibers, removing the sensitizing and activating solutions adsorbed on the fiber surface.

[0016] Based on the same technical concept, the present invention also provides a method for coating a continuous fiber surface, characterized in that it is implemented using the continuous fiber surface coating system described above, and includes the following steps: S1. The fiber is fed into the cleaning unit via the fiber guiding unit for cleaning. S2. The cleaned fibers are introduced into the sensitization unit through the fiber guiding unit and sensitized with sensitizing solution. S3. The sensitized fibers are introduced into the activation unit through the fiber guiding unit and activated with an activation solution. S4. The sensitized fibers are sent to the coating unit via the fiber guiding unit for coating.

[0017] As a further preferred embodiment of the above technical solution, in S1 the fibers are sequentially washed with a cleaning solution and water, wherein the cleaning solution includes one of acetone and anhydrous ethanol.

[0018] As a further preferred embodiment of the above technical solution, the sensitizing solution in S2 is an acidic stannous chloride solution. The stannous chloride solution is prepared by adding 0.1~1 mol / L HCl solution to 5~15 g / L SnCl solution to adjust the pH of the stannous chloride solution to 2~3.

[0019] As a further preferred embodiment of the above technical solution, the activation solution in S3 is a mixed solution of AgNO3 solution and ammonia water. The concentration of AgNO3 solution is 0.02~0.1mol / L, the concentration of ammonia water is 25%, and the addition amount is 5~10mL / L.

[0020] As a further preferred embodiment of the above technical solution, the fibers in S4 undergo chemical plating and / or electroplating treatment; the chemical plating solution is a mixture of copper sulfate, formaldehyde, potassium sodium tartrate, and sodium hydroxide, wherein the concentration of copper sulfate is 10-12 g / L, the concentration of formaldehyde is 8-10 mL / L, the concentration of potassium sodium tartrate is 20-40 g / L, and the concentration of sodium hydroxide is 16-18 g / L; the electroplating solution includes one of copper plating solution, nickel plating solution, and tin plating solution, wherein the copper plating solution is prepared by copper pyrophosphate, potassium pyrophosphate, ammonium citrate, ammonia, hydrogen peroxide, and activated carbon, wherein the concentration of copper pyrophosphate is 60-70 g / L, the concentration of potassium pyrophosphate is 280-320 g / L, and the concentration of ammonium citrate is 20-25 g / L. The concentrations of the following components are specified: g / L of ammonia, 2-3 ml / L of hydrogen peroxide, 30% (added at 1-2 mL / L), and 3-10 g / L of activated carbon. The electroplating nickel solution is prepared from nickel sulfate, nickel chloride, and boric acid. The nickel plating solution contains 360-380 g / L of nickel sulfate, 18-20 g / L of sodium chloride, 45-50 g / L of boric acid, 2.5-3 g of saccharin, 0.4-0.5 g / L of 1,4-butynediol, 0.15-0.2 g / L of polyethylene glycol, and 40-50 g / L of silicon chloride (<0.5 μm).

[0021] As a further preferred embodiment of the above technical solution, the electroless plating process is carried out with the assistance of ultrasound. The frequency range of the ultrasound is 20~40KHz, the period of the ultrasound is 3~6s, and the emission duration of the ultrasound in a single period is 6~12s.

[0022] As a further preferred embodiment of the above technical solution, the fibers include silicon carbide fibers, alumina fibers, and quartz fibers.

[0023] As a further preferred embodiment of the above technical solution, after the fiber in S4 has been coated, it is wound up using a winding machine at a speed of 10~50cm / min.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides a system for coating a continuous fiber surface, which can realize automated coating of continuous fiber surface; the fiber is kept in a continuous state throughout the process, which can achieve uniform traction, and the coating solution is stirred by ultrasound and aeration to accelerate the migration of coating ions, which can achieve uniform coating and controllable thickness of single or composite coating.

[0025] This invention provides a method for coating a continuous fiber surface. Compared to other chemical plating and electroplating methods, the coating process does not involve etching or cleaning the fibers. The entire coating process causes minimal damage to the fibers, resulting in high fiber strength retention after coating. The prepared fiber interface layer is uniform and consistent throughout, with minimal loss of internal silicon carbide fibers and no burrs. The invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0026] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the system for the continuous fiber surface coating of Example 1; Figure 2 Microscopic morphology of continuous copper-plated SiC fibers obtained from the continuous fiber surface coating system of Example 1; Figure 3 The image shows the microstructure of the coating on the SiC fiber cloth in Comparative Example 1. Figure 4 The image shows the microstructure of the SiC fiber coating in Comparative Example 3. Figure 5 The image shows the microstructure of the SiC fiber coating in Comparative Example 5. Figure 6 This is a schematic diagram of the wire collecting plate in Example 1; Figure 7 This is a schematic diagram of the fiber yarn frame in Example 1.

[0027] Legend: 1. Fiber yarn frame; 11. Longitudinal keel; 12. Transverse keel; 13. Fiber yarn spool support; 2. Guide wheel; 3. Yarn collecting plate; 31. Base; 32. Yarn collecting strip support; 33. Yarn collecting strip; 4. Yarn feeding device; 41. Tension roller; 42. Yarn guide roller; 51. Cleaning tank; 52. Water tank; 53. Yarn guide wheel; 6. Sensitization tank; 7. Washing tank; 8. Activation tank; 9. Ultrasonic generating device; 10. Chemical plating tank; 11. Electroplating tank; 111. Metal electrode plate; 112. Vent; 113. Conductive wheel; 12. Winding machine. Detailed Implementation

[0028] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0029] Example 1: like Figure 1 As shown, the continuous fiber surface coating system of this embodiment includes: Fiber guiding unit: includes a yarn feeding device, a guiding device (thread guide roller 53), and a winding machine 12 installed in front of the cleaning tank 51. The yarn feeding device is installed in front of the cleaning unit and includes a fiber yarn frame 1, a guide roller 2, a yarn collecting plate 3, a yarn discharging device 4, and a tension roller 41; Figure 7 As shown, the fiber yarn frame 1 is composed of transverse keels 12 and longitudinal keels 11. The longitudinal keels 11 are fixedly installed and arranged side by side, with slots spaced apart on them. The transverse keels 12 are detachably installed in the slots. Fiber bobbin supports 13 are provided on the transverse keels 12 for loading fiber bobbins. Multiple transverse keels 12 can be connected in parallel to load multiple fiber bobbins according to the needs of different fiber bundles. The fibers placed on the fiber yarn frame are guided by guide wheels 2 and then pass through the yarn collecting plate 3 (e.g., ...). Figure 6 As shown, the yarn collecting plate 3 consists of a base 31, a yarn collecting strip support 32, and a yarn collecting strip 33 fixed on the yarn collecting strip support 32. The yarn is introduced into the yarn dispensing device 4 (consisting of a tension roller 41 and a yarn guiding roller 42), so that the continuous fiber bundle is unfolded and laid out in parallel, and then stretched by the tension roller 41 before being sent into the cleaning unit. Cleaning unit: includes a separate cleaning tank 51 and a water tank 52. The cleaning unit is equipped with 5 wire guide rollers 53. The cleaning tank 51 is filled with cleaning fluid, and the water tank 52 is filled with water. There is one wire guide roller 53 below the liquid surface in the cleaning tank 51 and below the water level in the water tank 52. Sensitization unit: includes a sensitization tank 6 containing a sensitizing solution, 5 wire guide rollers 53 are provided in the sensitization tank 6, and 3 wire guide rollers 53 are provided below the sensitizing solution level, wherein the sensitizing solution is an acidic stannous chloride solution; Activation unit: includes an activation tank 8 containing an activation solution, with 5 wire guide rollers 53 inside the activation tank 8 and 3 wire guide rollers 53 below the activation solution level; wherein the activation solution is a mixture of AgNO3 solution and ammonia water; The plating unit includes a chemical plating tank 10 and an electroplating tank 11. The chemical plating tank 10 contains a chemical plating solution and has five wire guide rollers 53. Three wire guide rollers 53 are located below the chemical plating solution level. An ultrasonic generator 9 is also located at the bottom of the chemical plating tank 10. The ultrasonic waves in the ultrasonic generator 9 operate at dual frequencies, with a frequency range of 20 kHz. The working cycle of the ultrasonic generator 9 is 6 seconds, followed by a 3-second pause before starting the next cycle. The electroplating tank 11 contains an electroplating solution and has four wire guide rollers 53 located below the electroplating solution level. Three conductive rollers 113 connected to the negative terminal of a power supply are located above the electroplating solution. Three metal electrode plates 111 connected to the positive terminal of a power supply are also located in the electroplating tank 11 (located at the front, middle, and rear ends of the electroplating tank 11, respectively). A water washing tank 7 is provided between the sensitization tank 6 and the activation tank 8, and between the activation tank 8 and the electroless plating tank 10. An ultrasonic generator 9 is also provided in the sensitization tank 6 and the activation tank 8. A vent 112 is provided at the bottom of the electroless plating tank 10 and the bottom of the electroplating tank 11.

[0030] Example 2: The method for coating a continuous fiber surface in this embodiment uses the continuous fiber surface coating system of Example 1 to coat a copper layer on a continuous silicon carbide fiber surface. The specific method is as follows: S1. Cleaning: Silicon carbide fibers that have been desized at 600℃ for 1 hour are wound onto a fiber filament bobbin. The wound silicon carbide fiber bobbin is placed on the fiber yarn rack 1. After the continuous silicon carbide fiber bundle is unwound, it is guided to the yarn laying device 4 through the guide wheel 2 and the yarn collecting plate 3. After passing through the gap and adjusting to the same plane, the continuous fiber bundle is spread out and laid in parallel. Under the traction of the tension roller 41 with a tension of 80CN, the continuous silicon carbide fiber bundle is sent into the cleaning tank 51 and the water tank 52, so that the silicon carbide fibers are cleaned and washed with water respectively under the acetone cleaning liquid surface and the water level. S2. Sensitization: The cleaned silicon carbide fibers are introduced into the sensitization tank 6 through the thread guide wheel 53, allowing the sensitization solution to fully wet the continuous fibers for sensitization treatment (the sensitization solution in the sensitization tank 6 is prepared by dissolving stannous chloride in a 0.01 mol / L hydrochloric acid solution, with a stannous chloride addition ratio of 5 g / L). At the same time, ultrasound is applied throughout the sensitization process to cause the gas in the bundle to diffuse directionally into cavitation bubbles, so that the fibers are completely dispersed in the sensitization solution, thereby achieving the purpose of removing the gas in the bundle and preventing monofilament adhesion. S3, Activation: After passing through the sensitization tank 6, the fiber is introduced into the washing tank 7. After washing, a colloid is formed on the surface. Then, the fiber is introduced into the activation tank 8 to allow the activation solution to fully wet and activate the fiber (the activation solution in the activation tank 8 is prepared by adding about 8 ml / L of 25% ammonia water to 0.02 mol / L silver nitrate under magnetic stirring until a brown precipitate is formed and dissolved). Ultrasonic waves are applied throughout the activation process. S4. Chemical Plating: After the activated silicon carbide fiber is washed in the water washing tank 7, the fiber is introduced into the chemical plating tank 10 (the preparation method of the chemical copper plating solution in the chemical plating tank 10 is as follows: 40g of potassium sodium tartrate and 18g of sodium hydroxide are dissolved in 500ml of water to form solution B, 12g of copper sulfate is dissolved in 500ml of water and then 8ml of formaldehyde solution is added and stirred evenly to form solution A. Solution B is stirred continuously and solution A is slowly added to solution B. The pH is tested to be about 12). The fiber is repeatedly wrapped in the chemical plating solution to make the fiber longer when immersed in the plating solution. Ultrasonic assistance is applied during the plating process. The ultrasonic waves work at dual frequencies of 28KHZ and 40KHZ, and work periodically. After a 6-second cycle, there is a 3-second pause before starting the next cycle. S5. Electroplating: The chemically plated fibers are fed into the electroplating tank 11 via a conductive wheel 113 connected to the negative terminal of a safety power supply. (The electroplating solution in the electroplating tank 11 is a copper plating solution. The preparation method of the copper plating solution is as follows: dissolve 70g of copper pyrophosphate, 320g of potassium pyrophosphate, and 25g of ammonium citrate in 1L of clean water, add 3ml of ammonia water, mix evenly to obtain 1L of plating solution, add 150ml of 30% hydrogen peroxide and 10g of activated carbon, stir thoroughly, and heat in a water bath to 50℃ for 60 minutes. Then filter out the activated carbon and impurities using filter paper.) Three anode copper plates are placed in the electroplating tank 11 and connected to the positive terminal of a constant current power supply. The conductive wheel 113 is connected to the negative terminal of the constant current power supply. The constant DC current is set to 0.5A. After powering on, the ultrasonic generator 9 in the electroplating tank 11 is turned on to make the fibers evenly dispersed for electroplating. S6. After electroplating is completed, start the rewinder 12 and keep its rewinding speed at 10cm / min so that the fiber moves continuously in the plating tank and covers a continuous copper plating layer.

[0031] This successfully prepared multiple bundles of continuously copper-plated SiC fibers, with microstructures as follows: Figure 2 As shown, Figure 2 The left side shows the cross-section of the coated fiber, and the right side shows the surface of the coated fiber. The strength of the fiber was tested, and the results are shown in Table 1.

[0032] In this embodiment, a copper layer is plated on the surface of silicon carbide fibers, resulting in a uniform and continuous thickness without any breakage or discontinuity. The silicon carbide fiber body remains undamaged, and the strength of the fiber bundle does not significantly decrease after the copper layer is plated on the silicon carbide surface. The preform woven with continuously copper-plated fibers in this embodiment has a copper layer plated within the fiber bundle and at the fiber weaving overlaps, which ensures a complete and uninterrupted interface layer between the fiber and the matrix in the composite material, providing complete interface protection for the fiber reinforcement.

[0033] Table 1: Comparison of fiber bundle strength before and after copper plating in Example 1

[0034] Example 3: The method for coating a continuous fiber surface in this embodiment uses the continuous fiber surface coating system of Example 1 to coat a copper layer on a continuous silicon carbide fiber surface. The specific method is as follows: S1. Cleaning: Silicon carbide fibers that have been desized at 600℃ for 1 hour are wound onto a fiber filament bobbin and placed on a fiber yarn rack 1. After the continuous silicon carbide fiber bundle is unwound, it is guided to the yarn laying device 4 by the guide wheel 2 and the yarn collecting plate 3, so that the continuous fiber bundle is unfolded and laid out in parallel. Under the traction of the tension roller 41 with a tension of 80CN, the continuous silicon carbide fiber bundle is sent into the cleaning tank 51 and the water tank 52, so that the silicon carbide fibers are cleaned and washed with water respectively under the acetone cleaning liquid surface and the water level. S2. Sensitization: The cleaned silicon carbide fibers are introduced into the sensitization tank 6 through the thread guide wheel 53, allowing the sensitization solution to fully wet the continuous fibers for sensitization treatment (the sensitization solution in the sensitization tank 6 is prepared by dissolving 5g of stannous chloride in 100ml of 0.01mol / L hydrochloric acid solution and adding water to make up to 1L). At the same time, ultrasound is applied throughout the sensitization process to cause the gas in the bundle to diffuse directionally into cavitation bubbles, so that the fibers are completely dispersed in the sensitization solution, thereby achieving the purpose of removing the gas in the bundle and avoiding monofilament adhesion. S3, Activation: After passing through the sensitization tank 6, the fiber is introduced into the washing tank 7. After washing, a colloid is formed on the surface. Then, the fiber is introduced into the activation tank 8 to allow the activation solution to fully wet and activate the fiber (the activation solution in the activation tank 8 is prepared by adding about 8 ml / L of 25% ammonia water to 0.02 mol / L silver nitrate under magnetic stirring until a brown precipitate is formed and dissolved). Ultrasonic waves are applied throughout the activation process. S4. Chemical Plating: After the activated silicon carbide fibers are washed in water washing tank 7, they are introduced into chemical plating tank 10 (the chemical copper plating solution is prepared by dissolving 40g of potassium sodium tartrate and 18g of sodium hydroxide in 500ml of water to form solution B, and dissolving 12g of copper sulfate in 500ml of water and adding 8ml of formaldehyde solution and stirring until homogeneous to form solution A. Solution B is continuously stirred while solution A is slowly added to solution B, and the pH is tested to be approximately 12). The fibers are repeatedly wrapped in the chemical plating solution to ensure that the fiber immersion length in the plating solution is greater than 100cm. Ultrasonic waves are applied during the plating process. The ultrasonic waves operate at dual frequencies of 28kHz and 40kHz, and operate periodically. After a 6-second cycle, there is a 3-second pause before starting the next cycle. S5. Electroplating: The chemically plated fibers enter the electroplating tank 11 through the conductive wheel 113 connected to the negative terminal of the safety power supply (the electroplating solution in the electroplating tank 11 is a nickel plating solution. The preparation method of the nickel plating solution is to dissolve 350g of nickel sulfate, 60g of nickel chloride, and 40g of boric acid in 300ml of 50℃ hot water, mix them, add water to make up to 1000ml, let it stand to clarify, and then filter the precipitate with filter paper to complete the preparation of the nickel plating solution). Three anode copper plates are placed in the electroplating tank 11 and connected to the positive terminal of the constant current power supply. The conductive wheel 113 is connected to the negative terminal of the constant current power supply. The constant DC current is set to 0.7A. After the power is turned on, the ultrasonic generator 9 in the electroplating tank 11 is turned on to make the fibers evenly dispersed and electroplating is carried out. S6. After electroplating is completed, start the winding machine 12 and keep its winding speed at 10cm / min so that the fiber moves continuously in the plating tank and covers a continuous nickel plating layer.

[0035] This led to the successful preparation of multiple bundles of continuously nickel-plated SiC fibers.

[0036] Comparative Example 1: This comparative example does not use the continuous fiber surface coating system of Example 1. The specific process steps for the fiber surface coating are as follows: SiC fibers were woven into plain-weave SiC fiber cloth and copper-plated. The cloth was then subjected to high-temperature desizing at 600℃ in a muffle furnace for 1 hour. The cloth was then immersed in anhydrous ethanol in a cleaning tank to remove residual carbon and dust from the fiber surface. Finally, it was washed with water on the other side of the partition to remove the ethanol and complete the degreasing treatment for 5 minutes. To prepare the sensitizing solution, dissolve 5g of stannous chloride in 100ml of 0.01mol / L hydrochloric acid solution, add water to make up to 1L and pour into the sensitizing tank; apply ultrasound throughout the sensitization process to cause the gas in the bundle to diffuse directionally into cavitation bubbles, so that the fiber is completely dispersed in the sensitizing solution, and the sensitization time is 5 minutes. The fiber cloth was then placed into the second cleaning tank and soaked in clean water for 10 minutes, after which a colloid formed on the surface. An activation solution was prepared in an activation tank. 0.02 mol / L silver nitrate was added to 25% ammonia water under magnetic stirring until a brown precipitate was formed and dissolved. The activation process required ultrasonic treatment throughout and lasted for 5 minutes. The fibers were then washed in the third cleaning tank for 5 minutes. Add SiC fiber alkaline electroless copper plating solution to the electroless plating bath. The formula is as follows: dissolve 40g of potassium sodium tartrate and 18g of sodium hydroxide in 500ml of water to form solution B; dissolve 12g of copper sulfate in 500ml of water and then add 8ml of formaldehyde solution and stir until homogeneous to form solution A. While continuously stirring solution B, slowly add solution A to solution B. The pH test result is approximately 12. Ultrasonic waves are required during the plating process, which lasts for 30 minutes. After electroless copper plating, the SiC fiber cloth is clamped with a copper plate and connected to the cathode of a constant current power supply. The electroplated copper plate is connected to the anode of a constant current power supply. Then, after electroplating with 1.5A DC for 10 minutes, a copper-plated layer is obtained on the SiC fiber cloth.

[0037] In this comparative example, no electroplated layer was formed in the areas previously not covered by the electroless copper plating layer, and the SiC fiber bundles within them could not be uniformly dispersed. There was no obvious plating distribution at the overlapping areas of the SiC fibers, and the plating thickness varied considerably. The microstructure of the SiC fiber cloth plating is as follows: Figure 3 As shown.

[0038] Comparative Example 2: This comparative example does not use the continuous fiber surface coating system of Example 1. The specific process steps for the fiber surface coating are as follows: Unglued or desized silicon carbide fibers are fixed onto a plastic bracket; The fixed SiC fibers were placed in a cleaning tank and immersed in anhydrous ethanol to remove residual carbon and dust from the fiber surface. Then, the fibers were rinsed with water on the other side of the partition to remove the ethanol and complete the degreasing treatment for 5 minutes. To prepare the sensitization solution, dissolve 5g of stannous chloride in 100ml of 0.01mol / L hydrochloric acid solution, add water to bring the volume to 1L, and pour the solution into the sensitization tank. During the entire sensitization process, apply ultrasound to allow the gas within the fiber to diffuse directionally into cavitation bubbles, ensuring complete dispersion of the fiber in the sensitization solution. The sensitization time is 5 minutes. The fibers are then immersed in a second cleaning tank and washed with water for 10 minutes to form a colloid on the fiber surface.

[0039] An activation solution was prepared in an activation tank. 0.02 mol / L silver nitrate was added to 25% ammonia water under magnetic stirring until a brown precipitate was formed and dissolved, thus completing the preparation. Ultrasonic waves were applied throughout the activation process. The fibers were then washed in the third cleaning tank. Add an alkaline electroless copper plating solution for SiC fibers to the electroless plating bath. The formula is as follows: dissolve 40g of potassium sodium tartrate and 18g of sodium hydroxide in 500ml of water to form solution B; dissolve 12g of copper sulfate in 500ml of water and then add 8ml of formaldehyde solution and stir until homogeneous to form solution A. Slowly add solution A to solution B while continuously stirring solution B. The pH is tested to be approximately 12. Place the fixed fibers into the electroless plating bath. Ultrasonic waves are required during the plating process, which lasts for 30 minutes. After electroless copper plating, SiC fibers were clamped with a copper plate and connected to the cathode of a constant current power supply. The electroplated copper plate was connected to the anode of a constant current power supply. After electroplating with 1.5A DC for 10 minutes, no electroplating layer was formed in the areas that were not previously covered by the electroless copper plating layer.

[0040] In this comparative example, no coating appeared at the contact point between the copper-plated fiber and the plastic support, which affected the uniformity of the coating distribution. Furthermore, the fiber hardened after being fixed, which was not conducive to subsequent weaving.

[0041] Comparative Example 3: The specific process steps of this comparative example are different from those of Example 2, except that ultrasonic assistance is not used in S2 sensitization, S3 activation and S4 electroless plating in this comparative example.

[0042] The silicon carbide fibers with a nickel-plated surface prepared in this comparative example exhibit a "black core" phenomenon, where some monofilaments within the bundle are neither covered by the electroless copper plating nor the nickel plating. The coating distribution uniformity is also poor. Figure 4 The image shows the microstructure of the SiC fiber coating in Comparative Example 3. Comparative Example 4: The specific process steps of this comparative example are different from those of Example 2, except that this comparative example does not perform water washing after S2 sensitization and directly enters the activation tank for S3 activation.

[0043] The silicon carbide fibers with nickel plating prepared in this comparative example have partially exposed fibers, severe surface plating peeling, and poor plating adhesion.

[0044] Comparative Example 5: The specific process steps of this comparative example differ from those of Example 2 in that: ① the conductive wheel 113 of the system in Example 1 is not used, but is replaced with a sheet electrode; ② different concentration ranges of sensitizing solution and activating solution are used, and the specific steps and methods are as follows: S1. Cleaning: Silicon carbide fibers that have been desized at 600℃ for 1 hour are wound onto a fiber filament bobbin and placed on a fiber yarn rack 1. After the continuous silicon carbide fiber bundle is unwound, it is guided to the yarn laying device 4 by the guide wheel 2 and the yarn collecting plate 3, so that the continuous fiber bundle is unfolded and laid out in parallel. Under the traction of the tension roller 41 with a tension of 80CN, the continuous silicon carbide fiber bundle is sent into the cleaning tank 51 and the water tank 52, so that the silicon carbide fibers are cleaned and washed with water respectively under the surface of anhydrous ethanol cleaning liquid and under the surface of the water tank. S2. Sensitization: The cleaned silicon carbide fiber is introduced into the sensitization tank 6 through the thread roller 53, so that the sensitization solution can fully wet the continuous fiber for sensitization treatment (the sensitization solution in the sensitization tank 6 is prepared by dissolving 15g of stannous chloride in 100mL of 0.01mol / L hydrochloric acid solution and adding water to make up to 1L). S3, Activation: After passing through the sensitization tank 6, the fiber is introduced into the washing tank 7. After washing, a colloid is formed on the surface. Then, the fiber is introduced into the activation tank 8 to allow the activation solution to fully wet and activate the fiber (the activation solution in the activation tank is prepared by adding about 8 ml / L of 25% ammonia water to 0.1 mol / L silver nitrate under magnetic stirring until a brown precipitate is generated and dissolved). Ultrasonic waves are applied throughout the activation process. S4. Chemical Plating: After the activated silicon carbide fibers are washed in water washing tank 7, they are introduced into chemical plating tank 10 (the chemical copper plating solution is prepared by dissolving 40g of potassium sodium tartrate and 18g of sodium hydroxide in 500ml of water to form solution B, and dissolving 12g of copper sulfate in 500ml of water and adding 8ml of formaldehyde solution and stirring until homogeneous to form solution A. Solution B is continuously stirred while solution A is slowly added to solution B, and the pH is tested to be approximately 12). The fibers are repeatedly wrapped in the chemical plating solution to ensure that the fiber immersion length in the plating solution is greater than 100cm. No ultrasonic waves are applied during the plating process. S5. Electroplating: The chemically plated fiber enters the electroplating tank 11 through a sheet electrode connected to the negative terminal of a safety power supply. (The electroplating solution in the electroplating tank 11 is a nickel plating solution. The preparation method of the nickel plating solution is to dissolve 350g of nickel sulfate, 60g of nickel chloride, and 40g of boric acid in 300ml of 50℃ hot water, mix them, add water to make up to 1000ml, let it stand to clarify, and then filter the precipitate with filter paper to complete the preparation of the nickel plating solution.) Three anode copper plates are placed in the electroplating tank 11 and connected to the positive terminal of a constant current power supply. The conductive wheel 113 is connected to the negative terminal of the constant current power supply, and the constant DC current is set to 0.7A. S6. After electroplating is completed, start the winding machine 12 and keep its winding speed at 10cm / min to prepare multiple bundles of continuously nickel-plated SiC fibers.

[0045] The silicon carbide fibers with a nickel-plated surface prepared in this comparative example exhibited high resistance to fiber movement, resulting in fiber splitting and breakage, which reduced the fiber's mechanical properties and hindered weaving. Partially exposed fibers and severe surface coating peeling also resulted in poor coating adhesion. Figure 5 The image shows the microstructure of the SiC fiber coating in Comparative Example 5. The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application. The above are merely preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. For those skilled in the art, improvements and modifications obtained without departing from the technical concept of the present invention should also be considered within the protection scope of the present invention.

Claims

1. A continuous fiber surface coating system characterized by, It includes a cleaning unit, a sensitization unit, an activation unit, a coating unit, and a fiber guiding unit; the fiber guiding unit is used to transport the fibers through the cleaning unit, sensitization unit, activation unit, and coating unit in sequence.

2. The continuous fiber surface plating system of claim 1, wherein, The fiber guiding unit includes a yarn feeding device installed before the cleaning unit and a guiding device installed in the cleaning unit, sensitization unit, activation unit and coating unit; the yarn feeding device includes a fiber yarn rack (1), a yarn collecting plate (3) and a yarn dispensing device (4) arranged sequentially along the fiber transport direction. The fibers placed on the fiber yarn rack (1) are introduced into the yarn dispensing device (4) through the yarn collecting plate (3), so that the continuous fiber bundle is unfolded and laid out in parallel before being sent into the cleaning unit; the fiber guiding unit also includes a winding machine (12) installed after the coating unit.

3. The continuous fiber surface plating system of claim 1 or 2, wherein, The plating unit includes a chemical plating tank (10) and an electroplating tank (11) arranged in sequence; a conductive wheel (113) with the negative terminal of an external power supply is installed above the liquid level of the electroplating tank (11), and a metal electrode plate (111) with the positive terminal of an external power supply is also installed inside the electroplating tank (11); there are three metal electrode plates (111), which are symmetrically installed on the inner surface of the front end, the middle section and the inner surface of the rear end of the electroplating tank (11); the number of conductive wheels (113) is consistent with the number of metal electrode plates (111).

4. The continuous fiber surface plating system of claim 3, wherein, An ultrasonic generator (9) is installed in the sensitization unit, activation unit and chemical plating tank (10).

5. The continuous fiber surface coating system according to claim 1 or 2, characterized in that, A water washing tank (7) is provided between the sensitization unit and the activation unit, and between the activation unit and the coating unit, for cleaning the sensitized fiber and the activated fiber.

6. A method for coating a continuous fiber surface, characterized in that, The continuous fiber surface coating system according to any one of claims 1-5 is implemented by comprising the following steps: S1. The fiber is fed into the cleaning unit via the fiber guiding unit for cleaning. S2. The cleaned fibers are introduced into the sensitization unit through the fiber guiding unit and sensitized with sensitizing solution. S3. The sensitized fibers are introduced into the activation unit through the fiber guiding unit and activated with an activation solution. S4. The sensitized fibers are sent to the coating unit via the fiber guiding unit for coating.

7. The method for coating a continuous fiber surface according to claim 6, characterized in that, In S1, the fibers are sequentially washed with a cleaning solution and water, wherein the cleaning solution includes one of acetone and anhydrous ethanol.

8. The method for coating a continuous fiber surface according to claim 6, characterized in that, The sensitizing solution is an acidic stannous chloride solution; the activating solution is a mixture of AgNO3 solution and ammonia water.

9. The method for coating a continuous fiber surface according to any one of claims 6-8, characterized in that, The fibers in S4 undergo chemical plating and / or electroplating treatment; the chemical plating solution is a mixture of copper sulfate, formaldehyde, potassium sodium tartrate, and sodium hydroxide; the electroplating solution includes one of copper plating solution, nickel plating solution, and tin plating solution, wherein the copper plating solution is prepared by copper pyrophosphate, potassium pyrophosphate, ammonium citrate, ammonia, hydrogen peroxide, and activated carbon, and the nickel plating solution is prepared by nickel sulfate, nickel chloride, and boric acid.

10. The method for coating a continuous fiber surface according to claim 9, characterized in that, During the chemical plating process, plating is performed with the assistance of ultrasound. The frequency range of the ultrasound is 20~40KHz, the period of the ultrasound is 3~6s, and the emission duration of the ultrasound in a single period is 6~12s.

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