Surface electrolytic oxidation treatment method of high-thermal-conductivity mesophase pitch-based carbon fiber

Abstract

The invention relates to the technical field of carbon fiber surface treatment, in particular to a surface electrolytic oxidation treatment method for high-thermal-conductivity mesophase pitch-based carbon fibers, which comprises the following steps: removing impurities and oxide layers on the surfaces of the mesophase pitch-based carbon fibers through cleaning, decontamination and drying treatment; after a direct-current power supply is connected, carrying out electrolytic oxidation on the surface of the carbon fiber by adopting a constant-current or constant-voltage method; deionized water is used for cleaning residual electrolyte, and the carbon fiber with the surface subjected to electrolytic oxidation is obtained after dehydration and drying treatment. According to the surface electrolytic oxidation treatment method of the high-thermal-conductivity mesophase pitch-based carbon fiber, Soxhlet extraction deep cleaning treatment, hydrogen peroxide pre-activation and three-stage washing conductivity control treatment are designed, the current density is dynamically calculated and designed to avoid local electrolytic overheating, and the ID / IG ratio is monitored to protect a graphite microcrystalline structure; temperature, bubble generation rate and conductivity parameters are monitored and fed back, and the functional group increment and ILSS are effectively improved through pre-oxidation and electrolytic oxidation cooperative treatment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of carbon fiber surface treatment, in particular to a surface electrolytic oxidation treatment method of high-thermal-conductivity mesophase pitch-based carbon fiber. BACKGROUND

[0002] The surface electrolytic oxidation treatment of mesophase pitch-based carbon fiber can improve its interface performance, introduce active functional groups on the fiber surface through controllable oxidation, thereby optimizing its application effect in composite materials, improving the surface activity of carbon fiber, and further strengthening the interface of composite materials, thus having wide application prospects in semiconductor material heat dissipation, aerospace military materials, and new energy lightweight structures.

[0003] According to the search, the patent for invention with the Chinese patent publication number CN113502662A discloses a surface treatment method of pitch-based graphite carbon fiber. The surface treatment method of carbon fiber in the patent for invention introduces active amino groups on the inert surface of pitch-based graphite carbon fiber, so that the surface of graphite carbon fiber has higher activity and better wettability, improves the oxidation degree of anodic oxidation etching, and can occur amide grafting reaction with the resin matrix to give it higher interlaminar shear strength.

[0004] However, the surface treatment method of pitch-based graphite carbon fiber sets the current density too high and does not associate with the surface area of the fiber, which can easily cause local over-oxidation of carbon fiber, rough post-processing cannot achieve graded control, and residual electrolyte can corrode the fiber or affect the interface bonding, so the surface electrolytic oxidation treatment method of high-thermal-conductivity mesophase pitch-based carbon fiber is proposed. SUMMARY

[0005] (I) Technical problems solved

[0006] In view of the deficiencies in the prior art, the present application provides a surface electrolytic oxidation treatment method of high-thermal-conductivity mesophase pitch-based carbon fiber, which has the advantages of designing an efficient electrolysis system and monitoring and feedback optimizing the whole process parameters, solving the problems of low efficiency of the electrolysis system of the surface treatment method of pitch-based graphite carbon fiber and lack of parameter monitoring and verification mechanism in the above background technology.

[0007] (II) Technical solutions

[0008] To achieve the above-mentioned purpose of designing an efficient electrolysis system and monitoring and feedback optimizing the whole process parameters, the present application provides the following technical solutions: a surface electrolytic oxidation treatment method of high-thermal-conductivity mesophase pitch-based carbon fiber, comprising the following steps:

[0009] S1. Surface pretreatment: removing impurities and oxidation layers on the surface of mesophase pitch-based carbon fiber through cleaning, decontamination and drying treatment;

[0010] S2. Electrolysis preparation: The electrolyte of desired concentration is prepared by high purity reagents and deionized water, the electrodes are installed in the electrolytic cell and the carbon fibers are loaded, and the electrolyte is injected;

[0011] S3. Electrolytic oxidation treatment: After connecting the direct current power supply, the constant current or constant voltage method is adopted, and the treatment current or voltage and treatment time are set to electrolytic oxidize the surface of the carbon fiber;

[0012] S4. Post-treatment: The residual electrolyte is cleaned with deionized water, and after dehydration and drying treatment, the surface electrolytic oxidation carbon fiber is obtained.

[0013] Preferably, the mesophase pitch-based carbon fiber surface is pretreated, and the specific steps include:

[0014] 1) The carbon fiber bundle is placed in a filter paper cylinder to ensure that the filling degree in the cylinder is ≤80%, and the filter paper cylinder and the carbon fiber bundle are placed in the distillation bottle of the soxhlet extractor;

[0015] 2) The distillation bottle is injected with acetone as the cleaning solvent, and the carbon fiber bundle is heated and cleaned at a heating temperature of 56-60°C for 4-6h, until the color of the solvent in the distillation bottle changes from colorless to light yellow, and finally to colorless and transparent;

[0016] 3) The hydrogen peroxide H2O2 solution with a concentration of 0.01-0.05 mol / L is used as the oxidation infiltrant, and the carbon fibers with a diameter ≤10 μm are treated by immersion for 8-10 min, and the carbon fibers with a diameter >10 μm are treated by spraying for 15-20 min, to preliminarily introduce oxygen-containing functional groups;

[0017] 4) The deionized water is used to remove the residual solvent and soluble ions on the surface of the carbon fiber bundle in stages, and the first stage uses flowing deionized water to wash for 10 min, the second stage uses ultrasonic-assisted water washing for 30 min, and the third stage uses static immersion for 15 min, until the conductivity is ≤5 μs / cm;

[0018] 5) The cleaned carbon fiber bundle is hung in a drying oven, heated and dried at 80-120°C for 2-4h under nitrogen protection until the constant weight.

[0019] Preferably, the electrolyte is an ammonium nitrate solution prepared by high purity ammonium nitrate NH4NO3 and ultra-pure deionized water, and the concentration range is 0.3-0.8 mol / L, and the resistivity of the ultra-pure deionized water is ≥18.2 MΩ·cm, and the preparation steps include:

[0020] 1) The ammonium nitrate NH4NO3 and ultra-pure deionized water are weighed according to the mass fraction ratio of 3.86:100, and stirred in a magnetic stirrer at 500 rpm for 20-30 min until completely dissolved;

[0021] 2) Adjust the pH to 6.5-7.5 and filter the solution through a 0.22 μm polytetrafluoroethylene filter to remove residual particulate matter;

[0022] 3) Nitrogen was continuously introduced into the filtered solution for 15 minutes to remove dissolved oxygen in the solution and obtain an electrolyte.

[0023] Preferably, the electrode installation and fiber loading steps include:

[0024] 1) The installation distance between the cathode and anode conductive structures is set to 5 to 10 cm, and a double contact point structure of titanium basket and graphite guide roller is adopted. The guide roller diameter is set to ≥ 50 mm, and the porosity of the titanium basket is 80%;

[0025] 2) Cut the cleaned and dried carbon fiber bundle into 30-50 cm lengths, insert the carbon fiber bundle into the guide roller groove, press the end into the titanium basket, and adjust the guide roller height to make the fiber bundle completely immersed;

[0026] 3) Placing a platinum sheet as a cathode structure parallel to the fiber bundle, setting the cathode area: anode area ratio to ≥ 5:1, and measuring the carbon fiber tension data using a tension sensor.

[0027] Preferably, the positive electrode of the power supply is connected to the carbon fiber bundle, and the negative electrode of the power supply is connected to the platinum sheet, and the surface of the carbon fiber is subjected to electrolytic oxidation treatment, specifically including:

[0028] 1) After starting the DC power supply, the current density is calculated according to the current density formula (A / m 2 ) = total current (A) / fiber surface area (m2), where fiber surface area = π × single fiber diameter (μm) × immersion length (m) × number of fibers × 10 -6 When using the constant current method, the current density is set to 0.5~2.0A / m 2 , treat the carbon fiber surface for 3 to 8 minutes, and use a conductivity meter to detect the current fluctuation data in real time;

[0029] 2) When using the constant voltage method, the cell voltage of the electrolytic cell is set to 2.5-4.5V, the carbon fiber surface is treated for 3-8 minutes, and the voltage fluctuation data is detected in real time using a conductivity meter;

[0030] 3) After the set time is reached, the current is reduced to zero and the power is cut off, and the carbon fiber is lifted away from the electrolyte surface at a constant speed of 0.5m / min.

[0031] Preferably, after the carbon fibers are separated from the electrolyte, deionized water is used for three-stage washing, including: 1) in the first stage, deionized water is used for flowing washing for 2 minutes to reduce the surface conductivity of the fibers to ≤100 μS / cm;

[0032] 2) In the second stage, the ultrasonic cleaning machine is set to an ultrasonic frequency of 40kHz and a power density of 0.3W / cm3 , with deionized water and 0.1% EDTA ultrasonic treatment for 8 min, the surface conductivity is reduced to ≤10 μS / cm;

[0033] 3) The third stage adopts ultrapure deionized water immersion cleaning for 15 min, and the water is replaced for 3 times, and the surface conductivity is reduced to ≤2 μS / cm.

[0034] Preferably, the carbon fibers after cleaning are treated by negative pressure filtration and air knife blowing method, including:

[0035] 1) Selecting a Buchner funnel and laying a polytetrafluoroethylene filter membrane on the inside, laying the carbon fibers on the upper layer of the filter membrane, sealing above the funnel and connecting a rotary vane vacuum pump at the lower end of the funnel;

[0036] 2) The funnel is gradiently pressurized and filtered by the vacuum pump, and the filtration and dehydration are stopped when the moisture content of the carbon fibers is ≤3wt%;

[0037] 3) The distance between the slit air knife and the carbon fibers is 95-105 mm, high-purity nitrogen is used as the gas source, the nitrogen pressure of the air knife is set to 0.28-0.32 MPa, and the scanning speed of the air knife on the surface of the carbon fibers is controlled to be 15-25 mm / s;

[0038] 4) The surface of the carbon fibers is scanned and treated by a reciprocating blowing method, and the blowing and dehydration are stopped when the moisture content of the carbon fibers is ≤1.8wt%;

[0039] The dehydrated carbon fiber bundle is hung in a drying oven, heated and dried to constant weight under nitrogen protection at 80-120°C, and the carbon fibers are sealed and stored.

[0040] (Three) beneficial effects

[0041] Compared with the prior art, the present application provides a surface electrolytic oxidation treatment method of high-thermal-conductivity mesophase pitch-based carbon fibers, which has the following beneficial effects:

[0042] 1. The surface electrolytic oxidation treatment method of high-thermal-conductivity mesophase pitch-based carbon fibers realizes scientific staged pretreatment process through design of Soxhlet extraction deep cleaning treatment, hydrogen peroxide pre-activation and three-stage water washing conductivity control treatment.

[0043] 2. The surface electrolytic oxidation treatment method of high-thermal-conductivity mesophase pitch-based carbon fibers avoids local electrolytic overheating by dynamically calculating and designing current density, monitors I D / I G ratio to protect the graphite microcrystalline structure, and adjusts the electrolysis test process in real time through temperature, bubble generation rate and conductivity parameter monitoring feedback, so as to effectively improve the functional group increment and ILSS through pre-oxidation and electrolytic oxidation synergistic treatment.

[0044] 3. The surface electrolytic oxidation treatment method of the high-thermal-conductivity mesophase pitch-based carbon fiber, which realizes fine post-treatment by designing negative pressure suction filtration, gas-knife blowing dehydration and nitrogen protection step drying, and ensures the interface stability of the carbon fiber. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 A flow chart of the surface electrolytic oxidation treatment method of the carbon fiber of the present application;

[0046] Figure 2 A flow chart of the Soxhlet extraction cleaning method of the present application;

[0047] Figure 3 A layout schematic diagram of the electrolytic cell system of the present application;

[0048] Figure 4 A flow chart of the electrolytic oxidation treatment of the present application;

[0049] Figure 5 A flow chart of the deionized water washing of the present application;

[0050] Figure 6 A flow chart of the negative pressure suction filtration dehydration of the present application;

[0051] Figure 7 A flow chart of the gas-knife blowing dehydration of the present application. DETAILED DESCRIPTION

[0052] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application and the drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0053] Embodiment One

[0054] In the present embodiment, the Soxhlet extraction method is used to clean the surface impurities of the carbon fiber, wherein the Soxhlet extractor includes a distillation flask, an extraction tube, a condenser tube, a constant-temperature heating jacket, an ashless filter paper tube and absorbent cotton. The specific operation steps include:

[0055] 1) The carbon fiber is loosely packed into the filter paper tube, and the filling degree is ensured to be ≤80% to avoid hindering the solvent penetration due to over-tight packing. A layer of absorbent cotton is covered on the tube opening to prevent the fiber from floating, and the filter paper tube is placed into the extraction tube;

[0056] 2) A certain volume of acetone solvent is injected into the distillation flask, and the distillation flask-extraction tube-condenser tube is connected in sequence. The condenser tube is connected to the condenser water, and the condenser water flow rate is set to 1-2 L / min. The inlet water temperature of the condenser tube is controlled to be ≤15℃;

[0057] 3) Set the heating jacket temperature to 56-60°C, observe the solvent vapor rising to the condenser tube, and control the reflux speed of the condenser water to 3-5 times / hour, i.e. complete one siphon cycle every 12-20 min;

[0058] 4) Control the cleaning time for 4-6 h, observe the color of the solvent in the distillation flask from colorless-yellow-colorless transparent as the end point, the siphon liquid of the extraction tube has no oily suspension, then stop heating and naturally cool the distillation flask to room temperature, take out the filter paper tube, ventilate and drain the solvent, and recover the solvent in the distillation flask.

[0059] The verification method for the cleaning effect of the impurities on the surface of the carbon fiber includes:

[0060] 1) Weight method: According to the extraction rate formula: extraction rate (%) = [(m0-m1) / m0]x100%, wherein m0 is the mass of the fiber before extraction, and m1 is the mass of the fiber after extraction, the cleaning qualified standard is set to extraction rate > 98.5%;

[0061] 2) Infrared spectrum: When the disappearance of -CH2-stretching vibration peak at 2850-2960 cm -1 is detected by the infrared spectrometer, it indicates that the surface impurities are completely removed.

[0062] Example Two

[0063] In this example, before the power-on of the electrolytic oxidation treatment, the electrolytic cell needs to be systematically inspected, including:

[0064] 1) Pre-run the water cooling circulation system for 10 min, detect the electrolyte temperature by infrared temperature measurement, and ensure that it is qualified within the range of 25±1°C;

[0065] 2) Check the cleanliness of the cathode by observing that there is no bubble adhesion on the surface of the platinum sheet, and there is no spot in visual inspection;

[0066] 3) Detect the anode-cathode resistance of the electrolytic cell by using a multimeter, and the qualified standard needs to be >1kΩ to judge the continuity of the fiber conduction;

[0067] 4) Monitor the oxygen content of the electrolyte by a dissolved oxygen sensor, and the qualified standard needs to be ≤0.5ppm.

[0068] During the electrolytic oxidation process, the monitoring data includes:

[0069] 1) Monitor the electrolyte temperature fluctuation by using an immersion PT100 sensor, increase the cooling water flow when the electrolyte temperature >26°C, and ensure that the cooling water flow ≥5L / min;

[0070] 2) Monitor the bubble number per second in the anode area by using a high-speed camera, judge the bubble generation rate, and when the bubble generation rate >20 bubbles / cm 2• s time decrease 10% current density;

[0071] 3) On-line conductance monitor to control electrolyte conductivity, when the conductivity fluctuation is > ± 5%, fresh electrolyte is added.

[0072] The verification method of electrolytic oxidation treatment effect includes:

[0073] 1) In-situ Raman spectrum detection: through the spectrum instrument to detect the intensity ratio of D peak or G peak I D / I G , control the ratio of I D / I G at 0.05-0.08, when I D / I G > 0.12, it indicates that the carbon fiber surface is excessively oxidized;

[0074] 2) Anode potential monitoring: take Ag or AgCl as reference electrode, control the safety range of electrolytic voltage at 1.2-1.8V, when the voltage exceeds 1.8V, the water decomposition side reaction increases sharply.

[0075] Example three

[0076] In this embodiment, three-stage heating method is adopted in the drying oven, including:

[0077] 1) set the heating temperature at 80℃, after heating for 30min, free water is removed;

[0078] 2) set the heating temperature at 100℃, after heating for 60min, bound water is removed;

[0079] 3) set the heating temperature at 115℃, after heating for 45min, the deep drying treatment of carbon fiber is completed.

[0080] The verification method of carbon fiber drying treatment includes:

[0081] 1) Karl Fischer titration method is used for water residue detection, and the qualified standard of moisture is set at ≤0.5%;

[0082] 2) rapid infrared method is used for water residue detection, and the integral intensity of 1730cm -1 -OH characteristic peak is ensured to be <100a.u.

[0083] The detection of carbon fiber surface ion pollution, and the ICP-MS detection limit is shown in the following table:

[0084] Ion Na + ]] K + ]]> Cl - ]]> SO4 2- ]]> Limit ≤ 5 ppb ≤ 3 ppb ≤ 8 ppb ≤ 10 ppb

[0085] The surface electrolytic oxidation treatment method of the high-thermal-conductivity mesophase pitch-based carbon fiber has the advantages that scientific grading pretreatment processes are realized through design of Soxhlet extraction deep cleaning treatment, hydrogen peroxide pre-activation and three-stage water washing conductivity control treatment;

[0086] The local electrolytic overheating is avoided through dynamic calculation and design of current density, and I D / I G The ratio is monitored to protect the graphite microcrystalline structure, and the electrolysis test process is real-time regulated through monitoring and feedback of temperature, bubble generation rate and conductivity parameters, so that the functional group increment and ILSS are effectively improved through pre-oxidation and electrolytic oxidation synergistic treatment;

[0087] Through design of negative pressure suction filtration, air knife blowing dehydration and nitrogen protection step drying, fine post-treatment is realized, and the interface stability of the carbon fiber is ensured.

[0088] Although the embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for surface electrolytic oxidation treatment of high thermal conductive mesophase pitch-based carbon fibers, characterized by, The method comprises the following steps: S1. Surface pretreatment: removing impurities and oxidation layer on the surface of mesophase pitch-based carbon fiber by cleaning-decontamination-drying treatment; S2. Electrolysis preparation: preparing electrolyte with required concentration by high-purity reagents and deionized water, installing electrodes and loading carbon fiber in an electrolytic cell, and injecting electrolyte; S3. Electrolytic oxidation treatment: electrolytic oxidation treatment of the surface of carbon fiber by setting treatment current or voltage and treatment time after connecting a direct current power supply by using constant current or constant voltage method; S4. Post-treatment: cleaning residual electrolyte by deionized water, and obtaining carbon fiber with electrolytic oxidation surface after dehydration and drying treatment.

2. The surface electrolytic oxidation treatment method of high thermal conductive mesophase pitch-based carbon fiber according to claim 1, characterized by, The surface pretreatment of mesophase pitch-based carbon fiber comprises the following steps: 1) placing carbon fiber bundles in a filter paper cylinder to ensure that the filling degree in the cylinder is less than or equal to 80%, wrapping the filter paper cylinder with absorbent cotton at the cylinder opening, and placing the filter paper cylinder and the carbon fiber bundles in a distillation flask of a soxhlet extractor; 2) injecting the distillation flask with acetone as a cleaning solvent, heating the carbon fiber bundles at a temperature of 56-60°C for 4-6 hours, until the color of the solvent in the distillation flask changes from colorless to light yellow, and finally to colorless and transparent; 3) using 0.01-0.05 mol / L hydrogen peroxide H2O2 solution as an oxidation immersion agent, treating carbon fibers with a diameter of less than or equal to 10 μm by immersion for 8-10 minutes, and treating carbon fibers with a diameter greater than 10 μm by spraying for 15-20 minutes, to preliminarily introduce oxygen-containing functional groups; 4) removing solvent residues and soluble ions on the surface of the carbon fiber bundles in stages by deionized water, washing the carbon fiber bundles with flowing deionized water for 10 minutes in the first stage, ultrasonic-assisted water washing for 30 minutes in the second stage, and static immersion for 15 minutes in the third stage, until the electrical conductivity is less than or equal to 5 μs / cm; 5) hanging the cleaned carbon fiber bundles in a drying oven, and heating and drying them at 80-120°C for 2-4 hours to constant weight under nitrogen protection.

3. The surface electrolytic oxidation treatment method of high thermal conductive mesophase pitch-based carbon fiber according to claim 1, characterized by, The electrolyte is an ammonium nitrate solution prepared by high-purity ammonium nitrate NH4NO3 and ultra-pure deionized water, and the concentration range is 0.3-0.8 mol / L, and the resistivity of the ultra-pure deionized water is greater than or equal to 18.2 MΩ·cm, and the preparation steps comprise: 1) weighing ammonium nitrate NH4NO3 and ultra-pure deionized water according to a mass ratio of 3.86:100, stirring them in a magnetic stirrer at 500 rpm for 20-30 minutes until completely dissolved; 2) adjusting the pH value to 6.5-7.5 and filtering the solution with a 0.22 μm polytetrafluoroethylene filter membrane to remove residual particulate matter; 3) continuously introducing nitrogen into the filtered solution for 15 minutes to remove dissolved oxygen in the solution to obtain the electrolyte.

4. The surface electrolytic oxidation treatment method of high thermal conductive mesophase pitch-based carbon fiber according to claim 1, characterized by, The electrode installation and fiber loading steps comprise: 1) setting the installation distance of the cathode and anode conductive structures to be 5-10 cm, using a titanium basket and a graphite guide roller double-contact point structure, setting the diameter of the guide roller to be greater than or equal to 50 mm, and setting the porosity of the titanium basket to be 80%; 2) cutting the cleaned and dried carbon fiber bundles into lengths of 30-50 cm, inserting the carbon fiber bundles into the guide roller groove, and pressing the ends of the carbon fiber bundles into the titanium basket, and adjusting the height of the guide roller to completely immerse the carbon fiber bundles; 3) Place platinum sheet as cathode structure along the direction parallel to the fiber bundle, set the ratio of cathode area to anode area ≥5:1, and measure the carbon fiber tension data using a tension sensor.

5. The surface electrolytic oxidation treatment method of high thermal conductive mesophase pitch-based carbon fiber according to claim 1, characterized by, Connect the positive pole of the power supply to the carbon fiber bundle and the negative pole to the platinum sheet, and perform electrolytic oxidation treatment on the surface of the carbon fiber, which specifically includes: 1) After starting the direct current power supply, the current density is calculated according to the formula: current density (A / m 2 ) = total current (A) / fiber surface area (m2), wherein the fiber surface area = π x single fiber diameter (μm) x immersion length (m) x fiber number x 10 -6 , and when the constant current method is used, the current density is set to 0.5-2.0 A / m 2 , and the carbon fiber surface is treated for 3-8 min, and the current fluctuation data is detected in real time by using a conductance instrument; 2) When using the constant voltage method, set the cell voltage of the electrolytic cell to 2.5-4.5 V, and treat the surface of the carbon fiber for 3-8 min, using a conductance meter to detect voltage fluctuation data in real time; 3) After reaching the set time, reduce the current to zero and turn off the power, and lift the carbon fiber at a uniform speed of 0.5 m / min away from the electrolyte liquid surface.

6. The surface electrolytic oxidation treatment method of high thermal conductive mesophase pitch-based carbon fiber according to claim 1, characterized by, After the carbon fiber is separated from the electrolyte, deionized water is used for three-stage cleaning, including: 1) In the first stage, use deionized water to flow for 2 min to reduce the surface conductivity of the fiber to ≤100 μS / cm; 2) The second stage is set in the ultrasonic cleaning machine with ultrasonic frequency of 40 kHz, and the power density is 0.3 W / cm 3 , and the surface conductivity is reduced to ≤10 μS / cm by ultrasonic treatment with deionized water and 0.1% EDTA for 8 min. 3) In the third stage, use ultra-pure deionized water to soak and clean for 15 min, and repeat the water change for 3 times to reduce the surface conductivity to ≤2 μS / cm.

7. The surface electrolytic oxidation treatment method of high thermal conductive mesophase pitch-based carbon fiber according to claim 1, characterized by, Use negative pressure filtration and air knife blowing method to treat the dehydrated carbon fiber after cleaning, including: 1) Select a Buchner funnel and lay a polytetrafluoroethylene filter membrane inside it, lay the carbon fiber on the upper layer of the filter membrane, seal the upper part of the funnel, and connect a rotary vane vacuum pump to the lower end of the funnel; 2) Use the vacuum pump to perform gradient pressure filtration treatment on the funnel, and stop the filtration and dehydration when the moisture content of the carbon fiber is ≤3 wt%; 3) Set the distance between the slit air knife and the carbon fiber to 95-105 mm, use high-purity nitrogen as the gas source, set the nitrogen pressure of the air knife to 0.28-0.32 MPa, and control the scanning speed of the air knife on the surface of the carbon fiber to 15-25 mm / s; 4) Use the reciprocating blowing method to scan the surface of the carbon fiber, and stop blowing and dehydration when the moisture content of the carbon fiber is ≤1.8 wt%; Hang the dehydrated carbon fiber bundle in a drying oven, heat it to constant weight at 80-120°C under nitrogen protection, and store the carbon fiber in a sealed container.

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