Carbon fiber and preparation method thereof

Abstract

The invention relates to the field of carbon fibers, in particular to a carbon fiber and a preparation method thereof. The invention provides a method for preparing carbon fibers, which comprises the following steps: carrying out first-stage liquid phase oxidation treatment on graphitized fibers to introduce active functional groups into the surfaces of the graphitized fibers to obtain active graphitized fibers; and carrying out second-stage liquid-phase oxidation treatment on the active graphitized fibers by adopting an HF solution. According to the technical scheme, the first-stage liquid-phase oxidation treatment and the second-stage hydrofluoric acid oxidation treatment are combined, so that the ash content of the carbon fibers can be remarkably removed, the mechanical property of the carbon fibers is improved, and the mechanical property of the composite material is favorably improved; meanwhile, active functional groups are introduced to the surfaces of the graphitized fibers, and the carbon fibers are applied to preparation of the composite material, so that the interface effect of the composite material is improved, and the mechanical property of the composite material is further improved.

Description

Technical Field

[0001] This application relates to the field of carbon fibers, and more specifically, to a carbon fiber and a method for preparing the same. Background Art

[0002] As a new type of material, composite materials have excellent properties and are widely used in fields such as wind turbine blades, pressure vessels, sports and leisure, automotive industry, rail transit, carbon core cables, building bridges, electronics 3C, and medical.

[0003] With the continuous development of composite material technology, higher requirements are put forward for the performance of composite materials. Carbon fiber is a key material for preparing composite materials, and the performance of carbon fiber directly affects the performance of composite materials. Summary of the Invention

[0004] The purpose of the embodiments of this application is to provide a carbon fiber and a method for preparing the same.

[0005] In the first aspect, this application provides a method for preparing carbon fiber, including:

[0006] Subjecting the graphitized fiber to a first-stage liquid-phase oxidation treatment to introduce active functional groups on the surface of the graphitized fiber, obtaining an active graphitized fiber;

[0007] Subjecting the active graphitized fiber to a second-stage liquid-phase oxidation treatment using an HF solution.

[0008] In the above technical solution, the combination of the first-stage liquid-phase oxidation treatment and the second-stage hydrofluoric acid oxidation treatment can significantly remove the ash content of the carbon fiber, improve the mechanical properties of the carbon fiber, and is beneficial to enhancing the mechanical properties of the composite material; at the same time, by introducing active functional groups on the surface of the graphitized fiber and applying this carbon fiber to the preparation of composite materials, it is beneficial to enhancing the interface effect of the composite material and further beneficial to the mechanical properties of the composite material.

[0009] In other embodiments of this application, subjecting the active graphitized fiber to a second-stage liquid-phase oxidation treatment using an HF solution includes:

[0010] Subjecting the active graphitized fiber to treatment with an HF solution for 50 s to 250 s.

[0011] In other embodiments of this application, subjecting the active graphitized fiber to a second-stage liquid-phase oxidation treatment using an HF solution includes:

[0012] Subjecting the active graphitized fiber to a second-stage liquid-phase oxidation treatment using an HF solution with a mass concentration of 30% to 80%.

[0013] In other embodiments of this application, subjecting the active graphitized fiber to a second-stage liquid-phase oxidation treatment using an HF solution includes:

[0014] The activated graphitized fibers are subjected to a second-stage liquid-phase oxidation treatment with an HF solution having a mass concentration of 40% to 60%.

[0015] In other embodiments of the present application, the graphitized fibers are subjected to a first-stage liquid-phase oxidation treatment, including:

[0016] The graphitized fibers are subjected to a first-stage liquid-phase oxidation treatment with a strong acid solution.

[0017] In other embodiments of the present application, the graphitized fibers are subjected to a first-stage liquid-phase oxidation treatment, including:

[0018] The graphitized fibers are treated with a sulfuric acid solution or a nitric acid solution for 50 s to 250 s.

[0019] In other embodiments of the present application, the graphitized fibers are subjected to a first-stage liquid-phase oxidation treatment, including:

[0020] The graphitized fibers are subjected to a first-stage liquid-phase oxidation treatment with a sulfuric acid solution or a nitric acid solution.

[0021] In other embodiments of the present application, the graphitized fibers are subjected to a first-stage liquid-phase oxidation treatment, including:

[0022] The graphitized fibers are subjected to a first-stage liquid-phase oxidation treatment with a strong acid solution having a mass concentration of 50% - 97%.

[0023] In other embodiments of the present application, preparing graphitized fibers includes:

[0024] Treating polyacrylonitrile-based fibers into graphitized fibers.

[0025] In a second aspect, the present application provides a carbon fiber prepared by using the method for preparing a carbon fiber provided in any one of the foregoing first aspects.

[0026] In other embodiments of the present application, the modulus of the low-ash high-modulus carbon fiber is greater than 539 GPa.

[0027] In other embodiments of the present application, the ash content of the low-ash high-modulus carbon fiber is less than 0.020%. Detailed Description of the Embodiments

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. Apparently, the described embodiments are some, but not all, of the embodiments of the present application.

[0029] Accordingly, the following detailed description of the embodiments of the present application is not intended to limit the scope of the claimed present application, but merely represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the scope of protection of the present application.

[0030] With the continuous development of carbon fiber technology, higher requirements are put forward for the performance of carbon fibers. The performance of carbon fibers can be improved through post-treatment processes. However, the surface treatment process of anodic oxidation has some drawbacks. For example, the anodic oxidation surface treatment process is prone to damage the carbon fiber body, affecting the interfacial properties and mechanical properties of carbon fibers and the performance of subsequent composite materials; and the anodic oxidation surface treatment process has limited effect on reducing the ash content of carbon fibers, also affecting the performance of subsequent composite materials.

[0031] The surface of carbon fiber itself is inert, with low chemical activity and weak interfacial bonding force with resin-based materials, thus affecting the bonding performance of composites, reducing corrosion resistance, and changing the mechanical properties of composites. By treating the interfacial properties of carbon fibers, the comprehensive performance of composites can be improved. Currently, the common post-treatment method for carbon fibers is the surface treatment process of anodic oxidation. However, conventional anodic oxidation has limited improvement in the interfacial properties of carbon fibers. In order to improve the effect of carbon fiber interfacial properties, it is necessary to increase the current density of anodic oxidation treatment and more surface treatment stages, which will damage the carbon fiber body, affect the mechanical properties of carbon fibers, and affect the performance of subsequent composite materials.

[0032] Moreover, the anodic oxidation surface treatment process has limited effect on reducing the ash content of carbon fibers; in carbon fibers and their composites, ash content is an important indicator, which is composed of impurities and additives in the material. The amount of ash content directly affects the performance and service life of the material. Generally speaking, the higher the ash content, the corresponding decline in the mechanical properties and hardness of the material, and due to the existence of ash, the internal defects of the material will increase. Ash is an unstable substance, prone to combustion, oxidation and other reactions under high-temperature environments, thus affecting the stability and heat resistance of the material. However, carbon fibers, especially high-modulus carbon fibers, such as M40J, M46J, M50J and above high-modulus carbon fiber products, have a relatively high ash content, affecting the performance of composite materials and limiting their application markets.

[0033] The embodiments of the present application provide a method for preparing carbon fibers, including:

[0034] Performing a first-stage liquid-phase oxidation treatment on the graphitized fibers to introduce active functional groups on the surface of the graphitized fibers, obtaining active graphitized fibers;

[0035] Performing a second-stage liquid-phase oxidation treatment on the active graphitized fibers using an HF solution.

[0036] In the above technical solution, by combining primary liquid-phase oxidation and secondary hydrofluoric acid oxidation treatment, the ash content of high-modulus carbon fiber can be significantly removed, and the mechanical properties of the carbon fiber can be improved. Applying this carbon fiber to the preparation of composite materials is beneficial to enhancing the interfacial effect of the composite materials; and the mechanical properties of the composite materials.

[0037] Further, in some embodiments of the present application, a method for preparing low-ash high-modulus carbon fiber includes the following steps:

[0038] Step S1, preparing graphitized fiber.

[0039] Further, in some embodiments of the present application, the steps of preparing graphitized fiber include:

[0040] Processing polyacrylonitrile-based fiber into graphitized fiber.

[0041] Further optionally, in some embodiments of the present application, the above-mentioned processing of polyacrylonitrile-based fiber into graphitized fiber includes:

[0042] Obtaining graphitized fiber by subjecting polyacrylonitrile-based fiber to pre-oxidation, low-temperature carbonization, high-temperature carbonization and graphitization.

[0043] Further optionally, in some embodiments of the present application, for the above-mentioned pre-oxidation of polyacrylonitrile-based fiber, it can be selected to pre-oxidize polyacrylonitrile (PAN) raw yarn at 200°C to 300°C, so that the molecular structure of polyacrylonitrile is transformed into a nitrogen-containing ladder molecular structure, and the polyacrylonitrile fiber is converted into a carbon fiber structure.

[0044] Further optionally, in some embodiments of the present application, after the above-mentioned polyacrylonitrile-based carbon fiber is pre-oxidized, the pre-oxidized fiber is subjected to low-temperature carbonization at 300°C to 800°C. Low-temperature carbonization can further pyrolyze the unreacted polyacrylonitrile structure after pre-oxidation.

[0045] Further optionally, in some embodiments of the present application, after the above-mentioned polyacrylonitrile-based carbon fiber is subjected to low-temperature carbonization treatment, it can be selected to perform high-temperature carbonization treatment at 1000°C to 1500°C to further remove atoms such as hydrogen, nitrogen, and oxygen to form carbon fiber. Performing low-temperature carbonization first and then high-temperature carbonization is beneficial to forming a gradient heating from low to high, making the pyrolysis process gradual.

[0046] Further optionally, in some embodiments of the present application, after the above-mentioned polyacrylonitrile-based carbon fiber is subjected to high-temperature carbonization, it can be selected to perform graphitization treatment at 2500°C to 3000°C to finally obtain graphitized fiber.

[0047] Further optionally, in some embodiments of the present application, the transfer speed when processing the polyacrylonitrile-based fiber into a graphitized fiber is 150 m / h - 820 m / h.

[0048] Exemplarily, in some embodiments of the present application, the transfer speed when processing the polyacrylonitrile-based fiber into a graphitized fiber is 150 m / h, 155 m / h, 160 m / h, 165 m / h, 170 m / h, 175 m / h, 180 m / h, 200 m / h, 250 m / h, 300 m / h, 350 m / h, 400 m / h, 450 m / h, 500 m / h, 550 m / h, 600 m / h, 650 m / h, 700 m / h, 750 m / h, 800 m / h, 820 m / h, or a range between any two of the foregoing values.

[0049] In other alternative embodiments of the present application, the above-mentioned polyacrylonitrile-based carbon fiber can be obtained by purchasing commercially.

[0050] Further optionally, in some embodiments of the present application, the above-mentioned graphitized fiber can be a high-modulus carbon fiber above M40J.

[0051] Exemplarily, in some embodiments of the present application, the above-mentioned graphitized fiber can be a high-modulus carbon fiber product such as M40J, M46J, M50J and above.

[0052] Step S2: Perform a first-stage liquid-phase oxidation treatment on the graphitized fiber to introduce active functional groups on the surface of the graphitized fiber, and obtain an active graphitized fiber.

[0053] Further, in some embodiments of the present application, performing the first-stage liquid-phase oxidation treatment on the graphitized fiber includes:

[0054] Performing the first-stage liquid-phase oxidation treatment on the graphitized fiber with a strong acid solution.

[0055] In the above technical solution, performing the first-stage liquid-phase oxidation treatment on the graphitized fiber with a strong acid solution can effectively etch the fiber surface, generate oxygen-containing and nitrogen-containing active functional groups on the surface of the carbon fiber, increase the surface roughness and wettability of the carbon fiber, and at the same time avoid causing excessive damage to the strength of the carbon fiber; it is beneficial to the mechanical properties of the carbon fiber. Applying this carbon fiber to the preparation of a composite material is beneficial to improving the interface effect of the composite material; and the mechanical properties of the composite material.

[0056] Further, in some embodiments of the present application, performing the first-stage liquid-phase oxidation treatment on the graphitized fiber includes:

[0057] Performing the first-stage liquid-phase oxidation treatment on the graphitized fiber with a sulfuric acid solution or a nitric acid solution.

[0058] Exemplarily, in some embodiments of the present application, performing a first-stage liquid-phase oxidation treatment on the graphitized fiber includes:

[0059] Performing a first-stage liquid-phase oxidation treatment on the graphitized fiber using any one of a sulfuric acid solution or a nitric acid solution.

[0060] Further optionally, in some embodiments of the present application, performing a first-stage liquid-phase oxidation treatment on the graphitized fiber using a mixed solution of a sulfuric acid solution and a nitric acid solution; optionally, the sulfuric acid solution and the nitric acid solution in the above-mentioned mixed solution of the sulfuric acid solution and the nitric acid solution can be mixed in any proportion.

[0061] Further, in some embodiments of the present application, performing a first-stage liquid-phase oxidation treatment on the graphitized fiber includes:

[0062] Performing a first-stage liquid-phase oxidation treatment on the graphitized fiber using a strong acid solution with a mass concentration of 50%-97%.

[0063] Exemplarily, in some embodiments of the present application, performing a first-stage liquid-phase oxidation treatment on the graphitized fiber includes:

[0064] Performing a first-stage liquid-phase oxidation treatment on the graphitized fiber using a strong acid solution with a concentration value of 50%, 52%, 55%, 58%, 60%, 62%, 65%, 68%, 70%, 72%, 75%, 78%, 80%, 82%, 85%, 88%, 90%, 92%, 95%, 97% or a range between any two of the foregoing numerical values.

[0065] Further optionally, in some embodiments of the present application, the treatment time for performing the first-stage liquid-phase oxidation treatment on the graphitized fiber can be selected to be 50 s to 250 s.

[0066] In the above technical solution, the treatment time for performing the first-stage liquid-phase oxidation treatment on the graphitized fiber can be selected to be 50 s to 250 s; it can effectively achieve etching of the fiber surface, and generate oxygen-containing and nitrogen-containing active functional groups on the surface of the carbon fiber. Applying this carbon fiber to the preparation of a composite material is beneficial to improving the interfacial effect of the composite material; and the mechanical properties of the composite material.

[0067] Exemplarily, in some embodiments of the present application, the treatment time for the first-stage liquid-phase oxidation treatment of the graphitized fiber can be selected as 50 s, 55 s, 60 s, 65 s, 70 s, 75 s, 80 s, 85 s, 90 s, 95 s, 100 s, 105 s, 110 s, 115 s, 120 s, 125 s, 130 s, 135 s, 140 s, 150 s, 160 s, 180 s, 190 s, 200 s, 210 s, 220 s, 230 s, 240 s, 250 s, or the range between any two of the foregoing values.

[0068] Further optionally, in some embodiments of the present application, the graphitized fiber obtained in the foregoing step S1 is subjected to a first-stage liquid-phase oxidation treatment using an acid bath.

[0069] Further optionally, in some embodiments of the present application, when the first-stage liquid-phase oxidation treatment is performed using an acid bath, the transmission speed is selected to be the same as the production speed of the graphitized fiber in the foregoing step S1.

[0070] Exemplarily, in some embodiments of the present application, the transmission speed when the first-stage liquid-phase oxidation treatment is performed using an acid bath is 150 m / h - 820 m / h.

[0071] Exemplarily, in some embodiments of the present application, the transmission speed when the first-stage liquid-phase oxidation treatment is performed using an acid bath is 150 m / h, 155 m / h, 160 m / h, 165 m / h, 170 m / h, 175 m / h, 180 m / h, 200 m / h, 250 m / h, 300 m / h, 350 m / h, 400 m / h, 450 m / h, 500 m / h, 550 m / h, 600 m / h, 650 m / h, 700 m / h, 750 m / h, 800 m / h, 820 m / h, or the range between any two of the foregoing values.

[0072] Step S3: The activated graphitized fiber is subjected to a second-stage liquid-phase oxidation treatment using an HF solution.

[0073] In the above technical solution, by performing the second-stage liquid-phase oxidation treatment using an HF solution, the ash content in the carbon fiber can be effectively reduced, and the interlaminar shear strength of the carbon fiber can be further improved; it is beneficial to the modulus of the carbon fiber.

[0074] Further, in some embodiments of the present application, the second-stage liquid-phase oxidation treatment using an HF solution includes:

[0075] The activated graphitized fiber is treated with an HF solution for 50 s to 250 s.

[0076] In the above technical solution, the activated graphitized fiber is treated with an HF solution for 50 s to 250 s; this can effectively remove ash such as SixOy and silicate in the fiber and further improve the mechanical properties of the fiber.

[0077] Exemplarily, in some embodiments of the present application, the second-stage liquid-phase oxidation treatment with an HF solution includes:

[0078] The activated graphitized fiber is treated with an HF solution for 50 s, 55 s, 60 s, 65 s, 70 s, 75 s, 80 s, 85 s, 90 s, 95 s, 100 s, 105 s, 110 s, 115 s, 120 s, 125 s, 130 s, 135 s, 140 s, 150 s, 160 s, 180 s, 190 s, 200 s, 210 s, 220 s, 230 s, 240 s, 250 s or the range between any two of the foregoing values.

[0079] Further, in some embodiments of the present application, the second-stage liquid-phase oxidation treatment with an HF solution includes:

[0080] The activated graphitized fiber is subjected to the second-stage liquid-phase oxidation treatment with an HF solution having a mass concentration of 30% to 80%.

[0081] In the above technical solution, the activated graphitized fiber is subjected to the second-stage liquid-phase oxidation treatment with an HF solution having a mass concentration of 30% to 80%; within this concentration range, the effect of effectively reducing ash such as SixOy and silicate in the fiber can be achieved.

[0082] Further, in some embodiments of the present application, the above-mentioned second-stage liquid-phase oxidation treatment with an HF solution includes:

[0083] The activated graphitized fiber is subjected to the second-stage liquid-phase oxidation treatment with an HF solution having a concentration in the range of 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80% or the range between any two of the foregoing values.

[0084] Further optionally, in some embodiments of the present application, the second-stage liquid-phase oxidation treatment with an HF solution includes:

[0085] The activated graphitized fiber is subjected to the second-stage liquid-phase oxidation treatment with an HF solution having a mass concentration of 40% to 60%.

[0086] Exemplarily, in some embodiments of the present application, the above-mentioned activated graphitized fibers are subjected to a second-stage liquid-phase oxidation treatment with an HF solution having a mass concentration of 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60% or a concentration within the range between any two of the foregoing values.

[0087] In some embodiments of the present application, for the above-mentioned second-stage liquid-phase oxidation treatment, an acid tank is used for the second-stage liquid-phase oxidation treatment.

[0088] Further optionally, in some embodiments of the present application, when the above-mentioned second-stage liquid-phase oxidation treatment is carried out using an acid tank, the transmission speed is selected to be the same as the production speed of the graphitized fibers in the foregoing step S1.

[0089] Exemplarily, in some embodiments of the present application, the transmission speed when the above-mentioned second-stage liquid-phase oxidation treatment is carried out using an acid tank is 150 m / h - 820 m / h.

[0090] Exemplarily, in some embodiments of the present application, the transmission speed when the above-mentioned second-stage liquid-phase oxidation treatment is carried out using an acid tank is 150 m / h, 155 m / h, 160 m / h, 165 m / h, 170 m / h, 175 m / h, 180 m / h, 200 m / h, 250 m / h, 300 m / h, 350 m / h, 400 m / h, 450 m / h, 500 m / h, 550 m / h, 600 m / h, 650 m / h, 700 m / h, 750 m / h, 800 m / h, 820 m / h or a range between any two of the foregoing values.

[0091] Step S4, post-treatment.

[0092] The carbon fibers obtained after the second-stage liquid-phase oxidation treatment in the foregoing step S3 are washed, sized, dried, and wound.

[0093] Some embodiments of the present application provide a low-ash high-modulus carbon fiber, which is prepared by using the preparation method of the low-ash high-modulus carbon fiber provided in any of the foregoing embodiments.

[0094] Further, in some embodiments of the present application, the modulus of the above-mentioned low-ash high-modulus carbon fiber is greater than 539 GPa.

[0095] Further optionally, in some embodiments of the present application, the modulus of the above-mentioned low-ash high-modulus carbon fiber is 542 GPa - 550 GPa.

[0096] Exemplarily, in some embodiments of the present application, the modulus of the above-mentioned low-ash high-modulus carbon fiber is 542 GPa, 543 GPa, 544 GPa, 545 GPa, 546 GPa, 547 GPa, 548 GPa, 549 GPa, 550 GPa or the range between any two of the foregoing values.

[0097] Further optionally, in some embodiments of the present application, the modulus of the above-mentioned low-ash high-modulus carbon fiber is 542 GPa to 548 GPa.

[0098] Further, in some embodiments of the present application, the ash content of the above-mentioned low-ash high-modulus carbon fiber is less than 0.020%.

[0099] Further optionally, in some embodiments of the present application, the ash content of the above-mentioned low-ash high-modulus carbon fiber is 0.010% to 0.020%.

[0100] Exemplarily, in some embodiments of the present application, the ash content of the above-mentioned low-ash high-modulus carbon fiber is 0.010%, 0.011%, 0.012%, 0.013%, 0.014%, 0.015%, 0.016%, 0.017%, 0.018%, 0.019%, 0.020% or the range between any two of the foregoing values.

[0101] Further optionally, in some embodiments of the present application, the ash content of the above-mentioned low-ash high-modulus carbon fiber is 0.010% to 0.015%.

[0102] The features and properties of the present application will be further described in detail with reference to the following examples:

[0103] Example 1

[0104] A method for preparing carbon fiber is provided and prepared according to the following steps:

[0105] Step 1: Subject the polyacrylonitrile-based fiber to pre-oxidation treatment at 250°C; then perform low-temperature carbonization at 500°C; then perform high-temperature carbonization treatment at 1200°C; and finally perform graphitization treatment at 2800°C to obtain graphitized fiber.

[0106] Then, the graphitized fiber is transported at a transport speed of 500 m / h.

[0107] Step 2: Transport the graphitized fiber obtained in Step 1 to the first-stage acid tank at a transport speed of 500 m / h for the first-stage liquid-phase oxidation treatment. The first-stage liquid-phase oxidation treatment is carried out using concentrated nitric acid with a mass concentration of 68% for a treatment time of 200 s; after the treatment, activated graphitized fiber is obtained.

[0108] Step 3: Transfer the activated graphitized fibers obtained in the aforementioned Step 2 to the second-stage acid bath at a transmission speed of 500 m / h for the second-stage liquid-phase oxidation treatment. The second-stage liquid-phase oxidation treatment is carried out using hydrofluoric acid with a mass concentration of 48%, and the treatment time is 50 s.

[0109] Step 4: Transfer the graphitized fibers obtained in the aforementioned Step 3 to the cleaning bath at a transmission speed of 500 m / h, and perform water washing, sizing, drying, and winding to obtain the finished low-ash high-modulus carbon fibers. See Table 1 for details.

[0110] Examples 2 - 5

[0111] Provide a preparation method of carbon fibers, which is basically the same as the preparation steps of Example 1; the difference lies only in the process parameter of the second-stage liquid-phase oxidation treatment time in Step S3; see Table 1 for details.

[0112] Comparative Examples 1 - 5

[0113] Provide a preparation method of carbon fibers, which is different from Example 1 in that only primary treatment is carried out, that is, Step S3 is absent. See Table 1 for details.

[0114] Comparative Example 6

[0115] Provide a preparation method of carbon fibers, which is different from Example 1 in that only secondary treatment is carried out, that is, Step S2 is absent. See Table 1 for details.

[0116] Examples 6 - 9

[0117] Provide a preparation method of carbon fibers, which is basically the same as the preparation steps of Example 1; the difference lies only in the process parameters in Step S2 and Step S3; see Table 1 for details.

[0118] Experimental Examples

[0119] Test the performance of the carbon fiber products prepared in Examples 1 - 9 and Comparative Examples 1 - 5.

[0120] 1. Tensile strength and tensile modulus.

[0121] The tensile strength and tensile modulus are detected according to the GB / T 3362 - 2017 standard.

[0122] 2. Interlaminar shear strength.

[0123] The interlaminar shear strength is detected according to the GB / T 1450.1 - 2005 standard.

[0124] 3. Ash content

[0125] The ash content is detected according to the standard of FZ / T 50044-2018. The detection results of each example and comparative example are shown in Table 2.

[0126] Table 1

[0127]

[0128] Table 2

[0129]

[0130] It can be seen from the test results of the above table that:

[0131] The ash content of the carbon fiber in each example is significantly lower than that of the carbon fiber in each comparative example. Further, the modulus and interlaminar shear strength of the carbon fiber in each example are higher, showing the properties of high modulus and high interlaminar shear strength. Each example slightly damages the strength of the carbon fiber, but the damage is small; the tensile strength is above 4039 MPa.

[0132] In summary, through the combination of primary acid liquid phase oxidation and secondary hydrofluoric acid oxidation treatment, each example solution of the present application can further remove the ash content of high-modulus carbon fiber and improve the mechanical properties of the carbon fiber. Applying this kind of carbon fiber to the preparation of composite materials is beneficial to improving the interface effect of the composite materials; and the mechanical properties of the composite materials.

[0133] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A method for preparing carbon fiber, characterized in that, Including: Performing a first-stage liquid-phase oxidation treatment on the graphitized fiber to introduce active functional groups on the surface of the graphitized fiber, thereby obtaining an active graphitized fiber; Performing a second-stage liquid-phase oxidation treatment on the active graphitized fiber using an HF solution.

2. The method for preparing carbon fiber according to claim 1, wherein The performing of the second-stage liquid-phase oxidation treatment using an HF solution includes: Treating the active graphitized fiber with an HF solution for 50 s to 250 s.

3. The method for preparing carbon fiber according to claim 1, wherein The performing of the second-stage liquid-phase oxidation treatment using an HF solution includes: Performing a second-stage liquid-phase oxidation treatment on the active graphitized fiber using an HF solution with a mass concentration of 30% to 80%.

4. The method for preparing carbon fiber according to any one of claims 1-3, wherein The performing of the first-stage liquid-phase oxidation treatment on the graphitized fiber includes: Performing a first-stage liquid-phase oxidation treatment on the graphitized fiber using a strong acid solution.

5. The method for preparing carbon fiber according to claim 4, wherein The performing of the first-stage liquid-phase oxidation treatment on the graphitized fiber includes: Performing a first-stage liquid-phase oxidation treatment on the graphitized fiber using a sulfuric acid solution or a nitric acid solution.

6. The method for preparing carbon fiber according to claim 4, wherein The performing of the first-stage liquid-phase oxidation treatment on the graphitized fiber includes: Treating the graphitized fiber with a sulfuric acid solution or a nitric acid solution for 50 s to 250 s.

7. The method for preparing carbon fiber according to claim 4, wherein The performing of the first-stage liquid-phase oxidation treatment on the graphitized fiber includes: Performing a first-stage liquid-phase oxidation treatment on the graphitized fiber using a strong acid solution with a mass concentration of 50% - 97%.

8. The method for preparing carbon fiber according to claim 1, wherein The preparation of the graphitized fiber includes: Treating a polyacrylonitrile fiber to obtain a graphitized fiber.

9. A carbon fiber, characterized in that, Prepared by the method for preparing carbon fiber according to any one of claims 1-8.

10. The carbon fiber according to claim 9, wherein The modulus of the carbon fiber is greater than 539 GPa; Optionally, the ash content of the carbon fiber is less than 0.020%.

Images