Modified carbon fiber, preparation method thereof and composite material

Abstract

The invention discloses a modified carbon fiber, a preparation method thereof and a composite material, and relates to the technical field of carbon fiber surface modification. The modified carbon fiber comprises a carbon fiber matrix, a protective layer coating the surface of the carbon fiber matrix and a reinforcing layer arranged on the protective layer, the protective layer comprises a compound containing a phenolic hydroxyl group; the reinforcement layer includes a carbon material. According to the carbon fiber composite material, the protective layer is arranged on the carbon fiber matrix, so that the loss of the mechanical property of the carbon fiber body caused by the erosion effect of the reinforcing layer can be effectively inhibited, the formation of the reinforcing layer is not influenced, and the performance of the carbon fiber composite material is effectively improved.

Description

Technical Field

[0001] The present application relates to the technical field of carbon fiber surface modification, and in particular to a modified carbon fiber, a preparation method thereof, and a composite material. Background Art

[0002] In modern materials science, carbon fiber has attracted considerable attention for its exceptional properties, including high strength and high modulus. However, due to its low surface activity and strong chemical inertness, carbon fiber exhibits poor interfacial bonding with the resin matrix, resulting in low interfacial strength. Therefore, surface modification of carbon fiber is necessary.

[0003] Among them, introducing carbon nanotubes (CNTs) on the surface of carbon fiber can significantly enhance the interfacial bonding force between the fiber and the resin matrix, construct a more efficient stress transfer path, thereby improving the overall mechanical properties of the composite material, and providing a solid foundation for the application of carbon fiber composite materials in more complex working conditions and high-end fields.

[0004] In current industrial production, the Chemical Vapor Deposition (CVD) process is the most widely used and most compatible method for introducing CNTs into carbon fiber production lines. However, the metal catalysts used to grow CNTs (such as transition metals such as iron, cobalt, and nickel) tend to diffuse into the interior of the carbon fiber under high-temperature reaction conditions. This erosion process not only changes the microstructure of the carbon fiber, resulting in a decrease in the mechanical properties of the fiber itself, but also affects the growth quality and uniformity of carbon nanotubes on the carbon fiber surface, ultimately reducing the overall performance of carbon fiber composites. Summary of the Invention

[0005] In order to solve the above technical problems, the present application aims to provide a modified carbon fiber and a preparation method thereof and a composite material. The composite material prepared from the modified carbon fiber has excellent mechanical properties and interface properties.

[0006] According to a first aspect of the present application, a modified carbon fiber is provided, comprising a carbon fiber matrix, a protective layer coated on a surface of the carbon fiber matrix, and a reinforcing layer disposed on the protective layer;

[0007] The protective layer includes a compound containing a phenolic hydroxyl group;

[0008] The reinforcement layer includes a carbon material.

[0009] In some embodiments of the present application, the compound containing phenolic hydroxyl group includes one or more of catecholethylamine, catechol, gallic acid, tannic acid, and 2,3-dihydroxyaniline.

[0010] In some embodiments of the present application, the carbon material includes one or more of carbon spheres, carbon nanotubes, carbon nanofibers, graphene, and pyrolytic carbon.

[0011] In some embodiments of the present application, when the carbon material includes carbon nanotubes, the raw materials for forming the carbon nanotubes include a carbon source and a metal catalyst;

[0012] The carbon source includes one or more of ethanol vapor, methane, ethylene, acetylene, carbon monoxide, and acetone vapor;

[0013] The metal catalyst includes one or more of ferric nitrate, ferric chloride, nickel sulfate, nickel chloride, and cobalt acetate.

[0014] In some embodiments of the present application, the thickness ratio of the protective layer to the reinforcement layer is 0.82-1.21:1.

[0015] In some embodiments of the present application, the thickness of the protective layer is 149-603 nm.

[0016] According to a second aspect of the present application, a method for preparing a modified carbon fiber is provided. The method for preparing the modified carbon fiber is used to prepare any of the modified carbon fibers described above, and the method comprises:

[0017] Immersing a carbon fiber matrix in a solution of a compound containing a phenolic hydroxyl group, maintaining a first preset condition, to form a protective layer on the surface of the carbon fiber matrix, to obtain a first intermediate;

[0018] immersing the first intermediate in a solution of a metal catalyst and maintaining a second preset condition to load the metal catalyst on the first intermediate to obtain a second intermediate;

[0019] A carbon source is introduced into the second intermediate and the third preset condition is maintained to form a reinforcement layer on the second intermediate to obtain the modified carbon fiber.

[0020] In some embodiments of the present application, the first preset condition includes: the immersion time is 60-200s;

[0021] The second preset condition includes: an immersion rate of 5-10 m / min;

[0022] The third preset conditions include: temperature of 600-900° C., pressure of 0.01-0.10 MPa, and holding time of 60-90 seconds.

[0023] In some embodiments of the present application, before immersing the carbon fiber matrix in a solution of a compound containing a phenolic hydroxyl group, the preparation method further comprises:

[0024] The initial carbon fibers are subjected to a desizing treatment to obtain the carbon fiber matrix.

[0025] According to a third aspect of the present application, a composite material is provided, comprising any of the modified carbon fibers described above or a modified carbon fiber prepared by any of the methods for preparing the modified carbon fibers described above.

[0026] The technical solution provided by this application may have the following beneficial effects:

[0027] The present application can effectively suppress the loss of mechanical properties of the carbon fiber body caused by the erosion of the reinforcing layer by providing a protective layer on the carbon fiber matrix, and will not affect the formation of the reinforcing layer, thereby effectively improving the performance of the carbon fiber composite material.

[0028] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0030] Figure 1a This is a scanning electron microscope (SEM) image of a metal catalyst corroding a carbon fiber matrix in the related art;

[0031] Figure 1b SEM image of metal catalyst eroding carbon fiber matrix in related art;

[0032] Figure 1c SEM image of metal catalyst eroding carbon fiber matrix in related art;

[0033] Figure 1d SEM image of metal catalyst eroding carbon fiber matrix in related art;

[0034] Figure 2 is a schematic diagram of a cross-sectional structure of a modified carbon fiber according to an exemplary embodiment;

[0035] Figure 3 is a SEM image of a modified carbon fiber according to an exemplary embodiment;

[0036] Figure 4 It is a schematic flow chart of a method for preparing modified carbon fiber according to an exemplary embodiment.

[0037] Reference numerals:

[0038] 1. Carbon fiber matrix; 2. Protective layer; 3. Reinforcement layer. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the present application will be clearly and completely described below in combination with the embodiments of the present application and the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present application. It should be noted that, in the absence of conflict, the embodiments in the present application and the features in the embodiments can be arbitrarily combined with each other.

[0040] In related technologies, such as Figure 1a-Figure 1d As shown, when a reinforcement layer (such as carbon nanotubes) is directly formed on the surface of a carbon fiber matrix, the metal catalyst will corrode the carbon fiber matrix, resulting in a decrease in the mechanical properties of the carbon fiber matrix. It will also affect the growth quality and uniformity of carbon nanotubes on the surface of the carbon fiber matrix, thereby reducing the overall performance of the carbon fiber composite material.

[0041] Based on this, the present application provides a modified carbon fiber comprising a carbon fiber matrix, a protective layer coated on the surface of the carbon fiber matrix, and a reinforcing layer disposed on the protective layer; the protective layer comprises a compound containing a phenolic hydroxyl group; and the reinforcing layer comprises a carbon material. The protective layer disposed on the carbon fiber matrix effectively suppresses strength loss of the carbon fiber body due to corrosion of the reinforcing layer without affecting the formation of the reinforcing layer, thereby effectively improving the performance of the carbon fiber composite material.

[0042] Some specific implementation methods described below are intended to facilitate those skilled in the art to understand this embodiment, and this embodiment is not limited to some specific implementation methods described below.

[0043] like Figure 2 As shown, an exemplary embodiment of the present application provides a modified carbon fiber, which includes a carbon fiber matrix 1, a protective layer 2 coated on the surface of the carbon fiber matrix 1, and a reinforcing layer 3 arranged on the protective layer 2; the protective layer 2 includes a compound containing phenolic hydroxyl groups; and the reinforcing layer 3 includes a carbon material.

[0044] In this embodiment, the surface of the carbon fiber matrix 1 can be modified by providing a protective layer 2 on the carbon fiber matrix 1; the protective layer 2 includes a compound containing a phenolic hydroxyl group. On the one hand, the compound can react with the groups on the surface of the carbon fiber matrix 1 through functional groups such as the phenolic hydroxyl group, so as to form a protective layer 2 with strong adhesion on the surface of the carbon fiber matrix 1; on the other hand, the compound also has excellent chelating ability. The phenolic hydroxyl group can provide lone pairs of electrons to form coordination bonds with metal ions, and the conjugated structure of the benzene ring can make the electron distribution more uniform, thereby enhancing the coordination ability of the entire molecule. Therefore, the special molecular structure of the compound containing a phenolic hydroxyl group makes it an excellent chelating agent, which can quickly and accurately identify and capture metal ions in the surrounding environment, and lock the metal ions firmly by forming a stable chelate. This not only effectively prevents the potential damage of metal ions to the fiber, but also can achieve a uniform distribution of metal ions on the fiber surface.

[0045] Combine Figure 3 It can be seen that the protective layer 2 provided on the carbon fiber matrix 1 can effectively inhibit the erosion of the carbon fiber matrix 1 caused by the reinforcement layer 3, and can form a uniform reinforcement layer 3, thereby effectively improving the performance of the carbon fiber composite material.

[0046] The carbon fiber matrix 1 includes one or more of polyacrylonitrile-based carbon fiber, pitch-based carbon fiber, viscose-based carbon fiber, and phenolic-based carbon fiber. It should be noted that the carbon fiber matrix 1 is a carbon fiber multifilament with specifications including 6K, 12K, 24K, 48K, etc.

[0047] In an exemplary embodiment, the compound containing a phenolic hydroxyl group includes one or more of catecholethylamine, catechol, gallic acid, tannic acid, and 2,3-dihydroxyaniline.

[0048] In this embodiment, the compounds containing phenolic hydroxyl groups include one or more of catecholethylamine, catechol, gallic acid, tannic acid, and 2,3-dihydroxyaniline. In addition to phenolic hydroxyl groups, the above compounds also have functional groups such as amino groups. The nitrogen atoms in the phenolic hydroxyl groups and amino groups contain lone pairs of electrons, which can form coordination bonds with metal ions to form stable chelates to avoid the corrosion of the carbon fiber matrix 1 by the metal catalyst.

[0049] The compound containing a phenolic hydroxyl group can be any one of the aforementioned compounds, or a combination of several compounds. For example, the compound containing a phenolic hydroxyl group can include catecholethylamine and catechol in a mass ratio of 2.0-4.5:1. The protective layer 2 can be formed by self-polymerizing a compound containing a phenolic hydroxyl group to form a polymer coating of the compound; or the compound containing a phenolic hydroxyl group can be used as a reactive monomer and copolymerized with other monomers to form a polymer coating.

[0050] In an exemplary embodiment, the reinforcement layer 3 includes zero-dimensional, one-dimensional, two-dimensional and three-dimensional carbon materials, wherein the zero-dimensional, one-dimensional, two-dimensional and three-dimensional carbon materials include one or more of carbon spheres, carbon nanotubes, carbon nanofibers, graphene and pyrolytic carbon.

[0051] In this embodiment, the reinforcing layer 3 includes zero-dimensional, one-dimensional, two-dimensional and three-dimensional carbon materials. For example, the carbon source can be grown on the protective layer 2 on the surface of the carbon fiber matrix 1 to form carbon balls, carbon nanotubes, carbon nanofibers, graphene, and pyrolytic carbon through chemical vapor deposition, chemical deposition, pyrolysis and other methods to improve the interface performance of the carbon fiber matrix 1.

[0052] In one exemplary embodiment, when the carbon material includes carbon nanotubes, the raw materials for forming the carbon nanotubes include a carbon source and a metal catalyst;

[0053] The carbon source includes one or more of ethanol vapor, methane, ethylene, acetylene, carbon monoxide, and acetone vapor;

[0054] The metal catalyst includes one or more of ferric nitrate, ferric chloride, nickel sulfate, nickel chloride, and cobalt acetate.

[0055] In this embodiment, when the carbon material includes carbon nanotubes, a metal catalyst can be loaded on the protective layer 2 on the surface of the carbon fiber matrix 1 by chemical vapor deposition. A carbon source is introduced at high temperature, and the metal catalyst particles catalyze the decomposition of the carbon source. The generated carbon atoms precipitate on the surface of the metal catalyst and form carbon nanotubes.

[0056] The carbon source can be, for example, ethanol vapor. Using ethanol vapor as the carbon source can lower the reaction temperature, thereby avoiding the problem of decreased mechanical properties of the carbon fiber matrix 1 that may be caused by high temperatures. The carbon source can also be a compound of ethanol vapor and acetone vapor in a mass ratio of 1.0-2.5:1. The metal catalyst can be ferric nitrate, or a compound of ferric chloride and nickel chloride in a mass ratio of 2.3-4.2:1.

[0057] In an exemplary embodiment, the thickness ratio of the protective layer 2 to the reinforcement layer 3 is 0.82-1.21:1.

[0058] The thickness ratio of the protective layer 2 to the reinforcing layer 3 has a significant impact on the performance of the modified carbon fiber and the composite material prepared from the modified carbon fiber. If the thickness ratio of the protective layer 2 to the reinforcing layer 3 is too small, the metal catalyst may still corrode the carbon fiber matrix 1 when the reinforcing layer 3 is formed, and the protective layer 2 will not be able to provide good protection for the carbon fiber matrix 1. If the thickness ratio of the protective layer 2 to the reinforcing layer 3 is too large, the interface strength between the protective layer 2 and the reinforcing layer 3 will decrease, and the uniformity of the formation of the reinforcing layer 3 will also be affected. Therefore, in this embodiment, by controlling the thickness ratio of the protective layer 2 to the reinforcing layer 3 to be 0.82-1.21:1, the modified carbon fiber and the composite material prepared from the modified carbon fiber can maintain good overall performance.

[0059] For example, the thickness ratio of the protective layer 2 to the reinforcement layer 3 may be 0.82:1, 0.96:1, 1.13:1, 1.19:1, or 1.21:1. The thickness ratio of the protective layer 2 to the reinforcement layer 3 may also be any ratio between the exemplary thickness ratios, for example, the thickness ratio of the protective layer 2 to the reinforcement layer 3 may also be any ratio between 0.96 and 1.19:1.

[0060] In an exemplary embodiment, the thickness of the protective layer 2 is 149-603 nm.

[0061] If the thickness of the protective layer 2 is too low, it will be difficult to provide good protection for the carbon fiber matrix 1; if the thickness of the protective layer 2 is too high, it will be difficult to ensure its uniformity, and it will also increase the concentration of interfacial stress, affecting its adhesion to the carbon fiber matrix 1. Therefore, in this embodiment, the thickness of the protective layer 2 is controlled to be 149-603nm, so that it can provide better protection for the carbon fiber matrix 1. The thickness of the protective layer 2 can also be adjusted according to the type and thickness of the reinforcing layer 3. For example, the thickness of the protective layer 2 can be 149nm, 230nm, 308nm, 350nm, 440nm, 520nm, or 603nm. The thickness of the protective layer 2 can also be any thickness between the exemplary thickness values, for example, the thickness of the protective layer 2 can also be any thickness between 230-440nm.

[0062] For example, when the thickness of the protective layer 2 is 230 nm, the thickness of the reinforcement layer 3 may be 280 nm, and the thickness ratio of the protective layer 2 to the reinforcement layer 3 is 0.82:1. When the thickness of the protective layer 2 is 405 nm, the thickness of the reinforcement layer 3 may be 340 nm, and the thickness ratio of the protective layer 2 to the reinforcement layer 3 is 1.19:1. When the thickness of the protective layer 2 is 585 nm, the thickness of the reinforcement layer 3 may be 520 nm, and the thickness ratio of the protective layer 2 to the reinforcement layer 3 is 1.13:1. When the thickness of the protective layer 2 is 592 nm, the thickness of the reinforcement layer 3 may be 490 nm, and the thickness ratio of the protective layer 2 to the reinforcement layer 3 is 1.21:1.

[0063] like Figure 4 As shown, an exemplary embodiment of the present application provides a method for preparing modified carbon fiber, the preparation method comprising:

[0064] S110, immersing the carbon fiber matrix in a solution of a compound containing a phenolic hydroxyl group, maintaining the first preset condition, to form a protective layer on the surface of the carbon fiber matrix, and obtaining a first intermediate.

[0065] In step S110, the carbon fiber matrix 1 is impregnated with a solution, which is conducive to forming a uniform protective layer 2 on the surface of the carbon fiber matrix 1. The solvent used for the solution of the compound containing a phenolic hydroxyl group includes a (Tris)-HCl buffer solution, and the pH value of the (Tris)-HCl buffer solution can be 8.0-9.0. The mass ratio of the compound containing a phenolic hydroxyl group to the solvent includes 0.6-2.5:100. For example, the mass ratio of the compound containing a phenolic hydroxyl group to the solvent can be 0.6:100, 1.0:100, 1.6:100, or 2.5:100. The mass ratio of the compound containing a phenolic hydroxyl group to the solvent can also be any ratio between the exemplary ratios, for example, the mass ratio of the compound containing a phenolic hydroxyl group to the solvent can also be any ratio between 1.0-1.6:100.

[0066] S120, immersing the first intermediate in a solution of a metal catalyst, maintaining a second preset condition, so as to load the metal catalyst on the first intermediate to obtain a second intermediate.

[0067] In step S120, the first intermediate is immersed in a solution of a metal catalyst, so that the protective layer 2 is loaded with the metal catalyst. The concentration of the metal catalyst solution can be, for example, 0.05-0.30 mol / L. Exemplarily, the concentration of the metal catalyst solution can be 0.05 mol / L, 0.10 mol / L, 0.18 mol / L, 0.25 mol / L, or 0.30 mol / L. The concentration of the metal catalyst solution can also be any value between the exemplary concentration values, for example, the concentration of the metal catalyst solution can also be any value between 0.10-0.25 mol / L.

[0068] S130, introducing a carbon source into the second intermediate, maintaining the third preset condition, to form a reinforcement layer on the second intermediate, and obtain modified carbon fiber.

[0069] In step S130, under the action of the metal catalyst, the carbon source can be catalyzed to decompose, and the generated carbon atoms are precipitated on the surface of the metal catalyst to form a reinforcement layer 3. In particular, while the carbon source is introduced into the second intermediate, an inert gas (such as argon, nitrogen, etc.) can also be introduced at the same time to adjust the concentration of the carbon source to avoid excessive carbon deposition or uneven deposition caused by excessive carbon source concentration. The volume ratio of the inert gas to the carbon source can be 1.5-2.5:1; for example, the carbon source and the inert gas can be introduced into the reactor at a rate of 10L / min and 20L / min, respectively.

[0070] In an exemplary embodiment, the first preset condition includes: the immersion time is 60-200 seconds.

[0071] In this embodiment, the thickness of the protective layer 2 is adjusted by adjusting the immersion time of the carbon fiber matrix 1 in the solution of the compound containing phenolic hydroxyl groups. Exemplarily, the immersion time can be 60s, 100s, 150s, 180s, or 200s. The immersion time can also be any time between the exemplary immersion times, for example, the immersion time can also be any time between 100-180s. Among them, the carbon fiber matrix 1 can be passed through the solution tank of the compound containing phenolic hydroxyl groups at a certain rate to achieve continuous production; the immersion rate can be, for example, 5-10m / min.

[0072] In an exemplary embodiment, the second preset condition includes: an immersion rate of 5-10 m / min.

[0073] In this embodiment, the loading amount of the metal catalyst on the protective layer 2 is adjusted by adjusting the immersion rate of the first intermediate in the solution obtained by the metal catalyst. For example, the immersion rate can be 5.0 m / min, 6.5 m / min, 8.8 m / min, and 10.0 m / min. The immersion rate can also be any value between the exemplary immersion rates, for example, the immersion rate can also be any value between 6.5-8.8 m / min. The first intermediate can be immersed in the solution tank containing the metal catalyst at a certain rate to achieve continuous production.

[0074] In an exemplary embodiment, the third preset condition includes: a temperature of 600-900° C., a pressure of 0.01-0.10 MPa, and a holding time of 60-90 seconds.

[0075] In this embodiment, the temperature, pressure, and time are controlled to control the cracking of carbon, which is beneficial for adjusting the growth of carbon nanotubes and enhancing the uniformity of the layer 3, for example.

[0076] For example, in one embodiment, the third preset condition includes: a temperature of 600° C., a pressure of 0.01 MPa, and a holding time of 90 seconds.

[0077] In another embodiment, the third preset condition includes: a temperature of 750° C., a pressure of 0.05 MPa, and a holding time of 60-90 seconds.

[0078] In another embodiment, the third preset condition includes: a temperature of 900° C., a pressure of 0.10 MPa, and a holding time of 60 seconds.

[0079] In an exemplary embodiment, before immersing the carbon fiber matrix 1 in a solution of a compound containing a phenolic hydroxyl group, the preparation method further comprises:

[0080] The initial carbon fibers are desized to obtain a carbon fiber matrix 1.

[0081] In this embodiment, the initial carbon fibers are first subjected to a desizing treatment to remove the sizing on their surfaces and improve the interface bonding strength between the carbon fibers and the protective layer 2 .

[0082] The desizing treatment includes: maintaining the temperature at 300-400°C for 30-90 seconds in an argon atmosphere. For example, the initial carbon fibers can be placed in a heating furnace with both ends open, and a high-purity argon atmosphere is introduced into the furnace. The temperature is maintained at 300-400°C for 30-90 seconds to perform a continuous high-temperature desizing treatment on the initial carbon fibers to obtain a carbon fiber matrix.

[0083] For example, in one embodiment, the desizing treatment temperature is 300° C. and the holding time is 90 seconds.

[0084] In another embodiment, the desizing treatment temperature is 360° C. and the holding time is 60 seconds.

[0085] In another embodiment, the desizing treatment temperature is 400° C. and the holding time is 30 seconds.

[0086] An exemplary embodiment of the present application provides a composite material, which includes the modified carbon fiber according to any of the above embodiments or the modified carbon fiber prepared by the method for preparing the modified carbon fiber according to any of the above embodiments.

[0087] In this embodiment, the modified carbon fiber may be compounded with a resin material to form a composite material, wherein the resin material includes one or more of epoxy resin, phenolic resin, bismaleimide resin, and polyimide resin.

[0088] In order to more clearly explain the technical solution of the present application, the present application lists specific examples of the preparation method of modified carbon fiber, and the beneficial effects of selecting the above-mentioned ranges of the process parameters of each component will be illustrated by giving specific experimental data through specific examples.

[0089] Example

[0090] It should be noted that, unless otherwise specified, the raw materials in the following examples can be obtained commercially.

[0091] The initial carbon fiber is SYT49S-12K polyacrylonitrile-based carbon fiber, which has a tensile strength of 5300 MPa, a tensile modulus of 241 GPa, and a bulk density of 1.80 g / cm 3 ;

[0092] The solution of the compound containing phenolic hydroxyl group is prepared by mixing catecholethylamine and (Tris)-HCl buffer at a mass ratio of 1:100, and the pH value of the (Tris)-HCl buffer is 8.5;

[0093] The solution of the metal catalyst is an aqueous solution of ferric chloride (FeCl3);

[0094] The carbon source was a mixture of ethanol vapor (C2H5OH) and argon (Ar), the feed flow rate of ethanol vapor was 10 L / min, and the feed flow rate of argon was 20 L / min.

[0095] Example 1: A method for preparing modified carbon fiber, comprising the following steps:

[0096] (1) The initial carbon fibers were placed in a heating furnace with openings at both ends, and a high-purity argon atmosphere was introduced into the furnace. The temperature was maintained at 360°C for 50 seconds to perform continuous high-temperature desizing treatment on the initial carbon fibers to obtain a carbon fiber matrix.

[0097] (2) Immersing the carbon fiber matrix in a solution of catecholethylamine for 50 seconds to allow the catecholethylamine to undergo a self-polymerization reaction on the surface of the carbon fiber matrix to form a protective layer on the surface of the carbon fiber matrix, thereby obtaining a first intermediate.

[0098] (3) The first intermediate was immersed in a 0.20 mol / L ferric chloride solution at a rate of 5 m / min to obtain a second intermediate.

[0099] (4) A mixed gas of Ar / C2H5OH is introduced into the second intermediate at a temperature of 660°C and a pressure of 0.01 MPa for 70 seconds to grow carbon nanotubes (CNTs) on the surface of the second intermediate to form a reinforcement layer and obtain modified carbon fibers.

[0100] In order to more clearly explain the technical solution of the present application, the present application also lists Examples 2-10 of the preparation method of the modified carbon fiber, wherein the process parameters of Examples 2-10 are shown in Table 1.

[0101] Table 1 shows a specific embodiment of the method for preparing the modified carbon fiber in this application. It should be noted that, except for the parameters listed in Table 1, the other parameters of Examples 2-10 are substantially the same as those of Example 1.

[0102] In Table 1, the ratio C1 is the thickness ratio of the protective layer to the reinforcing layer.

[0103] Table 1 Process parameters of modified carbon fiber of embodiment

[0104]

[0105] Comparative Example:

[0106] Comparative Example 1: Unmodified SYT49S-12K polyacrylonitrile-based carbon fiber is used as Comparative Example 1.

[0107] Comparative Example 2: The main difference between this comparative example and Example 1 is that step (2) is not included, that is, carbon nanotubes are directly grown on the carbon fiber substrate to form a reinforcement layer.

[0108] Performance Testing

[0109] The tensile strength and tensile modulus of the carbon fibers of the embodiment and the comparative example were tested respectively; an epoxy resin-based composite material with a carbon fiber volume fraction of 56% was prepared, and the interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) of the composite material were tested, and the test results are recorded in Table 2.

[0110] Table 2 Performance test table of carbon fiber and composite materials

[0111] Tensile strength / MPa Tensile modulus / GPa IFSS / MPa ILSS / MPa Example 1 4723 239 62.3 97.7 Example 2 4952 241 65.1 105.5 Example 3 5089 241 68.8 111.0 Example 4 5266 241 76.6 122.6 Example 5 5125 241 70.7 119.8 Example 6 5195 240 69.8 109.1 Example 7 5158 241 60.1 102.3 Example 8 5211 241 59.7 104.7 Example 9 4901 240 61.6 105.5 Example 10 5125 241 63.3 102.7 Comparative Example 1 5300 241 51.2 85.6 Comparative Example 2 4178 212 57.5 77.6

[0112] Combining the data in Tables 1 and 2, it can be seen that the mechanical properties of the modified carbon fibers obtained by the method of the embodiment are retained to a large extent, and the interfacial properties are significantly improved. This shows that the modified carbon fibers prepared by the embodiments of the present application can effectively prevent the metal catalyst from corroding the carbon fiber matrix through a protective layer of a certain thickness, while improving the growth condition of CNTs.

[0113] In combination with Examples 1-10, it can be seen that the thickness value of the protective layer and the thickness ratio of the protective layer to the reinforcing layer have a significant effect on the mechanical properties of the modified carbon fiber and the comprehensive properties of the composite material. Among them, when the thickness value of the protective layer is 405-592nm and the thickness ratio of the protective layer to the reinforcing layer is 1.13-1.21:1, the modified carbon fiber and the composite material can have excellent mechanical properties and interface properties.

[0114] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements that are inherent to such process, method, article or apparatus.

[0115] The above embodiments are intended only to illustrate the technical solutions of the present application and are not intended to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they may still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents; and such modifications or replacements do not deviate from the spirit and scope of the technical solutions of the various embodiments of the present application.

Claims

1. A modified carbon fiber, characterized in that: The modified carbon fiber includes a carbon fiber matrix, a protective layer coated on the surface of the carbon fiber matrix, and a reinforcing layer arranged on the protective layer; The protective layer includes a compound containing a phenolic hydroxyl group; The reinforcement layer includes a carbon material.

2. The modified carbon fiber according to claim 1, characterized in that The compound containing phenolic hydroxyl group includes one or more of catecholethylamine, catechol, gallic acid, tannic acid, and 2,3-dihydroxyaniline.

3. The modified carbon fiber according to claim 1, characterized in that The carbon material includes one or more of carbon spheres, carbon nanotubes, carbon nanofibers, graphene, and pyrolytic carbon.

4. The modified carbon fiber according to claim 3, characterized in that When the carbon material includes carbon nanotubes, the raw materials for forming the carbon nanotubes include a carbon source and a metal catalyst; The carbon source includes one or more of ethanol vapor, methane, ethylene, acetylene, carbon monoxide, and acetone vapor; The metal catalyst includes one or more of ferric nitrate, ferric chloride, nickel sulfate, nickel chloride, and cobalt acetate.

5. The modified carbon fiber according to claim 1, characterized in that The thickness ratio of the protective layer to the reinforcement layer is 0.82-1.21:

1.

6. The modified carbon fiber according to any one of claims 1 to 5, characterized in that The thickness of the protective layer is 149-603 nm.

7. A method for preparing modified carbon fiber, characterized in that: The method for preparing the modified carbon fiber is used to prepare the modified carbon fiber according to any one of claims 1 to 6, and the method comprises: Immersing a carbon fiber matrix in a solution of a compound containing a phenolic hydroxyl group, maintaining a first preset condition, to form a protective layer on the surface of the carbon fiber matrix, to obtain a first intermediate; immersing the first intermediate in a solution of a metal catalyst and maintaining a second preset condition to load the metal catalyst on the first intermediate to obtain a second intermediate; A carbon source is introduced into the second intermediate and the third preset condition is maintained to form a reinforcement layer on the second intermediate to obtain the modified carbon fiber.

8. The method for preparing modified carbon fiber according to claim 7, characterized in that: The first preset condition includes: the immersion time is 60-200s; The second preset condition includes: an immersion rate of 5-10 m / min; The third preset conditions include: temperature of 600-900° C., pressure of 0.01-0.10 MPa, and holding time of 60-90 seconds.

9. The method for preparing modified carbon fiber according to claim 7, characterized in that: Before immersing the carbon fiber matrix in the solution of the compound containing phenolic hydroxyl groups, the preparation method further comprises: The initial carbon fibers are subjected to a desizing treatment to obtain the carbon fiber matrix.

10. A composite material, characterized in that The composite material comprises the modified carbon fiber according to any one of claims 1 to 6 or the modified carbon fiber prepared by the method for preparing the modified carbon fiber according to any one of claims 7 to 9.

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